Brake control apparatus and brake system

A brake system comprising:

• a stroke simulator;
• and
• a hydraulic pressure unit,
• the stroke simulator including
• a first chamber connected to a master cylinder, and
• a second chamber separated from the first chamber by a piston,
• the hydraulic pressure unit including
• a connection fluid passage that connects the master cylinder and a braking force application portion to each other, the braking force application portion being configured to apply a braking force to a wheel portion (FL to RR) according to a brake hydraulic pressure,
• a shut-off valve provided in the connection fluid passage,
• a hydraulic pressure source configured to supply brake fluid to a fluid passage of the connection fluid passage that is located between the shut-off valve and the braking force application portion,
• a pressure sensor configured to detect a hydraulic pressure in the master cylinder, and
• a control unit, the control unit including:
• a stroke-wheel cylinder hydraulic pressure characteristic setting portion configured to set a stroke-target wheel cylinder hydraulic pressure characteristic with respect to the pedal stroke;
• a stroke-target wheel cylinder hydraulic pressure calculation portion configured to calculate a first pressure value Pstr by referring to the stroke-target wheel cylinder hydraulic pressure characteristic with respect to the pedal stroke set by the stroke-wheel cylinder hydraulic pressure characteristic setting portion based on the pedal stroke detected by the stroke sensor;
• a master cylinder hydraulic pressure-wheel cylinder hydraulic pressure characteristic setting portion configured to set a master cylinder hydraulic pressure-target wheel cylinder hydraulic pressure characteristic with respect to the master cylinder hydraulic pressure;
• and
• a master cylinder hydraulic pressure-target wheel cylinder hydraulic pressure calculation portion configured to calculate a second pressure value Ppmc by referring to the master cylinder hydraulic pressure-target wheel cylinder hydraulic pressure characteristic with respect to the master cylinder hydraulic pressure set by the master cylinder hydraulic pressure-wheel cylinder hydraulic pressure characteristic setting portion based on the master cylinder hydraulic pressure detected by the master cylinder hydraulic pressure sensor,
• the control unit being configured to:
• acquire a piston stroke position of the piston,
• determine brake hydraulic pressure to generate in the braking force application portion based on the first pressure value in a case where the acquired piston stroke position is smaller than a preset predetermined position, and
• determine brake hydraulic pressure to generate in the braking force application portion based on the first pressure value and the second pressure value in a case where the acquired piston stroke position is equal to or greater than the preset predetermined position.