JP6007721B2 - Control device for variable valve timing mechanism - Google Patents

Description

  The present invention relates to a control device for a variable valve timing mechanism.

  As an internal combustion engine mounted on a vehicle such as an automobile, the relative rotation phase of the camshaft with respect to the crankshaft is set as shown in Patent Document 1 in order to make the valve timing (opening / closing timing) of an engine valve such as an intake valve or an exhaust valve variable. One having a variable valve timing mechanism to change is known. Such a variable valve timing mechanism is provided with a movable member that is displaced so as to change the relative rotational phase of the camshaft with respect to the crankshaft. In this mechanism, oil is supplied to and discharged from the advance side hydraulic chamber and the retard side hydraulic chamber adjacent to the movable member through a hydraulic circuit in a direction to change the relative rotational phase of the camshaft with respect to the crankshaft. The movable member is displaced.

The supply and discharge of the oil to and from the advance side hydraulic chamber and the retard side hydraulic chamber are realized by displacing a spool of an oil control valve provided on the hydraulic circuit.
Specifically, when the spool is displaced toward the reference side end in the entire displacement range, oil is supplied to the retard side hydraulic chamber and oil is discharged from the advance side hydraulic chamber. In this case, the movable member is displaced in the direction of expanding the retarded-side hydraulic chamber (reducing the advanced-side hydraulic chamber), whereby the relative rotation phase of the camshaft with respect to the crankshaft is changed to the retarded side. On the other hand, if the spool is displaced toward the end opposite to the reference side in the entire displacement range, oil is supplied to the advance side hydraulic chamber and oil is discharged from the retard side hydraulic chamber. Is called. In this case, the movable member is displaced in the direction of expanding the advance-side hydraulic chamber (reducing the retard-side hydraulic chamber), thereby changing the relative rotational phase of the camshaft with respect to the crankshaft.

  In the oil control valve, a range in which the relative rotational phase of the camshaft with respect to the crankshaft can be maintained (hereinafter referred to as a dead zone) is set in the entire spool displacement range. Therefore, when maintaining the relative rotation phase of the camshaft with respect to the crankshaft, the spool of the oil control valve is adjusted to a position within the dead zone.

JP 2000-345869 A

  By the way, a valve timing variable mechanism provided with a lock mechanism for fixing the movable member at a position other than the end of its displacement range is provided with a spring for urging the movable member toward the position. In the variable valve timing mechanism provided with the spring, a situation occurs in which the relative rotational phase of the camshaft with respect to the crankshaft is maintained at a position where the movable member is biased by the spring. Under these circumstances, when the torque fluctuation of the camshaft due to the opening / closing drive of the engine valve is transmitted to the movable member, the frequency of the torque fluctuation matches the vibration frequency of the spring, and a resonance state is obtained. The movable member vibrates in the displacement direction. Furthermore, when the volumes of the advance side hydraulic chamber and the retard side hydraulic chamber change as the movable member vibrates, air is sucked into the advance side hydraulic chamber and the retard side hydraulic chamber from the outside during the change. In this way, when air is sucked into the advance side hydraulic chamber or the retard side hydraulic chamber from the outside, vibration in the displacement direction of the movable member increases.

  In Patent Document 1, when the vibration is generated in the movable member, the displacement to the reference end of the displacement range of the movable member and the displacement to the other end are alternately performed, whereby the advance angle is increased. It is disclosed that oil containing air is discharged from the side hydraulic pressure and retard angle hydraulic chambers. However, even if such a technique of Patent Document 1 is used, the cam transmitted to the movable member in a situation where the relative rotational phase of the camshaft with respect to the crankshaft is maintained at the position where the movable member is biased by the spring. It cannot be suppressed that the vibration frequency of the shaft torque coincides with the vibration frequency of the spring and the resonance state occurs. For this reason, since the movable member vibrates in the displacement direction due to the occurrence of the resonance state, air is sucked from the outside into the advance side hydraulic chamber and the retard side hydraulic chamber again due to the vibration, Accordingly, it is inevitable that the vibration in the displacement direction of the movable member is repeatedly increased.

  Further, as disclosed in Patent Document 1, in order to discharge oil containing air from the advance side hydraulic and retard side hydraulic chambers, the displacement of the movable member to the reference end and the other end of the displacement range When the displacement is alternately performed, the relative phase of the camshaft with respect to the crankshaft is significantly deviated from the optimum phase (target phase) for engine operation. As a result, there is a possibility that the fuel consumption of the internal combustion engine is deteriorated and drivability is lowered.

  The present invention has been made in view of such a situation, and an object thereof is to suppress the occurrence of a resonance state in a movable member without causing deterioration in fuel consumption or drivability of an internal combustion engine, and the resonance. An object of the present invention is to provide a control device for a variable valve timing mechanism capable of suppressing an increase in vibration of a movable member due to occurrence of a state.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A control device for a variable valve timing mechanism that solves the above-described problem is that the movable member moves in the direction of displacement in a state where the relative rotational phase of the camshaft with respect to the crankshaft is maintained at a position where the movable member is biased by a spring. When it vibrates, reciprocal control is performed by the control means. Here, under the situation where the relative rotational phase of the camshaft with respect to the crankshaft is maintained at the position where the movable member is biased by the spring, the frequency of camshaft torque fluctuation transmitted to the movable member and the above-mentioned movable The movable member vibrates in the displacement direction due to the resonance with the vibration frequency of the spring biasing the member. Further, when the relative rotation phase of the camshaft with respect to the crankshaft is maintained, the spool is adjusted to a position within the dead zone that is a displacement range of the spool capable of realizing it. When the reciprocating control is started from this state, the adjustment of the spool to the first position corresponding to the upper limit of the dead zone and the adjustment of the spool to the second position corresponding to the lower limit of the dead zone are alternately performed through the same control. Done. The movable member reciprocates with a gentle and small width in the displacement direction by adjusting the hydraulic pressure in the advance side hydraulic chamber and the hydraulic pressure in the retard side hydraulic chamber based on the position adjustment of the spool in such reciprocation control. In the reciprocating motion of the movable member with such a small width, the relative rotational phase of the camshaft with respect to the crankshaft does not greatly deviate from the proper state (phase when held). Then, due to the reciprocating motion of the movable member with a gentle and small width, the frequency of the torque fluctuation of the camshaft transmitted to the movable member matches the frequency of the spring that biases the movable member, and the above-mentioned Occurrence of the resonance state is suppressed without causing deterioration of fuel consumption or drivability of the internal combustion engine. Furthermore, it is possible to suppress an increase in vibration of the movable member due to the occurrence of the resonance state.

  In the control apparatus for the valve timing variable mechanism, the control means performs learning control for learning the upper limit and the lower limit of the dead zone, and when the learning of the upper limit and the lower limit of the dead zone by the learning control is completed, It is preferable to perform reciprocal control. In this case, the upper limit and the lower limit of the dead zone are learned through learning control, so that the upper limit and the lower limit become appropriate values. For this reason, after the learning of the upper limit and the lower limit of the dead zone by the learning control is completed, the first position and the second position determined based on the upper limit and the lower limit can also be set to appropriate values. Therefore, the gentle reciprocation of the movable member in the reciprocating control in which the adjustment of the spool to the first position and the adjustment of the spool to the second position are alternately performed is performed more appropriately.

  In the control device for the variable valve timing mechanism, it is conceivable to employ a position that matches the upper limit of the dead zone as the first position and a position that matches the lower limit of the dead zone as the second position. In this case, when the spool is adjusted to the first position or the second position, the oil is supplied to or discharged from the advance side hydraulic chamber and the retard side hydraulic chamber little by little. By adjusting the hydraulic pressure in the advance-side hydraulic chamber and the hydraulic pressure in the retard-side hydraulic chamber through the oil supply / discharge, the movable member can be reciprocated more slowly and with a smaller width in the displacement direction.

  In the control device for the variable valve timing mechanism, the first position adopts a position that is set in a direction deviating from the dead band with respect to the upper limit of the dead band, and the second position is the same as the lower limit of the dead band. It is also conceivable to employ a position with a predetermined interval in a direction away from the dead zone. In this case, when the spool is adjusted to the first position or the second position, the oil is supplied to and discharged from the advance side hydraulic chamber and the retard side hydraulic chamber little by little and accurately. By adjusting the hydraulic pressure in the advance side hydraulic chamber and the hydraulic pressure in the retard side hydraulic chamber through the supply and discharge of such oil, the reciprocating motion of the movable member in the displacement direction in a gentle and small width can be performed more accurately. .

  In the control device for the variable valve timing mechanism, the control means displaces the spool as follows instead of adjusting the spool by the reciprocating control when learning of the upper limit and the lower limit of the dead zone by the learning control is incomplete. It is preferable that That is, the control means shifts the target phase of the relative rotation phase of the camshaft with respect to the crankshaft by a predetermined amount, and displaces the spool so that the relative rotation phase changes toward the target phase after the shift. Let In this case, when learning of the upper limit and the lower limit of the dead zone by learning control is incomplete, and there is a possibility that the upper limit and the lower limit are not appropriate, the first position and the second position determined based on the upper limit and the lower limit are used. If the reciprocating control is performed, the width of the reciprocating motion of the movable member may become too large. Thus, if the width of the reciprocating motion of the movable member becomes too large, the relative rotational phase of the camshaft with respect to the crankshaft is greatly deviated from the proper state, thereby causing problems such as deterioration in fuel consumption and drivability of the internal combustion engine. However, since the reciprocal control is not performed when the learning of the upper limit and the lower limit of the dead zone by the learning control is not completed, the occurrence of such a problem is suppressed. Even if reciprocal control is not performed as described above, instead, the relative rotational phase of the camshaft with respect to the crankshaft is adjusted toward the target phase after shifting as described above. As a result, the upper and lower limits of the dead zone may not be appropriate, so the movable member cannot be displaced properly due to the spool displacement, and the relative rotational phase of the camshaft relative to the crankshaft is adjusted to the target phase. Although there is a possibility of not being able to complete, the occurrence of the resonance state in the movable member can be suppressed.

  In the control device of the variable valve timing mechanism, the reciprocating control is performed by adjusting the relative rotation phase of the camshaft with respect to the crankshaft with respect to the target phase after adjusting the spool to one of the first position and the second position. It is preferable to realize the adjustment by adjusting the spool to the other one of the first position and the second position when the amount is deviated by the amount, and repeating the adjustment of the spool. In this case, the relative rotation phase of the camshaft relative to the crankshaft can be accurately suppressed from being maintained at the phase where the resonance state occurs due to the displacement of the spool based on the adjustment of the spool in the reciprocating control.

1 is a schematic diagram showing an internal combustion engine to which a control device for a variable valve timing mechanism is applied. The graph which shows the change aspect of the valve timing of an intake valve based on operation | movement of a valve timing variable mechanism. 1 is a schematic diagram showing a structure of a variable valve timing mechanism and a hydraulic circuit for hydraulically operating the mechanism. Changes in the oil flow rate when oil is supplied to and discharged from the advance side hydraulic chamber and the retard side hydraulic chamber of the variable valve timing mechanism, more specifically, the oil flow rate according to the spool position of the oil control valve. A graph showing changes. The flowchart which shows the control procedure of the valve timing of an intake valve. The flowchart which shows the execution procedure of a resonance suppression process.

Hereinafter, an embodiment of a control device for a variable valve timing mechanism will be described with reference to FIGS.
An internal combustion engine 1 shown in FIG. 1 is mounted on a vehicle such as an automobile. In this internal combustion engine 1, a throttle valve 13 is provided in an intake passage 3 connected to the combustion chamber 2 so as to be openable and closable. Air is sucked into the combustion chamber 2 through the intake passage 3 and the fuel injection valve 4 Fuel injected toward the intake port 3 a of the engine 1 is supplied to the combustion chamber 2. When the air / fuel mixture is ignited by the spark plug 5, the air / fuel mixture burns, the piston 6 reciprocates, and the crankshaft 7 that is the output shaft of the internal combustion engine 1 rotates. On the other hand, the air-fuel mixture after burning in the combustion chamber 2 is sent to the exhaust passage 8 as exhaust gas.

  The combustion chamber 2 and the intake passage 3 in the internal combustion engine 1 are communicated and blocked through the opening / closing operation of the intake valve 11. The intake valve 11 opens and closes as the intake camshaft 12 that receives the rotation transmission from the crankshaft 7 rotates. When the intake valve 11 opens along with the rotation of the intake camshaft 12, the torque (negative torque) in the direction opposite to the rotation direction of the intake camshaft 12 is based on the elastic force when the valve spring 11a is compressed. Act. Further, when the intake valve 11 is closed with the rotation of the intake camshaft 12, the torque (positive torque) in the same direction as the rotation direction of the intake camshaft 12 based on the elastic force when the valve spring 11a is expanded. Act.

  On the other hand, the combustion chamber 2 and the exhaust passage 8 in the internal combustion engine 1 are communicated and blocked through the opening / closing operation of the exhaust valve 14. The exhaust valve 14 opens and closes as the exhaust camshaft 15 that receives the rotation transmission from the crankshaft 7 rotates. When the exhaust valve 14 opens with the rotation of the exhaust camshaft 15, the torque (negative torque) in the direction opposite to the rotational direction of the exhaust camshaft 15 is based on the elastic force when the valve spring 14a is compressed. Act. Further, when the exhaust valve 14 is closed with the rotation of the exhaust camshaft 15, the torque (positive torque) in the same direction as the rotational direction of the exhaust camshaft 15 is based on the elastic force when the valve spring 14a is expanded. Act.

  The internal combustion engine 1 is provided with a variable valve timing mechanism 16 that changes the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 in order to make the opening / closing timing of the intake valve 11 variable. The variable valve timing mechanism 16 is hydraulically operated so as to change the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 through supply and discharge of oil by driving the oil control valve 25. By such an operation of the variable valve timing mechanism 16, the valve timing (opening / closing timing) of the intake valve 11 is made variable. Specifically, as shown in FIG. 2, both the valve opening timing and the valve closing timing of the valve 11 are advanced or retarded while the valve opening period of the intake valve 11 is kept constant.

Next, the variable valve timing mechanism 16 and the hydraulic circuit for performing the operation will be described in detail.
As shown in FIG. 3, the variable valve timing mechanism 16 includes a movable member 19 fixed to the intake camshaft 12 and a crankshaft 7 (on the axis of the intake camshaft 12 so as to surround the movable member 19. And a case 20 to which the rotation of FIG. 1) is transmitted. On the inner peripheral surface of the case 20, a plurality of protrusions 20a projecting toward the axis of the intake camshaft 12 are formed at predetermined intervals in the circumferential direction. A plurality of vanes 19 a that protrude in a direction away from the axis of the intake camshaft 12 are formed on the outer peripheral surface of the movable member 19 so as to be positioned between the protrusions 20 a. Thereby, the part located between each protrusion 20a in the case 20 is divided into the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 by the vane 19a. In other words, the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 are formed between the movable member 19 and the case 20.

  The movable member 19 can be displaced in the rotational direction around the axis of the intake camshaft 12. When the movable member 19 rotates relative to the case 20 in the clockwise direction in FIG. 3, the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 changes to the advance side, and the valve timing of the intake valve 11 advances. Change to the side. Further, when the movable member 19 rotates relative to the case 20 in the left rotation direction in the figure, the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 changes to the retard side, and the valve timing of the intake valve 11 becomes the retard side. To change. Therefore, in the variable valve timing mechanism 16, as described above, the movable member 19 is displaced in the direction of relative rotation with respect to the case 20, so that the relative rotation phase of the intake camshaft 12 relative to the crankshaft 7 is advanced or retarded. Change to the side is realized.

  The variable valve timing mechanism 16 is provided with a lock mechanism 51 that holds the valve timing of the intake valve 11 and releases the hold. The lock mechanism 51 fixes the movable member 19 to the case 20 at a position other than the end of the displacement range (for example, in the middle of the entire displacement range), thereby prohibiting relative rotation of the movable member 19 with respect to the case 20. Thereby, the valve timing of the intake valve 11 is maintained. Further, when the fixing of the movable member 19 to the case 20 by the lock mechanism 51 is released, the prohibition of relative rotation of the movable member 19 with respect to the case 20 is thereby released. A spring 17 is provided in the advance side hydraulic chamber 22 of the variable valve timing mechanism 16 to bias the movable member 19 toward the retard side. The movable member 19 is urged by the spring 17 toward a position where the movable member 19 and the case 20 are fixed by the lock mechanism 51 (a position other than the end of the displacement range of the movable member 19). The

  In the variable valve timing mechanism 16, a plurality of hydraulic circuits that connect the mechanism 16 and the oil pump 24 to the advance hydraulic chamber 22 and the retard hydraulic chamber 23 adjacent to the vane 19 a of the movable member 19 are configured. Oil is supplied and discharged through the oil passage. In the middle of the plurality of oil passages in the hydraulic circuit, the oil control valve 25 for changing the oil supply / discharge mode with respect to the valve timing variable mechanism 16 by these oil passages is provided. The oil control valve 25 is connected to the oil pump 24 via a supply oil passage 41 and is connected to an oil pan 42 for storing oil pumped up by the oil pump 24 via a discharge oil passage 43. ing. The oil control valve 25 is connected to the advance side hydraulic chamber 22 of the variable valve timing mechanism 16 via the advance side oil passage 44 and is retarded from the retard side hydraulic chamber 23 of the mechanism 16. The side oil passage 45 is connected.

  The oil control valve 25 includes a supply port 26 for connecting the supply oil passage 41, a discharge port 27 for connecting the discharge oil passage 43, an advance port 28 for connecting the advance side oil passage 44, and A retard port 29 for connecting the retard side oil passage 45 is formed. The oil control valve 25 includes a spool 30 that is displaced so as to switch the communication cut-off state between the ports 26 to 29, and a spring 31a that applies an elastic force to the spool 30 toward one side in the displacement direction. An electromagnetic solenoid 31b for applying an electromagnetic force to the spool 30 toward the other side in the displacement direction is provided. In the oil control valve 25, the communication cut-off state between the ports 26 to 29 is switched through position adjustment of the spool 30 based on the elastic force of the spring 31a and the electromagnetic force of the electromagnetic solenoid 31b. Oil is supplied to and discharged from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23.

  The position adjustment of the spool 30 in the oil control valve 25 is performed by changing the applied voltage of the electromagnetic solenoid 31b according to the duty ratio command value. The duty ratio command value is changed within a predetermined range of, for example, “0 to 100%”. The electromagnetic force of the electromagnetic solenoid 31b decreases as the value decreases within the range, while the electromagnetic solenoid increases as the value increases. The electromagnetic force of 31b becomes large.

  For this reason, when the duty ratio command value is reduced to reduce the electromagnetic force of the electromagnetic solenoid 31b, the biasing force of the spring 31a is larger than the electromagnetic force, and the spool 30 is moved to one side (left side in the figure) based on the biasing force. The supply port 26 and the retard port 29 communicate with each other, and the advance port 28 and the discharge port 27 communicate with each other. Further, as the duty ratio command value is decreased and the spool 30 is displaced to the left in the drawing, the oil flow area between the supply port 26 and the retard port 29 increases, while the advance port 28 and the discharge port 27 increase. The oil distribution area between and increases. On the other hand, when the duty ratio command value is increased to increase the electromagnetic force of the electromagnetic solenoid 31b, the electromagnetic force becomes larger than the urging force of the spring 31a, and the spool 30 is moved to the other side (right side in the figure) based on the electromagnetic force. The supply port 26 and the advance port 28 communicate with each other, and the retard port 29 and the discharge port 27 communicate with each other. Further, as the duty ratio command value is increased and the spool 30 is displaced to the right in the figure, the oil flow area between the supply port 26 and the advance port 28 increases, while the retard port 29 and the discharge port 27 increase. The oil distribution area between and increases.

  4 shows a change in the flow rate of the oil when the oil is supplied to and discharged from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 of the variable valve timing mechanism 16, more specifically, the spool 30 of the oil control valve 25. It is a graph which shows the change of the flow volume of the said oil according to a position (corresponding to duty ratio command value). In the figure, a solid line L1 indicates a change in the flow rate of oil supplied to the retard side hydraulic chamber 23, and a broken line L2 indicates a change in the flow rate of oil discharged from the advance side hydraulic chamber 22. Yes. A solid line L3 indicates a change in the flow rate of the oil supplied to the advance side hydraulic chamber 22, and a broken line L4 indicates a change in the flow rate of the oil discharged from the retard side hydraulic chamber 23.

  When the spool 30 is located in the region A1 in the entire displacement range, oil is not supplied to or discharged from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23, and the flow rate of the oil at that time is “0”. " When the spool 30 is positioned in the region A2 on the left side in the drawing from the region A1, the oil is supplied to the retard side hydraulic chamber 23, but the oil is discharged from the advance side hydraulic chamber 22. Instead, the flow rate of the oil becomes “0”. Further, when the spool 30 is positioned in the region A3 on the right side in the drawing with respect to the region A1, the oil is supplied to the advance side hydraulic chamber 22 but the oil is discharged from the retard side hydraulic chamber 23. Is not performed, and the flow rate of the oil becomes “0”.

  When the duty ratio command value decreases and the position of the spool 30 changes further to the left position in FIG. 4 than the area A2, the position of the spool 30 changes to the left position in FIG. As described above, the flow rate of oil supplied to the retard side hydraulic chamber 23 increases, and the flow rate of oil discharged from the advance side hydraulic chamber 22 increases as shown by the broken line L2. As a result, the hydraulic pressure in the advance-side hydraulic chamber 22 increases while the hydraulic pressure in the retard-side hydraulic chamber 23 decreases, whereby the movable member 19 rotates relative to the case 20 in the counterclockwise direction of FIG. . On the other hand, when the duty ratio command value increases and the position of the spool 30 changes to a position on the right side of the area A3 in FIG. 4, the solid line L3 indicates that the position of the spool 30 changes to the position on the right side in the figure. As shown, the flow rate of oil supplied to the advance side hydraulic chamber 22 increases, and the flow rate of oil discharged from the retard side hydraulic chamber 23 increases as shown by the broken line L4. As a result, the hydraulic pressure in the advance side hydraulic chamber 22 increases while the hydraulic pressure in the retard side hydraulic chamber 23 decreases, whereby the movable member 19 rotates relative to the case 20 in the clockwise direction of FIG. .

  Therefore, in the entire displacement range of the spool 30 shown in FIG. 4, the areas A1 to A3 are dead zones that are displacement ranges of the spool 30 that can realize the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7. It becomes. When the position of the spool 30 is adjusted from the lower limit R to the upper limit F of the dead zone, that is, in the regions A1 to A3, oil is discharged at least one of the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23. It will not be broken. Specifically, if the position of the spool 30 is adjusted in the region A1, the oil is not discharged from both the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23. At this time, no oil is supplied to the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23. If the position of the spool 30 is adjusted in the region A2, the oil is not discharged from the advance side hydraulic chamber 22 and the oil can be supplied to the retard side hydraulic chamber 23. Further, if the position of the spool 30 is adjusted in the region A3, the oil is not discharged from the retard side hydraulic chamber 23, and the oil can be supplied to the advance side hydraulic chamber 22. Become. Since the movable member 19 is restricted from being displaced with respect to the case 20 in these states, the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7, that is, the valve timing of the intake valve 11 is maintained.

  The position of the spool 30 within the entire displacement range of the spool 30 corresponds to the duty ratio command value. For this reason, by storing the duty ratio command values when the spool 30 is positioned at the lower limit R and the upper limit F of the dead zone as parameters corresponding to the lower limit R and the upper limit F, respectively, It is possible to specify a dead zone between the ratio command values. The duty ratio command value when the spool 30 is located at the lower limit R of the dead zone is hereinafter referred to as a lower limit duty ratio DR, and the duty ratio command value when the spool 30 is located at the upper limit F of the dead zone is hereinafter referred to as an upper limit duty ratio. It is called DF.

Next, the control device for the variable valve timing mechanism 16 will be described in detail with reference to FIG.
The control device includes an electronic control device 21 that executes various controls related to the operation of the internal combustion engine 1. The electronic control device 21 includes a CPU that executes various arithmetic processes related to the above control, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores CPU calculation results, and the like. Input / output ports for inputting / outputting signals are provided.

Various sensors shown below are connected to the input port of the electronic control unit 21.
An air flow meter 32 that detects the amount of air passing through the intake passage 3 (intake air amount).
A cam position sensor 33 that outputs a signal corresponding to the rotation position of the shaft 12 based on the rotation of the intake camshaft 12.

A crank position sensor 34 that outputs a signal corresponding to the rotation of the crankshaft 7.
A throttle position sensor 35 that detects the opening (throttle opening) of the throttle valve 13 provided in the intake passage 3.

An accelerator position sensor 37 that detects the amount of depression (accelerator operation amount) of the accelerator pedal 36 that is depressed by the driver of the vehicle.
The output port of the electronic control unit 21 includes a drive circuit for the fuel injection valve 4, a drive circuit for the spark plug 5, a drive circuit for the throttle valve 13, and a drive circuit for the variable valve timing mechanism 16 (oil control valve 25). The drive circuits of various devices are connected.

  The electronic control unit 21 then determines the engine operating state such as the engine speed and the engine load (the amount of air taken into the combustion chamber 2 per cycle of the internal combustion engine 1) based on the detection signals input from the various sensors. To grasp. The engine speed is obtained based on a detection signal from the crank position sensor 34. The engine load is calculated from the intake air amount of the internal combustion engine 1 obtained based on detection signals from the accelerator position sensor 37, the throttle position sensor 35, the air flow meter 32, and the like and the engine rotational speed. Further, the electronic control unit 21 uses a detection signal from the crank position sensor 34 and the cam position sensor 33 as a parameter corresponding to the actual valve timing of the intake valve 11 at a timing at which the lift amount of the intake valve 11 is maximized ( Measure the crank angle).

  The electronic control device 21 outputs a command signal to various drive circuits connected to the output port based on the engine operating state such as the engine load and the engine rotation speed and the measured value of the valve timing of the intake valve 11. Thus, fuel injection control, ignition timing control, intake air amount control, valve timing control of the intake valve 11 and the like in the internal combustion engine 1 are performed through the electronic control unit 21.

  The valve timing control of the intake valve 11 is performed, for example, so that the fuel consumption and output of the internal combustion engine 1 are the best. In such valve timing control, a duty ratio command value is calculated based on the engine operating state and the like, and the duty ratio of the applied voltage to the electromagnetic solenoid 31b (FIG. 3) of the oil control valve 25 is calculated based on the calculated duty ratio command value. Realized by adjusting. The duty ratio command value is calculated using, for example, the following equation: “Duty ratio command value D = feedback correction term P + holding duty learning value H (1)”.

  The feedback correction term P in the above equation (1) is used for feedback control for controlling the actual valve timing VT, which is an actual value of the valve timing of the intake valve 11, to the target valve timing VTt set based on the engine operating state. Value. This feedback correction term P is increased or decreased based on the difference between the two so that the actual valve timing VT approaches the target valve timing VTt. That is, when the actual valve timing VT is on the more advanced side than the target valve timing VTt, the feedback correction term P is decreased by the gain p and the duty ratio command value D is decreased. By reducing the duty ratio command value D in this way, the actual valve timing VT is retarded and brought closer to the target valve timing VTt. On the other hand, when the actual valve timing VT is behind the target valve timing VTt, the feedback correction term P is increased by the gain p and the duty ratio command value D is increased. By increasing the duty ratio command value D in this way, the actual valve timing VT is advanced to approach the target valve timing VTt.

  The hold duty learning value H in the above equation (1) is a value learned as the theoretical duty ratio command value D necessary for keeping the actual valve timing VT of the intake valve 11 constant. ) Is a center value for increasing / decreasing the duty ratio command value D obtained in () together with the increase / decrease of the feedback correction term P. The learning of the hold duty learning value H is performed when the difference between the actual valve timing VT and the target valve timing VTt becomes less than the determination value during feedback control of the actual valve timing VT to the target valve timing VTt. This is realized by setting the duty ratio command value D to the latest holding duty learning value H. The hold duty learning value H learned in this way becomes a value within a range corresponding to the dead zone of FIG.

  The electronic control device 21 performs learning control for learning the upper limit F and the lower limit R (more precisely, the upper limit duty ratio DF and the lower limit duty ratio DR) of the dead zone, that is, storing them in the nonvolatile RAM of the device 21. Such learning control is executed when a predetermined learning condition is satisfied after the start of the internal combustion engine 1 and until the learning of the upper limit F and the lower limit R is completed until the stop of the internal combustion engine 1 is completed. It is executed every time the condition is met.

  In the learning control described above, the duty ratio command value D is used to gradually advance the actual valve timing VT in a state where the relative rotation phase (actual valve timing VT) of the intake camshaft 12 with respect to the crankshaft 7 is kept constant. When is gradually increased, learning of the upper limit duty ratio DF is performed as follows. That is, when the actual valve timing VT starts to advance based on the gradually increasing duty ratio command value D as described above, electronic control is performed with the duty ratio command value D at that time as the latest upper limit duty ratio DF. The data is stored in the nonvolatile RAM of the device 21. Before the latest upper limit duty ratio DF is stored in the nonvolatile RAM, that is, before the completion of learning of the upper limit duty ratio DF, the previous value of the upper limit duty ratio DF is stored in the nonvolatile RAM. After the completion of the learning, the previous value is replaced with the latest upper limit duty ratio DF.

  In the learning control, the duty ratio command value D is gradually increased to gradually retard the valve timing of the intake valve 11 in a state where the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 is kept constant. When the value is made smaller, learning of the lower limit duty ratio DR is performed as follows. That is, when the valve timing of the intake valve 11 starts to be retarded based on the duty ratio command value D being gradually reduced as described above, the duty ratio command value D at that time is set as the latest lower limit duty ratio DR. The data is stored in the nonvolatile RAM of the electronic control device 21. Before the latest lower limit duty ratio DR is stored in the nonvolatile RAM, that is, before the learning of the lower limit duty ratio DR is completed, the previous value of the lower limit duty ratio DR is stored in the nonvolatile RAM. After completion of the learning, the previous value is replaced with the latest lower limit duty ratio DR.

  By the way, as shown in FIG. 3, the variable valve timing mechanism 16 is provided with a spring 17 that urges the movable member 19 toward a position other than the end of its displacement range. In the variable valve timing mechanism 16, the spool 30 of the oil control valve 25 is adjusted to a position in the dead zone at a position where the movable member 19 is urged by the spring 17, thereby intake air to the crankshaft 7. A situation occurs in which the relative rotational phase of the camshaft 12 is maintained.

  Under such circumstances, torque fluctuations (positive torque and negative torque alternately occur) due to the opening / closing drive of the intake valve 11 occur, and the torque fluctuations are transmitted to the movable member 19. When the frequency of the torque fluctuation matches the vibration frequency of the spring 17, the movable member 19 vibrates in the displacement direction. Further, when the volumes of the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 fluctuate due to the vibration of the movable member 19, air is transferred from the outside to the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 during the change. Is sucked. Thus, when air is sucked into the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 from the outside, vibration in the displacement direction of the movable member 19 increases.

  In order to cope with this, in the present embodiment, the movable member 19 is moved under the condition that the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained at the position where the movable member 19 is biased by the spring 17. When vibrating in the displacement direction, the following reciprocating control is performed through the electronic control unit 21. That is, in the reciprocating control, the spool 30 is adjusted to a position within the dead zone so as to maintain the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7, and the first corresponding to the upper limit F of the dead zone. The adjustment of the spool 30 to the first position P1 and the adjustment of the spool 30 to the second position P2 corresponding to the lower limit R of the dead zone are alternately performed. The first position P1 is an interval defined in a direction deviating from the dead zone upper limit F (the right direction in FIG. 4), for example, an interval corresponding to a 1% change in the duty ratio command value. It is possible to adopt the position where it was. Further, the second position P2 is an interval defined in a direction (left direction in FIG. 4) deviating from the dead zone lower limit R, for example, an interval corresponding to a 1% change in the duty ratio command value. It is possible to adopt the position where it was.

Next, the operation of the control device for the variable valve timing mechanism 16 will be described.
In a situation where the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained at a position where the movable member 19 of the mechanism 16 is biased by the spring 17, the torque of the intake camshaft 12 transmitted to the movable member 19. There is a possibility that the fluctuating frequency and the frequency of the spring 17 that urges the movable member 19 coincide with each other to enter a resonance state. And when the said movable member 19 vibrates about the displacement direction resulting from generation | occurrence | production of such a resonance state, the reciprocation control mentioned above is implemented. That is, the adjustment of the spool 30 to the first position P1 and the adjustment of the spool 30 to the second position P2 are alternately performed in a state where the spool 30 of the oil control valve 25 is adjusted to the position in the dead zone. . When the spool 30 is adjusted to the first position P <b> 1 or the second position P <b> 2 based on the position adjustment of the spool 30 in such reciprocating control, oil is supplied to and discharged from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23. It is done little by little and accurately.

  Then, based on the supply and discharge of the oil to and from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23, the hydraulic pressure in the advance side hydraulic chamber 22 and the hydraulic pressure in the retard side hydraulic chamber 23 are adjusted. The movable member 19 reciprocates with a gentle and small width in the displacement direction (the rotation direction about the axis of the intake camshaft 12). In the reciprocating motion of the movable member 19 with such a small width, the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 does not deviate greatly from the proper state (phase when held). Then, by the reciprocating motion of the movable member 19 with a gentle and small width, the frequency of the torque fluctuation of the intake camshaft 12 transmitted to the movable member 19 and the frequency of the spring 17 biasing the movable member 19 are obtained. The coincidence and the occurrence of the resonance state associated therewith are suppressed without causing deterioration in fuel consumption or drivability of the internal combustion engine 1. Furthermore, an increase in vibration of the movable member 19 due to the occurrence of the resonance state can also be suppressed.

  FIG. 5 is a flowchart showing a valve timing control routine for suppressing the occurrence of a resonance state in the movable member 19 by the reciprocating control. The valve timing control routine is periodically executed through the electronic control device 21 by, for example, a time interruption every predetermined time.

  The electronic control unit 21 determines whether or not the flag X is “0” as the process of step 101 (S101) of the routine. This flag X is used to determine whether or not the resonance suppression process for performing the reciprocal control is being performed, and is set to “0” while the resonance suppression process is stopped. During the execution of the resonance suppression process, “1” is set. If the flag X is “0 (stopped)”, the process proceeds to S102.

  The electronic control unit 21 determines whether or not the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained at the position where the movable member 19 is urged by the spring 17 as processing of S102. Incidentally, whether or not the movable member 19 is in a position to receive the biasing force from the spring 17 can be determined based on whether or not the actual valve timing VT is in a region where the biasing force acts. Whether or not the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained is determined whether or not the spool 30 of the oil control valve 25 is located in the dead zone, in other words, the duty ratio command value. A determination can be made based on whether D is a value between the lower limit duty ratio DR and the upper limit duty ratio DF. And if it is affirmation determination by S102, it will progress to S103.

  As the process of S103, the electronic control unit 21 determines whether or not the movable member 19 is vibrated in the displacement direction based on the presence or absence of a change in the actual valve timing VT. Here, when the movable member 19 is vibrated in the displacement direction of the movable member 19 based on the occurrence of the resonance state, an affirmative determination is made in S103 and the process proceeds to S104. The electronic control unit 21 sets the flag X described above to “1 (in progress)” as the process of S104. Further, the electronic control unit 21 executes the resonance suppression process so as to perform the reciprocal control for suppressing the occurrence of the resonance state in the movable member 19 as the process of S105, and then ends the valve timing control routine once. . If the flag X is set to “1” in the process of S104, a negative determination is made in the next process of S101, so that S102 to S104 are skipped and the process proceeds to S105.

  On the other hand, if a negative determination is made in S102 or S103, the process proceeds to S106. The electronic control unit 21 executes normal valve timing control as the process of S106. That is, the application of the oil control valve 25 to the electromagnetic solenoid 31b based on the duty ratio command value D obtained by the above equation (1) so that the actual valve timing VT is controlled to the target valve timing VTt set based on the engine operating state. Adjust the voltage duty ratio. Thereby, feedback control for controlling the actual valve timing VT of the intake valve 11 to the target valve timing VTt is performed. After such normal valve timing control of the intake valve 11 is executed, the electronic control unit 21 once ends this valve timing control routine.

FIG. 6 is a flowchart showing a resonance suppression routine that is executed through the electronic control device 21 every time the process proceeds to S105 in the valve timing control routine of FIG.
The electronic control unit 21 learns the upper limit duty ratio DF and the lower limit duty ratio DR (corresponding to the upper limit F and the lower limit R of the dead zone, respectively) by learning control after the start of the start of the internal combustion engine 1 as the process of S201 of the routine. Determine if it is complete. If the determination is affirmative, the electronic control unit 21 is a series corresponding to the above-described reciprocating control in order to suppress vibration in the displacement direction of the movable member 19 caused by the occurrence of the resonance state in the movable member 19. The processes (S202 to S210) are executed.

  That is, the electronic control unit 21 determines whether or not the flag XF is “0” as the process of S202. The flag XF is used to determine whether or not the spool 30 of the oil control valve 25 is being adjusted to the first position P1 in the reciprocating control, and the adjustment of the spool 30 to the first position P1 is performed. When it is not in the middle, it is set to “0”, while it is set to “1” during the adjustment of the spool 30 to the first position P1. Further, the electronic control unit 21 determines whether or not the flag XR is “0” as processing of S203. This flag XR is used to determine whether or not the spool 30 is being adjusted to the second position P2 in the reciprocating control. When the spool 30 is not being adjusted to the second position P2, the flag XR is “0”. Is set to “1” during the adjustment of the spool 30 to the second position P2.

  When the routine proceeds to S202 immediately after the start of the reciprocating control, the spool 30 is adjusted to a position in the dead zone so that the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained. The spool 30 is not being adjusted to the first position P1 or the second position P2. For this reason, both the flag XF and the flag XR are “0 (not being adjusted)”. Based on this, an affirmative determination is made in both S202 and S203, and the process proceeds to S204. The electronic control unit 21 sets a value obtained by adding a predetermined amount (1% in this example) to the upper limit duty ratio DF as the duty ratio command value D as the process of S204. By adjusting the duty ratio of the applied voltage of the oil control valve 25 based on the duty ratio command value D set in this way, the spool 30 of the oil control valve 25 is adjusted to the first position P1. When the spool 30 is adjusted to the first position P1 in this way, the electronic control unit 21 sets the flag XF to “1 (during adjustment)” as the process of S205. When the flag XF is set to “1” in this way, a negative determination is made in the next process of S202, so that S203 is skipped and the process proceeds to S204.

  When the spool 30 is adjusted to the first position P1 described above, the actual valve timing VT of the intake valve 11 changes to the advance side with respect to the target valve timing VTt. In other words, the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 changes toward the advance side with respect to the relative rotational phase (target phase) corresponding to the target valve timing VTt. In step S206, the electronic control unit 21 determines whether the actual valve timing VT has shifted to the advance side by a predetermined amount (in this example, 1 ° CA) with respect to the target valve timing VTt. . If it is affirmation determination here, it will progress to S207. In step S207, the electronic control unit 21 sets the flag XF to “0 (not being adjusted)” and sets the flag XR to “1 (being adjusted)”.

  As described above, when the flag XF is set to “0” and the flag XR is set to “1”, a negative determination is made in S203 and the process proceeds to S208. The electronic control unit 21 sets a value obtained by subtracting a predetermined amount (1% in this example) from the lower limit duty ratio DR as the duty ratio command value D as the process of S208. The spool 30 of the oil control valve 25 is adjusted to the second position P2 by adjusting the duty ratio of the applied voltage of the oil control valve 25 based on the duty ratio command value D thus set.

  As described above, when the spool 30 is adjusted to the second position P2, the actual valve timing VT of the intake valve 11 is changed to the retard side with respect to the target valve timing VTt. In other words, the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 changes to the retard side with respect to the relative rotational phase (target phase) corresponding to the target valve timing VTt. In step S209, the electronic control unit 21 determines whether the actual valve timing VT has shifted to the retard side by a predetermined amount (in this example, 1 ° CA) with respect to the target valve timing VTt. . If it is affirmation determination here, it will progress to S210. The electronic control unit 21 sets the flag XF to “1 (adjusting)” and sets the flag XR to “0 (not adjusting)” as the processing of S210.

  By the processes in S202 to S210, the reciprocating control for suppressing the vibration in the displacement direction of the movable member 19 due to the occurrence of the resonance state in the movable member 19 is realized. That is, after the adjustment of the spool 30 to the first position P1, the relative rotation phase (actual valve timing VT) of the intake camshaft 12 with respect to the crankshaft 7 is a predetermined amount (1) with respect to the target phase (target valve timing VTt). When the angle is shifted to the advance side by (° CA), the spool 30 is adjusted to the second position P2. Further, after adjusting the spool 30 to the second position P2, the relative rotational phase (actual valve timing VT) of the intake camshaft 12 with respect to the crankshaft 7 is a predetermined amount (1) with respect to the target phase (target valve timing VTt). When the angle is shifted to the retard side by (° CA), the spool 30 is adjusted to the first position P1. In the reciprocating control, the adjustment of the spool 30 to the first position P1 and the adjustment of the spool 30 to the second position P2 are thus alternately and repeatedly performed.

  On the other hand, in the process of S201, it is determined that learning of the upper limit duty ratio DF and the lower limit duty ratio DR (corresponding to the upper limit F and the lower limit R of the dead zone, respectively) by learning control is not completed after the start of the internal combustion engine 1 this time. Sometimes the process proceeds to S211. Here, when learning of the upper limit duty ratio DF and the lower limit duty ratio DR is incomplete, the upper limit duty ratio DF and the lower limit duty ratio DR may not be appropriate. At this time, if the reciprocating control (S202 to S210) using the first position P1 and the second position P2 determined based on the upper limit duty ratio DF and the lower limit duty ratio DR is performed, The width of the reciprocating motion may become too large. Thus, if the width of the reciprocating motion of the movable member 19 becomes too large, the relative rotational phase (actual valve timing VT) of the intake camshaft 12 with respect to the crankshaft 7 deviates greatly from the proper state, thereby deteriorating the fuel consumption of the internal combustion engine 1. And the problem of reduced drivability.

  For this reason, when the learning of the upper limit duty ratio DF and the lower limit duty ratio DR is incomplete, the electronic control unit 21 executes the VTt shifting process in S211 instead of the reciprocal control (S202 to S210). In the VTt shifting process, the target phase (target valve timing VTt) of the relative rotation phase of the intake camshaft 12 (actual valve timing VT) with respect to the crankshaft 7 is advanced or delayed by a predetermined amount (for example, 1 ° CA). The actual valve timing VT is controlled toward the target valve timing VTt after shifting to the corner side. Specifically, when the target valve timing VTt is shifted by 1 ° CA from a value determined based on the engine operating state through the VTt shifting process, the actual valve timing VT is controlled toward the target valve timing VTt after the shift. Thus, the duty ratio command value D is calculated using the above equation (1). Feedback control for adjusting the actual valve timing VT of the intake valve 11 to the target valve timing VTt is performed by adjusting the duty ratio of the applied voltage to the electromagnetic solenoid 31b of the oil control valve 25 based on the duty ratio command value D. Done.

  When learning of the upper limit duty ratio DF and the lower limit duty ratio DR is incomplete, it is possible to suppress the occurrence of the above-described problems associated with the execution of the reciprocating control by performing the VTt shifting process without performing the reciprocating control. Even if the reciprocal control is not performed, instead, the actual valve timing VT is adjusted toward the target valve timing VTt after the shift through the VTt shift processing. As a result, the upper limit duty ratio DF and the lower limit duty ratio DR may not be appropriate, so that the movable member 19 cannot be appropriately displaced due to the displacement of the spool 30, and the actual valve timing VT is set to the target valve timing. Although there is a possibility that the VTt cannot be adjusted, the occurrence of the resonance state in the movable member 19 can be suppressed. In order to suppress the occurrence of a situation where the actual valve timing VT cannot be adjusted to the target valve timing VTt, the feedback control gain p for adjusting the actual valve timing VT to the target valve timing VTt is set to be higher than usual at this time. It is preferable to increase the size.

  After the above-described reciprocating control (S202 to S210) or the VTt shifting process (S211) is performed, the electronic control unit 21 performs the target valve timing VTt (VTt shifting) set based on the engine operating state as the process of S212. At the time of execution of the process, it is determined whether or not the target valve timing VTt before shifting has changed according to the change in the engine operating state. Here, when the occurrence of the resonance state in the movable member 19 is suppressed through the reciprocal control or the VTt shifting process, if the target valve timing VTt changes according to the change in the engine operating state, the actual valve timing VT becomes the resonance frequency. There is no possibility of being held at the valve timing when the state occurs. Therefore, when an affirmative determination is made in S212, the process proceeds to S213 to stop the resonance suppression process for performing the reciprocal control or the VTt shifting process. The electronic control unit 21 sets the flag X to “0 (stopped)” as the processing of S213, and also sets the flag XF and the flag XR to “0 (not being adjusted)”. When the flag X is set to “0”, an affirmative determination is made in the process of S101 of the valve timing control routine of FIG. 5, and the process proceeds to S102. Furthermore, since a negative determination is made in S102 or S103 and the process proceeds to S106, normal valve timing control is performed in S106. As described above, the normal valve timing control is performed, so that the resonance suppression process for performing the reciprocal control or the VTt shifting process is stopped.

According to the embodiment described in detail above, the following effects can be obtained.
(1) In a situation where the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 is maintained at the position where the movable member 19 is urged by the spring 17, the torque fluctuation of the intake camshaft 12 transmitted to the movable member 19 And the vibration frequency of the spring 17 that urges the movable member 19 may coincide with each other to enter a resonance state. When the movable member 19 vibrates in the displacement direction due to the occurrence of such a resonance state, reciprocal control for suppressing the vibration is performed. In the reciprocating control, oil is supplied to and discharged from the advance-side hydraulic chamber 22 and the retard-side hydraulic chamber 23 little by little based on the position adjustment of the spool 30 of the oil control valve 25. By adjusting the hydraulic pressure and the hydraulic pressure in the retarded-side hydraulic chamber 23, the movable member 19 reciprocates slowly and with a small width in the displacement direction. In the reciprocating motion of the movable member 19 with such a small width, the relative rotational phase of the intake camshaft 12 with respect to the crankshaft 7 does not deviate greatly from the proper state (phase when held). Then, by the reciprocating motion of the movable member 19 with a gentle and small width, the frequency of the torque fluctuation of the intake camshaft 12 transmitted to the movable member 19 and the frequency of the spring 17 biasing the movable member 19 are obtained. The coincidence and the occurrence of the resonance state associated therewith are suppressed without causing deterioration in fuel consumption or drivability of the internal combustion engine 1. Furthermore, an increase in vibration of the movable member 19 due to the occurrence of the resonance state can also be suppressed.

  (2) The reciprocating control is performed when the learning in learning control for learning the upper limit F and the lower limit R (more precisely, the upper limit duty ratio DF and the lower limit duty ratio DR) of the dead zone is completed, that is, the upper limit is set by the same learning. This is performed in a state where the duty ratio DF and the lower limit duty ratio DR are appropriate. Accordingly, in the reciprocating control, the first position P1 and the second position P2 determined based on the upper limit duty ratio DF and the lower limit duty ratio DR become appropriate values, and the adjustment of the spool 30 to the first position P1 and the second position P2 By the reciprocating control in which the adjustment of the spool 30 is alternately performed, the gentle reciprocation of the movable member 19 can be performed more appropriately.

  (3) As the first position P1, a position having an interval determined in a direction deviating from the dead band with respect to the upper limit F of the dead band is adopted, and as the second position P2, a direction deviating from the dead band with respect to the lower limit R of the dead band. A position with a predetermined interval is adopted. In this case, when the spool 30 is adjusted to the first position P <b> 1 or the second position P <b> 2, oil is supplied to and discharged from the advance side hydraulic chamber 22 and the retard side hydraulic chamber 23 little by little and accurately. By adjusting the hydraulic pressure in the advance-side hydraulic chamber 22 and the hydraulic pressure in the retard-side hydraulic chamber 23 through the supply and discharge of such oil, the reciprocating movement of the movable member 19 in a gentle and small width in the displacement direction can be more accurately performed. Can be done.

  (4) In a situation where learning of the upper limit F and the lower limit R (more precisely, the upper limit duty ratio DF and the lower limit duty ratio DR) of the dead zone by learning control is not completed, the VTt shifting process is executed instead of the reciprocal control. By this VTt shifting process, the target phase (target valve timing VTt) of the relative rotation phase of the intake camshaft 12 with respect to the crankshaft 7 (actual valve timing VT) is advanced by a predetermined amount (for example, 1 ° CA) or Shifted to the retarded angle side. Then, the actual valve timing VT is controlled toward the target valve timing VTt after shifting as described above. For this reason, the problem with performing reciprocating control in a situation where learning of the upper limit duty ratio DF and the lower limit duty ratio DR is incomplete, that is, the width of the reciprocating motion of the movable member 19 in the reciprocating control becomes too large. It is possible to suppress the occurrence of the problem that the timing VT is greatly deviated from the appropriate state, which leads to deterioration in fuel consumption and drivability of the internal combustion engine 1. Even if the reciprocal control is not performed, instead, the actual valve timing VT is adjusted toward the target valve timing VTt after the shift through the VTt shift processing. As a result, the upper limit duty ratio DF and the lower limit duty ratio DR may not be appropriate, so that the movable member 19 cannot be appropriately displaced due to the displacement of the spool 30, and the actual valve timing VT is set to the target valve timing. Although there is a possibility that the VTt cannot be adjusted, the occurrence of the resonance state in the movable member 19 can be suppressed.

  (5) The reciprocating control is performed when the actual valve timing VT is shifted by a predetermined amount with respect to the target valve timing VTt after adjustment of the spool 30 to one of the first position P1 and the second position P2. This is realized by adjusting the spool 30 to the other one of the first position P1 and the second position P2, and repeating the adjustment of the spool 30. More specifically, after the adjustment of the spool 30 to the first position P1, when the actual valve timing VT is shifted to the advance side by a predetermined amount (1 ° CA) with respect to the target valve timing VTt), the second Adjustment of the spool 30 to the position P2 is performed. Furthermore, after the spool 30 is adjusted to the second position P2, when the actual valve timing VT is shifted to the retard side by a predetermined amount (1 ° CA) with respect to the target valve timing VTt, the first position P1 is reached. The spool 30 is adjusted. In the above-described reciprocating control, the adjustment of the spool 30 to the first position P1 and the adjustment of the spool 30 to the second position P2 are alternately and repeatedly performed so that the actual valve timing VT is maintained in a state where a resonance state occurs. Can be suppressed accurately.

In addition, the said embodiment can also be changed as follows, for example.
The reciprocating control is performed only when the learning of the upper limit duty ratio DF and the lower limit duty ratio DR in the learning control after the start of the internal combustion engine 1 is completed, but the above learning is completed. It may be carried out regardless of whether it is incomplete or incomplete. In this case, the VTt shifting process can be omitted.

  In the VTt shifting process, when performing feedback control for adjusting the actual valve timing VT to the target valve timing VTt, it is not always necessary to increase the gain of the control.

  The first position P1 used in the reciprocating control is a position where an interval corresponding to a 1% change in the duty ratio command value is placed in a direction deviating from the dead band upper limit F, but the interval is appropriately changed. Also good. In addition, the second position P2 used in the reciprocating control is a position where an interval corresponding to a 1% change in the duty ratio command value is placed in a direction deviating from the lower limit R of the dead zone, but the interval is appropriately changed. May be.

  The first position P1 may coincide with the upper limit F of the dead zone, and the second position P2 may coincide with the lower limit R of the dead zone. In this case, when the spool 30 is adjusted to the first position P1 or the second position P2, the oil supply / discharge to and from the advance-side hydraulic chamber 22 and the retard-side hydraulic chamber 23 is greater than that in the above embodiment. It is done little by little. By adjusting the hydraulic pressure in the advance side hydraulic chamber 22 and the hydraulic pressure in the retard side hydraulic chamber 23 through such oil supply and discharge, the movable member 19 is reciprocated more slowly and with a smaller width in the displacement direction. Can do.

  In the reciprocating control, the switching between the adjustment of the spool 30 to the first position P1 and the adjustment of the spool 30 to the second position P2 is performed by changing the actual valve timing VT to a predetermined amount (1 ° with respect to the target valve timing VTt). Although it is based on the fact that it has been shifted, the amount may be changed as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Combustion chamber, 3 ... Intake passage, 3a ... Intake port, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Crankshaft, 8 ... Exhaust passage, 11 ... Intake valve, DESCRIPTION OF SYMBOLS 11a ... Valve spring, 12 ... Intake cam shaft, 13 ... Throttle valve, 14 ... Exhaust valve, 14a ... Valve spring, 15 ... Exhaust cam shaft, 16 ... Valve timing variable mechanism, 17 ... Spring, 19 ... Movable member, 19a ... Vane, 20 ... case, 20a ... projection, 21 ... electronic control device (control means), 22 ... advance side hydraulic chamber, 23 ... retard side hydraulic chamber, 24 ... oil pump, 25 ... oil control valve, 26 ... Supply port, 27 ... discharge port, 28 ... advance port, 29 ... retard port, 30 ... spool, 31a ... spring, 31b ... electromagnetic solenoid, 32 ... airflow -Meter, 33 ... Cam position sensor, 34 ... Crank position sensor, 35 ... Throttle position sensor, 36 ... Accelerator pedal, 37 ... Accelerator position sensor, 41 ... Supply oil passage, 42 ... Oil pan, 43 ... Discharge oil passage, 44 ... Advance angle side oil passage, 45 ... retard angle side oil passage, 51 ... lock mechanism.

Claims (6)

A movable member that is displaced so as to change the relative rotational phase of the camshaft with respect to the crankshaft, a spring that biases the movable member toward a position other than the end of its displacement range, and the movable member that is used to displace the movable member An oil control valve for displacing the spool to supply and discharge oil to and from the advance side hydraulic chamber and the retard side hydraulic chamber, and when maintaining the relative rotational phase of the camshaft with respect to the crankshaft, In the control device for the variable valve timing mechanism that adjusts the spool to a position in the dead zone that is the displacement range of the spool capable of realizing
When the movable member vibrates in the displacement direction under the condition that the relative rotational phase of the camshaft with respect to the crankshaft is maintained at the position where the movable member is biased by the spring, the upper limit of the dead zone is reached. The first position, which is a position set in a direction away from the dead band with respect to the corresponding position or the upper limit , or a lower limit of the dead band or a gap set in a direction out of the dead band with respect to the lower limit. a control means for executing said spool adjustment to a second position corresponding to have the position,
When the spool is adjusted to the upper limit of the dead zone, oil can be supplied to the advance side hydraulic chamber, and when the spool is adjusted to the lower limit of the dead zone, oil is supplied to the retard side hydraulic chamber. Supply is possible,
When the control means performs the adjustment of the spool to the first position, and the measured value of the relative rotational phase deviates from the target phase by a predetermined amount on the advance side, the retard angle When the adjustment of the spool to the first position is completed to supply oil to the side hydraulic chamber, and the adjustment of the spool to the second position is being executed, the measured value of the relative rotational phase is The valve timing is characterized in that the adjustment of the spool to the second position is ended in order to supply oil to the advance side hydraulic chamber when a predetermined amount is shifted to the retard side with respect to the target phase. Control device for variable mechanism. The control means executes learning control for learning the upper limit and the lower limit of the dead zone, and when the learning of the upper limit and the lower limit of the dead zone by the learning control is completed, the learned upper limit and the lower limit are set. The control device for a variable valve timing mechanism according to claim 1 , wherein adjustment of the spool to the first position or the second position is executed based on the first position . The control device for a variable valve timing mechanism according to claim 2, wherein the first position matches an upper limit of the dead zone, and the second position matches a lower limit of the dead zone. The first position is a position set in a direction deviating from the dead band with respect to the upper limit of the dead band, and the second position is set in a direction deviating from the dead band with respect to the lower limit of the dead band. The control device for a variable valve timing mechanism according to claim 2, wherein the control device is at a position. The control means shifts the target phase of the relative rotational phase of the camshaft relative to the crankshaft by a predetermined amount when learning of the upper and lower limits of the dead zone by the learning control is incomplete, and after the shift The control device for a variable valve timing mechanism according to any one of claims 2 to 4, wherein the spool is displaced so that the relative rotational phase changes toward a target phase of the valve. After the adjustment of the spool to one of the first position and the second position, the control means is configured such that an actual value of a relative rotational phase of the camshaft with respect to the crankshaft is predetermined with respect to a target phase. when shifted by said first performs position and the spool adjustment to the second position the other of the valve timing according to any one of claims 1 to 5 to repeat the adjustment of these spool Control device for variable mechanism.