JPH0752626A - Suspension for vehicle - Google Patents

Abstract

PURPOSE:To prevent stress concentration of a 4WS vehicle provided with a leaf spring type suspension and also to make the longitudinal motion of an accel center essentially zero. CONSTITUTION:A suspension of a 4WS vehicle provided with a leaf spring type suspension has a nearly V shaped upper radius-rod 20 whose base end is connected to the upper center of an accel housing 5 and whose respective free ends are connected to either one side cross member 3 out of the cross members 3 and 4 positioned on the front side and the rear side of the accel housing and a pair of left and right lower radius-rods 21 and 22 whose respective one side ends are connected to lower left and right sides of the accel housing respectively and whose respective other side ends are connected to a steering device mounted on either on of other sides of the cross members 4 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system, and more particularly to a suspension system for a 4WS vehicle having a leaf spring type suspension.

[0002]

2. Description of the Related Art Generally, a suspension device for a truck employs a leaf spring (leaf spring). Especially, since the rear wheel has a large difference in weight between an empty vehicle and a loaded vehicle, the spring constant is constant when the vehicle is empty. Parent-child springs, etc. are adopted so that they are low and high when loaded. In addition, in order to facilitate entry into narrow alleys or turning in narrow spaces, the rear wheels are steered in the opposite phase to the front wheels according to the steering angle of the front wheels, and the 4WS function that reduces the minimum turning radius is adopted. Has been done.

As a suspension system for the leaf spring suspension 4WS, there is one having a structure as shown in FIGS. This suspension device has an equal-length parallel link structure so that the roll steering angle becomes 0 in a constant volume state, and a plurality of cross members connecting the left and right frames 1 and 2, for example, the fifth cross member 4 are connected. Each free end of the V-shaped upper radius rod 6 has ball joints 7,
7 ', the base end is connected to the upper center of the rear axle housing 5 via a ball joint 8, and the left and right lower radius rods 9 and 10 are respectively connected to the rear axle via ball joints 11 and 11'. At the lower left and right sides of the housing 5, the other ends are respectively ball joints 12, 1
The L-shaped links 14 and 15 are rotatably supported by brackets 13 and 13 'fixed to the left and right sides of the cross member 4 via 2', respectively.

The rear end of the power cylinder 16 for steering the rear wheels is attached to one side of the cross member 4 via a bracket 17, and the tip of the rod is connected to the other end of the L-shaped link 14. Further, both ends of the tie rod 18 are connected to the other ends of the L-shaped links 14 and 15, respectively.
The cross member 4 is located behind the cross member 3 in the vehicle body, and the rear axle housing 5 is arranged between the cross members 3 and 4.

When the rear axle housing 5 is vertically displaced according to a load, the upper radius rod 6 and the left and right lower radius rods 9 and 10 swing vertically with each ball joint as a fulcrum. In addition, the L-shaped links 14 and 15 rotate according to the expansion and contraction of the power cylinder 16,
Along with this, the left and right lower radius rods 9 and 10 move in opposite directions in the front-rear direction, the rear axle housing 5 is rotated around the base end of the upper radius rod 6 as a fulcrum, and the rear wheels are steered in an opposite phase to the front wheels. . 4WS by this
Control is performed.

[0006]

However, in the suspension device having the above structure, the free ends of the upper radius rods 6, the respective ends of the left and right lower radius rods 9, 10 and the power cylinder 16 are attached to the cross member 4. Therefore, the stress during traveling is concentrated on the cross member 4, and the strength needs to be increased accordingly. Further, if the strength of the cross member 4 is increased, not only the weight becomes heavy, but also it is not preferable in relation to the frame and other cross members.

Further, since the rear axle center (RAC) moves back and forth when the rear axle housing 5 is displaced up and down, it is necessary to increase the fitting length of the propeller shaft, which results in a heavy weight. Further, a roll steer angle occurs in an empty state and an overloaded state. That is, the suspension system of the leaf spring suspension 4WS of the equal length parallel link is represented as shown in FIG. 8, and the length (= L) between points A and B and C and D is represented by the upper radius rod 6 and the lower radius rod 9 (10). ), Point P to the rear axle center (R
AC), as the rear axle housing 5 moves up and down, the upper radius rod 6 and the lower radius rod 9 oscillate up and down as indicated by the one-dot chain line and two-dot chain line with respect to the constant volume state shown by the solid line. , The point P is displaced like P ′ and P ″. Along with this, the points P ′ and P ″ move backward from the position of the point P. The amount of movement is indicated by δ.

As a result, when the rear axle housing 5 is vertically displaced, the point P, that is, the rear axle center (R
(AC) moves in the front-rear direction, it is necessary to increase the fitting length of the propeller shaft. Further, there is a problem that a roll steer angle is generated in an empty state and an overloaded state. The present invention has been made in view of the above points, and a vehicle in which a load applied to an axle housing is dispersed to avoid stress concentration on a specific cross member and a movement amount of an axle center in a front-rear direction is reduced. It is an object of the present invention to provide a suspension device of.

[0009]

In order to achieve the above object, according to the present invention, there is provided a suspension system for a 4WS vehicle equipped with a leaf spring type suspension, the suspension system being substantially V-shaped, and the base end of which is the upper part of the axle housing. In the center, each free end is connected to one of the front and rear cross members of the axle housing, and an upper end rod is connected to the cross member, and one end is connected to the lower left and right sides of the axle housing, respectively. Each of the other ends includes a pair of left and right lower radius suds that are connected to a steering mechanism provided on the cross member on the other side.

The suspension device is a watt-type link mechanism composed of an upside radius rod, an axle housing, and a lower radius rod, and the length ratio of the upside radius rod and the lower radius rod is the ratio of the length of the axle shaft housed in the axle housing. It is preferable to set it equal to the ratio of the length from the axle center to the connecting point with the lower radius rod and the length from the axle center to the connecting point with the upper radius rod.

[0011]

The function of the axle housing is to be vertically displaced according to the loaded state, and accordingly the upper radius rod and the lower radius rod are vertically swung. The suspension device is a watt type link mechanism, and the load applied to the rear axle housing is dispersed. In addition, the length ratio between the Apparradius rod and the lower radius rod is set equal to the ratio between the length from the axle center to the connecting point with the lower ass rod and the length from the connecting point to the upper radius rod. Even if is displaced in the vertical direction, the axle center hardly moves in the front-back direction. This prevents the roll steer angle from being generated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The same members as those in FIGS. 5 to 7 are designated by the same reference numerals. 1 to 3, the apparatus rod 2
The base end of 0 is connected to the upper center of the rear axle housing 5 via a ball joint 8 and the free ends of the rear axle housing 5 are connected via ball joints 7 and 7 ', respectively.
On the other hand, the cross member 3 located on the front side is connected to the upper left and right sides. In addition, one end of each of the pair of left and right lower radius rods 21, 22 has a ball joint 11, 11 ', respectively.
Brackets 13 which are connected to the lower left and right sides of the rear axle housing 5 through the respective ends, and the other ends of which are fixed to the lower left and right sides of the cross member 4 located on the rear side of the rear axle housing 5 via ball joints 12 and 12 ', respectively. 1
Each of the L-shaped links 14 and 15 pivotally supported on 3'is connected to one end thereof.

The upper radius rod 20 and the lower radius rods 21 and 22 are arranged parallel to each other so as to support the rear axle housing 5 from the opposite direction (front and rear direction), and the upper radius rod 20 and the lower radius rods 21 and 22 are arranged. A watt-type link mechanism is formed by and. That is, in FIG. 4, points A and B are connecting points with the cross member 3 of the upper radius rod 20 and the rear axle housing 5, respectively, and points C and D are rear axle 5 and the cross member 4 of the lower radius rod 21, respectively.
And the length between points A and B (= L ₁ ) is the length of the Appalladias rod 20 and the length between points C and D (= L ₁ ).
Let L ₂ ) be the length of the lower radius rod 21 (22). The point P is the center of the rear axle in the rear axle housing 5, that is, the rear axle center (RAC), and the lengths between the points B and P and P and C are L ₃ and L ₄ , respectively. Then, the lengths of the apparradius rod 20 and the lower radius rod 21 (22) are set to L ₁ : L ₂ = L ₄ : L
Set it to ₃ .

The operation will be described below. When the rear axle housing 5 is vertically displaced according to the load, the upper radius rod 20 and the left and right lower radius rods 21 and 22 are vertically swung with each ball joint as a fulcrum. Further, the L-shaped links 14 and 15 are rotated in accordance with the expansion and contraction of the power cylinder 16, and accordingly, the left and right lower radius rods 21 and 22 are moved in opposite directions in the front-rear direction, and the rear axle housing 5 is moved to the upper radius rod 20. The rear wheel is turned around the fulcrum as a fulcrum, and the rear wheels are steered in reverse phase to the front wheels. Thereby, 4WS control is performed.

The load that the upside radius rod 20 receives is applied to the cross member 3, and the lower radius rod 2
The loads received by the members 1 and 22 are applied to the cross member 4. As a result, the load applied to the rear axle housing 5 is distributed to the cross members 3 and 4, and the stress generated in the cross member 4 is reduced. In addition, in FIG. 4, as the rear axle housing 5 is vertically displaced, the upside radius rod 2 is moved.
0, the lower radius rod 21 oscillates up and down as indicated by the one-dot chain line and two-dot chain line with respect to the constant volume state shown by the solid line.
At this time, the point P moves on a straight line S passing vertically through the point P like the points P ′ and P ″.
Is displaced substantially vertically in the vertical direction, and the amount of movement in the front-back direction becomes substantially zero. As a result, the roll steer angle does not occur.

[0016]

As described above, according to the present invention, the load applied to the axle housing is dispersed, stress concentration on a specific cross member is prevented, the durability of the vehicle body is improved, and the axle housing is improved. Since the front-back movement amount of the axle center becomes substantially zero with respect to the vertical displacement of, the fitting length of the propeller shaft can be shortened, and the weight can be reduced. Further, there is an excellent effect that the roll steer angle is prevented from occurring even in an empty or overloaded state.

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts showing an embodiment of a suspension system for a vehicle according to the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a cutaway side view of a main part of FIG.

FIG. 4 is a diagram showing the operation of the suspension device of FIG. 1.

FIG. 5 is a perspective view of a main part of a conventional suspension device.

FIG. 6 is a plan view of FIG.

7 is a cutaway side view of a main part of FIG.

FIG. 8 is a diagram showing the operation of the suspension device of FIG. 5;

[Explanation of symbols]

1, 2 Frames 3, 4 Cross members 5 Rear axle housings 7, 7 ', 8, 11, 11', 12, 12 'Ball joints 14, 15 L-shaped links 16 Power cylinders 18 Tie rods 20 Appradius rods 21, 22 Lower radius rods

Claims (3)

[Claims] 1. A suspension system for a 4WS vehicle provided with a leaf spring type suspension, which is substantially V-shaped and whose base end is located at the center of the upper part of the axle housing and each free end is located at the front and rear sides of the axle housing. Of the cross members, one end of which is connected to the lower left and right sides of the axle housing, and the other end of which is provided to the other cross member. And a pair of left and right lower radius suds respectively connected to the steering mechanism. 2. The suspension system for a vehicle according to claim 1, wherein the suspension system is a watt type link mechanism configured by the upper radius rod, the axle housing, and the lower radius rod. 3. In the watt type link mechanism, a length ratio of the upper radius rod and the lower radius rod is from an axle center of an axle shaft housed in the axle housing to a connection point with the lower radius rod. The vehicle suspension system according to claim 2, wherein a ratio of a length and a length from an axle center to a connection point with the upper radius rod is equal.