Control device of engine with variable valve timing mechanism

Abstract

An engine includes a variable valve timing (VVT) mechanism that changes an opening timing or a closing timing of at least one of an intake valve or an exhaust valve in accordance with an operating region of the engine, and an oil jet that injects oil in a piston direction under a pressure of a first predetermined oil pressure or more. The control device of the engine controls supply of an oil pressure to the VVT mechanism in such a manner that an upper limit of an oil pressure used by the VVT mechanism is set to be lower than a first predetermined oil pressure and an operating speed of the VVT mechanism is high in a direction in which an overlap amount between open periods between an intake valve and an exhaust valve increases and is low in a direction in which the overlap amount decreases.

1 . An engine control device of an engine including a variable valve timing mechanism that changes an opening timing or a closing timing of at least one of an intake valve or an exhaust valve by hydraulic driving in accordance with an operating region of the engine, and an oil jet that injects oil in a piston direction under a pressure of a first predetermined oil pressure or more, wherein
 an upper limit of an oil pressure used by the variable valve timing mechanism is set to be lower than the first predetermined oil pressure, and   supply of an oil pressure to the variable valve timing mechanism is controlled in such a manner that an operating speed of the variable valve timing mechanism is high in a direction in which an overlap amount between open periods of the intake valve and the exhaust valve increases, and is low in a direction in which the overlap amount decreases.   
     
     
         2 . The engine control device according to  claim 1 , wherein
 the engine includes a plurality of cylinders,   the engine selectively performs an all-cylinder operation in which all the plurality of cylinders operate and a reduced-cylinder operation in which one or more of the plurality of cylinders are suspended, and   the reduced-cylinder operation is performed by stopping valves of the one or more suspended cylinders under an action of a second predetermined oil pressure lower than the first predetermined oil pressure.   
     
     
         3 . The engine control device according to  claim 1 , wherein
 the variable valve timing mechanism by hydraulic driving is interposed at least in the exhaust valve, and   an amount of oil supply per a unit time in a phase change in a retarding direction in the exhaust valve is increased.   
     
     
         4 . The engine control device according to  claim 1 , wherein
 in a case where an oil temperature is lower than a predetermined oil temperature, an oil pressure is set at a relatively high pressure in a range lower than the first predetermined oil pressure, and   in a case where the oil temperature reaches the predetermined oil temperature, the oil pressure is set at a relatively low pressure in a range greater than or equal to an oil pressure necessary for maintaining an operation of the engine.   
     
     
         5 . The engine control device according to  claim 1 , wherein
 the variable valve timing mechanism by hydraulic driving is interposed at least in the exhaust valve, and   an oil consumption amount per a unit phase change amount in phase change is smaller in a retardation side than in an advance side in such a manner that an operating speed in phase change in a retarding direction in the exhaust valve is higher than an operating speed in phase change in an advancing direction in the exhaust valve.