JPH11336595A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately perform output torque lowering in an internal combustion engine in which a combustion mode can be switched between stratified combustion and uniform stoichiometric combustion. SOLUTION: An electronically controlled unit of an engine 11 switches a combustion mode among 'stratified combustion', 'weak stratified combustion', 'uniform lean combustion' and 'uniform stoichiometric combustion' in accordance with an operating condition of the engine 11. When a request for output torque lowering is made, the electronically controlled unit selects either one of reducing intake air amount, delaying ignition timing, reducing fuel injection amount, and delaying ignition timing and fuel injection timing, depending on the combustion mode of that time. The control mode thus selected for controlling torque lowering is performed to accomplish output torque lowering of the engine 11.

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 that switches a combustion mode between stratified combustion and homogeneous combustion.

[0002]

2. Description of the Related Art In recent years, in internal combustion engines for automobiles,
In order to achieve both improvement in fuel efficiency and obtaining sufficient engine output, an internal combustion engine of a type in which a combustion method is switched according to an engine operating state has been proposed and put into practical use. As this type of internal combustion engine, Japanese Unexamined Patent Publication No.
No. 93535 is described.

[0003] The internal combustion engine described in the publication has a fuel injection valve for supplying fuel to a combustion chamber. Then, at the time of high rotation and high load that requires high output, "homogeneous combustion" is performed in which a homogeneous mixture in which fuel is uniformly mixed with air is burned to obtain a sufficient engine output. This “homogeneous combustion” is executed by the fuel injected in the intake stroke of the internal combustion engine being evenly mixed with the air, and igniting the air-fuel mixture by the ignition plug in the combustion chamber. .

[0004] In addition, at low rotation and low load where very high output is not required, the fuel concentration around the spark plug is increased to improve the ignitability, and the average air-fuel ratio of the air-fuel mixture is made larger than the stoichiometric air-fuel ratio to improve fuel efficiency. "Stratified combustion" that can improve In this "stratified combustion", the fuel injected and supplied into the combustion chamber during the compression stroke of the internal combustion engine hits the depression of the piston head and is collected around the ignition plug, and the mixed fuel and the air in the combustion chamber are mixed. This is performed by igniting the air with a spark plug.

[0005] As described above, by switching the combustion system of the internal combustion engine between "homogeneous combustion" and "stratified combustion" according to the operating state of the engine, fuel efficiency can be improved and sufficient engine output can be obtained. Will be obtained.

In the internal combustion engine described in the above publication, the output shaft is connected to the automatic transmission, and the output torque of the internal combustion engine is transmitted to the automatic transmission. By the way, at the time of shifting of such an automatic transmission, the output torque of the internal combustion engine is reduced for the purpose of reducing shift shock. As an internal combustion engine in which such a torque down control at the time of shifting is performed, for example, an engine described in Japanese Patent Application Laid-Open No. 9-310627 is known.

In the internal combustion engine described in the publication, when a torque reduction is required during a gear shift, the engine output torque is forcibly reduced by the reduction of the intake air amount, the ignition timing is retarded, and the fuel supply amount is reduced. The engine output torque is forcibly reduced by at least one of the above. By reducing the output torque of the internal combustion engine as described above, even if a response delay occurs in a change in the amount of intake air with respect to a decrease in the amount of intake air, the engine output torque can be responsively improved by the ignition timing retard or the decrease in the amount of fuel supply. It can be forcibly reduced.

[0008]

As described above, the output torque of the internal combustion engine is reduced not only by the reduction of the intake air amount but also by the ignition timing retard and the fuel supply amount reduction, so that the output torque of the internal combustion engine such as at the time of gear shifting is changed. When the down is requested, the engine output torque can be reduced with good responsiveness.

However, the above-described torque-down control using a plurality of torque-down control methods such as a reduction in intake air amount, a retardation of ignition timing, and a reduction in fuel supply amount is applied to the above-described internal combustion engine in which the combustion method is switched. In the case where the method is applied, switching of the combustion method is not considered, so that an optimal torque-down control method according to the combustion method is not always used.

That is, if the ignition timing is excessively retarded during the "stratified combustion", combustion may become unstable due to the retardation of the ignition timing, causing a misfire. This is because during the "stratified combustion", it is necessary to perform ignition when there is an air-fuel mixture with a high fuel concentration around the spark plug, but the ignition timing is retarded as described above, so that the fuel around the spark plug is This is because ignition is performed when there is no high-concentration air-fuel mixture.

In addition, during "homogeneous combustion", if the amount of fuel injected is excessively reduced under the condition that the intake air amount of the internal combustion engine is kept constant, misfire will occur. As a result, the output torque cannot be significantly reduced depending on the fuel injection amount reduction, and the output torque reduction width due to the fuel injection amount reduction is small, and it is difficult to reduce the output torque to a required value. become.

[0012] These problems are caused not only when the output torque is required to be reduced at the time of shifting of the automatic transmission, but also when the output torque is required to prevent wheel spin in the traction control of the vehicle, or when the accelerator is pressed. Even when the output torque is required to be reduced in order to prevent a shock when the pedal is suddenly depressed, it is almost common.

The present invention has been made in view of such circumstances, and an object thereof is to appropriately reduce the output torque even in an internal combustion engine in which the combustion method is switched between stratified combustion and homogeneous combustion. An object of the present invention is to provide a control device for an internal combustion engine that can be executed.

[0014]

According to the first aspect of the present invention, there is provided an internal combustion engine in which a combustion system is switched between stratified combustion and homogeneous combustion in accordance with an engine operating state. In the control device of the internal combustion engine that executes the torque reduction control of the predetermined control method when the output torque reduction of the engine is requested, from among various control methods of the torque reduction control set according to the combustion method of the internal combustion engine,
Control method selecting means for selecting a control method of the torque down control based on a combustion method of the internal combustion engine when the output torque reduction is requested.

According to this configuration, since the control method of the torque-down control is selected according to the combustion method when the output torque reduction of the internal combustion engine is requested, the control method requires the same output torque reduction. The output torque can be appropriately set for the current combustion system, and the output torque can be appropriately reduced.

According to a second aspect of the present invention, in the first aspect of the invention, when the output torque reduction request in the stratified combustion is made, the control method selection means includes a fuel injection amount as a control method of the torque reduction control. Weight loss was selected.

According to this configuration, when the combustion method when the output torque reduction is requested is the stratified combustion, the output torque reduction is executed by reducing the fuel injection amount. When the fuel injection amount is reduced during stratified charge combustion, the distribution range of the air-fuel mixture is reduced in the presence of the air-fuel mixture having a high fuel concentration around the ignition plug, and the output torque is appropriately reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, the control method selecting means, when an output torque reduction request in stratified combustion is made, sets the fuel injection as a control method of the torque reduction control. In addition to the reduction in the amount, the ignition timing and the retardation of the fuel injection timing are selected.

According to this configuration, the output torque is reduced not only by the decrease in the fuel injection amount during stratified combustion but also by the retardation of the ignition timing and the fuel injection timing. If the ignition timing and fuel injection timing are retarded during stratified charge combustion, the combustion energy of the mixture is converted to reciprocating piston movement while maintaining the ignition in the presence of a mixture with high fuel concentration around the spark plug. Efficiency is reduced. Therefore, the output torque can be appropriately reduced in response to the output torque reduction request during stratified combustion, by the decrease in the fuel injection amount and the retardation of the ignition timing and the fuel injection timing.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the control method selecting means, when an output torque reduction request in homogeneous combustion is made, performs the torque reduction control. The retardation of the ignition timing is selected as the control method.

According to this configuration, when the combustion method when the output torque reduction is requested is homogeneous combustion, the output torque reduction is executed by retarding the ignition timing. And, when the ignition timing is retarded during homogeneous combustion,
The efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston is reduced, and the output torque is appropriately reduced.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the control method selecting means, when an output torque reduction request in homogeneous combustion is made, sets the ignition timing as a control method of the torque reduction control. In addition to the retard, the reduction of the intake air amount was selected.

With this configuration, the output torque can be reduced not only by adjusting the ignition timing during homogeneous combustion but also by adjusting the intake air amount. If the amount of intake air is reduced during homogeneous combustion, the amount of air-fuel mixture burned in the combustion chamber of the internal combustion engine decreases. Therefore, the output torque can be appropriately reduced in response to the output torque reduction request during the homogeneous combustion by the retardation of the ignition timing and the decrease in the intake air amount.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the combustion system of the internal combustion engine is switched at least between stratified combustion, homogeneous lean combustion, and homogeneous stoichiometric combustion. When the output torque of the internal combustion engine is requested and the combustion system of the engine is homogeneous lean combustion, the combustion system is forcibly switched to stratified combustion or homogeneous stoichiometric combustion prior to the torque down control. A forced switching means is further provided.

In homogeneous lean combustion, since the air-fuel mixture is burned at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, misfire is likely to occur due to a decrease in fuel injection amount or ignition timing delay. With this configuration, when homogeneous lean combustion is being performed when the output torque of the internal combustion engine is required to be reduced, the combustion mode is forcibly switched to stratified combustion or homogeneous stoichiometric combustion, and stratified combustion or homogeneous stoichiometric combustion is performed. In this state, the output torque is reduced. Therefore, even if the homogeneous lean combustion is performed when the torque down is requested, the misfire does not occur by the torque down control.

According to a seventh aspect of the present invention, there is provided an internal combustion engine in which the combustion mode is switched between stratified combustion and homogeneous combustion in accordance with the operating state of the engine. In a control device for an internal combustion engine that performs control, when an output torque reduction of the internal combustion engine is requested, forcible switching means for forcibly switching a combustion method to homogeneous stoichiometric combustion prior to the torque reduction control; And a torque-down control means for executing the torque-down control that is sometimes performed by a control method corresponding to homogeneous stoichiometric combustion.

According to this configuration, when the output torque of the internal combustion engine is required to be reduced, the combustion method is forcibly switched to homogeneous stoichiometric combustion. Then, the torque down control is performed by the control method of the torque down control according to the homogeneous stoichiometric combustion, so that the output torque is appropriately reduced.

According to an eighth aspect of the present invention, in the invention of the seventh aspect, the torque down control means executes ignition timing retard as torque down control performed at the time of the output torque down request.

According to this configuration, when the output torque of the internal combustion engine is required to be reduced, the combustion method is forcibly switched to homogeneous stoichiometric combustion, and the combustion energy of the air-fuel mixture is reciprocated by the piston by the ignition timing retard. The efficiency of conversion to movement is reduced, and the output torque is appropriately reduced.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, the torque-down control means performs a torque-down control performed at the time of the output torque-down request in addition to a retardation of the ignition timing and an intake air amount. Weight loss shall be performed.

According to this configuration, when the output torque of the internal combustion engine is required to be reduced, the combustion system is forcibly switched to homogeneous stoichiometric combustion, and not only the ignition timing is retarded but also the intake air amount is reduced. Also, the output torque is reduced. If the amount of intake air is reduced during homogeneous stoichiometric combustion, the amount of air-fuel mixture that burns in the combustion chamber of the internal combustion engine decreases. Therefore, the output torque can be appropriately reduced in response to the output torque reduction request by the retard of the ignition timing and the decrease in the intake air amount.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is applied to an in-line four-cylinder gasoline engine mounted on an automobile will be described below with reference to FIGS.

As shown in FIG. 1, the engine 11 has a total of four pistons 12 (only one is shown in FIG. 1) reciprocally provided in a cylinder block 11a. These pistons 12 are connected via a connecting rod 13 to a crankshaft 14 which is an output shaft. The reciprocating movement of the piston 12 is converted into rotation of the crankshaft 14 by the connecting rod 13. This crankshaft 14
It is connected to the wheels of an automobile via an automatic transmission (not shown) or the like.

A signal rotor 14a is attached to the crankshaft 14. This signal rotor 14
A plurality of protrusions 14b are provided at equal angles around the axis of the crankshaft 14 on the outer peripheral portion of a. A crank position sensor 14c is provided on the side of the signal rotor 14a. When the crankshaft 14 rotates and the projections 14b of the signal rotor 14a sequentially pass by the side of the crank position sensor 14c, the sensor 14c detects pulse-like detection corresponding to the passage of the projections 14b. A signal is output.

A cylinder head 15 is provided at the upper end of the cylinder block 11a, and a combustion chamber 16 is provided between the cylinder head 15 and the piston 12.
A pair of intake ports 17a and 17b provided in the cylinder head 15 and a pair of exhaust ports 18a and 18b are also connected to the combustion chamber 16 (one intake port 17b and one exhaust port in FIG. 1). 18b only).
These intake and exhaust ports 17a, 17b, 18a, 1
FIG. 2 shows a plane cross-sectional shape of 8b.

As shown in FIG.
Is a helical port extending in a curved manner, and the intake port 17b is a straight port extending in a straight line. When air passes through the intake port (helical port) 17a and is sucked into the combustion chamber 16, swirl is generated in the combustion chamber 16 in the direction indicated by the dashed arrow. The intake ports 17a and 17b and the exhaust ports 18a and 18b are provided with an intake valve 19 and an exhaust valve 20, respectively.

On the other hand, as shown in FIG. 1, an intake camshaft 21 and an exhaust camshaft 22 for opening and closing the intake valve 19 and the exhaust valve 20 are rotatably supported on the cylinder head 15. The intake and exhaust camshafts 21 and 22 are connected to the crankshaft 1 via a timing belt and gears (both not shown).
4 and the rotation of the crankshaft 14 is transmitted by the belt and the gears. Then, when the intake camshaft 21 rotates, the intake valve 19 is driven to open and close, so that the intake ports 17a and 17b and the combustion chamber 16 are communicated and shut off. Further, when the exhaust camshaft 22 rotates, the exhaust valve 20 is driven to open and close, and the exhaust ports 18a, 18b and the combustion chamber 16 are communicated and shut off.

In the cylinder head 15, on the side of the intake camshaft 21, a cam position sensor 21b for detecting a projection 21a provided on the outer peripheral surface of the shaft 21 and outputting a detection signal is provided. When the intake camshaft 21 rotates, the protrusion 21a of the shaft 21 passes by the side of the cam position sensor 21b. In this state, the cam position sensor 21b
Thus, the detection signal is output at predetermined intervals corresponding to the passage of the protrusion 21a.

The intake ports 17a and 17b and the exhaust ports 18a and 18b have an intake pipe 30 and an exhaust pipe 3 respectively.
1 is connected. The interior of the intake pipe 30 and the interior of the intake ports 17a and 17b constitute an intake passage 32, and the interior of the exhaust pipe 31 and the interior of the exhaust ports 18a and 18b constitute an exhaust passage 33.
It has become. In the middle of the exhaust passage 33, the engine 11
An exhaust gas purifying catalyst 33a for purifying exhaust gas is provided. On the other hand, a throttle valve 23 is provided in an upstream portion of the intake passage 32. This throttle valve 2
3 is rotated by the drive of the throttle motor 24 to adjust the opening. The opening of the throttle valve 23 is detected by a throttle position sensor 42.

The driving of the throttle motor 24 is controlled based on the amount of depression of an accelerator pedal 25 provided in the cabin of the automobile. That is, when the driver of the automobile depresses the accelerator pedal 25, the accelerator pedal 25
Is detected by the accelerator position sensor 26, and the drive of the throttle motor 24 is controlled based on the detection signal of the accelerator position sensor 26. This throttle motor 2
By adjusting the opening degree of the throttle valve 23 based on the drive control of No. 4, the air flow area of the intake passage 32 changes, and the amount of air taken into the combustion chamber 16 is adjusted.

In the intake passage 32, the throttle valve 2
A vacuum sensor 36 for detecting a pressure in the passage 32 is provided in a portion located downstream of the passage 3. Then, the vacuum sensor 36 outputs a detection signal corresponding to the detected pressure in the intake passage 32. A swirl control valve (SCV) 3 is provided in a portion of the intake passage 32 that is located downstream of the vacuum sensor 36 and communicates with the intake port (straight port) 17b.
4 are provided. The SCV 34 is rotated by driving the swirl motor 35 to adjust the opening.
Then, as the opening of the SCV 34 decreases, the amount of air passing through the intake port (helical port) 17a shown in FIG. 2 increases, and the swirl generated in the combustion chamber 16 increases.

On the other hand, as shown in FIG. 1, the cylinder head 15 is provided with a fuel injection valve 40 and a spark plug 41. Then, the fuel injected from the fuel injection valve 40 into the combustion chamber 16 is mixed with the air sucked into the combustion chamber 16 through the intake passage 32, so that the combustion chamber 1
A mixture of air and fuel is formed in 6. Further, the air-fuel mixture in the combustion chamber 16 is ignited by the ignition plug 41 and burns, and the air-fuel mixture after the combustion is sent to the exhaust passage 33 as exhaust gas and purified by the exhaust purification catalyst 33a. The ignition timing of the air-fuel mixture by the ignition plug 41 is adjusted by an igniter 41a provided above the ignition plug 41.

Next, the electrical configuration of the control device for the engine 11 in this embodiment will be described with reference to FIG. This control device includes an electronic control unit (hereinafter referred to as “EC”) for controlling the operating state of the engine 11, such as fuel injection amount control, fuel injection timing control, ignition timing control, and SCV opening control.
U ”) 92. This ECU 92 calculates
OM93, CPU94, RAM95 and backup R
It is configured as a logical operation circuit including the AM 96 and the like.

The ROM 93 is a memory that stores various control programs and maps and the like that are referred to when executing the various control programs.
The arithmetic processing is executed based on various control programs and maps stored in the OM 93. The RAM 95 is a CPU
94 is a memory for temporarily storing the calculation result at 94, data input from each sensor, and the like.
Reference numeral 6 denotes a nonvolatile memory for storing data to be stored when the engine 11 is stopped. And ROM93, CP
The U 94, the RAM 95, and the backup RAM 96 are connected to each other via a bus 97, and are also connected to an external input circuit 98 and an external output circuit 99.

The external input circuit 98 is connected to the crank position sensor 14c, the cam position sensor 21b, the accelerator position sensor 26, the vacuum sensor 36, the throttle position sensor 42, and the like.
On the other hand, the external output circuit 99 includes a throttle motor 2
4. The swirl motor 35, the fuel injection valve 40, the igniter 41a and the like are connected.

The ECU 92 configured as described above determines the engine speed NE based on the detection signal from the crank position sensor 14c. Further, based on the detection signals from the accelerator position sensor 26 and the vacuum sensor 36, the depression amount of the accelerator pedal 25 (accelerator depression amount) and the intake pressure are obtained, respectively. Then, based on the engine speed NE and the accelerator pedal depression amount or the engine speed NE and the intake pressure, a basic fuel injection amount Q0 representing the load of the engine 11 is obtained by referring to a known map. The basic fuel injection amount Q0 thus obtained is calculated as a larger value as the engine speed NE, accelerator depression amount, and intake pressure increase.

The ECU 92 determines the combustion mode of the engine 11 from the engine speed NE and the basic fuel injection amount Q0 with reference to the map shown in FIG.
Set ODE. This map includes a homogeneous stoichiometric combustion region A, a homogeneous lean combustion region B, a weak stratified combustion region C, and a stratified combustion region D. And the combustion mode FMO
For example, "FMODE = 0 (stratified combustion)" and "FMODE = DE" depend on which of the regions A to D the engine speed NE and the basic fuel injection amount Q0 are located in.
4 (weak stratified combustion), "FMODE = 8 (homogeneous lean combustion)", and "FMODE = 12 (homogeneous stoichiometric combustion)". When the combustion mode FMODE is set in this way, the ECU 92 sets the combustion mode FMODE.
, Ie, "stratified combustion", "weak stratified combustion", "homogeneous lean combustion", or "homogeneous stoichiometric combustion".

As is clear from the above map, as the operating state of the engine 11 shifts to high rotation and high load, the combustion method of the engine 11 is “stratified combustion”, “weak stratified combustion”, “homogeneous lean combustion”, It will sequentially change to “homogeneous stoichiometric combustion”. The reason for changing the combustion method is to use “homogeneous combustion” during high-speed and high-load operation where high power is required, to increase the engine output by reducing the air-fuel ratio of the air-fuel mixture, and to reduce the engine speed at low speeds that do not require very high output. At low load, the stratified charge combustion is performed to increase the air-fuel ratio to improve fuel efficiency.

When "FMODE = 12 (homogeneous stoichiometric combustion)", the ECU 92 determines the basic fuel injection amount Q0 from a known map based on the intake pressure obtained based on the detection signal from the vacuum sensor 36 and the engine speed NE. Ask. The ECU 92 controls the driving of the fuel injection valve 40 based on the final fuel injection amount Q obtained from the basic fuel injection amount Q0, and controls the fuel injection valve 4 during the intake stroke of the engine 11.
Inject fuel from zero. The ECU 92 corrects the basic fuel injection amount Q0 based on the detection signal from the oxygen sensor 37, and performs feedback control of the air-fuel ratio of the air-fuel mixture in the combustion chamber 16 to the stoichiometric air-fuel ratio. Further, the ECU 92
Controls the driving of the swirl motor 35 to control the SCV
The opening of 34 is adjusted so that the air-fuel mixture in the combustion chamber 16 is made uniform by swirling.

When “FMODE = 8 (homogeneous lean combustion)”, the ECU 92 obtains the accelerator depression amount based on the detection signal from the accelerator position sensor 26. Then, a basic fuel injection amount Q0 is obtained from a known map based on the obtained accelerator depression amount and the engine speed NE. The ECU 92 controls the driving of the fuel injection valve 40 based on the final fuel injection amount Q obtained from the basic fuel injection amount Q0, injects fuel from the fuel injection valve 40 during the intake stroke, and sets the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio. The value is set to a value larger than the fuel ratio (for example, 15 to 23). Further, the ECU 92 controls the opening of the SCV 34 by controlling the drive of the swirl motor 35, and stably burns the air-fuel mixture having an air-fuel ratio larger than the stoichiometric air-fuel ratio by the swirl.

"FMODE = 4 (weak stratified combustion)"
At this time, the ECU 92 obtains the basic fuel injection amount Q0 from the accelerator depression amount and the engine speed NE in the same manner as described above. The ECU 92 controls the driving of the fuel injection valve 40 based on the final fuel injection amount Q obtained from the basic fuel injection amount Q0, injects fuel into the intake stroke and the compression stroke of the engine 11, and adjusts the air-fuel ratio of the air-fuel mixture. A value (for example, 20 to 23) larger than the air-fuel ratio at the time of “homogeneous lean combustion” is set.

At the time of such "weak stratified combustion", the fuel injected and supplied during the intake stroke is evenly dispersed by the swirl into the air in the combustion chamber 16, and the fuel injected and supplied during the compression stroke is swirl and swirl. A depression 12 a (FIG. 1) provided in the head of the piston 12
Collected around one. The ECU 92 controls the drive of the swirl motor 35 to control the SCV 34 so that the swirl strength is suitable for the above-described dispersion and aggregation of the fuel.
Adjust the opening of. As described above, the fuel injection is performed in two stages, the intake stroke and the compression stroke, so that the air-fuel mixture is mixed in a combustion mode (weak stratified combustion) intermediate between the above-described "homogeneous lean combustion" and "stratified combustion" described later. Is performed, and the "weak stratified combustion" suppresses torque shock when switching between "homogeneous lean combustion" and "stratified combustion".

On the other hand, when "FMODE = 0 (stratified combustion)", the ECU 92 obtains the basic fuel injection amount Q0 from the accelerator depression amount and the engine speed NE in the same manner as described above. The ECU 92 controls the driving of the fuel injection valve 40 based on the final fuel injection amount Q obtained from the basic fuel injection amount Q0, injects fuel during the compression stroke of the engine 11, and reduces the air-fuel ratio of the air-fuel mixture to "weak stratified combustion". The air-fuel ratio is set to a value (for example, 25 to 50) larger than the air-fuel ratio at the time. Also, ECU
92 controls the driving of the swirl motor 35 to control the combustion chamber 1
The SCV 34 is driven and controlled so as to generate a swirl in the opening 6, and the opening degree of the SCV 34 is adjusted. The fuel injected and supplied by the swirl is collected around the ignition plug 41. By collecting fuel around the ignition plug 41 in this manner, the combustion chamber 16
Even if the average air-fuel ratio of the entire air-fuel mixture inside is larger than that during “weak stratified combustion”, the fuel concentration of the air-fuel mixture around the plug 41 is increased, and the good air-fuel mixture is ignited.

Next, an outline of the torque down control of the engine 11 executed through the ECU 92 having the above configuration will be described. The ECU 92 sets a required torque down speed TQDS for determining how fast the output torque should be reduced in response to the output torque reduction request of the engine 11. The engine 11 as described above
The output torque reduction request of, for example, when the shift of the automatic transmission is performed, when the wheel of the vehicle on which the traction control is performed causes a wheel spin, and when the accelerator pedal 25 is suddenly pushed to accelerate the vehicle rapidly. This will be done when you step on it. The required torque down speed TQDS is, for example, “TQDS
= 0 (no output torque down request) ”,“ TQDS = 1 ”
(Small required output torque reduction speed) "," TQDS =
2 (during output torque reduction request speed) "or" TQD
S = 3 (the output torque reduction request speed is large) ".

When the combustion mode of the engine 11 is “stratified combustion” or “weak stratified combustion”, the required torque down speed T
When the QDS is set to a value other than “0”, the output torque of the engine 11 is reduced by reducing the fuel injection amount and retarding the ignition timing and the fuel injection timing. That is, "T
When “QDS = 1 (small required output torque down speed)”, the control method of the torque down control of reducing the fuel injection amount by a small amount is selected. Further, when “TQDS = 2 (during output torque down request speed)”, a control method of torque down control in which the fuel injection amount is reduced by a large amount is selected, and the output torque of the engine 11 is increased by the large reduction in the fuel injection amount. Down is achieved. When the fuel injection amount is reduced in this way, the distribution range of the fuel-rich mixture present around the ignition plug 41 in the combustion chamber 16 is reduced, and the output torque of the engine 11 is reduced. Become.

Further, when "TQDS = 3 (high required output torque down speed)", not only the reduction of the fuel injection amount but also the control method of torque down control such as ignition timing and fuel injection timing retardation is selected. The output torque is also reduced by retarding the ignition timing and the fuel injection timing. When the ignition timing and the fuel injection timing are retarded in this way, the ignition in a state where the mixture having a high fuel concentration exists around the ignition plug 41 is maintained.
The efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston 12 decreases, and the output torque of the engine 11 decreases. Therefore, even when “TQDS = 3” during “stratified combustion” or “weakly stratified combustion” and the output torque reduction request speed is large, the fuel injection amount is reduced and the ignition timing and the fuel injection timing are retarded. Thus, the output torque of the engine 11 can be appropriately reduced without causing a misfire or the like.

On the other hand, when the combustion mode of the engine 11 is “homogeneous stoichiometric combustion” or “homogeneous lean combustion”, an output torque reduction request is issued and the required torque reduction speed T
QDS may be a value other than “0”. If an output torque reduction request is made during “homogeneous lean combustion”, EC
U92 forcibly switches the combustion mode of the engine 11 to "stratified combustion". This is the "homogeneous lean combustion"
The air-fuel ratio leaner than the stoichiometric air-fuel ratio (1 in this embodiment)
Due to the fact that the air-fuel mixture is burned in 5 to 23), if the ignition timing is retarded or the fuel injection amount is excessively reduced to reduce the output torque, misfire will occur.

When the engine 11 is executing “homogeneous stoichiometric combustion”, the required torque down speed T
When the QDS is set to a value other than “0”, the output torque of the engine 11 is reduced by controlling the closing of the throttle valve 23 (decreasing the intake air amount) and retarding the ignition timing. That is, when “TQDS = 1 (small required output torque down speed)”, the control method of the torque down control of closing the throttle valve 23 is selected. This is because when "TQDS = 1" and the output torque down request speed is low, the response delay of the output torque down occurs because the response of the output torque down is not excessively required. This is because even the closing control of 23 can sufficiently cope with the output torque reduction request.

When "TQDS = 2 (during output torque down request speed)", a control method of torque down control of retarding the ignition timing is selected, and the output torque of the engine 11 is reduced by the retardation of the ignition timing. Is achieved. When the ignition timing is retarded in this manner, the efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston 12 decreases, and the output torque of the engine 11 decreases. Further, when “TQDS = 3 (output torque down required speed is large)”, the control for closing the throttle valve 23 and the delay of the ignition timing are selected together as a control method of the torque down control, and by performing them, The output torque of the engine 11 is appropriately reduced. Since the output torque reduction due to the retardation of the ignition timing is performed with good responsiveness, sufficient responsiveness is obtained even when the required output torque reduction speed is medium or large when “TQDS = 2” or “TQDS = 3”. Thus, the output torque of the engine 11 can be reduced.

Next, when the output torque of the engine 11 is requested to decrease, the combustion mode switching procedure for forcibly switching the combustion mode to "stratified combustion" when the combustion mode is "homogeneous lean combustion" is shown. This will be described with reference to FIG. FIG. 5 is a flowchart showing a combustion mode switching routine for forcibly switching the combustion mode FMODE. This combustion mode switching routine is executed prior to the torque down control, and is executed through the ECU 92, for example, by interruption every predetermined time.

In this routine, the ECU 92 determines whether or not the required torque down speed TQDS is not "0", that is, whether or not a request to reduce the output torque of the engine 11 has been made, as the process of step S101. When it is determined that “TQDS ≠ 0” and the output torque reduction request has been made, the process proceeds to step S102, and whether or not the current fuel mode FMODE is “8” is determined.
That is, it is determined whether or not the current combustion method is “homogeneous lean combustion”. Then, when it is determined that “FMODE = 8” and the current combustion method is “homogeneous lean combustion”,
Proceed to step S103.

The ECU 92 forcibly sets the combustion mode FMODE to "0 (stratified combustion)" as the process of step S103, and then temporarily ends the combustion mode switching routine. It should be noted that also in the case where NO is determined in steps S101 and S102, the ECU 92 once ends the combustion mode switching routine. Step S10 above
When the combustion mode FMODE is forcibly set to “0 (stratified combustion)” in the process of 3, the ECU 92 sets the engine 1
The first combustion method is forcibly switched from "homogeneous lean combustion" to "stratified combustion". Therefore, when an output torque reduction request is made during “homogeneous lean combustion” where it is difficult to reduce the output torque due to ignition timing delay, intake air amount decrease, etc. due to misfiring, etc., it is easy to perform torque reduction control. It is forcibly switched to "combustion".

Next, throttle closing control, ignition timing retard,
An operation procedure of various flags for determining whether or not to perform the torque down control such as the fuel injection amount reduction and the ignition / fuel injection timing delay will be described with reference to FIG. FIG. 6 is a flowchart showing a flag operation routine for operating various flags according to the required torque down speed TQDS. This flag operation routine is executed by the ECU 92, for example, by interruption every predetermined time.

In this routine, the ECU 92 determines whether or not the required torque down speed TQDS is "1", that is, whether or not the required output torque down speed is small, as the process of step S201. Then, in the process of step S201, when it is determined that “TQDS = 1” and the output torque reduction request speed is small, the process proceeds to step S207.

The ECU 92 stores “1” in a predetermined area of the RAM 95 as the throttle close flag XDTRT and the small fuel decrease flag XDQL in the process of step S207. The throttle close flag XDTR
T is for determining whether or not to reduce the output torque by controlling the closing of the throttle valve 23 (reducing the amount of intake air). Further, the fuel small decrease flag XDQL
Is for determining whether or not to reduce the output torque due to a small decrease in the fuel injection amount.

In step S207, the ECU 92 determines whether the ignition retard flag XDSA and the fuel large decrease flag X
DQH and ignition / injection retard flag XDINT
Each “0” is stored in a predetermined area of the RAM 95. The ignition retard flag XDSA is for determining whether or not to reduce the output torque by retarding the ignition timing. The large fuel decrease flag XDQH is for determining whether or not to reduce the output torque due to a large decrease in the fuel injection amount. The ignition / injection retard flag XDINT is used to determine whether or not to reduce the output torque by retarding the ignition timing and the fuel injection timing.

Therefore, since “XDTRT = 1” and “XDQL = 1” are set in the process of step S207, when the output torque down request speed is low,
It is possible to adopt a control method of a torque down control such as a throttle closing control or a small decrease in a fuel injection amount. After executing the flag operation processing in step S207 as described above, the ECU 92 temporarily ends the flag operation routine.

On the other hand, if it is determined in step S201 that "TQDS = 1" and that the output torque reduction request speed is not low, the process proceeds to step S20.
Proceed to 2. The ECU 92 determines whether or not the required torque down speed TQDS is “2”, that is, whether or not the required output torque down speed is medium, as the process of step S202. If it is determined in step S202 that “TQDS = 2” and the output torque reduction request speed is medium, step S20 is performed.
Proceed to 6.

In the process of step S206, the ECU 92 sets the throttle close flag XDTRT, the ignition retard flag XDSA, the large fuel decrease flag XDQH, the small fuel decrease flag XDQL, and the ignition / injection retard flag XDINT to "0", respectively. “1”, “1”, “0”, and “0” are stored in a predetermined area of the RAM 95.

Accordingly, since “XDSA = 1” and “XDQH = 1” are set by the process of step S206, when the output torque reduction request speed is medium, the ignition timing is retarded and the fuel injection amount is greatly reduced. It is possible to adopt a control method of such torque down control. After executing the flag operation processing in step S206 as described above, the ECU 92 temporarily ends the flag operation routine.

On the other hand, if it is determined in step S202 that "TQDS = 2" and the output torque reduction request speed is not medium, step S20 is executed.
Proceed to 3. The ECU 92 determines whether or not the required torque down speed TQDS is “3”, that is, whether or not the required output torque down speed is large, as the process of step S203. If it is determined in the process of step S203 that “TQDS = 3” and the output torque reduction request speed is high, the process proceeds to step S20.
Go to 5.

In the process of step S205, the ECU 92 sets the throttle close flag XDTRT, the ignition retard flag XDSA, the large fuel decrease flag XDQH, the small fuel decrease flag XDQL, and the ignition / injection retard flag XDINT to "1", respectively. “1”, “1”, “0”, and “1” are stored in a predetermined area of the RAM 95.

Therefore, by the processing in step S205, “XDTRT = 1”, “XDSA = 1”, “XDQ
H = 1 ”and“ XDINT = 1 ”, the throttle closing control (reduction of intake air amount), retardation of ignition timing, large reduction of fuel injection amount, Further, it is possible to adopt a control method of torque down control such as ignition and retardation of injection timing. After executing the flag operation processing in step S205 as described above, the ECU 92 temporarily ends the flag operation routine.

On the other hand, if it is determined in step S203 that "TQDS = 3" and that the required output torque-down speed is not high, step S204 is executed.
Proceed to. When proceeding to step S204 in this way,
The required torque down speed TQDS is “0”,
This means that output torque reduction is not required. EC
U92 determines whether each flag XDT
“0” is stored in a predetermined area of the RAM 95 as RT, XDSA, XDQH, XDQL, and XDINT, respectively.

Therefore, all flags XDTRT, XDSA, XDQH, XDQ
L and XDINT are reset to "0".
After executing the flag operation processing in step S204 as described above, the ECU 92 temporarily ends the flag operation routine.

Next, the procedure for calculating the throttle closing amount for reducing the output torque will be described with reference to FIG. FIG. 7 is a flowchart showing a throttle closing amount calculation routine for calculating the throttle closing amount.
This throttle closing amount calculation routine is executed by the ECU 92, for example, by interruption at predetermined time intervals.
Note that the execution cycle of the throttle closing amount calculation routine is sufficiently longer than the execution cycle of the combustion mode switching routine (FIG. 5) and the flag operation routine (FIG. 6).

In the throttle closing amount calculation routine, E
In step S301, the CU 92 determines whether the combustion mode FMODE is “12”, that is, whether the current combustion method is “homogeneous stoichiometric combustion”. When it is determined that "FMODE = 12" and the current combustion method is "homogeneous stoichiometric combustion", the process proceeds to step S302, where "1" is stored as a throttle close flag XDTRT in a predetermined area of the RAM 95. It is determined whether or not. If NO is determined in either of the steps S301 and S302, the ECU 92 temporarily ends the throttle closing amount calculation routine.

If it is determined in step S302 that "XDTRT = 1", the flow advances to step S303. The ECU 92 calculates the throttle closing amount ΔTC based on the operating state of the engine 11 such as the engine speed NE and the accelerator pedal depression amount as the process of step S303, and then temporarily ends the throttle closing amount calculation routine.

After the throttle closing amount ΔTC is calculated in this manner, the ECU 92 controls the throttle valve 23 to the closing side by an amount corresponding to the throttle closing amount ΔTC based on a detection signal from the throttle position sensor 42 by another routine. I do. By this throttle closing control, the intake air amount of the engine 11 is reduced, and the engine 1
1 is achieved. Note that the amount of decrease in the output torque due to the throttle closing control is the throttle closing amount Δ
Although determined by the magnitude of TC, the throttle closing amount ΔTC of the present embodiment is calculated by the processing in step S303 as a value that can appropriately reduce the output torque without excessively decreasing the output torque. You.

As described above, the reason why the output torque is reduced by the throttle closing control (reduction of the intake air amount) is that the combustion method is “homogeneous stoichiometric combustion” and the output torque reduction is requested. This is when the required torque down speed TQDS becomes “1” or “3”. That is, in the state where “homogeneous stoichiometric combustion” is being performed, the required output torque reduction speed is small (“TQD
When S = 1 ”or large (“ TQDS = 3 ”), the throttle closing control is selected as the control method of the torque down control, and the output torque is reduced by the throttle closing control.

Next, an ignition timing control procedure for reducing the output torque will be described with reference to FIG. FIG. 8 is a flowchart showing an ignition timing operation routine for retarding the ignition timing by operating the target ignition timing when the output torque is reduced. This ignition timing operation routine is executed by the EC
The processing is executed by an interrupt at predetermined time intervals through U92, for example. The execution cycle of the ignition timing operation routine is as follows.
It is assumed that the period is sufficiently longer than the execution cycle of the combustion mode switching routine (FIG. 5) and the flag operation routine (FIG. 6).

In the ignition timing operation routine, the ECU 92
Is the combustion mode FMO as the process of step S401.
It is determined whether or not DE is “12”, that is, whether or not the current combustion method is “homogeneous stoichiometric combustion”. And
If it is determined that “FMODE = 12” and the current combustion method is “homogeneous stoichiometric combustion”, step S40
2 and the ignition retard flag XDSA is set to "1"
It is determined whether it is stored in a predetermined area of M95. If it is determined in step S402 that "XDSA = 1" is not satisfied, the ECU 92 once ends the ignition timing operation routine.

In step S 402,
If it is determined that “XDSA = 1”, the process proceeds to subsequent step S403. The ECU 92 calculates, as the target ignition timing SA, a value obtained by subtracting the homogeneous ignition timing delay amount ΔSA1 from the basic ignition timing SA0 as the process of step S403, and then temporarily ends the ignition timing operation routine. The basic ignition timing SA0 is calculated based on the engine speed NE and the intake pressure indicating the load by referring to a known map. The basic ignition timing SA thus calculated
0 is a value on the retard side as the engine 11 has a lower rotation and a higher load. In addition, the homogeneous ignition timing retard amount ΔSA1
Is calculated based on the operating state of the engine 11, such as the engine speed NE and the intake pressure.

After the target ignition timing SA is calculated by the process of step S403, the ECU 92 controls the drive of the igniter 41a based on the detection signal from the cam position sensor 21b according to another routine, so that the actual ignition timing is set to the target ignition timing. The actual ignition timing is retarded so as to coincide with the ignition timing SA. Due to the retardation of the ignition timing, the efficiency when the combustion energy of the air-fuel mixture is converted into the reciprocating movement of the piston 12 is reduced, and the output torque of the engine 11 is reduced. The amount of decrease in the output torque due to the retardation of the ignition timing is determined by the magnitude of the homogeneous-point ignition timing retardation ΔSA1, but the homogeneous-point ignition timing retardation ΔSA1 of the present embodiment has an excessively large output torque. It is calculated in the process of step S403 as a value that can appropriately reduce the output torque without lowering.

As described above, the reason why the output torque is reduced by retarding the ignition timing is that the combustion method is “homogeneous stoichiometric combustion” and the output torque reduction request is issued and the required torque reduction speed is set. This is when TQDS becomes “2” or “3”. That is, in the state where “homogeneous stoichiometric combustion” is being performed and the required output torque down speed is medium (“TQDS = 2”) or large (“TQDS = 3”), the control method of the torque down control is The ignition timing retard is selected, and the output torque is reduced by the ignition timing retard.

Therefore, when an output torque reduction request is made in a state where the engine 11 is in "homogeneous stoichiometric combustion", the throttle closing control is performed when the output torque reduction request speed is small ("TQDS = 1") and the output is reduced. When the required torque-down speed is medium (“TQDS = 2”), the ignition timing is retarded. When the required output torque reduction speed is high (“TQDS = 3”), both the throttle closing control and the ignition timing retard are performed. According to the various control methods of the torque reduction control, the output torque reduction of the engine 11 is appropriately executed in response to the output torque reduction request in the “homogeneous stoichiometric combustion”.

On the other hand, if it is determined in step S401 that the combustion mode is not “FMODE = 12” and that the combustion method is not “homogeneous stoichiometric combustion”, the flow proceeds to step S404. When the process proceeds to step S404 as described above,
This means that "stratified combustion" or "weak stratified combustion" is performed as the combustion method of the engine 11. The ECU 92 determines in step S404 that the ignition / injection retard flag XDI
It is determined whether or not “1” is stored in a predetermined area of the RAM 95 as NT. If it is determined in step S404 that “XDINT = 1” is not satisfied,
The ECU 92 once ends the ignition timing operation routine.

Further, in the process of step S404,
If it is determined that "XDINT = 1", the process proceeds to step S4.
Go to 05. The ECU 92 determines the stratified ignition timing retard amount Δ from the basic ignition timing SA0 as the process of step S405.
After the value obtained by subtracting SA2 is calculated as the target ignition timing SA, the ignition timing operation routine is temporarily terminated. The stratification ignition timing retardation amount ΔSA2 is calculated based on the operating state of the engine 11, such as the engine speed NE and the accelerator pedal depression amount.

After the target ignition timing SA is calculated by the processing in step S405, the ECU 92 controls the drive of the igniter 41a based on the detection signal from the crank position sensor 21b, and the actual ignition timing coincides with the target ignition timing SA. To retard the actual ignition timing. Further, the ECU 92 controls the drive of the fuel injection valve 40 to retard the fuel injection timing in synchronization with the retardation of the ignition timing by a combustion injection timing operation routine described later. Due to such retardation of the ignition timing and the fuel injection timing, the combustion energy of the air-fuel mixture is reciprocated by the piston 12 while the ignition in the state where the air-fuel mixture having a high fuel concentration is present around the ignition plug 41 is maintained. The conversion efficiency is reduced, and the output torque of the engine 11 is reduced.

Next, the control procedure of the fuel injection timing will be described with reference to FIG. FIG. 9 shows a fuel injection timing operation for delaying the fuel injection timing by operating the target fuel injection timing in synchronization with the ignition timing delay in “stratified combustion” or “weak stratified combustion” when the output torque is reduced. It is a flowchart which shows a routine. This fuel injection timing operation routine is executed by the ECU 92 through, for example, a time interruption at predetermined time intervals. It is assumed that the execution cycle of the fuel injection timing operation routine is sufficiently longer than the execution cycle of the combustion mode switching routine (FIG. 5) and the flag operation routine (FIG. 6).

In the fuel injection timing operation routine, the ECU
92 is a process in step S501 in which the combustion mode F
It is determined whether MODE is “0” or “4”, that is, whether the combustion mode is “stratified combustion” or “weak stratified combustion”. If it is determined that “FMODE = 0” or “FMODE = 4” and the combustion method is “stratified combustion” or “weakly stratified combustion”, the process proceeds to step S502 to set the ignition / injection retard flag XDINT. It is determined whether “1” is stored in a predetermined area of the RAM 95. Step S above
If NO is determined in any of 501 and 502, the ECU 92 once ends the fuel injection timing operation routine.

If it is determined in step S502 that "XDINT = 1", the flow advances to step S503. The ECU 92 performs the basic fuel injection timing AINJC0 as the process in step S503.
After subtracting the fuel injection timing delay amount ΔA from the target fuel injection timing AINJC, the fuel injection timing operation routine is temporarily terminated. The basic fuel injection timing AINJC0 is calculated based on the engine speed NE and the accelerator depression amount with reference to a known map. The basic fuel injection timing AINJC thus calculated
0 is a value on the retard side as the engine 11 has a lower rotation and a higher load. Further, the fuel injection timing retard amount ΔA is calculated based on the operating state of the engine 11 such as the engine speed NE and the accelerator pedal depression amount.

After the target fuel injection timing AINJC is calculated by the processing in step S503, the ECU 92
Controls the driving of the fuel injection valve 40 by another routine, and the actual fuel injection timing is set to the target fuel injection timing AINJC.
The actual fuel injection timing is retarded so as to match.
By the retardation of the fuel injection timing, the fuel injection timing is retarded in synchronization with the retardation of the ignition timing by the above-described ignition timing operation routine. Therefore, even if the ignition timing and the fuel injection timing are retarded as described above in order to reduce the output torque in “stratified combustion” or “weakly stratified combustion”, a mixture having a high fuel concentration exists around the ignition plug 41. The ignition in the fired state is maintained.

The amount of decrease in the output torque due to the retardation of the ignition timing and the fuel injection timing is determined by the stratification ignition timing retardation ΔSA2 and the fuel injection timing retardation ΔA. The stratified ignition timing retard amount ΔSA of the present embodiment
2 and the fuel injection timing delay amount ΔA are values that can appropriately reduce the output torque without excessively decreasing the output torque, and are the values of the processing in step S503 and the steps in the ignition timing operation routine (FIG. 8). It is calculated in the process of S405.

As described above, the reason why the output torque is reduced by retarding the ignition timing and the fuel injection timing is that the combustion method is “stratified combustion” or “weak stratified combustion” and the output torque is reduced. This is when the request for down is made and the required torque down speed TQDS becomes “3”. That is, in a state where “stratified combustion” or “weakly stratified combustion” is being performed, the output torque reduction request speed is large (“T
When QDS = 3 ”), the ignition timing and the fuel injection timing retard are selected as the control method of the torque down control, and the output torque is reduced by the ignition / injection timing retardation.

Next, a fuel injection amount control procedure for reducing the output torque will be described with reference to FIG. FIG.
8 is a flowchart showing a fuel injection amount operation routine for reducing the fuel injection amount by operating the final fuel injection amount when an output torque reduction request is made. This fuel injection amount operation routine is executed by the ECU 92 through, for example, a time interruption at predetermined time intervals. Note that the execution cycle of the ignition timing operation routine is sufficiently longer than the execution cycle of the combustion mode switching routine (FIG. 5) and the flag operation routine (FIG. 6).

In the fuel injection amount operation routine, the ECU 9
2 is a process in step S601, in which the combustion mode FM
It is determined whether the ODE is “0” or “4”, that is, whether the combustion method is “stratified combustion” or “weak stratified combustion”. Then, in the process of step S601, “FMODE =
If it is determined that the combustion method is not “0” or “FMODE = 4” and the combustion method is not “stratified combustion” or “weakly stratified combustion”, the ECU
A step 92 temporarily ends the fuel injection amount operation routine.

If it is determined in step S601 that “FMODE = 0” or “FMODE = 4” and that the combustion mode is “stratified combustion” or “weakly stratified combustion”, the process proceeds to step S602. Then, it is determined whether or not “1” is stored in the predetermined area of the RAM 95 as the small fuel reduction flag XDQL. Then, "XDQL =
If it is determined to be "1", the process proceeds to step S603.
The ECU 92 calculates the final fuel injection amount Q by subtracting the small fuel reduction value ΔQL from the basic fuel injection amount Q0 as the process of step S603. The small fuel decrease value ΔQL is calculated based on the operating state of the engine 11 such as the engine speed NE and the accelerator pedal depression amount. After the final fuel injection amount Q is calculated in this manner, the ECU 92
This fuel injection amount operation routine is temporarily ended.

On the other hand, if it is determined in step S602 that "XDQL = 1" is not satisfied, the flow advances to step S604 to determine whether "0" is stored in the predetermined area of the RAM 95 as the large fuel reduction flag XDQH. to decide. Then, in the process of step S604,
If it is determined that “XDQH = 1” is not satisfied, the ECU 92
Terminates the fuel injection amount calculation routine once. Further, in the processing of step S604, “XDQH =
If it is determined to be "1", the process proceeds to step S605. E
The CU 92 calculates, as the final fuel injection amount Q, a value obtained by subtracting the large fuel reduction value ΔQH from the basic fuel injection amount Q0 in the process of step S605. The large fuel decrease value ΔQH is calculated based on the operating state of the engine 11 such as the engine speed NE and the accelerator pedal depression amount. After the final fuel injection amount Q is calculated in this manner, the ECU 92 once ends the fuel injection amount operation routine.

After the final fuel injection amount Q is calculated by the processing of steps S603 and 605, the ECU 92
The driving of the fuel injection valve 40 is controlled by another routine to inject fuel into the combustion chamber 16 in an amount corresponding to the final fuel injection amount Q. This final fuel injection amount Q is the basic fuel injection amount Q0
Is calculated by subtracting the small fuel decrease value ΔQL or the large fuel decrease value ΔQH from the above, so that when an output torque reduction request of the engine 11 is made, the actual fuel injection amount is reduced and the output torque is reduced. become. The amount of decrease in the output torque due to the decrease in the fuel injection amount is determined by the magnitudes of the small fuel decrease value ΔDQL and the large fuel decrease value ΔDQH. The small fuel reduction value ΔQL and the large fuel reduction value ΔQH of the present embodiment are values at which the output torque can be appropriately reduced without excessively reducing the output torque, and are determined at steps S603 and S605 described above.
Is calculated in the processing of.

As described above, the reason why the output torque is reduced by decreasing the fuel injection amount is that the combustion method is “stratified combustion” or “weak stratified combustion” and an output torque reduction request is issued. Required torque down speed T
This is when the QDS becomes one of “1” to “3”. That is, when the stratified combustion or the weak stratified combustion is being performed and the required output torque-down speed is low to high (“TQDS = 1 to 3”), the torque-down control is performed. A reduction in the fuel injection amount is selected as the control method, and the output torque is reduced by reducing the fuel injection amount.

Therefore, if an output torque reduction request is made while the engine 11 is in "stratified combustion" or "weak stratified combustion", the output torque reduction request speed becomes small ("TQDS
= 1 ”), the fuel injection amount is reduced by a small amount, and the output torque reduction request speed is medium (“ TQDS = 2 ”).
In this case, the fuel injection amount is greatly reduced. Also, the output torque reduction request speed is large ("TQDS = 3")
In the case of, both the large reduction of the fuel injection amount and the retardation of the ignition timing and the fuel injection timing are performed. According to these various control methods of the torque down control, the output torque of the engine 11 is appropriately reduced in response to the output torque reduction request in “stratified combustion” and “weak stratified combustion”.

According to the present embodiment in which the processing described in detail above is performed, the following effects can be obtained. (1) The control method of the torque reduction control is selected according to the combustion method when the output torque reduction request of the engine 11 is made. Therefore, the selected control method of the torque-down control can be made appropriate for the combustion method at the time of the output torque-down request, and the output torque of the engine 11 whose combustion method is switched can be appropriately executed. it can.

(2) An output torque reduction request is made during "stratified combustion" or "weak stratified combustion", and when the required output torque reduction speed becomes small to large ("TQDS = 1 to 3"), the fuel injection amount is increased. Is selected, and the fuel injection amount is reduced to reduce the output torque of the engine 11. When the fuel injection amount is reduced in this manner, the distribution range of the fuel-rich mixture present around the ignition plug 41 in the combustion chamber 16 is reduced, so that the output torque of the engine 11 is appropriately reduced. be able to.

(3) In the state of “stratified combustion” or “weakly stratified combustion” and when the required output torque down speed is large (“TQDS = 3”), the fuel injection amount is used as the control method of the torque down control. And the ignition timing and the fuel injection timing are selected together. The ignition timing and the fuel injection timing for the output torque reduction are also executed in accordance with the decrease in the fuel injection amount. When the ignition timing and the fuel injection timing are retarded in this manner, the combustion energy of the air-fuel mixture is transferred to the piston 12 while the ignition in a state where the air-fuel mixture having a high fuel concentration exists around the ignition plug 41 is maintained. , The efficiency of conversion to the reciprocating movement of the engine 11 decreases, and the output torque of the engine 11 decreases. Therefore, even if “TQDS = 3” during “stratified combustion” or “weakly stratified combustion” and the output torque reduction request speed is large, the fuel injection amount is reduced,
The output torque of the engine 11 can be appropriately reduced without causing a misfire or the like by the ignition timing and the retardation of the fuel injection timing.

(4) If an output torque reduction request is made during “homogeneous lean combustion”, the combustion system of the engine 11 is forcibly switched to “stratified combustion”. Therefore, in order to burn the air-fuel mixture at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, if the ignition timing is retarded for reducing the output torque or the fuel injection amount is excessively reduced, misfire easily occurs. In such a state, the torque down control such as the fuel injection amount reduction and the ignition timing retard is not performed. Therefore, it is possible to prevent a misfire caused by performing the torque down control at the time of “homogeneous lean combustion”.

(5) If the required output torque reduction speed becomes small (“TQDS = 1”) during “homogeneous stoichiometric combustion”, the control method of the torque reduction control called throttle closing control (reduction of intake air amount) is selected. And engine 1
In 1), the intake air amount is reduced by the throttle closing control for reducing the output torque. When the throttle closing control is performed as described above, a response delay occurs in the reduction of the intake air amount, and the output torque does not decrease quickly. However, the output torque reduction request speed is small and the response of the output torque reduction is excessive. Therefore, the responsiveness of the output torque reduction by the throttle closing control is sufficient. Therefore, during “homogeneous stoichiometric combustion”, “TQDS
= 1 ", the output torque of the engine 11 can be appropriately reduced by the throttle closing control (reducing the amount of intake air).

(6) In the state of “homogeneous stoichiometric combustion”, the required output torque reduction speed is medium or large (“TQD
S = 2, 3 "), the control method of the torque down control of retarding the ignition timing is selected, and the ignition timing is retarded for decreasing the output torque of the engine 11. When the ignition timing is retarded, the efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston 12 is reduced, and the output torque of the engine 11 can be appropriately reduced. In addition, since the output torque is reduced with good response by retarding the ignition timing, “TQDS = 2” or “TQDS = 2”
QDS = 3 "and the output torque reduction request speed is medium or high, and the engine 11 has sufficient responsiveness.
Output torque can be reduced.

(7) In the state of “homogeneous stoichiometric combustion”, the required output torque reduction speed is large (“TQDS =
3)), the throttle closing control (reducing the amount of intake air) and the retard of the ignition timing are selected together as the control method of the torque down control. In order to reduce the output torque, both the throttle closing control and the ignition timing retard are executed. Even if “TQDS = 3 (the required output torque reduction speed is large)”, the output torque of the engine 11 is appropriately reduced. Can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, when the output torque reduction request is issued, the combustion method is forcibly switched to “homogeneous stoichiometric combustion”, so that only the control method of the torque reduction control suitable for “homogeneous stoichiometric combustion” is executed. Thus, the output torque can be reduced when the output torque is reduced. In the present embodiment, a combustion mode switching routine, a flag operation routine, a throttle closing amount calculation routine, and an ignition timing operation routine are different from those of the first embodiment, and the fuel injection amount timing operation routine and the fuel injection amount in the first embodiment are different. The processing corresponding to the operation routine is not executed. Therefore, in the present embodiment, only different parts from the first embodiment will be described, and detailed description of the same parts as the first embodiment will be omitted.

FIG. 11 is a flowchart showing a combustion mode switching routine according to this embodiment. This combustion mode switching routine is executed prior to the torque down control.
The processing is executed by the CU 92, for example, by interruption every predetermined time. In this routine, processing corresponding to step S102 of the combustion mode switching routine (FIG. 5) in the first embodiment is not performed, and processing (S702) corresponding to step S103 is different from that of the first embodiment.

In this routine, the ECU 92 determines whether or not the output torque reduction has been requested as the processing of step S701. Then, in the process of step S701, the fact that the output torque reduction is not requested (“T
QDS = 0 ”), the ECU 92 once ends the combustion mode switching routine. Step S
If it is determined in the process of 701 that the output torque reduction has been requested (“TQDS ≠ 0”), step S70
Proceed to 2. The ECU 92 forcibly sets the combustion mode FMODE to "12 (homogeneous stoichiometric combustion)" as the process of step S702, and then temporarily ends the combustion mode switching routine. When the combustion mode FMODE is forcibly set to "12 (homogeneous stoichiometric combustion)" in the process of step S702, the ECU 92 forcibly switches the combustion mode of the engine 11 to "homogeneous stoichiometric combustion". Therefore, when the output torque is required to be reduced, the combustion method is forcibly switched to “homogeneous stoichiometric combustion” regardless of which combustion method the engine 11 is executing.

FIG. 12 is a flowchart showing a flag operation routine according to the present embodiment. This flag operation routine is executed by the ECU 92, for example, by interruption every predetermined time. In this routine, steps S204 to S204 of the flag operation routine (FIG. 6) in the first embodiment are performed.
Only the processing (S804 to S807) corresponding to S207 is different from the first embodiment.

In the same routine, the ECU 92 determines which of the required torque downspeed TQDS is "0" to "3" by the processing of steps S801 to S803. If it is determined that “TQDS = 1 (output torque reduction required speed is small)”, step S80 is performed.
7, the ECU 92 determines that the throttle close flag SDT
The RT and the ignition retard flag XDSA are set to “1” and “0”, respectively. Therefore, when the output torque reduction request speed is low, a control method of torque reduction control called throttle closing control (reduction of intake air amount) is adopted. After executing the flag operation processing in step S807 as described above, the ECU 92 temporarily ends the flag operation routine.

When it is determined that "TQDS = 2 (during output torque reduction request speed)", step S8 is executed.
In step 06, the ECU 92 sets the throttle close flag SD
The TRT and the ignition retard flag XDSA are set to “0” and “1”, respectively. Therefore, when the output torque reduction request speed is medium, the control method of torque reduction control of retarding the ignition timing is adopted. After executing the flag operation processing of step S806 as described above,
The ECU 92 once ends the flag operation routine.

Further, when it is determined that "TQDS = 3 (output torque down required speed is large)", step S8 is performed.
05, the ECU 92 determines that the throttle close flag SD
The TRT and the ignition retard flag XDSA are each set to “1”. Therefore, when the output torque reduction request speed is high, the above two control methods of the torque reduction control, that is, the throttle closing control (reduction of the intake air amount) and the retardation of the ignition timing are employed together. After executing the flag operation processing of step S805 as described above, the EC
U92 ends this flag operation routine once.

On the other hand, when it is determined that “TQDS = 0 (no output torque reduction request)”, the ECU 92 sets the throttle close flag SDTRT and the ignition retard flag XD
SA is set to “0”. Therefore, step S8
By the process of 04, the flags XDTRT and XDSA are reset to “0”. After executing the flag operation process of step S804 as described above, the ECU 9
2 temporarily ends the flag operation routine.

FIG. 13 is a flowchart showing a throttle closing amount calculation routine according to this embodiment. This throttle closing amount calculation routine is executed by the ECU 92, for example, by interruption at predetermined time intervals. Note that the execution cycle of the throttle closing amount calculation routine is sufficiently longer than the execution cycle of the combustion mode switching routine (FIG. 11) and the flag operation routine (FIG. 12). In this throttle closing amount calculation routine, step S in the throttle closing amount calculation routine (FIG. 7) of the first embodiment is performed.
The processing corresponding to 301 is not performed.
The reason why the processing corresponding to step S301 can be omitted is that the combustion method is forcibly switched to "homogeneous stoichiometric combustion" when the output torque is reduced.

In the throttle closing amount calculation routine according to the present embodiment, the ECU 92 determines whether or not the throttle closing flag XDTRT is set to “1” in the process of step S901. If it is determined in step S901 that "XDTRT = 1" is not satisfied, the ECU 92 once ends the throttle closing amount calculation routine. If it is determined that “XDTRT = 1” in the process of step S901, the process proceeds to step S902. The ECU 92 calculates the throttle closing amount ΔTC as the process of step S902, and then temporarily ends the throttle closing amount calculation routine.

After the throttle closing amount ΔTC has been calculated in this manner, the ECU 92 executes another routine by an amount corresponding to the throttle closing amount ΔTC by another routine.
3 is controlled to the closing side. By this throttle closing control, the intake air amount of the engine 11 is reduced, and the output torque of the engine 11 is reduced. The output torque reduction by the throttle closing control (reduction of the intake air amount) is performed in such a manner that the output torque reduction is required and the mode is forcibly switched to “homogeneous stoichiometric combustion”, and the required torque reduction speed TQDS is “1”. Or, when it becomes “3”.

FIG. 14 is a flowchart showing an ignition timing operation routine according to this embodiment. This ignition timing operation routine is executed by the ECU 92 at, for example, a time interruption every predetermined time. The execution cycle of the ignition timing operation routine is the same as the combustion mode switching routine (FIG. 11).
And a period sufficiently longer than the execution cycle of the flag operation routine (FIG. 12). In this ignition timing operation routine,
Processing (S100) corresponding to steps S402 and S403 in the ignition timing operation routine (FIG. 8) of the first embodiment
1, S1002) is executed. In the ignition timing operation routine of the present embodiment, steps S401, S404, S4 in the ignition timing operation routine of the first embodiment.
The reason that the process corresponding to 05 can be omitted is that the combustion method is forcibly switched to "homogeneous stoichiometric combustion" when the output torque is reduced.

In the ignition timing operation routine of the present embodiment, the ECU 92 determines whether or not the ignition retard flag XDSA has been set to "1" in the process of step S1001. If it is determined in step S1001 that “XDSA = 1” is not satisfied, the ECU 92 determines
This ignition timing operation routine is temporarily ended. Further, in the process of step S1001, “XDSA = 1”
If it is determined to be, the process proceeds to step S1002. E
The CU 92 calculates, as the target ignition timing SA, a value obtained by subtracting the homogeneous ignition timing retard amount ΔSA1 from the basic ignition timing SA0 as the process of step S1002, and then temporarily ends the ignition timing operation routine.

After the target ignition timing SA is calculated by the processing in step S1002, the ECU 92 retards the actual ignition timing by another routine so that the actual ignition timing matches the target ignition timing SA. . Due to the retardation of the ignition timing, the efficiency when the combustion energy of the air-fuel mixture is converted into the reciprocating movement of the piston 12 is reduced, and the output torque of the engine 11 is reduced. The reason why the output torque is reduced by retarding the ignition timing is as follows.
When the output torque reduction is requested, it is forcibly switched to “homogeneous stoichiometric combustion”, and the required torque reduction speed TQ
This is when DS becomes “2” or “3”.

That is, in the present embodiment, when the required torque down speed TQDS is set to a value other than "0" at the time of the output torque reduction request of the engine 11, the combustion method of the engine 11 may be set regardless of the combustion method of the engine. The system is forcibly switched to "homogeneous stoichiometric combustion". Further, as a control method of the torque down control suitable for the “homogeneous stoichiometric combustion”, a throttle closing control (a reduction in the amount of intake air) and a retard of the ignition timing are executed.
1 is achieved.

That is, when "TQDS = 1 (output torque reduction required speed is small)", the output torque is reduced by a torque reduction control method called throttle closing control. Further, when “TQDS = 2 (during output torque reduction request speed)”, a control method of torque down control of retarding the ignition timing is selected, and the output torque of the engine 11 is reduced by the retardation of the ignition timing. . Further, when “TQDS = 3 (output torque reduction required speed is large)”, both the throttle closing control and the ignition timing retard are executed, and by performing them, the output torque of the engine 11 is appropriately reduced. It is planned.

According to the present embodiment in which the processing described above is performed, the following effects can be obtained. (8) When a request to reduce the output torque of the engine 11 is made, the combustion method is forcibly switched to “homogeneous stoichiometric combustion”, and throttle closing control (intake air) is performed as torque reduction control suitable for the “homogeneous stoichiometric combustion”. In this case, the ignition timing is retarded. That is, when the output torque reduction is requested and the output torque reduction request speed is low (“TQDS = 1”), the output torque of the engine 11 can be appropriately reduced by performing the throttle closing control. When the required output torque reduction speed is medium (“TQDS = 2”), the ignition timing is retarded, so that the engine 1
1 can be reduced. Further, when the required output torque reduction speed is high (“TQDS = 3”), both the throttle closing control and the ignition timing retard are performed, so that the output torque of the engine 11 can be appropriately reduced.

(9) If an output torque reduction request is issued during “homogeneous lean combustion”, the combustion system of the engine 11 is forcibly switched to “homogeneous stoichiometric combustion”, and a torque reduction suitable for the “homogeneous stoichiometric combustion” is performed. The output torque is reduced by the control. Therefore, in order to burn the air-fuel mixture at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, if the ignition timing is retarded for reducing the output torque or the fuel injection amount is excessively reduced, misfire easily occurs. In such a state, the torque down control such as the fuel injection amount reduction and the ignition timing retard is not performed. Therefore, it is possible to prevent the occurrence of misfire due to the fact that the torque down control is performed at the time of “homogeneous lean combustion”.

(10) When a request to reduce the output torque of the engine 11 is made, the combustion method is forcibly switched to “homogeneous stoichiometric combustion”, and therefore, a torque suitable for the output torque reduction in the “homogeneous stoichiometric combustion” It is sufficient to execute the down control, that is, the throttle closing control (reduction of the intake air amount) or the ignition timing retard. Therefore, in the engine 11 whose combustion mode is switched, the output torque reduction based on the output torque reduction request can be executed without performing complicated control.

The above embodiments can be modified as follows, for example. In the above embodiments, instead of executing the throttle closing control (reducing the amount of intake air) when the output torque is required to be reduced during “homogeneous stoichiometric combustion” and “TQDS = 1”, the ignition timing is retarded. May be executed to reduce the output torque.

In the above embodiments, when the output torque reduction request in “homogeneous stoichiometric combustion” is required and “TQD
When “S = 3”, it is not always necessary to execute the throttle closing control (reducing the amount of intake air).

In the first embodiment, when the output torque is reduced in “homogeneous lean combustion”, the combustion mode is forcibly switched to “stratified combustion”. Instead, the combustion mode is forcibly changed. Alternatively, the mode may be switched to "weak stratified combustion" or "homogeneous stoichiometric combustion".

In the first embodiment, when “TQDS = 3” at the time of output torque reduction request in “stratified combustion” or “weak stratified combustion”, the ignition timing and the fuel injection timing are not necessarily retarded. do not have to.

In each of the above embodiments, the control method of the torque down control includes throttle closing control (reduction of intake air amount), retardation of ignition timing, reduction of fuel injection amount, and retardation of ignition timing and fuel injection timing. However, other control methods of torque down control such as fuel cut may be adopted.

In the above embodiments, the throttle closing amount ΔTC, the ignition timing retardation ΔSA1, the ignition timing retardation ΔSA2, the stratification ignition timing retardation ΔSA2, the small fuel reduction value ΔQL, the large fuel reduction value ΔQH, and the fuel injection timing delay The angle amount ΔA may be a fixed value obtained in advance by an experiment or the like.

In each of the above embodiments, the present invention is applied to an engine 11 of a type in which the combustion mode is switched among four types of "stratified combustion", "weak stratified combustion", "homogeneous lean combustion", and "homogeneous stoichiometric combustion". However, the present invention is not limited to this. That is, the present invention may be applied to an engine of a type in which the same combustion system is switched between two or three combustion systems from among these combustion systems. In this case, if the “homogeneous lean combustion” is not performed, it is necessary to forcibly switch the combustion method to “stratified combustion” when the output torque is reduced in “homogeneous lean combustion” as in the first embodiment. Is gone.

[0136]

According to the first aspect of the present invention, the control method of the torque reduction control is selected according to the combustion method when the output torque reduction of the internal combustion engine is requested. It is possible to make it appropriate for the combustion system when torque down is requested, and to appropriately execute the output torque down.

According to the second aspect of the present invention, when the combustion mode when the output torque reduction is requested is the stratified combustion, the output torque reduction is executed by reducing the fuel injection amount. When the fuel injection amount is reduced during stratified charge combustion, the distribution range of the air-fuel mixture is reduced in the presence of the air-fuel mixture having a high fuel concentration around the ignition plug, and the output torque is appropriately reduced.

According to the third aspect of the present invention, the output torque is reduced not only by the decrease in the fuel injection amount during stratified combustion but also by the ignition timing and the retardation of the fuel injection timing. If the ignition timing and fuel injection timing are retarded during stratified combustion,
The efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston is reduced while maintaining the ignition in the presence of the air-fuel mixture having a high fuel concentration around the spark plug. Therefore, the output torque can be appropriately reduced in response to the request for reducing the output torque during stratified combustion, by reducing the fuel injection amount and the retardation of the ignition timing and the fuel injection timing.

According to the fourth aspect of the present invention, when the combustion method when the output torque reduction is requested is the homogeneous combustion, the output torque reduction is executed by retarding the ignition timing. If the ignition timing is retarded during homogeneous combustion, the efficiency of converting the combustion energy of the air-fuel mixture into the reciprocating movement of the piston is reduced, and the output torque is appropriately reduced.

According to the fifth aspect of the present invention, the output torque can be reduced not only by adjusting the ignition timing during homogeneous combustion but also by adjusting the intake air amount. If the amount of intake air is reduced during homogeneous combustion, the amount of air-fuel mixture burned in the combustion chamber of the internal combustion engine decreases. Therefore, the output torque can be appropriately reduced in response to a request for reducing the output torque during homogeneous combustion, by retarding the ignition timing and decreasing the intake air amount.

According to the sixth aspect of the present invention, when homogeneous lean combustion is performed when output torque reduction of the internal combustion engine is requested, the combustion mode is forcibly switched to stratified combustion or homogeneous stoichiometric combustion. The output torque is reduced in the state of stratified combustion or homogeneous stoichiometric combustion. Therefore, even if the homogeneous lean combustion is performed when the torque down is requested, the misfire does not occur by the torque down control.

According to the present invention, when the output torque of the internal combustion engine is required to be reduced, the combustion mode is forcibly switched to the homogeneous stoichiometric combustion. Then, the torque down control is performed by the control method of the torque down control according to the homogeneous stoichiometric combustion, so that the output torque is appropriately reduced. Therefore, even in an internal combustion engine whose combustion mode is switched, the output torque can be appropriately reduced.

According to the eighth aspect of the invention, when the output torque of the internal combustion engine is required to be reduced, the combustion system is forcibly switched to homogeneous stoichiometric combustion, and the combustion energy of the air-fuel mixture is controlled by the retardation of the ignition timing. Of the piston into reciprocating movement of the piston is reduced, and the output torque can be appropriately reduced.

According to the ninth aspect of the invention, when the output torque of the internal combustion engine is required to be reduced, the combustion mode is forcibly switched to the homogeneous stoichiometric combustion, and not only the ignition timing is retarded but also the intake air is reduced. The output torque can also be reduced by reducing the amount. If the amount of intake air is reduced during homogeneous stoichiometric combustion, the amount of air-fuel mixture that burns in the combustion chamber of the internal combustion engine decreases. Therefore, the ignition timing retard and
By reducing the intake air amount, the output torque can be appropriately reduced in response to the output torque reduction request.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an entire engine to which a control device according to a first embodiment is applied.

FIG. 2 is a sectional view of a cylinder head showing shapes of intake and exhaust ports in the engine.

FIG. 3 is a block diagram showing an electrical configuration of the control device.

FIG. 4 is a map referred to when determining the combustion mode of the engine.

FIG. 5 is a flowchart showing a combustion mode switching procedure according to the first embodiment.

FIG. 6 is a flowchart illustrating a flag operation procedure according to the first embodiment;

FIG. 7 is a flowchart illustrating a throttle closing amount calculation procedure according to the first embodiment;

FIG. 8 is a flowchart illustrating an ignition timing operation procedure according to the first embodiment;

FIG. 9 is a flowchart illustrating a fuel injection timing operation procedure according to the first embodiment.

FIG. 10 is a flowchart showing a fuel injection amount operation procedure according to the first embodiment;

FIG. 11 is a flowchart illustrating a combustion mode switching procedure according to the second embodiment.

FIG. 12 is a flowchart illustrating a flag operation procedure according to the second embodiment.

FIG. 13 is a flowchart illustrating a throttle closing amount calculation procedure according to the second embodiment.

FIG. 14 is a flowchart illustrating an ignition timing operation procedure according to the second embodiment.

[Explanation of symbols]

11 ... engine, 14 c ... crank position sensor,
21b: cam position sensor, 23: throttle valve, 24: throttle motor, 25: accelerator pedal, 26: accelerator position sensor, 36: vacuum sensor, 40: combustion injection valve, 41: spark plug, 41
a: igniter, 42: throttle position sensor,
92 ... Electronic control unit (ECU)

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02D 41/04 330 F02D 41/04 330B 330G 335 335C 335G 41/12 330 41/12 330B 43/00 301 43/00 301B 301J 301K 45/00 312 45/00 312F F02P 5/15 F02P 5/15 F

Claims (9)

[Claims] An internal combustion engine that switches a combustion mode between stratified combustion and homogeneous combustion in accordance with an engine operating state. When an output torque reduction of the engine is requested, a torque reduction control of a predetermined control method is executed. A control device for an internal combustion engine, wherein the torque is determined based on the combustion system of the internal combustion engine when the output torque reduction is requested from among various control systems of torque down control set according to the combustion system of the internal combustion engine. A control device for an internal combustion engine, comprising: a control method selecting means for selecting a control method of down control. 2. The control of an internal combustion engine according to claim 1, wherein said control method selection means selects a decrease in fuel injection amount as a control method of said torque down control when an output torque down request in stratified combustion is made. apparatus. 3. The control system selecting means, when an output torque down request in stratified combustion is made, controls the ignition timing and the fuel injection timing in addition to the reduction of the fuel injection amount as the control system of the torque down control. 3. The control device for an internal combustion engine according to claim 2, wherein the angle is selected. 4. The control method selecting means according to claim 1, wherein when an output torque reduction request is made in homogeneous combustion, the ignition timing is retarded as a control method of said torque reduction control. A control device for an internal combustion engine according to claim 1. 5. The control system selection means selects a reduction in intake air amount in addition to the retardation of the ignition timing as a control system of the torque down control when an output torque reduction request in homogeneous combustion is made. The control device for an internal combustion engine according to claim 4. 6. The control device for an internal combustion engine according to claim 1, wherein a combustion mode of said internal combustion engine is switched at least between stratified combustion, homogeneous lean combustion and homogeneous stoichiometric combustion. When the output torque of the internal combustion engine is requested and the combustion method of the engine is homogeneous lean combustion, forcible switching to forcibly switch the combustion method to stratified combustion or homogeneous stoichiometric combustion prior to the torque down control. A control device for an internal combustion engine, further comprising means. 7. An internal combustion engine in which a combustion mode is switched between stratified combustion and homogeneous combustion in accordance with an operation state of the engine. In the device, when an output torque reduction of the internal combustion engine is requested, forcible switching means for forcibly switching the combustion method to homogeneous stoichiometric combustion prior to the torque reduction control, and a torque reduction control performed at the time of the output torque reduction request. A control device for an internal combustion engine, comprising: a torque down control unit that executes a control method according to homogeneous stoichiometric combustion. 8. The control device for an internal combustion engine according to claim 7, wherein said torque down control means executes ignition timing retarding as torque down control performed when said output torque down request is made. 9. The control device for an internal combustion engine according to claim 8, wherein said torque-down control means executes a reduction in intake air amount in addition to a retardation of ignition timing as torque-down control performed when said output torque-down request is made. .