JP2010255498A - Variable valve timing control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the responsiveness of advance/retard operation within a range that the viscosity of oil supplied to a variable valve timing device (VCT) with an intermediate lock mechanism is high. <P>SOLUTION: It is determined whether or not a phase retaining hydraulic-pressure securing condition for securing hydraulic pressure retaining a VCT phase during idling is satisfied according to whether a predetermined time elapses after starting, and cooling water temperature (or oil temperature) is a determination threshold or below. When the phase retaining hydraulic pressure securing condition is satisfied, the VCT phase (in the vicinity of an intermediate lock phase) during idling is retained as it is without performing the lock control (lock operation of the intermediate lock mechanism). Even if the phase retaining hydraulic pressure securing condition is satisfied, when engine rotation fluctuation (or VCT phase fluctuation) is a predetermined value or larger during idling, it is determined that the VCT phase is not retained in the vicinity of the intermediate lock phase, and the lock control is performed to suppress the deterioration of idling stability. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a variable internal combustion engine that includes an intermediate lock mechanism that locks the rotational phase of a camshaft relative to the crankshaft of the internal combustion engine (hereinafter referred to as “VCT phase”) with an intermediate lock phase that is positioned approximately in the middle of the adjustable range. The invention relates to a valve timing control device.

  Conventionally, in a hydraulically driven variable valve timing device, as described in Patent Document 1 (Japanese Patent Laid-Open No. 9-324613) and Patent Document 2 (Japanese Patent Laid-Open No. 2001-159330), the engine is stopped. The lock phase is set approximately in the middle of the adjustable range of the VCT phase to expand the adjustable range of the valve timing (VCT phase). In this system, the intermediate lock phase that locks when the engine is stopped is set to a phase suitable for starting, the engine is started with this intermediate lock phase, the lock is released after the start is completed, and the VCT phase is set according to the engine operating state. The target VCT phase is controlled. In a variable valve timing device for an intake valve, for example, the intake valve timing is controlled on the retard side when the load is low such as during steady running, and the intake valve timing is controlled on the advance side when the load is high such as when accelerating. I have to.

JP-A-9-324613 JP 2001-159330 A

  By the way, when an acceleration request is generated while the VCT phase is locked at the intermediate lock phase by the intermediate lock mechanism, it is required to promptly release the lock and advance the VCT phase from the intermediate lock phase.

  However, when the temperature is low (when the engine is cold), the oil (hydraulic fluid) supplied to the variable valve timing device has a high viscosity, so the response of the hydraulic control to unlock the intermediate lock mechanism is affected. When the acceleration request is generated from the locked state, the unlocking is delayed and the acceleration responsiveness is impaired.

  Therefore, the problem to be solved by the present invention is to quickly advance the VCT phase when the advance angle request or the retard angle request is generated by the acceleration request or the like while the VCT phase is held at the intermediate lock phase. Variable valve timing for internal combustion engines that can be driven in the direction or retard angle direction and can improve the responsiveness of the advance / retard operation in the region where the viscosity of the oil (hydraulic oil) supplied to the variable valve timing device is high It is to provide a control device.

  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. An internal combustion engine comprising: a timing device; an intermediate lock mechanism that locks the VCT phase with an intermediate lock phase located within the adjustable range; and a hydraulic control device that controls the hydraulic pressure that drives the variable valve timing device and the intermediate lock mechanism. In a variable valve timing control device for an engine, a lock that executes lock control for controlling the hydraulic control device to lock the intermediate lock mechanism by causing a VCT phase to coincide with the intermediate lock phase when a lock request occurs Control means, and the lock control means ensures a hydraulic pressure capable of maintaining the VCT phase during idling. Means for determining whether or not a condition (hereinafter referred to as “phase holding oil pressure securing condition”) is established, and when determining that the phase holding oil pressure securing condition is established, And a means for holding the VCT phase at the time of idling without executing the lock operation). The intermediate lock phase may be positioned within the adjustable range, for example, may be positioned in the middle of the adjustable range, or may be provided on the advance side and the retard side with respect to the intermediate position. good.

  In general, when the temperature is low (when the internal combustion engine is cold), the viscosity of the oil supplied to the variable valve timing device is high, so there is less oil leakage from the hydraulic chamber in the variable valve timing device. For this reason, once the hydraulic pressure supplied to the variable valve timing device rises, there may be a case where it is possible to secure a hydraulic pressure that can maintain the VCT phase at a substantially constant phase even when the internal combustion engine speed decreases.

  Focusing on this point, in the present invention, it is determined whether or not a phase holding oil pressure securing condition capable of securing a hydraulic pressure capable of holding the VCT phase during idling is satisfied, and the phase holding oil pressure securing condition is established. Is determined, the lock control (the lock operation of the intermediate lock mechanism) is not executed, but the VCT phase during idle (near the intermediate lock phase) is maintained as it is. In short, in the state where the phase holding oil pressure securing condition is satisfied, the idle stability can be ensured by holding the VCT phase near the intermediate locking phase during idling without locking the intermediate locking mechanism. In order to prevent the intermediate lock mechanism from being locked, when the advance angle request or the retard angle request is subsequently generated due to an acceleration request or the like, the VCT phase is immediately driven in the advance angle direction or the retard angle direction without performing the unlock control. be able to. Thereby, the responsiveness of the advance / retard operation in the region where the viscosity of the oil supplied to the variable valve timing device is high can be improved while ensuring the idle stability.

  In this case, as in claim 2, the condition for ensuring the phase holding oil pressure is that a predetermined time has elapsed after the start of the internal combustion engine and that the oil temperature or the cooling water temperature is equal to or lower than a threshold temperature. good. Even when the temperature is low (when the internal combustion engine is cold), if a certain amount of time has elapsed from the start, the hydraulic pressure supplied to the variable valve timing device rises to a hydraulic pressure that can maintain the VCT phase, and at low temperatures (when the internal combustion engine is cold) ), Since the oil leakage from the hydraulic chamber (advance chamber or retard chamber) in the variable valve timing device is small, the increased hydraulic pressure after the start-up is difficult to decrease. Accordingly, if the predetermined time elapses after the start and the oil temperature or the cooling water temperature is equal to or lower than the determination threshold temperature is set as the phase holding oil pressure securing condition, the phase holding oil pressure securing condition can be properly determined.

  Further, as in the third aspect, even when the phase holding oil pressure securing condition is satisfied, when the fluctuation of the VCT phase or the rotational fluctuation of the internal combustion engine exceeds a predetermined value during idling, the lock control (intermediate lock mechanism It is advisable to execute a lock operation to suppress the deterioration of idle stability. The fact that the fluctuation of the VCT phase and the fluctuation of the rotational speed of the internal combustion engine become large during idling means that the VCT phase cannot be held near the intermediate lock phase.

  Further, considering that the oil temperature and the cooling water temperature at which the hydraulic pressure capable of maintaining the VCT phase is different when the oil grade (viscosity) is different, the variation in the VCT phase or the internal combustion state at the time of idling can be considered. The determination threshold temperature used for determining the phase holding oil pressure securing condition may be updated based on the oil temperature or the cooling water temperature when the engine rotational fluctuation exceeds a predetermined value. In this way, it is possible to provide a function of learning the determination threshold temperature used for determining the phase holding oil pressure securing condition, so that even if the oil in the internal combustion engine is replaced with a different grade, the grade of the replaced oil is changed. Accordingly, it is possible to appropriately change the determination threshold temperature used for determining the phase holding oil pressure securing condition.

  Further, as in claim 5, even when the phase holding oil pressure securing condition is satisfied, when the internal combustion engine rotational speed becomes lower than the predetermined rotational speed set lower than the normal idle rotational speed, the lock control (intermediate It is preferable to execute a locking mechanism). If the internal combustion engine rotational speed falls from the normal idle rotational speed, there is a possibility of engine stall (engine stall). Therefore, the intermediate lock mechanism is locked before reaching the engine stall, and the VCT phase is set to the intermediate lock phase when restarting. It is to be able to restart in a locked state, thereby ensuring restartability at the time of stall.

FIG. 1 is a schematic configuration diagram of the entire control system showing an embodiment of the present invention. FIG. 2 is a longitudinal side view for explaining the configuration of the variable valve timing device and the hydraulic control circuit. FIG. 3 is a longitudinal front view of the variable valve timing device. FIG. 4 is a time chart showing an example of the behavior of the actual VCT phase and the target VCT phase during lock control. FIG. 5 is a flowchart showing the processing flow of the lock control main routine. FIG. 6 is a flowchart showing the flow of the idle lock request determination routine.

Hereinafter, an embodiment in which the mode for carrying out the present invention is applied to a variable valve timing apparatus for an intake valve will be described.
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 (VCT) will be described based on FIG. 2 and FIG.
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 cam shaft 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 cam shaft phase is substantially within the adjustable range. Locked with an intermediate lock phase located in the middle. 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 biased in the lock direction (protrusion direction) by a spring 62 (biasing means). 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 present embodiment, the hydraulic control device that controls the hydraulic pressure that drives the variable valve timing device 18 and the lock pin 58 includes a hydraulic control valve 25 for phase control that controls the hydraulic pressure that drives the variable valve timing device 18, and a lock pin. The hydraulic control valve 26 for lock control for controlling the hydraulic pressure for driving the 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 (operating 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. The variable valve timing is controlled by the hydraulic control valve 25 for phase control. The hydraulic pressure (oil amount) supplied to the advance chamber 42 and the retard chamber 43 of the device 18 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. Is done. 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 calculates a target VCT phase (target valve timing) based on the engine operating conditions during variable valve timing control (phase feedback control), and the actual VCT phase (intake valve control) of the intake camshaft 16. The control duty (control amount) of the hydraulic control valve 25 for phase control is feedback-controlled by PD control or the like so that the actual valve timing) matches the target VCT phase (target valve timing). The hydraulic pressure supplied to the corner chamber 42 and the retard chamber 43 is feedback-controlled.

  Further, the engine control circuit 21 functions as a lock control means in the claims, and performs hydraulic control so as to lock the intermediate lock mechanism 50 by matching the VCT phase with the intermediate lock phase when a lock request is generated. Lock control for controlling the valves 25 and 26 is executed.

  Specifically, as shown in FIG. 4, when a lock request is generated, the target VCT phase is set to a phase that is delayed by a predetermined amount from the intermediate lock phase in anticipation of an advance operation during the lock mode. Then, the control of the retard mode for driving the actual VCT phase in the retard direction is started, the hydraulic pressure in the hydraulic chamber 63 for unlocking the intermediate lock mechanism 50 is released, and the lock pin 58 is attached in the lock direction by the spring 62. To force. After this, when it is determined that the actual VCT phase has clearly passed the intermediate lock phase in the retard direction (for example, when a predetermined time has elapsed since the start of the retard mode control), the retard mode is switched to the lock mode, The actual VCT phase is gradually advanced. Thereby, when the actual VCT phase coincides with the intermediate lock phase, the lock pin 58 is fitted into the lock hole 59, and the actual VCT phase is locked at the intermediate lock phase.

  The specific method of the lock control is not limited to the method shown in FIG. 4. In short, when the lock request is generated, the hydraulic control is performed so that the VCT phase matches the intermediate lock phase and the intermediate lock mechanism 50 is locked. The control valves 25 and 26 may be controlled.

  By the way, when an acceleration request is generated in a state where the actual VCT phase is locked by the intermediate lock phase by the intermediate lock mechanism 50, it is required to quickly release the lock and advance the VCT phase from the intermediate lock phase. .

  However, when the temperature is low (when the engine is cold), the viscosity of the oil (hydraulic oil) supplied to the variable valve timing device 18 is high, so that the response delay of the hydraulic control for releasing the lock of the intermediate lock mechanism 50 is delayed. The effect becomes large, and the unlocking delay when the acceleration request is generated from the locked state is delayed, and the acceleration response is impaired.

  Therefore, in this embodiment, whether or not the phase holding oil pressure securing condition that can secure the oil pressure capable of holding the actual VCT phase during idling is satisfied by executing the routines of FIGS. 5 and 6 by the engine control circuit 21. When it is determined that the condition for securing the phase holding oil pressure is satisfied, the actual VCT phase (near the intermediate lock phase) at the time of idling is not performed without executing the lock control (the lock operation of the intermediate lock mechanism 50). I try to keep it. In short, in the state where the phase holding oil pressure securing condition is established, the idling stability can be ensured by holding the actual VCT phase in the vicinity of the intermediate locking phase during idling without the intermediate locking mechanism 50 being locked. In addition, if the intermediate lock mechanism 50 is not locked, when the advance angle request or the retard angle request is subsequently generated due to an acceleration request or the like, the actual VCT phase is immediately advanced or delayed without performing the lock release control. It can be driven in the angular direction. Thereby, the responsiveness of the advance / retard operation in the region where the viscosity of the oil supplied to the variable valve timing device 18 is high can be improved while ensuring the idle stability. Hereinafter, the processing content of each routine of FIG.5 and FIG.6 is demonstrated.

[Lock control main routine]
The lock control main routine of FIG. 5 is executed at predetermined intervals during engine operation, and functions as lock control means in the claims. When this routine is started, first, at step 101, it is determined whether or not the throttle opening is less than a predetermined opening (throttle opening region for executing lock control), and the throttle opening is equal to or larger than the predetermined opening. If so, it is not the throttle opening range in which the lock control is executed, so this routine is terminated without executing the subsequent processing.

  On the other hand, if it is determined in step 101 that the throttle opening is less than the predetermined opening, the process proceeds to step 102, where the idle lock request determination routine of FIG. 6 is executed and an idle lock request is generated (ON). It is determined whether or not. Thereafter, the process proceeds to step 103, where it is determined whether or not the idle lock request is ON based on the processing result of the idle lock request determination routine in FIG. End the routine. As a result, when the phase holding oil pressure securing condition that can secure the oil pressure capable of holding the actual VCT phase during idling is satisfied, the actual VCT during idling is not performed without executing the lock control (the locking operation of the intermediate lock mechanism 50). The phase (near the intermediate lock phase) is maintained as it is.

  On the other hand, if it is determined in step 103 that the lock request during idling is ON, the process proceeds to step 104 where a lock control routine (not shown) is executed so that the actual VCT phase matches the intermediate lock phase. The intermediate lock mechanism 50 is locked so that the actual VCT phase is locked at the intermediate lock phase.

[Idle lock request determination routine]
The idle lock request determination routine of FIG. 6 is a subroutine executed in step 102 of the lock control main routine of FIG. When this routine is started, first, in step 201 and step 202, whether or not a phase holding oil pressure securing condition capable of securing a hydraulic pressure capable of holding the actual VCT phase during idling is satisfied is determined by the following two conditions (1 ) And (2).
(1) A predetermined time has elapsed since the start [Step 201]
(2) The cooling water temperature (or oil temperature) is not more than the threshold temperature for determination (step 202).

  Here, the “predetermined time” in the above condition (1) corresponds to the time required for the hydraulic pressure supplied to the variable valve timing device 18 after starting to rise to a hydraulic pressure capable of maintaining the VCT phase. It is set based on design data.

  In addition, the “determination threshold temperature” in the above condition (2) is an oil viscosity (an oil viscosity that can secure a hydraulic pressure capable of maintaining the actual VCT phase) with less oil leakage from the advance chamber 42 and the retard chamber 43. This corresponds to the upper limit temperature of the temperature range. The “determination threshold temperature” of the above condition (2) is learned by the processing of step 204 described later, and is a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21 (stored data even when the engine control circuit 21 is powered off). Is stored in a rewritable storage means).

  If “No” is determined in any one of Step 201 and Step 202, it is determined that the hydraulic pressure capable of maintaining the actual VCT phase cannot be secured during idling, and the phase holding hydraulic pressure securing condition is not satisfied, and Step 207 is performed. Then, the idle lock request is turned ON and this routine is terminated.

  On the other hand, if “Yes” is determined in both step 201 and step 202, it is determined that the hydraulic pressure capable of maintaining the actual VCT phase can be ensured during idling, and the phase holding hydraulic pressure ensuring condition is satisfied. Then, it is determined whether or not the engine rotation fluctuation (or fluctuation of the actual VCT phase) is equal to or greater than a predetermined value. As a result, if it is determined that the engine rotation fluctuation (or fluctuation of the actual VCT phase) is equal to or greater than the predetermined value, it is determined that the VCT phase cannot be held near the intermediate lock phase, and the process proceeds to step 204, where Based on the cooling water temperature (or oil temperature), the determination threshold temperature used in step 202 is learned, and the determination threshold temperature is updated and stored in a rewritable nonvolatile memory such as a backup RAM of the engine control circuit 21. At this time, the current cooling water temperature (or oil temperature) may be learned as it is as the determination threshold temperature, or the current cooling water temperature (or oil temperature) is reflected in the determination threshold temperature by annealing. You may do it. Thereafter, the process proceeds to step 207, where the idle lock request is turned on and this routine is terminated. In short, even if the conditions for securing the phase holding oil pressure are satisfied, if the engine rotation fluctuation (or VCT phase fluctuation) exceeds a predetermined value during idling, it is determined that the VCT phase cannot be held near the intermediate lock phase. Then, lock control (lock operation of the intermediate lock mechanism 50) is executed to suppress the deterioration of idle stability.

  On the other hand, if it is determined in step 203 that the engine rotation fluctuation (or fluctuation of the actual VCT phase) is less than the predetermined value, it is determined that the VCT phase is held near the intermediate lock phase, and the process proceeds to step 205. It is determined whether or not the engine rotation speed is equal to or lower than a predetermined rotation speed set lower than the normal idle rotation speed. As a result, if it is determined that the engine rotational speed is equal to or lower than the predetermined rotational speed, it is determined that there is a possibility of engine stalling, the process proceeds to step 207, the idle lock request is turned on, and this routine is terminated. In short, if the engine rotational speed falls below a predetermined rotational speed set lower than the normal idle rotational speed, there is a possibility that the engine stalls. Therefore, before the engine stalls, the intermediate lock mechanism 50 is locked and restarted. The restart can be performed while the VCT phase is locked at the intermediate lock phase.

  If it is determined in step 205 that the engine rotational speed is higher than the predetermined rotational speed, it is determined that the engine is not stalled, the process proceeds to step 206, the idling lock request is turned off, and this routine is terminated. When the idle lock request is OFF, the lock control (the lock operation of the intermediate lock mechanism 50) is not executed even during idle, and the idle VCT phase (near the intermediate lock phase) is maintained.

  According to the present embodiment described above, when it is determined that the phase holding oil pressure securing condition that can secure the oil pressure capable of holding the VCT phase during idling is satisfied, the lock control (the locking operation of the intermediate lock mechanism 50) is performed. Since the idle VCT phase (near the intermediate lock phase) is maintained without being executed, the VCT phase is maintained near the intermediate lock phase during idle without idling the intermediate lock mechanism 50. If the intermediate locking mechanism 50 is not locked, the VCT is immediately performed without performing the unlock control when an advance angle request or a retard angle request is generated due to an acceleration request or the like. The phase can be driven in the advance direction or the retard direction. Thereby, the responsiveness of the advance / retard operation in the region where the viscosity of the oil supplied to the variable valve timing device 18 is high can be improved while ensuring the idle stability.

  Further, in this embodiment, even when the condition for securing the phase holding oil pressure is satisfied, when the engine rotation fluctuation (or VCT phase fluctuation) exceeds a predetermined value during idling, the VCT phase is held near the intermediate lock phase. Since it is determined that it has not been performed and lock control (the lock operation of the intermediate lock mechanism 50) is executed, it is possible to suppress deterioration in idle stability.

  Furthermore, in consideration of the fact that when the oil grade (viscosity) is different, the cooling water temperature and the oil temperature at which the oil pressure capable of maintaining the VCT phase can be secured are different, in this embodiment, the engine rotation fluctuation (or VCT phase fluctuation). Based on the cooling water temperature (or oil temperature) when the temperature becomes equal to or higher than a predetermined value, the determination threshold temperature used for determining the phase holding oil pressure securing condition is learned, and this can be rewritten in the backup RAM or the like of the engine control circuit Since the non-volatile memory is updated and stored, even if the oil of the engine 11 is replaced with a different grade of oil, the determination threshold temperature used for the determination of the phase holding oil pressure securing condition is determined according to the replaced oil grade. It can be changed appropriately.

  Further, in this embodiment, even if the phase holding oil pressure securing condition is satisfied, there is a possibility that the engine stalls when the engine rotation speed falls below a predetermined rotation speed set lower than the normal idle rotation speed. Thus, the lock control (the lock operation of the intermediate lock mechanism 50) is executed, so that when the engine rotation speed falls from the normal idle rotation speed, the intermediate lock mechanism 50 is locked before reaching the engine stall. Thus, the restart can be performed while the VCT phase is locked at the intermediate lock phase at the time of restart, and restartability at the time of stall can be ensured.

  In addition, although the said Example is an Example which applied and applied this invention to the variable valve timing apparatus of an intake valve, you may implement and apply to the variable valve timing control apparatus of an exhaust valve.

  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 (lock control means), 25 ... Hydraulic control valve (hydraulic control device) for phase control, 26 ... Hydraulic control valve (hydraulic control device) for lock 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 (5)

A hydraulically driven variable valve timing device that adjusts the valve timing by changing the rotational phase of the camshaft relative to the crankshaft of the internal combustion engine (hereinafter referred to as “VCT phase”), and an intermediate lock that positions the VCT phase within its adjustable range In a variable valve timing control device for an internal combustion engine, comprising: an intermediate lock mechanism that locks in phase; and a hydraulic control device that controls the hydraulic pressure that drives the variable valve timing device and the intermediate lock mechanism;
Lock control means for performing lock control for controlling the hydraulic control device so as to lock the intermediate lock mechanism by causing the VCT phase to coincide with the intermediate lock phase when a lock request is generated;
The lock control means is configured to determine whether or not a condition capable of securing a hydraulic pressure capable of maintaining the VCT phase during idling (hereinafter referred to as “phase maintaining hydraulic pressure securing condition”) is satisfied; A variable valve timing control device for an internal combustion engine, characterized by comprising means for holding the VCT phase during idling without executing the lock control when it is determined that it is established.   2. The variable valve for an internal combustion engine according to claim 1, wherein the phase maintaining oil pressure securing condition is that a predetermined time elapses after the start of the internal combustion engine and the oil temperature or the cooling water temperature is equal to or lower than a threshold temperature. Timing control device.   The lock control means executes the lock control when the fluctuation of the VCT phase or the rotation fluctuation of the internal combustion engine exceeds a predetermined value at idling even when the phase holding oil pressure securing condition is satisfied. The variable valve timing control device for an internal combustion engine according to claim 1 or 2.   The lock control means determines a threshold temperature to be used for determining the phase holding oil pressure securing condition based on an oil temperature or a cooling water temperature when the fluctuation of the VCT phase or the fluctuation of the rotation of the internal combustion engine exceeds a predetermined value during the idling. The variable valve timing control apparatus for an internal combustion engine according to claim 3, wherein the variable valve timing control apparatus is updated.   The lock control means executes the lock control when the rotation speed of the internal combustion engine becomes lower than a predetermined rotation speed set lower than a normal idle rotation speed even when the phase holding oil pressure securing condition is satisfied. 5. The variable valve timing control device for an internal combustion engine according to claim 1, wherein the variable valve timing control device is an internal combustion engine.

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