Vehicle brake hydraulic pressure control apparatus

A vehicle brake hydraulic pressure control apparatus which controls to transmit hydraulic pressure generated in a hydraulic pressure source to wheel brakes, comprising:

• normally open linear solenoid valves which allows transmission of the hydraulic pressure from the hydraulic pressure source to the wheel brakes and whose valve opening amounts is adjusted by energization amounts thereof;
• normally closed solenoid valves which allow hydraulic pressures within the wheel brakes to escape therefrom;
• and
• a control unit which controls the energization amounts of the normally open linear solenoid valves and the normally closed solenoid valves so as to switch the hydraulic pressures within the wheel brakes to a pressure increasing state, a pressure holding state or a pressure reducing state, wherein
• the control unit comprises:
• an initial current value calculation unit which calculates an initial current value to open the normally open linear solenoid valves when the hydraulic pressure is shifted from the pressure reducing state or the pressure holding state to the pressure increasing state;
• a target current value setting unit which determines whether or not a pressure increasing cycle was performed last time and,
• if it is determined that the pressure increasing cycle was performed, the target current value setting unit setting a target current value based on a current value resulting when a pressure increasing had been completed before the last pressure increasing cycle,
• whereas, if it is determined that the pressure increasing cycle was not performed, the target current value setting unit:
• estimates a road surface friction coefficient,
• determines a control hydraulic pressure range based on the road surface friction coefficient,
• determines a target differential when a pressure increasing state ends by subtracting the control hydraulic pressure range from a differential pressure between an upstream pressure and a downstream pressure of the normally open linear solenoid valves resulting when the pressure increasing started, and
• sets a current corresponding to the target differential pressure as the target current value;
• and
• a valve opening amount adjusting unit which reduces the energization amount from the initial current value towards the target current value with a predetermined gradient.