JP2002089321A - Combustion control device in cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a using range of a stratified combustion by determining an operating zone where the stratified combustion is carried out depending on fuel volatility. SOLUTION: Fuel volatility is discriminated from a knock control amount, a condition for performing the stratified combustion is previously stored in a map for every discriminated volatility, and an actual operating condition is compared with the operating condition read out from the map selected according to the fuel volatility to changeover between the stratified combustion and a homogeneous combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus for a direct injection internal combustion engine having a function of setting a combustion mode to either stratified combustion or homogeneous combustion based on an engine operating state. .

[0002]

2. Description of the Related Art Conventionally, a direct injection internal combustion engine of the type in which fuel is directly injected into a combustion chamber is known. In such a direct injection internal combustion engine, for example, Japanese Patent Application Laid-Open No. 2-16
As disclosed in Japanese Patent No. 9834, the combustion mode is switched between stratified combustion and homogeneous combustion based on engine operating conditions such as engine speed and engine load. That is, when the engine operation state is in the low-speed low-load region, stratified charge combustion is set as the combustion mode, and fuel is injected and supplied during the compression stroke. The fuel injected and supplied into the combustion chamber in this manner is collected around the ignition plug by using the rise of the piston and reflection on the top surface of the piston, and a combustible mixture layer having a higher fuel concentration than the surroundings is formed around the ignition plug. It is formed. Then, the ignition plug ignites the formed combustible air-fuel mixture to perform stratified combustion that enables combustion in a state in which the mixture in the entire combustion chamber is significantly leaner than the stoichiometric air-fuel ratio. Is done. Further, in the engine operating state where the stratified combustion in the high rotation region or the high load region cannot be favorably performed, homogeneous combustion is set as the combustion mode, and fuel is injected and supplied during the intake stroke. The fuel injected and supplied into the combustion chamber in this manner is diffused throughout the combustion chamber, and a mixture having a substantially uniform fuel concentration is formed throughout the combustion chamber. Then, the ignition plug ignites the formed air-fuel mixture to perform homogeneous combustion.

[0003]

In order to further improve fuel efficiency, it is preferable to increase the frequency of stratified charge combustion as much as possible. Therefore, the engine operation range in which stratified combustion is performed may be expanded within a range that does not cause deterioration of combustion, but in this case, the following disadvantages cannot be ignored.

The following are conceivable reasons why the above-described stratified combustion cannot be performed well. That is, the fuel injected and supplied into the combustion chamber during the compression stroke is collected around the ignition plug by using the rise of the piston and the reflection on the top surface of the piston. A layer is formed. However, a predetermined time is required until a good combustible gas mixture is formed with the vaporization of the fuel. As a result, a high rotation region in which the time from fuel injection to ignition is short, and a fuel injection amount In a high-load region where the amount of air-fuel ratio increases, it is considered that sufficient time for forming a combustible air-fuel mixture layer cannot be secured, and stratified charge combustion cannot be performed well.
In addition, the properties of fuels used in the market vary, and the time required for the fuel to evaporate and form a good combustible mixture varies greatly depending on the fuel volatility. For this reason,
Even if the engine operation range in which stratified combustion is performed as wide as possible without causing deterioration of the combustion is set on the premise that fuel with low volatility is used, if fuel with high volatility is used, Since the time required to vaporize the gas and form a good combustible mixture layer is short, the engine operation region for performing the stratified combustion is narrowed more than necessary, and the fuel efficiency is deteriorated. Conversely, if the engine operation region is set to execute stratified combustion as wide as possible within a range that does not cause deterioration of the combustion on the assumption that a highly volatile fuel is used, if a low volatile fuel is used, Since the time required for the fuel to evaporate and form a good combustible air-fuel mixture is long, the engine operation range for executing the stratified combustion is unnecessarily widened, resulting in deterioration of combustion. The present invention has been made in view of such a conventional situation, and in-cylinder injection that can maximize the fuel efficiency by setting the combustion mode to either stratified combustion or homogeneous combustion in accordance with fuel volatility. It is an object of the present invention to provide a combustion control device for an internal combustion engine.

[0005]

[0006]

The structure for achieving the above object and the operation and effect thereof will be described below. In the invention described in claim 1, based on the engine operating state,
In a combustion control apparatus for an in-cylinder injection type internal combustion engine, wherein a combustion mode is set to one of stratified combustion and homogeneous combustion, a fuel volatility determining means for determining the volatility of fuel supplied to the in-cylinder injection type internal combustion engine; When the fuel volatility is determined to be high by the fuel volatility determining means, the stratified combustion region is changed to expand the operation region in which the stratified combustion is performed, when the volatility of the fuel is determined to be low. Means. According to such a configuration, the operation region in which stratified combustion is performed can be set in accordance with the volatility of the fuel, so that the volatility is lower than in the case where the stratified combustion region is uniformly determined assuming the use of a fuel with poor volatility. The stratified combustion region when a good fuel is used is expanded, and the frequency of stratified combustion increases, so that the fuel efficiency can be improved. Also, compared to the case where a stratified combustion region is determined uniformly assuming the use of a highly volatile fuel, there is a concern that deterioration in combustion in a high-speed region or a high-load region, etc., may be caused when a fuel with a low volatility is used. It is possible to prevent stratified combustion from being performed in the operating region where the combustion is performed.

[0007] In the invention described in claim 2, in addition to the structure of claim 1, the stratified combustion region changing means determines whether the fuel volatility is high by the fuel volatility determining means. When it is determined that the volatility is low, the operation region in which the stratified combustion is performed is extended to the high rotation side. According to such a configuration, the engine speed at which the stratified combustion is changed to the homogeneous combustion is not set uniformly assuming the use of a fuel with low volatility, but the volatilization rate is lower than when the fuel with low volatility is used. If you use a good fuel,
Since the operation region in which the stratified combustion is performed up to a higher engine speed can be set, the frequency of the stratified combustion increases, which is effective in improving the fuel efficiency. Also, compared to the case where the engine speed is changed to uniformly change the stratified combustion to the homogeneous combustion assuming the use of a highly volatile fuel, the deterioration of combustion in the high speed It is possible to prevent stratified combustion from being performed in an operation region where is concerned.

According to the third aspect of the present invention, in addition to the configuration of the first or second aspect, the stratified combustion region changing means determines whether or not the fuel volatility is determined to be high by the fuel volatility determining means. When the volatility of the fuel is determined to be low, the operation region in which the stratified combustion is performed is expanded to the high load side. According to such a configuration, the engine load for changing the stratified combustion to the homogeneous combustion is not set uniformly assuming the use of a fuel having low volatility, but the volatility of the engine is lower than when the fuel having low volatility is used. When a fuel with good fuel economy is used, the operation region in which the stratified combustion is performed up to a higher load can be set, so that the frequency of the stratified combustion is increased and the fuel efficiency can be improved. Also, compared to the case of determining the engine load to uniformly change stratified combustion to homogeneous combustion assuming the use of fuel with good volatility, when fuel with poor volatility is used, combustion deterioration in the high load region is worse. The stratified combustion can be prevented from being performed in the operating region in which there is a concern.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 2 is a configuration diagram showing a combustion control device applied to the present embodiment and a direct injection internal combustion engine 10 to which the device is applied. As shown in FIG. 2, the engine 10 includes a cylinder head 11 and
And a cylinder block 13 formed with a plurality of cylinders 12 (only one of which is shown in FIG. 2). A piston 14 is provided in each cylinder 12 so as to be able to reciprocate. A combustion chamber 15 is defined by the piston 14, the inner peripheral wall surface of the cylinder 12, and the cylinder head 11.

Each cylinder 12 has an injector 20 for directly injecting fuel into the combustion chamber 15 and a spark plug 21 for igniting a mixture of fuel and air injected from the injector 20. Is provided in correspondence with. This ignition plug 21 is an ignition coil 22
The ignition timing is adjusted by an igniter 23 incorporated in the ignition coil 22.

The engine 10 is provided with various sensors for detecting the operating state of the engine. A crank angle sensor 30 is disposed at a position separated by a predetermined distance from a rotor provided at the tip of the crankshaft. The crank angle sensor 30 is moved every time a tooth profile engraved on the outer peripheral surface of the rotor is passed as the rotor rotates. Outputs a pulse signal. Further, a cam angle sensor 31 is disposed at a position separated from the rotor provided on the cam shaft by a predetermined distance, and the cam angle sensor 31 is moved every time a tooth profile engraved on the outer peripheral surface of the rotor with the rotation of the rotor passes. Outputs a pulse signal. An accelerator sensor 32 is installed near the accelerator pedal, and the accelerator sensor 3
2 outputs a signal corresponding to the accelerator opening ACCP. A knock sensor 33 is disposed in the cylinder block 13, and the knock sensor 33 generates a signal (knock signal KCS) corresponding to the magnitude of knock generated in the internal combustion engine 10.
Is output. Further, a water temperature sensor 34 is disposed in the cylinder block 13, and a cooling water temperature TH of the internal combustion engine 10 is provided.
Outputs a signal corresponding to W.

The signals from these sensors 30 to 34 are sent to an electronic control unit 40. The electronic control unit 40 calculates the crank angle position based on the pulse signals from the crank angle sensor 30 and the cam angle sensor 31, and calculates the engine speed NE. The electronic control unit 40 also controls fuel injection timing, fuel injection amount control, ignition timing control, etc., based on output values from various sensors and according to map values, control constants, and control programs stored in the memory 41 in advance. Of various controls.

The in-cylinder injection type internal combustion engine 10 of this embodiment is controlled by the electronic control unit 40 to switch its combustion mode between stratified combustion and homogeneous combustion.

In stratified charge combustion, fuel is injected from the injector 20 during the compression stroke, and the pan 1
It collides with 6, is reflected and rises. Thereafter, with the rise of the piston, the mixture reaches the vicinity of the spark plug 21 while forming a mixture. At the time of arrival, an air-fuel mixture near the stoichiometric air-fuel ratio (A / F = 14.5) is formed near the ignition plug,
The periphery is in a state of only air, and the entire combustion chamber is leaner than the stoichiometric air-fuel ratio. When the ignition plug 21 is ignited in this state, the air-fuel mixture around the ignition plug can be burned. By providing the fuel distribution in the combustion chamber in such a manner, the entire combustion chamber can burn even in a lean state.

In this combustion mode, combustion can be performed in a wide lean air-fuel ratio range (A / F = 25 to 50), so that output control based on the fuel injection amount is possible, and the engine is operated with the throttle opening increased. Pumping loss can be reduced and fuel efficiency can be improved.

On the other hand, in the homogeneous combustion, the fuel is injected during the intake stroke, and at the subsequent ignition timing, the fuel and the intake air are almost uniformly mixed near the stoichiometric air-fuel ratio.

Here, in the stratified combustion, as described above, a certain time is required from the injection to the ignition, but the fuel injection is performed during the compression stroke, so that usable operating conditions are limited. That is, when the time from fuel injection to ignition is short, the fuel is insufficiently vaporized, so that a good air-fuel mixture cannot be formed in the vicinity of the ignition plug, and there is a possibility of misfiring. Therefore, in a high rotation region where the compression stroke itself is short, or in a high load region where a large amount of fuel is injected and time is required for vaporization, the time for forming the air-fuel mixture cannot be secured, so that the combustion is changed to homogeneous combustion.

Such a change in the combustion mode is caused by the engine load KL
And the engine operating state such as the engine speed NE. As the engine load KL, for example, a fuel injection amount per stroke set based on the accelerator opening ACCP and the engine speed NE is used.

FIG. 3 shows an operation region in which each combustion mode is performed. In this figure, a load determination value JKL (1) (1) () is used to determine whether the combustion mode suitable for the current engine operation state is set to stratified combustion or homogeneous combustion based on a comparison with the engine load KL. (Solid line in the figure) and JKL
(2) (broken line in the figure) is shown corresponding to the engine speed NE.

Here, two of JKL (1) and JKL (2)
Which of the two map values is set as JKL is determined by the fuel volatility determining means described later. If the current fuel is determined to be highly volatile, JKL
(1) A map value is set, and if it is determined that the volatility is low, a JKL (2) map value is set.

In this determination, when a light fuel is used, the volatility of the fuel is good, and the time required for forming the air-fuel mixture is shorter than that of the heavy fuel, so that the stratified combustion region is widened. Is set.

The determination of the combustion mode is performed as follows.
The engine load KL is the engine speed NE at that time (for example, “N
E1 ”) corresponding to the load determination value JKL (= JKL (1)
1 or less than JKL (2) 1) (KL <JK
L), it is determined that the current combustion mode is set to stratified combustion, and when the engine load KL is equal to or greater than the load determination value JKL (KL ≧ JKL), it is determined that the combustion mode is set to the homogeneous combustion region. You. The relationship between the load determination value JKL and the engine speed NE shown in FIG. 3 is determined based on experiments or the like in advance, and is stored in the memory 41 of the electronic control unit 40.

Next, a method of determining fuel volatility will be described. First, knocking control serving as a base will be described. FIGS. 4 and 5 are flowcharts showing a processing procedure in the knocking control. Electronic control unit 40
Executes the process shown in this flowchart as an interrupt process of a predetermined crank angle cycle.

In this process, it is first determined whether or not the currently selected combustion mode is homogeneous (FIG. 4).
Step 100). If the combustion mode is set to stratified combustion (step 100: NO), the process is temporarily terminated. That is, during the stratified charge combustion, the process related to the substantial knocking control is not executed. The ignition timing during the stratified combustion is set through a process different from this routine. The ignition timing during stratified combustion is
The ignition is performed when a fuel mixture injected from the injector 20 forms a gas mixture layer having a predetermined concentration near the ignition plug 21.

On the other hand, if it is determined that the combustion mode is set to homogeneous combustion (step 100: YES), the basic ignition timing AB is determined based on the engine load KL and the engine speed NE.
SE and maximum retardation AKMAX are calculated (step 1)
10).

Here, the basic ignition timing ABSE is an ignition timing at which the maximum engine output can be ensured in the engine operating state at that time, and based on the compression top dead center, the relative crank angle before the top dead center. Defined as CA.

The maximum retard amount AKMAX is the maximum amount when the basic ignition timing ABSE is retarded, and is set to a value that can reliably suppress knocking in the engine operating state at that time. ing.

The relationship between the basic ignition timing ABSE and the maximum retard value AKMAX and the engine operating state (engine load KL engine speed NE) is determined in advance based on experiments and the like.
The memory 41 of the electronic control unit 40 stores data for calculating the basic ignition timing ABSE and the maximum retardation value AKMAX.
Is stored in

Next, knock learning value AGKNK stored in memory 41 is read (step 12).
0).

The knock learning value AGKNK is used to advance the basic ignition timing ABSE by the maximum retardation value AKMAX by an amount corresponding to the maximum retardation value AKMAX (ABSE-AKMAX) in accordance with the knocking state. Through the processing of this routine, learning is gradually updated to a small value when knocking tends to occur frequently, and is gradually updated to a large value when knocking occurrence frequency is small. Value. Therefore, this knock learning value A
The GKNK reflects the octane number of the fuel used, the frequency of occurrence of steady knocking due to a change in the actual compression ratio due to the adhesion of carbon to the cylinder 12, and the like.

The knock learning value AGKNK is stored and held in the memory 41 as different values corresponding to a plurality of learning regions divided according to the engine speed NE. That is, when three learning regions such as a low-speed region, a medium-speed region, and a high-speed region are set according to the engine speed NE, three knock learning values AGKNK are respectively corresponding to the learning regions. Will exist. It is to be noted that the knock learning value AGKNK is separately provided in accordance with each learning region because the occurrence of knocking differs according to the engine speed NE, and the difference due to the engine speed NE is ignited. This is because it is necessary to appropriately control knocking by reflecting the timing.

Next, it is determined whether or not knocking has occurred in engine 10 based on knocking signal KCS output from knock sensor 33 (step 13).
0).

If it is determined that knocking has occurred (step 130: YES), a predetermined value α1 is added to the current knock control value AKCS, and the added value (AK
CS + α1) is set as a new knock control value AKCS (step 140).

The knock control value AKCS is for correcting the ignition timing according to the current knocking occurrence frequency. The knock control value AKCS is also equal to the knock learning value A.
Like GKNK, it is updated in accordance with the occurrence of knocking. However, while knock learning value AGKNK is gradually updated in accordance with the frequency of occurrence of knocking over a relatively long period of time, this knock control The value AKCS is different from the knock learning value AGKNK in that the value AKCS is frequently updated according to the presence or absence of knocking every moment.

On the other hand, when it is determined that knocking has not occurred (step 130: NO), a predetermined value α2 is subtracted from the current knock control value AKCS, and the subtraction value (AKCS-α2) is used as a new knock control. It is set as the value AKCS (step 145).

After the knock control value AKCS is updated in accordance with the presence or absence of the current occurrence of knocking, a knock retard reflection value AKNK is calculated based on the following equation (1) (step 150). This knock retard value AK
NK corresponds to a final retard amount when the basic ignition timing ABSE is retarded.

AKNK ← AKMAX−AGKNK + AKCS (1) Next, the knock control value AKCS is compared with a predetermined value β1 (step 160 in FIG. 5). Here, if it is determined that knock control value AKCS is greater than predetermined value β1, that is, if the frequency of occurrence of knocking is greater than the predetermined frequency (step 160: YES), current knock learning value AG
A predetermined value γ is subtracted from KNK, and the subtracted value (AGKN
K−γ) is set as a new knock learning value AGKNK (step 170).

On the other hand, knock control value AKCS is equal to predetermined value β1.
If it is determined that the following is satisfied (Step 160: N
O) Further, the knock control value AKCS is compared with a predetermined value β2 (step 165). If it is determined that knock control value AKCS is smaller than predetermined value β2, that is, if the frequency of occurrence of knocking is smaller than the predetermined frequency (step 165: YES), predetermined value γ is added to current knock learning value AGKNK. And the sum (AG
KNK + γ) is set as a new knock learning value AGKNK (step 175).

As described above, knock learning value AGKNK is a knock control value AK reflecting the knocking occurrence frequency.
After the update based on the magnitude of CS, or when it is determined that knock control value AKCS is in the range of (β2 ≦ AKCS ≦ β1) (steps 160 and 16)
5: NO), the knock learning value AGKNK is stored in the memory 41 as a value in the learning region corresponding to the current engine speed NE.
(Step 180).

Next, the knock retard reflection value AKNK is subtracted from the basic ignition timing ABSE, and the subtraction value (ABS-
AKNK) is set as the final ignition timing AOP (step 190). After executing this processing, the processing of this routine is temporarily terminated. The electronic control unit 40 outputs an ignition signal based on the final ignition timing AOP to the igniter 23 to execute ignition by the ignition plug 21.

Next, the means for determining the switching of the combustion mode will be described with reference to FIGS.

First, the concept of fuel volatility determination will be described with reference to FIG. A light fuel having a high volatility corresponds to a fuel having a low octane number, and a heavy fuel having a low volatility corresponds to a fuel having a high octane number. Therefore, fuel volatility can be determined from the knock control amount. Here, if the knock retard reflection value AKNK is used, a significantly different determination value is required for each of the engine speed NE and the engine load KL. Therefore, the knock learning value AGKNK and the knock maximum retard value AKM
The difference of AX, AKNKGQ = AKMAX−AGKNK (2), is used for fuel volatility determination. The knock learning value AGKNK is divided into several regions depending on the engine speed, but the value of the learning region that is used most frequently is used for fuel volatility determination. In this example, a knock learning value in a low-speed region is adopted.

The specific determination method is as follows: AKNKGQ calculated by equation (2) and a predetermined fuel volatility determination value AGKG
Compared to QD, it is determined that the fuel is light if AKNKGQ ≧ AGKGQD and heavy if AKNKGQ <AGKGQD. In addition, A near the determination value AGKGQD
Hysteresis is provided in the fuel volatility determination value for the purpose of preventing the determination from being frequently switched due to the rise and fall of KNKGQ.

Since the fuel volatility determination value AGKGQD changes depending on the water temperature and the intake air temperature as shown in FIG. 7, it is determined from a map using the water temperature and the intake air temperature as variables.

Next, the flowchart of FIG. 8 will be described. First, at the time of initial (ignition switch OF
It is determined whether F → ON) (step 210). When it is determined to be the initial time (step 210: YES)
Turns off the fuel volatility determination flag XAGKGQH and proceeds to step 230. If it is determined that it is not the time of the initialization, the process proceeds to step 230 without doing anything. Here, when the fuel volatility determination flag XAGKGQH is ON, it means that the fuel used is heavy fuel, and when OFF, it means that the fuel used is light fuel.

In steps 230 and 240, as described above, first, in step 230, the fuel volatility determination value AGKG is determined from a map using the water temperature or the intake air temperature as a variable.
QD is calculated, and in step 240, AKNKKGQ
Is calculated. Here, a knock learning value AGKNK uses a learning value in a low-speed region.

Next, in step 250, AKN
KGQ and AGKGQD are compared, and AKNKGQ <AG
In the case of KGQD (step 250: YES), XAG
KGQH is turned on, and it is determined that heavy fuel is being used. In step 250, AKNKKGQ ≧ AGK
In the case of GQD (step 250: NO), step 2
At 60, XAGKGQH = ON and AKNKKGQ
It is determined whether or not <AGKGQD + α> holds, and if it holds (step 260: YES), step 270
Turns on XAGKGQH at step 280. If it is not established (step 260: NO), at step 280, XAGKGQH
To OFF. Here, XAGKGQH is OFF →
There is a difference in the fuel volatility determination value between the ON condition (step 250) and the ON → OFF condition (step 260). The steps up to step 280 are the fuel volatility determining means, and the steps from step 290 are the stratified combustion region changing means.

First, at step 290, XAGKGQ
It is determined whether H is OFF. If H is OFF (step 290: YES), that is, if it is determined that the fuel to be used is light fuel, the routine proceeds to step 300, where the load determination value JKL for combustion switching is set to: The values read from the JKL (1) map are substituted for the engine speed and the engine load as variables. If XAGKGQH is ON in step 290 (step 290: NO), that is, if it is determined that the fuel used is heavy fuel, step 310
The numerical value read from the JKL (2) map is substituted for JKL. As shown in FIG. 3, the map value of the light fuel map JKL (1) has a larger stratified combustion range than that of the heavy fuel map JKL (2).

In the example of FIG. 3, the JKL (1) map expands the stratified combustion range in the entire operation range with respect to the JKL (2) map. It may be limited, or may be limited to the high load side.

Next, at step 320, the engine load KL
Is compared with the load determination value JKL. If KL <JKL (step 320: YES), the combustion mode is set to stratified combustion, and if KL ≧ JKL (step 320: NO).
Sets the combustion mode to homogeneous combustion.

As described above, according to the combustion control apparatus for a direct injection internal combustion engine according to the present embodiment, (1) the operation range in which stratified combustion is performed in accordance with the volatility of the fuel is determined by the engine speed, By being able to set for each load, the stratified combustion region when using a highly volatile fuel is expanded compared to when the stratified combustion region is determined uniformly assuming the use of a less volatile fuel, and the stratified combustion is reduced. Since the frequency of the operation is increased, the fuel efficiency can be improved. (2) Since the fuel volatility can be determined based on the occurrence of knocking in the engine 10, the determination can be made by a simple method without adding a new system.

(3) Further, since the fuel volatility determination value is made variable depending on the water temperature or the intake air temperature, highly accurate fuel volatility determination is possible. Each of the embodiments described above can be implemented by changing the configuration as described below.

The determination of fuel volatility may be made based on the degree of vapor generated from the fuel tank.

The fuel volatility determination value may be varied depending on both the water temperature and the intake air temperature.

The load determination value (map) for setting the combustion mode to either stratified combustion or homogeneous combustion is not limited to two types: a case where fuel volatility is high and a case where fuel volatility is low.
It may be configured to be variable according to fuel volatility. For example, the load determination value may be calculated from AKNKGQ used in the present embodiment.

[Brief description of the drawings]

FIG. 1 is an exemplary view showing control blocks of an electronic control computer according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a combustion control device and a direct injection internal combustion engine according to the present invention.

FIG. 3 is a cylinder injection type internal combustion engine 1 according to the embodiment of the invention;
A map showing a relationship between a combustion mode of 0 and an engine operation state.

FIG. 4 is a flowchart showing a processing procedure in knocking control.

FIG. 5 is a flowchart showing a processing procedure in knocking control.

FIG. 6 is a conceptual diagram of fuel volatility determination in the embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a fuel volatility determination value and a water temperature or an intake air temperature in the embodiment of the present invention.

FIG. 8 is a flowchart showing a processing procedure of combustion mode switching control according to the embodiment of the present invention.

[Explanation of symbols]

10 engine, 11 cylinder head, 12 cylinder, 13 cylinder block, 14 piston, 15
Combustion chamber, 20: injector, 21: spark plug, 22
... ignition coil, 23 ... igniter, 30 ... crank angle sensor, 31 ... cam angle sensor, 32 ... accelerator sensor, 3
3 ... knock sensor, 34 ... water temperature sensor, 35 ... intake air temperature sensor, 40 ... electronic control unit, 41 ... memory.

Claims (3)

[Claims] In a combustion control apparatus for an in-cylinder injection type internal combustion engine, wherein a combustion mode is set to one of stratified charge combustion and homogeneous combustion based on an engine operation state, fuel supplied to the in-cylinder injection type internal combustion engine is provided. Fuel volatility determining means for determining the volatility of the fuel, and when the fuel volatility determining means determines that the volatility of the fuel is high, the stratification is determined with respect to the case where the volatility of the fuel is determined to be low. A combustion control device for a direct injection internal combustion engine, comprising: a stratified combustion region changing means for expanding an operation region in which combustion is performed. 2. The stratified combustion region changing means according to claim 1, wherein said fuel volatility determining means determines that the fuel volatility is high, The combustion control device for a direct injection internal combustion engine according to claim 1, wherein an operation region in which combustion is performed is extended to a high rotation side. 3. The stratified combustion region changing means, wherein when the fuel volatility determining means determines that the fuel volatility is high, the stratified combustion region changing means determines whether the fuel volatility is determined to be low. The combustion control device for a direct injection internal combustion engine according to claim 1 or 2, wherein an operation region in which combustion is performed is expanded to a high load side.