JP2003049682A - Control system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate an internal combustion engine so that a combustion state without output fluctuation and with stability is maintained in a cold condition, in a control system for an internal combustion engine comprising a variable valve system capable of varying operation timing of an intake valve. SOLUTION: The variable valve system is provided to vary valve closing timing of the intake valve. In a cold operation of the internal combustion engine (Step 100), if a misfire is detected (Step 110), a target compression ratio tε is increased (Step 112), or if knocking is detected, the target compression ratio tε is decreased (Step 114). Target valve closing timing tIVC of the intake valve for realizing the target compression ratio tε is computed (Step 116). A maximum lift IVLMax and valve opening timing IVO of the intake valve are decided so as to bring an intake air quantity GN at a desired value while realizing the target valve closing timing tIVC (Step 120).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine provided with a variable valve mechanism that makes the operation timing of an intake valve variable.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 11-30134, there is known a variable valve mechanism that can change the opening / closing timing of an intake valve. According to the conventional variable valve mechanism described above, it is possible to freely change the opening / closing timing of the intake valve to the advance side or the retard side according to the operating state of the internal combustion engine.

When the closing timing of the intake valve is changed toward the intake bottom dead center, the compression ratio of the internal combustion engine can be substantially increased. The above publication discloses a technique for improving the output of the internal combustion engine by changing the closing timing of the intake valve so that the compression ratio of the internal combustion engine is increased during cold operation of the internal combustion engine. According to this technique, the output of the internal combustion engine can be stabilized during cold operation in which the combustion state tends to be unstable.

[0004]

However, according to the above-mentioned conventional variable valve mechanism, the intake air amount inevitably changes with the change of the closing timing of the intake valve. That is, in the above-mentioned conventional technique, no consideration has been given to the fact that the intake air amount changes due to the change of the closing timing of the intake valve.

When the intake air amount changes during the operation of the internal combustion engine, the output generated by the internal combustion engine changes. For this reason,
Although the above-mentioned conventional technique is effective in generating a stable output to the internal combustion engine during cold operation of the internal combustion engine, the output of the internal combustion engine slightly changes during the control process for obtaining the effect. Had a problem of causing.

The present invention has been made to solve the above problems, and operates an internal combustion engine in a cold state so as to maintain a stable combustion state without fluctuations in output. An object of the present invention is to provide a control device that can be operated.

[0007]

The invention according to claim 1 is
To achieve the above object, there is provided a control device for an internal combustion engine, comprising a variable valve mechanism for varying the closing timing of an intake valve, wherein the closing timing of the intake valve is changed during cold operation of the internal combustion engine. Intake valve closing timing changing means, so that the output change of the internal combustion engine due to the change of the opening timing of the intake valve is offset,
Output factor correction means for correcting at least one factor that determines the output of the internal combustion engine.

The invention according to claim 2 is the control device for an internal combustion engine according to claim 1, wherein the variable valve mechanism has a function of varying the valve opening timing of the intake valve, The output factor correction means includes an intake valve opening timing correction means for correcting the opening timing of the intake valve so that the intake air amount of the internal combustion engine becomes equal before and after the closing timing of the intake valve is changed. It is characterized by

The invention according to claim 3 is the control device for an internal combustion engine according to claim 1 or 2, wherein the variable valve mechanism has a function of varying a lift profile of the intake valve. The output factor correction means includes intake valve lift profile correction means for correcting the lift profile of the intake valve so that the intake air amount of the internal combustion engine becomes equal before and after the closing timing of the intake valve is changed. Is characterized by.

The invention according to claim 4 is the control device for an internal combustion engine according to any one of claims 1 to 3.
An electronic control throttle capable of realizing an arbitrary throttle opening regardless of the accelerator pedal depression amount is provided, and the output factor correction means is configured to change the intake air of the internal combustion engine before and after the closing timing of the intake valve is changed. It is characterized by comprising throttle opening correction means for correcting the throttle opening so that the amounts become equal.

The invention according to claim 5 is the control device for an internal combustion engine according to any one of claims 1 to 4.
A misfire detecting means for detecting misfire of the internal combustion engine is provided, and the intake valve closing timing changing means moves the closing timing of the intake valve to the intake bottom dead center side when the misfire of the internal combustion engine is detected. It is characterized by comprising a first changing means.

The invention according to claim 6 is the control device for an internal combustion engine according to any one of claims 1 to 5.
The engine includes a knocking detection means for detecting knocking of the internal combustion engine, wherein the intake valve closing timing changing means, when knocking of the internal combustion engine is detected, changes the closing timing of the intake valve in the direction of moving away from the intake bottom dead center. It is characterized by comprising a second changing means for moving.

According to a seventh aspect of the present invention, there is provided a control device for an internal combustion engine, comprising a variable valve mechanism for varying a valve overlap period in which both the exhaust valve and the intake valve are opened, the internal combustion engine cooling device comprising: During the inter-operation, a valve overlap period changing means for changing the valve overlap period, and at least one output for deciding the output of the internal combustion engine so that the output change of the internal combustion engine due to the change of the valve overlap period are offset. Output factor correction means for correcting a factor.

The invention according to claim 8 is the control device for an internal combustion engine according to claim 1, wherein the variable valve mechanism has a function of varying the valve opening timing of the intake valve, The valve overlap period changing means changes the valve overlap period by changing the valve opening timing of the intake valve.

The invention according to claim 9 is the control device for an internal combustion engine according to claim 7 or 8, wherein the variable valve mechanism has a function of varying the lift profile of the intake valve. The output factor correction means includes an intake valve lift profile correction means for correcting the lift profile of the intake valve so that the intake air amount of the internal combustion engine becomes equal before and after the change of the valve overlap period. And

The invention according to claim 10 is the same as claim 7
10. The control device for an internal combustion engine according to any one of claims 1 to 9, further comprising an electronic control throttle capable of realizing an arbitrary throttle opening regardless of a depression amount of an accelerator pedal, wherein the output factor correction means is A throttle opening correction means for correcting the throttle opening is provided so that the intake air amount of the internal combustion engine becomes equal before and after the change of the valve overlap period.

The invention according to claim 11 is the invention according to claim 7.
11. The control device for an internal combustion engine according to any one of claims 1 to 10, comprising misfire detection means for detecting misfire of the internal combustion engine, wherein the valve overlap period changing means is provided when misfire of the internal combustion engine is detected. And a first changing means for generating or extending the valve overlap period.

The invention according to claim 12 is the invention according to claim 7.
The control device for an internal combustion engine according to any one of claims 1 to 11, further comprising knocking detection means for detecting knocking of the internal combustion engine, wherein the valve overlap period changing means includes:
It is characterized by comprising a second changing means for shortening or eliminating the valve overlap period when knocking of the internal combustion engine is detected.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. It should be noted that elements common to each drawing are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1. FIG. 1 is a conceptual diagram for explaining the configuration of an internal combustion engine 10 according to the first embodiment of the present invention. The internal combustion engine 10 includes an intake valve 14 that opens and closes the intake port 12, and an exhaust valve 18 that opens and closes the exhaust port 16. Further, the internal combustion engine 10 includes a variable valve mechanism 20 as a drive source of the intake valve 12. Variable valve mechanism 2
With 0, the intake valve 14 can be opened and closed while freely changing the valve opening timing IVO, the valve closing timing IVC, and the lift profile of the intake valve 14 within the range prepared in advance. In the following description, the individual lift profiles realized by the variable valve mechanism 20 are the maximum lift amounts given to the intake valve 14 by those profiles.
It will be distinguished by IVLMax.

A surge tank 20 communicates with the intake port 12 of the internal combustion engine 10. In the surge tank 20,
A PM sensor 22 for detecting the intake pipe pressure PM is attached. An electronically controlled throttle 24 is arranged upstream of the surge tank 20. The electronically controlled throttle 24 can realize an arbitrary throttle opening degree TA regardless of the depression amount of the accelerator pedal. An air flow meter 28 for detecting the intake air amount Ga flowing through the intake passage 26 is arranged further upstream of the electronic control throttle 24.

The air flow meter 28, the electronically controlled throttle, and the PM sensor 22 described above are connected to the ECU (Electronic).
c Control Unit) 30 and is electrically connected. Further, the ECU 30 includes various actuators incorporated in the variable valve mechanism 20, various sensors for detecting the state of the variable valve mechanism 20, a rotation speed sensor 32 that outputs an output according to the rotation speed NE of the internal combustion engine, A knock sensor 34 for detecting knocking from vibration of the internal combustion engine 10, a cooling water temperature sensor 36 for detecting a cooling water temperature THW of the internal combustion engine 10, and the like are connected. The ECU 30 controls the variable valve mechanism 20, the electronically controlled throttle 24, and the like based on the outputs of those sensors.

By the way, after the internal combustion engine 10 is cold-started, until the warm-up of the internal-combustion engine 10 is sufficiently completed, the fuel is less likely to be vaporized than after the warm-up is completed. In particular, when a heavy fuel is used among the fuels used in the market, this tendency becomes prominent, and a good combustion state may not be maintained in the internal combustion engine 10. Hereinafter, the time when such a state may occur, that is, the time when a good combustion state may not be maintained when heavy fuel is used is referred to as “cold time”, and the internal combustion engine 10 in that state The time when the vehicle is operating is called "during cold operation".

The above-mentioned deterioration of the combustion state during cold operation can be prevented by creating a state in which the fuel is easily vaporized. In the internal combustion engine 10, for example, the vaporization property of the fuel can be improved by increasing the compression end temperature in the cylinder, that is, the cylinder internal temperature when the piston reaches the compression top dead center. Further, in the internal combustion engine 10 of the present embodiment, the compression end temperature can be increased by changing the valve closing timing IVC of the intake valve 14 to increase the substantial compression ratio ε.

FIG. 2 shows the valve closing timing in the internal combustion engine 10.
FIG. 6 is a diagram illustrating a state in which a compression ratio ε changes with a change in IVC. In FIG. 2, a curve and a curve are the intake valve opening period when the closing timing of the intake valve 14 is set to IVC1 slightly retarded from the intake bottom dead center (BDC), respectively.
And the compression stroke period. Further, the curve and the curve indicate that the closing timing of the intake valve 14 is the intake bottom dead center (BD
C) shows the intake valve open period and the compression stroke period when set to IVC2 which is advanced by a predetermined angle from C). As is apparent from these curves, in the internal combustion engine 10, when the closing timing of the intake valve 14 is set to IVC1, the compression ratio ε is larger than that when the closing timing is set to IVC2. Can be obtained.

That is, in the internal combustion engine 10 of this embodiment,
As shown in FIG. 3, the compression ratio ε can be increased as the closing timing IVC of the intake valve 14 approaches the intake bottom dead center, and as the valve closing timing IVC moves away from the intake bottom dead center, The compression ratio ε can be reduced. Therefore, in the present embodiment, when the favorable combustion state cannot be obtained during the cold operation of the internal combustion engine 10, the closing timing IVC of the intake valve 14
It is possible to improve the combustion state by changing the substantial compression ratio ε via and controlling the compression end temperature.

In the internal combustion engine 10, when the closing timing IVC of the intake valve 14 is changed, the intake air amount GN per one rotation is changed with the change, and as a result, the output of the internal combustion engine 10 is changed. Occurs. Therefore, the internal combustion engine 10
During the cold operation of, it is possible to simply change the closing timing IVC of the intake valve 14 without considering the change of the intake air amount GN.
Although the combustion condition can be improved, the passengers of the vehicle may feel uncomfortable.

Therefore, in this embodiment, when the closing timing IVC of the intake valve 14 is changed during the cold operation of the internal combustion engine 10, the opening timing of the intake valve 14 is controlled so that the intake air amount GN does not change. Simultaneously execute the process of changing the IVO at the appropriate time. Therefore, according to this embodiment, it is possible to generate only the effect of improving the combustion state without changing the output of the internal combustion engine 10.

FIG. 4 shows a flow chart of a routine executed by the ECU 30 in the present embodiment in order to realize the above functions. In the routine shown in FIG. 4, first, it is determined whether the cooling water temperature THW of the internal combustion engine 10 is 80 ° C. or higher (step 100). In this embodiment, 80 ° C.
Is the temperature set as the warm-up completion temperature. More specifically, it is the temperature set as the lower limit of the temperature at which the combustion state does not become unstable even when heavy fuel is used. When it is determined that THW> 80 ° C. is established, it is determined that it is no longer necessary to execute this routine for the purpose of stabilizing the combustion state, and thereafter this processing is promptly terminated. On the other hand, when it is determined that THW> 80 ° C. is not established, it is determined that the internal combustion engine 10 is in cold operation, and the processing of this routine is advanced.

That is, in step 100 above, TH
If it is determined that W> 80 ° C. is established, then the following parameters necessary for the processing of this routine are read (step 102).・ The rotational speed NE of the internal combustion engine ・ The intake pipe pressure PM ・ The opening timing IVO of the intake valve 14 ・ The closing timing IVC of the intake valve 14 ・ The maximum lift amount IVLMax of the intake valve 14 Of these parameters, NE and PM are The values detected by the rotation speed sensor 32 and the PM sensor 22 are read. Other parameters IVO, IVC and IVLM
As for ax, a value determined by another routine executed separately from this routine for controlling the state of the variable valve mechanism 20 is read.

Next, the intake air amount GN per revolution is calculated based on the various parameters NE, PM, IVO, IVC, and IVLMax read as described above (step 10).
4). The intake air amount GN is a value determined as a function of the above various parameters. In the present embodiment, the ECU 30
Stores a map or a calculation formula for calculating the intake air amount GN based on those parameters. In step 104, the intake air amount GN is calculated using the map or the calculation formula.

Next, based on the closing timing IVC of the intake valve 14, the substantial compression ratio ε of the internal combustion engine 10 realized by the present setting is calculated (step 106).

Next, according to the current settings, the internal combustion engine 10
In step 108, it is determined whether the normal combustion state is obtained, or more specifically, whether the internal combustion engine 10 is misfired or knocked. Whether or not knocking has occurred in step 108 is
The determination can be made by a known method based on the output of the knocking sensor 34. Further, whether or not a misfire has occurred can be determined based on whether or not the interval between pulses emitted from the rotation speed sensor 32 is unduly extended.

When it is determined in step 108 that the combustion state is normal, it is not necessary to improve the combustion state, and therefore, the current process is immediately terminated. On the other hand, when it is determined that the combustion state is not normal, it is determined whether the abnormal combustion is misfire or knocking (step 110).

When it is determined that the abnormal combustion occurring in the internal combustion engine 10 is a misfire, the target compression ratio tε is updated to the latest past target compression ratio tεO plus a predetermined correction value K1. (Step 112). If the target compression ratio tε is increased and as a result the actual compression ratio ε of the internal combustion engine 10 is increased, the compression end temperature in the cylinder rises and the fuel is easily vaporized. Further, when the fuel is in a state where it is easily vaporized, the fuel is easily burned and misfire is less likely to occur. Therefore, according to the processing of this step 112, the occurrence of misfire can be suppressed and the combustion state of the internal combustion engine 10 can be improved.

On the other hand, when it is determined in step 110 that the abnormal combustion occurring in the internal combustion engine 10 is knocking, the target compression ratio tε is a predetermined correction value K2 from the latest target compression ratio tεO. It is updated to the subtracted value (step 114). When the target compression ratio tε is reduced and as a result the actual compression ratio ε of the internal combustion engine 10 is increased,
The compression end temperature in the cylinder decreases, and knocking is less likely to occur. Therefore, according to the processing of this step 114, the occurrence of knocking can be suppressed and the combustion state of the internal combustion engine 10 can be improved.

When the target compression ratio tε is updated by the processing of step 112 or 114, next, the target valve closing timing t of the intake valve 14 for realizing the target compression ratio tε.
The IVC is calculated (step 116).

Next, based on the intake air amount GN per rotation calculated in step 104, the target valve closing timing tIVC calculated in step 116, the rotation speed of the internal combustion engine 10, and the intake pipe pressure PM, The target maximum lift amount tIVLMax and the target valve opening timing tIVO of the intake valve 14 are determined (step 118).

The intake air amount GN is the opening / closing timing IV of the intake valve 14.
O, IVC, lift profile of intake valve 14, internal combustion engine 1
It is uniquely determined for the rotational speed NE of 0 and the intake pipe pressure PM. For this reason, when the intake air amount GN to be supplied to the internal combustion engine 10 is determined and the closing timing IVC of the intake valve 14 is determined, the intake valve 14 to be realized with respect to the rotational speed NE and the intake pipe pressure PM is determined. The valve closing timing IVC and lift profile (maximum lift amount IVLMax) can be determined.

In this embodiment, the intake air amount GN and the valve closing timing
IVO, rotational speed NE, and intake pipe pressure PM, valve opening timing IVO
A map or an empirical formula for determining the maximum lift amount IVLMax is set in advance experimentally or by simulation. The map or empirical formula is the ECU
In step 118, the target maximum lift amount IVLMax and the target valve opening timing tIVO are determined by applying parameters such as the intake air amount GN and the target valve closing timing tIVC to the map or empirical formula. .

When the processing of step 118 is completed,
Next, the target valve opening timing tIVO determined in this routine,
A process of switching the cam profile, specifically, a process of operating various actuators of the variable valve mechanism 20 is performed so that the target valve closing timing tIVC and the target maximum lift amount tIVLMax are realized (step 120).

In the routine shown in FIG. 4, it is next determined whether or not the combustion state after switching the cam profile is normal (step 122). As a result, if the combustion state is normal, it is determined that the cam profile suitable for the cold operation is set, and the routine of this time is ended. On the other hand, if the combustion state is still not normal, the processing from step 110 onward is repeated to further correct the cam profile.

As described above, according to the routine shown in FIG. 4, the closing timing IVC of the intake valve 14 can be changed without affecting the intake air amount GN to be supplied to the internal combustion engine 10. Then, by appropriately changing the valve closing timing IVC, the compression ratio ε suitable for the cold operation can be realized and the combustion state of the internal combustion engine 10 can be maintained in a normal state. Therefore, according to the present embodiment, it is possible to improve the operating characteristics of the internal combustion engine 10 in the cold state without giving the occupants of the vehicle any discomfort.

In the first embodiment described above, the maximum lift amount IVLMax and the valve opening timing IVO of the intake valve 14 correspond to the "factor" in claim 1, and EC
The U30 executes the above step 120 so that the target valve closing timing tIVC calculated in the above step 116 is realized.
The "intake valve closing timing changing means" according to claim 1 is realized by switching the cam profile in step 1, and the ECU 30 controls the target maximum lift amount tIVLMax and the target valve opening timing calculated in step 118. The "output factor correction means" according to claim 1 is realized by switching the cam profile in step 120 so that tIVO is realized.

Further, in the above-described first embodiment,
The ECU 30 executes the above step 1 so that the target valve opening timing tIVO calculated in the above step 118 is realized.
By switching the cam profile at 20, the "intake valve opening timing correction means" according to claim 2 is realized.

Further, in the first embodiment described above,
The "intake valve lift profile correction means" according to claim 3 is realized by the ECU 30 switching the cam profile in step 120 so that the target maximum lift amount tIVLMax calculated in step 118 is realized. There is.

Further, in the above described first embodiment,
The ECU 30 implements the "misfire detection means" according to claim 5 by detecting the misfire of the internal combustion engine by the processing of steps 108 and 110, and the ECU 30
By executing the processing of steps 112 and 116, the "first changing means" according to claim 5 is realized.

Further, in the above described first embodiment,
The "knocking detection means" according to claim 6 is realized by the ECU 30 detecting the knocking of the internal combustion engine by the processing of steps 108 and 110, and E
The CU 30 executes the processing of steps 114 and 116 to implement the "second changing means".

Embodiment 2. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment has the configuration shown in FIG.
This can be realized by causing 30 to execute the routine shown in FIG. 5 described later, instead of the routine shown in FIG.

In the system of the first embodiment described above, when the closing timing IVC of the intake valve 14 is changed, in order to prevent the intake air amount GN from changing due to the influence thereof, the opening timing IVO of the intake valve 14 is changed. Has been fixed. On the other hand, the system of the present embodiment, when changing the closing timing IVC of the intake valve 14,
The feature is that the intake air amount GN is prevented from changing by correcting the throttle opening TA.

FIG. 5 is a flowchart of a routine executed by the ECU 30 in this embodiment to realize the above-mentioned characteristic function. In addition, in FIG.
The same steps as the steps shown in are attached with the same reference numerals, and the description thereof will be omitted or simplified.

That is, in the routine shown in FIG. 5, after the target valve closing timing tIVC of the intake valve 14 is calculated in response to the occurrence of misfire or knocking (steps 100 to 11).
6), the target throttle opening tTA for realizing the desired intake air amount GN is determined with respect to the target valve closing timing tIVC, the current rotational speed NE, and the intake pipe pressure PM (step 200).

The intake air amount GN is the opening / closing timing IV of the intake valve 14.
O, IVC, lift profile of intake valve 14, internal combustion engine 1
It is uniquely determined for the rotational speed NE of 0 and the intake pipe pressure PM. In the present embodiment, the opening timing IVO of the intake valve 14
And the valve closing timing IVC and the lift profile of the intake valve 14 are fixed, the valve closing timing IVC of the intake valve 14 is changed. Therefore, if the intake pipe pressure PM is constant, the intake air amount GN changes with the change of the valve closing timing IVC.

The intake pipe pressure PM approaches the atmospheric pressure as the throttle opening TA is opened, and becomes negative as the throttle opening TA is reduced. Further, the intake air amount GN increases as the intake pipe pressure PM approaches atmospheric pressure, and the intake pipe pressure PM
The smaller the PM becomes, the smaller the amount becomes. Therefore, when changing the closing timing IVC of the intake valve 14, the throttle opening TA
By modifying, the influence of the former change can be canceled by the latter modification, and the intake air amount GN can be maintained constant.

In this embodiment, the intake air amount GN and the valve closing timing
A map or an empirical formula for determining the throttle opening TA to be realized with respect to the IVO, the rotational speed NE, and the intake pipe pressure PM is set in advance experimentally or by simulation. The map or empirical formula is ECU30.
In step 200, the target throttle opening tTA is determined by applying parameters such as the intake air amount GN and the target valve closing timing tIVC to the map or empirical formula.

As a result, in this embodiment, as shown in FIG. 6, when the intake valve closing timing IVC is far from the intake bottom dead center, a large throttle opening TA is secured. Then, when the valve closing timing IVC is near the intake bottom dead center, the throttle opening TA is narrowed down. By performing such control, the intake air amount GN is maintained at a substantially constant value regardless of the change in the closing timing IVC of the intake valve 14.

When the processing of step 118 is completed,
Next, the target valve closing timing tIVC determined in this routine,
And a process of switching the cam profile and the throttle opening TA so that the target throttle opening tTA is realized, specifically, a process of operating various actuators of the variable valve mechanism 20 and the electronically controlled throttle 24. (Step 202).

When the above processing is completed, the combustion state is determined again in step 122 as in the case of the first embodiment, and if the combustion state is normal, the routine is terminated. On the other hand, if the combustion state is not normal, the process for correcting the valve closing timing IVC of the intake valve 14 is executed again.

As described above, according to the routine shown in FIG. 5, the intake air amount can be adjusted by modifying the throttle opening TA.
The combustion state of the internal combustion engine 10 can be improved while preventing the change in GN. Therefore, according to the system of the present embodiment, as in the case of the first embodiment, it is possible to improve the operating characteristics of the internal combustion engine 10 in the cold state without giving the occupants of the vehicle any discomfort. .

In the second embodiment described above, the throttle opening TA corresponds to the "factor" in claim 1, and the ECU 30 causes the target valve closing timing tIVC calculated in step 116 to be set. So that
The "intake valve closing timing changing means" according to claim 1 is realized by switching the cam profile in step 202, and the ECU 30 controls the target throttle opening degree calculated in step 200.
By controlling the electronically controlled throttle 24 in step 202 so that tTA is realized, the "output factor correction means" according to claim 1 and the "throttle opening correction means" according to claim 4 are realized. ing.

In the second embodiment described above, the relative relationship between the valve opening timing IVO and the valve closing timing IVC of the intake valve 14 and the valve closing timing IVC with the lift profile of the intake valve 14 fixed. However, the present invention is not limited to this. That is, the opening timing IVO of the intake valve and the lift profile may be changed according to a predetermined rule according to the operating state of the internal combustion engine 10.

Further, in the first and second embodiments described above, in order to maintain the intake air amount Ga, the opening timing IVO and the maximum lift amount IVLMax of the intake valve 12 are corrected or the throttle opening TA is changed. Although the modifications are made individually, the present invention is not limited thereto. That is, those modifications may be performed in combination.

Further, in the above-described first and second embodiments, the valve closing timing IV is maintained by keeping the intake air amount GN constant.
Although the output fluctuation of the internal combustion engine 10 due to the change of C is prevented, the method of preventing the output fluctuation of the internal combustion engine 10 is not limited to this. That is, the output of the internal combustion engine 10 can be controlled not only by the intake air amount GN but also by the fuel injection amount and the ignition timing. Therefore, the output fluctuation of the internal combustion engine 10 may be prevented by correcting the fuel injection amount and the ignition timing so that the influence of the change in the intake air amount GN due to the change in the valve closing timing IVC is offset.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 7 to 9. The system of the present embodiment has the configuration shown in FIG.
0 instead of the routine shown in FIG.
This can be realized by executing the routine shown in.

FIGS. 7A to 7C show the internal combustion engine 1
FIG. 3 is a diagram for explaining the principle of occurrence of internal EGR (Exhaust Gas Recirculation) at 0. FIG. 7A shows the exhaust stroke of the internal combustion engine 10. In the exhaust stroke, the piston moves toward the top dead center with the exhaust valve 18 open, so that the exhaust gas flows out of the cylinder to the exhaust port 16.

FIG. 7B shows a state in which both the exhaust valve 18 and the intake valve 14 are open in the process of shifting from the exhaust stroke to the intake stroke. Exhaust gas remains inside the exhaust port 16 when the internal combustion engine 10 shifts from the exhaust stroke to the intake stroke. Further, at this stage, a positive pressure is generated inside the exhaust port 16, while a negative pressure is generated inside the intake port 12. Therefore, during the period in which both the exhaust valve 18 and the intake valve 14 are open (during the valve overlap period), as shown in FIG. 7B, the exhaust gas remaining in the exhaust port 16 is A situation occurs in which the air flows back into the intake port 12 through the inside of the cylinder.

FIG. 7C shows a state after the exhaust valve 18 is closed and the transition to the intake stroke is completed. Internal combustion engine 10
When shifts to the intake stroke, the exhaust gas flowing back to the intake port 12 flows into the cylinder again. As a result, the internal combustion engine 10 is supplied with the air-fuel mixture containing the exhaust gas at a predetermined ratio. As described above, in the internal combustion engine 10, the valve overlap period occurs, so that a part of the exhaust gas flowing out to the exhaust port 16 again flows into the cylinder in the intake stroke. In this specification, this phenomenon is referred to as “internal EGR”, and the amount of exhaust gas sucked into the cylinder again by the internal EGR is referred to as “internal EGR amount”.

Since the exhaust gas is hotter than the air, the temperature of the air-fuel mixture taken into the internal combustion engine 10 becomes higher as the internal EGR amount increases. Further, the in-cylinder temperature (compression end temperature) immediately after the end of the compression stroke becomes higher as the intake air-fuel mixture has a higher temperature. Therefore, the compression end temperature of the internal combustion engine 10 becomes lower as the internal EGR amount is smaller, and becomes higher as the internal EGR amount is larger. The internal EGR amount generated in the internal combustion engine 10 is increased or decreased according to the length of the valve overlap period. Therefore, in the internal combustion engine 10, the compression end temperature can be controlled by extending the valve overlap period.

In the first and second embodiments described above, when misfire or knocking occurs, the compression ratio is changed to change the compression end temperature, and the change is used to improve the combustion state. . On the other hand, in the present embodiment, when misfire or knocking occurs, the compression end temperature is changed by expanding and contracting the valve overlap period, and the combustion state is improved by the change.

By the way, in the internal combustion engine 10, the valve overlap period can be expanded or contracted by changing the valve opening timing IVO of the intake valve 14, and can be generated or eliminated. However, the opening timing IVO of the intake valve 14
Is changed, the intake air amount GN per one rotation is changed accordingly, resulting in a change in the output of the internal combustion engine 10. Therefore, when the internal combustion engine 10 is in a cold operation, if the valve overlap period is simply changed without considering the change of the intake air amount GN, the combustion state can be improved, but the passengers of the vehicle feel uncomfortable. It may happen.

Therefore, in the present embodiment, when changing the valve overlap period during the cold operation of the internal combustion engine 10, the intake air amount GN is not changed and the intake valve 14 is opened at the same time as IVO. Appropriately change the valve closing timing IVC and maximum lift amount IVLMax. Therefore, according to the present embodiment, similarly to the case of the first or second embodiment, it is possible to generate only the effect of improving the combustion state without changing the output of the internal combustion engine 10.

FIG. 8 shows a flowchart of a routine executed by the ECU 30 in the present embodiment to realize the above function. In FIG. 8, the same steps as those shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted or simplified.

In the routine shown in FIG. 8, step 104
After the intake air amount GN is calculated at, the valve overlap period VOL is calculated based on the valve opening timing IVO of the intake valve 14 (step 300).

Next, when it is determined that a misfire has occurred in the internal combustion engine 10 (steps 108, 11)
0), the target valve overlap period tVOL is updated to a value obtained by adding a predetermined correction value k1 to the latest target valve overlap tVOLO in the past (step 302). When the target valve overlap tVOL is increased and as a result, the compression end temperature in the cylinder rises, the fuel is easily vaporized. When the fuel is in a state where it is easily vaporized, the fuel is easily combusted and misfire is less likely to occur. Therefore, according to the process of this step 302, the occurrence of misfire can be suppressed and the combustion state of the internal combustion engine 10 can be improved.

On the other hand, if it is determined that knocking has occurred in the internal combustion engine 10 (steps 108, 11).
0), the target valve overlap tVOL is updated to a value obtained by subtracting a predetermined correction value k2 from the latest target valve overlap tVOLO in the past (step 304). If the target valve overlap tVOL is reduced and the compression end temperature in the cylinder is reduced as a result, knocking is less likely to occur. Therefore, according to the process of this step 304, the occurrence of knocking can be suppressed and the combustion state of the internal combustion engine 10 can be improved.

In the routine shown in FIG. 8, after the processing of step 302 or 304 described above,
In order to realize the intake air amount GN per rotation calculated in 04 and to achieve the target valve overlap tVOL updated in step 302 or 304,
The closing timing IVC of the intake valve 14 read in step 102, the rotational speed NE of the internal combustion engine 10, and the intake pipe pressure PM
Based on the above, the target maximum lift amount tIVLMax and the target valve opening timing tIVO of the intake valve 14 are determined (step 30).
6).

In this embodiment, since the opening / closing timing of the exhaust valve 18 is fixed, the valve overlap VOL
Is determined by the valve opening timing IVO of the intake valve 14. EC
U30 has a target valve overlap tVOL and its tV.
The relationship with the target valve opening timing tIVO for realizing OL is stored. In step 306, first, the target valve opening timing tIVO of the intake valve 14 is determined according to the relationship.

The intake air amount GN of the internal combustion engine 10 is determined by the intake valve 1
4, the opening / closing timings IVO, IVC, the lift profile of the intake valve 14, the rotational speed NE of the internal combustion engine 10, and the intake pipe pressure PM are uniquely determined. In the present embodiment, as described above, the valve opening timing IVO of the intake valve 14 is determined in relation to the target overlap tVOL. Further, in the present embodiment, the closing timing IVC of the intake valve 14 is fixed in order to keep the compression ratio of the internal combustion engine 10 constant. Therefore, step 3 above
In 06, on the premise of those opening / closing valve timings IVO, IVC,
The maximum lift amount IVLMax is determined so that the desired intake air amount GN is realized with respect to the current rotational speed NE and the intake pipe pressure PM.

As a result, in the present embodiment, as shown in FIG. 9, when the intake valve opening timing IVO is retarded and, as a result, the intake valve 14 opening period is shortened, a large maximum lift is achieved. The quantity IVLMax is set. On the other hand, in order to secure the valve overlap VOL, when the opening timing of the intake valve 14 is advanced from the top dead center, the maximum lift amount IV
LMax is set small. By performing such control, the intake air amount GN is maintained at a substantially constant value regardless of the presence or absence or the length of the valve overlap.

When the processing of step 308 is completed,
Next, the cam profile is switched so that the target valve opening timing tIVO and the target maximum lift amount IVLMax determined in this routine and the valve closing timing IVC that is a fixed value are realized (step 308).

When the above processing is completed, the combustion state is determined again in step 122 as in the case of the first or second embodiment, and if the combustion state is normal, the routine ends. On the other hand, if the combustion state is not normal, the process for correcting the valve overlap VOL is executed again.

As described above, according to the routine shown in FIG. 8, the intake air amount GN is generated by generating / eliminating or extending / shortening the valve overlap VOL while appropriately changing the lift profile of the intake valve 14. It is possible to improve the combustion state of the internal combustion engine 10 while preventing the change in Therefore, according to the system of the present embodiment, as in the case of the first embodiment, it is possible to improve the operating characteristics of the internal combustion engine 10 in the cold state without giving the occupants of the vehicle any discomfort. .

In the third embodiment described above, the maximum lift amount IVLMax of the intake valve 14 corresponds to the "factor" in claim 7, and the ECU 30 sets the target calculated in step 306. The "valve overlap period changing means" according to claim 7 is realized by switching the cam profile in step 308 so that the valve opening timing tIVO is realized.
Further, the ECU 30 realizes the target maximum lift amount tIVLMax calculated in step 306,
The "output factor correction means" according to claim 7 is realized by switching the cam profile in step 308.

Further, in the above-mentioned third embodiment,
The "intake valve lift profile correction means" according to claim 9 is realized by the ECU 30 switching the cam profile in step 308 so that the target maximum lift amount tIVLMax calculated in step 306 is realized. There is.

Further, in the above-described third embodiment,
The ECU 30 implements the "misfire detection means" according to claim 11, by detecting the misfire of the internal combustion engine by the processing of steps 108 and 110.
However, the "first changing unit" according to claim 11 is realized by executing the processes of steps 302 and 306.

Further, in the above-described third embodiment,
The "knocking detection means" according to claim 12 is realized by the ECU 30 detecting knocking of the internal combustion engine by the processing of steps 108 and 110,
The "second changing means" according to claim 12 is realized by the ECU 30 executing the processes of steps 304 and 306.

In the third embodiment described above, the opening / closing timing of the exhaust valve 18 is fixed, but the present invention is not limited to this. That is, the opening / closing timing of the exhaust valve 18 is made variable and the opening / closing timing of the exhaust valve 18 is changed to thereby cause the valve overlap.
It may be possible to adjust VOL.

In the third embodiment described above, the internal E
The combustion state of the internal combustion engine 10 is improved by increasing or decreasing the GR amount. The internal EGR amount is regarded as corresponding to the valve overlap period VOL, and the combustion state is improved by using the valve overlap period VOL as a control parameter. However, strictly speaking, the internal EGR amount is VOL
Not only is the lift profile of the intake valve 14 affected. Therefore, in order to further improve the control accuracy, in steps 302 and 304, the target internal EGR amount tEGR is determined, and in step 3 above.
At 06, the target valve opening timing tIVO and the target maximum lift amount tIVLMax of the intake valve 14 may be obtained so that the tEGR is realized and the desired intake air amount GN is secured.

Further, in the above described third embodiment,
Although an attempt is made to prevent the output change of the internal combustion engine 10 by keeping the intake air amount GN constant, the method of preventing the output change is not limited to this. That is, as in the case of the third embodiment, the output change of the internal combustion engine 10 may be prevented by correcting the throttle opening.

[0090]

Since the present invention is constructed as described above, it has the following effects. Claim 1
According to the invention described above, when the internal combustion engine is in cold operation, the closing timing of the intake valve is changed to change the substantial compression ratio, and as a result, a stable combustion state can be realized. Further, according to the present invention, by correcting the factor that determines the output of the internal combustion engine, it is possible to prevent the output from changing with the change of the closing timing of the intake valve.

According to the second aspect of the present invention, the intake air amount of the internal combustion engine is kept constant by correcting the opening timing of the intake valve when changing the closing timing of the intake valve. It is possible to prevent the output of the internal combustion engine from changing.

According to the third aspect of the invention, the intake air amount of the internal combustion engine is kept constant by modifying the lift profile of the intake valve when changing the closing timing of the intake valve, and as a result, the internal combustion engine is It is possible to prevent the output of the engine from changing.

According to the invention described in claim 4, the intake air amount of the internal combustion engine is kept constant by modifying the throttle opening when changing the closing timing of the intake valve, and as a result, the internal combustion engine The output can be prevented from changing.

According to the fifth aspect of the present invention, when a misfire occurs in the internal combustion engine, the closing timing of the intake valve is moved to the intake bottom dead center side, whereby the substantial compression ratio can be increased. it can. When the compression ratio increases, the compression end temperature in the cylinder rises and misfiring hardly occurs, so that the combustion state of the internal combustion engine can be stabilized.

According to the sixth aspect of the present invention, when knocking occurs in the internal combustion engine, the closing timing of the intake valve is moved away from the intake bottom dead center, whereby the substantial compression ratio can be lowered. . When the compression ratio is lowered, the compression end temperature in the cylinder is lowered and knocking is less likely to occur, so that the combustion state of the internal combustion engine can be stabilized.

According to the seventh aspect of the invention, the internal EGR amount is changed by changing the overlap period during which the intake valve and the exhaust valve are both opened during cold operation of the internal combustion engine, and as a result, A stable combustion state can be realized. Further, according to the present invention, by correcting the factor that determines the output of the internal combustion engine, it is possible to prevent the output from changing due to the change of the overlap period.

According to the eighth aspect of the present invention, by changing the opening timing of the intake valve, the overlap period in which both the intake valve and the exhaust valve are in the open state can be changed.

According to the invention described in claim 9, the intake air amount of the internal combustion engine is kept constant by modifying the lift profile of the intake valve when the overlap period is changed, and as a result, the output of the internal combustion engine is changed. Can be prevented from changing.

According to the tenth aspect of the invention, the intake air amount of the internal combustion engine is kept constant by modifying the throttle opening when changing the overlap period, and as a result, the output of the internal combustion engine changes. Can be prevented.

According to the eleventh aspect of the present invention, when the internal combustion engine misfires, the internal EGR rate can be increased by generating or extending the overlap period. When the internal EGR amount increases, the compression end temperature in the cylinder rises and misfiring hardly occurs, so that the combustion state of the internal combustion engine can be stabilized.

According to the twelfth aspect of the invention, when knocking occurs in the internal combustion engine, the internal EGR amount can be reduced by shortening or eliminating the overlap period. When the amount of internal EGR decreases, the compression end temperature in the cylinder becomes low and knocking hardly occurs, so that the combustion state of the internal combustion engine can be stabilized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an internal combustion engine that constitutes a system according to first to third embodiments of the present invention.

FIG. 2 is a diagram (part 1) for explaining a relationship between a closing timing of an intake valve and a substantial compression ratio of an internal combustion engine.

FIG. 3 is a diagram (part 2) for explaining the relationship between the closing timing of the intake valve and the substantial compression ratio of the internal combustion engine.

FIG. 4 is a flowchart of a routine executed in the first embodiment of the present invention.

FIG. 5 is a flowchart of a routine executed in the second embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a cam profile of an intake valve and a throttle opening TA realized in the second embodiment of the present invention.

FIG. 7 is a diagram for explaining the principle of internal EGR that occurs with the occurrence of valve overlap in an internal combustion engine.

FIG. 8 is a flowchart of a routine executed in the third embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a valve overlap VOL and a cam profile of an intake valve, which is realized in the third embodiment of the present invention.

[Explanation of symbols]

10 Internal combustion engine 12 intake ports 14 Intake valve 16 Exhaust port 18 Exhaust valve 20 Variable valve mechanism 22 PM sensor 24 Electronically controlled throttle 30 ECU (Electronic Control Unit) 32 rpm sensor 34 Knocking sensor Intake air volume per GN revolution NE Internal combustion engine speed PM intake pipe pressure IVC intake valve closing timing IVO intake valve opening timing IVLMax Maximum intake valve lift tIVC Target intake valve closing timing tIVO Intake valve target opening timing tIVLMax Intake valve target maximum lift ε compression ratio tε Target compression ratio TA throttle opening tTA Target throttle opening VOL valve overlap tVOL Target valve overlap

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/22 F02D 41/22 301B 320 320 320 43/00 301 43/00 301K 301Z 45/00 312 45/00 312B 345 345A 345B 368 368B 368Z (72) Inventor Masanobu Kanamaru 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Satoshi Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture (72) Invention, Toyota Motor Corporation Person Masaaki Konishi 1 Toyota Town, Toyota-shi, Aichi F-term in Toyota Motor Corporation (reference) 3G084 BA05 BA23 CA02 DA28 DA38 EB09 FA00 FA07 FA11 FA20 FA24 FA25 FA33 3G092 AA11 BA01 DA01 DA02 DA03 DA12 DC01 EC10 FA15 FA16 GA01 GA02 HA01Z HA13Z HC05Z HC06Z HE01Z HE08Z 3G301 HA19 JA21 JA22 JA23 KA01 KA02 KA05 LA01 LA07 NC04 PA01Z PA07Z PC08Z PC09Z PE01Z PE08Z

Claims (12)

[Claims] 1. A control device for an internal combustion engine comprising a variable valve mechanism for varying the closing timing of an intake valve, the intake valve closing changing the closing timing of the intake valve during cold operation of the internal combustion engine. Valve timing changing means, and output factor correcting means for correcting at least one factor that determines the output of the internal combustion engine so that a change in the output of the internal combustion engine due to the change in the opening timing of the intake valve is offset. A control device for an internal combustion engine, characterized in that: 2. The variable valve mechanism has a function of varying the valve opening timing of the intake valve, and the output factor correcting means controls the internal combustion engine before and after changing the valve closing timing of the intake valve. 2. The control device for an internal combustion engine according to claim 1, further comprising intake valve opening timing correction means for correcting the opening timing of the intake valve so that the intake air amounts become equal. 3. The variable valve mechanism has a function of making a lift profile of the intake valve variable, and the output factor correcting means intakes an internal combustion engine before and after changing a closing timing of the intake valve. 3. The control device for an internal combustion engine according to claim 1, further comprising intake valve lift profile correction means for correcting the lift profile of the intake valve so that the air amounts become equal. 4. An electronically controlled throttle capable of realizing an arbitrary throttle opening regardless of the accelerator pedal depression amount, wherein the output factor correction means is provided before and after a change in the closing timing of the intake valve, 4. The control device for an internal combustion engine according to claim 1, further comprising throttle opening correction means for correcting the throttle opening so that intake air amounts of the internal combustion engine become equal. 5. A misfire detecting means for detecting a misfire of an internal combustion engine, wherein the intake valve closing timing changing means sets the closing timing of the intake valve to intake bottom dead when a misfire of the internal combustion engine is detected. The control device for an internal combustion engine according to any one of claims 1 to 4, further comprising first changing means for moving to a point side. 6. A knocking detection means for detecting knocking of the internal combustion engine, wherein the intake valve closing timing changing means sets the closing timing of the intake valve to intake bottom dead when knocking of the internal combustion engine is detected. The control device for an internal combustion engine according to any one of claims 1 to 5, further comprising a second changing unit that moves in a direction away from the point. 7. A control device for an internal combustion engine, comprising a variable valve mechanism for varying a valve overlap period in which both an exhaust valve and an intake valve are opened, the valve overlap being performed during cold operation of the internal combustion engine. Valve overlap period changing means for changing the period, and output factor correcting means for correcting at least one factor that determines the output of the internal combustion engine so that the change in the output of the internal combustion engine due to the change of the valve overlap period is offset. An internal-combustion-engine control device comprising: 8. The variable valve mechanism has a function of changing the valve opening timing of the intake valve, and the valve overlap period changing means changes the valve opening timing of the intake valve. The control device for an internal combustion engine according to claim 1, wherein the valve overlap period is changed. 9. The variable valve mechanism has a function of changing a lift profile of the intake valve, and the output factor correction means before and after changing the valve overlap period, the intake air amount of the internal combustion engine. 9. The control device for an internal combustion engine according to claim 7, further comprising an intake valve lift profile correction means for correcting the lift profile of the intake valve so that the values become equal to each other. 10. An electronic control throttle capable of realizing an arbitrary throttle opening regardless of the amount of depression of an accelerator pedal, wherein the output factor correction means is used before and after changing the valve overlap period. 10. The control device for an internal combustion engine according to claim 7, further comprising a throttle opening degree correction means for correcting the throttle opening degree so that the intake air amounts become equal. 11. A misfire detecting means for detecting a misfire of an internal combustion engine, wherein the valve overlap period changing means generates or extends the valve overlap period when a misfire of the internal combustion engine is detected. The control device for an internal combustion engine according to any one of claims 7 to 10, further comprising a changing unit. 12. A knocking detection means for detecting knocking of the internal combustion engine, wherein the valve overlap period changing means shortens or eliminates the valve overlap period when knocking of the internal combustion engine is detected. The control device for an internal combustion engine according to any one of claims 7 to 11, further comprising a changing unit.