JP6543068B2 - Vehicle suspension system - Google Patents

Description

  The present invention relates to a suspension device of a vehicle in which a link member connected to a wheel support member rotatably supporting a wheel is connected to a vehicle body via an elastic member.

  Conventionally, as a suspension device of a vehicle, there is a type in which a wheel support member rotatably supporting a wheel is connected to a vehicle body via a link member and a damper. In such a suspension device, generally, the link member and the damper are connected to the vehicle body so as to enable compliance steering via a mounting member such as a rubber bush, and when lateral force is input to the vehicle, geometrically The link member and the damper are displaced about the center of the determined roll, and the vehicle body rolls.

  Since an excessive generation of the vehicle body roll due to such lateral force leads to a decrease in steering stability, for example, Patent Document 1 supports a wheel support member that rotatably supports a wheel so as to be vertically swingable. Suspension system (link member) is disposed at a distance between the front and the rear of the vehicle, in which the imaginary roll axis assumed for the elastically supported suspension member is properly set in the suspension geometry A technique has been proposed to improve the steering stability of the vehicle by arranging the vehicle.

Japanese Patent Application Laid-Open No. 6-64421

  However, in an actual vehicle, since friction exists in the link portion of the link member and the actuating portion of the damper, when a small lateral force is input, such as at the time of straight ahead or minute steering, the link member or The damper hardly moves, and the mount member such as a rubber bush is mainly displaced to roll the vehicle body.

  Conventionally, the rigidity of a mounting member such as a rubber bush is determined from the balance between steering stability and vibration transmission characteristics, and if the rigidity of the mounting member is increased to suppress the roll at the time of small lateral force input, Although the movement is suppressed and the steering stability is improved, the damping and noise suppression performance is reduced. Conversely, if the rigidity of the mounting member is lowered, the vibration control and noise suppression performance will be improved, but the steering stability will be lowered, and the steering stability and the vibration suppression and noise suppression performance will be contradictory.

  The present invention has been made in view of the above circumstances, and controls the roll at the time of minute lateral force input without intentionally increasing the rigidity of the mount member, and improves the steering stability, and the damping and noise suppression performance. It is an object of the present invention to provide a suspension device of a vehicle that can achieve both.

A suspension system of a vehicle according to an aspect of the present invention is a suspension system of a vehicle in which a link member coupled to a wheel support member rotatably supporting a wheel is elastically coupled to a vehicle body via a mount member, The connection position of the left and right mount members to the vehicle body in the vehicle width direction is set above the connection position of the link member and the wheel support member, and the horizontal spring constant of the mount member is in the vertical direction. The elastic centers of the left and right mount members are disposed in the vicinity of the principal axis of inertia passing through the center of gravity of the vehicle while being set to a characteristic relatively larger than the spring constant .

  According to the present invention, it is possible to optimize the rigidity of the mount member without intentionally increasing the rigidity of the mount member and to suppress the roll at the time of minute lateral force input, thereby improving the steering stability, and suppressing vibration and noise. It is possible to achieve both the improvement of the performance.

An explanatory view showing a suspension device of a vehicle Appearance of transverse link Cross section of bush An explanatory view showing the relationship between the arrangement of the bush and the elastic center

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a suspension system of a vehicle, and in the present embodiment, a strut type suspension system disposed at the front of a vehicle body.

  The suspension device 1 has a left-right symmetrical structure in the vehicle width direction with respect to a center line extending in the longitudinal direction of the vehicle, and rotatably supports a wheel (front wheel) 2 which is a steering wheel via a hub (not shown). A strut unit 5 and a transverse link 10 are connected to an axle housing 3 as a wheel support member. In FIG. 1, F and R indicate the longitudinal direction of the vehicle, and U and D indicate the vertical direction of the vehicle.

  The strut unit 5 is configured by integrating the shock absorber 6 and the suspension spring 7 into one unit, the upper end on the suspension spring 7 side is attached to the vehicle body frame, and the lower end on the shock absorber 6 side is the axle housing 2 Is attached to the top of the. The strut unit 5 rotates around the turning shaft together with the axle housing 2 when the front wheel 2 is turned, and expands and contracts according to the stroke of the suspension device 1.

  Further, the transverse link 10 is a link member that connects the axle housing 3 to the vehicle body, and in the present embodiment, as shown in FIG. 2, it is configured as a lower arm formed in a substantially L shape. The traverse link (hereinafter referred to as "lower arm") 10 is connected to the lower portion of the axle housing 3 and is elastically supported at two points on the vehicle body side, and from the front side of the vehicle when the vehicle is stationary. When viewed, it is disposed with a predetermined inclination so that the connecting position with the vehicle body side inside the vehicle width direction is higher than the connecting position with the axle housing 3 outside the vehicle width direction.

  Specifically, the lower arm 10 is connected at one end to the lower portion of the axle housing 3 via the ball joint 11, and the axle housing 3 swings (rotates) about the center point of the ball joint 11 with respect to the lower arm 10. It is possible. Further, the lower arm 10 is connected to the vehicle body at two connecting portions arranged apart from each other in the longitudinal direction of the vehicle, and is a swing that is a straight line connecting the two connecting portions according to the stroke of the suspension device. It can swing (rotate) around the central axis.

  The front side connecting portion of the lower arm 10 to the vehicle body is via a bush 12 which is a mounting member at a side end portion of a front cross member 30 which is a beam shaped member extending in the vehicle width direction at the vehicle body lower portion at the front of the vehicle. It is connected. Further, the rear side connection portion of the lower arm 10 is connected via a bush 13 to a support plate 32 which is connected to the support member 31 of the cradle structure on which the front cross member 30 is suspended. In the present embodiment, the bushes 12 and 13 are filled with a rubber-based material having a vibration-proof function between the cylindrical outer cylinder and the inner cylinder, and the outer cylinder and the inner cylinder are bonded by vulcanization of rubber, etc. It is a rubber bush joined by

  The lower arm 10 is provided with cylindrical portions 10a and 10b into which the outer cylinders of the front and rear bushes 12 and 13 are press-fitted. The front cylindrical portion 10a is disposed such that the axial direction thereof substantially coincides with the longitudinal direction of the vehicle, and the rear cylindrical portion 10b is disposed substantially in the vertical direction. Each of the bushes 12 and 13 has an outer cylinder press-fit into the cylindrical portions 10a and 10b, and is connected to the front cross member 30 and the support plate 32 by a bolt inserted into the inner cylinder.

  Further, a stabilizer 20 extending in the vehicle width direction is connected to the front edge portions of the left and right lower arms 10 via a link 21. For example, when the left and right suspensions are relatively displaced in the reverse phase direction, for example, when the vehicle is rolling, the stabilizer 20 generates a resilient force by generating a spring reaction force by the middle portion being twisted.

  In the front cross member 30, a steering system 40 for steering the front wheel 2 in accordance with the operation of a steering wheel (not shown) is disposed. The steering system 40 includes a steering gear box 41 and tie rods 42.

  The steering gear box 41 includes, for example, a rack and pinion mechanism, and converts the rotational movement of the steering shaft 43 connected to the steering wheel into a linear movement in the vehicle width direction. The tie rod 42 is a rod-like member that connects the steering gear box 41 and the front end of the axle housing 3, transmits the movement of the steering rack to the axle housing 3, and steers the axle housing 3.

  The suspension device 1 having the above-described configuration receives the lateral force from the strut unit 5 and the lower arm 10 when the vehicle receives a lateral force or the like, and the strut unit 5 and the lower arm 10 center around the roll axis geometrically determined. Is displaced. As a result, a rotational moment is generated between the roll axis and the inertial main axis passing through the center of gravity of the vehicle, and the vehicle body rolls.

  On the other hand, when the input is very small, such as when going straight or when the minute steering is performed, friction is present in the strut unit 5 and the lower arm 10, so the strut unit 5 and the lower arm 10 hardly move due to this friction. At the time of micro lateral force input, the bush 12 is mainly displaced, and the vehicle body is rolled by the moment generated between the elastic centers of the right and left bushes 12 and the principal axis of inertia.

  The rigidity of the bush 12 may be increased in order to suppress the body roll when the minute lateral force is input to enhance the steering stability. However, if the rigidity of the bush 12 is increased, the vibration absorbing performance is lowered. Therefore, in the present embodiment, the connection position between lower arm 10 and front cross member 30 via bush 12 is inclined to be higher than the connection position between lower arm 10 and axle housing 3 While arranging, the elastic characteristics of the bush 12 in the vertical direction and the horizontal direction (vehicle width direction) are optimized, and the elastic centers of the left and right bushes 12 are set to be in the vicinity of the inertial main axis L (see FIG. 4).

  Specifically, as shown in FIG. 3, for example, as shown in FIG. 3, the elastic properties of the bush 12 are prevented from being disposed between the outer cylinder 12a press-fitted and fixed to the cylindrical portion 10a of the lower arm 10 and the inner cylinder 12b. In the rubber portion 12c made of a vibration rubber, an offset (hollow portion or recess) 12d is provided at opposite positions in the upper and lower radial directions to make the displacement anisotropic, and the vertical spring constant and the horizontal spring constant Are set to different characteristics. Incidentally, in order to make the displacement of the bush 12 have anisotropy, in addition to the formation of the ridge 12d, for example, a hard member such as an intermediate plate (interleaf) may be embedded, and these plural means May be used in combination.

  That is, the bush 12 connecting the lower arm 10 to the vehicle body side is disposed at a tilt angle so as to be higher than the joint position of the lower arm 10 with the axle housing 3 side. The spring constant of the above is optimized by setting it to a characteristic relatively larger than the spring constant in the vertical direction, and the elastic center is moved upward while suppressing the lateral displacement of the left and right bushes 12. As a result, it is possible to suppress the roll at the time of micro input without comparably increasing the rigidity of the bush 12 and to achieve both improvement in steering stability and improvement in the damping / noise suppression performance.

Here, as shown in FIG. 4, the span on one side between the left and right bushes 12 is b, the distance in the vertical direction between the bush 12 and the elastic center P is h, and the inclination angle of the lower arm 10 is α. Assuming that the spring constant in the tilt angle direction is Kq, and the spring constant in the direction orthogonal to the tilt angle direction is Kp, the relationship represented by the following equation (1) holds between them.
Kp / Kq = (h · cos ² α + b · sin α · cos α) / (b · sin α · cos α-h · sin ² α) (1)

  In the equation (1), the span b and the inclination angle α are known values according to the suspension geometry. On the other hand, the vertical distance HG from the bush 12 to the main axis of inertia can be calculated based on vehicle specifications. Therefore, for example, the spring constant Kq of the bush 12 is set in advance corresponding to the vehicle characteristics, and the span b and inclination angle α are applied to the equation (1) and the distance h is HG and the spring constant ratio Kp / Kq By determining the spring constant ratio Kp from the calculated spring constant ratio Kp / Kq, the elastic center P of the bush 12 can be made to coincide with the principal axis of inertia L.

  As described above, in the present embodiment, the spring constant of the bush is optimized to set the elastic center in the vicinity of the inertia main axis, so that the hardness of the bush is not increased intentionally, but the side during straight running or minute steering etc. It is possible to reduce the roll of the vehicle for minute input in the direction and apparently reduce the lateral displacement at the center of gravity position. As a result, it is possible to achieve both improvement in steering stability and improvement in damping performance and noise suppression performance, and in particular, by setting the elastic center of the bush on the steering wheel side near the inertia main shaft, struts by friction. It is possible to improve the stability and responsiveness in the minute steering where the unit 5 and the lower arm 10 hardly move.

1 Suspension Device 2 Wheel 3 Axle Housing 5 Strut Unit 10 Transverse Link (Lower Arm)
12 Bush 12c Rubber part 30 Front cross member 40 Steering system P Elastic center L Inertial main axis

Claims (3)

A suspension device for a vehicle, wherein a link member coupled to a wheel support member rotatably supporting a wheel is resiliently coupled to a vehicle body via a mount member,
The connection position of the left and right mount members to the vehicle body in the vehicle width direction is set above the connection position of the link member and the wheel support member, and the horizontal spring constant of the mount member is in the vertical direction. A suspension apparatus for a vehicle, wherein the elastic centers of the left and right mount members are set in the vicinity of an inertial main axis passing through the center of gravity of the vehicle, with a characteristic of being relatively larger than a spring constant .   The suspension device for a vehicle according to claim 1, wherein the mounting member is a bush having anti-vibration rubber.   The vehicle wheel suspension device according to claim 1 or 2, wherein the wheel support member is a support member for a steered wheel.

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