Hydraulic drive assembly.

摘要

A hydraulic drive assembly 10 includes a variable displacement pump 12 fluidly connected in a closed loop circuit 13 with a motor 14 driving an ancillary device 16 e.g. a fan. Auxiliary circuit A3 is also supplied by the pump. An auxiliary pump 26 provides fluid for a power steering circuit 32 and an auxiliary circuit A2. A recirculating passage 34 fluidly connects the power steering circuit to the closed loop circuit 13 downstream of the motor 14 to make-up losses and reduce the necessary reservoir 28 volume. The output of the pump 12 to drive the ancillary device is gradually adjusted by means of electronic control valve 42 and hydraulic control valves 48, 50. A control method is disclosed in which the displacement of the pump is based on an electronic control signal.