JP2005273870A - Rolling bearing device for vehicle wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing device for a vehicle wheel capable of eliminating the necessity for a turning process with a lathe after heat treatment. <P>SOLUTION: The outer ring 2 of this rolling bearing device for vehicle wheel is furnished on its inside surface with a heat treated hardened layer h to suppress the residual stresses as it is formed shallow and narrow so as to be interrupted in the axial direction between the raceways 2a and 2b laid in double rows. This applies alike to the inner shaft. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a wheel rolling bearing device that rotatably supports a non-drive wheel of an automobile.

  In a wheel rolling bearing device, for example, a hardened layer is formed by induction hardening around the outer ring raceway (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-4642 (page 3, FIGS. 1 and 2)

However, the amount of deformation of the workpiece increases as a result of quenching to form the hardened layer. Therefore, a turning process after quenching is required to finish the desired dimension.
In view of the conventional problems as described above, an object of the present invention is to provide a wheel rolling bearing device that does not require such a turning process.

The rolling bearing device for a wheel according to the present invention includes an outer ring in which a double-row raceway is provided on a heat-treated hardened layer formed on an inner peripheral surface, and one of the outer rings on a heat-treated hardened layer formed on an outer peripheral surface. An inner shaft provided with a facing track, an inner ring fitted on the inner shaft and provided with a track facing the other track of the outer ring on the outer peripheral surface, and each track of the outer ring, A heat treatment hardened layer formed on at least one of the outer ring and the inner shaft in the axial direction between the double-row tracks. Residual stress is suppressed by being shallow and narrow so as to be interrupted.
In the rolling bearing device for a wheel as described above, the residual stress generated by the structural transformation and the thermal stress is suppressed by the heat treatment hardened layer formed shallow and narrow so as to be interrupted in the axial direction between the double row raceways. Variation in diameter is reduced.

In the wheel rolling bearing device, the dimension of the portion interrupted in the axial direction is preferably 4.0 mm or more.
In this case, the residual stress can be reliably suppressed.

  According to the rolling bearing device for a wheel of the present invention, the residual stress is suppressed by the heat treatment hardened layer formed shallow and narrow so as to be interrupted in the axial direction between the double row raceways, and the variation in the outside diameter of the spigot is reduced. The outer ring and the inner shaft on which such a heat treatment hardened layer is formed can eliminate the need for a subsequent turning process.

  FIG. 1 is a cross-sectional view of a wheel rolling bearing device (hereinafter referred to as a rolling bearing device) according to an embodiment of the present invention. This rolling bearing device 1 is of a double-row angular ball bearing type, and includes an outer ring 2, an inner shaft 3, an inner ring 4, rolling elements 5 and 6 composed of a plurality of balls, and these rolling elements 5 and 6. Retainers 7 and 8, a seal 9 provided in a gap between the outer ring 2 and the inner shaft 3, and a nut 10 screwed to the inner shaft 2.

  The outer ring 2 is a fixed ring fixed to the vehicle body side, and double-row tracks 2a and 2b are formed on the inner peripheral side thereof. On the other hand, the rotating wheels are the inner shaft 3 and the inner ring 4. A track 3a is formed at a position of the inner shaft 3 facing the track 2a. Further, a track 4b is formed at a position of the inner ring 4 facing the track 2b.

  The inner shaft 3 includes a wheel mounting flange 3b on the right side. Four bolts 11 for fixing the wheel are fixed to the flange portion 3b. Further, a screw portion 3 c is formed at the left end portion of the inner shaft 3. The inner ring 4 is fitted to the outer periphery of a small-diameter portion 3d formed near the left end of the inner shaft 3, and is fixed to the inner shaft 3 by tightening a nut 10 screwed to the screw portion 3c.

Heat treatment hardening layers are applied to the inner peripheral surface including the tracks 2a and 2b of the outer ring 2, the outer peripheral surface including the track 3a of the inner shaft 3, and the outer peripheral surface of the inner shaft 3 on which the inner ring 4 is fitted by induction hardening. Is formed. Therefore, Table 1 and FIG. 2 below show the results of examining the main dimensions of the heat-treated and cured layer h for the outer ring 2 by changing the depth and range of the heat-treated and cured layer and the heating conditions. (A) to (d) in Table 1 correspond to (a) to (d) in FIG. In (a) to (d), the depth do targeted for the heat treatment hardened layer h in the contact angle direction of the tracks 2a and 2b and the depth dm measured after the heat treatment are as follows. Conventionally, the value of dm is set to 2 to 5 mm, and (a) is reference data aiming at shallowness below this lower limit.
(A) shallower than do = 2 mm, dm = 1.9 mm
(B) do = 2.0 mm, dm = 2.0, 2.2 mm
(C) do = 2.5 mm, dm = 2.4, 2.5 mm
(D) do = 3.5 mm, dm = 3.4, 3.5 mm
In addition to the value of dm, the main dimensions of the heat-treated and hardened layer h in other parts are shown in the drawing.

  In FIG. 2 and Table 1, (a) is a shallow aim, but compared with (b) to (d), the heating energy (proportional to the square of the current) is small, and instead the heating time is longer. Is set to As a result, in (a), the heat-treated hardened layer h is connected in the axial direction between the double-row tracks 2a and 2b. On the other hand, compared with (a), (b) to (d) have larger heating energy and shorter heating time. That is, it is a setting that quenches quickly in a short time with high output. As a result, the heat treatment hardened layer h is interrupted in the axial direction between the double-row tracks 2a and 2b, and is discontinuous.

  In the bottom column of Table 1, the variation in the outer diameter D1 (FIG. 1) of the outer ring 2 and the evaluation thereof are described. The variation in the outer diameter D1 of the outer ring 2 is 54 μm or less in the standard, and (a) is unsuitable, but (b) to (d) are good results below the standard value. Further, regarding (b) and (c), the evaluation from a high level target of 1/2 of the standard value is also good. This is understood to be a result of suppressing the residual stress (transformation stress, thermal stress) by forming the heat treatment hardened layer h so as to be discontinuous in the axial direction between the double-row orbits. Moreover, although (a) aims at shallowness, since the heat-treated hardened layer h is not interrupted, it is understood that the residual stress was not sufficiently suppressed. That is, shallow and narrow quenching so that the heat treatment cured layer h is interrupted contributes to the suppression of residual stress, but even if it is simply shallow, if the heat treatment cured layer h is connected, it does not contribute to the suppression of residual stress, The variation in the outer diameter D1 of the spigot increases.

  Further, in (b) to (d), the target depth becomes deeper in this order, so that the heating time becomes longer accordingly, and as a result, in the case of (d), (b) and (c) In comparison, the axial dimension X of the portion where the heat treatment cured layer h is interrupted is small. When the depth is further deeper than (d), it is difficult to reliably ensure that the heat-treated cured layer h is disconnected. Accordingly, the heat-treated hardened layer in the contact angle direction of the track is formed to be shallow and narrow at 2.0 to 3.5 mm so as to be interrupted in the axial direction between the double-row tracks, thereby suppressing the residual stress. preferable.

  Similarly, with respect to the inner shaft 3, the evaluation results of the variation in the outer diameter D2 of the spigot (FIG. 1) and the collapse of the flange portion 3b are shown in Table 2 and FIG. (A) to (c) in Table 2 correspond to (a) to (c) in FIG. Note that the conditions for the heat treatment are omitted.

  From Table 2 and FIG. 3, the standard value-based evaluation is good, but only (c) is good in the evaluation viewed from a high level target that is ½ of the standard value. (A) and (c) are substantially the same in the depth of the heat-treated hardened layer h in the contact angle direction of the track 3a, but the values of the variation in the outside diameter D2 of the spigot and the collapse of the flange 3b are greatly different. . As in the case of the outer ring 2, this is shallow so that the heat-treated hardened layer h is interrupted in the axial direction between the double-row tracks (the other track is positioned in the axial direction corresponding to the track 4b of the inner ring 4). It is understood that this is a result of the residual stress being suppressed by being formed narrow. In addition, it is understood that (b), although the heat treatment hardened layer h is not interrupted, the residual stress is not sufficiently suppressed despite aiming shallower than (a) and (c).

As described above, in both cases of the outer ring 2 and the inner shaft 3, shallow and narrow quenching so that the heat-treated hardened layer h is interrupted contributes to the suppression of residual stress. If h is connected, it does not contribute to the suppression of the residual stress, and the variations in the outer diameters D1 and D2 of the spigot and the collapse of the flange portion 3b increase. That is, the outer ring 2 and the inner shaft 3 are formed by quenching shallowly and narrowly so that the heat-treated hardened layer h is interrupted to suppress the residual stress, and reducing variations in the outer diameters D1 and D2 of the spigot and the collapse of the flange portion 3b. In both cases, the subsequent turning process can be made unnecessary.
Moreover, in order to suppress residual stress reliably, the axial direction dimension X of the part where the heat treatment hardened layer h is interrupted is equal to or greater than the lower limit value in FIGS. 4.0 mm or more is appropriate. This is substantially the same for the inner shaft 3.

  In addition, it is preferable that the heat treatment hardened layer interrupted in the axial direction between the double-row tracks as described above is formed on both the outer ring 2 and the inner shaft 3, but such heat treatment hardened layer is formed on only one of them. However, even if the other is conventional, the effect of process reduction can be obtained in that one of the turning processes can be omitted.

It is sectional drawing of the rolling bearing apparatus for wheels by one Embodiment of this invention. It is a figure which shows the state of the heat processing hardening layer of an outer ring | wheel. It is a figure which shows the state of the heat processing hardening layer of an inner shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing apparatus for wheels 2 Outer ring 2a, 2b Track 3 Inner shaft 3a Track 4 Inner ring 4b Track 5, 6 Rolling element h Heat treatment hardening layer

Claims (2)

An outer ring in which a double-row track is provided in the heat-treated hardened layer formed on the inner peripheral surface;
An inner shaft provided with a track facing one of the tracks of the outer ring in the heat-treated hardened layer formed on the outer peripheral surface;
An inner ring fitted to the inner shaft and provided with a track on the outer peripheral surface facing the other track of the outer ring;
A rolling element mounted between each track of the outer ring and the track of the inner shaft and the track of the inner ring opposed to each track;
The heat-treated hardened layer formed on at least one of the outer ring and the inner shaft is formed to be shallow and narrow so as to be interrupted in the axial direction between the double-row tracks so as to suppress residual stress. Rolling bearing device.   The rolling bearing device for a wheel according to claim 1, wherein the dimension of the portion interrupted in the axial direction is 4.0 mm or more.

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