JP2747768B2 - Undercarriage frame for trucks, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chassis frame for a truck or the like.

[0002]

2. Description of the Related Art A pair of left and right side rails extending in the vehicle longitudinal direction, and a plurality of cross members extending in the vehicle width direction and having both ends fixed to the side rails by rivets, bolts, and the like. In order to avoid interference with the bottom of the engine, the underframe on the front of the vehicle body on which the engine and transmission assembly are mounted An arcuate cross member is often used.

[0003] Due to the complexity of the shape, this type of cross member bent in the vertical direction has an upper and lower flange and a vertical web connecting the upper and lower flanges, each of which is a separate plate material. Although a welded structure having a work-shaped section formed and fixed integrally by welding is widely used, there is a disadvantage that the manufacturing cost is significantly increased.

Therefore, in order to greatly reduce the manufacturing cost of the cross member curved in the vertical direction, the cross member is bent similarly to a normal cross member extending substantially linearly in the vehicle width direction. The members were experimentally manufactured by press molding. The shape of the cross member is shown in the plan view of FIG. 3 and the front view of FIG.

[0005] In the drawings, reference numeral 10 generally indicates an undercarriage frame. The undercarriage frame extends in the front-rear direction of the vehicle body and has a pair of right and left side rails 12 each having a groove shape, and extends in the vehicle width direction. Further, a cross member 14 having both ends fastened to the side rail 12 by a fixing tool such as a rivet or a bolt is provided.

[0006] The cross member 14 is connected to the upper flange 1.
6 and a lower flange 18, and a longitudinal web 20 interconnecting one side edge of both flanges 16 and 18, having a groove-shaped cross-sectional shape, and both ends of the upper and lower flanges 16 and 18 in the vehicle width direction. The part is fastened to the upper and lower flanges 22 of the side rail 12 by rivets or bolts.

As best shown in the front view of FIG.
The cross member 14 as a whole has a large bow in the vertical direction and a downwardly convex bow shape. An engine mounting bracket 24 (not shown) is provided near an end of the web 20 adjacent to the side rail 12.
It is attached by a number of bolts 26.

As shown in the plan view of FIG. 3, the lower flange 18 is formed such that one-third to one-fourth of the entire length thereof is formed from the inner side in the vehicle width direction according to a normal design method. It is formed so as to gradually widen toward the rail 12 side, and in the illustrated case, the flange free edge 30 of the widened portion 18 'is formed so as to form a substantially quadratic curve.

The underframe 10 provided with the cross member 14 was subjected to tests by simulating the same load and running conditions as those of an actual vehicle, and the maximum stress occurring in each part of the cross member 14 was examined. The side rail 1 of the lower flange 18 as shown by the hatched portion P
It has been found that the maximum stress occurs in the nearest part adjacent to No. 2.

Now, the diagram of FIG. 2 in which the vertical axis indicates the maximum stress σ _max and the horizontal axis indicates the distance Xmm from the center line OO of the cross member 14 in the vehicle width direction will be described. Α shown by a chain line in the figure is a test result of the cross member 14 in which the free edge 30 of the widened portion 18 ′ of the lower flange has the shape shown in FIG. 3. Sigma ₁ in the figure shows the maximum stress acceptable from the viewpoint of durability, X _o represents the inner free edge of the flange 22 of the side rail 12. α-rays, the side rail nearest part p has exceeded the allowable limit stress sigma _1, this portion p is equivalent to high stress region P in FIG.

In order to reduce the maximum stress occurring in the high stress region P, the widened portion 18 'of the lower flange is further widened, and the shape of the free edge thereof is shown by a two-dot chain line in FIG. After performing the same test as described above, the maximum stress in the vicinity of the region P was reduced as shown by the dotted line β in the diagram of FIG. stress exceeding rectangular portion q to the allowable limit stress sigma ₁ of has been found to occur. The portion q in FIG. 2 corresponds to the high stress region Q in FIG.

As described above, when the shape of the lower flange 18 of the cross member 14 is designed by a normal setting method, it is difficult to ensure durability unless the flange width of the widened portion 18 'is further increased. Was confirmed. However, it is not preferable to further increase the flange width of the widened portion 18 'because of the increase in the weight, and the space required to avoid interference with the mounted engine and its auxiliary accessories. May not be feasible due to objective conditions.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a reasonable weight and dimensions.
Further, it is an object of the present invention to provide a chassis frame such as a truck having a cross member curved in the vertical direction, which has excellent durability and reliability and is extremely inexpensive as compared with the conventional welding structure.

[0014]

In order to achieve the above object, the present invention provides a pair of side rails extending in the front-rear direction of a vehicle body, and a pair of side rails extending in a vehicle width direction and having both ends arranged on the side rails. A cross member fixedly attached to the upper and lower flanges, wherein the cross member has a bow shape which is curved in the vertical direction as a whole and is convex downward, and one side of the upper and lower flanges. The cross member is formed by a press-formed material having a groove-shaped cross section composed of a vertical web connecting the edges, and the lower flange of the cross member gradually expands in width from the center portion in the vehicle width direction toward the side rail. And the free edge of the widened portion is a curved portion protruding toward the cross member web in the portion closest to the side rail and the cross member wing on the center side in the vehicle width direction therefrom. It proposes a chassis frame of the truck or the like, characterized in that it forms a gentle wave shape composed of a concave curved portion facing drive.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. (Note that members and portions that are substantially the same as or correspond to the cross member based on the conventional design method already described with reference to FIGS. 3 and 4 are denoted by the same reference numerals, and redundant description will be omitted. According to the present invention, the cross member 14 manufactured by press molding is used.
The shape of the free edge of the widened portion 18 ′ of the lower flange 18 is a first portion 30 a protruding toward the cross member web 20 at a portion closest to the side rail 12, and a cross member center line O from the first portion. The first portion 30a and the second portion 30b are smoothly connected as shown in the drawing, and are formed from a concave second portion 30b facing the cross member web 20 on the −O side.

The lower flange 18 of the cross member 14
The upper flange 1 of the cross member except for the planar shape of
6, the shape of the web 20, the side rail 12, the engine mount bracket 24, etc.
1 is substantially the same as that based on the conventional design method shown in FIG. 1, and therefore, the front shape of the chassis frame 10 shown in FIG. 1 is substantially the same as FIG.

[0017] Now, the radius of curvature R _a of the first portion 30a of the convex toward the cross member 20 of the lower flange 18, as a result of the maximum stress occurring in the region P in FIG. 3, was investigated by performing the same tests the as indicated by the solid line γ in FIG. 2 showing the flange width B _p that does not exceed the permissible limit stress sigma ₁ is set to be ensured.

On the other hand, the curvature radius _Rb of the concave second portion 30b facing the cross member web 20 of the lower flange 18 is shown.
The maximum stress occurring in the region Q of FIG. 3, as indicated by the solid line γ in FIG. 2, the flange width B _q which does not exceed the permissible limit stress sigma ₁ is set to be ensured You.

As described above, the planar shape of the other portion of the cross member 14, that is, the free edge 30 of the lower flange 18 where a stress greater than that of the upper flange 16 and the vertical web 20 is generated is changed to the cross member web near the side rail 12. 20
And a second portion 30b convex toward the cross member web 20 closer to the center line OO.
By forming a special shape having a gentle waveform consisting of the following, the maximum stress occurring in all parts of the lower flange 18 is lower than the allowable limit stress σ ₁ as shown by a solid line γ in FIG. As a result, there is an advantage that the durability and reliability of the cross member 14 and the chassis frame 10 can be effectively improved without particularly increasing the weight and size of the cross member 14.

As described above, the underframe for a truck or the like according to the present invention is provided with a pair of side rails extending in the vehicle longitudinal direction and the pair of side rails extending in the vehicle width direction. A cross member fixedly attached to the upper and lower flanges, wherein the cross member has a bow shape which is curved in the vertical direction as a whole and is convex downward, and one side of the upper and lower flanges. The cross member is formed by a press-formed material having a groove-shaped cross section composed of a vertical web connecting the edges, and the lower flange of the cross member gradually expands in width from the center portion in the vehicle width direction toward the side rail. And the free end of the widened portion has a convex curved portion facing the cross member web at the portion closest to the side rail and a cross member at the center side in the vehicle width direction therefrom. It is characterized by a gentle wavy shape consisting of a concave curved part facing the web, and the manufacturing cost is reduced by using a downwardly curved cross member disposed on the engine mounting part etc. as a press-formed product. There is an advantage that the cross member and the chassis frame can be effectively improved in durability and reliability without particularly increasing the weight and size of the cross member, while significantly reducing the width.

[Brief description of the drawings]

FIG. 1 is a partial plan view of a chassis frame according to an embodiment of the present invention.

FIG. 2 is a diagram showing a maximum stress generated in a lower flange of a cross member of the chassis frame shown in FIG. 1 in comparison with a stress in a lower flange of the cross member according to a normal design.

FIG. 3 is a partial plan view of an underframe including a cross member based on a conventional design method.

FIG. 4 is a partial front view of the chassis frame shown in FIG. 3;

[Explanation of symbols]

 10 chassis frame 12 side rail 14 cross member 18 lower flange of cross member

Claims (1)

(57) [Claims] 1. A vehicle comprising: a pair of side rails extending in a vehicle longitudinal direction; and a cross member extending in a vehicle width direction and having both ends fixed to the side rails. The cross member has a bow shape that is curved in the vertical direction as a whole and is convex downward, and has a groove-shaped cross-section formed by upper and lower flanges and a vertical web connecting one side edge of the upper and lower flanges. Further, the planar shape of the lower flange of the cross member is formed so as to gradually widen from the portion on the center side in the vehicle width direction toward the side rail side, and the free edge of the widened portion is A gentle wavy shape consisting of a curved portion protruding toward the cross member web at the portion closest to the side rail and a concave curved portion facing the cross member web closer to the center in the vehicle width direction than that. Underframes for trucks, etc.