Motor vehicle anti-lock hydraulic brake system reciprocating piston pump

摘要

The piston (40) is of composite construction and has an e.g. metal or ceramic core (42), located in an injection-moulded plastic sleeve (44) with a peripheral lip (82) which bears against the cylinder wall and provides a seal. The pump (12) has a piston which reciprocates in a bushing (10) and is driven by an eccentric (50), which runs against the exposed end (46) of the core. The core is made by a process which generates no swarf, e.g. extrusion or cold forming. The sleeve has an integral non-return valve (62), and can have an internal shoulder to retain the core. A tapered bung (84) can be inserted between the piston return spring (48) and the tapered inner wall (86) of the lip to press the lip against the bushing. Several alternative arrangements are described.