Patent ID: 6698199
Filing Date: 2004-03-02
Classification: F16H

Abstract:
A swash plate type hydraulic drive transmission comprising:rotors including cylinder blocks are supported in a casing so as to be rotatable about the axis of said cylinder blocks; plungers having an outer end brought into contact with and engaged with swash plates to form oil chambers between the plungers and the closed ends of cylinder holes, said plungers being slidably fitted in a plurality of said bottomed cylinder holes provided in said cylinder blocks in an annular arrangement; and distributing valves for allowing the oil chambers of the plungers moving to a side for expanding said oil chambers to be in communication with low pressure oil passages and for allowing the oil chambers of the plungers moving to a side for reducing said oil chambers to be in communication with high pressure oil passages, said distributing valves being provided to correspond to the plungers between the low pressure oil passages and the high pressure oil passages provided in said rotors and said oil chambers; wherein the distributing valves alternately switch, corresponding to the axial reciprocating motion of the plungers, communication and cutoff communication between a plurality of communication passages communicated to said oil chambers opening to the inner surface of the cylinder holes and a plurality of low pressure and high pressure ports respectively in communication with said low pressure oil passages and said high pressure oil passages opening to the inner surface of the cylinder holes, wherein the low pressure oil passage includes a first low pressure annular recess in communication with the low pressure oil passage and a second low pressure annular recess in communication with an inner end of the low pressure oil passage.