JPH01306308A - Rear suspension - Google Patents

Abstract

PURPOSE:To prevent the generation of a toe variation in a rear wheel of the bumping time of a suspension, to generate a toe-in displacement and to improve the safe steering of a vehicle by setting the arrangement and elasticity of each arm system. CONSTITUTION:The rigidities in the car body traverse direction of a bush 5(G point), bush 13(T point) and bush 14(A point) are respectively taken Kg, Kt and Ka, the components in the vertical face in the car body front and back directions of the distance between a CB axis and the G and H points are taken Lg, Lh respectively and the components in the vertical face in the car body front and back directions of the distance between a CH axis and the G and B points are respectively taken LG' and LB. In order to obtain the toe-in dis placement by the link interference surely for a suspension stroke without generat ing a toe variation the conditions of LG<2>.Kg<=LH<2>.Kt, LG.LG'.Kg<=LB<2>.Ka may be satisfied. The displacement in the toe-out direction of a rear wheel can thus be prevented and the safe steering of a vehicle can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a rear suspension used in a vehicle such as an automobile.

(Prior Art) In recent years, as the engine performance of automobiles continues to improve, there has been a demand for improved steering stability through improved suspension performance. It is also known that controlling cornering power (the so-called grip force that brings out the maximum tire performance) through toe control, as typified by 4WS, is important as an element to improve handling stability rather than suspension characteristics. ing. In order to effectively generate this cornering power, it is particularly effective to set the toe change of the rear wheel with respect to the suspension stroke to the toe-in (bump understeer) at the time of bump. It is desired to prevent the wheel from being displaced in the toe-out direction.

Conventionally, for example, according to Japanese Patent Publication No. 62-48606,
a wheel support member rotatably supporting a rear wheel; a trailing arm having a rear end connected to the wheel support member and having a front end pivotally connected to a vehicle body side member and extending substantially in the longitudinal direction of the vehicle body;
A pair of upper and lower lateral arms extending in the vehicle width direction and provided between the wheel support member and the vehicle body side member; A rear suspension is known in which the lateral arm and the assist arm are connected to the wheel support member or the vehicle body side through one pivoting means at each end of the lateral arm and the assist arm, respectively. .

In the above-mentioned conventional suspension, the assist arm is shorter than the lower lateral arm so that toe-in during bumping can be obtained through link interference during suspension stroke.

(Problem to be Solved by the Invention) However, the above conventional example attempts to obtain toe-in action at the time of bump by simply setting the length of the link. Since stiffness (or elasticity) was ignored,
Depending on the settings of the elasticity of the bushings, etc., link interference to obtain toe-in action may be completely absorbed by the deformation of the bushings, resulting in the rear wheel not being able to obtain the desired toe-in displacement, or toe-out displacement occurring. There was a problem.

For this reason, a suspension that does not at least cause toe-out displacement with respect to the vertical stroke of the rear wheel is desired.

[Structure of the invention]

(Means for Solving the Problems) The present invention was devised to solve the above problems, and by optimally setting the layout of each arm of the suspension and the rigidity of each arm system, the rear wheel A wheel support member that reliably prevents a toe change or obtains a toe-in displacement with respect to the vertical stroke of the vehicle, and that rotatably supports the rear wheel. a trailing arm pivotally connected to a side member and extending substantially in the longitudinal direction of the vehicle; an upper arm extending in the vehicle width direction and pivotally connected to an upper part of the wheel support member and the vehicle body side member; a lower arm that extends in the width direction and is pivotally connected between a lower part of the wheel support member and the vehicle body side member; a lower arm that extends in the vehicle width direction forward of the lower arm and below the upper arm and that is connected to the wheel; An assist arm is provided which is pivotally connected to the supporting member or the trailing arm and the vehicle body side member and is shorter than the lower arm, and the lower arm and the assist arm indicated in t interfere with the vertical stroke of the rear wheel. In the rear suspension, LG is a component of the distance between the axis connecting the outer end of the upper arm and the outer end of the lower arm and the elastic center support point of the trailing arm relative to the vehicle body in a vertical plane in the longitudinal direction of the vehicle body. LH is the component of the distance between the axis connecting the outer end of the lower arm and the outer end of the assist arm in a vertical plane in the longitudinal direction of the vehicle body. LG' is the component of the distance between the elastic center support point and the longitudinal direction of the vehicle body in a vertical plane in the longitudinal direction of the vehicle body, and LG' is the longitudinal component of the distance between the outer end of the lower arm and the axis connecting the outer end of the upper arm and the outer end of the assist arm. The component in the direction perpendicular to the plane is LB, the lateral stiffness of the elastic center support point of the trailing arm relative to the vehicle body is Kg, the lateral stiffness of the assist arm system is Kt, and the lateral stiffness of the lower arm system is Ka. In that case, LG”・Kg
≦LH2・Kt LG−LG′・Kg≦LB′ ・The arrangement and elasticity of the system for each arm are set so as to satisfy the following conditions.

(Function) According to the present invention, by setting the arrangement and elasticity of each arm system as described above, it is possible to prevent toe change or toe-in displacement in the rear wheels when the suspension bumps, thereby improving vehicle handling. It improves the performance.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

As shown in FIGS. 1 to 3, the rear wheel 1 is rotatably supported by a spindle 3 provided at the center of a knuckle 2, which serves as a wheel support member, and is supported by a rear part of a trailing arm 4 arranged approximately in the front-rear direction. The knuckle 2 is fixed by means such as welding. The front end of the trailing arm 4 is elastically supported by the vehicle body via a rubber bushing 5, and the center point of this rubber bushing 5 is represented by a point G in the drawing. Also,
The outer end of an upper arm 7 arranged in the vehicle width direction is pivotally attached to the upper part of the knuckle 2 at a position directly above the spindle 3 in a side view via a ball joint 6, and the inner end of the upper arm is attached via a rubber bush 8. It is elastically supported by the vehicle body. The center points of these ball joints 6 and rubber bushes 8 are represented by point 0 and point Q, respectively, in the illustration. Further, the outer end of an assist arm 9 arranged in the vehicle width direction is pivotally attached to a position forward of the spindle 3 at the bottom of the knuckle 2 via a ball joint 10, and a position rearward of the spindle 3 at the bottom of the knuckle 2. , the outer end of the lower arm 11 arranged in the vehicle width direction is connected to the ball joint 1.
It is pivotally connected via 2. The assist arm 9 is formed shorter than the lower arm 11, and the inner ends of the assist arm 9 and the lower arm 11 are each provided with a rubber bush 13.
．． It is elastically supported by the vehicle body via 14. The center points of these ball joints 10.12 and rubber bushes 13.14 are represented by point H, point B, point T, and point A, respectively, in the illustration. In addition, the reference numeral 15 in the figure indicates the fuel tank.
Further, 16 each represents a spare tire well.

Further, the trailing arm 4 described above is a rigid body having a closed cross-sectional structure, and the assist arm, upper arm, and lower arm are less than iron-clad, and the toe change of the suspension having the above configuration will be analyzed.

First, the stiffness of the bushings 5 (point G), bushings 13 (point T), and bushings 14 (point A) in the lateral direction of the car body is Kg, Kt, and Ka, respectively, and the amount of deflection of each bushing in the lateral direction of the car body is δg, respectively. Let δ be and δa. In addition, the components of the distances between the CB axis and points G and H in the vertical plane in the longitudinal direction of the vehicle body are LG and LH, respectively, and the components of the distances between the CH axis and points G and B in the vertical plane in the longitudinal direction of the vehicle body are LG and LH, respectively. '.

I will be LB.

Here, we will consider conditions under which no toe change occurs.

First, when considering the balance of moments around the CB axis, the following relationship holds: Kg・δg−LG=Kt・δt−LH (1).

In this case, the trailing arm 4 and the assist arm 9
Since is a rigid body, considering the ratio of the amount of deflection of the bushing 5 and the bushing 13 in the lateral direction of the vehicle body, the following relationship holds true: 6g - LH = δt - LG (2).

Rearranging the above equations (1) and (2), LG"・Kg=LH" ・Kt ... (3)
The following relationship is obtained, and this is the condition for preventing toe change when considering the balance of forces around the CB axis.

Next, considering the balance of moments around the CH axis, Kg-6g-LG'=Ka ・δa-LB-(
The relationship 4) holds true.

In this case, since the trailing arm 4 and the lower arm 11 are rigid bodies, considering the ratio of the amount of deflection in the lateral direction of the vehicle body between the bushings 5 and 14, δg - LB - δa
-LG'-(5) holds true.

Rearranging equations (4) and (5) above, LG' ・LG -Kg=LB2 ・Ka
-(6) is obtained, and this is the condition for preventing toe change when considering the balance of forces around the CH axis.

In the suspension configured as described above, there are two types of toe changes caused by link interference due to the suspension stroke.

■The assist arm interferes with the CB axis.

■The lower arm interferes with the CH axis.

Considering the above case (■), since the assist link 9 is shorter than the lower arm 11, if the moment generated by the assist link 9 that pulls the front part of the knuckle inward is greater than the supporting moment of the six-point bushing, the rear wheel will move in the toe-in direction. Displaced to.

Therefore, by changing the relationship in equation (1) above, Kg・6g
-LG<K t・δt−LH If the condition (7) is satisfied, toe-in displacement can be obtained with respect to the suspension stroke.

When the above equation (7) is rearranged by the above equation (2), LG'
・Kg<LH2・Kt...(8).

Also, considering the case (■) above, since the lower arm 11 is shorter than the assist link 9, if the moment generated by the lower arm pushing the rear part of the knuckle outward is greater than the supporting moment of the six-point bushing, the rear wheel will move in the toe-in direction. Displace.

Therefore, by changing the relationship in equation (4) above, Kg−δg−
If the condition LG′<Ka·δa−L B −(9) is satisfied, toe-in displacement can be obtained with respect to the suspension stroke.

When the above equation (9) is rearranged by the above equation (5), LG-
L, G'・Kg<L, B''・Ka −αQ.

Therefore, by selecting the arrangement of each arm and the rigidity of each bush so as to satisfy the α0 equation (8) above, it is possible to reliably obtain toe-in displacement due to link interference with respect to the suspension stroke as shown in FIG.

Therefore, in order to avoid at least toe-out displacement, from the above formulas (3), (6), and (8) 00, it is necessary to
'・Kg≦LH' ・Kt ・・・00LG
-LG'.Kg≦LB'.Ka -Q2).

Also, if the above QO (formula 121 is satisfied, Ka=Kt
It is possible to prevent toe-out displacement while using the bushings 13 and 14, and cost reduction effects can be obtained by sharing parts.

Note that the present invention is not limited to the above-mentioned embodiment at all, and for example, the assist arm may be attached to the trailing arm. Alternatively, the trailing arm may be a leaf spring as in the conventional example. In this case, a pseudo elastic center point is calculated taking into account the elasticity of the trailing arm and the elasticity of the bushing, and this elastic center point is It is necessary to make each setting based on the following. Furthermore, rubber bushings may be provided at both ends of the arms arranged in the vehicle width direction, or rubber bushings may be provided only at the outer ends, but in these cases, the stiffness of each arm system as a whole in the vehicle width direction is calculated and based on this. You need to configure each setting.

〔Effect of the invention〕

As described above in detail along with the embodiments, according to the present invention, displacement of the rear wheels in the toe-out direction can be reliably prevented by link interference with the suspension stroke, and the steering stability of the vehicle can be improved. This has the effect of providing a rear suspension that improves design performance and facilitates design work.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention, FIG. 2 is a side view of the same, FIG. 3 is a rear view of the same, and FIG. 4 is a characteristic diagram of the above embodiment. 2...knuckle, 4...trailing arm. 8... Upper arm, 13... Assist arm. 14...lower arm. 5.8, 13.14...Rubber bushing 6.10.12
... Ball joint applicant Mitsubishi Motors Corporation Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] A wheel support member that rotatably supports a rear wheel, and a trailing member having a rear portion connected to the wheel support member and having a front end pivotally connected to a vehicle body side member and extending approximately in the longitudinal direction of the vehicle body. an upper arm extending in the vehicle width direction and pivotally connected to the upper part of the wheel support member and the vehicle body side member; and an upper arm extending in the vehicle width direction and connecting the lower part of the wheel support member and the vehicle body side member. a lower arm that is pivotally connected between the lower arm and the lower arm that extends in the vehicle width direction forward of the lower arm and below the upper arm and that is pivotally connected to the wheel support member or the trailing arm and the vehicle body side member; and an assist arm that is shorter than the lower arm, and in which the lower arm and the assist arm interfere with the vertical stroke of the rear wheel, an axis connecting the outer end of the upper arm and the outer end of the lower arm; LG is the component of the distance between the elastic center support point of the trailing arm relative to the vehicle body in a vertical plane in the longitudinal direction of the vehicle body, and LG is the component between the axis connecting the outer end of the upper arm and the outer end of the lower arm and the outer end of the assist arm. LH is the component of the distance in the vertical plane in the vehicle longitudinal direction; The component is LG', the component of the distance between the axis connecting the outer end of the upper arm and the outer end of the assist arm and the outer end of the lower arm in a vertical plane in the longitudinal direction of the vehicle body is LB, the elastic central support of the trailing arm to the vehicle body. When the lateral stiffness of the vehicle body at the point is Kg, the lateral stiffness of the assist arm system is Kt, and the lateral stiffness of the lower arm system is Ka, then LG^2・Kg≦LH^2・Kt LG・LG A rear suspension characterized by setting the arrangement and elasticity of each arm system so as to satisfy the condition '・Kg≦LB^2・Ka