Vehicle brake hydraulic pressure control system

A vehicle brake hydraulic pressure control system, comprising:

• a hydraulic pressure supply source (M, 18) which outputs hydraulic pressure;
• a hydraulic pressure control unit (5) which is interposed between the hydraulic pressure supply source (M, 18) and wheel brakes (BA, BB) and which adjusts hydraulic pressures at the wheel brakes (BA, BB);
• a brake hydraulic pressure detecting unit which detects hydraulic pressures at the wheel brakes (BA, BB);
• and
• a controller (C) which comprises a target wheel brake pressure setting unit (30) which sets target hydraulic pressures for the wheel brakes (BA, BB) and which controls an operation of the hydraulic pressure control unit (5) so that the hydraulic pressures at the wheel brakes (BA, BB) become target hydraulic pressures set by the target wheel brake pressure setting unit (30),
• wherein the controller (C) comprises:
• a target fluid amount calculation unit (31) which obtains target fluid amounts for the wheel brakes (BA, BB) based on the target hydraulic pressures set by the target wheel brake pressure setting unit (30);
• an actual fluid amount calculation unit (32) which obtains actual fluid amounts for the wheel brakes (BA, BB) based on the hydraulic pressures detected by the brake hydraulic pressure detecting unit (23, 24),
• a target flow rate calculation unit (34) which obtains target flow rates for the wheel brakes (BA, BB) based on the target fluid amounts obtained by the target fluid amounts calculation unit (31) and the actual fluid amounts obtained by the actual fluid amount calculation unit (32), wherein the controller controls the operation of the hydraulic pressure control unit (5) based on the target flow rates obtained by the target flow rate calculation unit (34),
• a pressure build-up timer (57) which implements counting up normally except when a count value is cleared to “0” where the hydraulic pressure control unit (5) is controlled to shift from a pressure build-up mode in which the hydraulic pressure of the hydraulic pressure supply source (M, 18) is applied to the wheel brakes (BA, BB) to a pressure reducing mode in which the hydraulic pressures are released at the wheel brakes (BA, BB) or a pressure holding mode in which the hydraulic pressures at the wheel brakes (BA, BB) are held;
• and
• a pressure reducing timer (58) which implements counting up normally except when a count value is cleared to “0” when the hydraulic pressure control unit (5) is controlled to shift from the pressure reducing mode to the pressure build-up mode or the pressure holding mode, and
• the controller (C) increases a controlled variable of the hydraulic pressure control unit (5) as a high select value of the count values of the pressure build-up timer (57) and the pressure reducing timer (58) increases.