FR2880585A1 - Rear end device for use in motor vehicle, has tie rod connecting rear wheel of vehicle to cradle, where direction of tie rod converges with plane defined by connection points, at convergence point that is instantaneous center of rotation - Google Patents

Abstract

The device has a tie rod (4) connecting a rear wheel of a vehicle to a cradle. Direction (DE) of the tie rod converges with a plane defined by three connection points, respectively of an arm (3) with the wheel, the arm with the cradle towards the rear of vehicle in the movements of the vehicle, and center of connection of pivot, at a convergence point R that is an instantaneous center of rotation. An independent claim is also included for a motor vehicle comprising a rear end.

Description

REAR TRAIN OF A MOTOR VEHICLE

ARM TIRES

  The present invention relates. more particularly, but not limited to, a rear axle of a motor vehicle.

  A constraint of this type of device is that the stability of the vehicle must be maintained regardless of the driving conditions (bends, braking, ...), while maintaining flexibility and driving pleasure for I o the user.

  In a manner known in the state of the art, and as the present, for example, the document DE4037608, the connection of a wheel (for example a rear wheel) of a motor vehicle to the cradle of the train of said vehicle is carried out by means of a generally triangular generally shaped arm, one end of said piece being connected to said wheel, and the other two ends of said piece being connected at two distinct points to said cradle.

  Similarly, and as the present, for example, the document DE3833954, a set of three substantially straight arms ensures the connection of said wheel to said cradle, one of which is connected to said wheel and the other two are connected to said cradle at two distinct points, so that the different points of connection form a triangle. The assembly is made in such a way that each of said arms can respectively pivot around its different connection points.

  In such arrangements, when force is applied to said wheel (for example during a turn, or braking), the ends of the device (arm or arm assembly) pivot about a virtual center of rotation , located substantially between said connection points of said device on said cradle, thus causing a pivoting of the axis of said wheel.

  The longitudinal flexibility of the whole is, however, relatively limited. In addition, such devices have the notable effect of introducing a pivoting of said wheel towards the outside of the vehicle (during a braking, for example), or of increasing this pivoting (during a turn, for example ). This results in a more delicate control of the trajectory of said vehicle (oversteer of the vehicle).

  The purpose of the present invention is to propose a method of connecting a wheel, more particularly a rear wheel, of a motor vehicle, with the cradle of the train of said vehicle, having increased longitudinal flexibility, and replacing, in particular the oversteer effect found with the devices existing in the state of the art, by under-steering behavior, thereby increasing the control of the path of the vehicle during braking or cornering actions.

  The invention achieves its goal through a rear axle device of a motor vehicle, wherein, for each of the wheels of said train, an arm or a set of arms, generally of substantially triangular shape or whose ends substantially form a triangle , is linked, at one of its ends, to said wheel, and, at its two opposite ends, at two distinct points of the cradle of the rear axle of said vehicle, characterized in that it further comprises a link.

  Advantageously, one of the ends of said link is substantially connected to said wheel, and the opposite end of said link is connected to said cradle at a point substantially located between said two connection points of said other ends of said arm or set of arms. on said cradle.

  Advantageously, said rod is placed in such a way that the projections, in a horizontal plane, of the respective directions of the part of said rod connected to said cradle and of the side of said arm or set of arms closest to the rear of the vehicle, converge at a point substantially towards the rear and towards the outside of said vehicle.

  Advantageously, one of the links of said arm with said cradle is a flexible type connection, the other connection of said arm with said frame being a lo stiffer connection.

  Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended drawings in which: FIG. 1 is a schematic view of the kinematic connection diagram of a device known in the art. state of the art, - Figure 2 is a schematic view of the kinematic link diagram of a device according to the invention - Figure 3 is a schematic top view of a device according to the invention.

  In what follows, the invention will be described in its application to only one of the wheels of a rear axle of a motor vehicle: the same description will be extended to the other wheel of said rear axle of said vehicle.

  In an arrangement known in the state of the art, and shown in FIG. 1, the connection between the wheel 1 (schematically represented by its axis X in FIG. 1) and the cradle of the train 2 (schematically represented by the direction X 1) is provided by an arm or a set of arms 3 of generally triangular general shape or whose ends form substantially a triangle. For the sake of clarity in the description which follows, it will be considered that a single arm 3, of substantially triangular shape, provides the connection of said wheel 1 to said cradle 2, the number of elements constituting said arm or arm assembly 3 n ' not affecting the description of the invention.

  The connection of said arm 3 with said wheel 1 is materialized by the point A in FIG. 1, the connection of said arm 3 with said chassis 2 being represented respectively by the points B and C in FIG. 1, said points B and C being respectively closer to the front and rear of the vehicle during the movements of said wheel 1. As shown in the kinematic diagram of Figure 1, the connection of said arm 3 to said frame 2, in the devices existing in the state of the art, is a flexible type of connection, which can be schematically represented by a spring-type elastic connection. As a result, under the effect of an action exerted on said wheel 1 in a substantially transverse or longitudinal direction of the vehicle (shown schematically by the arrows F, or F2 in FIG. 1), said arm 3 and said wheel 1 rotate. substantially around a point R, or instantaneous center of rotation, located substantially between said points B and C. The main position of said point R substantially between said points B and C has the main consequence, as previously mentioned, of inducing a oversteer of the vehicle, and an unfavorable opening of the wheel, during braking operations.

  In the device according to the invention, and as shown in Figures 2 and 3, a rocket door 5 is pivotally mounted relative to said arm 3, the rocket door 5 having a pivot F of which are integral in rotation the axis of the wheel 1 and a lever arm 6. A connecting rod 4 connects said wheel 1 to said cradle 2, this link being articulated with the lever arm 6 integral with the pivot F, by a suitable element shown by the point D in FIGS. Said link 4 is, at its end opposite said point D, connected to the cradle 2 by an appropriate element shown by the point E in FIGS.

  It should be noted that, in such a configuration, the direction of said rod 4, materialized by said points D and E, converges with the plane defined by said connection points A, C, and F, respectively of said arm 3 with said wheel 1, said arm 3 with said cradle 2 towards the rear of said vehicle in the movements of said wheel 1, and the center of connection of the pivot F. In a preferred embodiment of the invention, furthermore, if the connection between said arm 3 and said frame 2 located closest to the front of the vehicle Io in the movements of said wheel 1, materialized by said point B in Figures 2 and 3, is a flexible type of connection, which can be schematized by a spring, the connection between said arm 3 and said frame 2 located closest to the rear of the vehicle in the movements of said wheel 1, represented by said point C in FIGS. 2 and 3, is a semi-rigid type connection, can be schematized by a ro tule.

  When a force FL or FT is applied to said wheel 1, respectively in the longitudinal or transverse direction of the vehicle, and as shown in FIG. 3, the presence of said link 4 and the convergence of said direction (DE) and said plane (ACF) cause the rotation of said wheel 1 around said convergence point of said direction (DE) and said plane (ACF), convergence point which is thus the instantaneous center of rotation R previously mentioned.

  In the device according to the invention, said instantaneous center of rotation R is thus displaced towards the outside and towards the rear of the vehicle: this then results in a tendency to understeer, as well as, during braking operations, a tendency to "pinch" said wheel into the vehicle interior, helping to improve the control of the trajectory of said vehicle. This phenomenon is shown schematically in FIG. 3 by the position 1 'in which said wheel 1 then comes during these operations.

  It should be noted that such a device also makes it possible, because of the different flexibility of the two connections made between said arm 3 and said chassis 2, to improve the longitudinal flexibility of the assembly.

  It should also be noted that such a device makes it possible to preserve an unobstructed architecture at the rear of the wheels.

Claims (8)

  1. Rear axle device of a motor vehicle, in which, for each of the wheels (1) of said train, an arm or a set of arms (3), generally of substantially triangular shape or whose ends form substantially a triangle, is connected by one of its ends (A) to said wheel (1) and, at its two opposite ends, to two distinct points (B) and (C) of the cradle (2) of the rear axle of said vehicle , characterized in that it further comprises a link (4).   2. Device according to claim 1, wherein the axis of the wheel (1) is mounted on a rocket door (5), characterized in that the rocket door (5) is pivotally mounted relative to the arm or to the arm assembly (3) via a pivot (F).   3. Device according to claim 1 or 2, characterized in that said rod (4) is connected to the wheel (1) by at least one appropriate element disposed substantially at a point (D), and that the end opposite said point (D) of said link (4) is connected to said cradle (2) at a point (E) substantially placed between said two connection points (B) and (C) of said ends of said arm or set of arms ( 3) to said cradle (2).   4. Device according to claim 3 when dependent on claim 2, characterized in that the rocket door (5) carries a lever arm (6) integral with the pivot (F), and in that the rod (4) is connected to the lever arm (6) substantially at the point (D).   5. Device according to one of claims 2 or 4, characterized in that the direction (DE) of said rod (4) and the plane defined by said points (A), (C), and (F), respectively connecting said arm or set of arms (3) with said wheel (1), connecting said arm or set of arms (3) with said cradle (2) closest to the rear of the vehicle in the movements of said wheel (1), and pivot of the rocket door (5) relative to the arm or to the set of arms (3), converge at a point (R).   6. Device according to the preceding claim, characterized in that said point (R) is substantially located behind and outside said vehicle.   7. Device according to any one of the preceding claims, wherein the connection of said arm or set of arms (3) with said cradle (2) closest to the front of said vehicle in the movements of said wheel (1) is a flexible type connection, characterized in that the connection of said arm or set of arms (3) with said cradle (2) closest to the rear of said vehicle in the movements of said wheel (1) is a connection type semi-rigid.   8. Motor vehicle equipped with a rear suspension device according to any one of claims 1 to 7.