阅读说明：本技术 中空轴构件、滚动装置 (Hollow shaft member and rolling device ) 是由 高桥彻 新部纯三 铃木秀忠 于 2020-03-10 设计创作，主要内容包括：该中空轴构件(10)具备：一对缩径部(11),其通过对形成为中空轴状的管状原料的两轴端部实施模锻加工而分别形成于该两轴端部；以及中间部(12),其配置于一对缩径部(11)之间,且具有比该一对缩径部(11)的外径大的外径。并且,中间部(12)与缩径部(11)的连接边界的形状形成为相对于轴向呈大致直角地降阶的直角降阶形状部(13),该直角降阶形状部(13)通过模锻加工而形成。通过这样的结构,能够提供实现了轻量化的滚动装置用的中空轴构件。(The hollow shaft member (10) is provided with: a pair of reduced diameter portions (11) formed on both axial end portions of a tubular raw material formed in a hollow shaft shape by performing die forging on the both axial end portions, respectively; and an intermediate portion (12) which is disposed between the pair of reduced diameter portions (11) and has an outer diameter larger than the outer diameter of the pair of reduced diameter portions (11). The shape of the connecting boundary between the intermediate portion (12) and the reduced diameter portion (11) is a right angle stepped-down shape portion (13) stepped down substantially at right angles to the axial direction, and the right angle stepped-down shape portion (13) is formed by die forging. With such a configuration, a hollow shaft member for a rolling device can be provided that is lightweight.)

1. A hollow shaft member, characterized in that,

the hollow shaft member includes:

a pair of reduced diameter portions formed on both axial end portions of a tubular raw material formed in a hollow shaft shape by performing die forging on the both axial end portions, respectively; and

an intermediate portion disposed between the pair of reduced diameter portions and having an outer diameter larger than the outer diameters of the pair of reduced diameter portions,

wherein the content of the first and second substances,

the shape of the boundary between the intermediate portion and the reduced diameter portion is a right angle stepped-down shape portion stepped down substantially at right angles to the axial direction, and the right angle stepped-down shape portion is formed by the swaging.

2. Hollow shaft member according to claim 1,

the pair of reduced diameter portions and the right angle stepped-down portion are formed by the swaging process performed after the annealing process is performed on both axial end portions of the tubular raw material formed in the hollow shaft shape.

3. Hollow shaft member according to claim 1 or 2,

when the metal structure of the cross section of the pair of reduced diameter portions and the right angle stepped-down shape portion is observed with a microscope, a metal flow line generated by the swaging process is formed.

4. Hollow shaft member according to any one of claims 1 to 3,

the intermediate portion has an inner diameter larger than the inner diameters of the pair of reduced diameter portions.

5. A rolling device is characterized in that a rolling device is provided,

the scroll device includes:

an inner member having a raceway surface formed on an outer surface of the intermediate portion of the hollow shaft member according to any one of claims 1 to 4;

an outer member having a raceway surface facing the raceway surface of the inner member; and

a plurality of rolling elements arranged to be rollable between the two raceway surfaces,

the rolling device is formed by assembling the outer member to the outside of the inner member via the plurality of rolling elements.

Technical Field

The present invention relates to a hollow shaft member and a rolling device provided with the hollow shaft member.

Background

A rolling device known as a ball screw device or a ball spline device includes: an inner member having a raceway surface on an outer surface thereof; and an outer member having a load track surface facing the track surface of the inner member and disposed outside the inner member. A plurality of rolling elements are interposed between the inner member and the outer member, so that the outer member can freely move relative to the inner member. As described above, since such a rolling device obtains a light operation by interposing a plurality of rolling elements between an inner member and an outer member, the rolling device is used in various fields such as robots, machine tools, medical instruments, and aircraft equipment.

However, in order to use the rolling device in various fields, the rolling device is required to be lightweight. For example, in a conventionally used method for reducing the weight of a rolling device, a rolling device is subjected to cutting to reduce the thickness, or hole. However, even if the rolling device is subjected to cutting, it is still difficult to achieve a significantly reduced rolling device weight. In particular, since shaft-like members such as a threaded shaft and a spline shaft used as inner members must have predetermined strength, it is difficult to reduce the weight.

Here, as a conventional technique for achieving weight reduction of a shaft-like member, it has been known to form a desired contour shape and achieve weight reduction by performing plastic working on a tubular raw material formed into a hollow shaft shape. For example, patent document 1 below discloses a method for manufacturing a hollow shaft by a process including a necking step of necking both end portions of a tubular raw material and a coining step of forming a jaw portion into a standard shape and size. Patent document 2 below discloses a technique for manufacturing a hollow shaft by swaging or upset forging in order to provide a hollow shaft that can be reduced in weight, load, and cost.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2001-121241

Patent document 2: japanese laid-open patent publication No. 2007-75824

Disclosure of Invention

Problems to be solved by the invention

As a method for reducing the weight of a screw shaft or a spline shaft as an inner member of a rolling device, the present inventors conceived a method for manufacturing a hollow shaft member such as a screw shaft or a spline shaft by subjecting both shaft ends of a tubular raw material formed into a hollow shaft shape to a die forging process. However, in order to use the hollow shaft member for a screw shaft, a spline shaft, or the like for a rolling device, it is necessary to form right-angle stepped-down portions, which are stepped down at substantially right angles with respect to the axial direction, with respect to both axial ends of the hollow shaft member. This is because, in order to use the screw shaft, spline shaft, or the like for the rolling device, it is necessary to provide bearings for supporting the shafts at both ends, and therefore, it is necessary to form right-angle stepped-down portions stepped down substantially at right angles.

However, as described in patent document 2, when the contour shape of the hollow shaft is formed by the swaging, the formed shape can only form a slope inclined in an inclined direction with respect to the axial direction, and it is very difficult to form a right-angle stepped-down portion stepped down at a substantially right angle. This is understood from the case where only the slope shape is present and the right angle stepped-down shape portion is not present in the contour shape of the hollow shaft shown in the drawing of patent document 2.

The column entitled "prior art" in patent document 1 describes the following: in the conventional technical knowledge based on patent document 1, it is known that it is very difficult to manufacture a hollow shaft member such as a screw shaft or a spline shaft, particularly a hollow shaft member having a right-angle stepped portion by performing a swaging process on both shaft ends of a tubular material formed into a hollow shaft shape.

The present invention provides a technical method for manufacturing a hollow shaft member having a right-angle stepped-down shape portion by die forging, by creating a new invention that breaks the above-described technical common knowledge of the prior art. It is another object of the present invention to provide a hollow shaft member for a rolling device, which is reduced in weight, which has been difficult in the related art, by proposing the above-described novel technical means.

Means for solving the problems

The hollow shaft member according to the present invention is characterized by comprising: a pair of reduced diameter portions formed on both axial end portions of a tubular raw material formed in a hollow shaft shape by performing die forging on the both axial end portions, respectively; and an intermediate portion disposed between the pair of reduced diameter portions and having an outer diameter larger than the outer diameters of the pair of reduced diameter portions, wherein a connection boundary between the intermediate portion and the reduced diameter portions is formed in a shape of a right-angle stepped-down portion stepped down substantially at right angles to an axial direction, and the right-angle stepped-down portion is formed by the swaging.

Effects of the invention

According to the present invention, it is possible to provide a hollow shaft member for a rolling device, which is reduced in weight, which has been difficult in the related art.

Drawings

Fig. 1 is a diagram showing the shape of a hollow shaft member according to the present embodiment, in which a partial view (a) shows the external appearance and a partial view (b) shows the cross section.

Fig. 2 is a flowchart for explaining a manufacturing process of the hollow shaft member according to the present embodiment.

Fig. 3 is a diagram showing an example of a specific processing step of the swaging processing shown in fig. 2, and in particular, a partial diagram (a) shows a raw material preparation (annealing completion) step, a partial diagram (b) shows a rough processing step, a partial diagram (c) shows an intermediate processing step, and a partial diagram (d) shows a finish processing step.

Fig. 4 is a cross-sectional view showing the shapes of a conventional article and an inventive article, in which a partial view (a) shows the conventional article in a solid state, a partial view (b) shows the conventional article in which weight reduction by drilling is achieved, and a partial view (c) shows the inventive article subjected to die forging.

Fig. 5 is a diagram showing a specific example of the hollow shaft member of the present embodiment.

Fig. 6 is a diagram showing another specific example of the hollow shaft member of the present embodiment.

Fig. 7 is a diagram illustrating a case where the hollow shaft member of the present embodiment is configured as a screw shaft of a ball screw device.

Fig. 8 is a view illustrating a case where the hollow shaft member of the present embodiment is configured as the spline shaft of the spline device.

Detailed Description

Preferred embodiments for carrying out the present invention will be described below with reference to the accompanying drawings. The following embodiments do not limit the inventions according to the respective aspects, and all combinations of features described in the embodiments are not essential to the means for solving the inventions.

First, an embodiment of a hollow shaft member manufactured by the present invention will be described with reference to fig. 1. Fig. 1 is a diagram showing the shape of a hollow shaft member according to the present embodiment, in which a partial view (a) shows the external appearance and a partial view (b) shows the cross section.

The hollow shaft member 10 of the present embodiment is formed by performing die forging on both axial end portions of a tubular raw material formed into a hollow shaft shape. In other words, the reduced diameter portions 11 are formed at both axial end portions of the hollow shaft member 10, respectively. Further, an intermediate portion 12 is formed between a pair of reduced diameter portions 11 formed at both axial end portions. The intermediate portion 12 has an outer diameter larger than the outer diameters of the pair of reduced diameter portions 11, and is a portion capable of functioning as an inner member of a rolling device such as a threaded shaft or a spline shaft, for example.

Further, a right-angle stepped-down portion 13 stepped down substantially at right angles to the axial direction is formed at a connection boundary between the intermediate portion 12 and the pair of reduced diameter portions 11. The right-angle stepped-down portion 13 is formed to provide a bearing for supporting the hollow shaft member 10 as an axis body, and the hollow shaft member 10 used as an inner member of a rolling device such as a screw shaft or a spline shaft can be reliably attached to the installation site by disposing the bearing at the formation site of the right-angle stepped-down portion 13. The pair of reduced diameter portions 11 and the right-angle stepped-down shape portion 13 formed in the hollow shaft member 10 according to the present embodiment are formed by a manufacturing process using swaging created by the present inventors. Next, a manufacturing process of the hollow shaft member 10 according to the present embodiment will be described with reference to the drawings, with reference to fig. 2 and 3.

Fig. 2 is a flowchart for explaining a manufacturing process of the hollow shaft member according to the present embodiment. Fig. 3 is a diagram showing an example of a specific processing step of the swaging process shown in fig. 2.

As shown in fig. 2, in the manufacturing process of the hollow shaft member 10 of the present embodiment, first, a tubular raw material formed into a hollow shaft shape is prepared (step S10). The material of the raw material is a material having high strength and hardness of metal that can be used as an inner member of the rolling device, and for example, bearing steel such as SUJ2, high carbon steel, or the like is used. Then, by applying annealing treatment to the prepared tubular raw material, treatment for reducing the hardness of the tubular raw material to which the swaging processing is subsequently applied is performed (step S11).

Next, the both axial end portions of the tubular raw material subjected to the annealing treatment are subjected to the swaging process to form the reduced diameter portion 11 and the right-angle stepped-down shape portion 13 (step S12). The swaging is a processing method also called rotary cold forging, and is a processing of rotating a divided tool called a die 31 and drawing a base material while knocking the base material. In forming the pair of diameter-reduced portions 11 and the right-angle stepped-down shape portion 13 of the present embodiment, for example, as shown in fig. 3, a method of gradually forming a final shape by dividing a swaging process into a plurality of processing steps of "(a) raw material preparation → (b) rough processing → (c) intermediate processing → (d) finish processing", or a method of forming a final shape at a time by a single processing step may be employed.

It should be noted that the reason why the swaging processing according to the present embodiment described above can be performed without any problem is that the effect of the processing for reducing the hardness of the raw material is effectively exerted by performing the annealing processing shown in step S11 on both axial end portions of the tubular raw material before the swaging processing shown in step S12, and it was confirmed by the test of the inventors that when the swaging processing is performed so that the annealing processing shown in step S11 is not performed, a trouble such as a crack occurs in the product.

When the swaging process shown in step S12 of fig. 2 is finished, the basic outline shape of the hollow shaft member 10 of the present embodiment has been formed, and then, as a final product, end-working (step S13) for completing the shaft end of the hollow shaft member 10, finishing (step S14) are performed, thereby completing the hollow shaft member 10 of the present embodiment.

When the hollow shaft member 10 of the present embodiment is used as an inner member of a rolling device, it is necessary to perform a treatment of forming a raceway surface with respect to the intermediate portion 12 or performing a quenching treatment to increase the surface hardness. In this case, for example, the machining process of forming the raceway surface in advance at the portion to be the intermediate portion 12 in the step of raw material preparation shown in step S10 in fig. 2, or the quenching process in the step of finishing shown in step S14 may be performed. In addition, although the pair of reduced-diameter portions 11, the hardness of which has been reduced by the annealing process performed in step S11, is expected to be somewhat increased by the work hardening caused by the execution of the swaging process performed in step S12, the quenching process for the pair of reduced-diameter portions 11 may be performed in the finishing process performed in step S14 in order to ensure the function as the inner member of the rolling device.

As described above, the pair of reduced diameter portions 11 and the right-angle stepped-down shape portion 13 forming the hollow shaft member 10 according to the present embodiment can be appropriately formed by a combination of the annealing process (step S11) and the swaging process (step S12). Therefore, when the metal structure of the cross section of the pair of reduced diameter portions 11 and the right angle stepped-down shape portion 13 is observed with a microscope, it can be confirmed that a metal flow (metal flow) is formed by the swaging. That is, it can be verified whether or not the manufacturing method of the present embodiment shown in fig. 2 and 3 is used by microscopic observation of the hollow shaft member 10 as a final product.

Next, referring to fig. 4 and table 1, the results of comparing the performance of the hollow shaft member 10 (invention product) manufactured by the manufacturing method of the present embodiment with that of the conventional hollow shaft member (conventional product) will be described. Here, fig. 4 is a cross-sectional view showing the shapes of the existing product and the invention product, in which a partial view (a) shows the existing product in a solid state, a partial view (b) shows the existing product in which weight reduction by drilling is achieved, and a partial view (c) shows the invention product. Table 1 is a graph showing the results of comparing the performance of the conventional article shown in fig. 4 (b) and the invention article shown in fig. 4 (c), and shows the results obtained by comparing the mass and the critical speed.

[ TABLE 1 ]

As shown in fig. 4, the conventional article and the invention article, which were compared in performance, used a hollow shaft member of the same steel type having the same length. Conventionally, a hole opened in the axial direction by drilling is formed for the purpose of reducing the weight. On the other hand, in the invention, since the tubular raw material formed into the hollow shaft shape is subjected to the die forging to form the outline shape, the internal cavity is also formed into a cavity shape along the outline shape.

As shown in table 1, the weight of the conventional product is 1.2kg, whereas the weight of the inventive product is 0.6kg and 50% of the weight of the conventional product, and the inventive product is a hollow shaft member of the same steel type and the same length, but the inventive product is actually reduced in weight by 50% of the conventional product. On the other hand, in order to evaluate a functional surface as an inner member of a rolling device, "critical speed (allowable rotation speed)" is setWhen compared, the existing product is about 3400min^-1In contrast, the invention showed about 5000min^-1The value of (c). That is, the product of the invention has an allowable rotation speed about 1.5 times as high as that of the conventional product, and it can be confirmed that the product of the invention is superior to the conventional product in performance indexes of a safety surface and a strength surface such as "critical speed (allowable rotation speed)". As is clear from the verification results, the hollow shaft member 10 (invention product) manufactured by the manufacturing method of the present embodiment can be reduced in weight, which has been difficult in the related art.

Further, the present invention can be made lighter than conventional ones, but this is because the conventional one is provided with the through-hole on the shaft only within the range of the inner diameters of the pair of reduced diameter portions located at both axial end portions, and on the other hand, the present invention can form a space along the inner diameter of the intermediate portion 12 located at the central portion of the shaft. That is, in the hollow shaft member 10 of the present embodiment, the inner diameter of the intermediate portion 12 can be made larger than the inner diameters of the pair of reduced diameter portions 11, and the weight reduction effect can be obtained more than that of the conventional art by realizing the above-described configuration.

Next, a specific example of the hollow shaft member 10 manufactured by the manufacturing method of the present embodiment described above is shown with reference to fig. 5 and 6. Here, fig. 5 is a diagram showing a specific example of the hollow shaft member of the present embodiment, and fig. 6 is a diagram showing another specific example of the hollow shaft member of the present embodiment.

Fig. 5 shows, for example, the following specific examples: a process including an annealing process (step S11) and a swaging process (step S12) is performed on a raw material having an outer diameter of about 5mm and a plate thickness of about 0.8mm, thereby forming a pair of reduced diameter portions 11, and three right-angle stepped-down shape portions 13 indicated by reference numeral A, B, C. The hollow shaft member 10 shown in fig. 5 is formed of QPD5 (equivalent to SUS440C), and can be used as a spline shaft, for example, by forming spline grooves in the intermediate portion 12.

Fig. 6 shows, for example, the following specific examples: a process including an annealing process (step S11) and a swaging process (step S12) is performed on a raw material having an outer diameter of about 15mm and a plate thickness of about 2.15mm, thereby forming a pair of reduced diameter portions 11, and two right-angle stepped-down shape portions 13 indicated by reference numeral D, E. The hollow shaft member 10 shown in fig. 6 is formed of high-carbon steel, and can be used as a threaded shaft, for example, by forming a thread groove in the intermediate portion 12.

In the specific example of fig. 6, it is understood that the inner peripheral surface of the intermediate portion 12 and the outer peripheral surface of the reduced diameter portion 11 are substantially at the same position in the axial direction at the boundary between the positions where the rectangular stepped-down portions 13 are formed. Therefore, when the thickness of the raw material is t and the reduction in the die forging deformation dimension is L, it is shown that the right-angle reduced shape portion 13 can be formed until the following inequality is satisfied.

Sheet thickness t ≦ machining deformation dimension L

As a specific machining result for confirming that the above inequality is satisfied, the inventors confirmed an actual value of 0.5mm in plate thickness t and 0.525mm in machining deformation dimension L (machining an outer diameter of 4.2mm to 3.15mm) for the ball spline, and confirmed an actual value of 2.15mm in plate thickness t and 2.5mm in machining deformation dimension L (machining an outer diameter of 15.3mm to 10.3mm) for the precision ball screw.

The specific structure and manufacturing process of the hollow shaft member 10 according to the present embodiment are described above. The hollow shaft member 10 of the present embodiment is particularly suitable for use as an inner member constituting a rolling device. Therefore, an example in which the hollow shaft member 10 of the present embodiment is applied to a rolling element screw device and a spline device will be described with reference to fig. 7 and 8.

(application example to Rolling element screw device)

The hollow shaft member 10 of the present embodiment can be configured as a screw shaft 71 of a ball screw device 70 as shown in fig. 7, for example. Fig. 7 is a diagram illustrating a case where the hollow shaft member of the present embodiment is configured as a screw shaft of a ball screw device. The ball screw device 70 includes a screw shaft 71 as an inner member, and a nut member 72 as an outer member rotatably mounted on the screw shaft 71 via a plurality of balls 73.

The screw shaft 71 is an inner member having a spiral rolling element rolling groove 71a as a raceway surface formed on an outer peripheral surface thereof, and the nut member 72 is an outer member having a spiral load rolling groove as a raceway surface formed on an inner peripheral surface thereof corresponding to the rolling element rolling groove 71 a. The nut member 72 is capable of reciprocating relative to the screw shaft 71 in accordance with relative rotational movement of the screw shaft 71 relative to the nut member 72.

The hollow shaft member 10 of the present embodiment can form the screw shaft 71 constituting the ball screw device 70, and the hollow shaft member 10 includes the pair of reduced diameter portions 11 and the right-angle stepped-down portion 13 formed by the combination of the annealing process (step S11) and the swaging process (step S12). At this time, the hollow shaft member 10 of the present embodiment can function as the screw shaft 71 by forming the rolling element rolling grooves 71a as the raceway surfaces in a spiral shape on the outer peripheral surface of the intermediate portion 12 of the hollow shaft member 10 of the present embodiment. By adopting such a configuration, it is possible to provide the hollow shaft member 10 for the ball screw device 70, which has been difficult in the related art and is lightweight.

(application example to spline device)

The hollow shaft member 10 of the present embodiment can be configured as, for example, a spline shaft 81 of a spline device 80 as shown in fig. 8. Fig. 8 is a view illustrating a case where the hollow shaft member of the present embodiment is configured as the spline shaft of the spline device.

Here, a description will be given of a simple structure of the spline device 80 shown in fig. 8, in which the spline device 80 includes a spline shaft 81 as an inner member, and a cylindrical outer cylinder 82 as an outer member movably attached to the spline shaft 81 via balls 83 as a plurality of rolling elements. A rolling element rolling surface 81a, which is a raceway surface that serves as a raceway for the balls 83 and extends in the axial direction of the spline shaft 81, is formed on the surface of the spline shaft 81. A loaded rolling element rolling surface, which is a raceway surface corresponding to the rolling element rolling surface 81a, is formed on the outer cylinder 82 attached to the spline shaft 81. A load rolling path is formed between a load rolling element rolling surface formed on the outer cylinder 82 and a rolling element rolling surface 81a formed on the spline shaft 81. A no-load return path through which the balls 83 released from the load move is formed beside the loaded rolling path. A retainer 84 for holding a plurality of balls 83 arranged in a loop is assembled to the outer cylinder 82. The plurality of balls 83 are provided so as to be freely rollable between the loaded rolling element rolling surface of the outer cylinder 82 and the rolling element rolling surface 81a of the spline shaft 81, and are provided so as to endlessly circulate through the unloaded return path, whereby the outer cylinder 82 can reciprocate relative to the spline shaft 81.

In the case of the spline device 80 shown in fig. 8, the spline shaft 81 constituting the spline device 80 can be formed by the hollow shaft member 10 of the present embodiment, in which the hollow shaft member 10 has the pair of reduced diameter portions 11 and the right-angle stepped-down portion 13 formed by the combination of the above-described annealing process (step S11) and the swaging process (step S12). At this time, the hollow shaft member 10 of the present embodiment can function as the spline shaft 81 by forming the rolling element rolling surface 81a as a raceway surface on the outer peripheral surface of the intermediate portion 12 of the hollow shaft member 10 of the present embodiment. By adopting such a configuration, it is possible to provide the hollow shaft member 10 for the spline device 80, which has been difficult in the related art and is lightweight.

Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes and improvements can be made to the above embodiments. As is clear from the description of the technical means, the means to which such changes or improvements have been made are also included in the technical scope of the present invention.

Description of the reference numerals

10 hollow shaft member (invention product, inner member), 11 reduced diameter portion, 12 intermediate portion, 13 right angle reduced shape portion, 31 die, 70 ball screw device (rolling device), 71 screw shaft (inner member), 71a rolling element rolling groove (raceway surface), 72 nut member (outer member), 73 balls (rolling element), 80 spline device (rolling device), 81 spline shaft (inner member), 81a rolling element rolling surface (raceway surface), 82 outer cylinder (outer member), 83 balls (rolling element), 84 retainer.