PURPOSE: To obtain an ideal distribution line for braking forces in a G-valve type pressure control valve by adapting a valve seat to be movable forward and backward in the moving direction of a gravity valve body and providing a regulating member to regulate the advancing amount of the gravity valve body.
CONSTITUTION: When a brake pedal is stepped on, a master cylinder is operated to introduce pressure oil into an input port 4 of a pressure control valve V, and the pressure oil is supplied to a rear wheel brake thrugh a valve chamber A, a valve hole 15a, a cylinder hole 11, and an output port 5. When a fixed reduced speed is given by the start of braking, a gravity valve body 17 ascends a slope 18, and is seated at a valve seat 15 to close a valve hole 15a. Subsequently, when a pressure- receiving piston 14 is shifted forward against a spring 19 by the increase of the stepping force on the pedal, the valve body 17 is checked its advance by a regulation pin 21, and separated from the valve seat 15. As the result, the pressure oil in the valve chamber A is conducted through the valve hole 15a, the cylinder hole 11, and the output port 5, and supplied to the rear wheel brake.