Pressure control device for hydraulic braking system

A pressure control device for a hydraulic braking system for an automotive vehicle, said pressure control device comprising:

• a first hydraulic pressure source pressurizing hydraulic fluid according to a braking action of a driver;
• a wheel cylinder through which braking force is applied to a wheel of the automotive vehicle;
• means for defining a main passage which communicates said first hydraulic pressure source and said wheel cylinder;
• a second hydraulic pressure source connected to said main passage;
• a wheel rotating condition detector detecting a rotating condition of the wheel and outputting a signal indicative of the rotating condition of the wheel;
• a wheel-cylinder pressure control device controlling hydraulic pressure of said wheel cylinder when said wheel rotating condition detector detecting one of a lock condition and a slippage condition;
• a switching device stopping the communication between said first hydraulic pressure source and said wheel-cylinder pressure control device and opening the communication between said second hydraulic pressure source and said wheel-cylinder pressure control device when said wheel rotating condition detector detects the slippage condition in acceleration;
• and
• means defining a first return passage through which said hydraulic pressure controlling device is communicated with said main passage, said first return passage returning hydraulic fluid in said wheel-cylinder pressure control device to said main passage during the slippage control in acceleration.