WO2008099741A1

WO2008099741A1 - Control system of internal combustion engine

Info

Publication number: WO2008099741A1
Application number: PCT/JP2008/051985
Authority: WO
Inventors: Nao Murase; Nobuhiko Koga; Shogo Suda
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-01-31
Filing date: 2008-01-31
Publication date: 2008-08-21
Also published as: JP4353252B2; JP2008185013A

Abstract

A technology capable of reducing exhaust emission suitably in the control system of a spark ignition internal combustion engine. The control system of a spark ignition internal combustion engine advances the ignition timing ahead of MBT when it is predicted that deposited fuel in the cylinder increases, and raises the compression ratio of the internal combustion engine. Since the peak values of inner pressure and inner temperature of the cylinder are raised sharply, vaporization and oxidation of the deposited fuel in the cylinder are accelerated. Consequently, unburnt fuel components discharged from the cylinder can be reduced sharply.

Description

Description Internal combustion engine control system Technical field

The present invention relates to a technique for controlling a spark ignition type internal combustion engine. Background art

When a spark ignition type internal combustion engine is in a cold start state, a technology to improve the warm-up performance of the internal combustion engine by advancing the ignition timing ahead of MBT (Minimum spark advance for Best Torque) This is disclosed in Japanese Patent Laid-Open No. 2000-240547.

Japanese Patent Laid-Open No. 2003-328794 discloses that during the idle-up operation after a cold start of the internal combustion engine, by reducing the expansion ratio due to the reduction of the compression ratio and significantly retarding the ignition timing, A technique for increasing the exhaust temperature is disclosed. Disclosure of the invention

The above-described conventional technology considers the warm-up property of the internal combustion engine, but does not consider the exhaust emission. Accordingly, an object of the present invention is to provide a technique suitable for reducing exhaust emission in a spark ignition type internal combustion engine control system.

In order to achieve the above object, the present invention uses a technique for advancing the ignition timing ahead of MBT in an internal combustion engine control system capable of advancing the ignition timing ahead of MBT. Reduced exhaust emissions.

The temperature in the cylinder (hereinafter referred to as “cylinder temperature”) as in the case where the internal combustion engine is in a cold state. Is low), the fuel tends to adhere to the wall surface in the cylinder. Most of the fuel adhering to the wall surface in the cylinder (hereinafter referred to as “in-cylinder adhering fuel”) is discharged from the cylinder without being burned without being used for combustion. At this time, if the catalyst disposed in the exhaust system of the internal combustion engine is in an inactive state, the above-mentioned unburned fuel component is discharged into the atmosphere without being purified by the catalyst.

In particular, when the internal combustion engine is started at an extremely low temperature, etc., the period from the start of the internal combustion engine to the time when the catalyst is activated becomes longer and the in-cylinder attached fuel amount increases. For this reason, there is a concern that the amount of unburned fuel components discharged into the atmosphere will be excessive. On the other hand, as a result of the inventor's earnest experiment and verification, when the ignition timing is advanced to the front of the MBT (hereinafter referred to as “over-advanced angle”) in a spark ignition type internal combustion engine, It has been found that unburned fuel components (eg, HC) discharged from the cylinders are significantly reduced.

When the ignition timing is over-advanced, the amount of air-fuel mixture that burns before compression top dead center increases, so the pressure increase / temperature increase effect due to the combustion of the air-fuel mixture and the pressure increase / temperature increase effect due to the piston ascending operation As a result, the peak of the cylinder pressure (hereinafter referred to as “in-cylinder pressure”) and the cylinder temperature are increased. As a result, vaporization and oxidation of fuel adhering to the cylinder and fuel before adhering to the Z or the wall surface in the cylinder are considered to be promoted.

In view of this, the control system for an internal combustion engine according to the present invention aims to reduce the unburned fuel component discharged from the cylinder by over-igniting the ignition timing. Since the unburned fuel component discharged from the cylinder is considered to decrease as the peak of the cylinder pressure and the cylinder temperature increases, the control system for the internal combustion engine according to the present invention performs internal combustion when the ignition timing is over-advanced. A high compression ratio of the engine was also attempted.

Specifically, the control system for an internal combustion engine according to the present invention includes an over-advance angle means for advancing the ignition timing of the spark ignition type internal combustion engine ahead of MBT, and a variable compression ratio for changing the compression ratio of the internal combustion engine. With the mechanism and the above-mentioned advance angle means, the ignition timing advances ahead of the MBT. Control means for increasing the compression ratio of the internal combustion engine by the variable compression ratio mechanism when the motor is turned.

According to such a configuration, in addition to the pressure increase / temperature increase effect of the in-cylinder pressure and the cylinder temperature due to the excessive advance angle of the ignition timing, the effect of pressure increase / temperature increase of the cylinder pressure and temperature due to the increase of the compression ratio can be obtained. . These synergistic effects further increase the peak of in-cylinder pressure and in-cylinder temperature. As a result, vaporization and vaporization of the fuel adhering to the cylinder and the fuel before adhering to the Z or the wall surface in the cylinder are further promoted, and the unburned fuel component discharged from the cylinder is further reduced.

Therefore, the control system for an internal combustion engine according to the present invention can suitably reduce the exhaust emission of the internal combustion engine by using both the ignition timing over-advance angle and the high compression ratio of the internal combustion engine. Further, if the ignition timing is over-advanced, the torque of the internal combustion engine may decrease, but it is also possible to compensate for the decrease in torque by increasing the compression ratio. Furthermore, since the peak of the in-cylinder pressure and the in-cylinder temperature is increased by increasing the compression ratio, it is possible to reduce the amount of advance at the time of over-advance.

The variable compression ratio mechanism according to the present invention can change the ratio (mechanical compression ratio) between the combustion chamber volume (the cylinder volume when the piston is at top dead center) and the cylinder volume when the piston is at bottom dead center. It may be a mechanism. The variable compression ratio mechanism according to the present invention is a mechanism that changes the ratio (effective compression ratio) between the combustion chamber volume and the cylinder volume when the intake valve is closed by changing the closing timing of the intake valve. May be.

The control system for an internal combustion engine according to the present invention may further include first acquisition means for acquiring the in-cylinder attached fuel amount. In this case, the control means performs an advance angle of the ignition timing by the advance angle means when the amount of adhered fuel acquired by the first acquisition means is equal to or greater than a predetermined amount, and a compression ratio by the variable compression ratio mechanism. You may try to raise the.

According to such a configuration, when the amount of fuel adhering to the cylinder exceeds a predetermined amount, the ignition timing is reduced. The advance angle and the compression ratio are increased. Therefore, the unburned fuel component discharged from the cylinder is suitably reduced under the condition that the in-cylinder attached fuel amount increases.

As the first acquisition means, a sensor that optically measures the thickness of the liquid film, a sensor that measures the electrical conductivity that changes depending on the thickness of the liquid film, and the like can be used. As the first acquisition means, it is also possible to use ECU that estimates and calculates the in-cylinder attached fuel amount from engine operating conditions.

The control system for an internal combustion engine according to the present invention may further include second acquisition means for acquiring an air-fuel ratio of an air-fuel mixture used for combustion in a cylinder of the internal combustion engine. In this case, the control means may cancel the increase in the compression ratio by the variable compression ratio mechanism when the air-fuel ratio acquired by the second acquisition means is lean.

When the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder is lean, the unburned fuel component discharged from the cylinder decreases. Furthermore, when the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder is lean, the unburned fuel component and oxygen in the exhaust gas react with the hornworm medium, and the catalyst quickly rises to the active temperature range. Let warm. Therefore, it is possible to reduce the exhaust emission without increasing the compression ratio by the variable compression ratio mechanism.

Also, if the amount of advance at the time of over-advancement is reduced when the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder is lean, the temperature of the exhaust gas increases. When the exhaust gas and temperature rise, the reaction between the unburned fuel component and oxygen in the catalyst is promoted. As a result, the catalyst is activated early. If the catalyst is activated early, the unburned fuel component discharged from the cylinder is purified by the catalyst, so that a large amount of unburned fuel component is not discharged into the atmosphere. Therefore, in the control system for an internal combustion engine according to the present invention, when the air-fuel ratio acquired by the second acquisition unit is lean, the control unit cancels the increase in the compression ratio by the variable compression ratio mechanism and You may make it reduce the amount of advance of the time.

As the second acquisition means, an air-fuel ratio sensor disposed in the exhaust passage of the internal combustion engine, An oxygen concentration sensor can be used. Further, as the second acquisition means, an ECU that calculates an air-fuel ratio from the intake air amount and the fuel injection amount can be used. Brief Description of Drawings

FIG. 1 is a diagram showing a schematic configuration of a control system for an internal combustion engine.

Fig. 2 is a diagram showing the relationship between the unburned fuel component (HC) discharged from the cylinder and the ignition timing.

FIG. 3 is a diagram showing the relationship between the ignition timing and the state in the cylinder.

FIG. 4 is a graph showing the relationship between the peak value of the in-cylinder pressure and the compression ratio.

FIG. 5 is a graph showing the relationship between the peak value of the in-cylinder temperature and the compression ratio.

Fig. 6 is a schematic diagram of the method for changing the compression ratio.

Fig. 7 is a timing chart showing the execution procedure of the attached fuel reduction control. FIG. 8 is a flowchart showing a routine for determining the ignition timing and the compression ratio in the adhered fuel reduction control. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine control system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. The cylinder 2 of the internal combustion engine 1 communicates with the intake passage 30 through the intake port 3 and also communicates with the exhaust passage 40 through the exhaust port 4.

The intake port 3 is provided with a fuel injection valve 5 that injects fuel into the cylinder 2. The intake passage 30 is provided with a throttle valve 6 that controls the amount of air flowing through the intake passage 30. In the intake passage 30 downstream of the throttle valve 6, An intake pressure sensor 7 for measuring the pressure (intake pressure) in the intake passage 30 is provided. An air flow meter 8 that measures the amount of air flowing through the intake passage 30 is provided in the intake passage 30 upstream of the throttle valve 6.

On the other hand, an exhaust purification device 9 is disposed in the exhaust passage 40. The exhaust purification device 9 includes a three-way catalyst, a storage reduction type NOx catalyst, and the like, and purifies exhaust when it is in a predetermined activation temperature range.

Further, the internal combustion engine 1 is provided with an intake valve 10 that opens and closes an open end of an intake port 3 that faces the inside of the cylinder 2, and an exhaust valve 11 that opens and closes an open end of the exhaust port 4 that faces the inside of the cylinder 2. ing. These intake valve 10 and exhaust valve 11 are driven to open and close by an intake camshaft 12 and an exhaust camshaft 13, respectively.

A spark plug 14 for igniting the air-fuel mixture in the cylinder 2 is arranged at the upper part of the cylinder 2. A piston 15 is slidably inserted into the cylinder 2. The piston 15 is connected to the crankshaft 17 through a connecting rod 16.

In the vicinity of the crankshaft 17, a crank position sensor 18 for detecting the rotation angle of the crankshaft 17 is disposed. Further, a water temperature sensor 19 for measuring the temperature of the cooling water circulating through the internal combustion engine 1 is attached to the internal combustion engine 1.

The intake side camshaft 12 is provided with a variable valve mechanism 120 that changes the phase of the intake side camshaft 12 relative to the crankshaft 17. The internal combustion engine 1 configured as described above is provided with an ECU 20. The ECU 20 is an electronic control unit that includes a CPU, ROM, RAM, and the like. This ECU 20 is electrically connected to various sensors such as the intake pressure sensor 7, air flow meter 8, crank position sensor 18, and water temperature sensor 19 described above, and the measured values of various sensors can be input. ing. The ECU 20 electrically controls the fuel injection valve 5, the throttle valve 6, the spark plug 14, and the variable valve mechanism 120 based on the measurement values of the various sensors described above. For example, the ECU 20 performs attached fuel reduction control for reducing the fuel attached to the wall surface in the cylinder 2.

Hereinafter, the adhered fuel reduction control in this embodiment will be described.

When the in-cylinder temperature is low, such as when the internal combustion engine 1 is in a cold state, the fuel tends to adhere to the wall surface in the cylinder. Most of the fuel adhering to the wall surface in the cylinder (in-cylinder attached fuel) is discharged from the cylinder without being burned without being used for combustion. At that time, if the exhaust purification device 9 is not heated to the activation temperature range, the unburned fuel component described above is discharged into the atmosphere without being purified.

In particular, when the internal combustion engine 1 is started at an extremely low temperature or the like, the period from the start of the internal combustion engine 1 to the activation of the exhaust gas purification device 9 becomes longer, and the in-cylinder attached fuel amount increases. For this reason, there is a possibility that unburned fuel components discharged into the atmosphere will increase excessively. On the other hand, in the attached fuel reduction control in the present embodiment, the ECU 20 advances the operation timing (ignition timing) of the spark plug 14 from the MBT when the amount of in-cylinder attached fuel is expected to increase. did.

According to the inventor's diligent experiment and verification, when the ignition timing is advanced from the MBT, as shown in FIG. 2, the ignition timing is exhausted from the cylinder 2 as the ignition timing advance amount increases. It has been found that the amount of unburned fuel component (HC) is reduced.

Although this mechanism has not been clearly clarified, it is thought to be due to the following mechanism.

Figure 3 shows when the ignition timing is advanced (over-advanced) before MBT (ST 1 in Fig. 3), when the ignition timing is set to MB T (ST2 in Fig. 3), FIG. 5 is a diagram showing the results of measuring the state in cylinder 2 in each case when the ignition timing is set to compression top dead center (TDC) (ST3 in FIG. 3). The solid line in Fig. 3 represents the case where the ignition timing was over-advanced, the broken line represents the case where the ignition timing was set to MB T, and the single dotted line represents the case where the ignition timing was set to the compression top dead center (TD C). It shows.

When the ignition timing is over-advanced, compared to when the ignition timing is set to MBT and when the ignition timing is set to compression top dead center (TD C), the mixture burns before compression top dead center. The amount of mind increases. For this reason, the peak of thermal energy generated by the combustion of the air-fuel mixture (see the heat generation rate, generated heat amount, and combustion mass ratio in Fig. 3) shifts to before compression top dead center.

Therefore, the in-cylinder pressure during the period from the compression stroke to the expansion stroke is based on a synergistic effect of the temperature increase / pressure increase effect due to the combustion of the air-fuel mixture and the compression effect due to the upward movement of the piston (operation from the bottom dead center to the top dead center) In addition, the peak value of the in-cylinder temperature increases significantly. As a result, it is considered that vaporization and oxidation of the fuel adhered to the cylinder and / or the fuel before adhering to the wall surface in the cylinder 2 are promoted.

Therefore, E C U 20 over-advanced the ignition timing when the amount of fuel adhering to the cylinder is expected to increase. The amount of fuel adhering to the cylinder is expected to increase when the internal combustion engine 1 is cold-started or when the internal combustion engine 1 is in a warm-up operation state.

Examples of cases where the measured value of the in-cylinder attached fuel amount exceeds the allowable amount, or the estimated value of the in-cylinder attached fuel amount exceeds the allowable amount, etc.

As a method of measuring the amount of fuel adhered to the cylinder, a sensor that optically measures the thickness of the liquid film is placed in the cylinder 2 and a sensor that measures the electrical conductivity is placed in the cylinder 2. A method for converting the measured value of the sensor into the in-cylinder attached fuel amount can be exemplified.

The method for estimating the amount of fuel adhering to the cylinder includes at least one of the coolant temperature, the cumulative fuel injection amount from the engine start, the cumulative intake air amount from the engine start, the fuel injection amount, the intake pressure, and the air / fuel ratio. To estimate from the correlation between the amount of fuel adhering to the cylinder be able to.

If the amount of fuel adhering to the cylinder is expected to increase and the spark plug 14 is actuated (ignited), the fuel adhering to the cylinder can be reduced and discharged from the cylinder 2 It is also possible to reduce the unburned fuel component.

According to the knowledge described in FIG. 3, it is considered that the unburned fuel component discharged from the cylinder 2 decreases as the peak of the cylinder pressure and the cylinder temperature increases. As a method of increasing the peak values of the in-cylinder pressure and the in-cylinder temperature, a method of increasing the compression ratio of the internal combustion engine 1 can be considered in addition to the method of over-advancing the ignition timing as described above.

4 and 5 are diagrams showing the relationship between the compression ratio and the peak value of the in-cylinder pressure, and the relationship between the compression ratio and the peak value of the in-cylinder temperature, respectively. 4 and 5, the peak values of the in-cylinder pressure and the in-cylinder temperature increase as the compression ratio of the internal combustion engine 1 increases.

Therefore, if the compression ratio of the internal combustion engine 1 is increased when the ignition timing is over-advanced, the peaks of the in-cylinder pressure and the in-cylinder temperature are further increased. As a result, it is possible to expect further reduction of the unburned fuel component discharged from the cylinder 2.

Therefore, in the attached fuel reduction control of the present embodiment, the ECU 20 increases the compression of the internal combustion engine 1 in addition to the ignition timing over-advance when the amount of in-cylinder attached fuel is expected to increase. did.

To increase the compression ratio of the internal combustion engine 1, the combustion chamber volume (the volume in the cylinder 2 when the piston 15 is located at the top dead center) and the cylinder 2 when the piston 15 is located at the bottom dead center An example is a method of changing the ratio (mechanical compression ratio) with the internal volume, or a method of changing the ratio (effective compression ratio) between the combustion chamber volume and the volume in the cylinder 2 when the intake valve 10 is closed. Can be shown.

Examples of the method for changing the mechanical compression ratio include a method using a variable compression ratio mechanism for changing the relative position of the crankcase and the cylinder block, a variable compression ratio mechanism for changing the length of the connecting rod, and the like. be able to. As a method of changing the effective compression ratio, a method of changing the closing timing of the intake valve 10 using a variable valve mechanism can be exemplified.

The internal combustion engine control system of the present invention can use either a method for changing the mechanical compression ratio or a method for changing the effective compression ratio. The following is an example of changing the compression ratio using a variable valve mechanism with a high penetration rate.

FIG. 6 is a diagram schematically showing a method for increasing the effective compression ratio by using the variable valve mechanism 120. The broken line in FIG. 6 indicates the valve opening period of the intake valve 10 when the over-advance angle is not performed, and the dashed line in FIG. 6 indicates the valve opening period of the intake valve 10 when the over-advance angle is performed. When the over-advanced ignition timing is in the non-execution state, the closing timing (IVC) of the intake valve 10 is set to a timing later than the intake bottom dead center (BDC). On the other hand, when the ignition timing is over-advanced, the ECU 20 advances the closing timing (IVC) of the intake valve 10 to the intake bottom dead center (BDC) (or the intake bottom dead center). (Advance to the vicinity of (BDC)). In this case, the volume in the cylinder 2 when the intake valve 10 is closed increases. As a result, the effective compression ratio of the internal combustion engine 1 is increased.

When the effective compression ratio of the internal combustion engine 1 is increased by such a method, the peak values of the in-cylinder pressure and the in-cylinder temperature are further increased due to the synergistic effect of the advance angle of the ignition timing and the increase of the effective compression ratio. As a result, the unburned fuel component discharged from the cylinder 2 can be extremely reduced.

By the way, it is considered desirable to increase the advance amount of the ignition timing in proportion to the increase in the in-cylinder attached fuel. However, if the ignition timing advance amount is excessively large, there is a possibility that the fuel entering the gap (clevis polyureum) between the piston 15 and the piston ring and the cylinder pore wall surface may increase.

The fuel that enters the clevis volume is easily discharged from the cylinder 2 without being used for combustion. For this reason, if the advance amount of the ignition timing increases excessively, There is concern that the amount of unburned fuel discharged from the plant will increase.

On the other hand, if the excessive advance angle of the ignition timing is combined with the high pressure reduction of the internal combustion engine 1 in the adhered fuel reduction control, the unburned fuel component exhausted from the cylinder 2 is not increased, and the excess It is also possible to reduce the amount of advancement. That is, when the advance timing of the ignition timing and the high compression of the internal combustion engine 1 are combined in the attached fuel reduction control, the ignition timing is discharged from the cylinder 2 without excessively increasing the advance amount of the ignition timing. Unburned fuel components can be reduced.

When the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder 2 is lean, unburned fuel components discharged from the cylinder 2 are reduced, and unburned fuel components and oxygen in the exhaust gas are reduced. It becomes easy to react with the exhaust purification device 9.

When the unburned fuel component and oxygen in the exhaust gas react with each other in the exhaust gas purification device 9, the exhaust heat purification device 9 can quickly rise in temperature to the activation temperature region by the reaction heat. When the exhaust purification device 9 rises to the activation temperature range early, the unburned fuel component discharged from the cylinder 2 is purified by the exhaust purification device 9.

Therefore, as shown in FIG. 7, the method for carrying out the adhered fuel reduction control is expected to increase the amount of adhered fuel in the cylinder, and the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder 2 is less than the theoretical air-fuel ratio. When (i.e., tl to t2 in FIG. 5), it is preferable to increase the effective compression ratio of the internal combustion engine 1 while the ignition timing is over-advanced. Also, when the air-fuel ratio of the air-fuel mixture changes to lean when the internal combustion engine 1 is highly compressed (t 2 in FIG. 5), the ignition timing over-advance angle It is preferable that the high compression of the internal combustion engine 1 is released.

The reaction between the unburned fuel component and oxygen in the exhaust purification device 9 is promoted as the temperature of the exhaust gas flowing into the exhaust purification device 9 increases. Therefore, if the air-fuel ratio of the air-fuel mixture changes to lean while the ignition timing over-advanced angle and high compression of the internal combustion engine 1 are being achieved, retard the ignition timing after MBT, and Z Or lower compression of internal combustion engine 1 Therefore, it is desirable to increase the exhaust temperature.

Next, the execution procedure of the attached fuel reduction control in this embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing a routine for determining the ignition timing and the compression ratio in the adhered fuel reduction control. This routine is a routine that is stored in advance in the ROM of the ECU 20 and is periodically executed by the ECU 20. In the routine of FIG. 8, the ECU 20 first calculates the in-cylinder attached fuel amount Dp fue 1 in S101.

In S102, the ECU 20 determines whether or not the in-cylinder attached fuel amount D p fue 1 calculated in S101 is equal to or greater than a predetermined amount. The predetermined amount may be determined such that the total amount of unburned fuel discharged from all cylinders 2 of the internal combustion engine 1 is less than the regulated amount.

If a negative determination is made in S102 (D p f u e 1 <predetermined amount), the E C U20 ends the execution of this routine. In this case, the ignition timing of the spark plug 14 is set to the normal ignition timing, and the closing timing of the intake valve 10 is set to the normal closing timing.

If an affirmative determination is made in S102 (D p fue 1 ≥predetermined amount), ECU20 proceeds to S103. In S103, the ECU 20 acquires the air-fuel ratio AZF of the air-fuel mixture that is used for combustion in the cylinder 2. For example, the ECU 20 may calculate the air-fuel ratio A / F based on the measured value of the air flow rate 8 and the fuel injection amount, or an air-fuel ratio sensor provided in the exhaust passage 40 of the internal combustion engine 1 The measured value of the oxygen concentration sensor may be read.

In S104, the ECU 20 determines whether or not the air-fuel ratio AZF acquired in S103 is lean (air-fuel ratio A_F> theoretical air-fuel ratio). If a negative determination is made in S104 (air-fuel ratio A / F≤theoretical air-fuel ratio), the ECU 20 proceeds to S105. In SI 05, the ECU 20 advances the ignition timing of the spark plug 14 ahead of the MBT. Further, the ECU 20 increases the effective compression ratio of the internal combustion engine 1 by advancing the valve closing timing (IVC) of the intake valve 10 to the intake bottom dead center.

In this case, since the peak values of the in-cylinder pressure and the in-cylinder temperature are greatly increased, the vaporization and oxidation of the fuel adhering to the cylinder and the fuel before adhering to the Z or cylinder 2 wall surface are promoted. As a result, the unburned fuel component discharged from the cylinder 2 of the internal combustion engine 1 becomes extremely small.

On the other hand, when an affirmative determination is made in S104 (air-fuel ratio AZF> theoretical air-fuel ratio), the ECU 20 proceeds to S106. In S106, the ECU 20 retards the ignition timing of the ignition plug 14 to the MBT or later. Further, the ECU 20 reduces the effective compression ratio of the internal combustion engine 1 by retarding the closing timing (I VC) of the intake valve 10 to the normal closing timing or later.

In this case, the combustion of the air-fuel mixture in cylinder 2 becomes slow (in other words, the combustion speed decreases). For this reason, the temperature of the exhaust gas discharged from the cylinder 2 rises. As a result, the unburned fuel component in the exhaust can react with the oxygen in the exhaust in the exhaust gas purification device 9, and the unburned fuel component released into the atmosphere is reduced.

As described above, when the ECU 20 executes the routine of FIG. 8, the over-advance angle means, the variable compression ratio mechanism, the control means, the first acquisition means, and the second acquisition means according to the present invention are realized. As a result, the exhaust emission of the internal combustion engine 1 can be suitably reduced when the in-cylinder fuel is expected to increase.

In this embodiment, the internal combustion engine in which the fuel injection valve is disposed in the intake port is taken as an example, but the fuel injection valve is disposed in the cylinder (that is, disposed in a position where fuel can be directly injected into the cylinder). Of course, the internal combustion engine may be used.

Claims

The scope of the claims

1. an over-advance means for advancing the ignition timing of the spark ignition type internal combustion engine before MB T; a variable compression ratio mechanism for changing the compression ratio of the internal combustion engine;

Control means for increasing the compression ratio of the internal combustion engine by the variable compression ratio mechanism when the ignition timing is advanced forward from 過により by the over-advance angle means;

An internal combustion engine control system comprising:

2. The apparatus according to claim 1, further comprising first acquisition means for acquiring an amount of fuel adhering to the cylinder of the internal combustion engine,

The control means advances the ignition timing by the over-advance angle means when the amount of attached fuel acquired by the first acquisition means is equal to or greater than a predetermined amount, and controls the compression ratio by the variable compression ratio mechanism. A control system for an internal combustion engine, characterized in that the engine is lifted.

3. The method according to claim 1 or 2, further comprising second acquisition means for acquiring an air-fuel ratio of an air-fuel mixture used for combustion in a cylinder of the internal combustion engine,

The control system for an internal combustion engine, wherein when the air-fuel ratio acquired by the second acquisition means is lean, the control means cancels an increase in the compression ratio by the variable compression ratio mechanism.

4. The control of the internal combustion engine according to claim 3, wherein when the air-fuel ratio acquired by the second acquisition unit is lean, the control unit retards the ignition timing after MBΤ. system. A spark plug for causing a spark in the cylinder of the internal combustion engine; A variable valve mechanism for changing the compression ratio of the internal combustion engine;

A control unit for controlling the spark plug and the variable valve mechanism;

A spark ignition internal combustion engine control system comprising:

The control unit calculates the amount of fuel adhering to the cylinder, and when the calculation result is equal to or greater than a predetermined amount, the operation timing of the spark plug is advanced before MB T and the internal combustion engine The control system for an internal combustion engine, wherein the variable compression ratio mechanism is controlled so that the compression ratio increases.