Patent ID: 9683584
Date: 2017-06-20
CPC Classifications: B60T,F15B

Claim:
1. A brake device for a vehicle, comprising: a master cylinder; a master piston slidably and liquid-tightly disposed in the master cylinder and forming a master chamber with the master cylinder for supplying a plurality of wheel cylinders with a master pressure; a servo chamber formed between the master piston and an intermittent wall of the master cylinder; a servo pressure generating means for generating a servo pressure to be supplied to the servo chamber and biasing the master piston in forward direction for generating the master pressure in the master chamber; a brake operation means operated by an operator of the vehicle; a target master pressure setting means for setting a target master pressure based on an operation amount of the brake operation means; a pressure increasing characteristic memorized based on a relationship between the servo pressure and the master pressure when the master pressure is increasing; a pressure decreasing characteristic memorized based on the relationship between the servo pressure and the master pressure when the master pressure is decreasing; and, a target servo pressure setting means for setting a target servo pressure in response to the target master pressure by selecting the pressure increasing characteristic or the pressure decreasing characteristic depending on a state of the master pressure either in a pressure increasing state or in a pressure decreasing state, wherein the master piston includes a second master piston forming a second master chamber in the master cylinder defined by a front bottom portion of the master cylinder and the second master piston to supply a second wheel cylinder among the plurality of wheel cylinders with a second master pressure and a first master piston forming a first master chamber in the master cylinder defined by the second master piston and the first master piston to supply a first wheel cylinder among the plurality of wheel cylinders with a first master pressure, wherein the servo chamber is formed between a rear surface of the first master piston and the intermittent wall of the master cylinder, wherein the pressure increasing characteristic is set based on a first pressure increasing characteristic obtained based on a relationship between the servo pressure and the first master pressure and a second pressure increasing characteristic obtained based on a relationship between the servo pressure and the second master pressure when the servo pressure is increasing, and wherein the pressure decreasing characteristic is set based on a first pressure decreasing characteristic obtained based on the relationship between the servo pressure and the first master pressure and a second pressure decreasing characteristic obtained based on the relationship between the servo pressure and the second master pressure when the servo pressure is decreasing.