JP3572435B2 - Control unit for diesel engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device that switches a fuel injection pattern according to operating conditions of a diesel engine.
[0002]
[Prior art]
In recent years, there has been an increasing demand for lower pollution and higher output of diesel engines, and various proposals have been made for combustion techniques.
[0003]
As a conventional combustion technology for a diesel engine, there is one in which most of the fuel is subjected to low-temperature premix combustion by extending the ignition delay period. This is because the decrease in the oxygen concentration due to an increase in the amount of EGR in which the exhaust gas is recirculated to the combustion chamber and the delay in the fuel injection timing prolong the ignition delay period from the start of fuel injection to ignition. This is a method in which evaporation and mixing of fuel are sufficiently promoted during the period, and the proportion of premixed combustion of fuel is increased rather than diffusion combustion. When the proportion of premixed combustion increases, combustion noise tends to increase due to rapid combustion, but the oxygen concentration decreases due to an increase in the amount of EGR, and the fuel injection timing is retarded and the ignition delay period is extended. Due to the temperature drop at the start of combustion, the combustion speed is reduced, so the combustion noise is greatly reduced, and at the same time, the diffusion combustion ratio is low, and the combustion at low temperature suppresses the emission of NOx, smoke and particulate matter. (Reference material: Preprints, 96, 1996-5, 85 tribute).
[0004]
Further, as a conventional combustion technique for a diesel engine, there is a technique for performing pilot injection of fuel prior to main injection of fuel. By performing the pilot injection, it is possible to suppress a sudden increase in pressure due to premixed combustion in the initial stage of combustion, significantly reduce combustion noise, and suppress NOx emissions.
[0005]
In this injection system, for example, as shown in FIG. 11, fuel pressurized by a fuel supply pump 21 is stored in a pressure accumulating chamber 22 and guided from the pressure accumulating chamber 22 to a nozzle 23 facing each cylinder. When the nozzle 23 is closed, the passages 24 and 25 in the nozzle 23 communicate with each other, high-pressure fuel is guided to the upper part of the hydraulic piston 26 and the nozzle chamber 27, and the pressure receiving area of the hydraulic piston 26 By being larger than the pressure receiving area, the needle valve 28 is in a seated state, and no fuel is injected. When the nozzle 23 is opened, the solenoid valve 29 is opened to shut off the passages 24 and 25 and communicate between the passages 25 and 30, so that the pressure applied to the hydraulic piston 26 decreases and the needle valve 28 is lifted, and fuel injection is performed. When the solenoid valve 29 is closed again, high-pressure fuel is guided to the hydraulic piston 26, the needle valve 28 is in a seated state, and fuel injection is stopped (Reference data: Proceedings of the 13th Symposium on Internal Combustion Engines) , 73 tribute).
[0006]
Further, for example, Japanese Patent Application Laid-Open No. 61-212662 discloses an injection system in which a flow passage area of a high-pressure fuel passage in a nozzle is adjusted to suppress an initial injection rate.
[0007]
[Problems to be solved by the invention]
However, in the low-temperature premixed combustion system, it is necessary to increase the EGR amount in order to suppress the combustion speed, and if the EGR amount is increased, the intake fresh air amount is reduced. On the contrary, there is a problem that smoke and particulate matter increase. In addition, when the EGR amount is increased in a high load range, the temperature of the intake gas rises, so that the compression end temperature rises, so that the ignition delay period cannot be sufficiently lengthened and the emission deteriorates.
[0008]
In order to realize low-temperature premixed combustion, it is necessary to inject fuel as much as possible during the ignition delay period, and it is desirable not to perform pilot injection prior to main injection.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to achieve both low emission and low noise by switching a fuel injection pattern according to operating conditions in a diesel engine control device. .
[0010]
[Means for Solving the Problems]
The control apparatus for a diesel engine according to the first aspect controls an injection unit that enables pilot injection of fuel prior to main injection of fuel, and controls an EGR amount in which exhaust gas is recirculated to a combustion chamber according to operating conditions. In a diesel engine including EGR control means, compression end temperature judgment means for judging the compression end temperature of the combustion chamber, and pilot injection of fuel prior to the main injection is not performed as the compression end temperature decreases, or Injection control means for reducing the pilot injection amount or shortening the interval between the pilot injection and the main injection is provided.
[0011]
According to a second aspect of the present invention, there is provided a control apparatus for a diesel engine, which controls an injection means enabling pilot injection of fuel prior to main injection of fuel, and an EGR amount in which exhaust gas is recirculated to a combustion chamber according to operating conditions. In a diesel engine provided with EGR control means, means for determining the oxygen concentration DO2int of the intake gas, and not performing pilot injection of fuel prior to the main injection as the oxygen concentration DO2int decreases, or reducing the pilot injection amount Injection control means for reducing or shortening the interval between the pilot injection and the main injection is provided.
[0012]
According to a third aspect of the present invention, in the control apparatus for a diesel engine according to the second aspect, the pilot injection of the fuel prior to the main injection is not performed., Or reduce the pilot injection amount, or shorten the interval between pilot injection and main injectionThe maximum value of the oxygen concentration DO2int of the intake gas, which limits the operation range, is increased as the engine speed Ne decreases, and is increased as the fuel injection amount decreases.
[0013]
According to a fourth aspect of the present invention, there is provided a diesel engine control device that controls an injection unit that enables pilot injection of fuel prior to main injection of fuel, and an EGR amount of exhaust gas recirculated to a combustion chamber according to an operating condition. Means for detecting, as a EGR rate REGR, a ratio of an EGR amount to an intake fresh air amount in a diesel engine having an EGR control means.When,Injection control means for not performing pilot injection of fuel prior to the main injection as the EGR rate REGR increases, reducing the pilot injection amount, or shortening the interval between pilot injection and main injection.The minimum value of the EGR rate REGR for limiting the operation range in which the pilot injection of fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened, is set as the engine speed Ne. The configuration is changed based on the fuel injection amount.
[0014]
According to a fifth aspect of the present invention, in the control apparatus for a diesel engine according to the fourth aspect of the present invention, the pilot injection of the fuel prior to the main injection is not performed., Or reduce the pilot injection amount, or shorten the interval between pilot injection and main injectionThe minimum value of the EGR rate REGR, which limits the operation range, is reduced as the engine speed Ne decreases, and is increased as the fuel injection amount decreases.
[0015]
The control device for a diesel engine according to claim 6 is, BurningA diesel engine comprising: injection means for enabling pilot injection of fuel prior to fuel main injection; and EGR control means for controlling the amount of EGR in which exhaust gas is returned to the combustion chamber in accordance with operating conditions.Means for detecting a ratio of the EGR amount to the fresh intake air amount as an EGR rate REGR;Means for detecting engine load;As the EGR rate REGR increases, the pilot injection of fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened,Injection control means for not performing pilot injection of fuel prior to the main injection as the engine load increases, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection is provided.
[0016]
The control device for a diesel engine according to claim 7 is, BurningA diesel engine comprising: injection means for enabling pilot injection of fuel prior to fuel main injection; and EGR control means for controlling the amount of EGR in which exhaust gas is returned to the combustion chamber in accordance with operating conditions.Means for detecting a ratio of the EGR amount to the fresh intake air amount as an EGR rate REGR;Means for detecting an excess air ratio of the engine;As the EGR rate REGR increases, the pilot injection of fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened,A fuel injection control means which does not execute pilot injection of fuel prior to the main injection as the excess air ratio of the engine decreases, or reduces the pilot injection amount, or shortens the interval between the pilot injection and the main injection. And
[0017]
The control device for a diesel engine according to claim 8,The invention according to any one of claims 1 to 5, wherein an injection means for enabling pilot injection of the fuel prior to the main injection of the fuel, and an EGR amount by which the exhaust gas is recirculated to the combustion chamber according to operating conditions. In a diesel engine comprising EGR control means for controlling the engine load, means for detecting engine load, and not performing pilot injection of fuel prior to the main injection as the engine load increases, or reducing the pilot injection amount, Or shorten the interval between pilot injection and main injectionAnd an injection control means.
[0018]
The control device for a diesel engine according to claim 9,The invention according to any one of claims 1 to 5, wherein an injection means for enabling pilot injection of the fuel prior to the main injection of the fuel, and an EGR amount by which the exhaust gas is recirculated to the combustion chamber according to operating conditions. In a diesel engine including EGR control means for controlling the engine, the means for detecting the excess air ratio of the engine, and the pilot injection of the fuel prior to the main injection is not performed as the excess air ratio of the engine decreases, or Reduce the pilot injection amount or shorten the interval between pilot injection and main injectionAnd an injection control means.
Claim10The diesel engine control device described in 1 above includes a diesel injection rate varying means for varying the fuel injection rate, and an EGR control means for controlling the amount of EGR in which the exhaust gas is recirculated to the combustion chamber in accordance with the operating conditions. The engine includes a means for determining the oxygen concentration DO2int of the intake gas and an injection control means for increasing the initial fuel injection rate as the oxygen concentration DO2int decreases.
[0019]
Claim11Diesel engine control device according to claim10In the invention described in the above, the maximum value of the oxygen concentration DO2int of the intake gas, which limits the operation region in which the initial fuel injection rate is increased, is increased as the engine speed Ne decreases, and the fuel injection amount is reduced. It was designed to be higher as it became.
[0020]
Claim12The diesel engine control device described in 1 above includes a diesel injection rate varying means for varying the fuel injection rate, and an EGR control means for controlling the amount of EGR in which the exhaust gas is recirculated to the combustion chamber in accordance with the operating conditions. The engine includes means for detecting the ratio of the EGR amount to the fresh intake air amount as the EGR rate REGR, and injection control means for increasing the initial fuel injection rate as the EGR rate REGR increases. .
[0021]
ClaimThirteenDiesel engine control device according to claim12In the invention described in the above, the minimum value of the EGR rate REGR that limits the operation range in which the initial fuel injection rate is increased is reduced as the engine speed Ne is reduced, and the fuel injection amount is reduced. The height was increased accordingly.
[0022]
Claim14The diesel engine control device described in 1 above includes a diesel injection rate varying means for varying the fuel injection rate, and an EGR control means for controlling the amount of EGR in which the exhaust gas is recirculated to the combustion chamber in accordance with the operating conditions. In the engine,Compression end temperature determining means for determining a compression end temperature of the combustion chamber;Means for detecting engine load;As the compression end temperature decreases, the initial fuel injection rate increases,Injection control means for increasing the initial fuel injection rate as the engine load increases.
[0023]
ClaimFifteenThe diesel engine control device described in 1 above includes a diesel injection rate varying means for varying the fuel injection rate, and an EGR control means for controlling the amount of EGR in which the exhaust gas is recirculated to the combustion chamber in accordance with the operating conditions. In the engine,Compression end temperature determining means for determining a compression end temperature of the combustion chamber;Means for detecting an excess air ratio of the engine;As the compression end temperature decreases, the initial fuel injection rate increases,Injection control means for increasing the initial fuel injection rate as the excess air ratio of the engine decreases.
According to a sixteenth aspect of the present invention, there is provided the diesel engine control device according to any one of the tenth to thirteenth aspects, wherein the injection rate variable means for varying the fuel injection rate and the exhaust gas according to the operating conditions. In a diesel engine having EGR control means for controlling the amount of EGR returned to the combustion chamber, means for detecting the engine load, and injection control means for increasing the initial fuel injection rate as the engine load increases It was provided with.
According to a seventeenth aspect of the present invention, there is provided the diesel engine control device according to any one of the tenth to thirteenth aspects, wherein the injection rate variable means for varying the fuel injection rate and the exhaust gas according to the operating conditions. In a diesel engine having EGR control means for controlling the amount of EGR returned to the combustion chamber, a means for detecting an excess air ratio of the engine, and an initial fuel injection rate as the excess air ratio of the engine decreases And an injection control means for increasing the pressure.
[0024]
Function and Effect of the Invention
2. The control device for a diesel engine according to claim 1, wherein pilot injection of fuel is performed prior to main injection with an increase in compression end temperature, a pilot injection amount is increased, or an interval between pilot injection and main injection. , The rapid pressure increase at the beginning of combustion is suppressed, and the combustion noise is reduced.
[0025]
With the configuration in which the execution of the pilot injection is restricted as the compression end temperature decreases, the region where the low-temperature premix combustion is performed is expanded, and the emission is reduced.
[0026]
3. The control apparatus for a diesel engine according to claim 2, wherein the pilot injection is performed, the pilot injection amount is increased, or the interval between the pilot injection and the main injection is increased as the oxygen concentration DO2int of the intake gas increases. As a result, a sudden increase in pressure at the beginning of combustion is suppressed, and combustion noise is reduced.
[0027]
With the configuration in which the execution of the pilot injection is restricted as the oxygen concentration DO2int of the intake gas decreases, the region where the low-temperature premixed combustion is performed is expanded, and the emission is reduced.
[0028]
4. The control device for a diesel engine according to claim 3, wherein the pilot injection is not performed., Or reduce the pilot injection amount, or shorten the interval between pilot injection and main injectionSince the maximum value of the oxygen concentration DO2int of the intake gas that limits the operation range is increased as the engine speed Ne decreases and is increased as the fuel injection amount decreases, the engine speed Ne is increased. The higher the temperature, the higher the temperature of the EGR gas, the higher the intake gas temperature of the engine, the higher the compression end temperature, and the shorter the ignition delay period. By making a good determination, it is possible to ensure the maximum region where low-temperature premix combustion is performed.
[0029]
The control apparatus for a diesel engine according to claim 4, wherein pilot injection of fuel is performed as the EGR rate REGR, which is a ratio of the EGR amount to the fresh intake air amount, decreases, or the pilot injection amount is increased. By increasing the interval between the pilot injection and the main injection, a sharp increase in pressure at the beginning of combustion is suppressed, and the combustion noise is reduced.
[0030]
With the configuration in which the execution of the pilot injection is restricted as the EGR rate REGR increases, the region where low-temperature premix combustion is performed is expanded, and the emission is reduced.
Further, the minimum value of the EGR rate REGR that limits the operation region in which the pilot injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened is determined based on the engine speed Ne and the fuel injection amount. With the configuration that changes, it is possible to maximize the region where low-temperature premix combustion is possible in accordance with the engine speed Ne and the fuel injection amount.
[0031]
In the diesel engine control device according to claim 5, the pilot injection is not performed., Or reduce the pilot injection amount, or shorten the interval between pilot injection and main injectionSince the minimum value of the EGR rate REGR that limits the operation region is reduced as the engine speed Ne decreases, the temperature of the EGR gas increases as the engine speed Ne increases, and the engine speed increases. In response to the rise of the intake gas temperature, the rise of the compression end temperature, and the shortening of the ignition delay period, it is possible to maximize the region where low-temperature premix combustion is possible.
[0032]
Since the minimum value of the EGR rate REGR, which limits the operation range in which the pilot injection is not performed, is increased with the decrease in the fuel injection amount, it is possible to cope with the decrease in the oxygen concentration due to the increase in the fuel injection amount. Thus, the region where low-temperature premix combustion can be performed can be maximized.
[0033]
The control device for a diesel engine according to claim 6,By performing the pilot injection of the fuel as the EGR rate REGR, which is the ratio of the EGR amount to the intake fresh air amount, decreases, or by increasing the pilot injection amount, or by increasing the interval between the pilot injection and the main injection, A sudden increase in pressure at the beginning of combustion is suppressed, and combustion noise is reduced. Further, the configuration in which the execution of the pilot injection is restricted as the EGR rate REGR increases increases the range in which low-temperature premix combustion is performed, thereby reducing emissions. further,By not performing pilot injection with an increase in engine load, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection, the diffusion combustion ratio is reduced and the generation of smoke is suppressed. .
[0034]
The control device for a diesel engine according to claim 7,By performing the pilot injection of the fuel as the EGR rate REGR, which is the ratio of the EGR amount to the intake fresh air amount, decreases, or by increasing the pilot injection amount, or by increasing the interval between the pilot injection and the main injection, A sudden increase in pressure at the beginning of combustion is suppressed, and combustion noise is reduced. Further, the configuration in which the execution of the pilot injection is restricted as the EGR rate REGR increases increases the range in which low-temperature premix combustion is performed, thereby reducing emissions. further,Suppress diffusion combustion and reduce the generation of smoke by not performing pilot injection or reducing the pilot injection amount or shortening the interval between pilot injection and main injection as the excess air ratio of the engine decreases. it can.
[0035]
The control device for a diesel engine according to claim 8,By not performing pilot injection with an increase in engine load, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection, the diffusion combustion ratio is reduced and the generation of smoke is suppressed. .
[0036]
The control apparatus for a diesel engine according to claim 9, wherein the pilot injection is not performed, the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened as the excess air ratio of the engine decreases. Thereby, diffusion combustion can be suppressed, and generation of smoke can be suppressed.
[0037]
Claim10In the control device for a diesel engine described in (1), by reducing the initial injection rate with an increase in the oxygen concentration DO2int of the intake gas, a sudden increase in pressure at the beginning of combustion is suppressed, and the combustion noise is reduced.
[0038]
With the configuration in which the suppression of the initial injection rate is restricted as the oxygen concentration DO2int of the intake gas decreases, the region where low-temperature premix combustion is performed is expanded, and the emission is reduced.
[0039]
Claim11In the control device for a diesel engine described in the above, the maximum value of the oxygen concentration DO2int of the intake gas that limits the operation region where the initial injection rate is increased is increased as the engine speed Ne decreases, and the fuel injection amount is increased. As the engine speed Ne increases, the temperature of the EGR gas increases, the temperature of the intake gas of the engine increases, the compression end temperature increases, and the ignition delay period decreases as the engine speed Ne increases. Accordingly, it is possible to accurately determine a region where low-temperature premix combustion can be performed, and to secure a maximum region where low-temperature premix combustion can be performed.
[0040]
Claim12In the diesel engine control device described in the above, the initial injection rate is reduced along with the decrease in the EGR rate REGR, which is the ratio of the EGR amount to the intake fresh air amount, thereby suppressing a rapid pressure increase at the beginning of combustion. In addition, combustion noise can be reduced.
[0041]
With the configuration in which the suppression of the initial injection rate is limited as the EGR rate REGR increases, the region where low-temperature premixed combustion is performed is expanded, and low emission is achieved.
[0042]
ClaimThirteenIn the diesel engine control device described in (1), the minimum value of the EGR rate REGR that limits the operation range in which the initial injection rate is increased is reduced as the engine speed Ne decreases, so that the engine speed Ne is reduced. As the temperature increases, the temperature of the EGR gas increases, the temperature of the intake gas of the engine increases, the compression end temperature increases, and the low-temperature premix combustion can be performed in response to the shortened ignition delay period. The area can be maximized.
[0043]
Since the minimum value of the EGR rate REGR, which limits the operation range in which the initial injection rate is increased, is increased as the fuel injection quantity is reduced, it is possible to cope with a decrease in the oxygen concentration due to an increase in the fuel injection quantity. As a result, the region where low-temperature premix combustion can be performed can be secured to the maximum.
[0044]
Claim14In the diesel engine control device described in the above,By reducing the initial injection rate as the compression end temperature increases, a sharp pressure increase at the beginning of combustion is suppressed, and the combustion noise is reduced. In addition, the configuration in which the suppression of the initial injection rate is limited as the compression end temperature decreases reduces the area where low-temperature premixed combustion is performed, thereby reducing emissions. further,By suppressing the initial injection rate as the engine load increases, the diffusion combustion ratio can be suppressed, and the generation of smoke can be suppressed.
[0045]
ClaimFifteenIn the diesel engine control device described in the above,By reducing the initial injection rate as the compression end temperature increases, a sharp pressure increase at the beginning of combustion is suppressed, and the combustion noise is reduced. In addition, the configuration in which the suppression of the initial injection rate is limited as the compression end temperature decreases reduces the area where low-temperature premixed combustion is performed, thereby reducing emissions. further,By increasing the initial injection rate as the excess air rate of the engine decreases, the diffusion combustion rate can be suppressed, and the generation of smoke can be suppressed.Furthermore, the configuration in which the suppression of the initial injection rate is limited as the excess air rate increases increases the range in which low-temperature premixed combustion is performed, thereby reducing emissions.
[0046]
In the diesel engine control device according to the fifteenth aspect, by suppressing the initial injection rate as the engine load increases, the diffusion combustion ratio can be suppressed, and the generation of smoke can be suppressed.
In the diesel engine control device according to the sixteenth aspect, by increasing the initial injection rate as the excess air rate of the engine decreases, the diffusion combustion ratio can be suppressed, and the generation of smoke can be suppressed. In addition, the configuration in which the suppression of the initial injection rate is restricted as the excess air rate increases increases the range in which low-temperature premix combustion is performed, thereby reducing emissions.
[0047]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0048]
In FIG. 1, 1 is a diesel engine main body, 2 is an exhaust passage, 3 is an intake passage, and 18 is a turbocharger that supercharges intake air by using pressure energy of exhaust gas of the engine 1.
[0049]
In FIG. 1, reference numeral 11 denotes a fuel supply pump. The fuel pressurized by the supply pump 11 is stored in the pressure accumulating chamber 12 via the pressure regulator 15. The high-pressure fuel in the accumulator 12 is guided to a nozzle 13 facing each cylinder of the engine 1. The fuel pressure in the accumulator 12 adjusted by the pressure regulator 15 is controlled by the control unit 20 according to the operating state. The control unit 20 receives each detected value Ne of the engine speed sensor 10 and the detected value Pf of the pressure sensor 14 provided in the pressure accumulating chamber 12, and sets a target fuel injection amount Qf and a target value set in advance according to the engine speed Ne. Feedback control is performed so as to approach the pressure.
[0050]
The nozzle 13 provided as an injection means for enabling pilot injection of fuel prior to the main injection of fuel is opened and closed via an electromagnetic valve, and its valve opening timing (fuel injection timing) and valve opening period (fuel injection amount) are determined. It is controlled by the control unit 20 according to the operation state. The control unit 20 calculates the target fuel injection amount Qf in accordance with the detection values Ne and Acc of the engine speed sensor 10 and the accelerator opening sensor 19, and brings the fuel injection amount of the nozzle 13 closer to the target fuel injection amount Qf. The valve opening period of the nozzle 13 is controlled.
[0051]
In FIG. 1, reference numeral 4 denotes an EGR passage that connects the exhaust passage 2 and the intake passage 3, and reference numeral 5 denotes an EGR valve that opens and closes the EGR passage 4. By opening the EGR valve 5 and recirculating the EGR gas to the intake passage 3, the oxygen concentration in the cylinder is reduced, the combustion temperature of the fuel is reduced, and the generation of NOx is suppressed. The lift L (opening) of the EGR valve 5 is controlled by the control unit 20 according to the operating state.
[0052]
By the way, when the EGR rate REGR is increased, the generation of NOx is suppressed, but on the other hand, the generation amount of particulate matter tends to increase.
[0053]
In response to this, the control unit 20 increases the EGR amount in accordance with the operating conditions to lower the oxygen concentration, and delays the fuel injection timing to around the top dead center to perform low-temperature premix combustion.
[0054]
By lengthening the ignition delay period from the start of fuel injection to ignition, and by sufficiently evaporating and mixing the fuel during the ignition delay period, the rate of premix combustion of fuel rather than diffusion combustion increases. When the proportion of premixed combustion increases, combustion noise tends to increase due to rapid combustion, but the oxygen concentration decreases due to an increase in the amount of EGR, and the fuel injection timing is retarded and the ignition delay period is extended. By lowering the temperature at the start of combustion, the combustion speed is reduced, so that the combustion noise is greatly reduced.At the same time, the diffusion combustion ratio is low, and by burning at low temperature, NOx, smoke and particulate matter It is also possible to suppress emissions.
[0055]
However, in the above-described low-temperature premixed combustion, it is necessary to increase the EGR amount in order to suppress the combustion speed, and if the EGR amount is increased, the intake fresh air amount is reduced. On the contrary, there is a problem that smoke and particulate matter increase. In addition, when the EGR amount is increased in a high load range, the temperature of the intake gas rises, so that the compression end temperature rises, so that the ignition delay period cannot be sufficiently lengthened and the emission deteriorates. Therefore, it is necessary to lower the EGR rate REGR in a high load region.
[0056]
To cope with this, in this embodiment, there are provided means for determining the compression end temperature of the combustion chamber and means for determining the oxygen concentration DO2int of the intake gas. The control unit 20 determines a region where the compression end temperature is higher than a predetermined value or the oxygen concentration DO2int of the intake gas is higher than a predetermined value and in which low-temperature premixed combustion is not possible, and in this region, the nozzle is controlled prior to the main fuel injection. 13 is opened for a short time, and fuel is pilot-injected (preceding injection).
[0057]
By setting a region where low-temperature premixed combustion is possible according to the compression end temperature and oxygen concentration of the combustion chamber in this way, it is possible to accurately determine whether low-temperature premixed combustion is possible, and achieve both low emission and low noise. it can. By performing pilot injection in a region where low-temperature premixed combustion is not possible, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and noise is reduced.
[0058]
As the data for calculating the oxygen concentration DO2int of the intake gas of the engine 1 in which the fresh air and the EGR gas are mixed, the control unit 20 detects the new intake air amount Qair detected by the air flow meter 9 and the engine speed sensor 10 to detect it. The engine speed Ne, the intake pressure Pint detected by the pressure sensor 6 provided in the intake manifold, the exhaust pressure Pexh detected by the pressure sensor 7 provided in the exhaust manifold, the lift L of the EGR valve 5 and The target fuel injection amount Qf is input.
[0059]
Further, as data for calculating the compression end temperature, the control unit 20 inputs the intake air temperature Tint detected by the temperature sensor 8 provided in the intake manifold.
[0060]
The flowchart of FIG. 2 shows a routine for performing pilot injection according to operating conditions, and is executed by the control unit 20 at regular intervals.
[0061]
First, at Step 1, the engine speed Ne, the target fuel injection amount Qf, the intake pressure Pint, the exhaust pressure Pexh, the intake temperature Tint, the intake fresh air amount Qair, and the lift L of the EGR valve 5 are read.
[0062]
Subsequently, the process proceeds to Step 2, in which the EGR amount QEGR is calculated from the difference between the intake pressure Pint and the exhaust pressure Pexh and the lift L of the EGR valve 5 by the following equation.
[0063]
QEGR = f (L) × (Pexh-Pint)^1/2  … (1)
In calculating the EGR amount QEGR, the volume efficiency of fresh air is calculated according to the intake fresh air amount Qair and the engine speed Ne, the intake pressure Pint is calculated from the volume efficiency, and the volume efficiency and the fuel injection amount are calculated. The exhaust pressure Pexh may be calculated from the engine speed Ne. Further, the intake air temperature Tint may be calculated from the volumetric efficiency, the EGR amount QEGR, and the fuel injection amount.
[0064]
Subsequently, the process proceeds to Step 3, where the oxygen concentration DO2EGR of the EGR gas is calculated by the following equation based on the intake fresh air amount Qair, the target fuel injection amount Qf, and the engine speed Ne.
[0065]
DO2EGR = 0.21−C1 × Qf / (Qair / Ne) (2)
However, C1 is a constant.
[0066]
Subsequently, the process proceeds to Step 4, and the oxygen concentration DO2int of the intake gas of the engine 1 in which the fresh air and the EGR gas are mixed is calculated by the following equation based on the EGR amount QEGR, the EGR gas oxygen concentration DO2EGR, and the intake fresh air amount Qair.
[0067]
DO2int = (0.21 × Qair + DO2EGR × QEGR) / (Qair + QEGR) (3)
Subsequently, the program proceeds to Step 5, in which the compression end temperature is searched based on the preset map shown in FIG. 3 according to the temperature Tint in the intake manifold of the intake passage 3 and the calculated oxygen concentration DO2int of the intake gas.
[0068]
In FIG. 3, the compression end temperature decreases as the temperature Tint in the intake manifold decreases. This is because the compression start temperature decreases as the temperature Tint in the intake manifold decreases.
[0069]
In FIG. 3, the compression end temperature decreases as the oxygen concentration DO2int of the intake gas decreases. This is because the oxygen concentration DO2int of the intake gas decreases and the CO₂, H₂This is because the specific heat ratio of the suction gas decreases due to the high concentration of O.
[0070]
Subsequently, the process proceeds to Step 6, in which the current operating state is in a region where low-temperature premix combustion is possible or low-temperature premix combustion in accordance with the compression end temperature and the oxygen concentration DO2int of the intake gas based on the map shown in FIG. It is determined whether or not the region is impossible.
[0071]
When it is determined that the current operation state is in the region where low-temperature premix combustion is possible, the process proceeds to Step 7, where fuel injection without pilot injection is performed, and low-temperature premix combustion is performed. As a result, the combustion speed is reduced, so that the combustion noise is greatly reduced, and at the same time, the emission of NOx, smoke and particulate matter can be suppressed by burning at a low diffusion combustion rate and at a low temperature.
[0072]
If it is determined that the current operating state is in a region where low-temperature premix combustion is not possible, the process proceeds to Step 8, and pilot injection is performed. As a result, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and combustion noise is reduced.
[0073]
In FIG. 4, the region where low-temperature premix combustion is possible is set to a region where the compression end temperature is lower than the region where low-temperature premix combustion is not possible. Further, as the oxygen concentration DO2int of the intake gas increases, the combustion is switched from low-temperature premixed combustion without pilot injection to combustion with pilot injection. As a result, the lower the compression end temperature, the longer the ignition delay period, the lower the combustion speed, and the lower the oxygen concentration, the lower the combustion speed. As much as possible.
[0074]
Next, as another embodiment, the control unit 20 increases the maximum value of the oxygen concentration DO2int of the intake gas, which limits the region where low-temperature premix combustion is possible, as the engine speed Ne increases, and increases the fuel injection amount. May be set higher as the number increases. As a result, the region where low-temperature premixed combustion is performed is expanded, and emission is reduced.
[0075]
The flowchart of FIG. 5 shows a routine for performing the pilot injection according to the operating conditions, and is executed by the control unit 20 at regular intervals.
[0076]
First, in Step 1, the engine speed Ne, the target fuel injection amount Qf, the intake pressure Pint, the exhaust pressure Pexh, the intake fresh air amount Qair, and the lift L of the EGR valve 5 are read.
[0077]
Subsequently, the process proceeds to Step 2, in which the EGR amount QEGR is calculated from the difference between the intake pressure Pint and the exhaust pressure Pexh and the lift L of the EGR valve 5 by the following equation.
[0078]
QEGR = f (L) × (Pexh-Pint)^1/2  … (1)
Subsequently, the process proceeds to Step 3, where the oxygen concentration DO2EGR of the EGR gas is calculated by the following equation based on the intake fresh air amount Qair, the target fuel injection amount Qf, and the engine speed Ne.
[0079]
DO2EGR = 0.21−C1 × Qf / (Qair / Ne) (2)
However, C1 is a constant.
[0080]
Subsequently, the process proceeds to Step 4, and the oxygen concentration DO2int of the intake gas of the engine 1 in which the fresh air and the EGR gas are mixed is calculated by the following equation based on the EGR amount QEGR, the EGR gas oxygen concentration DO2EGR, and the intake fresh air amount Qair.
[0081]
DO2int = (0.21 × Qair + DO2EGR × QEGR) / (Qair + QEGR) (3)
Subsequently, the process proceeds to Step 5, in which the maximum value of the oxygen concentration DO2int of the intake gas at which low-temperature premix combustion can be performed in accordance with the engine speed Ne and the fuel injection amount is searched based on the map shown in FIG. A low-temperature premixed combustion where the oxygen concentration DO2int of the current intake gas is lower than the searched maximum value or a low-temperature premixed combustion where the oxygen concentration DO2int of the current intake gas is higher than the searched maximum value is impossible. Area is determined.
[0082]
When it is determined that the current operation state is in the region where low-temperature premix combustion is possible, the process proceeds to Step 7, where fuel injection without pilot injection is performed, and low-temperature premix combustion is performed. As a result, the combustion speed is reduced, so that the combustion noise is significantly reduced, and at the same time, the diffusion combustion ratio is small and the combustion is performed at a low temperature, whereby the emission of NOx, smoke and particulate matter can be suppressed.
[0083]
If it is determined that the current operating state is in the region where low-temperature premixed combustion is not possible, the process proceeds to Step 8, in which pilot injection is performed, and low-temperature premixed combustion is not performed. As a result, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and combustion noise is reduced.
[0084]
In FIG. 6, the maximum value of the oxygen concentration DO2int of the intake gas at which low-temperature premix combustion can be performed increases as the engine speed Ne decreases and increases as the fuel injection amount decreases. It is set as follows. As a result, as the engine speed Ne increases or the fuel injection amount increases, the temperature of the EGR gas increases and the temperature of the intake gas of the engine 1 increases, so that the compression end temperature increases and the ignition delay period increases. The region where low-temperature premix combustion can be performed is accurately determined in response to the shortening, and the region where low-temperature premix combustion is performed can be maximized.
[0085]
Next, as still another embodiment, means for detecting the ratio of the EGR amount to the intake fresh air amount as the EGR rate REGR is provided, and a low temperature premix combustion in which the EGR rate REGR is lower than a predetermined value is impossible. Alternatively, in this region, the fuel may be pilot-injected by opening the nozzle 13 for a short time before the main injection of the fuel. As a result, the region where low-temperature premixed combustion is performed is expanded, and emission is reduced.
[0086]
The flowchart of FIG. 7 shows a routine for performing pilot injection according to operating conditions, and is executed by the control unit 20 at regular intervals.
[0087]
First, in Step 1, the engine speed Ne, the target fuel injection amount Qf, the intake pressure Pint, the exhaust pressure Pexh, the intake fresh air amount Qair, and the lift L of the EGR valve 5 are read.
[0088]
Subsequently, the process proceeds to Step 2, in which the EGR amount QEGR is calculated from the difference between the intake pressure Pint and the exhaust pressure Pexh and the lift L of the EGR valve 5 by the following equation.
[0089]
QEGR = f (L) × (Pexh-Pint)^1/2  … (1)
Subsequently, the process proceeds to Step 3, where the EGR rate REGR is calculated by the following equation based on the intake fresh air amount Qair and the EGR amount QEGR.
[0090]
REGR = QEGR / Qair (4)
Subsequently, the process proceeds to Step 4, in which the minimum value of the EGR rate REGR of the intake gas at which the low-temperature premix combustion can be performed in accordance with the engine speed Ne and the target fuel injection amount Qf is searched based on the map shown in FIG. Then, the low-temperature premixed combustion in which the low-temperature premixed combustion in which the current intake gas EGR rate REGR is larger than the searched minimum value is possible or the low-temperature premixed combustion in which the current intake gas EGR rate REGR is equal to or less than the searched minimum value is performed. It is determined whether the area is impossible.
[0091]
When it is determined that the current operation state is in the region where low-temperature premix combustion is possible, the process proceeds to Step 5, where fuel injection without pilot injection is performed, and low-temperature premix combustion is performed. As a result, the combustion speed is reduced, so that the combustion noise is significantly reduced, and at the same time, the diffusion combustion ratio is small and the combustion is performed at a low temperature, whereby the emission of NOx, smoke and particulate matter can be suppressed.
[0092]
If it is determined that the current operating state is in the region where low-temperature premix combustion is not possible, the process proceeds to Step 6, in which pilot injection is performed, and low-temperature premix combustion is not performed. As a result, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and combustion noise is reduced.
[0093]
In FIG. 8, the minimum value of the EGR rate REGR at which low-temperature premix combustion can be performed decreases as the engine speed Ne decreases and increases as the target fuel injection amount Qf decreases. Accordingly, when the target fuel injection amount Qf increases, the effect of reducing the oxygen concentration in the EGR gas is large, and as the engine speed Ne increases, the temperature of the EGR gas increases. Corresponding to the fact that the intake gas temperature of the engine 1 becomes higher, the compression end temperature rises, and the ignition delay period becomes shorter, the region where low-temperature premix combustion is possible is accurately determined, and low-temperature premix combustion is performed. The area can be maximized.
[0094]
Next, as still another embodiment, a high load region in which pilot injection is prohibited may be set. In this high load region, smoke emission is suppressed by shortening the fuel injection period without performing pilot injection.
[0095]
The flowchart of FIG. 9 shows a routine for performing pilot injection according to operating conditions, and is executed by the control unit 20 at regular intervals.
[0096]
First, in Step 1, the engine speed Ne, the target fuel injection amount Qf, the intake pressure Pint, the exhaust pressure Pexh, the intake temperature Tint, the intake fresh air amount Qair, and the lift L of the EGR valve 5 are read.
[0097]
Subsequently, the process proceeds to Step 2, in which the EGR amount QEGR is calculated from the difference between the intake pressure Pint and the exhaust pressure Pexh and the lift L of the EGR valve 5 by the following equation.
[0098]
QEGR = f (L) × (Pexh-Pint)^1/2  … (1)
Subsequently, the process proceeds to Step 3, where the oxygen concentration DO2EGR of the EGR gas is calculated by the following equation based on the intake fresh air amount Qair, the target fuel injection amount Qf, and the engine speed Ne.
[0099]
DO2EGR = 0.21−C1 × Qf / (Qair / Ne) (2)
However, C1 is a constant.
[0100]
Subsequently, the process proceeds to Step 4, and the oxygen concentration DO2int of the intake gas of the engine 1 in which the fresh air and the EGR gas are mixed is calculated by the following equation based on the EGR amount QEGR, the EGR gas oxygen concentration DO2EGR, and the intake fresh air amount Qair.
[0101]
DO2int = (0.21 × Qair + DO2EGR × QEGR) / (Qair + QEGR) (3)
Subsequently, the program proceeds to Step 5, in which the compression end temperature is searched based on the preset map shown in FIG. 3 according to the temperature Tint in the intake manifold of the intake passage 3 and the calculated oxygen concentration DO2int of the intake gas.
[0102]
Subsequently, the process proceeds to Step 6, in which the current operating state is in a region where low-temperature premix combustion is possible or low-temperature premix combustion in accordance with the compression end temperature and the oxygen concentration DO2int of the intake gas based on the map shown in FIG. It is determined whether or not the region is impossible.
[0103]
If it is determined that the current operation state is in the region where low-temperature premix combustion is possible, the process proceeds to Step 8, where fuel injection without pilot injection is performed, and low-temperature premix combustion is performed. As a result, the combustion speed is reduced, so that the combustion noise is significantly reduced, and at the same time, the diffusion combustion ratio is small and the combustion is performed at a low temperature, whereby the emission of NOx, smoke and particulate matter can be suppressed.
[0104]
If it is determined that the current operation state is in the region where low-temperature premix combustion is not possible, the process proceeds to Step 7, and the current operation is performed according to the engine speed Ne and the target fuel injection amount Qf based on a preset map. It is determined whether the state is a high load region where pilot injection is prohibited or a region where pilot injection is possible.
[0105]
Here, if it is determined that the current operating state is in a region where pilot injection is possible, the process proceeds to Step 8, in which pilot injection is performed, and low-temperature premix combustion is not performed. As a result, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and combustion noise is reduced.
[0106]
On the other hand, if it is determined that the region is where the pilot injection is prohibited, the process proceeds to Step 8, where fuel injection without pilot injection is performed. Thus, the emission of smoke is suppressed by shortening the fuel injection period and advancing the fuel injection timing from the compression top dead center. In addition, when the turbocharger 18 is provided, the supercharging pressure increases at a high load, and the intake air temperature rises, so that the compression end temperature rises, the ignition delay period is shortened, and even if pilot injection is not performed. Combustion noise can be prevented from increasing.
[0107]
Next, as still another embodiment, the high load region where the pilot injection is prohibited may be set to a region where the excess air ratio λ with respect to the engine speed is smaller than a predetermined value. In this high load region, smoke emission is suppressed by shortening the fuel injection period without performing pilot injection.
[0108]
The flowchart of FIG. 10 shows a routine for performing the pilot injection according to the operating conditions, and is executed by the control unit 20 at regular intervals.
[0109]
To explain this, first, in the routine of Step 1 to Step 6, the current operation state is changed according to the compression end temperature and the oxygen concentration DO2int of the intake gas based on the preset map shown in FIG. It is determined whether the low-temperature premix combustion is possible or the low-temperature premix combustion is not possible.
[0110]
When it is determined that the current operating state is in the region where low-temperature premix combustion is possible, the process proceeds to Step 10, where fuel injection without pilot injection is performed, and low-temperature premix combustion is performed. As a result, the combustion speed is reduced, so that the combustion noise is significantly reduced, and at the same time, the diffusion combustion ratio is small and the combustion is performed at a low temperature, whereby the emission of NOx, smoke and particulate matter can be suppressed.
[0111]
If it is determined that the current operating state is in a region where low-temperature premix combustion is not possible, the process proceeds to Step 7, and the excess air ratio λ is calculated by the following equation.
[0112]
λ = C2 × (Qair + QEGR) × DO2int / Qf (5)
Here, C2 is a constant.
[0113]
Subsequently, the process proceeds to Step 8 to determine whether the current operation state is a high load region in which pilot injection is prohibited or a region in which pilot injection is possible according to the engine speed Ne and the excess air ratio λ based on a preset map. judge.
[0114]
Here, if it is determined that the current excess air ratio λ is greater than or equal to the predetermined value, the process proceeds to Step 9 where pilot injection is performed and low-temperature premix combustion is not performed. As a result, a sudden increase in pressure due to premixed combustion at the beginning of combustion is suppressed, and combustion noise is reduced.
[0115]
On the other hand, if it is determined that the current excess air ratio λ is smaller than the predetermined value, the process proceeds to Step 10, where fuel injection without pilot injection is performed. Thus, the emission of smoke is suppressed by shortening the fuel injection period and advancing the fuel injection timing from the compression top dead center. In addition, when the turbocharger 18 is provided, the supercharging pressure increases at a high load, and the intake air temperature rises, so that the compression end temperature rises, the ignition delay period is shortened, and even if pilot injection is not performed. Combustion noise can be prevented from increasing.
[0116]
In this manner, the pilot injection is prohibited as the excess air ratio λ becomes smaller, so that the pilot injection causes an increase in the amount of smoke emission and the like, even during transient operation or when the air pressure is low at high altitude. It is possible to accurately determine a high-load region and suppress an increase in smoke due to pilot injection.
[0117]
In each of the above embodiments, the pilot injection may be performed by reducing the pilot injection amount or narrowing the interval between the pilot injection and the main injection even in the operation region where the pilot injection is not performed.
[0118]
As still another embodiment, a configuration may be employed in which a nozzle for changing the fuel injection rate is provided, and a single fuel injection is performed in one cycle in a region where low-temperature premixed combustion is not possible to reduce the initial fuel injection rate. Good. As a result, a sudden increase in pressure due to premixed combustion in the initial stage of combustion is suppressed to reduce emissions, and a sharp increase in pressure due to premixed combustion in the initial stage of combustion is suppressed, thereby reducing noise.
[Brief description of the drawings]
FIG. 1 is a system diagram of an engine showing an embodiment of the present invention.
FIG. 2 is a flowchart showing control contents.
FIG. 3 is a characteristic diagram showing a relationship between a compression end temperature and an intake gas oxygen concentration and an intake air temperature.
FIG. 4 is a characteristic diagram showing a relationship between a region where low-temperature premixed combustion is possible and a region where low-temperature premixed combustion is not possible with respect to the intake gas oxygen concentration and the compression end temperature.
FIG. 5 is a flowchart showing control contents according to another embodiment.
FIG. 6 is a characteristic diagram showing a relationship between a maximum oxygen concentration at which low-temperature premix combustion is possible with respect to an engine speed and a fuel injection amount.
FIG. 7 is a flowchart showing control contents of still another embodiment.
FIG. 8 is a characteristic diagram showing a relationship between a minimum EGR rate at which low-temperature premix combustion is possible with respect to an engine speed and a fuel injection amount.
FIG. 9 is a flowchart showing control contents according to still another embodiment.
FIG. 10 is a flowchart showing control contents according to still another embodiment.
FIG. 11 is an injection system diagram showing a conventional example.
[Explanation of symbols]
1 engine
2 Exhaust passage
3 Intake passage
4 EGR passage
5 EGR valve
6 Intake pressure sensor
7 Exhaust pressure sensor
8 Intake air temperature sensor
9 Air flow meter
10 Engine speed sensor
13 nozzle
20 control unit

Claims (17)

Injection means for enabling pilot injection of fuel prior to main injection of fuel,
A diesel engine comprising: an EGR control unit configured to control an amount of EGR in which exhaust gas is recirculated to the combustion chamber in accordance with an operating condition.
Compression end temperature determining means for determining a compression end temperature of the combustion chamber;
The fuel injection control means for not performing the pilot injection of the fuel prior to the main injection as the compression end temperature decreases, or reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection. Diesel engine control device. Injection means for enabling pilot injection of fuel prior to main injection of fuel,
A diesel engine comprising: an EGR control unit configured to control an amount of EGR in which exhaust gas is recirculated to the combustion chamber in accordance with an operating condition.
Means for determining the oxygen concentration DO2int of the intake gas;
The fuel injection control means for not performing pilot injection of fuel prior to the main injection as the oxygen concentration DO2int decreases, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection. Diesel engine control device. The maximum value of the oxygen concentration DO2int of the intake gas, which does not execute the pilot injection of the fuel prior to the main injection , or reduces the pilot injection amount, or limits the operation region in which the interval between the pilot injection and the main injection is shortened, is set to the engine speed Ne. 3. The control device for a diesel engine according to claim 2, wherein the control unit is configured to increase as the fuel injection amount decreases and to increase as the fuel injection amount decreases. Injection means for enabling pilot injection of fuel prior to main injection of fuel,
A diesel engine comprising: an EGR control unit configured to control an amount of EGR in which exhaust gas is recirculated to the combustion chamber in accordance with an operating condition.
Means for detecting a ratio of the EGR amount to the fresh intake air amount as an EGR rate REGR ;
Injection control means for not performing pilot injection of fuel prior to the main injection as the EGR rate REGR increases, or reducing the pilot injection amount, or shortening the interval between pilot injection and main injection ,
The minimum value of the EGR rate REGR that limits the operation range in which the pilot injection of the fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened, is set to the engine speed Ne and the fuel injection. A control device for a diesel engine, wherein the control device is configured to change based on the amount . The engine rotation speed Ne is reduced to a minimum value of the EGR rate REGR that limits the operation range in which the pilot injection of the fuel prior to the main injection is not performed , or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened. The control device for a diesel engine according to claim 4, wherein the control device is configured to decrease the fuel injection amount and increase the fuel injection amount as the fuel injection amount decreases. Injection means for enabling pilot injection of fuel prior to main injection of fuel,
A diesel engine comprising: an EGR control unit configured to control an amount of EGR in which exhaust gas is recirculated to the combustion chamber in accordance with an operating condition.
Means for detecting a ratio of the EGR amount to the fresh intake air amount as an EGR rate REGR;
Means for detecting engine load;
As the EGR rate REGR increases, the pilot injection of fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened, and the engine load increases. And a fuel injection control means for reducing the pilot injection amount prior to the main injection, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection. Injection means for enabling pilot injection of fuel prior to main injection of fuel,
A diesel engine comprising: an EGR control unit configured to control an amount of EGR in which exhaust gas is recirculated to the combustion chamber in accordance with an operating condition.
Means for detecting a ratio of the EGR amount to the fresh intake air amount as an EGR rate REGR;
Means for detecting an excess air ratio of the engine;
As the EGR rate REGR increases, the pilot injection of fuel prior to the main injection is not performed, or the pilot injection amount is reduced, or the interval between the pilot injection and the main injection is shortened, and the excess air ratio of the engine is reduced. The diesel engine according to claim 1, further comprising: injection control means for not performing pilot injection of fuel prior to the main injection, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection. Control device. Injection means for enabling pilot injection of fuel prior to main injection of fuel,
  A diesel engine comprising:
  Means for detecting engine load;
  Injection control means for not performing pilot injection of fuel prior to the main injection as the engine load increases, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection is provided. The control device for a diesel engine according to any one of claims 1 to 5, wherein Injection means for enabling pilot injection of fuel prior to main injection of fuel,
  A diesel engine comprising:
  Means for detecting an excess air ratio of the engine;
  Injection control means for not performing pilot injection of fuel prior to the main injection as the excess air ratio of the engine decreases, reducing the pilot injection amount, or shortening the interval between the pilot injection and the main injection. The control device for a diesel engine according to any one of claims 1 to 5, characterized in that: Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Means for determining the oxygen concentration DO2int of the intake gas;
  A control system for a diesel engine, comprising: injection control means for increasing an initial fuel injection rate as the oxygen concentration DO2int decreases. The maximum value of the oxygen concentration DO2int of the intake gas, which limits the operation range in which the initial injection rate of the fuel is increased, increases as the engine speed Ne decreases, and increases as the fuel injection amount decreases. The control device for a diesel engine according to claim 10, wherein: Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Means for detecting a ratio of the EGR amount to the intake fresh air amount as an EGR rate REGR,
  A control system for a diesel engine, comprising: injection control means for increasing an initial fuel injection rate as the EGR rate REGR increases. A configuration in which the minimum value of the EGR rate REGR, which limits the operation range in which the initial fuel injection rate is increased, is reduced as the engine speed Ne decreases, and is increased as the fuel injection amount decreases. The control device for a diesel engine according to claim 12, wherein: Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Compression end temperature determining means for determining a compression end temperature of the combustion chamber;
  Means for detecting engine load;
  A diesel engine comprising: injection control means for increasing the initial fuel injection rate as the compression end temperature decreases and increasing the initial fuel injection rate as the engine load increases. Control device. Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Compression end temperature determining means for determining a compression end temperature of the combustion chamber;
  Means for detecting an excess air ratio of the engine;
  Injection control means for increasing the initial injection rate of the fuel as the compression end temperature decreases and increasing the initial injection rate of the fuel as the excess air ratio of the engine decreases. Diesel engine control device. Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Means for detecting engine load;
  14. The diesel engine control device according to claim 10, further comprising: an injection control unit configured to increase an initial fuel injection rate as the engine load increases. Injection rate varying means for varying the fuel injection rate;
  A diesel engine comprising:
  Means for detecting an excess air ratio of the engine;
  14. The control apparatus for a diesel engine according to claim 10, further comprising: an injection control unit configured to increase an initial fuel injection rate as the excess air ratio of the engine decreases. .

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