JP4524966B2 - Diesel engine control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control system for a diesel engine.
[0002]
[Prior art]
Diesel engine exhaust gas contains CO, HC, NOx, black smoke, and the like.
NOx is more easily generated as the in-cylinder temperature of the diesel engine is higher, and black smoke is generated when the fuel is exposed to a high temperature in a low oxygen concentration region. Therefore, when the air density in the cylinder is high, rapid combustion occurs and the temperature becomes high and NOx is generated. When the air density is low, fuel dehydrogenation occurs and black smoke is generated.
[0003]
EGR is the mainstream for reducing NOx, but when EGR is performed, the oxygen concentration decreases. Therefore, if NOx is reduced by EGR or the like, a large amount of black smoke is discharged. That is, NOx and black smoke were in a trade-off relationship.
On the other hand, in the prior art described in JP-A-8-86251, a large amount of EGR is performed to reduce NOx emissions and retard the fuel injection timing to lower the combustion peak temperature in the cylinder. This makes it possible to simultaneously reduce NOx and black smoke.
[0004]
[Problems to be solved by the invention]
However, in the above-described prior art, the in-cylinder combustion becomes slow by retarding the fuel injection timing. Therefore, if the retard amount is increased to a dark cloud in order to lower the in-cylinder combustion peak temperature, the misfire of the diesel engine There was a risk of exceeding the limit (ie, misfire).
As a result, there arises a problem that, for example, the combustion stability at a low temperature start is deteriorated. Further, at the time of acceleration, since the acceleration becomes slow due to the slow combustion speed, if the driver steps on the accelerator too much in order to obtain the desired acceleration, there arises a problem that emission and fuel consumption deteriorate.
[0005]
Normally, the fuel injection timing is not retarded during acceleration, but is generally advanced to obtain a feeling of acceleration. However, if the fuel injection timing is advanced, NOx and black smoke are increased, so it is difficult to achieve simultaneous reduction of NOx and black smoke while obtaining a desired acceleration feeling.
The present invention has been made based on the above circumstances, and an object thereof is to provide a control system capable of realizing simultaneous reduction of NOx and black smoke without causing a diesel engine to misfire. Another object of the present invention is to provide a control system capable of realizing simultaneous reduction of NOx and black smoke while obtaining a desired acceleration feeling when the diesel engine is accelerated.
[0006]
[Means for Solving the Problems]
(Invention of Claim 1)
The present invention is estimated by an injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine, an in-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine, and the in-cylinder oxygen concentration estimation means. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration.
Further, when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value, pilot injection is performed prior to the main injection.
[0007]
As the retard amount of the fuel injection timing is increased, the in-cylinder combustion speed becomes slower and eventually reaches the misfire limit. The amount of retardation that reaches the misfire limit varies depending on the in-cylinder oxygen concentration (in-cylinder air-fuel ratio). That is, the larger the in-cylinder oxygen concentration, the larger the retard amount until reaching the misfire limit. Therefore, by controlling the retard amount of the fuel injection timing based on the in-cylinder oxygen concentration, simultaneous reduction of NOx and black smoke can be realized without causing the diesel engine to misfire.
Also, if pilot injection is executed prior to main injection, the compression end temperature in the cylinder rises and the ignition delay can be shortened. As a result, misfire of the diesel engine can be prevented, and simultaneous reduction of NOx and black smoke can be realized.
[0008]
(Invention of Claim 2)
In the control system of the diesel engine according to claim 1,
The injection timing control means controls the retard amount of the fuel injection timing according to the fuel injection amount when the diesel engine is accelerated.
During the acceleration operation, the fuel injection amount changes (increases), and accordingly, the in-cylinder oxygen concentration also changes (decreases). Therefore, by controlling the retard amount of the fuel injection timing in accordance with the fuel injection amount, simultaneous reduction of NOx and black smoke can be realized without causing the diesel engine to misfire.
[0009]
(Invention of Claim 3)
The present invention relates to an injection timing calculating means for calculating a fuel injection timing from an operating state of a diesel engine, an in-cylinder oxygen concentration estimating means for estimating an in-cylinder oxygen concentration of the diesel engine, and an in-cylinder when the diesel engine is accelerated. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the oxygen concentration estimation means.
Further, when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value, pilot injection is performed prior to the main injection.
[0010]
During acceleration, since the fuel is injected in an increased amount, the peak temperature in the cylinder rises. If the fuel injection timing is retarded during this acceleration, the in-cylinder pressure decreases and the fuel is injected into the cylinder where the temperature has decreased after passing through the top dead center. , NOx and black smoke emission can be suppressed.
Also, if pilot injection is executed prior to main injection, the compression end temperature in the cylinder rises and the ignition delay can be shortened. As a result, misfire of the diesel engine can be prevented, and simultaneous reduction of NOx and black smoke can be realized.
[0011]
(Invention of Claim 4)
In the control system of the diesel engine as described in any one of Claims 1-3,
The injection timing control means limits the retard amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less.
The amount of retardation that reaches the misfire limit of a diesel engine varies depending on the in-cylinder oxygen concentration. The smaller the in-cylinder oxygen concentration, the less the amount of retardation reaches the misfire limit. Therefore, when the in-cylinder oxygen concentration is less than or equal to the predetermined value, by limiting the retard amount of the fuel injection timing, misfire of the diesel engine can be prevented, and simultaneous reduction of NOx and black smoke can be realized.
[0012]
(Invention of Claim 5)
In the control system of the diesel engine as described in any one of Claims 1-3,
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value.
As described in the invention of claim 4, when the in-cylinder oxygen concentration becomes small, the misfire limit is reached even with a slight retardation amount. Therefore, when the in-cylinder oxygen concentration is below a predetermined value, the fuel injection timing is advanced. (Advance from the fuel injection timing when the in-cylinder oxygen concentration is a predetermined value) can prevent misfire of the diesel engine, and can realize simultaneous reduction of NOx and black smoke.
[0014]
(Invention of Claim 6 )
The control system for a diesel engine according to any one of claims 1 to 5 , wherein the predetermined value is determined by information relating to an engine operating state such as a cooling water temperature and an engine speed of the diesel engine. Thereby, the predetermined value most suitable for the driving | running state of a diesel engine can be selected.
[0015]
(Invention of Claim 7)
The present invention is estimated by an injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine, an in-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine, and the in-cylinder oxygen concentration estimation means. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration.
The injection timing control means limits the retard amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value.
Further, the predetermined value is determined by information related to the engine operating state such as the cooling water temperature of the diesel engine and the engine speed.
(Invention of Claim 8)
The present invention is estimated by an injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine, an in-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine, and the in-cylinder oxygen concentration estimation means. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration.
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value.
Further, the predetermined value is determined by information related to the engine operating state such as the cooling water temperature of the diesel engine and the engine speed.
(Invention of Claim 9)
The diesel engine control system according to claim 7 or 8, wherein the injection timing control means controls the retard amount of the fuel injection timing in accordance with the fuel injection amount when the diesel engine is accelerated.
(Invention of Claim 10)
The present invention relates to an injection timing calculating means for calculating a fuel injection timing from an operating state of a diesel engine, an in-cylinder oxygen concentration estimating means for estimating an in-cylinder oxygen concentration of the diesel engine, and an in-cylinder when the diesel engine is accelerated. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the oxygen concentration estimation means.
The injection timing control means limits the retard amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value.
Further, the predetermined value is determined by information related to the engine operating state such as the cooling water temperature of the diesel engine and the engine speed.
(Invention of Claim 11)
The present invention relates to an injection timing calculating means for calculating a fuel injection timing from an operating state of a diesel engine, an in-cylinder oxygen concentration estimating means for estimating an in-cylinder oxygen concentration of the diesel engine, and an in-cylinder when the diesel engine is accelerated. Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the oxygen concentration estimation means.
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes equal to or less than a predetermined value.
Further, the predetermined value is determined by information related to the engine operating state such as the cooling water temperature of the diesel engine and the engine speed.
(Invention of Claim 12 )
The control system for a diesel engine according to any one of claims 1 to 11 , further comprising EGR means for returning a part of the exhaust discharged from the diesel engine into the intake air, and the EGR amount according to an operating state of the diesel engine. Control. EGR is effective for reducing NOx, but at the same time is a factor that produces black smoke. On the other hand, if the fuel injection timing is retarded, the mixing of fuel and air is promoted, so that generation of black smoke can be suppressed. Therefore, the simultaneous reduction of NOx and black smoke can be effectively realized by using both EGR and the delay angle of the fuel injection timing.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is an overall configuration diagram showing a control system of a diesel engine.
This control system is applied to a diesel engine (hereinafter referred to as engine 1) equipped with a common rail fuel injection device (described below).
[0017]
The common rail fuel injection device includes a common rail 3 that stores fuel pumped from the high-pressure pump 2 and an injector 5 (installed for each cylinder of the engine 1) connected to the common rail 3 via a high-pressure pipe 4. The high-pressure fuel accumulated in the common rail 3 is injected from the injector 5 into the cylinder of the engine 1 (in-cylinder 6). The high pressure pump 2 has a built-in feed pump for pumping fuel from the fuel tank 7.
[0018]
A pressure sensor 8 that detects the fuel pressure in the common rail 3 is attached to the common rail 3, and the fuel pressure (sensor value) detected by the pressure sensor 8 is output to the ECU 9.
The ECU 9 calculates the fuel pumping period of the high-pressure pump 2 based on the signal from the crank angle sensor 11 attached to the crankshaft 10 of the engine 1 and the signal from the cam angle sensor 13 attached to the camshaft 12. The fuel discharge amount of the high-pressure pump 2 is controlled so that the target common rail pressure is obtained based on the fuel pressure detected by the pressure sensor 8.
[0019]
Further, the ECU 9 determines the target fuel injection amount from information such as the accelerator opening detected by the accelerator sensor 14, the engine speed detected by the crank angle sensor 11, and the engine cooling water temperature detected by the water temperature sensor 15. In order to calculate and achieve the fuel injection amount, the injector 5 is driven by an open / close command calculated from the fuel pressure in the common rail 3 for each operating state of the engine 1.
[0020]
The exhaust gas combusted in the cylinder 6 during the operation of the engine 1 passes through the exhaust pipe 16 and is purified and discharged by the exhaust purification device 17 installed in the exhaust pipe 16. The exhaust pipe 16 is provided with an exhaust turbine 18A constituting a supercharger 18 (variable nozzle turbo), and the intake pipe 19 is provided with a compressor 18B. The supercharger 18 is controlled based on a signal from an intake pressure sensor 20 that detects the intake pressure of the engine 1 and a signal from a VNT drive amount sensor 21 that detects a VNT drive amount of the supercharger 18.
[0021]
On the other hand, the intake air sucked into the intake pipe 19 through an air cleaner (not shown) is mixed with EGR gas recirculated from the exhaust pipe 16 to the intake pipe 19 by the EGR means described below and guided to the cylinder 6 of the engine 1. .
The EGR means includes an EGR passage 22 that communicates the intake pipe 19 and the exhaust pipe 16, an EGR valve 23 that adjusts the flow rate (EGR amount) of EGR gas that recirculates through the EGR passage 22, and an EGR cooling device that is provided in the EGR passage 22. 24 etc.
[0022]
The EGR valve 23 is controlled by the ECU 9 according to the operating state of the engine 1. Specifically, based on signals from an air flow meter 25 that detects the intake air amount, an EGR valve opening sensor 26 that detects the opening of the EGR valve 23, and an intake air temperature sensor 27 that detects the temperature of the intake air. The feedback control is performed so as to obtain an optimum EGR amount.
The EGR cooling device 24 can increase the charging efficiency of the EGR gas introduced into the cylinder 6 by cooling the EGR gas with cooling water, for example.
The intake pipe 19 is provided with an intake throttle 28 for increasing the intake negative pressure by reducing the intake air amount when performing a large amount of EGR.
[0023]
Next, control of the fuel injection timing according to the present invention will be described.
As shown in FIG. 2, the ECU 9 calculates the current in-cylinder oxygen concentration from the operation information of the engine 1 and calculates the fuel injection timing from the in-cylinder oxygen concentration, the engine speed, and the engine coolant temperature. . As shown in FIG. 3, the fuel injection timing is retarded from the fuel injection timing calculated by the conventional system (position indicated by a broken line: the in-cylinder oxygen concentration is not used).
[0024]
The operation information of the engine 1 includes, for example, the engine speed, the engine cooling water temperature, the exhaust oxygen concentration, the intake air temperature, the intake air pressure, the atmospheric pressure, and the like. Here, the in-cylinder oxygen concentration can be obtained from the exhaust oxygen concentration. Hereinafter, the in-cylinder oxygen concentration is defined as the exhaust oxygen concentration. The exhaust oxygen concentration is detected by an O ₂ sensor 29 installed in the exhaust pipe 16. The O ₂ sensor 29 is of a known limit current type and generates a limit current corresponding to the oxygen concentration in the exhaust gas.
[0025]
a) At start-up When the engine is started, since the O ₂ sensor 29 is not activated, the engine is started at the fuel injection timing set in the ECU 9 in advance. After the O ₂ sensor 29 is activated, the fuel injection timing is determined from the engine coolant temperature, the engine speed, and the exhaust oxygen concentration (output of the O ₂ sensor 29). Note that the fuel injection timing at the start obtained from the exhaust oxygen concentration or the like is delayed from the fuel injection timing calculated from the operating state of the diesel engine.
[0026]
At the time of starting, since the engine 1 is not sufficiently warmed up, the engine cooling water temperature is low and the compression end temperature in the cylinder 6 is low. As a result, the time from fuel injection to fuel self-ignition becomes long, and misfires occur. It is likely to occur. In addition, if the in-cylinder oxygen concentration is low due to EGR, misfire is more likely to occur. Therefore, the optimal fuel injection timing can be set from the engine coolant temperature, the engine speed, and the in-cylinder oxygen concentration. In this case, as shown in FIG. 4, since the engine cooling water temperature is low, the ignition delay becomes large. Therefore, in order to prevent misfire and ensure combustion stability, the fuel injection timing is the same operating condition as after engine warm-up. It will be advanced at.
[0027]
b) When the engine cooling water temperature exceeds a predetermined temperature after starting the engine during steady operation, the optimum fuel injection timing is similarly set from the engine cooling water temperature, the engine speed, and the exhaust oxygen concentration (output of the O ₂ sensor 29). To do.
[0028]
c) During acceleration, the driver depresses the accelerator to obtain the necessary engine output. At this time, the fuel injection amount can change with a high response, but the intake air is delayed by about 300 to 2000 msec due to the influence of the response of the EGR valve 23, the supercharge delay of the supercharger 18, the inertia delay of the intake air, and the like. Therefore, immediately after the accelerator is depressed, a large amount of fuel is injected into the cylinder 6 where the air-fuel ratio is small and the amount of oxygen is small. In particular, in the control that retards the injection timing with a large amount of EGR and lowers the combustion temperature, the engine is usually operated in a state where the air-fuel ratio is small (the oxygen concentration is small).
[0029]
Therefore, immediately after acceleration, the in-cylinder oxygen concentration is insufficient, the fuel is incompletely burned, and the necessary engine output cannot be obtained. As a result, when the driver further depresses the accelerator, incomplete combustion is further promoted, combustion is not stabilized, and eventually misfire occurs (see FIG. 5).
Therefore, during acceleration, smooth acceleration can be achieved without misfire by determining the fuel injection timing from the engine coolant temperature, engine speed, and exhaust oxygen concentration (output of the O ₂ sensor 29) (see FIG. 6). ). That is, by limiting the retard amount of the fuel injection timing at the time of acceleration, it is possible to avoid engine misfire even at a rich air-fuel ratio compared to the conventional case.
[0030]
According to the control system described in the present embodiment, the fuel injection timing is set using the in-cylinder oxygen concentration (in-cylinder air-fuel ratio), so that the in-cylinder peak temperature always caused by combustion is kept below a predetermined temperature. It can be controlled (see FIG. 3). As a result, NOx and black smoke can be reduced at the same time, and combustion stability during starting and the like can be ensured, and both drivability and emission reduction during acceleration can be accurately achieved.
[0031]
(Second embodiment)
The difference from the first embodiment is during acceleration. At regular times, as in the first embodiment, the fuel injection timing is determined from the engine speed, the engine coolant temperature, and the exhaust oxygen concentration (output of the O ₂ sensor 29).
At the time of acceleration, as described in the first embodiment, incomplete combustion may be promoted, leading to misfire. Therefore, a limit exhaust oxygen concentration is set for each engine speed, and when the exhaust oxygen concentration (output of the O ₂ sensor 29) is less than or equal to the limit exhaust oxygen concentration, the fuel injection timing is less than or equal to the limit exhaust oxygen concentration. It fixes to the value just before. Thereby, smooth acceleration is possible without causing misfire.
[0032]
(Third embodiment)
Differences from the second embodiment will be described.
During acceleration, a limit exhaust oxygen concentration is set for each engine speed, and if the exhaust oxygen concentration (output of the O ₂ sensor 29) falls below the limit exhaust oxygen concentration, the deviation from the limit exhaust oxygen concentration The fuel injection timing is determined from the engine speed.
As a result, the fuel injection timing can be advanced only in the region where the exhaust oxygen concentration is insufficient, so that smooth acceleration is possible.
[0033]
(Fourth embodiment)
Differences from the second embodiment will be described.
At the time of acceleration, a limit exhaust oxygen concentration is set for each engine speed, and when the exhaust oxygen concentration (output of the O ₂ sensor 29) becomes lower than the limit exhaust oxygen concentration, it becomes lower than the limit exhaust oxygen concentration. Pilot injection is performed prior to main injection only in the region. As a result, as shown in FIG. 7, the compression end temperature in the cylinder 6 can be raised, so that the ignition timing can be advanced even at the same fuel injection timing, so that smooth acceleration is possible.
[0034]
(5th Example)
Differences from the other embodiments will be described.
When obtaining the in-cylinder oxygen concentration (the air-fuel ratio of the in-cylinder 6), without using the output of the O ₂ sensor 29, various information relating to the engine operating state such as the intake air amount, intake pressure, fuel injection amount command value, etc. Calculate by calculation. In this case, the present invention can be achieved without adding the O ₂ sensor 29 to the conventional system.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of the present control system.
FIG. 2 is a block diagram schematically illustrating a procedure for calculating fuel injection timing.
FIG. 3 is a characteristic diagram showing a correlation between fuel injection timing and in-cylinder temperature.
FIG. 4 is a characteristic diagram showing the relationship between engine coolant temperature and ignition delay.
FIG. 5 is a characteristic diagram showing a relationship between in-cylinder air-fuel ratio and ignition delay.
FIG. 6 is a time chart of the present control system.
FIG. 7 is a characteristic diagram showing a change in in-cylinder temperature when pilot injection is performed.
[Explanation of symbols]
1 engine (diesel engine)
6 In-cylinder 9 ECU
22 EGR passage (EGR means)
23 EGR valve (EGR means)

Claims (12)

Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the cylinder oxygen concentration estimated by the cylinder oxygen concentration estimation means ,
A control system for a diesel engine that performs pilot injection prior to main injection when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less . In the control system of the diesel engine according to claim 1,
The control system for a diesel engine, wherein the injection timing control means controls a retard amount of the fuel injection timing according to a fuel injection amount when the diesel engine is accelerated. Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means when the diesel engine is accelerated. Prepared ,
A control system for a diesel engine that performs pilot injection prior to main injection when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less . In the control system of the diesel engine as described in any one of Claims 1-3,
The diesel engine characterized in that the injection timing control means limits a retard amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less. Control system. In the control system of the diesel engine as described in any one of Claims 1-3,
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less. Features a diesel engine control system. In the control system of any diesel engine according to claim 1,
The control system for a diesel engine, wherein the predetermined value is determined by information relating to an engine operation state such as a cooling water temperature and an engine speed of the diesel engine. Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the cylinder oxygen concentration estimated by the cylinder oxygen concentration estimation means,
The injection timing control means limits the retard amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less,
The control system for a diesel engine, wherein the predetermined value is determined by information relating to an engine operation state such as a cooling water temperature and an engine speed of the diesel engine. Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
Injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the cylinder oxygen concentration estimated by the cylinder oxygen concentration estimation means,
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less,
The control system for a diesel engine, wherein the predetermined value is determined by information relating to an engine operation state such as a cooling water temperature and an engine speed of the diesel engine. The control system for a diesel engine according to claim 7 or 8,
The control system for a diesel engine, wherein the injection timing control means controls a retard amount of the fuel injection timing according to a fuel injection amount when the diesel engine is accelerated. Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
An injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means when the diesel engine is accelerated. Prepared,
The injection timing control means limits the retardation amount of the fuel injection timing when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means becomes a predetermined value or less,
The control system for a diesel engine, wherein the predetermined value is determined by information relating to an engine operation state such as a cooling water temperature and an engine speed of the diesel engine. Injection timing calculation means for calculating the fuel injection timing from the operating state of the diesel engine;
In-cylinder oxygen concentration estimation means for estimating the in-cylinder oxygen concentration of the diesel engine,
An injection timing control means for retarding the fuel injection timing calculated by the injection timing calculation means based on the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means when the diesel engine is accelerated. Prepared,
The injection timing control means advances the fuel injection timing by a deviation from the predetermined value when the in-cylinder oxygen concentration estimated by the in-cylinder oxygen concentration estimation means is equal to or less than a predetermined value,
The control system for a diesel engine, wherein the predetermined value is determined by information relating to an engine operation state such as a cooling water temperature and an engine speed of the diesel engine. In the control system of the diesel engine as described in any one of Claims 1-11,
A diesel engine control system comprising an EGR means for returning a part of exhaust discharged from the diesel engine into intake air, and controlling an EGR amount in accordance with an operating state of the diesel engine.

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