阅读说明：本技术 高强度的转向小齿轮 (High-strength steering pinion ) 是由 A.胡克 于 2019-07-18 设计创作，主要内容包括：本发明涉及一种高强度的转向小齿轮,具体而言本发明涉及一种用于制造转向小齿轮(10)的方法和转向小齿轮(10)。设置成,转向小齿轮(10)由根据EN ISO 683-17的可贝氏体化的滚动轴承钢构成并且通过贝氏体化构造成高强度的转向小齿轮(10)。(The invention relates to steering pinions with high strength, in particular methods for producing steering pinions (10) and steering pinions (10). The steering pinion (10) is made of a bainitized rolling bearing steel according to EN ISO 683-17 and is formed by bainiting into a high-strength steering pinion (10).)

1. Method for producing a steering pinion (10), characterized in that a blank of the steering pinion (10) is produced from bainitic rolling bearing steel according to EN ISO 683-17, which is subsequently bainitic for increasing the hardness.

2. Method according to claim 1, characterized in that, for producing a bore hole (12) in the blank of the steering pinion (10), the bore hole (12) is first brought (step a)) into the blank as a previous profile (12V) before the bainitization and the steering pinion (10) is subsequently bainitized (step b)), and the surface of the bore hole (12) is finally post-processed (step c)) for changing the surface quality of the bore hole (12) for producing a final profile (12E).

3. Method according to claim 2, characterized in that (step a)) the previous profile (12V) of the bore hole (12) is mechanically drilled into the steering pinion (10) or brought into the steering pinion (10) by means of electrochemical machining before the bainitization (step b)).

4. Method according to claim 2, characterized in that the final profile (12E) of the drill hole (12) is post-treated (step c)) by means of electrochemical machining after bainitization (step b)) of the steering pinion (10) for changing the surface quality of the previous profile (12V) of the drill hole (12).

5. Method according to claim 3 or 4, characterized in that the previous profile (12V) and/or the final profile (12E) are brought in/post-processed (steps a) and c)) by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM).

6. Method according to claim 5, characterized in that the steering pinion (10) consists of a rolling bearing steel according to EN ISO 683-17, denoted 100Cr6, having a chemical composition of 0.93 to 1.05 carbon (C:), 0.15 to 0.35 silicon (Si:) and 0.25 to 0.45 manganese (Mn:) and 1.35 to 1.6 chromium (Cr:) and possibly other small amounts of chemicals in weight%.

7. Method according to claim 1 or 2, characterized in that the blank of the steering pinion (10) or the steering pinion (10) provided with the previous profile (12V) as a bore (12) is subjected to a sub-step of carrying out a bainitization (step b)' of the steering pinion (10)

Heating (step b 1)) to an austenitizing temperature;

cooling (step b 2)) in a salt bath to a temperature above the martensite-steel curve (3) between 250 ℃ and 500 ℃;

maintaining (step b 3)) the temperature between 250 ℃ and 500 ℃ above the martensite-steel curve (3) in the salt bath between a few minutes and a few hours on the beta hardness curve (2);

cool (step b 4)) to room temperature.

Steering pinion (10) of the kind , characterized in that the steering pinion (10) consists of bainitized rolling bearing steel according to EN ISO 683-17 and is bainitized.

9. Steering pinion (10) according to claim 8, characterized in that the steering pinion (10) has a bore (12) which is produced according to at least of the method steps according to claims 2 to 7, wherein the final contour (12E) of the bore (12) is post-treated by electrochemical machining of a previously bainitized roller bearing steel according to EN ISO 683-17, so that the side wall (12E-1) of the final contour (12E) of the bore (12) has a smooth and structural system surface which is typical for the electrochemical machining.

10. Steering pinion (10) according to claim 9, characterised in that at least the side wall (12E-1) of the final profile (12E) of the bore (12) has a depth (R) with an average roughness depth (R) by means of the electrochemical machining_z) Is less than or equal to</= 5 μm smooth surface.

11. Steering pinion (10) according to claim 9 or 10, characterized in that the previous profile (12V) and/or the final profile (12E) are/is constructed by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM).

Technical Field

The invention relates to a method for producing a steering pinion of a steering system, in which a rotary lever can be arranged in the assembled state, and to a steering pinion.

Background

Document DE 102004003541 a1 discloses steel for high-strength pinion shafts for use in the production of pinion shafts for use in steering systems of motor vehicles, and a corresponding production method. The steel of the present invention with the specific composition mentioned in the literature causes less occurrence of flaking during hobbing, has high surface hardness, notch impact toughness and torsional strength after high-frequency hardening, and is subjected to less heat treatment load during high-frequency hardening.

Document DE 102006059050 a1 describes a method for the heat treatment of a rolling bearing component made of a fully hardened, bainitic rolling bearing steel with an inherent compressive stress and a martensite fraction and a residual austenite fraction in the edge region, in which the heat treatment is carried out in two stages, in which the workpiece is first quenched (sometimes called quenched) starting from the austenitizing temperature in a salt bath having a temperature slightly below the martensite initial temperature and is held so long until a temperature equilibrium occurs, in which the workpiece is then transferred to a second bath whose temperature is slightly above the martensite initial temperature and is held above the martensite initial temperature.

The document DE 102006046765 a1 discloses a two-stage method in which a conventional mechanical, preferably cutting, Machining of the material to be machined, in particular of the material of the crankshaft, which is subsequently referred to as the workpiece, takes place in the method step, it is considered that the Machining quantity in the geometric form must be corrected by the value of the Machining quantity of the subsequent ElectroChemical Machining (that is to say its material removal), in the subsequent second method step a conventionally prepared chamber is machined by means of an ElectroChemical Machining method, for which purpose a known device is used for ElectroChemical Machining — a method of ElectroChemical Machining (ECM-ElectroChemical Machining method) or also a method of ElectroChemical Machining, so-called Pulsed ElectroChemical Machining (PECM-Pulsed ElectroChemical Machining), which is developed in addition, characterized in that, in the case of Machining, there is no direct contact between the tool (Werkzeug, sometimes referred to as a tool) and the Machining target (workpiece) in the Machining, for which the tool and the workpiece are moved relative to each other, and, there is a preferably a higher electrical current flow between the tool (ECM-ElectroChemical Machining) and the workpiece, as a cathodic Machining process, which is carried out by the ElectroChemical Machining process, as a cathodic Machining process, which is preferably carried out by a cathodic current, as a cathodic Machining process of ElectroChemical Machining of a higher than the ElectroChemical Machining voltage, which is carried out by a cathodic Machining of 0 mm.

Reference is additionally made to document DE 102010032326 a1, which likewise describes a method and a device for producing chambers (boreholes) by means of electrochemical machining (ECM) or pulsed electrochemical machining (PECM).

Disclosure of Invention

The present invention is based on the object of improving the properties of workpieces, in particular steering pinions, based on the prior art mentioned.

The invention relates to a method for producing a steering pinion.

It is provided that the blank of the steering pinion is produced from a bainitizable roller bearing steel according to EN ISO 683-17, which is subsequently bainitized (sometimes referred to as austempering) for increasing the hardness, as a result of which the steering pinion has advantageously higher ductility and impact toughness and wear resistance.

The steering pinion is advantageously dimensionally more stable by bainiting than conventional steering pinions and has a particularly tough structure. A hardness at about 58 HRC (hardness according to rockwell) was achieved. Since the bearing of the steering pinion is also bainitized, a longer life cycle of the steering pinion according to the invention can be achieved in an advantageous manner due to the higher fracture strength compared to a martensitic hardened steering pinion.

The inherent compressive stresses in the edge regions of the bainitized steering pinion are smaller, so that all regions of the steering pinion can be subjected to higher loads, the smaller strength states which occur locally in the case of conventionally produced steering pinions can be eliminated in an advantageous manner by bainiting .

Preferably, it is provided that, for producing the bore in the blank of the steering pinion, before the bainitization:

first bringing (step a)) the bore hole as a previous contour into a "soft" blank, and

just after bainiting the steering pinion (step b)), the latter is then

Final post-treatment (step c)) of the surface of the bore hole for changing the surface structure and surface quality of the bore hole for producing the final profile ("hard").

In a preferred embodiment of the invention, it is provided that the preceding contour of the drilled hole is drilled into the steering pinion mechanically or by means of electrochemical machining before the bainitization (step b)).

It is preferably provided that the final contour of the drilled hole is post-treated (step c)) by means of electrochemical machining after bainitization of the steering pinion (step b)) for changing the surface quality and surface structure of the preceding contour of the drilled hole.

In an alternative embodiment, it is provided that the previous and/or final contour is/are introduced/post-processed in steps a) and c) by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM).

The steering pinion according to the invention is produced from a rolling bearing steel according to EN ISO 683-17, denoted 100Cr6, in a blank having a chemical composition of 0.93 to 1.05 carbon (C:), 0.15 to 0.35 silicon (Si:) and 0.25 to 0.45 manganese (Mn:) and 1.35 to 1.6 chromium (Cr:) and, if appropriate, other small amounts of chemical substances in weight%. According to the invention, the steering pinion is regarded as a blank, which still does not have a bore hole. In other words, other structures shown in FIG. 1 may have been constructed.

By subjecting the blank of the steering pinion (without a bore hole) or the steering pinion provided with a bore hole as a previous profile to the following sub-step, bainitization, known per se, takes place in step b) and is carried out according to the invention at the steering pinion.

Heating (step b 1)) the steering pinion to the austenitizing temperature.

Cooling (step b 2)) the steering pinion in the salt bath to a temperature above the martensite-steel curve between 250 ℃ and 500 ℃.

The temperature above the martensite-steel curve 3 between 250 ℃ and 500 ℃ is maintained in the salt bath (step b 3)) between a few minutes and a few hours on the beta hardness curve 2.

Cooling the steering pinion (step b 4)) to room temperature.

After the method, a high-strength bainitized steering pinion is present.

The steering pinion has the above-mentioned characteristics independently of the borehole to be provided.

If the steering pinion comprises boreholes produced according to at least of the method steps according to claims 2 to 7, the final contour of the boreholes of the steering pinion is or can be post-processed by electrochemical machining of a previously bainitized roller bearing steel according to EN ISO 683-17.

The final contoured sidewall of the bore is thus configured at least by electrochemical machining such that the final contoured sidewall of the bore has a smooth and structural surface typical of electrochemical machining.

The surface of the side wall of the final contour of the bore hole is advantageously smoother and more structural than a machined surface and has an optically detectable surface structure typical for electrochemical machining.

The skilled person can distinguish the machined surface structure from the surface structure produced by electrochemical machining by inspection with an optical microscope.

In the case of electrochemical machining, a structural polishing action and a structural flattening of the surface of the bore hole of the steering pinion are typically caused in an advantageous manner, wherein it can be determined in particular that a structural difference without surface parameters is determined over the entire region in which the electrochemical machining is carried out, as is the case in contrast in the case of mechanical machining in the manner typical here.

In a preferred embodiment of the invention, the side walls of the final contour of the drilled hole can be provided with an average roughness depth (R) by electrochemical machining_z) Even less than/equal to 5 μm.

Thus, in addition to the realisability of a smooth surface (average roughness depth (R))_z) May be less than/equal to </═ 5 μm), it is particularly advantageous that the surfaces of the bores on all the steering pinions thus produced by electrochemical machining (ECM, PECM) have a very similar structure, wherein there are no marks formed in the case of machining in an advantageous and typical manner, it being possible to determine such marks in the case of each machining of some type , wherein, in particular in the case of machined bores, the examination by a microscope shows partly strong (undesired) differences in the surface structure.

It was determined that in the case of conventional mechanical hardening processes, the surface quality, for example the mean roughness depth (R)_z) There are almost identical measured values in terms, but optically distinct surface structures.

The different surface structures are formed in particular by tool wear, which advantageously does not occur in the case of electrochemical machining (ECM, PECM), thus avoiding optically different surface structures.

This optically determinable structural difference of the surface significantly affects the subsequent engagement process between the surface structure of the final contour of the bore hole and the surface structure of the rotary lever (so-called rotary lever engagement) in the case of machining, which is carried out in order to bring the steering pinion and the rotary lever into the assembled state, as explained in detail below.

The surface structure of the bore hole and the rotary lever is particularly relevant for the continuous retainability of the rotary lever in the bore hole of the steering pinion as an assembly unit in the assembled state, in particular in the context of the fact that the forces to be absorbed by the steering pinion via the rotary lever are always subject to higher requirements.

Preferably, it is provided that the previous contour and/or the final contour is/are constructed by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM).

Drawings

The invention is explained below with embodiments according to the dependent figures. Wherein:

FIG. 1 shows a steering pinion in perspective view;

FIG. 2 shows the steering pinion in side view prior to the production of the final contour of the bore hole, wherein the steering pinion is shown in section above a middle line extending in the axial direction;

figure 3 shows the steering pinion in a side view according to figure 2 during the production of the final contour of the bore hole of the steering pinion,

fig. 4 shows a temperature T-time T-diagram for the purpose of clearly illustrating the method according to the invention.

List of reference numerals

10 steering pinion

10.1 bearing area

10.2 second bearing region

10.3 overload protection zone

10.4 tooth region

10.5 body

12 drilling

12V previous Profile

Side wall of 12V-1 previous contour

12E Final Profile

12E-1 Final Profile sidewall

K cathode

A machining allowance

1 austenitic hardness curve

2 Bainite hardness curve (isothermal quenching)

3 martensite-steel-curve.

Detailed Description

Fig. 1 shows a steering pinion 10 in a perspective view.

The steering pinion 10 comprises an -th bearing region 10.1 extending in the axial direction and a second bearing region 10.2 extending in the axial direction, between which a toothed region 10.4, which likewise extends in the axial direction, is formed.

The steering pinion 10 is mounted as part of the steering system in a vehicle-body-side bearing carrier via bearings embodied in the bearing regions 10.1 and 10.2, an overload protection region 10.3 is coupled to the steering pinion 10 in the axial direction at the -th bearing region 10.1, the overload protection region 10.3 having an overload protection shape.

A rotary lever, not shown, is pressed into the bore 12 in the assembled state on the side of the overload protection region 10.3 of the steering pinion 10, so that a form-and friction-fit connection is produced between the rotary lever and the side wall 12E-1 of the bore 12. The rotary lever transmits the steering movement of the steering wheel, not shown, which is in operative connection with the rotary lever, to a steering pinion 10, which steering pinion 10 is in connection with a toothed region 10.4, for example, a rack.

It is clear that a fixed connection between the rotary lever and the bore 12 (thus pressing the rotary lever into the bore 12) is of particular interest after engagement of the rotary lever.

The drilling 12 is now carried out by first being mechanically (in the so-called soft state) carried into the steering pinion 10 with the previous contour 12V, then the steering pinion 10 is hardened as a whole, wherein induction hardening or case hardening (Einsatzhärten) is mostly used in order to harden the toothing, in particular of the toothing region 10.4, in the case of induction hardening the material structure of the previous contour 12V around the drilling 12 remains soft, while the material structure in the edge region of the steering pinion 10 is hardened.

The previous contour 12V is then mechanically reworked by a further mechanical step , so that the material is mechanically eroded with a predefinable machining allowance a.

The final profile 12E of the borehole 12 is finally constructed after this ablation of material.

The final machining is now carried out by means of a spindle or friction, wherein the machining takes into account whether the material structure surrounding the bore hole 12 is in a so-called soft state (according to induction hardening) or in a so-called hard state (according to case hardening).

It has been demonstrated that the surface properties do not fluctuate in this practice depending on the hardening method used, so that solutions are sought in order to avoid this fluctuation in surface properties.

According to the invention, it is provided that the previous contour 12V of the borehole 12 is mechanically produced in step a) in a further variant of embodiment .

In a second embodiment variant, provision is made for the previous contour 12V of the drilled hole 12 to be formed in step a) by electrochemical machining.

According to the invention, of these two variants are immediately followed by a step b) -bainiting of the steering pinion 10, so that in step c) for the final machining, that is to say for producing the final contour 12E of the bore hole 12, there is a soft previous contour 12V of the bore hole 12 and after bainiting there is a hard previous contour 12V of the bore hole 12.

In both embodiment variants, it is possible according to the invention to construct the final contour 12E in step c) by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM), as shown in fig. 2 and 3 in overview.

Fig. 2 shows a section through the upper half of a steering pinion 10 embodied in the form of a cylinder, so that it becomes apparent that both the toothed region 10.4 and the body 10.5 immediately following the steering pinion 10 are hardened in step b) by bainitization, wherein it is also apparent that the previous contour 12V of the bore 12 is formed in the -th bearing region 10.1 of the steering pinion 10.

The bore 12 is coupled to an opening of the overload shape of the steering pinion 10, wherein the opening is surrounded by the rim as an overload shape, which forms an overload protection region 10.3, seen in the axial direction.

Fig. 2 shows the set machining allowance a clearly indicating the material region that is to be ablated by electrochemical machining (ECM) or by pulsed electrochemical machining (PECM) so that the final contour 12E of the borehole 12 can be formed from the previous contour 12V.

The sidewall 12V-1 of the previous profile 12V is thus shown in FIG. 2.

The principle of method step c) for producing the final contour 12E of the borehole 12 is clearly illustrated in fig. 3.

For the electrochemical machining (ECM or PECM), the cathode K used as a tool in step c) and the workpiece (in particular the steering pinion 10) are moved relative to one another such that the geometry of the cathode K is shaped within the previous contour 12V of the bore hole 12.

For this purpose, a voltage is applied between the cathode K and the steering pinion 10, the steering pinion 10 acting as an anode. For the machining, a gap, which is present between the cathode and the steering pinion 10 and is preferably less than 1mm, is flushed with electrolyte as is described, for example, only in document DE 102006046765 a 1. The material erosion in the previous contour 12V of the bore hole 12 is thus achieved electrochemically, and the dissolved material is flushed out of the processing zone as metal hydroxide by the electrolyte.

In particular, the PECM method has a much smaller gap width between the cathode K and the steering pinion 10, preferably a gap width of 0.01 to 0.2mm, and therefore has an essentially higher processing accuracy (higher image fidelity of the cathode geometry) than the ECM method, so the PECM method represents a preferred embodiment variant. It is unique to the PECM method that the process current is not present continuously as in the case of the ECM method, but rather is delivered as a pulsed current. The method of electrochemical machining is furthermore distinguished by a fast process time and a high machining stability.

Furthermore, it has proven to be advantageous to mechanically oscillate the movement between the cathode K and the steering pinion 10 in step c) in the event of material degradation with a machining allowance a, since the electrolyte is exchanged here in a sufficient manner.

The advantage of the electrochemical machining (ECM or PECM) is, in particular, that the machining, in the case of a hard structural state caused by bainitization, results in a particularly smooth surface of the side wall 12E-1 of the final contour 12E, and the steering pinion 10 as a whole is configured as a high-strength steering pinion 10.

The bainitization thus produces various effects in step b). The steering pinion 10 as a whole is high-strength after bainitization. That is to say that not only is the material structure in the region of the bore hole 12 to be introduced high-strength, but the steering pinion 10 as a whole is hardened in an advantageous manner.

The bainitized surface of the final profile 12E of the bore 12 meets the desired and reproducible parameters in terms of surface quality after electrochemical machining (ECM or PECM).

This has the effect that the steering pinion is no longer subjected to times to heat or mechanical stress by electrochemical machining (ECM or PECM) after hardening, so that no inherent stresses are produced in the steering pinion 10.

The method steps for producing the final contour 12E of the bore hole 12 take place in a contactless manner with respect to the machining tool (cathode), wherein in particular at least one surface with a surface quality R can be achieved_z＜/＝5μm（R_z= average roughness depth or average value from measured roughness depths) of the sidewall 12E-1 of the final profile 12E. Machining-induced texture and burrs, which can be formed in the case of conventional practice, are advantageously avoided.

In addition, as an effect, not only R of the final contour 12E of the borehole 12 can be obtained_zVery high surface quality of 5 [ mu ] m relative to conventional methods, and as a further effect, achieved is, for example, R_zThe surface quality of 5 [ mu ] m is reproducible and essentially has no fluctuation width in the structural surface properties thereof, wherein the surface properties can be identified in particular optically microscopicallyThere is no structural difference in nature in which the essential advantages of the method according to the invention are formed.

Thus, when the electrochemical machining (ECM or PECM) is carried out in the case of a hard structural state of the material to be ablated by bainiting, R is achieved without problems, in particular in the lower region of the producible surface quality_zSurface quality of 5 μm.

Finally, it is also advantageous that the machining tool (cathode) is approximately wear-free. Furthermore, less process time is required. A cycle time of 4 to 5s results for method step c) with a depth of the borehole of, for example, 18mm and a feed rate of, for example, 4 mm/s.

It is clear that the bainitization is fundamentally independent of the introduction of the bore 12 and can be carried out in order to increase the hardness of the steering pinion 10 in all the regions 10.1, 10.2, 10.3 and 10.4 (in particular the toothed region 10.4) which are not mentioned and are mentioned above in detail.

The invention advantageously produces a synergistic effect, so that in the above-described manner, the material hardness of the steering pinion 10 as a whole and the surface quality of the bore 12, as well as the surface structure of the system of the final contour 12E of the bore 12, which is typical for electrochemical machining, can be reproducibly formed in the above-described manner.

According to the invention, an assembly unit can be produced in which the rotary rod is pressed into the finished electrochemically machined final contour 12E of the bore 12 of the bainitized steering pinion 10 by rotary rod engagement into the bore 12.

The assembly unit is part of a steering system according to the invention, which is distinguished by the fact that the rotary rod is pressed into the final contour 12E of the bore 12 by means of a joint connection, wherein the side wall 12E-1 of the final contour 12E of the bore 12 has a smooth and structural surface , which is typical for electrochemical machining.

Fig. 4 additionally shows a temperature T-time T-diagram for the clear illustration of the method according to the invention in step b).

Curve 1 clearly shows that cooling to a temperature below the martensite-steel curve 3 lying between 250 ℃ and 500 ℃ is achieved within a short time after heating the austenitic steel to the austenitizing temperature.

Curve 2 clearly shows that the steel, which is bainitized according to the invention in step b 1), is heated to the austenitizing temperature, which is then cooled in step b 2) in the salt bath to a temperature above the martensite-steel curve 3 of between 250 ℃ and 500 ℃. In this case, it is provided that in step b 3) a temperature above the martensite-steel curve 3 of between 250 ℃ and 500 ℃ is maintained in the salt bath on the so-called bainitic hardness curve 2 for a few minutes to a few hours, after which finally cooling to room temperature is carried out in step b 4).