JP5182527B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a control technique for optimally injecting fuel according to oxygen concentration in intake air.

Conventionally, in-cylinder direct injection internal combustion engines (for example, diesel engines) are pilots that aim to reduce exhaust properties, white smoke, and combustion noise, and inject a small amount of fuel prior to main injection in addition to main injection. The jet is being performed.
The injection timing of main injection and pilot injection is the best combustion state of the main injection fuel based on the experimental results in the standard operating state of the engine (steady operation with constant cooling water temperature, boost pressure, intake air temperature, etc.). The basic main injection timing map that is the injection timing that is generated and the basic pilot injection timing map that is the injection timing at which the combustion noise can be best reduced without causing deterioration of white smoke or exhaust properties are determined.

However, in an actual engine, repeated acceleration / deceleration causes a delay in the response of the EGR device and the supercharger, and the combustion state in the combustion chamber deviates greatly from the optimum state, resulting in white smoke or combustion noise. There is a problem that gets worse.
For this reason, for example, the acceleration operation interval from the transition to the transient operation to the return to the steady operation is divided into two, and based on the deviation between the measured value of the oxygen concentration or oxygen amount and the target value during the steady operation. If the deviation is large, a small pilot injection amount is injected on the relatively advanced side, and the main injection is performed before the compression top dead center by shortening the injection interval between the pilot injection and the main injection. When the deviation is small, the pilot injection amount is relatively increased, and the injection interval between the pilot injection and the main injection is lengthened to complete the combustion of the pilot injected fuel, and then the main injection is performed. A fuel injection control device for a diesel engine has been developed that can significantly improve the exhaust noise and fuel consumption while suppressing the deterioration of combustion noise during acceleration operation (Patent Document 1).

JP 2002-276444 A

  In the fuel injection control device of the diesel engine disclosed in Patent Document 1, in a fuel rich region where the oxygen concentration or the oxygen amount is transiently insufficient with respect to the target value, a small number of pilots are used to suppress an excessive increase in the ignition delay period. The injection is performed at a relatively advanced angle side, and the injection interval between the pilot injection and the main injection is shortened to complete the main injection before the compression top dead center. Also, in the fuel rich region where it takes time to raise the boost pressure and the amount of oxygen is insufficient with respect to the target value, the pilot injection amount is made relatively large, and the pilot interval between the pilot injection and the main injection is made longer. The main injection is performed after the combustion of the injected fuel is completely terminated.

However, during transient operation, etc., the oxygen concentration of the intake air containing the EGR gas depends on the change in the mixing ratio of the EGR gas and the intake air or the oxygen concentration of the EGR gas even if the mixing ratio of the EGR gas and the intake air is the same. Not only in a thin state but also in a state in which the oxygen concentration is high, it may affect the combustion of the main injection.
In an internal combustion engine that burns in a state where the amount of oxygen is much higher than the stoichiometric air-fuel ratio, such as a diesel engine, it has been found that the concentration of oxygen concentration has a greater influence on the ignition of main combustion than the slight fluctuation of the amount of oxygen did.

For this reason, the oxygen concentration of the intake air containing the EGR gas is high, so that the ignition of the main injection becomes steep, unlike the steady state, the combustion noise increases, the generation of vibrations, and the exhaust properties may deteriorate. There is.
The present invention has been made to solve such a problem, and the object of the present invention is to make the fuel injection the optimum injection timing even in a state where the oxygen concentration of the intake air containing the EGR gas is high. Another object of the present invention is to provide a fuel injection control device for an internal combustion engine that can prevent deterioration of combustion noise and drivability regardless of the oxygen concentration, and can improve exhaust properties.

In order to achieve the above object, a fuel injection control device for an internal combustion engine according to claim 1 performs main injection for injecting fuel and pilot injection prior to the main injection, and main injection timing and pilot injection in a standard operation state. In a fuel injection control device for an internal combustion engine in which an amount and a pilot injection timing are set, target oxygen concentration setting means for setting a target oxygen concentration of intake air drawn into the combustion chamber from the intake passage during operation, and the combustion chamber Based on the calculation result of the oxygen concentration deviation calculating means , the oxygen concentration deviation calculating means for calculating the oxygen concentration deviation by subtracting the target oxygen concentration from the actual oxygen concentration of the intake air sucked into the standard operation, and the main injection timing correction means for correcting the injection timing of the state of the main injection to the oxygen concentration deviation, based on the calculation result of the oxygen concentration deviation calculating means, the normal operation like With the pilot injection timing correction means for correcting in accordance with the oxygen concentration deviation injection timing of the pilot injection, and the main injection timing correction means, the main injection timing the oxygen concentration deviation is the threshold value of the oxygen concentration deficient side If smaller than the correction determination deviation, the main injection timing is corrected so that the injection timing is injected earlier than the injection timing of the main injection in the standard operation state, and the oxygen concentration deviation is a threshold value on the oxygen concentration excess side. If it is larger than the timing correction determination deviation, the main injection timing is corrected so as to inject the injection timing later with respect to the injection timing of the main injection in the standard operation state, and the pilot injection timing correction means If the pilot injection timing correction judgment deviation, which is the threshold value on the oxygen concentration deficiency side, is smaller than the pilot injection timing in the standard operation state, the injection timing should be delayed. If the oxygen concentration deviation is larger than the pilot injection timing correction determination deviation which is the threshold value on the oxygen concentration excess side, the injection timing is made to be injected earlier than the pilot injection timing in the standard operation state. and features that you correct the pilot injection timing.

Further, in the fuel injection control device for an internal combustion engine according to claim 2 , in the invention of claim 1 , if the oxygen concentration deviation is smaller than a pilot injection amount correction determination deviation which is a threshold value on the oxygen concentration deficient side , the pilot in the standard operation state If the pilot injection amount is corrected so that more fuel is injected with respect to the injection amount, and the oxygen concentration deviation is larger than the pilot injection amount correction determination deviation which is the threshold value on the oxygen concentration excess side , the pilot injection in the standard operation state Pilot injection amount correction means for correcting the pilot injection amount so as to inject the fuel with respect to the amount is provided.

Further, in the fuel injection control device for an internal combustion engine according to claim 3 , in the invention of claim 1 or 2 , the oxygen concentration deviation is smaller than the pre-injection determination deviation which is a threshold on the oxygen concentration deficient side, or the oxygen concentration deviation. Is larger than a pre-injection determination deviation which is a threshold value on the oxygen concentration excess side , a pre-injection for adding fuel after the pilot injection and before the main injection is added to determine the injection amount of the pre-injection A determining means is provided.

According to the first aspect of the invention , the main injection timing correction in which the oxygen concentration deviation calculated by subtracting the target oxygen concentration from the actual oxygen concentration of the intake air sucked into the combustion chamber is a threshold on the oxygen concentration deficient side. If the deviation is smaller than the judgment deviation, the main injection timing is corrected so that the injection timing is injected earlier than the main injection timing in the normal operation state, and the oxygen concentration deviation is a threshold value on the oxygen concentration excess side. If the deviation is larger than the determination deviation, the main injection timing is corrected so that the injection timing is delayed later than the injection timing of the main injection in the normal operation state, and the pilot whose oxygen concentration deviation is a threshold value on the oxygen concentration deficient side If the injection timing correction judgment deviation is smaller, the pilot injection timing is corrected so that the injection timing is injected later than the pilot injection timing in the normal operation state, and the oxygen concentration deviation is a threshold value on the oxygen concentration excess side. Is greater than the pilot injection timing correction determined deviation is, the pilot injection timing of the normal operation state, and corrects the pilot injection timing so as to inject early injection timing.

As a result, when the oxygen concentration is high, it is possible to suppress an abrupt increase in cylinder pressure, and it is possible to suppress poor ignition and slow combustion when the oxygen concentration is low. Furthermore, the combustion timing of the pilot injection can be made appropriate, and the cylinder temperature and pressure during the main combustion by the main injection can be made appropriate, thereby suppressing the ignition and combustion of the main combustion from becoming steep or slow. Therefore, combustion noise due to steep cylinder pressure during transition can be reduced and ignition can be ensured, so that generation of unburned gas can be suppressed and exhaust properties can be improved, and vibration due to poor ignition can be prevented. By suppressing the occurrence, it is possible to prevent deterioration of drivability.

According to the invention of claim 2 , if the oxygen concentration deviation is smaller than the pilot injection amount correction determination deviation on the oxygen concentration deficient side in the pilot injection amount correcting means, the fuel is increased with respect to the pilot injection amount in the standard operation state. If the pilot injection amount is corrected so as to be injected and the oxygen concentration deviation is larger than the pilot injection amount correction judgment deviation on the oxygen concentration excess side, the pilot injection amount is injected so that the fuel is injected less than the pilot injection amount in the normal operation state. I am trying to correct.

As a result, an air-fuel mixture with an appropriate amount of fuel can be created in the combustion chamber, and a sharp increase in cylinder pressure and poor ignition can be suppressed during main combustion by main injection .

Also, according to the invention of claim 5, the oxygen concentration deviation in the pre-injection quantity determining means pre-injection determination deviation is less than the oxygen concentration deficient side, or the pre-injection determination deviation of the oxygen concentration deviation is oxygen-rich side If larger, a pre-injection for injecting fuel after the pilot injection and before the main injection is added.

  Thereby, ignition of main combustion by main injection can be ensured by pre-combustion by pre-injection, and vibration due to generation of unburned gas and poor ignition can be suppressed, so that drivability can be improved. In addition, since the steepness of the cylinder pressure can be suppressed, combustion noise can be reduced.

It is a schematic block diagram of the fuel-injection control apparatus of the internal combustion engine which concerns on the 1st reference example of this invention. It is a block diagram which shows the internal structure of ECU in the fuel-injection control apparatus of the internal combustion engine which concerns on the 1st reference example of this invention. It is a characteristic view of the main injection timing correction amount in the oxygen concentration deviation according to the first reference example of the present invention. It is a flowchart which shows the control routine of the fuel-injection control which concerns on the 1st reference example of this invention. It is a graph which shows the change of the injection signal in the crank angle which concerns on the 1st reference example of this invention, a heat release rate, and a cylinder pressure. It is a graph which shows the change of the injection signal in the crank angle which concerns on the 1st reference example of this invention, a heat release rate, and a cylinder pressure. It is a block diagram which shows the internal structure of ECU in the fuel-injection control apparatus of the internal combustion engine which concerns on the 2nd reference example of this invention. It is a characteristic view of the additional pre-injection amount in the oxygen concentration deviation according to the second reference example of the present invention. It is a flowchart which shows the control routine of the fuel-injection control which concerns on the 2nd reference example of this invention. It is a flowchart which shows the control routine of the fuel-injection control which concerns on the 2nd reference example of this invention. It is a graph which shows the change of the injection signal in the crank angle which concerns on the 2nd reference example of this invention, a heat release rate, and a cylinder pressure. It is a graph which shows the change of the injection signal in the crank angle which concerns on the 2nd reference example of this invention, a heat release rate, and a cylinder pressure. It is a block diagram showing the internal structure of an ECU in the fuel injection control apparatus for an internal combustion engine according to the actual施例of the present invention. It is a characteristic diagram of the pilot injection correction amount in the oxygen concentration deviation of the actual施例of the present invention. It is a characteristic diagram of the pilot injection timing correction quantity in the oxygen concentration deviation of the actual施例of the present invention. It is a flowchart showing a control routine of the fuel injection control according to the actual施例of the present invention. It is a flowchart showing a control routine of the fuel injection control according to the actual施例of the present invention. It is a flowchart showing a control routine of the fuel injection control according to the actual施例of the present invention. Injection signal at a crank angle of the actual施例of the present invention, is a graph showing a change in heat generation rate and the cylinder pressure. Injection signal at a crank angle of the actual施例of the present invention, is a graph showing a change in heat generation rate and the cylinder pressure.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Reference Example]
Figure 1 shows a schematic block diagram of a fuel injection control device for an internal combustion engine according to the first exemplary embodiment of the present invention, FIG. 2, the ECU in the fuel injection control apparatus for an internal combustion engine according to the first exemplary embodiment of the present invention The block diagram which shows an internal structure is shown.

Hereinafter, the configuration of the fuel injection control device for the internal combustion engine of the first reference example of the present invention will be described.
As shown in FIG. 1, the engine 1 is a multi-cylinder direct injection type internal combustion engine (for example, a common rail type diesel engine). Specifically, the high pressure fuel accumulated in the common rail is supplied to the fuel injection nozzle 16 of each cylinder. The fuel injection nozzle 16 can inject the fuel into the combustion chamber 11 of each cylinder at an arbitrary injection timing and injection amount.

  Each cylinder of the engine 1 is provided with a piston 3 that can slide up and down. The piston 3 is connected to a crankshaft (not shown) via a connecting rod 4. Further, a flywheel (not shown) is provided at one end of the crankshaft, and a crank angle sensor 18 for detecting the rotational speed of the crankshaft is provided on the flywheel.

In addition, an intake passage 9 and an exhaust passage 13 are communicated with the combustion chamber 11.
The intake passage 9 is provided with an intake valve 10 for connecting and blocking the combustion chamber 11 and the intake passage 9, and the exhaust passage 13 is an exhaust valve for connecting and blocking the combustion chamber 11 and the exhaust passage 13. 12 is provided.
Further, upstream of the intake passage 9, an intake duct 5 for sucking in fresh air, an air cleaner 6 for removing dust in the sucked fresh air, and a turbocharger 7 for compressing the sucked fresh air using exhaust energy. The compressor housing (not shown) and the intercooler 8 for cooling the compressed fresh air are provided so as to communicate with each other.

In addition, an air flow sensor 19 is provided downstream of the air cleaner 6 and upstream of the intercooler 8. The boost sensor 20 detects the pressure of the intake air sucked into the combustion chamber 11, and the temperature of the intake air is adjusted. An intake air temperature sensor 21 to be detected is provided so as to protrude into the intake passage 9.
Further, downstream of the exhaust passage 13, a turbine housing (not shown) for introducing exhaust gas from the turbocharger 7 and an exhaust pipe 14 provided with a catalyst in the passage are provided so as to communicate with each other.

The intake passage 9 and the exhaust passage 13 are provided with an EGR passage 17 for returning a part of the exhaust gas to the intake air so as to communicate with each other. The EGR passage 17 is an EGR that adjusts the EGR amount (exhaust flow rate). A valve 15 is provided.
Various devices and various sensors such as the EGR valve 15, the fuel injection nozzle 16, the crank angle sensor 18, the air flow sensor 19, the boost sensor 20, and the intake air temperature sensor 21 perform comprehensive control of the engine 1. And an electronic control unit (hereinafter referred to as ECU) 2 that includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), etc. The ECU 2 controls the operation of various devices based on information from various sensors.

Specifically, referring to FIG. 2, a block diagram showing an internal configuration of the ECU 2 in the fuel injection control device for an internal combustion engine according to the first reference example of the present invention is shown. Will be described.
Sensors such as a fuel injection nozzle 16, an air flow sensor 19, a boost sensor 20, and an intake air temperature sensor 21 are electrically connected to the input side of the ECU 2, and detection information from these various devices and various sensors is received. Entered.

On the other hand, an EGR valve 21 and a fuel injection nozzle 22 are electrically connected to the output side of the ECU 2.
Thus, the ECU 2 sets the target oxygen concentration setting unit (target oxygen concentration setting means) 42, the main injection amount / injection timing setting unit 43, and the pilot injection timing based on the values detected by the crank angle sensor 18 and the air flow sensor 19.・ From the target intake oxygen concentration map, main injection timing map, pilot injection amount map, and pilot injection timing map, which are prepared in advance by the injection amount setting unit 47 so that the engine is in an optimum operating state in steady operation. The target oxygen concentration, main injection timing, pilot injection amount, and pilot injection timing are set from the current operating state of the engine 1 (engine speed, load, etc.).

  The oxygen concentration calculation unit 40 is based on the detected values of the air flow sensor 19, the boost sensor 20 and the intake air temperature sensor 21 and the fuel injection amount injected by the fuel injection nozzle 16 detected by the fuel injection amount detection unit 41. Then, the intake amount of fresh air, the EGR amount recirculated to the intake air, and the oxygen concentration in the recirculated EGR amount are calculated, and the oxygen concentration of the intake air sucked into the combustion chamber 11 is calculated.

An oxygen concentration deviation calculating unit (oxygen concentration deviation calculating means) 44 calculates an oxygen concentration deviation from the target oxygen concentration and the oxygen concentration of the air sucked into the combustion chamber 11, and a main injection timing correction unit main injection timing. The correction means) 45 corrects the main injection timing based on the oxygen concentration deviation, and supplies an injection signal to the fuel injection nozzle 16.
Hereinafter, the operation and effect of the fuel injection control device for an internal combustion engine according to the first reference example of the present invention configured as described above will be described in detail.

FIG. 3 is a characteristic diagram of the main injection timing correction amount in the oxygen concentration deviation according to the first reference example of the present invention, where the horizontal axis represents the oxygen concentration deviation and the vertical axis represents the main injection timing correction amount. The characteristic diagrams are set according to engine operating conditions such as engine speed. FIG. 4 is a flowchart showing a control routine of fuel injection control executed by the ECU 2, and FIG. 5 shows changes in the injection signal, heat generation rate, and cylinder pressure at the crank angle when the oxygen concentration is higher than the target oxygen concentration. FIG. 6 shows changes in the injection signal, the heat generation rate, and the cylinder pressure at the crank angle when the oxygen concentration is lower than the target oxygen concentration. 5 and 6, the horizontal axis indicates the crank angle, the vertical axis indicates the injection signal, the heat generation rate, and the cylinder pressure. The thick line or hatching indicates the first reference example, and the thin line or no hatching indicates the conventional example. . In the description of this reference example, the main injection timing correction determination deviation on the oxygen concentration deficient side is represented as a first predetermined oxygen concentration deviation, and the main injection timing correction determination deviation on the oxygen concentration excess side is represented as a second predetermined oxygen concentration deviation. .

As shown in FIG. 4, in step S10, the target oxygen concentration setting unit 42 preliminarily performs an experiment on the engine 1 based on a target intake oxygen concentration map created so that the engine 1 is in an optimum operating state in steady operation. The target oxygen concentration Dt is set from the operating situation.
In step S12, the main injection timing is determined from the operation status of the engine 1 based on the target main injection timing map prepared in advance by the main injection amount / injection timing setting unit 43 so as to bring the engine 1 into an optimum operating state through experiments. Set.

In step S14, the pilot is determined based on the operating state of the engine 1 based on the pilot injection amount map and the pilot injection timing map that are targets that have been prepared in advance so that the engine 1 is in an optimal operating state through experiments at the pilot injection amount / injection timing 47. Set the injection amount and pilot injection timing.
In step S16, the air flow sensor 19 detects a fresh air intake amount Qa which is an intake amount of fresh air drawn from the intake duct 5.

In step S <b> 18, the boost sensor 20 detects the intake air pressure Pi that is the pressure of the intake air taken into the combustion chamber 11 in the intake passage 9.
In step S20, the intake air temperature Ti, which is the temperature of the intake air taken into the combustion chamber 11 in the intake passage 9, is detected by the intake temperature sensor 21.
In step S22, the fuel injection amount detection unit 41 detects a fuel injection amount Qf that is the amount of fuel injected into the combustion chamber 11 by the fuel injection nozzle 16.

In step S24, the oxygen concentration calculation unit 40 calculates the EGR amount Qe circulated into the intake passage 9 from the fresh air intake amount Qa, the intake air pressure Pi, and the intake air temperature Ti.
In step S26, the oxygen concentration calculator 40 calculates an oxygen concentration De that is the concentration of oxygen contained in the EGR amount Qe from the fuel injection amount Qf.
In step S28, the oxygen concentration calculation unit 40 uses the fresh air intake amount Qa, the EGR amount Qe, and the oxygen concentration De to determine the oxygen concentration in the intake passage 9 that is the oxygen concentration in the air sucked into the combustion chamber 11 in the intake passage 9. Di is calculated.

In step S30, the oxygen concentration deviation ΔD is calculated by the oxygen concentration deviation calculating unit 44 from the following equation (1).
Oxygen concentration deviation ΔD = Intake passage oxygen concentration Di−Target oxygen concentration Dt (1)
In step S32, the main injection timing correction unit 45 determines whether or not the oxygen concentration deviation ΔD is smaller than the first predetermined oxygen concentration deviation. If the determination result is true (Yes) and smaller than the first predetermined oxygen concentration deviation, the process proceeds to step S36, and the main injection timing is advanced based on the main injection timing correction amount and oxygen concentration deviation graph shown in FIG. And exit from the routine. If the determination result is false (No) and greater than or equal to the first predetermined oxygen concentration deviation, the process proceeds to step S34.

  In step S34, the main injection timing correction unit 45 determines whether or not the oxygen concentration deviation ΔD is larger than the second predetermined oxygen concentration deviation. If the determination result is true (Yes) and larger than the second predetermined oxygen concentration deviation, the process proceeds to step S38, and the main injection timing is retarded based on the main injection timing correction amount and oxygen concentration deviation graph shown in FIG. And exit from the routine. If the determination result is false (No) and less than or equal to the second predetermined oxygen concentration deviation, the routine is exited.

Thus, according to the fuel injection control device for an internal combustion engine according to the first reference example of the present invention, the injection timing of the main injection is advanced or retarded based on the oxygen concentration of the intake air sucked into the combustion chamber 11. Like to do.
As a result, as shown in FIG. 5, when the oxygen concentration of the air sucked into the combustion chamber 11 is high, the cylinder pressure in this reference example (solid line) is sharper than that in the conventional example (thin line). Can be suppressed. Further, as shown in FIG. 6, when the oxygen concentration of the air sucked into the combustion chamber 11 is low, it is possible to suppress the ignition failure and the slow combustion in this reference example as compared with the conventional example.

Therefore, according to the fuel injection control device for an internal combustion engine according to the first reference example of the present invention, in a state where the oxygen concentration is high and a state where the oxygen concentration is low,
(1) Combustion noise due to steep cylinder pressure during transition can be reduced.
(2) Since ignition can be ensured, generation of unburned gas can be suppressed and exhaust properties can be improved.
(3) Generation of vibration due to poor ignition can be suppressed and drivability can be prevented from deteriorating.
[Second Reference Example]
Next, a second reference example will be described.

FIG. 7 is a block diagram showing the internal configuration of the ECU in the internal combustion engine fuel injection control apparatus according to the second reference example of the present invention.
In the second reference example, as shown in FIG. 7, with respect to the first reference example, and to add the pre-injection amount determining unit 46 will be described with the difference from the first reference example points below. In the description of this reference example, the pre-injection determination deviation on the oxygen concentration deficient side is represented as a third predetermined oxygen concentration deviation, and the pre-injection determination deviation on the oxygen concentration excess side is represented as a fourth predetermined oxygen concentration deviation.

  The ECU 102 calculates the oxygen concentration deviation from the target oxygen concentration and the oxygen concentration of the air sucked into the combustion chamber 11 by the oxygen concentration deviation calculating unit 44, and the main injection timing correcting unit 45 calculates the main oxygen concentration based on the oxygen concentration deviation. The injection timing is corrected, and a pre-injection determining unit (pre-injection amount determining means) 46 adds a pre-injection that injects a small amount of fuel after the pilot injection and before the main injection based on the oxygen concentration deviation. An injection signal is supplied to the injection nozzle 16.

The operation and effect of the control apparatus for an internal combustion engine according to the second reference example of the present invention configured as described above will be described below.
FIG. 8 is a characteristic diagram of the additional pre-injection amount in the oxygen concentration deviation according to the second reference example of the present invention, where the horizontal axis represents the oxygen concentration deviation and the vertical axis represents the additional pre-injection amount. The characteristic chart is set according to the operating state of the engine 1 such as the engine speed. 9 and 10 show a flowchart showing a control routine of fuel injection control executed by the ECU 102, and FIG. 11 shows an injection signal, a heat generation rate, and a cylinder at a crank angle when the oxygen concentration is higher than the target oxygen concentration. FIG. 12 shows changes in the injection signal, heat generation rate, and cylinder pressure at the crank angle when the oxygen concentration is lower than the target oxygen concentration. 11 and 12, the horizontal axis indicates the crank angle, the vertical axis indicates the injection signal, the heat generation rate, and the cylinder pressure. The thick line or hatching indicates the second reference example, and the thin line or no hatching indicates the conventional example. .

As shown in FIG. 9, in steps S10 to S38, the oxygen concentration deviation ΔD is calculated from each set value and each detected value as in the first reference example, and the oxygen concentration deviation ΔD is calculated by the main injection timing correction unit 45. Based on this, the main injection timing is corrected to the advance side or the retard side, and the process proceeds to step S40.
As shown in FIG. 10, in step S40, the pre-injection amount determination unit 46 determines whether or not the oxygen concentration deviation ΔD is smaller than the third predetermined oxygen concentration deviation. If the determination result is true (Yes) and is smaller than the third predetermined oxygen concentration deviation, the process proceeds to step S44, pre-injection is added based on the graph of the additional pre-injection amount and oxygen concentration deviation shown in FIG. Exit. If the determination result is false (No) and greater than or equal to the third predetermined oxygen concentration deviation, the process proceeds to step S42.

  In step S42, the pre-injection amount determination unit 46 determines whether or not the oxygen concentration deviation ΔD is larger than the fourth predetermined oxygen concentration deviation. If the determination result is true (Yes) and is larger than the fourth predetermined oxygen concentration deviation, the process proceeds to step S44, and the pre-injection is added based on the graph of the additional pre-injection amount and the oxygen concentration deviation shown in FIG. Exit. If the determination result is false (No) and less than or equal to the fourth predetermined oxygen concentration deviation, the routine is exited.

Thus, according to the fuel injection control device for an internal combustion engine according to the second reference example of the present invention, the injection timing of the main injection is advanced or retarded based on the oxygen concentration of the intake air sucked into the combustion chamber 11. Thus, a pre-injection for injecting a small amount of fuel after the pilot injection and before the main injection is added.
Thus, as shown in FIG. 11, when the oxygen concentration of the air sucked into the combustion chamber 11 is high, in this reference example (solid line) compared to the conventional example (thin line), by adding pre-injection, It is possible to forcibly reduce the ignition delay of the main combustion, and to suppress a steep increase in the cylinder pressure more stably. Further, as shown in FIG. 12, when the oxygen concentration of the air sucked into the combustion chamber 11 is low, in this reference example, by adding pre-injection, ignition failure and combustion are further slowed down compared to the conventional example. Therefore, combustion can be further stabilized.

Therefore, according to the fuel injection control device for an internal combustion engine according to the second reference example of the present invention, in a state where the oxygen concentration is high and a state where the oxygen concentration is low,
(1) Further, combustion noise due to steep cylinder pressure during transition can be reduced.
(2) Further, it is possible to suppress the occurrence of vibration due to poor ignition, and it is possible to prevent deterioration of drivability.
[Real施例]
Next, examples of the present invention will be described.

Figure 13 is a block diagram showing the internal structure of an ECU in the fuel injection control apparatus for an internal combustion engine according to the actual施例of the present invention. In the description of the present embodiment, the pilot injection amount correction determination deviation on the oxygen concentration deficiency side is the fifth predetermined oxygen concentration deviation, the pilot injection amount correction determination deviation on the oxygen concentration excess side is the sixth predetermined oxygen concentration deviation, oxygen The pilot injection timing correction determination deviation on the insufficient concentration side is represented as a seventh predetermined oxygen concentration deviation, and the pilot injection timing correction determination deviation on the oxygen concentration excess side is represented as an eighth predetermined oxygen concentration deviation.

As shown in FIG. 13, in the embodiment, a pilot injection amount correction unit (pilot injection amount correction unit) 48 and a pilot injection timing correction unit (pilot injection timing correction unit) 49 are added to the first reference example. Differences from the first reference example will be described below.
The ECU 202 calculates the oxygen concentration deviation from the target oxygen concentration and the oxygen concentration of the air sucked into the combustion chamber 11 by the oxygen concentration deviation calculating unit 44, and the main injection timing correcting unit 45 calculates the main oxygen concentration based on the oxygen concentration deviation. The injection timing is corrected, the pilot injection amount correction unit 48 and the pilot injection timing correction unit 49 correct the injection amount and injection timing of the pilot injection based on the oxygen concentration deviation, and supply the injection signal to the fuel injection nozzle 16. .

Hereinafter, a description of the operation and effect of the fuel injection control apparatus for an internal combustion engine according to the actual施例of the present invention configured this way.
Figure 14 is a characteristic diagram of the pilot injection correction amount in the oxygen concentration deviation of the actual施例of the present invention, the horizontal axis represents the oxygen concentration deviation and the vertical axis represents the pilot injection quantity correction, FIG. 15, the oxygen It is a characteristic view of the pilot injection timing correction amount in the concentration deviation, the horizontal axis indicates the oxygen concentration deviation, and the vertical axis indicates the pilot injection timing correction amount. The characteristic chart is set according to the operating state of the engine 1 such as the engine speed. FIGS. 16, 17 and 18 are flowcharts showing a control routine of fuel injection control executed by the ECU 202. FIG. 19 shows changes in the injection signal, heat generation rate, and cylinder pressure at the crank angle when the oxygen concentration is higher than the target oxygen concentration, and FIG. 20 shows the crank when the oxygen concentration is lower than the target oxygen concentration. The change in injection signal, heat release rate and cylinder pressure at the corners is shown. 19 and 20, the horizontal axis indicates the crank angle, the vertical axis indicates the injection signal, the heat generation rate, and the cylinder pressure. The thick line or hatched indicates the present embodiment, and the thin line or no hatch indicates the conventional example.

As shown in FIG. 16, in steps S10 to S38, the oxygen concentration deviation ΔD is calculated from each set value and each detected value as in the first reference example, and the oxygen concentration deviation ΔD is calculated by the main injection timing correction unit 45. Based on this, the main injection timing is corrected to the advance side or the retard side, and the process proceeds to step S50.
As shown in FIG. 17, in step S50, the pilot injection amount correction unit 48 determines whether or not the oxygen concentration deviation ΔD is smaller than the fifth predetermined oxygen concentration deviation. If the determination result is true (Yes) and smaller than the fifth predetermined oxygen concentration deviation, the process proceeds to step S54, and the pilot injection amount is increased on the increase side based on the pilot injection amount correction amount and oxygen concentration deviation graph shown in FIG. The process proceeds to step S60. If the determination result is false (No) and greater than or equal to the fifth predetermined oxygen concentration deviation, the process proceeds to step S52.

  In step S52, the pilot injection amount correction unit 48 determines whether or not the oxygen concentration deviation ΔD is larger than a sixth predetermined oxygen concentration deviation. If the determination result is true (Yes) and greater than the sixth predetermined oxygen concentration deviation, the process proceeds to step S56, and the pilot injection amount is reduced on the basis of the pilot injection amount correction amount and oxygen concentration deviation graph shown in FIG. The process proceeds to step S60. If the determination result is false (No) and less than or equal to the sixth predetermined oxygen concentration deviation, the process proceeds to step S60.

  As shown in FIG. 18, in step S60, the pilot injection timing correction unit 49 determines whether or not the oxygen concentration deviation ΔD is smaller than the seventh predetermined oxygen concentration deviation. If the determination result is true (Yes) and smaller than the seventh predetermined oxygen concentration deviation, the process proceeds to step S64, and the injection timing of pilot injection is retarded based on the pilot injection timing correction amount and oxygen concentration deviation graph shown in FIG. And exit from the routine. If the determination result is false (No) and greater than or equal to the seventh predetermined oxygen concentration deviation, the process proceeds to step S62.

  In step S62, the pilot injection timing correction unit 49 determines whether or not the oxygen concentration deviation ΔD is larger than an eighth predetermined oxygen concentration deviation. If the determination result is true (Yes) and greater than the eighth predetermined oxygen concentration deviation, the process proceeds to step S66, and the pilot injection timing is advanced based on the pilot injection timing correction amount and oxygen concentration deviation graph shown in FIG. And exit from the routine. If the determination result is false (No) and less than or equal to the eighth predetermined oxygen concentration deviation, the routine is exited.

Thus, according to the control apparatus for an internal combustion engine according to the actual施例of the present invention, based on the oxygen concentration of intake air sucked into the combustion chamber 11, so as to advance or retard the injection timing of the main injection In addition, the injection amount of the pilot injection is increased or decreased, and the injection timing of the pilot injection is advanced or retarded.
Accordingly, as shown in FIG. 19, when the oxygen concentration of the air sucked into the combustion chamber 11 is high, the main injection timing is retarded in this embodiment (solid line) compared to the conventional example (thin line). By reducing the pilot injection amount and advancing the injection timing, it is possible to suppress a sharp increase in cylinder pressure. Further, as shown in FIG. 20, when the oxygen concentration of the air sucked into the combustion chamber 11 is low, in this embodiment, the pilot injection amount is increased with the main injection timing as an advance, compared with the conventional example, and the injection is performed. By retarding the timing, it is possible to suppress poor ignition and slowing of combustion, and to stabilize ignition and combustion.

Therefore, according to the fuel injection control apparatus for an internal combustion engine according to the actual施例of the present invention, the oxygen-enriched condition and oxygen concentration in the thin state,
(1) Further, combustion noise due to steep cylinder pressure during transition can be reduced.
(2) Further, it is possible to suppress the occurrence of vibration due to poor ignition, and it is possible to prevent deterioration of drivability.

Although the description of the embodiment of the invention is finished as above, the embodiment of the present invention is not limited to the embodiment.
For example, in the above embodiment, the engine 1 is a common rail type diesel engine, but the present invention is not limited to this, and it is only necessary to appropriately control the fuel injection amount and the fuel injection timing.
Similarly, the turbocharger 7 and the intercooler 8 are not necessarily provided.
Similarly, the oxygen concentration calculation unit 11 calculates the oxygen concentration of the intake air sucked into the combustion chamber 11. However, the present invention is not limited to this, and the linear O2 protrudes into the intake passage 9. A sensor may be provided to detect the oxygen concentration in the intake passage 9.

In the above embodiment, each oxygen concentration deviation on the oxygen concentration deficient side is distinguished from each of the first, third, fifth, and seventh predetermined oxygen concentration deviations, but some or all of these may be the same value. .
Similarly, each oxygen concentration deviation on the oxygen concentration excess side is distinguished from the second, fourth, sixth, and eighth predetermined oxygen concentration deviations, respectively, but some or all of these may be the same value.

1 engine (internal combustion engine)
2, 102, 202 Electronic control unit 9 Intake passage 11 Combustion chamber 13 Exhaust passage 16 Fuel injection nozzle 19 Air flow sensor 20 Boost sensor 21 Intake temperature sensor 40 Oxygen concentration calculation unit 41 Fuel injection amount detection unit 42 Target oxygen concentration setting unit ( Target oxygen concentration setting means)
43 Main injection amount / injection timing setting unit 44 Oxygen concentration deviation calculation unit (deviation side determination means and oxygen concentration deviation calculation means)
45 Main injection timing correction unit (Main injection timing correction means)
46 Pre-injection amount determining unit (pre-injection amount determining means)
47 Pilot injection amount / injection timing setting unit 48 Pilot injection amount correcting unit (pilot injection amount correcting means)
49 Pilot injection timing correction unit (pilot injection timing correction means)

Claims (3)

In a fuel injection control device for an internal combustion engine in which main injection for injecting fuel and pilot injection prior to the main injection are performed, and a main injection timing, a pilot injection amount, and a pilot injection timing in a standard operation state are set,
Target oxygen concentration setting means for setting a target oxygen concentration of intake air that is sucked into the combustion chamber from the intake passage during operation;
Oxygen concentration deviation calculating means for calculating an oxygen concentration deviation by subtracting the target oxygen concentration from the actual oxygen concentration of the intake air sucked into the combustion chamber;
Main injection timing correcting means for correcting the injection timing of the main injection in the standard operation state according to the oxygen concentration deviation based on the calculation result of the oxygen concentration deviation calculating means ;
Pilot injection timing correcting means for correcting the injection timing of pilot injection in the standard operation state according to the oxygen concentration deviation based on the calculation result of the oxygen concentration deviation calculating means ,
If the oxygen concentration deviation is smaller than a main injection timing correction determination deviation which is a threshold value on the oxygen concentration deficient side, the main injection timing correction means injects the injection timing earlier than the injection timing of the main injection in the standard operation state. If the oxygen concentration deviation is larger than the main injection timing correction determination deviation which is a threshold value on the oxygen concentration excess side, the injection timing is delayed with respect to the injection timing of the main injection in the standard operation state. Correct the main injection timing to inject,
If the oxygen concentration deviation is smaller than the pilot injection timing correction determination deviation which is a threshold value on the oxygen concentration deficient side, the pilot injection timing correcting means may inject the injection timing later than the pilot injection timing in the standard operation state. If the pilot injection timing is corrected and the oxygen concentration deviation is larger than the pilot injection timing correction determination deviation which is a threshold value on the oxygen concentration excess side, the injection timing is injected earlier than the pilot injection timing in the standard operation state. the fuel injection control device for an internal combustion engine, characterized that you correct the pilot injection timing. If the oxygen concentration deviation is smaller than the pilot injection amount correction determination deviation which is a threshold value on the oxygen concentration deficient side , the pilot injection amount is corrected so as to inject more fuel than the pilot injection amount in the standard operation state, and the oxygen If the concentration deviation is larger than the pilot injection amount correction judgment deviation that is the threshold value on the oxygen concentration excess side , the pilot injection amount correction that corrects the pilot injection amount so as to inject less fuel than the pilot injection amount in the standard operation state The fuel injection control device for an internal combustion engine according to claim 1 , further comprising means. If the oxygen concentration deviation is smaller than the pre-injection determination deviation which is the threshold value on the oxygen concentration deficient side, or if the oxygen concentration deviation is larger than the pre-injection determination deviation which is the threshold value on the oxygen concentration excess side, then after the pilot injection, 3. The fuel injection control for an internal combustion engine according to claim 1, further comprising pre-injection amount determining means for adding a pre-injection for injecting fuel before the main injection and determining an injection amount of the pre-injection. apparatus.

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