Abstract:
A suspension system including two lateral arms whose lower arms are disposed at the front and rear of the center of wheels is provided. One end of the two lateral arms is mounted to a cross member while the other end is connected to a carrier assembly. The outer wheels of a turning vehicle automatically form a toe-in according to the movement of a turning vehicle, thus inducing an understeer and improving driving stability of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is based on, and claims priority from, Korean Application Serial Number 10-2004-0070832, filed on Sep. 6, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates to a suspension system of a vehicle. More particularly, the present invention relates to a rear suspension system adapted to automatically change the toe of wheels according to the vehicle movement. 
   BACKGROUND OF THE INVENTION 
   One type of suspension system has two lateral arms in which lower arms are disposed at the front and rear of the center of wheels. The two lateral arms are mounted at one end thereof to a cross member while the other end is connected to a carrier assembly. 
   Generally, the two lateral arms are a front arm and rear arm, which are disposed toward the front and rear of the vehicle. The front arm and rear arm are typically fixed via hinge pins to the cross member to thereby vertically pivot in relation to the cross member according to the vertical movement of vehicle wheels in relation to the vehicle body. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention are provided to automatically align rear wheels in a toe-in according to the movement of a turning vehicle, thereby inducing an understeer and improving the driving stability of the vehicle. 
   A suspension system having an automatic toe control function includes a cross member, and a front arm pivotably connected to the cross member. A rear arm is pivotably connected to the cross member. A rear link arm is equipped with a member rotational shaft and an arm rotational shaft. The member rotational shaft is pivotably connected to the cross member, and the arm rotational shaft is pivotably connected to the rear arm and is parallel to the member rotational shaft. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which: 
       FIG. 1  is a perspective view illustrating a suspension system according to an embodiment of the present invention; 
       FIG. 2  illustrates an operation state of the present invention when observed from the rear of the vehicle; 
       FIG. 3  illustrates an operation state of the present invention when observed from the top of the vehicle; and 
       FIG. 4  illustrates another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a front arm  3  and a rear arm  5  are pivotably connected to a cross member  1 . Cross member  1  is coupled to the vehicle body, and front arm  3  is pivotably connected to cross member  1  via a hinge pin  7  (see  FIG. 3 ). 
   Rear arm  5  is pivotably connected to cross member  1  via a rear link arm  9 . Rear link arm  9  is integrally mounted with a member rotational shaft  11  and arm rotational shaft  13 . Member rotational shaft  11  is pivotably connected to cross member  1 , and arm rotational shaft  13  is pivotably connected to rear arm  5 . Arm rotational shaft  13  is parallel to member rotational shaft  11 . Arm rotational shaft  13  of rear link arm  9  is disposed lower than member rotational shaft  11 . 
   Rear arm  5  and front arm  3  are coupled with a carrier assembly (not shown), which is coupled to wheels. Hinge pin  7  and rear link arm  9  are coupled to reinforcements  15 , respectively, to stably be supported by reinforcements  15 . 
   The operation of the embodiment of the present invention will now be described in detail with reference to  FIGS. 2 and 3 . 
   When a vehicle makes a turn, angular acceleration results in a force that is centered at the vehicle center of gravity and the vehicle tilts in a direction away from the turn center. The outer suspension state of a turning vehicle is expressed in dotted lines in  FIG. 2  while the outer suspension state for a forward driving is expressed in solid lines. 
   The outer wheels of a turning vehicle are upwardly shifted toward the vehicle body, thus front arm  3  and rear arm  5  pivot in the counterclockwise direction as illustrated in  FIG. 2  and support the wheel in relation to the vehicle body. When rear arm  5  supports the wheel by being pivoted in the counterclockwise direction, member rotational shaft  11  and arm rotational shaft  13  deviate from an identical axis. As illustrated in  FIG. 2 , arm rotational shaft  13  slightly pivots in the counterclockwise direction in relation to the member rotational shaft  11 , and rear arm  5  moves away from the turn center of the turning vehicle. 
   Though front arm  3  does not move away from the turn center of the turning vehicle, rear arm  5  slightly moves away from the turn center of the turning vehicle (see  FIG. 3 ). Therefore, carrier assembly connected to front arm  3  and rear arm  5  pivot and cause a toe-in of the wheel. 
   The shifting degree of rear arm  5  away from the turn center of the turning vehicle varies according to the size of the turning angle, causing an automatic toe-in of the wheel in response to the turning degree of the vehicle. If the outer wheels of the turning vehicle bump (moving toward an upper side of the vehicle body), the arm rotational shaft connected to the relevant rear arm moves and then the rear arm shifts toward the exterior of the vehicle body. This adjusts the wheels to be in the toe-in when observing from the top of the vehicle, and the understeer function is increased in the vehicle. 
   According to another embodiment of the present invention, rear arm  5  and cross member  1  are connected via rear link arm  9  and, simultaneously, front arm  3  is connected to cross member  1  via a front link arm  17  in  FIG. 4 . 
   Front link arm  17  is mounted with a member rotational shaft  11 ′ pivotably connected to cross member  1 , and an arm rotational shaft  13 ′ pivotably connected to front arm  3 . Arm rotational shaft  13 ′ is parallel to member rotational shaft  11 ′. Arm rotational shaft  13 ′ of front link arm  17  is located higher than member rotational shaft  11 ′. 
   Rear arm  5  of  FIG. 4  moves similar to the embodiment of  FIG. 1 . If the outer wheels of a turning vehicle bump, arm rotational shaft  13  connected to rear arm  5  moves toward the exterior of the vehicle to induce a toe-in. Front arm  3  also induces a toe-in of the wheel with arm rotational shaft  13 ′ of front link arm  17  being shifted inwardly to the vehicle. The configuration of  FIG. 4  forms a larger toe-in than that of  FIG. 1  by a movement of front arm  3  and front link arm  17 , together with, a movement of rear link arm  9  of rear arm  5 . 
   In a third embodiment of the present invention, front arm  3  and front link arm  17  are connected as illustrated in  FIG. 4  and rear arm  5  is connected to crossmember  1  in the conventional manner, thus front arm  3  inwardly moves to the vehicle by the operation of front arm  3  and front link arm  17  and a toe-in is formed during a vehicle turn. 
   The toe-in effect automatically generated during a vehicle turn induces an understeer and increases driving stability of the vehicle. 
   As apparent from the foregoing, there is an advantage in that the outer wheels of a turning vehicle automatically form a toe-in according to the movement of the turning vehicle in a suspension system, thereby inducing an understeer and improving driving stability of the vehicle.