JP5239949B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that injects a small amount of fuel prior to main injection.

  The ignition timing in a diesel engine is basically controlled by the fuel injection timing, but the actual ignition timing is not detected directly, and whether or not the actual ignition timing correctly matches the desired ignition timing. Is generally unknown. The ignition timing in a diesel engine affects the NOx emissions and fuel consumption rate in the exhaust gas, and controlling the actual ignition timing to the desired ignition timing is a trade-off between NOx emissions and fuel consumption rate. It is important to achieve both.

  Patent Document 1 discloses a technique in which a vibration sensor (a so-called knock sensor) is attached to a cylinder block of a diesel engine, and when the amplitude reaches a certain level, the ignition timing is simply determined. .

Japanese Patent Application Laid-Open No. 9-144583

  However, even if the ignition timing can be accurately determined, in an internal combustion engine that injects a small amount of fuel prior to the main injection, the fuel is low when the combustion caused by the main injection is not stable. With cetane fuel, even if the injection amount of the injection prior to the main injection is increased, if the temperature at the compression end is not sufficiently high, the amount of heat generated due to the injection prior to the main injection will not increase, resulting from the main injection. There is a problem that combustion cannot be stabilized.

  Therefore, the control device for an internal combustion engine of the present invention injects a small amount of fuel prior to the main injection, and when the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio, the combustion of the fuel injected by the main injection is performed. If it is determined that there is an ignition delay, the gas temperature in the combustion chamber is raised.

  According to the present invention, when the combustion becomes unstable when the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio, the gas temperature in the combustion chamber is raised to raise the compression end temperature, thereby improving the combustion stability and smoke. Suppression can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing of the diesel engine to which the control apparatus which concerns on one Example of this invention is applied. The flowchart which shows the flow of the process for ignition timing detection. Explanatory drawing which shows an example of a sampling period. Explanatory drawing which shows an example of the frequency range of the vibration acceleration integrated | accumulated. Explanatory drawing which shows the change of the cylinder pressure and vibration acceleration in different injection time (A)-(D). The characteristic view which shows the characteristic of a 1st control map. Explanatory drawing which shows the integrated value and detection value in three different injection timings. Explanatory drawing which shows the relationship between the detected value and actual ignition timing in three different driving conditions (A)-(C). The flowchart which shows the flow of a process of correction | amendment of injection timing. The characteristic view which shows the characteristic of a 2nd control map. The characteristic view which shows the characteristic of a 3rd control map. The characteristic view which shows the characteristic of a target injection time map. The characteristic view which shows the characteristic of a combustion period map. The characteristic view which shows together the characteristic line showing the smoke performance with respect to an EGR rate and injection timing, and the characteristic line showing the parameter | index which made the torque fluctuation dimensionless. The characteristic view which shows the amount of heat generation in a combustion chamber. The flowchart which shows the flow of the process of correction | amendment of the injection timing in case an exhaust air fuel ratio is made rich. Explanatory drawing which showed the detection signal of the knock sensor and the amount of heat generation in a cylinder in the state where the exhaust air-fuel ratio is enriched. Explanatory drawing which showed what integrated the absolute value of the detection signal of a knock sensor in the state where the exhaust air-fuel ratio is rich.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an overall configuration of a diesel engine 1 to which the present invention is applied. The diesel engine 1 includes a common rail type fuel injection device. The diesel engine 1 has a fuel injection nozzle 3 at the upper center of a combustion chamber 2 of each cylinder, and fuel pressurized by a supply pump 4 is stored in a pressure accumulation chamber (common rail). ) After being stored in 5, it is distributed to the fuel injection nozzles 3 of the respective cylinders and injected according to the opening and closing of the respective fuel injection nozzles 3. The pressure accumulating chamber 5 is provided with a fuel pressure sensor 6 for detecting fuel pressure (rail pressure).

  The diesel engine 1 also includes a turbocharger 11 that is provided with an exhaust turbine 12 and a compressor 13 coaxially. An intercooler 15 is interposed in the intake passage 14 from the compressor 13 to the combustion chamber 2. An EGR passage 17 is provided between the exhaust passage 16 extending from the combustion chamber 2 to the exhaust turbine 12 and the intake passage 14, and an EGR cooler 18 and an EGR control valve 19 are interposed in the EGR passage 17. Has been. An air cleaner 21 and an air flow meter 22 are provided upstream of the compressor 13 in the intake passage 14.

  A known knock sensor 26 that is an acceleration sensor and responds to vibration of the cylinder block 25 is attached to the side wall of the cylinder block 25 that is a part of the engine body. Although this knock sensor 26 may be provided for each cylinder, in this embodiment, an appropriate position at which vibration of each cylinder can be detected is selected and one knock sensor 26 is provided in the cylinder block 25. The detection signal of the knock sensor 26 is input to the control unit 30, and based on this, the fuel injection timing from the fuel injection nozzle 3 is delayed and corrected, as will be described later.

  In the exhaust passage 16 on the downstream side of the exhaust turbine 12, as an exhaust gas purifying catalyst, in order from the upstream side, an oxidation catalyst 27, an NOx purification catalyst 28 for adsorbing, desorbing and purifying NOx in the exhaust, and exhaust gas A particulate trapping filter or DPF 29 is provided as an exhaust aftertreatment device that traps exhaust particulate (PM) therein and periodically removes or regenerates the deposited PM by a method such as combustion.

  In addition to the detection signals of the knock sensor 26 and the air flow meter 22 described above, the control unit 30 as a control unit detects a crank angle sensor 31 that detects a crank angle (engine speed) of the crankshaft, and a supercharging pressure. A supercharging pressure sensor 32, a first oxygen sensor 33 as air-fuel ratio detection means for detecting the oxygen concentration upstream of the oxidation catalyst 27 in the exhaust passage, and an oxygen temperature between the NOx purification catalyst 28 and the DPF 29 in the exhaust passage are detected. The second oxygen sensor 34, the inlet temperature sensor 35 for detecting the inlet temperature of the DPF 29, the outlet temperature sensor 36 for detecting the outlet temperature of the DPF 29, the DPF differential pressure sensor 37 for detecting the differential pressure before and after the DPF 29, and the cooling water temperature. A water temperature sensor that detects the amount of depression, an accelerator opening sensor that detects the amount of accelerator pedal depression, and an intake air temperature Detection signals of the sensors such as the intake air temperature sensor is input. Based on these detection signals, the control unit 30 controls the pressure of the intake throttle valve 38 that adjusts the throttle amount of the intake passage 14 and the opening of the variable nozzle of the turbocharger 11 in addition to the fuel injection nozzle 3. A control signal is output to the control valve 39 and the like to control its operation.

  FIG. 2 is a flowchart showing a flow of processing for detecting the actual ignition timing executed in the control unit 30. This routine is repeatedly executed at a very short predetermined calculation interval (for example, every predetermined crank angle or predetermined time).

  First, in step (hereinafter simply referred to as S) 1, various signals such as a crank angle detected by the crank angle sensor 31 are read. In S2, it is determined whether the crank angle is within a predetermined sampling period Δθsmp (see FIG. 3) in the combustion cycle of each cylinder. If it is not in the sampling period Δθsmp, an integrated value described later is initialized to 0 in S10.

  As shown in FIG. 3, the sampling period Δθsmp includes at least the ignition timing, and is set to a period of, for example, about 50 ° CA from the start timing, that is, the integration start timing θs, so as to extract the combustion pressure generation period. Further, the sampling period may be variable according to the engine operating conditions. For example, the rise of the pressure increase rate dP / dθ and the rise of heat generation are detected and estimated, and the period from the uncontrolled combustion period to the afterburn period Also good. In addition to main fuel injection (main injection), pre-injection that produces a fire by injecting a small amount of fuel prior to main fuel injection, or after-burning that burns the remaining fuel by injecting a small amount of fuel after main fuel injection When performing injection, it is desirable to set the sampling period so as not to overlap with these injection periods in order to avoid the influence of the vibration. The integration start timing θs is set at least before the ignition timing and after the main fuel injection start timing as will be described later.

  If it is within the sampling period, the process proceeds to S3, the knock signal output from the knock sensor 26, that is, the vibration acceleration is read, and the band pass filter process (or high pass filter process) is performed in S4, and the frequency that is clearly considered as noise. Only a signal in a predetermined frequency range ΔFrq excluding the band is extracted. As shown in FIG. 4, the predetermined frequency range ΔFrq is set to a range of about 5 kHz to 10 kHz, or about 5 kHz to 20 kHz so as to extract vibration due to combustion. The range around 2 to 4 kHz generally includes a large amount of vibration components accompanying the driving of the fuel injection nozzle 3 that are generated repeatedly in the combustion period, and it is desirable to eliminate at least this.

In S5, the value (absolute value) corresponding to the amplitude of the vibration acceleration is integrated every predetermined sampling period, and the integrated value is updated. The sampling period (calculation interval) is, for example, a unit crank angle of 1 ° CA, or is set to 1 / (360 / 0.25 × Ne / 60) × 10 ⁶ [μs] or the like. In this embodiment, the square value of vibration acceleration that reverses positive and negative is sequentially accumulated as absolute value accumulation.

  In S6, the ignition timing determination level S_SL is set based on the engine operating conditions at that time, that is, the load (torque, fuel injection amount), engine speed, fuel pressure, and the like. That is, as shown in FIG. 8, the ignition timing determination level S_SL is variable according to the engine speed or the like. In S7, the integrated value Sθ for each crank angle is compared with the ignition timing determination level S_SL.

  If the integrated value Sθ has not reached the ignition timing determination level S_SL, this routine ends. On the other hand, when the integrated value Sθ reaches the ignition timing determination level S_SL, the process proceeds to S8 and S9, and the actual ignition timing rT_ign is calculated based on the arrival time when the integrated value Sθ reaches the ignition timing determination level S_SL. Specifically, an elapsed time from the integration start time to the arrival time is calculated (S8), and this elapsed time is converted into a crank angle to obtain an actual ignition timing rT_ign (crank angle).

  In the above example, processing is performed on a real time basis. However, a series of processing including sampling and the like can also be performed on a crank angle basis. In this case, from the real time in S9 to the crank angle. The conversion process is omitted, and the actual ignition timing rT_ign (crank angle) can be obtained directly from the arrival time (crank angle).

  FIG. 5 is a characteristic diagram showing changes in in-cylinder pressure and vibration acceleration output from the knock sensor 26 at different injection timings (A) to (D). As the injection timing (main fuel injection start timing) is retarded, the in-cylinder pressure increase region α1 and the vibration increase region α2 due to ignition combustion are also retarded. Therefore, the integration start timing θs is set according to the main fuel injection start timing, and more specifically, after the main fuel injection start timing, more specifically, a predetermined transmission that takes into account a response delay due to a vibration transmission system such as a cylinder block. It is set to a timing (MIT + θn) delayed by the delay period θn from the main fuel injection start timing MIT. More specifically, the transmission delay period θn is set according to the engine speed and the fuel injection amount with reference to the first control map MAP1 shown in FIG. As shown in the figure, the transmission delay period θn is set to increase as the engine speed increases and to increase as the fuel injection amount increases. Thereby, noise components other than ignition combustion by fuel injection can be accurately removed.

  Further, as shown in FIG. 5, the intensity (amplitude) of the vibration acceleration decreases as the fuel injection start timing is delayed from the top dead center. Therefore, preferably in S6 described above, the ignition timing determination level S_SL is decreased as the fuel injection start timing is delayed from the top dead center.

  FIG. 7 shows changes in the integrated value (integrated value) when the main fuel injection start timing MIT (ATDC) is different, and variations and errors in the actual ignition timing with respect to the detected value. The “detected value” is a crank angle (ATDC) at an arrival time when the above-described integrated value reaches the ignition timing determination level S_SL. The actual ignition timing is set based on this detection value. In this example, the actual ignition timing is about 15 ° advanced from the detection value. As shown in FIG. 7, the variation in the actual ignition timing with respect to the detected value (crank angle at the arrival time) is suppressed to a small range of about ± 0.7 ° CA regardless of the main fuel injection start timing. The actual ignition timing can be accurately obtained by eliminating the influence of noise vibration other than the combustion caused by the injection.

  FIG. 8 shows the relationship between the detected value and the actual ignition timing under three operating conditions (A) to (C) with different exhaust representative points. As shown in the figure, even when the engine operating conditions are different, the error of the actual ignition timing with respect to the crank angle of the arrival timing, that is, the detected value, is suppressed to a small range of ± 1.2 ° CA or less. Thus, the actual ignition timing can be obtained with high accuracy regardless of the engine operating conditions.

  The actual ignition timing rT_ign determined in this way can be used for various controls in the diesel engine 1. FIG. 9 shows, as an example, correction of the injection timing IT using the normal actual ignition timing rT_ign. The flowchart about is shown. Here, first, in S11, the target ignition timing tT_ign is calculated by referring to the second control map (MAP2) shown in FIG. 10 based on the engine operating condition at that time, that is, the load (torque) and the engine speed. Set. This second control map is obtained by assigning a desired ignition timing for each operating point. Basically, the target injection timing IT is assigned to the engine operating conditions (load and engine speed) in FIG. The characteristic is similar to the target injection timing map shown.

  Next, in S12, a difference ΔT (= rT_ign−tT_ign) between the target injection timing tT_ign and the estimated actual ignition timing rT_ign is obtained. In S13, the injection timing correction amount IT_FB corresponding to the difference ΔT is obtained with reference to the third control map (MAP3) shown in FIG. That is, the injection timing and the ignition timing are not in a “one-to-one” relationship. For example, even if the injection timing is changed by 1 ° CA, the ignition timing does not change by 1 ° CA. Since these differ depending on conditions, in consideration of these, the correction amount IT_FB necessary to bring the actual ignition timing rT_ign closer to the target injection timing tT_ign is assigned as the third control map. The correction amount IT_FB obtained based on the third control map is added to the injection timing IT at that time in S14. The correction amount IT_FB may be learned and stored as a correction amount for each operating point as necessary.

  By the way, the sampling period is set to 50 ° CA from the integration start time, for example. However, the sampling period is not necessarily a fixed range, and the engine operating conditions, particularly the fuel injection amount Qf, rail pressure Pf, injection It may be configured to be variably set in consideration of the timing IT and the like. For example, the combustion period θbrn correlates with the rail pressure Pf and the fuel injection amount Qf, and can be calculated with reference to, for example, a combustion period map having characteristics as shown in FIG.

  If the start time θs of the sampling period is set as “θs = IT + θn” and θn is variably set as “θf = IT + θn + θbrn”, where θn is a predetermined transmission delay period, the minimum sampling including only the combustion period A period can be given. This is advantageous in avoiding the influence when pre-injection and after-injection are performed before and after, for example.

  In the case of low cetane fuel, if the compression end temperature is not sufficiently high even if the fuel injection amount by pre-injection is increased, the heat generation amount of combustion of the fuel injected by pre-injection will not increase, and the fuel will be injected by main fuel injection. Fuel combustion may not be stable. When the atmosphere in the cylinder is rich, as shown in FIG. 14, if the injection timing of the main fuel injection is advanced, the combustion of the fuel injected by the main fuel injection tends to be stable, but the smoke is There is a tendency to get worse. The solid line in FIG. 14 is a characteristic line representing the smoke performance with respect to the injection timing and the EGR rate, and the smoke performance tends to be better as the injection timing is retarded and the EGR rate is increased. Further, the broken line in FIG. 14 is a characteristic line representing an index in which the torque variation with respect to the injection timing and the EGR rate is made dimensionless. The torque variation decreases as the injection timing advances and the EGR rate decreases. Combustion stability tends to improve.

  Further, it is possible to increase the compression end temperature by increasing the EGR and stabilize the combustion of the fuel injected by the main fuel injection, but as shown in FIG. 15, if the EGR is excessively increased, Although the heat generation of the fuel injected by the pre-injection becomes active, the heat generation of the fuel injected by the main fuel injection is weakened due to the decrease in the combustion speed due to the excessive ratio of the inert gas.

  Therefore, when the exhaust air-fuel ratio is enriched in association with the release processing of NOx from the NOx purification catalyst 28 by the rich spike or the release of sulfur poisoning of the NOx purification catalyst 28, control is performed as shown in FIG. That is, based on the signal detected by the knock sensor 26, the integrated value of the vibration signal resulting from the combustion of the fuel injected by the pre-injection and the integrated value of the vibration signal resulting from the combustion of the fuel injected by the main fuel injection The gas temperature in the combustion chamber 2 is raised so that the ratio of the above becomes within a predetermined range. This is because when the exhaust air-fuel ratio is normally enriched, the intake air is throttled and enriched, so the pressure rise at the compression top dead center is small, that is, the temperature rise is small. This is because the fuel becomes difficult to ignite.

  In S21, it is determined whether or not the sulfur poisoning cancellation or rich spike execution condition is satisfied. If satisfied, the process proceeds to S22 to enrich the exhaust air-fuel ratio, and if not, the current condition is determined. End the routine.

In S22, it is determined whether or not the conditions of the following expressions (1) and (2) are satisfied. If not satisfied, the process proceeds to S23, and if not, the current routine is terminated. . That is, when it is determined that there is an ignition delay in the combustion caused by the main fuel injection, the integrated value of a predetermined section of the vibration signal resulting from the combustion of the fuel injected by the pre-injection and the fuel injected by the main fuel injection The gas temperature in the combustion chamber 2 is improved so that the ratio of the vibration signal resulting from the combustion to the integrated value of the predetermined section is within a predetermined range.
[Equation 1]
| (RT_ign) − (tT_ign) | <ε1 (1)
[Equation 2]
| (RSpre / rSmain) / (tSpre / tSmain) −predetermined value | <ε2 (2)
Here, rT_ign is the actual ignition timing of the fuel injected by the main fuel injection as described above, and tT_ign is the target ignition timing of the fuel injected by the main fuel injection as described above. From the equation (1), it is determined that there is no ignition delay when the deviation between the actual ignition timing rT_ign and the target ignition timing tT_ign is smaller than a predetermined value ε1, and it is determined that there is an ignition delay otherwise. doing.

  In addition, rSpre in the equation (2) is an integrated value of a predetermined period A of a vibration signal caused by combustion of fuel injected by pre-injection detected by the knock sensor 26, and rSmain is detected by the knock sensor 26. This is an integrated value of a predetermined period B of a vibration signal resulting from combustion of fuel injected by main fuel injection.

  The predetermined period A is a period including the start timing of the pre-injection and the injection period of the pre-injection, and is a period corresponding to, for example, 25 deg in crank angle. The predetermined period B is a period including the start timing of the main fuel injection and the injection period of the main fuel injection, and is a period corresponding to, for example, 60 deg in crank angle. The pre-injection period and the main fuel injection period can be calculated from the injection amount and the rail pressure, respectively.

  FIG. 17 is an explanatory diagram showing the detection signal detected by the knock sensor 26 and the amount of heat generated in the cylinder when the exhaust air-fuel ratio is rich. FIG. 18 shows a result obtained by integrating the absolute value of the detection signal of the knock sensor 26 by integrating the predetermined period A and a result obtained by integrating the predetermined value B by a predetermined period.

  As shown in FIG. 17 and FIG. 18, the above-described rSpre is calculated by integrating the absolute value of the detection signal detected by the knock sensor 26 for a predetermined period A, and the detection signal detected by the knock sensor 26. The above-described rSmain is calculated by integrating the absolute value of B for a predetermined period B.

  tSpre is a target value of an integrated value of a predetermined period A of a vibration signal caused by combustion of fuel injected by pre-injection detected by the knock sensor 26, and tSmain is determined by main fuel injection detected by the knock sensor 26. This is the target value of the integrated value for a predetermined period B of the vibration signal resulting from the combustion of the injected fuel.

In S23, it is determined whether or not the fuel injection amount in the pre-injection is smaller than a predetermined amount. If the fuel injection amount is small, the process proceeds to S24, and the fuel injection amount in the pre-injection is increased. Here, it is known that the fuel injection amount in the pre-injection does not contribute to the combustion stability even if the fuel injection amount is too large. For example, a value of about 4 (mm ³ / st) is set as the predetermined amount in S23. It is desirable.

  In S25, it is determined whether or not the EGR rate is smaller than a predetermined value. If the EGR rate is low, the process proceeds to S26, and if not, the process proceeds to S27 and the injection timing of the main fuel injection is advanced. Here, if the EGR rate is increased too much, the ratio of the inert gas in the combustion chamber 2 increases and the possibility of misfire increases, so it is desirable to set a value of, for example, about 15% as the predetermined amount in S25. .

  In this embodiment, even if the combustion becomes unstable while the exhaust air-fuel ratio is rich, it is caused by the combustion of the fuel injected by the pre-injection based on the signal detected by the knock sensor 26. Increasing the gas temperature in the combustion chamber 2 so that the ratio between the integrated value of the vibration signal to be generated and the integrated value of the vibration signal resulting from the combustion of the fuel injected by the main fuel injection is within a predetermined range, Combustion stability can be ensured while suppressing smoke.

  In the above-described embodiment, the EGR rate is increased as a means for increasing the gas temperature in the combustion chamber 2, but a glow plug is disposed in the combustion chamber 2, and the gas in the combustion chamber 2 is disposed by the glow plug. You may make it raise temperature.

  In the embodiment described above, the combustion state in the combustion chamber 2 is detected using the knock sensor 26. However, if an in-cylinder pressure sensor for detecting the in-cylinder pressure is provided in each cylinder, the in-cylinder pressure sensor is used. It may be used to detect the combustion state in the combustion chamber 2. Further, by using the in-cylinder pressure sensor instead of the knock sensor 26, the integrated value of the predetermined amount of the heat generation amount in the cylinder resulting from the combustion of the fuel injected by the pre-injection detected by the in-cylinder pressure sensor, and the main fuel The gas temperature in the combustion chamber 2 may be increased so that the ratio of the amount of heat generated in the cylinder resulting from the combustion of the fuel injected by the injection to the integrated value of the predetermined section is within a predetermined range. Good.

  The technical ideas of the present invention that can be grasped from the above-described embodiments will be listed together with their effects.

  (1) a fuel injection valve for directly injecting fuel into the combustion chamber, a means for detecting the exhaust air-fuel ratio, a combustion state detection means for detecting the combustion state in the combustion chamber using a signal resulting from combustion in the combustion chamber, Combustion chamber gas temperature raising means for raising the gas temperature in the combustion chamber, and the fuel injection valve injects a small amount of fuel prior to the main injection, and the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio On the other hand, when it is determined by the combustion state detection means that there is an ignition delay in the combustion of the fuel injected by the main injection, the gas temperature in the combustion chamber is raised by the combustion chamber gas temperature raising means. As a result, when combustion becomes unstable when the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio, the gas temperature in the combustion chamber is raised to raise the compression end temperature, thereby realizing combustion stability and smoke suppression. can do.

  (2) In the control device for an internal combustion engine according to (1), specifically, the combustion chamber gas temperature increasing means increases the gas temperature in the combustion chamber by increasing the EGR rate.

  (3) In the control device for an internal combustion engine according to (1), specifically, the combustion chamber gas temperature increasing means increases the gas temperature in the combustion chamber by a glow plug.

  (4) In the control device for an internal combustion engine according to any one of (1) to (3), specifically, the combustion state detection means is a knock sensor attached to an internal combustion engine body constituting a combustion chamber. It is.

  (5) In the control device for an internal combustion engine according to any one of (1) to (3), specifically, the combustion state detection means is an in-cylinder pressure sensor that directly detects an in-cylinder pressure of each cylinder. is there.

  (6) The control apparatus for an internal combustion engine according to (4), specifically, the main injection is performed when it is determined by the combustion state detection means that there is an ignition delay in the combustion of the fuel injected by the main injection. A ratio between an integrated value of a predetermined section of the vibration signal caused by the combustion of fuel injected by the previously performed injection and an integrated value of the predetermined section of the vibration signal caused by the combustion of fuel injected by the main injection is predetermined. The gas temperature in the combustion chamber is raised so that it falls within the range of.

DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Combustion chamber 3 ... Fuel injection nozzle 26 ... Knock sensor 30 ... Control unit

Claims (6)

A fuel injection valve that directly injects fuel into the combustion chamber;
Means for detecting the exhaust air-fuel ratio;
Combustion state detection means for detecting the combustion state in the combustion chamber using a signal resulting from combustion in the combustion chamber;
Combustion chamber gas temperature raising means for raising the gas temperature in the combustion chamber,
The fuel injection valve injects a small amount of fuel prior to the main injection, and when the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio, the fuel injection valve delays the ignition of the fuel injected by the main injection by the combustion state detecting means. When it is determined that there is, the control device for an internal combustion engine, wherein the gas temperature in the combustion chamber is raised by the gas temperature raising means in the combustion chamber.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion chamber gas temperature increasing means increases the gas temperature in the combustion chamber by increasing an EGR rate.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion chamber gas temperature raising means raises the gas temperature in the combustion chamber by a glow plug.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the combustion state detection means is a knock sensor attached to an internal combustion engine body constituting a combustion chamber.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the combustion state detection means is an in-cylinder pressure sensor that directly detects an in-cylinder pressure of each cylinder.   When the combustion state detection means determines that there is an ignition delay in the combustion of the fuel injected by the main injection, the integration of a predetermined section of the vibration signal resulting from the combustion of the fuel injected by the injection performed prior to the main injection The gas temperature in the combustion chamber is increased so that the ratio between the value and the integrated value of a predetermined section of the vibration signal resulting from the combustion of the fuel injected by the main injection is within a predetermined range. Item 5. The control device for an internal combustion engine according to Item 4.

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