To provide a gear pump or a motor capable of preventing deterioration of delivery flow performance in operation conditions wherein temperature and pressure of hydraulic fluid are high.
A gasket 5 partitioning a high pressure side and a low pressure side of a pressure balance region is attached on a movable side plate 4, and a recession 51a communicating with the high pressure side of the pressure balance region is provided on a jointing surface of the gasket 5 jointed to the movable side plate 4. An amount of the hydraulic fluid flowing into the recession 51a is not reduced even under the high temperature and high pressure condition, and thereby lowering of hydraulic pressure F pushing the movable side plate 4 becomes relatively small. As a result, the pressure balance with respect to the movable side plate 4 is maintained, and deterioration of the delivery flow performance can be restrained.
SUGANO TADASHI
OKADA KENICHI
Keiko Inoue
Sadaya Sano