Reference position learning device of adjustable valve device

The present invention relates to a reference position learning device for a variable valve device that learns a control reference position when controlling a variable valve device for an internal combustion engine.

In recent years, in internal combustion engines installed in vehicles, valve opening / closing characteristics (valve timing, valve lift amount, valve opening period, etc.) of intake valves and exhaust valves have been improved for the purpose of improving output, reducing fuel consumption, reducing exhaust emissions, etc. Some are equipped with a variable valve device that can be changed.

For example, a variable valve device that changes the valve timing changes the valve timing of the intake valve and exhaust valve that are opened and closed by the camshaft by changing the rotation phase (camshaft phase) of the camshaft with respect to the crankshaft. I have to. At that time, when the camshaft phase is detected based on the output signal of the crank angle sensor and the output signal of the cam angle sensor and the variable valve device is controlled to the mechanical movable limit position (for example, the latest retard angle position). Learn with the camshaft phase as the reference position. Then, by controlling the variable valve device so that the actual advance angle amount of the current camshaft phase with respect to this reference position (that is, the actual advance angle amount of the valve timing) matches the target advance angle amount, the control accuracy of the valve timing is controlled. There is something to secure.

In an internal combustion engine provided with such a variable valve device, the intake air amount can be adjusted by varying the valve timing. However, as described above, in a system in which the mechanical movable limit position of the variable valve device is used as the reference position for variable valve control, the mechanical movable limit position (that is, the reference position) for each variable valve device due to manufacturing variations, changes over time, etc. ) And the variation of the intake air amount for each internal combustion engine, the relationship between the reference position of the variable valve control and the intake air amount is deviated, and there is a drawback that the control accuracy of the intake air amount by the variable valve control is lowered. ..

Therefore, for example, as described in Patent Document 1 (Patent No. 3161152), the variable valve device advances from the most retarded angle position with reference to the negative pressure of the intake pipe at the mechanicalmost retarded angle position. There is a method in which a control reference position is set on the corner side, and the reference position is corrected by using the advance angle amount of the valve timing and the change amount of the intake pipe negative pressure in a predetermined operating state.<patcit num="1"><text>Japanese Patent No. 3161152 (pages 6 to 7, Fig. 6, etc.)</text></patcit>

<p> However, the variable valve control system of Patent Document 1 is mechanical because the control reference position is set and corrected with reference to the negative pressure of the intake pipe at the mechanical maximum retardation position of the variable valve device. A variable valve device that does not have a movable limit position has a drawback that a reference position for variable valve control cannot be set.</p><p> The present invention has been made in consideration of such circumstances, and therefore, an object of the present invention is to be able to learn the control reference position without using the mechanical movable limit position of the variable valve device. A variable valve device that can learn accurate control reference positions that eliminate the effects of manufacturing variations and changes over time in variable valve devices and internal combustion engines, and can improve the accuracy of intake air volume control by variable valve control. The purpose is to provide a reference position learning device for the above.</p>

<p> In order to achieve the above object, the reference position learning device of the variable valve device according to claim 1 of the present invention controls a variable valve device that changes the valve opening / closing characteristics of the intake valve and / or the exhaust valve of the internal combustion engine. In a system that learns the control reference position at the time, the intake air amount of the internal combustion engine is detected by the intake air amount detecting means, and the control position of the variable valve device when the detected intake air amount matches a predetermined reference intake air amount. Is used as the control reference position and is learned by the reference position learning means.</p><p> In this way, the control reference position can be learned without using the mechanical movable limit position of the variable valve device, and the variable valve device that does not have the mechanical movable limit position can also be adopted. Moreover, even if there are variations in the mechanical movable limit position of each variable valve device due to manufacturing variations, changes over time, etc., and variations in the intake air amount for each internal combustion engine, the intake air amount at the control reference position is kept at a constant value (reference suction). Air volume), and it is possible to learn an accurate control reference position that eliminates the effects of manufacturing variations of variable valve devices and internal combustion engines, and improves the accuracy of intake air volume control by variable valve control. be able to.</p><p> By the way, since the intake air amount changes depending on the operating conditions of the internal combustion engine (for example, rotation speed, throttle opening, etc.), the control reference position (the detected intake air amount is the reference intake) under the operating conditions in which the influence on the intake air amount is significantly different. It is not possible to accurately learn the control reference position by learning the control position) that matches the amount of air.</p><p> Therefore, as in claim 2, it is preferable to control the variable valve device so that the detected intake air amount matches the reference intake air amount when the internal combustion engine is in a predetermined operating condition to learn the control reference position. .. In this way, the control reference position can be learned under the same operating conditions in which the influence on the intake air amount is the same, and the control reference position can be learned accurately.</p><p> Further, as the method for detecting the intake air amount, for example, as in claim 3, the detected intake air amount may be calculated based on the output of the air flow meter that detects the air flow rate in the intake pipe of the internal combustion engine. Since the air flow rate in the intake pipe changes according to the amount of intake air sucked into the cylinder of the internal combustion engine and the output of the air flow meter changes, the detected intake air amount can be calculated accurately by using the output of the air flow meter. be able to.</p><p> Further, as in claim 4, the detected intake air amount may be calculated based on the output of the intake pipe pressure sensor that detects the intake pipe pressure of the internal combustion engine. Since the intake pipe pressure changes according to the amount of intake air sucked into the cylinder of the internal combustion engine and the output of the intake pipe pressure sensor changes, the output of the intake pipe pressure sensor can be used to accurately determine the detected intake air amount. Can be calculated.</p><p> Further, as in claim 5, the detected intake air amount may be calculated based on the output of the in-cylinder pressure sensor that detects the in-cylinder pressure of the internal combustion engine. Since the in-cylinder pressure changes according to the amount of intake air sucked into the cylinder of the internal combustion engine and the output of the in-cylinder pressure sensor changes, the output of the in-cylinder pressure sensor can be used to accurately determine the detected intake air amount. Can be calculated. In this case, the in-cylinder pressure sensor may be provided only in the representative cylinder, but if the in-cylinder pressure sensor is provided for each cylinder, the calculation accuracy of the detected intake air amount can be improved.</p><p> Further, as in claim 6, the detected intake air amount may be calculated based on the output of the exhaust gas sensor that detects the air-fuel ratio or the oxygen concentration of the exhaust gas of the internal combustion engine and the fuel injection amount. Since the air-fuel ratio and oxygen concentration of the exhaust gas change according to the intake air amount and the fuel injection amount of the internal combustion engine, the output of the exhaust gas sensor changes. The amount of air can be calculated accurately.</p><p> The methods for detecting the intake air amount according to claims 3 to 6 may be carried out individually, but if they are carried out in appropriate combinations, the detection accuracy of the intake air amount can be improved.</p><p> By the way, since the detected intake air amount changes depending on the environmental conditions such as atmospheric pressure and temperature, the control reference position ( If the detected intake air amount is learned (the control position that matches the reference intake air amount), an error will occur in the learned value of the control reference position due to the difference in environmental conditions.</p><p> Therefore, as in claim 7, it is preferable to correct the detected intake air amount based on at least one of the atmospheric pressure, the intake air temperature, and the cooling water temperature. In this way, the control reference position can be learned using the detected intake air amount excluding the error due to the difference in the environmental conditions, and the accurate control reference position excluding the error due to the difference in the environmental conditions can be learned. be able to.</p>

Hereinafter, two Examples 1 and 2 in which the present invention is applied to a variable valve timing device for an intake valve will be described.

Example 1 of the present invention will be described with reference to FIGS. 1 to 5. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting the air flow rate in the intake pipe 12 is provided on the downstream side of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening degree is adjusted by a DC motor or the like and a throttle opening degree sensor 16 for detecting the throttle opening degree are provided.

Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and the surge tank 17 is provided with an intake pipe pressure sensor 18 for detecting the pressure in the intake pipe 12. Further, the surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached near the intake port of the intake manifold 19 of each cylinder. There is. Further, an ignition plug 21 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 21.

On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas, and the air-fuel ratio or richness of the exhaust gas is provided on the upstream side of the catalyst 23. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) that detects lean, etc. is provided. Further, a cooling water temperature sensor 25 for detecting the cooling water temperature is attached to the cylinder block of the engine 11.

Further, as shown in FIG. 2, in the engine 11, the power from the crankshaft 26 is transferred to the intake side camshaft 30 and the exhaust side camshaft 31 via the timing chains 27 (or timing belt) via the sprockets 28 and 29. It is supposed to be transmitted. Further, a motor-driven variable valve timing device 32 is provided on the intake side camshaft 30 side. By varying the rotation phase (camshaft phase) of the intake side camshaft 30 with respect to the crankshaft 26 by this variable valve timing device 32, the valve timing of the intake valve 33 driven to open and close by the intake side camshaft 30 can be changed. It has become.

Further, a cam angle sensor 34 that outputs a cam angle signal for each predetermined cam angle is attached to the outer peripheral side of the intake side cam shaft 30. On the other hand, on the outer peripheral side of the crankshaft 26, a crank angle sensor 35 that outputs a crank angle signal for each predetermined crank angle is attached.

The output signals of the various sensors described above are input to the engine control circuit (hereinafter referred to as "ECU") 36. This ECU 36 is mainly composed of a microcomputer, and by executing various engine control programs stored in the built-in ROM (storage medium), the fuel injection amount of the fuel injection valve 20 and the fuel injection amount of the fuel injection valve 20 can be adjusted according to the engine operating state. Controls the ignition timing of the spark plug 21.

Next, a schematic configuration of the variable valve timing device 32 will be described with reference to FIG. The phase variable mechanism 37 of the variable valve timing device 32 has an outer gear 38 with internal teeth arranged concentrically with the intake side camshaft 30 and an outer gear 38 with external teeth arranged concentrically on the inner peripheral side of the outer gear 38. It is composed of an inner gear 39 and a planetary gear 40 that is arranged between the outer gear 38 and the inner gear 39 and meshes with the inner gear 39. The outer gear 38 is provided so as to rotate integrally with the sprocket 28 which rotates in synchronization with the crankshaft 26, and the inner gear 39 is provided so as to rotate integrally with the intake side cam shaft 30. Further, the planetary gear 40 plays a role of transmitting the rotational force of the outer gear 38 to the inner gear 39 by turning around the inner gear 39 in a circular orbit in a state of being meshed with the outer gear 38 and the inner gear 39, and also the inner gear. By changing the rotation speed (revolution speed) of the planetary gear 40 with respect to the rotation speed of 39 (rotation speed of the intake side camshaft 30), the rotation phase of the inner gear 39 (that is, the camshaft phase) with respect to the outer gear 38 is adjusted. It has become.

On the other hand, the engine 11 is provided with a motor 41 for changing the turning speed of the planetary gear 40. The rotary shaft 42 of the motor 41 is arranged coaxially with the intake side camshaft 30, the outer gear 38, and the inner gear 39, and the rotary shaft 42 of the motor 41 and the support shaft 43 of the planetary gear 40 are connected to extend in the radial direction. It is connected via a member 44. As a result, as the motor 41 rotates, the planetary gear 40 can rotate (rotate) around the support shaft 43 while turning (revolving) the circular orbit around the inner gear 39. Further, the motor 41 is equipped with a motor rotation speed sensor 45 (see FIG. 1) that detects the rotation speed RM of the motor 41 (rotational speed of the rotation shaft 42).

When maintaining the current intake valve timing (valve timing of the intake valve 33), the variable valve timing device 32 matches the rotation speed RM of the motor 41 with the rotation speed RC of the intake side camshaft 30 to match the planetary gear. Match the rotation speed of 40 with the rotation speed of the inner gear 39 (rotation speed of the outer gear 38). As a result, the rotation phase of the inner gear 39 with respect to the outer gear 38 (that is, the camshaft phase) is maintained as it is, and the intake valve timing is maintained as it is.

When advancing the intake valve timing, the rotation speed RM of the motor 41 is made faster than the rotation speed RC of the intake side camshaft 30, and the revolution speed of the planetary gear 40 is made faster than the rotation speed of the inner gear 39. To do. As a result, the rotation phase of the inner gear 39 with respect to the outer gear 38 is advanced, and the intake valve timing is advanced.

On the other hand, when the intake valve timing is retarded, the rotation speed RM of the motor 41 is made slower than the rotation speed RC of the intake side camshaft 30, and the revolution speed of the planetary gear 40 is made slower than the rotation speed of the inner gear 39. To do. As a result, the rotation phase of the inner gear 39 with respect to the outer gear 38 is retarded, and the intake valve timing is retarded.

By executing each program for variable valve timing control shown in FIGS. 4 and 5 described later, the ECU 36 executes the camshaft phase VT (intake camshaft 30 with respect to the crankshaft 26) based on the cam angle signal and the crank angle signal. The actual advance angle amount ΔVT of the current camshaft phase VT (that is, the actual advance angle amount ΔVT of the intake valve timing) with respect to the control reference position VT0, which will be described later, matches the target advance angle amount ΔVTtg. The variable valve timing device 32 is feedback-controlled.

At that time, the ECU 36 is a variable valve timing device so that the detected intake air amount detected based on the output of the air flow meter 14 or the like matches the design reference intake air amount when the engine operating condition is a predetermined operating condition. By controlling 32 and learning the camshaft phase VT when the detected intake air amount matches the reference intake air amount as the control reference position VT0, the variable valve when the detected intake air amount matches the reference intake air amount. The control position of the timing device 32 is learned as the control reference position VT0.

Hereinafter, the processing contents of each program for variable valve timing control shown in FIGS. 4 and 5 executed by the ECU 36 will be described.

[Variable valve timing control]

The variable valve timing control program shown in FIG. 4 is executed at a predetermined cycle during engine operation. When this program is started, first, in step 101, the input time of the cam angle signal output from the cam angle sensor 34 and the input time of the crank angle signal output from the crank angle sensor 35 are read, and then the step Proceeding to 102, the cam shaft phase VT (rotation phase of the intake cam shaft 30 with respect to the crank shaft 26) is calculated based on the input time of the crank angle signal and the input time of the cam angle signal.

After that, the process proceeds to step 103, and whether or not the current control position of the variable valve timing device 32 is the control reference position VT0 is determined based on whether or not the current camshaft phase VT is the control reference position VT0.

As a result, when it is determined that the control reference position is VT0, the process proceeds to step 104, and the control reference position learning program shown in FIG. 5 described later is executed to learn the control reference position VT0. After that, the process proceeds to step 105, and the learning value of the control reference position VT0 stored in the rewritable non-volatile memory such as the backup RAM (not shown) of the ECU 36 is updated with the learning value of the control reference position VT0 this time. After that, the process proceeds to step 106.

On the other hand, if it is determined in step 103 that the control reference position is not VT0, the process proceeds to step 106 without learning and updating the control reference position VT0 (steps 104 and 105).

In this step 106, the target advance amount ΔVTtg of the intake valve timing according to the engine operating state or the like is calculated using a map or the like, and this target advance amount ΔVTtg is added to the control reference position VT0 to obtain the camshaft phase VT. Calculate the target value VTtg.

VTtg = VT0 + ΔVTtg After that, the process proceeds to step 107, and by controlling the variable valve timing device 32 so that the camshaft phase VT matches the target value VTtg, the actual advance angle amount of the intake valve timing with respect to the control reference position VT0. The variable valve timing device 32 is controlled so that ΔVT matches the target advance amount ΔVTtg.

[Control reference position learning]

The control reference position learning program shown in FIG. 5 executed in step 104 of FIG. 4 serves as a reference position learning means within the scope of claims. When this program is started, first, in step 201, it is determined whether or not it is in a learnable driving state (for example, an idle driving state), and if it is determined that it is not in a learnable driving state, step 202 This program is terminated without executing the subsequent processing related to control reference position learning.

On the other hand, if it is determined in step 201 that the driving state is learnable, the processing related to the control reference position learning after step 202 is executed as follows. First, in step 202, the throttle opening degree is fixed to a predetermined opening degree. Further, in a system equipped with an ISC (idle speed control) valve, the ISC valve opening is fixed at a predetermined opening. In this case, it is preferable that the predetermined opening degree for fixing the throttle opening degree and the ISC valve opening degree is set to an idle rotation speed slightly higher than the normal idle rotation speed in order to avoid engine stall. Further, the control amount (valve lift amount, EGR opening degree, etc.) of the intake system other than the intake valve timing is also fixed to a predetermined value.

In this way, after fixing the engine operating conditions during idle operation to predetermined operating conditions, the process proceeds to step 203, and the variable valve timing device 32 is controlled so that the camshaft phase VT becomes the design reference position. Here, the design reference position is, for example, a reference position set by assuming that the dimensional error and assembly error of all parts are the minimum values (0) at the design stage, and the initial value of the control reference position VT0 is It is set to this design reference position.

After that, the process proceeds to step 204, and the detected intake air amount is calculated based on the output of the air flow meter 14. Since the air flow rate in the intake pipe 12 changes according to the amount of intake air sucked into the cylinder of the engine 11, the output of the air flow meter 14 changes. Therefore, if the output of the air flow meter 14 is used, the detected intake air amount can be determined. It can be calculated with high accuracy. Further, in this step 204, the detected intake air amount is determined based on at least one of the atmospheric pressure detected by the atmospheric pressure sensor 46, the intake air temperature detected by the intake air temperature sensor 47, and the cooling water temperature detected by the cooling water temperature sensor 25. to correct. As a result, the detected intake air amount detected under the current environmental conditions is corrected to the detected intake air amount under the reference environmental conditions when the design reference intake air amount described later is set. The process of step 204 serves as an intake air amount detecting means in the claims.

After that, the process proceeds to step 205, and it is determined whether or not the detected intake air amount matches the design reference intake air amount. Here, the design reference intake air amount is, for example, the intake air amount at the reference position set by assuming that the dimensional error and the assembly error of all parts are the minimum values (0) at the design stage.

As a result, if it is determined that the detected intake air amount matches the reference intake air amount, this program is terminated while keeping the control reference position VT0 at the design reference position.

On the other hand, if it is determined in step 205 that the detected intake air amount does not match the reference intake air amount, the process proceeds to step 206 and the variable valve so that the detected intake air amount matches the reference intake air amount. Controls the timing device 32.

After that, the process proceeds to step 207, and when the detected intake air amount matches the reference intake air amount by learning the camshaft phase VT when the detected intake air amount matches the reference intake air amount as the control reference position VT0. The control position of the variable valve timing device 32 of is learned as the control reference position VT0. The learning value of the control reference position VT0 is stored in a rewritable non-volatile memory such as the backup RAM of the ECU36, and is stored and retained even when the engine is stopped, and the learning value of the control reference position VT0 can be used at the next engine operation. It has become like.

In the first embodiment described above, the control position of the variable valve timing device 32 when the detected intake air amount matches the design reference intake air amount is learned as the control reference position VT0. Therefore, the variable valve timing The control reference position VT0 can be learned without using the mechanical movable limit position (latest angle position or maximum advance angle position) of the device 32, and it is also used for variable valve devices that do not have a mechanical movable limit position. can do. Moreover, even if there are variations in the mechanical movable limit position for each variable valve timing device 32 and variations in the intake air amount for each engine 11 due to manufacturing variations, changes over time, etc., the intake air amount at the control reference position VT0 remains constant. (Reference intake air amount) can be used, and accurate control reference position VT0 that eliminates the effects of manufacturing variations and aging of the variable valve timing device 32 and engine 11 can be learned, and variable valve control is used. The accuracy of intake air amount control can be improved.

Further, in the first embodiment, when the engine operating condition is a predetermined operating condition, the variable valve timing device 32 is controlled so that the detected intake air amount matches the reference intake air amount to learn the control reference position VT0. Therefore, the control reference position VT0 can always be learned under the same operating conditions, and the control reference position VT0 can be learned accurately.

Moreover, in the first embodiment, the detected intake air amount is corrected based on the atmospheric pressure, the intake air temperature, the cooling water temperature, etc., and the detected intake air amount detected under the current environmental conditions is used as the detected intake air amount under the reference environmental conditions. Therefore, even under different environmental conditions, the control reference position VT0 can always be learned using the detected intake air amount under the reference environmental conditions, and accurate control that eliminates errors due to differences in environmental conditions. The reference position VT0 can be learned.

In the first embodiment, the detected intake air amount is corrected based on the atmospheric pressure, the intake air temperature, the cooling water temperature, and the like, but the reference intake air amount may be corrected instead of the detected intake air amount.

Further, in the first embodiment, the detected intake air amount is calculated based on the output of the air flow meter 14, but the detected intake air amount may be calculated based on the output of the intake pipe pressure sensor 18. Since the intake pipe pressure changes according to the amount of intake air sucked into the cylinder of the engine 11 and the output of the intake pipe pressure sensor 18 changes, the output of the intake pipe pressure sensor 18 can be used to determine the detected intake air amount. It can be calculated with high accuracy.

Further, an in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine 11 may be provided, and the detected intake air amount may be calculated based on the output of the in-cylinder pressure sensor. Since the in-cylinder pressure changes according to the amount of intake air sucked into the cylinder of the engine 11 and the output of the in-cylinder pressure sensor changes, the output of the in-cylinder pressure sensor can be used to accurately determine the detected intake air amount. Can be calculated. In this case, the in-cylinder pressure sensor may be provided only in the representative cylinder, but if the in-cylinder pressure sensor is provided for each cylinder, the calculation accuracy of the detected intake air amount can be improved.

Further, the detected intake air amount may be calculated based on the output of the exhaust gas sensor 24 and the fuel injection amount. Since the air-fuel ratio changes according to the intake air amount and the fuel injection amount of the engine 11 and the output of the exhaust gas sensor 24 changes, the detected intake air amount can be accurately detected by using the output of the exhaust gas sensor 24 and the fuel injection amount. It can be calculated well.

These methods for detecting the amount of intake air may be carried out individually, but if they are carried out in combination as appropriate, the accuracy of detecting the amount of intake air can be improved.

In Example 2 of the present invention, the movable range of the camshaft phase VT is divided into a plurality of learning regions by executing the variable valve timing control program shown in FIG. 6, and the control reference position VT0 is learned for each learning region. I try to do it.

In the variable valve timing control program shown in FIG. 6, after calculating the camshaft phase VT based on the cam angle signal and the crank angle signal (steps 301 and 302), the process proceeds to step 303 and corresponds to the current camshaft phase VT. Read the control reference position VT0 of the learning area to be used.

After that, the process proceeds to step 304, and it is determined whether or not the current camshaft phase VT is the control reference position VT0 in the corresponding learning region. As a result, if it is determined that the control reference position is VT0, the process proceeds to step 305, and the control reference position learning program shown in FIG. 5 described above is executed to learn the control reference position VT0 in the corresponding learning area. ..

Specifically, after fixing the engine operating conditions during idle operation to predetermined operating conditions, the variable valve timing device 32 is set so that the detected intake air amount matches the design reference intake air amount in the corresponding learning area. Control and learn the camshaft phase VT when the detected intake air amount matches the reference intake air amount as the control reference position VT0 in the corresponding learning area.

After that, the process proceeds to step 306, and the learning value of the control reference position VT0 stored in the corresponding learning area is updated with the learning value of the control reference position VT0 this time.

After that, the process proceeds to step 307, and the target advance amount ΔVTtg of the intake valve timing according to the engine operating state or the like is calculated from a map or the like in the corresponding learning area, and the target advance amount ΔVTtg is controlled in the corresponding learning area. Calculate the target value VTtg of the camshaft phase VT by adding it to the reference position VT0. VTtg = VT0 + ΔVTtg

After that, the process proceeds to step 308, and by controlling the variable valve timing device 32 so that the camshaft phase VT matches the target value VTtg, the actual advance angle amount of the intake valve timing with respect to the control reference position VT0 in the corresponding learning area. The variable valve timing device 32 is controlled so that ΔVT matches the target advance amount ΔVTtg.

In the second embodiment described above, the movable range of the camshaft phase VT is divided into a plurality of learning regions, and the control reference position VT0 is learned for each learning region, so that the variable valve timing control accuracy is further improved. Can be made to.

In each of the above Examples 1 and 2, the control reference position is learned in the idle operation state, but the present invention is not limited to this, and a stable operation state (for example, a fuel cut period, a steady operation state, etc.) At this time, the control reference position may be learned.

Further, in the above Examples 1 and 2, the present invention is applied to a variable valve timing device that changes the valve timing of the intake valve, but the present invention is a variable that changes the valve lift amount and the valve opening period of the intake valve. It can be widely applied to a valve device, a variable valve device that changes the valve opening / closing characteristics (valve timing, valve lift amount, at least one of valve opening period) of an exhaust valve, and the like.

Further, the present invention is not limited to the motor-driven variable valve device, but can also be applied to a hydraulically driven variable valve device and an electromagnetically driven valve whose valve opening / closing characteristics can be changed.

<figref num="1">It is a schematic block diagram of the whole engine control system in Example 1 of this invention.</figref><figref num="2">It is a schematic block diagram of a variable valve timing control system.</figref><figref num="3">It is a schematic block diagram of the variable valve timing device.</figref><figref num="4">It is a flowchart which shows the process flow of the variable valve timing control program of Example 1.</figref><figref num="5">It is a flowchart which shows the processing flow of the control reference position learning program.</figref><figref num="6">It is a flowchart which shows the process flow of the variable valve timing control program of Example 2.</figref>

Code description

11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 21. .. Ignition plug, 22 ... Exhaust pipe, 24 ... Exhaust gas sensor, 25 ... Cooling water temperature sensor, 32 ... Variable valve timing device, 33 ... Intake valve, 34 ... Cam angle sensor , 35 ... Crank angle sensor, 36 ... ECU (Intake air amount detection means, Reference position learning means)