Abstract:
A wet clutch comprising at least one friction disk ( 10 ) which is loaded by a piston ( 5 ) against an end disk ( 4 ). In order to run a forced pressure medium flow over the friction surfaces ( 11, 12 ) of the wet clutch, two pressures cavities ( 7, 8 ) having a connection in the region of the friction surfaces, are loaded with varying pressures. In order to improve such arrangements, the invention proposes that the leakage flow flowing over the supports of the friction disks is limited.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is filed under 35 U.S.C. §120 and §365(c) as a continuation of International Patent Application No. PCT/DE2009/001535 filed Oct. 29, 2009 which application claims priority from Germany Patent Application No. 10 2008 056 637.3 filed on Nov. 10, 2008 which applications are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a friction clutch including at least one friction disk that is loaded by a piston relative to an end disk. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wet clutches of this type have been known in the art for quite a while as converter lock up clutches in hydrodynamic torque converters or as single or twin clutches in a drive train between drive units and transmissions of motor vehicles. Friction energy is generated in particular during slippage of the wet clutch at the friction surfaces providing frictional engagement for the wet clutch. The friction energy heats up the friction surfaces which can damage or destroy the friction liners provided at the friction surfaces and possibly also friction medium that are not integrated in the flow. 
         [0004]    Therefore friction liners are being proposed which include grooves with a radial portion so that a pressure medium flow is provided for a defined pressure gradient between a portion radially outside of the friction surfaces and a radially inner portion. The pressure medium flow provides a cooling for the friction surfaces. In order to establish a pressure gradient two pressure cavities can be configured on both sides of the friction surfaces. The pressure cavities are loaded with a variable pressure from the pressure medium. Thus, leakage flows in particular for not yet completely compressed friction surfaces can reduce the pressure medium flow over the friction surfaces during a slippage of the wet clutch during which a forced pressure medium flow due to an increased heat introduction in this operating condition is particularly important. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Thus it is an object of the invention to propose a wet clutch which has reduced leakage flows. 
         [0006]    The object is achieved through a wet clutch with at least one friction disk that is disposed in a housing and loaded by an axially displaceable piston against an end disk forming a reaction bearing with respect to the piston. The friction disk is supported torque-proof radially within friction surfaces forming a frictional engagement between the at least one friction disk, the piston and the end disk for a closed wet clutch. The torque-proof support is provided through a profile like an outer or inner teething at a complementary profile of an output component of the wet clutch. The friction surfaces define two pressure cavities at least in a non-open condition of the wet clutch, so that a forced pressure medium flow is run over the friction surfaces by adjusting various pressures of the pressure medium and a leakage flow between the two pressure cavities over the profiles is limited by at least one seal device. When using plural friction disks they, for example, arranged in an alternating manner on the input side and on the output side. The input side friction disks can be engaged at the housing respectively torque-proof and axially moveable within limits. A respective friction disk can include a metal surface and a complementary friction surface with a friction liner. The friction liners can be arranged preferably on both sides at the friction disks arranged on the output side. In an example embodiment, the friction liners are so-called paper liners which can include grooves with a radial component in order to provide a pressure medium flow. An open wet clutch is in an operating condition in which the wet clutch does not transfer any torque. A wet clutch that is not open therefore includes a slipping condition in which a partial moment is already being transferred and it includes the closed condition without any substantial slippage. Since no friction heat is generated when the wet clutch is open a leakage flow can be tolerated in this condition and/or the pressure difference between the two pressure cavities can be set to zero so that neither a forced pressure medium flow over the friction surfaces nor leakage flows are generated. According to the invention leakage flows are eliminated in particular or at least reduced when a forced pressure medium flow over the friction liners, for example, for cooling the friction liners and/or for protecting the pressure medium is required for a slipping or closed wet clutch. 
         [0007]    The wet clutch is driven on the input side by the housing which is coupled with a drive unit like an internal combustion engine. The output component of the wet clutch can transfer a torque that is controlled by the wet clutch to another output component as a function of an operating condition. In an example embodiment, the wet clutch is used in a torque converter. The torque is transferred to an output hub with a torsion vibration damper connected there between when the torque converter is intentionally locked up and subsequently transmitted to a transmission input shaft. Thus, the input component of the torsion vibration damper and the output component of the wet clutch can be configured integral in one piece. In order to transfer torque the at least one friction disk and the output component can be coupled torque proof, e.g. through a profile like an inner teething or outer teething and a profile complementary thereto. 
         [0008]    Alternatively, the output component and the input component or another output component can be configured separately from one another and can be connected with one another like e.g. riveted together, wherein the output component of the friction clutch is configured as a disk support in this case, wherein the disk support centers the at least one friction disk and receives it torque-proof. 
         [0009]    In an example embodiment, driving the at least one friction disk torque-proof through the output component provides high leakage flows, so that the seal device according to the invention is arranged between the output component and the at least one friction disk. Thus, a sealing surface can be provided radially within the friction surfaces at the side oriented towards the output component of the friction disk adjacent to the output component. A complementary seal surface at the output component is associated with the seal surface the friction disk. The seal device is arranged between the two seal surfaces. In an example embodiment, the output component of the wet clutch and the input component of the torsion vibration damper or the other output component, the complementary seal surface can be provided at these components. 
         [0010]    In an example embodiment, the serial flow-through is provided for the friction surfaces between plural friction disks or for the outer friction disks between the piston and the friction disk or the end disk and the friction disk. Thus, for plural friction disks that are e.g. arranged in an alternating manner on the input side and on the output side an input side friction disk that is connected torque-proof with the housing on the radial outside can include a seal device to the end disk and the radially inner friction disks can include respective seal devices relative to one another or to the output component or the input component. When using plural input side friction disks, seal devices can also be provided between the friction disks. 
         [0011]    In order to furthermore eliminate or exclude a leakage between the end disk, which, in an example embodiment is received axially fixated and torque-proof at the housing, the end disk can be sealed relative to the housing e.g. in axial and/or radial direction. 
         [0012]    The sealing devices for sealing leakage flows can be radial and/or axial sealing devices, thus a seal device can be provided, for example, for sealing components that are movable relative to one another in axial directions within limits. The seal device maintains its sealing properties at least over a portion of the axial travel. For example, in order to compensate for the axial travel of the at least one friction disk between an open and a closed operating condition of the wet clutch, a seal device can be provided that has elastic properties in axial direction, which facilitate a seal function at least in closed and slipping operating condition of the wet clutch. The seal function can be removed in closed condition so that the requirements with respect to an axial elasticity of the seal device can be engineered accordingly and focused on the seal function. A sealing device of this type can be formed e.g. from a disk spring and/or a seal membrane which contact under an axial preload at least the slipping and closed operating conditions of the wet clutch at both seal surfaces of the adjacent friction disk on the one hand side and the output component of the wet clutch or the input component of the torsion vibration damper or another output component on the other hand side. Alternatively the at least one seal device can be an elastomeric seal which is arranged between these components in the same manner. Another advantageous embodiment of a seal device includes a flow through limiter, e.g. a filter, a disk with a nozzle or similar. It is appreciated that the seal devices can be advantageously provided in the same manner for the other seal position like between the friction disks between a friction disk and the end disk and similar. 
         [0013]    An advantageous embodiment with a disk support that is connected with an output component like an input component of a torsion vibration damper can provide a seal device which is formed by a seal plate which is attached between the disk support and the output component, wherein the seal device forms a seal surface to the at least one friction disk. Alternatively the seal plate can be centered on the output component in an axially floating manner, wherein the seal plate is e.g. axially loaded against the output component through an axially effective energy storage device like a disk spring and forms a seal surface to the at least one friction disk. The seal surfaces of the seal plates can thus be adjusted with respect to an axial preload against the seal surface at the friction disk so that a gap is created for an open operating condition of the wet clutch so that a detrimental friction torque is not provided in an open operating condition. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0015]      FIGS. 1 through 7  illustrate respective embodiments of wet clutches with a forced pressure medium flow between two pressure cavities over the friction surfaces of the wet clutch. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]      FIG. 1  illustrates the upper half of the wet clutch  1  arranged in a housing  2  about a rotation axis  3  in a sectional view. The housing  2  is driven by a drive unit which is not illustrated, e.g. an internal combustion engine and introduces a torque through the end disk  4  permanently connected with the housing  2  and the piston  5  connected with the housing  2  in a torque-proof and axially movable manner. The housing includes three pressure cavities  6 ,  7 ,  8  which are loadable with pressure independently from one another through a pressure supply device like a pump and respective switch valves. Thus, plural supply lines that are not illustrated and respective outlets are provided between the transmission, which is not illustrated, and the pressure cavities  6 ,  7 ,  8 . For example a supply line or an outlet is connected through a pass through  9  with the pressure cavity  7 . When the pressure of the pressure cavity  6  increases relative to the pressure cavity  7 , the piston  5  is axially moved and loads a particular friction disk  10  against the end disk  4  as illustrated in this embodiment. Consequently, a frictional engagement between the friction surfaces  11 ,  12  and the friction surfaces  13 ,  14  of the piston  5  and the end disk  4  is provided. Thus, the friction surfaces  11 ,  12  of the friction disk  10  are formed by friction liners  15 ,  16  which are applied to the friction disk  10  on both sides and include grooves with a radial portion which are not illustrated through which a forced pressure medium flow runs for a pressure difference between the pressure cavities  7 ,  8 . 
         [0017]    The friction disk  10  is engaged torque proof through a profile  17  like e.g. an inner teething in a complementary profile  18  like e.g. an outer teething. The profile  18  is arranged at an output component  19  which is the input component  20  of a torsion vibration damper  21  in the illustrated embodiment. In order to prevent a leakage flow and thus a reduction of the forced pressure medium flow over the friction surfaces  11 ,  12 ,  13 ,  14  a seal device  22  is provided in the illustrated embodiment, wherein the seal device seals the leakage caused by the profiles  17 ,  18  at least for a slipping or closed wet clutch. Thus, annular seal surfaces  23 ,  24  are provided radially within the friction liners  15 ,  16  at the friction liner  10  and the output component  19 , wherein the disk spring  25  contacts the annular seal surfaces in a preloaded condition of the disk spring. The spring characteristics of the disk spring  25  centered at the profile  18  can thus be configured so that no preload or only a low preload is provided when the wet clutch  1  is open. This way a load moment of the wet clutch caused by a friction of a friction disk  10  and an output component  19  rotating relative to one another is reduced or eliminated for an open wet clutch  1 . 
         [0018]    Furthermore, the two pressure cavities  7 ,  8  are separated from one another through the end disk  4 , the output component  19  and the output hub  26 . The forced pressure medium flow can be generated by a positive pressure in the pressure cavity  7  or the pressure cavity  8 . For a positive pressure in the pressure cavity  8  the pressure medium is initially pressed from the radial inside through the friction liner  15  into the intermediary space  27  and from there in radially inward direction through the friction liner  16  into the pressure cavity  7  and let out through the pass through  9 . The pressure medium flow is provided through the positive pressure in the pressure cavity  7  in opposite direction radially outward through the friction liner  16  into the intermediary space  27  and from there in radially inward direction through the friction liner  15  into the pressure cavity  8  which can be e.g. a converter cavity with a turbine shell and a pump shell. In order to obtain even cooling effects of both serially flowed friction liners an alternating pressure loading of the pressure cavity  7 ,  8  with higher pressure can be provided. 
         [0019]      FIG. 2  provides a wet clutch  1   a  that is configured similar to the wet clutch  1  of  FIG. 1 , wherein the wet clutch  1   a  includes a seal device  22   a  that is formed from an elastomeric seal which is different from the seal device  22  in  FIG. 1 . This can be a seal ring  25   a  made from an elastic plastic material, e.g. Viton®, EPDM or similar whose elasticity is advantageously configured so that a gap to one or both seal surfaces  23   a  or  24   a  is formed for an open wet clutch  1   a . The seal ring  25   a  e.g. configured as an elastomeric seal is centered on the profile  18 . 
         [0020]    In order to increase the forced pressure medium flow through the friction liners  15 ,  16  the end disk  4  can be sealed on the radial outside through the seal  28  or through an axially effective seal  29  towards the housing  2 . This way the pressure cavity  8  is sealed better relative to the intermediary cavity  27  so that a pressure gradient between the intermediary cavity  27  and the pressure cavity  8  is maintained which is necessary for maintaining the pressure medium flow through the friction liner  15 . It is appreciated that a respective seal can be omitted for a tight connection between an end disk  4  and the housing  2 . In order to increase the sealing between the two pressure cavities  7 ,  8  a seal  30  can be arranged between the output component  19  and the output shaft  26 , wherein the seal is advantageously configured as a shaft seal  30  as illustrated for a configuration of the output component  19  as an input component  20  of the torsion vibration damper  21 , wherein the input component is centered and rotatably received on the output hub  26 . 
         [0021]      FIG. 3  illustrates an embodiment of a wet clutch  1   b  in which contrary to the wet clutches  1 ,  1   a  of  FIGS. 1 and 2  plural, thus output side friction disks  10   a ,  10   b  are provided between which an input side friction disk  4   a  is arranged that is torque-proof with the housing and movable within limits in axial direction. The two pressure cavities  7 ,  8  as illustrated in  FIG. 1  are sealed through the disk spring  25  between the friction disk  10   b  adjacent to the output component  19  with an axially broadened profile  18  for accordingly receiving two friction disks  10   a ,  10   b  and the output component  19 . In order to obtain a serial flow through of the friction liners  15 ,  15   a ,  16 ,  16   a  furthermore a seal device  22   b  is provided between the two friction disks  10   a ,  10   b  and another seal device  22   c  is provided between the end disk  4  and the friction disk  4   a  radially outside of the friction liners  15 ,  15   a ,  16 ,  16   a  so that two intermediary cavities  27 ,  27   a  are formed. 
         [0022]    This provides a forced pressure medium flow through the friction liner  15   a  into the intermediary cavity  27   a  for a pressure in the pressure cavity  8  that is higher than a pressure in the pressure cavity  7 . The disk spring  25   c  prevents a transition of the pressure medium between the friction disk  4   a  and the housing  2  into the intermediary space  27  so that the pressure medium is pressed from the intermediary space  27   a  through the friction liner  16   a  into the intermediary space  27   b  arranged within the friction liners. The disk spring  25  prevents a direct transition of the pressure medium into the pressure cavity  7 . Therefore the pressure medium flows from the intermediary space  27   b  through the friction liner  15  and subsequently through the friction liner  16  into the pressure cavity  7 . For a pressure reversal the pressure medium takes a reverse path through the intermediary cavities  27 ,  27   a ,  27   b  and the friction liners  15 ,  15   a ,  16 ,  16   a.    
         [0023]      FIG. 4  illustrates a wet clutch  1   c  that is similar to the wet clutch  1   b  of  FIG. 3  with the difference that at least one opening  31  is provided in the friction disk  4   a , wherein the opening connects the intermediary spaces  27 ,  27   a  with one another. Consequently the friction liners  15 ,  15   a ,  16 ,  16   a  are flowed through partially in series and partially in parallel. For example the friction liners  15 ,  16  can be flowed through in parallel for a positive pressure in the pressure cavity  8  after a flow through of the friction liner  15   a , while the friction liner  16   a  is flowed through serially after the friction liners  15 ,  15   a  by a partial flow of the pressure medium which initially flows through the friction liner  15  and fills the intermediary space  27   b.    
         [0024]      FIG. 5  illustrates a wet clutch  1   d  that is modified relative to the preceding wet clutches  1 ,  1   a ,  1   b ,  1   c  in which the output component  19  is formed by the disk support  32 . The disk support  32  is connected torque-proof with the input component  20  of the torsion vibration damper  21  in the illustrated embodiment, e.g. as illustrated herein riveted together through rivets  33 . The seal device  22   d  between the two pressure cavities  7 ,  8  is formed in the illustrated embodiment through a seal plate  25   d  which is axially mounted between the input component  20  and the disk support  32  through rivets  33  and includes a seal surface  34  on a radial outside towards the friction disk  10 , wherein the seal surface contacts under a preload for a slipping or closed wet clutch  1   d  and seals a leakage that occurs through the profiles  17 ,  18 . 
         [0025]      FIG. 6  thus illustrates a modified embodiment of a wet clutch  1   e  that is similar to the wet clutch  1   d  according to  FIG. 5  with the difference that the seal device  22   e  in the form of the seal plate  25   e  is centered in a floating manner on the axial onset of the input component  20  and preloaded through the energy storage device  36  that is effective in an axial direction and centered on the onset  35 , wherein the energy storage device is e.g. configured as a disk spring that is preloaded at least for a slipping or closed wet clutch  1   e  through the seal surface  34  against which the friction disk  10  is preloaded. 
         [0026]      FIG. 7  illustrates an alternative embodiment of a wet clutch  1   f  in which the disk component  20   b  connected with the input component  20   a  and riveted together with the turbine shell  38  of a torque converter, wherein the turbine shell is only indicated, is centered on the drive hub  26 , so that the input component  20   a  shall be illustrated in a radially shortened manner contrary to the input components  20  of  FIGS. 1 ,  5  and  6 . An axial onset  37  of the input component  20   a  thus has the profile  18  in which the friction disk  10  is engaged torque-proof and thus forms an output component  19 . A seal for the two pressure cavities  7 ,  8  through the profile  18  is formed by the disk spring  25  according to the descriptions provided regarding  FIG. 1 . The sealing in the portion of the output component  19  and the drive hub  26  is provided by a seal plate  39  which is connected with the output component  19  through the rivets  40  which simultaneously provide centering of the disk spring  25  and wherein the seal plate is axially applied to the flange  41 . 
       REFERENCE NUMERALS AND DESIGNATIONS 
       [0000]    
       
           1  Wet clutch 
           1   a  Wet clutch 
           1   b  Wet clutch 
           1   c  Wet clutch 
           1   d  Wet clutch 
           1   e  Wet clutch 
           1   f  Wet clutch 
           2  Housing 
           3  Rotation axis 
           4  End disk 
           4   a  Friction disk 
           5  Piston 
           6  Pressure cavity 
           7  Pressure cavity 
           8  Pressure cavity 
           9  Pass through 
           10  Friction disk 
           10   a  Friction disk 
           10   b  Friction disk 
           11  Friction surface 
           12  Friction surface 
           13  Friction surface 
           14  Friction surface 
           15  Friction liner 
           15   a  Friction liner 
           16  Friction liner 
           16   a  Friction liner 
           17  Profile 
           18  Profile 
           19  Output component 
           20  Input component 
           20   a  Input component 
           20   b  Disk component 
           21  Torsion vibration damper 
           22  Seal device 
           22   a  Seal device 
           22   b  Seal device 
           22   c  Seal device 
           22   d  Seal device 
           22   e  Seal device 
           23  Seal surface 
           23   a  Seal surface 
           24  Seal surface 
           24   a  Seal surface 
           25  Disk spring 
           25   a  Seal ring 
           25   b  Disk spring 
           25   c  Disk spring 
           25   d  Seal plate 
           25   e  Seal plate 
           26  Output hub 
           27  Intermediary space 
           27   a  Intermediary space 
           27   b  Intermediary space 
           28  Seal 
           29  Seal 
           30  Seal 
           31  Opening 
           32  Disk support 
           33  Rivet 
           34  Seal surface 
           35  Onset 
           36  Energy storage device 
           37  Onset 
           38  Turbine shell 
           39  Seal plate 
           40  Rivet 
           41  Flange