EP1479898B1

EP1479898B1 - Combustion control apparatus for internal combustion engine

Info

Publication number: EP1479898B1
Application number: EP20040011991
Authority: EP
Inventors: Tatsumasa Sugiyama; Masato Tsuzuki; Masahiko Ishikawa; Nobuki Kobayashi; Jun Tahara; Hidenaga Kato
Original assignee: Toyota Industries Corp; Toyota Motor Corp
Current assignee: Toyota Industries Corp; Toyota Motor Corp
Priority date: 2003-05-22
Filing date: 2004-05-19
Publication date: 2013-04-03
Anticipated expiration: 2024-05-19
Also published as: EP1479898A2; JP2004346835A; EP1479898A3; JP4175952B2

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a combustion control apparatus for an internal combustion engine for controlling the combustion state of an air fuel mixture in each combustion chamber.

2. Description of the Related Art

In the past, there have been developed internal combustion engines that can selectively switch between low temperature combustion in which the generation of soot is suppressed by increasing the amount of burnt gas components in a combustion chamber more than the amount of burnt gas components at the time when the amount of soot generated becomes maximum due to the burnt gas components in the combustion chamber being increased, and ordinary combustion in which the amount of unburnt gas components in the combustion chamber is less than the amount of burnt gas components at the time when the amount of soot generated becomes maximum.
In such internal combustion engines, the low temperature combustion and the ordinary combustion are switched over based on a predetermined condition such as the operating condition of an engine, etc. For example, a first patent document (for example, see Japanese patent No. 3094974 (corresponding to EP0907013 and US5890360 )) discloses an internal combustion engine in which low temperature combustion is carried out when the operating condition of the engine is in a low load operating range, and ordinary combustion is carried out when the engine operating condition is in a high load operating range, but when an oxidation catalyst arranged on an exhaust passage is not activated, ordinary combustion is performed so as to suppress the discharge or emission of unburnt hydrocarbons even if the engine operating condition is in the low load operating range.
In addition, in lean burn internal combustion engines that selectively switch between the low temperature combustion and the ordinary combustion, combustion or burning of an air fuel mixture is carried out with an air fuel ratio of a mixture in the combustion chamber being held considerably higher than the stoichiometric air fuel ratio at the time of ordinary combustion, whereas combustion or burning is carried out with the air fuel ratio of the mixture in the combustion chamber being held relatively low at the time of low temperature combustion in which the amount of burnt gas components in the mixture is large with a small proportion of air.
On the other hand, when a required load (i.e., an engine load required by a driver) in the internal combustion engine is changed such as upon acceleration or deceleration of a vehicle on which the engine is mounted, the amount of fuel to be injected into the combustion chamber (hereinafter referred to as "actual fuel injection amount") is increased or decreased to an amount of injection fuel corresponding to the required load (hereinafter referred to as "required fuel injection amount"), but when the actual fuel injection amount increases rapidly, there will take place deterioration of driveability resulting from an abrupt increase in the engine torque, generation of combustion noise and misfiring, etc.. Accordingly, in internal combustion engine, the actual fuel injection amount is generally controlled to change gradually even upon a change in the required load.
Moreover, the combustion of a mixture in the combustion chamber, when carried out at a low air fuel ratio thereof such as at the time of low temperature combustion, is liable to become unstable in comparison with the case where the combustion of a mixture in the combustion chamber is carried out at a high air fuel ratio of the mixture such as at the time of ordinary combustion, and hence it is necessary to more accurately control the air fuel ratio of the mixture in the combustion chamber so as to obtain stable combustion. Therefore, in case where the required load of the engine is changed at the time of low temperature combustion, if the actual fuel injection amount is caused to change at the same change rate or speed as that at which combustion is carried out at a high air fuel ratio, there will be a fear that the combustion might become unstable, thus increasing the amount of smoke to be discharged or emitted from the engine or inviting misfiring.
Accordingly, in the past, in internal combustion engines that selectively switch between the combustion of a mixture at an air fuel ratio thereof in the combustion chamber higher than a predetermined air fuel ratio (hereinafter referred to as "high air fuel ratio combustion") and the combustion of a mixture in the combustion chamber at an air fuel ratio thereof lower than or equal to the predetermined air fuel ratio (hereinafter referred to as "low air fuel ratio combustion"), as in the internal combustion engines that selectively switches between the ordinary combustion and the low temperature combustion, when the required load is changed to increase or decrease the actual fuel injection amount such as at the time of acceleration or deceleration, fuel injection is controlled in such a manner that the change rate or speed, at which the actual fuel injection amount is gradually changed at the time of low air fuel ratio combustion, is made slower than a change rate or speed at which the actual fuel injection amount is gradually changed at the time of high air fuel ratio combustion (for example, see Japanese patent No. 3336968 (corresponding to EP99113774.6 and US6209515 )).
In this connection, note that there are following documents that are relevant to the present invention.
Japanese patent No. 3341683 (corresponding to EP99113774.6 and US6209515 ),
Japanese patent No. 3331974 (corresponding to EP99113774.6 and US6209515 ),
Japanese patent No. 3116876 (corresponding to EP0879946 and US5937639 ), and
Japanese patent application laid-open No. 2000-110670 (corresponding to EP99111890.2 and US6152118 ).
In the low air fuel ratio combustion, it is necessary to reduce the amount of air in the combustion chamber as well as to control the air fuel ratio of a mixture in the combustion chamber in a more accurate manner. Thus, an operating range of the engine in which the low air fuel ratio combustion can be carried out in a stable manner is limited to a low load operating range. Therefore, in the internal combustion engines that selectively switch between high air fuel ratio combustion and low air fuel ratio combustion, as stated above, an operating range of the engine in which low air fuel ratio combustion is carried out is decided to be a low load operating range or a part thereof, and hence a high load operating range becomes an operating range of the engine in which high air fuel ratio combustion is carried out. Also, in the past, the high air fuel ratio combustion and the low air fuel ratio combustion are selectively switched over based on the number of revolutions of the engine and the actual fuel injection amount. That is, the combustion state in the combustion chamber is switched into the low air fuel ratio combustion when the actual fuel injection amount becomes an amount of injection fuel corresponding to the low load operating range, whereas the combustion state in the combustion chamber is switched into the high air fuel ratio combustion when the actual fuel injection amount becomes an amount of injection fuel corresponding to the high load operating range.
However, when a request for accelerating the vehicle to speeds corresponding to the high load operating range, in which high air fuel ratio combustion is performed, is made while low air fuel ratio combustion is being carried out in the low load operating range for example, the rate of increase of the actual fuel injection amount is made slower at the time of low air fuel ratio combustion than that at the time of high air fuel ratio combustion so as to perform stable combustion, as stated above. As a consequence, it takes a certain period of time for the actual fuel injection amount to reach a threshold for switching the combustion in the combustion chamber between the low air fuel ratio combustion and the high air fuel ratio combustion. That is, it takes time until the combustion state is switched into the high fuel ratio combustion. Accordingly, there will be a fear that the time needed for the actual fuel injection amount to reach the required fuel injection amount might be increased, thus impairing the acceleration performance of the vehicle.

SUMMARY OF THE INVENTION

In view of the above, the present invention is intended to provide, in an internal combustion engine which selectively switches between high air fuel ratio combustion and low air fuel ratio combustion, a technique which is capable of obtaining stable combustion as well as better acceleration or deceleration performance of the engine.
In order to solve the above-mentioned problems, the present invention adopted the following solution. That is, according to the present invention, in a combustion control apparatus for an internal combustion engine in which a combustion state in a combustion chamber is selectively switched between high air fuel ratio combustion and low air fuel ratio combustion, a switching determination parameter for switching the combustion state from the low air fuel ratio combustion into the high air fuel ratio combustion is made to be a required fuel injection amount corresponding to a required load of the engine, and a switching determination parameter for switching the combustion state from the high air fuel ratio combustion into the low air fuel ratio combustion is made to be an actual fuel injection amount which is an amount of fuel to be injected into the combustion chamber each time fuel injection is performed.
More specifically, according to the present invention, there is provided a combustion control apparatus for an internal combustion engine in which a combustion state in a combustion chamber is selectively switched between high air fuel ratio combustion in which combustion is performed at an air fuel ratio of a mixture in the combustion chamber higher than a predetermined air fuel ratio, and low air fuel ratio combustion in which combustion is performed at an air fuel ratio of the mixture in the combustion chamber lower than or equal to the predetermined air fuel ratio, characterized in that
a fuel injection control part is provided which includes a required fuel injection amount calculation part that calculates a required fuel injection amount which is an amount of injection fuel corresponding to a required load of the engine and an actual fuel injection amount calculation part that calculates an actual fuel injection amount which is an amount of fuel to be injected into the combustion chamber each time fuel injection is performed, and the fuel injection control part gradually changes, upon change of the required load, the actual fuel injection amount to the required fuel injection amount, and controls the change speed of the actual fuel injection amount, which is gradually changed when the combustion state is in the low air fuel ratio combustion, to be more gradual than that when the combustion state is in the high air fuel ratio combustion,
wherein a switching determination parameter for switching the combustion state from the low air fuel ratio combustion into the high air fuel ratio combustion is made to be the required fuel injection amount, and a switching determination parameter for switching the combustion state from the high air fuel ratio combustion into the low air fuel ratio combustion is made to be the actual fuel injection amount.
Here, note that the predetermined air fuel ratio is a relatively low air fuel ratio in which when combustion is performed at an air fuel ratio lower than or equal to the predetermined air fuel ratio, combustion is liable to become unstable due to a small amount of air, and hence it is necessary to more accurately control the amount of air and the amount of fuel supplied for the combustion so as to provide good combustion. One example of the predetermined air fuel ratio is an upper limit of the air fuel ratio at the time of low temperature combustion. Another example may be a value between from the neighborhood of the stoichiometric air fuel ratio up to about an air fuel ratio (A/F) of 25. Therefore, the low air fuel ratio combustion is not limited to combustion at an air fuel ratio richer than the stoichiometric air fuel ratio.
As described above, in the past, even when the driver of a vehicle makes a request for acceleration or deceleration of the vehicle. the actual fuel injection amount is controlled so that it does not become the required fuel injection amount at once but is increased or decreased gradually. In this case, the actual fuel injection amount is changed more gradual at the time of low air fuel ratio combustion than at the time of high air fuel ratio combustion. Stated in other words, the actual fuel injection amount changes more quickly at the time of high air fuel ratio combustion than at the time of low air fuel ratio combustion.
Here, note that in case where the operating condition of the engine is in an operating range in which the low air fuel ratio combustion is performed (hereinafter referred to as "low air fuel ratio combustion range") and the combustion state is in the low air fuel ratio combustion, when an request is made for acceleration or deceleration to an operating range in which the high air fuel ratio combustion is performed (hereinafter referred to as "high air fuel ratio combustion range"), the required fuel injection amount immediately becomes an injection fuel amount corresponding to the high air fuel ratio combustion range. At this time, in the present invention, a parameter used when the combustion state is switched from the low air fuel ratio combustion into the high air fuel ratio combustion is the required fuel injection amount, so the combustion state is switched into the high air fuel ratio combustion at once. Thus, the actual fuel injection amount changes more quickly, making it possible to obtain better acceleration or deceleration performance.
On the other hand, in the present invention, a parameter used when the combustion state is switched from the high air fuel ratio combustion into the low air fuel ratio combustion is the actual fuel injection amount. Accordingly, in case where the operating condition of the engine is in the high air fuel ratio combustion range and the combustion state is in the high air fuel ratio combustion, when a request is made for acceleration or deceleration to the low air fuel ratio combustion range, the combustion state is switched into the low air fuel ratio combustion after the actual fuel injection amount has become a fuel injection amount corresponding to the low air fuel ratio combustion range, namely, after the operating condition of the engine has become the low air fuel ratio combustion range. As a result, the combustion state is by no means switched into the low air fuel ratio combustion when the operating condition of the engine is in an operating range in which the low air fuel ratio combustion is difficult to be performed, and hence more stable low air fuel ratio combustion can be carried out.
Preferably, in the present invention, in case where the combustion state is switched into the high air fuel ratio combustion when the operating condition of the engine is in a high load operating range, and switched into the low air fuel ratio combustion when the operating condition of the engine is in a low load operating range, a switching determination parameter for switching the combustion state at the time of a transient operation, such as for example acceleration, from the low load operating range into the high load operating range may be made to be the required fuel injection amount, and a switching determination parameter for switching the combustion state at the time of a transient operation, such as for example deceleration, from the high load operating range into the low load operating range may be made to be the actual fuel injection amount.
According to such an arrangement, in case where the operating condition of the engine is in the low load operating range and the combustion state is in the low air fuel ratio combustion, the combustion state is switched into the high air fuel ratio combustion at once when a request is made for acceleration to the high load operating range in which the high air fuel ratio combustion is performed. As a result, the actual fuel injection amount changes more quickly, and better acceleration performance can be obtained.
On the other hand, in case where the operating condition of the engine is in the high load operating range and the combustion state is in the high air fuel ratio combustion, when a request is made for deceleration to the low load operating range in which the low air fuel ratio combustion is performed, the combustion state is switched into the low air fuel ratio combustion after the operating condition of the engine has become the low air fuel ratio combustion range. As a result, more stable low air fuel ratio combustion can be carried out.
Preferably, in the present invention, the required fuel injection amount calculation part may calculate the required fuel injection amount based on the number of revolutions of the engine and the degree of opening of an accelerator pedal.
Preferably, in the present invention, in case where the fuel injection control part sets a variable fuel amount, which is a fuel injection amount able to be increased or decreased each time fuel injection is carried out when the actual fuel injection amount is gradually changed, separately for the low temperature combustion and the ordinary combustion, respectively, the variable fuel amount is separately set for the high air fuel ratio combustion and the low air fuel ratio combustion, respectively, and the fuel injection control part sets a variable fuel amount at the time of low air fuel ratio combustion to be smaller than a variable fuel amount at the time of high air fuel ratio combustion.
By properly setting the variable fuel amount, the actual fuel injection amount can be controlled to change gradually even when the required load is changed. Also, by setting the variable fuel amount at the time of low air fuel ratio combustion to be smaller than the variable fuel amount at the time of high air fuel ratio combustion, it is possible to control the change rate or speed of the actual fuel injection amount, which is gradually changed at the time of low air fuel ratio combustion, to be more gradual than the change speed of the actual fuel injection amount, which is gradually changed at the time of high air fuel ratio combustion. Accordingly, the air fuel ratio of the mixture in the combustion chamber can be controlled more accurately at the time of low air fuel ratio combustion, thereby making it possible to suppress an increase in the amount of smoke to be emitted and generation of misfiring.
Preferably, in the present invention, the combustion state in the combustion chamber is switched into the high air fuel ratio combustion when the operating condition of the engine is in the high load operating range, and switched into the low air fuel ratio combustion when the operating condition of the engine is in the low load operating range, as stated above. In this case, when the required load increases, the actual fuel injection amount calculation part compares an actual fuel injection amount, which was calculated upon the last fuel injection and which is added by the variable fuel amount, with the required fuel injection amount, and calculates the value of the small one as a current actual fuel injection amount, whereas when the required load decreases, the actual fuel injection amount calculation part compares the actual fuel injection amount, which was calculated upon the last fuel injection and which is subtracted by the variable fuel amount, with the required fuel injection amount, and calculates the value of the greater one as a current actual fuel injection amount.
By calculating the actual fuel injection amount each time fuel injection is performed in this manner, when the required load increases such as upon acceleration for example, the actual fuel injection amount is successively increased by the variable fuel amount each time fuel injection is performed until it reaches the required fuel injection amount, whereas when the required load decreases such as upon deceleration for example, the actual fuel injection amount is successively decreased by the variable fuel amount each time fuel injection is performed until it reaches the required fuel injection amount.
Further, in the present invention, it is preferred that when the actual fuel injection amount upon each fuel injection is calculated in the above manner, a comparison is made between the actual fuel injection amount calculated upon each fuel injection and the required fuel injection amount, and the value of the greater one may be made as a switching determination parameter for switching the combustion state.
By determining the switching determination parameter in this manner, a switching determination parameter for switching the combustion state at the time of a transient operation from the low load operating range into the high load operating range can be made to be the required fuel injection amount, and a switching determination parameter for switching the combustion state at the time of a transient operation from the high load operating range into the low load operating range can be made to be the actual fuel injection amount.
In the case of a combustion control apparatus for an internal combustion engine according to the present invention in which a combustion state is selectively switched between low temperature combustion and ordinary combustion, the low air fuel ratio combustion may be the low temperature combustion, and the high air fuel ratio combustion may be the ordinary combustion.
According to such an arrangement, better acceleration or deceleration performance can be obtained, and at the same time more stable low temperature combustion can be carried out, thus making it possible to suppress the generation of soot. Here, note that in the case of such an arrangement, it is preferred that the predetermined air fuel ratio be an upper limit of the air fuel ratio at the time of low temperature combustion.
Preferably, in the present invention, in case where the low air fuel ratio combustion is made to be the low temperature combustion, and the high air fuel ratio combustion is made to be the ordinary combustion, an operating range of the engine, in which the combustion state is controlled to be the low temperature combustion, is made as a low temperature combustion range, and an operating range of the engine, in which the combustion state is controlled to be the ordinary combustion, is made as an ordinary combustion range. In this case, by using the required fuel injection amount as a switching determination parameter for switching the combustion state from the low temperature combustion into the ordinary combustion, the combustion state is switched from the low temperature combustion into the ordinary combustion when the required fuel injection amount becomes an fuel injection amount corresponding to a threshold between the low temperature combustion range and the ordinary combustion range.
Preferably, in this case, by using the actual fuel injection amount as a switching determination parameter for switching the combustion state from the ordinary combustion into the low temperature combustion, the combustion state is switched from the ordinary combustion into the low temperature combustion when the actual fuel injection amount becomes a fuel injection amount corresponding to a threshold between the low temperature combustion range and the ordinary combustion range.
In a preferred form of the present invention, in an internal combustion engine with an exhaust gas purification catalyst, which has a property of gradually accumulating sulfur components in an exhaust gas, disposed on an exhaust passage, in order to raise the temperature of the exhaust gas purification catalyst as well as to make an ambient atmosphere a rich one for the release of the accumulated sulfur components therefrom, combustion is performed at a low air fuel ratio of a mixture in a combustion chamber to lower the air fuel ratio of the exhaust gas, and a reducing agent is further added to the exhaust passage at a location upstream of the exhaust gas purification catalyst (hereinafter this control is referred to as "sulfur poisoning regeneration control"). In such a case, the low air fuel ratio combustion may be combustion in the combustion chamber at the time of the sulfur poisoning regeneration control, or the low temperature combustion may be combustion in the combustion chamber at the time of the sulfur poisoning regeneration control,
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a view showing the schematic construction of an internal combustion engine and its combustion control apparatus according to the present invention.
Fig. 2 is a view showing a low temperature combustion range and an ordinary combustion range according to a first embodiment of the present invention.
Fig. 3 is a view explaining the switching control of the combustion state carried out by the combustion control apparatus for an internal combustion engine according to the first embodiment of the present invention.
Fig. 4 is a flow chart showing a combustion state switching control routine executed by the combustion control apparatus for an internal combustion engine according to the first embodiment of the present invention.
Fig. 5 is a view showing a low temperature combustion range, a high EGR combustion range and an ordinary combustion range according to a second embodiment of the present invention.
Fig. 6 is a view showing the flow of signals around an ECU according to the first embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a combustion control apparatus for an internal combustion engine according to the present invention will be described in detail while referring to the accompanying drawings. Here, reference will be made to the case where the present invention is applied to a diesel engine.

Fig. 1 is a view that illustrates the schematic construction of an internal combustion engine and its combustion control apparatus according to a first embodiment of the present invention.
The internal combustion engine (hereinafter also referred to simply as an engine), generally designated at reference numeral 1 as illustrated in Fig. 1, is a multi-cylinder diesel engine having four cylinders 2. The engine 1 is provided with fuel injection valves 3, one for each cylinder 2, for directly injecting fuel into a combustion chamber of each cylinder 2. The respective fuel injection valves 3 are connected with an accumulator or common rail 4 that serves to accumulate or pressurized up the fuel to a prescribed pressure. A common rail pressure sensor 4a is mounted on the common rail 4 for generating an electric signal corresponding to the pressure of the fuel in the common rail 4.
The common rail 4 is in communication with a fuel pump 6 through a fuel feed pipe 5. The pump 6 is driven to operate by the rotational torque of an output shaft or crankshaft of the engine 1 which serves as a drive source, and a pump pulley 6a mounted on an input shaft of the fuel pump 6 is operatively connected through a belt 7 with a crankshaft pulley 1 a mounted on the crankshaft of the engine 1.
In the fuel injection system as constructed in this manner, the fuel supplied to the common rail 4 by the fuel pump 6 through the fuel feed pipe 5 is accumulated or pressurized up to a predetermined pressure in the common rail 4 and distributed to the fuel injection valves 3 of the respective cylinders 2. Thereafter, when a drive current is applied to the fuel injection valves 3, the fuel injection valves 3 are operated to open so that fuel is injected from the fuel injection valves 3 into the corresponding cylinders 2, respectively.
An intake manifold 18 is connected with the engine or engine proper 1 in such a manner that it is in communication with the combustion chambers of the respective cylinders 2 through intake ports (not illustrated), respectively.
The intake manifold 18 is connected with an intake pipe 9, on which an air cleaner box 10, an air flow meter 11 for generating an electric signal corresponding to the mass of the intake air flowing in the intake pipe 9, a compressor housing 15a of a centrifugal supercharger (turbocharger) 15, an intercooler 16 and a throttle valve 13 are sequentially mounted in this order from an upstream side of the intake pipe 9. A throttle actuator 14 for driving the throttle valve 13 to open and close is mounted on the throttle valve 13, so that the flow rate of the intake air flowing in the intake pipe 9 is adjusted in accordance with the opening and closing movement of the throttle valve 13.
On the other hand, an exhaust manifold 18 is connected with the engine or engine proper 1 in such a manner that it is in communication with the combustion chambers of the respective cylinders 2 through exhaust ports 30, respectively.
The exhaust manifold 18 is connected with a turbine housing 15b of the centrifugal supercharger 15. Also, the turbine housing 15b is connected with an exhaust pipe 19. An exhaust gas purification catalyst 20 is disposed on the exhaust pipe 19 which is connected with an unillustrated muffler at a location downstream of the exhaust gas purification catalyst 20.
In addition, an exhaust gas recirculation device 40 is attached to the internal combustion engine 1 for recirculating a part of the exhaust gas flowing in the exhaust system of the engine 1 into the intake system. The exhaust gas recirculation device 40 includes an exhaust gas recirculation passage (EGR passage) 25 formed to extend from the exhaust manifold 18 through the interior of cylinder heads to a joint portion of the intake manifold 18, an exhaust gas recirculation flow regulation valve (EGR valve ) 26 in the form of an electromagnetic valve or the like for adjusting the flow rate of the exhaust gas flowing in the EGR passage 25 (hereinafter referred to as EGR gas) in proportion to the magnitude of a voltage applied thereto, and an EGR cooler 27 arranged in the EGR passage 25 at a location upstream of the EGR valve 26 for cooling the EGR gas flowing in the EGR passage 25.
In the exhaust gas recirculation device 40 constructed in this manner, when the EGR valve 26 is opened, a part of the exhaust gas flowing in the exhaust manifold 18 passes through the EGR passage 25 and flows into the joint portion of the intake manifold 18 while being cooled by the EGR cooler 27. The EGR gas flowing into the intake manifold 18 forms into an air fuel mixture while being mixed with fresh air coming from the upstream side of the intake manifold 18, and is distributed to the combustion chambers of each cylinder 2.
Here, note that when the EGR gas containing inert gas components, which do not combust or burn on their own and which have heat absorbing or endothermic property as in the case of water (H₂O), carbon dioxide (CO₂) or the like. Therefore, when it is mixed with an air fuel mixture, the combustion temperature of the mixture is lowered, thus suppressing the amount of generation of nitrogen oxides (NOx).
An electronic control unit (ECU) 35 for controlling the engine 1 is provided in conjunction with the engine 1 as constructed in the above manner. This ECU 35 serves to control the operating conditions of the engine 1 in accordance with the operating state of the vehicle and driver's requirements.
Various kinds of sensors such as the common rail pressure sensor 4a, the air flow meter 11, an intake pipe pressure sensor 17 for sensing the pressure of intake air in the intake pipe 9, a crank position sensor 33 for sensing the rotational angle or position of the crankshaft, an accelerator opening sensor 36 for sensing the degree of opening or depression of an accelerator pedal, etc., are connected to the ECU 35 through electric wiring, so that the output signals of these sensors are input to the ECU 35.
On the other hand, the fuel injection valves 3, the throttle actuator 14, the EGR valve 26 and the like are also connected to the ECU 35 through electric wiring, so that they can be controlled by the ECU 35.
The ECU 35 includes a CPU, a ROM, a RAM and the like, and calculates, for example, the number of revolutions of the engine based on time intervals between pulses in the output signal of the crank position sensor 33, as well as the amount of the intake air supplied to each combustion chamber based on the output signals of the air flow meter 11 and the intake pipe pressure sensor 17.
Here, note that the internal combustion engine 1 according to this embodiment operates to selectively switch between a low temperature combustion state (corresponding to the low air fuel ratio combustion according to the present invention), in which the amount of generation of soot is suppressed by making, under the control of the exhaust gas recirculation device 40, the amount of the EGR gas (corresponding to the burnt gas components in the present invention) supplied to each combustion chamber greater than an amount of EGR gas at the time when the amount of generation of soot, which increases in accordance with the increasing amount of the EGR gas supplied to each combustion chamber, becomes maximum in a state of fuel injection timing, at which fuel is injected into each combustion chamber, being fixed, and an ordinary combustion state (corresponding to the high air fuel ratio combustion according to the present invention), in which the EGR gas in each combustion chamber is less than the above-mentioned amount of EGR gas with which the amount of generation of soot becomes maximum.
Since combustion is liable to become unstable in the low temperature combustion because of the amount of the EGR gas supplied to each combustion chamber being increased so as to reduce the amount of intake air therein, it is necessary to control the air fuel ratio of the mixture in each combustion chamber in a more accurate manner. Therefore, an operating range of the engine in which low temperature combustion can be performed in a stable manner is limited to the low load operating range. Accordingly, in the internal combustion engine 1 according to this embodiment, as shown in Fig. 2, a first operating range of the engine in which the low temperature combustion is performed (hereinafter referred to as a low temperature combustion range) and a second operating range of the engine in which the ordinary combustion is performed (hereinafter referred to as an ordinary combustion range) are respectively set based on the number of revolutions and the engine load, and the low temperature combustion range is set in the low load operating range.
Moreover, at the time of ordinary combustion, combustion is carried out at an air fuel ratio of the mixture in each combustion chamber considerably higher than the stoichiometric air fuel ratio, whereas at the time of low temperature combustion in which the amount of EGR gas is large and the amount of intake air is small, as stated above, combustion is carried out at an air fuel ratio of the mixture in each combustion chamber lower than that at the time of ordinary combustion.
Next, reference will be made to the fuel injection control in the internal combustion engine 1 according to this embodiment.
In the internal combustion engine 1 according to this embodiment, when the required load of the engine is changed as in the case of acceleration or deceleration of the vehicle, the actual fuel injection amount is controlled to change gradually to reach the required fuel injection amount so as to avoid generation of defects such as deterioration of driveability due to a rapid change in the engine torque, combustion noise and misfiring, etc..
Further, a variable amount of injection fuel (hereinafter referred to as a variable fuel amount), which is able to be increased or decreased each time fuel injection is carried out, is set separately for the low temperature combustion and the ordinary combustion, so that the change of the actual fuel injection amount becomes more gradual at the time of the low temperature combustion than at the time of the ordinary combustion. That is, this variable fuel amount is set smaller in the low temperature combustion than in the ordinary combustion, and the amount of injection fuel is controlled in a different manner at the time of low temperature combustion and at the time of ordinary combustion, based on the required fuel injection amount, the variable fuel amount, the number of revolutions of the engine, etc.
The reason for this is as follows. In the low temperature combustion, combustion is performed at an air fuel ratio of the mixture in each combustion chamber lower than that in the ordinary combustion, as stated above, and hence is liable to become unstable as compared with that at the time of ordinary combustion. Thus, there is a fear that if the actual fuel injection amount is changed at the same speed or rate as that at the time of ordinary combustion, the amount of smoke to be emitted from the engine might be increased and/or misfiring might be induced.
Now, reference will be made to the combustion state switching control operation of the combustion control apparatus for an internal combustion engine according to this embodiment while referring to Fig. 3.
When a request is made by the driver for accelerating the engine speed up to the ordinary combustion range during the low temperature combustion of the engine so that the degree of opening of the accelerator pedal detected by the accelerator opening sensor 36 increases, the required fuel injection amount eqgov inevitably increases at once, as shown by the fuel injection amount indicated at a solid line in Fig. 3. As referred to above, however, the actual fuel injection amount eqfin does not immediately become the required fuel injection amount eqgov but gradually increases, as shown by the fuel injection amount indicated at a broken line in Fig. 3.
In case where the actual fuel injection amount eqfin is used as a determination parameter for switching the combustion state in each combustion chamber from the low temperature combustion into the ordinary combustion, the combustion state is switched from the low temperature combustion into the ordinary combustion when the actual fuel injection amount eqfin becomes a fuel injection amount (i.e., indicated by an alternate long and short dash line in Fig. 3) corresponding to a threshold between the low temperature combustion range and the ordinary combustion range, as shown by the combustion state indicated at a broken line in Fig. 3. In contrast to this, in the combustion switching control according to this embodiment, the required fuel injection amount eqgov is used as a determination parameter for switching the combustion state in each combustion chamber from the low temperature combustion into the ordinary combustion. In this case, the combustion state in each combustion chamber is switched from the low temperature combustion into the ordinary combustion when the required fuel injection amount eqgov becomes the fuel injection amount corresponding to the threshold between the low temperature combustion range and the ordinary combustion range, as shown by the combustion state indicated at a solid line in Fig. 3. In other words, according to the combustion switching control of this embodiment, the combustion state can be switched into the ordinary combustion more early at the time of acceleration.
On the other hand, when the degree of opening of the accelerator pedal detected by the accelerator opening sensor 36 decreases according to a driver's request for decelerating the engine speed up to the low temperature combustion range while the internal combustion engine 1 is performing the ordinary combustion, the required fuel injection amount eqgov inevitably decreases at once. In this case, however, the actual fuel injection amount eqfin does not become the required fuel injection amount eqgov at once but gradually decreases, as stated above. At this time, in the combustion control apparatus according to this embodiment, the combustion is switched from the ordinary combustion into the low temperature combustion when the actual fuel injection amount eqfin becomes the fuel injection amount corresponding to the threshold between the low temperature combustion range and the ordinary combustion range.
That is, in the combustion control apparatus for an internal combustion engine according to this embodiment, a switching determination parameter used when the combustion state is switched from the low temperature combustion into the ordinary combustion, namely a switching determination parameter used upon switching of the combustion state during acceleration, is the required fuel injection amount eqgov, whereas a switching determination parameter used when the combustion state is switched from the ordinary combustion into the low temperature combustion, namely a switching determination parameter used upon switching of the combustion state during deceleration is the actual fuel injection amount eqfin.
According to such combustion switching control, at the time of acceleration, the combustion state is switched into the ordinary combustion more early so that the actual fuel injection amount can be increased more quickly, thereby making it possible to provide better acceleration performance.
On the other hand, at the time of deceleration, the combustion state is switched into the low temperature combustion after the actual fuel injection amount has become a fuel injection amount corresponding to the low temperature combustion range, namely, after the operating condition of the internal combustion engine 1 has been changed into the low temperature combustion range, so that more stable low temperature combustion can be carried out, thus making it possible to suppress the emission of smoke, misfiring and deterioration of combustion noise.
Next, reference will be made to a combustion state switching control routine executed by the combustion control apparatus for an internal combustion engine according to this embodiment while referring to a flow chart shown in Fig. 4.
The flow chart in Fig. 4 illustrates the combustion state switching control routine according to this embodiment. This combustion state switching control routine is executed by the ECU 35 each time fuel is injected into each combustion chamber, and it is stored in advance in the ROM of the ECU 35.
In this routine, first in step S101, the ECU 35 detects whether the current combustion state is the low temperature combustion or the ordinary combustion. In this connection, note that the combustion state at this time may be detected from the result of the last execution of this routine.
Then, the routine or control flow goes to step S102 where the ECU 35 calculates the required fuel injection amount eqgov based on the number of revolutions N of the engine and the degree of opening D of the accelerator pedal.
Thereafter, the control flow proceeds to step S103 where the ECU 35 calculates a variable fuel amount Δ Q corresponding to the combustion state detected in step S101, and then it advances to step S104.
When in step S104, the degree of opening D of the accelerator pedal increases, i.e., when the vehicle or engine is accelerated, the ECU 35 compares an actual fuel injection amount eqfin', which was calculated when this routine was last executed and which is added by the variable fuel amount Δ Q calculated in step S103, with the required fuel injection amount eqgov calculated in step S102, and calculates the value of the small one as a current actual fuel injection amount eqfin. On the other hand, when in step S104, the degree of opening D of the accelerator pedal decreases, i.e., when the vehicle or engine is decelerated, the ECU 35 compares the actual fuel injection amount eqfin', which was calculated when this routine was last executed and which is subtracted by the variable fuel amount Δ Q calculated in step S103, with the required fuel injection amount eqgov calculated in step S102, and calculates the value of the greater one as a current actual fuel injection amount eqfin.
In other words, at the time of acceleration, the actual fuel injection amount eqfin is successively increased by the variable fuel amount Δ Q each time fuel injection is performed until it reaches the required fuel injection amount eqgov. On the other hand, at the time of deceleration, the actual fuel injection amount eqfin is successively decreased by the variable fuel amount Δ Q each time fuel injection is performed until it reaches the required fuel injection amount eqgov.
Subsequently, the control flow advances to step S105 where the ECU 35 makes a comparison between the required fuel injection amount eqgov calculated in step S102 and the actual fuel injection amount eqfin calculated in step S104, and calculates the value of the greater one as a determination fuel injection amount eqmdcb, which becomes a combustion state switching determination parameter.
Then, the control flow proceeds to step S106 where the ECU 35 determines a combustion state into which the current combustion is to be switched, based on the determination fuel injection amount eqmdcb and the number of revolutions N of the engine calculated in step S105, after which the control flow goes to step S107.
In step S107, the ECU 35 switches the combustion state in each combustion chamber into the combustion state determined in step S106, and then completes the execution of this routine.
According to this combustion state switching control routine, the determination fuel injection amount eqmdcb at the time of acceleration becomes the required fuel injection amount eqgov, and the determination fuel injection amount eqmdcb at the time of deceleration becomes the actual fuel injection amount eqfin. That is, at the time of acceleration, the combustion state is switched over by using the required fuel injection amount eqgov as a switching determination parameter, whereas at the time of deceleration, the combustion state is switched over by using the actual fuel injection amount eqfin as a switching determination parameter.
Here, reference will be made to the flow of signals around the ECU 35 in this embodiment while referring to Fig. 6. In Fig. 6, broken line arrows (1) and (2) represent the flow of signals from the crank position sensor 33 and the accelerator opening sensor 36 to the ECU 35, respectively, and broken line arrow (3) represents the flow of a signal from the ECU 35 to the fuel injection valves 3.
A fuel injection amount control program 101 for calculating the amount of fuel to be injected into each combustion chamber is stored in the ECU 35, and includes a required fuel injection amount calculation program 102 for calculating the required fuel injection amount eqgov and an actual fuel injection amount calculation program 103 for calculating the actual injection fuel amount eqfin.
By executing the required fuel injection amount calculation program 102, the required injection fuel amount eqgov is calculated based on the number of revolutions N of the engine and the degree of opening D of the accelerator pedal, and by executing the actual fuel injection amount calculation program 103, the actual fuel injection amount eqfin is calculated each time fuel injection is carried out. Also, by executing the fuel injection control program 101, fuel injections by the fuel injection valves 3 are controlled based on the required fuel injection amount eqgov and the actual fuel injection amount eqfin calculated by the calculation programs 102, 103, respectively. That is, the required fuel injection amount calculation program 102 constitutes a required fuel injection amount calculation part according to the present invention, and the actual fuel injection amount calculation program 103 constitutes an actual fuel injection amount calculation part according to the present invention. In addition, the fuel injection amount control program 101 constitutes a fuel injection amount control part according to the present invention.

(MODIFICATION)

In the above-mentioned embodiment, reference has been made to the case where the combustion state in each combustion chamber is switched by acceleration from the low temperature combustion into the ordinary combustion, whereas it is switched by deceleration from the ordinary combustion into the low temperature combustion. However, there may be a case in which a part of the low load operating range is made to be a low temperature operating range, and another part of the low load operating range, which is lower in load than this low temperature operating range, is made to be an ordinary combustion range. In this case, the combustion state can be occasionally switched by deceleration from the low temperature combustion into the ordinary combustion, but at such a time, too, the required fuel injection amount is made to be a switching determination parameter used when the combustion state is switched from the low temperature combustion into the ordinary combustion, similar to the above-mentioned case. As a result, the actual fuel injection amount can be decreased more quickly at the time of deceleration in which the combustion state is switched from the low temperature combustion into the ordinary combustion. Accordingly, better deceleration performance can be obtained.

Now, reference will be made to a combustion control apparatus for an internal combustion engine according to a second embodiment of the present invention.
The construction of the internal combustion engine and its combustion control apparatus according to this second embodiment is similar to the one shown in Fig. 1 as explained in the above-mentioned first embodiment.
In the internal combustion engine 1 of this second embodiment, combustion is selectively switched among the low temperature combustion, the ordinary combustion, and high EGR combustion where the amount of the EGR gas supplied to each combustion chamber by the exhaust gas recirculation device 40 is less than an amount of EGR gas when the amount of soot generated becomes maximum and where the amount of EGR gas becomes substantially maximum among EGR gas amounts in which the amount of soot generated is within an allowable range.
In the high EGR combustion, the amount of the EGR gas supplied to each combustion chamber is less than that at the time of low temperature combustion, but greater than that at the time of ordinary combustion. As a result, in the high EGR combustion, it is necessary to make the amount of the intake air supplied to each combustion chamber smaller than that at the time of ordinary combustion. Accordingly, it is difficult to perform the high EGR combustion in a stable manner in the high load operating range. In order to cope with such a situation, in the internal combustion engine 1 in this embodiment, the low temperature combustion range is set to be in the low load operating range as in the above-mentioned first embodiment, but a high EGR combustion range, which is an operating range of the engine where the high EGR combustion is performed, is set to be in a medium load operating range, as shown in Fig. 5.
In addition, since in the high EGR combustion, the amount of the EGR gas supplied to each combustion chamber is large and the amount of the intake air supplied thereto is small, in comparison with those in the ordinary combustion, as stated above, the air fuel ratio of the mixture in each combustion chamber is lower than that in the ordinary combustion, as in the low temperature combustion, and hence combustion is liable to become unstable. Thus, in the high EGR combustion, it is necessary to more accurately control the air fuel ratio of the mixture in each combustion chamber so as to obtain stable combustion.
In the internal combustion engine 1 of this second embodiment, when the required load of the engine is changed as in the case of acceleration or deceleration of the vehicle, the actual fuel injection amount is controlled to change gradually to reach the required fuel injection amount so as to avoid generation of defects such as deterioration of driveability due to a rapid change in the engine torque, combustion noise and misfiring, etc., as in the case of the above-mentioned first embodiment.
Further, as stated above, in the high EGR combustion, combustion is liable to become unstable as compared with that at the time of ordinary combustion, and there is a fear that if the actual fuel injection amount is changed at the same speed or rate as that at the time of ordinary combustion, the amount of smoke to be emitted from the engine might be increased and/or misfiring might be induced. Therefore, the variable fuel amount is set separately for the high EGR combustion and the ordinary combustion, respectively, so that the change of the actual fuel injection amount becomes more gradual at the time of high EGR combustion than at the time of ordinary combustion. That is, similar to the low temperature combustion, a variable fuel amount in the high EGR combustion is set to a value smaller than the variable fuel amount in the ordinary combustion. Thus, the amount of injection fuel is controlled in a different manner at the time of high EGR combustion and at the time of ordinary combustion, based on the required fuel injection amount, the variable fuel amount, the number of revolutions of the engine, etc.
In the combustion control apparatus for an internal combustion engine according to this embodiment, a switching determination parameter used when the combustion state is switched from the high EGR combustion into the ordinary combustion is made to be the required fuel injection amount, as when switched from the low temperature combustion into the ordinary combustion in the first embodiment, whereas a switching determination parameter used when the combustion state is switched from the ordinary combustion into the high EGR combustion is made to be the actual fuel injection amount, as when switched from the ordinary combustion into the low temperature combustion in the first embodiment. That is, a switching determination parameter used for switching the combustion state at the time of acceleration is the actual fuel injection amount, whereas a switching determination parameter used for switching the combustion state at the time of deceleration is the actual fuel injection amount.
According to such combustion switching control, at the time of acceleration, the combustion state is switched into the ordinary combustion more early so that the actual fuel injection amount can be increased more quickly, thereby making it possible to provide better acceleration performance. On the other hand, at the time of deceleration, the combustion state is switched into the high EGR combustion after the actual fuel injection amount has become a fuel injection amount corresponding to the high EGR combustion range, namely, after the operating condition of the internal combustion engine 1 has been changed into the high EGR combustion range, so that more stable high EGR combustion can be carried out, thus making it possible to suppress the emission of smoke, misfiring and deterioration of combustion noise.
Although in the above description, the internal combustion engine 1 is a multi-cylinder internal combustion engine, the present invention is of course applied to a single-cylinder internal combustion engine having a single cylinder, too.
According to a combustion control apparatus for an internal combustion engine constructed in accordance with the present invention, the internal combustion engine, which selectively switches between high air fuel ratio combustion and low air fuel ratio combustion, can perform stable combustion and at the same time provide better acceleration or deceleration performance.
While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.
There is provided a combustion control apparatus which serves to enable the
There is provided a combustion control apparatus which serves to enable the engine to perform stable combustion and provide better acceleration or deceleration performance. Specifically, a switching determination parameter for switching from low air fuel ratio combustion into high air fuel ratio combustion is made to be a required fuel injection amount (eqgov), which is an amount of fuel injected into the combustion chamber corresponding to an engine load required by a driver. A switching determination parameter for switching from the high air fuel ratio combustion into the low air fuel ratio combustion is made to be an actual fuel injection amount (eqfin), which is an amount of fuel injected into the combustion chamber upon each fuel injection.

Claims

A combustion control apparatus for an internal combustion engine in which a combustion state in a combustion chamber is selectively switched between high air fuel ratio combustion in which combustion is performed at an air fuel ratio of a mixture in said combustion chamber higher than a predetermined air fuel ratio, and low air fuel ratio combustion in which combustion is performed at an air fuel ratio of the mixture in said combustion chamber lower than or equal to said predetermined air fuel ratio, characterized in that
a fuel injection control part (101) is provided which includes a required fuel injection amount calculation part (102) that calculates a required fuel injection amount (eqgov) which is an amount of injection fuel corresponding to a required load of said engine (1) and an actual fuel injection amount calculation part (103) that calculates an actual fuel injection amount (eqfin) which is an amount of fuel to be injected into said combustion chamber each time fuel injection is performed, and said fuel injection control part (101) gradually changes, upon change of said required load, said actual fuel injection amount (eqfin) to said required fuel injection amount (eqgov), and controls the change speed of said actual fuel injection amount (eqfin), which is gradually changed when said combustion state is in said low air fuel ratio combustion, to be more gradual than that when said combustion state is in said high air fuel ratio combustion,
wherein a switching determination parameter for switching said combustion state from the low air fuel ratio combustion into said high air fuel ratio combustion is made to be said required fuel injection amount (eqgov), and a switching determination parameter for switching said combustion state from said high air fuel ratio combustion into said low air fuel ratio combustion is made to be said actual fuel injection amount (eqfin).
The combustion control apparatus for an internal combustion engine as set forth in claim 1, characterized in that
the combustion state in said combustion chamber is switched into said high air fuel ratio combustion when the operating condition of said internal combustion engine (1) is in a high load operating range, and switched into said low air fuel ratio combustion when the operating condition of said internal combustion engine (1) is in low load operating range;
a switching determination parameter for switching said combustion state at the time of a transient operation from said low load operating range into said high load operating range is made to be said required fuel injection amount (eqgov); and
a switching determination parameter for switching said combustion state at the time of a transient operation from said high load operating range into said low load operating range is made to be said actual fuel injection amount (eqfin).
The combustion control apparatus for an internal combustion engine as set forth in claim 1 or 2, characterized in that said required fuel injection amount calculation part (102) calculates said required fuel injection amount (eqgov) based on the number of revolutions (N) of said engine (1) and the degree of opening (D) of an accelerator pedal.
The combustion control apparatus for an internal combustion engine as set forth in claim 1 or 2, characterized in that said fuel injection control part (101) sets a variable fuel amount (ΔQ), which is a fuel injection amount able to be increased or decreased each time fuel injection is carried out when said actual fuel injection amount (eqfin) is gradually changed, separately for said low temperature combustion and said ordinary combustion, respectively, and said fuel injection control part (101) further sets said variable fuel amount (Δ Q) at the time of low air fuel ratio combustion to be smaller than said variable fuel amount (Δ Q) at the time of high air fuel ratio combustion.
The combustion control apparatus for an internal combustion engine as set forth in claim 2, characterized in that
said fuel injection control part (101) sets a variable fuel amount (Δ Q), which is a fuel injection amount able to be increased or decreased each time fuel injection is carried out when said actual fuel injection amount (eqfin) is gradually changed, separately for said low temperature combustion and said ordinary combustion, respectively, and said fuel injection control part (101) sets said variable fuel amount (Δ Q) at the time of said low air fuel ratio combustion to be smaller than said variable fuel amount (Δ Q) at the time of said high air fuel ratio combustion;
when said required load increases, said actual fuel injection amount calculation part (103) compares an actual fuel injection amount (eqfin'), which was calculated upon the last fuel injection and which is added by said variable fuel amount (Δ Q), with the required fuel injection amount (eqgov), and calculates the value of the small one as a current actual fuel injection amount (eqfin); and
when said required load decreases, said actual fuel injection amount calculation part (103) compares the actual fuel injection amount (eqfin'), which was calculated upon the last fuel injection and which is subtracted by said variable fuel amount (ΔQ), with the required fuel injection amount (eqgov), and calculates the value of the greater one as a current actual fuel injection amount (eqfin).
The combustion control apparatus for an internal combustion engine as set forth in claim 5, characterized in that a comparison is made between said current actual fuel injection amount (eqfin) and said required fuel injection amount (eqgov), and the value of the greater one is made to be a switching determination parameter for switching said combustion state.
The combustion control apparatus for an internal combustion engine as set forth in claim 1 or 2, characterized in that said internal combustion engine (1) selectively switches between low temperature combustion in which generation of soot is suppressed by increasing the amount of burnt gas components in said combustion chamber more than the amount of burnt gas components therein at the time when the amount of soot generated becomes maximum due to the burnt gas components in said combustion chamber being increased, and ordinary combustion in which the amount of unburnt gas components in said combustion chamber is less than the amount of burnt gas components at the time when the amount of soot generated becomes maximum, and makes said low air fuel ratio combustion as said low temperature combustion, and said high air fuel ratio combustion as said ordinary combustion.
The combustion control apparatus for an internal combustion engine as set forth in claim 7, characterized in that said predetermined air fuel ratio is an upper limit of an air fuel ratio at the time of low temperature combustion.
The combustion control apparatus for an internal combustion engine as set forth in claim 7, characterized in that
an operating range of said internal combustion engine (1) in which said combustion state is made to be said low temperature combustion is made as a low temperature combustion range, and an operating range of said internal combustion engine (1) in which said combustion state is made to be said ordinary combustion is made as an ordinary combustion range; and
by using said required fuel injection amount (eqgov) as a switching determination parameter for switching said combustion state from said low temperature combustion into said ordinary combustion, said combustion state is switched from said low temperature combustion into said ordinary combustion when said required fuel injection amount (eqgov) becomes an fuel injection amount corresponding to a threshold between said low temperature combustion range and said ordinary combustion range.
The combustion control apparatus for an internal combustion engine as set forth in claim 7, characterized in that
an operating range of said internal combustion engine (1) in which said combustion state is made to be said low temperature combustion is made as a low temperature combustion range, and an operating range of said internal combustion engine (1) in which said combustion state is made to be said ordinary combustion is made as an ordinary combustion range; and
by using said actual fuel injection amount (eqfin) as a switching determination parameter for switching said combustion state from said ordinary combustion into said low temperature combustion, said combustion state is switched from said ordinary combustion into said low temperature combustion when said actual fuel injection amount (eqfin) becomes a fuel injection amount corresponding to a threshold between said low temperature combustion range and said ordinary combustion range.
The combustion control apparatus for an internal combustion engine as set forth in claim 1 or 2, further characterized by an exhaust gas purification catalyst (20) disposed in an exhaust passage (19) of said internal combustion engine (1) and having a property of gradually accumulating sulfur components in an exhaust gas discharged from said engine (1),
wherein said low air fuel ratio combustion is combustion that is performed at the time of sulfur poisoning regeneration control to decrease the air fuel ratio of said exhaust gas due to combustion at a lowered air fuel ratio of the mixture in said combustion chamber so as to raise the temperature of said exhaust gas purification catalyst (20) and make an ambient atmosphere a rich one for the release of the accumulated sulfur components.
The combustion control apparatus for an internal combustion engine as set forth in claim 7, further characterized by an exhaust gas purification catalyst (20) disposed in an exhaust passage (19) of said internal combustion engine (1) and having a property of gradually accumulating sulfur components in an exhaust gas discharged from said engine (1),
wherein said low temperature combustion is combustion that is performed at the time of sulfur poisoning regeneration control to decrease the air fuel ratio of said exhaust gas due to combustion at a lowered air fuel ratio of the mixture in said combustion chamber so as to raise the temperature of said exhaust gas purification catalyst (20) and make an ambient atmosphere a rich one for the release of the accumulated sulfur components.