Abstract:
The invention relates to a propeller shaft assembly for connecting the front gearbox output to the drive input of a rear axle drive of a passenger car. Said propeller shaft assembly comprises at least two propeller shaft portions  9, 10 . Both are supported by an intermediate bearing  11  arranged in the connecting region. At the gearbox output end, there is provided a first joint  12 . In the connecting region between the two propeller shaft portions  9, 10 , there is provided a third joint  14 . All joints  12, 13, 14  are provided in the form of constant velocity fixed joints. Additionally, towards the ends, there is provided a plunging element  16, 30  which is provided in the form of a rolling contact member guide which rollingly permit displacements along the longitudinal axis  32  and which additionally effect the transmission of torque. This assembly prevents any vibrational excitement either at the gearbox output end or at the axle drive end from reaching the propeller shaft assembly. As a result, the intermediate bearing  11  is not affected by vibrations. In this way, there are achieved quiet running characteristics, and any noise in the form of structure-borne sound is not transmitted.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a propeller shaft assembly for connecting the front gearbox output to the drive input of the rear axle drive of a motor vehicle, especially of a passenger car. 
     Such propeller shaft assemblies known from the technical literature, for example Prof. Dipl.-Ing. Jörnson Reimpell: Fahrwerktechnik 1, 5 th  edition, Vogel-Verlag, p. 285, FIG. 3.1/21, comprise two propeller shaft portions which are connected to one another by a constant velocity plunging joint. At the ends of the propeller shaft portions intended to be connected to the front gearbox output and to the rear drive input, there are arranged universal joints. The propeller shaft serving to be connected to the gearbox output is associated with a resilient intermediate bearing which serves for additionally supporting the propeller shaft assembly on the floor assembly of the motor vehicle. The connection at the front end between the universal joint and the gearbox output is effected by a sleeve which is associated with a joint yoke of the universal joint and which comprises a bore with longitudinal toothing by means of which it is slid onto a correspondingly toothed shaft in the neck of the gearbox output. The constant velocity plunging joint connecting the two propeller shaft portions permits angular movements as well as displacing movements between the inner joint part and the outer point part, so that any changes in distance and position between the intermediate bearing and the rear drive input are compensated for. However, the resistance against such displacement is high. 
     In the assembly described, the smooth running characteristics are improved as compared to those propeller shaft assemblies wherein the between the two propeller shaft portions is a universal joint, but any movement vibrations generated by the gearbox, by the axle drive of the rear axle and resulting from the displacement of the articulation center of the universal joint, are transmitted by the front and rear propeller shaft portions into the attached assemblies. The intermediate bearing is also excited by vibrations. 
     The propeller shaft assembly is subject to movement vibrations and structure-borne sound vibrations introduced by the gearbox output and the rear drive input. In addition, as far as the rear propeller shaft portion is concerned, there are temporarily increased articulation angles. The problem is that constantly changing torque values and rotational speeds are transmitted from the front engine and gearbox unit to the rear axle. Load values suddenly increasing to 10 times the nominal torque, and rotational speeds up to 10,000 revolutions per minute are no rarity. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to propose a propeller shaft assembly which largely disconnects any vibrations introduced in the longitudinal direction and which, itself, does not generate any rotational vibrations. 
     In accordance with the invention, the objective is achieved by providing a propeller shaft assembly for connecting the front gearbox output to the drive input of the rear axle drive of a motor vehicle, such as a passenger car. The assembly includes a joint at each end for providing a connection to the front gearbox output and to the rear drive input, and includes plunging elements arranged near the joints to be connected to the front gearbox output and to the rear drive input. The plunging elements are provided in the form of a rolling contact member guide which permits plunging movements along a longitudinal axis and effect the transmission of torque. All of the joints are provided in the form of constant velocity fixed joints which only permit angular movements. 
     The advantage of the present embodiment is that any vibrations which can be transmitted by the front gearbox or by the rear axle drive into the propeller shaft assembly, and thus into the intermediate bearing, can be disconnected close to the vibration generating elements. There exist floating centering conditions. 
     According to a further embodiment, there are provided at least two propeller shaft portions, at least one intermediate bearing and one constant velocity fixed joint at each end for providing a connection to the front gearbox output and to the rear drive input, and one such joint between the two adjoining propeller shaft portions. Furthermore, the plunging elements are associated with the front propeller shaft portion and the rear propeller shaft portion. It is thus possible to keep the intermediate bearing largely free from vibration loads. This means that the intermediate bearing can be designed more easily for damping radial vibrations. 
     A particularly advantageous way of arranging the plunging elements consists in integrating same into the inner parts of the constant velocity fixed joints associated with the front gearbox output and the rear drive input. 
     According to a further embodiment of the invention, it is proposed that the joints each comprise an outer part with a cavity and two circumferentially distributed sets of outer running grooves which extend from the two open ends of the outer part in opposite directions in an undercut-free way in meridian planes around the longitudinal axis of the outer part. The inner part arranged in the cavity of the outer part is provided with inner running grooves which are arranged in accordance with the outer running grooves and which, like the outer running grooves, start from the same open ends and extend in an undercut-free way in meridian planes around the longitudinal axis. Between the outer part and the inner part, there is arranged a joint cage whose windows are open towards the outer running grooves and the inner running grooves. Said windows accommodate joint balls of which one each is arranged in a pair of outer and inner running grooves. 
     Said constant velocity fixed joints are advantageous in that they run in a low-friction way and even at larger articulation angles, they have a long service life. In particular, this is the case if, per type of running groove, there are used at least five balls, i.e., a total of at least ten joint balls. The running characteristics are then smoother, too, because the mass of said joint balls is much smaller than in the case of the usual joints which are provided with six balls. Furthermore, the torque transmitting capacity is improved at higher articulation angles because more balls participate in the transmission of torque. Smooth running characteristics are particularly important when using such joints in the propeller shaft of a passenger car where high rotational speeds occur. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention is diagrammatically illustrated in the drawings wherein: 
     FIG. 1 is a diagrammatic illustration of a driveline of a passenger car, having a propeller shaft assembly in accordance with the invention. 
     FIG. 2 shows a propeller shaft assembly in a scale which is enlarged as compared to FIG. 1, with all components being aligned relative to one another. 
     FIG. 3 is a section along line III—III according to FIG. 4 through a constant velocity fixed joint arranged towards the rear drive input. 
     FIG. 4 is a longitudinal section through the rear constant velocity fixed joint according to FIG. 3 along the sectional line IV—IV of FIG.  3 . 
     FIG. 5 is a longitudinal section through the intermediate bearing and the constant velocity fixed joint adjoining same, with the components being in the aligned position relative to one another, i.e., all components have the same longitudinal axis in common. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the driveline for a four-wheel drive vehicle. The two front wheels  1  and the two rear wheels  2  are driven. FIG. 1 also shows the gearbox  3  with the gearbox output  4 . In the region of the rear axle, there is provided the axle drive  5  with the drive input  6 . The two front wheels  1  are driven by sideshafts  7 . The two rear wheels  2  are driven by the sideshafts  8 , starting from the axle drive  5 . The connection between the gearbox  3  and the axle drive  5  is provided by a propeller shaft assembly in accordance with the invention which comprises two propeller shaft portions  9  and  10 . The propeller shaft assembly is additionally supported on the floor assembly of the vehicle by an intermediate bearing  11  which is arranged approximately centrally. 
     In the first propeller shaft portion  9 , the propeller shaft assembly comprises a first joint  12  in the form of a constant velocity fixed joint arranged near the gearbox output  4 . For connecting the two propeller shaft portions  9 ,  10 , there is provided a second joint  13  in the form of a constant velocity fixed joint. At the end of the second propeller shaft portion  10 , there is arranged a third joint  14  in the form of a constant velocity fixed joint which, via connecting means, is connected to the drive input  6  of the axle drive  5  in the region of the rear axle. In most applications, the propeller shaft portions  9 ,  10  rotate at a speed which is higher than the speed introduced by the engine into the manual or automatic gearbox. The reduction to the speed of the rear wheels  2  takes place in the axle drive  5 . Whereas, for example, the propeller shaft assembly with the propeller shaft portions  9 ,  10  and the associated joints  12 ,  13 ,  14  have to rotate at speeds of up to 10,000 revolutions per minute, the speeds of the sideshafts  8  for driving the rear wheels  2  reach approximately up to 2,500 revolutions per minute. 
     FIG. 2, in an enlarged scale, show an inventive propeller shaft assembly in a longitudinal section. All its components are shown to be aligned along a common longitudinal axis  32 . 
     On the left, there is shown the first joint  12  in the form of a constant velocity fixed joint which will be described in greater detail with reference to FIGS. 3 and 4. The joint comprises an outwardly directed flange by means of which the outer part of the joint  12  is connected to the gearbox output  4  shown in FIG. 1, with a damping element  15  being arranged therebetween. In this embodiment, the damping element  15  consists of a material whose modulus of elasticity deviates from that of the joint  12 . 
     Into the inner part of the joint  12 , there is inserted a first plunging element  16  in the form of a rolling contact member guide. The balls of said first plunging element  16  are guided in the inner plunging grooves of a first plunging journal  17 . Furthermore, the first joint  12  is closed by a sealing sleeve  19  which may be associated with a cap for example which is connected to the outer part of the joint  12 . The small diameter of the sealing sleeve  19  is connected to the first plunging journal  17 . The first plunging journal  17 , away from the joint  12 , comprises a widened region to which a first tube  18  is connected. Said first tube  18 , in turn, is connected to attaching means of a sleeve  20  which comprises a toothed bore. Via toothing  22 , a first journal  21  is connected to the sleeve  20  in a rotationally fast way. The first journal  21  comprises a bearing seat  23  and a flange portion. The above-mentioned components are associated with the first propeller shaft portion  9 . 
     The inner ring of a rolling contact bearing  24  is held on the bearing seat  23 . The outer ring of the rolling contact bearing  24  is connected to a damping element  25  received in a housing  26 . Said components form the intermediate bearing  11 . The housing  26  is to be secured to the floor assembly of the passenger car. 
     At the end of the flange of the first journal  21 , which end faces away from the propeller shaft portion  9 , there is connected the outer part of the second joint  13  provided in the form of a constant velocity fixed joint. A second journal  27  is connected to the inner part of the second joint  13  by a set of toothing. The second journal  27 , away from the second joint  13 , comprises a widened region to which there is welded a second tube  28  whose other end is welded to a widened portion of the second plunging journal  29 . 
     The second plunging journal  29 , by means of balls of a second plunging element  30 , is connected in a rotationally fast way to the inner part of the third joint  14  provided in the form of a constant velocity fixed joint. The plunging element  30  is provided in the form of a rolling contact member guide. 
     The outer part of the third joint  14  is connectable via a second damping element  31  to the drive input  6  of the rear axle drive  5  by means of a flange connection. 
     By arranging the plunging elements  16 ,  30  near the ends of the two propeller shaft portions  9 ,  10  it is ensured that any vibrations originating from the gearbox  3  and axle drive  5  according to FIG.  1  and acting on the first joint  12  and the third joint  14  respectively in the direction of the longitudinal axis  32  cannot be passed onto the propeller shaft assembly and, thus, not into the intermediate bearing  11 . The two propeller shaft portions  9  and  10  are held and centered by the intermediate bearing  11  in the direction of the longitudinal axis  32 . 
     FIG. 2 shows all components in the aligned position. Under normal installation conditions, the position of the gearbox output deviates from that of the intermediate bearing  11  and of that of the drive input of the axle drive, so the joints  12 ,  13 ,  14  operate at an articulation angle. In particular, this is the case in the region of the second propeller shaft portion  10 , with the two joints  13 ,  14  compensating for angular movements carried out in the region of the rear axle as a result of the axle drive, i.e., the position of its drive input relative to the intermediate bearing  11 . Because the plunging elements  16 ,  30  are designed as rolling contact member guide, it is possible to achieve a particularly low-friction connection which does not pass on the vibrations in the direction of the longitudinal axis. There is thus achieved particularly smooth running characteristics. However, smooth running is also influenced by the design of the joints  12 ,  13 ,  14 . In principle, they are of identical design, but the second joint  13  differs from the first joint  12  and the third joint  14  in that it is not associated with an additional plunging element. The joints  12  and  14  are substantially of identical design. There may be variations in the region of the connections. The design of said joints  12 ,  14  will now be explained in greater detail with reference to the third joint  14 , also in respect of the integration of the plunging element  30 , by referring to FIGS. 3 and 4. 
     The design of the third joint  14  and of the second plunging element  30  integrated into same will be described jointly with reference to FIGS. 3 and 4. 
     The third joint  14 , provided in the form of a constant velocity fixed joint, comprises the outer part  33  formed as a plate metal part from a circular blank or a tube, and a flange  34  to be connected either to the gearbox output or to the axle drive input. Between the two open ends  36 ,  37 , the outer point part  33  is provided with a continuous space which at one end, at the end  37 , is closed by the cap  35 . The cap  35  comprises a flange which is designed identically to the flange  34 , and rests on the flange  34  and is connected thereto. The inner face  38  is provided with circumferentially distributed first outer running grooves  39  and second outer running grooves  40 , which alternate on the circumference around the longitudinal axis  32 . They are arranged in planes which are distributed around the longitudinal axis and contain same. The first outer running grooves  39  extend in the respective associated plane in a curve-like and undercut-free way, starting from the first open end  36 . The second outer running grooves  40  arranged between two first outer running grooves  39  start from the second open end  37  and extend in meridian planes with reference to the longitudinal axis  32  in a curve-like and undercut-free way towards the first open end  36 . The first outer running grooves  39  and the second outer running grooves  40  are formed into the outer part  33  formed from a plate metal sheet or from a tube. 
     Furthermore, the third joint  14  comprises an inner part  41  whose outer face  44 , which is spherical with reference to the joint center O, is provided with formed-in first inner running grooves  42  and second inner running grooves  43 . The first inner running grooves  42  start from the first open end  36  and extend towards the second open end  37  of the outer part  33  in an undercut-free and curve-like way and are arranged in meridian planes with reference to the longitudinal axis  32  so as to be positioned opposite the second outer running grooves  40 . 
     Between the inner face  38  of the outer part  33  and the outer face  44  of the inner part  41 , there is arranged a joint cage  45 . The joint cage  45  comprises a hollow-sperical inner cage face  46  by means of which the cage  45  is guided on the spherical outer face  44  of the inner part  41 . The outer cage face  47  is arranged at a distance from the inner face  38  of the outer part  41 . 
     Between the inner cage face  46  and the outer cage face  47 , there are provided windows  48  which are circumferentially distributed and arranged in accordance with the pairs of first outer running grooves  39  and first inner running grooves  42  as well as pairs of second outer running grooves  40  and second inner running grooves  43 . Said windows  48  contain joint balls  49  whose centers are arranged in one plane which contains the joint center O. The joint balls  49  project radially outwardly beyond the outer cage face  47  and radially inwardly beyond the inner cage face  46  and engage the associated opposed first outer running grooves  39  and first inner running grooves  42  as well as second outer running grooves  40  and second inner running grooves  43  for torque transmitting purposes. They are held by the joint cage  45  in the angle-bisecting plane when the outer part  33  is articulated relative to the inner part  42  and guided into said plane as a result of the shape relative to the inner part  42  and guided into said plane as a result of the shape of the running grooves. 
     The inner part  41  and the outer part  33 , additionally, are nondisplaceable in the direction of the longitudinal axis  32 . This results from the running grooves which extend in opposite directions and are provided in the form of the two sets of first outer running grooves  39  and first inner running grooves  42  as well a second outer running grooves  40  and second inner running grooves  43 , in connection with the joint cage  45  being guided on the inner part  41 . In other words, the inner part  41  and the outer part  33  are held and centered on the articulation center O. 
     FIG. 3 shows that one pair each of a first outer running groove  39  and a first inner running groove  42  alternates on the circumference with a pair of a second outer running groove  40  and a second inner running groove  43  and that, in total, there are provided five such pairs of running grooves. In this embodiment, a total of ten joint balls  52  participates in the transmission of torque. 
     In addition, the inner part  41 , at both ends, is increased in length sleeve-like beyond the portions containing the first and second inner running grooves  42 ,  43 . The inner part  41  comprises a continuous bore in which there are arranged outer plunging grooves  50  which are circumferentially distributed around the longitudinal axis  32 . The grooves  50  are associated with the second plunging element  30  and extend parallel to the longitudinal axis  32 . Balls  52  are held in said outer plunging grooves  50  by a plunging cage  53  so as to roll along the longitudinal axis  32 , with the rolling movement being limited by stop rings  54  at the ends. The rolling movement is limited in that the balls  52  arranged at the ends come to rest against one of the stop rings  54 , thus limiting the axial movement of the plunging cage  53  in the inner part  41 . Each of the outer plunging grooves  50  contains a plurality of balls  52  arranged one behind the other. 
     The second plunging journal  29  extends into the plunging cage  53  and comprises inner plunging grooves  51  which are distributed around the longitudinal axis  32  in accordance with the outer plunging grooves  50  and which are engaged by the balls  52  to effect a transmission of torque between the second plunging journal  29  and the inner part  41 . 
     With reference to the longitudinal axis  32 , the inner plunging grooves  51  are longer than the outer plunging grooves  50 . The maximum amount by which the second plunging journal  29  can be inserted into the inner part  41  is illustrated in FIG. 4 in dash-dotted lines. Of course, the plunging elements described can also be arranged near the joints to be connected to the front gearbox output  4  and to the rear drive input  6 , rather than partly integrated into the inner part  41  as described. Thus, the plunging elements could be arranged toward the input of the rear drive  6  and the gearbox output  4 , or between the constant velocity fixed joints  12 ,  13 ,  14  and the propeller shaft portions  9 ,  10 . 
     In operation, the outer part  33  experiences vibrations from the axle drive, for example, and which extend in the direction of the longitudinal axis  32 . As a result of the plunging element  30  in the form of the rolling contact member guide, however, said vibrations are not passed onto the second plunging journal  29 . In practice, the vibrations introduced into the outer part  33  are disconnected from the remaining part of the second propeller shaft portion  10  and thus also from the first propeller shaft portion  9 , so that the intermediate bearing  11  remains unaffected by any vibrations in the direction of the longitudinal axis  32 . 
     FIG. 5 shows the assembly in the region of connection between the two propeller shaft portions  9  and  10 . It is possible to identify the way in which the sleeve  20  associated with the first propeller shaft portion  9  is connected by toothing  22  to the first journal  21 . It is also possible to see the cylindrical bearing seat  23 . The inner ring of the rolling contact bearing  24  is positioned on said bearing seat  23  and axially held between a shoulder in the region of transition to the flange-like shape of the first journal  21  and a securing ring. It can also be seen that the outer bearing ring of the rolling contact bearing  24  is provided with a damping element  25  which, in turn, on its outer circumference, is secured in a housing  25  made of metal. The damping element  25  is preferably designed to dampen radial vibrations in respect of the longitudinal axis  32 . It is practically not subjected to any excitation in the direction of the longitudinal axis  32  because no axial vibrations can be introduced as a result of the two plunging elements described in connection with FIG.  2 . 
     Furthermore, in the region of connection between the two propeller shaft portions  9 ,  10 , there is provided a second joint  13  in the form of a constant velocity fixed joint which, in respect of its design principle regarding the way in which the running grooves extend and are arranged, corresponds to the embodiment of the third joint  14  as described. The outer joint part  55  of the second joint  13  is firmly connected to the flange-like enlargement of the first journal  21 . The inner joint part  56  of the second joint  13  is axially firmly connected in a rotationally fast way to the second journal  27  by toothing  57 . No plunging element is provided in the region of the second joint  13 .