Patent ID: 8281757

Claim:
A variable valve train control device comprising: a variable valve train which uses a hydraulic actuator to vary a valve opening characteristic of an intake valve or an exhaust valve of an internal combustion engine; oil temperature acquisition means for detecting or estimating an oil temperature; a hydraulic control valve for controlling oil pressure acting on the hydraulic actuator in accordance with a duty value of a control signal; first feedback control means for exercising duty value feedback control to calculate a duty value in accordance with a deviation between an actual valve opening characteristic and a target valve opening characteristic; second control means which, when predefined second control execution conditions are established, exercises second control instead of the duty value feedback control to vary the duty value in a pulsed manner between a retention duty value, which retains an operation of the hydraulic actuator, and a forced drive duty value, which forcibly drives the hydraulic actuator; initial pulse extension means which, when the oil temperature is lower than a predetermined temperature, ensures that the initial pulse width generated after the start of the second control is wider than normal; initial response lag acquisition means for acquiring a response lag between the instant at which the initial pulse of the second control rises and the instant at which the hydraulic actuator starts operating; and initial pulse width correction means which, when the response lag is shorter than a predetermined period of time, shortens the initial pulse that is set by the initial pulse extension means.