阅读说明：本技术 利用能量束热处理含铁材料的方法和设备 (Method and apparatus for heat treatment of ferrous materials using an energy beam ) 是由 保拉·桑乔迪亚斯 伊拉蒂·伊格莱西亚斯瓦勒 赫苏斯·多明格斯科夫雷罗斯 于 2016-05-06 设计创作，主要内容包括：利用能量束热处理含铁材料的方法和设备。本发明涉及用于物体的热处理的方法和设备,比如用于硬化具有复杂形状的物体,比如曲轴。该方法包括步骤：将能量束(1)、比如激光束投射到物体(1000)的表面上；操作扫描器(2)以便重复地扫描所述束(1),以使原光斑(11)根据第一扫描图案移位,以便在物体的表面上建立有效光斑(12)；以及使所述有效光斑(12)相对于物体(1000)的表面移位。所述束遵循在扫描器(2)和物体(11)的表面之间的光路径,并且在光路径中布置束偏转装置(3、3A),用以重定向所述束。束偏转装置可以靠近物体的表面布置。(A method and apparatus for heat treating ferrous materials with an energy beam. The present invention relates to a method and apparatus for heat treatment of objects, such as for hardening objects having complex shapes, such as crankshafts. The method comprises the following steps: projecting an energy beam (1), such as a laser beam, onto a surface of an object (1000); operating the scanner (2) so as to repeatedly scan the beam (1) to displace the primary spot (11) according to a first scanning pattern so as to establish an effective spot (12) on the surface of the object; and displacing the effective spot (12) relative to the surface of the object (1000). The beam follows an optical path between the scanner (2) and the surface of the object (11), and beam deflecting means (3, 3A) are arranged in the optical path for redirecting the beam. The beam deflection means may be arranged close to the surface of the object.)

1. Method for the thermal treatment of an object, said method comprising the step of heating at least one selected portion of the object (1000) by:

projecting an energy beam (1) onto the surface of an object (1000) so as to generate a primary spot (11) on the surface of said object,

operating a scanner (2) to repeatedly scan the beam (1), displacing the primary spot (11) according to a first scanning pattern so as to create an effective spot (12) on the surface of the object, the effective spot having a two-dimensional energy distribution, and

displacing the effective spot (12) relative to the surface of the object (1000) to progressively heat the at least one selected portion of the object,

wherein the beam follows an optical path between the scanner (2) and the primary light spot (11), and

wherein a beam deflection device (3, 3A) is arranged in the light path for redirecting the beam (1) onto the surface of the object;

wherein the beam deflection means (3, 3A) are mirrors;

wherein the mirror (3A) comprises at least one curved portion for deflecting the beam.

2. The method of claim 1, wherein the optical path comprises a first portion (X1) extending between the scanner and the beam deflection device and a second portion (X2) extending between the beam deflection device and the primary spot, the second portion (X2) being smaller than the first portion (X1).

3. The method of claim 1, wherein the beam deflection device comprises a plurality of regions (31, 32, 33), and wherein the step of operating the scanner comprises directing the beam to at least two different ones of the plurality of regions, each of the plurality of regions corresponding to at least one portion of the first scan pattern.

4. The method according to claim 1, wherein the mirror comprises at least three different substantially flat surface portions (31, 32, 33) having different spatial orientations.

5. The method of claim 4, wherein the object is a crankshaft (1000), wherein the three different substantially planar surface portions comprise a first surface portion (31), a second surface portion (32), and a third surface portion (33), the method comprising: directing the beam towards a journal (1001, 1002) of the crankshaft using the first surface portion; directing the beam towards a fillet (1004) and/or a wall (1005) at a first end of the journal using the second surface portion; and directing the beam using the third surface portion towards a fillet (1004) and/or a wall (1005) at the second end of the journal.

6. The method according to claim 4 or 5, wherein the second surface portion (32) and the third surface portion (33) are arranged facing each other at an angle larger than 100 degrees and smaller than 170 degrees.

7. The method according to any of the preceding claims, wherein the object is a crankshaft (1000), and wherein the beam deflection device is arranged such that: when the method is performed, the beam deflection device is arranged between two walls or counterweights of the crankshaft, at least at some moments in time.

8. The method according to any of the preceding claims, wherein the beam deflection device (3, 3A) and the scanner (2) are displaced synchronously with each other.

9. The method according to any of the preceding claims, wherein the beam deflection device (3, 3A) is stationary with respect to the scanner (2).

10. A method according to any one of the preceding claims, wherein the scanner (2) is operated to scan the beam in two dimensions so as to provide an effective spot (12) having a width in a first direction and a length in a second direction.

11. A method according to any of the preceding claims, wherein the effective spot is displaced relative to the surface by rotating the object.

12. The method according to any of the preceding claims, wherein the two-dimensional energy distribution is dynamically adjusted during the displacement of the effective spot in order to avoid overheating of more heat sensitive sub-areas.

13. A method according to any of the preceding claims, wherein the object is a ferrous material, for example steel, such as medium carbon steel.

14. The method of any preceding claim, wherein the energy beam is a laser beam.

15. Apparatus for the thermal treatment of an object, comprising:

-a mechanism (200) for supporting an object (1000);

-means (24) for generating an energy beam (1);

-a scanner (2), the scanner (2) being for directing the energy beam onto a surface of the object (1000) so as to generate a primary spot (11) on the surface, the scanner being arranged for repeatedly scanning the beam (1) in two dimensions to displace the primary spot (11) according to a first scanning pattern to create an effective spot (12) on the surface of the object, the effective spot having a two-dimensional energy distribution,

-means for displacing the effective spot (12) with respect to the surface of the object (1000) for progressively heating at least one selected portion of the object,

-and a beam deflection device (3, 3A), the beam deflection device (3, 3A) being arranged for receiving a beam from the scanner (2) and redirecting the beam towards the object (1000);

wherein the beam deflection means (3, 3A) are mirrors;

wherein the mirror (3A) comprises at least one curved portion for deflecting the beam.

16. Apparatus according to claim 15, wherein the beam deflection device (3, 3A) is placed in the optical path between the scanner and the object, wherein the optical path comprises a first portion (X1) and a second portion (X2), the first portion (X1) extending between the scanner and the beam deflection device, the second portion (X2) extending between the beam deflection device and a position on the object where the primary spot is to be generated, the second portion (X2) being smaller than the first portion (X1).

17. The apparatus according to claim 15, wherein the beam deflection device comprises a plurality of regions (31, 32, 33), and wherein the scanner is arranged for directing the beam to at least two different regions of the plurality of regions, each of the plurality of regions corresponding to at least one portion of the first scan pattern.

18. The apparatus of claim 15, wherein the mirror comprises at least three different substantially flat surface portions (31, 32, 33) having different spatial orientations.

19. Apparatus according to claim 18, arranged for heat treatment of a crankshaft (1000), wherein the three different substantially flat surface portions comprise a first surface portion (31), a second surface portion (32) and a third surface portion (33), the apparatus being arranged for: directing the beam towards a journal (1001, 1002) of the crankshaft using the first surface portion; directing the beam towards a fillet (1004) and/or a wall (1005) at a first end of the journal using the second surface portion; and directing the beam using the third surface portion towards a fillet (1004) and/or a wall (1005) at the second end of the journal.

20. The apparatus according to claim 18 or 19, wherein the second surface portion (32) and the third surface portion (33) are arranged facing each other at an angle larger than 100 degrees and smaller than 170 degrees.

21. Apparatus according to any one of claims 15-20, arranged for heat treatment of a crankshaft (1000), wherein the beam deflection device is arranged such that: when the apparatus performs the heat treatment, the beam deflecting device is arranged between two walls or counterweights of the crankshaft, at least at some moments in time.

22. The apparatus according to any of claims 15-21, wherein the beam deflection device (3, 3A) and the scanner (2) are arranged to be displaced synchronously with each other.

23. The apparatus according to any of claims 15-22, wherein the beam deflection device (3, 3A) is stationary with respect to the scanner (2).

24. Apparatus according to any of claims 15-23, wherein the scanner (2) is arranged for scanning the beam in two dimensions so as to provide an effective spot (12) having a width in a first direction and a length in a second direction.

25. Apparatus according to any of claims 15-24, arranged for displacing the effective spot relative to the surface by rotating the object.

26. Apparatus according to any of claims 15-25, arranged for dynamically adjusting the two-dimensional energy distribution during the displacement of the effective spot, so as to avoid overheating of more heat-sensitive sub-areas.

27. The apparatus according to any of claims 15-26, wherein the means (24) for generating an energy beam (1) is a means for generating a laser beam.

Technical Field

The present invention relates to the treatment of an object with an energy beam, for example for the purpose of hardening one or more surface portions of the object.

Background

It is well known in the art to perform heat treatment of objects with an energy beam, such as a laser beam, for example, to harden ferrous material, such as medium carbon steel, by heating the ferrous material to an elevated temperature below its melting temperature, followed by quenching it, i.e. cooling it sufficiently rapidly to form hard martensite. Heat treatment with an energy beam is also known for other purposes, for example, for softening one or more selected portions of a previously hardened object, such as a metal sheet object.

For example, case hardening may be used to increase the wear resistance of the material, and sometimes also to increase the fatigue strength caused by residual compressive stresses. Case hardening may be useful for hardening surfaces that will experience substantial wear in use, for example bearing surfaces, such as journal surfaces of crankshafts.

The use of an energy beam, such as a laser beam, for the heat treatment of a workpiece, such as case hardening, involves several advantages: the laser beam is substantially independent of the workpiece, is easily controlled, does not require vacuum, and does not produce combustion products. In addition, because the laser beam typically only locally heats the metal product or workpiece, the remainder of the workpiece can act as a heat sink, ensuring rapid cooling, which is also known as self-quenching: the cold interior of the workpiece may constitute a sufficiently large heat sink to quench the hot surface by conducting heat to the interior at a sufficiently high rate to allow martensite to form at the surface. Thus, the need for an external cooling medium (such as a cooling fluid) may be eliminated.

One problem involved in using an energy beam as a heat source in, for example, a metal hardening process, is that the width of the heated region is limited by the size of the spot projected on the surface of the workpiece. It is known to use optics to adjust the shape of the spot, for example to provide a substantially rectangular spot with a more or less uniform energy distribution. Alternatively, a scanning device (such as a scanning mirror associated with the drive device) may be used to repeatedly move the spot on the trajectory such that the heat source may be considered a rectangular source, whereby the rectangular source may be moved along the trajectory, for example by rotating a workpiece such as a crankshaft, for example to produce relative movement between the workpiece and the beam source.

Despite its advantages, laser hardening is not generally used, because it seems to be the view that the production rate is not high enough for many practical applications of the technology, and because it is difficult to achieve heating all the components to be heated to the desired extent. For example, in the case of case hardening, proper heating is critical to ensure that hardening and tempering are achieved at the necessary depth and are not damaged by overheating.

For example, crankshafts (the components of an engine used to convert reciprocating linear piston motion into rotation) are complex products that are generally considered difficult to harden by laser. FIG. 1 shows an example of a crankshaft. Crankshaft 1000 is a forged or cast steel product having two or more centrally located coaxial cylindrical journals 1001 (also referred to as "main journals") and one or more offset cylindrical crankpin journals 1002 (also referred to as "connecting rod journals"), these crankpin journals 1002 being separated by counterweights and webs that form walls 1005 that extend generally perpendicular to the journal's surface. The complex shape of the product may make it difficult to "scan" the surface correctly with the laser beam; the traces or regions to be hardened may have different widths, and/or be asymmetric, and/or be arranged in different planes (as is the case with the surfaces of the wall 1005 and journals 1001, 1002). Moreover, special care is required with regard to the fillet 1004, i.e. the transition between the journal and the wall 1005. In addition, the presence of the oil lubrication hole 1003 must also be taken into account.

Now, therefore, for hardening of crankshafts, high-frequency induction heating is often used, followed by a polymer-based water quenching process. However, while this process has proven useful for achieving the desired hardening, it has some drawbacks. For example, the inductor that generates heating by induction must be designed according to the specific configuration of the crankshaft, which reduces flexibility: adapting induction machines to new crankshafts can be time consuming and costly. Furthermore, heating by induction is costly in terms of the energy required to heat the crankshaft to the desired extent. In addition, the cooling process is complex, costly and challenging from an environmental standpoint due to the large amount of cooling fluid required to be used. In addition, parameters such as cooling fluid temperature and flow rate must be carefully controlled to ensure a proper hardening process.

Thus, the use of lasers as heat sources for hardening is an attractive alternative in terms of flexibility, environmental protection, energy consumption and cost.

Attempts have been made to adapt the heat treatment to the particular characteristics of the object to be heat treated. For example, DE-3905551-A1 teaches that the energy distribution within the laser beam can be adjusted to suit the geometry of the surface to be heated. The laser beam is applied to a concave surface at a corner of a circle.

It is well known in the art to use mirrors arranged at suitable positions to direct the laser beam onto the surface to be treated at suitable angles of incidence, see for example WO-2014/201788-a1, US-2014/0261283-a1, DE-102009034472-a1, WO-2006/114445-a1 and JP-59-076816-a 2.

In the case of laser surface treatment of products with complex surfaces, such as camshafts or crankshafts, care must be taken to reach and harden different parts of the surface. For example, DE-102010048645-a1 discusses problems reaching certain parts, such as the part towards the end of the journal, the fillet or the wall of the counterweight near the fillet, with reference to the hardening process of the crankshaft. In order to achieve a suitable coupling of the laser beam with the material in the area to be heated, it is for example desirable to form a suitable angle between the beam and the surface, for example it may be desirable for the laser beam to be close to perpendicular or orthogonal to the surface to be treated. When the angle is not appropriate, the laser beam may be reflected off the surface to a large extent so that the energy is not absorbed. DE-102010048645-a1 discusses these problems and teaches solutions based on the use of a scanning mirror which redirects the laser light and can be rotated to displace the laser spot projected onto the surface to be treated relative to the surface.

JPS627821A teaches laser treatment of a fillet of a crankshaft, i.e., splitting a laser beam so as to heat different portions of the fillet to a uniform temperature for uniform quenching, and directing the laser beam toward the fillet using a mirror. JPS61227132A also teaches quenching of a journal of a crankshaft that includes rounded corners, in which case a mirror is used to scan the laser beam along the journal.

Many prior art measures for heat treating, such as hardening, workpieces, such as crankshafts, based on an energy beam are basically based on projecting the beam onto the surface to be treated, generating a spot on the surface, so that heating of the surface takes place according to the spot, and then displacing the spot along and/or across the surface area to be hardened, for example along a meandering trajectory over said surface area, until the entire surface area has been heated.

The content of WO-2014/037281-a2, which is incorporated herein by reference, teaches different methods based on dynamic adjustment of the two-dimensional energy distribution of a spot, for example a virtual or effective spot produced by a fast and repeated two-dimensional scan of the original spot. For example, in one embodiment disclosed in WO-2014/037281-a2, a method for laser hardening of a surface of a workpiece comprises:

projecting a laser beam from a laser source onto a journal of the crankshaft to produce a laser spot on the region;

generating a relative movement between the workpiece surface and the laser source, for example by rotating a crankshaft, allowing thereby to project the laser spot onto different parts of said surface area;

repeatedly scanning the laser beam in two dimensions across respective portions of the journal during said relative movement so as to produce a two-dimensional equivalent effective laser spot on the journal, said effective laser spot having an energy distribution;

wherein the energy distribution is adjusted such that it is different in the more heat sensitive subareas, such as in the area close to the oil lubrication hole, than in the less heat sensitive subareas, in order to prevent overheating of the more heat sensitive subareas. Scanning in two dimensions can be performed at high speed, such that the scanning pattern to produce the effective spot repeats at a frequency in excess of 10Hz, 50Hz, 100Hz, or more. Some features, such as the scanning pattern, the speed of the primary spot along the scanning pattern (e.g., along different segments of the scanning pattern), and/or the power of the laser beam, may be dynamically adjusted to optimize the manner in which heating is performed in order to avoid overheating of areas near the oil lubrication holes, for example. The scanner, such as a two-dimensional scanner or a three-dimensional scanner, is advantageously arranged at a distance from the journal which is several times the length of the journal. Thus, the primary laser spot can be rapidly displaced along and across the surface of the journal without extreme demands on the speed of the components of the scanner (e.g., the scan mirror). Also, in this manner, the angle of incidence of the laser beam onto the crankshaft journal is substantially the same along the entire journal from one end of the journal to the other end of the journal.

Figures 2A-2C show how the two-dimensional energy distribution of the effective laser spot 12 (i.e. the energy distribution along and across the surface of the object, i.e. the energy distribution along and across the effective spot when projected onto the surface of the object) can be adjusted to accommodate the oil lubrication hole when applying the teachings of WO-2014/037281-a 2. The oil lubrication hole 1003 is positioned in a surface of a journal of the crankshaft, and the surface extends in a first direction parallel to the rotational axis of the crankshaft and in a second circumferential direction W. In fig. 2A, a substantially rectangular equivalent effective laser spot 12 is used, the effective laser spot 12 having a leading portion 12A of higher power density and a trailing portion 12B of lower power density. However, as shown in fig. 2B, as the oil lubrication hole 1003 approaches the effective laser spot 12 due to relative motion between the surface of the crankshaft and the laser source (e.g., due to rotation of the crankshaft about its longitudinal axis), the energy distribution is generally adjusted by reducing the power or energy density toward the center of the leading portion 12A to avoid overheating of the area near the oil lubrication hole 1003. Here, the effective laser spot is substantially U-shaped. Subsequently, once the oil lubrication hole 1003 has passed through the leading portion 12A, the original energy distribution at the leading portion is restored, while the energy distribution at the trailing portion 12B is adjusted by decreasing the energy or power density towards the center of the trailing portion to accommodate the oil lubrication hole 1003. Here, the effective laser spot 12 substantially takes an inverted U shape. That is, as the oil lubrication hole passes through the effective laser spot, the energy distribution is adjusted so that less energy is applied to the more heat sensitive areas near the oil lubrication hole than to the surface to be hardened that is remote from the oil lubrication hole. The area around the oil lubrication hole can be hardened without damaging the more heat sensitive sub-area close to the oil lubrication hole; the lateral part of the U-shaped effective laser spot is used for the region at the side of the hardened oil lubrication hole. The variation in energy distribution shown in fig. 2A-2C may be obtained, for example, by adjusting the scanning pattern, and/or by adjusting the manner in which the beam power is distributed along the scanning pattern (e.g., by adjusting the manner in which the laser beam is turned on and off during different segments of the scanning pattern), and/or by adjusting the scanning speed corresponding to different segments of the scanning pattern, etc.

Fig. 3 schematically shows how the surfaces of two journals of a crankshaft are hardened in regions 1001A and 1002A, respectively, which extend along the main part of the respective journal. In the case of the hardened region 1001A, it extends over most of the main journal 1001 from proximate one fillet 1004 to proximate the other fillet 1004. The fillet is of an undercut type; this type of undercut is typically provided for handling the fillet by rolling.

Disclosure of Invention

Sometimes, it may be desirable to also harden the fillet and even a portion of the wall beyond the fillet; the wall is typically substantially perpendicular to the surface of the journal. For example, fig. 4 schematically shows a cross section along the longitudinal axis of a journal of a crankshaft, wherein hardening is performed not only between the fillets but also at and beyond the fillets. As shown in fig. 4, the hardened zone includes: a portion 1005A extending above the fillet along a portion of one wall 1005; a portion 1004A at the rounded corner; a portion 1001A between the fillets corresponding to the surface of the journal 1001; a portion 1004A at another rounded corner; and a portion 1005A above the fillet corresponding to the opposing wall 1005.

A problem when trying to obtain such hardening using the method disclosed in WO-2014/037281-a2 is that although the laser beam is substantially perpendicular to the surface of the journal 1001, it is not substantially perpendicular to the wall 1005. This is schematically illustrated in fig. 5, where fig. 5 shows a laser beam 1 projected from a schematically illustrated scanner 2, which laser beam traces a scanning pattern on one journal of the crankshaft as shown. Although the laser beam 1 will be generally perpendicular to the surface of the crankshaft all along the journal 1002, the angle of incidence will differ at the fillet due to the curvature of the fillet, and the laser beam will actually be generally parallel to the wall 1005. This is to be understood when viewing fig. 5, which fig. 5 schematically illustrates how a scanner (e.g. two-dimensional scanner 2) can be used to focus a laser beam onto a journal 1002 of a crankshaft and to rapidly displace the original laser spot 11 to follow a scanning pattern (shown schematically as a set of parallel lines in fig. 5) in order to create a larger virtual or effective laser spot 12. As long as the effective spot 12 is confined to the surface of the journal between the fillets 1004 and as long as the effective spot 12 is confined to a fairly restricted portion of the journal in the circumferential direction of the journal, the beam 1 will be substantially perpendicular to the journal surface throughout the effective spot 12. However, this will not be the case if the effective spot extends to cover the fillet and a portion of the wall 1005 above the fillet. Here, the incident angles will be different; in fact, as can be seen in fig. 5, the laser beam is substantially parallel to the wall 1005.

Based on the teachings of DE-102010048645-A1, one possible solution to this problem would be to position the scanner near the journal 1002 between the walls 1005. Thus, the laser beam projected onto the wall will no longer be substantially parallel to the wall. However, this approach would have other drawbacks.

One of these drawbacks is that the angle of incidence between the laser beam and the surface of the journal will vary significantly as the beam sweeps along the journal parallel to the longitudinal axis of the journal. Another and possibly larger drawback lies in the fact that the scanner will need to perform a larger angular sweep of the laser beam. When the scanner is relatively far from the surface of the journal, sweeping the beam from one end of the journal to the opposite end may require only a small change in the position of the corresponding scanning mirror or mirrors, etc., such as a few degrees or less. If the scanner is placed closer to the surface, the angular motion of the mirror must be increased for a given scan pattern.

Also, for a given speed of the primary spot along the scan pattern or along a segment of the scan pattern, if the scanner is arranged closer to the surface, the speed of movement of the component (such as one or more mirrors of the scanner) must be increased accordingly. This can be problematic, especially if a high speed of the primary spot is desired (which is often the case), since a high repetition rate of the scan pattern is often desired to minimize temperature fluctuations between successive sweeps of the primary spot along the scan pattern, as explained in WO-2014/037281-a 2.

A first aspect of the invention relates to a method for heat treatment of an object, e.g. for the purpose of hardening, softening, etc. In some embodiments of the invention, the object is a ferrous material, such as steel, such as medium carbon steel. In some embodiments of the invention, the object is a crankshaft or a camshaft. In some embodiments of the invention, the object is a metal sheet object.

The method includes the steps of heating at least one selected portion of the object:

projecting an energy beam, such as a laser beam, onto the surface of the object, so as to produce a primary spot on the surface of the object,

operating the scanner to repeatedly scan the beam to displace the primary spot according to the first scanning pattern to create an effective spot on the surface of the object, the effective spot having a two-dimensional energy distribution, an

The effective spot is displaced relative to the surface of the object, for example by moving the surface of the object relative to the scanner or moving the scanner relative to the surface of the object, or both, to progressively heat the at least one selected portion of the object. That is, the effective spot may be displaced until the entire selected portion of the object has been heated.

According to the invention, the beam follows an optical path between the scanner and the primary spot, and a beam deflection device is arranged in the optical path for redirecting the beam onto the surface of the object.

Thus, and although the scanner itself is arranged at a distance or significant distance from the surface onto which the beam is projected (e.g. to allow relatively fast movement of the primary spot along the first scan pattern, while the movement of one or more mirrors of the scanner or other beam deflecting means of the scanner is relatively slow, and/or to allow a relatively large extension of the first scan pattern in at least one direction, without requiring a very large amplitude of angular movement of the respective mirror or mirrors of the scanner or other deflecting means), the beam deflecting means may be arranged closer to the surface of the object, such as relatively closer to the surface, for example in the case of a crankshaft, even between counterweights. For example, in some embodiments of the invention, the scanner may be arranged at a distance of 1000mm or more from the surface 100 onto which the original spot is projected, while the beam deflection means may be arranged at a distance of 10 to 100mm from the surface. In many embodiments of the invention, the beam deflection means are generally rather small and simple in construction, and their function is primarily to redirect the beam towards different sub-portions of the selected portion to be heated. For example, when the object is a crankshaft, at one time the beam deflector may redirect the beam towards a journal of the crankshaft, and at another time, towards a fillet and/or wall at one end of the journal, and at another time, towards a fillet and/or wall at another end of the journal. These different times may correspond to different portions of the scanning pattern followed by the beam from the scanner, that is, different portions of the beam scanning pattern. Thus, during one sweep of the beam along its scan pattern, the beam may be successively redirected to the journal, to the fillet and/or wall at one end of the journal, and to the fillet and/or wall at the other end of the journal.

Thus, a scanner arranged at a distance or a significant distance from the journal of the crankshaft can be combined with a suitable angle between the laser beam and the curved journal, its fillet and the adjacent wall portion. For example, in embodiments when the object is a crankshaft of a car or truck, the scanner may typically be arranged at a distance of 100mm to 1000mm or more from the journal to be heated, while the beam deflector may be arranged closer to the journal, e.g. at a distance of 10mm to 100mm from the surface of the journal. It is generally desirable that the distance between the active surface of the beam deflecting means and the journal is not significantly larger than the width of the journal, such as not more than 1, 1.5 or 2 times the width of the journal, in order to allow suitable angles of incidence between the beam and different sub-portions of the surface to be heated.

That is, due to the use of the beam deflection means, the first scanning pattern may extend over different parts of the object, such as over journals and fillets and additionally walls close to the fillets, while the angle between the beam and the corresponding surface will always be much larger than 0, e.g. always larger than 30, 45, 60 degrees or more. Thus, the drawbacks described above with respect to fig. 5 are overcome. The beam deflection means may thus be used to redirect the beam during scanning of the beam.

In some embodiments of the invention, the object is a camshaft or crankshaft, and the selected portion to be heat treated may include a journal, and a fillet at an end of the journal, and/or a portion of a wall proximate to the fillet.

Although reference has been made to heat treatment, such as laser hardening, of objects, such as crankshafts and camshafts, these are merely examples. The method may be applicable to different kinds of heat treatments, which are performed with an energy beam and a scanner, and to different kinds of objects. The method may be particularly advantageous in the case of heat treatment of objects having complex shapes, for example when a scanner is to be used for heat treatment of surface portions having different orientations in space.

In many embodiments of the present invention, the energy beam is a beam of electromagnetic radiation, such as a laser beam. The effective spot may be generated and adjusted using any of the techniques described, for example, in WO-2014/037281-a2, which is incorporated herein by reference.

According to the described invention, at a given moment, the effective spot resulting from the scanning of the primary spot heats a portion of said selected portion and is displaced on the surface of the object until the selected portion has been heated as required. The displacement of the effective spot relative to the surface may be performed according to a second scanning pattern. That is, the real/raw spot, i.e. the spot produced by the beam at any given moment, is scanned according to a first scanning pattern to produce an effective spot, and the effective spot can be displaced according to a second scanning pattern. Thus, two types of movements are combined or superimposed: the movement of the primary spot according to the first scan pattern and the movement of the effective spot according to the second scan pattern may be a simple straight line in some embodiments of the invention. For example, when the object to be heat-treated is a crankshaft, the effective spot may be displaced with respect to the surface of the journal including the fillet and the wall portion near the fillet by rotation of the crankshaft, so that the effective spot is displaced in the circumferential direction of the journal.

The term "two-dimensional energy distribution" refers to the way in which the energy applied by the energy beam is distributed over the effective spot, e.g. during one sweep of the primary spot along the first scanning pattern. The term "two-dimensional energy distribution" refers to how the energy is distributed along and across the surface of the object when the effective spot is projected onto a non-planar portion or area (e.g., a curved portion or area, such as a portion or area having curved features), i.e., to the energy distribution along and across the effective spot when projected onto the surface of the object.

The first scan pattern is typically determined at least by the beam scan pattern according to which the scanner scans the beam and the beam deflection means which redirects the beam. Thus, both the scanner and the beam deflection device determine in combination the first scanning pattern, i.e. the scanning pattern which the original spot follows on the surface of the object.

The invention allows for relatively rapid heating of a relatively large area of the surface of the object, since the effective spot can have a relatively large size, such as, for example, 4, 10, 15, 20 or 25 times as large as the size (area) of the original spot. Thus, heating certain areas of the object to a desired extent in terms of temperature and duration can be achieved more quickly than performing the heating by simply displacing the primary spot over the entire area, for example following a sinusoidal or meandering pattern or following a straight line. The use of an effective spot having a larger area allows for high productivity while still allowing for a relatively large amount of time to heat one or more relevant portions of the surface, for example allowing for less aggressive heating without compromising productivity.

The area of the primary spot can be much smaller than the area of the effective spot. For example, in some embodiments of the invention, the primary spot size is less than 4mm, at least during a portion of the process²E.g. less than 3mm². The size of the raw spot can be altered during the process to optimize the way each particular portion of the object is heat treated for quality and productivity.

On the other hand, the use of an effective spot produced by repeatedly scanning the raw spot in two dimensions according to a first scanning pattern enables the creation of an effective spot having a selected two-dimensional energy distribution that is substantially independent of the particular optics (lenses, mirrors, etc.) used, and that can be tailored and adjusted to vary the viewing angle (including the speed at which thermal processing is performed (e.g., in terms of cm per minute)²Or an hourly termination unit) and quality) allows for enhanced and optimized heating of the object. For example, heat may be distributed such that the energy density of the leading portion of the effective spot is highAt the tail portion, thereby increasing the speed at which the desired temperature of the surface is reached, and the tail portion may be used to maintain the heating for a sufficient time to reach the desired depth and/or quality, thereby optimizing the speed of displacement of the effective spot relative to the surface of the object without compromising the quality of the thermal process. Furthermore, the two-dimensional energy distribution may be adjusted, for example, according to the properties of the object, so as to apply less heat in the area close to the edge of the object or the opening of the object (e.g., an oil lubrication hole in a crankshaft), where cooling due to heat transfer is slower. Moreover, the effective spot may be adjusted according to the three-dimensional shape of the object, e.g., to adapt the heating to the curvature, width, etc. in the heated region of the object, and to adapt the heating to the configuration of the heated portion of the object. The shape and/or two-dimensional energy distribution of the effective spot can be adjusted as desired, thereby adapting the process to the particular portion of the object to be heated at any given time. In some embodiments of the invention, the two-dimensional energy distribution may be varied according to the respective radiation location on the object, for example, taking into account the heat removal capacity of the surrounding area. In some embodiments of the invention, the two-dimensional energy distribution may vary taking into account desired properties of the product in different areas of the product, such as different requirements for hardness, rigidity, softness, toughness, and so forth.

In addition, the use of an effective spot generated by scanning of the original spot increases the flexibility in terms of e.g. the adaptability of the system to different objects to be produced. For example, the need to replace or adjust the optics involved may be reduced or avoided. The adjustment may be made more frequently, at least in part, by making adjustments only to software that controls the scanning of the primary spot and thus the two-dimensional energy distribution of the effective spot.

The expression "first scanning pattern" does not mean that the primary spot must always follow the same scanning pattern when generating the effective spot, but is merely intended to distinguish the scanning pattern of the primary spot for generating the effective spot from the scanning pattern or trajectory along which the effective spot is displaced or scanned relative to the object to be subjected to the thermal treatment; the scan pattern followed by the effective spot is sometimes referred to as the second scan pattern.

In many embodiments of the invention, the velocity or time-averaged velocity or average velocity at which the primary spot is displaced according to the first scanning pattern is significantly higher than the velocity at which the effective spot is displaced relative to the surface of the object. The high speed of the primary spot along the first scan pattern reduces temperature fluctuations within the effective spot during each sweep of the primary spot along the first scan pattern.

In most prior art systems that utilize energy beam thermal processing, the area heated at each instant in time corresponds generally to the original spot projected by the beam onto the surface. That is, in most prior art arrangements, the size of the area heated at each instant corresponds substantially to the size of the original spot, and the width of the track heated corresponds substantially to the width of the original spot in a direction perpendicular to the direction of displacement of the original spot, which in turn is determined by the source of the beam (e.g. the laser) and the beam shaping mechanism (e.g. the optics used).

Of course, the invention does not exclude the possibility of performing parts of the thermal treatment that operate in a conventional manner with the original spot. For example, the primary spot may be displaced to perform heating corresponding to the outline or contour of the area to be heated, or to heat certain details of the object to be heated, while the above-mentioned effective spot may be used to perform heating of other parts or areas of the surface, such as a major part of the area to be heated. The skilled person will select the range over which heating will be performed using the effective spot rather than the primary spot, depending on such things as productivity and the need to carefully tailor the profile of the area to be heated or some part of the object being subjected to heat treatment. For example, the original spot may be used to outline the area to be heated, while the active spot is used to heat the surface within the outlined area. In some embodiments of the invention, during the process, the first scan pattern may be modified to reduce the size of the effective spot until it finally corresponds to the original spot, and vice versa.

That is, it is not necessary to use an effective spot to perform all the heating that has to occur during the thermal treatment of the object. However, at least a portion of the thermal processing is performed using the effective spot described above. For example, it may be preferred to apply the beam to establish the effective spot as described above during at least 50%, 70%, 80% or 90% of the time during which the beam is applied to the object, i.e. by repeatedly scanning the primary spot according to the first scanning pattern.

In some embodiments of the invention, the two-dimensional energy distribution of the effective spot is dynamically adjusted during the displacement of the effective spot relative to the object surface. Thereby, for example in the case of a crankshaft, an adaptation of the effective spot to the range or area of the object currently being heated can be achieved in order to prevent overheating of the area close to the oil lubrication hole. The expression "dynamically adjusting" is used to indicate that the adjustment can be performed dynamically during the displacement of the effective spot. Different mechanisms may be used to achieve this dynamic adjustment, some of which are mentioned below. For example, in some embodiments of the present invention, the scanner may be operated to effect dynamic adjustment (e.g., by adjusting the operation of a galvo or other scanning mechanism so as to alter the first scanning pattern, and/or to alter the velocity of the primary spot along the scanning pattern or along one or more segments or portions thereof), and/or the beam power and/or size of the primary spot may be adjusted. The dynamic adjustment may be controlled using open loop control or closed loop control. The dynamic adjustment may affect the energy distribution pattern in a given area of the effective spot and/or the actual shape of the effective spot and, therefore, the shape of the area heated at a given moment (not taking into account the fact that the original spot moves and only the effective spot). For example, the length and/or width of the effective spot may be dynamically adjusted during the process.

In some embodiments of the present invention, the adjustment of the two-dimensional energy distribution of the effective spot is performed by adjusting the power of the beam (e.g., selectively turning the beam on and off). This includes interrupting the beam at the beam source and other approaches, such as by disrupting the path of the beam, for example, with a shutter, and combinations thereof. For example, when a laser such as a fiber laser is used, the laser beam can be turned on and off very quickly, thus enabling a desired energy distribution to be obtained by turning the laser beam on and off while following a scanning pattern. Thus, heating may be achieved by activating the laser beam during scanning of certain lines or portions of lines of the pattern. For example, a pixilated approach may be employed, according to which a two-dimensional energy distribution is determined by the on/off state of the laser during different portions or segments of the first scan pattern.

In some embodiments of the invention, the adjustment of the two-dimensional energy distribution of the effective spot is performed by adjusting the first scan pattern.

In some embodiments of the invention, the adjustment of the two-dimensional energy distribution of the effective spot is performed by adjusting a rate of movement of the primary spot along at least a portion of the first scan pattern.

That is, the two-dimensional energy distribution can be adjusted, for example, by adjusting the power of the beam (e.g., by switching between different power states, such as switching between on and off), and/or by adjusting the scan pattern (e.g., adding or omitting segments, or altering the orientation of segments, or changing the pattern entirely with another pattern), and/or by adjusting the rate of movement of the beam along the scan pattern, such as along one or more segments of the scan pattern. Selection between different mechanisms for adjusting the two-dimensional energy distribution may be made based on circumstances such as the ability of the equipment to change rapidly between power states of the beam, the ability of the scanner to alter the pattern to follow, and/or the speed at which the primary spot moves along the scanned pattern.

In some embodiments of the invention, the focal point of the beam is dynamically adjusted during the displacement of the primary spot along the first scanning pattern, and/or during the displacement of the effective spot relative to the object being produced. For example, when using a laser beam, the laser focus along the optical axis may be dynamically altered during the process, for example to change or maintain the size of the primary laser spot while the primary laser spot is displaced along the first scanning pattern, and/or while the effective laser spot is displaced relative to the object surface. For example, the optical focus may be adjusted to keep the size of the primary spot constant while the primary spot is moved over the surface of the object (e.g., to compensate for variations in the distance between the laser source or scanner and the location of the primary laser spot on the surface of the object).

In some embodiments of the invention, the size of the primary spot is dynamically adjusted during displacement of the primary spot along the first scanning pattern, and/or during displacement of the effective spot relative to the surface of the object, so as to alter the two-dimensional energy distribution and/or size of the effective spot.

In some embodiments of the invention, during at least one stage in the method, the effective spot may comprise a leading portion having an energy density higher than a trailing portion of the effective spot (this arrangement may be preferred when it is desired to rapidly reach a certain temperature and then provide sufficient energy input to, for example, maintain the material at the required temperature for a certain amount of time), or the effective spot may comprise a leading portion having an energy density lower than a trailing portion of the effective spot (this arrangement may be preferred when the material is first preheated for a certain time before it is desired to bring the material to a certain temperature). In some embodiments of the invention, the effective spot comprises a middle portion, and the middle portion has a higher energy density than the leading and trailing portions of the effective spot. In some embodiments of the present invention, the effective spot is characterized by a substantially uniform energy distribution with a substantially constant energy density throughout the effective spot.

As indicated above, the two-dimensional energy distribution may be dynamically adjusted while performing the method, e.g. such that it is different with respect to different parts of the object surface.

In some embodiments of the invention, the time-averaged velocity or average velocity of the primary spot along the first scan pattern is substantially higher than the time-averaged velocity or average velocity of the displacement of the effective spot relative to the object surface. For example, the average velocity of the primary spot along the first scan pattern may preferably be at least ten times, more preferably at least 100 times, higher than the average velocity of the displacement of the effective spot relative to the object. The high speed of the primary spot reduces temperature fluctuations within the effective spot during one sweep of the primary spot along the first scan pattern.

In some embodiments of the invention, the beam is scanned according to said first scanning pattern such that said first scanning pattern is repeated by the beam at a frequency of more than 10, 25, 50, 75, 100, 150, 200 or 300Hz (i.e. the repetition rate per second of the scanning pattern). A high repetition rate may be appropriate to reduce or prevent undesirable temperature fluctuations in the area heated by the effective spot between each scan cycle (i.e., between each sweep of the beam along the first scan pattern). In some embodiments of the invention, the first scan pattern remains constant, and in other embodiments of the invention, the first scan pattern is altered between some or all sweeps of the beam along the first scan pattern.

In some embodiments of the invention, the size (i.e. area) of the effective spot, such as the average size of the effective spot during the process, or such as the size of the effective spot at least one instant in the process, such as the maximum size of the effective spot during the process, is 4, 10, 15, 20 or 25 times larger than the size of the original spot. For example, in some embodiments of the invention, there is about 3mm²Can be used to produce a primary spot having a size greater than 10mm²An effective spot of a size of, for example, more than 50mm²Or 100mm²Or a larger size effective spot. The effective spot size may be dynamically altered during the process, but a large average size may generally be preferred to improve productivity, and a large maximum size may be useful to improve productivity during at least a portion of the process.

The method may be performed under the control of an electronic control mechanism, such as a computer.

As indicated above, the first scan pattern is determined, at least in part, by the manner in which the scanner scans the beam (i.e., the beam scan pattern). The first scanning pattern is also influenced by the beam deflection means. In some embodiments of the invention, the first scanning pattern and/or the beam scanning pattern is a polygonal scanning pattern comprising a plurality of lines. For example, the (first and/or beam) scanning pattern may be a polygon, such as a triangle, square or rectangle, pentagon, hexagon, heptagon, octagon, and the like. The polygon need not be a regular polygon, for example, in some embodiments the lines that make up the polygon may be more or less curved, and the edges of the polygon where the lines meet may be rounded, and so on.

In some embodiments of the present invention, the first scanning pattern and/or the beam scanning pattern comprises a plurality of lines, such as a plurality of straight or curved lines, which in some embodiments of the present invention are arranged substantially parallel to each other. In some embodiments of the invention, there are two, three, four or more of these lines.

In some embodiments of the invention, the first scanning pattern and/or the beam scanning pattern comprises at least three segments and said scanning of the energy beam is performed such that said beam and/or primary spot follows at least one of said segments more frequently than at least another of said segments. This arrangement is advantageous because it improves the manner and flexibility in which the scan pattern can be used to provide a sufficient and (where desired) symmetrical or substantially symmetrical energy distribution. For example, one of the segments may serve as a path or bridge to be followed by the beam as it moves between two other segments, such that transfer of the spot projected by the beam between different parts of the scanning pattern (such as the tip and the start) may be performed using a segment of the scanning pattern (such as an intermediate segment) for the transfer, whereby the transfer may generally be performed without turning off the beam and without distorting the symmetry of the two-dimensional energy distribution (when such symmetry is desired).

In some embodiments of the invention, the scanning pattern comprises at least three substantially parallel straight or curved lines distributed one after the other in a first direction, said lines extending generally in a second direction, wherein said at least three lines comprise a first line, at least one intermediate line and a last line arranged one after the other in said first direction, wherein the scanning of the beam is performed such that the beam and/or the original spot follows said intermediate line more frequently than said beam follows said first line and/or said last line. That is, for example, a bundle may follow twice as much as the intermediate line on average as it follows the first and last lines, e.g., each time a bundle moves from a first line toward a last line and from a last line toward a first line, the bundle will travel along the intermediate line. That is, one or more intermediate lines may act as a kind of bridge followed by the beam and/or projected spot as it moves between the first and last lines.

This arrangement has been found to be feasible and easy to implement, and it has been found that a sufficient energy distribution can generally be achieved by adjusting the scanning speed without substantially adjusting the power of the beam. It is also possible to alter the power of the beam during scanning in order to tailor the energy distribution, but a fast switching of the power is not always possible or desirable, and having the beam (such as a laser beam) at a low power level or switched off during a substantial part of the scanning cycle may imply a sub-optimal use of the capacity of the equipment, which is a serious drawback when the equipment (such as a laser equipment) is used for the thermal treatment of an object. Thus, it is often desirable to use beam operation entirely in the on state to fully utilize the available power.

It is generally desirable to use three or more lines arranged in this way, i.e. three or more lines arranged one after the other in a direction different from (e.g. perpendicular to) the direction in which the lines extend, in order to achieve a considerable extension of the effective spot not only in the direction along the lines, but also in other directions, in order to make the effective spot sufficient for heating a sufficiently wide area to a sufficiently high temperature and to maintain the temperature at one or more desired levels for a sufficient period of time, while allowing the effective spot to travel at a relatively high speed, allowing for a high production rate. Thus, a considerable extension of the effective spot in two dimensions is generally advantageous.

In some embodiments of the invention, the first scanning pattern or beam scanning pattern comprises at least three substantially parallel lines or segments arranged one after the other in a first direction (e.g. the direction in which the effective spot travels during the process), the lines extending in a second direction (e.g. a direction perpendicular to the first direction). In some embodiments of the invention, the at least three lines comprise a first line, at least one intermediate line and a last line arranged successively in the first direction, and the scanning of the beam is performed such that the beam and/or the projected spot is scanned along said lines according to a sequence according to which the beam and/or spot follows said intermediate line, said last line, said intermediate line and said first line in sequence after proceeding along said first line.

The above definition does not imply that the scanning must start with the first line but only shows the sequence of the above lines where the beam and/or spot tracks or follows the scanning pattern. Moreover, it is not excluded that the beam and/or the spot may follow other lines (such as lines interconnecting the first line, the last line and intermediate lines) and/or further intermediate lines between following some or all of the lines mentioned above (such as before or after).

That is, in these embodiments, after moving along the first line, the beam and/or spot always follows the intermediate line twice before moving along the first line again. Although a more direct forward approach may have been used to perform the scan such that after said last line the beam and its projected spot return directly to said first line, it has been found that the sequence followed according to these embodiments of the invention is suitable for achieving a symmetrical energy distribution about an axis of symmetry extending in said first direction.

In some embodiments of the invention, the scan pattern comprises a plurality of said intermediate lines. The number of lines may be selected by an operator or process designer or equipment designer depending on, for example, the size of the primary spot projected by the beam and the desired extension of the effective spot, for example in the first direction. For example, in some embodiments, the minimum number of lines may be three lines, but in many practical implementations a greater number of lines may be used, such as four, five, six, ten or more, when counting the first, last and middle lines. In some embodiments of the invention, the number of lines is altered to alter the energy distribution while the effective spot of light travels along the portion of the surface to be heated.

In some embodiments of the invention, the beam and/or the primary spot is displaced at a higher speed along said at least one intermediate line than along said first and said last line. This is generally preferred in order to achieve a sufficient energy distribution in said first direction, at least during a part or a substantial part of the process. When moving along the intermediate lines, or at least when moving along one or some of the intermediate lines, the higher speed of the beam compensates for the fact that: the beam moves twice along the middle line as the beam moves along the first and last lines. For example, in some embodiments of the invention, the speed at which the beam and/or the primary spot move along the intermediate line may be about twice the rate of the beam/spot along the first and/or last line. The speed may be different for different intermediate lines. The speed of each line may be selected according to the desired energy distribution in the first direction. Now, while the effective spot travels along the area to be heated, the speed at which the effective spot is displaced along different lines or segments of the scanning pattern can be dynamically altered, e.g. in a way that the energy distribution is adjusted to optimize the process, e.g. in order to improve the quality of e.g. hardened and/or tempered products.

In some embodiments of the invention, the scanning pattern further comprises lines extending in said first direction between the ends of the first, last and intermediate lines, whereby the beam and/or primary spot follows said lines extending in said first direction when moving between said first, said intermediate and said last lines. In some embodiments of the invention, the beam/spot is displaced at a higher speed along said line extending in the first direction than along said first and said last line, at least during a part of the process.

In some embodiments of the present invention, the beam is shifted along the scan pattern while not turning the beam on and off and/or while maintaining the power of the beam substantially constant. This enables scanning to be performed at high speed, regardless of the capacity of the equipment (such as laser equipment) to switch between different power levels (such as between on and off), and it enables the use of equipment that may not allow very fast switching between power levels. Furthermore, it allows an efficient use of the available output power, i.e. an efficient use of the capacity of the equipment in terms of power.

In some embodiments of the invention the first scanning pattern may be implemented according to the teachings of WO-2014/037281-a2, for example according to the teachings with respect to fig. 9-11 thereof.

In some embodiments of the invention, the optical path comprises a first portion extending between the scanner (e.g. the last scanning mirror or focusing lens of the scanner) and the beam deflection device and a second portion extending between the beam deflection device and the primary optical spot, the second portion being smaller than the first portion. That is, basically, the beam deflecting means is arranged closer to the original spot than to the scanner. As indicated above, it is generally desirable to have the scanner at a substantial distance from the surface onto which the primary spot is projected to allow for a broad first scan pattern and/or a high speed of the primary spot along the scan pattern without requiring wide and rapid angular movement of the beam deflecting components of the scanner (such as one or more mirrors of the scanner). Instead, it is generally desirable to have the beam deflector closer to the surface portion to be heat treated, e.g. in the case of a crankshaft, it may be preferred to have the beam deflector arranged such that during rotation of the crankshaft it will be arranged between the counterweights or walls close to the journals, such that the beam may be redirected from the beam deflector at an angle as close to 90 degrees as possible, preferably greater than 30 degrees and even more preferably greater than 45 degrees, and onto the walls, fillets and also onto the journals of the crankshaft. In the case of crankshafts for motor vehicles such as automobiles and trucks, the first portion may sometimes preferably be in the range of 200-1000mm or more, while the second portion is preferably in the range of 10-100mm, including the end points of the range. In some embodiments of the invention in which the object is a crankshaft, the active surface of the beam deflecting means (i.e. the surface reflecting the beam, for example) is preferably arranged at a distance from the surface of the journal to be heated which is not more than 1, 1.5 or 2 times the width of the journal (i.e. the length of the journal along its longitudinal axis).

In some embodiments of the invention, the beam deflection means is a mirror. A mirror is a suitable beam deflecting device, for example, for redirecting a light beam, such as a laser beam.

In some embodiments of the invention, the beam deflection means comprises a plurality of regions and the step of operating the scanner comprises directing the beam to at least two different ones of said plurality of regions, each of said plurality of regions corresponding to at least one portion of said first scan pattern. For example, the regions may comprise different regions of a curved mirror, or different flat or substantially flat regions or sections of the mirror oriented at different angles relative to the scanner. Thus, during scanning of the beam to cause the primary spot to follow the first scanning pattern, the beam may be deflected by the beam deflection means towards different parts of the object, e.g. during one part of the first scanning pattern the beam may be deflected towards a journal and/or a fillet of the crankshaft, and during other parts of the first scanning pattern the beam may be directed towards the fillet and/or a wall near the fillet.

In some embodiments of the invention, the mirror comprises at least three different substantially planar surface portions having different spatial orientations (i.e. oriented at different angles relative to the scanner) such that each of these surface portions may be arranged to redirect the beam towards a selected portion or region of the object. Thus, during scanning of the laser beam with the scanner, the beam may be successively deflected first by one of said portions, then by another of said portions, and then by a third of said portions, thus being redirected towards a different part of the object to be heat-treated. The use of a flat mirror portion may sometimes be preferred to reduce distortion of the shape of the original spot. In some embodiments of the invention in which the object is a crankshaft, the three different substantially planar surface portions comprise a first surface portion, a second surface portion, and a third surface portion, and the method comprises directing the beam toward a journal of the crankshaft using the first surface portion, directing the beam toward a fillet and/or wall at a first end of the journal using the second surface portion, and directing the beam toward a fillet 1004 and/or wall at a second end of the journal using the third surface portion. It has been found that in this way it becomes possible to heat the shaft journals as well as the walls and the fillets with beams directed at the respective surface portions at suitable angles, in particular beams which are far from parallel to these surface portions, thereby overcoming the problem explained in relation to fig. 5. For example, in case the beam deflection means are arranged close to the journal (e.g. at a distance from the journal similar to the width of the journal), the angle may be kept above 30 degrees, preferably above 45 degrees.

In some embodiments of the invention, the second surface portion and the third surface portion are arranged facing each other at an angle greater than 100 degrees and less than 170 degrees. Thus, each of these portions may be used to direct the beam towards the fillet furthest away from it, i.e. the left one of these surface portions may redirect the beam towards the right and the right one of these surface portions may redirect the beam towards the left, thereby facilitating the beam to reach the fillet and/or the wall at an angle as close to vertical as possible, preferably at an angle of more than 45 degrees.

In some embodiments of the invention, the mirror comprises at least one curved portion for deflecting the beam. Mirrors with curvature, such as mirrors with a cross-section comprising a circular segment shape, such as substantially U-shaped or parabolic mirrors, may have certain advantages, such as redirection of the beam may occur without abrupt jumps, such as jumps occurring when the beam is displaced from one of the flat portions towards the other of the flat portions of the above-described embodiments due to discontinuities at the boundary between the two flat portions arranged at an angle to each other. However, a disadvantage of the curved mirror is that it may distort the shape of the original spot. This may generally be undesirable.

In some embodiments of the invention, the object is a crankshaft 1000, and the beam deflection device is arranged such that: when performing the method, at least at some times, the beam deflection device is arranged between two walls or counterweights of the crankshaft. An advantage of the above combination of scanner and beam deflector is that in some embodiments the beam deflector may be arranged very close to the journal of the crankshaft to be heat treated. For example, the beam deflection means may have a relatively small size, and a very simple construction, such as in the form of a mirror having two or more reflecting surfaces arranged at an angle to each other, or a mirror having only one curved surface.

In some embodiments of the invention, the beam deflection device and the scanner are displaced synchronously with each other. For example, the beam deflector may be directly or indirectly attached or coupled to the scanner such that it moves with the scanner, or the beam deflector may be displaced by a separate drive mechanism, such as by a drive mechanism synchronized with those of the scanner. The beam deflector and the scanner may be operated as one unit and may be displaced as one unit relative to the object, e.g. before starting the heat treatment of a part of the object, e.g. positioning the scanner and the beam deflector in a suitable longitudinal position along the object, such as corresponding to a selected journal of the crankshaft; and/or during said heat treatment, for example, in order to maintain a distance from the surface of the connecting rod journal during rotation of the crankshaft about the axis of the main journal.

In some embodiments of the invention, the beam deflection device is stationary relative to the scanner. This means that the beam deflection means are not actively used for displacing the primary spot. Instead, the displacement of the primary spot is controlled by the scanner. The beam deflection means is only used for deflecting the beam received from the scanner. The beam deflection means may comprise a plurality of regions for redirecting the beam towards different parts or sub-parts of the object. Thus, for a given beam deflection arrangement, the first scan pattern is substantially determined by the manner in which the scanner scans the beam. In other embodiments of the invention, the beam deflection means may be movable, for example in synchronization with the scanning performed by the scanner, in order to facilitate the displacement of the primary spot along the first scanning pattern.

In some embodiments of the invention, the scanner is operable to scan the beam in two dimensions so as to provide an effective spot having a width in a first direction and a length in a second direction. Thereby, both the width and the length may be significantly larger than the maximum diameter of the primary spot. The advantages of this method have already been explained above.

In some embodiments of the invention, the effective spot is displaced relative to the surface by rotation of the object. For example, when the object is a crankshaft, the crankshaft may rotate along its longitudinal axis such that the effective spot moves along the journal in a circumferential direction of the journal, and optionally also along the fillet and adjacent portions of the wall. Thus, for example, in some embodiments, hardening of the journal (including the fillets and portions of the walls) may be achieved by sweeping the effective spot once around the journal in a circumferential direction.

In some embodiments of the invention, the two-dimensional energy distribution is dynamically adjusted during the displacement of the effective spot in order to avoid overheating of more heat-sensitive sub-areas, such as the area close to the oil lubrication hole of the crankshaft.

Another aspect of the invention relates to an apparatus for thermal processing of an object (e.g., a crankshaft). The apparatus comprises:

-a mechanism for supporting an object;

-means for generating an energy beam;

a scanner for directing an energy beam onto the surface of the object so as to generate a primary spot on said surface, the scanner being arranged to scan the beam repeatedly in two dimensions to displace the primary spot according to a first scanning pattern to create an effective spot on the surface of the object having a two-dimensional energy distribution,

a mechanism for displacing the effective spot relative to the surface of the object (e.g. by moving the surface of the object relative to the scanner, or moving the scanner relative to the surface of the object, or both; e.g. in the case of a crankshaft, the crankshaft may be rotated so as to expose different parts of the circumference of the journal to the scanner) to progressively heat at least one selected portion of the object (i.e. the effective spot may be displaced until the selected portion of the object has been heated),

and a beam deflection device arranged to receive the beam from the scanner and redirect the beam towards the object.

The advantages involved with this arrangement are clear from our description of the method above. The beam deflection means is advantageously arranged such that in the path of light from the scanner (e.g. from the last scanning mirror or focusing lens of the scanner) to a position on a surface on which the primary spot is projected (e.g. a journal of a crankshaft), the first portion corresponds to the portion from the scanner to the beam deflection means and the second portion corresponds to the portion from the beam deflection means to the surface of the object, i.e. the primary spot. The first portion is preferably longer than the second portion, such as twice as long, three times as long, or more. For example, in many practical applications involving crankshafts in general and crankshafts, in particular for automobiles or trucks, the first portion is equal to or greater than 200mm, such as 200mm to 1000mm or more, and the second portion is equal to or greater than 10mm, but not more than 100 mm.

Drawings

In order to complete the description and to provide a better understanding of the invention, a set of drawings is provided. The accompanying drawings form an integral part of the description and illustrate embodiments of the invention and are not to be construed as limiting the scope of the invention but merely as examples of how the invention may be carried out. The drawings include the following figures:

FIG. 1 is a schematic perspective view of a crankshaft as known in the art.

Fig. 2A-2C schematically show how the energy distribution of the effective laser spot is adjusted when hardening the area around the oil lubrication hole according to the prior art method known from WO-2014/037281-a 2.

FIG. 3 is a schematic illustration of a cross-section along the longitudinal axis of two journals of a crankshaft after laser hardening the surfaces of the journals between the fillets.

FIG. 4 is a schematic illustration of a cross-section along the longitudinal axis of two journals of a crankshaft after laser hardening the surface extending from a location above one fillet, along the journal to a location above the other fillet.

Fig. 5 is a schematic perspective view of a crankshaft onto which a laser beam is projected according to the teachings of WO-2014/037281-a2 to produce an effective laser spot by scanning a raw spot along a scanning pattern.

Fig. 6 is a schematic perspective view of a system or apparatus according to one possible embodiment of the invention.

Fig. 7 is a perspective view of a beam deflecting device according to a first embodiment of the present invention.

Fig. 8 is a side view showing how the beam deflection device of fig. 7 may be arranged to redirect the beam towards the workpiece.

Fig. 9A-9D schematically illustrate how the beam deflection means of fig. 7 deflects the beam onto different portions of the crankshaft during the sweep of the raw laser spot along the first scan pattern.

Fig. 10 is a perspective view of a beam deflection apparatus according to another embodiment of the present invention.

Fig. 11A and 11B are schematic perspective views of portions of an apparatus according to another embodiment of the invention.

Fig. 12A and 12B are schematic side views of part of an apparatus according to this embodiment of the invention during two non-phases of the scanning of the primary spot along the first scanning pattern.

Fig. 13A and 13B are schematic perspective views of a detail of the apparatus during the stage shown in fig. 12A and 12B, respectively.

Fig. 14 schematically illustrates an effective laser spot generated by a scanning pattern comprising a plurality of parallel lines.

Fig. 15A and 15B illustrate one possible beam scanning pattern comprising a plurality of parallel lines.

Fig. 16A and 16B illustrate beam scanning patterns for generating an effective laser spot according to an embodiment of the present invention.

Fig. 17A and 17B illustrate beam scanning patterns for generating an effective laser spot according to another embodiment of the present invention.

Fig. 18 schematically shows the relationship between the beam scanning pattern and the first scanning pattern according to one possible embodiment of the invention.

Detailed Description

Fig. 6 shows a device according to one possible embodiment of the invention. The apparatus comprises a frame structure housing a laser source (schematically shown at 100) which provides laser light via a light guide 24 to a scanner 2 mounted on a scanner carriage 101, the scanner carriage 101 being displaceable in a vertical direction parallel to the vertical Z-axis of the apparatus by a first scanner carriage drive mechanism 102, e.g. by a servo motor or any other suitable drive mechanism. Alternatively, the scanner 2 may also be driven horizontally, parallel to the horizontal X-axis of the device, along a horizontal rail 104, by a second scanner carriage drive mechanism 103, such as another servo motor or other suitable drive mechanism.

On the other hand, the apparatus comprises two workpiece carriages 200, each capable of accommodating two workpieces 1000 in parallel (in this embodiment, the workpieces are crankshafts), and comprising a drive mechanism (not shown) for rotating each workpiece along a central axis (in this embodiment, the central axis corresponds to a longitudinal axis passing through the center of the main journal of the crankshaft), said axis being parallel to the X-axis of the apparatus. On the other hand, each workpiece carriage 200 is associated with a workpiece carriage drive mechanism 201 (e.g., a servomotor or any other suitable drive mechanism), which workpiece carriage drive mechanism 201 is arranged for displacing the workpiece carriage horizontally, parallel to the Y-axis of the apparatus, perpendicular to the X-axis.

References to horizontal and vertical directions are only used to simplify the explanation and any other orientation of the axes is clearly possible and within the scope of the invention.

In the present case, the laser source 100 and the scanner 2 are first used to harden a relevant portion of the surface of one workpiece 1000 in a first one of the workpiece carriages 200, then they are used to harden a relevant portion of the surface of another workpiece 1000 in said first one of the workpiece carriages 200, and then the scanner is moved along the rail 104 to face a second one of the workpiece carriages 200 for hardening the surface of the workpiece 1000 arranged therein. When the scanner 2 is operating on a workpiece in a second one of the workpiece carriages, the workpiece in the first one of the workpiece carriages may be unloaded and replaced by a new workpiece to be processed by the scanner.

Obviously, many alternative possibilities exist. For example, there may be only one workpiece per workpiece carriage, or there may be more than two workpieces per workpiece carriage. There may be one scanner per workpiece carriage (i.e., a second scanner carriage with its corresponding scanner may be added to the track 104). Also, several arrangements as in the arrangement of fig. 6 or variations thereof may be arranged in parallel. Furthermore, each scanner carriage 101 may be provided with more than one scanner 2, so that several workpieces in the workpiece carriage may be subjected to the laser hardening process simultaneously. The relationship between the number of scanners, the number of workpiece carriages, and the number of workpieces may be selected to optimize the use of more expensive components in the system, as well as to optimize productivity, for example by allowing loading and unloading of workpieces without stopping operation of the system. In some embodiments of the invention, multiple scanners may be used to simultaneously direct laser beams to the same crankshaft, for example, to simultaneously act on different journals of the crankshaft or the same journal of the crankshaft.

In some embodiments of the present invention, during heat treatment of the connecting rod journal 1002, the central axis of the connecting rod journal 1002 is radially displaced from the central axis of the main journal, the scanner 2 moves vertically parallel to the Z axis and the workpiece carriage 200 moves horizontally parallel to the Y axis during rotation of the respective crankshaft workpiece 1000 in the workpiece carriage 200, in order to maintain a constant distance between the scanner and the surface onto which the laser beam is projected. In other embodiments of the invention, the crankshaft may be movable parallel to the Z-axis and the Y-axis. Additionally or alternatively, the scanner may be arranged to move parallel to the Z and Y axes.

The operation of the first laser carriage drive mechanism 102 and the second laser carriage drive mechanism 103, as well as the operation of the workpiece carriage drive mechanism 201 and the drive mechanism for rotating the workpiece 1000 in the workpiece carriage 200, may be controlled by an electronic control mechanism such as a computer, computer system, or PLC (not shown in fig. 6).

The scanner comprises elements for modifying the direction of the laser beam. Such scanners are well known in the art and typically include one or more scanning mirrors whose angle can be adjusted under computer control according to a scanning function (e.g., a sinusoidal function, a triangular function, etc.). A single axis scanner (e.g., a scanner having a scan mirror pivotable about an axis, or the like) may be used to scan the laser beam parallel to the X axis, i.e., perpendicular to the direction in which the surface of the workpiece 1000 moves relative to the scanner 2 as a result of rotation of the workpiece 1000. Thus, a fast scan across the relevant part of the surface may produce a virtual spot that extends in the X-direction much larger than the extension of the spot when not scanned: thus, the initial spot is transformed into a wider virtual or effective spot (with a larger extension in the X-direction), but with a smaller power density, since the power of the beam is distributed over a larger area.

In the case of a two-axis scanner (e.g., in the case of a scanner with a two-axis mirror or two single-axis mirrors), the laser beam may be moved in two directions, e.g., parallel to the X-axis on the one hand and parallel to the Y-axis on the other hand, and combinations thereof. Thus, in addition to scanning the surface perpendicular to the direction of movement of the surface relative to the scanner, i.e., in addition to scanning the surface "along" the journal surface in the direction of the X axis, the laser beam may also scan the surface in the direction of its movement, i.e., parallel to the Y axis; thereby, the surface of the journal of the crankshaft may also be scanned in the circumferential direction of the journal. Moreover, the laser beam may describe a path that combines motion in the X-direction and motion in the Y-direction (i.e., when projected onto a circular journal of a crankshaft in a circumferential direction). Thus, the beam may follow a path having a complex shape, such as a triangle, an ellipse, a trapezoid, etc. Thus, with the capabilities of the scanner, a virtual or equivalent effective laser spot can be generated having a desired extent and shape in the X-direction and in the Y or circumferential direction. In the case of a so-called XYZ scanner, in addition to the possibility of movement in the X-direction and the Y-direction, a focusing lens is provided which can be displaced in the Z-direction by some kind of drive mechanism, allowing dynamic adjustment of the size of the laser spot. Thus, both the position of the spot and the size of the spot can be controlled and adjusted to optimize the hardening process. Also, instead of or in addition to displacement of the focusing lens or the like, the size of the laser spot may be controlled and adjusted by moving the scanner parallel to the Z-axis with the first scanner carriage drive mechanism. Furthermore, the system may comprise a mechanism for changing the power distribution within the laser spot, as is known from, for example, the above-mentioned DE-3905551-a 1.

In fig. 6, the beam deflector 3 has been schematically shown attached to the scanner. In other embodiments of the invention, the beam deflection means 3 are provided separately from the scanner, for example with its own drive mechanism, in order to be positioned, for example, synchronously with the scanner.

Fig. 7 shows a beam deflection device 3 according to one possible embodiment of the invention in the form of a mirror with three different flat or substantially flat surface portions 31, 32, 33, which three different flat or substantially flat surface portions 31, 32, 33 are arranged in different spatial orientations, i.e. at different angles with respect to, for example, a scanner. The mirror also includes a connection 34 to the beam deflector to receive a cooling fluid.

Fig. 8 is a side view schematically illustrating how a mirror 3 like the mirror of fig. 7 may be arranged below a scanner (not shown) to reflect and thereby redirect the beam 1 towards the workpiece 1000.

Fig. 9A-9D show how three different surface portions are used to redirect the beam to different portions of the crankshaft in the area of the journal 1001 to be heat treated by the beam during one sweep of the primary spot along the first scan pattern, according to one embodiment of the invention. In fig. 9A, it is shown how a scanner (not shown) directs a laser beam to project an original spot of light onto the surface of the crankshaft via a beam deflection device. Here, the beam impinges on the upper right surface portion 33 of the mirror, as indicated by the arrow, which redirects and redirects the beam towards the left fillet 1004 of the journal to the wall 1005. In fig. 9B it can be seen how the beam impinges on the lower surface portion 31 of the mirror, whereby the beam is redirected onto the surface of the journal. In fig. 9C, the primary spot continues its movement along the first scanned pattern, still being reflected by the lower surface portion 31 of the mirror, and thus still being directed onto the surface of the journal. However, in fig. 9D, the beam is reflected by the upper left surface portion 32 of the mirror and is thereby redirected towards the right rounded corner 1004 and the wall 1005.

It can be readily appreciated from fig. 9A-9D how, by suitable operation of the scanner, the beam can impinge on the surface of the journal 1001, on the fillet 1004 and also on the adjacent portion of the wall 1005 at a larger angle (e.g. about 45 degrees or more) than the beam according to fig. 5 would impinge on the wall during one single sweep of the primary spot along the first scan pattern. Clearly the arrangement of figures 9A-9D means that there will be a jump in the first scan pattern (e.g. from the left part to the right part of the journal between figures 9A and 9B), but this is true for many other scan patterns, including many of those known from WO-2014/037281-a 2.

As in WO-2014/037281-a2, the first scanning pattern may be dynamically adjusted during circumferential displacement of the effective spot along the journal so that the two-dimensional energy distribution is different when an oil lubrication hole 1003 is present than when no such oil lubrication hole is present in the region heated by the effective spot.

Fig. 10 schematically shows another embodiment of the beam deflection means 3A, where the beam deflection means 3A has an elongated mirror surface 35, which elongated mirror surface 35 has a cross-section corresponding to a segment of a circle or the like. An advantage of such a continuous mirror surface, i.e. without the discontinuities that are present in the mirror 3 of fig. 7 between the three surface portions 31, 32 and 33, is that abrupt jumps or discontinuities in the direction of the beam can be avoided. However, the curved surface of the mirror 3A tends to distort the shape of the original spot, which may be disadvantageous in some situations.

It is clear that the beam-deflecting means can be configured in an infinite number of ways, for example combining planar surface portions and curved surface portions, and/or combining surface portions having different curvatures and/or variable curvatures. The skilled person will be able to select a suitable geometry of the beam deflecting means in view of, for example, the properties of the object to be processed.

Fig. 11A and 11B show an alternative embodiment of the invention, in which a beam deflector 3 similar to that of fig. 7 is used, but in which the wider surface portion 31 is arranged above the two narrower surface portions 32, 33. In fig. 11A, it is shown how the beam deflector 3 is attached to the scanner 2 by means of a simple L-shaped attachment. Any other suitable attachment means may be used, and in other embodiments of the invention the beam deflection means may be separate from the scanner, attached to other parts of the system, for example to a separate drive mechanism that displaces the beam deflection means in synchronism with the scanner 2. In fig. 11A and 11B, it can be seen how a schematically illustrated laser source 24 provides a laser beam 1, which laser beam 1, after passing through a collimator lens 25, passes through a scanner 2, where two scanning mirrors 21 and 22 (shown in fig. 11B) are used to scan the laser beam 1 in two dimensions. The laser beam is directed from the scanning mirror through the focusing lens 23 onto the beam deflection means 3, which beam deflection means 3 has three reflecting surface portions 31, 32 and 33. The beam deflection means reflects the beam 1 onto a surface portion of the crankshaft in order to heat said portion for hardening. In this case, the portion corresponds to the connecting rod journal 1002.

The laser beam is scanned according to a beam scanning pattern and reflected by the beam deflection means such that the projected primary spot follows a suitable first scanning pattern on the workpiece surface. In fig. 12A and 13A, it can be seen how, at one stage of the process, during scanning of the beam, the beam is directed onto the surface portion 31 of the beam deflection means from which it is reflected onto the surface of the journal, so that the primary spot 11 moves along and/or across the surface of the journal 1002. In fig. 12B and 13B, the bundle 1 has reached the surface portion 32 such that it is redirected towards the rounded corner 1004 and the sidewall portion 1005, thereby heating these portions. Thus, during one sweep of the beam along the beam scanning pattern, the raw spot 11 moves along the first scanning pattern, heating a portion of the journal 1002 and portions of the fillets 1004 and walls 1005 at both ends of the journal.

From this description and as is readily understood from e.g. fig. 11A-13B, with a suitably arranged beam deflection means 3, the beam will always reach the respective surface portion (journal, fillet, wall) at an angle of e.g. between 45 and 90 degrees. For example, it may be preferred that the mirror is arranged at a distance from the journal which is about the width of the journal, preferably not more than said width, or not more than 1.5 times said width, or not more than twice said width.

In fig. 12A, a first part X1 of the light path (between the last mirror 22 of the scanner or the focusing lens 23 of the scanner on the one hand and the surface of the beam deflection means on the other hand) and a second part X2 of the light path (between the surface of the beam deflection means 3 and the primary light spot projected onto the surface of the object to be treated) have been represented. Typically, the first portion X1 is significantly larger than the second portion X2, such as more than twice X2. For example, in the case of hardening a crankshaft for a vehicle (such as an automobile), X1 may typically be selected preferably in the range of 200mm to 1000mm or more, while X2 is typically selected in the range of 10mm to 100 mm.

It is also clear from the above that the first scanning pattern, i.e. the scanning pattern that the primary spot 11 follows on the surface of the object, can be significantly different from the scanning pattern that the beam follows before the beam deflection means.

As explained above, for a given primary spot size, a large extension of the effective spot in the direction of travel can be achieved by providing a scanning pattern comprising more than two lines arranged one after the other in the direction of travel, such as is schematically shown in fig. 14, wherein the effective laser spot 12 is generated by a plurality of parallel lines extending in a second direction perpendicular to the first direction of relative movement between the effective laser spot and the surface being treated (e.g. in the above-described embodiment the first direction may be the circumferential direction W of the surface of the journal of the crankshaft).

Such a scanning pattern may be realized by: the primary spot is repeatedly scanned in a second direction perpendicular to the first direction (the direction of travel of the effective spot), shifting the beam by a small distance in the first direction between each scanning step in order to track a plurality of parallel lines. Once the original spot has completed the scanning pattern, it will return to its original position and the scanning pattern is executed again. The frequency at which this occurs is preferably high in order to avoid undesirable temperature fluctuations within the effective spot 12.

Depending on the design of the beam deflection means, the beam scanning pattern followed by the beam before the beam deflection means may be more or less different from the first scanning pattern followed by the primary spot on the surface of the object, e.g. depending on the shape of the surface of the beam deflection means and whether there is a discontinuity in said surface.

The laser beam may be switched off when it is displaced towards a new line to be followed, and/or between the last line completing the scanning pattern and the first line returning to the scanning pattern. However, turning the laser beam on and off takes time and can slow the scanning frequency. Also, the time during which the laser beam is turned off is lost time in terms of efficient use of the laser for heating.

Fig. 15A and 15B show one possible beam scanning pattern, which comprises three main lines a-c of the scanning pattern (shown as continuous lines), the dashed lines showing the paths followed by the laser spot or beam between said lines. In fig. 15B, the arrows schematically show the way in which the actual laser spot/beam travels over the surface to be hardened while following the scanning pattern.

Now, the scanning pattern involves the problem that the thermal distribution will be asymmetric if the primary spot follows the scanning pattern. The same problem exists if at the end of the pattern, the laser beam returns vertically to line a when the last line c is completed (i.e., from the head of the arrow of line c in fig. 15B).

A more symmetrical energy distribution about the W axis can be obtained with a scanning pattern according to one of fig. 16A and 16B, which again comprises three parallel lines a-c interconnected by a line d, which the actual laser spot follows when moving between them. As shown in fig. 16B, the laser beam proceeds from the first line a as follows: a-d 1-b-d 2-c-d 3-b-d 4.

That is, the spot travels twice as far along the middle line b as the spot travels through the first and last lines: for each time the spot travels along the first line a and the last line c, the spot travels twice along the middle line b. Thereby, a completely symmetrical scanning pattern with respect to the W axis, i.e. for example with respect to the circumferential direction of the journals of the crankshaft, can be obtained.

The energy distribution along the W axis can be set by adjusting, for example, the distance between lines a-c and the speed at which the laser beam or spot travels along the lines. The energy distribution can be dynamically adjusted by adjusting the speed and/or scanning pattern without turning the laser beam on and off or without substantially adjusting the power of the laser beam. Thus, the tailoring of the energy distribution can be achieved by adjusting the distribution of lines (e.g., the first, last, and middle lines a-c), and by adjusting the velocity of the beam along the different segments a-d of the scan pattern (including d1-d 4). The distribution of the segments and the speed of the segments may be dynamically modified while the effective laser spot travels along the surface area to be hardened (such as around the journal of a crankshaft) in order to adjust the energy distribution to avoid overheating of the more heat sensitive sub-areas, such as the sub-areas near the oil lubrication hole, or the previously hardened areas where the effective laser spot approaches before its end of travel around the circumference of the surface area to be hardened (such as the surface of the journal of a crankshaft). Also, the scanning pattern may be adjusted by adding or deleting segments during the travel of the effective laser spot along the surface to be hardened.

The same principle can be applied to other scan patterns, such as the scan patterns of fig. 17A and 17B, which include additional intermediate lines B. Here, the actual laser spot s follows a path a-d 1-b-d 2-b-d 3-c-d 4-b-d 5-b-d 6.

As indicated above, the beam scanning pattern and the first scanning pattern may be different, since the first scanning pattern is not only determined by the beam scanning pattern but also by the beam deflection means. The first scanning pattern may be designed for optimizing the energy distribution, and is sometimes determined by the capacity of the equipment used, e.g. the capacity of the scanner. As explained above, it can sometimes be advantageous to operate with a scanning pattern that allows the beam to be maintained in a "start-up" state throughout operation, in order to efficiently utilize, for example, the capacity of the laser equipment used. The present invention presents a useful tool for a person skilled in the art to be able to design a suitable beam deflection device and/or beam scanning pattern taking into account a number of aspects, such as the desired result in terms of the first scanning pattern, the capacity of the scanner, the capacity of the laser equipment used, etc.

Fig. 18 schematically shows the relationship between the beam scanning pattern and the first scanning pattern in an embodiment using the beam deflecting means 3 shown in fig. 7. In the embodiment of FIG. 18, the beam is scanned in two dimensions to heat not only the surface of the journal 1002 as well as the surface corresponding to the fillet 1004 and the wall 1005 just above the fillet. This is achieved by the beam scanning pattern shown by segments A, B, C, D-E and F-G on beam deflection means 3. The first three segments are the three parallel lines A, B and C projected on surface portion 31 of mirror 3, while segments D-E are projected on surface portion 33 and segments F-G are projected on surface portion 32. The beam is reflected onto the crankshaft, whereby the primary spot follows a scanning pattern on the crankshaft comprising five lines, namely segments a ', B ' and C ' extending parallel to the longitudinal axis of the journal, also along the surface of the journal, and two segments D ' -E ' and F ' -G ' extending perpendicular to the first three segments and substantially following the circumferential direction of the journal and corresponding to the respective fillets 1004 and walls 1005.

This is merely an example and it would be obvious to one skilled in the art to use the teachings provided by the present disclosure and select a scan pattern and beam deflection means that best correspond to the specific purpose to be achieved. Also, in certain embodiments of the present invention, the skilled person may combine the use of beam deflecting means with direct radiation, for example. For example, the beam may be scanned such that a part of the first scanning pattern corresponds to the direct radiation of the surface, i.e. without deflecting the beam with the beam deflection means, and such that another part of the first scanning pattern corresponds to the deflected beam. For example, in a preferred embodiment of the invention, the journals of the crankshaft may be heated by directing the beam directly onto the journals, while the wall portions and/or the fillets near the fillets may be heated during another portion of the first scan pattern, wherein the beam is directed onto and redirected by the beam deflection means.

Although the invention has been described with reference to a specific product, i.e. a crankshaft, this is only an example and the invention is obviously not limited to this specific use. However, the invention may be particularly useful in the context of products having features of complex surfaces with portions oriented at significantly different angles relative to the position of the scanner.

In this document, the terms "comprise" and derivatives thereof (such as "comprises" and the like) are not to be taken in an exclusive sense, i.e. these terms are not to be interpreted as excluding the possibility that what is described and defined may include additional elements, steps or the like.

The invention is obviously not limited to the specific embodiments described herein, but also encompasses any variants that may be considered by a person skilled in the art (for example with respect to material selection, dimensions, components, configuration, etc.), within the general scope of the invention as defined by the claims.