Abstract:
A shaft assembly comprises a tubular shaft and a joint, wherein at least a portion of the joint is disposed within the tubular shaft. The present invention may also include a shaft assembly comprising a shaft and a constant velocity joint wherein the constant velocity joint is integrated into the shaft by inserting at least a portion of the constant velocity joint into the shaft. In one method of the invention, the method comprises the steps of integrating a constant velocity joint into a propeller shaft by inserting at least a portion of the constant velocity joint into the propeller shaft.

Description:
TECHNICAL FIELD 
     The present invention generally relates to a shaft assembly and in particular, to a propeller shaft, or a drive shaft, with an integrated constant velocity joint. 
     BACKGROUND 
     The propeller shaft, or drive shaft, connects a transmission output shaft to a differential shaft of a vehicle. Generally, universal joints are used to connect the propeller shaft to both the transmission output shaft on one end and the differential shaft on the other end. The universal joint should permit articulation to accommodate changes in driving angle (or road incline) between the propeller shaft and the connected output shaft or differential shaft. 
     Constant velocity joints are universal joints that are able to transfer torque from the transmission output shaft to the differential pinion shaft at generally large driving angles efficiently and smoothly. One type of constant velocity joint includes a tripod outer race; roller bearings; and a tripod inner member. Further, a rubber boot protects the constant velocity joint from exposure to dirt and moisture. 
     Typically, for use in with the propeller shaft, the constant velocity joint is welded onto the end of a tubular section of the propeller shaft. Therefore, it is desirable that the configuration of the outer race of the constant velocity joint corresponds to the configuration of the tubular section of the propeller shaft to provide an optimal surface area for welding the constant velocity joint to the propeller shaft.  FIG. 1  illustrates the present practice of joining a tripod constant velocity joint  100  to a tubular section of a propeller shaft  14 . The tripod constant velocity joint  100  is attached to the propeller shaft  14  by welding, as illustrated  FIG. 1  by welding bead, W. To have optimal surface area for welding the constant velocity joint  100  to the propeller shaft  14 , outer race  110  is generally cylindrical. However, producing the cylindrical tripod outer race  110  is difficult using traditional manufacturing extrusion processes. Specifically, it is difficult to control the width and form of roller tracks of the outer race within the tolerances required for use of the constant velocity joint in a high-speed propeller shaft. 
       FIG. 2  illustrates the difficulties with trying to attach a typical tripod constant velocity joint outer race  120 , produced by the traditional manufacturing extrusion process, to the propeller shaft  14 . The constant velocity joint  100  is provided with a tripod outer race  120  that is secured to an end of the propeller shaft  14 . As illustrated, gaps exist between the tripod outer race  120  and the propeller shaft  14 . 
     SUMMARY OF THE INVENTION 
     A shaft assembly comprises a tubular shaft and a joint, wherein at least a portion of the joint is disposed within the tubular shaft. The present invention may also include a shaft assembly comprising a shaft and a constant velocity joint wherein the constant velocity joint is integrated into the shaft by inserting at least a portion of the constant velocity joint into the shaft. In one method of the invention, the method comprises the steps of integrating a constant velocity joint into a propeller shaft by inserting at least a portion of the constant velocity joint into the propeller shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cutaway perspective view of a prior art constant velocity tripod joint with a cylindrical outer race attached to a propeller shaft. 
         FIG. 2  is a cutaway perspective view of a tripod constant velocity joint attached to a cylindrical propeller shaft by conventional methods. 
         FIG. 3  is a cutaway perspective view of a tripod constant velocity joint integrated into a propeller shaft according to an embodiment of the present invention. 
         FIG. 4  is a front view of the tripod outer race of the constant velocity joint according to an embodiment of the present invention. 
         FIG. 5  is a cutaway perspective view of an outer race of the tripod constant velocity joint according to an embodiment of the present invention. 
         FIG. 6  is a perspective view of a seal for the constant velocity joint according to an embodiment of the present invention. 
         FIG. 7  is a front view of the constant velocity joint integrated into the propeller shaft and sealed according to an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of the constant velocity joint integrated into the propeller shaft, with a tripod inner member removed for clarity, taken along line  8 - 8  of  FIG. 7  according to an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of the constant velocity joint integrated into the propeller shaft taken along line  8 - 8  of  FIG. 7  according to an alternate embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of the constant velocity joint integrated into the propeller shaft taken along line  8 - 8  of  FIG. 7  according to a further alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Tripod type constant velocity joints are one of a number of types of constant velocity joints. Referring to  FIG. 3 , generally shown at  10  is a cutaway of a tripod constant velocity joint  11  integrated into a first rotating shaft  14 , such as, for example, a drive shaft, a propeller shaft, or the like. The constant velocity joint  11  is secured to a second rotating shaft (not shown), such as a propeller shaft, or the like. The propeller shaft  14  is typically a hollow cylindrical tube. In the illustrated embodiment, the propeller shaft  14  has an end  14   a , an inner surface  14   b  and an internal diameter  15 . 
       FIG. 4  illustrates the tripod constant velocity joint  11 . The tripod constant velocity joint  11  includes a tripod outer race  12 , roller bearings  13 , a tripod inner member  17  and a rubber boot (not shown).  FIG. 5  simply illustrates the tripod outer race  12  of the constant velocity joint  11 . The tripod outer race  12  has an exposed surface  12   a , an inner surface  16  and an outer surface  18 . The tripod outer race  12  also includes cylindrical lobes  20 , flutes, or the like. The lobes  20  are located at three equally spaced locations about the circumference of the tripod outer race  12 . The outer surface  18  of the outer race  12  generally corresponds in shape to the lobes  20 . Each of the bearings  13  engages a respective lobe  20 . It can be appreciated that the present invention can be practiced with an outer race having any number of lobes. 
     The outer race  12  has a contour and thickness that varies in relation to the location of the lobes  20 . For example, the outer race  12  has a relatively larger thickness  19  in between the lobes  20  and a relatively smaller thickness  21  at the lobes  20 . However, it can be appreciated that the present invention may also be practiced with the outer race  12  having a uniform, constant thickness or any variation thereof. 
     The outer race  12  has an external dimension  23  generally measured between diametrically opposed portions of the outer race  12 . According to an embodiment of the present invention, the constant velocity joint  11  is integrated into the propeller shaft  14  by inserting the constant velocity joint  11  into the propeller shaft  14 . Thus, the external dimension  23  of the outer race  12  is machined to be slightly smaller than the internal diameter  15  of the propeller shaft  14 . However, it should be noted that the present invention may be practiced with the external dimension  23  of the outer race being a slightly larger dimension than the internal diameter  15  of the propeller shaft  14 , thereby creating an interference, friction, or press fit when the constant velocity joint  11  is inserted into the propeller shaft  14 . 
     Referring back to  FIG. 3 , once the constant velocity joint  11  is inserted into the propeller shaft  14 , a friction, or interference, fit is formed between the outer race  12  and the propeller shaft  14 . When the propeller shaft  14  is rotated, a rotational force is transmitted from the propeller shaft  14  through the outer race  12  of the constant velocity joint  11 , through the bearings  13  and the inner member  17  to the second rotating shaft (note shown). Further, if a central axis (not shown) of the propeller shaft  14  is not aligned with a central axis (not shown) of the second rotating shaft, each of the bearings  13  displaces relative to the lobes  20 . Such movement of the bearings  13  ensures that rotation of the propeller shaft  14  and the second rotating shaft at a constant velocity is achieved. 
     Alternatively, the outer race  12  may be tack welded, resistance welded, spot welded, or the like, at locations  30  along the outer race  12 , as shown in FIGS.  3  and  8 - 9 . The resistance welds  30  are located at areas where the outer race  12  and the propeller shaft  14  are in contact with each other. In another embodiment of the present invention, the exposed surface  12   a  of the outer race  12  may be generally welded to the circumference  14   a  of propeller shaft  14  by, for example, gas metal arc welding (MIG welding), laser welding, or the like. In yet a further embodiment of the present invention, the propeller shaft  14  may be crimped, for instance by hydromechanical forming, around the outer race  12  to secure the constant velocity joint  11  within the propeller shaft  14 . It will be appreciated that the invention is not limited by the manner in which the constant velocity joint  11  is secured the propeller shaft  14 , and that the invention can be practiced by any suitable means for securing the constant velocity joint  11  with the propeller shaft  14 . 
       FIG. 6  illustrates a seal  40  that can be used to prevent grease and other contaminants from entering into the propeller shaft  14 . The seal  40  has a diameter that generally corresponds to the internal diameter  15  of the propeller shaft  14  and includes an aperture  42  shaped to correspond to the shape of the outer race  12 . Furthermore, a portion of the seal  40  is disposed within a gap formed between the outer race  12  and the propeller shaft  14 , and includes three portions  44  that extend inwardly to seal the outer race  12  around lobes  20 , and ridges  46  to engage the outer surface  18  of the outer race  12 . It can be appreciated that the present invention may be practiced with a seal  40  having any shape so long as the propeller shaft  14  and the integrated constant velocity joint  11  are properly sealed from grease and other contaminants.  FIGS. 7 and 8  illustrate the outer race  12  integrated into propeller shaft  14  and sealed with the seal  40 . Seal  40  may be secured to an end of the joint such that an end  14   a  of propeller shaft  14  is flush with an end of seal  40 . 
     It can be appreciated that the outer race  12  may be integrated into the propeller shaft  14  such that the exposed surface  12   a  of the outer race  12  is substantially flush with the end  14   a  of the propeller shaft  14  or disposed at a distance from the end  14   a  of the propeller shaft  14 . For instance, the constant velocity joint  11  may be integrated into the propeller shaft  14  such that the exposed surface  12   a  of the outer race  12  extends beyond the end  14   a  of the propeller shaft  14 , as illustrated in  FIG. 9 . Alternatively, the constant velocity joint  11  may be integrated into the propeller shaft  14  such that the exposed surface  12   a  of the outer race  12  is located at a distance within the propeller shaft  14 , as illustrated in  FIG. 10 . It should be noted that  FIGS. 9 and 10  show seal  40  as having a lip  50  that engages and seals the outer surface  14   a  of the propeller shaft  14 . 
     Integrating the constant velocity joint  11  into the propeller shaft  14  according to the present invention allows for ease in manufacturing of the tripod outer race  12  without decreasing the performance of the constant velocity joint  11 . The tripod outer race  12  may be manufactured with the outer and inner surfaces  16 ,  18  corresponding in shape, and the propeller shaft  14  may be manufactured as a hollow cylindrical tube. However, the constant velocity joint  11  may still be integrated into the propeller shaft  14  even with the tripod outer race  12  and the propeller shaft  14  having different configurations. 
     The embodiments disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the invention. Although various embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of the invention as described in the following claims.