Oil pump system of an engine for a vehicle

Abstract

Reduction of engine power loss and enhancement of fuel consumption may be achieved by an oil pump system of an engine for a vehicle including an oil sump reserving engine oil used for lubrication of the engine, a hydraulic pump pumping the engine oil, a main relief valve that is disposed on an output line of the hydraulic pump and controls an output pressure of the output line depending on the output pressure and a control pressure, and an auxiliary relief valve that redirects the output pressure to the main relief valve as a control pressure depending on operating condition of the engine.

1 . An oil pump system of an engine for a vehicle comprising:
 an oil sump reserving engine oil used for lubrication of the engine;   a hydraulic pump pumping the engine oil;   a main relief valve disposed in an output line of the hydraulic pump and controls an output pressure of the output line depending on the output pressure and a control pressure; and   an auxiliary relief valve that redirects the output pressure to the main relief valve as a control pressure depending on operating condition of the engine.   
     
     
         2 . The oil pump system of  claim 1 , wherein the hydraulic pump is a constant displacement pump. 
     
     
         3 . The oil pump system of  claim 1 , wherein the main relief valve comprises an elastic member exerting an elastic force in an opposite direction to which the output pressure and the control pressure is applied. 
     
     
         4 . The oil pump system of  claim 3 , wherein the main relief valve further comprises:
 a valve body comprising a first port receiving a pressurized oil from the output line, a second port exhausting the oil received through the first port, and a third port receiving a control oil from the auxiliary relief valve; and   a valve spool comprising a first land receiving the oil pressure of the pressurized oil received through the first port and a second land receiving the control oil received through the third port,   wherein the elastic member elastic member is arranged between the second land and the valve body so as to exert an elastic force to push the valve spool toward the first port.   
     
     
         5 . The oil pump system of  claim 1 , wherein the auxiliary relief valve is controlled by a solenoid valve controlled by an engine control unit. 
     
     
         6 . The oil pump system of  claim 5 , wherein the solenoid valve is a proportional control solenoid valve and is duty controlled depending on driving condition of the engine. 
     
     
         7 . The oil pump system of  claim 5 , wherein the engine control unit duty controls the solenoid valve based on signals from a sensor unit including an engine RPM sensor, an oil temperature sensor, and a coolant temperature sensor. 
     
     
         8 . The oil pump system of  claim 5 , wherein the auxiliary relief valve comprises:
 a valve body comprising a first port receiving the pressurized oil of the output line, a second port supplying the oil received through the first port to the third port of the main relief valve, and a third port selectively exhausting the oil received through the first port.   a valve spool comprising a first land selectively communicating the first port and the second port and a second land selectively communicating the third port to the first and second ports and in cooperation with the first land.