The pressure control valve has a valve element (19) in a cylindrical bore and held against a valve seat (13) by a variable spring (17). The valve element has a recess (32) on one side linked to the front end of the element by internal ducts to form a hydraulic pressure area when the valve is under pressure. This provides a damping force proportional to the applied pressure. The front end of the valve element is conical and is pressed into the valve seat. A flange surrounds the top of the cone. The pressure ducts link the flange to the hydraulic pressure area. Grooves around the valve element provide some hydraulic damping around the valve element.
