Abstract:
A production method involving forming an inner joint part of a constant velocity universal ball joint in the form of a hub member ( 11 ) which comprises a central through-aperture ( 14 ) with inner toothing ( 16 ) for receiving a shaft journal ( 12 ), and ball tracks ( 15 ) for receiving torque transmitting balls on the outer circumference, wherein a blank with largely finish-formed ball tracks is produced by non-chip-forming deformation; wherein, at the blank, outer surfaces and a smooth through-aperture ( 14 ) are finish-turned; and wherein, during simultaneous working stages, the ball tracks ( 15 ) are calibrated by non-chip-forming deformation and the inner toothing ( 16 ) in the through-aperture ( 14 ) is produced by pressing in a non-chip-forming way.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a process of producing, by forming and machining, an inner joint part of a constant velocity universal ball joint in the form of a hub member which comprises a central through-aperture with inner toothing for receiving a shaft journal, and tracks for receiving torque transmitting balls on the outer circumference. The invention further relates to a process for producing a shaft journal for being inserted into the above-mentioned inner joint part. Furthermore, the invention is referred to a hub member and shaft journal assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     A connecting assembly between an inner joint part and an inserted driveshaft of the foregoing type is known from DE 42 40 131 C2. The inner toothing comprises a delimited axial length inside the through-aperture which continues on an untoothed portion. The end of the inner toothing serves as an axial stop for the shaft toothing of the inserted driveshaft. The inner toothing is produced in a blind hole in the inner joint part. The inner toothing can be produced only by introducing a toothing tool corresponding to the complete shaft toothing into the blind hole and by pressing the outer joint part on to the toothing tool through radial deformation. This requires a relatively high deformation rate involving high forces and a large amount of energy. An accurate position of the toothing run-out serving as a stop for the shaft toothing of the inserted shaft journal is also difficult to achieve.  
       SUMMARY OF THE INVENTION  
       [0003]     It is therefore an object of the present invention to provide a method of producing an inner joint part of the initially mentioned type, which permits production with a reduced amount of energy and a greater degree of accuracy. The present invention provides a method involving process stages wherein a blank with largely finish-formed ball tracks is produced by non-chip-forming deformation; and wherein, at the blank, outer surfaces and a smooth through-aperture are finish-turned. The method also provides that, during simultaneous working stages, the ball tracks are calibrated by non-chip-forming deformation, and the inner toothing in the through-aperture is produced by pressing or profile slotting in a non-chip-forming way by a mandrel.  
         [0004]     Because the shaft toothing is produced on a continuous through-aperture, the radial deformation rate is reduced. The substantially simultaneously to that performed calibration of the ball tracks by radial mechanical deformation and radial mechanical holding results in that none of the two deformation processes has a disadvantageous effect on the dimensional accuracy of the respective other surfaces to be deformed, i.e. the production of the inner toothing does not lead to inaccurate track dimensions and the calibration of the ball tracks does not adversely affect the finish-dimensions of the inner toothing. In this way, subsequent machining can be avoided and a substantially higher degree of dimensional accuracy can be observed at the inner toothing and at the ball tracks. It is desirable that the inner joint part be held in the clamping device of the calibrating tool until the production of the inner toothing is complete.  
         [0005]     According to one embodiment, the inner toothing is slotted in a predetermined limited length as far as a toothing run-out inside the through-aperture, with the through-aperture continuing in an untoothed portion. The toothing end of the inner toothing can serve as an axial stop for the shaft journal, so that there is need only for a securing element acting in the opposite direction, such as a securing ring at the projecting-through shaft end.  
         [0006]     According to another method of the above-mentioned type, during calibrating and slotting, a workpiece holding device for the hub member serves as an axial stop for the tool used for profile slotting. In this way, the workpiece holding device becomes the reference and stop face for the workpiece on the one hand, and for the tool for producing the inner toothing on the other hand. This permits the toothing run-out to be produced with the greatest precision regarding its axial position in the workpiece.  
         [0007]     According to a further method, the blank with the finish-formed ball tracks is produced by forging and, after the outer faces and the smooth through-aperture have been turned thereafter, the blank is deburred prior to being calibrated and, finally, the ball tracks, after having been calibrated, are induction-hardened only.  
         [0008]     A method for producing a shaft journal for being inserted into the above-mentioned inner joint part includes the following process stages: at a distance from the shaft end, forming a first conical step which serves as a stop face relative to the toothing run-out of the inner toothing at the inner joint part, and a larger second conical step which is positioned at a greater distance from the shaft end and which forms the toothing end of the shaft toothing, wherein the shaft toothing from the first step to the toothing run-out is finished by being drawn through a die. In this way, the function of the stop of the shaft journal relative to the toothing run-out of the inner toothing of the hub member is taken over by a specially produced conical face which can be produced at an accurate axial distance from the securing mechanism, such as a groove provided for accommodating a securing ring. Said conical face is positioned at an axial distance from a second conical face which is to form the toothing end of the shaft toothing which is produced by drawing. Warping and the formation of burr or the like at the second conical face, which always occur at the start of the process of drawing the shaft toothing, thus cannot have an adverse effect on the positional accuracy of the stop face relative to the shaft end and thus of the shaft journal relative to the inner joint part. The shaft toothing is produced in a length which, in a finish-mounted position, extends beyond the through-aperture of the inner joint part, so that the accurate toothing length of the shaft toothing, which is very difficult to set during the drawing operation, is also without great significance.  
         [0009]     An inventive device for carrying out the present method comprises a base plate on to which an inner joint part can be placed and on which there is supported a calibrating tool which can be fed in radially and which is divided into at least three parts, a mandrel which can be fed in axially and which is arranged coaxially relative to the calibrating tool and comprises approximately the diameter of the through-aperture and, close to its lower end, a forming crown of a short length for producing the inner toothing. It is thus possible to press the inner toothing without generating any adverse effects on the ball track shape. To be able to set the accurate position of the toothing run-out, the present invention also provides that the mandrel is lowered until it stops against the base plate and that the forming crown is arranged at a predetermined distance from the lower end of the mandrel. To further improve the accuracy of the toothing, the forming crown comprises in both axial directions pointing forming wedges.  
         [0010]     One embodiment of an inventive assembly comprises an inner joint part and a shaft journal as well as illustrations of the inventive process, including an inventive device for carrying out the process.  
         [0011]     Other advantages and features of the invention will also become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0013]     In the drawings:  
         [0014]      FIG. 1  shows a mounted assembly including an inner joint part and a shaft journal in accordance with one embodiment of the invention.  
         [0015]      FIG. 2  shows the assembly according to  FIG. 1  in a dismantled condition.  
         [0016]      FIG. 3  shows an inner joint part according to  FIG. 2  in the form of a detail.  
         [0017]      FIGS. 4A and 4B  show a shaft journal according to  FIG. 2  including a detailed portion of the shaft journal.  
         [0018]      FIGS. 5A-5D  show four production stages of the inner joint part in accordance with the invention.  
         [0019]      FIG. 6  shows an inner joint part with a calibrating tool and a drawing tool in a plan view.  
         [0020]      FIG. 7  shows an inner joint part with a calibrating tool and a drawing tool in an axial section along line  7 - 7  of  FIG. 6 .  
         [0021]      FIG. 8  shows the final stage of producing the inner joint part with the calibrating tool and the drawing tool in an axial section. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]      FIG. 1  shows an assembly including an inner joint part  11 , a shaft journal  12  and a securing ring  13  in which the below-mentioned individual characteristics can be identified. The inner joint part  11  comprises a through-aperture  14  and ball grooves  15  for receiving torque transmitting balls. The through-aperture comprises a portion with an inner toothing  16 , a run-out  17  of the shaft toothing as a well a smooth bore  18  with a reduced diameter. Into the hub member  11  there is inserted the shaft  12  whose shaft toothing  19  complements the inner toothing and whose toothing run-out  20  is positioned at a distance from the inner joint part. A stop cone  22  in front of the toothing start  21  is axially supported on the toothing run-out  17  of the inner toothing  16  of the inner joint part  11  to prevent the shaft journal  12  from being introduced further, which would be possible bearing in mind the toothing length. The stop cone is followed by a cylindrical portion  24  with a reduced diameter which engages the smooth bore  18  of the inner joint part. Further towards the shaft end, the cylindrical portion  24  comprises an annular groove  23  accommodating the securing ring  13  which rests against the end face of the inner joint part  11  and thus prevents the shaft journal  12  from being pulled out of the inner joint part  11 . The annular groove  23  is deep enough such that, when the circumferentially slotted securing ring  13  is completely radially compressed, it disappears in the annular groove. In this way, when the securing ring is pre-fitted, the shaft journal  12  can be slid into the inner joint part  11 .  
         [0023]      FIG. 2  shows these parts, i.e. the inner joint part  11 , the shaft journal  12  and the securing ring  13  in the above-mentioned configuration prior to being assembled. When the shaft journal  12  is pressed into the inner joint part  11 , the securing ring  13  is automatically compressed at the inner chamfer  25  of the through-aperture  14  for assembly purposes and, after the shaft journal  12  has been passed through as far as the annular groove  23  included through the inner joint part  11 , the securing ring  13  springs back out of said annular groove  23 .  
         [0024]      FIG. 3  shows the inner joint part as illustrated in  FIG. 2  with the above-mentioned details. To that extent, reference is made to the above-mentioned description.  
         [0025]      FIGS. 4A and 4B  show the shaft journal  12  together with the details shown in  FIG. 2 , with the size of the detail X having been increased. It clearly shows that the contact cone  22 , which delimits axial insertion, is axially offset from the toothing start  21 , so that warping and the formation of burr at the toothing start, which occur when drawing the outer toothing  19 , cannot adversely affect the positional accuracy of the contact cone  21  relative to the shaft end.  
         [0026]      FIGS. 5A-5D  show the inner joint part  11  during different production stages. Illustration  5 A shows a forged inner joint part wherein the tracks  15  are largely finish-formed and wherein countersunk portions  31 ,  32  are formed in from the two end faces  26 ,  27  between which an intermediate wall  33  has remained.  
         [0027]     Illustration  5 B shows the next production stage wherein the above-mentioned intermediate wall has been pierced by a mandrel or the like, and the through-aperture  14  is open.  
         [0028]     In illustration  5 C, the through-aperture  14  has been turned out. Furthermore, the outer faces of the forged part, i.e. the end faces  26 ,  27  and the circumferential face  28 , are finish-turned.  
         [0029]     Illustration  5 D shows the last production stage prior to the operation of hardening the ball tracks  15  and the toothing, wherein the ball tracks  15  are calibrated and wherein the inner toothing  16  is produced by non-chip forming deformation, with the distance between the toothing run-out  17  and the end face  27  being accurately dimensioned.  
         [0030]      FIGS. 6 and 7  show the tools for calibrating the ball tracks and for producing the inner toothing at an inner joint part  11 . On the base plate  40  there is positioned a holding ring  41  and a workpiece holding device  49 . Into the holding ring  41  there is inserted a six-part calibrating tool  42  which can be radially fed in by sets of wedge pieces  52 ,  53 . The parts of the forming tool  42  are shown to comprise forming jams  43 . Behind the sets of wedge pieces there are positioned exchangeable adjusting pieces  54 . The inner wedge pieces  52  are acted upon by an axially adjustable pressure die  55 . A central mandrel  44  is coaxially arranged relative to said pressure die in an axially adjustable holding device  45 , which central mandrel  44  can be lowered through the inner joint part  11  as far as the supporting workpiece holding device  49 . A forming crown  46  is arranged at an accurately determined level at the mandrel  44 . The forming crown  46  comprises front forming wedges  47  which form the inner toothing at the inner joint part, as well as rear forming wedges  48  which facilitate the withdrawal of the mandrel  44 . Underneath the workpiece holding device  49  there can be seen an axially adjustable ejector  51  in a guide  50 . The ejector  51  can also lift the workpiece holding device  49  for tooling purposes.  
         [0031]      FIG. 8  is an axial section through an inner joint part  11  and of a set of tools which illustrates the stages of calibrating the ball tracks  15  and pressing the inner toothing  16 . The inner joint part  11  has been inserted into the six-part calibrating tool  42 . The parts of the calibrating tool  42  are shown to comprise the forming jaws  43 . When the tool set is actuated by the pressure die  55 , the forming jaws  43  are fed radially inwardly, so that the ball tracks  15  are calibrated. The inner joint part  11  is positioned on the workpiece holding device  49 . Furthermore, the central mandrel  44  is shown in its holding device  45 . The mandrel  44  has been lowered through the inner aperture  14  as far as the supporting workpiece holding device  49 . At an accurately determined level, the mandrel  44  has been arranged at the forming crown  46  which, by means of front forming wedges  47 , effects the forming of the inner toothing  16  and determines the accurate position of the toothing run-out  17  relative to the end face  27 , with rear forming wedges  48  facilitating the withdrawal of the mandrel  44  while at the same time smoothing the inner toothing  16 . After the mandrel  44  has been withdrawn and after the load on the pressure die  55  has been relieved, the ejector  51 , by means of the workpiece holding device  49 , is able to eject the inner joint part out of the forming jaws.  
         [0032]     From the foregoing, it can be seen that there has been brought to the art a new and improved hub member and shaft journal assembly and method. While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. Thus, the invention covers all alternatives, modifications, and equivalents as may be included in the spirit and scope of the appended claims.