Brake device

A brake device comprising:

• a mechanical pressure regulating part including:
• a high-pressure port, to which fluid pressure of high pressure is supplied;
• a low-pressure port, to which fluid pressure of lower pressure than the fluid pressure to be supplied to the high-pressure port is supplied;
• a plurality of pilot pressure input ports including a first pilot pressure input port to which pilot fluid pressure is supplied;
• an output port which outputs fluid pressure corresponding to the pressure supplied to the first pilot pressure input port by the fluid pressures supplied to both of the high-pressure port and the low-pressure port, to a driving fluid pressure chamber which drives a master piston;
• wherein the mechanical pressure regulating part outputs fluid pressure, corresponding to a highest fluid pressure among the fluid pressures supplied to the plurality of pilot pressure input ports, to the output port;
• a cylinder;
• a plurality of pistons which slide in the cylinder;
• and
• a plurality of pilot fluid pressure chambers which are formed by the cylinder and the plurality of pistons, respectively, and which communicate with the plurality of pilot pressure input ports, respectively, the plurality of pistons including first and second pistons, and the plurality of pilot fluid pressure chambers including first and second of pilot fluid pressure chambers;
• a high-pressure source which is connected to the high-pressure port and the first pilot pressure input port, and which accumulates fluid pressure of a brake fluid pumped by an electric pump;
• a low-pressure source which is connected to the low-pressure port and the first pilot pressure input port, and which supplies lower pressure than the high-pressure source;
• an electrically-operated pilot pressure generating part which includes a pressure boost control valve for controlling flow of the brake fluid between the high-pressure source and the first pilot pressure input port, and a pressure reduction control valve for controlling flow of the brake fluid between the low-pressure source and the first pilot pressure input port, and which outputs desired fluid pressure to the first pilot pressure input port by controlling the flow of the brake fluid with the pressure boost control valve and the pressure reduction control valve;
• wherein the pressure boost control valve is a control valve of a normally closed type, and the pressure reduction control valve is a control valve of a normally open type;
• a mechanical pilot pressure generating part which is connected to a second of the pilot pressure input ports, and which generates the pilot fluid pressure corresponding to an operating amount of a brake operating member;
• wherein the mechanical pilot pressure generating part is connected to the second pilot pressure input port which communicates with the first pilot fluid pressure chamber formed by the first piston driven by the output fluid pressure from the mechanical pilot pressure generating part,
• wherein the electrically-operated pilot pressure generating part is connected to the first pilot pressure input port which communicates with the second pilot fluid pressure chamber formed by the second piston driven by the output fluid pressure from the electrically-operated pilot pressure generating part, and
• wherein the first piston driven by the output fluid pressure from the mechanical pilot pressure generating part is also driven by movement of the second piston driven by the output fluid pressure from the electrically-operated pilot pressure generating part.