JP4760561B2 - Combustion control system for compression ignition internal combustion engine - Google Patents

Description

  The present invention relates to a combustion control technique for a compression ignition type internal combustion engine capable of switching between two operation modes having different EGR gas amounts introduced into a cylinder.

  As an internal combustion engine mounted on a vehicle or the like, a compression ignition type internal combustion engine capable of switching between a premixed combustion operation mode and a diffusion combustion operation mode is known.

  In the premixed combustion operation mode, it is necessary to form a premixed gas in the cylinder by performing fuel injection earlier than the diffusion combustion operation mode. However, if fuel injection is performed earlier than the diffusion combustion operation mode, the fuel may ignite prematurely before the premixed gas is formed. Therefore, in the premixed combustion operation mode, the fuel ignition delay period is increased by introducing a larger amount of EGR gas into the cylinder than in the diffusion combustion operation mode.

  By the way, when the internal combustion engine shifts from the fuel cut operation mode or the diffusion combustion operation mode to the premixed combustion operation mode, the amount of EGR gas introduced into the cylinder does not increase immediately. There is a possibility of not being able to understand.

On the other hand, conventionally, when the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode, the fuel injection timing is changed to the injection timing of the premixed combustion operation mode during the period when the EGR gas amount is smaller than the desired amount. A method has been proposed in which the fuel injection amount is made smaller than the amount commensurate with the required torque while being advanced to (for example, see Patent Document 1).
JP 2004-124732 A

  By the way, since the conventional technology immediately advances the fuel injection timing from the injection timing in the diffusion combustion operation mode to the injection timing in the premixed combustion operation mode, there is a possibility that the combustion state suddenly changes to induce torque fluctuation and noise. There is. Further, when the EGR gas concentration in the cylinder is extremely low, such as when the internal combustion engine shifts from the diffusion combustion operation mode to the premix combustion operation mode immediately after the fuel cut operation, the fuel injection timing is immediately set to the premix combustion operation mode. If it is changed to the injection timing, pre-ignition may not be avoided even if the fuel injection amount is small.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a combustion control system for a compression ignition type internal combustion engine capable of switching between a diffusion combustion operation mode and a premixed combustion operation mode. The present invention provides a technique capable of suppressing the occurrence of combustion fluctuations and pre-ignition when the combustion operation mode is shifted to the premixed combustion operation mode.

  In order to solve the above-described problems, the present invention provides a combustion control system for a compression ignition type internal combustion engine that can switch between two operation modes in which the amount of EGR gas introduced into a cylinder is different. When the operation mode is shifted from the low operation mode to the operation mode in which the EGR gas amount is relatively large, the fuel is divided into a plurality of times and injected, and the start timing of the most recent fuel injection is advanced stepwise.

More specifically, the present invention introduces a diffusion combustion operation mode in which a predetermined amount of EGR gas is introduced into the cylinder and fuel injection is started at a predetermined timing near the compression top dead center, and a larger amount of EGR gas than the predetermined amount is supplied to the cylinder. In a combustion control system for a compression ignition internal combustion engine that can be switched between a premixed combustion operation mode that is introduced into the engine and starts fuel injection earlier than the predetermined time,
When the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode, fuel is injected by dividing into a main fuel injection that starts at the predetermined timing and a preliminary fuel injection that starts earlier than the main fuel injection. In addition, the start timing of the preliminary fuel injection is advanced step by step.

  According to such a combustion control system for a compression ignition type internal combustion engine, the start timing of the preliminary fuel injection is gradually advanced, so that it is possible to prevent the ignition timing from being excessively advanced. Further, since the start timing of the main fuel injection is fixed at a predetermined time, fluctuations in the ignition timing are also suppressed. As a result, when the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode, a rapid change in the combustion state is suppressed.

  The combustion control system for a compression ignition type internal combustion engine according to the present invention advances the start timing of the most recent preliminary fuel injection while increasing the number of preliminary fuel injections when the preliminary fuel injection start timing is advanced. You may make it make it. At this time, it is assumed that the fuel for the increased preliminary fuel injection is subtracted from the injection amount of the main fuel injection.

  Note that the foremost preliminary fuel injection refers to preliminary fuel injection that is performed at the earliest time among a plurality of preliminary fuel injections.

  In this case, the time when the premixed gas is formed in the cylinder is gradually advanced, and the amount of the premixed gas is gradually increased. As a result, a rapid change in the ignition timing is suppressed, and the combustion state of the internal combustion engine smoothly transitions from the diffusion combustion state to the premixed combustion state.

  At this time, the timing for increasing the number of preliminary fuel injections and the timing for advancing the start timing of the last preliminary fuel injection may be determined according to the EGR gas concentration in the cylinder. That is, as the EGR gas concentration in the cylinder becomes higher, the number of preliminary fuel injections may be increased and the start timing of the previous preliminary fuel injection may be advanced.

  The fuel ignition delay period becomes longer as the EGR gas concentration in the cylinder becomes higher. Therefore, if the EGR gas concentration in the cylinder increases, the premixed gas formation timing is advanced and the premixed gas formation amount increases. The rapid change of the is less likely to occur.

  Further, in the present invention, the start timing of the foremost preliminary fuel injection may be limited after a predetermined advance angle guard timing.

  Examples of the advance guard timing include the fuel injection timing in the premixed combustion operation mode (the timing at which fuel injection is started) or the earliest fuel injection timing in the range of the fuel injection timing at which bore flushing can be suppressed. it can.

  The combustion control system for a compression ignition type internal combustion engine according to the present invention, after the start timing of the last preliminary fuel injection reaches the advance angle guard timing, is sequentially terminated from the fuel injection having the latest start timing, and is terminated. You may make it add the fuel for fuel injection to the injection quantity of the last preliminary fuel injection.

  When the start timing of the foremost preliminary fuel injection reaches the advance guard time, the EGR gas concentration in the cylinder is somewhat high. For this reason, if the injection amount of the foremost preliminary fuel injection is gradually increased, it is possible to increase the amount of the premixed gas (or decrease the air-fuel ratio of the premixed gas) while suppressing premature ignition. Become.

  By the way, there may be a case where the injection amount of the main fuel injection is relatively large when the start timing of the most recent preliminary fuel injection reaches the advance guard timing. In such a case, when the fuel for the main fuel injection is added to the injection amount of the foremost preliminary fuel injection at the end of the main fuel injection, the injection amount of the foremost preliminary fuel injection rapidly increases and the ignition timing is increased. May fluctuate.

  In contrast, the combustion control system for a compression ignition type internal combustion engine according to the present invention, after the start timing of the previous preliminary fuel injection reaches the advance angle guard timing, sequentially ends the preliminary fuel injection with the latest start timing. The fuel for the completed preliminary fuel injection may be added to the injection amount of the previous preliminary fuel injection.

  In this case, the main fuel injection is continued even after the start timing of the foremost preliminary fuel injection reaches the advance guard time. Therefore, fluctuations in the ignition timing due to a rapid increase in the injection amount of the foremost preliminary fuel injection are prevented. Furthermore, since the fuel injected by the preliminary fuel injection burns using the fuel injected by the main fuel injection as a fire type, the ignition timing is maintained at an appropriate position.

  Note that the combustion control system for the compression ignition type internal combustion engine of the present invention terminates the main fuel injection and removes fuel for the main fuel injection after all the preliminary fuel injections except the previous preliminary fuel injection are completed. You may make it add to the injection quantity of the last preliminary fuel injection.

  At the time when all the preliminary fuel injections except the previous preliminary fuel injection are finished, the EGR gas concentration in the cylinder is sufficiently high. For this reason, if the main fuel injection is continued even after all the preliminary fuel injections except the previous preliminary fuel injection are terminated, the ignition delay period of the fuel injected by the main fuel injection may become excessively long. There is. If the ignition delay period of the fuel injected by the main fuel injection becomes excessively long, the ignition timing will be delayed from the desired timing, leading to a decrease in torque, an increase in the amount of smoke generated, misfiring, or knocking. there is a possibility.

  On the other hand, when the main fuel injection is terminated at the time when all the preliminary fuel injections except for the most recent preliminary fuel injection are terminated, it is possible to suppress the occurrence of problems due to the increase in the ignition delay period.

  By the way, there may be a case where the injection amount of the main fuel injection is relatively large at the time when all the preliminary fuel injections other than the foremost preliminary fuel injection are terminated. In such a case, when the fuel for the main fuel injection is added to the injection amount of the foremost preliminary fuel injection at the end of the main fuel injection, the injection amount of the foremost preliminary fuel injection rapidly increases and the ignition timing is increased. May fluctuate.

  Accordingly, the combustion control system for a compression ignition type internal combustion engine according to the present invention provides a start timing of the main fuel injection while continuing the main fuel injection after all the preliminary fuel injections other than the previous preliminary fuel injection are terminated. May be advanced step by step.

  According to such a configuration, the injection amount of the foremost preliminary fuel injection does not increase rapidly, and the occurrence of problems due to the ignition delay of the fuel injected by the main fuel injection can be suppressed.

  At this time, the combustion control system for the compression ignition type internal combustion engine according to the present invention may correct the advance amount based on the actual combustion state in the cylinder. In this case, fluctuations in ignition timing and misfires can be suppressed.

  Examples of the parameters that serve as indicators of the combustion state include engine speed, intake air amount, fuel injection amount, crankshaft angular acceleration, in-cylinder pressure, and the like.

The EGR gas concentration in the present invention is the concentration of gas burned in the cylinder (burned gas), and more specifically, the concentration of carbon dioxide (CO ₂ ), water (H ₂ O), and the like. .

  According to the present invention, in a combustion control system for a compression ignition type internal combustion engine capable of switching between a diffusion combustion operation mode and a premixed combustion operation mode, the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode. Sometimes combustion fluctuations and pre-ignition can be suppressed. Therefore, the internal combustion engine can suitably shift from the diffusion combustion operation mode to the premixed combustion operation mode.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) capable of appropriately switching between a premixed combustion operation and a diffusion combustion operation.

  The internal combustion engine 1 includes a fuel injection valve 3 that can inject fuel directly into each cylinder 2 and an intake passage 4 that guides air into each cylinder 2. A compressor 50 and an intercooler 6 of a centrifugal supercharger (turbocharger) 5 are arranged in the intake passage 4.

  The intake air supercharged by the compressor 50 is cooled by the intercooler 6 and then guided into each cylinder 2. The intake air introduced into each cylinder 2 is ignited and burned in the cylinder 2 together with the fuel injected from the fuel injection valve 3.

  Gas burned in each cylinder 2 (burned gas) is discharged to the exhaust passage 7. The exhaust discharged into the exhaust passage 5 is released into the atmosphere via the turbine 51 and the exhaust purification catalyst 8 disposed in the middle of the exhaust passage 5.

  As the exhaust purification catalyst 8, a NOx storage reduction catalyst having oxidation ability and NOx storage ability, a particulate filter having oxidation ability and PM trapping ability, a particulate filter carrying a storage reduction type NOx catalyst, or the like is used. It can be illustrated.

  The intake passage 4 and the exhaust passage 7 described above are connected to each other by an EGR passage 9. In the middle of the EGR passage 9, an EGR valve 10 that adjusts the flow rate of exhaust gas (hereinafter referred to as “EGR gas”) flowing through the EGR passage 9, and an EGR cooler for cooling the EGR gas flowing through the EGR passage 9 11 is arranged.

  In addition, an intake throttle valve 12 is disposed in a portion of the intake passage 4 downstream of the intercooler 6 and upstream of the connection portion of the EGR passage 9.

The fuel injection valve 3, the EGR valve 10, and the intake throttle valve 12 described above are electrically controlled by the ECU 13. The ECU 13 is attached to the internal combustion engine 1, the measured value of the air flow meter 14 disposed in the intake passage 4, the measured value of the air-fuel ratio sensor (A / F sensor) 15 disposed in the exhaust passage 5 downstream from the exhaust purification catalyst 8. The fuel injection valve 3, the EGR valve 10, and the intake throttle valve 12 are controlled using the measured value of the crank position sensor 16 and the measured value of the accelerator position sensor 17 as parameters.

  For example, when the engine operating state determined from the load (accelerator opening degree) Accp and the engine speed Ne of the internal combustion engine 1 is in the premixed combustion region shown in FIG. 2, the ECU 13 is earlier than the compression top dead center of each cylinder 2. A premixed combustion operation is performed in which fuel is injected from the fuel injection valve 3 (in the initial or middle stage of the compression stroke) to form a premixed gas, and the premixed gas is compressed and ignited near the compression top dead center.

  When the engine operation state determined from the load Accp and the engine speed Ne of the internal combustion engine 1 is in the diffusion combustion operation region shown in FIG. 2, the ECU 13 sends fuel from the fuel injection valve 3 near the compression top dead center of each cylinder 2. A diffusion combustion operation is performed to cause diffusion combustion by injecting.

  By the way, when the internal combustion engine 1 shifts from the diffusion combustion operation to the premixed combustion operation, the EGR gas introduced into the cylinder 2 cannot immediately increase to a desired amount. On the other hand, if the fuel injection timing is immediately switched from the injection timing for the diffusion combustion operation mode (near compression top dead center) to the injection timing for the premixed combustion operation mode (initial stage or middle stage of the compression stroke), Since the fuel injection timing becomes too early with respect to the EGR gas concentration, torque fluctuation and noise may occur.

  On the other hand, in the combustion control system of the present embodiment, when the internal combustion engine 1 shifts from the diffusion combustion operation mode to the premixed combustion operation mode, the ECU 13 divides the fuel into a plurality of times and injects the fuel in the foremost fuel. The start time of injection was gradually advanced.

  FIG. 3 is a timing chart showing the procedure for changing the fuel injection parameters in the process in which the internal combustion engine 1 shifts from the diffusion combustion operation mode to the premixed combustion operation mode.

  First, as shown in FIG. 3A, the ECU 13 starts the main fuel injection M that is started at the same time as the fuel injection timing (Tdf in FIG. 3) in the diffusion combustion operation mode, and is earlier than the main fuel injection M. The fuel is injected divided into the preliminary fuel injection S that is started at the beginning.

  At that time, the sum of the injection amount of the main fuel injection M and the injection amount of the preliminary fuel injection S is set to be equal to the amount commensurate with the required torque of the internal combustion engine 1. This is for suppressing the torque fluctuation of the internal combustion engine 1.

  Further, the injection amount of the preliminary fuel injection S is preferably set as small as possible. This is because the change in the combustion state due to the addition of the preliminary fuel injection S is minimized, and the pre-ignition of the fuel injected by the preliminary fuel injection S is suppressed. Therefore, the injection amount of the preliminary fuel injection S may be set to the minimum injection amount Qmin that the fuel injection valve 3 can inject.

Next, the ECU 13 gradually increases the number of preliminary fuel injections S (hereinafter referred to as “the number of preliminary fuel injections”) (see (b), (c), and (d) of FIG. 3). Specifically, the ECU 13 increases the number of preliminary fuel injections as the EGR gas concentration (the concentration of CO ₂ or H ₂ O) in the cylinder 2 increases.

  The EGR gas concentration in the cylinder 2 can be estimated using the engine speed and the measured value (intake air amount) of the air flow meter 14 as parameters. This is because the EGR gas transport delay becomes shorter as the engine speed increases, and the EGR path (path returning from the cylinder 2 to the cylinder 2 via the exhaust passage 7, the EGR passage 9, and the intake passage 4 as the intake air amount increases). This is because the amount of gas introduced into the cylinder 2 via the cylinder) increases.

Further, the EGR gas concentration in the cylinder 2 can be predicted from the engine speed and the fuel injection amount (total fuel injection amount of the preliminary fuel injection S and the main fuel injection M). This is because the EGR gas transport delay becomes shorter as the engine speed increases, and the concentration of CO ₂ and H ₂ O in the gas introduced into the cylinder 2 through the EGR path increases as the fuel injection amount increases. Because it becomes.

  Returning to FIG. 3, the ECU 13 subtracts the fuel amount corresponding to the increase in the number of preliminary fuel injections from the injection amount of the main fuel injection M when increasing the number of preliminary fuel injections. This is to prevent the torque of the internal combustion engine 1 from deviating from the required torque.

  Further, the ECU 13 has a constant fuel injection interval (in this case, including the interval Δt1 between the main fuel injection M and the preliminary fuel injection S and the interval Δt2 between the preliminary fuel injection S and the auxiliary fuel injection S). To. This is because if the fuel injection interval becomes indefinite, variations in the injection amounts of the main fuel injection S and the preliminary fuel injection S may occur due to fluctuations or pulsations in the injection pressure.

  By the way, if the number of preliminary fuel injections is increased while the fuel injection intervals Δt1 and Δt2 are kept constant, the start timing of the foremost preliminary fuel injection S is advanced every time the number of preliminary fuel injections increases. Become. For this reason, if the fuel injection intervals Δt1 and Δt2 are set long, there is a possibility that the ignition timing of the fuel fluctuates to induce torque fluctuation and noise.

  In contrast, the ECU 13 sets the fuel injection intervals Δt1 and Δt2 as short as possible so that the start timing of the foremost preliminary fuel injection S is not rapidly advanced.

  When the number of preliminary fuel injections is increased by the above-described procedure, the start timing of the previous preliminary fuel injection S reaches a predetermined advance angle guard timing (see (d) of FIG. 3). The advance guard time corresponds to the fuel injection start time in the premixed combustion operation mode or the earliest fuel injection time within the range of fuel injection time at which bore flushing can be suppressed.

  After the start timing of the most recent preliminary fuel injection S reaches the advance angle guard timing, the ECU 13 sequentially ends the fuel injection with the latest start timing, and the fuel for the fuel injection that has been terminated is terminated with the previous preliminary fuel injection. It adds to the injection quantity of S.

  Specifically, as shown in FIG. 3E, the ECU 13 first ends the main fuel injection M and adds the injection amount of the main fuel injection M to the injection amount of the previous preliminary fuel injection S. Subsequently, as shown in (f), (g), and (h) of FIG. 3, the ECU 13 sequentially ends the preliminary fuel injection S that has the latest start timing, and the injection of the preliminary fuel injection S that has ended. The amount is added to the injection amount of the previous preliminary fuel injection S.

  According to the procedure described above, in the process of shifting the internal combustion engine 1 from the diffusion combustion operation mode to the premixed combustion operation mode, the premixed gas formation timing is gradually advanced as the EGR gas concentration in the cylinder 2 increases. At the same time, since the amount of the premixed gas gradually increases, a rapid change in the ignition timing is suppressed. As a result, the internal combustion engine 1 can perform a smooth transition without generating torque fluctuations or noise.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

The difference between the present embodiment and the first embodiment described above is that, in the first embodiment described above, the main fuel injection M is terminated when the foremost preliminary fuel injection S reaches the advance guard time. In this embodiment, the main fuel injection M is continued and the last preliminary fuel injection S is sequentially terminated.

  When the main fuel injection M is terminated at a time when the injection amount of the main fuel injection M is relatively large when the start timing of the foremost preliminary fuel injection S reaches the advance guard time, the combustion state rapidly May fluctuate. Further, when the injection of the main fuel injection M is added to the injection amount of the foremost preliminary fuel injection S, the injection amount of the foremost preliminary fuel injection S increases rapidly, so that the occurrence of premature ignition cannot be avoided. There is a possibility.

  On the other hand, in the combustion control system of the present embodiment, as shown in FIG. 4, at the time when the start timing of the foremost preliminary fuel injection S reaches the advance guard time (see (d) of FIG. 4). When the injection amount of the fuel injection M is relatively large, the main fuel injection M is continued and the final preliminary fuel injection S is sequentially terminated. At this time, the injection amount of the preliminary fuel injection S that has been completed is added to the injection amount of the previous preliminary fuel injection S.

  According to such a method, it is possible to suppress fluctuations in the combustion state caused by the main fuel injection M being terminated at once.

  Further, the injection amount of the preliminary fuel injection S that has been completed is added to the injection amount of the preliminary fuel injection S that has been completed, but since the injection amount of the preliminary fuel injection S per time is extremely small, The injection amount of the fuel injection S does not increase rapidly. Therefore, the occurrence of pre-ignition caused by the rapid increase in the injection amount of the foremost preliminary fuel injection S is also suppressed.

  In addition, after all the preliminary fuel injections S except for the foremost preliminary fuel injection S are completed, the ECU 13 ends the main fuel injection M and changes the injection amount of the main fuel injection M to the injection of the previous preliminary fuel injection S. Add to the quantity.

  By the way, it is conceivable that the injection amount of the main fuel injection M becomes very large at the time when all the preliminary fuel injections S except for the foremost preliminary fuel injection S are completed. In such a case, a method of gradually decreasing the injection amount of the main fuel injection M and gradually increasing the injection amount of the foremost preliminary fuel injection S can be considered.

  However, the EGR gas concentration in the cylinder 2 is relatively high at the time when all the preliminary fuel injections S other than the foremost preliminary fuel injection S are terminated. For this reason, if the main fuel injection M is continued even after all the preliminary fuel injections S except the foremost preliminary fuel injection S are terminated, the ignition delay period of the fuel injected by the main fuel injection M becomes excessive. Since it becomes longer, there is a possibility that a decrease in torque, an increase in the amount of smoke generated, misfire, or knocking may be induced.

  On the other hand, after all the preliminary fuel injections S except the frontmost preliminary fuel injection S are finished, a method of gradually advancing the start timing of the main fuel injection M is appropriate.

  Specifically, as shown in FIG. 5, when the ECU 13 finishes all the preliminary fuel injections S except for the foremost preliminary fuel injection S (see (g) of FIG. 5), the main fuel injection M starts. Advance the time gradually.

  It is preferable that the advance amount at that time be increased as the EGR gas concentration increases. Further, the ECU 13 may correct the advance amount based on the actual combustion state. Specifically, the ECU 13 estimates the increase amount of the in-cylinder pressure due to the combustion of the fuel based on the in-cylinder pressure sensor and the angular acceleration of the crankshaft, and increases the advance amount as the estimated increase amount decreases. Such correction may be performed.

  According to such a method, the injection amount of the foremost preliminary fuel injection S does not increase rapidly, and the occurrence of problems due to the ignition delay of the fuel injected by the main fuel injection M is suppressed. Can do.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows the map for switching a premix combustion operation and a diffusion combustion operation. 2 is a timing chart showing a procedure for changing a fuel injection parameter in a process in which the internal combustion engine shifts from a diffusion combustion operation mode to a premixed combustion operation mode in the first embodiment. 6 is a timing chart showing a first change procedure of a fuel injection parameter in a process in which an internal combustion engine shifts from a diffusion combustion operation mode to a premixed combustion operation mode in Embodiment 2. 7 is a timing chart showing a second procedure for changing a fuel injection parameter in a process in which the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Intake passage 7 ... Exhaust passage 9 ... EGR passage 10. ... EGR valve 11 ... EGR cooler 12 ... Intake throttle valve 13 ... ECU
14 .... Air flow meter 15 .... A / F sensor 16 .... Crank position sensor

Claims (9)

A diffusion combustion operation mode in which a predetermined amount of EGR gas is introduced into the cylinder and fuel injection is started at a predetermined time near the compression top dead center, and a larger amount of EGR gas than the predetermined amount is introduced into the cylinder and the predetermined time In a combustion control system for a compression ignition internal combustion engine capable of switching between a premixed combustion operation mode in which fuel injection is started earlier,
When the internal combustion engine shifts from the diffusion combustion operation mode to the premixed combustion operation mode, fuel is injected by dividing into a main fuel injection that starts at the predetermined timing and a preliminary fuel injection that starts earlier than the main fuel injection. In addition, the start timing of the preliminary fuel injection is advanced in stages,
The number of pre備燃fuel injection stepwise advancing the start timing of the preliminary fuel injection foremost with increasing preliminary fuel injection amount of the fuel that has been increased compression, characterized in that it is subtracted from the main fuel injection A combustion control system for an ignition type internal combustion engine. Oite to claim 1, the higher the EGR gas concentration in the cylinder increases, the compression ignition type internal combustion engine, characterized in that advancing the start timing of the preliminary fuel injection foremost with increasing the number of the preliminary fuel injection combustion Control system. Oite to claim 1 or 2, the start timing of the preliminary fuel injection foremost, combustion control system of a compression ignition type internal combustion engine, characterized in that it is limited after a predetermined advance angle guard timing. Oite to claim 3, after the start timing of the preliminary fuel injection foremost reaches the advance guard timing is start timing is sequentially terminated from slowest fuel injection, foremost the fuel injection amount of the fuel was terminated A combustion control system for a compression ignition type internal combustion engine, which is added to the preliminary fuel injection. Oite to claim 3, after the start timing of the preliminary fuel injection foremost reaches the advance guard timing is start timing is sequentially terminated from the slowest preliminary fuel injection, pre-fuel injection amount of the fuel was terminated Is added to the foremost preliminary fuel injection, a combustion control system for a compression ignition type internal combustion engine. Oite to claim 5, after all of the preliminary fuel injection with the exception of preliminary fuel injection foremost was ended is that the main fuel injection is terminated, it adds the main fuel injection amount of the fuel to the pre-fuel injection foremost A combustion control system for a compression ignition type internal combustion engine. Oite to claim 5, after all of the preliminary fuel injection with the exception of preliminary fuel injection foremost was ended, the compression ignition type internal combustion engine, characterized in that stepwise advances the start timing of the main fuel injection Combustion control system. Oite to claim 7, as the EGR gas concentration in the cylinder increases, the combustion control system of a compression ignition type internal combustion engine, characterized in that advancing the start timing of the main fuel injection. Combustion control system of a compression ignition type internal combustion engine Oite to claim 7 or 8, advance amount in accordance with the combustion state in the cylinder, characterized in that it is corrected.

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