JP2748060B2 - Strengthening method of rear axle housing for automobile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for enhancing the fatigue strength of a rear axle housing of an automobile.

[0002]

2. Description of the Related Art The lower surface of a rear axle housing used in an automobile is subjected to a tensile stress due to the weight of the vehicle and a dynamic load accompanying traveling. In order to increase the strength of the rear axle housing used under such severe conditions, conventionally, after quenching the rear axle housing, it is tempered to a relatively high temperature to form a troostite or sorbite structure. There were many.

However, such refining requires quenching and tempering, which requires a great deal of time, so that the processing efficiency is poor. Furthermore, it is necessary to heat the parts that do not necessarily need to be strengthened in the same way as the parts that need to be strengthened, and if the rear axle housing is made thinner and lighter to reduce the weight of the car, the strength will be increased accordingly. Was reduced.

In order to solve such a problem, for example, as disclosed in JP-A-59-24543, the rear axle housing is formed of a casting, and after machining each part, the rear axle housing is formed on the surface of the rear axle housing. It is also effective to perform shot peening.

[0005] However, in the case where improvement in strength is desired in spite of being forced to reduce the weight as in recent years, there is a problem that it is not always possible to achieve sufficient reinforcement only by performing shot peening.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the fatigue strength of a rear axle housing for an automobile without increasing the weight.

[0007]

In order to solve the above-mentioned problems, the present invention provides an automobile having a spring seat formed on an upper surface.
Support each end of the rear axle housing for
The shot peening is performed on the lower surface of the rear axle housing while applying a compressive load to the spring seat .

[0008]

When a compressive load is applied to the spring seat formed on the upper surface of the rear axle housing supported at both ends, the load is applied as a bending external force to the rear axle housing, and a tensile stress is generated on the lower surface of the rear axle housing. . When the lower surface of the rear axle housing to which the tensile stress is applied is shot peened to extend its surface layer and the load on the spring seat is removed, a high compressive residual stress is applied to the lower surface of the rear axle housing. Is left.

Therefore, according to the automobile using the rear axle housing subjected to the strengthening treatment according to the present invention, the tensile stress generated on the lower surface of the rear axle housing due to the weight of the vehicle body is effectively canceled by the compressive residual stress. As a result, the fatigue strength of the rear axle housing is further increased. Therefore, the fatigue strength of the rear axle housing can be increased without increasing the weight, or the rear axle housing can be made thinner and lighter without reducing the fatigue strength.

[0010]

FIG. 1 is a schematic front view showing an example of a processing state by a method for strengthening an automobile rear axle housing according to the present invention, wherein axle pipes 2 and 2 are provided at both ends of a banjo type automobile rear axle housing 1. And springs 3, 3 are formed on the upper surface 1a of the rear axle housing 1, so that springs (not shown) attached to the spring seats 3, 3 are attached to the vehicle body. 4 and 4 are the rear axle housings 1 corresponding to the spring seats 3 and 3, respectively.
Arm for mounting a spring provided on the upper surface 1a of the
Reference numeral 5 denotes an arm for mounting a torque rod provided on the lower surface 1b of the rear axle housing 1.

Rear axle housing 1 constructed as described above
In order to improve the fatigue strength of the axle pipes 2, 2, the present invention applies a downward load P to the spring seats 3, 3 with the lower surfaces of the axle pipes 2, 2 placed on the fulcrums 6, 6. The load P functions as an external bending force to apply a tensile stress to the lower surface 1b of the rear axle housing 1.

The lower surface 1b of the rear axle housing 1 to which the tensile stress has been applied in this way is subjected to shot peening to harden the surface. 7, 7 are shots to be ejected.

That is, since shot peening is applied to the lower surface 1b of the rear axle housing 1 while a tensile stress is applied to the lower surface 1b, the surface layer of the lower surface 1b of the rear axle housing 1 Subject to plastic deformation due to collision. For this reason, external force P is removed (unloading) at the end of shot peening.
Then, a large compressive stress is left on the lower surface 1b of the rear axle housing 1.

Therefore, in an automobile having the rear axle housing 1 reinforced in this manner, a tensile stress is applied to the lower surface 1b of the rear axle housing 1 due to the weight of the vehicle, and the lower surface 1b
Even if a dynamic stress is applied, the tensile stress due to the vehicle weight or the like is effectively canceled by the compressive residual stress, and the fatigue strength of the rear axle housing 1 is further increased.

Therefore, the fatigue strength of the rear axle housing 1 can be increased without increasing the weight of the rear axle housing 1, or the rear axle housing 1 can be made thinner and lighter without reducing the fatigue strength. .

A compressive load is applied to the spring seats 3, 3 with both ends (axle pipes 2, 2) of the rear axle housing 1 as fulcrums, and a tensile load is generated on the lower surface thereof.
The rear axle how
Load in comparison with the case where tensile load is applied to the entire jing 1
The device can be downsized and simplified.
The support stability of the through housing is enhanced, and the distribution of the tensile stress generated on the lower surface 1b of the rear axle housing 1 can be approximated to the distribution of the tensile stress generated by the vehicle weight . Accordingly, a distribution of the compressive residual stress in a state closer to an ideal state is obtained as compared with a case where a load P is applied with the other portion as a fulcrum or a tensile stress is generated on the lower surface of the rear axle housing 1 by another method.
And economical enhancement without excess or shortage.

[0017]

As is apparent from the above description, according to the present invention, it is possible to efficiently reinforce only necessary parts without performing refining with poor processing efficiency.
The fatigue strength of the rear axle housing can be significantly improved without increasing the weight, or
The rear axle housing can be made thinner and lighter to reduce the weight of the vehicle body. Also, rear axle how
Compressive load on spring seat with both ends of jing as fulcrum
To generate a tensile load on the lower surface
For example, pulling the entire rear axle housing
Simplify the size of the load device compared to when a load is applied
Able to support the rear axle housing
Stability can be increased and the rear axle
The distribution of the tensile stress generated on the underside of the housing is determined by the vehicle weight.
Distribution of tensile stress generated on the lower surface of the housing
To a more ideal state
Distribution of the compressive residual stress in the solid state.
Can be made economically.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an example of a processing situation by a method for reinforcing a rear axle housing for a vehicle according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 rear axle housing 1a upper surface 1b lower surface 2 axle pipe 3 spring seat 6 fulcrum 7 shot P load

Claims (1)

(57) [Claims] 1. An automatic apparatus having a spring seat formed on an upper surface.
Support both ends of the rear axle housing
While applying a compressive load to the spring seat,
Shot peening on the underside of the axle housing
A method of reinforcing of the rear axle housing for a motor vehicle, characterized in that to.