JP2014114847A - Manufacturing method of inner cylindrical body of wheel bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an inner cylindrical body of a wheel bearing device, capable of combining easiness of formation of a female spline and improvement in dimension accuracy.SOLUTION: Provided is a method of manufacturing an inner cylindrical body 10 of a wheel bearing device in which a female spline 27 is formed in an inner peripheral surface 26. The method includes: a first heat treatment process that performs heat treatment to the outer peripheral surface side of a primary intermediate product having a cylindrical shape; a spline formation process that after the first heat treatment process, forms the female spline 27 with respect to the inner peripheral surface of the primary intermediate product to manufacture a secondary intermediate product; and a second heat treatment process that performs heat treatment to an inner peripheral surface side 11 of the secondary intermediate product.

Description

  The present invention relates to a method of manufacturing an inner cylinder which is a component part of a wheel bearing device provided in, for example, an in-wheel motor unit.

  In recent years, in addition to automobiles using engines, development of automobiles that travel by generating a driving force by a motor has been developed, and as wheel bearing units that can be applied to automobiles using such motors, An in-wheel motor unit is known (see, for example, Patent Document 1).

  The in-wheel motor unit includes, for example, a motor, a speed reducer, and a wheel bearing device. Among these, the wheel bearing device can attach the wheel and transmit the rotational force output from the reduction gear to the wheel. This wheel bearing device includes a rotating wheel that rotates integrally with an output shaft (drive shaft) of a speed reducer, a fixed wheel that is provided on the outer side in the radial direction and is fixed to the vehicle body side, and the rotating wheel and the fixed wheel. And a plurality of rolling elements (balls) interposed therebetween.

  In order to rotate the rotating wheel integrally with the output shaft of the speed reducer, a male spline is formed on the outer peripheral surface of the output shaft, and a female spline is formed on the inner peripheral surface of the rotating wheel. .

JP 2011-207375 A (see FIG. 1)

  The rotating wheel of the wheel bearing device has a cylindrical shape, and a female spline is formed on the inner peripheral surface of the rotating wheel, but there is an abnormal noise at the fitting portion between the reduction gear and the output shaft (male spline). In order to prevent vibrations and vibrations from occurring, it is necessary to manage the dimensional accuracy of the female spline on the rotating wheel side.

FIG. 8 is a longitudinal sectional view of the rotating wheel 80. The rotating wheel 80 includes, for example, a cylindrical inner cylindrical body (made of steel) 81 and a bearing ring member 83 in which a raceway surface 82 for rolling a rolling element (ball) is formed on the outer peripheral surface, A female spline 84 is formed on the inner peripheral surface of the inner cylinder 81.
Moreover, in this inner cylinder 81, before attaching the bearing ring member 83, in order to harden each part of the inner cylinder 81, it heat-processes (hardening process) with respect to the inner peripheral surface side 85 and the outer peripheral surface side 86 Is done.

Here, if heat treatment is performed on both the inner peripheral surface side 85 and the outer peripheral surface side 86 of the inner cylinder 81 before forming the female spline 84, the hardness of the inner peripheral surface side 85 of the inner cylinder 81 will be described. Increase, the formation of the female spline 84 may be difficult.
On the other hand, when the female spline 84 is formed first and then heat treatment is performed on both the inner peripheral surface side 85 and the outer peripheral surface side 86 of the inner cylinder 81, the female spline 84 (spline teeth) is affected by the heat treatment. ) May be greatly distorted and the dimensional accuracy may be reduced.
Therefore, an object of the present invention is to provide a method for manufacturing an inner cylinder of a wheel bearing device that can achieve both the ease of forming a female spline and the improvement of dimensional accuracy.

  The present invention relates to a method for manufacturing an inner cylinder of a wheel bearing device in which a female spline is formed on an inner peripheral surface, and the first heat treatment is performed on the outer peripheral surface side of a cylindrical intermediate product. A heat treatment step, a spline forming step for producing a secondary intermediate product by forming a female spline on the inner peripheral surface of the primary intermediate product after the first heat treatment step, and an inner peripheral surface of the secondary intermediate product And a second heat treatment step for performing heat treatment on the side.

According to the present invention, before the female spline is formed on the inner peripheral surface of the primary intermediate product, the heat treatment (first heat treatment step) has been completed on the outer peripheral surface side of the primary intermediate product. Heat treatment does not reduce the dimensional accuracy of the female spline.
Further, since the heat treatment (first heat treatment step) performed before the formation of the female spline is not the inner peripheral surface side where the female spline is formed but the outer peripheral surface side, the inner peripheral surface where the female spline is formed is heat treated. Therefore, it is possible to prevent the hardness from increasing and the formation of the female spline from becoming difficult. Furthermore, since a female spline is formed on the inner peripheral surface and then a heat treatment (second heat treatment step) is performed on the inner peripheral surface side, the inner peripheral surface side is increased in hardness by the heat treatment, making it difficult to form the female spline. Can be prevented. Although the female spline may be distorted by the heat treatment on the inner peripheral surface side, it differs from the heat treatment from both the inner peripheral surface side and the outer peripheral surface side as in the prior art, so the amount of heat input is smaller than before. The generated distortion is reduced as compared with the conventional case.
As described above, according to the present invention, both the ease of forming the female spline and the improvement of the dimensional accuracy can be achieved.

  According to the present invention, it is possible to prevent the formation of the female spline from becoming difficult, and further to prevent a decrease in the dimensional accuracy of the female spline and to achieve both the ease of forming the female spline and the improvement of the dimensional accuracy. Is possible.

It is a longitudinal cross-sectional view of an inner cylinder. It is a longitudinal cross-sectional view of the wheel bearing apparatus. It is the figure which looked at the inner cylinder body from the axial direction. It is a flowchart explaining the manufacturing method of an inner cylinder. It is a longitudinal cross-sectional view of a primary intermediate product. It is a longitudinal cross-sectional view of a secondary intermediate product. It is explanatory drawing of a spline formation process. It is a longitudinal cross-sectional view of a rotating wheel.

  FIG. 1 is a longitudinal sectional view of an inner cylinder 10 which is a component part of a wheel bearing device used in an in-wheel motor unit. Although not shown, the in-wheel motor unit is a wheel bearing unit that can be applied to a vehicle that travels by generating a driving force by the motor, and includes a motor, a speed reducer that reduces the rotational speed of the motor, and a wheel. Bearing device 20 (see FIG. 2). The wheel bearing device 20 can be attached with a wheel (not shown) and can transmit the rotational force output from the reduction gear to the wheel.

  The wheel bearing device 20 includes a rotating wheel 21 that rotates integrally with the output shaft (drive shaft) of the speed reducer, a fixed wheel 22 that is provided on the outer side in the radial direction and is fixed to the vehicle body side, and the rotating wheel 21 and the fixed wheel. And a plurality of rolling elements (balls) 23 interposed between the two. And the inner cylinder 10 shown in FIG. 1 is one of the components for comprising the rotating wheel 21 shown in FIG. That is, as shown in FIG. 2, the rotating wheel 21 is a short cylindrical track ring in which a cylindrical inner cylinder 10 and a raceway surface 25 for rolling the rolling elements (balls) 23 are formed on the outer peripheral surface. And a member 24.

  FIG. 3 is a view of the inner cylinder 10 of FIG. 1 as viewed from the axial direction. As shown in FIGS. 1 to 3, a female spline (internal gear) 27 is formed on the inner peripheral surface 26 of the inner cylindrical body 10. In the present embodiment, a plurality of spline teeth 28 are long and linearly formed along a straight line parallel to the center line L of the inner cylinder 10 on the inner peripheral surface 26 of the inner cylinder 10.

As shown in FIG. 1, the inner cylinder 10 includes a cylindrical main body portion 16 and a flange portion 17 extending radially outward from one axial side of the main body portion 16. A wheel side member (not shown) such as a wheel or a brake rotor is attached to the portion 17.
The inner cylinder 10 is made of steel, and can be, for example, carbon steel (medium-high carbon steel) or bearing steel.

  The inner cylinder 10 is heat-treated (quenched) on the inner peripheral surface side 11 and the outer peripheral surface side 12 in order to increase the hardness of each part. Then, with respect to the inner cylinder 10 on which the female spline 27 has been formed and the inner peripheral surface side 11 and the outer peripheral surface side 12 have been heat-treated, the bearing ring member 24 (see FIG. 2) is removed on the other axial side. The bearing ring member 24 is prevented from coming off by being fitted and plastically deforming the end on the other axial side of the inner cylindrical body 10 outward in the radial direction to form the caulking portion 15.

Hereinafter, a method for manufacturing the inner cylinder 10 shown in FIG. 1 will be described. FIG. 4 is a flowchart illustrating a method for manufacturing the inner cylinder 10.
First, a primary intermediate product W1 (see FIG. 5) having a cylindrical shape is formed by forging from a cylindrical material (not shown) (St1 in FIG. 4).

In FIG. 5, heat treatment is performed on the outer peripheral surface side 12 of the primary intermediate product W1 (first heat treatment step of FIG. 4: St2). The outer peripheral surface 31 of the primary intermediate product W1 is the outer peripheral surface 32 of the inner cylinder 10 shown in FIG.
The heat treatment (quenching) in the first heat treatment step St <b> 2 is induction hardening, and is hardened so that the hardness of the outer peripheral surface 31 is in the range of HRC58 to 64, for example.

  Then, after this first heat treatment step St2, a female spline 27 is formed on the inner peripheral surface 33 of the primary intermediate product W1 to produce a secondary intermediate product W2 (see FIG. 6) (spline formation step of FIG. 4). : St3). The inner peripheral surface 34 of the secondary intermediate product W2 becomes the inner peripheral surface 26 of the inner cylinder 10 (FIG. 1).

The female spline 27 is formed by cutting the inner peripheral surface 33 of the primary intermediate product W1 (see FIG. 5). Particularly in this embodiment, the female spline 27 is formed by broaching. For example, as shown in FIG. 7 (in FIG. 7, the shape of the primary intermediate product W1 is simplified), a cylindrical shaft-shaped broach (cutting tool) 40 is connected to the inner periphery of the primary intermediate product W1. By reciprocating in the axial direction (vertical direction in FIG. 7) with respect to the surface 33, a plurality of spline teeth 28 are formed simultaneously on the entire circumference of the inner circumferential surface 33 of the primary intermediate product W1. The contour shape in the cross section of the blade portion of the broach 40 corresponds to the overall shape of the female spline 27.
Although not shown, the broach 40 can be a tapered shaft. Further, FIG. 7 illustrates the case where a plurality of spline teeth 28 are simultaneously formed on the entire circumference of the inner peripheral surface 33, but in addition to this, the number of spline teeth 28 (number of strips) gradually increases. Thus, the spline teeth 28 may be formed stepwise, for example, the spline teeth 28 may be formed one by one or plural. In this case, although not shown in the drawing, a plurality of blade rows including a linear broach in which the blades are arranged in a row along the longitudinal direction or a plurality of blades arranged in the longitudinal direction are further arranged in the circumferential direction. A broach can be used.

In the first heat treatment step (St2 in FIG. 4), as described above, the heat treatment is performed only on the outer peripheral surface side 12 of the primary intermediate product W1 (FIG. 5). It is also conceivable to affect the inner peripheral surface side 11 of W1. That is, it is conceivable that the inner peripheral surface side 11 also becomes slightly hard (the structure changes).
However, the hardness of the inner peripheral surface 33 of the primary intermediate product W1 after the first heat treatment step (St2) is HRC30 or less.

  The value of this hardness is a hardness that does not make it difficult to form the female spline 27 by cutting in the spline forming step (St3). The first heat treatment step is temporarily performed on the primary intermediate product W1. The female spline 27 is formed on the inner peripheral surface 33 of the primary intermediate product W1 after performing the first heat treatment step (St2) under the same cutting conditions as when the female spline is formed on the inner peripheral surface side without being performed. Is possible.

  In particular, when heat-treating the outer peripheral surface side 12 in order to effectively suppress the inner peripheral surface side 11 of the primary intermediate product W1 (see FIG. 5) from becoming unnecessarily hardened by the first heat treatment step (St2). That is, in the first heat treatment step, it is preferable to cool the inner peripheral surface side 11 so that the inner peripheral surface side 11 is not quenched, that is, the structure is not changed by quenching. This cooling can be performed with cooling water, or may be air cooling.

Then, heat treatment is performed on the inner peripheral surface side 11 of the secondary intermediate product W2 (see FIG. 6) on which the female spline 27 is formed (second heat treatment step: St4 in FIG. 4). The inner cylinder 10 (see FIG. 1) is used.
The heat treatment in the second heat treatment step St4 is induction hardening, and is hardened so that the hardness of the inner peripheral surface 34 of the secondary intermediate product W2 is, for example, HRC 40 or more.
Thereafter, a polishing finish is performed on a predetermined portion on the outer peripheral surface side 12 of the secondary intermediate product W2 after the second heat treatment step (finishing step St5).

As described above, according to the method for manufacturing the inner cylinder 10 according to the present embodiment, before forming the female spline on the inner peripheral surface 33 of the primary intermediate product W1 (see FIG. 5), the primary intermediate product W1 Since the first heat treatment step has been completed for the outer peripheral surface side 12, the dimensional accuracy of the female spline 27 (see FIG. 6) is not reduced by the heat treatment for the outer peripheral surface side 12.
Further, since the first heat treatment step performed before the formation of the female spline 27 is not the inner peripheral surface side 11 where the female spline 27 is formed but the outer peripheral surface side 12, It is possible to prevent the peripheral surface 33 from becoming hard due to heat treatment and making it difficult to form the female spline 27.

  Furthermore, in FIG. 6, since the second heat treatment step is performed on the inner peripheral surface side 11 after the female spline 27 is formed on the inner peripheral surface 34, the inner peripheral surface side 11 is increased in hardness by the heat treatment. The formation of the female spline 27 can be prevented from becoming difficult. The heat treatment on the inner peripheral surface side 11 may cause distortion in the formed female spline 27. However, since the heat treatment from both the inner peripheral surface side and the outer peripheral surface side is different from the conventional one, the generated distortion is caused. Is reduced compared to the conventional case.

  As mentioned above, according to the manufacturing method of the inner cylinder 10 of this embodiment, it can prevent that the dimensional accuracy of the female spline 27 falls large by heat processing, and also formation of the female spline 27 becomes difficult. Therefore, it is possible to achieve both improvement in dimensional accuracy of the female spline 27 and ease of formation of the female spline 27. Further, no subsequent polishing is required for the female spline 27, which can contribute to cost reduction.

In the spline formation step (St3) of the present embodiment, the female spline 27 is formed in advance by predicting (considering) the distortion of the female spline 27 caused by the second heat treatment step (St4).
That is, as described above, the spline teeth 28 of the female spline 27 formed on the secondary intermediate product W2 (FIG. 6) may be distorted by the second heat treatment process. A female spline 27 having a shape different from the design value is formed in advance.

  Specifically, when the tooth surface of the spline tooth 28 is inclined to one side in the circumferential direction by the second heat treatment, that is, when the warp of the spline tooth 28 to the one side in the circumferential direction occurs, On the other hand, the spline teeth 28 that are deformed in advance to the other side in the circumferential direction with respect to the amount of inclination (the amount of warpage) are formed. Thereby, when distortion occurs in the second heat treatment step, the shape of the spline teeth 28 approaches the design value (design shape). In addition, the inclination amount (warpage amount) of the spline teeth 28 in the circumferential direction in the second heat treatment step is the largest portion, for example, about 10 to 30 μm.

  In order to form the female spline 27 (spline teeth 28) deformed in advance with respect to such a design shape by broaching, the shape of the blade of the broach is made to correspond to this, or the broach is made in the circumferential direction. The broach that can obtain the design shape may be linearly reciprocated while the force is applied in the direction in which the broach is inclined in the circumferential direction.

  In addition, as described above, the female spline 27 is formed in a shape different from the design value in advance with respect to the distortion amount. For this purpose, the secondary spline 27 is once formed on the secondary intermediate product W2 in which the female spline is formed according to the design value. The second heat treatment step is performed, the amount of strain of the female spline is measured, and the measured value is fed back to the spline formation step.

  As described above, after the female spline 27 is formed on the inner peripheral surface 34 (that is, after the spline forming step), the second heat treatment step is performed on the inner peripheral surface side 11 so that the female heat treatment is performed by the second heat treatment step. Even if the spline 27 is distorted more than an allowable value, in the spline forming process, the female spline 27 is formed by predicting in advance the distortion of the female spline 27 by the second heat treatment process on the inner peripheral surface side 11. Thus, it is possible to keep the dimensional accuracy of the female spline 27 within the allowable range.

  As mentioned above, according to the manufacturing method of the inner cylinder 10 which concerns on this embodiment, after finishing the 1st heat treatment process about the outer peripheral surface side 12 first with respect to the primary intermediate product W1 used as the inner cylinder 10, A female spline 27 is formed on the inner peripheral surface side 11 (spline forming step). Then, by performing the second heat treatment step on the inner peripheral surface side 11, compared to the case where both the inner peripheral surface side and the outer peripheral surface side are heat-treated later as in the conventional case, the strain (female heat treatment of the female spline 27 ( Deformation) can be mitigated, and the inner cylinder 10 having the female spline 27 with high accuracy can be manufactured.

  Moreover, the manufacturing method of the inner cylinder of the wheel bearing device of the present invention is not limited to the illustrated form, and may be other forms within the scope of the present invention, and the scope of the invention described in the claims. It can change suitably in the inside. Further, the shape of the inner cylinder 10 manufactured by this manufacturing method is not limited to the illustrated shape.

  For example, in the above-described embodiment, the case where the female spline 27 (spline teeth 28) is simultaneously formed in the spline forming step for the entire circumferential direction of the inner peripheral surface 33 of the primary intermediate product W1 has been described. The surface 33 may be divided into a plurality of regions, and female splines may be sequentially formed for each of these regions.

  Moreover, although the case where the manufactured inner cylinder 10 was used for an in-wheel motor unit was demonstrated, not only this but the inner cylinder 10 can be used also for other apparatuses. For example, it is also possible to manufacture the inner cylinder used for the wheel bearing apparatus for motor vehicles which drive | works with an engine with the manufacturing method of this invention.

  10: Inner cylinder 11: Inner peripheral surface side 12: Outer peripheral surface side 21: Rotating wheel 26: Inner peripheral surface of inner cylindrical body 27: Female spline 33: Inner peripheral surface of primary intermediate product W1: Primary intermediate product W2: Secondary intermediate product

Claims (3)

A method of manufacturing an inner cylinder of a wheel bearing device in which a female spline is formed on an inner peripheral surface,
A first heat treatment step for performing heat treatment on the outer peripheral surface side of the primary intermediate product having a cylindrical shape;
After the first heat treatment step, a spline forming step for producing a secondary intermediate product by forming a female spline on the inner peripheral surface of the primary intermediate product;
A second heat treatment step for performing heat treatment on the inner peripheral surface side of the secondary intermediate product;
A method for producing an inner cylinder of a wheel bearing device.   2. The inner cylindrical body of the wheel bearing device according to claim 1, wherein in the spline forming step, a female spline having a shape different from a design value is formed by predicting in advance the distortion of the female spline generated by the second heat treatment step. Manufacturing method.   The inner cylinder body of the wheel bearing device according to claim 1 or 2, wherein, in the first heat treatment step, when the heat treatment is performed on the outer peripheral surface side of the primary intermediate product, the inner peripheral surface side is cooled. Method.

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