An automotive brake control system with a skid control unit and a traction and vehicle dynamics control unit, comprising:
- an operating-pressure generating device (MC) for generating a brake fluid pressure (Pm) based on a magnitude of depression of a brake pedal;
- a wheel-brake cylinder (WC) being adapted to be attached to a road wheel for generating a braking force applied to the road wheel;
- a brake circuit (1;
- 2) connected between said operating pressure generating device (MC) and said wheel-brake cylinder (WC);
- a skid control hydraulic unit fluidly disposed in said brake circuit, and operated in response to a control signal, and including a fluid-pressure control valve unit (5, 6) being capable of operating at a selected one of three modes consisting of a pressure-reduction mode, a pressure-hold mode and a pressure build-up mode to reduce, hold, or build up a wheel-cylinder pressure of said wheel-brake cylinder (WC), a return pump (4) returning brake fluid in said wheel-brake cylinder (WC) via a return line (10a, 4f ) to a downstream line of said brake circuit, and a reservoir (7) connected to the return line for temporarily storing the brake fluid from said wheel-brake cylinder (WC);
- a pressure apply device including a pressure apply pump (8) operated in response to a control signal and a pressure apply piston unit (51) operated in response to a discharge pressure from said pressure apply pump (8);
- said pressure apply piston unit (51) comprising:
- a cylindrical housing (52);
- and
- a piston (53) axially slidably accommodated in said cylindrical housing (52) and dividing an internal space of said cylindrical housing (52) into a pressure apply chamber (51a) and a pressure introduction chamber (51b), said pressure apply chamber (51a) being connected via a pressure apply circuit (32) to said skid control hydraulic unit (4, 5, 6, 7), and said pressure introduction chamber (51b) being connected to a pressure-apply discharge circuit (8a) connected to an outlet of said pressure apply pump (8) so that brake fluid in said pressure apply chamber (51a) is directed to said skid control hydraulic unit with a sliding motion of said piston (53) when the discharge pressure is introduced from said pressure apply pump (8) into said pressure introduction chamber (51b);
- a control unit (CU) generating the control signals respectively transmitted to said skid control hydraulic unit and said pressure apply device so that during skid control said skid control hydraulic unit comes into operation and so that during traction and vehicle dynamics control a pressure apply action of said pressure apply device is executed with said skid control hydraulic unit being in an operative state;
- a single motor (M) having a driving connection with both said return pump (4) and said pressure apply pump (8);
- a circulation circuit (37) intercommunicating said pressure-apply discharge circuit (8a) and a pressure-apply suction circuit (8b) connected to an inlet of said pressure apply pump (8):
- and
- a circulation mode-select valve (45) disposed in said circulation circuit (37) for establishing fluid communication of said circulation circuit (37) in a de-energized position and for shutting off the fluid communication of said circulation circuit (37) in an energized position,
- wherein said control unit (CU) operates to close said circulation mode-select valve (45) only during the traction and vehicle dynamics control.