Solenoid valve for compression-type engine retarder

Abstract

A solenoid valve for use with a solenoid as park of an engine retarder braking system includes a valve body arranged with a plurality of apertures and which receives an upper check valve pin, a lower check valve pin, and a biasing spring which acts on both check valve pins. The solenoid includes a coil and moveable armature and the braking system includes a high pressure circuit with a master piston and cylinder and a slave piston and cylinder. The two cylinders are connected by a flow passageway. The housing has a fluid inlet, a fluid outlet, and an access port. The fluid inlet receives low pressure oil which acts upon one side of the lower check valve pin. The opposite side of the lower check valve pin is acted upon by the fluid in the high pressure circuit and by the biasing spring. When the pressure difference allows the lower check valve pin to move out of its sealed position against the fluid inlet, oil is introduced into the high pressure circuit. When the upper check valve pin is sealed against the access port and the lower check valve pin is sealed against the fluid inlet, the high pressure circuit is sealed closed, allowing upward movement of the master piston to pressurize the oil in the circuit and create downward movement in the slave piston, which causes the corresponding exhaust valves to open.