JPH0653449B2 - 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, it is preferable to improve the turning performance of the vehicle by setting the rear wheels (to be exact, the rear wheels located on the outer peripheral side in the steering turning direction) in a toe-out state when steering at low speed. On the other hand, when cornering or changing lanes at high speed, it is preferable to ensure stability by putting the rear wheels in a toe-in state.

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.

(Objects of the Invention) The present invention has been made in view of the above circumstances, and is a non-linear nonlinear 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-out 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-out 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 provided at the front end of these trailing arms connected 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 the vehicle, and a lateral rod that is provided to extend 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 soft in a small displacement range and large in a displacement range. It is characterized by having a hard elastic characteristic.

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 elastic characteristics that are soft in the small displacement range and hard in the large displacement range, the lateral forces are compared. When it is relatively small, the lateral rod has a small effect, and the rear wheel on which the lateral force acts is greatly affected by the support structure of the trailing arm and causes a toe-out change. When a larger lateral force is exerted, the influence of the lateral rod comes out, the change in the toe-out direction of the rear wheel is suppressed, and the characteristic changes in the toe-in 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 octagonal shape so that the distance between them is wider at the rear end than at the front ends of the arms 5a, 5b, and the lateral rod 8 is
A cross member 3 arranged at a position coaxial with a line connecting wheel centers of the left and right rear wheels 1a and 1b is connected to a vehicle body 4 on the vehicle rear side. 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. It is made of rubber filled between the inner cylinder 12 and the cylindrical inner cylinder 12. The elastic member 7 has a pair of arc-shaped holes 13 located on both left and right sides of the inner cylinder 12 parallel to the axis of the inner cylinder 12. Is formed so as to penetrate through. Due to the formation of the pair of holes 13, the deflection when a lateral load is applied to the elastic member 7 has different characteristics at a predetermined load f ₀ as a boundary, as shown in FIG. come. That is, the elastic member 7 is soft in the small displacement range (spring constant k ₁ ) and hard in the large displacement range (spring constant k ₁ ).
₂ ) It has elastic properties.

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

As shown in FIG. 4, first, consider a case where a lateral force G ₁ due to a relatively small centripetal acceleration acts on the rear wheels 1a and 1b due to steering steering to the right when the vehicle speed is low.

The left and right trailing arms 5a and 5b, which are arranged in an eight-shape that spreads rearward from the front, are connected to the vehicle body at the front end through elastic members 6a and 6b, and the rear end extends in the vehicle width direction. Although rigidly connected to the member 3, if the rear ends of both arms 5a and 5b are swingably connected to the cross member 3, when a lateral force G is applied to the wheel 1a, the cross is performed. The member 3 includes both arms 5a and 5a.
It will rotate counterclockwise around the intersection P of the extension line of b as the instantaneous center.

On the other hand, the trailing arms 5a and 5b of this embodiment are
Although its rear 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.
This shows almost the same operation as the structure in the case of 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 the 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 The momentary center (which is considered to be a rigid body) is in front of the point of application of the lateral force G, and a counterclockwise rotational moment acts on the rear wheels 1a, 1b.

Here, the elastic member 7 of the connecting portion of the lateral rod 8
3 has a soft spring constant k ₁ in the region (f ₁ ) in which a small lateral force due to centripetal acceleration acts, as shown in FIG. 3, the lateral rod is x _{1 in the} drawing. It is considered that the rear wheels 1a, 1b are acted upon by a counterclockwise rotational moment about the intersection P as an instantaneous center, and the rear wheels 1a, 1b are indicated by broken lines in the figure. To be displaced. At this time, the rear wheel 1a makes a toe-out change to the left with respect to the original position (δ ₁ ).

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 a soft k ₁ to a hard k ₂ , so that the effect of restraining the displacement by the lateral rod 8, that is, the action of displacing in the toe-in direction is caused. growing. (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 ₂ (e). Therefore, in this case, 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 undergo a toe-in change (δ ₂ ). Therefore, δ ₂ −δ for the original position shown by the solid line in FIG.
A toe-in change of ₁ will be made.

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-out is used for small lateral force due to comparatively small centripetal acceleration that acts when cornering at low and medium speeds, while it acts relatively when lane change occurs at high speed. Toe-in is applied to a large lateral force associated with a large centripetal acceleration by changing the connecting positions of the elastic members 7 and 6a, the lateral rod 8 to the vehicle body 4 and the eight-shaped shapes of the trailing arms 5a and 5b in the above embodiment. It is made by proper selection. By changing these specifications, various toe characteristics expanded on the toe-out side as shown by the one-dot chain line and two-dot chain line in the figure can be obtained. You can

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 it has a structure that is soft and has a hard 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 non-linear characteristic expanded in the toe-out direction. Therefore, it is possible to improve the turning ability of the vehicle during cornering at low and medium speeds when a relatively small lateral force acts on the rear wheels. On the other hand, it is possible to improve the grip of the wheels on the road surface at the time of lane change or the like during high-speed traveling in which a relatively large lateral force acts on the rear wheels. Further, by changing the elastic characteristics and other specifications of the elastic member, various toe controls can be performed as desired within the range of the non-linear toe characteristics expanded in the toe-out 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) References JP-A-60-148707 (JP, A) real-opening Sho-57-80306 (JP, U) real-opening Sho-60-46310 (JP, U) real-opening Sho-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. Are 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 softly and largely displaced in a small displacement range. A rear suspension device for an automobile, which is characterized by having a hard elastic property in a range.