A hydraulic coupling having a multi-plate friction clutch assembly operably connecting
a pair of rotary members and a hydramechanical clutch actuator for automatically
controlling engagement of the friction clutch assembly. The clutch actuator includes
a hydraulic fluid pump, a hydraulically-actuated rotary operator, and a ball ramp
mechanism. The hydraulic fluid pump is operable to draw low pressure fluid from
a sump and deliver high pressure fluid to a series of actuation chambers defined
between coaxially aligned first and second components of the rotary operator. The
magnitude of the fluid pressure delivered to the actuation chamber controls the
angular movement of the second component relative to the first component. Translational
movement of the second cam member results in a compressive clutch engagement force
being exerted on the friction clutch assembly, thereby controlling the drive torque
transferred from the first rotary member to the second rotary member.