Patent ID: 8128380

Claim:
An axial piston fluid pump or motor of the swashplate or bent axis type having a fixed housing which includes two fluid flow passages which open through a support surface of the housing, a cylinder drum rotatable in both directions relative to the fixed housing and including pistons reciprocating in chambers in the drum, and a control plate clamped between the rotatable drum and the support surface of the housing, the control plate being fixed relative to housing and having two control passages, each control passage being in register with a respective fluid flow passage in the housing and comprising a plurality of individual circumferentially spaced control passage sections through which fluid flows between the fluid flow passages and the cylinder chambers, the control passage sections of each control passage being separated from each other by bridges, and at least one of the bridges between the passage sections of each control passage being provided with a pressure balance opening through the bridge connecting one side of the control plate with the other side of the control plate for the flow of fluid between the fluid flow passages and the cylinder chambers.