JP5375245B2 - Control device for variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a variable valve timing (VVT) mechanism capable of imparting a performance chance for valve timing control even in engine cold time. <P>SOLUTION: An electronic control unit 16 controls a VVT mechanism 15 capable of varying the valve timing of an engine valve by being driven by supply of oil, and detects responsiveness of the VVT mechanism 15 at its time by driving the VVT mechanism 15 in the engine cold time, and determines whether the VVT mechanism 15 can be surely moved backward to the most ignition timing advance position being an initial position when stopping an engine, based on its detection result. The electronic control unit 16 permits the performance of cold valve timing control by driving the VVT mechanism 15 on condition of being determined as being surely movable backward to the initial position. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a control device for a variable valve timing mechanism that is driven by oil supply to vary the valve timing of an engine valve.

  As is well known, a hydraulic variable valve timing mechanism (VVT mechanism) that is driven by oil supply to vary the valve timing of an engine valve (intake / exhaust valve) as a mechanism employed in an on-board internal combustion engine. Is in practical use. Conventionally, devices disclosed in Patent Documents 1 and 2 are known as devices for diagnosing such abnormality of the VVT mechanism.

  In the diagnostic device of Patent Document 1, a state in which the deviation between the target value and the actual value of the displacement angle of the VVT mechanism is equal to or greater than a predetermined determination value is a determination time set based on the engine speed and the oil temperature of the VVT mechanism. When the above is continued, it is determined that there is an abnormality in the VVT mechanism. Note that when the oil temperature is low, the viscosity of the oil increases, so that the responsiveness of the VVT mechanism decreases even if it is not abnormal. Therefore, in the diagnostic device of Patent Document 1, when the oil temperature is low, the determination time is set longer to distinguish between a decrease in responsiveness due to an increase in oil viscosity and a decrease in responsiveness due to abnormality. Can be diagnosed.

  Further, in the diagnostic device of Patent Document 2, it is determined that there is an abnormality in the VVT mechanism when the operating speed of the VVT mechanism is equal to or lower than a determination value. In the same diagnostic device, when the oil temperature is low, the determination value is set to a small value to distinguish between a decrease in responsiveness due to an increase in oil viscosity and a decrease in responsiveness due to abnormality. The diagnosis is made possible.

Japanese Patent Laid-Open No. 11-247873 JP 10-31802 A

  By the way, in such a VVT mechanism, when the engine is cold, the viscosity of the oil becomes too high, and the responsiveness of the VVT mechanism is extremely lowered. Therefore, conventionally, when the engine is cold, valve timing control by driving the variable valve timing mechanism is prohibited. One of the prohibitions of valve timing control when the engine is cold is as follows. That is, in many of the VVT mechanisms, the initial position located at the time of starting the engine is set to one end of the operating range, that is, the most advanced angle position or the most retarded angle position, and the operation of the VVT mechanism is performed while the engine is stopped. It is mechanically locked at its initial position. In order to ensure the startability of the internal combustion engine, it is necessary to reliably return the VVT mechanism to the initial position when the engine is stopped. However, when the engine is cold, even if it is not abnormal, the responsiveness of the VVT mechanism is remarkably deteriorated, and it is difficult to guarantee the return to the initial position when the engine is stopped.

  In recent years, it has been required to ensure high emission performance even before the activation of a catalyst for exhaust purification, and in order to meet this demand, implementation of valve timing control in a low temperature environment is demanded. For example, if the valve timing of the exhaust valve is retarded before the activation of the catalyst, the expansion process of the internal combustion engine becomes longer, and the combustion time of the air-fuel mixture in the cylinder is extended. Emission can be suppressed. However, in a low temperature environment in which the viscosity of the oil is greatly increased and the responsiveness of the VVT mechanism is significantly deteriorated, the return to the initial position of the VVT mechanism when the engine is stopped cannot be guaranteed, so that the oil temperature rises sufficiently. Until now, the implementation of valve timing control must be abandoned.

  The present invention has been made in view of such a situation, and a problem to be solved is to provide a control device for a variable valve timing mechanism that can give an opportunity to perform valve timing control even when the engine is cold. There is to do.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention according to claim 1 is a control device for a variable valve timing mechanism that is driven by oil supply to vary the valve timing of the engine valve. To detect the responsiveness of the variable valve timing mechanism at that time, and at the same time to the initial position that is located at the start of the engine and set at one end of the operating range of the variable valve timing mechanism when the engine is stopped. A determination unit that determines whether or not the variable valve timing mechanism can be reliably moved back based on a detection result thereof, and that the determination unit determines that the variable valve timing mechanism can be moved back to the initial position and that the vehicle is running it on condition is, the implementation of the valve timing control when the engine is cold in by driving the variable valve timing mechanism Comprising a permission unit that variable, wherein the determining means, throttle opening degree, on condition that one of the accelerator operation amount and the engine rotational speed is not less than the determination value, the variable valve according to the detection of the response Even if the engine is stopped while the timing mechanism is being driven, it is confirmed that the variable valve timing mechanism can be reliably moved back to the initial position, and the responsiveness is determined on the condition that the same is confirmed. The gist of the invention is to allow the variable valve timing mechanism to be driven according to detection of the responsiveness and to drive the variable valve timing mechanism according to the responsiveness detection in a direction away from the initial position .

  In the above configuration, when the engine is cold, the variable valve timing mechanism is driven and its response is detected, and whether or not the variable valve timing mechanism can be reliably returned to the initial position when the engine is stopped is determined from the detected response. Is determined. When the engine can be returned to the initial position when the engine is stopped, execution of valve timing control is permitted.

  In principle, even when the engine is cold, for which valve timing control is prohibited, when oil with low viscosity is used, it may be possible to return to the initial position when the engine is stopped. In such a case, the valve timing control by driving the variable valve timing mechanism can be performed to some extent. In the above configuration, instead of giving up the valve timing control when the engine is cold, it is possible to determine whether or not the variable valve timing mechanism can be returned to the initial position when the engine is stopped. For example, the valve timing control when the engine is cold is permitted. That is, in the control apparatus for the variable valve timing mechanism of the present invention, when the engine is cold, in which the valve timing control is basically prohibited, an opportunity to perform the valve timing control by actively searching for a condition that allows the valve timing control to be performed. To find out. Therefore, it is possible to provide an opportunity for performing valve timing control even when the engine is cold, and as a result, it is possible to improve the emission performance when the engine is cold.

  Here, the engine cold state does not mean before the completion of warm-up of the internal combustion engine, but refers to a time when the oil temperature is low before normal variable valve timing control becomes impossible.

Incidentally, Many of the variable valve timing mechanism, the initial position is to be located when the engine is started, is set at one end of its operating range, i.e. the most advanced position and the most retarded position. In such a case, the first drive of the variable valve timing mechanism after engine startup is performed in a direction away from the initial position. That is, when the initial position is set to the most advanced position, the first drive of the variable valve timing mechanism after the engine is started is performed in the retard direction. When the initial position is set to the most retarded position, the first drive of the variable valve timing mechanism after the engine is started is performed in the advance direction.

In this regard, in the above-described configuration, the variable the initial position at one end of the operating range of the valve timing mechanism is set, the variable valve timing determining means to perform in a direction away from the initial position driving mechanism according to the detection of the response due to the configuration, and it is possible to perform the first of the determination at the time of driving the variable valve timing mechanism after engine startup. Therefore, the valve timing control can be performed early when the engine is cold.

Incidentally, the internal combustion engine may be suddenly stopped even during the driving of the variable valve timing mechanism related to the detection of the responsiveness for the determination. In such a case, depending on the situation, the variable valve timing mechanism may not be returned to the initial position when the engine is stopped. Therefore, in the above configuration, even if the engine is stopped during the driving of the variable valve timing mechanism related to the response detection, it has been confirmed that the variable valve timing mechanism can be reliably returned to the initial position. The determination means is configured to allow driving of the variable valve timing mechanism related to the responsiveness detection . Thus , only when the time required for returning to the initial position can be sufficiently secured before the internal combustion engine is stopped, the drive for detecting the responsiveness for the above determination is permitted. As a result, the return to the initial position of the variable valve timing mechanism when the engine is stopped can be guaranteed. More specifically, throttling opening, as a condition that any one of the accelerator operation amount and the engine rotational speed is equal to or larger than the reference value, so as to permit the driving of the variable valve timing mechanism according to the detection responsiveness By configuring the determination means, it is possible to guarantee the return to the initial position even in the event of a sudden engine stop during driving related to the determination.

Further, when the vehicle is running, it is necessary to go through a process of vehicle deceleration → vehicle stop → ignition off operation until the engine stops, and there is a sufficient time until the engine stops. Therefore, if the execution of the valve timing control when the engine is cold is permitted only while the vehicle is running, the condition relating to the determination that the engine can be returned to the initial position when the engine is stopped can be relaxed. . Therefore, in the above arrangement, the condition that the vehicle is traveling, at Rukoto configure the permission means to allow the implementation of the valve timing control when the engine is cold, the variable valve timing mechanism only while the vehicle is traveling Therefore, it is only necessary to guarantee the return to the initial position of the engine, and the opportunity for performing the valve timing control when the engine is cold can be increased.

The determination as to whether or not the vehicle is running can be made based on the gear stage of the in-vehicle transmission, the vehicle speed, the throttle opening, and the accelerator operation amount. Thus, for example, as described in claim 2, there gear-vehicle transmission in drive range and the vehicle speed, on condition that one of the throttle opening and the accelerator operation amount is equal to or larger than the reference value, the vehicle is traveling In this case, the permitting means may be configured to permit the operation of the variable valve timing mechanism when the engine is cold. In such a case, as described in claim 3 , the permission means allows the vehicle speed, throttle opening, and accelerator operation amount at which the operation of the variable valve timing mechanism is permitted to be variable according to the oil temperature. Also good. The time required to return to the initial position changes due to the change in the viscosity of the oil according to the oil temperature. By changing the permitted vehicle speed and the permitted accelerator operation amount according to the oil temperature, the variable valve timing The operation of the mechanism can be allowed in a wider range.

Even when the oil viscosity is high and the responsiveness of the variable valve timing mechanism is low, it may be possible to return to the initial position unless the variable valve timing mechanism has a large displacement angle. Therefore, as described in claim 4 , if the target displacement angle of the variable valve timing mechanism when the permission means permits the execution of the valve timing control is made variable in accordance with the oil temperature, the rebound can be achieved. The control mode of the variable valve timing mechanism can be adapted to the required change in time.

Since the responsiveness of the variable valve timing mechanism is low when the engine is cold, precise valve timing control after completion of warm-up is not desired. Therefore, when the engine is cold, it is desirable to simplify the control even if the operation of the variable valve timing mechanism is permitted. The simplification of the valve timing control is performed, for example, as described in claim 5 by using a map for calculating the target displacement angle of the variable valve timing mechanism when the permission means permits the execution of the valve timing control as an engine speed. In a three-dimensional orthogonal coordinate system in which the engine load and the target displacement angle are the x-axis, y-axis, and z-axis, respectively, a mesa shape having the xy-axis plane as the bottom surface and the z-axis as the height direction is formed. This can be realized by using a three-dimensional map.

As described above, according to the valve timing control when the engine is cold, it is possible to improve the emission performance before the catalyst warm-up is completed. Therefore, if the purpose is only to improve the emission performance before the catalyst warm-up is completed, the operation of the variable valve timing mechanism when the engine is cold is allowed only before the activation of the catalyst as described in claim 6. The above permission means may be configured.

In valve timing control, responsiveness and convergence are improved by learning a control command value (holding command value) of a variable valve timing mechanism necessary for maintaining a constant displacement angle. However, when the engine is cold, the oil viscosity is high, and the responsiveness and convergence are poor, making it difficult to accurately learn the holding command value. Also, when the engine is cold, the change in responsiveness due to the oil temperature is significant, and the oil temperature or the engine cooling water temperature correlated therewith can be largely reflected in the valve timing control. For example, the feedback gain can be changed according to the oil temperature. Is desirable. Therefore, as described in claim 7 , when the engine is cold, the correction map of the proportional term in the feedback control of the displacement angle of the variable valve timing mechanism is calculated based on the deviation between the actual displacement angle and the target displacement angle of the variable valve timing mechanism and the engine coolant temperature. Alternatively, a two-dimensional map with the oil temperature may be used, and learning of the control command value of the variable valve timing mechanism necessary for keeping the displacement angle constant may be prohibited. In this case, since learning of the holding command value is prohibited when the engine is cold, it is possible to avoid learning an inappropriate value for the holding command value. In addition, the convergence of the valve timing control is improved by making the correction map of the feedback proportional term a two-dimensional map of the deviation between the actual displacement angle and the target displacement angle of the variable valve timing mechanism and the engine cooling water temperature or oil temperature. Will be able to.

When low-temperature, high-viscosity oil whose responsiveness deteriorates is used, a constant response delay occurs when the valve timing is changed regardless of the engine speed. In order to perform the determination in consideration of this, as described in claim 8 , the initial position is determined by whether or not the time during which the displacement angle of the variable valve timing mechanism is equal to or greater than the determination line is equal to or greater than the determination value. The determination means is configured to determine whether or not reliable return movement is possible, and the determination line is held at “0” until a predetermined time has elapsed from the start of operation of the variable valve timing mechanism, and thereafter It may be set so that the value gradually increases with the passage of time.

Even if it is determined that the operation of the variable valve timing mechanism is impossible, the variable valve timing mechanism may become operable after the engine coolant temperature or the oil temperature of the variable valve timing mechanism rises to some extent. Therefore, as described in claim 9, after the reliable backward to the initial position is once determined impossible even, at least one of the engine cooling water temperature and the oil temperature is waiting for timing elevated above the determination value, the If the determination means is configured to perform the determination again, the opportunity for performing the valve timing control when the engine is cold can be further increased.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the whole structure about the control apparatus of the variable valve timing mechanism which concerns on one Embodiment of this invention. The graph which shows the relationship between engine stop time, VVT return time, and oil temperature. The graph which shows the relationship between VVT operation time from the most advanced position to the most retarded position VVT operation time, the most retarded position to the most advanced position, and the oil temperature. Regarding the determination line in the responsiveness determination control applied to the above embodiment, (a) shows a setting mode when the response delay is not considered, and (b) shows a setting mode when the response delay is considered. chart. The time chart which shows an example of the control aspect of the responsiveness determination control applied to the embodiment. The flowchart of the implementation determination routine of the responsiveness determination control employ | adopted as the same embodiment. The flowchart of the responsiveness determination control routine employ | adopted as the same embodiment. The flowchart of a responsiveness determination control routine. The graph which shows the setting aspect of the cold target displacement angle map applied to the embodiment. The graph which shows the setting aspect of the target displacement angle map at the time of a warm applied to the embodiment. The graph which shows the setting aspect of the upper limit guard value of the target displacement angle applied to the embodiment. The flowchart of the execution determination routine of cold VVT control employ | adopted as the embodiment. The flowchart of the target displacement angle calculation routine of the cold VVT control employ | adopted as the embodiment. The graph which shows the setting aspect of the calculation map of the control command value of the VVT mechanism applied to the embodiment. The graph which shows the setting aspect of the water temperature correction factor calculation map of the control command value of the VVT mechanism applied to the embodiment. The time chart which shows an example of the control aspect of the cold time VVT control in the embodiment. The time chart which shows the other example of the control aspect of the cold VVT control in the embodiment. The graph which shows the setting aspect of the permission vehicle speed of the cold VVT control in other Embodiment 1 of this invention. The graph which shows the setting aspect of the target displacement angle upper limit guard value of the cold VVT control in other Embodiment 2 of this invention.

Hereinafter, an embodiment of a control device for a variable valve timing mechanism according to the present invention will be described in detail with reference to FIGS.
FIG. 1 shows the overall structure of a control apparatus for a variable valve timing mechanism according to the present embodiment. Note that the control device for the variable valve timing mechanism of the present embodiment is configured as a device that controls the variable valve timing mechanism that makes the valve timing of the exhaust valve of the in-vehicle internal combustion engine variable.

  The oil pump 11 pumps oil from the oil pan 10, pressurizes the oil control valve 12, and discharges it. The oil control valve 12 is connected to a variable valve timing mechanism (VVT) 15 via an advance oil passage 13 and a retard oil passage 14. The VVT mechanism 15 operates based on the hydraulic pressure applied via the advance oil passage 13 and the retard oil passage 14, and changes the relative rotational phase of the exhaust camshaft with respect to the crankshaft of the internal combustion engine, thereby providing an exhaust valve. The valve timing is configured to be changed.

  The oil control valve 12 operates by receiving a duty signal from the electronic control unit 16 as a control command value, and applies hydraulic pressure to the VVT mechanism 15 via the advance oil passage 13 and the retard oil passage 14. Alternatively, the hydraulic pressure drain from the VVT mechanism 15 is adjusted. The VVT mechanism 15 operates as follows. First, when the oil control valve 12 applies the hydraulic pressure via the advance oil passage 13 and drains the oil pressure via the retard oil passage 14, the VVT mechanism 15 rotates the exhaust camshaft to the advance side. Advance the valve timing of the exhaust valve. When the hydraulic pressure is applied from the oil control valve 12 through the retarded oil passage 14 and the hydraulic pressure is drained through the advanced oil passage 13, the VVT mechanism 15 rotates the exhaust camshaft to the retarded side. , Retard the valve timing of the exhaust valve. On the other hand, when the oil control valve 12 is neutral and the hydraulic pressure applied via the advance oil passage 13 and the hydraulic pressure applied via the retard oil passage 14 are balanced, the VVT mechanism 15 is a valve of the exhaust valve. Keep the timing constant.

  In this VVT mechanism 15, the initial position that is located when the engine is started is set at the end on the advance side of the operating range of the VVT mechanism 15, that is, the most advanced position. The VVT mechanism 15 is mechanically locked at its most advanced position by a built-in lock mechanism while the engine is stopped.

  Incidentally, in the following description, the operation amount of the VVT mechanism 15 is indicated by a displacement angle [°] of the VVT mechanism 15 toward the retarded angle with the most advanced angle position which is the initial position as a reference “0 °”. In this VVT mechanism 15, the maximum displacement angle toward the retarded angle in the control is set to “35 °”.

  On the other hand, the electronic control unit 16 is input with detection signals from various sensors 17 that detect the operating condition of the internal combustion engine and the traveling condition of the vehicle. Examples of such sensors include a water temperature sensor that detects the temperature of engine cooling water, an oil temperature sensor that detects the temperature of engine oil, an intake air temperature sensor that detects the temperature of intake air, a throttle sensor that detects the opening of a throttle valve, and an internal combustion engine There are an air flow meter that detects the intake air amount of the engine, a crank angle sensor that detects the rotational phase of the crankshaft, a cam angle sensor that detects the rotational phase of the camshaft, a vehicle speed sensor that detects the vehicle speed, and the like.

(Responsiveness judgment control)
Next, responsiveness determination control performed when the engine is cold will be described.
When the engine is cold, the viscosity of the oil used for the operation of the VVT mechanism 15 is high, and sufficient responsiveness cannot be ensured. Therefore, precise valve timing control as when the engine is warm cannot be desired at all. Nonetheless, even when the engine is cold, the VVT mechanism 15 is driven with low responsiveness and, although limited, performs valve timing control to improve emissions before the exhaust purification catalyst is activated. A certain effect can be obtained. Therefore, the implementation of valve timing control is required even when the engine is cold, but there are the following obstacles to its realization.

  That is, if the VVT mechanism 15 is located at a position other than the most advanced angle position, which is the initial position, at the time of starting the engine, a significant hindrance occurs in starting the internal combustion engine. Therefore, it is necessary to position the VVT mechanism 15 at the most advanced angle position when the engine is started. For this purpose, it is necessary to return the VVT mechanism 15 to the most advanced position when the engine is stopped. However, since the responsiveness of the VVT mechanism 15 is remarkably lowered when the engine is cold, there is a possibility that when the VVT mechanism 15 is operated, the VVT mechanism 15 cannot be returned to the most advanced position when the engine is stopped. . Of course, from the standpoint of startability of the internal combustion engine, the inability to return to the most advanced position of the VVT mechanism 15 when the engine is stopped is unacceptable. Therefore, valve timing control when the engine is cold is not possible when the engine is stopped. If the return to the most advanced position is not guaranteed, it cannot be performed.

  Therefore, in this embodiment, when the engine is cold, the responsiveness of the VVT mechanism 15 is verified, and the valve timing control when the engine is cold is performed on the condition that the return to the most advanced position when the engine is stopped can be guaranteed. To allow. More specifically, the VVT mechanism 15 is driven to detect its responsiveness when the engine is cold, and the VVT mechanism 15 is reliably restored to its most advanced position, which is its initial position, when the engine is stopped from the detected responsiveness. It is determined whether or not the engine can be moved. When it is determined that the engine can be moved backward, the execution of the valve timing control when the engine is cold is permitted.

  Here, the relationship between the responsiveness of the VVT mechanism 15, the engine stop time, and the oil temperature will be considered. FIG. 2 shows how the operating time of the VVT mechanism 15 changes from the displacement angle “35 °” to the displacement angle “0 °” depending on the oil temperature. Also shown in the figure is a one-dot chain line showing how the engine stop time from the state where the engine is stopped at the engine speed “1500 rpm”, that is, the time from the start of the engine stop operation to the stop of the internal combustion engine due to the oil temperature. Are also shown.

  As shown in the figure, when the oil temperature is “4 ° C.” or less, the operation time of the VVT mechanism 15 exceeds the engine stop time, and the return to the most advanced position when the engine is stopped cannot be guaranteed. In this case, the valve timing control cannot be performed at an extremely low temperature when the oil temperature is below freezing point.

  However, this is based on the premise that the engine is stopped from a stopped state. If the engine is stopped only when the vehicle is running, the vehicle is decelerated → the vehicle is stopped → the ignition until the engine is stopped. It is necessary to go through a process such as turning off, so that the return to the most advanced position can be delayed. Therefore, in the present embodiment, the valve timing control when the engine is cold is performed only while the vehicle is running, so that the valve timing control when the engine is cold is allowed in a wider temperature range. .

  Note that the operation time of the VVT mechanism 15 shown in FIG. 2 is based on the premise that standard oil is used, and the operation time varies depending on the properties of the oil in use. In addition, the operation time varies depending on individual differences of the VVT mechanism 15 and its hydraulic system and the state of deterioration over time. Therefore, in order to increase the opportunity for performing the valve timing control when the engine is cold as much as possible, it is necessary to confirm the actual responsiveness of the VVT mechanism 15 and verify whether the valve timing control can be performed.

  The responsiveness of the VVT mechanism 15 that needs to be confirmed here relates to the backward movement to the most advanced position, that is, the operation of the VVT mechanism 15 to the advanced angle side. However, as described above, the VVT mechanism 15 is positioned at the most advanced angle position when the engine is started, and the confirmation of the responsiveness of the VVT mechanism 15 with respect to the operation toward the advanced angle side is once performed by retarding the VVT mechanism 15. This can only be done after driving to the side, and verification of responsiveness takes time.

  FIG. 3 shows the verification results of the operation speed for each of the drive to the advance side and the drive to the retard side of the VVT mechanism 15. In the figure, when the two types of oils “10W30” and “20W50” are used, the drive of the VVT mechanism 15 on the retard side from the displacement angle “0 °” to the displacement angle “35 °”, the displacement angle “ The relationship between the operation time of each drive of the VVT mechanism 15 and the oil temperature with respect to the advance side from 35 ° to the displacement angle “0 °” is shown. As is clear from the figure, there is a clear correlation between the change tendency of the operation time toward the advance side and the operation time toward the retard side with respect to the oil temperature. Therefore, from the detection result of the responsiveness of the VVT mechanism 15 toward the retarded side, that is, in the direction away from the most advanced angle position which is the initial position, the responsiveness of the VVT mechanism 15 in the backward movement to the most advanced angle position. Can be roughly estimated. Therefore, in the present embodiment, the responsiveness of the VVT mechanism 15 is detected when the VVT mechanism 15 is first driven after the engine is started with respect to the retarded side, and the VVT mechanism 15 is set to the most advanced position when the engine is stopped. It is determined based on the detection result whether or not it is possible to reliably return the actuator.

  Here, an outline of the control (responsiveness determination control) related to the determination of the responsiveness regarding whether or not to return to the most advanced angle position when the engine is stopped in the present embodiment will be described. The determination of responsiveness in the present embodiment is largely performed in the following manner. That is, in the present embodiment, a time (OK time) in which the actual displacement angle of the VVT mechanism 15 after the start of driving for responsiveness determination exceeds a preset determination line (OK time) is measured, and the time is specified. Whether it is possible to return to the most advanced position when the engine is stopped is determined based on whether or not it is equal to or greater than a determination value (VVT control permission determination time).

  Next, the setting of the determination line related to the determination of responsiveness as described above will be considered. As a determination line setting mode, as shown in FIG. 4A, first, a line setting that gradually increases with time from the time t0, which is the start of driving of the VVT mechanism 15 related to responsiveness determination, is considered. It is done. In this case, if the actual displacement angle of the VVT mechanism 15 has always exceeded the determination line as shown by the broken line A in the figure, of course, the return to the most advanced angle position when the engine is stopped is of course. Is determined to be possible (OK determination).

  By the way, when using deteriorated oil with high low temperature viscosity, it has been confirmed that the actual displacement angle of the VVT mechanism 15 rises very slowly after the start of driving. In this case, the actual displacement angle of the VVT mechanism 15 after the start of driving changes as indicated by a broken line B in FIG. When the actual displacement angle changes as shown by the broken line B in the figure, if the judgment line is set as shown in the figure, the actual displacement angle is below the judgment line until time t1, and the engine is stopped. It is determined that the backward movement to the most advanced position at that time is impossible (NG determination).

  However, even when the actual displacement angle changes as shown by the broken line B, if the actual displacement angle has reached the vicinity of the target displacement angle within the specified time, the most advanced angle when the engine is stopped Returning to position may be possible. Therefore, in the present embodiment, in consideration of the response delay of the actual displacement angle in such a case, the determination line is set as shown in FIG. That is, in this embodiment, the value is held at “0” from time t0 when the operation of the VVT mechanism 15 is started until time t2 when a predetermined time has elapsed, and thereafter, the value gradually increases as time elapses. Judgment lines are set to do this. In such a case, the OK determination is made not only when the actual displacement angle changes as shown by the broken line A in the figure but also when the actual displacement angle changes as shown by the broken line B.

  Next, details of the responsiveness determination control will be described with reference to FIG. The responsiveness determination control in the present embodiment is performed through four stages from stage 0 to stage 3.

  In stage 0, monitor preparation is performed, that is, preparation for detection of responsiveness of the VVT mechanism 15 related to responsiveness determination is performed. Specifically, in stage 0, when the target displacement angle and actual displacement angle of VVT mechanism 15 are both at the most advanced angle position, the target displacement angle exceeds the monitor start target displacement angle determination value, that is, the target displacement angle. It is a period until it is confirmed that the change has been started. In the case of FIG. 5, the period ga up to time t3 corresponds to stage 0.

  When the change of the target displacement angle related to the responsiveness determination is started at time t3, the stage 1 is shifted from time t3. Stage 1 is a step response detection period. Specifically, the stage 1 is continued until the establishment time of the precondition for the responsiveness determination exceeds the specified establishment determination time C2, and the target displacement angle exceeds the step response determination value. That is, the stage 1 reaches the later of the time t4 when the target displacement angle exceeds the step response determination value and the time t5 when the establishment time exceeds the establishment determination time C2 (time t5 in the case of the figure).

  When stage 1 ends, stage 2, which is a period of waiting for responsive stability, is started. Specifically, the stage 2 is maintained in a state in which the target displacement angle exceeds the step response determination value, and the detection time that is an elapsed time from the start of the stage 2 becomes a predetermined determination start time. Will continue. This stage 2 is provided in order to exclude the unstable behavior of the VVT mechanism 15 immediately after the change of the target displacement angle from the determination of responsiveness.

  When stage 2 is completed, the process proceeds to stage 3 where the responsiveness of the VVT mechanism 15 is actually detected. The stage 3 is continued until the detection time, which is an elapsed time from the start of the stage 2, reaches the determination end time, during which time the actual displacement angle of the VVT mechanism 15 exceeds the determination line (OK). Time) is measured. When the determination end time is reached, it is determined whether the determination is OK or NG based on whether the measured OK time is equal to or longer than the VVT control permission determination time.

Note that if the NG determination is made, at least one of engine cooling water temperature and the oil temperature is waiting for time to rise above the determination value, and to re-implement the response determination. Here, with the integrated value of the intake air amount after NG determination (integration Ga) exceeds redetermination shift determination value prescribed, the engine cooling water temperature, a redetermination is determined that the oil temperature rises above determination value Like to do.

  FIG. 6 shows a flowchart of an execution determination routine related to determination as to whether or not such responsiveness determination control can be performed. The processing of this routine is repeatedly performed periodically by the electronic control unit 16 while the engine is cold.

  When the processing of this routine is started, the electronic control unit 16 first checks in step S10 whether or not the cold valve timing (VT) control premise flag is “ON”. This cold VT control premise flag is a flag that is set to “ON” on condition that there is no abnormality in sensors and actuators necessary for valve timing control and that the throttle opening is equal to or greater than a determination value. It has become. If the cold VT control premise flag is “ON”, the electronic control unit 16 proceeds to step S20, and if it is “OFF”, the electronic control unit 16 ends the processing of this routine as it is.

  The reason that the cold VT control premise flag “ON” condition is that the throttle opening is equal to or greater than the determination value is as follows. The internal combustion engine may be suddenly stopped even during driving of the VVT mechanism 15 for such response determination. In such a case, depending on the situation, there is a possibility that the VVT mechanism 15 cannot be moved back to the most advanced position when the engine is stopped. In order to avoid this, even if the engine is stopped while the VVT mechanism 15 related to the responsiveness detection for determining the responsiveness is being driven, the VVT mechanism 15 can be reliably returned to the most advanced position. It is necessary to allow the drive of the VVT mechanism 15 on the condition that it is confirmed that. Therefore, here, the drive of the VVT mechanism 15 related to the responsiveness determination is permitted on the condition that the throttle opening is equal to or greater than the determination value, so that the most advanced angle of the VVT mechanism 15 even in the case of a sudden engine stop during the determination. The return to the position is guaranteed.

  When the process proceeds to step S20, the electronic control unit 16 confirms the response determination history (determination history) after the current engine start in step S20. If there is an OK determination history, the electronic control unit 16 shifts the process to step S40, sets the determination request flag to “OFF” in step S40, and ends the current routine. If it is not determined, that is, if there is no determination history, the electronic control unit 16 sets the determination request flag to “ON” in step S50 and ends the processing of this routine.

  On the other hand, if there is a history of NG determination, the electronic control unit 16 confirms in step S30 whether or not the integrated Ga of the previous NG determination transition exceeds the re-determination transition determination value. If the integrated Ga is less than or equal to the redetermination transition determination value (S30: NO), the electronic control unit 16 sets the determination request flag to “OFF” in step S40, and ends the processing of this routine. To do. On the other hand, if the integrated Ga exceeds the redetermination transition judgment value (S30: NO), the electronic control unit 16 sets the judgment history to “redetermined” in step S60, and then sets the judgment request flag to “ON” in step S50. To complete this routine.

  7 and 8 show a flowchart of the response determination control routine. The processing of this routine is also repeatedly performed periodically by the electronic control unit 16 when the engine is cold.

  When this routine is started, the electronic control unit 16 first checks in step s100 whether or not the determination request flag is “ON”. If the determination request flag is “OFF” (S100: NO), the electronic control unit 16 resets the stage to “0” in step S280, and sets each of the precondition fulfillment time, detection time, and OK time. The counter is cleared, the processing of this routine is terminated, and the determination is restarted from the beginning.

  If the determination flag is “ON” (S100: YES), the electronic control unit 16 confirms the current stage in step S110. Here, if the current stage is “0”, the electronic control unit 16 proceeds to step S120, if the current stage is “1”, proceeds to step S130, and if the current stage is “2” or “3”. The process proceeds to step S180.

  If the current stage is “0”, the electronic control unit 16 confirms in step S120 whether or not both the previous target displacement angle and actual displacement angle were the most advanced position. Here, if either or both of the previous target displacement angle and actual displacement angle are not the most advanced position (S120: NO), the electronic control unit 16 advances the process to step S280, and in each step S280, each counter Clear from the beginning and repeat the determination from the beginning. If both the previous target displacement angle and actual displacement angle are the most advanced position (S120: YES), the electronic control unit 16 proceeds to step S130.

  When the process proceeds to step S130, the electronic control unit 16 confirms whether or not the target displacement angle exceeds the monitor start target displacement angle in step S130. If the target displacement angle is equal to or smaller than the monitor start target displacement angle (S130: NO), the electronic control unit 16 advances the process to step S280 and repeats the determination from the beginning.

  If the target displacement angle exceeds the monitor start target displacement angle (S130: YES), the electronic control unit 16 advances the process to step S140. In step S140, the precondition satisfaction time is counted up, and the stage is moved. Proceed to “1”. In step S150, the electronic control unit 16 checks whether the target displacement angle exceeds the step response determination value. If not (NO), the electronic control unit 16 ends the processing of this routine as it is. Continue judgment.

  On the other hand, if the target displacement angle exceeds the step response determination value (S150: YES), the electronic control unit 16 advances the process to step S160, and in step S160, the precondition satisfaction time exceeds the satisfaction determination time C2. Check if it exists. If the precondition establishment time does not exceed the establishment determination time C2 (S160: NO), the electronic control unit 16 advances the processing to step S280 and repeats the determination from the beginning.

  If the precondition establishment time exceeds the establishment determination time C2 (S160: YES), the electronic control unit 16 advances the process to step S170. Then, in step S170, the electronic control unit 16 clears the count of precondition fulfillment time, shifts to stage 2, and advances the process to step S180.

  When the process proceeds to step S180, the electronic control unit 16 counts up the detection time and calculates an NG determination value in step S180. The NG determination value indicates the value of the determination line at the current time. In step S190, the electronic control unit 16 confirms whether or not the target displacement angle exceeds the step response determination value. If not (NO), the process proceeds to step S280, and the determination is repeated from the beginning. .

  On the other hand, if the target displacement angle exceeds the step response determination value (S190: YES), the electronic control unit 16 proceeds to step S200, and in step S200, whether the detection time exceeds the determination start time. Confirm whether or not. If the detection time does not exceed the determination start time (S200: NO), the electronic control unit 16 ends the current process and continues the determination, and if not (S200: YES), the electronic control unit 16 performs the process. Proceed to step S210.

  After shifting to step S210, the electronic control unit 16 shifts to stage 3 in step S210, and in subsequent step S220, checks whether or not the actual displacement angle is greater than or equal to the NG determination value. Here, if the actual displacement angle is less than the NG determination value (S220: NO), the electronic control unit 16 proceeds directly to step S240, and if it is greater than or equal to the NG determination value (S220: YES), the OK time is set in step S230. After counting up, the process proceeds to step S240.

  In step S240, the electronic control unit 16 confirms whether or not the detection time has reached the determination end time in step S240. If not (NO), the current process is ended and the determination is made. Continue. On the other hand, if the detection time has reached the determination end time (S240: YES), the electronic control unit 16 proceeds to step S250 and performs responsiveness determination. That is, if the OK time is equal to or longer than the VVT control permission determination time, the fact is recorded in the determination history as an OK determination (S260). If the OK time is less than the VVT control permission determination time, an NG determination is recorded in the determination history as NG determination (S270). Then, the electronic control unit 16 proceeds to step S280, resets the stage and clears each counter, and completes the current response determination.

(Cold valve timing control)
Subsequently, as a result of the responsiveness determination, the valve timing control when the engine is cold performed when it is determined that the return to the most advanced angle position is possible when the engine is stopped is shown in FIGS. Explanation will be made with reference to FIG.

  In the present embodiment, as described above, the cold valve timing control is performed only during vehicle travel so that the VVT mechanism 15 is driven only when there is a certain margin in the engine stop time. Yes. Specifically, the cold valve timing control is performed only when the automatic transmission of the vehicle is in the travel range (D range) and at least one of the vehicle speed is equal to or greater than a certain value and the throttle opening is equal to or greater than a certain value. To allow.

  Further, since the responsiveness of the VVT mechanism 15 is low when the engine is cold, it is not possible to desire precise valve timing control after completion of warm-up. Therefore, when the engine is cold, it is desirable to simplify the control even if the operation of the VVT mechanism 15 is permitted.

  Therefore, in the present embodiment, the calculation timing of the target displacement angle of the VVT mechanism 15 in the cold valve timing control is set as shown in FIG. 9 to simplify the valve timing control. As shown in FIG. 9, the calculation map of the target displacement angle of the VVT mechanism 15 in the cold valve timing control is an orthogonal three-axis with the engine speed, the engine load, and the target displacement angle as the x-axis, y-axis, and z-axis, respectively. In the three-dimensional coordinate system, a three-dimensional map having a mesa shape with the xy axis plane as the bottom surface and the z axis as the height direction. Note that the mesa shape indicates a table plate shape in which the cross section forms a trapezoid. On the other hand, FIG. 10 shows a calculation map of the target displacement angle of the VVT mechanism 15 in normal valve timing control after completion of warm-up. As is clear from the comparison of these calculation maps, the calculation map for the target displacement angle of the cold valve timing control is simpler than that for the warm time.

  The cold valve timing control is performed for the purpose of ensuring emission performance before activation of the exhaust purification catalyst mounted on the vehicle. Therefore, after the warm-up of the exhaust purification catalyst is completed, the significance of implementing the cold valve timing control becomes less significant. Therefore, in the present embodiment, the operation of the VVT mechanism 15 by the cold valve timing control is permitted only before catalyst activation.

  Specifically, a calculation map of the upper limit guard value of the target displacement angle as shown in FIG. 11 is prepared, and when the accumulated Ga after engine start becomes a certain amount or more, the upper limit guard value of the target displacement angle of the VVT mechanism 15 is set. As “0”, the target displacement angle is fixed to “0 °”, that is, the displacement angle of the VVT mechanism 15 is fixed to the most advanced position. The integrated Ga value at which the upper limit guard value is “0” is variable depending on the cooling water temperature at the start of the engine (starting water temperature), and the upper limit guard value becomes “0” as the starting water temperature is higher. The implementation period of the cold valve timing control is shortened so that the integrated Ga value becomes small.

  FIG. 12 shows a flowchart of an execution determination routine for determining whether or not to execute cold valve timing (VT) control. The processing of this routine is repeatedly performed periodically by the electronic control unit 16 when the engine is cold.

  When the processing of this routine is started, the electronic control unit 16 first checks in step S300 whether the start mask time has elapsed. The start mask time is a time set to suspend execution of various controls after the engine is started until the state of the internal combustion engine is stabilized. If the start mask time has not elapsed (S300: NO), the electronic control unit 16 sets the upper limit guard value to “0” (S320), sets the control premise flag to “OFF” (S360), and further permits control. The flag is set to “OFF” (S400), and the process of this routine is terminated. If the start mask time has elapsed (S300: YES), the electronic control unit 16 proceeds to step S310 and confirms whether there are any abnormalities in the sensors and actuators necessary for valve timing control. If there is an abnormality (S310: NO), the electronic control unit 16 sets the upper limit guard value to “0” (S320), sets the control premise flag to “OFF” (S360), and further sets the control permission flag to “OFF”. (S400), the processing of this routine is terminated. If there is no abnormality, the electronic control unit 16 proceeds to the process of step S330.

  In step S330, the electronic control unit 16 calculates an upper guard value based on the starting water temperature and the integrated Ga using the calculation map shown in FIG. 11 in step S330. If the upper limit guard value calculated here is “0” (S330: NO), the warm-up of the catalyst has already been completed, and the cold valve timing control is no longer necessary. The premise flag and the control permission flag are set to “OFF” (S360, S400), and the process of this routine is terminated. On the other hand, if the upper limit guard value is larger than “0” (S330: YES), the electronic control unit 16 proceeds to the process of step S350.

  In step S350, the electronic control unit 16 sets the control premise flag to “ON” in step S350. In subsequent step S370, the electronic control unit 16 checks whether or not all of the automatic transmission (AT) oil temperature, the water temperature, and the intake air temperature exceed the determination value T1. Here, if any of the AT oil temperature, the water temperature, and the intake air temperature is equal to or lower than the determination value T1 (S370: NO), the electronic control unit 16 assumes that it is extremely cold and is not suitable for the operation of the VVT mechanism 15. In step S400, the control permission flag is set to “OFF”, and the processing of this routine is terminated.

  On the other hand, if the AT oil temperature, the water temperature, and the intake air temperature all exceed the determination value T1 (S370: YES), the electronic control unit 16 sets the automatic transmission of the vehicle to the travel range (D range) in step S380. It is confirmed whether at least one of the vehicle speed is equal to or higher than a certain value and the throttle opening is equal to or larger than a certain value is satisfied. If a negative determination is made here (S370: NO), that is, if the vehicle is not traveling, the electronic control unit 16 sets the control permission flag to “OFF” in step S400 and ends the processing of this routine. If an affirmative determination is made here (S370: YES), the electronic control unit 16 sets the control permission flag to “ON” in step S390 and ends the processing of this routine.

  FIG. 13 shows a flowchart of a target displacement angle calculation routine at the time of cold valve timing control. The processing of this routine is also repeatedly performed periodically by the electronic control unit 16 when the engine is cold.

  When this routine is started, the electronic control unit 16 first checks in step S500 whether or not the control premise flag is “ON”. If the control premise flag is “OFF” (S500: NO), warm valve timing (VT) control is prioritized (S510), and normal valve timing control after completion of warm-up is performed. On the other hand, if the control premise flag is “ON” (S500: YES), the cold valve timing (VT) control is prioritized and the cold valve timing control is performed.

  When the cold valve timing control is to be performed, the electronic control unit 16 confirms whether or not the control permission flag is “ON” in step S530. If the control permission flag is “OFF” (S530: NO), the electronic control unit 16 sets the target displacement angle to “0” in step S540 and ends the processing of this routine.

  On the other hand, if the control permission flag is “ON” (S540: YES), the electronic control unit 16 uses the calculation map of FIG. 9 to calculate the target based on the engine rotational speed NE and the engine load KL in step S550. The displacement angle is calculated. In step S56, the electronic control unit 16 performs a guard process based on the upper limit guard value calculated using the calculation map of FIG. 11 on the target displacement angle calculated in the previous step S550. Proceed to step S570.

  In step S570, the electronic control unit 16 confirms whether the result of the responsiveness determination is not NG determination, and if it is not NG determination (YES), that is, if it is OK determination, it is calculated in steps S550 and S560. If the value is NG determination (NO) “0” (S540), the target displacement angle is set, and the processing of this routine is finished.

  After setting the target displacement angle, the electronic control unit 16 calculates a duty signal that is a control command value to the oil control valve 12 based on the actual displacement angle and the deviation between the target displacement angles, and performs feedback control of the displacement angle. To do. Specifically, the duty command value is basically obtained from a calculation map based on the actual displacement angle, the deviation between the target displacement angles and the engine speed NE as shown in FIG. That is, the proportional term of the feedback control of the valve timing is obtained from this calculation map.

  In the present embodiment, the base value of the duty command value calculated from the calculation map of FIG. 14 is calculated from a correction map based on the actual displacement angle, the deviation between the target displacement angles and the cooling water temperature as shown in FIG. The final duty command value is obtained by multiplying the correction coefficient. According to this correction map, the control gain at the time of driving the VVT mechanism 15 to the retard side at the time of extremely low temperature is greatly increased. On the other hand, depending on the oil temperature, oil leakage from the clearances between the components of the hydraulic system of the VVT mechanism 15 decreases, and the responsiveness of the VVT mechanism 15 increases. Therefore, in such a temperature range, the correction coefficient is a value less than “1”. Is set to According to such correction, the convergence of the valve timing control can be improved by reflecting the influence of the oil temperature on the responsiveness of the VVT mechanism 15.

  By the way, in normal valve timing control during the warm time, the response and convergence are improved by learning the control command value (holding duty) of the VVT mechanism 15 necessary for maintaining the displacement angle constant. However, when the engine is cold, the oil viscosity is high, and the response and convergence are poor, making it difficult to accurately learn the holding duty. Therefore, in the present embodiment, in the cold valve timing control, learning of the holding duty is prohibited to avoid learning an inappropriate value for the holding duty.

  FIG. 16 shows an example of the control mode of the control device for the variable valve timing mechanism of this embodiment. At time t10 in the figure, the control premise flag is “ON”. However, at this time, the control permission flag is “OFF”, and the target displacement angle of the VVT mechanism 15 remains “0”. When the control permission flag is turned “ON” at the subsequent time t11, the target displacement angle is set to the most retarded angle position, and responsiveness determination is started. In the example of the figure, an OK determination is made in this first response determination, and thereafter, the VVT mechanism 15 is driven to the retard side whenever the vehicle travels.

  In the example of the figure, after time t12, the upper limit guard value is decreased, and the target displacement angle is also decreased accordingly. Then, the cold valve timing control is completed at time t13 when the upper limit guard value becomes “0”, and thereafter normal valve timing control during the warm period is started.

  FIG. 17 shows another example of the control mode of the control device for the variable valve timing mechanism of this embodiment. Also in the example in the figure, the control premise flag is turned “ON” at time t20 and the control permission flag is “ON” at time t21, and the responsiveness determination is started from time t21. In the example of the figure, NG determination is made in the first response determination from time t21, and after the determination, the target displacement angle is set to “0 °”. Therefore, even during the traveling period of the vehicle from time t23 to time t24, the target displacement angle and the actual displacement angle are kept at “0 °”.

  Further, in the example of the figure, the responsiveness is determined again from time t25. The determination at this time is OK determination, and thereafter, at time t26, the upper limit guard value becomes “0”, and cold valve timing control is performed until the control is completed.

  In this embodiment, the electronic control unit 16 corresponds to the determination unit and the permission unit. In the VVT mechanism 15 to which this embodiment is applied, the most advanced position is set to the initial position.

According to the control apparatus for the variable valve timing mechanism of the present embodiment described above, the following effects can be obtained.
(1) In this embodiment, the electronic control unit 16 drives the VVT mechanism 15 when the engine is cold and detects the responsiveness of the VVT mechanism 15 at that time, and is positioned when the engine is started when the engine is stopped. Whether or not the VVT mechanism 15 can be reliably moved back to the most advanced position is determined based on the detection result. The electronic control unit 16 permits the valve timing control to be performed when the engine is cold while the VVT mechanism 15 is driven, on the condition that it is determined that the valve can be reliably moved back to the most advanced position. . In principle, even when the engine is cold, for which valve timing control is prohibited, when oil with low viscosity is used, it may be possible to return to the initial position when the engine is stopped. In such a case, the valve timing control by driving the VVT mechanism 15 can be performed to some extent. In the present embodiment, it is possible to determine whether or not the VVT mechanism 15 can return to the most advanced position when the engine is stopped, instead of giving up the valve timing control when the engine is cold. If so, the execution of the valve timing control when the engine is cold is permitted. That is, in the control apparatus for the variable valve timing mechanism of the present embodiment, when the engine is cold, in which valve timing control is basically prohibited, the conditions for enabling the valve timing control are actively searched to perform the valve timing control. I try to find opportunities. Therefore, it is possible to provide an opportunity for performing valve timing control even when the engine is cold, and as a result, it is possible to improve the emission performance when the engine is cold.

  (2) In the present embodiment, the electronic control unit 16 sets the most advanced angle position, which is one end of the operating range of the VVT mechanism 15, as the initial position, and the VVT mechanism related to detection of responsiveness for responsiveness determination. 15 is performed in a direction away from the most advanced position, which is the initial position, that is, on the retard side. For this reason, it is possible to determine the responsiveness when the VVT mechanism 15 is first driven after the engine is started, and it is possible to perform the valve timing control early when the engine is cold.

  (3) In this embodiment, the electronic control unit 16 reliably returns the VVT mechanism 15 to the most advanced position even if the engine is stopped while the VVT mechanism 15 related to detection of responsiveness is being driven. The driving of the VVT mechanism 15 related to the detection of the responsiveness is allowed on the condition that it is confirmed that it is possible. More specifically, the electronic control unit 16 allows the drive of the VVT mechanism 15 related to detection of responsiveness on the condition that the throttle opening is equal to or greater than a determination value. In this case, the VVT related to the detection of the responsiveness for the above determination is only possible when the time required for the return to the most advanced angle position can be sufficiently secured before the internal combustion engine is stopped. The drive of the mechanism 15 is permitted, and the return of the VVT mechanism 15 to the most advanced angle position when the engine is stopped can be guaranteed.

  (4) In this embodiment, the electronic control unit 16 permits the execution of the valve timing control when the engine is cold, on the condition that the vehicle is running. More specifically, the electronic control unit 16 satisfies at least one of whether the gear stage of the in-vehicle transmission is in the travel range, the vehicle speed is greater than or equal to the determination value, and the throttle opening is greater than or equal to the determination value. On the condition that this is done, the operation of the variable valve timing mechanism when the engine is cold is allowed. If the vehicle is running, it is necessary to go through a process of deceleration of the vehicle → stop of the vehicle → off operation of the ignition until the engine stops, and there is a sufficient time until the engine stops. Therefore, if the execution of the valve timing control when the engine is cold is permitted only while the vehicle is running, the condition relating to the determination that the engine can be returned to the initial position when the engine is stopped can be relaxed. . In this case, it is only necessary to guarantee the return of the variable valve timing mechanism to the initial position only while the vehicle is traveling, and the opportunity for performing the valve timing control when the engine is cold can be increased.

  (5) In the present embodiment, a map for calculating the target displacement angle of the VVT mechanism 15 when the execution of the cold valve timing control is permitted, and the engine rotational speed NE, the engine load KL, and the target displacement angle are set on the x-axis. In the three-dimensional coordinate system of three orthogonal axes, the y-axis and the z-axis, a three-dimensional map having a mesa shape with the xy axis plane as the bottom surface and the z axis as the height direction is used. Since the responsiveness of the VVT mechanism 15 is low when the engine is cold, precise valve timing control after completion of warm-up is not desired. Therefore, when the engine is cold, it is desirable to simplify the control even if the operation of the VVT mechanism 15 is permitted. In that respect, if the map for calculating the target displacement angle is configured as described above, the cold valve timing control can be suitably simplified.

  (6) In this embodiment, the electronic control unit 16 permits the operation of the VVT mechanism 15 when the engine is cold only before catalyst activation. Therefore, after achieving the purpose of improving the emission before the activation of the catalyst, it becomes possible to prevent the VVT mechanism 15 whose responsiveness is still insufficient from being driven unnecessarily.

  (7) In this embodiment, when the engine is cold, the electronic control unit 16 uses the correction map of the proportional term in the feedback control of the displacement angle of the VVT mechanism 15 as the deviation between the actual displacement angle and the target displacement angle of the VVT mechanism 15. A two-dimensional map with the engine coolant temperature is used. At the same time, learning of the control command value (holding duty) of the VVT mechanism 15 necessary for keeping the displacement angle constant is prohibited. Therefore, when the engine is cold, learning of the holding command value is prohibited, and it is possible to avoid learning an inappropriate value for the holding duty. Further, by making the correction map of the feedback proportional term a two-dimensional map of the deviation between the actual displacement angle and the target displacement angle of the VVT mechanism 15 and the engine coolant temperature, the convergence of the valve timing control can be improved. Become.

  (8) In this embodiment, the electronic control unit 16 determines whether or not it is possible to reliably return to the most advanced position depending on whether or not the time during which the displacement angle of the mechanism is equal to or greater than the determination line is equal to or greater than the determination value. The above determination line is set to “0” until a predetermined time has elapsed from the start of the operation of the VVT mechanism 15, and thereafter, the value thereof is set to gradually increase as time elapses. Yes. When low-temperature, high-viscosity oil whose responsiveness deteriorates is used, a constant response delay occurs when the valve timing is changed regardless of the engine speed. In that respect, if the determination line set as described above is employed, more accurate response determination can be performed in consideration of such response delay.

(9) In the present embodiment, the electronic control unit 16, reliable even backward is made once the NG determination impossible, timing engine coolant temperature and oil temperature rises above the determination value to the most advanced position The response determination is re-executed after waiting. For this reason, it is possible to further increase the opportunities for performing the valve timing control when the engine is cold.

(Other embodiment 1)
In the above embodiment, the electronic control unit 16 satisfies at least one of whether the gear stage of the in-vehicle transmission is in the travel range, the vehicle speed is greater than or equal to the determination value, and the throttle opening is greater than or equal to the determination value. If it is determined that the vehicle is running, the operation of the variable valve timing mechanism is permitted when the engine is cold. In addition, depending on the change of the oil viscosity according to the oil temperature, the time required for the backward movement to the most advanced angle position which is the initial position of the VVT mechanism 15 also changes. Therefore, when the oil temperature is high and the oil viscosity is low, the cold valve timing control can be allowed in a wider range. Therefore, by making the determination value of the vehicle speed and throttle opening according to the determination that the vehicle is running depending on the oil temperature, the operation of the VVT mechanism 15 in the cold state can be allowed in a wider range.

  FIG. 18 shows an example of variable setting of the vehicle speed (permitted vehicle speed) and the throttle opening (permitted throttle opening) permitting the cold valve timing control. As shown in the figure, the permitted vehicle speed and the permitted throttle opening are set to smaller values as the oil temperature rises.

(Other embodiment 2)
Even when the oil temperature is low, the oil viscosity is high, and the responsiveness of the VVT mechanism 15 is low, if the displacement angle of the VVT mechanism 15 is not so large, it is possible to return to the most advanced position, which is the initial position. May be. That is, even when the oil viscosity is high and it is difficult to return from the most retarded position to the most advanced position when the engine is stopped, the return to the initial position is guaranteed by limiting the displacement angle of the VVT mechanism 15. can do. Therefore, if the target displacement angle of the VVT mechanism 15 in the cold valve timing control is made variable according to the oil temperature, the control mode of the variable valve timing mechanism is adapted to the change in time required for the backward movement. Will be able to. For example, FIG. 19 shows a setting mode of the maximum displacement angle of the VVT mechanism 15 permitted during the cold valve timing control. As shown in the figure, the cold valve timing control can be performed in a wider range by setting the maximum displacement angle smaller as the oil temperature is lower and the oil viscosity is higher.

(Other embodiment 3)
When a sensor for directly detecting the oil temperature is not provided, the oil temperature is estimated from the cooling water temperature of the internal combustion engine, the integrated Ga from the start of the engine, or the like. On the other hand, the responsiveness of the VVT mechanism 15 has a correlation with the oil temperature. Therefore, the oil temperature is predicted from the responsiveness detection result of the VVT mechanism 15 at the time of responsiveness determination, and the predicted value is compared with the estimated value of the oil temperature based on the cooling water temperature, the integrated Ga, etc., and according to the predicted value. By correcting the estimated value, it is possible to estimate the oil temperature more accurately.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the electronic control unit 16, after the reliable backward to the initial position is once determined impossible, at least one of engine cooling water temperature and the oil temperature is waiting for time to rise above the determination value, The responsiveness determination was performed again. However, if there is no time delay for performing re-determination before catalyst activation, re-determination may not be performed from the beginning.

  In the above embodiment, the electronic control unit 16 is set to “0” until a predetermined time has elapsed from the start of the operation of the VVT mechanism 15, and thereafter, the value thereof is set to gradually increase as time elapses. The determination of responsiveness was performed using the determined determination line. However, if any of the oils assumed to be used does not have a characteristic that the rise of the actual displacement angle of the VVT mechanism 15 after the start of driving is very dull, a holding time of “0” is provided. Alternatively, the determination line may be set.

  In the above embodiment, when the engine is cold, the electronic control unit 16 uses the correction map of the proportional term in the feedback control of the displacement angle of the VVT mechanism 15 as the deviation between the actual displacement angle and the target displacement angle of the VVT mechanism 15 and the engine cooling water temperature. And a two-dimensional map. Of course, when the oil temperature is detected, the correction map may be a two-dimensional map of the deviation between the actual displacement angle and the target displacement angle and the oil temperature.

  In the above embodiment, learning of the holding duty of the VVT mechanism 15 is prohibited during cold valve timing control. If the holding duty can be appropriately learned even during the cold time, the holding duty may be learned also during the cold valve timing control.

  In the above embodiment, the electronic control unit 16 permits the cold valve timing control only before catalyst activation. However, if there is a purpose of the cold valve timing control other than the improvement of the emission before the catalyst activation, the execution period of the cold valve timing control may be determined regardless of whether the catalyst is activated.

  In the above embodiment, the calculation map of the target displacement angle at the time of cold valve timing control is the three orthogonal axes 3 with the engine speed NE, the engine load KL, and the target displacement angles as the x-axis, y-axis, and z-axis, respectively. In the dimensional coordinate system, a three-dimensional map having a mesa shape with the xy axis plane as the bottom surface and the z axis as the height direction is used. However, if possible, the target displacement angle at the time of cold valve timing control may be calculated using a finer calculation map such as a calculation map for normal valve timing control at the warm time.

  In the above embodiment, the electronic control unit 16 determines that the vehicle is running by using the gear stage of the in-vehicle transmission, the vehicle speed, and the throttle opening, and permits the execution of the cold valve timing control. It is also possible to perform determination while the vehicle is running using the operation amount. Most simply, it is possible to determine whether the vehicle is running using only the vehicle speed.

  In the above embodiment, the electronic control unit 16 permits the driving of the VVT mechanism 15 with the cold valve timing control only while the vehicle is running. Of course, if the return to the initial position of the VVT mechanism 15 when the engine is stopped can be guaranteed even when the vehicle is stopped, the driving of the VVT mechanism 15 by the cold valve timing control is permitted even when the vehicle is stopped. You may do it.

  In the above-described embodiment, the electronic control unit 16 puts the throttle opening at or above the determination value into one of the “ON” conditions of the cold VT control premise flag, so that the sudden engine during the responsiveness determination The return of the VVT mechanism 15 to the initial position with respect to the stop is guaranteed. A similar guarantee can be made based on the accelerator operation amount, the vehicle speed, the engine speed, and the like in addition to the throttle opening.

  In the above embodiment, the electronic control unit 16 drives the VVT mechanism 15 related to the responsiveness determination on the condition that the return to the initial position of the VVT mechanism 15 with respect to the sudden engine stop during the responsiveness determination is guaranteed. Had to allow. However, if it is not necessary to worry about a sudden engine stop during the responsiveness determination, the drive of the VVT mechanism 15 related to the responsiveness determination may be permitted regardless of the presence or absence of the guarantee.

  In the above embodiment, the electronic control unit 16 detects the responsiveness of the VVT mechanism 15 in the direction away from the most advanced angle position, which is the initial position, that is, in the retarded angle direction, and determines the responsiveness. . However, when there is a margin in the time until the determination is completed, the VVT mechanism 15 is driven in the direction close to the most advanced angle position, which is the initial position, that is, the advanced angle direction, and the responsiveness determination is performed. Also good. In this case, since the response of the VVT mechanism 15 in the advance direction necessary for the backward movement to the initial position is detected and the response is determined, more accurate determination can be performed. Become.

  In the above embodiment, the case where the initial position where the VVT mechanism 15 is located at the time of starting the engine is the most advanced angle position, but the VVT mechanism in which the initial position is set to the most retarded position is also applicable to the above embodiment. Responsiveness determination control and cold valve timing control can be similarly applied. In this case, the drive of the VVT mechanism related to the responsiveness determination is performed in the advance direction, which is a direction away from the initial position in this case, so that the responsiveness determination is performed when the first VVT mechanism is driven after the engine is started. It becomes possible to carry out.

  The control device according to the present invention can be applied to a VVT mechanism in which an initial position is set at an intermediate position other than the most advanced angle position and the most retarded angle position. In this case, if the responsiveness is determined by driving the VVT mechanism in the advance direction or the retard direction in the direction that is first driven after the engine is started, valve timing control can be performed early when the engine is cold. Will be able to do.

  In the above embodiment, the case where the VVT mechanism 15 that makes the valve timing of the exhaust valve variable is the target of control has been described. However, the response determination control and the cold valve timing control of the above embodiment control the valve timing of the intake valve. Even when the variable VVT mechanism is the target, it can be applied in the same manner as in the above embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Oil pan, 11 ... Oil pump, 12 ... Oil control valve, 13 ... Advance angle oil path, 14 ... Delay angle oil path, 15 ... Variable valve timing mechanism (VVT mechanism), 16 ... Electronic control unit (determination means, Permission means), 17 ... sensors.

Claims (9)

In a control device for a variable valve timing mechanism that is driven by oil supply to vary the valve timing of an engine valve,
When the engine is cold, the variable valve timing mechanism is driven to detect the responsiveness of the variable valve timing mechanism at that time, and when the engine is stopped, the variable valve timing mechanism is positioned when the engine is started and is one end of the operating range of the variable valve timing mechanism. Determination means for determining whether or not the variable valve timing mechanism can be reliably moved back to the initial position set to the initial position based on the detection result;
Allowing the valve timing control to be performed when the variable valve timing mechanism is driven and the engine is cold, provided that the determination means determines that the vehicle can travel back to the initial position without fail. Permission means to
Equipped with a,
The determination means is configured to stop the engine during the driving of the variable valve timing mechanism for detecting the responsiveness on condition that any one of a throttle opening, an accelerator operation amount, and an engine rotation speed is a determination value or more. Even if it is made, it is confirmed that the variable valve timing mechanism can be surely moved back to the initial position, and the variable valve timing mechanism related to the detection of the responsiveness is provided on the condition that the same is confirmed. The variable valve timing mechanism control apparatus according to claim 1, wherein the variable valve timing mechanism is driven in a direction away from the initial position . The permission means confirms that the vehicle is traveling on the condition that the gear stage of the in-vehicle transmission is in the traveling range and any one of the vehicle speed, the throttle opening, and the accelerator operation amount is not less than a determination value. The control device for the variable valve timing mechanism according to claim 1 , wherein the valve timing control is allowed to be performed when the engine is cold. 3. The control device for a variable valve timing mechanism according to claim 2 , wherein any one of a vehicle speed, a throttle opening degree, and an accelerator operation amount that allows the valve timing control to be performed by the permission unit is variable according to an oil temperature. The variable valve timing mechanism according to any one of claims 1 to 3 , wherein a target displacement angle of the variable valve timing mechanism when the permission unit permits execution of the valve timing control is variable according to an oil temperature. Control device. A map for calculating the target displacement angle of the variable valve timing mechanism when the permission means permits the execution of the valve timing control is represented by an engine rotational speed, an engine load, and the target displacement angle as x-axis, y-axis, the x-y axis plane as the bottom surface in the three-dimensional coordinate system of the orthogonal three axes and the z-axis, according to claim 1-4, characterized in that it has a three-dimensional map which forms a mesa shape that a height direction of z-axis The control apparatus of the variable valve timing mechanism of any one of Claims. The control device for a variable valve timing mechanism according to any one of claims 1 to 5 , wherein the permission means permits the valve timing control when the engine is cold only before catalyst activation. When the engine is cold, a correction map of a proportional term in the feedback control of the displacement angle of the variable valve timing mechanism is a two-dimensional map of the deviation between the actual displacement angle and the target displacement angle of the variable valve timing mechanism and the engine cooling water temperature or oil temperature. The control device for a variable valve timing mechanism according to any one of claims 1 to 6 , wherein learning of a control command value of the variable valve timing mechanism necessary for maintaining a constant displacement angle is prohibited. The determination means determines whether or not reliable return to the initial position is possible depending on whether or not the time during which the displacement angle of the variable valve timing mechanism is equal to or greater than a determination line is equal to or greater than a determination value.
The determination line is set to "0" until a predetermined time has elapsed from the start of operation of the variable valve timing mechanism, and thereafter, the determination line is set to gradually increase as time elapses. control device for a variable valve timing mechanism according to any one of 1-7. It said determination means, after temporarily determined impossible a reliable return movement to the initial position, at least one of the engine cooling water temperature and the oil temperature is waiting for time to rise above the determination value, re-performing the determination The control apparatus of the variable valve timing mechanism of any one of Claims 1-8 .

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