JP6173163B2 - Combustion control device - Google Patents

Description

  The present invention relates to a combustion control device for an engine that performs premixed compression ignition (PCCI) combustion.

  As a combustion control device for an engine that performs premixed compression ignition combustion, for example, as described in Patent Document 1, a device that injects fuel from an injector in a plurality of times from the middle stage to the latter stage of a cylinder compression stroke is known. ing.

JP 2004-3439 A

  However, when premixed compression ignition combustion is performed as in the above prior art, if the outside air temperature rises, an appropriate heat generation rate waveform (combustion waveform) cannot be obtained, leading to an increase in combustion noise.

  An object of the present invention is to provide a combustion control device that can suppress an increase in combustion noise when the outside air temperature rises.

  The present invention relates to an engine combustion control apparatus that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, and a second fuel injection after the first fuel injection is performed. As described above, the injection valve control means for controlling the fuel injection valve and the temperature detection means for detecting the outside air temperature are provided, and the injection valve control means determines the fuel injection timing of the first fuel injection and the second fuel injection. A first injection timing retarding means for retarding the fuel injection timing of the first fuel injection when the outside air temperature detected by the temperature detecting means is higher than the reference temperature, and a temperature detecting means. When the detected outside air temperature is higher than the reference temperature, the second amount is set such that the retard amount of the fuel injection timing of the second fuel injection is smaller than the retard amount of the fuel injection timing of the first fuel injection. Retard the fuel injection timing of the fuel injection It is characterized in that it has a 2 injection timing retard means. Note that the outside air temperature here includes not only the outside air temperature itself but also a temperature corresponding to the outside air temperature.

  When the outside air temperature rises, the ignitability of the fuel is improved and the ignition timing is advanced. As a result, the heat generation rate waveform (combustion waveform) is greatly different from that at the reference temperature. Therefore, in the present invention, when the outside air temperature is higher than the reference temperature, the fuel injection timing of the first fuel injection and the second fuel injection performed thereafter is retarded and the fuel of the second fuel injection is By making the retard amount of the injection timing smaller than the retard amount of the fuel injection timing of the first fuel injection, the heat generation rate waveform can be brought close to that at the reference temperature. Thereby, an increase in combustion noise when the outside air temperature rises can be suppressed.

  Preferably, the first injection timing retarding means retards the fuel injection timing of the first fuel injection so that the ignition timing by the first fuel injection is equivalent to the ignition timing at the reference temperature. In this case, since the first heat generation peak due to the first fuel injection substantially coincides with that at the reference temperature, combustion noise can be reliably reduced.

  Preferably, the second injection timing retarding means is configured to reduce the maximum value of the sound pressure at the time of combustion by the first fuel injection by the sound pressure at the time of combustion by the second fuel injection. Delay the fuel injection timing of fuel injection. In this case, since the maximum value of the sound pressure during combustion by the first fuel injection is reduced, the combustion noise can be reliably reduced.

  At this time, the second injection timing retarding means converts the sound wave of the sound pressure during combustion by the second fuel injection into the sound pressure during the frequency band in which the sound pressure during combustion by the first fuel injection has a maximum value. It is preferable to retard the fuel injection timing of the second fuel injection so as to cancel out by the pressure wave. In this case, since the sound pressure in a specific frequency band becomes low, combustion noise in a specific frequency band can be reduced. As a result, overall (all frequency band) combustion noise can be reduced.

  Furthermore, preferably, it further includes air-fuel ratio control means for controlling the air-fuel ratio in the combustion chamber to be maintained at the air-fuel ratio at the reference temperature when the outside air temperature detected by the temperature detection means is higher than the reference temperature. In this case, since the combustion of the fuel / air premixed gas is appropriately performed, it is possible to suppress an increase in smoke and unburned HC and CO.

  According to the present invention, it is possible to suppress an increase in combustion noise when the outside air temperature rises. Thereby, it is possible to realize excellent premixed compression ignition combustion.

It is a schematic structure figure showing a diesel engine provided with one embodiment of a combustion control device concerning the present invention. It is a flowchart which shows the detail of the process sequence performed by ECU shown in FIG. It is a graph which shows the concept which makes the pressure wave of the sound pressure at the time of the combustion by the 2nd fuel injection interfere with the pressure wave of the sound pressure at the time of the combustion by the 1st fuel injection. It is a graph which compares and shows an example of a heat release rate waveform. It is a graph which compares and shows an example of the frequency characteristic (spectrum) of a sound pressure. It is a graph which compares and shows an example of a combustion noise.

  Hereinafter, a preferred embodiment of a combustion control device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a diesel engine provided with an embodiment of a combustion control device according to the present invention. In the figure, a diesel engine 1 according to this embodiment is a four-cylinder in-line diesel engine. The diesel engine 1 includes an engine body 2, and the engine body 2 is provided with four cylinders 3.

  Each cylinder 3 is provided with an injector (fuel injection valve) 5 for injecting fuel into the combustion chamber 4. The injector 5 injects fuel radially from the injection nozzle 5a. Each injector 5 is connected to a common rail 6, and high-pressure fuel stored in the common rail 6 is constantly supplied to each injector 5.

  An intake passage 7 for sucking air into the combustion chamber 4 is connected to the engine body 2 via an intake manifold 8. In addition, an exhaust passage 9 for discharging exhaust gas after combustion is connected to the engine body 2 via an exhaust manifold 10.

  In the intake passage 7, an air cleaner 11, a compressor 13 of the turbocharger 12, an intercooler 14, and a throttle valve 15 are provided from the upstream side toward the downstream side. The exhaust passage 9 is provided with a turbine 16 of the turbocharger 12 and a DPF 17 with a catalyst from the upstream side toward the downstream side.

  The diesel engine 1 also includes an exhaust gas recirculation (EGR) unit 18 that recirculates a part of the exhaust gas after combustion into the combustion chamber 4 as exhaust gas recirculation gas (EGR gas). The EGR unit 18 is provided so as to connect the intake passage 7 and the exhaust manifold 10, and an EGR passage 19 that recirculates the EGR gas, and an EGR that adjusts the recirculation amount of the EGR gas from the exhaust manifold 10 to the intake passage 7. The EGR cooler 21 that cools the EGR gas that passes through the valve 20, the EGR passage 19, the bypass passage 22 that is connected to the EGR passage 19 so as to bypass the EGR cooler 21, and the EGR gas passage on the EGR cooler 21 side Or it has the switching valve 23 switched to the bypass channel | path 22 side.

  Each injector 5, throttle valve 15, EGR valve 20 and switching valve 23 are controlled by an electronic control unit (ECU) 24. A crank angle sensor 25, an accelerator opening sensor 26, and an outside air temperature sensor 27 are connected to the ECU 24.

  The crank angle sensor 25 is a sensor that detects the rotational speed (engine rotational speed) of the engine body 2 by detecting the rotational angle (crank angle) of a crankshaft to which a piston (not shown) is coupled. The accelerator opening sensor 26 is a sensor that detects a depression angle (accelerator opening) of an accelerator pedal as a load (engine load) of the engine body 2. The outside air temperature sensor 27 is a sensor (temperature detecting means) that detects the outside air temperature of the engine body 2, and is disposed in the air cleaner 11, for example.

  Here, the injector 5, the throttle valve 15, the EGR unit 18, the ECU 24 and the sensors 25 to 27 constitute the combustion control device 28 of the present embodiment. The combustion control device 28 sucks air into the combustion chamber 4 and injects fuel from each injector 5 into the combustion chamber 4 in a plurality of times for each cycle of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke. (Split injection) and control to perform premixed compression ignition combustion.

  FIG. 2 is a flowchart showing details of a processing procedure executed by the ECU 24. This process is a process for inputting the detection signals of the sensors 25 to 27 and performing predetermined steps to control the injector 5 and the EGR valve 20.

  In the figure, first, the first fuel injection (first fuel injection) is performed based on the engine speed detected by the crank angle sensor 25 and the accelerator opening (engine load) detected by the accelerator opening sensor 26. Then, the fuel injection amount and fuel injection timing of the second fuel injection (second fuel injection) to be performed thereafter are determined (step S101). Here, the first fuel injection and the second fuel injection are main fuel injections for performing premixed compression ignition combustion.

  Subsequently, it is determined whether or not the outside air temperature detected by the outside air temperature sensor 27 is higher than a reference temperature (for example, 25 ° C.) (step S102). When it is determined that the outside air temperature is higher than the reference temperature, the EGR valve 20 is controlled so that the air-fuel ratio in the combustion chamber 4 is maintained at the air-fuel ratio obtained at the reference temperature (step S103).

  When the outside air temperature becomes higher than the reference temperature, the air sucked into the combustion chamber 4 expands, so that the air density decreases and the amount of air sucked into the combustion chamber 4 decreases. For this reason, smoke is likely to be generated, and unburned CO and HC increase. Therefore, the amount of intake air into the combustion chamber 4 is increased by controlling the EGR valve 20 to reduce the amount of recirculation of EGR gas into the intake passage 7. As a result, when fuel is supplied into the combustion chamber 4 by the injector 5, combustion of the premixed mixture of fuel and air is appropriately performed, so smoke and unburned HC and CO are reduced. can do.

  Subsequently, the fuel injection amount of the second fuel injection determined in step S101 is reduced according to the outside air temperature and the engine load (step S104). At this time, as the outside air temperature deviation (= outside air temperature−reference temperature) increases, the amount of reduction increases, and as the engine load increases, the amount of reduction increases.

  When the outside air temperature becomes higher than the reference temperature, the delay in fuel ignition due to the second fuel injection is shortened, so the premixing time from the end of the second fuel injection to the start of ignition of the fuel is shortened. Smoke is likely to occur due to insufficient premixing with air. Therefore, by reducing the fuel injection amount of the second fuel injection in accordance with the outside air temperature and the engine load, the execution time of the second fuel injection is shortened. Therefore, the ignition of the fuel starts from the end of the second fuel injection. The premixing time until the start becomes longer, and the fuel and air are sufficiently premixed. Thereby, smoke can be further reduced.

  Subsequently, the fuel injection amount of the first fuel injection is increased by an amount corresponding to the reduction of the fuel injection amount of the second fuel injection (step S105). As a result, the total fuel injection amount of the first fuel injection and the second fuel injection becomes the same amount as the total fuel injection amount determined in step S101, so that engine torque corresponding to the engine speed and engine load is output. can do.

  Subsequently, the fuel injection timing of the first fuel injection determined in step S101 is retarded (step S106). At this time, it is preferable to retard the fuel injection timing of the first fuel injection so that the ignition timing of the pre-mixture by the first fuel injection is equivalent to the ignition timing of the pre-mixture obtained at the reference temperature. . As a result, the first heat generation peak (combustion peak) due to the first fuel injection almost coincides with that at the reference temperature.

  Subsequently, the fuel injection timing of the second fuel injection determined in step S101 is retarded (step S107). At this time, the fuel injection timing of the second fuel injection is retarded so that the retardation amount of the fuel injection timing of the second fuel injection is smaller than the retard amount of the fuel injection timing of the first fuel injection. .

  Specifically, as shown in FIG. 3, the pressure wave of the sound pressure at the time of combustion caused by the first fuel injection is made to interfere with the pressure wave of the sound pressure at the time of combustion caused by the second fuel injection. The fuel of the second time so that the pressure wave of the sound pressure is canceled by the pressure wave of the sound pressure of the second fuel injection in the frequency band where the sound pressure during the combustion by the fuel injection is the maximum value. It is preferable to retard the fuel injection timing of the injection.

  For example, the optimal fuel injection timing data of the second fuel injection corresponding to the fuel injection amount and the outside air temperature of the first and second fuel injections is prepared by checking in advance as an injection timing correction table and prepared. The fuel injection timing of the second fuel injection is set using the injection timing correction table. As a result, the interval (heat generation peak interval) between the first heat generation peak due to the first fuel injection and the second heat generation peak due to the second fuel injection becomes close to that at the reference temperature.

  In FIG. 3, a one-dot chain line L indicates a pressure wave of sound pressure during combustion by the first fuel injection, a broken line M indicates a pressure wave of sound pressure during combustion by the second fuel injection, and a solid line N indicates the interference between the pressure waves of the two.

  After step S107 is executed, each injector 5 is controlled so that the first fuel injection is performed according to the fuel injection amount changed in step S105 and the fuel injection timing changed in step S106 (step S108). Then, each injector 5 is controlled such that the second fuel injection is performed according to the fuel injection amount changed in step S104 and the fuel injection timing changed in step S107 (step S109).

  On the other hand, when it is determined in step S102 that the outside air temperature is equal to or lower than the reference temperature, steps S103 to S107 are not executed, and the first fuel injection is performed according to the fuel injection amount and fuel injection timing determined in step S101. Thus, each injector 5 is controlled (step S108). Then, each injector 5 is controlled so as to perform the second fuel injection according to the fuel injection amount and the fuel injection timing determined in step S101 (step S109).

  In the above, the ECU 24 constitutes the injection valve control means for controlling the fuel injection valve 5 so that the second fuel injection is performed after the first fuel injection is performed. The EGR unit 18 and the ECU 24 control the air-fuel ratio so that the air-fuel ratio in the combustion chamber 4 is maintained at the air-fuel ratio at the reference temperature when the outside air temperature detected by the temperature detecting means 27 is higher than the reference temperature. Configure the means.

  At this time, steps S101, S102, and S104 to S109 shown in FIG. 2 function as the injection valve control means, and the steps S102 and S103 function as a part of the air-fuel ratio control means. More specifically, step S101 functions as a determination unit that determines the fuel injection timings of the first fuel injection and the second fuel injection. Steps S102 and S106 function as first injection timing retarding means for retarding the fuel injection timing of the first fuel injection when the outside air temperature detected by the temperature detecting means 27 is higher than the reference temperature. In steps S102 and S107, when the outside air temperature detected by the temperature detecting means 27 is higher than the reference temperature, the retard amount of the fuel injection timing of the second fuel injection is delayed from the fuel injection timing of the first fuel injection. It functions as second injection timing retarding means for retarding the fuel injection timing of the second fuel injection so as to be smaller than the angular amount.

  By the way, when the outside air temperature becomes higher than the reference temperature, the ignitability of the fuel increases, so that the ignition timing of the fuel advances, and the heat generation rate waveform at that time is obtained at the reference temperature (see FIG. 4). ) Greatly resulting in increased combustion noise. In order to solve such a problem, it is conceivable to retard the fuel injection timings of the first fuel injection and the second fuel injection.

  However, if the fuel injection timings of the first fuel injection and the second fuel injection are retarded by the same amount, the two heat generation peak intervals in the heat generation rate waveform become different from those at the reference temperature. Further, as described above, since the fuel injection amount of the second fuel injection is decreased and the fuel injection amount of the first fuel injection is increased by that amount, the excitation force of the first fuel injection increases, The excitation force of the second fuel injection decreases. Therefore, the frequency band in which the sound pressure is canceled in the combustion noise spectrum is different from that at the reference temperature, and the maximum value of the sound pressure is increased because the amount of sound pressure cancellation is smaller than that at the reference temperature. As a result, a heat release rate waveform that substantially matches that at the reference temperature cannot be obtained, and the combustion noise level becomes higher than that at the reference temperature.

  In contrast, in the present embodiment, when the outside air temperature is higher than the reference temperature, the ignition timing of the premixed gas by the first fuel injection is equivalent to the ignition timing of the premixed gas obtained at the reference temperature. The fuel injection timing of the first fuel injection is retarded, and the pressure wave of the sound pressure in the frequency band where the sound pressure during combustion by the first fuel injection becomes the maximum value is The fuel injection timing of the second fuel injection is retarded so as to cancel out by the pressure wave of the sound pressure. By doing in this way, the delay amount of the fuel injection timing of the second fuel injection becomes smaller than the retard amount of the fuel injection timing of the first fuel injection, and the heat generation rate waveform almost coincident with the reference temperature. Can be obtained. Thereby, combustion noise when the outside air temperature rises can be reduced.

  FIG. 4 shows a comparison of examples of heat release rate waveforms. In the figure, the broken line P shows the heat generation rate waveform at the reference temperature (25 ° C.). A one-dot chain line Q indicates a heat generation rate waveform in the conventional control in which the retard amount of the fuel injection timing of the first and second fuel injections is equal when the temperature is higher by 20 ° C. than the reference temperature. The solid line R represents heat generation in the present control in which the retard amount of the fuel injection timing of the second fuel injection is smaller than the retard amount of the fuel injection timing of the first fuel injection when the temperature is 20 ° C. higher than the reference temperature. A rate waveform is shown. In any case, the engine speed is 1300 rpm.

Here, in the conventional control and the main control, the retard amount of the fuel injection timing of the first main fuel injection is the ignition timing of the premixed gas obtained when the ignition timing of the premixed gas by the first fuel injection is obtained at the reference temperature. The amount is equivalent to the same time. As a result, as can be seen from FIG. 4, the first heat generation peak of the heat generation rate waveform in the conventional control and the main control substantially coincides with the first heat generation peak of the heat generation rate waveform at the reference temperature.

At the reference temperature, the heat generation peak interval of the heat generation rate waveform is X ₁ (about 3.5 ° CA≈0.45 ms). In the conventional control, the heat generation peak interval of the heat generation rate waveform is X ₂ (about 4.0 ° CA≈0.51 ms), which is longer than the heat generation peak interval of the heat generation rate waveform at the reference temperature. Yes. On the other hand, in this control, the delay amount of the fuel injection timing of the second fuel injection is made smaller than the retard amount of the fuel injection timing of the first fuel injection, so that the heat generation peak interval of the heat generation rate waveform is X ₃ (about 3.4 ° CA≈0.44 ms), which is close to the heat generation peak interval of the heat generation rate waveform at the reference temperature.

  FIG. 5 shows a comparison of examples of frequency characteristics (spectrums) of sound pressure generated in the combustion chamber 4 (inside the cylinder). In the figure, a broken line P indicates frequency characteristics at the reference temperature. A one-dot chain line Q indicates a frequency characteristic in the conventional control in which the retardation amount of the fuel injection timing of the first and second fuel injections is equal when the temperature is higher by 20 ° C. than the reference temperature. A solid line R represents a frequency characteristic in the present control in which the retard amount of the fuel injection timing of the second fuel injection is smaller than the retard amount of the fuel injection timing of the first fuel injection when 20 ° C. is higher than the reference temperature. Is shown. In any case, the engine speed is 1300 rpm. Further, in the conventional control and the main control, the retard amount of the fuel injection timing of the first main fuel injection is the same as that shown in FIG.

  In the conventional control, the frequency at which the combustion noise is canceled is greatly different from that at the reference temperature, and the maximum value of the sound pressure is high. As a result, as shown in FIG. 6, the combustion noise is higher than that at the reference temperature.

  In this control, so that the pressure wave of the sound pressure at the time of combustion by the first fuel injection is offset by the pressure wave of the sound pressure at the time of combustion by the second fuel injection, The fuel injection timing of the second fuel injection is retarded. Specifically, as shown in FIG. 3, the pressure wave of the sound pressure at the time of combustion by the second fuel injection is, for example, 1/2 cycle with respect to the pressure wave of the sound pressure at the time of combustion by the first fuel injection. It is adjusted to shift. As a result, the frequency band in which the combustion noise is canceled is shifted to the high frequency side (see arrow X), and the maximum value of the sound pressure is reduced (see arrow Y). Thereby, the combustion noise of overall (all frequency bands) can be reduced. As a result, as shown in FIG. 6, the combustion noise can be reduced to a level equivalent to that at the reference temperature.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, an injection timing correction table is prepared in advance, and the fuel injection timing of the second fuel injection is retarded using the injection timing correction table. Absent. For example, an in-cylinder pressure sensor that detects the pressure in the combustion chamber 4 (in-cylinder) is provided, and the frequency band in which the sound pressure during combustion by the first fuel injection becomes the maximum value based on the detection value of the in-cylinder pressure sensor. It is also possible to calculate the fuel injection timing of the second fuel injection that cancels the fuel injection.

  In the above embodiment, the pressure wave of the sound pressure is canceled by the pressure wave of the sound pressure at the time of combustion by the second fuel injection in the frequency band in which the sound pressure at the time of combustion by the first fuel injection is the maximum value. As described above, the fuel injection timing of the second fuel injection is calculated, but the method is not particularly limited. For example, in a frequency band other than the frequency band where the sound pressure during combustion by the first fuel injection is the maximum value, the pressure wave of the sound pressure is canceled by the pressure wave of the sound pressure during combustion by the second fuel injection. Even if the fuel injection timing of the second fuel injection is calculated so as to reduce the maximum value of the sound pressure at the time of combustion by the first fuel injection, the effect of this embodiment is exhibited. Furthermore, the fuel injection timing of the second fuel injection is calculated so as to reduce the maximum value of the sound pressure at the time of combustion by the first fuel injection using the sound pressure at the time of combustion by the second fuel injection. You may do it.

  In the above embodiment, the outside air temperature sensor 27 for detecting the outside air temperature of the engine body 2 is provided, and when the outside air temperature is higher than the reference temperature, the fuel injection timings of the first fuel injection and the second fuel injection are set. Although it is retarded, it is not particularly limited to the form, and when the temperature corresponding to the outside air temperature is detected and the temperature is higher than the reference temperature, the fuel of the first fuel injection and the second fuel injection The injection timing may be retarded. Examples of the temperature corresponding to the outside air temperature include the temperature of the air sucked into the combustion chamber 4 (intake air temperature). For example, the intake air temperature sensor that detects the intake air temperature is disposed on the downstream side of the connection portion of the intake passage 7 with the EGR passage 19.

  Further, in the above embodiment, the air-fuel ratio in the combustion chamber 4 is maintained at the air-fuel ratio at the reference temperature by adjusting the flow rate of the EGR gas by the EGR valve 20, but as a method for controlling the air-fuel ratio, In particular, the invention is not limited thereto, and for example, the supercharging pressure of the turbocharger may be adjusted.

  In the above embodiment, when the outside air temperature is higher than the reference temperature, the fuel injection amount of the second fuel injection is reduced and the fuel injection amount of the first fuel injection is increased by the reduced amount. If the noise level is within an allowable range, the processing (steps S104 and S105 shown in FIG. 2) may be omitted.

  Further, in the above embodiment, the main fuel injection is performed twice per cycle, but the main fuel injection may be performed three times or more per cycle. When the main fuel injection is performed three times or more, the last main fuel injection corresponds to the second fuel injection, and the main fuel injection immediately before corresponds to the first fuel injection.

  DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 4 ... Combustion chamber, 5 ... Injector (fuel injection valve), 18 ... EGR unit (air-fuel ratio control means), 24 ... ECU (injection valve control means, determination means, first injection timing retarding means) , Second injection timing retarding means, air-fuel ratio control means), 27 ... outside air temperature sensor (temperature detection means), 28 ... combustion control device.

Claims (5)

In an engine combustion control device that performs premixed compression ignition combustion,
A fuel injection valve for injecting fuel into the combustion chamber of the engine;
Injection valve control means for controlling the fuel injection valve so that the second fuel injection is performed after the first fuel injection is performed;
Temperature detecting means for detecting the outside air temperature ;
A sensor for detecting the rotational speed of the engine;
A sensor for detecting the load of the engine ,
The injection valve control means includes
Determining means for determining a fuel injection amount and a fuel injection timing of the first fuel injection and the second fuel injection based on a rotational speed of the engine and a load of the engine ;
When the outside air temperature detected by the temperature detection means is higher than a reference temperature, the fuel injection timing of the first fuel injection is set to be greater than the fuel injection timing of the first fuel injection determined by the determination means. A first injection timing retarding means for changing the fuel injection timing to the retarded fuel injection timing ;
When the outside air temperature detected by said temperature detecting means is higher than the reference temperature, before Symbol second fuel injection timing of the fuel injection, the fuel injection of the second fuel injection determined by the determining means have a second injection timing retard means for changing the fuel injection timing is retarded from the timing,
The first injection timing retarding means changes the fuel injection timing of the first fuel injection so that the ignition timing by the first fuel injection is equivalent to the ignition timing at the reference temperature,
The second injection timing retarding means reduces the maximum sound pressure during combustion by the first fuel injection by the sound pressure during combustion by the second fuel injection. Change the fuel injection timing of the injection,
The first fuel injection and the second fuel injection are main fuel injections for performing premixed compression ignition combustion,
The injection valve control means is the fuel injection of the first fuel injection changed by the first injection timing retarding means when the outside air temperature detected by the temperature detection means is higher than the reference temperature. The first fuel injection is performed according to the timing, and then the second fuel injection is performed according to the fuel injection timing of the second fuel injection changed by the second injection timing retarding means. A combustion control device for controlling a fuel injection valve . The second injection timing retarding means is responsive to the fuel injection amounts of the first fuel injection and the second fuel injection determined by the determining means, and the outside air temperature detected by the temperature detecting means. The combustion control apparatus according to claim 1 , wherein the fuel injection timing of the second fuel injection is changed . The second injection timing retarding means includes a combustion peak caused by the first fuel injection performed in accordance with the fuel injection timing changed by the first injection timing retarding means in the heat release rate waveform, and the first The first injection timing is set so that the interval between the combustion peak due to the second fuel injection and the combustion peak due to the first fuel injection at the reference temperature is close to the interval between the combustion peak due to the second fuel injection. 2. The fuel injection timing of the second fuel injection is changed by a retard amount smaller than the retard amount of the fuel injection timing of the first fuel injection changed by the retard means. Or the combustion control apparatus of 2. The second injection timing retarding means converts the pressure wave of the sound pressure into a sound pressure at the time of combustion by the second fuel injection in a frequency band in which the sound pressure at the time of combustion by the first fuel injection becomes a maximum value. The combustion control device according to any one of claims 1 to 3 , wherein the fuel injection timing of the second fuel injection is changed so as to cancel out by the pressure wave. Air-fuel ratio control means for controlling the air-fuel ratio in the combustion chamber to be maintained at the air-fuel ratio at the reference temperature when the outside air temperature detected by the temperature detection means is higher than the reference temperature ;
When the outside air temperature detected by the temperature detecting means is higher than the reference temperature, the injection valve control means sets the fuel injection amount of the second fuel injection determined by the determining means to the outside air temperature and with reduced depending on the load of the engine, that having a means for increasing by decrease amount of the fuel injection amount of the second fuel injection the fuel injection amount of the determined first fuel injection by said determining means The combustion control device according to any one of claims 1 to 4 , wherein

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