JPH0653448B2 - Rear suspension device for automobile - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear suspension device for an automobile, and more particularly to a rear wheel toe control structure in a torsion axle type rear suspension.

(Prior Art) As one of vehicle rear suspension devices, for example, a torsion axle type rear suspension disclosed in Japanese Utility Model Laid-Open No. 58-58906 is widely known. That is, the general configuration of the rear suspension device by this system is as shown in FIGS. 7a and 7b in perspective view and plan view,
A pair of support members 2a, 2b that rotatably support the left and right rear wheels 1a, 1b, a cross member 3 having both ends connected to the support members 2a, 2b and extending in the vehicle width direction, and a rear end of the cross member 3. A pair of trailing arms 5 which are fixed to the cross member 3 and whose front end is connected to the vehicle body 4 and which can be swung up and down and flexed (deformed) in the vehicle width direction.
a and 5b, and elastic members 6a, which are respectively provided at connecting portions of the front ends of the trailing arms 5a and 5b to the vehicle body 4, and elastically support the arms so as to be displaceable at least in the front-rear direction.
6b and a lateral rod 8 which is provided so as to extend in the vehicle width direction and has one end connected to the cross member 3 and the other end connected to the vehicle body through elastic members 7, respectively, and further trailing arms 5a, 5b. A lower end of a shock absorber 9 having an upper end fixed to the vehicle body 4 is connected to a fixed portion of the rear end to the cross member 3, and a torsion bar 10 is provided inside the cross member 3.

In order to improve the running performance of the vehicle, it is preferable that not only the front wheels be turned in the traveling direction but also the toe control of the rear wheels can be performed when the steering is turned. That is, for steering steering at a slight angle that is performed when traveling straight ahead, the rear wheels (to be precise, the rear wheels located on the outer peripheral side in the steering turning direction) are put in the toe-in state to understeer, and the vehicle travels. On the other hand, it is preferable to improve stability. On the other hand, in the case where hard cornering is performed, it is preferable to set the rear wheels in a toe-out state to weaken the particularly strong understeer particularly in the FF type vehicle.

In order to obtain the above characteristics, the toe control of the rear wheels should be performed according to the lateral force that accompanies the change in centripetal acceleration that acts on the rear wheels during steering. In the axle type rear suspension, when a lateral force is applied to the rear wheels, the rear wheels will be toe-in or toe-in depending on which side of the vehicle longitudinal direction the lateral rod is attached to the vehicle body with respect to the line of action of this lateral force. Since the toe changes to only one of the toe outs, proper toe control cannot be performed. That is, for example, in FIG. 7b, when the lateral force G is applied to the rear wheels 1a and 1b, the lateral rod 8 is mounted on the vehicle body 4 at the rear side of the vehicle from the line of action of the lateral force G. Occurs, the trailing arm 5b on the right side is displaced rearward by the elastic member 6b being deformed, and the trailing arm 5a on the left side is displaced forward by deforming the elastic member 6a, so that the rear wheels 1a, 1b are displaced to the right. The rear wheel 1a is in the toe-in state. At this time, the lateral force G also deforms the elastic members 7 at both ends of the lateral rod 8. However, since the pair of trailing arms 5a and 5b are arranged in parallel with each other, the cross member 3 is opposed to this deformation. It only displaces in the vehicle width direction and does not affect the toe change of the rear wheel 1a. When the lateral rod 8 is attached to the vehicle body 4 at the front side of the line of action of the lateral force G, the rear wheel is acted by the action opposite to the above.
1a is in a toe-out state. In any case, the toe state is either toe-in or toe-out with respect to the lateral force G, and the degree of the toe change simply increases as the lateral force G increases with the centripetal acceleration. With such a conventional rear suspension device, toe control cannot be properly performed.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is a non-linear expansion of the toe characteristics of the rear wheel with respect to the lateral force associated with the centripetal acceleration acting on the rear wheel in the toe-in direction. An object of the present invention is to provide a rear suspension device for an automobile having a toe control function which can be characterized.

(Structure of the Invention) In the rear suspension device for a vehicle according to the present invention, the position of the instantaneous center at the time of the rotational displacement of the rear wheel when a lateral force is applied is set by appropriately setting the arrangement shape of the pair of trailing arms. The toe change of the rear wheel due to the arrangement shape of the trailing arm and the toe change of the rear wheel due to the placement position of the lateral rod are combined to make a nonlinear control. In order to obtain a toe characteristic that expands in the toe-in direction, the trailing arm is connected to the vehicle body and the cross member, the lateral rod is connected to the vehicle body, and the lateral rod connecting portion. The elastic characteristics of the elastic member are modified. That is, a pair of support members that rotatably support the left and right rear wheels, a cross member that connects the pair of support members, a rear end is connected to the cross member, and a front end is connected to the vehicle body. A pair of trailing arms that can swing up and down and that can be deformed in the vehicle width direction, and the arms that are respectively provided at the connecting portions of the front ends of these trailing arms to the vehicle body can be displaced at least in the longitudinal direction. A rear suspension device for an automobile, comprising: an elastic member elastically supported on a vehicle body; and a lateral rod that extends in the vehicle width direction and has one end connected to the cross member and the other end connected to the vehicle body via an elastic member. A pair of trailing arms are disposed such that the spacing between the arms is wider at the rear end of the arms than at the front end thereof. Is connected to the vehicle body on the vehicle rear side from the line connecting the wheel centers of the left and right rear wheels, and the elastic member provided at the connecting portion of the lateral rod is hard in a small displacement range and soft in a large displacement range. It is characterized by having paddle elastic properties.

As a result, the rear wheel (a rigid body including the cross member and the rear wheel support member) is first supported by the trailing arm that is arranged in an eight-shape and is deformable in the vehicle width direction. The instantaneous center of the rotational displacement of the rear wheel due to the trailing arm support when a lateral force is applied to the
It is located in front of the vehicle from the line connecting the wheel centers of the left and right rear wheels. That is, this means that the rear wheel supported only by the trailing arm is displaced in the toe-out direction. (Of course, this displacement is in the relatively small displacement region in the initial stage because it is based on the idea of the instantaneous center.) On the other hand, the lateral rod is located in front of the vehicle from the line connecting the wheel centers of the left and right rear wheels. Since it is connected to the vehicle body on the side, the rear wheel toe change direction becomes toe-in when a lateral force restrained by this lateral rod acts.

In such a supporting structure of the trailing arm and the lateral rod, in the present invention, since the elastic member of the lateral rod connecting portion has the elastic characteristic of being hard in the small displacement range and being soft in the large displacement range, the lateral force is relatively large. When it is small, the influence of the support structure by the trailing arm is small, and the rear wheel on which the lateral force acts is greatly affected by the lateral rod and causes a toe-in change. When a larger lateral force is applied, the support structure of the trailing arm exerts an influence, the change in the toe-in direction of the rear wheels is suppressed, and the characteristic changes in the toe-out direction.

The elastic member provided at the connecting portion of the lateral rod is
It is needless to say that they may be provided at both ends of the lateral rods, but they may be provided at a connecting portion between one of the cross member and the vehicle body, and the same effect can be obtained in either case.

Above "Line connecting the wheel centers of the left and right rear wheels"
Is slightly shifted to the front side of the vehicle by the pneumatic trail with respect to the line of action of the lateral force acting on the rear wheels, so the term "line connecting the wheel centers of the left and right rear wheels" is strictly speaking. It means the "line of action of the lateral force acting on the rear wheel".

Embodiment An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The same parts as those in FIGS. 7a and 7b are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a plan view showing a rear suspension device for an automobile according to this embodiment.

The pair of trailing arms 5a, 5b are arranged in an eight shape so that the mutual distance is wider at the rear end than at the front end of the arms 5a, 5b, and the lateral rods are arranged on the left and right rear wheels 1a. , 1b are connected to the vehicle body 4 on the rear side of the vehicle with respect to the cross member 3 arranged at a position coaxial with the line connecting the wheel centers. Each of these trailing arms 5a, 5b is made of a plate material whose width in the vertical direction is wider than that in the vehicle width direction, so that it can be bent in the vehicle width direction. The elastic member 7 provided at the connecting portion of the lateral rod 8 to the vehicle body 4 is fixed to the cylindrical outer cylinder 11 at the end of the lateral rod 8 and the vehicle body side, as shown in detail in FIG. The elastic member 7 is made of rubber filled between the cylindrical inner cylinder 12 and a pair of arc-shaped holes 13 located on the left and right sides of the cylinder 12 in parallel with the axis of the inner cylinder 12. It is formed so as to penetrate therethrough, and a resin plate 14 is press-fitted into each hole 13. Since the resin plate 14 is press-fitted into the pair of holes 13, the deflection when a lateral load is applied to the elastic member 7 is characterized by a predetermined load fo as shown in FIG. Will be different. That is, the elastic member 7 has elastic characteristics that are hard in the small displacement range (spring constant k ₁ ) and soft in the large displacement range (spring constant k ₂ ).

4 and 5 are plan views showing the operation of this embodiment.

As shown in FIG. 4, first, the rear wheels 1a and the rear wheels 1a and
Consider a case where a lateral force G ₁ due to a relatively small centripetal acceleration acts on 1b.

As shown in FIG. 3, the elastic characteristic (spring constant) of the elastic member 7 at the connecting portion of the lateral rod 8 has a hard spring constant k in the region (f ₁ ) where a small lateral force due to centripetal acceleration acts.
_Since it is ₁ , the effect of restraining the displacement by the lateral rod 8, that is, the action of displacing in the toe-in direction becomes large, and the rear wheels 1a and 1b are displaced as shown by the broken lines in the figure, and as a result, the rear wheels 1a and 1b are Toe-in changes (δ ₁ ). (Note that such a displacement in the toe-in direction causes a clockwise rotation moment because the connecting portion of the lateral rod 8 to the vehicle body 4 is located on the vehicle rear side with respect to the line of action of the lateral force G ₁ (e). It is caused by the action).

As shown in FIG. 5, a larger lateral force G is applied to the rear wheels 1a and 1b.
_In the region (f ₂ ) where ₂ acts, the spring constant of the elastic member 7 shifts from hard k ₁ to soft k ₂ , but the behavior of the rear wheels 1a, 1b in this region (f ₂ ) will be considered.

The trailing arms 5a and 5b, which are arranged in an eight shape in which the rear side is wider than the front side, are connected at the front end through elastic members 6a and 6b of the vehicle body, and the rear end is a cross member 3 extending in the vehicle width direction. It is rigidly connected to, but if temporarily,
Assuming that the rear ends of both arms 5a and 5b are swingably connected to the cross member 3, when the lateral force G is applied to the wheel 1a, the cross member 3 is extended by the extension lines of both arms 5a and 5b. It will rotate counterclockwise around the intersection P as an instantaneous center.

On the other hand, the trailing arms 5a and 5b of this embodiment are
Although its lower end is rigidly connected to the cross member 3, it can be flexed (deformed) in the vehicle width direction because it is made of a plate material that is wide in the vertical direction.
The operation is almost the same as the structure in the case of being swingably connected. That is, strictly speaking, the arms 5a, 5
Although the instantaneous center of the cross member 3 slightly changes depending on the bending rigidity of b, it always exists near the point P in front of the line connecting the elastic members 6a and 6b.
Therefore, in a region not restrained by the lateral rod 8, when a lateral force G is applied to the rear wheel 1a from the left side in the traveling direction, the cross member 3 and the rear wheels 1a and 1b connected to the cross member 3 (these are one rigid body). It is considered that the momentary center of) is in front of the point of action of the lateral force G, and a counterclockwise rotational moment acts on the rear wheels 1a, 1b.

Therefore, in the vicinity of the region (f ₂ ) where the degree of restraint of the lateral rod 8 is low, it is considered that a counterclockwise rotation moment with the vicinity of the intersection P as the instantaneous center acts.
The rear wheels 1a and 1b are displaced as shown by the broken line in the figure. Due to the above displacement, the rear wheel 1a undergoes a toe-out change to the left (δ
₂ ). Therefore, there is a toe-out change of δ ₂ −δ _{1 with} respect to the original position shown by the solid line in FIG.

FIG. 6 is a graph showing the toe characteristics of the rear wheel 1a with respect to the centripetal acceleration G.

As shown by the solid line in the figure, toe-in is used for small lateral force due to comparatively small centripetal acceleration used during slight steering turning performed when traveling straight, etc., while hard cornering is performed Toe-out is applied to a large lateral force that accompanies a relatively large centripetal acceleration that acts on the vehicle body 4 and the elastic member 7 and the lateral rod 8 connected to the vehicle body 4 and the trailing arms 5a and 5b. This is done by appropriately selecting the shape of a figure eight, etc. By changing these specifications, various toes expanded to the toe-in side, for example, as shown by the one-dot chain line and two-dot chain line in the figure. The characteristics can be obtained.

Incidentally, in the above embodiment, the lateral rod 8 is appropriately used.
Although the operation has been described assuming that only the elastic members 7 on the vehicle body 4 side among the elastic members 7 at both ends are deformed, the same operation and effect as in the above-described embodiment can be obtained even when both elastic members 7 are deformed. Of course.

(Effects of the Invention) As described in detail above, in the rear suspension device for an automobile according to the present invention, the distance between the pair of trailing arms in the torsion axle type rear suspension is wider at the rear end than at the front end of the arms. The lateral rod is connected to the vehicle body on the vehicle rear side of the line connecting the wheel centers of the left and right rear wheels, and the elastic member provided at the lateral rod connecting portion is in the small displacement range. Since the structure is hard and has a soft elastic characteristic in a large displacement range, the toe characteristic of the rear wheel against the lateral force due to the centripetal acceleration acting on the rear wheel is changed to a nonlinear characteristic expanded in the toe-in direction. Therefore, a relatively small lateral force acts on the rear wheels, and the steering is made understeer at a slight angle when traveling straight ahead. While it is possible to improve the running stability of both, it is possible to weaken the understeer tendency that occurs at the time of hard cornering in which a relatively large lateral force acts on the rear wheels, and especially under strong FF FF. It is effective for vehicles of the type. Further, by changing the elastic characteristics and other specifications of the elastic member, various controls can be performed as desired within the range of the non-linear toe characteristics expanded in the toe-in direction.

[Brief description of drawings]

1 is a plan view showing an example of a vehicle rear suspension device according to the present invention, FIG. 2 is an enlarged perspective view of a II portion of FIG. 1, and FIG. 3 is a graph showing elastic characteristics of the elastic member shown in FIG. 4 and 5 are plan views showing the operation of the device, FIG. 6 is a graph showing the toe characteristic of the device, and FIGS. 7a and 7b are a perspective view and a plan view showing a conventional rear suspension device. 1a, 1b ... rear wheel, 2a, 2b ... support member 3 ... cross member, 4 ... vehicle body 5a, 5b ... trailing arm 6a, 6b, 7 ... elastic member 8 ... lateral rod

Continuation of the front page (56) Reference JP-A-60-148707 (JP, A) Actual opening 57-80306 (JP, U) Actual opening 60-46310 (JP, U) Actual opening 50-77630 (JP , U)

Claims (1)

[Claims] 1. A pair of support members for rotatably supporting left and right rear wheels, a cross member for connecting the pair of support members, a rear end connected to the cross member, and a front end for a vehicle body. A pair of trailing arms that are vertically swingable and deformable in the vehicle width direction, and at least the front-rear direction of the trailing arms, which are respectively provided at the connecting portions of the front ends of the trailing arms to the vehicle body. A rear suspension device for an automobile, comprising: an elastic member elastically supported so as to be displaceable to a vehicle body; and a lateral rod that extends in the vehicle width direction and has one end connected to the cross member and the other end connected to the vehicle body via the elastic member. The pair of trailing arms are arranged such that a distance between the arms is wider at a rear end of the arms than at a front end thereof. Is connected to the vehicle body on the vehicle rear side from the line connecting the wheel centers of the left and right rear wheels, and the elastic member provided at the connecting portion of the lateral rod is hard in a small displacement range and is in a large displacement range. A rear suspension device for an automobile, which is characterized by having soft elastic characteristics.