Abstract: A hydraulic unit for a vehicle brake system that enables limiting wheel brake slip is known. To that end, the hydraulic unit has at least one piston pump, which is drivable by an electric motor and empties a reservoir that is filled on the occasion of the limitation of wheel brake slip. This reservoir comprises a cylinder, embodied in the manner of a blind bore, as well as a piston that divides a storage chamber from a spring chamber in the cylinder, a spring, and a closure element that prevents water from entering the cylinder if the hydraulic unit should become immersed in water. A pressure equalization conduit begins at the spring chamber and leads into the interior of the motor, so that a displacement of the piston for taking up pressure fluid in the storage chamber is effected essentially only by friction of the piston and forces of the spring. A conduit is also provided, by means of which pressure fluid that emerges from the piston pump at the eccentric can be carried away.

Abstract: The invention relates to a piston, through which a fluid can flow, for a piston pump, which piston has a longitudinal bore into which a spring-loaded inlet valve body is inserted. In order to be able to bring a helical compression spring, which loads the inlet valve body, to bear against an annular shoulder in the longitudinal bore and to be able to check and if necessary improve its seating after installation, the invention proposes to produce the inlet valve body in two parts comprising the inlet valve disk and the inlet valve stem and to join these two parts to one another after the helical compression spring has been correctly inserted into the piston. The inlet valve disk can for example be joined to the inlet valve stem by ultrasonic welding, thermoplastic riveting or screwing.