Electronically-controlled hydraulically-actuated coupling

Abstract

A power transmission device includes a friction clutch operable to selectively transfer torque between an input member and an output member. An actuator is operable to provide an actuating force to the friction clutch. The actuator includes an electric motor having an output shaft drivingly coupled to a pump. The pump is operable to provide pressurized fluid to a piston acting on the friction clutch.

1 . A power transmission device comprising:
 a housing having a wall member and an end wall that cooperate to define an interior cavity, a piston bore being formed in the end wall and intersecting the interior cavity;   an first shaft received through the end wall and rotatably disposed in the housing along a first rotational axis;   a hub coupled for rotation with the first shaft;   a plurality of first friction plates coupled for rotation with the hub;   an second shaft rotatably mounted in the housing;   a plurality of second friction plates coupled for rotation with the second shaft and interleaved with the first friction plates;   an annular piston received in the piston bore and configured to translate axially along the first rotational axis, the first shaft being received through the annular piston;   an actuator mounted to the end wall, the actuator including a pump and an electric motor for driving the pump, the pump including an outlet, the electric motor having an output shaft that is rotatable about a second rotational axis that is oriented generally perpendicular to the first rotational axis;   a first incompressible fluid being disposed in the interior cavity; and   a second incompressible fluid disposed in a conduit connecting the outlet of the pump and piston bore, wherein the first and second incompressible fluids are different.   
   
   
       2 . The power transmission device of  claim 1 , wherein an annular hub is formed is formed in the end wall and wherein the annular piston sealingly engages the annular hub. 
   
   
       3 . The power transmission device of  claim 2 , wherein a bearing set is received in the annular hub, the bearing set supporting an end of the first shaft. 
   
   
       4 . The power transmission device of  claim 1 , wherein one of the first and second shafts includes an aperture into which a portion of the other one of the first and second shafts is received. 
   
   
       5 . The power transmission device of  claim 4 , wherein a bearing is received in the aperture, the bearing being disposed between the first and second shafts. 
   
   
       6 . The power transmission device of  claim 1 , wherein an endcap is removably coupled to the housing to close an end of the interior cavity opposite the end wall. 
   
   
       7 . The power transmission device of  claim 1 , wherein the pump includes a gerotor. 
   
   
       8 . The power transmission device of  claim 1 , wherein the actuator includes a means for limiting a pressure of the second incompressible fluid. 
   
   
       9 . The power transmission device of  claim 8 , wherein the pump is configured to leak from the outlet to low pressure inlet side of the pump when a pressure of the second incompressible fluid is greater than a predetermined pressure. 
   
   
       10 . The power transmission device of  claim 8 , wherein the means for limiting pressure includes a relief valve. 
   
   
       11 . The power transmission device of  claim 1 , further including means for removing substantially all incompressible fluid from the piston bore. 
   
   
       12 . The power transmission device of  claim 1 , further comprising a reservoir for providing the second incompressible fluid to an inlet of the pump, the reservoir being arrange longitudinally along an axis that is orthogonal to the first and second rotational axes. 
   
   
       13 . The power transmission device of  claim 1 , wherein the second friction plates are mounted in a drum and the drum is coupled for rotation with the second shaft. 
   
   
       14 . The power transmission device of  claim 1 , further comprising means to lock the friction clutch in a mode that transmits rotary power between the first and second shafts. 
   
   
       15 . The power transmission device of  claim 14 , wherein the locking means includes a two-position valve. 
   
   
       16 . The power transmission device of  claim 1 , wherein the pump includes first and second pump housing halves that mate in a plane that is perpendicular to the second rotational axis. 
   
   
       17 . The power transmission device of  claim 16 , wherein the outlet of the pump includes a first annular slot that is formed through a face of the first pump housing half that is adjacent the second pump housing half. 
   
   
       18 . The power transmission device of  claim 17 , wherein the pump includes an inlet, the inlet including a second annular slot that is formed through the face of the first pump housing. 
   
   
       19 . A power transmission device comprising:
 a housing having a wall member and an end wall that cooperate to define an interior cavity, a piston bore being formed in the end wall and intersecting the interior cavity;   an first shaft received through the end wall and rotatably disposed in the housing along a first rotational axis;   a hub coupled for rotation with the first shaft;   a plurality of first friction plates coupled for rotation with the hub;   an second shaft rotatably mounted in the housing;   a plurality of second friction plates coupled for rotation with the second shaft and interleaved with the first friction plates;   an annular piston received in the piston bore and configured to translate axially along the first rotational axis, the first shaft being received through the annular piston;   an actuator mounted to the end wall, the actuator including a pump and an electric motor for driving the pump, the pump including an outlet, the electric motor having an output shaft that is rotatable about a second rotational axis that is oriented generally perpendicular to the first rotational axis;   a first incompressible fluid being disposed in the interior cavity; and   a second incompressible fluid disposed in a conduit connecting the outlet of the pump and piston bore, wherein the first and second incompressible fluids are different;   wherein an annular hub is formed is formed in the end wall and wherein the annular piston sealingly engages the annular hub;   wherein a bearing set is received in the annular hub, the bearing set supporting an end of the first shaft;   wherein one of the first and second shafts includes an aperture into which a portion of the other one of the first and second shafts is received;   wherein a bearing is received in the aperture, the bearing being disposed between the first and second shafts;   wherein an endcap is removably coupled to the housing to close an end of the interior cavity opposite the end wall;   wherein the pump includes a gerotor; and   wherein the actuator includes a means for limiting a pressure of the second incompressible fluid.