JP2002089311A - Internal combustion engine - Google Patents

Abstract

(57) An object of the present invention is to unnecessarily increase the amount of nitrogen oxide (NOx) discharged from an internal combustion engine of a compression ignition type equipped with an EGR device and an EGR cooler. It is another object of the present invention to provide a technique for preventing clogging of an EGR cooler. An internal combustion engine according to the present invention includes an exhaust recirculation passage that guides a part of the exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, and an exhaust recirculation passage that is provided in the exhaust recirculation passage and flows through the exhaust recirculation passage. In an internal combustion engine provided with a cooling mechanism for cooling exhaust gas, the fuel injection timing of the closest cylinder located closest to the connection portion between the exhaust passage and the exhaust recirculation passage is advanced in comparison with other cylinders. Thus, the amount of unburned fuel components contained in the exhaust gas discharged from the closest cylinder is reduced, thereby reducing the amount of unburned fuel components contained in the recirculated gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine mounted on an automobile or the like, and more particularly, to a compression ignition type internal combustion engine provided with an exhaust gas recirculation device (EGR device).

[0002]

2. Description of the Related Art In recent years, internal combustion engines mounted on automobiles and the like,
Particularly, in a compression ignition type diesel engine capable of burning an air-fuel mixture in an excess oxygen state, it is required to reduce the amount of nitrogen oxides (NOx) discharged from the internal combustion engine.

In response to such a demand, Japanese Patent Application Laid-Open No. 5-321
Exhaust gas recirculation (E
An internal combustion engine provided with a GR (Exhaust Gas Recirculation) device has been proposed.

The EGR device recirculates a part of the exhaust gas flowing through the exhaust system of the internal combustion engine to the intake system to thereby inactivate water (H ₂ O) and carbon dioxide (CO ₂ ) contained in the exhaust gas. Gas components are introduced into the combustion chamber of the internal combustion engine together with fresh air,
Utilizing the non-combustibility and endothermic properties of the inert gas component, the maximum combustion temperature of the air-fuel mixture is reduced, thereby reducing the nitrogen oxides (NO
_x ) is a device for reducing the generation amount.

As one of the EGR devices as described above, an EGR cooler that cools exhaust gas flowing through the EGR passage is provided in the middle of an EGR passage that guides a part of the exhaust gas flowing through the exhaust system of the internal combustion engine to the intake system. Some have been proposed.

An EGR device equipped with an EGR cooler cools the exhaust gas by the EGR cooler when a part of the exhaust gas flowing through the exhaust system is recirculated to the intake system, thereby reducing the temperature rise of the air-fuel mixture due to the heat of the exhaust gas. It is intended to further reduce the maximum combustion temperature of the air-fuel mixture, thereby further reducing the generation amount of nitrogen oxides (NOx).

[0007]

In an EGR device equipped with an EGR cooler, when the exhaust gas is cooled by the EGR cooler, an SOF (Soluble Organic Component) such as an unburned fuel component or an unburned oil component contained in the exhaust gas is used. Fraction:
The soluble organic fraction) component is liquefied and easily adheres to the wall of the passage in the EGR cooler.

[0008] SO adhering to the wall of the passage in the EGR cooler
When the amount of the F component increases, the passage in the EGR cooler becomes clogged, and it becomes difficult to recirculate a desired amount of exhaust gas from the exhaust system to the intake system. As a result, nitrogen oxides (NO
x) may be increased.

On the other hand, it is conceivable to increase the maximum combustion temperature of the air-fuel mixture by advancing the fuel injection timing of each cylinder and reduce the amount of the SOF component discharged from each cylinder. When the combustion temperature is increased, the amount of nitrogen oxide (NOx) is increased instead of the amount of the SOF component, and there is a problem that the NOx reduction effect of the EGR device is reduced by half.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In a compression ignition type internal combustion engine provided with an EGR device and an EGR cooler, nitrogen oxides ( An object of the present invention is to provide a technique for preventing clogging of an EGR cooler without unnecessarily increasing the amount of NOx).

[0011]

The present invention employs the following means to solve the above-mentioned problems.

That is, an internal combustion engine according to the present invention comprises: a compression ignition type internal combustion engine having a plurality of cylinders; an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage; A cooling mechanism provided in the middle of the exhaust gas recirculation passage to cool the exhaust gas flowing through the exhaust gas recirculation passage; and a fuel injection timing of a cylinder closest to a connecting portion between the exhaust gas passage and the exhaust gas recirculation passage is set to another cylinder. And a fuel injection timing control means for advancing the fuel injection angle.

In the internal combustion engine configured as described above, part of the exhaust gas flowing through the exhaust passage flows into the exhaust gas recirculation passage,
After being cooled by a cooling mechanism provided in the exhaust recirculation passage, it is guided to the intake passage.

The low-temperature exhaust gas (hereinafter, referred to as recirculated gas) introduced into the intake passage is supplied into each cylinder of the internal combustion engine together with fresh air flowing upstream of the intake passage, and is injected from the fuel injection valve. The fuel is burned using the fuel as the ignition source.

At this time, since the combustion temperature of each cylinder is reduced by the inert component contained in the recirculated gas, the amount of nitrogen oxides (NOx) generated during combustion is reduced.

When the exhaust gas is recirculated as described above, the fuel injection timing control means controls the fuel in the cylinder closest to the connection between the exhaust passage and the exhaust recirculation passage (hereinafter referred to as the closest cylinder). The injection timing is advanced.

Here, in a compression ignition type internal combustion engine, combustion is performed using fuel injected from a fuel injection valve as an ignition source. Therefore, when the fuel injection timing is changed, the combustion start timing is changed accordingly. Will be. Further, in the compression ignition type internal combustion engine, the maximum combustion temperature of the air-fuel mixture tends to increase when the combustion start timing is advanced, and the maximum combustion temperature of the air-fuel mixture tends to decrease when the combustion start timing is retarded.

Therefore, if the fuel injection timing of the closest cylinder is advanced relative to the other cylinders, the combustion start timing of the closest cylinder is advanced relative to the other cylinders. A period (hereinafter, referred to as a combustion period) from a combustion start timing to an exhaust valve opening timing in the connected cylinder becomes longer than the other cylinders, and the highest combustion temperature of the recently connected cylinder becomes higher than other cylinders. Will be.

When the combustion period of the closest cylinder is longer than that of the other cylinders and the maximum combustion temperature is higher than that of the other cylinders, the fuel components and oil components in the closest cylinder are completely burned. Therefore, the amount of SOF (Soluble Organic Fraction) components contained in the exhaust gas discharged from the closest cylinder is smaller than that of other cylinders.

When the amount of the SOF component contained in the exhaust of the closest cylinder decreases, the amount of SOF contained in the recirculated gas decreases accordingly.
The amount of the OF component also decreases. This is because the exhaust discharged from the cylinder located closest to the connection between the exhaust passage and the exhaust recirculation passage is more likely to flow into the recirculation passage than the exhaust discharged from the other cylinders. It is based on.

As described above, when the fuel injection timing of the closest cylinder is advanced compared to the other cylinders, the maximum combustion temperature is increased only for the closest cylinder, so that the nitrogen oxidation discharged from the entire internal combustion engine is increased. The amount of the SOF component contained in the recirculated gas is reduced while an unnecessary increase in the amount of the substance (NOx) is suppressed. As a result, it is possible to suppress the adhesion of the SOF component in the cooling mechanism without reducing the NOx reduction effect by the exhaust gas recirculation.

Also, an internal combustion engine according to the present invention includes a compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, A cooling mechanism provided in the middle of the exhaust gas recirculation passage to cool exhaust gas flowing through the exhaust gas recirculation passage; and a fuel injection amount of a cylinder closest to a connection portion between the exhaust gas passage and the exhaust gas recirculation passage, to another cylinder. And a fuel injection amount control means for reducing the fuel injection amount.

In the internal combustion engine configured as described above, when a part of the exhaust gas is recirculated to the intake passage by the exhaust recirculation passage, the internal combustion engine is located at a position closest to a connection portion between the exhaust passage and the exhaust recirculation passage. The fuel injection amount of a certain closest cylinder is reduced as compared with the other cylinders.

In this case, since the amount of fuel supplied to the closest cylinder is smaller than that of the other cylinders, the amount of fuel remaining in the closest cylinder is smaller than that of the other cylinders. The amount of the SOF component contained in the exhaust gas discharged is smaller than in the other cylinders.

As a result, the SOF contained in the recirculated gas
The amount of the component decreases, and the amount of the SOF component adhering to the cooling mechanism as the recirculated gas passes through the cooling mechanism decreases.

Also, an internal combustion engine according to the present invention has a compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, A cooling mechanism provided in the middle of the exhaust gas recirculation passage to cool the exhaust gas flowing through the exhaust gas recirculation passage; main fuel injection means for injecting the main fuel used for combustion into each of the cylinders; and a main fuel for each of the cylinders A secondary fuel injection means for secondaryly injecting fuel prior to the injection of the main fuel, and an injection timing of the main fuel to a cylinder closest to a connection portion of the exhaust passage and the exhaust recirculation passage, as compared with other cylinders. Fuel injection timing control means for delaying the angle and / or the auxiliary fuel injection timing as compared to other cylinders.

In the internal combustion engine configured as described above, when the exhaust gas is recirculated through the exhaust gas recirculation passage,
The fuel injection timing control means advances the main fuel injection timing and / or delays the auxiliary fuel injection timing for the closest cylinder closest to the connection between the exhaust passage and the exhaust recirculation passage.

When the injection timing of the main fuel is advanced, as described above, the combustion period of the closest cylinder becomes longer than the other cylinders, and the maximum combustion temperature becomes higher than the other cylinders. As a result, the amount of the SOF component contained in the exhaust gas discharged from the closest cylinder is reduced.

On the other hand, when the injection timing of the auxiliary fuel is retarded, the period from the injection timing of the auxiliary fuel to the injection timing of the main fuel is shortened. It is not necessary to unnecessarily diffuse and reach the vicinity of the inner wall surface of the cylinder.

Here, since combustion may become unstable in the vicinity of the cylinder inner wall surface due to a shortage of air or a decrease in the combustion temperature, the auxiliary fuel may reach the vicinity of the cylinder inner wall surface at the injection timing of the main fuel. If it has already diffused, the auxiliary fuel near the cylinder inner wall surface may remain unburned.

On the other hand, if the injection timing of the auxiliary fuel is retarded and the auxiliary fuel does not reach the vicinity of the inner wall surface of the cylinder before the main fuel is injected, the combustion of the auxiliary fuel may occur. Since the remainder is suppressed, the amount of the SOF component contained in the exhaust gas discharged from the closest cylinder is reduced.

Therefore, if the main fuel injection timing for the closest cylinder is advanced and / or the auxiliary fuel injection timing is delayed for the closest cylinder while the exhaust gas is being recirculated through the exhaust gas recirculation passage, the closest fuel injection is performed. S contained in the exhaust gas discharged from the cylinder
The amount of the OF component decreases, and accordingly, the amount of the SOF component contained in the recirculated gas decreases. As a result, the amount of the SOF component adhering to the cooling mechanism when the recirculated gas passes through the cooling mechanism is reduced.

Incidentally, instead of changing the injection timing of the main fuel and / or the auxiliary fuel, the injection amount of the main fuel and / or the auxiliary fuel may be reduced, or the injection of the main fuel and / or the auxiliary fuel may be performed. Both the change of the timing and the reduction of the main fuel and / or the auxiliary fuel may be performed.

The internal combustion engine according to the present invention includes a compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, A cooling mechanism provided in the middle of the exhaust gas recirculation passage to cool the exhaust gas flowing through the exhaust gas recirculation passage; main fuel injection means for injecting the main fuel used for combustion into each of the cylinders; and a main fuel for each of the cylinders A secondary fuel injection means for secondaryly injecting fuel after the injection of the main fuel and / or the secondary fuel with respect to a cylinder closest to a connecting portion between the exhaust passage and the exhaust recirculation passage. And a fuel injection timing control means for advancing the fuel injection timing.

In the thus configured internal combustion engine, when the exhaust gas is recirculated through the exhaust gas recirculation passage,
The fuel injection timing control means advances the injection timing of the main fuel and / or the auxiliary fuel for the closest cylinder closest to the connection portion between the exhaust passage and the exhaust recirculation passage.

When the injection timing of the main fuel is advanced, as described above, the combustion period of the closest cylinder becomes longer than that of the other cylinders, and the maximum combustion temperature becomes higher than that of the other cylinders. As a result, the amount of the unburned fuel component contained in the exhaust from the closest cylinder decreases, and accordingly, the amount of the unburned fuel component contained in the recirculated gas also decreases.

On the other hand, when the injection timing of the auxiliary fuel is advanced,
The auxiliary fuel is injected into the high-temperature and high-pressure combustion gas, and the auxiliary fuel is easily burned, so that the remaining unburned auxiliary fuel is suppressed, so that the amount of the SOF component contained in the exhaust gas recently discharged from the directly-closed cylinder is reduced. I do.

Therefore, when the injection timing of the main fuel and / or the auxiliary fuel to the closest cylinder is advanced while the exhaust gas is being recirculated through the exhaust recirculation passage, the exhaust gas discharged from the closest cylinder is advanced. , The amount of the SOF component contained in the recirculation gas decreases accordingly. As a result, the amount of the SOF component adhering to the cooling mechanism when the recirculated gas passes through the cooling mechanism is reduced.

It is to be noted that, instead of changing the injection timing of the main fuel and / or the auxiliary fuel, the injection amount of the main fuel and / or the auxiliary fuel may be reduced, or the injection of the main fuel and / or the auxiliary fuel may be performed. Both the change of the timing and the reduction of the main fuel and / or the auxiliary fuel may be performed. Further, the injection of the auxiliary fuel may be prohibited for the closest cylinder.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the internal combustion engine according to the present invention will be described with reference to the drawings. Here, a case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to the present invention and its intake and exhaust systems.

The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2.

The internal combustion engine 1 has a fuel injection valve 3 for directly injecting fuel into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure. The common rail 4 is provided with a common rail pressure sensor 4a for outputting an electric signal corresponding to the pressure of the fuel in the common rail 4.

The common rail 4 is in communication with a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6
Is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source. The pump pulley 6 attached to the input shaft of the fuel pump 6 is connected to the output shaft (crankshaft) of the internal combustion engine 1. It is connected to the attached crank pulley 1a via a belt 7.

In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 is transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure corresponding to the rotating torque.

The fuel discharged from the fuel pump 6 is
The fuel is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.

Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown). .

The intake branch pipe 8 is connected to the intake pipe 9,
The intake pipe 9 is connected to an air cleaner box 10. An air flow meter 11 that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 9 and an electric current corresponding to the temperature of the intake air flowing through the intake pipe 9 are provided at an intake pipe 9 downstream of the air cleaner box 10. An intake air temperature sensor 12 that outputs a signal is attached.

An intake throttle valve 13 for adjusting the flow rate of intake air flowing through the intake pipe 9 is provided at a position of the intake pipe 9 immediately upstream of the intake branch pipe 8. The intake throttle valve 13 includes an intake throttle actuator 1 that is configured by a stepper motor or the like and drives the intake throttle valve 13 to open and close.
4 is attached.

The intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 which operates using heat energy of exhaust gas as a driving source. And
An intercooler 16 for cooling intake air, which has been compressed in the compressor housing 15a and has become high temperature, is provided in the intake pipe 9 downstream of the compressor housing 15a.
Is provided.

In the intake system configured as described above, the intake air flowing into the air cleaner box 10 passes through the intake pipe 9 after dust and the like in the intake are removed by an air cleaner (not shown) in the air cleaner box 10. And flows into the compressor housing 15a.

The intake air flowing into the compressor housing 15a is compressed by rotation of a compressor wheel provided in the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has become high temperature is cooled by the intercooler 16, and then flows into the intake branch pipe 8 with the flow rate adjusted by the intake throttle valve 13 as necessary. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.

On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with a combustion chamber of each cylinder 2 via an exhaust port 100.

The exhaust branch pipe 18 is connected to the centrifugal turbocharger 15.
Of the turbine housing 15b. The turbine housing 15b is connected to the exhaust pipe 19. The exhaust pipe 19 is connected downstream to a muffler (not shown).

An exhaust gas purifying catalyst 20 for purifying harmful gas components in exhaust gas is disposed in the exhaust pipe 19. The exhaust gas purification catalyst 20 is
Is a catalyst capable of removing or purifying nitrogen oxides (NOx) contained in the exhaust gas even when the air-fuel ratio of the exhaust gas flowing into the exhaust gas is a lean air-fuel ratio. Type NOx catalyst, selective reduction type NOx catalyst, and the like.

An exhaust pipe 19 downstream of the exhaust purification catalyst 20 has an air-fuel ratio sensor 23 for outputting an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust pipe 19, An exhaust temperature sensor 24 that outputs an electric signal corresponding to the temperature is attached.

The exhaust pipe 19 downstream of the air-fuel ratio sensor 23 and the exhaust temperature sensor 24 is provided with an exhaust throttle valve 21 for adjusting the flow rate of exhaust gas flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 configured by a stepper motor or the like and driving the exhaust throttle valve 21 to open and close.

In the exhaust system configured as described above, the air-fuel mixture (burned gas) burned in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port 100, and then to the exhaust branch pipe. From 18 flows into the turbine housing 15b of the centrifugal supercharger 15. The exhaust gas that has flowed into the turbine housing 15b rotates a turbine wheel rotatably supported in the turbine housing 15b by using thermal energy of the exhaust gas. At this time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.

The exhaust gas discharged from the turbine housing 15b flows through an exhaust pipe 19 into an exhaust gas purifying catalyst 20, where harmful gas components in the exhaust gas are removed or purified. The exhaust gas from which the harmful gas components have been removed or purified by the exhaust purification catalyst 20 is discharged into the atmosphere via a muffler after the flow rate is adjusted by an exhaust throttle valve 21 as necessary.

The internal combustion engine 1 is provided with an exhaust gas recirculation mechanism for recirculating a part of the exhaust gas flowing through the exhaust system of the internal combustion engine 1 to the intake system. The exhaust gas recirculation mechanism is configured to extend from the exhaust port 100 of the first (# 1) cylinder 2 of the four cylinders 2 of the internal combustion engine 1 to the collection portion of the intake branch pipe 8 through the inside of the cylinder head. A circulation passage (EGR passage) 25, and a flow regulating valve (EGR valve) 26 that includes an electromagnetic valve or the like and changes the flow rate of exhaust gas (hereinafter, referred to as EGR gas) flowing in the EGR passage 25 according to the magnitude of the applied power 26
And an EGR provided in the EGR passage 25 upstream of the EGR valve 26 to cool the EGR gas flowing through the EGR passage 25.
A cooler 27 is provided.

The EGR passage 25 is preferably formed so as to penetrate a cooling water passage (not shown) formed in the cylinder head or to be close to the cooling water passage. This is because the EGR gas flowing in the EGR passage 25 is cooled by the cooling water flowing in the cooling water passage, so that the capacity of the EGR cooler 27 can be reduced.

In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 becomes conductive, and a part of the exhaust gas flowing in the exhaust branch pipe 18 flows to the EGR passage 25. Inflow.

The EGR gas flowing into the EGR passage 25 is first cooled by the cooling water flowing through the cooling water passage in the cylinder head, and then cooled by exchanging heat with a predetermined refrigerant in the EGR cooler 27. .

The low-temperature EGR gas cooled in the cylinder head and by the EGR cooler 27 is guided to the gathering portion of the intake branch pipe 8, and mixes with fresh air flowing from the upstream of the intake branch pipe 8 so as to mix with each cylinder 2. And is burned using the fuel injected from the fuel injection valve 3 as an ignition source.

Here, the EGR gas contains an inert gas component such as water (H ₂ O) and carbon dioxide (CO ₂ ) that does not burn itself and has endothermic properties. Therefore, if EGR gas is contained in the air-fuel mixture,
The maximum combustion temperature of the air-fuel mixture is lowered, and the nitrogen oxides (N
Ox) is suppressed.

Further, in the exhaust gas recirculation mechanism according to the present embodiment, since the EGR gas is cooled in the cylinder head and in the EGR cooler 27, the temperature of the EGR gas itself decreases and the volume of the EGR gas decreases. Will be. As a result, when the EGR gas is supplied into the combustion chamber, the ambient temperature in the combustion chamber does not unnecessarily rise, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber is reduced unnecessarily. No more.

The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's requirements.

The ECU 35 has a common rail pressure sensor 4
a, air flow meter 11, intake air temperature sensor 12, intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust gas temperature sensor 24, crank position sensor 33, water temperature sensor 3
4. Various sensors such as the accelerator opening sensor 36 are connected via electric wiring, and the output signals of the various sensors are E
The data is input to the CU 35.

On the other hand, the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26 and the like are connected to the ECU 35 via electric wiring.
The above-described units are controlled by the ECU 35.

Here, as shown in FIG. 3, the ECU 35 is connected to a C
A PU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357.
And an A / D converter (A / D) 355 connected to.

The input port 356 inputs output signals of a sensor that outputs a digital signal, such as the crank position sensor 33, and converts those output signals to C.
The data is transmitted to the PU 351 and the RAM 353.

The input port 356 is connected to the common rail pressure sensor 4a, the air flow meter 11,
2, intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust temperature sensor 24, water temperature sensor 34, accelerator opening sensor 3
6 and the like, an output signal of a sensor that outputs a signal in an analog signal format is input via the A / D 355, and the output signal is transmitted to the CPU 351 and the RAM 353.

The output port 357 is connected to the fuel injection valve 3,
The control signal output from the CPU 351 is connected to the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, and the like via electric wiring, and transmits the control signal output from the CPU 351 to the fuel injection valve 3, the intake throttle actuator 14, and the exhaust throttle. The signal is transmitted to the actuator 22 or the EGR valve 26.

The ROM 352 includes a fuel injection control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and EGR. An application program such as an EGR control routine for controlling the valve 26 is stored.

The ROM 352 stores various control maps in addition to the application programs described above. The control map includes, for example, a fuel injection amount control map indicating a relationship between an operation state of the internal combustion engine 1 and a basic fuel injection amount (basic fuel injection time), and a relation between the operation state of the internal combustion engine 1 and the basic fuel injection timing. Fuel injection timing control map,
An intake throttle valve opening control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the intake throttle valve 13, and the exhaust throttle showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the exhaust throttle valve 21. Valve opening control map, operating state of internal combustion engine 1 and EGR
It is an EGR valve opening control map or the like showing a relationship with the target opening of the valve 26.

The RAM 353 stores an output signal from each sensor, a calculation result of the CPU 351 and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data each time the crank position sensor 33 outputs a pulse signal.

The backup RAM 354 is a non-volatile memory capable of storing data even after the operation of the internal combustion engine 1 is stopped.

The CPU 351 operates in accordance with an application program stored in the ROM 352 to control fuel injection, intake throttle control, exhaust throttle control, EG
Execute R control.

For example, in the fuel injection control, the CPU 351
First, the amount of fuel to be injected from the fuel injection valve 3 is determined, and then the timing at which fuel is to be injected from the fuel injection valve 3 is determined.

When determining the fuel injection amount, the CPU 35
1 reads the engine speed and the output signal (accelerator opening) of the accelerator opening sensor 36 stored in the RAM 353. The CPU 351 accesses the fuel injection amount control map in the ROM 352 and calculates a basic fuel injection amount (basic fuel injection time) corresponding to the engine speed and the accelerator opening. The CPU 351 is an air flow meter 1
1. The basic target fuel injection time is corrected by using the output signal values of the intake air temperature sensor 12, the water temperature sensor 34, and the like as parameters to determine the final target fuel injection time.

Here, the combustion process in the compression ignition type diesel engine is generated in the combustion chamber during the premixed combustion period in which the fuel injected into the combustion chamber becomes self-igniting as a combustible mixture, and in the premixed combustion period. Combustion is continued and diffused by injecting fuel into the burned combustion gas, and is broadly divided into a diffusion combustion period. If the premixed combustion period becomes unnecessarily long, the combustion pressure in the combustion chamber becomes excessively high. At the same time, the combustion temperature becomes excessively high, and the generation amount of nitrogen oxides (NOx) may increase.

On the other hand, the CPU 351 is configured to inject the fuel to be injected during one stroke of each cylinder 2 in two separate steps. That is, the CPU 351 performs pilot injection for pilot-injecting a part of the fuel to be injected into the combustion chamber, and performs main injection for injecting the remaining fuel when the pilot-injected fuel is ignited. I made it.

Specifically, the CPU 351 determines the pilot injection time using the engine speed and the target fuel injection time as parameters, and then determines the main injection time using the pilot injection time and the target fuel injection time as parameters.

When determining the fuel injection timing, the CPU 3
51 accesses the fuel injection timing control map in the ROM 352 and calculates a pilot injection timing and a main injection timing corresponding to the engine speed and the accelerator opening.

When the fuel injection time and the fuel injection timing are determined as described above, the CPU 351 compares the fuel injection timing with the output signal of the crank position sensor 33,
When the output signal of the crank position sensor 33 coincides with the fuel injection timing, the application of drive power to the fuel injection valve 3 is started. The CPU 351 controls the fuel injection valve 3
When the elapsed time from the start of the application of the drive power to the fuel injection time reaches the fuel injection time, the application of the drive power to the fuel injection valve 3 is stopped.

In the intake throttle control, the CPU 351
Reads the engine speed and the accelerator opening stored in the RAM 353, for example. The CPU 351 is a ROM
An intake throttle valve opening control map 352 is accessed to calculate a target intake throttle valve opening corresponding to the engine speed and the accelerator opening. The CPU 351 applies drive power corresponding to the target intake throttle valve opening to the intake throttle actuator 14. At this time, the CPU 351 detects the actual opening of the intake throttle valve 13 and performs feedback control of the intake throttle actuator 14 based on the difference between the actual opening of the intake throttle valve 13 and the target intake throttle valve opening. You may make it.

In the exhaust throttle control, the CPU 351
For example, when the internal combustion engine 1 is in a warm-up operation state after a cold start, or when a vehicle interior heater is in an operating state, the exhaust throttle actuator is driven to close the exhaust throttle valve 21 in the valve closing direction. 22 is controlled.

In this case, the load on the internal combustion engine 1 increases, and the fuel injection amount is correspondingly increased. As a result, the calorific value of the internal combustion engine 1 increases, so that it is possible to promote warming up of the internal combustion engine 1 and to secure a heat source for the vehicle interior heater.

In the EGR control, the CPU 351
The engine speed, the accelerator opening, the output signal (cooling water temperature) of the water temperature sensor 34, and the like stored in the RAM 353 are read, and it is determined whether or not the execution condition of the EGR control is satisfied.

The above-mentioned EGR control execution conditions are as follows: the coolant temperature is equal to or higher than a predetermined temperature; the internal combustion engine 1 has been continuously operated for a predetermined time or more from the start; Conditions such as certain conditions can be exemplified.

If the CPU 351 determines that the EGR control execution condition described above is satisfied,
An EGR valve opening control map 52 is accessed to calculate a target EGR valve opening corresponding to the engine speed and the accelerator opening. The CPU 351 applies drive power corresponding to the target EGR valve opening to the EGR valve 26. on the other hand,
When it is determined that the EGR control execution condition as described above is not satisfied, the CPU 351 controls the EGR valve 26 to be kept in the fully closed state.

Furthermore, in the EGR control, the CPU 351
EGR valve 2 using intake air amount of internal combustion engine 1 as a parameter
The so-called EGR valve feedback control for performing feedback control of the opening degree of the valve 6 may be performed.

In the EGR valve feedback control, for example, the CPU 351 determines the target intake air amount of the internal combustion engine 1 using the accelerator opening, the engine speed and the like as parameters. At this time, the relationship between the accelerator opening, the engine speed, and the target intake air amount may be mapped in advance, and the target intake air amount may be calculated from the map, the accelerator opening, and the engine speed. .

When the target intake air amount is determined by the above procedure, the CPU 351 reads the output signal value (actual intake air amount) of the air flow meter 11 stored in the RAM 353, and reads the actual intake air amount and the target intake air amount. Compare with air volume.

When the actual intake air amount is smaller than the target intake air amount, the CPU 351 closes the EGR valve 26 by a predetermined amount. In this case, from the EGR passage 25 to the intake branch pipe 8
The amount of EGR gas flowing into the engine decreases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 decreases. As a result, the amount of fresh air sucked into the cylinder 2 of the internal combustion engine 1 increases by an amount corresponding to the decrease in the EGR gas.

On the other hand, when the actual intake air amount is larger than the target intake air amount, the CPU 351 opens the EGR valve 26 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 8 from the EGR passage 25 increases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 increases. As a result, the amount of fresh air sucked into the cylinder 2 of the internal combustion engine 1 decreases by an amount corresponding to the increase in the EGR gas.

In the exhaust gas recirculation mechanism, the EGR gas is supplied to the cooling water flowing through the cooling water passage in the cylinder head and to the EGR gas.
Since the EGR gas is cooled by the GR cooler 27, if the EGR gas contains SOF components such as unburned hydrocarbons (HC), the SOF components are liquefied by cooling, and are liquefied by cooling. Easily adheres to the passage wall surface or the like. In particular, the passage in the EGR cooler 27
Since the cross-sectional area is smaller than that of the passage 25, clogging is likely to occur due to adhesion of the SOF component.

When the passage in the EGR cooler 27 is clogged, a desired amount of EG is transferred from the exhaust system of the internal combustion engine 1 to the intake system.
It becomes difficult to recirculate the R gas, and nitrogen oxides (N
Ox) may be increased.

Therefore, in the internal combustion engine according to the present embodiment, while the EGR control is being executed, the pilot injection timing of the first (# 1) cylinder 2 is retarded relative to the other cylinders 2 and The main injection timing is advanced relative to the other cylinders 2.

When the pilot injection timing of the first (# 1) cylinder 2 is retarded relative to the other cylinders 2, the period from the pilot injection timing to the main injection timing of the first (# 1) cylinder 2 becomes longer. Therefore, the pilot injection fuel does not unnecessarily diffuse in the first (# 1) cylinder 2 to reach the cylinder wall surface before the main injection is performed.

If the pilot injection fuel does not diffuse to the cylinder wall surface before the main injection is performed in the first (# 1) cylinder 2, fuel unburned due to insufficient air near the cylinder wall surface or a decrease in combustion temperature will occur. To be suppressed,
SO contained in the exhaust gas discharged from the first (# 1) cylinder 2
The amount of the F component decreases.

On the other hand, when the main injection timing of the first (# 1) cylinder 2 is advanced, the combustion start timing of the first (# 1) cylinder 2 is advanced as compared with the other cylinders, and the first injection is started. (# 1) The period from the start of combustion in the cylinder 2 to the opening of the exhaust valve (hereinafter referred to as the combustion period) is longer than that of the other cylinders 2, and the highest combustion temperature of the closest cylinder is set to the other cylinders 2. It is higher than that.

The combustion period of the first (# 1) cylinder 2 becomes longer than that of the other cylinders 2, and at the same time, the maximum combustion temperature becomes higher than that of the other cylinders 2.
As the fuel component in the first (# 1) cylinder 2 becomes easier to completely burn, the amount of the SOF component contained in the exhaust gas discharged from the first (# 1) cylinder 2 decreases.

Therefore, when the pilot injection timing of the first (# 1) cylinder 2 is retarded relative to the other cylinders 2 and the main injection timing is advanced relative to the other cylinders 2, 1 The amount of the SOF component contained in the exhaust of the number (# 1) cylinder 2 becomes extremely small. In the internal combustion engine 1 according to the present embodiment, 1
The EGR passage 25 is connected to the exhaust port 100 of the # 2 (# 1) cylinder 2.
And the exhaust of the first (# 1) cylinder 2 is EGR
Since it flows into the EGR passage 25 as gas,
When the amount of the SOF component contained in the exhaust of the first (# 1) cylinder 2 decreases, the amount of the SOF component contained in the EGR gas also decreases accordingly.

As a result, the EGR gas is supplied to the EGR cooler 27.
When passing through, the amount of the SOF component adhering to the passage wall surface in the EGR cooler 27 becomes extremely small, so that the clogging of the EGR cooler 27 is suppressed.

When the fuel is completely burned by retarding the pilot injection timing and advancing the main injection timing, the maximum combustion temperature in the cylinder 2 is increased, and the amount of generated nitrogen oxides (NOx) is increased. However, in the present embodiment, since the retardation of the pilot injection timing and the advancement of the main injection timing are performed only for the first (# 1) cylinder 2, the remaining second (#) 2) The maximum combustion temperature in the cylinders 2 and 3 (# 3) cylinders 2 and 4 (# 4) does not unnecessarily increase, and the second (# 2) cylinders 2 and 3 (# 3) do not unnecessarily increase. ) In the cylinders 2 and 4 (# 4) cylinder 2, the amount of generated nitrogen oxides (NOx) does not increase.

As a result, the total amount of nitrogen oxides (NOx) contained in the exhaust gas discharged from the entire internal combustion engine 1 does not increase excessively.

Hereinafter, the fuel injection control according to the present embodiment will be specifically described with reference to the flowchart of FIG.

The flowchart shown in FIG. 3 is a flowchart showing a fuel injection control routine. This fuel injection control routine is a routine that is repeatedly executed by the CPU 351 at predetermined time intervals (for example, every time the crank position sensor 33 outputs a pulse signal), and is stored in the ROM 352 in advance.

In the fuel injection control routine, the CPU 351
First, in S301, data such as the engine speed and the output signal value (accelerator opening) of the accelerator opening sensor 36 are read from the RAM 353.

In S302, the CPU 351 determines the cylinder 2 for which the fuel injection timing and the fuel injection amount are to be determined. As this determination method, a method of determining based on the rotation angle position of the crankshaft calculated based on the output signal of the crank position sensor 33 can be exemplified.

In S303, the CPU 351 executes the processing in S3.
The pilot injection time, the main injection time, the pilot injection timing, and the main injection timing are determined using the data such as the engine speed and the accelerator opening read in 01 as parameters.

In S304, the CPU 351 determines whether or not the operating state of the internal combustion engine 1 is in the execution region of the EGR control, in other words, whether or not the separate EGR control is being executed.

If it is determined in step S304 that the EGR control is not being executed, the CPU 351 proceeds to step S30.
7, the fuel injection valve 3 of the cylinder 2 determined in S302 is controlled in accordance with the pilot injection time, the main injection time, the pilot injection timing, and the main injection timing determined in S303, and the execution of this routine is performed once. finish.

If it is determined in step S304 that the EGR control is being executed, the CPU 351 proceeds to step S305.
Then, it is determined whether the cylinder (the target cylinder for the fuel injection control) determined in S302 is the first (# 1) cylinder 2 or not.

If it is determined in S305 that the target cylinder for fuel injection control is the first (# 1) cylinder 2,
The CPU 351 proceeds to S306, in which the pilot injection timing determined in S303 is retarded by a first predetermined amount and the main injection timing is advanced by a second predetermined amount. The first and second predetermined amounts may be fixed values, or may be variable values that are changed based on the engine speed and the accelerator opening.

In S 307, the CPU 351 determines that the S 3
The fuel injection valve 3 of the first (# 1) cylinder 2 is controlled in accordance with the pilot injection timing and the main injection timing corrected in 06 and the pilot injection time and the main injection time determined in S303.

On the other hand, if it is determined in S305 that the target cylinder for fuel injection control is not the first (# 1) cylinder 2, the CPU 351 proceeds to S307, and proceeds to S307.
The fuel injection valve 3 of the target cylinder is controlled in accordance with the pilot injection timing, pilot injection time, main injection timing, and main injection time determined in Step 3.

As described above, when the CPU 351 executes the fuel injection control routine, the main injection unit, the sub injection unit, and the fuel injection timing control unit according to the present invention are realized.

Therefore, according to the internal combustion engine 1 of the present embodiment, nitrogen oxides (NOx)
SOF contained in the EGR gas while suppressing the generation amount of
Since the component amount decreases, the N
It is possible to suppress the adhesion of the SOF component in the EGR cooler 27 without reducing the Ox reduction effect.

As a result, it is possible to prevent clogging of the EGR cooler 27 without deteriorating exhaust emission of the entire internal combustion engine 1, and to suppress deterioration of exhaust emission caused by clogging of the EGR cooler 27. It becomes possible.

In the internal combustion engine 1 according to the present embodiment,
The EGR is performed by correcting the pilot injection timing and the main injection timing of the cylinder (closest cylinder) closest to the connection portion between the exhaust passage and the EGR passage of the internal combustion engine.
Although the example in which the amount of the SOF component contained in the gas is reduced has been described, the amount of the SOF component contained in the EGR gas is reduced by reducing the pilot injection amount and / or the main injection amount of the closest cylinder. You may.

Also, in the present embodiment, an example has been described in which the present invention is applied to an internal combustion engine in which the fuel injection amount to be injected into each cylinder is divided into two injections: pilot injection and main injection. When the present invention is applied to an internal combustion engine in which the fuel injection amount to be injected into each cylinder is injected by one fuel injection, the fuel injection timing of the closest cylinder during the execution of the EGR control is advanced and / or You may make it decrease the amount of SOF components contained in EGR gas by reducing the injection amount.

Further, in the present embodiment, an example has been described in which the present invention is applied to an internal combustion engine in which injection of sub-fuel (pilot injection) is performed prior to injection of main fuel (main injection) for each cylinder. However, after execution of main fuel injection (main injection) for each cylinder, secondary fuel injection (post injection)
When the present invention is applied to an internal combustion engine in which
The post injection timing of the closest cylinder is advanced and / or the post injection amount is reduced by reducing the post injection amount during the R control execution period.
The amount of the SOF component contained in the GR gas may be reduced, or the amount of the SOF component contained in the EGR gas may be reduced by prohibiting the post injection to the closest cylinder during the EGR control execution period. Is also good.

[0125]

In the internal combustion engine according to the present invention, when the exhaust gas is recirculated through the exhaust gas recirculation passage, the cylinder closest to the connecting portion between the exhaust gas passage and the exhaust gas recirculation passage (the closest cylinder). Since only the fuel injection timing is advanced, nitrogen oxides (NOx) exhausted from the entire internal combustion engine
The amount of the SOF component contained in the recirculated gas is reduced while an unnecessary increase in the amount is suppressed.

Therefore, according to the internal combustion engine of the present invention,
It is possible to suppress the adhesion of the SOF component in the cooling mechanism without reducing the NOx reduction effect by the exhaust gas recirculation, and as a result, to prevent the cooling mechanism from being clogged without deteriorating the exhaust emission of the entire internal combustion engine. Becomes possible.

The main fuel injection means for injecting the main fuel used for combustion by the internal combustion engine to each cylinder according to the present invention;
When auxiliary fuel injection means for injecting fuel secondary to each cylinder prior to injection of main fuel is provided, the main fuel injection timing of the closest cylinder is advanced and / or compared to other cylinders. By delaying the injection timing of the auxiliary fuel as compared with the other cylinders, the amount of the SOF component contained in the exhaust of the closest cylinder can be reduced, and as a result, the exhaust emission of the entire internal combustion engine is deteriorated. It is possible to reduce the amount of the SOF component contained in the recirculated gas without the need.

Further, the main fuel injection means for injecting the main fuel supplied to the cylinder for combustion by the internal combustion engine according to the present invention, and the sub-fuel injection means for injecting the fuel after the main fuel is injected into each cylinder. When the fuel injection means is provided, the injection timing of the main fuel and / or the auxiliary fuel of the closest cylinder is advanced compared to the other cylinders, so that the amount of the SOF component contained in the exhaust of the closest cylinder is reduced. As a result, it is possible to reduce the amount of the SOF component contained in the recirculated gas without deteriorating the exhaust emission of the entire internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and an intake / exhaust system thereof according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of an ECU.

FIG. 3 is a flowchart showing a fuel injection control routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Fuel supply pipe 6 ... Fuel pump 18 ... Exhaust branch pipe 19 ... exhaust pipe 20 ... exhaust purification catalyst 21 ... exhaust throttle valve 23 ... air-fuel ratio sensor 25 ... EGR passage 26 ... EGR valve 27 ... EGR cooler 33 ... crank position Sensor 34 Water temperature sensor 35 ECU 351 CPU 352 ROM 353 RAM 354 Backup RAM

Continued on the front page F-term (reference) 3G062 AA01 AA03 AA05 BA04 BA05 ED08 GA06 GA08 GA15 GA17 3G066 AA07 AA11 AA13 AB02 AC09 AD12 CD26 DA04 DA09 DC04 DC05 DC11 DC13 DC14 DC18 DC19 DC24 3G092 AA02 AA17 AA18 AB03 BB02 BB03 BB02 DG09 EA01 EA02 EA03 EA04 FA17 FA18 HA01Z HA04Z HA05Z HB03Z HD01Z HD04Z HE03Z HE08Z HF08Z 3G301 HA02 HA11 HA13 JA25 JA26 LB11 LC01 MA11 MA18 MA23 MA26 MA27 ND06 ND12 NE01 NE06 NE11 NE12 PA01Z PA07Z03 PD03

Claims (5)

[Claims] A compression ignition type internal combustion engine having a plurality of cylinders; an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage; A cooling mechanism for cooling the exhaust flowing through the exhaust recirculation passage; and a fuel injection for advancing a fuel injection timing of a cylinder closest to a connection portion between the exhaust passage and the exhaust recirculation passage in comparison with other cylinders. An internal combustion engine, comprising: timing control means. 2. A compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, and provided in the exhaust recirculation passage. A cooling mechanism for cooling the exhaust flowing through the exhaust recirculation passage; and a fuel injection amount for reducing a fuel injection amount of a cylinder closest to a connection portion between the exhaust passage and the exhaust recirculation passage as compared with other cylinders. An internal combustion engine comprising: a control unit. 3. A compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, and provided in the exhaust recirculation passage. A cooling mechanism that cools the exhaust gas flowing through the exhaust gas recirculation passage; a main fuel injection unit that injects main fuel to be used for combustion into each of the cylinders; An auxiliary fuel injection means for injecting fuel, an injection timing of main fuel for a cylinder closest to a connection portion of the exhaust passage and the exhaust recirculation passage, and an advance timing and / or an injection timing of auxiliary fuel for other cylinders. And a fuel injection timing control means for retarding the fuel injection timing relative to other cylinders. 4. A compression ignition type internal combustion engine having a plurality of cylinders, an exhaust recirculation passage for guiding a part of exhaust flowing through an exhaust passage of the internal combustion engine to an intake passage, and provided in the exhaust recirculation passage. A cooling mechanism that cools exhaust gas flowing through the exhaust gas recirculation passage; a main fuel injection unit that injects main fuel used for combustion into each of the cylinders; And a fuel injection timing for advancing the injection timing of the main fuel and / or the auxiliary fuel to the cylinder closest to the connection portion of the exhaust passage and the exhaust recirculation passage in comparison with other cylinders. An internal combustion engine comprising: a control unit. 5. A fuel injection amount control means for reducing an injection amount of a main fuel and / or an auxiliary fuel to a cylinder closest to a connecting portion of the exhaust passage and the exhaust recirculation passage as compared with other cylinders. The internal combustion engine according to claim 3 or 4, wherein: