Control device for internal combustion engine

1. A control device for an internal combustion engine,

the internal combustion engine including a variable valve operating device that makes variable an opening period of an intake valve that opens and closes an intake port,

wherein, where an opening period that is included in an actual opening period identified by an opening timing and a closing timing of the intake valve and which is located in a crank angle period from an intake top dead center to the closing timing is referred to as an effective opening period, the control device is configured, in an engine operating condition in which knocking is easy to occur, to increase the effective opening period when an intake gas temperature in the intake port is higher than a wall temperature of the intake port as compared to when the intake gas temperature is lower than the wail temperature.

2. The control device according to claim 1 ,

wherein, in changing the effective opening period in the engine operating condition in which knocking is easy to occur, the control device is configured to change the closing timing without changing the opening timing.

3. The control device according to claim 1 ,

wherein the internal combustion engine includes a water temperature sensor configured to detect an engine cooling water temperature of an engine cooling water that cools an engine main body, and

wherein the control device is configured to estimate the wall temperature based on the engine cooling water temperature detected by the water temperature sensor.

4. The control device according to claim 3 ,

wherein the control device is configured, in a course of an engine warm-up in which the engine cooling water temperature is lower than a certain value, to estimate the wall temperature based on the engine cooling water temperature in consideration of a response delay of the wall temperature with respect to an increase of the engine cooling water temperature.