Pressure control valve

摘要

A pilot poppet (44) is unseated when a pressure in a back pressure chamber (39) exceeds a spring (47) preload force to communicate the back pressure chamber (39) with a relief port (33). The pressure in a pressure port (32) is communicated to the back pressure chamber (39) through a radial clearance between a piston poppet (61) which extends through a relief poppet (31) and the relief poppet (31). A spring (62) maintains the piston poppet (61) engaged with the pilot poppet (44). Alternatively, the piston poppet and pilot poppet may be integral (66). The relief poppet (31) is unseated by a pressure difference between the back pressure chamber (39) and the pressure port (32) to communicate the pressure port (32) with the relief port (33) since communication of the back pressure chamber (39) with the relief port (33) causes the pressure in the back pressure chamber (39) to drop. The relief poppet (31 ) seats when the pressure in the pressure port (32) drops below the pressure in the back pressure chamber (39). The pressure receiving area (AR) of the piston poppet (61) is made as small as possible to reduce the net force on the pilot poppet (44) and thereby the pressure drop in the pressure port (32). The ratio of a pressure receiving area (AP) of the pilot poppet (44) to the pressure receiving area (AR) of the piston poppet (61) is at least 1.1.