JP2001164908A - Variable valve timing control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve a problem on worsening of startability due to defective locking and the generation of noise, in a variable valve timing device with an intermediate lock mechanism. SOLUTION: Whether movement of a variable timing device is excellent or defective depends upon whether a cooling water temperature is within a given temperature range (T1 < a cooling water temperature < T2). Provided the cooling water temperature is within a range of a given temperature, it is decided that movement of the variable valve timing device is excellent. Meanwhile, in case of a cooling water temperature being a lower limit valve T1 or less or an upper limit value T2 or more of the given temperature range, it is decided that movement of the variable valve timing device is defective, a target cam shaft phase is set to the vicinity of a lock position (a lock position ±α) and the cam shaft phase is controlled to the vicinity of the lock position. This constitution performs lock in a state that a cam shaft phase reliably coincides with a lock position when an engine is brought into a stop even in a state that movement of the variable valve timing device is defective, and a problem on worsening of startability and the generation of noise is dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine provided with a variable valve timing device, which sets a rotational phase of a camshaft with respect to a crankshaft (hereinafter referred to as a "camshaft phase") at a substantially middle lock position in an adjustable range thereof. TECHNICAL FIELD The present invention relates to a variable valve timing control device for an internal combustion engine having a lock mechanism that locks a valve.

[0002]

2. Description of the Related Art In recent years, an internal combustion engine mounted on a vehicle is increasingly employing 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. 12, 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 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 to relatively rotate the housing 1 and the rotor 2 (vane 4), so that the rotational phase of the cam shaft with respect to the crank shaft (cam shaft (Phase), so that the valve timing is variably controlled.

A conventional vane-type variable valve timing control apparatus has a camshaft phase most retarded when the engine is stopped (when the oil pressure is lowered) in order to prevent noise caused by vibration of the vane 4 at the time of starting. The relative rotation between the housing 1 and the rotor 2 (vane 4) is locked by the lock pin 7 in the retarded phase. Therefore, at the time of starting, since the engine is started with the most retarded phase, the most retarded phase is set to a phase suitable for starting.

However, in this configuration, since the most retarded phase is limited by the starting phase (lock position), the adjustable range of the valve timing (camshaft phase) is limited by the lock position, and the valve position is limited. There is a disadvantage that the adjustable range of timing is narrow.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. Hei 9-324613, the valve timing (camshaft phase) is adjusted by setting the lock position when the engine is stopped at a substantially intermediate position in the adjustable range of the camshaft phase. It has been proposed to increase the possible range.

[0006]

The lock pin 7, which locks the camshaft phase at the lock position, is urged in the lock direction by a spring, and is held at the unlock position by hydraulic pressure during operation of the engine. Since the oil pressure is increased by an oil pump driven by the power of the engine, when the engine is stopped, the oil pressure is reduced, the lock pin 7 is fitted into the lock hole by the spring, and the camshaft phase is shifted to the lock position. Becomes locked. However, lock pin 7
In order to fit into the lock hole, the positions of both need to be matched.
As described in the specification of Japanese Patent No. 31, an invention is filed in which an oil pressure is controlled so as to move a camshaft phase to a lock position when the engine is stopped.

However, when the engine is stopped, the rotational speed of the oil pump is also reduced and the oil pressure is reduced. Therefore, if the operation of the variable valve timing device is in a poor state, the camshaft phase is locked until the engine is stopped. It may not be able to be moved to the point where it cannot be locked. If the camshaft phase cannot be locked at the lock position when the engine is stopped, the valve timing (camshaft phase) will be the target at the next start until the engine speed (oil pump speed) increases and the oil pressure rises. Value (near lock position)
As a result, the engine is started at a valve timing that deviates from the target value, so that the startability is deteriorated and the engine start time is lengthened. In addition, if the engine is started without locking the camshaft phase, the position of the vane 4 is not fixed until the hydraulic pressure rises, so that there is a problem that the vane 4 collides with the housing 1 to generate noise.

The present invention has been made in view of such circumstances, and an object thereof is to prevent a situation in which the camshaft phase cannot be locked at the lock position when the internal combustion engine is stopped. It is an object of the present invention to provide a variable valve timing control device for an internal combustion engine that can avoid problems such as deterioration of startability and noise due to a failure.

[0009]

In order to achieve the above object, a variable valve timing control apparatus for an internal combustion engine according to the present invention has a lock failure prevention control means when the operation of the variable valve timing apparatus is poor. Thus, the hydraulic control valve is controlled so that the camshaft phase is located at or near the lock position. With this configuration, when the operation of the variable valve timing device is poor, the camshaft phase continues to stay at or near the lock position, so that when the internal combustion engine is stopped, even if the operation of the variable valve timing device is poor, Thus, it is possible to reliably lock the camshaft phase in accordance with the lock position. This makes it possible to start with the camshaft phase locked reliably at the next start, thereby avoiding problems such as poor startability and noise due to poor lock.

Further, the hydraulic control valve may be controlled so that the camshaft phase is locked at the lock position when the movement of the variable valve timing device is poor. With this configuration, when the operation of the variable valve timing device is in a poor state, the camshaft phase is locked at the locked position (or the operation is continued without being unlocked after the start, and the locked state is maintained). Even if the operation of the timing device is poor, it is possible to stop the internal combustion engine in a state where the camshaft phase is securely locked when the internal combustion engine is stopped. This makes it possible to start with the camshaft phase locked reliably at the next start, thereby avoiding problems such as poor startability and noise due to poor lock.

In this case, the operation of the variable valve timing device changes depending on the viscosity of the oil in the hydraulic circuit. For example, if the oil temperature is lower than the appropriate temperature range, the oil viscosity becomes larger than the appropriate viscosity range. Since the increase in the oil pressure is delayed, the operation of the variable valve timing device is deteriorated. Also, if the oil temperature is higher than the appropriate temperature range, the oil viscosity becomes smaller than the appropriate viscosity range, and the oil pressure easily leaks from the minute gap inside the variable valve timing device. The operation of the valve timing device becomes poor.

In consideration of such characteristics, it may be determined based on the oil temperature whether or not the operation of the variable valve timing device is in a poor state.
Thereby, it is possible to accurately determine whether or not the operation of the variable valve timing device is in a bad state.

Alternatively, it is determined whether or not the operation of the variable valve timing device is in a bad state based on temperature information such as a cooling water temperature and an engine temperature which are correlated with the oil temperature. You may do it. With this configuration, it is possible to accurately determine whether or not the operation of the variable valve timing device is in a poor state, as in the case of determining based on the oil temperature described above. In addition, since the output of a cooling water temperature sensor or the like generally provided for operation control of the internal combustion engine can be used as substitute information of the oil temperature, it is not necessary to newly provide an oil temperature sensor, and the number of parts is reduced, and the cost is reduced. The down request can be satisfied.

According to a fifth aspect of the present invention, it may be determined whether or not the operation of the variable valve timing device is in a poor state based on a deviation between the actual camshaft phase and the target camshaft phase. With this configuration, it is possible to determine whether or not the operation is in a bad state while actually monitoring the operation of the variable valve timing device. Therefore, it is possible to determine a cause other than the oil temperature (oil viscosity) (for example, a bite of a foreign substance or the like). ) Has the advantage that even if the movement of the variable valve timing device deteriorates, it can be accurately detected.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] An embodiment (1) in which the present invention is applied to a variable valve timing control device for an intake valve will be described below with reference to FIGS.
As shown in FIG. 1, a DOHC engine 1 which is an internal combustion engine
1 is such that power from a crankshaft 12 is transmitted to an intake side camshaft 16 and an exhaust side camshaft 17 by a timing chain 13 via respective sprockets 14 and 15. However, the crankshaft 12 is provided on the intake side camshaft 16.
Is provided with a variable valve timing device 18 for adjusting the advance amount of the intake side camshaft 16 with respect to.

A cam angle sensor 19 for outputting a cam angle signal at a plurality of cam angles for cylinder discrimination is provided on the outer peripheral side of the intake side camshaft 16, and on the outer peripheral side of the crankshaft 12. A crank angle sensor 20 for outputting a crank angle signal at every predetermined crank angle is provided. 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 the frequency of the output pulse of the crank angle sensor 20. Is used to calculate the engine speed. Various sensors (intake pressure sensor 2
2, an output signal of the water temperature sensor 23, the throttle sensor 24, etc.) is 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, performs variable valve timing control, and controls the actual valve timing of the intake valve (the actual cam timing of the intake cam shaft 16). The variable valve timing device 18 is feedback-controlled so that the shaft phase) matches the target valve timing (target camshaft phase). The oil in the oil pan 27 is supplied to the oil pressure control circuit of the variable valve timing device 18 through an oil pressure control valve 29 by an oil pump 28, and the oil pressure is controlled by the oil pressure control valve 29. The actual valve timing is controlled.

Next, the configuration of the variable valve timing device 18 with the intermediate lock mechanism will be described with reference to FIGS. Housing 31 of variable valve timing device 18
Is fastened by bolts 32 to a sprocket 14 rotatably supported on the outer periphery of the intake side camshaft 16. As a result, the rotation of the crankshaft 12 is controlled by the sprocket 14 and the housing 31 via the timing chain 13.
The sprocket 14 and the housing 31 rotate in synchronization with the crankshaft 12.

On the other hand, the intake camshaft 16 is rotatably supported by a cylinder head 33 and a bearing cap 34, and a rotor 35 is fastened to one end of the intake camshaft 16 by a bolt 37 via a stopper 36. Have been. The rotor 35 is housed in the housing 31 so as to be relatively rotatable.

As shown in FIG. 3 and FIG.
A plurality of fluid chambers 40 are formed inside 1, and each fluid chamber 40 is partitioned into an advance chamber 42 and a retard chamber 43 by a vane 41 formed on the outer periphery of the rotor 35. And, on the outer peripheral portion of the rotor 35 and the outer peripheral portion of the vane 41,
Each of the seal members 44 is attached,
Are urged in the outer peripheral direction by a leaf spring 45 (see FIG. 2). Thereby, the gap between the outer peripheral surface of the rotor 35 and the inner peripheral surface of the housing 31 and the gap 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, annular advance grooves 46 and retard grooves 47 formed on the outer periphery of the intake camshaft 16 are connected to predetermined ports of the hydraulic control valve 29, respectively. When the oil pump 28 is driven by power, the oil pumped from the oil pan 27 is supplied to the advance groove 46 and the retard groove 47 via the hydraulic control valve 29. The advance oil passage 48 connected to the advance groove 46 is connected to the intake camshaft 1.
6 is formed so as to communicate with an arc-shaped advance oil passage 49 (see FIG. 3) formed on the left side surface of the rotor 35 through the interior of the rotor 6. Is in communication with On the other hand, the retard oil passage 50 connected to the retard groove 47 is
The arc-shaped retarded oil passage 51 is formed so as to penetrate through the inside of the intake-side camshaft 16 and communicate with an arc-shaped retarded oil passage 51 (see FIG. 4) formed on the right side surface of the rotor 35. It communicates with the retard chamber 43.

The hydraulic control valve 29 is a four-port, three-position switching valve that drives a valve body with a solenoid 53 and a spring 54, and determines the position of the valve body by a position for supplying hydraulic pressure to the advance chamber 42 and a retard chamber. The position is switched between a position where oil pressure is supplied to 43 and a position where oil pressure is not supplied to both the advance chamber 42 and the retard chamber 43. When the power supply to the solenoid 53 is stopped, the valve body is automatically switched to a position for supplying hydraulic pressure to the advance chamber 42 by the spring 54, and hydraulic pressure acts in a direction for advancing the camshaft phase.

In a state where a hydraulic pressure equal to or more 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 rotation of the housing 31 causes the rotation of the rotor 35 via oil.
(The vane 41), and the intake-side camshaft 16 is rotationally driven integrally with the rotor 35. During operation of the engine, the hydraulic pressure in the advance chamber 42 and the retard chamber 43 is controlled by the hydraulic control valve 29 to relatively rotate the housing 31 and the rotor 35 (vane 41), so that the intake-side cam with respect to the crankshaft 12. The rotation timing of the shaft 16 (hereinafter referred to as “camshaft phase”) is controlled to vary the valve timing of the intake valve. The sprocket 14 accommodates a torsion coil spring 55 (see FIG. 2) that assists the hydraulic pressure for relatively rotating the rotor 35 in the advance direction during the advance control by a spring force.

As shown in FIGS. 3 and 4, stopper portions 56 are formed on both sides of one of the vanes 41 to regulate the relative rotation range of the rotor 35 (vane 41) with respect to the housing 31. The stopper portion 56 regulates the most retarded phase and the most advanced phase of the camshaft phase. Further, the lock pin receiving hole 57 formed in the other vane 41 has the housing 31 and the rotor 35 (the vane 4).
A lock pin 58 for locking relative rotation with 1) is housed, and the lock pin 58 is fitted into a lock hole 59 (see FIG. 2) provided in the housing 31 to adjust the camshaft phase. It is locked at a substantially middle position (lock position) of the possible range. This lock position is set to a position suitable for starting.

As shown in FIGS. 6 and 7, the lock pin 5
8 is slidably inserted into a cylindrical member 61 fitted on the inner periphery of the lock pin receiving hole 57, and is urged by a spring 62 in the lock direction (projection direction). Further, a gap between the cylindrical member 61 and the lock pin 58 is partitioned into a lock hydraulic chamber 64 and a lock release hydraulic chamber 65 by a valve portion 63 formed at a central outer peripheral portion of the lock pin 58. In order to supply hydraulic pressure from the advance chamber 42 to the lock hydraulic chamber 64 and the lock release hold hydraulic chamber 65, the vane 41 has a lock oil passage 66 communicating with the advance chamber 42 and a lock release hold An oil passage 67 is formed.
The housing 31 has a lock hole 59 and a retard chamber 43.
And a lock release oil passage 68 is formed.

As shown in FIG. 6, when the lock pin 58 is locked, the valve portion 63 of the lock pin 58 closes the oil passage 67 for holding and releasing the lock, and the lock oil passage 66 communicates with the lock hydraulic chamber 64. State. Thereby, the advance chamber 42
The lock hydraulic chamber 64 supplies hydraulic pressure to the lock hydraulic chamber 64, and the hydraulic pin and the spring 62 hold the lock pin 58 in the lock hole 59 so that the camshaft phase is locked at the lock position.

While the engine is stopped, the hydraulic pressure in the lock hydraulic chamber 64 (the hydraulic pressure in the advance chamber 42) decreases.
As a result, the lock pin 58 is held at the lock position. Therefore, the engine is started with the lock pin 58 held at the lock position, and the lock release control is performed when the discharge pressure of the oil pump 28 increases to some extent after the engine is started. When the hydraulic pressure of the lock hole 59 (the hydraulic pressure of the retard chamber 43) increases by this lock release control, the lock of the lock pin 58 is released by the hydraulic pressure as follows. By the lock release control after the engine starts,
The lock hole 5 from the retard chamber 43 through the unlocking oil passage 68
The hydraulic pressure (force in the unlocking direction) supplied to the lock hydraulic chamber 64 and the spring 6
When the lock pin 58 is larger than the resultant force (force in the lock direction) with the spring force of No. 2, the lock pin 58 is pushed out of the lock hole 59 by the hydraulic pressure of the lock hole 59 and moves to the lock release position in FIG. Is released.

In this unlocked state, as shown in FIG. 7, the valve portion 63 of the lock pin 58 closes the lock oil passage 66, and the lock release holding oil passage 67 is connected to the lock release holding hydraulic chamber 65. It will be in the state of communication. Accordingly, the 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 (the hydraulic pressure of the advance chamber 42) and the hydraulic pressure of the lock hole 59 (the retard angle). The lock pin 58 is held at the unlocked position against the spring 62 by the pressure of the chamber 43).

During the operation of the engine, the advance chamber 42 and the retard chamber 4
3, the lock pin 58 is held at the unlocked position by the hydraulic pressure, and the housing 31 and the rotor 35 can be relatively rotated (that is, the variable valve timing control is possible). ).

During operation of the engine, the engine control circuit 21
Calculates the actual valve timing of the intake valve (the actual camshaft phase of the intake-side camshaft 16) based on the output signals of the crank angle sensor 20 and the cam angle sensor 19, and calculates the intake pressure sensor 22, the water temperature sensor 23, etc. The target valve timing of the intake valve (the target camshaft phase of the intake camshaft 17) is calculated based on the outputs of various sensors that detect the engine operating state. 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 matches the target valve timing. Thus, by controlling the oil pressure in the advance chamber 42 and the retard chamber 43 to relatively rotate the housing 31 and the rotor 35, the camshaft phase is changed, and the actual valve timing of the intake valve is set to the target valve timing. Match.

Thereafter, when the engine 11 is stopped,
When the engine rotation speed decreases, the discharge pressure of the oil pump 28 decreases, so that the hydraulic pressure of the advance chamber 42 and the retard chamber 43 decreases. As a result, the hydraulic pressure of the lock release holding hydraulic chamber 65 (the hydraulic pressure of the advance chamber 42) and the hydraulic pressure of the lock hole 59 (the hydraulic pressure of the retard chamber 43) are reduced, and the spring force of the spring 62 is reduced to these hydraulic pressures. When it overcomes, the lock pin 58 projects by the spring force of the spring 62 and fits into the lock hole 59. However, lock pin 5
In order for 8 to be fitted into the lock hole 59, the two positions must match, that is, the camshaft phase must match the lock position.

When the engine 11 stops, the engine rotation speed (the rotation speed of the oil pump 28) decreases and the oil pressure decreases, so that the camshaft phase naturally shifts 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 to lock the camshaft phase at the lock position. However, when the camshaft phase is already on the retard side from the lock position when the engine 11 is stopped, the lock pin 58 is locked even if the camshaft phase is changed to the retard side due to a decrease in oil pressure. Since it does not reach 59, the camshaft phase cannot be locked at the lock position.

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, this control is referred to as “lock control”). During the lock control, the energization of the solenoid 53 of the hydraulic control valve 29 is stopped, and the hydraulic control valve 2
The valve body is switched to a position for supplying oil pressure to the advance chamber 42 by the spring 54 of No. 9, and the oil pressure is applied in a direction for advancing the camshaft phase, and at the same time, the oil pressure of the retard chamber 43 is discharged to the drain. At this time, after the engine stop command, the fuel injection is stopped, so that the engine rotation speed (oil pump rotation speed) is reduced and the oil pressure is reduced. With the aid of the spring force of the torsion coil spring 55 in the advance direction, the advance of the camshaft phase can be controlled by hydraulic pressure. If the camshaft phase is already advanced from the lock position at the start of the lock control, the above-described advance control of the camshaft phase may not be performed.

However, if the operation of the variable valve timing device 18 is in a poor state when the engine is stopped, the camshaft phase may not reach the lock position before the engine is stopped, and may stop and cannot be locked. Problems such as poor startability and noise due to poor locking occur.

As a countermeasure, the engine control circuit 21
Executes a lock failure prevention control program shown in FIG. 8 stored in a ROM (storage medium) at predetermined time intervals or at predetermined crank angle intervals, thereby serving as a lock failure prevention control means for preventing a lock failure from occurring. Fulfill. When this program is started, first, in step 101, first, in step 101, the variable valve is determined depending on whether or not the cooling water temperature, which is the oil temperature substitute temperature information, is within a predetermined temperature range (T1 <cooling water temperature <T2). It is determined whether the operation of the timing device 18 is good or bad. Here, the predetermined temperature range is set to a temperature range in which the operation of the variable valve timing device 18 is good.

Accordingly, if the cooling water temperature is within the predetermined temperature range, it is determined that the operation of the variable valve timing device 18 is good, and this program is terminated as it is, but the cooling water temperature is lower than the lower limit value T1 of the predetermined temperature range or If it is equal to or more than the upper limit value T2, it is determined that the operation of the variable valve timing device 18 is bad, and the routine proceeds to step 102, where the target camshaft phase is shifted to the vicinity of the lock position (lock position + predetermined value α or lock position-predetermined value The lock failure prevention control for setting the camshaft phase near the lock position by setting α) is executed. here,
The lock position used for setting the target camshaft phase may be either a learned value or a design median value. When the lock position is set near the lock position (lock position ± predetermined value α), the predetermined value α is kept constant. Although it may be a value, it may be changed according to the cooling water temperature (oil temperature).

An example of the lock failure prevention control by the above-described lock failure prevention control program will be described with reference to a time chart of FIG. In the example of FIG. 9, when the camshaft phase is feedback-controlled to the target camshaft phase according to the operation state, the lock failure prevention control is performed when the cooling water temperature rises and exceeds the upper limit value T2 of the predetermined temperature range. Is started, the target camshaft phase is set near the lock position (lock position ± α), and the camshaft phase is feedback-controlled near the lock position. With this configuration, when the operation of the variable valve timing device 18 is poor, the camshaft phase continues to stay near the lock position, so that when the engine is stopped, even if the operation of the variable valve timing device 18 is poor,
By the lock control, the camshaft phase can be reliably locked to the locked position. This makes it possible to start with the camshaft phase locked reliably at the next start, thereby avoiding problems such as poor startability and noise due to poor lock.

In this embodiment (1), the camshaft phase is controlled near the lock position when the operation of the variable valve timing device 18 is in a bad state, but the camshaft phase is matched with the lock position. May be controlled. In this case, during the lock failure prevention control, since the hydraulic pressure of either the advance chamber 42 or the retard chamber 43 is high, the lock pin 58 (camshaft phase) matches the lock hole 59 (lock position). Even so, the lock pin 58 is held at the unlock position by hydraulic pressure.

[Embodiment (2)] In the embodiment (2) of the present invention, the lock failure prevention control program shown in FIG. 10 is repeatedly executed at a predetermined cycle to judge that the operation of the variable valve timing device 18 is bad. If the cooling water temperature is out of the predetermined temperature range (step 2),
From 01, the process proceeds to step 202 to execute lock control. In this lock control, the camshaft phase (lock pin 5
8) is matched with the lock position (lock hole 59), and the hydraulic pressure of the advance chamber 42 and the retard chamber 43 is reduced, whereby the lock pin 58 is fitted into the lock hole 59 by the spring force of the spring 62. And lock the camshaft phase at the lock position.

In this way, when the operation of the variable valve timing device 18 is in a bad state, the camshaft phase is locked at the lock position (or the operation is continued without being unlocked after the start, without being unlocked). Therefore, even if the operation of the variable valve timing device 18 is poor, it is possible to stop the engine with the camshaft phase locked when the engine is stopped. This makes it possible to start with the camshaft phase locked reliably at the next start, thereby avoiding problems such as poor startability and noise due to poor lock.

In the embodiments (1) and (2) described above, the cooling water temperature is used as data for judging whether or not the operation of the variable valve timing device is in a bad state.
The engine temperature or the like may be used. In short, the temperature information having a correlation with the oil temperature may be used. Needless to say, the oil temperature is detected by the oil temperature sensor and the operation of the variable valve timing device 18 is poor. It may be determined whether or not this is the case. As in the above embodiments (1) and (2), if temperature information such as a cooling water temperature that is correlated with the oil temperature is used, the output of a cooling water temperature sensor or the like generally provided for engine control is output. Since it can be used as substitute information of temperature, there is no need to newly provide an oil temperature sensor, and there is an advantage that the demand for reduction in the number of parts and cost can be satisfied.

In each of the embodiments (1) and (2),
When the cooling water temperature (oil temperature) is equal to or lower than the predetermined temperature T1 and equal to or higher than the predetermined temperature T2, any of the variable valve timing devices 18
Of the variable valve timing device 18 may be determined only when the temperature is equal to or lower than the predetermined temperature T1 (that is, when the viscosity of the oil is large).

[Embodiment (3)] In Embodiment (3) of the present invention, the lock failure prevention control program shown in FIG. 11 is repeatedly executed at a predetermined cycle, and the operation of the variable valve timing device 18 is poor. It is determined based on the deviation ΔVT between the target camshaft phase VTT and the actual camshaft phase VT (steps 301 to 305). In particular,
First, in step 301, a deviation (camshaft phase shift) ΔVT between the target camshaft phase VTT and the actual camshaft phase VT is calculated by the following equation. ΔVT = VTT−VT

Thereafter, at step 302, the camshaft phase shift ΔVT is compared with the judgment value A. If the camshaft phase shift ΔVT is larger than the judgment value A, the operation of the variable valve timing device 18 is poor. Since there is a possibility, the process proceeds to step 303, and the time counter CT for counting the duration of ΔVT> A is counted up. If the camshaft phase shift ΔVT is equal to or smaller than the determination value A, it is determined that the operation is normal. To step 304, where the time counter CT
Clear the value of.

Then, in the next step 305, it is determined whether or not the value of the time counter CT has exceeded a predetermined time B.
If the time CT is equal to or less than the predetermined time B, it is determined that the operation is normal, and this program is terminated. However, if the value of the time counter CT exceeds the predetermined time B, it is determined that the operation of the variable valve timing device 18 is bad. to decide.

In short, if the state in which the camshaft phase deviation ΔVT is larger than the determination value A continues for a predetermined time B or more, it is determined that the operation of the variable valve timing device 18 is bad. Judge as normal. It should be noted that the determination value A may be set to a relatively large value, and the movement of the variable valve timing device 18 may be immediately determined to be bad when the camshaft phase shift ΔVT exceeds the determination value A.

Also in this embodiment (3), the lock failure prevention control (step 306) when it is determined that the operation of the variable valve timing device 18 is bad may be the same as in the above-mentioned embodiment (1) or (2). .

In the embodiment (3) described above, it is possible to determine whether or not the movement of the variable valve timing device 18 is in a bad state while actually monitoring the movement of the variable valve timing device 18. Therefore, other than the oil temperature (oil viscosity). If the movement of the variable valve timing device 18 becomes poor due to the cause (for example, foreign matter is caught), there is an advantage that it can be detected with high accuracy.

The present invention relates to each of the above embodiments (1) to (5).
The configuration is not limited to (3), and the configuration of the variable valve timing device and the configuration of the lock mechanism may be appropriately changed. Further, the present invention can be applied to the variable valve timing device of the exhaust valve without departing from the gist. Various changes can be made within the scope.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire control system showing an embodiment (1) of the present invention.

FIG. 2 is a longitudinal sectional view of a variable valve timing device.

FIG. 3 is a sectional view taken along the line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB in FIG. 2;

FIG. 5 is a sectional view taken along the line CC of FIG. 4;

FIG. 6 is a partially enlarged sectional view showing a locked state of a lock pin.

FIG. 7 is a partially enlarged cross-sectional view showing an unlocked state of a lock pin.

FIG. 8 is a flowchart showing a processing flow of a lock failure prevention control program according to the embodiment (1) of the present invention;

FIG. 9 is a time chart showing the behavior of the lock failure prevention control of the embodiment (1).

FIG. 10 is a flowchart showing a processing flow of a lock failure prevention control program according to the embodiment (2) of the present invention;

FIG. 11 is a flowchart showing a processing flow of a lock failure prevention control program according to the embodiment (3) of the present invention;

FIG. 12 is a sectional view of a conventional variable valve timing device.

[Explanation of symbols]

11 ... engine (internal combustion engine), 12 ... crankshaft, 13
... Timing chains, 14, 15 ... Sprockets, 1
6 ... intake cam shaft, 17 ... exhaust cam shaft, 18 ... variable valve timing device, 19 ... cam angle sensor, 20 ... crank angle sensor, 21 ... engine control circuit (lock failure prevention control means), 28 ... oil pump, 29 ... Hydraulic control valve, 3
DESCRIPTION OF SYMBOLS 1 ... Housing, 35 ... Rotor, 40 ... Fluid chamber, 41 ...
Vane, 42: advance chamber, 43: retard chamber, 53: solenoid, 54: spring, 58: lock pin (lock mechanism), 59: lock hole (lock mechanism), 62: spring (lock mechanism).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA19 BA22 BA23 BA25 BA38 CA06 CA18 CA21 CA24 CA25 CA52 DA06 DA08 DA22 DA25 FA38 GA10 3G092 AA11 BB06 DA09 DF04 DF09 DG05 EA09 EA13 EA14 FA29 FA38 FA44 FB05 FB06 HE08Y

Claims (5)

[Claims] 1. A variable valve timing device that varies a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft of an internal combustion engine (hereinafter, referred to as a “camshaft phase”). A lock mechanism is provided for locking the camshaft phase at a substantially intermediate lock position of the adjustable range when valve timing control is not performed, and hydraulic pressure for driving the lock mechanism and the variable valve timing device is controlled by a hydraulic control valve. In the variable valve timing control device for an internal combustion engine, a lock failure prevention control means that controls the hydraulic control valve to position the camshaft phase at or near the lock position when the variable valve timing device is in a poor motion state. A variable valve timing control device for an internal combustion engine, comprising: 2. A variable valve timing device that varies a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft of an internal combustion engine (hereinafter referred to as a “camshaft phase”). A lock mechanism is provided for locking the camshaft phase at a substantially intermediate lock position of the adjustable range when valve timing control is not performed, and hydraulic pressure for driving the lock mechanism and the variable valve timing device is controlled by a hydraulic control valve. A variable valve timing control device for an internal combustion engine, comprising: lock failure prevention control means for controlling the hydraulic control valve to lock the camshaft phase at the lock position when the movement of the variable valve timing device is poor. A variable valve timing control device for an internal combustion engine. 3. The internal combustion engine according to claim 1, wherein the lock failure prevention control means determines whether or not the operation of the variable valve timing device is in a bad state based on an oil temperature. Variable valve timing control device for the engine. 4. The lock failure prevention control means determines whether or not the operation of the variable valve timing device is in a poor state based on temperature information such as a cooling water temperature and an engine temperature which are correlated with the oil temperature. The variable valve timing control device for an internal combustion engine according to claim 1 or 2, wherein 5. The lock failure prevention control means determines whether the operation of the variable valve timing device is in a bad state based on a deviation between an actual camshaft phase and a target camshaft phase. 3. The variable valve timing control device for an internal combustion engine according to claim 1, wherein