JP4992782B2 - Control device for variable valve mechanism - Google Patents

Description

  The present invention relates to a control device for a variable valve mechanism that can change the operation timing of an intake valve or an exhaust valve of an internal combustion engine, and more particularly, to change a valve overlap between an intake valve and an exhaust valve immediately after a cold start. The present invention relates to a control device for a variable valve mechanism.

In general, an internal combustion engine (engine) is provided with an exhaust purification catalyst (hereinafter simply referred to as a catalyst) composed of a three-way catalyst or the like in the middle of an exhaust passage in order to reduce HC or the like in exhaust gas. However, since the exhaust gas component such as HC cannot be sufficiently purified until the catalyst reaches the activation temperature, the purification efficiency of HC or the like is reduced at the time of cold start or the like.
For this reason, at the time of cold start or immediately after the cold start (hereinafter collectively referred to as cold start), the ignition timing is retarded in order to raise the catalyst temperature to the activation temperature early, and the air-fuel ratio is calculated theoretically. There is known a technique of operating in a so-called light lean mode in which the air / fuel ratio (stoichiometric) is slightly leaner than that. In the light lean mode, combustion stability is high and healthy combustion can be obtained, so that the ignition timing can be significantly retarded, so that a relatively high temperature exhaust gas can be discharged into the exhaust passage. Thus, the catalyst can be raised in temperature early.

  On the other hand, if an overlap period (hereinafter referred to as valve overlap or VOL) of the valve opening timing between the exhaust valve and the intake valve is set between the exhaust stroke and the subsequent intake stroke, so-called internal EGR occurs and HC emission occurs. It is known that the amount is reduced. This is because part of the burned gas (exhaust gas) that has become hot by setting the VOL blows back to the intake port, and this burnt gas promotes vaporization of the liquefied fuel that adheres to the intake port wall. It is considered that unburned fuel that is peeled off from the cylinder wall at the end of the exhaust stroke and concentratedly blows back to the intake port without being exhausted.

In recent years, a variable valve mechanism that controls the opening and closing timing (valve timing) of the intake valve and the exhaust valve independently is widely known. During cold start, the variable valve mechanism is operated to expand the valve overlap. By doing so, internal EGR can be promoted and further HC reduction can be achieved.
For example, Patent Document 1 below discloses a technique in which a valve overlap at the time of starting the engine is set based on the engine coolant temperature or the intake valve temperature. More specifically, a technique is disclosed in which the overlap period is set longer as the coolant temperature or the intake valve temperature is lower. For this reason, in the technique of Patent Document 1, as a result, at the time of cold start, a large valve overlap is set first, and then the valve overlap is gradually reduced.
JP 2006-329144 A

However, in an engine equipped with such a variable valve mechanism, in-cylinder combustion may become unstable during a transient operation immediately after cold start (that is, when VOL is changed), leading to misfire, and VOL If the value is too large, the amount of internal EGR in the intake air becomes excessive, and the combustion may become unstable, leading to misfire.
The present invention has been devised in view of such problems, and uses a parameter indicating the direct combustion state to set a valve overlap at the time of cold start as large as possible while maintaining a stable combustion state, thereby cooling the engine. It is an object of the present invention to provide a control device for a variable valve mechanism that can greatly reduce the amount of HC discharged at the time of starting an engine.

Therefore, the control device of the variable valve mechanism of the present invention detects a variable controllable variable valve mechanism the valve overlap of an intake valve of an internal combustion engine and the exhaust valve, the combustion state of the internal combustion engine combustion At the time of cold start of the state detection means and the internal combustion engine, the variable valve mechanism has a maximum valve overlap when the index indicating the combustion fluctuation obtained from the combustion state detection means is within a predetermined value or less. The control means retards the ignition timing of the internal combustion engine at the cold start and sets the target air-fuel ratio to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio for a predetermined time. Once passed, it is characterized that you end the control of the movable variable valve mechanism during the cold state starting (claim 1).

The control device for a variable valve mechanism according to the present invention includes a variable valve mechanism capable of variably controlling a valve overlap between an intake valve and an exhaust valve of an internal combustion engine, and a combustion state detection for detecting a combustion state of the internal combustion engine. And when the internal combustion engine is cold started, the variable valve mechanism is controlled so that the valve overlap is maximized when the index indicating the combustion fluctuation obtained from the combustion state detecting means is within a predetermined value or less. And a control means for controlling the variable valve mechanism so that the valve overlap is maximized within a range not exceeding a second predetermined value smaller than the predetermined value. When the predetermined value is exceeded, control is performed so as to maintain the valve overlap at that time, and when the predetermined value is exceeded, control is performed so as to decrease the valve overlap (Claim 2).
The control means, at the time of cold state starting, as well as retarding the ignition timing of the internal combustion engine, it is preferable to set the target air-fuel ratio to the lean lean air-fuel ratio than the stoichiometric air-fuel ratio (claim 3).
For the purpose of preventing hunting, the predetermined value may have a range. That is, the variable valve mechanism is operated so that the valve overlap is maximized in a range where the predetermined value has a predetermined lower limit value and a predetermined upper limit value, and the index indicating combustion fluctuation does not exceed the lower limit value. If the lower limit is exceeded, the valve overlap at that point is maintained. Even in such a state, when the upper limit value is exceeded due to disturbance or the like, the valve overlap is reduced .

According to the control device for a variable valve mechanism of the present invention, at the time of cold start, the valve overlap is set using a parameter directly indicating the combustion state in the cylinder, so that the valve overlap is minimized without causing misfire. Can be set larger. Therefore, there is an advantage that the internal EGR at the time of cold start can be increased and the HC emission amount can be greatly reduced.
Further, the combustion in the cylinder becomes somewhat slow due to the increase in internal EGR, so that the intake air amount increases, and the catalyst temperature rise effect can be enhanced by increasing the exhaust gas flow rate. That is, when the internal EGR increases, the combustion speed decreases, the output becomes insufficient, and the rotation decreases. Therefore, combustion is improved by increasing the amount of air to maintain rotation and increasing the gas temperature during compression. As a result, the amount of exhaust gas increases.

Hereinafter, a control apparatus for a variable valve mechanism according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an engine equipped with the apparatus. In the figure, 1 is an engine, 2 is an intake passage connected to an intake port 4 of the engine 1, and 3 is an exhaust passage connected to an exhaust port 5 of the engine.
A piston 19 is slidably accommodated in the cylinder 23 of the engine 1, and the piston 19 is connected to a crankshaft (not shown) via a connecting rod 20. An ignition plug 21 for spark ignition of the air-fuel mixture in the cylinder 23 is provided so as to face the combustion chamber 24.

An intake valve 10 and an exhaust valve 11 are respectively provided in the openings of the intake port 4 and the exhaust port 5 on the combustion chamber 24 side. These intake and exhaust valves 10 and 11 are intake air that rotates in synchronization with a crankshaft (not shown). Each of the camshaft 12 and the exhaust camshaft 13 is driven to open the valve.
Each of the valve mechanisms on the intake side and the exhaust side is provided with known variable valve mechanisms 31 and 32 that can change the opening / closing timing of the intake valve 10 and the exhaust valve 11, that is, the valve timing.

The variable valve mechanisms 31 and 32 need only be able to change a valve overlap period in which at least the valve closing period of the exhaust valve 11 and the valve opening period of the intake valve 10 overlap, and may be provided only on the intake side. However, it may be provided only on the exhaust side. Here the intake variable valve mechanism 31 and the exhaust variable valve mechanism 32, for example, by changing the phase between the Kamupu re not shown and cam shaft 12, intake and exhaust valves 10 relative to the crank angle , 11 can be continuously advanced or retarded.

  On the other hand, in the intake passage 2, in order from the upstream side, an air cleaner 6 that removes dust from the intake air, an air flow sensor 8 that detects the intake air amount, a throttle valve 7 that adjusts the intake air amount, and intake air to suppress intake pulsation. A surge tank 16 for temporarily storing air and a fuel injection valve (injector) 14 for injecting fuel toward the intake port 4 are provided. The throttle valve 7 of the present embodiment is a so-called electronically controlled throttle that is controlled to open and close by electronic control, but is not limited to this. In addition, an air-fuel ratio sensor 9 for detecting the air-fuel ratio of the exhaust and an exhaust purification catalyst 22 for purifying the exhaust are interposed in this order from the upstream side.

  Information detected by the air flow sensor 8 and the air-fuel ratio sensor 9 is read into a control unit (ECU) 15 as control means. In addition, the control unit 15 includes a water temperature sensor 18 that detects the coolant temperature, an accelerator opening sensor 25 that is attached to the accelerator pedal 26 to detect the accelerator opening, and detects the number of revolutions of the engine 1. A crank angle sensor (engine speed sensor) 17 for detecting the crank angle is connected, and the ECU 15 calculates a required intake air amount, a target air-fuel ratio and the like based on these detection signals, and opens the throttle valve 7. The control of the engine speed, the fuel injection amount, and the ignition timing are executed.

  Incidentally, the ECU 15 calculates the combustion fluctuation rate COV Pi as an index indicating the combustion fluctuation of the engine 1 by a known method based on the crank angular velocity obtained from the crank angle sensor 17. In addition, it has shown that combustion is getting worse, so that combustion fluctuation rate COV Pi becomes large, and it has shown that combustion is stable, so that combustion fluctuation rate COV Pi becomes small. Here, the calculation method of the combustion fluctuation rate COV Pi will be described. First, the in-cylinder pressure is measured by a sensor, and Pi (the indicated mean effective pressure) is calculated from the obtained measurement value. Then, a standard deviation of N cycles (for example, 100 cycles) is obtained, and this standard deviation is divided by an average Pi of N cycles. The value obtained thereby becomes the combustion fluctuation rate COV Pi.

  In the present embodiment, the crank angle sensor 17 functions as a combustion state detection means for detecting the combustion state of the engine 1, but the combustion state detection means is not limited to the above-described one. For example, the ignition coil of each cylinder The combustion state may be confirmed by detecting the ionic current from. In this case, the ion current generation time corresponds to the combustion period, and the fluctuation rate of the ion current generation time correlates with the combustion fluctuation rate. For this reason, a combustion state can be judged using this ion current.

Further, the ECU 15 determines that the current operating state is the cold start when the water temperature is equal to or lower than a predetermined temperature (for example, 70 ° C.) based on information from the water temperature sensor 18. And when it determines with it being at the time of a cold start, the catalyst temperature rising control for raising a catalyst temperature is performed.
In this case, the ignition timing is significantly retarded, and the air-fuel ratio is slightly leaner than the stoichiometric air-fuel ratio (stoichiometric) from the rich air-fuel ratio at the start (for example, A / F = 15.5). It is adapted to change gradually to. At the same time, the operation of the intake side variable valve mechanism 31 and the exhaust side variable valve mechanism 32 is controlled to gradually expand the VOL.

  Incidentally, when the engine 1 is started (during cranking), the air-fuel ratio once becomes a rich air-fuel ratio, but thereafter, the target air-fuel ratio is gradually changed to a slightly lean air-fuel ratio as described above. At this time, the intake-side variable valve mechanism 31 and the exhaust-side variable valve mechanism 32 until the air-fuel ratio becomes a predetermined air-fuel ratio slightly richer than the light lean air-fuel ratio (for example, A / F = 15.0). Both are held at a predetermined initial phase angle at which the VOL is set to be relatively small. This is because, when the engine is started, sufficient hydraulic pressure to operate the variable valve mechanisms 31 and 32 is not generated, and if the valve overlap is suddenly increased immediately after the start when the combustion is not stable, the combustion stability is further increased. It is because there is a possibility of making it worse.

After reaching the predetermined air-fuel ratio, the VOL period is gradually extended with the combustion fluctuation rate COV Pi of the engine 1 as a parameter. Specifically calculates the fluctuation rate of the combustion COV Pi by the ECU based on the crank angle velocity obtained from the crank square spine capacitors 17, exceeded a predetermined value (referred combustion variation limit, or the misfire limit) The actuators of the variable valve mechanisms 31 and 32 are gradually actuated so that the VOL becomes as large as possible within the range.

Here, the horizontal axis of FIG. 2 indicates the valve closing timing [° ATDC] of the exhaust valve, and the vertical axis indicates the valve opening timing [° BTDC] of the intake valve. The solid line indicates the characteristics of the HC emission amount, and the number indicates the emission amount [g / h]. Moreover, the broken line has shown the characteristic of combustion fluctuation rate COV Pi , and the number has shown the combustion fluctuation rate [%].
In this embodiment, at the time of cold start, the VOL is gradually changed from the point b to the point a in FIG. Here, the point b in FIG. 2 is an operating point in the normal operation (in the warm state), and there is no overlap (negative overlap). In addition, when operating at such a point b in spite of the cold start, there is no problem with combustion fluctuation (combustion fluctuation rate of 15% or less) and a stable combustion state can be obtained. The HC emission amount is about 2 [g / h], which is a relatively high value.

On the other hand, the point a is the retarded side after the exhaust valve closing timing after the top dead center, the opening timing of the intake valve is the advanced side before the top dead center, and the total valve overlap period is The HC emission amount at this operating point is 0.4 [g / h].
In this embodiment, the combustion fluctuation rate COV Pi is used as an index that directly represents the combustion state of the engine 1, and this combustion fluctuation rate COV Pi exceeds a preset combustion fluctuation limit (for example, 21% in this embodiment). as HC emissions minimum and ing with no range, by controlling the operation of the variable valve mechanism 31, 32, without causing a misfire in the cylinder, to set the valve overlap amount to a maximum it can. In the example shown in FIG. 2, the HC at the cold start could be reduced to about 20% (reduction rate 80%).

  As described above, in the present embodiment, the intake side variable valve mechanism 31 is arranged so that the valve overlap between the intake valve 10 and the exhaust valve 11 gradually increases while constantly monitoring the combustion fluctuation rate COV Pi during the cold start. And the exhaust side variable valve mechanism 32 is controlled so that the valve overlap is maintained when the combustion fluctuation rate COV Pi reaches a predetermined value, and the valve overlap is reduced when the combustion fluctuation rate COV Pi exceeds the predetermined value. ing.

  Since the control apparatus for a variable valve mechanism according to an embodiment of the present invention is configured as described above, its operation will be described below with reference to the flowchart of FIG. First, in step S1, it is determined whether or not it is immediately after the cold start based on the information of the temperature sensor 18 and the like. Take control. The normal control refers to, for example, controlling the operation of the variable valve mechanisms 31 and 32 corresponding to the operation range determined by the load and the rotational speed, and also adjusting the ignition timing and the fuel injection amount based on the load and the rotational speed. It means to control.

If it is determined in step S1 that it is immediately after the cold start, the process proceeds to step S3, in which it is determined whether or not the idle switch is on, that is, whether or not the engine is idling. If it is determined that the engine is not idling, the process proceeds to the above-described step S2 through the route No, and the normal control is again performed and the process returns.
On the other hand, if it is determined in step S3 that the engine is idling, the process proceeds to step S4, where catalyst temperature increase control at the time of cold start is started, and whether a predetermined time has elapsed since the start of this catalyst temperature increase control is determined. Is done. Instead of the above conditions, a condition that the water temperature has risen to a predetermined water temperature may be applied.

Here, when it is determined that the catalyst temperature increase control has passed a predetermined time (or the water temperature has reached a predetermined temperature), the control at the cold start is completed (catalyst temperature increase control end determination), and the Yes route After that, the process proceeds to step S2. If the catalyst temperature increase control has not elapsed for a predetermined time (or the water temperature has not reached the predetermined temperature), the process proceeds to step S5, where the ignition timing is retarded and the air-fuel ratio is set to light lean. The initial phase angle is maintained until the air / fuel ratio reaches a predetermined air / fuel ratio .

In step S6, it is determined whether or not a predetermined time for variable valve phase angle control has elapsed. If not, the process proceeds to step S7, where the combustion fluctuation rate COV Pi of the engine 1 is equal to or less than the predetermined fluctuation rate. It is determined whether or not. If the combustion fluctuation rate COV Pi of the engine 1 is equal to or less than a predetermined fluctuation rate (combustion fluctuation limit) , the combustion state is very good, and the current phase angle of the variable valve mechanisms 31 and 32 is determined in step S8. It is determined whether or not it is less than the maximum phase angle permitted by the mechanism. If it is less than or equal to the maximum phase angle, the process proceeds to step S9. Just change. If it is determined in step S8 that the phase angle is the maximum, the process returns as it is.

In step S8, the intake-side variable valve mechanism 31 and the exhaust-side variable valve mechanism 32 are collectively represented. However, the intake-side variable valve mechanism 31 and the exhaust-side variable valve mechanism 32 each have a maximum phase angle. It may be determined whether or not. In this case, if the intake side variable valve mechanism 31 has a margin to the maximum phase angle, an instruction is output to advance the intake valve opening timing by a predetermined phase, and the exhaust side variable valve mechanism 31 if there is room up to the phase angle to the valve mechanism 32, and outputs an instruction to retard closing timing of the exhaust valves by a predetermined phase.

Further, if it is determined in step S7 that the combustion fluctuation rate COV Pi of the engine 1 is larger than the predetermined fluctuation rate, further expansion of the valve overlap may cause misfire, so the process proceeds to step S10. The phase angle of the variable valve mechanisms 31 and 32 is reduced by a predetermined phase so that the valve overlap is reduced. In this case as well, it may be determined whether or not the current phase angle of the variable valve mechanisms 31 and 32 is equal to or smaller than the minimum phase angle permitted by the mechanism. In this case, misfire suppression is performed by a method other than phase angle control such as air-fuel ratio control. Further, the determination criterion may be the initial phase angle instead of the minimum phase angle.

On the other hand, if it is determined in step S6 that the predetermined time for variable valve phase angle control has elapsed, the flow proceeds to step S11, and the variable valve mechanisms 31 and 32 maintain the initial temperature control while maintaining the catalyst temperature increase control. It is changed to a corner. Here are you set the predetermined time, since the catalyst temperature increase control causes the ignition timing is re Tado, since as they are operating conditions may become sluggish at the start, in order to solve this problem.

Then, in addition to by repeatedly executing such steps S1～S1 1 routine, it is possible to raise the temperature of the catalyst can be set as large as possible a valve overlap to the extent that does not cause misfire early, There is an advantage that the amount of HC emission can be greatly reduced.
Next, a specific example of the operation of the present apparatus will be described with reference to the time chart of FIG. 4. (a) shows the closing timing of the exhaust valve 11 by the exhaust side variable valve mechanism 32, and (b) shows the intake side. The opening timing of the intake valve 10 by the variable valve mechanism 31 is shown. In both (a) and (b), the upper side is the advance side, and the lower side is the retard side. (C) is the temperature of the front catalyst 22 (FCC) provided immediately after the exhaust port 3, (d) is the HC discharge amount, (e) is the air-fuel ratio, (f) is the intake air amount, (g) Indicates ignition timing, and (h) indicates engine speed characteristics.

Now, when the ignition is turned on to start the engine at t1, as shown in FIGS. 4 (f) and 4 (h), the throttle valve 7 is opened and the intake air amount is increased, and the engine speed after cranking is increased. To do. At this time, as shown in FIGS. 4E and 4G, the air-fuel ratio A / F is changed to the rich side and the ignition timing is advanced. At this time, the HC discharge amount temporarily increases as shown in FIG.

When it is determined that the engine 1 has completely exploded (t = t3), the catalyst temperature increase control is started. Specifically, the air-fuel ratio is made lean and the ignition timing is retarded, so that the catalyst temperature rises as shown in FIG.
On the other hand, as shown in FIGS. 4A and 4B, when the hydraulic pressure rises due to the ignition ON (t = t1) and the variable valve mechanisms 31 and 32 become operable (t = t2), the variable valve mechanism 31 and 32 are operated, and the valve closing timing (EC) of the exhaust valve 11 and the valve opening timing (IO) of the intake valve 10 are set to predetermined initial phase angles. Such an initial phase angle is maintained until the air-fuel ratio reaches a predetermined air-fuel ratio.

When the air-fuel ratio becomes the predetermined air-fuel ratio (t = t4), the VOL is gradually expanded so that the combustion fluctuation rate COV Pi does not exceed the predetermined value thereafter. In the example shown in FIG. 4, even if the phase angle reaches the maximum phase angle allowable by the variable valve mechanisms 31 and 32 (t = t5), the combustion fluctuation rate COV Pi is within a predetermined value, so t5 Thereafter, the maximum phase angle is maintained.
Then, the expansion of the valve overlap increases the internal EGR and reduces the HC emission amount as shown in FIG. 4 (d). Further, after the catalyst temperature increase control is started and a predetermined time elapses (t = t6), the mode shifts to the normal control mode, and the valve overlap is reduced as shown in FIGS. 4 (a) and 4 (b). Go. At the same time, as shown in FIG. 4 (e), the air-fuel ratio is changed to stoichiometric, and the ignition timing is gradually advanced.

In this embodiment, the transition to the normal control mode is triggered by the duration of the catalyst temperature increase control (corresponding to step S4 in FIG. 3), but the catalyst temperature may be triggered. In this case, when the catalyst temperature becomes equal to or higher than the predetermined temperature, the mode shifts to the normal control mode. In addition to this, the normal control mode may be shifted to the water temperature as a trigger.
As described above, according to the control apparatus for a variable valve mechanism according to an embodiment of the present invention, the valve overlap is set using the parameter indicating the direct combustion state at the time of cold start, so misfire is prevented. The valve overlap can be set as large as possible without incurring. Therefore, the internal EGR at the time of cold start can be increased, and the HC emission amount can be greatly reduced.

In addition, the internal EGR makes the combustion in the cylinder somewhat slow, so that the intake air amount increases, and the catalyst temperature rise effect can be enhanced by increasing the exhaust gas flow rate.
In the present invention, since the combustion fluctuation rate is directly monitored, misfire immediately after the cold start can be surely prevented.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in order to prevent the hunting of the control, it may make myself lifting the range to the predetermined value (predetermined variation rate). In this case, set the lower limit and upper limit for the above-mentioned predetermined value, and operate the variable valve mechanism so that the valve overlap is maximized so long as the indicator COV Pi indicating combustion fluctuation does not exceed the lower limit. we will expand, if it exceeds the lower limit value, maintains the valve overlap at that time. Even in such a state, if the upper limit is exceeded due to disturbance or the like, the valve overlap is reduced. Thereby, the control of the variable valve mechanism can be stabilized, and hunting can be prevented.

  In the above-described embodiment, the case where the variable valve mechanism is provided on both the intake side and the exhaust side has been described. However, the variable valve mechanism may be provided only on either the intake side or the exhaust side. Further, the variable valve mechanism is not particularly limited as long as it can change the opening / closing timing of the intake valve or the exhaust valve. In the present embodiment, the variable valve mechanism is configured such that the operation timing of the intake valve or the exhaust valve can be continuously changed, but the variable valve mechanism is configured so that it can be changed in stages. May be.

It is a mimetic diagram showing an engine to which a control device of a variable valve mechanism concerning one embodiment of the present invention is applied. It is a figure explaining the effect | action of the control apparatus of the variable valve mechanism concerning one Embodiment of this invention. It is a flowchart explaining the effect | action of the control apparatus of the variable valve mechanism concerning one Embodiment of this invention. It is a time chart explaining the effect | action of the control apparatus of the variable valve mechanism concerning one Embodiment of this invention.

Explanation of symbols

1 engine (internal combustion engine)
10 Intake valve 11 Exhaust valve 15 ECU (control means)
17 Crank angle sensor or engine speed sensor (combustion state detection means)
31 Intake side variable valve mechanism 32 Exhaust side variable valve mechanism

Claims (3)

A variable valve mechanism capable of variably controlling the valve overlap between the intake valve and the exhaust valve of the internal combustion engine;
Combustion state detection means for detecting the combustion state of the internal combustion engine;
At the time of cold start of the internal combustion engine, control means for controlling the variable valve mechanism so that the valve overlap is maximized when the index indicating the combustion fluctuation obtained from the combustion state detection means is within a predetermined value or less. equipped with a door,
The control means retards the ignition timing of the internal combustion engine during the cold start and sets the target air / fuel ratio to a lean air / fuel ratio that is leaner than the stoichiometric air / fuel ratio. It characterized that you end the control of the movable variable valve mechanism, the control device of the variable valve mechanism. A variable valve mechanism capable of variably controlling the valve overlap between the intake valve and the exhaust valve of the internal combustion engine;
Combustion state detection means for detecting the combustion state of the internal combustion engine;
At the time of cold start of the internal combustion engine, control means for controlling the variable valve mechanism so that the valve overlap is maximized when the index indicating the combustion fluctuation obtained from the combustion state detection means is within a predetermined value or less. equipped with a door,
The control means controls the variable valve mechanism so that the valve overlap is maximized within a range not exceeding a second predetermined value smaller than the predetermined value, and when the second predetermined value is exceeded, controlled to maintain the valve overlap at that time, if it exceeds the predetermined value, characterized that you control so as to reduce the valve overlap, control unit of the variable valve mechanism. The control means, at the time of cold state starting, as well as retarding the ignition timing of the internal combustion engine, and sets the target air-fuel ratio to the lean lean air-fuel ratio than the stoichiometric air-fuel ratio, according to claim 1 or 2 The control apparatus of the variable valve mechanism as described .

Images