JPS632713A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To improve the straight advance stability by constituting an elastic bush with three cylinders via elastic members so that the deflection quantity of the elastic bush is made larger when the lateral force is large and when it is small, than when it is medium in the said device utilizing the elastic bush. CONSTITUTION:An elastic bush R2 is constituted of an inner cylinder 21, a middle cylinder 22, and an outer cylinder 22; the first elastic member 24 applied with a pre-load by a spacer 25 is inserted between the inner cylinder 21 and middle cylinder 23; and the second elastic member 26 softer than the first elastic member 24 is inserted between the middle cylinder 22 and outer cylinder 23. According to this constitution, while the lateral force is small, the second elastic member 26 is flexed, and the ratio of the deflection quantity against the lateral force is made large. After the second elastic member 26 is fully flexed, the first elastic member 24 is not substantially flexed due to the pre-load, and the deflection quantity is small. When the lateral force becomes equal to the pre-load or greater, the deflection quantity of the first elastic member 24 is increased. According to this constitution, the straight advance performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automobile suspension device that performs toe control of rear wheels by utilizing the deflection of an elastic bushing.

(Prior Art) When an automobile turns, a lateral load (lateral force) toward the turning center acts on the left and right wheels, especially the wheels on the outside with respect to the turning center. In this case, changing the rear wheels so that they point inward toward the vehicle in the direction of travel (toe-in change) in response to lateral force is effective in preventing oversteering and improving the vehicle's driving stability. This fact is widely known, and examples of prior art based on this technical idea include, for example, Japanese Patent Application Laid-Open No. 58-188708.
There is a suspension structure according to the publication.

The suspension structure described in the publication includes a float connection between a rear suspension arm and a rear wheel support member that rotatably supports the rear wheel using one ball joint and two bushings. By appropriately setting the position of the joint with respect to the center of the rear wheel, the displacement of at least one elastic member in response to lateral force is effectively utilized, thereby accurately changing the toe-in of the wheel. . More specifically, the at least one resilient bushing has a pre-compressed elastic bushing interposed between the inner cylinder and the outer cylinder so that the lateral force is a predetermined value corresponding to the pre-EE'M force. When this happens, the rear wheels are moved in the toe-in direction. In other words, when the lateral force is less than the predetermined value, displacement of the rear wheels in the toe-out direction due to the lateral force is allowed to improve the maneuverability of the vehicle.

(Problem to be Solved by the Invention) However, with the suspension structure described in the above publication, the displacement of the rear wheels in the toe-out direction when the lateral force is small causes the behavior of the vehicle to become too sensitive, resulting in This poses an unfavorable problem in terms of ensuring stability.

Therefore, one object of the present invention is to provide a suspension system for an automobile that can improve the turning performance of an automobile when the lateral force is moderate, while ensuring stability both when the lateral force is small and when the lateral force is large. Our goal is to provide the following.

(Problems to be Solved by the Invention) In order to achieve the above-mentioned object, the present invention has the following configuration. That is, a rear suspension constituent member that is swingably supported by the vehicle body, a rear wheel support member that rotatably supports the rear wheel, and a rear suspension member that is interposed between the rear suspension constituent member and the rear wheel support member, respectively. a suspension device for an automobile, comprising: a hole joint and at least one elastic bushing, and the rear wheel is changed in a toe-in direction using the ball joint as a rocking fulcrum by deflection deformation of the elastic bushing. In the above, the elastic bushing includes an inner cylinder, a middle cylinder, and an outer cylinder each having an inner and outer triple structure, and a first member interposed between the inner cylinder and the middle cylinder, and the middle cylinder. a second elastic member interposed between the outer cylinder and one of the i-members is precompressed, and the other elastic member is applied with a lateral force when the one elastic member starts to deflect; The elastic bushing is set to deflect with a lateral force sufficiently smaller than , and the ratio of the amount of deflection of the elastic bushing to the lateral force is made larger when the lateral force is large and when the lateral force is small than when the lateral force is medium. The structure is as follows.

(Example) Examples of the present invention will be described below based on the attached drawings.

In FIG. 1 showing the suspension structure for the right rear wheel, 1 is a semi-trailing arm as a suspension component, and one fork-shaped end 1a of the arm is attached to a subframe 2 disposed in the vehicle width direction. On the other hand, they are connected via elastic bushings 9 so as to be able to swing vertically.

Further, 3 is a wheel hub as a rear wheel support member that rotatably supports a rear wheel (right rear wheel in FIG. 1) 4, and is integrally formed in a substantially trifurcated shape. Further, 5 is a differential gear box, 6 is a drive shaft that connects the differential gear box 5 and the rear wheel 4 supported by the wheel hub 3, 7 is a strut assembly, and 8
is a stabilizer.

The wheel hub 3 and the other end 1b of the semi-trailing arm 1 are located between the first arm portion 11 of the wheel hub 3 and the first bracket 14 of the semi-trailing arm 1, as shown in FIGS. 1 to 3. The pole joint (P) is provided between the second arm part 12 of the wheel hub 3 and the second bracket 15 of the semi-trailing arm 1 and can be appropriately elastically deformed. and a second elastic bush R1 which is provided between the third arm portion 13 of the wheel hub 3 and the third bracket 16 of the semi-trailing arm 1 and which is appropriately elastically deformable.
They are connected by a total of three support points of the elastic bush R2, and can swing appropriately around the ball joint P (float connection).

The arrangement structure of the ball joint P, the first elastic bushing R1, and the second elastic bushing R2 that connect the wheel hub 3 and the semi-trailing arm 1 allows the suspension to function effectively and control not only the lateral force but also the lateral force. This is the technical basis for accurately expressing toe-in changes of the rear wheel 4 in response to various loads such as power, and therefore, the specific details of the second elastic bushing R2, which is the main subject of the present invention, are as follows. Before describing the configuration in detail, the arrangement structure of these three support points will be explained with reference to FIG. 4.

FIG. 4 is a simplified diagram of the right rear wheel 4 viewed from the side of the vehicle body (that is, from inside the vehicle). In this simplified diagram, the ball joint P is located in the fourth quadrant and the first The elastic bushing R1 is in the first quadrant and the second elastic bushing R2 is in the first quadrant.
are located in the third quadrant.

Further, the first elastic bush R1 is arranged so that its axis is inclined toward the rear outer side of the vehicle body, and the second elastic bush R2 is arranged so that its axis direction is inclined toward the rear inner side of the vehicle body. It is arranged so that In addition,:
In the jfJ4 diagram, a rectangular coordinate system (x, y, z) is constructed by setting a Y-axis in the horizontal left-right direction based on the wheel center O with respect to the coordinates (X, Z). Further, the coordinate system (L, M, N) is a coordinate system whose origin is the center of the ball join) P by parallelly moving the coordinate system (X, Y, z).

Further, the ball joint P, the first elastic bush R
, and each attachment point of the second bushing R2 (the center of the ball joint P, the central point of each axis of the first and second bushings R1 and R2) The mounting surface Q is the intersection line q with the vertical plane containing the wheel center axis (i.e. the YZ plane of the above coordinate system (x, y, z))
In, let W be the offset amount from wheel center 0 on the rear wheel center axis (Y axis), G be the offset on the rear wheel contact surface, and let each offset in the inward direction of the vehicle body be plus (+). The above W is plus (+)! (that is, inside the vehicle body) and G is negative (-) ffl (outside the vehicle body).

Next, the effect on the toe-in change of the rear wheel 4 when the ball joint P, the first elastic bushing R1, and the second elastic bushing R2 are arranged as described above will be described.

■Since the lateral force S acts on the rear wheel contact point in the +Y force direction (inward of the vehicle body), rotate the mounting surface Q of the above ΔPRI R2 counterclockwise around the ball joint P approximately around the L axis. Acts as a moment force. Therefore, the mounting surface Q is rotationally displaced about the L axis inward of the vehicle body with the ball joint P as the center, and the rear wheel 4 undergoes toe-in change.

■The brake force B acts in the +X-axis direction (toward the rear of the vehicle body) with respect to the wheel grounding point, so depending on the (-) amount of G, the mounting surface Q is moved counterclockwise approximately around the L-axis around the ball joint P. Acts as a moment force to rotate. Therefore, the mounting surface Q is rotationally displaced inward of the vehicle body around the ball joint P, and the rear wheel 4 undergoes a toe-in change. At this time, the moment force in the counterclockwise direction around the M axis caused by the brake force B prevents the first elastic push R from being displaced inward of the vehicle body (that is, the forward movement of the rear wheel 4) which impedes the toe-in effect. Therefore, it is preferable to provide a stopper at the axial front end of the first bushing R1 in order to ensure the toe-in change.

■Engine braking force E acts in the child direction (toward the rear of the vehicle body) with respect to the wheel center 〇, so the mounting surface Q is moved to the ball joint P by the (+) amount of W and the (-) amount of G.
It acts as a moment force that rotates clockwise approximately around the M axis with . At that time, the axis of the first elastic bushing R1 is directed outward toward the rear of the vehicle, and the second elastic bushing R2
The axes of the two are located toward the rear and inward of the vehicle body, and the rigidity of the elastic bushings generally has a characteristic of being easily elastically deformed in the axial direction. The rotation of the rear wheel 4 changes to change the toe-in of the rear wheel 4.

In this case, an outward force is applied to the second elastic bush R2, which generates a force that causes toe-out movement around the L axis, so the displacement of the second elastic bush R2 in the outward direction of the vehicle body is restricted. By preventing the rear wheels 4 from moving in the toe-out direction, the toe-in change described above can be easily and reliably performed.

■Engine driving force is - relative to wheel center 〇.
Since it acts in the X direction (towards the front of the vehicle body), the (+) amount of W acts as a moment force that rotates the mounting surface Q approximately counterclockwise around the L axis around the ball joint P. Therefore, as in the case of brake force B above,
The mounting surface Q is rotationally displaced inward of the vehicle body around the ball joint P, and the rear wheel 4 changes in toe-in.

Next, details of the second bushing R2 that determines the toe change of the rear wheel 4 in response to a lateral force will be explained with reference to FIGS. 5 to 10.

First, in FIG. 5, the second elastic bush R2 has an inner cylinder 21, a middle cylinder 22, and an outer cylinder 23, each having a triple structure inside and outside.
It is equipped with Between this inner cylinder 21 and middle cylinder 22,
A first elastic member 24 and a spacer 25 are interposed, and a second elastic member 26 is interposed between the inner cylinder 22 and the outer cylinder 23. The support shaft 27 fixed to the third bracket 16 of the semi-trailing arm 1 is fitted into the inner cylinder 21 without play (see Fig. 6), and the outer cylinder 23 is inserted into the wheel hub 3. Fits into the third arm part 13 without play,
Retained.

As is particularly clear from FIG. 7, the spacer 25 has a substantially half-moon cross section, and is constructed by covering the surface of a metal-shaped main body 25a with a coating layer 25b made of fluororesin. The spacer 25 has its arcuate surface seated on the inner circumferential surface of the middle cylinder 22, and its flat surface seated on a flat surface 21a formed on the inner cylinder 21. The spacer 25 is tightly fitted between the inner cylinder 21 and the middle cylinder 22, and applies precompression (precompression PI - see FIG. 1O) to the first elastic member 24.

More specifically, in the state shown in FIG. 7 with the spacer 25 removed, the gap A and the gap B are BAA, while in the state with the spacer 25 removed, the axis of the inner cylinder 21 is 1 is slightly displaced inward in the vehicle width direction from the axis 2 of the outer cylinder 23! It is said that Then, in the state shown in FIGS. 5 and 6 with the spacer 25 installed, both the shafts 6 are
Sentence! and sentence 2 are made to match. As a result, the first elastic member 24 has a lateral force (indicated by the symbol P) that is a force equivalent to the precompression force P1 (e.g., equivalent to 0.4G).
When it is smaller than , there is almost no deflection deformation, and the precompression force P1
The deflection begins when the lateral force becomes greater than the force equivalent to .

On the other hand, the second elastic member 26 is made relatively soft and will deflect with a lateral force that is sufficiently smaller than the lateral force required to deflect the first elastic member 24.

By setting the deflection characteristics of the first and second elastic members 24 and 26 as described above, the combined deflection characteristics, that is, the deflection characteristics of the second elastic bush R2, are as shown in FIG. 10. As is clear from FIG. 10, considering the case where the lateral force gradually increases from zero, when the lateral force is small, the amount of deflection δ with respect to the lateral force (P) is due to the deflection of the i2 elastic member 26. The proportion of After the second elastic member 26 is sufficiently bent, that is, the first
From Figure 61 (see also Figure 8) onwards, the first ? Since the elastic member 24 is not substantially deflected due to precompression, and the second elastic member 26 is also almost completely deflected, the ratio of the amount of deflection to the lateral force is small. Furthermore, is lateral force the first? When the force becomes equal to or more than the precompression force P1 of the #-type member 24, the first-rate member 24 also begins to deflect, and the ratio of the amount of deflection to the lateral force increases again. Further, when the lateral force increases, the spacer 25 is separated from the inner cylinder 21 (see FIG. 9). In this way, when the lateral force is small and when it is large,
The ratio of the amount of deflection to the lateral force is increased compared to when the lateral force is moderate.

FIG. 11 shows how the toe of the rear wheel 4 changes with respect to the lateral force obtained by the deflection characteristics of the second elastic bushing R2 as described above. As can be easily understood from FIG. 11, in the present invention, while ensuring straight-line stability when the lateral force is small and stability when the lateral force is large, turning performance when the lateral force is moderate is achieved. is ensured. Note that the characteristic line as shown in FIG. 11 may also have a characteristic that rotates clockwise or counterclockwise about the origin 0. Note that the toe-out tendency is largely influenced by the deflection characteristics of the elastic bushing 9 interposed at the connecting portion of the semi-trailing arm 1 to the subframe 2.

Although the embodiment has been described above, the second member 26 between the inner cylinder 22 and the outer cylinder 23 may be used as the member to which precompression is applied. Further, in order to provide precompression, in addition to separately using the spacer 25, various conventional methods can be adopted. Furthermore, the suspension arm may be of any appropriate type, such as a wishbone type.

(Effects of the Invention) As is clear from the above description, the present invention ensures stability when the lateral force is large and turning performance when the lateral force is moderate, while providing straight-line stability when the lateral force is small. In addition, the present invention can be easily put into practice because it is only necessary to modify the deflection characteristics of the conventionally existing elastic members.6

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a suspension to which the present invention is applied. FIG. 2 is a plan view of FIG. 1. FIG. 3 is a diagram of FIG. 2 viewed from the outside of the vehicle. FIG. 4 is a schematic diagram showing the arrangement relationship between a ball joint and an elastic bushing at a joint portion between a rear suspension component and a rear wheel support member. FIG. 5 is a radial cross-sectional view showing an elastic bushing for toe control against lateral forces. FIG. 6 is a sectional view taken along the axis of FIG. 5. Figure 7 is an exploded view of Figure 5. 8 and 9 are diagrams showing how the elastic bushing shown in FIG. 5 changes depending on the magnitude of lateral force. FIG. 10 is a deflection characteristic diagram of the elastic bushing shown in FIG. 5. FIG. 11 is a graph showing toe change characteristics obtained using the elastic bushing shown in FIG. 1: Semi-trailing arm (rear suspension component) 2: Subframe (vehicle body) 3: Wheel hub (rear wheel support member) 4: Rear wheel P: Ball joint R2: Second elastic bush 21: Inner cylinder 22: Medium Cylinder 23: Outer tube 24: First elastic member 25 Varnish spacer (for pre-compression) 26: Second elastic member Fig. 2 tJT Fig. 3 Fig. 5 Fig. 8 Fig. 9 Fig. 10 Fig. th d2 j

Claims (1)

[Claims] (1) A rear suspension component that is swingably supported by the vehicle body, a rear wheel support member that rotatably supports the rear wheel, and a rear wheel support member that is interposed between the rear suspension component and the rear wheel support member, respectively. A suspension device for an automobile, comprising one ball joint and at least one elastic bush, wherein the rear wheel is changed in a toe-in direction using the ball joint as a rocking fulcrum by deflection deformation of the elastic bush, The elastic bushing includes an inner cylinder, a middle cylinder, and an outer cylinder each having an inner and outer triple structure, and a first elastic member interposed between the inner cylinder and the middle cylinder, and a first elastic member interposed between the inner cylinder and the outer cylinder. a second elastic member interposed therebetween, one of the elastic members being precompressed;
When the other elastic member is set to deflect with a lateral force that is sufficiently smaller than the lateral force when the one elastic member starts to deflect, and the ratio of the amount of deflection of the elastic bush to the lateral force is large when the lateral force is large. and a suspension device for an automobile characterized in that when the lateral force is small, the lateral force is larger than when the lateral force is medium.