JPH11247720A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the discharge amount of black smoke and HC, in an internal combustion engine provided with an exhaust gas recirculation means for recirculating exhaust gas to an intake system. SOLUTION: An internal combustion engine is provided with an exhaust gas recirculation passage 15 for recrivulating exhaust gas flowing in an exhaust system of the internal combustion engine to an intake system, an exhaust gas recirculation fuel injection means 18 for injecting fuel into the exhaust gas recirculation passage 15, and a premixing range 17 provided on the way of the exhaust recirculation passage 15 and for mixing fuel injected from the exhaust gas recirculation fuel injection means 18 to exhaust gas flowing in the exhaust gas recirculation passage 15. Fuel evaporated in the premixing range 17 and exhaust gas are homogeneously mixed to each other while fuel injected from the exhaust gas recirculation fuel injection means 18 is evaporated by heat of exhaust 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 an internal combustion engine having an exhaust gas recirculation path.

[0002]

2. Description of the Related Art Gasoline engines, diesel engines and the like are known as internal combustion engines mounted on automobiles and the like. For diesel engines, to reduce emissions of black smoke along with reducing the nitrogen oxides in the exhaust (NO _X) and hydrocarbons (HC) and the like, is required to improve the exhaust emission.

In response to such a demand, Japanese Patent Laid-Open No. 9-158
A diesel engine described in Japanese Patent Publication No. 810 is known. The diesel engine includes a preliminary injection device that injects fuel during intake air, a main injection device that injects fuel into the combustion chamber, a controller that controls the preliminary injection device and the main injection device according to an operation state of the engine, and an engine. And an intake air temperature adjusting means for variably controlling the intake air temperature in accordance with the operating state of the engine.

[0004] The controller injects fuel from the preliminary injection device during the period from the start of the suction stroke to the middle stage of the suction stroke. In this case, the fuel injected from the preliminary injection device is supplied to the combustion chamber while being mixed with the intake air. Subsequently, the fuel and intake air supplied into the combustion chamber are:
Since the temperature of the intake air rises during the compression stroke, the vaporization of the fuel is promoted using the intake air as a heat source. Then, the vaporized fuel and the intake air are homogeneously mixed with each other to form a lean mixture.

Subsequently, the controller injects fuel from the main injector near the compression top dead center. At this time, the lean air-fuel mixture in the combustion chamber ignites and burns the fuel injected from the main injection device using nuclei. At that time, because it contains excess oxygen and nitrogen in the lean, generation of black smoke and NO _X is suppressed.

On the other hand, the intake air temperature adjusting means is realized by, for example, an exhaust gas recirculation device (EGR device) comprising a recirculation passage from the exhaust passage to the intake passage and a flow control valve for controlling a flow rate in the recirculation passage. When the fuel injection amount is small, such as when the diesel engine is in a low load operation range, the exhaust gas recirculation amount is increased to correct the intake air temperature, thereby stabilizing the lean combustion and reducing the combustion temperature. It is intended to suppress the generation amount of NO _X by suppressing it.

[0007]

In the above-described diesel engine, fuel from the preliminary injection device is supplied to a mixed gas of recirculated exhaust gas and fresh air. Since the fuel is cooled, even if the fuel is injected into such a mixed gas, the fuel is not sufficiently vaporized. For this reason, a liquid fuel is supplied to the combustion chamber of the diesel engine, which may cause an increase in black smoke and HC.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and reduces the emission of black smoke and HC in an internal combustion engine having an exhaust gas recirculation passage for recirculating exhaust gas to an intake system. The purpose is to:

[0009]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
An internal combustion engine according to the present invention includes: an exhaust gas recirculation passage that recirculates exhaust gas flowing through an exhaust system of the internal combustion engine to an intake system; an exhaust gas recirculation fuel injection unit that injects fuel into the exhaust gas recirculation passage;
A pre-mixing region provided in the exhaust gas recirculation passage for mixing the fuel injected from the exhaust gas recirculation fuel injection means with the exhaust gas flowing through the exhaust gas recirculation passage.

In the thus configured internal combustion engine, fuel is injected into the exhaust gas flowing through the exhaust gas recirculation passage. Therefore, the fuel is vaporized by receiving the heat of the exhaust gas, and is then homogeneously mixed with the exhaust gas in the premixing region. Mix. The mixture thus formed is supplied to the combustion chamber of the internal combustion engine via the intake system. That is, in the combustion chamber, a mixture containing sufficiently vaporized fuel is burned, and the generation of black smoke, hydrocarbon (HC), and the like is suppressed.

Further, the internal combustion engine according to the present invention has a pressure accumulation chamber for storing fuel at a predetermined pressure, fuel injection means for injecting the fuel accumulated in the pressure accumulation chamber toward a combustion chamber of the internal combustion engine, An exhaust gas recirculation passage that recirculates exhaust gas flowing through the exhaust system of the engine to an intake system; an exhaust gas recirculation fuel injection unit that injects fuel accumulated in the accumulator into the exhaust gas recirculation passage; A premixing region for mixing the fuel injected from the exhaust gas recirculation fuel injection means with the exhaust gas flowing through the exhaust gas recirculation passage.

In the internal combustion engine configured as described above, the fuel whose pressure has been raised to a predetermined pressure in the accumulator is injected into the exhaust gas recirculation passage, so that atomization of the fuel is promoted. The atomized fuel is easily vaporized by receiving the heat of the exhaust gas flowing in the exhaust gas recirculation passage. Therefore, even in an operation region where the exhaust gas temperature is low, it is possible to form a good air-fuel mixture in which the sufficiently vaporized fuel and the exhaust gas are homogeneously mixed. That is, it is possible to form a good air-fuel mixture without being affected by the operation state of the internal combustion engine.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an internal combustion engine according to the present invention. The internal combustion engine is a diesel engine 1 having four cylinders 2, and includes a fuel injection valve 3 facing a combustion chamber of each cylinder 2 for each cylinder 2.

The fuel injection valve 3 realizes a fuel injection means according to the present invention, and is connected to a common rail 7 via a fuel distribution pipe 6. In addition, common rail 7
Is connected to a supply pump 9 via a first fuel supply pipe 8, and this supply pump 9 is connected to a feed pump 11 via a second fuel supply pipe 10.

The feed pump 11 comprises a fuel tank 1
The fuel is sucked by a strainer (not shown) arranged in the inside 2, and the sucked fuel is sent to the supply pump 9. The supply pump 9 sends the fuel from the feed pump 11 to the common rail 7 at a predetermined pressure. The common rail 7 realizes a pressure accumulating chamber according to the present invention, and accumulates fuel fed from the supply pump 11 at a predetermined pressure. The fuel stored in the common rail 7 is applied to the fuel injection valve 3 via the fuel distribution pipe 6 and is injected into the combustion chamber of each cylinder 2 when the fuel injection valve 3 is opened.

Next, an intake branch pipe 4 and an exhaust branch pipe 5 are connected to the diesel engine 1. An intake pipe 13 is connected to the intake branch pipe 4, and an air flow meter 22 that outputs an electric signal corresponding to the flow rate of fresh air flowing through the intake pipe 13 is attached in the middle of the intake pipe 13. on the other hand,
An exhaust pipe 14 is connected to the exhaust branch pipe 5.
Reference numeral 4 is connected downstream to a muffler via an exhaust purification catalyst (not shown). In the middle of the exhaust pipe 14, this exhaust pipe 1
An exhaust gas temperature sensor 35 that outputs an electric signal corresponding to the temperature of the exhaust gas flowing through the inside 4 is attached.

The intake pipe 13 and the exhaust pipe 14 communicate with each other via an exhaust gas recirculation passage 15, and a part of the exhaust gas flowing through the exhaust pipe 14 is recirculated to the intake pipe 13. A flow control valve (EGR valve) 1 for adjusting an exhaust gas recirculation amount is provided at a connection portion between the exhaust gas recirculation passage 15 and the intake pipe 13.
6 are provided.

The EGR valve 16 comprises a valve element which repeats opening and closing, and a solenoid for driving the valve element. A drive pulse signal having a duty ratio corresponding to the ratio of the valve opening time and the valve closing time of the valve element. Is applied, the solenoid drives the valve body in accordance with the drive pulse signal to adjust the amount of exhaust gas recirculation in the exhaust gas recirculation passage 15.

Subsequently, a premixing chamber 17 having a diameter larger than that of the exhaust gas recirculation passage 15 is formed in the exhaust gas recirculation passage 15, and the injection hole of the premixing chamber 17 faces the inside of the premixing chamber 17. The fuel injection valve 18 is attached. The premixing chamber 17 realizes the premixing region according to the present invention, and the fuel injection valve 1 for fumigation is provided.
8 realizes the exhaust gas recirculation fuel injection means according to the present invention.

The fuel injection valve for fumigation 18
Is connected to the common rail 7 through a fuel distribution pipe 19, so that the fuel raised to a predetermined pressure by the common rail 7 can be injected into the premixing chamber 17.

The return passage 20 is provided in the premixing chamber 17.
The return passage 20 is connected to the exhaust gas recirculation passage 1.
5 and the exhaust pipe 14 is connected to the exhaust pipe 14 downstream from the connection site. Then, the return passage 20 and the premixing chamber 17
A relief valve 21 that opens when the pressure in the premixing chamber 17 reaches a predetermined value or more and connects the return passage 20 is attached to the connection portion with the relief valve 21.

The diesel engine 1 has a crank position sensor 24 which outputs a pulse signal each time a crankshaft (not shown) rotates by a predetermined angle, and a cooling water temperature sensor 36 which outputs an electric signal corresponding to the temperature of engine cooling water. Is attached.

Then, the crank position sensor 24,
Various sensors such as the cooling water temperature sensor 36, the air flow meter 22, and the exhaust temperature sensor 35 are connected to an electronic control unit for engine control: the ECU 23 via electric wiring. The ECU 23 further includes an atmospheric pressure sensor 37 that outputs an electric signal according to the atmospheric pressure, and an accelerator position sensor 34 that outputs an electric signal according to the amount of depression of an accelerator pedal 33 (accelerator opening). Connected via

The ECU 23 includes a fuel injection valve 3, an EGR valve 16, a fuel injection valve 1 for fumigation.
8 and the like are connected via electric wiring. And ECU2
3 inputs the output signal of each sensor via electric wiring,
The operating state of the diesel engine 1 is determined based on these output signals, and then the fuel injection valve 3, the EGR valve 16, the fumigation fuel injection valve 18 and the like are controlled in accordance with the determined operating state.

More specifically, as shown in FIG. 2, the ECU 23 includes a CP which is interconnected by a bidirectional bus 25.
U26, ROM27, RAM28, backup RAM
29, an input port 30, an output port 31, and an analog / digital converter (A / D) 32 connected to the input port 30.

The input port 30 is connected to the crank position sensor 24, the accelerator position sensor 34, and the like via electric wiring, and transmits output signals from the sensors to the CPU 26 and the RAM 28 via the bidirectional bus 25. .

Further, the input port 30 is connected to the air flow meter 22, the exhaust gas temperature sensor 35, and the cooling water temperature sensor 3.
6. It is connected to the atmospheric pressure sensor 37 and the like via the A / D 32, and transmits output signals from the sensors to the CPU 26 and the RAM 28 via the bidirectional bus 25.

The backup RAM 29 is a non-volatile memory that retains the stored contents even after the operation of the diesel engine is stopped, and stores various learning values and the like. The RA
M28 stores the output signal value of each sensor, various calculation results calculated by the CPU 26, and the like. As the calculation result, an engine speed or the like calculated from the output signal value of the crank position sensor 24 can be exemplified.

Subsequently, the ROM 27 stores application programs to be executed by the CPU 26, various maps, and the like. The application program includes a required fuel amount control routine for calculating an amount of fuel to be supplied to the combustion chamber of each cylinder 2, a fuel injection valve 3 for each cylinder 2.
In-cylinder injection control routine for determining the valve opening timing of the engine, and fumigation for determining whether the valve opening timing of the fumigation fuel injection valve 18 is performed in synchronization with the engine speed or asynchronously A control routine, a fumigation timing control routine for determining the valve opening timing of the fumigation fuel injection valve 18, and the like can be exemplified.

The maps stored in the ROM 27 include a required fuel amount control map for determining the amount of fuel to be supplied to the combustion chamber of each cylinder 2 (required fuel amount: QFIN), and a fuel injection for fumigation. Fuel amount that can be injected from the valve 18 (fumigation possible injection amount: QFINF
F) a fumigation control map for determining M)
Limit injection for determining the upper limit value of the fuel amount that can be injected from the fumigation fuel injection valve 18, that is, the maximum value (limit injection amount: QAFM) of the fuel amount that can be injected within a range where black smoke is not generated. The amount control map, the EGR valve opening control map for determining the opening of the EGR valve 16, and the basic valve opening timing of the fuel injection valve 3 (basic in-cylinder injection timing: A
BASE), a basic in-cylinder injection timing control map, and an atmospheric pressure correction advance amount control for determining a correction amount (atmospheric pressure correction advance amount: APIM) of the basic in-cylinder injection timing according to the atmospheric pressure. Map, correction amount of basic in-cylinder injection timing according to cooling water temperature (cooling water temperature correction advance amount: A
THW), an engine coolant temperature correction advance amount control map for determining the fuel injection temperature, a case where fuel injection for fumigation is performed in synchronization with the engine speed, that is, within a desired period even at an injection timing synchronized with the engine speed. Basic fumigation timing control for determining the fumigation fuel injection valve 18 opening timing (basic fumigation timing: ABSFM1) when fumigation injection quantity (QFM) injection can be completed. When fuel injection for map and fumigation is performed asynchronously with the engine speed, that is, at an injection timing synchronized with the engine speed due to the occurrence of a rapid acceleration request or the like, the fumigation injection amount (QFM) is within a desired period. When the injection cannot be completed, the timing of opening the fumigation fuel injection valve 18 Asynchronous Few Mi interrogation Timing: ABSFM2) can be exemplified asynchronous diffuser Mi interrogation timing control map or the like for determining the.

The required fuel amount control map includes, for example, as shown in FIG. 3, the engine speed (NE) and the accelerator opening (AC).
2 is a map showing a relationship between the engine speed (NE) and the accelerator opening (ACC).
When P) is specified, the required fuel amount: QFIN is determined.

As shown in FIG. 4, for example, the fumigation control map includes an exhaust gas flow rate (GEX), an exhaust gas temperature (TEX), and a fumigation possible injection quantity (QFIN).
4 is a map showing the relationship with the exhaust gas flow rate (GE).
When X) and the exhaust temperature (TEX) are specified, the fumigation possible injection amount (QFINFM) is determined. That is, since the amount of energy corresponding to the latent heat of vaporization of the exhaust gas is determined from the exhaust gas flow rate (GEX) and the exhaust gas temperature (TEX), the fuel amount that can be vaporized with this energy amount (fumigation possible injection amount: QFINFM) is determined. It is done. Note that the exhaust gas flow rate (GEX) may be estimated based on the engine speed (NE) and the intake air amount (GN). The exhaust flow rate may be calculated from the oxygen concentration, or may be directly detected by attaching an air flow meter near the premixing chamber 17.

The limit injection amount control map includes, for example, as shown in FIG. 5, the engine speed (NE) and the intake air amount (GN).
Is a map showing a relationship between the engine speed and the limit injection amount (QAFM). When the engine speed (NE) and the intake air amount (GN) are specified, the limit injection amount (QAFM) is determined. I have.

Here, the fumigation possible injection amount (Q) determined by the fumigation control map is used.
If (FINFM) is equal to or less than the limit injection amount (QAFM) determined by the limit injection amount control map, the fumigation possible injection amount (QFINFM) should be actually injected from the fumigation fuel injection valve 18. It is set as a fuel amount (fumigation injection amount: QFM). On the other hand, the fumigation possible injection amount (Q
When (FINFM) is larger than the limit injection amount (QAFM), the limit injection amount (QAFM) is set as the fumigation injection amount (QFM).

The EGR valve opening control map includes a fumigation injection amount (QFM = min (QFINFM, QAF
M)) is a map assuming a case where the required fuel amount (QFIN) can be satisfied only by (QFM ≧ QFIN). This EGR valve opening control map is, for example, shown in FIG.
As shown in the figure, the engine speed (NE) and the required fuel amount (QF
FIG. 6 is a map showing a relationship between IN) and the EGR valve opening. When the engine speed (NE) and the required injection amount (QFIN) are specified, the EGR valve opening is determined.
When the fumigation injection amount (QFM) is smaller than the required fuel amount (QFIN), the EGR valve opening is fully opened.

The basic in-cylinder injection timing control map indicates that the fumigation injection amount (QFM) is the required fuel amount (QF).
IN), that is, a map assuming a case where QFIN is smaller than QFM (QFIN> QFM), that is, a case where the required fuel amount (QFIN) cannot be satisfied with only the fuel injected from the fumigation fuel injection valve 18. The basic in-cylinder injection timing control map includes, for example, an engine speed (NE), a fuel amount to be injected from the fuel injector 3 (QFIN-QFM), and a valve opening timing of the fuel injector 3 as shown in FIG. 5 is a map showing a relationship between the engine speed (NE) and the fuel amount (QF) to be injected from the fuel injection valve 3.
IN-QFM), the valve opening timing (ABASE) of the fuel injection valve 3 is determined.

The atmospheric pressure correction advance amount control map is, for example,
As shown in FIG. 8, the atmospheric pressure and the atmospheric pressure correction advance amount (API
M) is a map showing the relationship with M), and when the atmospheric pressure is specified, the atmospheric pressure correction advance amount (APIM) is determined.

The coolant temperature correction advance amount control map is, for example, a map showing the relationship between the coolant temperature and the coolant temperature correction advance amount (ATHW) as shown in FIG. Then, the cooling water temperature correction advance amount is determined.

The basic fumigation timing control map is, for example, as shown in FIG.
E) and basic fumigation timing (ABSFM
2 is a map showing a relationship with the engine speed (NE).
Is specified, the basic fumigation timing (ABSFM1) is determined.

As shown in FIG. 11, for example, the asynchronous fumigation timing control map includes the engine speed (NE) and the asynchronous fumigation timing (AB).
This is a map showing the relationship with SFM2), and when an engine speed (NE) is specified, asynchronous fumigation timing is determined.

Here, returning to FIG. 2, the CPU 26
It operates according to the application program stored in M27, and calculates control values for the fuel injection valve 3, the EGR valve 16, the fumigation fuel injection valve 18 and the like from the output signals of each sensor and each map. Then, the CPU 26
According to the calculated control value, the fuel injection valve 3 and the EGR valve 1
6. Control the fumigation fuel injection valve 18 and the like.

Subsequently, the output port 31 transmits the various control values calculated by the CPU 26 to the fuel injection valve 3, the fumigation fuel injection valve 18, and the EGR valve 16.
Hereinafter, the operation and effect of the present embodiment will be described.

The CPU 26 executes a required fuel amount control routine as shown in FIG. 12 at predetermined time intervals when the diesel engine 1 is operating. In the required fuel amount control routine, the CPU 26 first calculates the engine speed (NE) from the output signal of the crank position sensor 24 in S1201, and calculates the calculated engine speed (NE) as R
It is stored in a predetermined area of the AM 28.

Subsequently, the CPU 26 proceeds to S1202,
An output signal value (accelerator opening: ACCP) of the accelerator position sensor 34 is input. Then, the CPU 26
In S1203, the required fuel amount control map in the ROM 27 is accessed, and the required injection amount (QFIN) specified by the engine speed (NE) calculated in S1201 and the accelerator opening (ACCP) input in S1202.
Is calculated, and the process proceeds to S1204.

In S1204, the CPU 26 determines whether the RAM 2
8, the output signal value (intake air amount: GN) of the air flow meter 22 is read, and then in S1205, the engine speed NE calculated in S1201 and the intake air amount GN read in S1204 are read. The exhaust flow rate (GEX) of the diesel engine 1 is calculated.

Subsequently, in S1206, the CPU 26 accesses the RAM 28, reads out the output signal value (exhaust temperature: TEX) of the exhaust temperature sensor 35, and executes S1207.
Proceed to.

In step S1207, the CPU 26 reads the ROM2
7 is accessed, and the exhaust gas flow rate (GEX) calculated in S1205 and S1
Fumigation possible injection amount (QFINFM) determined by exhaust temperature (TEX) read at 206
Is calculated.

Next, the CPU 26 proceeds to S1208,
The limit injection amount control map stored in the ROM 27 is accessed, and the engine speed (NE) calculated in S1201 is accessed.
And a limit injection amount (QAFM) determined by the intake air amount (GN) read in S1204.

Then, in S1209, the CPU 26 determines whether or not the fumigation possible injection amount (QFINFM) calculated in S1207 is equal to or less than the limit injection amount (QAFM).

At S1209, the fumigation possible injection amount (QFINFM) is changed to the limit injection amount (QAF).
M) If it is determined to be less than or equal to
10 and the fumigation possible injection amount (QFIN
FM) is set as the fumigation injection amount (QFM).

On the other hand, in step S1209, the fumigation possible injection amount (QFINFM) is changed to the limit injection amount (Q
AFM), the CPU 26 proceeds to S1
Proceeding to 211, the limit injection amount (QAFM) is set as the fumigation injection amount (QFM).

After completing the processing of S1210 or S1211, the CPU 26 proceeds to S1212, and the required fuel amount (QFIN) calculated in S1203 is changed to the fumigation injection amount (QFIN) set in S1210 or S1211. QFM) is determined.

In step S1212, the required fuel amount (QF
IN) is larger than the fumigation injection amount (QFM), the CPU 26 determines that the required injection amount (Q
FIN 12), and
Proceed to.

In step S1213, the CPU 26 sets the EG
The opening of the R valve 16 is set to fully open (duty ratio 100%), and then in step S1214, the fumigation injection amount (QFM) is subtracted from the required injection amount (QFIN), and the amount of fuel injected by the fuel injection valve 3 is increased. (In-cylinder injection amount = QFIN-Q
FM).

Then, the CPU 26 proceeds to S1215, and executes in-cylinder injection control and fumigation control in parallel. Here, the in-cylinder injection control is performed by, for example, a CPU.
26 is realized by executing an in-cylinder injection control routine as shown in FIG. In this in-cylinder injection control routine, the CPU 26 accesses the basic in-cylinder injection timing control map stored in the ROM 27 in S1301, and determines the engine speed (NE) and the in-cylinder injection amount (QFIN-Q).
FM) and the basic in-cylinder injection timing (A
BASE).

Subsequently, the CPU 26 proceeds to S1302, accesses the RAM 28, reads the output signal value (atmospheric pressure) of the atmospheric pressure sensor 37, and then reads the output signal value (atmospheric pressure) of the atmospheric pressure sensor 37 into the atmospheric pressure correction advance amount control map stored in the ROM 27 in S1303. Access is made and an atmospheric pressure correction advance amount (APIM) determined by the atmospheric pressure is calculated.

Further, the CPU 26 accesses the RAM 28 in S1304, reads the output signal value (cooling water temperature) of the cooling water temperature sensor 36, and reads R
The cooling water temperature correction advance amount control map stored in the OM 27 is accessed to calculate a cooling water temperature correction advance amount (ATHW) determined by the cooling water temperature.

In step S1306, the CPU 26 calculates the basic in-cylinder injection timing (ABASE) calculated in step S1301, the atmospheric pressure correction advance angle (APIM) calculated in step S1303, and calculates the value in step S1305. The cooling water temperature correction advance amount (ATHW) is added and the injection timing of the fuel injection valve 3 (in-cylinder injection timing: A
TRG = ABASE + APIM + ATHW).

Subsequently, in S1307, the CPU 26 monitors the in-cylinder injection timing (ATRG) calculated in S1306 and the output signal value of the crank position sensor 24. In-cylinder injection is performed by applying a drive current.

On the other hand, the fumigation control is realized, for example, by the CPU 26 executing a fumigation control routine as shown in FIG. In the fumigation control routine, the CPU 26
First, in S1401, the previous required fuel amount (QFIN) stored in a predetermined area of the RAM 28 is read.

Then, the CPU 26 determines in step S1402 that the current required injection amount (QFI) stored in the RAM 28
N) is also read. Subsequently, the CPU 26 proceeds to S1403 and subtracts the previous required fuel amount (QFIN) from the current required fuel amount (QFIN), and determines whether or not the obtained value is larger than a predetermined value.

If it is determined in step S1403 that the value obtained by subtracting the previous required fuel amount (QFIN) from the current required fuel amount (QFIN) is larger than the predetermined value, the CPU 26 determines whether a sudden acceleration request or the like has occurred. It is considered that the injection of the fumigation injection amount (QFM) cannot be completed within the desired period at the injection timing synchronized with the engine speed due to the occurrence, and “1” is set in the asynchronous injection flag storage area of the RAM 28 in S1404. Set.

On the other hand, in step S1403, the current required fuel amount (QFIN) is changed to the previous required fuel amount (QFIN).
Is determined to be equal to or less than the predetermined value, the CPU 26 completes the injection of the fumigation injection amount (QFM) within a desired period even at an injection timing synchronized with the engine speed. Can be considered as S
At 1405, “0” is set in the asynchronous injection flag storage area of the RAM.

After completing the processing of S1404 or S1405, the CPU 26 proceeds to S1406 and executes fumigation timing control. This fumigation timing control is performed by the CPU 26 as shown in FIG.
This is realized by executing a fumigation timing control routine as shown in FIG.

In the fumigation timing control routine, the CPU 26 first determines in S1501
The engine speed (NE) stored in the RAM 28 is read, and then the basic fumigation timing control map stored in the ROM 27 is accessed, and the basic fumigation timing (ABSFM1) determined by the engine speed (NE) is obtained. Is calculated.

Subsequently, the CPU 26 proceeds to S1502, accesses the asynchronous injection flag storage area of the RAM 28, and determines whether or not "1" is stored. Said S
If it is determined in step 1502 that “0” is stored in the asynchronous injection flag storage area, the CPU 26
Goes to S1504, where the crank position sensor 24
Is monitored, and when the output signal value of the crank position sensor 24 matches the basic fumigation timing (ABSFM1) calculated in S1501, the drive current is supplied to the fumigation fuel injection valve 18. And the opening degree (full open) of the EGR valve 16 set in S1213 of the required fuel amount control routine.
, The EGR valve 16 is controlled.

In this case, the fumigation fuel injection valve 18 injects the high-pressure fuel accumulated by the common rail 7.
Is atomized and diffused into the premixing chamber 17.

On the other hand, when the EGR valve 16 is opened, the intake pipe 1 is opened.
Since the intake pipe negative pressure generated in the exhaust pipe 3 is applied to the exhaust pipe 14 via the exhaust gas recirculation path 15 and the premix chamber 17, a part of the high-temperature exhaust gas flowing in the exhaust pipe 14 is sucked into the exhaust gas recirculation path 15. And reaches the premixing chamber 17.

As a result, the fuel diffused into the premixing chamber 17 receives the latent heat of vaporization of the exhaust sucked into the premixing chamber 17 and mixes with the exhaust while being vaporized to form an air-fuel mixture. This air-fuel mixture passes through the exhaust gas recirculation passage 15 and flows into the intake pipe 13.
And is supplied to each cylinder 2 of the diesel engine 1 through the intake branch pipe 4, and the fuel injection valve 3 of each cylinder 2
It is burned together with the fuel injected from the.

The fuel injected from the fuel injection valve 18 for fumigation as described above is sufficiently vaporized by receiving the heat of the exhaust gas and mixed with the residual oxygen and the like in the exhaust gas, so that it is burned in the diesel engine 1. Does not generate black smoke when exposed.

Further, the exhaust pipe 1 is
Exhaust gas recirculated from the exhaust pipe 4 to the intake pipe 13 is deprived of heat by the fuel in the premixing chamber 17, and its temperature is reduced. Therefore, the combustion temperature in each cylinder 2 can be reduced, and the generation of NOX can be suppressed. Can be.

If it is determined in step S1502 that "1" is stored in the asynchronous injection flag storage area, the CPU 26 proceeds to step S1503, and proceeds to step S1503.
8, the engine speed (NE) stored in the ROM 27 is read, and then the asynchronous fumigation timing control map stored in the ROM 27 is accessed, and the engine speed (N) is read.
The asynchronous fumigation timing (ABSFM2) determined by E) is calculated.

Subsequently, in S1504, the CPU 26
Monitors the output signal value of the crank position sensor 24, and when the output signal value of the crank position sensor 24 matches the asynchronous fumigation timing (ABSFM2) calculated in S1503, the fuel for fumigation is monitored. A drive current is applied to the injection valve 18, and the EGR valve 16 is controlled in accordance with the opening degree (full opening) of the EGR valve 16 set in S1213 of the required fuel amount control routine.

In this case, the fuel injection valve for fumigation 18 can inject a large amount of fumigation injection (QFM) within a desired period by injecting fuel asynchronously with the engine speed. Becomes

Here, returning to the required fuel amount control routine of FIG. 12, if it is determined in S1212 that the required fuel amount (QFIN) is equal to or smaller than the fumigation injection amount (QFM), the CPU 26 sets The required injection amount (QFI) is determined only by the fuel injection from the fuel injection valve 18.
N) is satisfied (that is, there is no need to inject fuel from the fuel injection valve 3), and the process proceeds to S1216.

In S1216, the CPU 26 determines whether the RO
The EGR valve opening control map stored in M27 is accessed, and the engine speed (NE) calculated in S1201 and S
An EGR valve opening degree specified by the required fuel amount (QFIN) calculated in 1203 is calculated.

Subsequently, the CPU 26 proceeds to S1217 to execute fumigation control. This fumigation control is performed by the CPU 26 as shown in FIG.
This is realized by executing the fumigation control routine of FIG. 4 and the fumigation timing control routine of FIG.

According to the above-described embodiment, since fuel is injected into the high-temperature exhaust gas in the premixing chamber, the injected fuel is sufficiently vaporized by the latent heat of vaporization of the exhaust gas and uniformly mixed with the exhaust gas. can do. As a result, in the combustion chamber of the diesel engine, sufficiently vaporized fuel is supplied and burned, so that the amount of black smoke and HC emissions is reduced.

Further, in the present embodiment, since the fuel pressurized by the common rail is injected into the premixing chamber, atomization of the fuel is promoted, and the atomized fuel is vaporized by receiving the latent heat of vaporization of the exhaust gas. easy.

As a result, even if the exhaust gas has a low latent heat of vaporization, that is, the exhaust gas has a low temperature, the fuel can be easily vaporized and a good air-fuel mixture can be formed. Therefore, according to the present embodiment, a good air-fuel mixture can be formed even in an operation region where the exhaust gas temperature is low, so that black smoke or H2 gas can be formed without depending on the operation state of the diesel engine.
It is possible to reduce the amount of C discharged.

The exhaust gas supplied to the premixing chamber is deprived of heat energy by the fuel injected from the fumigation fuel injection valve, and its temperature is reduced. Will be supplied,
It is also possible to lower the combustion temperature in the combustion chamber and reduce the amount of NOx generated.

[0083]

In the internal combustion engine according to the present invention, fuel is injected into the exhaust gas flowing through the exhaust gas recirculation passage and mixed with the exhaust gas in the premixing region. Therefore, the fuel is sufficiently vaporized by receiving the heat of the exhaust gas. At the same time, it mixes with the exhaust gas to form a good air-fuel mixture. As a result, in the combustion chamber of the internal combustion engine,
Since the air-fuel mixture containing the fuel in the vaporized state is supplied and the air-fuel mixture is burned, generation of black smoke, hydrocarbon (HC), and the like is suppressed.

Further, when adopting a structure in which the fuel stored in the pressure storage chamber is injected into the exhaust gas recirculation passage, atomization of the injected fuel is promoted, so that the fuel easily receives the heat of the exhaust and is easily vaporized. It is easy to form a good air-fuel mixture. That is, even in an operation region where the exhaust gas temperature is low, a mixture containing sufficiently vaporized fuel can be formed, and black smoke or hydrocarbon (H2) can be formed regardless of the operation state of the internal combustion engine.
C) can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an internal combustion engine according to the present invention.

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

FIG. 3 is a diagram showing a specific example of a required fuel amount control map;

FIG. 4 is a diagram showing a specific example of a fumigation control map.

FIG. 5 is a diagram showing a specific example of a limit injection amount control map.

FIG. 6 is a diagram showing a specific example of an EGR valve opening control map;

FIG. 7 is a diagram showing a specific example of a basic in-cylinder injection timing control map;

FIG. 8 is a diagram showing a specific example of an atmospheric pressure correction advance angle control map;

FIG. 9 is a diagram showing a specific example of a coolant temperature correction advance amount control map;

FIG. 10 is a diagram showing a specific example of a basic fumigation timing control map.

FIG. 11 is a diagram illustrating a specific example of an asynchronous fumigation timing control map.

FIG. 12 is a flowchart illustrating a required fuel amount control routine.

FIG. 13 is a flowchart illustrating an in-cylinder injection control routine.

FIG. 14 is a flowchart illustrating a fumigation control routine.

FIG. 15 is a flowchart illustrating a fumigation timing control routine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine (internal combustion engine) 2 ... Cylinder 3 ... Fuel injection valve 7 ... Common rail 13 ... Intake pipe 14 ... Exhaust pipe 15 ... Exhaust recirculation passage 16 ... EGR valve 17 ...・ Premixing chamber (premixing area) 18 ・ ・ Fumigation fuel injection valve (exhaust gas recirculation fuel injection means) 23 ・ ・ ECU 24 ・ ・ Crank position sensor 35 ・ ・ Exhaust temperature sensor 36 ・ ・ Cooling water temperature sensor 37 ..Atmospheric pressure sensors

Claims (2)

[Claims] An exhaust gas recirculation passage for recirculating exhaust gas flowing through an exhaust system of an internal combustion engine to an intake system; an exhaust gas recirculation fuel injection unit for injecting fuel into the exhaust gas recirculation passage; And a premixing region for mixing the fuel injected from the exhaust gas recirculation fuel injection means with the exhaust gas flowing through the exhaust gas recirculation passage. 2. An accumulator for accumulating fuel at a predetermined pressure, a fuel injection means for injecting the fuel accumulated in the accumulator toward a combustion chamber of the internal combustion engine, and an exhaust gas flowing through an exhaust system of the internal combustion engine. An exhaust gas recirculation passage for recirculating to the intake system; an exhaust gas recirculation fuel injection means for injecting fuel accumulated in the pressure accumulation chamber into the exhaust gas recirculation passage; and an exhaust gas recirculation fuel passage provided in the exhaust gas recirculation passage. An internal combustion engine comprising: a premixing region for mixing fuel injected from the injection means and exhaust gas flowing through the exhaust gas recirculation passage.