Pressure control apparatus including seating valve controlled by electric current incremented upon valve opening depending upon pressure difference across the valve

A hydraulically operated braking system for a motor vehicle, comprising:

• a hydraulic pressure source;
• at least one wheel brake cylinder each for braking a corresponding one of at least one wheel of the motor vehicle;
• a seating valve including a valve member and a valve seat and disposed in a fluid passage which is provided for connecting said hydraulic pressure source and said at least one wheel brake cylinder, said seating valve being placed in a closed state thereof with said valve member being seated on said valve seat so as to disconnect said fluid passage, said valve member receiving a pressure difference of a working fluid across said seating valve such that said pressure difference acts on said valve member in a first direction for moving the valve member away from said valve seat so as to place said seating valve in an open state thereof;
• an elastic member which biases said valve member in a second direction for moving said valve member to be seated on said valve seat;
• a valve driving device operated with an electric current applied thereto, to generate a drive force acting on said valve member in said first direction;
• and
• a control device which controls an amount of said electric current to be applied to said valve driving device, to thereby control said valve driving device,
• and wherein said control device comprises a stepping control device which increments the amount of said electric current when said seating valve is operated from said closed state into said open state, said stepping control device determining an increment of the amount of said electric current such that said increment decreases with an increase in said pressure difference,
• said control device further comprising a replacing device which is operable when the pressure in said at least one wheel brake cylinder is increased from an atmospheric pressure, said replacing device replacing said increment with a value larger than said increment as determined by said stepping control device.