Load-responsive braking pressure control device especially for vehicle brake systems

摘要

A load-responsive brake pressure control device for vehicle brake systems includes a control valve actuatable by a stepped piston. The stepped piston has one surface of a larger axially effective area which is acted upon in the valve closing direction by the pressure prevailing downstream of the valve, and another surface of a smaller axially effective area which is acted upon in the valve closing direction by the pressure prevailing upstream of the valve. A load-responsive spring acts in the opening direction of the valve on a movable component of a cylinder-and-piston unit, especially on a flange of a cylinder component of such a unit, to urge the same into its initial position in which it abuts a stop surface of a support. The cylinder and piston components of the unit together define a chamber which communicates with a flow path having a stationary portion accommodating a sealing element bounding a passage of a reduced cross section. The stepped piston carries a plunger which penetrates into the passage after a predetermined amount of movement of the stepped piston in the closing direction, so as to entrap the fluid present in the chamber of the unit. Thereafter, further movement of the stepped piston in the closing direction is hindered by the pressure of the entrapped fluid, until this pressure rises to a level at which the movable component of the unit yields in opposition to the spring force. Then, the valve will close and the pressure downstream thereof will be maintained at a level determined by the ratio of the axially effective areas of the aforementioned surfaces of the stepped piston.