Brake pressure control device for automotive vehicles

A brake pressure proportioning control device for a hydraulic brake system for an automotive vehicle, said brake system operated by hydraulic pressure adapted to proportionally reduce fluid pressure applied to a rear wheel brake included in said system, said device comprising:

• a housing defining an inlet chamber, at least one hydraulic fluid inlet and one hydraulic fluid outlet in said housing each communicating with said inlet chamber, said inlet adapted to be connected to a source of operating fluid pressure, said outlet adapted to be connected to said rear wheel brake;
• pressure reducing valve means in said housing disposed between said inlet chamber and said outlet causing a proportionally reduced fluid pressure to be established between said inlet chamber and said outlet, said pressure reducing valve means including a regulating piston having one end protruding into said inlet chamber and having a sealing seat formed on said one end and a through bore extending through said sealing seat from said one end to another end of said regulating piston, said regulating piston subjected to fluid pressure in said inlet chamber at said one end and to fluid pressure of said outlet at said another end and configured to be urged in a direction towards said one end by the net effect of said fluid pressure;
• said pressure reducing valve means including a valve closing member located opposite said sealing seat to be movable thereon to close said bore;
• regulating spring means urging said regulating piston in a direction away from said valve closing member;
• a control piston mounted in said inlet chamber;
• said valve closing member being supported by said control piston;
• said control piston mounted to be displaceable towards and away from said sealing seat, spring means urging said control piston towards said sealing seat, said control piston configured to be moved away from said sealing seat due to the effects of fluid pressure in said inlet chamber acting thereon, causing said valve closing member to be moved away from said sealing seat at said one end of said regulating piston with increasing fluid pressure in said inlet chamber to prevent operation of said pressure reducing valve means;
• vehicle deceleration responsive means operative to prevent said displacement of said control piston upon the vehicle deceleration reaching a predetermined rate to thereafter allow operation of said pressure reducing valve means;
• and flow restriction means defining a restrictive flow path disposed between said inlet and said inlet chamber substantially reducing the rate of build up of fluid pressure in said inlet chamber upon development of a predetermined rate of increase of fluid pressure said inlet, whereby a substantial reduction in the rate of build up of fluid pressure in said inlet chamber occurs upon a sudden development of elevated fluid pressure at said inlet.