Hydraulic coupling arrangement for 4WD vehicle

摘要

A hydraulic coupling arrangement used for a 4WD vehicle for imparting a drive torque of an engine to auxiliary drive wheels based on a first rotational difference between main and auxiliary drive wheels. A first rotary shaft is coupled to the main drive wheel and a second rotary shaft is coupled to the auxiliary drive wheel. A hydraulic pump of the coupling arrangement is adapted to be driven according to a second rotational difference between the first and second rotary shafts for generating an oil pressure corresponding to the second rotational difference. A clutch connects the first rotary shaft with the second rotary shaft based on the oil pressure generated by the hydraulic pump. A first oil passage extends to the clutch. First and second ports are formed in the hydraulic pump and function as inlet and outlet ports or vice versa based on the second rotational difference and a rotational direction of the first rotary shaft. One of the ports is communicated with the first oil passage and the other port is communicated with an oil chamber defined in the coupling arrangement for normally holding the working oil.