JP5427051B2 - Engine valve timing control device - Google Patents

Description

  The present invention relates to an engine valve timing control device having a variable valve timing mechanism for advancing or retarding a rotational phase of a cam angle with respect to a crank angle of an engine by hydraulic pressure.

  In recent years, an engine having a variable valve timing mechanism system that varies a rotational phase between a crankshaft and a camshaft of an engine has been put into practical use, and at least one of an intake valve and an exhaust valve according to an engine operating state. The valve timing can be changed continuously.

  Such a variable valve timing mechanism is generally a hydraulic drive type driven by hydraulic pressure, as disclosed in Patent Document 1. In this hydraulically driven variable valve timing mechanism, a rotor attached to the tip of an intake camshaft is rotatably housed in a housing that is connected to an intake cam pulley so as to be integrally rotatable, and a vane provided on the rotor is provided. By controlling the hydraulic pressure supplied to the advance chamber and retard chamber divided by the hydraulic control valve, the rotor is rotated relatively, and the relative rotation phase of the intake cam shaft with respect to the intake cam pulley is adjusted to change the valve timing. To do.

Japanese Patent Laying-Open No. 2005-2992

  As disclosed in Patent Document 1, in a variable valve timing mechanism of a type that determines the cam position by supplying hydraulic pressure to the advance side and the retard side, respectively, a control point for holding the current angle (holding) Point). Specifically, this holding point is a control amount for the hydraulic control valve when the advance angle speed of the variable valve timing mechanism becomes zero, and is affected by temperature (such as engine thermal expansion) and individual differences of the variable valve timing mechanism. It varies somewhat depending on external factors such as.

  For this reason, conventionally, a control point where the cam angle is stable during valve timing control is learned as a holding point to prevent deviation from the actual valve timing due to the influence of temperature, individual differences of the variable valve timing mechanism, etc. I have to.

  However, when learning the holding point, when the variable valve timing mechanism housing is in contact with the vane, such as the most retarded position or the most advanced position, the vane is pressed against the housing to stabilize the angle. It is difficult to determine whether the angle is stable by controlling the holding point correctly. For this reason, when the holding point is learned in the vicinity of the most retarded angle position or the most advanced angle position, erroneous learning occurs, and the control amount at the next control may become inappropriate, and the responsiveness may deteriorate.

  The present invention has been made in view of the above circumstances, and provides an engine valve timing control device capable of preventing erroneous learning of a holding point in the vicinity of the most retarded angle position or the most advanced angle position of the variable valve timing mechanism. The purpose is that.

In order to achieve the above object, an engine valve timing control apparatus according to the present invention is provided with a variable valve timing mechanism that advances or retards the rotational phase of a cam angle with respect to the crank angle of an engine by hydraulic pressure. The holding point learning is performed by classifying the holding point for holding the amount of advancement of the variable valve timing mechanism constant into a range near the most retarded position, a normal range, and a range near the most advanced angle position. A learning range restriction unit that restricts the learning range of the most retarded angle position vicinity range and the learning range of the most advanced angle position vicinity range based on the holding point acquired by learning of the normal range, and the holding When the sticking of the learning value of the point to the advance side upper limit value or the retard side lower limit value is monitored, and it is determined that the learned value is stuck to the advance side upper limit value, the advance side control range is set to the set value When it is determined that the learning value is stuck to the retard side lower limit while shifting to the retard side and limiting the direction to prevent noise generation due to mechanical contact of the movable part of the variable valve timing mechanism, A control range limiting section that shifts the control range on the retard side to the advance side by a set value and limits the direction to prevent noise generation due to mechanical contact of the movable part of the variable valve timing mechanism. And

  According to the present invention, erroneous learning of the holding point in the vicinity of the most retarded angle position or the most advanced angle position of the variable valve timing mechanism can be prevented, and optimum valve timing control can always be performed.

Overall configuration diagram of engine with variable valve timing mechanism Explanatory drawing showing the schematic configuration of the variable valve timing mechanism Flow chart showing the main process of learning control Holding point learning process flowchart Flow chart of learning value upper limit sticking determination processing Flow chart of learning value lower limit sticking determination processing

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an engine with a variable valve timing mechanism (hereinafter simply referred to as “engine”). In FIG. 1, the engine 1 is a horizontally opposed engine in which a cylinder block 1a is divided into two left and right banks (a left bank on the right side and a right bank on the left side) centered on a crankshaft 1b. Yes.

  First, the intake / exhaust system of the engine 1 will be described. Cylinder heads 2 are provided in both the left and right banks of the cylinder block 1a of the engine 1, respectively. An intake manifold 3 communicates with each intake port of the cylinder head 2, and an injector 11 is disposed immediately upstream of the intake port of each cylinder of the intake manifold 3. A spark plug 12 that exposes the discharge electrode to the combustion chamber is provided for each cylinder of the cylinder head 2.

  The intake manifold 3 communicates with the throttle chamber 5 through an air chamber 4 in which intake passages of the cylinders gather. A throttle valve 5 a that is driven by a throttle actuator 10 is interposed in the throttle chamber 5. Further, an air cleaner 7 is attached upstream of the throttle chamber 5 via an intake pipe 6, and the chamber 8 is communicated with an air intake passage connected to the air cleaner 7.

  On the other hand, an exhaust manifold 14 is communicated with each exhaust port of the cylinder head 2, and an exhaust pipe 15 is communicated with a collecting portion of the exhaust manifold 14. A catalytic converter 16 is interposed in the exhaust pipe 15 and communicates with the muffler 17.

  Next, the valve train of the engine 1 will be described. An intake cam shaft 19 and an exhaust cam shaft 20 are disposed in each cylinder head 2 of the left and right banks of the engine 1, and the rotation of the crankshaft 1 b is transmitted to the cam shafts 19 and 20. The transmission of rotation of the crankshaft 1b to the intake camshaft 19 and the exhaust camshaft 20 is transmitted to a crank pulley 21 fixed to the crankshaft 1b, a timing belt 22, an intake cam pulley 23 interposed in the intake camshaft 19, This is performed via an exhaust cam pulley 24 and the like fixed to the exhaust cam shaft 20. Each of the camshafts 19 and 20 is maintained at a rotation angle of 2 to 1 with the crankshaft 1b by the intake cam provided on the intake camshaft 19 and the exhaust cam provided on the exhaust camshaft 20. Based on this, the intake valve 25 and the exhaust valve 26 are driven to open and close.

  Further, in each valve system of the left and right banks, a hydraulically driven variable valve timing mechanism 27in that continuously changes the rotational phase (displacement angle) of the intake camshaft 19 with respect to the crankshaft 1b, and a crank of the exhaust camshaft 20 A hydraulically driven variable valve timing mechanism 27ex that continuously changes the rotational phase with respect to the shaft 1b is provided.

  In the present embodiment, the engine 1 includes variable valve timing mechanisms 27in and 27ex on the intake side and the exhaust side, respectively, but the present invention is not limited to this, and the intake side and The present invention is also applied to an engine having a variable valve timing mechanism on either the exhaust side.

  The intake side variable valve timing mechanism 27in is provided between the intake camshaft 19 and the intake cam pulley 23, and relatively rotates the intake cam pulley 23 and the intake camshaft 19 by hydraulic pressure controlled by the cam angle control valve 28in. On the other hand, the variable valve timing mechanism 27ex on the exhaust side is provided between the exhaust camshaft 20 and the exhaust cam pulley 24 and relatively rotates the exhaust cam pulley 24 and the exhaust camshaft 20 by the hydraulic pressure controlled by the cam angle control valve 28in. Let

  The variable valve timing mechanism 27in on the intake side and the variable valve timing mechanism 27ex on the exhaust side have the same configuration, and the variable valve timing mechanism 27in will be schematically described as a representative example of the variable valve timing mechanism 27in on the intake side. As shown in FIG. 2, a rotor 51 attached to the tip end portion of the intake cam shaft 19 is housed in a housing 50 that is connected to the intake cam pulley 23 so as to be integrally rotatable. By relatively rotating the rotor 51 by hydraulic pressure, the relative rotation phase of the intake cam shaft 19 with respect to the intake cam pulley 23 is changed, and the valve timing of the intake valve 25 is changed.

  Specifically, a vane 51 a provided on the rotor 51 is rotatably accommodated in a fan-shaped space formed in the housing 50. Each fan-shaped space is divided into an advance chamber (advanced hydraulic chamber) 52a and a retard chamber (retarded hydraulic chamber) 52b by a vane 51a. It is connected to the cam angle control valve 28in through the hydraulic passage 54 for use.

  The cam angle control valve 28in is a port of a main hydraulic passage 56 that supplies hydraulic pressure from an oil pan 1c through an engine-driven oil pump (not shown) and a check valve 55, an advance hydraulic passage 53, and a retard hydraulic pressure. A control valve that switches each port of the passage 54, a port of a drain passage 57, which will be described later, and the like. An electromagnetic solenoid 60 having a mover 60a and a spool valve 61 that is driven forward and backward by the electromagnetic solenoid 60 to open and close each port. It is configured.

  The spool valve 61 has a spool 63 that switches each port in a sleeve 62 disposed in the center of the rotor 51, and a spring 64 that urges the spool 63 in a direction to contact the movable element 60a of the electromagnetic solenoid 60. It is configured to accommodate. The same applies to the cam angle control valve 28ex on the exhaust side.

  The cam angle control valves 28in and 28ex are duty-controlled by an electronic control unit (hereinafter abbreviated as “ECU”) 100 formed of a microcomputer or the like, and the spool 63 of the spool valve 61 is controlled via the mover 60a of the electromagnetic solenoid 60. Each port is switched by driving back and forth. That is, when the energizing current of the electromagnetic solenoid 60 is increased or decreased according to the duty ratio of the duty control and the spool 63 of the spool valve 61 moves in the axial direction via the mover 60a of the electromagnetic solenoid 60, the main hydraulic passage 56, the advance angle The ports of the hydraulic pressure passage 53 and the retarding hydraulic passage 54 are switched to switch the oil flow direction and adjust the opening of the passage. As a result, the magnitude of the hydraulic pressure supplied to the advance chamber 52a and the retard chamber 52b is adjusted, and the opening / closing timing of the intake valve 25 and the exhaust valve 26 is controlled to the advance or retard side.

  In addition, the variable valve timing mechanisms 27in and 27ex lock the camshaft rotation phase at a phase corresponding to the predetermined timing in order to fix the valve timing at a predetermined timing in a low oil pressure state such as when the engine is started. A locking mechanism 70 is provided. The lock mechanism 70 mainly includes a lock hole 50a provided in the housing 50 and a lock pin 71 disposed so as to be immersible in the lock hole 50a.

  The lock pin 71 is housed in a lock pin hole 51 b formed in the rotor 51 in a state in which the lock pin 71 is urged toward the lock hole 50 a by the spring 72. The lock pin hole 51b forms a cylinder in which the lock pin 71 can slide in a state facing the lock hole 50a. Here, the lock hole 50a also serves as an unlocking hydraulic chamber for applying hydraulic pressure to the lock pin 71 and releasing the engagement of the lock pin 71 with the lock hole 50a. The lock hole 50 a is connected to the spool valve 61 via the hydraulic circuit 74.

  When the hydraulic circuit 74 is communicated with the drain passage 57 by the cam angle control valve 28in (28ex) and the hydraulic pressure of the lock hole 50a is below a predetermined value, the lock pin 71 is inserted into the lock hole 50a by the biasing force of the spring 72, and the housing The relative rotation of the rotor 51 with respect to 50 is mechanically locked. In the present embodiment, the engagement position between the lock pin 71 and the lock hole 50a is set so as to be locked at an intermediate position between the most retarded angle position and the most advanced angle position. On the other hand, when the hydraulic circuit 74 is communicated with the main hydraulic passage 56 and the drain passage 57 is closed, a predetermined hydraulic pressure is applied from the main hydraulic passage 56 to the lock hole 50 a via the hydraulic passage 74. By this hydraulic pressure, the lock pin 71 is disengaged from the lock hole 50a against the urging force of the spring 72, and the lock is released (unlocked).

  Next, sensors for detecting the state of the engine 1 will be described. A throttle sensor 30 for detecting the opening degree of the throttle valve 5 a is interposed in the throttle valve 5 a of the throttle chamber 5, and an intake air amount sensor 31 is interposed immediately downstream of the air cleaner 7 of the intake pipe 6. . On the other hand, air-fuel ratio sensors 32 and 33 are disposed on the upstream and downstream sides of the catalytic converter 16 in the exhaust pipe 15.

  In addition, a crank angle sensor 35 is provided on the outer periphery of the crank rotor 34 that is attached to the crankshaft 1b of the cylinder block 1a, and a water temperature sensor 37 is exposed to the cooling water passage 36 that communicates the left and right banks of the cylinder block 1a. In addition, an oil temperature sensor 29 is exposed to the oil pan 1c below the cylinder block 1a. Further, the cylinder block 1a is provided with a knock sensor 38 including a piezo-type sensor that detects vibration transmitted to the cylinder block 1a by knocking generated in the left bank or the left bank.

  As a sensor for detecting the operating position of the intake side variable valve timing mechanism 27in, a cam position sensor 40 for detecting the intake cam position is provided on the outer periphery of a cam rotor 39 fixed to the rear end of the intake cam shaft 19. It is opposite. Further, a cam position sensor 42 for detecting the exhaust cam position is provided on the outer periphery of the cam rotor 41 fixed to the rear end of the exhaust camshaft 20 as a sensor for detecting the operating position of the exhaust side variable valve timing mechanism 27ex. It is opposite.

  The output signals from the sensors described above are input to the ECU 100 and processed to detect the engine operating state. The ECU 100 processes signals from the sensors, switches, and the like according to a control program stored therein in advance, and controls the cam angle control valve of the above-described injector 11, throttle actuator 10, and intake side variable valve timing mechanism 27in. 28in, the control amount for the cam angle control valve 28ex and the like of the variable valve timing mechanism 27ex on the exhaust side is calculated, and engine control such as fuel injection control, ignition timing control, throttle control, and valve timing control is performed.

  Here, in the valve timing control, a target valve timing that is each control target value of the rotational phase of the intake camshaft 19 and the exhaust camshaft 20 is set based on the engine operating state, for example, the engine load and the engine speed. At the same time, the actual rotation angle of the crankshaft 1b and the intake camshaft 19 are determined from the crank pulse indicating the crank angle output from the crank angle sensor 35 and the cam position pulse indicating the cam position output from the cam position sensors 40 and 42. The actual valve timing, which is the phase difference from the actual rotation angle of the exhaust camshaft 20, is calculated. The cam angle control valves 28in and 28ex are driven by duty control so that the actual valve timing converges to the target valve timing, and the variable valve timing mechanisms 27in and 27ex are feedback-controlled.

  In addition, the ECU 100 learns a holding point for holding the current angle in the valve timing control. The holding point learning is specifically learning for a control amount such as a duty ratio and a current value given to the cam angle control valves 28in and 28ex. For example, in feedback control based on the deviation between the target advance value VTTGT and the actual advance value VT, a value obtained by adding the holding current value to the feedback current value of the deviation by proportional differential control or the like is set in the cam angle control valves 28in and 28ex. As a control current value, a duty ratio giving this control current value is determined.

  The holding current value is a current value for maintaining the spool 63 of the cam angle control valves 28in and 28ex at a point at which the vane 51a does not displace to the advance side or the retard side, i.e., a predetermined speed. This is a current value for maintaining a steady state converged to the target valve timing. The control point giving this holding current value is learned for each individual variable valve timing mechanism as a holding point in feedback control.

  In learning of such a holding point, if learning is performed in the vicinity of the most retarded position or the most advanced position, whether the cam angle is stable at the most retarded position or the most advanced position, It is difficult to determine whether the control is operating correctly and the cam angle is stable, and there is a risk of erroneous learning.

  Therefore, the ECU 100 performs learning by classifying the learning range of the holding points into “normal range”, “most retarded position vicinity range”, and “most advanced angle position vicinity range” by the function as the holding point learning unit. And by limiting the learning range of the most retarded angle position vicinity range and the learning range of the most advanced angle position vicinity range with the function as the learning range restriction unit with reference to the holding point acquired by learning of the normal range, Prevent false learning.

  In this case, mislearning can be prevented by limiting the learning range of the most retarded angle vicinity range or the most advanced angle vicinity range, but in the learning of the most retarded angle vicinity range or the most advanced angle vicinity range, the most retarded angle during learning There is a possibility that the control state in which the housing 50 and the vane 51a of the variable valve timing mechanisms 27in and 27ex are in contact with each other as in the position or the most advanced angle position may occur. For this reason, depending on the material of the housing 50 and the vane 51a, there is a possibility that noise due to the contact between the housing 50 and the vane 51a may occur.

  Therefore, the ECU 100 further monitors whether the learning value is stuck to the advance side upper limit value or the retard side lower limit value by the function as the control range restriction unit, thereby determining whether or not the vane 51a and the housing 50 come into contact with each other. Estimate. When it is determined that the learning value has stuck to the advance side upper limit value or the retard side lower limit value, it is determined that there is a possibility that the vane 51a and the housing 50 come into contact with each other, and the current control range is changed to the variable valve timing mechanism. The generation of noise is suppressed by limiting to the direction in which the movable part is not in contact.

  Specifically, the functions of the ECU 100 related to the holding point learning described above are realized by the program processing shown in the flowcharts of FIGS. Hereinafter, this program processing will be described.

  The flowchart of FIG. 3 shows the main process of learning control. In this main process, in the first steps S1 and S2, the learning range of the holding point is set to the range near the most retarded position, the normal range, and the most advanced position. Judgment is made to categorize the scope. Specifically, first, in step S1, it is checked whether or not the current advance angle value (cam angle) VT is less than the advance angle side set value A1 (absolute value). The set value A1 is a threshold value for determining whether or not the current advance value is near the most advanced position.

  As a result, in step S1, if VT ≧ A1, the process in the vicinity of the most advanced angle position in steps S13 to S19 is performed. If VT <A1, the advance value VT is further set to the set value A2 (absolute in step S2). Value) is checked to see if it is greater. The set value A2 is a threshold value for determining whether or not the current advance angle value is in the vicinity of the most retarded angle position. When VT ≦ A2, the process in the vicinity of the most retarded angle position in steps S23 to S29 is performed. In the case of VT> A2, processing in the normal range of steps S3 to S6 is performed.

  First, the normal range process in steps S3 to S6 will be described. In this normal range processing, learning is performed within a predetermined range. Therefore, in step S3, a set value (absolute value) A3 is set as a learning upper limit value Lmax, and in step S4, a set value ( (Absolute value) A4 is set and the process proceeds to step S5. Here, the set values A3 and A4 define the entire learnable range, and learning in the vicinity of the most retarded angle position or the most advanced angle position cannot be learned beyond these values. .

  In step S5, the holding point learning process shown in the flowchart of FIG. 4 to be described later is performed within the range between the learning upper limit value Lmax and the learning lower limit value Lmin set previously. In step S6, the learning value (holding point learning value) Lh obtained by the holding point learning process is stored as a learning reference value Lref serving as a reference for learning in the advance side or retard side region (Lref). ← Lh) Exit this process.

  Next, the learning process in the vicinity of the most advanced angle position in steps S13 to S19 will be described. In the learning process for the most advanced angle position vicinity range, first, in step S13, a value obtained by adding the setting value α to the learning reference value Lref is compared with the setting value A3, and the smaller value is set as the learning upper limit value Lmax. (Lmax ← min (Lref + α, A3)). Next, the process proceeds to step S14, and a value obtained by subtracting the set value β from the learning reference value Lref is set as a learning lower limit Lmin (Lmmin ← Lref−β). The setting value α defines a range where mis-learning is possible, and the setting value β defines a range where mis-learning is not possible. In the processing at, the upper limit value of learning is set to a smaller value by comparing Lref + α and A3.

  Next, the process proceeds to step S15, where the holding point learning process is performed within a range limited by the learning upper limit value Lmax and the learning lower limit value Lmin set on the advance side, and the learning value sticks to the upper limit value in step S16. The learning value upper limit sticking determination process of FIG. The holding point learning process in FIG. 4 and the learning value upper limit sticking determination process in FIG. 5 will be described later.

  Thereafter, the process proceeds to step S17, and the value of the learned value sticking flag F indicating that the learned value is stuck to the upper limit value or the lower limit value is referred to. The learning value sticking flag F indicates that the learning value is stuck when F = 1. In the process of the most advanced angle, F = 1 and the learning value sticks to the upper limit value. ing.

  If it is determined in step S17 that F = 0 and the learning value does not stick to the upper limit value, the process is terminated. If F = 1 and the learning value sticks to the upper limit value, the process proceeds to step S18 and the advance side is reached. Limit the control range. In step S19, the holding point learning value Lh is returned to the learning reference value Lref (Lh ← Lref), and the process is exited.

  Originally, the control range of the valve timing is set narrower than the physical movable range of the variable valve timing mechanism, but it remains the normal control range due to individual differences of components, errors in angle calculation criteria, etc. Then, the housing 50 and the vane 51 may come into contact with each other and noise may be generated. Accordingly, the movable portion of the variable valve timing mechanism is shifted by a set value θ that is determined in advance in consideration of individual differences of components of the variable valve timing mechanism, errors in the angle calculation reference, etc. from the original control range. Noise generation due to mechanical contact (contact between the housing 50 and the vane 51a) is prevented.

Next, the learning processing on the most retarded side in steps S23 to S29 will be described. First, in step S23, a value obtained by adding the set value β to the learning reference value Lref is set as a learning upper limit Lmax (Lmax ← Lref + β). Furthermore, in step S24, the value obtained by subtracting the set value α from the learning reference value Lref is compared with the set value A4, and the larger value is set as the learning lower limit Lmin (L min ← max (Lref−α, A4 )). In the learning on the retard side, contrary to the learning on the advance side, mislearning is likely to occur in the direction in which the advance amount decreases, so the lower limit of learning is set to the larger of Lref-α and A4. Set to value.

  In step S25, the holding point learning process is performed within a range limited by the learning upper limit value Lmax and the learning lower limit value Lmin set on the retard side, and in step S26, is the learning value stuck to the lower limit value? The learning value lower limit sticking determination process of FIG. 6 for determining whether or not is performed is executed. The learning value lower limit sticking determination process will be described later together with the learning value upper limit sticking determination process.

  Next, the process proceeds to step S27, and the value of the learned value sticking flag F is referred to. In the processing near the retard position, F = 1 indicates that the learning value is stuck to the lower limit value, and when F = 0 (when the learning value is not stuck to the lower limit value), this processing is performed. If F = 1 and the learning value is stuck to the lower limit value, the variable valve timing mechanism can be moved by shifting the retarded control range to the advanced side by the set value θ in step S28. Prevents noise generation due to mechanical contact of parts. Thereafter, in step S29, the holding point learning value Lh is returned to the learning reference value Lref (Lh ← Lref), and the process is exited.

  Next, the holding point learning process of FIG. 4 will be described. In this holding point learning process, in the first step S501, whether or not the deviation between the target advance value VTTGT and the actual advance value VT is less than the set value A5, that is, the actual advance value VT is smaller than the target advance value VTGT. It is checked whether or not the state is converged within a certain range. As a result, when | VTTTGT−VT | ≧ A5, it is determined that the state is not suitable for learning, and the present process is exited without performing learning. When | VTTTGT−VT | <A5, the process proceeds to step S502. It is checked whether or not the target advance value VTTGT has changed.

  As a result, if the target advance value VTTGT has changed in step S502, it is determined that the control state is not yet stable, and the process is exited. On the other hand, if the target advance value VTTGT has not changed in step S502, it is determined that the control state is stable, and the process proceeds to step S503, where the current control amount VVT is less than or equal to the learning upper limit value Lmax. Find out.

  As a result, if VVT> Lmax in step S503, the holding point learning value Lh is limited to the learning upper limit value Lmax (Lh ← Lmax) in step S506, and the process is exited. On the other hand, if VVT ≦ Lmax in step S503, it is further checked in step S504 whether the control amount VVT is greater than or equal to the learning lower limit Lmin. As a result, if VVT ≧ Lmin, the current control amount VVT is held as the holding point learning value Lh in step S505 (Lh ← VVT). If VVT <Lmin, the holding point learning value Lh is set to the learning lower limit value in step S507. Limit by Lmin (Lh ← Lmin), and exit this process.

  Next, the learning value upper limit sticking determination process of FIG. 5 and the learning value lower limit sticking determination process of FIG. 6 will be described. The sticking of the learning value to the upper limit value or the lower limit value is determined by the duration of the state where the learning value is the upper limit value or the lower limit value, and the learning value sticking flag F is set / cleared according to the determination result.

  First, in the learning value upper limit sticking determination process of FIG. 5, it is checked in the first step S601 whether or not the current learning value L has reached the learning upper limit value Lmax. As a result, when L = Lmax, the counter CT for counting the duration of the state in which the learning value L is the learning upper limit value Lmax in step S602 is counted up (CT ← CT + 1), and the process proceeds to step S603. If L ≠ Lmax, the counter CT is cleared (CT ← 0) in step S605, and the process proceeds to step S603.

  In step S603, it is determined whether or not the counter value CT has reached the set value C1, thereby determining sticking of the learning value. If CT ≧ C1, it is determined that the learning value is stuck to the upper limit value, and the learning value sticking flag F is set (F ← 1) in step S604, and the process is exited. On the other hand, if CT <C1, the learning value sticking flag F is cleared (F ← 0) in step S606, and the process is exited.

  The learning value lower limit sticking determination process in FIG. 6 is the same, and whether the current learning value L has reached the learning lower limit value Lmin in step S601 ′ instead of step S601 with respect to the learning value upper limit sticking determination process in FIG. Check for no. In step S603, if CT ≧ C1, it is determined that the learning value is stuck to the lower limit value.

  As described above, in the present embodiment, when learning the holding point in the vicinity of the most retarded angle position or the most advanced angle position, the learning range is limited based on the learning reference value acquired in the normal range learning. Prevent learning. Thereby, it is possible to always leave the optimum valve timing control, and it is possible to improve the control response.

  Further, when it is determined that the learning value has stuck to the lower limit value on the most retarded angle side or the upper limit value on the most advanced angle side, the current control range is not in contact with the movable portion of the variable valve timing mechanism. Therefore, generation of noise due to mechanical contact of the movable part can be avoided in advance, and the driver is not uncomfortable.

1 Engine 1b Crankshaft 19 Intake camshaft 20 Exhaust camshaft 27in, 27ex Variable valve timing mechanism 28in, 28ex Cam angle control valve 100 Electronic control unit (holding point learning unit, learning range limiting unit, control range limiting unit)

Claims (1)

An engine valve timing control device having a variable valve timing mechanism for advancing or retarding a rotational phase of a cam angle with respect to a crank angle of an engine by hydraulic pressure,
A holding point learning unit that learns by classifying a holding point for holding the advance amount of the variable valve timing mechanism constant into a most retarded position vicinity range, a normal range, and a most advanced angle position vicinity range;
A learning range limiter that limits the learning range of the most retarded angle position vicinity range and the learning range of the most advanced angle position vicinity range with reference to the holding point acquired by learning of the normal range ;
The sticking of the learning value of the holding point to the advance side upper limit value or the retard side lower limit value is monitored, and if it is determined that the learned value is stuck to the advance side upper limit value, the advance side control range is set to the set value. When it is determined that the learning value has stuck to the retard side lower limit value while shifting to the retard side only to limit the direction to prevent noise generation due to mechanical contact of the movable part of the variable valve timing mechanism, A control range limiting section that shifts the control range on the retard side to the advance side by a set value and limits the direction to prevent noise generation due to mechanical contact of the movable part of the variable valve timing mechanism. An engine valve timing control device.

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