Valve timing control apparatus

Abstract

Disclosed is a valve timing control apparatus capable of avoiding inadvertent realization of a locked state by effectively preventing pulsating pressure of fluid generated in association with torque variation of a cam shaft from having any effect on a fluid passageway used for lock releasing. The apparatus includes a first fluid passageway for feeding/discharging fluid to/from an advanced angle chamber, a second fluid passageway for feeding/discharging fluid to/from a retarded angle chamber, a third fluid passageway for feeding/discharging fluid to/from a locking mechanism capable of locking relative rotation between an inner rotor and an outer rotor, a first switching valve for controlling the feeding/discharging of the fluid to/from the first fluid passageway and the second fluid passageway, a second switching valve for controlling the feeding/discharging of the fluid to/from the third fluid passageway, a pump for feeding fluid to the first switching valve and the second switching valve, and a check valve for inhibiting communication of the fluid from the first switching valve to the second switching valve and allowing communication of the fluid from the second switching valve to the first switching valve.

1 . A valve timing control apparatus comprising:
 an inner rotor rotatable in unison with a valve opening/closing rotational shaft of an internal combustion engine;   an outer rotor mounted to be rotatable relative to said inner rotor over a predetermined range and rotatable by a force transmitted thereto from a crank shaft of the internal combustion engine;   a fluid pressure chamber formed between said inner rotor and said outer rotor and divided by a partitioning portion into an advanced angle chamber and a retarded angle chamber;   a first fluid passageway for feeding/discharging fluid to/from said advanced angle chamber;   a second fluid passageway for feeding/discharging fluid to/from said retarded angle chamber;   a locking mechanism capable of locking relative rotation between said inner rotor and said outer rotor;   a third fluid passageway for feeding fluid to said locking mechanism to cause this locking mechanism to release its locking state and discharging fluid from said locking mechanism to cause this locking mechanism to provide the locking state;   a first switching valve for controlling the feeding/discharging of the fluid to/from said first fluid passageway and said second fluid passageway;   a second switching valve for controlling the feeding/discharging of the fluid to/from said third fluid passageway;   a pump for feeding fluid to said first switching valve and said second switching valve; and   a check valve for inhibiting communication of the fluid from said first switching valve to said second switching valve and allowing communication of the fluid from said second switching valve to said first switching valve.   
     
     
         2 . The valve timing control apparatus according to  claim 1 , wherein the fluid fed from said pump can be fed to said first switching valve with bypassing said second switching valve and can be fed to said second switching valve with bypassing said first switching valve. 
     
     
         3 . The valve timing control apparatus according to  claim 1 , wherein the fluid fed from said pump can be fed to said first switching valve through said check valve and can be fed to said second switching valve with bypassing said check valve. 
     
     
         4 . The valve timing control apparatus according to  claim 1 , wherein the apparatus further comprises:
 a first connecting passageway for connecting said pump to said first switching valve; and   a second connecting passageway for connecting a branching point of said first connecting passageway to said second switching valve;   wherein said check valve is disposed between said branching point and said first switching valve.   
     
     
         5 . The valve timing control apparatus according to  claim 4 , wherein an aperture area of said check valve when the fluid is being fed from said pump to said first switching valve is greater than a passageway aperture area of said first connecting passageway. 
     
     
         6 . The valve timing control apparatus according to  claim 4 , wherein the passageway aperture area of said first connecting passageway is greater than the passageway aperture area of said second connecting passageway.