| 摘要 |
A hydraulic power assist steering system (10) for a vehicle having steerable wheels comprises a housing (14) and a rack (16). The system also comprises a fluid motor (20) for moving the rack (16). The fluid motor (20) includes a piston (10) fixedly connected to the rack (16) and a pump (36). The piston (10) has first and second opposite end faces (82, 84) against which hydraulic fluid is directed by the pump (36) to effect movement of the piston (10), and thereby the rack (16), relative to the housing (14). The piston (10) has a wall (60) including a first end portion (64) connected with the rack (16) at a first axial location along the rack, a second end portion (66) connected with the rack at a second axial location along the rack, and a central portion (62) extending between and interconnecting the first and second end portions of the wall. The central portion (62) of the wall (60) has an outer peripheral groove (70) for receiving a seal ring (86) for engagement with the housing (14). The first end portion (64) and the second end portion (66) and the central portion (62) of the piston (10) define a cavity (80) in the piston. The cavity (80) has an annular configuration extending around the rack (16) inside of the wall (60). |
