Apparatus for and method of controlling engine

1. A controlling apparatus for an engine provided with: a variable operation angle mechanism that is provided for varying a valve operation angle of an engine valve driven by a camshaft, and is capable of varying a center phase of the valve operation angle in response to a variation in the valve operation angle; and a variable valve timing mechanism provided for varying a rotating phase of the camshaft relative to a crankshaft of the engine, the controlling apparatus comprising:

a detecting unit that detects an operating state of the engine;

a first calculating unit that calculates a target valve operation angle based on the operating state;

a second calculating unit that calculates a target rotating phase based on the operating state;

a correcting unit that corrects the target rotating phase based on the target valve operation angle;

a first operating unit configured to calculate a first manipulated variable of the variable operation angle mechanism, based on the target valve operation angle, to thereby output the first manipulated variable; and

a second operating unit configured to calculate a second manipulated variable of the variable valve timing mechanism, based on the target rotating phase corrected by the correcting unit, to thereby output the second manipulated variable,

wherein the second calculating unit calculates, if the valve operation angle takes a reference value thereof, a target rotating phase which brings the center phase of the valve operation angle of the engine valve to approach a target center phase which is set depending on the operating state of the engine.

2. The controlling apparatus according to claim 1 ,

wherein the engine valve comprises an intake valve, and

wherein the variable operation angle mechanism varies a center phase of a valve operation angle of the intake valve in an advance direction in response to a decrease in the valve operation angle.

3. The controlling apparatus according to claim 2 ,

wherein the variable operation angle mechanism is configured to operate under such a condition that a ratio of a change amount of an opening timing of the intake valve to a change amount of the valve operation angle is set to be equal to or more than 20% and equal to or less than 40%.

4. The controlling apparatus according to claim 2 ,

wherein the variable operation angle mechanism is configured to operate under such a condition that a ratio of a change amount of an opening timing of the intake valve to a change amount of the valve operation angle is set to be 30%.

5. The controlling apparatus according to claim 1 ,

wherein the correcting unit comprises

a correction value calculating unit that calculates a correction value based on the target valve operation angle, and

an add-subtract unit that performs addition of and subtraction between the target rotating phase and the correction value.

6. The controlling apparatus according to claim 5 ,

wherein the correcting value calculating unit calculates the correction value having a greater absolute value as the target valve operation angle separates apart from the reference value.

7. The controlling apparatus according to claim 5 ,

wherein the correction value calculating unit calculates a difference between a center phase of the valve operation angle for when the valve operation angle takes the reference value thereof and the rotating phase takes a reference value thereof, and a center phase of the valve operation angle for when the rotating phase takes the reference value thereof and the valve operation angle takes a target value thereof, and then calculates the correction value based on the difference.

8. The controlling apparatus according to claim 1 , further comprising:

a load detecting unit that detects a variation in an engine load; and

a gain setting unit that sets a larger gain in the first and second operating units, as the variation in the engine load turns abrupt.

9. The controlling apparatus according to claim 1 , further comprising:

a diagnosing unit that diagnoses whether or not a failure of the variable operation angle mechanism occurs; and

a failsafe unit that controls the variable valve timing mechanism so that the center phase of the valve operation angle of the engine valve is varied in a direction separating apart from a top dead center of a piston, when it is determined that the failure of the variable operation angle mechanism occurs.

10. The controlling apparatus according to claim 9 ,

wherein the failsafe unit controls the variable valve timing mechanism at a larger gain than that of when the variable operation angle mechanism is normal.

11. The controlling apparatus according to claim 9 ,

wherein the engine valve comprises an intake valve, and

wherein the failsafe unit is configured to set a target rotating phase in the variable valve timing mechanism to be a most retarded position, when the failure of the variable operation angle mechanism occurs.

12. A controlling method of an engine provided with: a variable operation angle mechanism that is provided for varying a valve operation angle of an engine valve driven by a camshaft, and is capable of varying a center phase of the valve operation angle in response to a variation in the valve operation angle; and a variable valve timing mechanism provided for varying a rotating phase of the camshaft relative to a crankshaft of the engine, the controlling method comprising the steps of:

detecting an operating state of the engine;

calculating a target valve operating angle based on the operating state;

calculating a target rotating phase based on the operating state;

correcting the target rotating phase based on the target valve operation angle:

calculating a first manipulated variable of the variable operation angle mechanism based on the target valve operation angle;

outputting the first manipulated variable;

calculating a second manipulated variable of the variable valve timing mechanism based on the corrected target rotating phase; and

outputting the second manipulated variable,

wherein the step of calculating the target rotating phase is executed, if the valve operation angle takes a reference value thereof, to obtain a target rotating phase which brings the center phase of the valve operation angle of the engine valve to approach a target center phase which is set depending on the operating state of the engine.

13. The controlling method according to claim 12 ,

wherein the step of correcting the target rotating phase comprises the steps of:

calculating a correction value based on the target valve operation angle; and

performing addition of and subtraction between the target rotating phase and the correction value.

14. The controlling method according to claim 13 ,

wherein the step of calculating the correction value is executed to obtain the correction value having a greater absolute value as the target valve operation angle separates apart from the reference value.

15. The controlling method according to claim 13 ,

wherein the step of calculating the correction value comprises the steps of:

calculating a difference between a center phase of the valve operation angle for when the valve operation angle takes the reference value thereof and the rotating phase takes a reference value thereof, and a center phase of the valve operation angle for when the rotating phase takes the reference value thereof and the valve operation angle takes a target value thereof; and

calculating the correction value based on the difference.

16. The controlling method according to claim 12 , further comprising the steps of:

detecting a variation in an engine load; and

setting a larger gain for calculating the first and second manipulated variables as the variation in the engine load turns abrupt.

17. The controlling method according to claim 12 , further comprising the steps of:

diagnosing whether or not a failure of the variable operation angle mechanism occurs; and

controlling the variable valve timing mechanism so that the center phase of the valve operation angle of the engine valve is varied in a direction separating apart from a top dead center of a piston, when it is determined that the failure of the variable operation angle mechanism occurs.

18. A controlling apparatus for an engine provided with: a variable operation angle mechanism that is provided for varying a valve operation angle of an engine valve driven by a camshaft, and is capable of varying a center phase of the valve operation angle in response to a variation in the valve operation angle; and a variable valve timing mechanism provided for varying a rotating phase of the camshaft relative to a crankshaft of the engine,

the apparatus comprising:

detecting means for detecting an operating state of the engine;

first calculating means for calculating a target valve operation angle based on the operating state;

second calculating means for calculating a target rotating phase based on the operating state;

correcting means for correcting the target rotating phase based on the target valve operation angle;

first operating means for calculating a first manipulated variable of the variable operation angle mechanism, based on the target valve operation angle, thereby outputting the first manipulated variable; and

second operating means for calculating a second manipulated variable of the variable valve timing mechanism, based on the target rotating phase corrected by the correcting means, thereby outputting the second manipulated variable,

wherein the second calculating means calculates, if the valve operation angle takes a reference value thereof, a target rotating phase which brings the center phase of the valve operation angle of the engine valve to approach a target center phase which is set depending on the operating state of the engine.