Vehicle suspension system

Abstract: A wheel support (1) rotatably supports a dirigible wheel (2). An upper wheel-support support member (3) connects an upper portion of the wheel support to the vehicle body, and a lower wheel-support support member (4) connects a lower portion of the wheel support to the vehicle body. The upper and lower wheel-­ support support members are arranged to respectively define upper and lower pivot points which define an imaginary kingpin axis. At least one (3) of the upper and lower wheel-support support members (3, 4) is formed of a pair of separate link members (5, 6) one end of each of which is pivoted on the vehicle body at different portions (7) of the vehicle body and the other end of each of which is rotatably connected to the wheel support at different portions (8) of the wheel support. The upper and lower wheel-support support members are arranged so that the upper portion of the wheel support is displaced more inward than the lower portion thereof when the wheel makes a turn as the outer wheel, and so that the upper portion of the wheel support is displaced less inward than the lower portion thereof when the wheel makes a turn as the inner wheel.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a vehicle suspension system, and more particularly to a vehicle suspension system for supporting dirigible wheels of a vehicle. Description of the Prior Art As the vehicle suspension system for supporting the dirigible wheels, there have been known a wishbone type suspension in which upper and lower ends of each wheel support member for supporting a dirigible wheel for rotation are connected to the vehicle body respectively by way of upper and lower arms extending in the transverse direction of the vehicle body, and a strut type suspension in which a strut is used for connecting the upper end of the wheel support member to the vehicle body in place of the upper arm in the wishbone type suspension. See Japanese Patent Publication No. 52(1977)-9889 (DE-A-19 38 850), for example. In this known suspension system the link members of the upper wheel-support support member are arranged in a substantially transverse direction of the vehicle body, however in such a way that during cornering a negative camber is present on both steerable wheels. The dirigible wheels supported by such a suspension system should be controlled, in order to increase the road gripping force and to improve the turning performance, so that the inner wheel has a positive camber and the outer wheel has a negative camber when they are making a turn. As a means for controlling the camber of the dirigible wheels during turning in the manner described above, there has been known an arrangement disclosed in Japanese Unexamined Patent Publication No. 58(1983)-67508 (US-A-44 40 420) in which a pair of link members forming the upper arm are disposed so that the axis of symmetry thereof is set at an acute angle to the wheel axis and is positioned on the rear side of the wheel axis, and the imaginary kingpin axis (imaginary pivot axis) of the outer wheel is moved rearward to increase the caster angle so that the outer wheel has a negative camber. The first part of Claim 1 is based on this prior art. However, since the two link members must be disposed so that the axis of symmetry thereof is set at an acute angle to the wheel axis, one of the link members must be connected to the vehicle body at a substantially outer portion of the vehicle body. This makes it difficult to apply the arrangement to conventional vehicles, as they are. In view of the foregoing observations the primary object of the present invention is to provide a vehicle suspension system as stated in the first part of claim 1 which is apt to generate a negative camber on the outer wheel and a positive camber on the inner wheel when cornering, and which can be easily applied to conventional vehicles as they are. This object is achieved by the features stated in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front elevational view of a suspension system in accordance with an embodiment of the present invention, Figure 2 is a cross-sectional view taken along line II-II in Figure 1, Figure 3 is a cross-sectional view taken along line III-III in Figure 1, Figure 4 is a schematic perspective view of the suspension system shown in Figure 1, and Figures 5(a) to 5(c) are schematic views showing various arrangements of the link members. DESCRIPTION OF THE PREFERRED EMBODIMENTS In Figures 1 to 4 which show a wishbone type suspension in accordance with an embodiment of the present invention, a wheel support 1 for rotatably supporting a dirigible wheel 2 is connected to the vehicle body VB by way of an upper wheel-support support member (an upper arm 3 in this particular embodiment) which defines an upper one of the pivot points defining an imaginary kingpin axis (to be described later) and a lower wheel-support support member (a lower arm 4 in this particular embodiment) which defines a lower one or the other of the pivot points defining the imaginary kingpin axis. The upper arm 3 comprises separate forward and rearward link members 5 and 6 which extend in the transverse direction of the vehicle body. One end of each of the link members 5 and 6 is pivotally mounted on the vehicle body VB by way of rubber bushings 7 at portions removed from each other in the longitudinal direction of the vehicle body VB, and the other end of each of the link members 5 and 6 is connected for rotation to the upper end portion of the wheel support 1 by way of ball joints 8 at portions removed from each other in the longitudinal direction of the vehicle body VB. The lower arm 4 comprises a single bifurcated member (a so-called A-shaped arm) having an apex and a pair of legs. The ends of the legs of the lower arm 4 are pivotally mounted on the vehicle body VB by way of rubber bushings 9 at portions removed from each other in the longitudinal direction of the vehicle body, and the apex of the lower arm 4 is connected for rotation to the lower end portion of the wheel support 1 by way of a ball joint 10. The wheel support 1 is provided with a rearwardly projecting knuckle arm portion 1a and the free end of the arm portion 1a is connected to one end of a tie rod 11. The other end of the tie rod 11 is pivotally connected to one end of a steering rack member 11a. When a steering force is transmitted to the wheel support member 1 by way of the tie rod 11 and the arm portion 1a of the wheel support 1, the dirigible wheel 2 is turned about the imaginary kingpin axis k which is the straight line passing through the intersection of the extensions of the axes of the link members 5 and 6, and the junction of the lower arm 4 to the wheel support 1, i.e., the ball joint 10. Figures 5(a) to 5(c) show various arrangements of the forward and rearward link members 5 and 6 divided according to the angles α and β by which the link members 5 and 6 are inclined with respect to the transverse direction of the vehicle body as viewed in plan when the vehicle is running straight. It is assumed that the angle α is positive when the forward link member 5 is inclined forward (upward as seen in the figures) with respect to the transverse direction of the vehicle body, and it is assumed that the angle β is positive when the rearward link member 6 is inclined rearward (downward as seen in the figures) with respect to the transverse direction of the vehicle body. In the arrangement shown in Figure 5(a), the angles α and β are both positive and the angle α is larger than the angle β (0<β<α). In the arrangement shown in Figure 5(b), the angle β is zero and the angle α is positive (β=0<α). In the arrangement shown in Figure 5(c), the angle β is negative and the angle α is positive (β<0<α). Further, in Figures 5(a) to 5(c), the position of the link members 5 and 6 and the wheel support 1 when the vehicle is running straight is shown by the solid line, the position of the link members 5 and 6 and the wheel support 1 when the wheel makes a turn as the outer wheel is shown by the chain line, and the position of the link members 5 and 6 and the wheel support 1 when the wheel makes a turn as the inner wheel is shown by the dashed line. In the embodiments described above, the upper wheel-support support member, i.e. the link members 5 and 6, are arranged so that, when the dirigible wheel on the wheel support 1 makes a turn as the outer wheel in response to operation of the steering wheel, the displacement in the transverse direction of the vehicle body of a point on the upper portion of the wheel support is positive (when the displacement toward the inner side of the vehicle body is assumed to be positive) at least at the beginning of the turn, and so that, when the dirigible wheel on the wheel support 1 makes a turn as the inner wheel in response to operation of the steering wheel, the former displacement is negative at least at the beginning of the turn. In Figures 5(a) to 5(c), points indicated at P1 and P2 are shown as typical points on the upper and lower wheel-support support members 3 and 4 which are symmetrical to each other with respect to the horizontal plane including the wheel center. The point P1 is the middle point between the junctions of the link members 5 and 6 and the upper end portion of the wheel support 1 and the point P2 is the junction of the A-shaped arm and the lower end portion of the wheel support 1. The point P2 does not undergo displacement as the wheel makes a turn. In order to satisfy the condition described above in the embodiment shown in Figures 1 to 4, the arrangement of the link members 5 and 6 must be one of those shown in Figures 5(a) to 5(c). In any one of the embodiments described above, when the wheel 2 is turned to make a turn as the outer wheel as indicated at 2' in Figures 2 and 3, the wheel support 1 which is swung in response to the turning of the wheel 2 is caused to tilt inward at the top to make negative the camber of the wheel 2 since the upper and lower wheel-support support member 3 and 4 are arranged so that the upper portion of the wheel support 1 is displaced inwardly as described above. On the other hand, when the wheel 2 is turned to make a turn as the inner wheel as indicated at 2'' in Figures 2 and 3, the wheel support 1 is caused to tilt outwardly at the top to make positive the camber of the wheel 2, at least at the beginning of the turn. As can be understood from the description above, in accordance with the present invention, the link members 5 and 6 can be arranged relatively freely, and the junctions of the link members 5 and 6 and the vehicle body (the rubber bushings 7) need not be disposed at a substantially outer portion of the vehicle body. Accordingly the present invention can be applied to conventional vehicles, as they are. In the embodiments described above the junctions of the link members 5 and 6 and the upper or lower end portion of the wheel support 1 are removed from each other solely in the longitudinal direction of the vehicle body so that the pivotal axis joining the junctions of the link members 5 and 6 to the vehicle body extends in the longitudinal direction of the vehicle body.

Claims: A vehicle suspension system for supporting a dirigible wheel of the vehicle, comprising a wheel-support (1) which rotatably supports the dirigible wheel (2), an upper wheel-support support member (3) comprising a pair of separate link members (5, 6) one end of each of which is pivoted on the vehicle body and the other end of each of which is pivoted on the wheel-support, and a lower wheel-support support member (4) substantially extending in the transverse direction of the vehicle body and comprising a single arm member one end of which is pivoted on the vehicle body at two different connecting points (9) and the other end of which is pivoted on the wheel support (1) at a single point (10), the upper and lower wheel-support support members (3, 4) being arranged to respectively define upper and lower pivot points defining an imaginary kingpin axis (k) characterized in that said link members (5, 6) extend substantially in the transverse direction of the vehicle, whereby the connecting line of the pivot points (7) of the link members (5, 6) on the vehicle body and the connecting line of the pivot points (8) of the link members (5, 6) on the wheel support (1), in the straight ahead position of the wheel, are substantially parallel to the longitudinal axis of the vehicle, and the front link member (5) is inclined with respect to the transverse direction of the vehicle body by an angle α greater than an angle β by which the rear link member (6) is inclined with respect to the transverse direction of the vehicle body, as viewed in plan when the vehicle is running straight, it being assumed that the angle α is positive when the front link member (5) is inclined forward with respect to the transverse direction, when viewed from the outer pivot point to the inner pivot point, and the angle β is positive when the rear link member (6) is inclined rearward with respect to the transverse direction, when viewed from the outer pivot point to the inner pivot point, whereby the dirigible wheel (2) has a negative camber when turned, at least at the beginning of the turn, as the outer wheel when cornering and a positive camber when turned, at least at the beginning of the turn, as the inner wheel when cornering. A vehicle suspension system as defined in claim 1, characterized in that the single arm member is bifurcated and has an apex and a pair of legs, the ends of the legs being pivotally mounted on the vehicle body at different points (9) and the apex being connected to the wheel support at a single point (10). A vehicle suspension system as defined in any of claims 1 or 2, characterized in that the wheel support (2) is provided with a rearwardly extending knuckle arm portion (1a) connected to a steering force transmission member (11) to drive the wheel support in response to operation of a steering wheel.

Inventors: EDAHIRO TAKESHI, INOUE HITOSHI, KONDO TOSHIRO, TAKATA NAOTO, EDAHIRO, TAKESHI, INOUE, HITOSHI, KONDO, TOSHIRO, TAKATA, NAOTO
Applicants: MAZDA MOTOR, MAZDA MOTOR CORPORATION
Application year: 1987
Main classification: B60G3
IPC codes: B60G3