JP2000326864A - Ladder type vehicle frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance torsional rigidity without increasing the number and weight of cross members or the number of other parts, i.e., to reduce frame weight without reducing torsional rigidity. SOLUTION: This vehicle frame comprises a pair of side rails 1 (1R, 1L) connected together in the form of a ladder by means of three or more cross members 21 or the like, and a corner formed by the side rails and the first cross member located above a rear suspension trunnion is stiffened by a stiffener 31 (31RT, 31LT). In this case, the second cross members 221, 222 adjacent to the first cross member 21 are located in positions such that on at least either the front or rear side of the first cross member, the following requirement within a stiffened area stiffened by the stiffener is met: z/s=0.5-0.75 (z: distance between centers of widths of first and second cross members, s: length of stiffened area).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ladder-type vehicle frame. A vehicle frame such as a truck frame is a frame for mounting main components of the vehicle such as a carrier, a cab, an engine and other driving devices, and a suspension, and also serves as a skeleton of the entire vehicle body. A structure in which a pair of left and right side rails extending in the vehicle length direction are fixedly connected in a ladder shape by a plurality of cross members is often used. A vehicle frame having this structure is called a ladder-type vehicle frame.

[0002]

2. Description of the Related Art In general, rigidity required for a vehicle frame is roughly classified into vertical bending rigidity and torsional rigidity. Also,
The main loads that act on the vehicle frame include vertical loads such as the vehicle's own weight and bed load, and the reaction force coming from the suspension while traveling, and the lateral asymmetry that acts on the suspension when traveling on curved or uneven terrain. There is a load of.

In designing a ladder-type vehicle frame,
After securing sufficient strength so that it does not break down under these loads, the side rails should be able to secure sufficient rigidity to keep the distortion displacement due to the load below a certain amount, and take care not to waste economically. And the shape and arrangement of each cross member must be determined. The method of calculating the vertical bending performed at that time will be described with reference to the example of FIG. FIG. 6A is a composite diagram of a truck side view and a load distribution diagram, where 10 is a frame (which means a ladder-type vehicle frame, the same applies hereinafter), 11 is an axle, and 12 is a trunnion. flame
The ten side rails are regarded as simple static beams, and the load distribution reflects the load from the cab, engine and bed. Further, in a vehicle having a trunnion type suspension as in this example, even if the rear wheels are biaxial, they are connected to the vehicle frame 1 via one trunnion 12, so that the simple statically-determined beam is supported at each of the front and rear fulcrums. (A front wheel fulcrum P at the front wheel axle position and a rear wheel fulcrum Q at the rear wheel trunnion position).

FIG. 6B is a distribution diagram of a bending moment M in the longitudinal direction of the frame calculated from the load distribution of FIG. The value obtained by dividing the bending moment M by the section coefficient Z determined by the geometrical cross-sectional shape of the side rail is the maximum bending stress σ acting on the side rail. That the maximum bending stress σ is sufficiently smaller than the material yield stress is a necessary condition for the side rail not to break.

The bending moment M is distributed so as to have peaks at the front wheel fulcrum P and the rear wheel fulcrum Q, and the peak height at the rear wheel fulcrum Q is particularly large (FIG. 6).
(B)). A frame having a uniform cross-sectional shape in the longitudinal direction for such a bending moment distribution makes the frame extremely heavy and uneconomical. Therefore, the frame is usually designed to have a different cross-sectional shape in the longitudinal direction.

FIG. 6 (c) is a plan view of a frame showing a typical design example. As shown, both side rails 1 have a substantially constant reference cross-sectional shape in the longitudinal direction. At the rear wheel fulcrum Q position, a triangular stiffener 3 is attached as a reinforcing material for a corner formed by the side rail 1 and the cross member 2. By providing the stiffener 3, the section modulus Z of the side rail 1 is distributed as shown in FIG. 6D, and as a result, the bending stress distribution is smoothed as shown in FIG. Become.

In the literature (Nakamura et al., “Ladder type truck
Frame rigidity "Nissan Diesel Technical Report, No.47, 198
According to (5, p7), the cross member is rigid against the vertical load.
Has little to do with gender or strength. So, so far
By the calculation, the design of the side rail portion is almost fixed. Next
FIG. 7 shows the calculation of rigidity and strength against torsional load.
This will be described with reference to an example. As shown, the torsional rigidity
The stiffness GJ) is determined by the left and right rear wheel fulcrums Q, Q _aThe fixed point
And the left and right front wheel fulcrums P, P_aMake a couple F with the action point
Defined as a function of the displacement ΔY of the frame 10 when used
The distance between the points PQ is H, and the distance between the left and right couple action points is b.
Is given by the following equation (1).

GJ = FbH / tan ⁻¹ (2ΔY / b) (1) With respect to the torsional rigidity and strength of the entire frame, besides the bending and torsional rigidity of the side rails, the strength of each cross member The strength of the stiffness against bending and torsion and their arrangement influence. However, since the design of the side rail is almost determined by the above-described bending calculation based on the vertical bending load, it is usual to adjust the rigidity, the number, and the position of the cross member to design the side rail.

Among these, regarding the position of the cross member, Nakamura et al. Have studied using an element model in the above-mentioned document. As shown in FIG. 8, when the cross members are arranged at equal intervals, the minimum displacement, That is, it is known that the maximum rigidity can be obtained (the type-specific mark in the figure represents the cross-sectional shape of the member). In view of this, it is customary that the cross members are arranged at equal intervals unless there is a special problem of mutual engagement. Therefore, only the number of cross members and the rigidity of a single cross member remain as free design items for adjusting torsional rigidity and strength.

[0010] The torsional rigidity and the breaking strength against torsional load cannot be easily derived.
Only a large-scale experiment or a complicated numerical calculation by the FEM (finite element method) can be correctly evaluated. However, it has been known that the torsional stiffness has a large effect on the steering stability and the riding comfort during curved running, and it is necessary to consider the torsional stiffness at the time of designing to a necessary and sufficient value.

However, in order to improve the torsional rigidity of the frame in order to obtain the required rigidity, since the free design items are as described above, there is no other way but to reinforce or increase the number of cross members. This leads to an increase in the frame weight. Alternatively, there is a technique for improving the torsional rigidity by stretching a gap between cross members as disclosed in JP-A-10-181631.
Problems such as an increase in the number of parts and interaction with various parts occur, and they are not a practical solution to the problem.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and improves the torsional rigidity of a ladder-type vehicle frame without increasing the number and weight of cross members and the number of other parts. The purpose is to provide. In other words, an object of the present invention is to provide a ladder-type vehicle frame in which the weight of the frame is reduced without reducing the torsional rigidity.

[0013]

First, the knowledge on which the present invention is based will be described. This finding is that when the rigidity of the side rails is not uniform in the longitudinal direction, the optimal arrangement position of the cross member shifts from the optimal arrangement position when the rigidity is uniform to a position biased toward the high rigidity side. It is. FIG. 9 shows two end members of a two-side rail 1 having a uniform cross section (ie, rigidity) in the longitudinal direction as two partial members of two ladder-type vehicle frames. Consider a model ladder 101 fixedly connected by a cross member 2X. For this model ladder 101, the cross member 2A position is a fixed point A, the cross member 2X position is a position variable X, and the cross member 2B position is an action point B FIG. 9 is a schematic diagram showing a relationship between a displacement amount ΔY calculated by applying a constant torsional load as a value and a position variable X. As shown in the figure, as long as the side rail rigidity is uniform in the longitudinal direction, similar to the above-mentioned document,
When the position variable X takes a value corresponding to the midpoint M of the line segment AB, it is concluded that the displacement amount ΔY takes a minimum value, that is, the equidistant arrangement of the cross members corresponds to the maximum state of frame torsional rigidity.

However, in general, the frame is partially reinforced by a stiffener. Particularly, in a frame to which a trunnion type suspension is connected, a tough stiffener (generally having a triangular or trapezoidal plane shape) is provided at the front and rear portions of the rear suspension. Attached (Fig. 6
(C)), the side rail rigidity (section modulus) is not uniform in the longitudinal direction (FIG. 6 (d)).

Therefore, the present inventor examined whether the same holds true even when the side rail rigidity is not uniform in the longitudinal direction. FIG. 10 is an example of the result of this study. FIG. 9 shows a model ladder 102 in which the corner formed by the cross member 2A on the fixed point A side and both side rails 1 is reinforced with the stiffener 3 in the same manner as in FIG. FIG. 9 is a schematic diagram illustrating a relationship between a calculated displacement amount ΔY and a position variable X.
As shown, the displacement ΔY is extremely small (torsion rigidity is extremely large)
Of the position variable X (that is, the optimal arrangement position of the cross member 2X) is not a value equivalent to the middle point M of the line segment AB but a line segment M
A value corresponding to a certain section in A. That is, the optimal arrangement position of the cross member shifts from the optimal arrangement position when the rigidity is uniform to a position biased toward the high rigidity side. However, when the cross member 2X comes too close to the cross member 2A, the torsional rigidity decreases. This increases the effect of restraining torsion by passing the cross member to the high-rigidity side of the side rail. However, if the cross member is brought too close to the cross member located at the fixed point A, the cross member located at the action point B is It is presumed that the interval between them is too large, and conversely, the rigidity is reduced.

The optimal arrangement position of the cross member 2X substantially corresponds to the position where the side rail rigidity starts to increase, although there is a slight variation depending on detailed conditions.
The position and the cross member 2A position (point A; cross member 2A
And the distance between the position of the cross member 2A (point A) and the starting point of reinforcement of the side rail 1 by the stiffener 3 (point Γ) is s, the ratio z / s is 0.5
It is a position that falls within the range of ~ 0.75.

Here, the reinforcement starting point is such that the stiffener projecting between the left and right side rails has a widening start point (a portion where the width change rate from the end to the center in the longitudinal direction of the stiffener changes from zero to positive) in its extension. In the case, it refers to the widening start point, and when there is no point, it refers to the point closest to the widening start point among the overhanging inside points, and two or more of the left, right, upper, and lower that contact one side of the same cross member In the case where the dimensions of the stiffeners protruding at the corners of the stiffeners are different from each other, the stiffener points to the point farthest from the cross member among the reinforcement starting points determined for each stiffener.

The section in the longitudinal direction of the frame from the reinforcement starting point (point の in FIG. 10) to the width center of the cross member (point A in FIG. 10) is referred to as a stiffener reinforcement area. The length of the reinforcement zone is the distance s. The reinforcing area extends to the front side and the rear side of the cross member. The present invention has been made based on the above findings, and the gist of the present invention is a ladder-type vehicle frame described below.

(1) A pair of side rails are connected in a ladder shape by three or more cross members, and a corner formed by the side rails and the first cross member located above the rear suspension trunnion is reinforced by a stiffener. In the ladder-type vehicle frame, a second cross member adjacent to the first cross member is provided on at least one of a front side and a rear side of the first cross member, in a reinforced region by the stiffener according to the following condition. A ladder-type vehicle frame, wherein the ladder-type vehicle frame is located at a position to be filled.

Z / s = 0.5 to 0.75 where z: distance between the center of the width of the first and second cross members s: length of the reinforcing area (2) Further, the second cross member has The ladder-type vehicle frame according to (1), wherein the ladder-shaped vehicle frame has a U-shape, and an opening of the U-shape faces the first cross member.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first cross member according to the present invention (1) includes a cross member 2A shown in FIG.
(C) The cross member 2 at the position of the rear wheel fulcrum Q corresponds to this. The second cross member has the cross member shown in FIG.
2X, or the cross member 2 adjacent on both sides to the cross member 2 (first cross member) at the position of the rear wheel fulcrum Q in FIG. 6C.

FIG. 10 shows that the first and second cross members 2X (the second cross member) are located on the front side and the rear side of the cross member 2A (the first cross member). The ratio z / s of the distance z between the width center of the member and the distance s from the center of the width of the first cross member to the reinforcement start point 同 on the same side as the second cross member (that is, the length of the reinforcement area) is 0.5 to 0.5.
It is shown that the torsional rigidity can be maximized by setting the position of the second cross member so as to fall within the range of 0.75.

Further, by setting the position of the second cross member not only on one side but also on both sides of the first cross member in the same manner as described above, the torsional rigidity can be further increased as compared with the case of only one side. Conventionally, the cross member 2X is located approximately at the center of the front and rear cross members 2A and 2B (the width center distance L between both members), and z ≒ L / 2. Conventionally, the second cross member (2X) is hardly arranged between the reinforcement start point に よ る by the stiffener 3 and the first cross member (2A) (that is, in the reinforcement area). It was located very close to Γ. That is, conventionally, z / s is substantially equal to 1 or 1
It was bigger. Therefore, in order to achieve the maximum torsional rigidity, it is necessary to increase the weight of components and the number of parts. On the other hand, according to the present invention, z / s: 0.5
Since the maximum of torsional rigidity can be achieved only by setting the position of the second cross member so that 0.70.75 is satisfied, the highest torsional rigidity can be obtained without increasing the weight or the number of parts.

According to the present invention (2), the requirements relating to the shape and orientation of the second cross member are added to the present invention (1) to further increase the torsional rigidity. Figure 1 for this requirement
This will be described with reference to FIG. Figure 11 is a general shape of the second cross member, a three-dimensional view showing the orientation example, as shown, the first cross member 2 ₁ a front side, a second cross member adjacent to the rear side 2 _{In general, 21} and ₂₂ have a U-shaped cross section. Regarding the orientation, as shown in (a), the U-shaped opening is often directed to the front side,
(B) There is also one opposite to the second cross member 2 _21, rather than general norms regarding how to determine, determined by the convenience of individual design. However, in the present invention, FIG.
The orientation of (b), that is, the second cross member 2 ₂₁ , 2
By opening portion ₂₂ of the U-shaped to the orientation facing the first cross member 2 _1, the torsional rigidity is further improved.

Regarding the relationship between the orientation of the cross member and the torsional rigidity, see the literature (Onuma et al .: "Truck frame rigidity and its prediction method")
According to 1988, p643), for objects with a U-shaped cross section, the shear center defined by the material mechanics (the load point at which no torsion occurs even when a bending shear force is applied) is behind the U-shape ) (The position of point O in FIG. 12).

Therefore, FIG. 12 corresponding to FIG.
In the orientation of (a) (referred to as orientation I), the bending force F _B acting point from the side rails 1 to the cross member 2 ₂₁ (second cross member on the front side) (junction point) of the point O outer ( in a first cross member position η opposite side) corresponding to the rear wheel supporting point, twisting in the rotation direction indicated by the bending force F _B by arrow 61 occurs naturally. This torsion does not become a resistance to deformation of the side rail 1 because the rotation direction is the same as the rotation direction of the side rail 1 when the point O is considered as the rotation center.

On the other hand, (referred to as orientation II) orientation shown in FIG. 12 (b) corresponding to FIG. 11 (b) in the bending force F _B acting point from the side rails 1 to the cross member 2 ₂₁ is the point O inside ( on the same side) and the first cross member position η corresponding to the rear wheel supporting point, twisting in the rotation direction indicated by the bending force F _B by arrow 62 occurs naturally. This torsion acts as a resistance to deformation of the side rail 1 because the rotation direction is opposite to the rotation direction of the side rail 1 when the point O is considered as the center of rotation. For this reason, the orientation II has a smaller deformation amount (ΔY in equation (1)) under the same torsional load than the orientation I, that is, a higher torsional rigidity.

In the present invention, since the cross member is disposed at a position on the high rigidity side of the side rail (a specific position in the reinforcing area by the stiffener), the effect of improving the torsional rigidity by adding the above requirements becomes particularly large. As described above, according to the present invention, the torsional rigidity of the ladder-type vehicle frame can be improved without increasing the weight, or the increase in the torsional rigidity is directed to the reduction of the thickness of the cross member to reduce the frame weight. Can be achieved.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fifth type (conventional example) frame (ladder type vehicle frame) shown in FIG. 5 is used as a base, and a part thereof (frame main part 50) is changed to a form conforming to the present invention. 4
The first to fourth types of frames shown in Table 1 were prototyped and used as examples, and the torsional rigidity of each type was measured. In addition, (a) of FIGS.
1 is a plan view, and FIG. 1B is a side view. FIG. 1 to FIG. 4 show only a main part of the frame, and other parts (the same parts as the fifth type) are omitted. The same or equivalent members are denoted by the same reference numerals.

In FIG. 5, reference numeral 1 denotes a pair of left and right side rails (discriminated by suffixes L and R, the same applies hereinafter).
There are a total of nine cross members arranged from the front side to the rear side in i order. The side rails 1L and 1R have a U-shaped cross section, and both ends of each of the cross members 2a to 2i are fixed to the side rails 1L and 1R with rivets, bolts, or the like. Of these cross members 2a to 2i, the cross member 2f is disposed immediately above a trunnion bracket (not shown) for supporting the rear suspension, and thus corresponds to the _first cross member 21 and the front side. , Rear cross members 2e and 2g correspond to the second cross members 2 ₂₁ and ₂₂₂ .

Cross member 2f (first cross member 2)
₁ ) has an I-shaped cross section. The cross member 2b is of a so-called alligator type. Remaining cross members 2a, 2c-2
e, 2g to 2i all have a U-shaped cross section. The orientation of each cross member is as shown in FIG. The side rails 1 are reinforced by stiffeners around the front suspension position and the rear suspension position. The stiffener 30, which reinforces the periphery of the front suspension position, is of a lamination type having a U-shaped cross section, and is fixed to U-shaped grooves of the left and right side rails. The stiffener 31, which reinforces the periphery of the rear suspension position, is of the Mt. Fuji type formed by joining triangular plate members, and has upper and lower side rails (subscripts T,
B, the same applies hereinafter). Although small stiffeners other than the stiffeners 30 and 31 are provided in some places, they are not shown because they are small parts unrelated to the main subject.

This frame is composed of the first cross member 2 ₁
Starting point of reinforcement with stiffener 31 on the front and rear sides of
_1, has a Γ _2. Reinforcing starting gamma ₁ from the first width center of the cross member 2 _1, the distance to the gamma ₂ (front side of the reinforcement area of the rear-side length) is labeled as s1, s2. The second cross member 2 _21, 2 ₂₂ and the width center distance between the first cross member 2 ₁ title and z1, z2.

In the fifth type (conventional type) shown in FIG. 5, z1 / s1>
1 and z2 / s2> 1, and the second cross member 2 ₂₁ on the front side is the first cross member 2
It has an orientation opposite to ₁ . The first type in FIG.
In type z1 / s1: 0.5 ~0.75 those of the second cross member 2 ₂₁ of the front-side as satisfied arranged close to the first cross member 2 _1, second type of Fig. 2, 5 in type z2 / s2: 0.5 ~0.75 those placed closer to the second cross member 2 ₂₂ of the rear side to the first cross member 2 ₁ as is satisfied, third-type of FIG. 3, the first The second on the rear side so that z2 / s2: 0.5 to 0.75 is satisfied in the mold
In the fourth type shown in FIG. 4, the orientation of the second cross member 221 on the front side is reversed in the third type, and the cross member ₂₂₂ of the third type is arranged closer to the _first cross member ₂₁ . The opening of the character is opposed to the _first cross member 21.

The distance ratio z / s of each type (front side; z1 / s1
, Rear side; z2 / s2), cross member orientation, and torsional rigidity are shown in Table 1. The orientation of the cross member was indicated by a symbol, and the torsional stiffness was indicated by a relative index with the fifth type (conventional example) being 100.

[0035]

[Table 1]

As shown in Table 1, the first material satisfying the requirements of the present invention is
The fourth to fourth types have higher torsional rigidity than the conventional type.
In addition, the third and fourth types satisfying the requirements of the present invention (1) on both sides are higher in torsional rigidity than the first and second types satisfying only one side of the first cross member. In comparison between the third mold and the fourth mold, the fourth mold in which the orientation of the second cross member is optimized according to the present invention (2) has higher torsional rigidity.

In this embodiment, the stiffener around the first cross member is of Mt. Fuji type, but the present invention is not limited to the stiffener. Further, in the present embodiment, the stiffeners around the first cross member are arranged above and below between the left and right side rails, and the stiffeners have the same shape. Even in the case where the shapes are different, the present invention can be implemented by determining the reinforcing starting point and the reinforcing area based on the above-described definition and achieving a corresponding effect.

[0038]

Thus, according to the present invention, it is possible to increase the torsional rigidity without increasing the number of cross members and weight of the vehicle frame, or to reduce the weight of the frame without reducing the torsional rigidity of the frame. This has an excellent effect that it can be achieved.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a side view, respectively, showing a main part of a first type (example) frame.

FIG. 2 is a plan view (a) and a side view (b) showing a main part of a second type (example) frame.

FIGS. 3A and 3B are a plan view and a side view showing a main part of a third type (example) frame. FIGS.

FIGS. 4A and 4B are a plan view and a side view, respectively, showing a main part of a fourth type (example) frame.

FIGS. 5A and 5B are a plan view and a side view showing an entire frame of a fifth type (conventional example).

6A and 6B are explanatory diagrams of a vertical bending calculation method, where FIG. 6A is a composite diagram of a track side view and a load distribution diagram, FIG. 6B is a bending moment distribution diagram, FIG. 6C is a frame plan view, and FIG. FIG. 3 is a side rail section sectional coefficient distribution diagram, and FIG. 3E is a side rail bending stress distribution diagram.

FIG. 7 is an explanatory diagram of a definition of torsional rigidity.

FIG. 8 is a view showing conventional knowledge about a relationship between a cross member position and torsional rigidity.

FIG. 9 is a schematic diagram showing a relationship between torsional rigidity of a model ladder having uniform side rail rigidity in the longitudinal direction and a cross member position.

FIG. 10 is a schematic diagram showing the relationship between the torsional rigidity of a model ladder whose side rail rigidity is not uniform in the longitudinal direction and the cross member position.

FIG. 11 is a three-dimensional view showing a general shape and orientation example of a second cross member.

FIG. 12 is an operation explanatory view of the present invention (2).

[Explanation of symbols]

Reference Signs List 1 side rail 2 cross member 2 ₁ first cross member 2 ₂₁ second cross member (front side) 2 ₂₂ second cross member (rear side) 3, 30, 31 stiffener 10 frame (ladder type vehicle frame) 11 Axle 12 Trunnion 50 Frame main part 101 Model ladder (without stiffener) 102 Model ladder (with stiffener)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Yoshida 3-1-1 Hinodai, Hino-shi, Tokyo Hino Motors, Ltd. Vehicle R & D department (72) Inventor Takaro Iguchi Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba No. 1 Inside the Technical Research Institute, Kawasaki Steel Corporation

Claims (2)

[Claims] 1. A pair of side rails are connected in a ladder shape by three or more cross members, and a corner formed by the side rails and a first cross member located above a rear suspension trunnion is reinforced by a stiffener. In the ladder ladder-type vehicle frame, a second cross member adjacent to the first cross member satisfies the following condition in a region reinforced by the stiffener on at least one of a front side and a rear side of the first cross member. A ladder-type vehicle frame, characterized in that it is in a position. Z / s = 0.5 to 0.75 where, z: distance between the width centers of the first and second cross members s: length of the reinforcing area 2. The ladder-type vehicle frame according to claim 1, wherein the second cross member has a U-shaped cross section, and an open portion of the U-shape faces the first cross member.