JPH0571369A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve durability and reliability by reducing the number of operation times to vary a valve overlap amount of a valve timing varying mechanism while combustion being stabilized during idling state of an internal combustion engine. CONSTITUTION:A valve timing control device comprises a valve timing varying mechanism 24, a throttle opening sensor 14, and a car speed sensor 20. A CPU 52 decides it based on detecting signals from two sensors 14 and 20 whether or not an engine is in an idling state. By controlling the valve timing varying mechanism 24, the CPU 52 adjusts a valve overlap to a given value (10 deg.) when the engine is in a non-idling state and adjusts the overlap to a value (0 deg.) lower than the given value when it is in an idling state. Further, when a combustion state is stable during transfer from a non-idling state to an idling state, the CPU 52 forcibly prohibits operation to vary a valve overlap amount of the valve timing varying mechanism 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for controlling the opening / closing operation timing of intake / exhaust valves of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, intake and
There is a variable valve timing mechanism that allows the opening / closing timing (valve timing) of the exhaust valve to be advanced or delayed. A technique for controlling the variable valve timing mechanism is disclosed in, for example, Japanese Patent Laid-Open No. 62-13708.
There is one disclosed in the publication. According to this technique, when the operating state of the engine is a non-idle state, the valve overlap of the intake valve and the exhaust valve is set to a predetermined value, and when the idle state is reached, the variable valve timing mechanism is operated to set the valve overlap to 0. ing. This reduces the amount of residual gas in the combustion chamber and stabilizes combustion.

[0003]

However, combustion is sometimes stable even in the idle state. Therefore, if the variable valve timing mechanism is operated every time the system shifts to the idle state even in such a case, the number of times the mechanism is operated becomes extremely large. Then, this affects the durability and reliability of the variable valve timing mechanism.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to stabilize the combustion when the internal combustion engine is in an idle state, and at the same time, perform the number of times the valve overlap amount of the variable valve timing mechanism is changed. It is an object of the present invention to provide a valve timing control device for an internal combustion engine, which can reduce the fuel consumption and improve durability and reliability.

[0005]

In order to achieve the above object, the present invention, as shown in FIG. 1, sets the valve timing of a valve for opening and closing an air passage to the combustion chamber of an internal combustion engine M1.
A valve timing variable mechanism M2 for adjusting according to the operating state of the internal combustion engine M1, operating state detecting means M3 for detecting the operating state of the internal combustion engine M1, and operation of the internal combustion engine M1 by the operating state detecting means M3. Idle state determination means M4 for determining whether or not the valve is in an idle state based on the state, and when the operating state by the idle state determination means M4 is a non-idle state, the valve overlap of the valve is previously set by the variable valve timing mechanism M2. The valve timing of the internal combustion engine is provided with a timing switching control means M5 that makes the valve overlap by the variable valve timing mechanism M2 smaller than the predetermined value when the predetermined operating condition is in the idle state. In the control device, the combustion state for detecting the combustion state of the internal combustion engine M1 is detected. And detection means M6, the internal combustion engine M
When the operating state of No. 1 shifts from the non-idle state to the idle state and the combustion state by the combustion state detecting means M6 is stable, the valve overlap amount of the valve timing variable mechanism M2 by the timing switching control means M5 is A prohibiting means M7 for forcibly prohibiting the changing operation is provided.

[0006]

When the operating state detecting means M3 detects the operating state of the internal combustion engine M1, the idle state determining means M4 determines based on the operating state whether or not the engine is in the idle state. If the determination result is the non-idle state, the timing switching control means M5 controls the valve timing variable mechanism M2 to set the valve overlap of the valve to a predetermined value. As a result, the intake efficiency is increased by utilizing the inertia and a high output is obtained.

Further, when the operating state by the idle state judging means M4 is the idle state, the timing switching control means M5 controls the valve timing variable mechanism M2 to make the valve overlap smaller than the predetermined value. This reduces the amount of residual gas in the combustion chamber and stabilizes combustion.

During the valve timing switching control as described above, the combustion state of the internal combustion engine M1 is detected by the combustion state detecting means M6. When the idle state determination means M4 determines that the operating state of the internal combustion engine M1 has changed from the non-idle state to the idle state,
When the combustion state by the combustion state detecting means M6 is stable, the prohibiting means M7 forcibly prohibits the operation of changing the valve overlap amount of the valve timing variable mechanism M2 by the timing switching control means M5.

Accordingly, the number of change operations of the entire mechanism is reduced by the amount by which the changing operation of the valve timing variable mechanism M2 is prohibited by the prohibiting means M7.

[0010]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 is a diagram showing a schematic configuration of an engine 1 as an internal combustion engine mounted on an automobile. The engine 1 includes a piston 3 in a cylinder 2, and a combustion chamber 4 formed above the piston 3 is in communication with an intake passage 5 and an exhaust passage 6. A communication portion between the combustion chamber 4 and the intake passage 5 and a communication portion between the combustion chamber 4 and the exhaust passage 6 are opened and closed by an intake valve 7 and an exhaust valve 8 which are reciprocated by the camshafts 9 and 10.

The engine 1 introduces a mixture of the outside air from the intake passage 5 and the fuel injected from the fuel injection valve 11 into the combustion chamber 4 via the intake valve 7. Then, the engine 1 explodes the air-fuel mixture in the combustion chamber 4 by the spark plug 12 to obtain a driving force, and then exhausts the exhaust gas to the exhaust passage 6 via the exhaust valve 8.

The intake passage 5 is provided with a throttle valve 13 which is opened / closed in conjunction with the operation of an accelerator pedal (not shown). By opening / closing the throttle valve 13, the amount of intake air into the intake passage 5 is increased. Adjusted. In the vicinity of the throttle valve 13, the same throttle valve 1
3, a throttle opening sensor 14 for detecting the fully closed state and the opening thereof is attached. An air flow meter 16 for detecting the amount of intake air is arranged upstream of the throttle valve 13. Air flow meter 16
Incorporates an intake air temperature sensor 17 for detecting the temperature of the air taken in by the engine 1.

The ignition voltage distributed by the distributor 18 is applied to the ignition plug 12. The distributor 18 distributes the high voltage output from the igniter 19 to each spark plug 12 in synchronization with the crank angle of the engine 1. The ignition timing of each spark plug 12 is the high voltage from the igniter 19. Determined by output timing. The distributor 18 is provided with a rotation speed sensor 21 that constitutes a part of combustion state detection means, and detects a pulse signal corresponding to the rotational angular velocity of the crankshaft of the engine 1.

On the other hand, an oxygen sensor 22 for detecting the oxygen concentration in the exhaust gas is attached to the exhaust passage 6. Further, a water temperature sensor 23 for detecting the cooling water temperature THW is attached to the cylinder block 1a of the engine 1. Further, the vehicle speed sensor 20 for detecting the vehicle speed is
It is provided in a transmission (not shown). The vehicle speed sensor 20 constitutes an operating condition detecting means together with the throttle opening sensor 14.

In addition, in this embodiment, a variable valve timing mechanism 24 for adjusting the valve opening timing and valve closing timing of the intake valve 7 is provided. Next, the variable valve timing mechanism 24 will be described in detail.

As shown in FIG. 3, a camshaft 9 for driving the intake valve 7 is rotatably supported by the engine 1 by a cylinder head 1b and a bearing cap 30. Further, journal oil passages 25, 26 for supplying lubricating oil to the cam journal 9a are formed in the cylinder head 1b and the cam shaft 9, respectively. And the oil pump 2 while the engine is running
The lubricating oil sucked up from the oil pan 28 by 7
The journal oil passages 25, 26 through the oil filter 29
And is supplied to the cam journal 9a.

The variable valve timing mechanism 24 is provided at the front end (left end in FIG. 3) of the camshaft 9. The variable mechanism 24 has a plurality of outer teeth 31 on the outer circumference and a pulley body 33 having a housing recess 32 on the front side, and is fixed by a bolt 34 at the tip of the camshaft 9 so as to cover the housing recess 32. And a cap 35. A viscous coupling (viscous coupling) 36 for cushioning is provided between the open end of the pulley body 33 and the outer periphery of the cap 35. The viscous coupling 36 includes an outer plate 37 press-fitted and fixed to the pulley body 33 and an inner plate 38 formed on the cap 35, and a high-viscosity viscous fluid is sealed between the two 37, 38. ..

A ring gear 39 is interposed between the pulley body 33 and the cap 35 to connect the both 33, 35. That is, the ring gear 39 is housed in the housing recess 32 of the pulley body 33 that is sealed by the cap 35. The ring gear 39 has helical teeth on both teeth 39a and 39b provided on the inner and outer circumferences thereof, and is rotatable relative to the camshaft 9 by moving in the axial direction. The teeth 39a and 39b are in mesh with the inner teeth 33a of the pulley body 33 and the inner teeth 35a of the cap 35, respectively. The pulley body 33 is drivingly connected to a crankshaft (not shown) of the engine 1 via a timing belt 41 that is hooked around the outer teeth 31 of the pulley body 33.

Therefore, by transmitting the rotation of the crankshaft to the pulley main body 33, the pulley main body 33 and the cap 35 connected by the ring gear 39 are integrally rotated, and the camshaft 9 is rotationally driven.

A pressure chamber 44 is formed on the front end side of the ring gear 39 in the accommodation recess 32 of the pulley body 33. In the pressure chamber 44, the cylinder head 1b and the camshaft 9 are provided.
The control oil sent through the control oil passages 42, 43 and the like formed therein acts. Similarly, in the accommodation recess 32, the rear end side of the ring gear 39 is a spring chamber 45, and the spring chamber 45 accommodates a balancing spring 46 opposed to the control oil pressure.

The variable valve timing mechanism 24 also includes an oil switching valve 47. The oil switching valve 47 is for supplying or stopping a part of the lubricating oil sent from the oil filter 29 to the journal oil passage 25 to the pressurizing chamber 44 via the control oil passages 42 and 43. Then, when the oil switching valve 47 is closed during engine operation, the ring gear 39 is positioned on the front side as shown in FIG. 3 due to the urging force of the spring 46. In this embodiment, the valve overlap between the intake valve 7 and the exhaust valve 8 at this time is set to a predetermined value (for example, 10 °).

On the other hand, when the oil switching valve 47 is opened from the above state, the control oil is introduced into the pressurizing chamber 44. As a result, control hydraulic pressure is applied to the front end side of the ring gear 39, and the ring gear 39 is rotated while moving rearward against the biasing force of the spring 46. As a result, the camshaft 9 is twisted, and the relative positions of the camshaft 9 and the pulley body 33 in the rotational direction are changed. In this embodiment, the valve overlap at this time is smaller than the predetermined value (10 °) (for example, 0).
°) is set. Further, when the camshaft 9 is twisted, backlash is generated in the ring gear 39, but rattling due to the backlash is buffered by the action of the viscous coupling 36, and generation of abnormal noise is suppressed.

A return oil passage 48 is provided in a part of the pulley main body 33 and the camshaft 9 in order to return the control oil leaking from the pressurizing chamber 44 of the accommodation recess 32 to the spring chamber 45 to the oil pan 28. Has been formed. Oil return holes 49 are formed in the cylinder head 1b and the bearing cap 30, which support the camshaft 9, respectively.

As shown in FIG. 2, the throttle opening sensor 14, the air flow meter 16, and the intake air temperature sensor 1 described above are used.
7, vehicle speed sensor 20, rotation speed sensor 21, oxygen sensor 2
2 and the water temperature sensor 23 are electronic control devices (hereinafter simply referred to as “E
(Hereinafter referred to as "CU") 51 is electrically connected to the input side. Further, each fuel injection valve 11, the igniter 19 and the oil switching valve 47 are electrically connected to the output side of the ECU 51.

The ECU 51 includes a central processing unit (hereinafter referred to as CPU) 52 as an idle state determination means, a timing switching control means, a combustion state detection means, and a prohibition means,
A read only memory (hereinafter referred to as ROM) 53, a random access memory (hereinafter referred to as RAM) 54, an input port 55, and an output port 56 are provided, and these are connected to each other by a bus 57. The CPU 52 executes various arithmetic processes according to a preset control program, and the ROM 53 stores in advance control programs and initial data required for the CPU 52 to execute arithmetic processes. The RAM 54 also temporarily stores the calculation result of the CPU 52.

The CPU 52, via the input port 55, the throttle opening sensor 14, the air flow meter 16, the intake air temperature sensor 17, the vehicle speed sensor 20, the rotation speed sensor 21,
The signals from the oxygen sensor 22 and the water temperature sensor 23 are input. Based on these detection signals, the CPU 52 uses the fuel injection valve 11 and the igniter 1 connected to the output port 56.
9 is driven to execute well-known combustion injection control and ignition timing control.

Next, the operation of the present embodiment constructed as described above will be described. FIG. 4 is a flowchart for controlling the valve timing of the intake valve 7 among the processes executed by the CPU 52, which is executed by a regular interrupt every predetermined time.

When the processing shifts to this routine, the CPU
52 first determines whether or not the operating state at that time is the idle state. For that purpose, the CPU 52 executes the step 1
In 01, it is determined whether the throttle valve 13 is fully closed based on the detection signal from the throttle opening sensor 14,
In step 102, it is determined whether the vehicle speed detected by the vehicle speed sensor 20 is 0 km / h. When the throttle valve 13 is fully closed and the vehicle speed is 0 km / h, CP
U52 determines that the operating state at that time is the idle state.

Next, the CPU 52 determines in step 103 whether the combustion state of the engine 1 is stable. As a method of making this determination, for example, the engine speed NE corresponding to the angular velocity of the crankshaft is detected by the engine speed sensor 21, and the variation amount ΔNE occurring in each combustion stroke is calculated based on the engine speed NE, and When the fluctuation amount ΔNE exceeds the allowable range, a method of determining that combustion is unstable (for example, refer to Japanese Patent Laid-Open No. 61-258955), and in addition to the same method, the load of the engine 1 is detected, Expand the allowable range as the load increases or decreases.
A method of reducing and determining the magnitude of the fluctuation amount ΔNE based on the allowable range and determining the combustion state (Japanese Patent Application No. 2-880).
No. 93) or the like is used.

If the combustion is unstable in step 103, the CPU 52 outputs a control signal for opening the oil switching valve 47 in step 104 and terminates this routine. Then, the control oil is supplied to the pressurizing chamber 44, the control oil pressure is applied to the front end of the ring gear 39, and the ring gear 39 moves backward while rotating. as a result,
The relative positions of the cam shaft 9 and the pulley main body 33 in the rotational direction are changed, the opening timing and closing timing of the intake valve 7 are delayed, and the valve overlap of the intake / exhaust valves 7, 8 becomes 0 °. This reduces the amount of residual gas in the combustion chamber 4 and stabilizes combustion.

On the other hand, if the throttle valve 13 is not fully closed in step 101 or the vehicle speed is 0 km in step 102.
If it is not / h, the CPU 52 determines that the operating state at that time is the non-idle state. And the CPU 52
Outputs a control signal for closing the oil switching valve 47 in step 105, and ends this routine. Then, the supply of the control oil to the pressurizing chamber 44 is stopped and the control oil pressure is not applied to the front end of the ring gear 39, so that the urging force of the spring 46 returns the ring gear 39 to the position shown in FIG. As a result, the camshaft 9
And the pulley main body 33 in the rotational direction are changed, the opening timing and closing timing of the intake valve 7 are advanced, and the valve overlap of the intake / exhaust valves 7 and 8 is zero.
The predetermined value is larger than 10 ° (10 ° in this case). As a result, the intake efficiency is increased by utilizing the inertia, and a high output is obtained.

During such valve timing switching control, when the CPU 52 determines in step 103 that combustion is being performed stably, the CPU 52 maintains the operating state of the valve timing variable mechanism 24 at that time. That is,
If the combustion state is stable when the operating state of the engine 1 shifts from the non-idle state to the idle state, the CPU 52 causes a control signal for closing the oil switching valve 47 despite the idle state. Continues to be output. As a result, the valve overlap amount of the variable valve timing mechanism 24 is maintained at the predetermined value without changing the valve overlap amount. On the contrary, when the engine 1 is in the idle state and the combustion shifts from the unstable state to the stable state, the CPU 52 outputs a control signal for opening the oil switching valve 47. Keep doing. As a result, the valve overlap is maintained at 0 ° without changing the valve overlap amount of the variable valve timing mechanism 24.

As described above, in this embodiment, when the combustion is stable after shifting from the non-idle state to the idle state,
That is, when it is not necessary to stabilize the combustion by setting the valve overlap to 0 °, the variable valve timing mechanism 2
Since the change operation of the valve overlap amount of 4 is forcibly prohibited, the number of change operations of the entire mechanism 24 is reduced accordingly. In addition, in the present embodiment, when the combustion transitions from the unstable state to the stable state, the valve overlap amount of the variable valve timing mechanism 24 is not changed, but the valve overlap amount at that time is maintained. Since this is done, the number of change operations is further reduced. Therefore, in this embodiment, the number of change operations can be reduced and durability and reliability can be improved as compared with the conventional technique in which the valve overlap amount is changed to 0 ° each time the idle state is entered. .. (Second Embodiment) Next, a second embodiment of the present invention will be described.

The valve timing control system for an internal combustion engine according to the second embodiment comprises the same engine 1 and its peripheral devices (see FIG. 2) as in the first embodiment, and is different only in the processing by the CPU 52. Therefore, the operation of the second embodiment will be described based on the flowchart of FIG. In this embodiment, the combustion state detecting means is composed of the intake air temperature sensor 17, the water temperature sensor 23 and the CPU 52.

When the processing shifts to this routine, the CPU
First, in step 201, 52 determines whether or not the operating state at that time is an idle state. This determination is performed in the same manner as the processing of steps 101 and 102 in the first embodiment. When the determination result is the idle state, the CPU 52 estimates in steps 202 and 203 whether the combustion state is stable. That is, a predetermined time (for example, 20
Second) has elapsed. Also, step 20
3, the cooling water temperature THW by the water temperature sensor 23 is equal to or higher than a predetermined temperature (for example, 90 ° C.), and the intake air temperature sensor 17
It is determined whether the intake air temperature THA is higher than a predetermined temperature (for example, 50 ° C.).

If the predetermined time has not elapsed in step 202, the CPU 52 immediately after the engine 1 is started, the combustion chamber 4
It is estimated that combustion is unstable due to low temperature, fuel adhesion to the wall surface of the intake passage 5, and the like. Also,
In step 203, the CPU 52 determines that the cooling water temperature THW is equal to or higher than the predetermined temperature and the intake air temperature THA is equal to or higher than the predetermined temperature.
It is presumed that the combustion is unstable because the engine 1 is in a high temperature state and vapor lock is likely to occur. If the combustion is unstable in this way, the CPU 52 proceeds to step 2
At 04, a control signal for opening the oil switching valve 47 is output, and this routine ends. Then, the ring gear 39 of the oil switching valve 47 moves rearward while rotating, and the valve overlap of the intake / exhaust valves 7 and 8 becomes 0 °. This reduces the amount of residual gas in the combustion chamber 4 and stabilizes combustion.

On the other hand, when the CPU 52 determines in step 201 that the operating state at that time is the non-idle state,
In step 205, a control signal for closing the oil switching valve 47 is output, and this routine ends.
Then, the ring gear 3 of the oil switching valve 47
9 is returned to the position shown in FIG. 3 by the urging force of the spring 46, and the valve overlap of the intake / exhaust valves 7 and 8 becomes a predetermined value (10 ° in this case). As a result, the intake efficiency is increased by utilizing the inertia, and a high output is obtained.

During such valve timing switching control, when the CPU 52 determines in steps 202 and 203 that combustion is being carried out in a stable manner, step 20
Go to 5. Then, the CPU 52 continues to output the control signal for closing the oil switching valve 47, even though the operating state at that time is the idle state. As a result, the valve overlap is maintained at the predetermined value without changing the overlap by the variable valve timing mechanism 24.

As described above, in this embodiment, when the combustion is stable even in the idle state, that is, when it is not necessary to stabilize the combustion by setting the valve overlap to 0 °, the variable valve timing mechanism. Since the change operation of the overlap of 24 is forcibly prohibited, the number of change operations of the entire mechanism 24 is reduced accordingly. Therefore, similarly to the first embodiment, the number of changing operations of the variable valve timing mechanism 24 can be reduced to improve durability and reliability.

Further, in the prior art, the combustion is stabilized by always setting the valve overlap to 0 ° in the idle state. However, in this case, the inertial effect of intake air cannot be obtained and the intake air amount decreases. , Engine output is insufficient. For this reason, when the vehicle is to be started next from the idle state, sufficient start acceleration may not be obtained, and there is a risk of rattling. Therefore, from the standpoint of this starting acceleration, a large valve overlap is required. On the other hand, in the present embodiment, the valve overlap is set to 0 ° only when the combustion is unstable in the idle state.
Thus, the combustion is stabilized, and when the combustion is stable even in the idle state, the valve overlap is set to a predetermined value (10 °). In other words, the valve overlap is set to a large value in preparation for the next start. Therefore, in the present embodiment, both stabilization of combustion in the idle state and prevention of the rattling of acceleration when starting from the idle state are effective.

If the valve overlap is small when starting from the idle state, the internal EGR
As (burnt gas in the combustion chamber) decreases, NOx increases and knocking may occur. However, in the present embodiment, the valve overlap is set to the predetermined value (10 °) when the combustion is stable even in the idle state as described above, so that the decrease of the internal EGR is suppressed and the deterioration of the emission is prevented. can do.

The present invention is not limited to the configuration of the above-mentioned embodiment, and may be arbitrarily modified within the scope not departing from the gist of the invention as follows. (1) The predetermined value of the valve overlap of the intake / exhaust valves 7 and 8 when the oil switching valve 47 is closed may be appropriately changed to a value other than 10 °. Further, the valve overlap when the oil switching valve 47 is opened may be a value other than 0 ° as long as it is a value smaller than the predetermined value. (2) The method for determining the combustion state in step 103 of FIG. 4 is to detect the degree of rocking of the engine 1 by a displacement gauge such as an acceleration sensor, and if the degree is smaller than a predetermined value, A method may be used in which the combustion is stable, and when it exceeds the predetermined value, the combustion is determined to be unstable. (3) When the combustion state is stable in step 103 of FIG. 4, in the first embodiment, the operation state of the variable valve timing mechanism 24 at that time is maintained.
After the process of step 103, the process may proceed to step 105 and a control signal for closing the oil switching valve 47 may be output to set the valve overlap to a predetermined value of 10 °. (4) In the first embodiment, the variable valve timing mechanism 2
The teeth 39a, 39b on the inner and outer circumferences of the ring gear 39 in FIG.
Both have helical teeth, but one of the teeth 39
Only a and 39b may be helical teeth. (5) The opening timing and closing timing of the exhaust valve 8 as well as the intake valve 7 may be controlled.

[0044]

As described above in detail, according to the present invention, when the combustion state is stable when the operating state of the internal combustion engine is changed from the non-idle state to the idle state, the valve of the variable valve timing mechanism is used. Since the change operation of the overlap amount is forcibly prohibited, the number of times of the change operation of the valve overlap amount of the variable valve timing mechanism is reduced while stabilizing the combustion when the internal combustion engine is idle It has an excellent effect that the reliability and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a valve timing control device for an internal combustion engine in a first embodiment embodying the present invention.

FIG. 3 is a sectional view of a variable valve timing mechanism in the first embodiment.

FIG. 4 is a flow chart for explaining the operation of the first embodiment.

FIG. 5 is a flow chart for explaining the operation of the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 4 ... Combustion chamber, 5 ... Intake passage, 6 ... Exhaust passage, 7 ... Intake valve, 8 ... Exhaust valve, 14 ... Throttle opening sensor which constitutes a part of operation state detection means, Reference numeral 17 ... Intake air temperature sensor forming part of combustion state detecting means, 20 ... Vehicle speed sensor forming part of operating state detecting means, 21 ... Rotation speed sensor forming part of combustion state detecting means, 23 ... Combustion A water temperature sensor forming a part of the state detecting means, 24 ... A variable valve timing mechanism,
52 ... CPU constituting idle state determination means, timing switching control means, combustion state detection means, and prohibition means

Claims (1)

[Claims] 1. A valve timing variable mechanism for adjusting valve timing of a valve for opening and closing an air passage to a combustion chamber of an internal combustion engine according to an operating state of the internal combustion engine, and detecting an operating state of the internal combustion engine. An operating state detecting means, an idle state determining means for determining whether or not the operating state of the internal combustion engine is idle based on the operating state detecting means, and when the operating state by the idle state determining means is a non-idle state A timing at which the valve overlap of the valve is set to a predetermined value by a variable valve timing mechanism, and when the operating state is an idle state, the valve overlap by the variable valve timing mechanism is set to a value smaller than the predetermined value. In a valve timing control device for an internal combustion engine, comprising a switching control means, Combustion state detection means for detecting the combustion state of the combustion engine, and when the operating state of the internal combustion engine transitions from a non-idle state to an idle state, if the combustion state by the combustion state detection means is stable, timing switching A valve timing control device for an internal combustion engine, comprising: a prohibiting unit that forcibly prohibits the operation of changing the valve overlap amount of the variable valve timing mechanism by the control unit.