Patent Publication Number: US-2009223773-A1

Title: Friction clutch for a torque transmission device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Patent Application No. 10 2008 012 860.0, filed on Mar. 6, 2008, which application is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The invention relates to a friction clutch or a torque transmission device equipped with it, wherein the friction clutch features at least a clutch cover and at least a pressure plate, connected non-rotatably in an axially displaceable manner, and the actuation means for exerting axial force on the pressure plate between the clutch cover and the pressure plate. The invention relates particularly to the so-called twin clutches. 
     BACKGROUND OF THE INVENTION 
     Friction clutches of the type mentioned above—whether single-disc, twin-disc or multiple-disc clutches—retain some measure of imbalance after assembly; thus, the reason why the entire clutch assembly must be balanced in most cases. Already, trials have been made to minimize the residual imbalance, by initially balancing at least an individual component, but still, rebalancing has proved necessary in most cases. To eliminate such residual imbalances, it is common practice to later remove material from different components, for example, by introducing balancing holes or by removing material from the edge regions of component parts. It is also common practice to weld balancing weights or to use balancing rivets. 
     For very compact assemblies, however, it is often not possible to use the above-mentioned balancing methods, because, for instance, owing to very complex design of the components, it is not possible to weld properly without distorting the components. Moreover, in many cases, it is not possible to accommodate the dolly blocks for supporting the riveting forces required to fix balancing rivets. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a simple and cost-effective balancing possibility for friction clutches, especially twin clutches. In particular, it should be ensured that optimal balancing of the clutch assembly is facilitated without material removal and without the effect of significant axial forces on the components of the friction clutch. 
     According to the invention, this object is achieved in that at least one constituent part must feature recesses in which screw elements used as balancing weights can be screwed to balance the friction clutch. Several groups of recesses distributed circumferentially can be provided advantageously on at least one component part of the friction clutch. 
     The screw elements used as a balancing weight can advantageously feature a threaded section that automatically forms the fixing thread. 
     Recesses for the screw elements can be provided advantageously on a clutch cover. For this purpose, the clutch cover can have several radially protruding regions on its outer circumference, in which corresponding recesses are formed. 
     Screw elements with different weights can find application advantageously. The screw elements, for instance, can be formed in a manner such that they have a threaded section and an adjoining screw head forming a balancing weight. The screw head can thereby advantageously feature a socket for a screw driving tool. 
     The friction clutch can advantageously form a so-called twin clutch comprising two single-disc clutches which can be actuated separately. The twin clutch can comprise a momentum disc or a flywheel with which a clutch cover is connected for drive purposes, wherein also a connection cover can be provided, which can be coupled with a pressure plate of one of the clutches. The two pressure plates of the twin clutch can be axially displaceable and loadable by means of actuation means that are effective between the clutch cover and the two pressure plates. One of the covers can feature at least recesses for receiving the balancing weights. The annular inertial mass designated here as flywheel is advantageously disposed axially between the pressure plates of the two clutches and can be coupled either indirectly or directly with the drive shaft of an engine. It can be suitable when the connection cover is connected with the pressure plate that faces the engine when operating the friction clutch. 
     For the design of the friction clutch it can be particularly advantageous when the clutch cover connected with the flywheel is at least partially accommodated inside the connection cover and has radially protruding sections, on its circumference, in which the recesses are provided for receiving the screw elements used as balancing weight. 
     The connection cover can feature several lobes, extending axially along its outer circumference, which form fastening sections for coupling with a pressure plate, whereby the radial sections of the coupling cover—when viewed in the circumferential direction of the friction clutch—are respectively provided between two such lobes. 
     It is particularly functional when the recesses for receiving the balancing weights relative to the rotation axis of the friction clutch are spaced such that they are at least axially accessible even in the assembled state of the twin clutch. Thus, particularly, when screw elements are used as balancing weight, they can be anchored in corresponding recesses by means of an axially applicable screw driving tool. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Further advantages, features, and details of the invention can be derived from the following description of an exemplary embodiment. 
       The figures are as follows: 
         FIG. 1  shows a section of a torque transmission device that comprises a friction clutch executed according to the invention; and, 
         FIG. 2  shows a partial perspective view of the friction clutch according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A part of a power train  1  of a motor vehicle is depicted in  FIG. 1 . A twin clutch  6  is disposed between a drive unit  3 , particularly of an internal combustion engine, from which a crankshaft  4  originates, and a transmission  5 . A torsional vibration damping device  8  is interposed between the drive unit  3  and the twin clutch  6 . The torsional vibration damping device  8  is operational as a dual mass flywheel in this case. 
     The crankshaft  4  of the internal combustion engine  3  is connected non-rotatably by means of screws  9 ,  10  with an input part  11  of the torsional vibration damping device  8 . The input part  11  of the torsional vibration damping device  8  essentially has the shape of a circular disc, extending in radial direction, which forms a vibration damper cage outwards. On the input part  11  a ring gear  12  is fixed radially outwards. In the vibration damper cage, at least one energy storage device, in particular a spring device  16 , is accommodated at least partially. In the spring device  16 , an output part  18  engages with the torsional vibration damping device  8 . Between the input part  11  and the output part  18 , a friction ring  19  is fixedly disposed on the input part  11 . 
     Radially inside, the output part  18  of the torsional vibration damping device  8  is detachably engaged by means of an axially inserted connection  20 , thus it is detachably, non-destructively, connected with the clutch-cover part  22 . A flywheel formed as an intermediate pressure plate  26  is fastened with the help of rivet connections, to the clutch-cover part  22  in the section drawing, of which only one is visible. On the driven side, friction linings  29  of a first clutch disc  31  can be clamped between the intermediate pressure plate  26  and a pressure plate  28 . The first clutch disc  31  is non-rotatably connected with a first transmission input shaft  35 , via a hub part  33 , which is formed as a solid shaft. The first transmission input shaft  35  is rotatably disposed inside a second transmission input shaft  36  which is formed as a hollow shaft. A hub part  38  is rotatably mounted, with the help of a roller bearing  37 , on the driven-side end of the second transmission input shaft  36  that is part of the intermediate pressure plate  26 . On the transmission side, friction linings  40  of a second clutch disc  42  can be clamped between the intermediate pressure plate  26  and a pressure plate  39 . The second clutch disc  42  is connected non-rotatably via a hub part  43  with the second transmission input shaft  36 . 
     The twin clutch  6  features a clutch cover  44  that is axially displaceable relative to the pressure plates  28 ,  39 , though non-rotatably. The intermediate pressure plate  26  is non-rotatably connected with the clutch cover  44 . The clutch cover  44  and the intermediate pressure plate  26  are connected with the crankshaft  4  via the clutch-cover part  22  and the torsional vibration damping device  8 . The twin clutch  6  is actuated in a common manner via actuation devices  46 ,  47  which interact with actuation elements, such as the actuation levers  48 ,  49 . 
     The pressure plate  28  is connected with the actuation levers  49  via a pot-shaped pulling element  50 , which is connected non-rotatably with the pressure plate  28 , via several axial lobes  51  distributed over the circumference. This connection is by means of rivet connections  52  in the depicted exemplary embodiment, which interact with radial lobes  53  aligned outwards on the axial lobes  51 . 
     The actuation levers  48 ,  49  are supported on the clutch cover  44  in a swivel-capable manner. The actuation levers  48 ,  49  can be formed advantageously by a plurality of levers disposed in annular arrangement, wherein the levers can be formed with an annular region formed with them as a single piece. The levers can be component of a disc-spring-like component. As is apparent from  FIG. 2 , the intermediate pressure plate  26  has several radial lobes  54  distributed over the circumference, on which the clutch cover  44  is fixed. This fixture can likewise occur by means of a riveted connection  55 . However, also other connections, for example, screw connections can find application. 
     From  FIG. 2 , it is apparent that the clutch-cover  44  features radially protruding regions  56  on its circumference, which are formed like a lobe. In the depicted exemplary embodiment, these radial regions  56  are for connecting the cover  44  with the radial lobes  54  of the intermediate pressure plate  26 . 
     In the radial regions  56  a multiple of number of recesses  57 , distributed in the circumferential direction is preferably provided, which are formed to receive the balancing elements  58 . In the depicted exemplary embodiment, the balancing elements  58  are formed by screw elements  59 . The balancing elements  58  have tool sockets  60  for a fixing tool  61 . In the depicted exemplary embodiment, the balancing elements  58 , formed by screw elements  59 , can be inserted into the recesses  57  by means of the fixing tool  61  formed as an Allen key. The screw elements  59  preferably form the so-called thread-tapping or self-cutting screws, which facilitate the application of smooth recesses  57 . 
     The screw elements  58  have a threaded section  62  and a screw head  63  formed as a balancing mass. Screw elements  58  with different masses or weights can find application in a preferable manner. Thus, the threaded section  62  can be uniform, the screw heads  63 , however, can be formed in different sizes. 
     The pulling element  50  which is axially movable by means of actuation levers  49  and connected non-rotatably with the pressure plate  28  can be designated also as a connection cover  50 . From  FIG. 2 , it is apparent that the radial regions  56  of the clutch cover  44 —viewed in circumferential direction of the twin clutch  6 —are provided respectively between the two axial lobes  51 . 
     From  FIG. 2  it is also apparent that the recess  57 , in relation to the rotation axis of the twin clutch  6 , is disposed in such a manner that the balancing elements  58  can be brought into the latter also with a mounted twin clutch  6 . Thus, it can be particularly functional when the recesses  57  are disposed at least essentially radially outside the regions axially opposite them. In this manner, it is ensured that the screw elements  59  can be screwed in by means of the fixing tool  61  in the corresponding recesses  57 . It is functional when the recesses  57  are placed in the radial regions  56  in a manner such that they are disposed offset radially outwards opposite a fictitious enveloping surface of the connection cover  50 . 
     In the depicted exemplary embodiment, the radial regions, which serve for receiving the balancing elements  58  and for fastening with the intermediate pressure plate  26 , are the same. Different radial regions  56  could be distributed over the circumference, however, upon demand, are formed only for receiving the balancing elements  58  or fastening elements  55 . However, also regions can be provided, which can receive both the balancing elements  58  as well as the fastening elements  55 . 
     The embodiment according to the invention is not limited to the described exemplary embodiment, but can very generally find application in twin clutches. Thus, for instance, the intermediate pressure plate  26  can be connected non-rotatably with a disc driven by an engine without interposition of a torsional vibration damping device  8 . The manner of centering or supporting the clutch assembly or the twin clutch  6  can be different also from that depicted in  FIG. 1 . Thus, for instance, the twin clutch  6  can be kept centered directly via a disc driven by the engine, so that the bearing  37  can be omitted. 
     The twin clutch  6  could be centered also, at least partially, via the transmission cover or a component part connected with the latter. Centering or supporting the twin clutch  6  must thereby take place such that also an axial support of the actuation forces exerted on the actuation levers  48 ,  49  is guaranteed. 
     The embodiment according to the invention has the advantage that the balancing elements can be fixed practically without exertion of an axial force on the anchoring regions provided. Therefore, neither the supporting elements nor dolly blocks are required, for example, in order to mount balancing elements  58  formed as screw elements. As balancing elements  58 , also the so-called blind rivets could find application advantageously, and they practically do not require any axial force to anchor them in a recess. The balancing elements  58  could be formed advantageously also by self-locking elements that are slidable onto the fastening regions  56 . Such elements can be formed as clamps for instance and have anchoring regions that engage by locking in place when slid in corresponding contours, for example, with recesses of radial regions  56 . Such elements can thereby at least be partially self-resilient or be anchored by plastic deformation, for example, by compression, so that they are secured against the centrifugal force acting on them. 
     List of Reference Symbols: 
     
         
           1  drive train 
           2  - 
           3  drive unit 
           4  crankshaft 
           5  transmission 
           6  twin clutch 
           7  - 
           8  torsional vibration damping device 
           9  screw connection 
           10  screw connection 
           11  input part 
           12  ring gear 
           13  - 
           14  - 
           15  - 
           16  spring device 
           17  - 
           18  output part 
           19  friction ring 
           20  axial inserted-connection 
           21  - 
           22  clutch-cover part 
           23  - 
           24  - 
           25  - 
           26  intermediate pressure plate 
           27  - 
           28  pressure plate 
           29  friction linings 
           30  - 
           31  first clutch disc 
           32  - 
           33  hub part 
           34  - 
           35  first transmission input shaft 
           36  second transmission input shaft 
           37  roller bearing 
           38  hub part 
           39  pressure plate 
           40  friction linings 
           41  - 
           42  second clutch disc 
           43  hub part 
           44  clutch cover 
           45  - 
           46  actuation device 
           47  actuation device 
           48  actuation levers 
           49  actuation levers 
           50  pulling element 
           51  axial lobes 
           52  riveted connections 
           53  radial lobes 
           54  axial lobes 
           55  riveted connection 
           56  radially protruding regions 
           57  recess 
           58  balancing elements 
           59  screw elements 
           60  tool socket 
           61  fixing tool 
           62  threaded section 
           63  screw heads