Brake control device for vehicle
A brake control device includes an electric pump, a pressure adjustment valve that adjusts a hydraulic pressure of a brake fluid discharged by the electric pump to an adjustment hydraulic pressure and supplies the brake fluid in a rear wheel cylinder, and a master unit provided with a servo chamber into which brake fluid at the adjustment hydraulic pressure is supplied and in which the adjustment hydraulic pressure is converted into a forward force of a master piston, and a master chamber fluidically separated from the servo chamber by the master piston and connected to the front wheel cylinder and in which a rearward force converted from the hydraulic pressure in the front wheel cylinder and is applied to the master piston. Also included is an input unit provided with an input chamber and a simulator, and a controller configured to control the electric pump and the pressure adjustment valve.
1. A brake control device for a vehicle that adjusts hydraulic pressures in a front wheel cylinder and a rear wheel cylinder in response to an operation of a brake operation member of the vehicle, the brake control device comprising:
a pressure adjustment unit provided with 1) an electric pump connected to a reservoir of the vehicle, and 2) a pressure adjustment valve configured to adjust a hydraulic pressure of a brake fluid discharged by the electric pump to an adjustment hydraulic pressure;
a switching valve operable between an open state in which the switching valve does not cut off the adjustment hydraulic pressure from fluid communication with the front wheel cylinder and a closed state in which the switching valve cuts off the adjustment hydraulic pressure from fluid communication with the front wheel cylinder;
a master unit provided with 1) a servo chamber in which the adjustment hydraulic pressure is converted into a forward force of a master piston, and 2) a master chamber that is fluidically separated from the servo chamber by the master piston and that is connected to the front wheel cylinder and in which a rearward force that is converted from the hydraulic pressure in the front wheel cylinder and is applied to the master piston, a direction of the rear force being opposite to a direction of the forward force;
a master cylinder valve operable between an open state in which the master cylinder valve does not cut off the master chamber from fluid communication with the front wheel cylinder and a closed state in which the master cylinder valve cuts off the master chamber from fluid communication with the front wheel cylinder;
an input unit provided with an input chamber whose volume changes corresponding to an operation of the brake operation member and a simulator that is configured to apply an operation force to the brake operation member in response to a flow of the brake fluid from the input chamber; and
a controller configured to control the electric pump and the pressure adjustment valve,
wherein, during normal braking including regenerative cooperation control, the master cylinder valve is set to the open state and the switching valve is set to the closed state, and
wherein the pressure adjustment unit, in a state in which the master cylinder valve is set to the open state and the switching valve is set to the closed state, supplies the adjustment hydraulic pressure to the servo chamber via a front wheel servo fluid passage and directly supplies the adjustment hydraulic pressure to the rear wheel cylinder via a rear wheel servo fluid passage.
2. The brake control device according to claim 1 , further comprising:
a switching unit configured to selectively achieve a first state in which the master chamber and the front wheel cylinder are in a communication state and the front wheel cylinder and the rear wheel servo fluid passage are in a non-communication state, and a second state in which the master chamber and the front wheel cylinder are in a non-communication state and the front wheel cylinder and the rear wheel servo fluid passage are in a communication state;
the switching unit includes the master cylinder valve and the switching valve; and
a fluid unit configured to reduce the hydraulic pressure in the front wheel cylinder by discharging the brake fluid in the front wheel cylinder to a suction portion of the electric pump, and reduce the hydraulic pressure in the rear wheel cylinder by discharging the brake fluid in the rear wheel cylinder to the suction portion of the electric pump, wherein
the controller is configured to
perform a slip control that is at least one of an anti-skid control for preventing locking of wheels of the vehicle and a vehicle stability control for stabilizing a yaw motion of the vehicle, and
the switching unit is configured to
achieve the first state when the slip control is not performed, and
achieve the second state when the slip control is performed.