JPH0277303A - Structure of wheel bearing section - Google Patents

Abstract

PURPOSE:To prevent fatigue strength from lowering by applying induction hardening to the portion from the vicinity of the corner section of a hub body to the outer bearing pivoting portion of a sleeve section through the corner section in the structure of a wheel bearing section used for a car or the like. CONSTITUTION:An induction hardening end section 2g is not to be further than the width center position of an outer bearing 3a whose actual stress is small because of being pivoted by the outer bearing 3a, and the total induction hardening depth of the vicinity of the corner section 2c is to be from 7 to 8mm and to be made shallower gently and continuously in order as hardening portions approach from the corner section 2c to the pivoting portion of the outer bearing 3a. This makes it possible to obtain higher strength than conventional type structure resulting in the reduction in weight. In addition, the reduction of a hardening range leads to the introduction of an induction hardening equipment of small output resulting in the shortening of hardening time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wheel bearing structure, particularly to a wheel bearing structure used in automobiles and the like.

(Prior art) The conventional wheel bearing structure has a drive v2 as shown in FIG.
A serration 1a is carved on the outer periphery of the joint stem 1 which is rotatably driven from a position through a joint stem 1, and a serration 1a is provided with a hub body 2a and a sleeve portion 2b extending integrally from the hub body 2a. A hub 2 consisting of
The hub 2 and the joint stem 1 are fixed together via the washer 1d by a tightening nut IC that is screwed into the threaded part 1b formed at the top of the joint stem 1, and the hub 2 is fitted onto the outer periphery of the sleeve part 2b. It is rotatably supported by the housing 4 via an outer bearing 3a and an inner bearing 3b (see Japanese Patent Publication No. 57-14532). As shown by hatching in FIG. 3, the hub 2 has improved wear resistance over the entire length of the sleeve portion 2b of the hub 2 and the rising edge i2d near the corner portion 2C via the corner portion 2C.
Fully hardened by induction hardening to improve fatigue strength
2e is formed.

Stress in the sleeve portion 2b caused by repeated loads from the wheels is applied to the bearing 3as3b in the area supported by the outer bearing 3a1 and the inner bearing 3b.
Due to the influence of the stiffness of the inner ring of the bearing 3, although it is small,
In areas other than the support area by as3b, the sleeve part 2
You will receive only b.

Therefore, the stress becomes large in the portions of the sleeve portion 2b other than the portions supported by the bearings 3ax3b.

Furthermore, large tensile residual stress is generated at the end of the induction hardened region, which is a factor that greatly reduces fatigue strength. Therefore, induction hardening is performed over a wide range so that the end of the induction hardening becomes the end 2f of the sleeve portion 2b to prevent the fatigue strength from decreasing.

(Problem M to be solved by the invention) As mentioned above, the conventional induction hardening applied to hubs requires a high-output induction hardening device because it is performed over a wide area, and furthermore, induction hardening takes a long time, so it is difficult to manage At the same time, this has led to a rise in equipment costs and, therefore, an increase in product costs.

Further, in the sleeve portion 2b other than the supporting portion of the bearing 3at3b, there is a portion where the apparent section modulus of the sleeve is low. If the range of induction hardening reaches the end of the sleeve, high tensile residual stress may occur inside the region with a low section modulus. In such a case, there is a possibility that the expected improvement in fatigue strength may not be obtained.

As a countermeasure to this problem, there have been cases in which it has been necessary to increase the diameter of the sleeve portion.

Therefore, in view of the above points, the present invention makes it possible to perform induction hardening in a short time using equipment with low output by reducing the range of induction hardening, and by reducing the diameter of the sleeve portion, the overall size can be reduced. An object of the present invention is to provide a wheel bearing structure that can reduce weight.

(Means for Solving the Problems) The present invention has a hub consisting of a hub body and a sleeve portion integrally extended through a corner portion of the hub body, which is fitted onto the outer periphery of a geo-ind stem, and the outer periphery of the sleeve portion is lined up. In a bearing structure that is rotatably supported on a housing via two bearings, an inner bearing and an outer bearing, the distance from the vicinity of the corner of the hub body to the outer bearing support part of the sleeve through the corner It is characterized by being induction hardened.

(Example) Examples of the wheel bearing structure of the present invention will be described below with reference to FIGS. 1 and 2. Note that in Figures 1 and 2, the 3rd
For convenience of explanation, parts corresponding to the figures are given the same reference numerals.

Serrations 1a are provided on the outer periphery of a closed stem 1 which is rotationally driven by a drive device via a diagonal. The hub 2 that fits into the serrations 1a to attach and rotate a wheel (not shown) consists of a hub body 2a on a disk to which the wheel is attached, and a corner portion 2c of the hub body 2a.
A sleeve portion 2b protruding in a cylindrical shape through the hub body 2
It is formed integrally with a. The inner peripheral surface of the sleeve portion 2b is provided with serrations that engage with the serrations la formed on the outer periphery of the closed stem 1, so that the closed stem 1 and the hub 2 are engaged so that they do not rotate relative to each other. death,
A tightening nut lc is screwed into a threaded portion 1b provided at the tip of the sealed stem 1, and the hub 2 and the sealed stem 1 are firmly connected via a washer 1d. The outer periphery of the sleeve portion 2b is connected to the housing 4 by an outer bearing 3a and an inner bearing 3b arranged at an appropriate distance apart.
The housing 4 and the hub 2 are rotatably attached to each other.

Reference numeral 3C denotes a seal that protects rotating members such as the outer bearing 3a and inner bearing 3b from muddy water and the like entering from the outside, and prevents grease and the like filled inside from flowing out.

As shown in FIG. 2, which shows an enlarged view of the continuous portion of the hub body 2a and sleeve portion 2b of the hub 2 having the wheel bearing structure configured as described above, tensile residual stress is generated in the induction hardening area. The end portion 2g of the induction hardening where the strength decreases is supported by the outer bearing 3a and extends to the width center position of the outer bearing 3a where the generated stress is small, and the total hardened layer depth l due to the induction hardening near the corner portion 2c is set to 7 to 7. By cooling slowly at a depth of 8, the gradient of decrease in hardness in the depth direction from the effective hardened layer near the corner 2c is made gentler, reducing residual stress and preventing a decrease in strength, thereby preventing cracks, etc. In addition, by making the total hardened layer depth gradually shallower as it moves from the corner portion 2c to the support portion of the outer bearing 3a, the residual stress in the axial direction at the end of the induction hardening can be reduced. This reduces the occurrence of fatigue and prevents a decrease in fatigue strength.

In order to confirm the effects of induction hardening described above, the following strength test was conducted. A rotary bending fatigue strength test was performed by repeatedly applying a moment load of 130 gfm to a test frame of the same shape as hub 2 by forging and quenching and tempering carbon steel 543C. As a result, it broke near corner 8B 2 c after 130,000 bending tests. occurred. In addition, similar to the above, a test piece of carbon steel 543G forged and tempered was subjected to induction hardening from the rising part 2d near the corner part 2c of the hub body 2a to the end part 2f of the sleeve part 2b, and the rotating bending fatigue strength was obtained under the same conditions as above. As a result of the test, the sleeve part 2b broke due to the edge turning load applied 700,000 times, and the test piece that had been induction hardened from the thick wall part 2h of the hub body 2a to the end part 2f of the sleeve part. Cracks occurred in the sleeve portion 2b due to repeated loading of 580,000 to 800,000 times.

In contrast to these rotating bending fatigue strength test results, the test piece subjected to the induction hardening of the present invention showed that the thick part 2h of the hub body, which is a part that has relatively little influence on actual driving, was tested! Slight cracks were discovered after 930,000 repeated loads.

These test results also show that the depth of the entire hardened layer of induction hardening near the corner portion 2c of the hub is increased, and the outer bearing 3a
It has been found that the hub of the present invention, in which the width of the bearing portion of the hub is made gradually shallower toward the center of the width, has a special effect.

(Effects) According to the present invention, high strength can be obtained compared to conventional methods by applying induction hardening only to a narrow area from the vicinity of the corner of the hub body to the outer bearing support of the sleeve. This not only increases the degree of freedom in the design of the wheel bearing structure, but also reduces the weight.As the hardening range is reduced, induction hardening equipment with a small output is sufficient, and the hardening time is reduced. It is expected that the time period will be shortened and manufacturing costs will be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a detailed explanatory diagram of the present invention, FIG. 2 is an explanatory diagram of the main part thereof, and FIG. 3 is an explanatory diagram of a conventional example. 1... White stem, 2... Hub, 2a...
Hub body, 2b...Sleeve part, 2C...Corner part, 3a...Outer bearing, 3b...Inner bearing, 4...Housing

Claims (3)

[Claims] (1) A hub consisting of a sleeve part integrally extended through the hub body and the corner part of the hub body is fitted onto the outer periphery of the joint stem, and two inner bearings and an outer bearing are arranged side by side on the outer periphery of the sleeve part. In a bearing structure rotatably supported by a housing via a bearing,
A wheel bearing structure characterized in that a region from near the corner of the hub body to the outer bearing support portion of the sleeve through the corner is induction hardened. (2) A claim characterized in that the total hardened layer depth of the induction hardening near the corner portion of the hub is deepened, and the total hardened layer depth gradually becomes shallower as it moves to the support portion of the outer bearing. Structure of the first term. (3) The structure according to claim 2, wherein the total hardening layer depth of the induction hardening near the corner portion of the hub is about 7 to 8 mm.