JP2010255497A - Variable valve timing control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of the deviation of a holding duty learning value on the stability of valve timing control, in a variable valve timing device for an internal combustion engine. <P>SOLUTION: The control characteristic of the variable valve timing device (VCT) is a nonlinear control characteristic having high response regions having high VCT response speeds at both sides of a low response region having a low VCT response speed, and a true holding duty exists in the low response region. The true holding duty exists in the vicinity of the high response region at an advance side due to an influence of cam torque. Therefore, when the learning value of the holding duty is slightly deviated to the advance side, there is a possibility of causing overshoot or the like. By this, a value with a holding duty offset by a predetermined amount in a retard direction being a direction separated from the high response region at the advance side within the low response region is learned as the holding duty learning value. At this time, the offset of a holding controlled variable is set so that the holding duty learning value reaches a value within a predetermined range in the vicinity of the center of the low response region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a variable valve timing control device for an internal combustion engine having a function of learning a holding control amount (holding duty) necessary for holding the actual valve timing (actual VCT phase) constant.

  Recently, in an internal combustion engine mounted on a vehicle, a hydraulically driven variable valve timing that changes the valve timing (opening / closing timing) of an intake valve and an exhaust valve of the internal combustion engine for the purpose of improving output, reducing fuel consumption, and reducing emissions. The number of devices equipped with equipment is increasing. This hydraulically driven variable valve timing device drives the variable valve timing device as described in Patent Document 1 (Japanese Patent Laid-Open No. 2007-224744) and Patent Document 2 (Japanese Patent Laid-Open No. 2004-251254). When calculating the control amount (control duty) of the hydraulic control valve that controls the hydraulic pressure to be controlled, the feedback control amount according to the deviation between the target valve timing (target VCT phase) and the actual valve timing (actual VCT phase) The control amount of the hydraulic control valve is set based on the holding control amount (holding duty) necessary to hold the valve timing constant, and the hydraulic control valve is driven by this control amount to advance the variable valve timing device. The valve timing is advanced or retarded by changing the flow rate (hydraulic pressure) of hydraulic oil supplied to the chamber or the retard chamber.

  At this time, the holding control amount is learned in consideration of fluctuations in the holding control amount due to manufacturing variations and changes over time of the variable valve timing device and the hydraulic control valve. In the conventional holding control amount learning process, when the actual valve timing is substantially consistent with the target valve timing and stable (when the deviation between the two continues within a predetermined value), the hydraulic control valve at that time The control amount is learned (updated and stored) as the holding control amount.

JP 2007-224744 A JP 2004-251254 A

  By the way, in recent years, the demand for improving the response speed of the variable valve timing device has been increasing. For example, when a variable valve timing device is used as a means of the Atkinson cycle, the intake valve timing is controlled by the most retarded phase during steady running, and the intake valve timing is rapidly advanced when acceleration is requested to quickly increase the intake air amount. Therefore, in the variable valve timing apparatus for the intake valve, an improvement in response speed in the advance direction is required.

  However, if the response speed of the variable valve timing device is improved, the response speed will inevitably change sharply, and even if there is a slight deviation in the learning value of the holding control amount, overshoot and hunting are likely to occur. There is a possibility that the stability of the timing control is lowered.

  Therefore, the problem to be solved by the present invention is to provide a variable valve timing control device for an internal combustion engine that can reduce the influence of the deviation of the learning value of the holding control amount on the stability of the valve timing control.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a hydraulically driven variable valve that adjusts the valve timing by changing the rotational phase of the camshaft (hereinafter referred to as “VCT phase”) with respect to the crankshaft of the internal combustion engine. In a variable valve timing control device for an internal combustion engine for controlling hydraulic pressure for driving a timing device, variable valve timing control means for controlling a control amount of the variable valve timing device so that an actual VCT phase coincides with a target VCT phase; Holding control amount learning means for learning a holding control amount necessary for holding the actual VCT phase constant based on a control amount of the variable valve timing device when a holding control amount learning execution condition is established. The holding control amount learning means includes the variable valve timing when the holding control amount learning execution condition is satisfied. Control amount of grayed device is obtained so as to learn the value obtained by a predetermined amount offset (real holding control amount) in the advance direction or the retard direction as the holding control amount learning value.

  In this configuration, since the value obtained by offsetting the holding control amount by a predetermined amount in the advance direction or the retarding direction is learned as the holding control amount learning value, the VCT response speed (change in the actual VCT phase with respect to the control amount of the variable valve timing device) It is possible to learn by offsetting the holding control amount in the direction where the speed is smaller, and to prevent overshooting or hunting from occurring due to the hold control amount learning value shifting in the direction where the VCT response speed is larger. It is possible to reduce the influence of the deviation of the learning value of the amount on the stability of the variable valve timing control.

  In this case, the control characteristic of the variable valve timing device is a non-linearity having a low response region (dead zone) where the VCT response speed is small and a high response region where the VCT response speed is larger than the low response region. If the holding control amount exists in the low response region and a value obtained by offsetting the holding control amount by a predetermined amount in the low response region is learned as the holding control amount learning value. good. In short, the offset amount of the holding control amount may be set so that the holding control amount learning value falls within the low response region. If the hold control amount learned value is within the low response region, the steady deviation between the target VCT phase and the actual VCT phase is slightly increased even if the hold control amount learned value is slightly deviated from the true hold control amount. Thus, the occurrence of overshoot and hunting can be prevented, and the influence on the stability of the variable valve timing control can be reduced.

  According to a third aspect of the present invention, the control characteristic of the variable valve timing device is a non-linear control characteristic having two high response regions having different VCT response speeds on both sides of the low response region, and is different from the low response region. There may be two holding control amounts, and a value obtained by offsetting the holding control amount by a predetermined amount to the intermediate side between the two holding control amounts may be learned as the holding control amount learning value. In this way, even when two different holding control amounts exist in the low response region, it is possible to cope with one holding control amount learning value, and the variable valve timing when there are two holding control amounts exists. The control processing can be simplified.

  Further, the present invention is applied to a variable valve timing device configured to assist the change of the actual VCT phase with a spring force in one of the two high response regions as in the fourth aspect. May be. In this case, the holding control amount may be offset so that the holding control amount learning value is positioned between the holding control amount in the spring-equipped region and the holding control amount in the no-spring region.

  Further, the offset amount of the holding control amount may be set so that the holding control amount learning value falls within a predetermined range near the center of the low response region. In this way, even if the hold control amount learned value is slightly deviated, the hold control amount learned value can be reliably stored in the low response region.

  Further, according to the present invention, as in claim 6, the variable valve timing device is variable in a direction to reduce a deviation (steady deviation) between the actual VCT phase and the target VCT phase when the variable valve timing device is controlled by the hold control amount learning value. A configuration including target tracking control means for executing target tracking control that gradually corrects the control amount of the valve timing device is preferable. In this way, the steady deviation between the actual VCT phase and the target VCT phase generated by the hold control amount learning value deviating from the true hold control amount is gradually reduced by the target tracking control, and finally the actual VCT phase is obtained. Can converge to the target VCT phase.

  In this case, as in claim 7, the correction by the target follow-up control means based on at least one of the control amount by the variable valve timing control means, the hold control amount, and the correction amount by the target follow-up control means, or a combination thereof. It may be determined whether to reset the amount. In this way, the correction amount by the target follow-up control means is unnecessary based on at least one of the control amount by the variable valve timing control means, the hold control amount, and the correction amount by the target follow-up control means, or a combination thereof. Whether or not the correction amount by the target follow-up control means is determined to be unnecessary, the correction amount by the target follow-up control means can be reset.

  Specifically, as in claim 8, (1) when the target VCT phase changes by a predetermined amount or more, (2) the direction in which the deviation between the target VCT phase and the actual VCT phase is reduced and the correction by the target tracking control means When the direction is opposite, (3) the correction amount by the target follow-up control means when at least one of the conditions when the variable valve timing control means is controlled in a mode other than the VCT phase control mode is satisfied May be reset. For example, when the target VCT phase changes by a predetermined amount or more, the variable valve timing control unit is controlled so that the deviation between the actual VCT phase and the target VCT phase becomes small. The correction amount by is not necessary. In addition, when the direction in which the deviation between the target VCT phase and the actual VCT phase is reduced is opposite to the correction direction by the target tracking control means, the correction amount by the target tracking control with respect to the hold control amount learning value sets the actual VCT phase as the target. Since it works in a direction away from the VCT phase, the correction amount by the target follow-up control is unnecessary. Also, modes other than the VCT phase control mode by the variable valve timing control means (for example, the lock mode for controlling the actual VCT phase to the lock phase, the most retarded angle mode for controlling to the most retarded angle phase, and the most advanced for controlling to the most advanced angle phase). When the control is performed in the (angular mode), the correction amount by the target follow-up control is unnecessary.

  Further, as in claim 9, when the actual VCT phase is located in a region where learning of the hold control amount by the hold control amount learning unit is prohibited, target tracking control is executed without learning the hold control amount. You may make it do. In this way, the actual VCT phase can be converged to the target VCT phase by the target tracking control even in the region where learning of the hold control amount is prohibited.

  Further, as in claim 10, the holding control amount learning execution condition is that at least the actual VCT phase is stable and the deviation between the target VCT phase and the actual VCT phase is not less than a first predetermined value. The execution condition of the target follow-up control is preferably set as a condition that at least a deviation between the target VCT phase and the actual VCT phase is within a range between the first predetermined value and a second predetermined value smaller than the first predetermined value. In this way, it is possible to start the target follow-up control after updating the hold control amount learning value and converge the actual VCT phase to the target VCT phase.

  Note that conditions other than the above may be added to the holding control amount learning execution condition and the target follow-up control execution condition. For example, variable valve timing control such that the oil temperature or cooling water temperature of the internal combustion engine is in a predetermined temperature range (for example, the temperature range after completion of warm-up), that no abnormality in the VCT control system is detected by the self-diagnosis function, etc. It may be a condition that the execution condition is satisfied.

FIG. 1 is a schematic configuration diagram of the entire control system showing Embodiment 1 of the present invention. FIG. 2 is a longitudinal side view illustrating the configuration of the variable valve timing device and the hydraulic control circuit according to the first embodiment. FIG. 3 is a longitudinal front view of the variable valve timing device according to the first embodiment. FIG. 4 is a diagram for explaining the relationship between the VCT response characteristic, the true holding duty, and the holding duty learning value of the variable valve timing device according to the first embodiment. FIG. 5 is a time chart showing an example of control when the target VCT phase changes stepwise toward the advance side. FIG. 6 is a flowchart illustrating a processing flow of the holding duty learning control routine according to the first embodiment. FIG. 7 is a diagram for explaining the relationship between the deviation between the target VCT phase and the actual VCT phase, the holding duty learning execution region, and the target tracking control execution region. FIG. 8 is a flowchart showing the flow of processing of the target tracking control routine of the first embodiment. FIG. 9 is a diagram illustrating the relationship between the spring-loaded area A, the spring-less area B, and the holding duty learning value according to the second embodiment. FIG. 10 is a diagram for explaining the relationship between the VCT response characteristic, the true holding duty, and the holding duty learning value of the variable valve timing apparatus according to the second embodiment. FIG. 11 is a flowchart illustrating a processing flow of the holding duty learning control routine according to the second embodiment.

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

A first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, in an engine 11 that is an internal combustion engine, power from a crankshaft 12 is transmitted to an intake side camshaft 16 and an exhaust side camshaft 17 via sprockets 14 and 15 by a timing chain 13. It is like that. However, the intake side camshaft 16 is provided with a variable valve timing device 18 (VCT) that adjusts the advance amount (VCT phase) of the intake side camshaft 16 with respect to the crankshaft 12.

  A cam angle sensor 19 that outputs a cam angle signal pulse at a specific cam angle for cylinder discrimination is installed on the outer peripheral side of the intake side cam shaft 16, while a predetermined angle is provided on the outer peripheral side of the crank shaft 12. A crank angle sensor 20 that outputs a crank angle signal pulse for each crank angle is provided. The output signals from the cam angle sensor 19 and the crank angle sensor 20 are input to an engine control circuit 21, which calculates the actual valve timing (actual VCT phase) of the intake valve and the crank angle sensor 20. The engine speed is calculated based on the frequency (pulse interval) of the output pulses. Further, output signals from various sensors (intake pressure sensor 22, water temperature sensor 23, throttle sensor 24, etc.) for detecting the engine operating state are input to the engine control circuit 21.

  The engine control circuit 21 performs fuel injection control and ignition control according to the engine operating state detected by the various sensors, and also performs variable valve timing control (phase feedback control), and actual valve timing (actual VCT of the intake valve). The hydraulic pressure for driving the variable valve timing device 18 is feedback-controlled so that the phase) matches the target valve timing (target VCT phase).

Next, the configuration of the variable valve timing device 18 will be described with reference to FIGS.
A housing 31 of the variable valve timing device 18 is fastened and fixed with bolts 32 to a sprocket 14 that is rotatably supported on the outer periphery of the intake camshaft 16. Thereby, the rotation of the crankshaft 12 is transmitted to the sprocket 14 and the housing 31 via the timing chain 13, and the sprocket 14 and the housing 31 rotate in synchronization with the crankshaft 12.

  On the other hand, a rotor 35 is fastened and fixed to one end of the intake side camshaft 16 with a bolt 37. The rotor 35 is housed in the housing 31 so as to be relatively rotatable.

  As shown in FIG. 3, a plurality of hydraulic chambers 40 are formed inside the housing 31, and each of the hydraulic chambers 40 is advanced and retarded by a vane 41 formed on the outer periphery of the rotor 35. It is divided into and. At both sides of at least one vane 41, a stopper portion 56 is formed that restricts the relative rotation range of the rotor 35 (vane 41) with respect to the housing 31, and the actual VCT phase (cam shaft phase) is adjusted by the stopper portion 56. The most retarded angle phase and the most advanced angle phase of the possible range are regulated.

  The variable valve timing device 18 is provided with an intermediate lock mechanism 50 that locks the VCT phase with an intermediate lock phase located approximately in the middle of the adjustable range. The configuration of the intermediate lock mechanism 50 will be described. Any one or a plurality of vanes 41 is provided with a lock pin accommodation hole 57, and the lock pin accommodation hole 57 has a relative relationship between the housing 31 and the rotor 35 (vane 41). A lock pin 58 for locking the rotation is accommodated so as to protrude, and the lock pin 58 protrudes toward the sprocket 14 and fits into the lock hole 59 of the sprocket 14, so that the VCT phase is substantially in the middle of the adjustable range. Locked with an intermediate lock phase located at. This intermediate lock phase is set to a phase suitable for starting the engine 11. The lock hole 59 may be provided in the housing 31.

  The lock pin 58 is urged in the lock direction (projection direction) by the spring 62. Further, between the outer peripheral portion of the lock pin 58 and the lock pin accommodation hole 57, an unlocking hydraulic chamber for controlling the hydraulic pressure for driving the lock pin 58 in the unlocking direction is formed. The housing 31 is provided with a spring 55 (see FIG. 2) such as a torsion coil spring that assists the hydraulic pressure that relatively rotates the rotor 35 in the advance angle direction by the spring force during the advance angle control.

  In the first embodiment, the hydraulic control device that controls the hydraulic pressure that drives the variable valve timing device 18 and the lock pin 58 includes the phase control hydraulic control valve 25 that controls the hydraulic pressure that drives the variable valve timing device 18, The lock control hydraulic control valve 26 for controlling the hydraulic pressure for driving the pin 58 is individually provided. The hydraulic pressure control valve 25 for phase control is constituted by, for example, a 5-port, 3-position type spool valve, and the hydraulic pressure control valve 26 for lock control is constituted by, for example, a 3-port, 2-position type spool valve.

  The oil in the oil pan 27 is pumped up by an oil pump 28 driven by the power of the engine 11 and supplied to the hydraulic control valves 25 and 26, and the variable valve timing device 18 is advanced by the hydraulic control valve 25 for phase control. The hydraulic pressure (oil amount) supplied to the corner chamber 42 and the retard chamber 43 is controlled, and the hydraulic pressure (oil amount) for driving the lock pin 58 in the unlocking direction is controlled by the hydraulic control valve 26 for lock control. A check valve 29 is provided on the inlet port side of the phase control hydraulic control valve 25 to prevent oil backflow.

  It should be noted that a hydraulic control valve in which the phase control hydraulic control valve 25 and the lock control hydraulic control valve 26 are integrated may be used.

  The engine control circuit 21 functions as variable valve timing control means in the claims, and calculates a target VCT phase (target valve timing) based on engine operating conditions during variable valve timing control (phase feedback control). Thus, for example, the control duty (control amount) of the hydraulic control valve 25 for phase control is set so that the actual VCT phase of the intake camshaft 16 (actual valve timing of the intake valve) matches the target VCT phase (target valve timing). Feedback control is performed on the hydraulic pressure supplied to the advance chamber 42 and the retard chamber 43 of the variable valve timing device 18 by feedback control by PD control or the like. Further, the engine control circuit 21 keeps the actual VCT phase constant based on the control duty of the hydraulic control valve 25 for phase control when a predetermined holding duty learning execution condition (holding control amount learning execution condition) is satisfied. It also functions as a holding control amount learning means that learns the holding duty (holding control amount) necessary to hold the feedback control amount. During variable valve timing control, the feedback control amount is set to the holding duty learning value (holding control amount learning value). Add to find the control duty.

Control duty = holding duty learning value + feedback control amount
Feedback control amount = Kp · ΔVT + Kd · d (ΔVT) / dt
d (ΔVT) / dt = [ΔVT (i) −ΔVT (i−1)] / dt

  Here, Kp is the proportional gain, Kd is the differential gain, ΔVT is the deviation between the target VCT phase and the actual VCT phase, ΔVT (i) is the current deviation, ΔVT (i-1) is the previous deviation, and dt is the calculation cycle. It is.

  Next, the relationship between the actual VCT phase change speed (VCT response speed) with respect to the control duty of the variable valve timing device 18, the holding duty, and the holding duty learning value will be described with reference to FIG.

  The control characteristic of the variable valve timing device 18 is a non-linear control characteristic having a high response region having a large VCT response speed compared to the low response region on both sides of a low response region (dead zone) where the VCT response speed is small. There is a real holding duty in the region. The true holding duty does not exist near the center of the low response region, but exists near the advanced response side high response region due to the influence of the torque of the intake camshaft 16. For this reason, if the learning value of the holding duty is shifted to the advance side even a little, overshoot and hunting are likely to occur, and the stability of the variable valve timing control may be lowered.

  Therefore, in the first embodiment, the control duty (real holding duty) when the holding duty learning execution condition is satisfied is set in the retarding direction, which is a direction away from the advanced response side in the advanced response side in the low response region. A value offset by a predetermined amount is learned as a holding duty learning value, and this holding duty learning value is stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21 (the stored data is held even when the engine control circuit 21 is powered off). The rewritable storage means) is updated and stored.

  At this time, the holding duty offset amount is set so that the holding duty learning value becomes a value within a predetermined range near the center of the low response region. In this way, even if the holding duty learning value is slightly deviated, the holding duty learning value can be reliably kept within the low response region. If the holding duty learning value falls within the low response region, the steady-state deviation between the target VCT phase and the actual VCT phase is slightly increased even if the holding duty learning value slightly deviates from the true holding duty. And hunting can be prevented, and the influence on the stability of the variable valve timing control can be reduced.

  Further, the engine control circuit 21 also functions as target tracking control means in the claims, and controls the variable valve timing device 18 with the hold duty learning value when a predetermined target tracking control execution condition is satisfied. The target follow-up control is executed in which the control duty (holding duty learning value) is gradually corrected with the correction duty in a direction to reduce the deviation (steady deviation) between the actual VCT phase and the target VCT phase.

Control duty at the time of target tracking control = holding duty learned value + correction duty In this way, the steady deviation between the actual VCT phase and the target VCT phase generated when the holding duty learned value deviates from the true holding duty is set as the target tracking. The actual VCT phase can be finally made to converge to the target VCT phase by gradually decreasing it by control.

  Next, an example of holding duty learning control and target tracking control according to the first embodiment will be described with reference to FIG. FIG. 5 is a time chart showing a control example when the target VCT phase changes stepwise toward the advance side.

  In the example of FIG. 5, since the deviation between the target VCT phase and the actual VCT phase is increased stepwise at the time t1 when the target VCT phase changes stepwise toward the advance side, the control duty depends on the deviation. It changes in a stepped manner to the high response area on the advance side. As a result, the actual VCT phase is rapidly advanced, and the actual VCT phase becomes substantially constant from the time t2 elapses. As the actual VCT phase advances, the control duty gradually approaches the holding duty, and when the actual VCT phase becomes substantially constant, the control duty becomes substantially constant at the holding duty. If this state continues for a while, the holding duty learning execution condition is satisfied, and a value obtained by offsetting the control duty (real holding duty) at that time by a predetermined amount in the retarding direction is learned as the holding duty learning value, and this holding is performed. The duty learning value is updated and stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21.

  Since the deviation between the target VCT phase and the actual VCT phase still remains at the time t3 when the hold duty learning value is updated, the control duty again changes in a stepwise manner to the advanced response side on the advance side according to the deviation. To do. As a result, the actual VCT phase is rapidly advanced and eventually the actual VCT phase becomes substantially constant. At this stage, the holding duty learning value is a value obtained by offsetting the actual holding duty by a predetermined amount in the retard direction. Therefore, there is a steady deviation between the target VCT phase and the actual VCT phase.

  Therefore, at the time t4 when the deviation between the target VCT phase and the actual VCT phase is within the first predetermined value and the target tracking control execution condition is satisfied, the target tracking control is started and the control duty (holding duty learning value) is set. By gradually correcting the correction duty to the advance side, the actual VCT phase is gradually brought closer to the target VCT phase. Thus, when the deviation between the target VCT phase and the actual VCT phase falls within the second predetermined value, it is determined that the actual VCT phase has converged (substantially coincides) with the target VCT phase, and the target tracking control is terminated. Here, as shown in FIG. 7, the second predetermined value is set to a value smaller than the first predetermined value.

  The holding duty learning control and the target follow-up control according to the first embodiment described above are executed by the engine control circuit 21 according to the routines shown in FIGS. The processing contents of each routine will be described below.

[Holding duty learning control routine]
The holding duty learning control routine of FIG. 6 is repeatedly executed at a predetermined cycle during engine operation (during the power-on period of the engine control circuit 21). When this routine is started, first, in step 101, it is determined whether or not the actual VCT phase is stable based on whether or not the amount of change of the actual VCT phase per predetermined time is within a predetermined value. If it is determined that the VCT phase is not stable, it is determined that the holding duty learning execution condition is not satisfied, and this routine is terminated without performing the subsequent processing.

  On the other hand, if it is determined in step 101 that the actual VCT phase is stable, the process proceeds to step 102 where the absolute value of the deviation between the target VCT phase and the actual VCT phase is greater than or equal to a first predetermined value (see FIG. 7). As a result, if it is determined that the absolute value of the deviation between the target VCT phase and the actual VCT phase is greater than or equal to the first predetermined value, it is determined that the holding duty learning execution condition is satisfied, and the process proceeds to step 103. A value obtained by adding a predetermined offset amount to the current control duty (real holding duty) is learned as a holding duty learning value, and this holding duty learning value is stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21. Update memorize. The processing of these steps 101 to 103 serves as holding control amount learning means in the claims.

  On the other hand, if it is determined in step 102 that the absolute value of the deviation between the target VCT phase and the actual VCT phase is less than the first predetermined value, the holding duty learning execution condition is not satisfied, and the process proceeds to step 104. It is determined whether or not the absolute value of the deviation between the target VCT phase and the actual VCT phase is greater than or equal to a second predetermined value (see FIG. 7). As a result, when the absolute value of the deviation between the target VCT phase and the actual VCT phase is determined to be greater than or equal to the second predetermined value, that is, the range between the first predetermined value and the second predetermined value smaller than the first predetermined value. If it is within the range, it is determined that the target tracking control execution condition is satisfied, and the routine proceeds to step 105, where the target tracking control routine of FIG. 8 is executed.

  On the other hand, if it is determined in step 104 above that the absolute value of the deviation between the target VCT phase and the actual VCT phase is less than the second predetermined value, the target tracking control execution condition is not satisfied, and the target tracking control routine of FIG. 8 is executed. This routine is terminated without doing so.

[Target tracking control routine]
The target tracking control routine of FIG. 8 is a subroutine executed in step 105 of the holding duty learning control routine of FIG. 6 and serves as target tracking control means in the claims. When this routine is started, first, in step 201, it is determined whether or not the correction duty reset condition for target tracking control is satisfied. At least one of the following three conditions (1) to (3) is set: Judgment is made based on whether or not it is satisfied.

(1) When the target VCT phase changes by more than a predetermined amount
(2) When the direction to reduce the deviation between the target VCT phase and the actual VCT phase is opposite to the correction direction by target tracking control
(3) Control in a mode other than the VCT phase control mode (for example, the lock mode for controlling the actual VCT phase to the lock phase, the most retarded angle mode for controlling to the most retarded phase, and the most advanced angle mode for controlling to the most advanced angle phase). If

  For example, when the target VCT phase changes by a predetermined amount or more, the deviation between the actual VCT phase and the target VCT phase is controlled by variable valve timing control (phase feedback control). The correction duty by target tracking control is unnecessary. Further, when the direction in which the deviation between the target VCT phase and the actual VCT phase is reduced is opposite to the correction direction by the target tracking control means, the correction duty by the target tracking control with respect to the hold duty learning value becomes the target VCT. Since it works in the direction away from the phase, the correction duty by the target tracking control is unnecessary. In addition, it is controlled in a mode other than the VCT phase control mode (for example, a lock mode for controlling the actual VCT phase to the lock phase, a most retarded angle mode for controlling to the most retarded phase, and a most advanced angle mode for controlling to the most advanced angle phase). In such a case, the correction duty by the target tracking control is not necessary.

  Therefore, if at least one of the above three conditions (1) to (3) is satisfied, it is determined that the correction duty reset condition for the target follow-up control is satisfied, and the routine proceeds to step 202 where the correction duty is set. Reset to set correction duty = 0.

  On the other hand, if none of the above three conditions (1) to (3) are satisfied, it is determined in step 201 that the correction duty reset condition for the target tracking control is not satisfied, and the process proceeds to step 203. It is determined whether or not the absolute value of the deviation between the VCT phase and the actual VCT phase is within a range between the first predetermined value and the second predetermined value. As a result, if it is determined that the absolute value of the deviation is not within the range between the first predetermined value and the second predetermined value, it is determined that the target follow-up control execution condition is not satisfied, and this routine is executed without performing the subsequent processing. finish.

On the other hand, if it is determined in step 203 that the absolute value of the deviation is within the range between the first predetermined value and the second predetermined value, it is determined that the target follow-up control execution condition is satisfied, and the process proceeds to step 204. Then, it is determined whether or not the deviation between the target VCT phase and the actual VCT phase is a positive value (that is, the target VCT phase is more advanced than the actual VCT phase). As a result, if it is determined that the deviation is a positive value (that is, the target VCT phase is more advanced than the actual VCT phase), the process proceeds to step 205, and a value obtained by subtracting a predetermined amount from the previous correction duty is newly corrected. The correction duty is stored in a volatile memory such as a RAM of the engine control circuit 21 or a rewritable nonvolatile memory such as a backup RAM.
Correction duty = Correction duty (previous value)-Predetermined amount

If it is determined in step 204 that the deviation between the target VCT phase and the actual VCT phase is a negative value (that is, the target VCT phase is retarded from the actual VCT phase), the process proceeds to step 206 and the previous correction duty is set. A value obtained by adding a predetermined amount to a new correction duty is stored in a volatile memory such as a RAM of the engine control circuit 21 or a rewritable nonvolatile memory such as a backup RAM.
Correction duty = Correction duty (previous value) + predetermined amount

  The correction duty reset condition for target tracking control is not limited to the above conditions (1) to (3), but the control duty for variable valve timing control (phase feedback control), the true holding duty, and the correction duty for target tracking control. It may be determined whether to reset the correction duty by the target tracking control based on at least one of them or a combination thereof. In this way, the correction duty by the target tracking control is set based on at least one of the control duty of the variable valve timing control (phase feedback control), the true holding duty, the correction duty by the target tracking control, or a combination thereof. By monitoring whether or not the correction duty is unnecessary, when it is determined that the correction duty by the target tracking control is unnecessary, the correction duty by the target tracking control can be reset.

  Moreover, conditions other than the above may be added to the holding duty learning execution condition and the target tracking control execution condition. For example, variable valve timing control such that the oil temperature or cooling water temperature of the engine 11 is in a predetermined temperature range (for example, the temperature range after completion of warm-up), that no abnormality in the VCT control system is detected by the self-diagnosis function, etc. It may be a condition that the execution condition of (phase feedback control) is satisfied.

  According to the first embodiment described above, in consideration of the fact that the real holding duty existing in the low response region is close to the high response region on the advance side due to the cam torque, the real holding duty is Since the value that is offset by a predetermined amount in the retarding direction, which is the direction away from the high response area on the advance side in the low response area, is learned as the hold duty learning value, the hold duty learning value is slightly on the advance side. Even if they deviate, the hold duty learning value can be reliably kept within the low response region. If the hold duty learning value falls within the low response range, even if the hold duty learning value slightly deviates from the true hold duty, the steady-state deviation between the target VCT phase and the actual VCT phase becomes slightly larger, The occurrence of chute and hunting can be prevented, and the influence on the stability of the variable valve timing control can be reduced.

  In the first embodiment, a spring 55 (see FIG. 2) such as a torsion coil spring that assists the housing 31 of the variable valve timing device 18 with a spring force that hydraulically rotates the rotor 35 in the advance direction during advance angle control. In the second embodiment of the present invention shown in FIGS. 9 to 11, the range in which the spring 55 acts is set to the range from the most retarded phase to immediately before the intermediate lock phase, Assuming fail-safe at restart after abnormal stop such as engine stall etc., when starting with the actual VCT phase retarded from the intermediate lock phase with the lock pin 58 removed from the lock pin accommodation hole 57, During cranking by a starter (not shown), the spring force of the spring 55 assists the advance operation of advancing the actual VCT phase from the retard side to the intermediate lock phase, and the lock pin 58 is locked. The fitting by written Mari accommodation hole 57 is configured to be locked.

  When starting with the actual VCT phase on the advance side of the intermediate lock phase, the torque of the intake camshaft 16 acts in the retarding direction during cranking, so the actual VCT phase is determined by the torque of the intake camshaft 16. Can be retarded from the advance side to the intermediate lock phase to lock the lock pin 58 into the lock pin receiving hole 57.

  In the configuration in which the spring force of the spring 55 is applied to only a part of the variable range of the actual VCT phase as in the second embodiment, as shown in FIG. The holding duty in the VCT response speed characteristic of the springless region B is different from the VCT response speed characteristic of B, and the advance response side high response region is influenced by the torque of the intake side camshaft 16 as in the first embodiment. However, the holding duty in the VCT response speed characteristic of the spring-loaded region A exists near the retarded side high response region due to the influence of the spring force of the spring 55.

  As described above, in the second embodiment, in consideration of the existence of two different holding duties in the low response region, a value obtained by offsetting the holding duty by a predetermined amount to the intermediate side between the two holding duties is a holding duty learning value. Like to learn. In this case, the holding duty is offset so that the holding duty learning value is positioned between the holding duty of the spring-loaded region A and the holding duty of the non-spring region B, and the holding duty offset value is set to the holding duty offset value. It is set to fall within a predetermined range (within the target holding duty learning range) near the center of the low response region. In this way, even when there are two different holding duties in the low response region, it is possible to cope with one holding duty learning value, and calculation of variable valve timing control when there are two holding duties The processing can be simplified, and even if the holding duty learning value is slightly deviated, the holding duty learning value can surely fall within the low response region.

  Further, as shown in FIG. 9, a learning prohibition region for prohibiting learning of the holding duty exists between the region A with spring and the region B without spring. Since the limit phase of the range in which the spring force acts on the spring 55 varies depending on the manufacturing variation / assembly variation of the spring 55 and the temporal change of the spring force, in the second embodiment, the manufacturing variation / assembly variation of the spring 55 The range in which the spring force of the spring 55 acts reliably without being influenced by these even if there is a change in the spring force with time is set as the region A with spring. Accordingly, in the learning prohibited area adjacent to the spring-equipped area A, it is unclear whether the spring force of the spring 55 is actually acting. In this learning prohibited area, the true holding duty is delayed from the advance side. Since it is unclear which direction the corner is deviating, learning of the holding duty is prohibited, and only the target follow-up control is executed so that the actual VCT phase is converged and held at the target VCT phase.

  The holding duty learning control and target tracking control of the second embodiment described above are executed by the engine control circuit 21 according to the holding duty learning control routine of FIG.

  The holding duty learning control routine of FIG. 11 is repeatedly executed at a predetermined cycle during engine operation (during the power-on period of the engine control circuit 21). When this routine is started, first, at step 301, it is determined whether or not the actual VCT phase is stable based on whether or not the amount of change of the actual VCT phase per predetermined time is within a predetermined value. If it is determined that the phase is not stable, it is determined that the holding duty learning execution condition is not satisfied, and this routine is terminated without performing the subsequent processing.

  On the other hand, if it is determined in step 301 that the actual VCT phase is stable, the process proceeds to step 302 where the absolute value of the deviation between the target VCT phase and the actual VCT phase is equal to or greater than a first predetermined value (see FIG. 7). As a result, if it is determined that the absolute value of the deviation between the target VCT phase and the actual VCT phase is greater than or equal to the first predetermined value, it is determined that the holding duty learning execution condition is satisfied, and the process proceeds to step 303. It is determined whether or not the actual VCT phase is located in the region with spring A. If it is determined that the actual VCT phase is located in the region with spring A, the process proceeds to step 305 and the current control duty (real holding duty) is determined. A value obtained by subtracting the predetermined offset amount α is learned as a holding duty learning value, and this holding duty learning value is updated and stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21.

  In short, as shown in FIG. 10, when the actual VCT phase is located in the spring-loaded region A, the holding duty is close to the retarded side high response region due to the spring force of the spring 55. By learning a value obtained by offsetting the duty by a predetermined amount α in the advance direction as a holding duty learning value, the holding duty learning value is within a predetermined range (within the target holding duty learning range) near the center of the low response region. Fit.

  On the other hand, if it is determined in step 303 that the actual VCT phase is not located in the region with spring A, the process proceeds to step 304, where it is determined whether or not the actual VCT phase is located in the region without spring B. Is determined to be located in the spring-loaded region B, the process proceeds to step 306, where a value obtained by adding a predetermined offset amount α to the current control duty (real holding duty) is learned as a holding duty learning value, and this holding duty is The learning value is updated and stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21.

  In short, as shown in FIG. 10, when the actual VCT phase is located in the no-spring region B, the holding duty is close to the advanced response region on the advance side due to the influence of the torque of the intake camshaft 16. By learning a value obtained by offsetting the holding duty by a predetermined amount α in the retard direction as a holding duty learning value, the holding duty learning value is within a predetermined range near the center of the low response region (within the target holding duty learning range). ).

  If it is determined “No” in both step 303 and step 304, it is determined that the actual VCT phase is located in the learning prohibited area, and the process proceeds to step 308 without learning the holding duty, and the target tracking control is performed. Execute. This target tracking control is executed by the target tracking control of FIG.

  If it is determined in step 302 that the absolute value of the deviation between the target VCT phase and the actual VCT phase is less than the first predetermined value, the holding duty learning execution condition is not satisfied, and the process proceeds to step 307, where It is determined whether or not the absolute value of the deviation between the phase and the actual VCT phase is greater than or equal to a second predetermined value (see FIG. 7). As a result, when the absolute value of the deviation between the target VCT phase and the actual VCT phase is determined to be greater than or equal to the second predetermined value, that is, the range between the first predetermined value and the second predetermined value smaller than the first predetermined value. If it is within the range, it is determined that the target follow-up control execution condition is satisfied, the process proceeds to step 308, and the target follow-up control similar to that in the first embodiment is executed.

  On the other hand, if it is determined in step 307 that the absolute value of the deviation between the target VCT phase and the actual VCT phase is less than the second predetermined value, the target tracking control execution condition is not satisfied, and the target tracking control is not executed. This routine ends.

  In the second embodiment described above, a value obtained by offsetting the holding duty by a predetermined amount to the intermediate side between the two holding duties in consideration of the existence of different holding duties in the spring-loaded area A and the spring-free area B. Since learning is performed as the holding duty learning value, even when there are two different holding duties, it is possible to cope with one holding duty learning value, and variable valve timing control when there are two holding duties This calculation process can be simplified, and even if the hold duty learning value is slightly deviated, the hold duty learning value can be reliably kept within the low response region.

  In addition, in the second embodiment, when the learning prohibited area is set between the spring-loaded area A and the spring-less area B, and the actual VCT phase is located in the learning prohibited area, the target duty is not learned without learning. Since the follow-up control is executed, the actual VCT phase is converged to the target VCT phase by the target follow-up control even in the learning prohibition region where it is unknown whether the spring force of the spring 55 is actually acting. Can do.

  The first and second embodiments are embodiments in which the present invention is embodied by applying the present invention to a variable valve timing device for an intake valve. However, the embodiments are applied to a variable valve timing control device for an exhaust valve. Also good.

  In addition, it goes without saying that the present invention can be implemented with various modifications within a range not departing from the gist, such as the configuration of the variable valve timing device 18 and the configurations of the hydraulic control valves 25 and 26 may be appropriately changed.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Crankshaft, 13 ... Timing chain, 14, 15 ... Sprocket, 16 ... Intake camshaft, 17 ... Exhaust camshaft, 18 ... Variable valve timing device (VCT), 19 ... Cam angle Sensor: 20 ... Crank angle sensor, 21 ... Engine control circuit (variable valve timing control means, holding control amount learning means, target tracking control means), 25 ... Hydraulic control valve (hydraulic control device) for phase control, 26 ... Lock Hydraulic control valve (hydraulic control device) for control, 28 ... oil pump, 31 ... housing, 35 ... rotor, 40 ... hydraulic chamber, 41 ... vane, 42 ... advance chamber, 43 ... retard chamber, 50 ... intermediate lock Mechanism, 55 ... Spring, 58 ... Lock pin, 59 ... Lock hole

Claims (10)

Variable valve timing control for an internal combustion engine for controlling hydraulic pressure for driving a hydraulically driven variable valve timing device that adjusts valve timing by changing a rotational phase of a cam shaft (hereinafter referred to as "VCT phase") with respect to a crankshaft of the internal combustion engine In the device
Variable valve timing control means for controlling the control amount of the variable valve timing device so that the actual VCT phase matches the target VCT phase;
Holding control amount learning means for learning a holding control amount necessary to hold the actual VCT phase constant based on a control amount of the variable valve timing device when a predetermined holding control amount learning execution condition is satisfied. And
The holding control amount learning means holds a value obtained by offsetting a control amount of the variable valve timing device by a predetermined amount in the advance direction or the retard direction when the holding control amount learning execution condition is satisfied. A variable valve timing control device for an internal combustion engine characterized by learning as a value. The control characteristics of the variable valve timing device are a low response region where the actual VCT phase change speed (hereinafter referred to as “VCT response speed”) with respect to the control amount of the variable valve timing device is small, and the VCT response speed is the low response region. Is a non-linear control characteristic having a large high response region, and the holding control amount exists in the low response region,
2. The variable internal combustion engine according to claim 1, wherein the holding control amount learning means learns, as the holding control amount learning value, a value obtained by offsetting the holding control amount by a predetermined amount within the low response region. Valve timing control device. The control characteristic of the variable valve timing device is a non-linear control characteristic having two high response regions with different VCT response speeds on both sides of the low response region, and two different holding control amounts in the low response region. Exists,
The holding control amount learning unit learns, as the holding control amount learning value, a value obtained by offsetting the holding control amount by a predetermined amount to an intermediate side between the two holding control amounts. A variable valve timing control device for an internal combustion engine.   The variable valve timing device is configured to assist the change of the actual VCT phase with a spring force in one of the two high response regions. A variable valve timing control device for an internal combustion engine.   The offset amount of the holding control amount is set so that the learning value of the holding control amount falls within a predetermined range near the center of the low response region. A variable valve timing control device for an internal combustion engine.   Execute target follow-up control that gradually corrects the control amount of the variable valve timing device in a direction to reduce the deviation between the actual VCT phase and the target VCT phase when the variable valve timing device is controlled with the hold control amount learning value. 6. The variable valve timing control device for an internal combustion engine according to claim 1, further comprising target tracking control means for performing the control.   Whether to reset the correction amount by the target follow-up control means based on at least one of the control amount by the variable valve timing control means, the hold control amount, and the correction amount by the target follow-up control means, or a combination thereof The variable valve timing control device for an internal combustion engine according to claim 6, further comprising means for determining   (1) When the target VCT phase changes by a predetermined amount or more, (2) When the direction of reducing the deviation between the target VCT phase and the actual VCT phase is opposite to the correction direction by the target tracking control means, (3) Means for resetting the correction amount by the target follow-up control means when at least one of the conditions when the control is performed in a mode other than the VCT phase control mode by the variable valve timing control means is provided; The variable valve timing control apparatus for an internal combustion engine according to claim 6, wherein the variable valve timing control apparatus is an internal combustion engine.   Means for executing target follow-up control by the target follow-up control means without learning the hold control amount when an actual VCT phase is located in a region where learning of the hold control amount by the hold control amount learning means is prohibited The variable valve timing control device for an internal combustion engine according to any one of claims 6 to 8, characterized by comprising: The holding control amount learning execution condition is that at least the actual VCT phase is stable and the deviation between the target VCT phase and the actual VCT phase is equal to or greater than a first predetermined value,
The execution condition of the target tracking control is characterized in that at least a deviation between the target VCT phase and the actual VCT phase is in a range between the first predetermined value and a second predetermined value smaller than the first predetermined value. A variable valve timing control device for an internal combustion engine according to any one of claims 6 to 9.

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