Abstract:
A wet clutch comprising a first plate carrier and a second plate carrier which have different diameters, as well as an oil bath in which the plate carriers are arranged concentrically and rotatable with respect to one another. Here, the first plate carrier includes on its circumference a deflection element, by means of which oil which is moving tangentially with respect to the first plate carrier is deflected radially in the direction of the second plate carrier.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national stage application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2013/059322 filed on May 6, 2013, which application claims priority from German Patent Application No. DE 10 2012 208518.1 filed on May 22, 2012, which applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a wet clutch for use in a drivetrain of a motor vehicle. In particular, the invention relates to a wet clutch for bridging a hydrodynamic torque converter. 
       BACKGROUND OF THE INVENTION 
       [0003]    In a drivetrain of a motor vehicle, a drive motor is connected to a transmission by means of a clutch device. The clutch device comprises a hydrodynamic torque converter, which transmits a torque from the drive motor to the transmission as long as an input side and an output side of the torque converter have different speeds of rotation. Thus the torque converter is helpful in particular for starting up the motor vehicle. In order to minimize flow losses within the torque converter, a friction clutch may be used to connect the input side to the output side torsionally as soon as the rotational speed difference has fallen below a predetermined value, for example because the motor vehicle has been started up. In another embodiment, the transmission of torque from the drive motor to the transmission can also be achieved without a hydrodynamic converter, by means of the friction clutch alone. 
         [0004]    The clutch is preferably a friction-disk clutch, which runs in a fluid bath, in particular in an oil bath. An outer plate carrier and an inner plate carrier, which have different diameters, are rotatably supported concentric to each other. At the same time, one of the plate carriers is connected to the input side and the other is connected to the output side of the clutch device. In the radial intermediate space between the plate carriers there is an axial stack of a plurality of plates. The individual plates are torsionally connected alternately to the inner and the outer plate carriers. If an axial force acts on the stack of plates, friction between the plates increases, so that torque can be transmitted between the input side and the output side. 
         [0005]    If the friction-disk clutch is in the disengaged or partially disengaged state, the plate carriers can have different speeds of rotation. One of the plate carriers may be stationary relative to an external reference system, such as a housing, or may rotate only slowly. The oil surrounding the friction-plate clutch is accelerated in the circumferential direction by the more rapidly rotating plate carrier, and is driven radially outward under the influence of centrifugal force. This ensures a throughput of oil through this plate carrier for the purpose of cooling and lubrication. The oil, on a circular path, is slowed down however on the more slowly rotating plate carrier, so that the flow in the circumferential direction or in the radial direction may practically come to a standstill there. The second plate carrier may thus be subjected only to a flow of oil too weak to ensure cooling or lubrication. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    A wet clutch according to the invention includes a first plate carrier and a second plate carrier which have different diameters, as well as an oil bath in which the plate carriers are arranged concentrically and rotatable relative to each other. At the same time, the first plate carrier includes on its circumference a deflection element, in order to deflect oil which is moving tangentially relative to the first plate carrier, radially in the direction of the second plate carrier. 
         [0007]    A flow of oil to the second plate carrier can be ensured by the use of the deflection element. The deflection element is preferably attached to the plate carrier which rotates generally more rapidly than the other plate carrier relative to an external reference system such as a housing when the wet clutch is disengaged. In that respect, the first plate carrier may be connected in particular to an output shaft of a drive motor, and the second plate carrier may be connected to the input shaft of a transmission. At the same time, it may be unimportant whether the first plate carrier is the inner one and the second the outer one, or vice versa. In both cases, the deflection element may be used for an improved supply of oil to the respective other plate carrier. 
         [0008]    In a preferred embodiment, the first plate carrier has a radial opening, to whose rear side in the direction of flow the deflection element is attached, the deflection element extending tangentially contrary to the direction of flow and radially away from the second plate carrier. 
         [0009]    In this way, the deflection element can form a type of vane, against which the tangentially flowing oil streams and which deflects it into a radial direction, or at least utilizes a back pressure of the oil to convey part of the oil in the radial direction. The oil can pass through the opening and be conveyed further in the direction of the second plate carrier. 
         [0010]    In an especially preferred embodiment, the plate carrier is producible from a metal sheet, and the deflection element can be produced by folding up the sheet on one side in the area of the opening. This enables a simple, cost-effective production of the first plate carrier, and thus of the wet clutch. 
         [0011]    In a variant of the invention, the first plate carrier has radial toothing for torsional connection to a plate, the deflection element being located in the area of the toothing. At the same time, the toothing may also be used to bring about the radial flow of oil by means of the deflection element. 
         [0012]    In particular, the deflection element may be formed by a tooth flank of the toothing. In this way, the design element of the toothing can serve an additional purpose. Complexity of the wet clutch may thus be increased only slightly, or not at all, by the deflection element. 
         [0013]    In an especially preferred embodiment, the tooth flange extends tangentially contrary to the direction of flow and radially away from the second plate carrier, which introduces an opening for the flow of oil into the tooth flange. The oil can thus pass through the plate carrier in the tangential direction at a bearing tooth flank, at which the torque of the plate carrier is transferred to a plate. The tooth flank can thereby be better penetrated by a flow of oil in a highly loaded region, and thus be protected from excessive temperature and increased wear. 
         [0014]    In one embodiment, the opening is located at a radius of the toothing which faces radially away from the second plate carrier. Stated differently, the opening can be located at a base circle of the toothing, if the first plate carrier is the inner plate carrier, and at an outside circle of the toothing if the first plate carrier is the outer plate carrier. Variants are also possible, however, in which the opening is located at the radius of the toothing which faces radially toward the second plate carrier. 
         [0015]    The toothing may comprise a plurality of tooth flanks, which extend radially at different distances from the second plate carrier. For example, each second, third or generally nth (where n≧2) tooth flange of the toothing in the circumferential direction can extend further in the radial direction than the other tooth flanks. The other tooth flanks can thus represent a relatively small obstacle for oil flowing in the circumferential direction, while the longer tooth flank is better able to function as a deflection element. 
         [0016]    Furthermore, the wet clutch may include a plate, where the plate has toothing which corresponds to the toothing of the first plate carrier, and where the toothing of the plate has a radial cutout in the area of the opening. The teeth of the toothing of the plate may also be sufficiently short in the radial direction that they do not impede flow in the area of the opening. This will improve the transporting effect of the deflection element. 
         [0017]    In particular, the radial cutout may have a trapezoidal or triangular cross section between the toothing of the plate and the toothing of the first plate carrier in the area of the opening. 
         [0018]    It is therefore the object of the invention to prepare a wet clutch whose plate carriers are adequately washed by the fluid surrounding them under all operating conditions. The invention fulfills this object by means of a wet clutch having the features of the independent claim. Subordinate claims describe preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention will now be described in greater detail by reference to the accompanying figures, in which the figures represent the following: 
           [0020]      FIG. 1  is a schematic depiction of a wet clutch; 
           [0021]      FIG. 2  is a detail of one of the wet clutches from  FIG. 1  in a first embodiment; and, 
           [0022]      FIGS. 3 to 8  illustrate details from  FIG. 2  in additional embodiments. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1A  shows a first schematic depiction of wet clutch  100 . In housing  105 , radially outer plate carrier  115  and radially inner plate carrier  120  are positioned rotatably around axis of rotation  110 . Inner plate carrier  120  has a smaller radius than outer plate carrier  115 . One of the plate carriers  115 ,  120  serves as the input side, the other as the output side of wet clutch  100 . 
         [0024]    In the radial gap between inner plate carrier  120  and outer plate carrier  115  are a number of ring-shaped plates  125 , arranged in an axial stack. Within the stack, one of plates  125  is torsionally connected to outer plate carrier  115 , and axially adjacent plate  125  is torsionally connected to inner plate carrier  120 . 
         [0025]    Engaging element  130 , for example in the form of a hydraulic piston or a spring element, is provided in order to press the stack of plates  125  together in the axial direction when necessary. As this occurs, a frictional force between plates  125  increases, so that an increased torque can be transmitted between outer plate carrier  115  and inner plate carrier  120 . 
         [0026]    Wet clutch  100  runs in oil bath  135 , which is at least partially subjected to a flow, which is represented by arrows. At a radially outer region of inner plate carrier  120  is deflection element  140 , in order to deflect oil which is flowing tangentially along inner plate carrier  120  in the radial direction and to accelerate it in the direction of outer plate carrier  115 . 
         [0027]    The depiction in  1 B shows a different embodiment of wet clutch  100  from  FIG. 1A . Here, deflection element  140  is attached to outer plate carrier  115 , and is designed so that the flow of oil of oil bath  135 , which grazes a surface area of outer plate carrier  115 , is deflected radially inward to inner plate carrier  120 . In the depicted embodiment, inner plate carrier  120  is connected to housing  105  or is integrated with it. 
         [0028]    Deflection element  140  can thus be employed optionally on inner plate carrier  120  or on outer plate carrier  115 , in order to deflect tangentially flowing oil in each case in the direct on of the other plate carrier  115  or  120 , respectively. 
         [0029]    With reference to  FIGS. 2 through 8 , in the following section various embodiments of friction clutch  100  will be presented in greater detail, starting purely by way of example from inner plate carrier  120 , whose deflection elements  140  deflect the oil radially outward. In a corresponding manner, the features which are shown and described may also be used however to provide deflection element  140  on outer plate carrier  115 , in order to deflect the oil, which is flowing by tangentially, radially inward to inner plate carrier  120 . 
         [0030]      FIG. 2  shows a detail of one of wet clutches  100  from  FIG. 1  in a first embodiment. The depiction is made as a sectional view perpendicular to axis of rotation  110 . 
         [0031]    Inner plate carrier  120  has toothing  205 , which is engaged torsionally by toothing  210  of radially outer subsequent plate  125 . The individual teeth of toothings  205  and  210  are trapezoid-shaped. In the base circle of toothing  205  there are radial openings  215  between the teeth of toothing  205 , in order to allow a stream of oil of oil bath  135  in the radial direction. 
         [0032]    Deflection element  140  is attached to a rear end of each opening  215  in the direction of flow. This deflection element extends radially inward and tangentially contrary to the direction of flow of the oil of oil bath  135 . In a different embodiment than the one depicted, this section of deflection element  140  which extends radially outward may also be, for example, of an S-shaped or Z-shaped design instead of a straight one. In the depicted embodiment, an optional tangential appendage is provided on each of deflection elements  140 , in order to seal a tooth of toothing  205  of inner plate carrier  120  against the oil of oil bath  135 , and thus to reduce a flow resistance of inner plate carrier  120 . 
         [0033]      FIG. 3  shows a variation of the embodiment shown in  FIG. 2 . Openings  215  and deflection elements  140  are located at the same positions as in the embodiment shown in  FIG. 2 , but deflection elements  140  are integrated with inner plate carrier  120 , in that deflection elements  140  are unfolded or bent out from the sheet metal material of inner plate carrier  120  on one side. This can be achieved, for example, by means of a stamping and bending process. 
         [0034]      FIG. 4  shows another embodiment of wet clutch  100 , corresponding to the depictions of  FIGS. 2 and 3 . Here, toothings  205  and  210  of inner plate carrier  120  or of plate  125  which correspond to each other are designed so that tooth flank  405  extends from oil bath  135  in the radial direction contrary to the direction of flow of the oil. Preferably this is bearing tooth flank  405 ; that is, in reference to  FIG. 4 , either inner plate carrier  120  drives plate  125  in the clockwise direction, or plate  125  drives inner plate carrier  120  counter-clockwise. Opening  215  is introduced here into tooth flank  405  which is inclined contrary to the direction of flow. An opposing tooth flank  405  extends in the radial direction, and in various embodiments may be inclined in or contrary to the direction of flow of the oil from oil bath  135  in the circumferential direction. The tooth of toothing  205 ,  210  formed by adjacent tooth flanks  405  can thereby assume a trapezoidal or rectangular form in cross section. 
         [0035]      FIG. 5  shows another embodiment of wet clutch  100 , corresponding to the depictions of  FIGS. 2 through 4 . Here, the teeth of toothings  205 ,  210  have the described trapezoidal form, where the spacing of adjacent tooth flanks  405  of a tooth decreases with increasing radius. Tooth flank  405  inclined contrary to the direction of flow of the oil from oil bath  135  again fulfills the function of deflection element  140 . Opening  215  is located in the area of the outside circle of toothing  205  of inner plate carrier  120 , or in the area of the base circle of toothing  210  of plate  125 , and forms a passageway for the oil in the radial direction. 
         [0036]    In the embodiment depicted in  FIG. 5 , teeth of toothings  205 ,  210  are alternately of different heights in the radial direction. In other embodiments, in general every nth (where n≧2) tooth of toothings  205 ,  210  is longer or shorter than the other teeth. 
         [0037]      FIG. 6  shows another embodiment of wet clutch  100 , corresponding to the depictions of  FIGS. 2 through 5 . Contrary to the embodiment shown in  FIG. 5 , openings  215  are again located in tooth flanks  405  of toothings  205 ,  210 , inclined contrary to the direction of flow of the oil from oil bath  135 . Here, openings  205  are introduced only on tooth flanks  405  of the teeth of toothings  205 ,  210  which are elongated in the radial direction. Tooth flank  405 , which is located opposite tooth flank  405  having opening  215  on the radially elongated tooth, is inclined relative to a radius to axis of rotation  110  in the same direction as tooth flank  405  having opening  215 . The tooth delimited by the two tooth flanks  405  thus has a trapezoidal form, with the width of the tooth increasing in the circumferential direction with increasing radius. 
         [0038]      FIG. 7  shows a detail corresponding to  FIGS. 2 through 6  of another embodiment of wet clutch  100 . Here, toothings  205 ,  210  are distinguished corresponding to the radially elongated teeth of the embodiment shown in  FIG. 6 . In this case, an alternating radial length of the teeth has been dispensed with; however, the teeth have alternating different widths in the circumferential direction. In the area of opening  215 , radial cutout  705  is introduced into toothing  210  of plate  125 , so that the tooth of toothing  210  of plate  125  effectively extends less in the radial direction than toothing  205  of inner plate carrier  120  would allow. Cutout  705 , or the free remaining space between toothings  205  and  210 , has a trapezoidal shape. In the depicted embodiment, the trapezoid opens with increasing radius from axis of rotation  110 ; an opposite design is likewise possible. 
         [0039]      FIG. 8  shows another embodiment of wet clutch  100 , corresponding to the depiction of  FIGS. 2 through 7 . In particular, a variant of the embodiment shown in  FIG. 7  is depicted. Here, cutouts  705 , or a free-remaining space between toothing  210  of the plate  125  and toothing  205  of inner plate carrier  120 , have a triangular form on each tooth. 
         [0040]    The different features of the embodiments shown in  FIGS. 2 through 8  or described above are freely combinable with each other. In particular, the forms of the teeth of toothings  205 ,  210  have their alternating or cyclically recurring radial lengths and tangential widths; differently shaped cutouts  705  and the inclinations of tooth flanks  405  can be freely combined with each other. It is crucial here that deflection element  140  exists, which is set up to deflect oil of oil bath  135  from a tangential direction of motion into a radial direction to outer plate carrier  115 . 
         [0041]    As described already at the beginning, the features depicted or described may also be employed on outer plate carrier  115  instead of on inner plate carrier  120 . The radial relationships are exchanged here, in that a deflection of the oil from oil bath  135  in the direction of the inner plate carrier  120  takes place radially toward the inside, instead of radially toward the outside, as described above. 
         [0042]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           FIG. 1  schematic depiction of a wet clutch 
           FIG. 2  a detail of one of the wet clutches from  FIG. 1  in a first embodiment 
           FIGS. 3-8  the detail from  FIG. 2  in additional embodiments 
           100  Wet clutch 
           105  Housing 
           110  Axis of rotation 
           115  Outer plate carrier 
           120  Inner plate carrier 
           125  Plate 
           130  Engaging element 
           135  Oil bath 
           140  Deflection element 
           205  Toothing of the plate carrier 
           210  Toothing of the plate 
           215  Opening 
           405  Tooth flank 
           705  Cutout