JPH0655945A - Bearing structure for differential device - Google Patents

Abstract

PURPOSE:To reconcile reduction of uneven abrasion of a bearing and facilitation of pre-load setting by reducing a press-in load of this inner race even if a fastening margin of the inner race of the bearing is set large to a drive pinion shaft. CONSTITUTION:In a bearing structure of a differential device constituted in such a way that a drive pinion shaft 12 is supported rotatably freely with a bearing 30 to a differential gear 10, and a pre-load is set when shaft force based on fastening of a nut to this drive pinion shaft 12 is made to act through an inner race 32 of the bearing 30, annular grooves 36 are formed on the inner peripheral surface of the inner race 32 in the bearing 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a differential gear which is a final reduction gear for a drive train of a vehicle.

[0002]

2. Description of the Related Art For example, in Japanese Utility Model Publication No. 2-36735,
A bearing structure for a drive pinion shaft in a differential device is disclosed. As shown in this publication, the drive pinion shaft is rotatably supported on the differential carrier by front and rear bearings (tapered roller bearings). Then, in the assembling process of this differential device, an axial force is applied to the inner race of the front bearing based on the tightening torque of the nut with respect to the front end of the drive pinion shaft, whereby preload (preload) setting of both bearings is performed. Done.

[0003]

Among the bearings, the inner race of the front bearing in particular cannot transmit a large amount of the axial force to the other, so that the tightening margin for the drive pinion shaft cannot be increased. Uneven wear is likely to occur. The cause of this uneven wear is said to be the minute slip that occurs between the race surface and the roller.
It was found that this can be suppressed by increasing the tightening margin of the inner race (making it tighter). However, if the tightening allowance is increased, the press-fitting load of the inner race on the drive pinion shaft naturally increases and exceeds the tightening limit torque of the nut, so that the preload cannot be set. Therefore, it has been considered difficult to reduce uneven wear of the front bearing and easily set the preload.

A technical problem of the present invention is that even if the tightening margin of the inner race of the bearing with respect to the drive pinion shaft is set to be large, the press-fit load of this inner race is kept small to reduce uneven wear of the bearing and to easily set the preload. It is to achieve compatibility with

[0005]

In order to solve the above-mentioned problems, the bearing structure of the differential device according to the present invention is constructed as follows. That is, the drive pinion shaft is rotatably supported by the bearing with respect to the differential carrier, and the bearing of the differential device in which the preload is set by applying an axial force based on the tightening of the nut to the drive pinion shaft through the inner race of the bearing. In the structure, an annular groove is formed on the inner peripheral surface of the inner race of the bearing.

[0006]

According to this structure, the contact area between the drive pinion shaft and the inner race of the bearing is
It becomes smaller by the amount of the annular groove formed in the inner race. For this reason, even when the tightening margin of the inner race with respect to the drive pinion shaft is set to be large when the differential device is assembled, the press-fitting load can be suppressed to be small. Therefore, the setting work of the preload by tightening the nut can be easily performed as before, and the uneven wear of the bearing is reduced.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 2 is a sectional view showing the bearing structure of the differential device. As is apparent from this drawing, the drive pinion shaft 12 incorporated in the differential carrier 10 is rotatably supported with respect to the carrier 10 by a front bearing 30 and a rear bearing 40 using tapered roller bearings. . A drive pinion 14 that meshes with a ring gear of a differential case (not shown) is integrally formed at the rear end of the drive pinion shaft 12, and a spline 16 and a spline 16 follow at the front end. The male screw 18 is formed.

The cylindrical portion of the companion flange 20 is fitted to the spline 16 of the drive pinion shaft 12 so that torque can be transmitted. A nut 22 is fastened to the male screw 18 of the drive pinion shaft 12. The axial force applied to the companion flange 20 according to the tightening torque of the nut 22 acts on the inner race 32 of the front bearing 30 through the tubular portion thereof. On the other hand, the axial force in the opposite direction to the drive pinion shaft 12 applied by tightening the nut 22 is
The rear bearing 40 through the drive pinion 14
It acts on the inner race 42. In this way, axial forces in opposite directions acting on the inner races 32, 42 of the bearings 30, 40 are received by the spacer 24 interposed between the inner races 32, 42 on the one hand, and by the spacer 24 on the other hand. It is received by the differential carrier 10 through the respective rollers 34, 44 and the outer races 33, 43. As a result, both bearings 3
Preloads of the same magnitude are applied to 0 and 40, respectively.
This preload is adjusted by the tightening torque of the nut 22.

A part of the front bearing 30 is shown in an enlarged sectional view in FIG. As is apparent from this drawing, the inner race 3 in the front bearing 30 is
On the inner peripheral surface of 2, two annular grooves 36 are formed in a portion that avoids both axial end portions and the central portion. Therefore, the inner peripheral surface of the inner race 32 comes into contact with the drive pinion shaft 12 only at both end portions and the central portion. Generally, the fitting stress σ of the inner race of the bearing with respect to the shaft is obtained by the following mathematical formula 1, and the press-fitting load P is obtained by the mathematical formula 2.

[0010]

[Equation 1] Mathematical Expression 2 P = σ × πdB In these expressions, E is the longitudinal elastic modulus, Δde is the effective interference of the fitting portion, di is the average inner diameter of the inner race, d is the shaft diameter, and B is the fitting portion length. . From the above formula, it can be seen that the press-fit load P is proportional to the tightening margin Δde.

On the other hand, FIG. 3 shows the front bearing 30.
The relationship between the tightening margin of the inner race 32 and the worn area of the roller 34 is shown based on the measurement data of the test. From FIG. 3, by increasing the tightening margin of the inner race 32 (making it tight), the wear area of the roller 34 is obviously reduced. Further, in FIG. 4, when the tightening margin of the inner race 32 is small (see A in FIG. 4) and in the middle (B in FIG. 4).
(See FIG. 4) and a large case (see FIG. 4C), the wear shape of the roller 34 is shown. As is clear from this drawing, the uneven wear of the roller 34 decreased as the tightening margin of the inner race 32 increased, and in the case shown in FIG. 4C, the uneven wear of the roller 34 was almost eliminated.

The tightening margin of the inner race 32 and the press-fitting load thereof are in a proportional relationship as described above,
In the present embodiment, the annular groove 36 of the inner race 32 apparently reduces the length B of the fitting portion in the above mathematical expression 2. That is, the contact area between the inner peripheral surface of the inner race 32 and the drive pinion shaft 12 becomes small, and even if the tightening margin of the inner race 32 is, for example, 35 μm or more, the press-fitting load can be suppressed to the same level as the conventional one. Becomes Particularly, the press-fitting load of the inner race 32 on the front bearing 30 needs to be kept within a range in which the preload can be set based on the tightening torque of the nut 22, which is possible in the present embodiment.

[0013]

As described above, according to the present invention, the tightening margin of the bearing can be set large while the press-fitting load of the inner race of the bearing with respect to the drive pinion shaft is kept within the range as before, and the bearing deviation can be set. Wear can be reduced and preload can be easily set.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing a part of a front bearing.

FIG. 2 is a cross-sectional view showing a bearing structure of a differential device.

FIG. 3 is a characteristic diagram showing the relationship between the tightening margin of the inner race and the wear area of the roller.

FIG. 4 is an explanatory view showing the wear shape of the roller for each tightening margin of the inner race.

[Explanation of symbols]

 10 Differential Carrier 12 Drive Pinion Shaft 22 Nut 30 Bearing (Front Bearing) 32 Inner Race 36 Annular Groove

Claims (1)

[Claims] 1. A drive pinion shaft is rotatably supported by a bearing with respect to a differential carrier, and a preload is set by applying an axial force based on the tightening of a nut to the drive pinion shaft through an inner race of the bearing. A bearing structure for a differential device, wherein an annular groove is formed on an inner peripheral surface of an inner race of the bearing.