Patent Publication Number: US-2010119301-A1

Title: Device for the rotationally fixed connection of a pin gearbox to an articulated  body  of a drive coupling of a drive shaft

Description:
The invention relates to a device for the rotationally fixed connection of a drive-effective pin of a gearbox to an articulated body of a drive coupling of a drive shaft. 
     Drive trains usually comprise a drive engine and at least one gearbox which are drivingly connected to one another by means of shafts. In motor vehicles the drive shaft of the drive engine drives an input shaft of a gearbox, which may be in the form, for example, of a multi-step or stepless gearbox, via a starting element, for example a friction clutch or a hydrodynamic torque converter. The at least one output shaft of said gearbox is connected to an input element of a differential gear from which emerge axle drive shafts with which associated vehicle wheels are drivable. If the drive engine and the gearbox are arranged at the front of the motor vehicle and the vehicle has rear-wheel or all-wheel drive, a drive shaft, also referred to as a propeller shaft, leads from the gearbox output shaft to the differential gear arranged in the region of the rear axle. In order to compensate for the different installed positions in the vehicle with respect to all three spatial axes, such axle drive shafts or propeller shafts have drive couplings which make possible problem-free transmission of the torque delivered by the drive engine. 
     In the production of a motor vehicle the rotationally fixed connection of two shafts in a drive train cannot always be carried out without difficulty because of confined installation conditions. For this reason the drive engine and the gearbox are usually assembled together as the power train prior to installation in the motor vehicle and are then fastened to supporting parts of the vehicle. In the case of power trains installed at the front of a vehicle with rear-wheel drive or all-wheel drive, the differential gear is also fastened to the vehicle and only then is the propeller shaft connected in a rotationally fixed manner to the gearbox output shaft and the input element or a pin of the differential gear. 
     The means for drivingly connecting the propeller shaft to the gearbox output shaft and to the input element of the differential gear must be configured such that they can be disconnected at any time, for example in a workshop, to make possible a repair of components of this drive train. In the case of known drive shafts and propeller shafts the aforementioned rotationally fixed connection is effected, for example, by means of a fastening flange on the respective ends of the propeller shaft and of the pin of the differential gear, which are located flush against one another and through the axial bores of which screws are inserted. 
     Furthermore, DE 44 19 342 C1 describes a device for connecting two shafts the end faces of which are in flush abutment with one another. In order to connect the two shafts it is provided in this document that the device consists of two clamping sleeves which are screwed to one another axially by means of threads, each clamping sleeve being associated with and bearing axially against a respective shaft. On their end faces which bear against one another the shafts each have a collar of predetermined axial length projecting from their outer periphery, the collars being provided with torque transmitting means on their outer faces. The first clamping sleeve has a bore which is provided with torque-transmitting means which can be brought axially into form-fitting engagement with the torque transmitting means of the collars, and further has a surface provided with a thread. The second clamping sleeve is provided with a thread which fits the thread of the first clamping sleeve. Apart from the fact that the forming of additional collars on the end faces of the shafts entails high complexity and cost, this shaft coupling has a comparatively large diameter because of its design structure. 
     Against this background it is the object of the invention to provide a device for the rotationally fixed connection of a drive pin of a gearbox to an articulated body of a drive coupling of a drive shaft which can be produced at low cost, which simplifies assembly and disassembly of the parts to be connected, makes possible reliable transmission of torque and has a comparatively small diameter. 
     This object is achieved by the features of the main claim, while advantageous configurations and developments of the invention are apparent from the dependent claims. 
     According to the features of the main claim, therefore, the invention relates to a device for the rotationally fixed connection of a drive-effective pin of a gearbox to an articulated body of a drive coupling of a drive shaft. In order to achieve the set object, it is provided with this device that the pin and the articulated body of the drive coupling have mutually corresponding respective external axial toothings and internal axial toothings which are able to mesh together, and that axial securing of articulated body and pin is made possible by an axially displaceable bushing arranged on the pin which can be fastened to a connecting portion of the articulated body. 
     It should be pointed out here that the drive-effective pin may be, for example, the axial end of an input shaft of a gearbox with variable ratio, or a drive-effective pin of a differential gear. 
     According to an especially advantageous configuration it is provided that the pin has a displacement portion and an end portion with an external axial toothing, that a circumferential groove in which a circlip is arranged is formed between the displacement portion and the external axial toothing, that the circlip forms an axial stop for a bushing arranged on the displacement portion and for an end face of the hollow-cylindrical articulated body, that the bushing can be positioned on a connecting portion of the articulated body remote from its track in order to connect the pin to the articulated body, that an internal axial toothing is formed in the hollow-cylindrical opening of the articulated body to receive the external axial toothing of the pin, and that a radially inner cylindrical surface of the bushing is connectable non-positively and/or positively to a radially outer cylindrical surface of the articulated body. 
     The structure of the device according to the invention makes possible rapid and simple assembly and disassembly of the propeller shaft to and from the transmission, in particular to and from a differential gear, without it being necessary for this purpose to tighten a plurality of screws at locations which are difficult to access, as is otherwise usual. 
     The circlip represents a simple but precise axial delimitation and axial stop for the bushing on the articulated body. In this case the bushing may be in the form of a screw socket which can be screwed with a corresponding thread to the outer surface of the articulated body as axial protection against unintended pulling apart of the drive connection. After the bushing has been slid onto the pin and the circlip has then been inserted in its circumferential groove on the pin, the articulated body of the drive shaft is placed against the pin and the bushing is connected to the articulated body. Time-consuming and costly screw-assembly of a plurality of separate studs is thereby dispensed with. 
     In addition, the device according to the invention is significantly more space-saving and cost-effective than conventional devices for the rotationally fixed and axially secured connection of a propeller shaft to a transmission, in particular to a differential gear. Furthermore, a weight reduction can also be achieved with a device configured according to the invention. 
     Moreover, it may be provided that the radially inner cylindrical surface of the bushing and the radially outer cylindrical surface of the articulated body are provided with respective mutually corresponding screw threads. 
     Alternatively, it may be provided that the radially inner cylindrical surface of the bushing and the radially outer cylindrical surface of the articulated body are provided with a respective mutually corresponding bayonet connection, or it may be provided that the radially inner cylindrical surface of the bushing and the radially outer cylindrical surface of the articulated body are connected to one another by a press-fit connection which can be released non-destructively by the application of a large force. 
     In other practical developments it may be provided that the circlip is in the form of a spring ring, a Seeger ring or an O-ring. The use of an O-ring, for example made of a rubber-elastic material, is possible because it does not have to absorb large axial forces acting on one side and at the same time it has a sealing effect in the direction of the drive coupling. 
     According to an advantageous development of the invention it is provided that the circlip preferably has an angular cross section or a round or oval cross section. The circlip is so dimensioned in relation to the forces acting thereon that, firstly, it securely ensures the axial connection of pin and articulated body and, secondly, it requires a receiving groove as shallow as possible in the pin, whereby the mechanical strength of the pin is not reduced in an undesired manner. 
     Thus, it is preferably provided that the radial depth of the circumferential groove in the pin is less than half the radial extension of the material of the circlip. It is further preferably provided that the circlip can be received completely on its radially outer side, and at least partially in the axial direction, in an opening of the bushing. 
     Finally, it should be pointed out that the articulated body referred to multiple times may be in the form of a coupling inner part or a coupling outer part, that is, a hub or a bell of a drive coupling, which each have tracks for rolling bodies in known fashion. 
    
    
     
       Appended to the description for clarification of the invention is a drawing in which: 
         FIG. 1  shows a first exemplary embodiment of a connecting device according to the invention in a perspective view, 
         FIG. 2  shows a device according to  FIG. 1  in the assembled state in longitudinal section with a first circlip, 
         FIG. 3  shows a second exemplary embodiment of a device according to the invention similar to that in  FIG. 1  but with a second circlip, and 
         FIG. 4  shows the device according to  FIG. 3  in the assembled state in longitudinal section. 
     
    
    
     Accordingly,  FIGS. 1 to 4  show a device  1 ,  1 ′ for the rotationally fixed connection of an articulated body  2  of a drive coupling of a motor vehicle drive shaft to a drive-effective pin  3  of a gearbox. In these exemplary embodiments the articulated body is in the form of a coupling hub or coupling inner part  2  which has on a track portion  7  axially oriented tracks  5  for rolling bodies (not shown) of the drive coupling. Axially opposite thereto the coupling inner part  2  has a connecting portion  4  which will be described in more detail below. 
     For connection to the pin  3 , shown partially schematically, of a transmission (not further illustrated) of the motor vehicle, the coupling inner part  2  has a central hollow-cylindrical opening  9  which is provided with profiling in the form of an internal axial toothing  8  for transmission of torque. In order to establish the drive train connection, the coupling inner part  2  can be fitted axially onto the pin  3 , which has an outer axial toothing  11  corresponding to the inner axial toothing  8 . The propeller shaft can be installed in the finished state with the drive coupling (not completely illustrated) and connected to the gearbox at the drive-engine end when said propeller shaft is fastened to the pin  3 . 
     No later than shortly before the pin  3  is inserted into the central opening  9  of the coupling inner part  2 , a circlip and then a bushing  12  is fitted onto a displacement portion  10  of the pin  3 . According to a first exemplary embodiment in  FIGS. 1 and 2 , the circlip is in the form of an O-ring  13  and, according to the second exemplary embodiment of  FIGS. 3 and 4 , in the form of a Seeger ring  24  with a rectangular cross-sectional profile. The smallest bore diameter of the bushing  12  corresponds to, or is slightly greater than, the diameter of the pin  3 , or of the displacement portion  10  thereof. 
     The bushing  12  is first pushed as far as possible onto a displacement portion  10  of the pin  3  and the circlip  13  is slid onto the pin  3  until it snaps into a comparatively shallow circumferential groove  6 ,  14  in the pin  3 , which marks the axial end of the displacement portion  10 . The circlip  13 ,  24  functions with its opposite sides  15  and  16  as an axial stop for an end face  17  of an axial opening  25  of the bushing  12  oriented toward the coupling inner part  2 , and for an end face  18  of the coupling inner part  2  ( FIGS. 2 and 4 ). 
     After the circlip  13 ,  24  has been fitted to the pin  3  and is fixed in the circumferential groove  6 ,  14 , the coupling inner part  2  is slid onto the pin  3  until the end face  18  of the coupling inner part  2  abuts the side  16  of the circlip  13 ,  24  oriented in this direction. In this way the correct axial distance between the coupling inner part  2  and the pin  3  is already established and a torque transmission is made possible. The bushing  12  is then slid in the direction of the coupling inner part  2 , so that the captive axial connection between the pin  3  and the coupling inner part  2  can be produced. 
     For this purpose, in the exemplary embodiment illustrated in  FIGS. 3 and 4 , the bushing  12  has on its inner cylindrical surface  19  an internal thread shown in  FIG. 4  which corresponds to an external thread in the outer cylindrical surface  20  of a connecting portion  4  of the coupling inner part  2 .  FIG. 4  shows this threaded connection  26  in longitudinal section. The bushing  12  is therefore in the form of a screw socket which is screwed onto the coupling body  4 . 
     In deviation from the exemplary embodiment represented in  FIG. 3 , however, it is also possible to provide the inner cylindrical surface  19  of the bushing  12  and the outer cylindrical surface  20  of the coupling inner part  2  with other mutually corresponding connecting means. For example, it is possible to form bayonet connections, snap-in connections or press-fit surfaces on the bushing  12  and the coupling body  4 . 
     The circlip  13  shown in  FIGS. 1 and 2  is in the form of a metal spring ring, so that it can be easily slid onto the pin  3  and snap into the circumferential groove  14 . However, it is also possible for the circlip  13  to be configured differently. Such an alternative configuration is represented in  FIGS. 3 and 4 , which show an inventive device  1 ′ which corresponds largely to the device  1  represented in  FIG. 1  and use the same reference numerals for identical parts. 
     The configuration of the device  1 ′ according to  FIG. 3  differs from that according to  FIG. 1  essentially by a different variant of the circlip, which here is in the form of a Seeger ring  24  and engages in a correspondingly shaped circumferential groove  6  of the pin  3 . A geometrically adapted recess  25  corresponding to the outer shape of the Seeger ring  24  is formed in the bushing  12 , so that, when the bushing  12  and the coupling inner part  2  are in axial abutment with the Seeger ring  24 , the correct axial spacing of the two parts with respect to one another is established. In order to ensure a certain tolerance, the circlip  13 ,  24  may be made of an elastomeric material. 
     As  FIGS. 2 and 4  make clear, the groove  6 ,  14  in the pin  10  is not very deep, in order to reduce the mechanical strength of the pin  10  as little as possible with predefined dimensions and material properties. Preferably, the circumferential groove  6 ,  14  is formed only so deep that it accommodates less than half the radial extension of the material of the circlip  13 ,  24 . In order to prevent the circlip  13 ,  24  from slipping out of this shallow circumferential groove  6 ,  14 , the opening  25  of the bushing  12  is adapted geometrically in such a manner that the circlip  6 ,  14  is received therein completely on its radially outer side, and at least partially in the axial direction. 
     REFERENCES 
     
         
           1  Device 
           1 ′ Device 
           2  Articulated body; coupling inner part of a drive coupling 
           3  Pin 
           4  Connecting portion of coupling inner part 
           5  Track of coupling inner part 
           6  Circumferential groove 
           7  Track portion of coupling inner part 
           8  Internal axial toothing of coupling inner part 
           9  Hollow-cylindrical opening of coupling inner part 
           10  Displacement portion of pin 
           11  External axial toothing of pin 
           12  Bushing 
           13  Circlip, O-ring 
           14  Circumferential groove 
           15  Side of circlip 
           16  Side of circlip 
           17  End face of bushing 
           18  End face of coupling inner part 
           19  Inner cylindrical surface of bushing 
           20  Outer cylindrical surface of coupling inner part 
           21  Inner cylindrical surface of coupling inner part 
           24  Circlip, Seeger ring 
           25  Opening in bushing 
           26  Threaded connection, thread