Brake pressure control device

A brake pressure control device comprising:

• a brake valve;
• an air master cylinder for braking a wheel by an air pressure that is provided from said brake valve;
• and
• an air control valve, coupled between said brake valve and said air master cylinder, for selectively providing the air pressure from the brake valve into communication with said air master cylinder and selectively reducing a pressure level of the air pressure from the brake valve, said air control valve comprising:
• an input port coupled to said brake valve for receiving the air pressure that is provided from said brake valve;
• an exhaust port coupled to open air and to a back pressure chamber of the air master cylinder;
• an output port coupled to the air master cylinder;
• a pipe passageway coupled between the input port, exhaust port and output port,
• at least one diaphragm provided within said pipe passageway;
• and
• a release valve which is connected between the exhaust port and the output port for releasing air pressure from the output port to the exhaust port during a brake releasing operation,
• wherein said air control valve includes only one diaphragm within the pipe passageway.