Hydraulic couplings are used in a variety of motor vehicle driveline applications for limiting slip and transferring drive torque between a pair of rotary members. In 4WD and AWD applications, hydraulic couplings are used to control the transfer of drive torque from a driven member to a non-driven member in response to speed differentiation therebetween. In limited slip applications, such as used in association with a differential in an axle assembly, a full-time transfer case or a transaxle, hydraulic couplings have been used to limit slip and bias the torque split between a pair of driven rotary members. Examples of known hydraulic couplings that are adapted for use in such driveline applications include viscous couplings, geared traction units and hydraulically-actuated friction clutches.
One type of hydraulic coupling that has proven to be successful in many driveline applications includes a gerotor pump which generates hydraulic pressure to engage a multi-plate friction clutch in response to and as a function of the speed differentiation between the rotary members. Examples of such hydraulic couplings are disclosed in U.S. Pat. Nos. 5,310,388 and 5,827,145. Commonly-owned U.S. Pat. Nos. 6,378,682 and 6,626,787 each disclose an improved version of such a hydraulic coupling that is equipped with a control valve for automatically releasing engagement of the friction clutch in response to the occurrence of an over-pressure or over-temperature condition. However, a need still exists to provide means for releasing engagement of the friction clutch in coordination with actuation of certain brake-based vehicle control systems such as, for example, anti-lock brake systems and/or electronic stability control systems.
USPTO Backgrounds
USPTO Backgrounds