JP4264983B2 - Variable valve timing control device for internal combustion engine - Google Patents

Description

  The present invention includes an internal combustion engine having a variable valve timing device, and a lock mechanism that locks a rotational phase of a camshaft with respect to a crankshaft (hereinafter referred to as “camshaft phase”) at a lock position that is substantially in the middle of the adjustable range. The present invention relates to a variable valve timing control device for an internal combustion engine.

  In recent years, an increasing number of internal combustion engines mounted on vehicles adopt a variable valve timing control device for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. For example, as shown in FIG. 15, the basic configuration of a vane type variable valve timing control device is connected to a housing 1 that rotates in synchronization with a crankshaft of an engine and a camshaft of an intake (or exhaust) valve. The rotor 2 is coaxially arranged, and the fluid chamber 3 formed in the housing 1 is divided into an advance chamber 5 and a retard chamber 6 by a vane 4 provided in the rotor 2. Then, the hydraulic pressure in the advance chamber 5 and the retard chamber 6 is controlled by a hydraulic control valve so that the housing 1 and the rotor 2 (vane 4) are rotated relative to each other, thereby rotating the cam shaft relative to the crankshaft (cam shaft). The valve timing is variably controlled by changing the phase.

  The conventional variable valve timing control device of the vane system is the most retarded angle phase in which the camshaft phase is most retarded when the engine is stopped (when the hydraulic pressure is lowered) in order to prevent noise caused by the vibration of the vane 4 at the start. Thus, the relative rotation between the housing 1 and the rotor 2 (vane 4) is locked by the lock pin 7. Therefore, since the engine is started at the most retarded phase at the start, the most retarded phase is set to a phase suitable for starting.

  However, in this configuration, since the most retarded angle phase is limited by the phase (lock position) at the start, the adjustable range of the valve timing (cam shaft phase) is limited by the lock position, and the valve timing is adjusted. There is a disadvantage that the possible range is narrow.

Therefore, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 9-324613), the valve timing (cam shaft phase) is set by setting the lock position when the engine is stopped to a substantially intermediate position within the adjustable range of the cam shaft phase. It has been proposed to expand the adjustable range.
JP-A-9-324613 (first page to second page, etc.)

  However, the lock position has individual differences (variations) due to manufacturing errors and the like. Further, during the unlocking control, a hydraulic pressure in the unlocking direction is applied to the lock pin 7, but the hydraulic pressure during the unlocking control is not necessarily suitable for unlocking due to manufacturing variations of the lock position, manufacturing variations of the hydraulic control valve, and the like. However, there was a problem that the lock release was delayed and the valve timing control was adversely affected.

  The present invention has been made in view of such circumstances, and an object of the present invention is to optimize the control amount at the time of unlocking control of the hydraulic control valve so that the unlocking can be performed promptly. .

In order to achieve the above object, an invention according to claim 1 is a variable valve timing device that varies a valve timing by changing a rotational phase of a cam shaft (hereinafter referred to as a “cam shaft phase”) with respect to a crankshaft of an internal combustion engine. The variable valve timing device is provided with a lock mechanism that locks the camshaft phase at a lock position substantially in the adjustable range when variable valve timing control is not performed. The lock mechanism and the variable valve timing device In the variable valve timing control apparatus for an internal combustion engine that controls the hydraulic pressure for driving the hydraulic control valve, during the unlocking control for controlling the hydraulic control valve to unlock the locking mechanism, the control amount of the hydraulic control valve ( (Hereinafter referred to as “unlock control amount”) is continuously learned by the unlock learning means and Discontinue updating of the lock release control amount learning value, it is obtained so as to terminate the learning. In this way, even if there are large variations in manufacturing of the lock position and manufacturing of the hydraulic control valve, etc., the unlock control amount of the hydraulic control valve can be optimized according to the characteristics of each system. The performance can be improved.

  In this case, as in claim 2, when the unlocking cannot be performed during the unlocking control, the unlocking control amount of the hydraulic control valve is preferably corrected in a direction in which the unlocking is easy. In this way, unlocking can be performed more reliably.

Further, as in claim 3, when unlocking is not possible even when the unlocking control amount of the hydraulic control valve is corrected during unlocking control, it is determined that the unlocking is not successful (lock stuck) and that the unlocking is defective. In some cases, learning of the unlock control amount may be stopped and the learned value of the unlock control amount may be set to the initial value or the learned value at the previous unlock control . In this way, it is possible to prevent erroneous learning of the unlock control amount, and to detect unlock failure without adding a new sensor or the like.

  In this case, as in the fourth aspect of the invention, it is preferable to perform control so that the locked state is maintained when it is determined that the lock release is defective (lock lock). In this way, it is not necessary to perform useless hydraulic feedback control when an unlock failure occurs, and it is possible to perform an operation corresponding to the camshaft phase fixed at the lock position.

  In this case, as described in claim 5, when the unlock control amount of the hydraulic control valve is corrected more than a predetermined number of times during the unlock control, or when the unlock control amount is out of the predetermined range. It is good to determine that it is defective. In this way, the correction of the unlock control amount can be stopped at the time when the unlock failure is detected, and unnecessary correction is not required.

  Further, as described in claim 6, when it is determined that the unlocking is defective, the learning value of the unlocking control amount may be set to an initial value (for example, a design median value) or a learning value at the previous unlocking control. Thereby, the learning value of the unlocking control amount at the time of unlocking failure can be returned to an appropriate value, and erroneous learning of the unlocking control amount can be prevented.

  Further, as in the seventh aspect, when the unlocking cannot be performed during the unlocking control, the unlocking control may be performed again in an operation region where the hydraulic pressure supplied to the hydraulic control valve is high. In other words, if the unlock control is performed again in the operating region where the hydraulic pressure supplied to the hydraulic control valve is high, the hydraulic pressure in the unlocking direction applied to the lock mechanism can be increased, and the resistance force for unlocking is slightly increased. If it is, it can be unlocked.

  Hereinafter, an embodiment in which the present invention is applied to an intake valve variable valve timing control apparatus will be described with reference to FIGS. As shown in FIG. 1, in the DOHC engine 11 that is an internal combustion engine, the power from the crankshaft 12 is transmitted to the intake side camshaft 16 and the exhaust side camshaft 17 via the sprockets 14 and 15 by the timing chain 13. It has become so. However, the intake side camshaft 16 is provided with a variable valve timing device 18 that adjusts the advance amount of the intake side camshaft 16 with respect to the crankshaft 12.

  A cam angle sensor 19 that outputs a cam angle signal at a plurality of cam angles 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 for each crank angle is installed. The output signals of 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 of the intake valve and outputs the frequency of the output pulse of the crank angle sensor 20. From this, the engine speed is calculated. 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 based on these various input signals, and also performs variable valve timing control, and actual valve timing of the intake valve (actual advance angle amount of the intake side camshaft 16). The feedback control of the variable valve timing device 18 is performed so as to match the target valve timing (target advance amount). The oil in the oil pan 27 is supplied to the hydraulic control circuit of the variable valve timing device 18 through the hydraulic control valve 29 by the oil pump 28, and the hydraulic pressure is controlled by the hydraulic control valve 29. The actual valve timing is controlled.

  Next, the configuration of the variable valve timing device 18 with an intermediate lock mechanism 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, the intake side camshaft 16 is rotatably supported by a cylinder head 33 and a bearing cap 34, and a rotor 35 is fastened and fixed to one end portion of the intake side camshaft 16 with a bolt 37 via a stopper 36. . The rotor 35 is housed in the housing 31 so as to be relatively rotatable.

  As shown in FIGS. 3 and 4, a plurality of fluid chambers 40 are formed inside the housing 31, and each fluid chamber 40 is retarded from the advance chamber 42 by a vane 41 formed on the outer periphery of the rotor 35. It is partitioned into a corner chamber 43. Seal members 44 are attached to the outer periphery of the rotor 35 and the outer periphery of the vane 41, and each seal member 44 is urged in the outer peripheral direction by a leaf spring 45 (see FIG. 2). Thereby, the clearance between the outer peripheral surface of the rotor 35 and the inner peripheral surface of the housing 31 and the clearance between the outer peripheral surface of the vane 41 and the inner peripheral surface of the fluid chamber 40 are sealed by the seal member 44.

  As shown in FIG. 2, an annular advance groove 46 and a retard groove 47 formed on the outer peripheral portion of the intake side camshaft 16 are connected to predetermined ports of the hydraulic control valve 29, respectively. By driving the pump 28, the oil pumped up from the oil pan 27 is supplied to the advance groove 46 and the retard groove 47 through the hydraulic control valve 29. The advance oil passage 48 connected to the advance groove 46 passes through the inside of the intake side camshaft 16 and communicates with an arcuate advance oil passage 49 (see FIG. 3) formed on the left side surface of the rotor 35. The arcuate advance oil passage 49 communicates with each advance chamber 42. On the other hand, the retarding oil passage 50 connected to the retarding groove 47 penetrates the inside of the intake side camshaft 16 to an arcuate retarding oil passage 51 (see FIG. 4) formed on the right side surface of the rotor 35. The arc retarded oil passage 51 is formed so as to communicate with each other, and communicates with each retarded angle chamber 43.

  The hydraulic control valve 29 is a four-port three-position switching valve that drives the valve body with a solenoid 53 and a spring 54, and the position of the valve body is hydraulic to the advance chamber 42 and to the retard chamber 43. The position is switched between a position where the hydraulic pressure is supplied and a position where no hydraulic pressure is supplied to either the advance chamber 42 or the retard chamber 43. When the energization of the solenoid 53 is stopped, the valve element is automatically switched to a position where the hydraulic pressure is supplied to the advance chamber 42 by the spring 54 so that the hydraulic pressure works in a direction to advance the camshaft phase.

  In a state where the hydraulic pressure higher than a predetermined pressure is supplied to the advance chamber 42 and the retard chamber 43, the vane 41 is fixed by the hydraulic pressure of the advance chamber 42 and the retard chamber 43, and the housing 31 is rotated by the rotation of the crankshaft 12. The rotation is transmitted to the rotor 35 (vane 41) through the oil, and the intake side camshaft 16 is rotationally driven integrally with the rotor 35. During engine operation, the intake side cam with respect to the crankshaft 12 is controlled by controlling the hydraulic pressure in the advance chamber 42 and the retard chamber 43 by the hydraulic control valve 29 to rotate the housing 31 and the rotor 35 (vane 41) relative to each other. The valve timing of the intake valve is varied by controlling the rotation phase of the shaft 16 (hereinafter referred to as “cam shaft phase”). Note that the sprocket 14 accommodates a torsion coil spring 55 (see FIG. 2) that assists the hydraulic pressure that causes the rotor 35 to relatively rotate in the advance direction at the time of advance angle control with a spring force.

  Further, as shown in FIGS. 3 and 4, stopper portions 56 for restricting the relative rotation range of the rotor 35 (vane 41) with respect to the housing 31 are formed on both side portions of any one vane 41. The portion 56 regulates the most retarded angle phase and the most advanced angle phase of the cam shaft phase. Furthermore, a lock pin 58 for locking relative rotation between the housing 31 and the rotor 35 (vane 41) is accommodated in the lock pin accommodation hole 57 formed in the other vane 41, and this lock pin 58 is accommodated in the housing. The camshaft phase is locked at a substantially intermediate position (lock position) within the adjustable range by being fitted into a lock hole 59 (see FIG. 2) provided in 31. This lock position is set to a position suitable for starting.

  As shown in FIGS. 6 and 7, the lock pin 58 is slidably inserted into the cylindrical member 61 fitted to the inner periphery of the lock pin accommodation hole 57, and is locked in the locking direction (protruding direction) by the spring 62. It is energized. Further, a gap between the cylindrical member 61 and the lock pin 58 is divided into a lock hydraulic chamber 64 and a lock release holding hydraulic chamber 65 by a valve portion 63 formed at the center outer peripheral portion of the lock pin 58. Then, in order to supply hydraulic pressure from the advance chamber 42 to the lock hydraulic chamber 64 and the lock release holding hydraulic chamber 65, the vane 41 has a lock oil passage 66 communicating with the advance chamber 42 and an unlock release holding fluid. An oil passage 67 is formed. The housing 31 is formed with an unlocking oil passage 68 that communicates the lock hole 59 and the retard chamber 43.

  As shown in FIG. 6, when the lock pin 58 is locked, the valve portion 63 of the lock pin 58 closes the lock release holding oil passage 67, and the lock oil passage 66 communicates with the lock hydraulic chamber 64. . As a result, hydraulic pressure is supplied from the advance chamber 42 to the lock hydraulic chamber 64, and the lock pin 58 is held in the lock hole 59 by this hydraulic pressure and the spring 62, and the camshaft phase is locked at the lock position. The

  While the engine is stopped, the hydraulic pressure in the lock hydraulic chamber 64 (the hydraulic pressure in the advance chamber 42) decreases, but the lock pin 58 is held in the locked position by the spring 62. Therefore, the engine is started with the lock pin 58 held in the locked position, and the lock release control is performed when the discharge pressure of the oil pump 28 rises to some extent after the engine is started. When the hydraulic pressure in the lock hole 59 (hydraulic pressure in the retarding angle chamber 43) is increased by this lock release control, the lock pin 58 is unlocked by the hydraulic pressure as follows. The hydraulic pressure (force in the unlocking direction) supplied from the retard chamber 43 through the unlocking oil passage 68 to the lock hole 59 by the unlocking control after the engine is started is the hydraulic pressure of the lock hydraulic chamber 64 (the hydraulic pressure of the advance chamber 42). ) And the spring force of the spring 62 (force in the lock direction), the lock pin 58 is pushed out of the lock hole 59 by the hydraulic pressure of the lock hole 59 and moved to the unlock position in FIG. 58 is unlocked.

  In this unlocked state, as shown in FIG. 7, the valve portion 63 of the lock pin 58 blocks the lock oil passage 66, and the unlocking and holding oil passage 67 communicates with the unlocking and holding hydraulic chamber 65. It becomes a state. As a result, hydraulic pressure is supplied from the advance chamber 42 to the hydraulic chamber 65 for holding and releasing the lock, and the hydraulic pressure of the hydraulic chamber 65 for holding and releasing the lock (hydraulic pressure of the advanced chamber 42) and the hydraulic pressure (retarding angle) of the lock hole 59. The lock pin 58 is held in the unlocked position against the spring 62 by the hydraulic pressure of the chamber 43.

  During engine operation, the hydraulic pressure of either the advance chamber 42 or the retard chamber 43 is high, so that the lock pin 58 is held at the unlocked position by the hydraulic pressure, and the housing 31 and the rotor 35 rotate relative to each other. It is held in a possible state (that is, a state in which variable valve timing control is possible).

  During engine operation, the engine control circuit 21 calculates the actual valve timing of the intake valve (the actual cam shaft phase of the intake camshaft 16) based on the output signals of the crank angle sensor 20 and the cam angle sensor 19, and performs the suction operation. The target valve timing of the intake valve (target cam shaft phase of the intake camshaft 17) is calculated based on the outputs of various sensors that detect engine operating conditions such as the atmospheric pressure sensor 22 and the water temperature sensor 23. Then, the hydraulic control valve 29 of the variable valve timing device 18 is feedback-controlled so that the actual valve timing of the intake valve coincides with the target valve timing. As a result, the hydraulic pressure in the advance chamber 42 and the retard chamber 43 is controlled to rotate the housing 31 and the rotor 35 relative to each other, thereby changing the camshaft phase and setting the actual valve timing of the intake valve to the target valve timing. Match.

  After that, when the engine 11 is stopped, if the engine rotation speed decreases, the discharge pressure of the oil pump 28 decreases, so the hydraulic pressure in the advance chamber 42 and the retard chamber 43 decreases. As a result, the hydraulic pressure in the unlocking hydraulic chamber 65 (the hydraulic pressure in the advance chamber 42) and the hydraulic pressure in the lock hole 59 (hydraulic pressure in the retard chamber 43) are reduced, and the spring force of the spring 62 is reduced to these hydraulic pressures. When it is overcome, the lock pin 58 protrudes and fits into the lock hole 59 by the spring force of the spring 62. However, in order for the lock pin 58 to be fitted into the lock hole 59, it is a condition that both positions are coincident with each other, that is, the cam shaft phase is coincident with the lock position.

  When the engine 11 stops, the engine rotation speed (rotation speed of the oil pump 28) decreases and the hydraulic pressure decreases, so the camshaft phase naturally changes to the retard side due to the load torque of the camshaft 16. In the process, as shown in FIG. 6, the lock pin 58 is fitted into the lock hole 59, and the camshaft phase is locked at the lock position. However, when the engine 11 is stopped, if the camshaft phase is already on the retard side with respect to the lock position, the lock pin 58 is not locked even if the camshaft phase has changed to the retard side due to a decrease in hydraulic pressure. Since it does not reach 59, the camshaft phase cannot be locked at the lock position.

Therefore, the engine control circuit 21 controls the hydraulic control valve 29 to advance the camshaft phase for locking when the camshaft phase needs to be locked at the lock position, such as when the engine is stopped (hereinafter, referred to as “the camshaft phase”). This control is called “lock control”). During the lock control, the energization of the solenoid 53 of the hydraulic control valve 29 is stopped, and the valve body is switched to the position where the hydraulic pressure is supplied to the advance chamber 42 by the spring 54 of the hydraulic control valve 29 to advance the camshaft phase. Simultaneously, the hydraulic pressure is applied in the direction, and the hydraulic pressure in the retard chamber 43 is discharged to the drain. At this time, since the fuel injection is stopped after the engine stop command, the engine rotation speed (oil pump rotation speed) decreases and the hydraulic pressure decreases. The camshaft phase advance can be controlled by hydraulic pressure with the spring force in the advance direction of the torsion coil spring 55 as an assist. If the cam shaft phase is already on the advance side of the lock position at the start of the lock control, the cam shaft phase advance control described above may not be performed.
Further, the engine control circuit 21 executes the lock position learning program shown in FIG. 8 stored in the ROM (storage medium) every predetermined time or every predetermined crank angle, so that the actual camshaft phase VT is set during the lock control. It plays a role as a lock position learning means for learning the lock position based on it. When this program is started, first, in step 101, the actual cam shaft phase change amount ΔVT is calculated from the deviation between the actual cam shaft phase current value VT (i) and the previous value VT (i-1).
ΔVT = VT (i) -VT (i-1)

In the next step 102, an actual cam shaft phase smoothed value VTSM (i) obtained by smoothing the actual cam shaft phase VT is calculated by the following equation.
VTSM (i) = VTSM (i-1) + {VT (i) -VTSM (i-1)} / S1
Here, VTSM (i-1) is the previous actual cam shaft phase smoothing value, and S1 is the smoothing constant.

  Thereafter, in step 103, it is determined whether or not the change in the actual cam shaft phase VT has become smaller depending on whether or not the lock control is being performed and the absolute value of the actual cam shaft phase change amount ΔVT is smaller than a predetermined value K1. When the lock control is not being performed, or when the actual cam shaft phase change amount ΔVT is equal to or greater than the predetermined value K1, the program is terminated without performing the subsequent learning process because it is clearly not in the locked state.

  On the other hand, when the lock control is being performed and the absolute value of the actual cam shaft phase change amount ΔVT is smaller than the predetermined value K1, the actual cam shaft phase VT is approaching the locked state, so the lock position is learned as follows. . First, in step 104, it is determined whether or not the learning number CGR of the lock position counted by the learning number counter is less than a predetermined value K2. If the learning number CGR is less than the predetermined value K2, the process proceeds to step 105, where It is determined whether the deviation between the camshaft phase smoothing value VTSM (i) and the previous lock position learning value GROK (i-1) is greater than a predetermined value K3.

When the deviation between the actual cam shaft phase smoothed value VTSM (i) and the previous lock position learned value GROK (i-1) is larger than the predetermined value K3, the actual cam shaft phase smoothed value VTSM (i) is It is determined that the value has not yet converged to a constant value (that is, the cam shaft phase is not locked), and the routine proceeds to step 106, where the lock position learning value GROK (i is calculated using the actual cam shaft phase smoothed value VTSM (i). ) Is calculated by the following annealing formula.
GROK (i) = GROK (i-1) + {VTSM (i) -GROK (i-1)} / S2

  Here, S2 is an annealing constant. After calculating the lock position learning value GROK (i), the routine proceeds to step 107, where the lock position learning value GROK (i) is within the allowable manufacturing variation range (predetermined value K4 <GROK (i) <predetermined value K5). If it is within this range, the process proceeds to step 108, the counter of the learning number CGR is incremented, and this program is terminated. If the lock position learning value GROK (i) is out of the allowable range of manufacturing variation, it is determined that the lock position learning value GROK (i) is stuck at a position other than the lock position, and the process proceeds to step 109, where the lock position learning value GROK (i) is determined. And the lock position learning value GROK (i) is set to an initial value (design median value) or a learning value at the previous lock control.

  If the deviation between the actual cam shaft phase smoothed value VTSM (i) and the previous lock position learned value GROK (i-1) is equal to or less than the predetermined value K3 before the learning number CGR reaches the predetermined value K2, It is determined that the actual camshaft phase smoothing value VTSM (i) has converged to a constant value (that is, the camshaft phase is locked), the process proceeds to step 110, the learning completion flag is turned on (ON), and the next step In 111, the learning number CGR counter is cleared and the program is terminated.

  On the other hand, before the deviation between the actual camshaft phase smoothing value VTSM (i) and the previous lock position learning value GROK (i-1) becomes equal to or smaller than the predetermined value K3, the learning number CGR is equal to the predetermined value K2. Is reached, the incomplete lock state (half-lock state) is determined, and the routine proceeds to step 112 where the lock position learning value GROK (i) is reset and the lock position learning value GROK (i) is set to the initial value (design). Set to the median) or the learned value for the previous lock control. Thereafter, the process proceeds to step 113, where lock release control is performed. In this way, the incompletely locked state can be returned to the unlocked state by the lock release control, and the normal lock state can be obtained by the next lock control. In step 114, the learning number CGR counter is cleared and the program is terminated.

  An example of the learning process of the lock position learning value GROK by the lock position learning program described above will be described with reference to FIGS. Here, FIG. 9 shows the behavior of the lock position learning process at the normal time, and FIG. 10 shows the behavior of the lock position learning process at the abnormal time. During the lock control, the actual cam shaft phase VT is controlled to the advance side, and the lock position learning value GROK gradually approaches the lock position. In the normal state, as shown in FIG. 9, during the lock control, the actual cam shaft phase VT reaches the lock position and enters the lock state, whereby the lock position learning value GROK converges to a constant value. At this time, it is determined that the lock is completed, the learning completion flag is turned on (ON), and the learning of the lock position learning value GROK is ended.

  As described above, in the normal state, it does not take a long time until the actual cam shaft phase VT is locked at the locked position. However, when the lock state is incompletely locked (half-locked state), even if the lock control is continued for a long time, The phase VT is not fixed, and the lock position learning value GROK does not converge to a constant value. Therefore, as shown in FIG. 10, when the learning number CGR reaches a predetermined value K2 before the lock position learning value GROK converges to a constant value, it is determined as an incomplete lock state (half lock state), The lock position learning value GROK is reset and the lock position learning value GROK is set to an initial value (design median value) or a learning value at the previous lock control.

  Even if the lock position learning value GROK converges to a certain value before the number of learning times CGR reaches the predetermined value K2, if the lock position learning value GROK is out of the allowable range of manufacturing variation, other than the lock position. The lock position learning value GROK is reset and the lock position learning value GROK is set to the initial value (design median value) or the learning value at the previous lock control.

  In the present embodiment, the incomplete lock state is determined when the learning frequency CGR of the lock position learning value GROK reaches the predetermined value K2, but this is not possible when the learning time (lock control time) reaches the predetermined value. You may make it judge that it is a complete lock state.

  Further, the engine control circuit 21 executes the unlocking learning program shown in FIGS. 11 and 12 stored in the ROM (storage medium) at every predetermined time or every predetermined crank angle, so that the hydraulic control is performed during the unlocking control. It plays a role as unlocking learning means for learning the control amount of the valve 29 (hereinafter referred to as “unlocking control amount”).

  When this program is started, first, in step 201, the target camshaft phase VTT is compared with the actual camshaft phase VT so that the target camshaft phase VTT is advanced or retarded from the actual camshaft phase VT. Determine if it is located. When the target camshaft phase VTT is positioned on the advance side with respect to the actual camshaft phase VT (when VTT ≧ VT), the routine proceeds to step 202, where the unlock control amount DVT is set to the advance side learning value GDVTA. Performs unlock control. On the other hand, when the target camshaft phase VTT is positioned on the retard side with respect to the actual camshaft phase VT (when VTT <VT), the routine proceeds to step 203, where the unlock control amount DVT is set to the retard side learning value GDVTD. And unlock control.

  Thereafter, in step 204, it is determined whether or not the lock is released depending on whether or not the absolute value of the deviation between the actual cam shaft phase VT and the lock position learning value GROK is greater than a predetermined value K7. If the absolute value of the deviation between the actual camshaft phase VT and the lock position learning value GROK is less than or equal to the predetermined value K7, it is determined that the lock is in effect, and the learning value of the unlock control amount DVT is updated as follows. To do.

First, in step 205, it is determined whether or not the current unlocking control amount DVT is the advance side learning value GDVTA (that is, whether or not it has passed through step 202). Proceeding to 206, the advance side learning value GDVTA is corrected to the retard side by a predetermined value K8 and updated.
GDVTA = GDVTA−predetermined value K8

  Thereafter, in step 207, it is determined whether or not the advance side learning value GDVTA is smaller than the predetermined value K10 that is the allowable limit value (retard side), and if the advance side learning value GDVTA is equal to or greater than the predetermined value K10. For example, the process returns to step 201 and the above-described processing is repeated. Accordingly, the advance learning value GDVTA is corrected and updated by the predetermined value K8 to the retard side until unlocking is detected, and the unlock control amount DVT is corrected to the retard side by the predetermined value K8 and locked. The process for executing the release control is repeated.

  If the advance side learning value GDVTA becomes smaller than the predetermined value K10 before the unlocking is detected, it is determined that the unlocking is defective (lock stuck), and the process proceeds to step 208 to advance the advance side learning. The value GDVTA is reset, and the advance side learning value GDVTA is set to the initial value (design median value) or the advance side learning value GDVTA at the previous lock release control. In the next step 212, lock control is performed. Keep locked.

On the other hand, if it is determined in step 205 that the current unlocking control amount DVT is the retarded side learning value GDVTD (that is, if it passes through step 203), the process proceeds to step 209, and the retarded side learned value GDVTD. Is corrected by a predetermined value K9 on the retard side and updated.
GDVTD = GDVTD−predetermined value K9

  Thereafter, in step 210, it is determined whether or not the retard side learning value GDVTD is smaller than the predetermined value K11 that is the allowable limit value (the retard side). If the retard side learning value GDVTD is equal to or greater than the predetermined value K11. For example, the process returns to step 201 and the above-described processing is repeated. As a result, until the unlocking is detected, the retarded learning value GDVTD is corrected and updated by the predetermined value K9 to the retarded side, and the unlocking control amount DVT is corrected by the predetermined value K9 to the retarded side and locked. The process for executing the release control is repeated.

  If the retarded-side learning value GDVTD becomes smaller than the predetermined value K11 before unlocking is detected, it is determined that the unlocking is defective (lock stuck), and the process proceeds to step 211, where the retarded-side learning is performed. The value GDVTD is reset, and the retard side learning value GDVTD is set to the initial value or the retard side learning value GDVTD at the time of the previous lock release control, and in the next step 212, the lock control is performed and the lock state is maintained. .

  On the other hand, when the absolute value of the deviation between the actual cam shaft phase VT and the lock position learning value GROK is larger than the predetermined value K7 in step 204 during the lock release control, it is determined that the lock is released, Proceeding to step 213 in FIG. 12, the lock release flag is turned on. Thereafter, in step 214, it is determined whether or not the current unlocking control amount DVT is the advance side learning value GDVTA (that is, whether or not it has passed step 202), and if it is the advance side learning value GDVTA, Proceeding to step 215, whether or not the advance side learning value GDVTA is overcorrected to the advance side depending on whether or not the actual cam shaft phase VT is larger than the target cam shaft phase VTT + predetermined value K12 (advance side). Determine. If the advance side learning value GDVTA is not overcorrected to the advance side, the program is terminated as it is, but if the advance side learning value GDVTA is overcorrected to the advance side, the process proceeds to step 216. The advance side learning value GDVTA is corrected to the retard side by a predetermined value K13.

  On the other hand, if it is determined in step 214 that the current unlocking control amount DVT is the retard side learning value GDVTD (that is, if step 203 is passed), the process proceeds to step 217, where the actual camshaft phase VT is set to the target value. Whether or not the retard side learning value GDVTD is overcorrected to the retard side is determined depending on whether or not the camshaft phase VTT is smaller than the predetermined value K14 (retard side). If the retarded side learning value GDVTD is not overcorrected to the retarded side, the program is terminated as it is, but if the retarded side learned value GDVTD is overcorrected to the retarded side, the process proceeds to step 218. The retard learning value GDVTD is corrected to the advance side by a predetermined value K15.

  An example of learning processing of the unlock control amount DVT by the unlock learning program described above will be described with reference to FIGS. Here, FIG. 13 shows the behavior of the unlock learning process at normal time, and FIG. 10 shows the behavior of the unlock learning process at the time of abnormality. For example, when the target camshaft phase VTT is set to the advance side from the lock position GROK, as shown in FIG. 13, the unlock control amount DVT is set to the advance side learning value GDVTA and the unlock control is started. . During the unlock control, the unlock control amount DVT is corrected to the retard side by the predetermined value K8 until the unlock is detected, and the advance side learning value GDVTA is corrected to the retard side by the predetermined value K8. Repeat the update process. As a result, when the deviation between the actual cam shaft phase VT and the lock position learning value GROK becomes larger than the predetermined value K7, it is determined that the lock has been released, and the lock release flag is turned on to turn on the advance side learning. The learning of the value GDVTA ends. At this time, when the advance side learning value GDVTA is overcorrected to the advance side, the advance side learning value GDVTA is corrected to the retard side by a predetermined value K13.

  On the other hand, when a lock release failure (lock fixation) occurs, the lock release is not detected even if the lock release control is continued for a long time. During the unlocking control, the process of correcting the advance side learning value GDVTA to the retard side is repeated many times until the unlocking is detected, and eventually, as shown in FIG. 14, the advance side learning value GDVTA is smaller than a predetermined value K10 that is an allowable limit value. At this point, it is determined that there is a lock release failure (lock stuck), the advance side learning value GDVTA is reset, and the advance side learning value GDVTA is set to the initial value (design median value) or the advance at the previous unlock control. The corner side learning value GDVTA is set, lock control is performed, and the lock state is maintained.

  According to the present embodiment described above, since the lock position is learned during the lock control, even if the manufacturing variation of the lock position is large, the actual lock position is learned and based on the learned value. The determination of unlocking can be performed, and the determination of unlocking can be performed with high accuracy without being affected by the manufacturing variation of the lock position. Note that the learning value of the lock position may be used for purposes other than the lock release determination (for example, lock determination).

  In the present embodiment, the unlock control amount of the hydraulic control valve 29 is learned during the unlock control. Therefore, even if the manufacturing variation of the lock position, the manufacturing variation of the hydraulic control valve 29, etc. are large, The unlock control amount can be optimized according to the characteristics of the system, and the unlock performance can be improved.

  In addition, in this embodiment, when learning the unlock control amount, the retard side learning value and the advance angle are determined depending on whether the target cam shaft phase during the unlock control is retarded or advanced with respect to the actual cam shaft phase. Since the learning is performed separately on the side learning value, the unlock control amount can be learned so that the actual camshaft phase can be quickly converged to the target camshaft phase after unlocking. The convergence of the phase to the target camshaft phase can be improved. However, the present invention may simplify the learning process by using only one learning value for the unlock control amount.

  In the unlocking learning program of FIG. 11 and FIG. 12, when the learning value of the unlocking control amount becomes smaller than a predetermined value, it is determined that the unlocking failure (locking sticking) is detected. Value) may be determined to be a lock release failure when it is repeated a predetermined number of times or more.

  Further, when the unlocking cannot be performed during the unlocking control, the unlocking control may be performed again in the operation region where the hydraulic pressure supplied to the hydraulic control valve 29 is high. In this way, the unlocking control can be performed again by increasing the hydraulic pressure in the unlocking direction applied to the lock pin 58, and the unlocking resistance force (friction resistance force of the lock pin 58, etc.) becomes slightly heavy. If it is, it can be unlocked.

  In addition, in the present invention, only one of the lock position and the unlock control amount may be learned, the configuration of the variable valve timing device and the configuration of the lock mechanism may be changed as appropriate, and The present invention can also be applied to a variable valve timing device for an exhaust valve, and various modifications can be made without departing from the scope of the invention.

It is a schematic block diagram of the whole control system which shows one Embodiment of this invention. It is a longitudinal cross-sectional view of a variable valve timing device. It is sectional drawing shown along the AA line of FIG. It is sectional drawing shown along the BB line of FIG. It is sectional drawing shown along the CC line of FIG. It is a partial expanded sectional view which shows the lock state of a lock pin. It is a partial expanded sectional view which shows the lock release state of a lock pin. It is a flowchart which shows the flow of a process of a lock position learning program. It is a time chart which shows the behavior of the lock position learning process at the time of normal. It is a time chart which shows the behavior of the lock position learning process at the time of abnormality. It is a flowchart which shows the flow of a process of a lock release learning program (the 1). It is a flowchart which shows the flow of a process of a lock release learning program (the 2). It is a time chart which shows the behavior of the lock release learning process at the time of normal. It is a time chart which shows the behavior of the lock release learning process at the time of abnormality. It is sectional drawing of the conventional variable valve timing apparatus.

Explanation of symbols

  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, 19 ... Cam angle sensor, 20 ... Crank angle sensor, 21 ... Engine control circuit (unlock learning means), 28 ... oil pump, 29 ... hydraulic control valve, 31 ... housing, 35 ... rotor, 40 ... fluid chamber, 41 ... vane, 42 ... advance chamber , 43 ... retarding chamber, 53 ... solenoid, 54 ... spring, 58 ... lock pin (lock mechanism), 59 ... lock hole (lock mechanism), 62 ... spring (lock mechanism)

Claims (7)

A variable valve timing device is provided that varies the valve timing by changing the rotational phase of the cam shaft relative to the crankshaft of the internal combustion engine (hereinafter referred to as “cam shaft phase”). The variable valve timing device performs variable valve timing control. A variable valve for an internal combustion engine that has a lock mechanism that locks the camshaft phase at a lock position substantially in the middle of the adjustable range when there is not, and that controls the hydraulic pressure that drives the lock mechanism and the variable valve timing device with a hydraulic control valve In the timing control device,
During the unlocking control for controlling the hydraulic control valve to unlock the locking mechanism, the control amount of the hydraulic control valve (hereinafter referred to as “unlocking control amount”) is continuously learned, and the unlocking is performed when the unlocking is performed. A variable valve timing control apparatus for an internal combustion engine, comprising: an unlock learning unit that stops updating the learning value of the control amount and ends the learning.   2. The variable valve timing control device for an internal combustion engine according to claim 1, further comprising means for correcting an unlock control amount of the hydraulic control valve in a direction in which the unlock is easily performed when the unlock cannot be performed during the unlock control. . Means for determining that the unlocking is not successful even if the unlocking control amount of the hydraulic control valve is corrected during the unlocking control, and learning of the unlocking control amount when it is determined that the unlocking is defective. The variable valve timing control device for an internal combustion engine according to claim 2, further comprising means for canceling and setting the learned value of the unlock control amount to an initial value or a learned value at the previous unlock control. .   4. The variable valve timing control device for an internal combustion engine according to claim 3, further comprising means for controlling to maintain a locked state when it is determined that the unlocking failure is detected.   A means for determining a lock release failure when the unlock control amount of the hydraulic control valve is repeatedly corrected a predetermined number of times or more during the unlock control, or when the unlock control amount is out of a predetermined range; The variable valve timing control device for an internal combustion engine according to claim 3 or 4, characterized in that: The unlocking learning means, according to claim 1 or 2, characterized in that setting the learning value when the unlocking control amount of the initial value or the preceding unlocking control learning value when it is determined that the unlocking failure Variable valve timing control device for internal combustion engine.   The internal combustion engine according to any one of claims 1 to 6, further comprising means for performing unlocking control again in an operation region where the hydraulic pressure supplied to the hydraulic control valve is high when unlocking cannot be performed during the unlocking control. Variable valve timing control device.

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