VARIABLE VALVE TIMING APPARATUS WITH REDUCED POWER CONSUMPTION AND CONTROL METHOD THEREOF

Abstract

A convergence determination of intake valve phase control is made by comparing a phase deviation of an intake valve from a target phase with a convergence determination value. At the time of convergence, it is determined that the intake valve phase has reached the target phase, so that the required phase-change amount of a camshaft is set to zero and therefore the actuator operation amount is also set to zero. At the time of engine stop when the target phase has a fixed value, after convergence of the intake valve phase control, the operation of the actuator is stopped. In addition, during the course of engine stop, the convergence determination value is set to be switched from the time of engine operation so that the convergence determination of the intake valve phase control is made in more relaxed conditions compared with at the time of engine operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic showing a configuration of an engine of a vehicle on which a variable valve timing apparatus is mounted according to an embodiment of the present invention.

FIG. 2 shows a map defining the phase of an intake camshaft.

FIG. 3 is a cross section showing an intake VVT mechanism.

FIG. 4 is a cross section along A-A in FIG. 3.

FIG. 5 is a (first) cross section along B-B in FIG. 3.

FIG. 6 is a (second) cross section along B-B in FIG. 3.

FIG. 7 is a cross section along C-C in FIG. 3.

FIG. 8 is a cross section along D-D in FIG. 3.

FIG. 9 shows the reduction gear ratio of the intake VVT mechanism as a whole.

FIG. 10 shows a relation between the phase of a guide plate relative to a sprocket and the phase of the intake camshaft.

FIG. 11 is a schematic block diagram illustrating a control structure for an intake valve phase using the variable valve timing apparatus in accordance with the present embodiment.

FIG. 12 is a block diagram illustrating rotational speed control for an electric motor as an actuator of the variable valve timing apparatus in accordance with the present embodiment.

FIG. 13 schematically shows speed control for the electric motor.

FIG. 14 is a flowchart illustrating a target value convergence determination in the intake valve phase control in the variable valve timing apparatus in accordance with the embodiment of the present invention.

Claims

1. A variable valve timing apparatus changing an opening/closing timing of at least any one of an intake valve and an exhaust valve provided to an engine, comprising: an actuator,a change mechanism changing said opening/closing timing by changing difference in rotational phase of a camshaft driving the valve having said opening/closing timing changed, from a rotational phase of a crankshaft, at an amount of change according to an operation amount of said actuator; andan actuator operation amount setting portion setting the operation amount of said actuator, based on a deviation between said opening/closing timing at present of the valve having said opening/closing timing changed and a target value thereof,said actuator operation amount setting portion includingconvergence determination means for setting the operation amount of said actuator to approximately zero, when an absolute value of said deviation is equal to or smaller than a determination value, anddetermination value switching means for setting, in changing said opening/closing timing during a course of engine stop, said determination value in said convergence determination means at a value larger than said determination value in changing said opening/closing timing at a time of engine operation.

2. The variable valve timing apparatus according to claim 1, further comprising power supply stopping means for stopping power supply to said actuator when the absolute value of said deviation becomes equal to or smaller than the determination value, in changing said opening/closing timing during the course of engine stop.

3. The variable valve timing apparatus according to claim 1, wherein said actuator is formed of an electric motor and the operation amount of said actuator is a rotational speed difference of said electric motor relative to said camshaft, andsaid change mechanism changes said opening/closing timing such that a ratio between the operation amount of said actuator and the amount of change of said opening/closing timing differs and a change direction of said opening/closing timing is identical, between a case where said opening/closing timing is in a first region and a case where said opening/closing timing is in a second region.

4. The variable valve timing apparatus according to claim 1, wherein in changing said opening/closing timing during a course of stopping said engine, the target value of said opening/closing timing is set at a prescribed value suitable for a next engine start.

5. A variable valve timing apparatus changing an opening/closing timing of at least any one of an intake valve and an exhaust valve provided to an engine, comprising: an actuator;a change mechanism changing said opening/closing timing by changing difference in rotational phase of a camshaft driving the valve having said opening/closing timing changed, from a rotational phase of a crankshaft, at an amount of change according to an operation amount of said actuator; anda control unit setting the operation amount of said actuator, based on a deviation between said opening/closing timing at present of the valve having said opening/closing timing changed and a target value thereof, whereinsaid control unit sets the operation amount of said actuator to approximately zero, when an absolute value of said deviation is equal to or smaller than a determination value, and in addition, in changing said opening/closing timing during a course of engine stop, sets said determination value at a value larger than said determination value in changing said opening/closing timing at a time of engine operation.

6. The variable valve timing apparatus according to claim 5, wherein said control unit gives an instruction to stop power supply to said actuator when an absolute value of said deviation becomes equal to or smaller than the determination value, in changing said opening/closing timing during the course of engine stop.

7. The variable valve timing apparatus according to claim 5, wherein said actuator is formed of an electric motor and the operation amount of said actuator is a rotational speed difference of said electric motor relative to said camshaft, andsaid change mechanism changes said opening/closing timing such that a ratio between the operation amount of said actuator and the amount of change of said opening/closing timing differs and a change direction of said opening/closing timing is identical, between a case where said opening/closing timing is in a first region and a case where said opening/closing timing is in a second region.

8. The variable valve timing apparatus according to claim 5, wherein in changing said opening/closing timing during a course of stopping said engine, the target value of said opening/closing timing is set at a prescribed value suitable for a next engine start.

9. A control method of a variable valve timing apparatus changing an opening/closing timing of at least any one of an intake valve and an exhaust valve provided to an engine, said variable valve timing apparatus includingan actuator,a change mechanism changing said opening/closing timing by changing difference in rotational phase of a camshaft driving the valve having said opening/closing timing changed, from a rotational phase of a crankshaft, at an amount of change according to an operation amount of said actuator, andan actuator operation amount setting portion setting the operation amount of said actuator, based on a deviation between said opening/closing timing at present of the valve having said opening/closing timing changed and a target value thereof, said control method comprising:a convergence determination step of setting the operation amount of said actuator to approximately zero, when an absolute value of said deviation is equal to or smaller than a determination value; anda determination value switching step of setting, in changing said opening/closing timing during a course of engine stop, said determination value at said convergence determination step at a value larger than said determination value in changing said opening/closing timing at a time of engine operation.

10. The control method of a variable valve timing apparatus according to claim 9, further comprising a power supply stopping step of stopping power supply to said actuator when an absolute value of said deviation becomes equal to or smaller than the determination value, in changing said opening/closing timing during the course of engine stop.

11. The control method of a variable valve timing apparatus according to claim 9, wherein said actuator is formed of an electric motor and the operation amount of said actuator is a rotational speed difference of said electric motor relative to said camshaft, andsaid change mechanism changes said opening/closing timing such that a ratio between the operation amount of said actuator and the amount of change of said opening/closing timing differs and a change direction of said opening/closing timing is identical, between a case where said opening/closing timing is in a first region and a case where said opening/closing timing is in a second region.

12. The control method of a variable valve timing apparatus according to claim 9, wherein in changing said opening/closing timing during a course of stopping said engine, the target value of said opening/closing timing is set at a prescribed value suitable for a next engine start.