JP2005016407A - Control device for spark ignition type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand a compression self-ignition combustion region into a high-speed high-load side and effectively suppress knocking in a region in the high-speed high-load side of the compression self-ignition combustion region. <P>SOLUTION: This control device for a spark ignition type engine has an EGR control means 32 comprised of a valve operation control means 33 for controlling operation of an intake/exhaust valve such that hot burned gas by internal EGR is left inside a combustion chamber and a cold EGR control means 34 for controlling introduction of cooled external EGR. In this control device, EGR is controlled in an operation region in a low-speed low-load side of the compression self-ignition combustion region, such that the hot burned gas is left inside the combustion chamber. In the operation region in the high-speed high-load side of the compression self-ignition combustion region, the EGR is controlled such that cooled EGR gas is introduced into inside of the combustion chamber. In addition, this control device is provided with a means 36 for performing ignition assist at the time of compression self-ignition combustion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark ignition engine that burns an air-fuel mixture in a combustion chamber by compression self-ignition in a partial load region during warm conditions.
[0002]
[Prior art]
Recently, compression self-ignition has been studied as a technique for improving fuel consumption in spark ignition engines (gasoline engines), and this compression self-ignition is mixed at a high temperature and high pressure in the combustion chamber at the end of the compression stroke, just like a diesel engine. Qi self-ignite. According to this compression self-ignition, since the entire combustion chamber burns at once, the combustion efficiency is improved, the fuel consumption is greatly improved, the generation of NOx is suppressed, and the emission is advantageously improved.
[0003]
As a technique for effectively performing such compression self-ignition, there has been proposed a technique in which a large amount of hot burned gas is left in the combustion chamber by so-called internal EGR. For example, in the engine described in Patent Document 1, in a predetermined partial load region, after the exhaust valve is closed, the intake valve is opened so that a negative overlap (a period in which both the intake and exhaust valves are closed) is performed. ) Is increased, the amount of internal EGR is increased, and the temperature in the combustion chamber is increased by this internal EGR so that compression self-ignition is performed.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-152919
[Problems to be solved by the invention]
According to the conventional apparatus as described above, compression self-ignition is effectively performed in the region of relatively low speed and low load by the combustion chamber temperature rising action by the internal EGR, but the combustion chamber temperature is high on the high speed and high load side. It rises too much and knocking easily occurs. In the region where knocking is likely to occur, internal EGR and self-compression ignition are stopped (the intake and exhaust valves are set to normal timing and forced ignition is performed), but compression is possible as much as possible in order to improve fuel consumption and emissions. It is desirable to widen the auto-ignition combustion area, and there remains room for improvement in this regard.
[0006]
In view of such circumstances, the present invention can expand the compression self-ignition combustion region to the high-speed / high-load side, and is effective in knocking in the high-speed / high-load side of the compression self-ignition combustion region. The present invention provides a control device for a spark ignition engine that can be suppressed to a low level.
[0007]
[Means for Solving the Problems]
The present invention relates to a compression ignition combustion region which is an operation region in which combustion is performed by compression self-ignition in a spark ignition engine in which an air-fuel mixture in a combustion chamber is combusted by compression self-ignition in a partial load region at a warm time. In the operation region on the low speed and low load side, EGR control is performed so that hot burned gas remains in the combustion chamber. In the operation region on the high speed and high load side in the compression self-ignition combustion region, the cooled EGR gas is transferred to the combustion chamber. EGR control means for adjusting the temperature in the combustion chamber at the time of self-compression ignition by performing EGR control so as to be introduced into the engine, and when ignitability is reduced by introduction of at least cooled EGR gas in the compression self-ignition combustion region And an ignition assist means for promoting compression self-ignition.
[0008]
According to the present invention, in the operation region on the low-speed and low-load side in the compression self-ignition combustion region, the combustion chamber temperature is increased by the hot burned gas remaining in the combustion chamber, so that compression self-ignition combustion is favorably performed. . Further, in the operation region on the high speed and high load side in the compression self-ignition combustion region, the temperature in the combustion chamber tends to rise too much, but the introduction of the cooled EGR gas suppresses an excessive temperature rise and knocks. Is prevented. Although the introduction of EGR gas prevents knocking, it tends to make compression self-ignition less likely to occur, but good compression self-ignition combustion is ensured by performing the ignition assist.
[0009]
In other words, knocking occurs when trying to perform compression self-ignition combustion in the past, so even in a relatively high speed and high load region where compression self-ignition combustion was not performed, by introduction of cooled EGR gas and ignition assist, The compression self-ignition combustion is favorably performed while knocking is avoided, and the compression self-ignition combustion region is expanded.
[0010]
In the present invention, the EGR control means reduces the amount of hot burned gas remaining in the combustion chamber as the load increases in the compression self-ignition combustion region, and reduces the amount of cooled EGR gas introduced into the combustion chamber. It is preferable that the amount be controlled to increase as the load increases in the high load side operation region in the compression self-ignition combustion region.
[0011]
In this manner, in the compression self-ignition combustion region, the ratio of the hot burned gas and the cooled EGR gas is corrected so as to correct the tendency that the temperature in the combustion chamber tends to rise excessively as the load increases. Is adjusted.
[0012]
The EGR control means includes a valve operation control means for controlling the internal EGR by controlling the operation of the intake / exhaust valves, and a cold EGR for controlling the external EGR returned from the exhaust passage through the EGR passage having the cooling means. What is necessary is just to include a control means.
[0013]
In this way, the amount of hot burned gas and the amount of cooled EGR gas can be adjusted effectively.
[0014]
Further, the ignition assist means may be an ignition control means for igniting the air-fuel mixture in the succeeding cylinder before the compression top dead center.
[0015]
If it does in this way, compression self-ignition will be accelerated | stimulated by the rapid rise of the pressure by ignition just before said compression top dead center.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
1 and 2 schematically show an embodiment of an engine to which the present invention is applied. In these drawings, the engine body 1 has a plurality of cylinders 2, pistons 3 are fitted in the respective cylinders 2, and combustion chambers 4 are formed above the pistons 3.
[0018]
A spark plug 5 is provided at the top of the combustion chamber 4 of each cylinder 2, and the tip of the plug faces the combustion chamber 4. An ignition circuit 6 capable of controlling ignition timing by electronic control is connected to the spark plug 5.
[0019]
An intake port 7 and an exhaust port 8 are opened to the combustion chamber 4 of each cylinder 2, and an intake passage 9 and an exhaust passage 10 are connected to these ports 7 and 8. The intake port 7 is provided with a fuel injection valve 11 for supplying and supplying fuel. The fuel injection valve 11 includes a needle valve and a solenoid (not shown). When a pulse signal (described later) is input, the fuel injection valve 11 is driven and opened for a time corresponding to the pulse width at the pulse input timing. An amount of fuel corresponding to the valve time is injected. The intake passage 9 is provided with a throttle valve 12 for adjusting the intake air amount.
[0020]
The intake port 7 and the exhaust port 8 are opened and closed by an intake valve and an exhaust valve. In the illustrated example, two intake valves 13a and 13b and two exhaust valves 14a and 14b are provided for each cylinder.
[0021]
In order to adjust the internal EGR (hot burned gas remaining in the combustion chamber) with respect to the combustion chamber 4, the opening / closing timing of at least one of the intake and exhaust valves can be changed. In the present embodiment, a variable valve lift mechanism 15 is provided for one of the two exhaust valves 14a, 14b per cylinder, and a phase valve timing is provided for the exhaust valves 14a, 14b. A variable mechanism 20 is provided.
[0022]
The variable valve lift mechanism 15 stops the valve operating state for compression self-ignition combustion in which the exhaust valve 14a is opened in the intake stroke in addition to the exhaust stroke by two types of cams 16a and 16b, and the operation in the intake stroke. Thus, it is possible to switch to the normal combustion valve operating state in which the exhaust valve 14a is operated only in the exhaust stroke.
[0023]
The specific structure of the variable valve lift 15 is as shown in FIG. 3, and this structure will be described with reference to the valve operation explanatory view of FIG.
[0024]
The variable valve lift mechanism 15 shown in FIG. 3 has a first cam 161 and a second cam 162 disposed on the camshaft 16, and the first cam 161 opens the exhaust valve 14a in the exhaust stroke, and the second cam The cam nose of these two types of cams 161 and 162 is displaced by approximately 90 ° in camshaft rotation angle (approximately 180 ° in crank angle) so that the exhaust valve 14a is opened during the intake stroke. In FIG. 4, Ex is the valve opening characteristic of the exhaust valve 14a by the first cam 161, ExI is the valve opening characteristic of the exhaust valve 14a by the second cam 162, and In is the valve opening characteristic of the intake valves 13a and 13b. As shown in this figure, in the valve opening characteristic Ex by the first cam 161, the exhaust valve 14a is opened substantially during the exhaust stroke period, and in the valve opening characteristic ExI by the first cam 161, the valve opening period of the exhaust valve 14a is the intake air. It is shorter than the valve opening period of the valve (In), and is opened only for a part of the intake stroke.
[0025]
These cams 161 and 162 are in contact with intermediate portions of the first rocker arm 171 and the second rocker arm 172 whose base end portions are supported on the rocker shaft 17 so as to be able to swing, and the distal end of the first rocker arm 171 is contacted. The exhaust valve 14a is connected to the first rocker arm 171 and the second rocker arm 172 can be connected to and separated from the first rocker arm 171 by a switching mechanism.
[0026]
Although not shown, the switching mechanism includes a plunger that can move over plunger holes provided in the rocker arms 171 and 172, and the plunger is actuated by hydraulic pressure to displace the plungers via the plungers. It is possible to switch between a connected state in which the arms 171 and 172 are connected so as to swing together and a separated state in which the rocker arms 171 and 172 swing independently. In the connected state, the swing of the first rocker arm 171 accompanying the rotation of the first cam 161 and the swing of the second rocker arm 172 accompanying the rotation of the second cam 162 are both transmitted to the exhaust valve 14a and exhausted. While the opening operation (Ex) in the stroke and the opening operation (ExI) in the intake stroke are performed, in the separated state, the swing of the second rocker arm 172 accompanying the rotation of the second cam 162 is transmitted to the exhaust valve 14a. By not being able to do so, only the opening operation (Ex) in the exhaust stroke is performed. Note that the exhaust valve 14b not provided with the variable valve lift mechanism 15 is always only opened in the exhaust stroke.
[0027]
A control valve 18 (see FIG. 2) for controlling supply and discharge of hydraulic pressure is provided for the switching mechanism.
[0028]
Further, the variable valve timing mechanism 20 shown in FIGS. 1 and 2 changes the opening / closing timing of the exhaust valves 14a and 14b by changing the phase of the camshaft with respect to the crankshaft. In the illustrated embodiment, a variable valve timing mechanism 21 is also provided for the intake valves 13a and 13b.
[0029]
Further, as shown in FIG. 1, the engine is provided with an EGR passage 22 that connects the exhaust passage 10 and the intake passage 9 in order to guide the EGR gas cooled by the external EGR to the combustion chamber. In addition, an EGR cooler 23 is provided as a cooling means for cooling the EGR gas, and an EGR valve 24 for controlling the amount of EGR gas is provided.
[0030]
As shown in FIG. 2, the ignition circuit 6, the fuel injection valve 11, the control valve 18 of the variable valve lift mechanism 15, the variable valve timing mechanisms 20, 21 and the EGR valve 24 are controlled by an ECU (engine control unit) 30. . The ECU 30 receives signals from various sensors such as a throttle opening sensor 25 that detects the opening of the throttle valve 12, a rotation speed sensor 26 that detects the engine speed, and a water temperature sensor 27 that detects the temperature of the engine coolant. It is designed to be entered.
[0031]
The ECU 30 functionally includes an operating state determination unit 31, an EGR control unit 32 including a valve operation control unit 33 and a cold EGR control unit 34, an ignition control unit 35, and a fuel injection control unit 36.
[0032]
Based on the signal from the water temperature sensor 27, the operating state determination means 31 determines whether or not the water temperature is warmer than a predetermined temperature. The engine operating state is examined based on the engine load obtained from the signal or the like and the engine rotational speed obtained from the signal from the rotational speed sensor 26 to determine which region in the operational region map shown in FIG. . Here, the map shown in FIG. 6 will be described. A partial load region extending over a low / medium load and a low / medium speed is defined as a compression self-ignition combustion region A, and a region B on the higher load side and the higher speed side is defined as a normal combustion region. It is said that. Further, the low-speed / low-load side region in the compression self-ignition combustion region A is a hot EGR region A1 in which a large amount of hot burned gas from the internal EGR remains in the combustion chamber. The region on the high speed side and the high load side is a cold EGR region A2 where the cooled external EGR gas is introduced in addition to the internal EGR.
[0033]
The valve operation control means 33 controls the valve lift variable mechanism 15 by controlling the control valve 18 according to the operation state determined by the operation state determination means 31, and also controls the valve timing variable mechanism 20, By these controls, the hot EGR amount (internal EGR amount) is controlled.
[0034]
Specifically, when the operation state is in the compression self-ignition combustion region A, the variable valve lift mechanism 15 is controlled so that the valve operation state for compression self-ignition shown in FIG. Thereby, since the exhaust valve 14a is opened during the intake stroke, the exhaust flows backward from the exhaust port 8 and flows into the combustion chamber 4 to obtain a large amount of hot EGR. In this case, as the opening / closing operation (characteristic ExI in FIG. 4) of the exhaust valve 14a during the intake stroke shifts to the delay side, a larger amount of fresh air flows into the combustion chamber first, so the ratio of hot EGR decreases. Therefore, a relatively early valve timing as indicated by a solid line in FIG. 4 is set on the low load side of the compression self-ignition combustion region A, and as the compression load on the high load side of the compression self-ignition combustion region A is reached, a two-dot chain line in FIG. The valve timing variable mechanism 20 is controlled so as to reduce the ratio of hot EGR by delaying the valve timing (characteristics Ex and ExI) of the exhaust valve as shown in FIG.
[0035]
Instead of controlling the valve timing of the exhaust valve in this way, as shown in FIG. 5, the valve timing of the exhaust valve is fixed while the valve timing of the intake valve is fixed using the variable valve timing mechanism 21 for the intake valve. The ratio of hot EGR can also be changed by changing. In this case, on the low load side of the compression self-ignition combustion region A, the intake valve (characteristic In) is set to a relatively slow valve timing (slow closing advantageous for reducing pumping loss) as shown by a solid line in FIG. As the ignition combustion region A becomes higher, the hot EGR ratio may be reduced by increasing the valve timing (characteristic In) of the intake valve as indicated by a two-dot chain line in FIG.
[0036]
The cold EGR control unit 34 controls the cold EGR amount (external EGR amount) by controlling the EGR valve 24 according to the operation state determined by the operation state determination unit 31. Specifically, the EGR valve 24 is closed in the hot EGR region A1 in the compression self-ignition combustion region A, and the EGR valve 24 is opened in the cold EGR region A2, and the opening thereof is increased as the load increases. I am doing so.
[0037]
Therefore, the change in the EGR rate of the hot EGR and the cold EGR according to the change of the load in the compression self-ignition combustion region A is as shown in FIG. That is, only the hot EGR is given in the low load side region (corresponding to the hot EGR region A1 in FIG. 6) in the compression self-ignition combustion region A, and the EGR rate decreases as the load increases. Further, in the high load side region (corresponding to the cold EGR region A2 in FIG. 6) in the compression self-ignition combustion region A, cold EGR is given in addition to hot EGR, and the hot EGR is increased as the load increases. As the EGR rate decreases, the EGR rate of cold EGR increases.
[0038]
Returning to FIG. 2, the ignition timing control means 35 in the ECU 30 controls the ignition timing of the engine by the spark plug 5 according to the operating state, and particularly in the compression ignition combustion region A, as ignition assist means for promoting compression self-ignition. It functions and is ignited (shown with a symbol S in FIG. 4) at a timing before the compression top dead center and in the vicinity of the compression top dead center.
[0039]
The fuel injection control means 36 controls the injection amount and the injection timing from the fuel injection valve 11 according to the operating state. The air-fuel ratio is controlled by the control of the fuel injection amount by the fuel injection control means 36 and the control of the intake air amount by the control of a throttle valve drive motor or the like (not shown). In the compressed self-ignition combustion region A, the stoichiometric air-fuel ratio is controlled. The leaner air-fuel ratio (the excess air ratio λ is λ> 1) is controlled.
[0040]
In addition, the fuel injection timing is set within the intake stroke, but particularly in the compression self-ignition combustion region A, the fuel injection timing is surely ensured in the situation where the exhaust valve 14a opens during a part of the intake stroke as shown in FIG. The fuel is injected at the timing when the intake air flows into the combustion chamber. For example, the fuel is injected until after the exhaust valve opening period (ExI) during the intake stroke. Alternatively, the fuel may be injected before the exhaust valve opening period (ExI) during the intake stroke, or the fuel is divided before and after the exhaust valve opening period (ExI) during the intake stroke. You may make it spray.
[0041]
According to the apparatus of the present embodiment as described above, in the compression self-ignition combustion region A that is a predetermined partial load region, a large amount is obtained by controlling the exhaust valve 14a to open even during the intake stroke as shown in FIG. Hot EGR is obtained, and compression self-ignition is performed by raising the temperature in the combustion chamber 4 with this hot EGR.
[0042]
When compression self-ignition is performed in this way, even if the air-fuel ratio is lean or a large amount of EGR is introduced, the entire combustion chamber burns at once due to simultaneous multi-point ignition, so avoid slow combustion that does not contribute to work. The fuel efficiency is greatly improved. Furthermore, when rapid combustion by compression self-ignition is performed, the reaction between oxygen and nitrogen is avoided as much as possible, so that generation of NOx is sufficiently suppressed, which is advantageous in improving emissions.
[0043]
Further, in the cold EGR region A2, which is the high-speed side and high-load side region in the compression self-ignition combustion region A, in addition to hot EGR, cold EGR is introduced into the combustion chamber and hot EGR is increased as the load increases. The ratio of the combustion chamber temperature decreases and the ratio of the cold EGR increases. On the high speed / high load side, the combustion chamber temperature is increased by the cold EGR so that the combustion chamber temperature does not rise excessively due to hot EGR and causes knocking. Is adjusted.
[0044]
In addition, when cold EGR is introduced in addition to hot EGR in this way, knocking can be effectively prevented, but the increase in the combustion chamber temperature is suppressed, and compression self-ignition may not occur easily. The compression self-ignition is promoted by the control by 35 as the ignition assist means.
[0045]
That is, the ignition is performed immediately before the compression top dead center, so that the pressure around the spark plug 5 rapidly increases. The temperature inside the combustion chamber is considerably high due to hot EGR while avoiding an excessive temperature rise due to the mixing of cold EGR, and the compression is caused by this temperature and the sudden rise in pressure due to ignition just before the compression top dead center. Self-ignition is performed well.
[0046]
Thus, even in a relatively high speed / high load area where knocking is likely to occur with hot EGR alone, it is effective while preventing knocking by suppressing excessive temperature rise due to mixing of cold EGR and ignition assist. Since the self-compression ignition can be performed, the compression self-ignition combustion region can be expanded to the high speed / high load side, and the improvement effect of fuel consumption and emission can be enhanced.
[0047]
Further, in the hot EGR region A1, which is the low-speed / low-load side region in the compression self-ignition combustion region A, the combustion chamber temperature is inherently low, so that only the hot EGR is used, and the EGR rate becomes lower at the lower load side. By increasing the value, self-ignitability is improved. In this embodiment, the ignition assist is performed also in this region A1, so that the compression self-ignition is favorably performed even in an extremely low speed / low load region where the temperature is not easily raised by the hot EGR alone. .
[0048]
On the other hand, in the normal combustion region B, which is a fully open load or a region close to the high load side and high speed side, the variable valve lift mechanism 15 is switched to a state where the exhaust valve 14a is opened only in the exhaust stroke, and hot EGR is introduced. Normal combustion by forced ignition is performed in a state where the engine is stopped and the EGR valve 24 is also closed.
[0049]
In addition, the specific structure of the apparatus of the present invention is not limited to the above embodiment, and can be variously changed. Some examples will be described below.
[0050]
(1) In addition to the configuration of the above embodiment, a valve stop mechanism is provided for one of the two intake valves 13a and 13b per cylinder, and the operation of the intake valve 13a is stopped at low load. (Or the lift amount is minimized), and an intake swirl may be generated. In this case, if the intake valve 13a that is deactivated (or minimal lift) and the exhaust valve 14a that is opened even in the intake stroke at low load are arranged to face each other, the flow of the intake swirl and the internal EGR is smooth. Done.
[0051]
(2) In the above embodiment, the variable valve lift mechanism 15 is provided for the one exhaust valve 14a. Instead, the variable valve lift mechanism is provided for the one intake valve 13a, and compression self-ignition combustion is performed. In the region, as shown in FIG. 8, the intake valve may be opened (InE) in the exhaust stroke in addition to the opening (In) in the intake stroke. In this way, part of the exhaust is blown back to the intake port during the exhaust stroke, and this flows into the combustion chamber in the next intake stroke and becomes hot EGR (internal EGR).
[0052]
(3) In addition to the above example, the internal EGR may be caused by a method in which the intake valve is opened after the exhaust valve is closed, and a negative overlap (a period during which both the intake and exhaust valves are closed). ) May be set.
[0053]
(4) In the above embodiment, the fuel injection valve is provided at the intake port. However, the fuel injection valve may be provided so as to inject fuel directly into the combustion chamber. Becomes higher.
[0054]
(5) In the above embodiment, the ignition assist is always performed in the compression self-ignition combustion region A, but the ignition assist is performed at least when the cold EGR region A2 in the compression self-ignition combustion region A is introduced. You just have to do it. For example, the ignition assist may be performed in an extremely low load region in the cold EGR region A2 and the hot EGR region A1, and the ignition assist may be stopped in an operation region in which compression self-ignition combustion is favorably performed by the hot EGR.
[0055]
【The invention's effect】
As described above, according to the control device of the present invention, the EGR control is performed so that the hot burned gas remains in the combustion chamber in the operation region on the low speed and low load side in the compression self-ignition combustion region. In the operating region on the high speed and high load side, the EGR control is performed so that the cooled EGR gas is introduced into the combustion chamber, and the ignition assist is performed. Therefore, the compression auto ignition combustion is performed in the compression auto ignition combustion region. In particular, even in an operation region on the relatively high speed and high load side, knocking is prevented and good compression self-ignition combustion is ensured. Therefore, the compression self-ignition combustion region can be expanded.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an entire engine including a control device according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of an engine or the like.
FIG. 3 is a perspective view showing a variable valve lift mechanism.
FIG. 4 is an explanatory diagram showing an example of valve operation.
FIG. 5 is an explanatory diagram showing another example of valve operation.
FIG. 6 is an explanatory diagram showing a map of an operation region.
FIG. 7 is an explanatory diagram showing a relationship between an engine load and an EGR rate of hot EGR and cold EGR.
FIG. 8 is an explanatory view showing another embodiment of the valve operation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine body 5 Spark plug 8 Ignition circuit 11 Fuel injection valve 13a, 13b Intake port 14a, 14b Exhaust port 15 Valve lift variable mechanism 20, 21 Valve timing variable mechanism 22 EGR passage 23 EGR cooler 24 EGR valve 30 ECU
32 EGR control means 33 Valve operation control means 34 Cold EGR control means 35 Ignition control means

Claims (4)

In a spark ignition engine that burns an air-fuel mixture in a combustion chamber by compression self-ignition in a partial load region during warm,
In the operation region on the low-speed and low-load side of the compression self-ignition combustion region that is an operation region in which combustion is performed by compression self-ignition, EGR control is performed so that hot burned gas remains in the combustion chamber, and the compression self-ignition combustion region EGR control means for adjusting the temperature in the combustion chamber during self-compression ignition by performing EGR control so that the cooled EGR gas is introduced into the combustion chamber in the high speed and high load side operation region
A control device for a spark ignition type engine, comprising: an ignition assisting means for accelerating compression self-ignition when ignitability is reduced by introduction of at least cooled EGR gas in a compression self-ignition combustion region. The EGR control means reduces the amount of hot burned gas remaining in the combustion chamber as the load increases in the compression self-ignition combustion region, and reduces the amount of cooled EGR gas introduced into the combustion chamber. 2. The control device for a spark ignition engine according to claim 1, wherein control is performed so that the load increases as the load increases in an operation region on a high load side in the compression self-ignition combustion region. The EGR control means includes a valve operation control means for controlling the internal EGR by controlling the operation of the intake / exhaust valves, and a cold EGR for controlling the external EGR returned from the exhaust passage through the EGR passage having the cooling means. The control device for a spark ignition type engine according to claim 1 or 2, further comprising control means. 2. The spark ignition engine control apparatus according to claim 1, wherein the ignition assist means comprises ignition control means for igniting an air-fuel mixture in the succeeding cylinder before compression top dead center.

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