US Patent 10458506 Solenoid valve

A solenoid valve includes a valve seat provided in a main flow passage, a main valve body configured to open or close the main flow passage, a pilot passage that branches from the main flow passage, an orifice provided in the pilot passage, a back-pressure chamber connected to the pilot passage downstream from the orifice to bias the main valve body to a closing direction by virtue of an internal pressure, a pilot valve disposed in the pilot passage downstream from a connection point to the back-pressure chamber to control an internal pressure of the back-pressure chamber, a solenoid configured to control a valve opening pressure of the pilot valve, and a second orifice provided between the back-pressure chamber and the pilot valve.