Patent Publication Number: US-2003224860-A1

Title: Constant velocity joints

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a constant velocity joint, and more particularly, to reducing vibration of a tripod constant velocity joint for use in a driving axle of a vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002] A constant velocity joint allows driving and driven axles to operate smoothly at identical velocities even though an intersection angle between the driving and driven axles is increased. In general, the constant velocity joint is spline-coupled to a driving axle of a front wheel drive vehicle or a rear differential side gear in an independent suspension system.  
       [0003] The driving axle of the vehicle is generally provided with two constant velocity joints with a portion coupled to a transmission side and a portion coupled to a wheel side.  
       [0004] In the conventional tripod joint, a bearing is interposed between a roller assembly and a trunnion assembly. The assemblies of the roller, the trunnion and the bearing are installed equiangularly at three positions onto a driving axle. The assembly is then coupled within a housing which is itself coupled to a transmission. In use, as the housing is rotated, the roller is rotated, and consequently the driving axle is rotated. Thus, a driving force from the transmission side is transmitted to the driving axle at a constant velocity.  
       [0005] However, vibration is often produced in the vehicle due to an axial force transmitted to the driving axle.  
       [0006] In use, a front portion of the vehicle becomes “nose up” due to an increase in engine torque upon low-speed acceleration. This results in an increase in the intersection angle between the driving axle and the housing. The axial force results in vibration of the vehicle because a friction force is created between the roller and a groove of the housing in a direction of the trunnion, and also between the roller and the trunnion.  
       [0007] Vibrationless joints have been attempted. However, prior attempts at such joints have not solved the problem. This is because vibrationless joints generate a force component corresponding to the friction force between the roller and the trunnion which is transmitted directly to the driving axle. Therefore, the axial force is not completely reduced and vibration remains in the system. Furthermore, conventional vibrationless joints are expensive.  
       SUMMARY OF THE INVENTION  
       [0008] Embodiments of the present invention provide cost effective structures that reduce vibration generated in a constant velocity joint.  
       [0009] Vibration can be reduced according to the invention, inter alia, by causing sliding friction forces between the rollers and the trunnions to be transmitted, not to a driving axle, but to a housing. Thus, the friction forces can be cancelled in the transmission side. Furthermore, no additional spline processing is required since grooves formed in an insert can be manufactured through the forging process.  
       [0010] According to one embodiment of the present invention a housing is made in the form of a substantially cylindrical shell. Trunnions are installed at three positions equiangularly on an inner circumferential surface of the housing, and bearings coupled to the respective trunnions. Rollers are also coupled to the outsides of the respective bearings, and a driving axle comprising an insert with three grooves formed equiangularly on an outer periphery thereof, such that the axle can be coupled into the housing with the rollers installed therein. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] Advantages and features of the present invention will become apparent from the following description given in conjunction with the accompanying drawings, in which:  
     [0012]FIG. 1 is a perspective view of a constant velocity joint according to an embodiment of the present invention;  
     [0013]FIG. 2 is a side view of the constant velocity joint according to an embodiment of the present invention; and  
     [0014]FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0015] Hereinafter, a preferred embodiment of the present invention will be explained in detail with reference to the accompanying drawings.  
     [0016] As shown in the figures, a constant velocity joint of the present invention comprises a housing  10 . Trunnions  20  are installed, preferably, at three positions equiangularly in an inner circumferential region of the housing  10 . The inner circumferential region being the area within the interior of the housing  10 . Bearings  30  are then coupled to the respective trunnions  20  and rollers  40  are coupled to the outside of the respective bearings  30 . A driving axle  50 , in which an insert  52  with grooves  51  formed at three positions equiangularly on an outer periphery thereof, is coupled to an end of the axle, such that the axle can be coupled into the housing  10  with the rollers  40  installed therein.  
     [0017] The rolling surfaces of the rollers  40  make contact with the groves  51 . Both surfaces, the rolling surface of the rollers  40  and the roller receiving surface of the grove  51  are substantially spherical. A friction force, due to rolling action of each roller  40  is therefore minimized so that any axial motions are not produced in the driving axle  50 .  
     [0018] Further, the trunnions  20  are fitted into holes formed equiangularly along a circumference of the housing  10 , and then fixed thereto through, for example, a press-fit process, with an adhesive, or the like. Thereafter, the bearings  30  and the rollers  40  are sequentially installed around the trunnions  20  fixed to the housing  10 .  
     [0019] It is preferred that a needle bearing in the form of the cylindrical shell for surrounding the trunnion  20  is used as the bearing  30 .  
     [0020] Preferably, each of the trunnions  20  further comprise a spacer  21  for preventing the bearing  30  from coming into contact with the relevant groove  51  of the insert  50 .  
     [0021] The grooves  51 , formed in the insert  52 , can be manufactured, for example, through a general forging process. Thus, any additional spline processing is not needed.  
     [0022] Hereinafter, an operation and effect of the present invention will be described with reference to FIGS.  1 - 3 . Sliding friction force with respect to the trunnion  20  is basically transferred to the housing  10  rather than the driving axle  50 , so that it can be cancelled in a transmission side. In use, friction force between the roller  40  and the bearing  30 , rotational friction force between the roller  40  and the housing with respect to an axis of the trunnion  20 , and axial (linear) friction force between the roller  40  and the housing with respect to the axis of the trunnion  20  is decreased, and a spin force of the roller  40  is also reduced. Therefore, an amount of the axial force to be transmitted to the driving axle  50  is decreased, and thus, the vibration of the vehicle is reduced.  
     [0023] Although the present invention has been described in connection with the preferred embodiment with reference to the accompanying drawings, the preferred embodiment is intended not to limit the invention but to exemplify a best mode of the present invention. It will be understood by those skilled in the art that various changes or modifications may be made thereto without departing from the spirit and scope of the invention. Therefore, the present invention is defined only by the appended claims which should be construed as covering such changes or modifications.