Abstract: A clutch assembly, including: a secondary piston assembly; a primary piston including a portion located radially outward of the secondary piston assembly; a first chamber at least partially formed by a first side of the primary piston; a second chamber at least partially formed by the secondary piston assembly and a second side of the primary piston; and a check valve connecting the first and second chambers. For a first force applied by fluid in the first chamber: the primary piston remains axially stationary; the fluid flows from the first chamber into the second chamber; and the secondary piston assembly displaces in a first axial direction to contact a clutch pack. For an increase of the first force to a second force: fluid flow between the first and second chambers is blocked by the check valve; and the primary piston and the secondary piston assembly displace in the first axial direction to close the clutch pack.

Abstract: A torque transmission unit having a friction clutch and a hydraulic actuation system. The hydraulic actuation system includes a stepped piston unit having a stepped piston which has a first piston section movable in a first pressure space and a second piston section movable in a second pressure space. The first pressure space and a portion of the second pressure space can be brought into fluid communication by means of an overflow line based on a position of the first piston section. The hydraulic actuation system also includes an actuation piston unit having an actuation piston that cooperates with the friction clutch. A third pressure space is associated with the actuation piston and is in fluid communication with the second pressure space via a pressure line.

Abstract: A limited slip differential transmission of the closed type in which a pressurized lubricant is fed to the rotating gears and a series of limited slip clutch plates. The clutch plates are engaged by pressurized control fluid. A valve assembly having a spool valve is responsive to engagement pressure to permit discharge of a portion of pressurized fluid from the clutch plates to a sump chamber and the transmission to purge debris that may have accumulated in the clutch plates. The spool valve is arranged so that fluid is passed only during an intermediate movement of the valve to minimize any pressure loss from the lubricating fluid for the transmission and limited slip clutches.

Abstract: The invention relates to a friction clutch having a single-acting actuator which is a piston-cylinder unit and is connected in a controllable fashion to a pressurized fluid source. In order to be able to carry out a fast pilot stroke up to the point at which the clutch makes contact, the piston-cylinder unit has a stepped piston whose first step of small diameter delimits, by means of its cylinder, a first pressure space, and whose second step of relatively large diameter delimits, by means of its cylinder, a second pressure space, a pressure line being connected to the first pressure space and, by means of a first non-return valve which opens at a certain pressure, to the second pressure space, and it also being possible for the second pressure space to be connected via a discharge line and a suction line, which contains a second non-return valve, to the fluid reservoir. The invention also relates to a drive device having clutches of said type.