Patent Publication Number: US-2023132839-A1

Title: Multi-plate clutch

Description:
TECHNICAL FIELD 
     The disclosure relates to a multi-plate clutch, for example for an electric drive train of a motor vehicle. 
     BACKGROUND 
     Multi-plate clutches include a plurality of friction plates arranged axially one behind the other. They serve to transmit a torque between two shafts in a frictionally engaged manner. In one case of application, multi-plate clutches can serve as a passive transmission element, wherein a torque which can be transmitted between a driven input shaft and a coaxially arranged output shaft is limited. In this case, no active actuation of the multi-plate clutch is provided, for example by a hydraulic piston or other type of force application. The maximum transmittable torque is also referred to as the triggering torque. By limiting the torque within the multi-plate clutch, the components in a drive train can be protected from damage due to excessive loads. 
     The friction plates are usually preloaded against each other, for example by means of a spring element. The preload adjusts the torque or frictional torque within the multi-plate clutch. 
     It is an object of the disclosure to optimize the adjustment of the preload force. 
     SUMMARY 
     A multi-plate clutch according to the disclosure comprises an outer plate carrier, an inner plate carrier and a set of plates of alternately arranged outer plates and inner plates, which is arranged radially between the outer plate carrier and the inner plate carrier and which is delimited by two end plates engaging at opposite ends of the set of plates, wherein each end plate rests against an annular axial supporting contour on the end face facing away from the set of plates, and wherein the supporting contours differ in their effective diameter at which they contact the associated end plate, and wherein the supporting contours apply an axial force on the set of plates such that the plates are elastically deformed into a conical shape. 
     The effective diameter denotes in particular the mean diameter of the annular contact surface of the supporting contour with the end plate. 
     The annular supporting contour does not necessarily have to be circular and continuous, it is also conceivable that the supporting structure is elliptical and/or corrugated and/or has interruptions. 
     The multi-plate clutch according to the disclosure has the advantage that the set of plates itself functions as a spring pack. In particular, the individual plates are preloaded against each other due to the conical preloading. Thus, a spring to preload the set of plates can be omitted. The elastic preloading of the set of plates is caused by the different effective diameters of the supporting contours. The axes of the force application are arranged coaxially to each other and centrically to an axis of rotation of the plates. 
     According to one embodiment, one of the supporting contours rests against the end plate in the radial direction in the area of the radially outer third, in particular quarter, of the outer diameter of the outer plates, and the other supporting contour rests against the set of plates in the area of an inner third, in particular quarter, of the inner diameter of the outer plates. In this way, the greatest possible lever arm is achieved, resulting in a particularly effective preloading of the set of plates. 
     The contact surfaces of the supporting contours are preferably positioned such that each contact surface, as seen in the axial direction, overlaps completely with the inner plate or outer plate. 
     Particularly preferably, one of the supporting contours is directly adjacent to the outer core diameter of the outer plates, and/or the other supporting contour is adjacent to the inner core diameter of the outer plates. 
     For example, at least one of the annular supporting contours is formed on a separate supporting ring. This simplifies the assembly of the multi-plate clutch. 
     The supporting ring can be guided with the outer diameter thereof on the outer plate carrier. In this way, the supporting ring can be positioned particularly easily. More precisely, the supporting ring is automatically centered in the outer plate carrier. 
     For example, the supporting ring has at its radially inner edge a collar which is bent towards the set of plates and by means of which it rests against the end plate. This allows the contact surface of the supporting ring to be flexibly positioned at a distance from an inner wall of the outer plate carrier. 
     According to one embodiment, the outer plate carrier is pot-shaped and the supporting contour is formed as a supporting ring which is received in the outer plate carrier and is axially fixed to the outer plate carrier by means of a fixing element. The fixing element is, for example, a retaining ring. The set of plates can thus be received and fixed in the outer plate carrier, the outer plate carrier forming a housing of the multi-plate clutch. In this way, a compact design of the multi-plate clutch is achieved. 
     One of the two supporting contours can be integrally formed in the outer plate carrier, in particular on an axial wall of the outer plate carrier directed towards the set of plates. This reduces the number of components of the multi-plate clutch, which simplifies the assembly of the multi-plate clutch. 
     According to one embodiment, the supporting contour is a raised portion in the outer plate carrier. This makes it particularly easy to demold the supporting contour in the outer plate carrier. 
     The resting surface of the supporting contours on the plates is preferably at most one fifth of the end face of the plates. In this way, a particularly purposeful introduction of force into the set of plates is possible. If the area of the supporting contours were too large, the plates would only be pressed axially against each other and not conically clamped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an electric drive train with a multi-plate clutch according to the disclosure, and 
         FIG.  2    shows an exploded view of the multi-plate clutch according to the disclosure of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows, partly schematically, an electrically operated drive train  10  in a sectional view. 
     The electrically operated drive train  10  comprises an input shaft  12  and an output shaft  14  which is arranged coaxially with the input shaft  12 , and an electric machine  16 . 
     The electric machine  16  can be operated as a motor or as a generator. 
     The electric machine  16  drives the input shaft  12  of the drive train  10 . 
     The output shaft  14  is used, for example, to drive a drive axle or an input shaft of a transmission. 
     The input shaft  12  and the output shaft  14  are connected by a multi-plate clutch  18  for transmitting a torque. 
     The multi-plate clutch  18  is shown in an exploded view in  FIG.  2   . 
     The multi-plate clutch  18  serves to limit the maximum transmittable torque between the input shaft  12  and the output shaft  14 . By limiting the torque, the components of the drive train  10  are protected from damage due to excessive load. 
     The multi-plate clutch  18  comprises a plurality of friction plates arranged axially one behind the other, which are in particular made of steel. 
     More specifically, the multi-plate clutch  18  comprises an outer plate carrier  20  and an inner plate carrier  22 , and a set of plates  24  arranged radially between the outer plate carrier  20  and the inner plate carrier  22 . 
     The set of plates  24  has alternately arranged outer plates  26  and inner plates  30 . 
     The outer plate carrier  20  is configured to be pot-shaped and forms a housing of the multi-plate clutch  18  in which the set of plates  24  is accommodated. 
     In the example embodiment, the outer plate carrier  20  is connected to the output shaft  14  in a rotationally fixed manner. 
     In the example embodiment, the inner plate carrier  22  is connected to the input shaft  12  in a rotationally fixed manner. 
     The outer plates  26  are in toothed engagement with the outer plate carrier  20 . The inner plates  30  are in toothed engagement with the inner plate carrier  22 . 
     For this purpose, grooves  34  are provided along an inner wall  32  of the outer plate carrier  20 , which extend in the axial direction and in which the teeth  36  of the outer plates  26  are received. 
     Similarly, grooves  40  are provided along an outer wall  38  of the inner plate carrier  22 , which extend in the axial direction and in which the teeth  42  of the inner plates  30  are received. 
     The outer plates  26  and inner plates  30  of the set of plates  24  are preloaded against each other. The preload force creates a frictional connection between the input shaft  12  and the output shaft  14 . In particular, the preload force determines the torque or friction torque within the set of plates  24 . 
     According to the disclosure, the preload is achieved by each end plate  44  resting against an annular axial supporting contour  48 ,  50  on the end face  46  facing away from the set of plates  24 , the supporting contours differing in their effective diameter at which they contact the associated end plate  44 . 
     The supporting contours  48 ,  50  apply an axial force on the set of plates  24  such that the plates  26 ,  30  are elastically deformed into a conical shape. 
     The conical shape assumed by the set of plates  24  is shown only schematically in  FIG.  1    as a superimposed dashed line for better illustration. 
     The end plates  44  of the set of plates  24 , which terminate at the end face, are preferably thicker than the other plates  26 ,  30 . This serves to distribute the preload forces within the set of plates  24  evenly over the friction surfaces. 
     To prevent an undesired deformation of the end plates  44  under thermal load, they can have a plurality of interruptions distributed around the circumference, in particular slots  52  (see  FIG.  2   ). 
     As can be seen particularly well in the sectional view in  FIG.  1   , one of the supporting contours  48  rests against the end plate  44  in the radial direction in the area of the radially outer third, in particular quarter, of the outer diameter of the outer plates  26 . 
     The further supporting contour  50  rests against the set of plates  24 , in particular the end plate  44 , in the area of an inner third, in particular a quarter, of the inner diameter of the outer plates  26 . 
     Both supporting contours  48 ,  50  rest against the end plate  44  over the entire surface. 
     The resting surface of the supporting contours  48 ,  50  on the end plates  44  is at most one fifth of the end surface of the end plates  44 . 
     One of the two supporting contours  48  is formed on a separate supporting ring  54 . 
     The supporting ring  54  is guided with its outer diameter on the outer plate carrier  20 , in particular on the inner wall  32  of the outer plate support  20 . 
     The supporting ring  54  is thus received in the outer plate carrier  20 . 
     A fixing element  56  is furthermore provided, by means of which the supporting ring  54  is axially fixed to the outer plate carrier  20 . 
     At its radially inner edge, the supporting ring  54  has a collar  58  which is bent towards the set of plates  24  and by means of which it rests against the end plate  44 . 
     The supporting contour  48  is arranged on one end face of the collar  58 . 
     The further supporting contour  50  is integrally formed in the outer plate carrier  20 , more specifically on an axial wall of the outer plate carrier  20  directed towards the set of plates  24 . 
     In the example embodiment, the supporting contour  50  is a raised portion  60  in the outer plate carrier  20 . 
     During operation of the multi-plate clutch, if the maximum transmittable torque is exceeded, the outer plates  26  coupled to the outer plate carrier  20  can twist relative to the inner plates  30  connected to the inner plate carrier  22 . As a result, a differential speed between the two shafts  12 ,  14  is possible for a short time. The resulting friction torque between the friction plates reduces this differential speed again when the maximum transmittable torque is undershot and restores the equality of the shaft speeds. The clutch is thus also capable of damping short-term shocks or vibrations in the drive train which are above the maximum transmittable torque of the multi-plate clutch  18 . 
     To achieve a particularly good friction behavior, the friction surfaces of the outer plates  26  and/or the inner plates  30  are structured. For example, grooves are provided on the friction surfaces in which oil can be guided. Alternatively, it is also conceivable that the friction surfaces are chemically and/or mechanically and/or thermally processed to produce a defined surface roughness. Due to the structuring, a friction lining can be dispensed with.