system of valves to control the pressure of entering a liquid in a pump at high pressure, and relative sovrapre valve

摘要

The capacity of a high-pressure pump (6) is regulated by a valve system including a variable-capacity on-off valve (23) and an overpressure valve (31). The overpressure valve has a valve body (33) having a cylindrical wall (35) forming a cavity (34) in which slides a shutter (37) having a lateral wall (51) and an end wall (52). The shutter (37) is pushed into a closed position by a calibrated spring (58). The cylindrical wall (35) has first holes (44) for allowing the passage of enough fuel to lubricate the inside of the pump (6), and second holes (47) for supplying the pump (6) via a supply conduit (68) and for draining any surplus fuel into a recirculating conduit (32). The first holes (44) and the second holes (47) are opened by different displacements of the lateral wall (51) of the shutter (37); and the end wall (52) has a calibrated air vent hole (64).