Patent ID: 7040216

Claim:
A hydraulic motor comprising: an output shaft ( 2 ); a cylinder ( 4 ) arranged around the output shaft ( 2 ) and receiving a plurality of pistons ( 6 ) expanding by reason of hydraulic pressure; a diagonal plate ( 7 ) that contacts the plurality of the expanding pistons ( 6 ), thereby to exert rotational force to the cylinder ( 4 ); a brake disc ( 21 ) disposed outside the cylinder ( 4 ) and rotating therewith; a motor casing ( 11 , 12 ) receiving the cylinder ( 4 ) and the brake disc ( 21 ); a brake driving device ( 25 ) that presses an outer periphery of the brake disc ( 21 ) on an inner peripheral surface of the motor casing ( 11 , 12 ) to brake the brake disc ( 21 ); a first chamber ( 14 ) and a second chamber ( 15 ) in the motor casing ( 11 , 12 ) defined by the brake disc ( 21 ); and a communicating passage ( 30 or 40 ) formed bypassing the brake disc ( 21 ) to communicate the first chamber ( 14 ) with the second chamber ( 15 ).