Method and device for two-stage variable oil pump controlled through combined valve

The invention discloses a method and device for a two-stage variable oil pump controlled through a combined valve. The device is mainly composed of a variable vane pump, a filter, an engine, a safetyvalve, the combined valve and the like; the variable vane pump comprises a pump oil inlet chamber, a pump oil outlet chamber and a pump adjusting oil chamber; a solenoid valve is provided with three oil ports; the combined valve includes a low pressure valve element, a high pressure valve element, a spring, a low pressure control chamber, a high pressure control chamber, an inner chamber and a closed volume cavity oil discharging hole formed by a low pressure valve element oil discharge tank, a high pressure valve element oil discharge tank and high and low pressure valves; the three oil portsof the solenoid valve are respectively connected with an engine oil sump, a pump oil outlet way and the low pressure control chamber; through dual control of the solenoid valve and the combined valve, the two-stage variable d