JP2000085392A - Axle case center cover - Google Patents

Abstract

(57) [Problem] To provide a center cover capable of increasing bending rigidity of an axle case and reducing stress concentration. SOLUTION: A center cover 23 having bulges 25 and 26 formed on both left and right sides of a substantially bottomed cylindrical central body 24 is welded to an axle housing 9 of an axle case 22. The bulging portions 25 and 26 of the center cover 23 have linear portions 27 and 28 and ribs.
30 and 31 are formed, and the oil plug hole 37
The flat part 32 for drilling a hole is recessed, and the inclined parts 33 and 34
Are formed to provide rib-like portions 35 and 36. The bulging portions 25 and 26 having the ribs 30 and 31 can increase bending rigidity in the front-rear direction of the axle case 22 and reduce stress concentration. The flat portions 32 can be formed by the inclined portions 33 and 34 and the rib portions 35 and 36 without lowering the bending rigidity of the center cover 23. As a result, the plate thickness of the axle case 22 can be reduced, and the unsprung weight can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center cover of an axle case for supporting a drive shaft of a vehicle such as an automobile.

[0002]

2. Description of the Related Art As an example, an axle suspension system for a rear wheel (drive wheel) of an automobile will be described with reference to FIG. The arrow F in the figure indicates the front of the vehicle (same in each figure). As shown in FIG. 8, the suspension device 1
A so-called five-link type rear wheel suspension device, comprising two lower links 4 and two upper links 5 extending in the longitudinal direction of the vehicle through a rear axle 3 connecting left and right hubs 2 (wheels);
It is positioned by one lateral link 6 extending in the vehicle width direction, and has a structure in which a suspension spring 7 and a hydraulic shock absorber 8 are interposed between the rear axle 3 and a vehicle body (not shown).
The reaction force of the driving force and braking force of the wheel is mainly the lower link 4
The upper link 5 and the lateral link 6 mainly receive the lateral load.

The rear axle 3 includes an axle housing 9 at the center and an axle case 12 including left and right axle tubes 10 and 11, and a differential gear (not shown) and a final gear supported by a differential carrier 13 in the axle housing 9. (Not shown), and a drive shaft (not shown) is inserted into the axle tubes 10 and 11 to form an integral structure. The hub 2 is connected to the drive shaft and protrudes from the differential carrier 13. A propeller shaft (not shown) is connected to a drive pinion shaft 14 of the final gear.

Next, regarding the conventional axle case 12,
This will be described with reference to FIGS. As shown in FIG. 9 and FIG. 10, the axle case 12 is formed by welding housing members 15 and 16 each having a substantially semi-circular arc shape, which is divided into upper and lower halves, and having an interior space for accommodating a differential gear and a final gear. A housing 9 is formed, and an axle tube 10 is welded to both ends of the axle housing 9 so that the insides thereof can communicate with each other. A substantially bottomed cylindrical center cover 18 is welded to the axle housing 9 so as to cover a circular opening 17 formed at one end (rear end) thereof so as to face the differential gear and the final gear. Further, a differential carrier 13 having a differential gear and a final gear mounted thereon is attached by a bolt 19 to a circular opening formed on the other end (front end) side. In FIG. 10, the welded portions of the respective members are indicated by oblique lines.

[0005] The bottom of the center cover 18 is formed in a substantially spherical shape so that half of the axle tube 10 side (left side) is convex outward, and half of the axle tube 11 side (right side) is formed flat. An oil plug hole 21 is provided in the flat portion 20 formed on the axle tube 11 side.

[0006]

When a front-rear load is applied to the rear axle 3 due to a driving force, a braking force, or the like of the vehicle, a stress generated in the axle case 12 causes a circular welding between the axle housing 9 and the center cover 18. It has been found that the information is concentrated at four locations (upper, lower, left and right) on the part (part A in FIG. 10). The direction of the maximum principal stress generated in the axle case 9 is shown in FIG. As shown in FIG. 11, since the cross section of the axle case 12 is rapidly increased at the mounting portion of the center cover 18 of the axle housing 9, the four welded portions (upper, lower, left and right portions B in FIG. 11) In ()), the line indicating the direction of the maximum principal stress is sharply dense.

FIG. 12 shows the analysis result of the stress distribution generated in the axle case 12 by the finite element method. The hatched portions in FIG. 12 indicate portions where a relatively large stress is generated, and four portions (upper, lower, left, and right) on the circular welded portion between the axle housing 9 and the center cover 18 (C in FIG. 12).
It can be seen that the largest stress is generated in the part (1).

As described above, since stress concentrates on the welded portion between the axle housing 9 and the center cover 18, the welded portion is easily broken. Therefore, in order to obtain sufficient strength, the thickness of each member must be reduced. It must be large enough. However, an increase in the plate thickness causes an increase in the unsprung weight of the suspension device, causing a deterioration in fuel efficiency, ride comfort and steering stability, and also causes a problem that the manufacturing cost of the axle case increases.

Also, as shown in FIG. 13, there is a conventional center cover 18A in which the front shape of the center cover 18A is substantially rhombic. In this case, the flexural rigidity of the axle case with respect to the longitudinal load is increased. Left and right tops of the diamond (Fig. 13
, The stress is concentrated on the portion (D) of FIG.

[0010] The present invention has been made in view of the above points, and has as its object to provide an axle case center cover capable of reducing stress concentration.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 includes an axle housing for accommodating a differential and a final gear and having an opening opposed thereto, and an axle housing for the axle housing. A center cover that is mounted on an axle case having an axle tube coupled to the left and right sides and through which a drive shaft is inserted, and that covers an opening of the axle housing; In addition, the base end portion smoothly connected to the central body portion is the widest, the width gradually narrows toward the left and right end portions, and a bulging portion is formed in which the left and right end portions are the narrowest linear portions. It is characterized by having been done.

With this configuration, the bending rigidity of the axle case in the front-rear direction is increased, and the shape and size of the cross section gradually changes from the left and right axle tubes toward the center axle housing. , Stress is dispersed.

According to a second aspect of the present invention, in the configuration of the first aspect, the bulging portion is formed with a rib extending in the left-right direction from the central body to the linear portion. .

With this configuration, the bending rigidity of the axle case in the front-rear direction is increased.

[0015] The invention of claim 3 provides the above-mentioned claim 1 or 2
Wherein the bottom of the central body portion is formed in a curved shape convex outward.

With this configuration, the space inside the center cover is increased, and the rigidity of the bottom is increased.

According to a fourth aspect of the present invention, in the configuration of the third aspect, a flat portion having an oil plug hole is recessed on one of the left and right sides of the bottom of the central body portion. A rib-shaped portion extending in the left-right direction is formed vertically.

With this configuration, a flat portion can be formed by the rib-shaped portion without lowering the bending rigidity, and an oil plug can be provided in the axle housing.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The axle case according to the present embodiment has a structure generally similar to that of the conventional example shown in FIGS. 9 to 11 except that the shape of the center cover is different. The same parts as those described above are denoted by the same reference numerals, and only different parts will be described in detail.

As shown in FIGS. 1 to 5, in the axle case 22 according to the present embodiment, a center cover 23 is welded to the axle housing 9 so as to cover the opening 17 at one end. The center cover 23 has bulging portions 25 and 26 formed by bulging the left and right sides of a substantially bottomed cylindrical central main body 24 in the front shape shown in FIG. The left and right bulges 25 and 26 are the widest at the base end that smoothly connects to the center main body, and gradually narrow toward the left and right ends.
Straight portions 27 and 28 having the narrowest width W are formed at both left and right ends.

The bottom of the center main body 24 is formed in a substantially spherical shape (curved surface) convex outward, and has a side surface shown in FIG.
The center of the bottom of the central body 24 is the highest, and the left and right bulges 25,
26 has the highest height H on the side of the central body 24, and is gently inclined to form straight portions 27 and 28 having the lowest height H at both ends. The left and right bulges 25 and 26 extend in the center and in the left-right direction, respectively, and have one end smoothly connected to the spherical bottom of the central body 24 and the other end connected to the linear portions 27 and 28. rib
30 and 31 are projected.

On one side (right side in the figure) of the left and right sides of the central main body 24, there is formed a flat portion 32 which extends substantially in parallel with the mounting surface 29 to the axle housing 9. The flat portion 32 is formed such that one side is connected to the rib 31 of the right bulging portion 26 and is connected to the spherical portion at the bottom of the central main body 24 through the inclined portions 33 and 34 formed on both sides in the vertical direction. Have been. As a result, the rib-like portions 35 extending in the horizontal direction above and below the flat portion 32,
36 are formed. The flat portion 32 is provided with an oil plug hole 37 (screw hole) into which an oil plug (not shown) is mounted.

The center cover 23 is formed with a flange 38 over the entire periphery of the mounting surface 29 to the axle housing 9. By welding the flange 38, the center cover 23 is attached to the axle housing 9. It is to be combined.

The operation of the embodiment constructed as described above will now be described.

The axle case 22 accommodates a differential gear and a final gear supported by the differential carrier 13 in the axle housing 9 and inserts a drive shaft into the left and right axle tubes 10 and 11 in the same manner as the conventional zero. The hub 2 of the wheel is attached to both ends of the rear axle 3 to constitute the rear axle 3, and the lower link 4 of the suspension device,
The upper link 5, the suspension spring 7, and the hydraulic shock absorber 8 support the vehicle body.

In the axle case 22 according to the present embodiment,
By forming the bulging portions 26 and 27 on the left and right sides of the center cover 24, the bending rigidity against the load in the front-rear direction is increased, and the cross section from the left and right axle tubes 10 and 11 to the central axle housing 9 side is increased. Since the shape and size gradually change, the stress can be dispersed,
Breakage due to stress concentration can be prevented. FIG. 6 shows the direction of the maximum principal stress generated in the axle case 22. FIG.
As shown in FIG. 11, the curve representing the direction of the maximum principal stress does not sharply become dense as compared with the conventional case in FIG. 11, and excessive stress concentration is prevented.

At this time, by forming the ribs 30 and 31 extending in the left-right direction on the bulging portions 26 and 27, the bending rigidity against the load in the front-rear direction can be effectively increased. Since the linear portions 27 and 28 are provided at the left and right ends of the center cover 27, stress is not concentrated on the left and right ends of the center cover as in the conventional diamond shape shown in FIG.

On both sides of the flat portion 32 in the vertical direction, inclined portions 33,
By forming the ribs 35 and 36 by forming the flat portion 32, the flat portion 32 can be formed without lowering the bending rigidity of the center cover 23.
Can be formed, and by the inclined portions 33 and 34,
Stress concentration on the boundary between the spherical portion at the bottom of the central main body 24 and the flat portion 32 can be prevented.

In this manner, the flexural rigidity of the axle case 22 with respect to the load in the front-rear direction can be increased and the concentration of stress can be prevented, so that the plate thickness of the axle case 22 can be reduced, and the unsprung weight can be reduced. Therefore, it is possible to improve ride comfort, steering stability, and fuel efficiency by reducing fuel consumption, and to reduce manufacturing costs.

FIG. 7 shows the analysis result of the stress distribution generated in the axle case 22 by the finite element method. In FIG. 7, the hatched portion indicates a portion where a relatively large stress is generated, but no portion where the stress is excessively concentrated is recognized as compared with the conventional example in FIG.

In this embodiment, the rear axle is described as an example. However, the present invention is not limited to this, and is similarly applied to, for example, a front axle of a four-wheel drive vehicle and an axle case of an axle suspension device. can do. Further, in the present embodiment, the center cover is welded to the axle housing. However, the present invention is not limited to this, and the center cover is similarly detachably connected to the axle housing by bolts. Can be applied.

[0032]

As described above in detail, according to the center cover of the axle case according to the first aspect of the present invention, by providing the bulging portion, the bending rigidity of the axle case in the front-rear direction is increased, and Since the cross-sectional shape and size gradually change from the axle tube side toward the central axle housing side, stress is dispersed and stress concentration is prevented. As a result, the thickness of the axle case can be reduced, and the ride comfort is reduced by reducing the unsprung weight.
Steering stability and fuel economy can be improved, and manufacturing costs can be reduced.

According to the center cover of the second aspect of the present invention,
By providing the ribs on the bulging portion, the bending rigidity of the axle case in the front-rear direction can be increased.

According to the center cover of the third aspect of the present invention,
By forming the bottom of the center main body in a curved shape, the space inside the center cover can be increased and the rigidity of the bottom can be increased.

According to the center cover of the fourth aspect of the present invention, the flat portion having the oil plug hole is recessed and the rib-like portion is formed, so that the rib-like portion does not reduce the bending rigidity. Part can be formed,
An oil plug can be provided in the axle housing.

[Brief description of the drawings]

FIG. 1 is a perspective view of an axle case equipped with a center cover according to an embodiment of the present invention.

FIG. 2 is a perspective view of a center cover according to the embodiment of the present invention.

FIG. 3 is a front view of a center cover according to the embodiment of the present invention.

FIG. 4 is a side view of the center cover of FIG. 3;

FIG. 5 is an exploded perspective view of the axle case of FIG.

6 is a diagram showing the direction of the maximum principal stress generated when a load in the front-rear direction is applied to the axle case of FIG. 1;

FIG. 7 is a diagram showing a result of analysis by a finite element method of a stress distribution generated when a longitudinal load is applied to the axle case of FIG. 1;

FIG. 8 is a perspective view of an axle suspension device.

FIG. 9 is a perspective view of an axle case equipped with a conventional center cover.

FIG. 10 is an enlarged front view of the axle case shown in FIG. 9;

11 is a view showing the direction of the maximum principal stress generated when a load in the front-rear direction acts on the axle case of FIG. 9;

FIG. 12 is a diagram showing a result of analysis by a finite element method of a stress distribution generated when a longitudinal load is applied to the axle case of FIG. 9;

FIG. 13 is a front view of an axle case equipped with a conventional substantially diamond-shaped center cover.

[Explanation of symbols]

 9 Axle housing 10,11 Axle tube 17 Opening 22 Axle case 23 Center cover 24 Central body 25,26 Swelling part 27,28 Linear part 30,31 Rib 32 Flat part 35,36 Rib part 37 Oil plug hole

Claims (4)

[Claims] 1. An axle case having an axle housing for accommodating a differential and a final gear and having openings opposed thereto, and an axle tube coupled to both left and right sides of the axle housing to allow a drive shaft to pass therethrough. A center cover that covers an opening of the axle housing, wherein a base end portion that smoothly connects to the central body portion is the widest on both left and right sides of the substantially bottomed cylindrical central body portion; A center cover of an axle case, characterized in that the width gradually narrows toward the portion, and a bulging portion is formed, which is a linear portion having the narrowest left and right ends. 2. The axle case center cover according to claim 1, wherein a rib extending in the left-right direction from the central body portion to the linear portion is formed in the bulging portion. 3. The axle case center cover according to claim 1, wherein a bottom portion of the central main body portion is formed in a curved shape convex outward. 4. A flat portion having an oil plug hole is recessed on one of the left and right sides of the bottom of the central body portion, and rib-shaped portions extending in the left-right direction are formed above and below the flat portion. The center cover of an axle case according to claim 3, wherein: