JP2010144677A - Fuel injection control device and control method of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To implement a correction specialized in variation of combustion caused by intake air temperature in an internal combustion engine. <P>SOLUTION: An intake air temperature sensor 26 detects intake air temperatures of the internal combustion engine 1. A cylinder internal pressure sensor 22 detects cylinder internal pressures. A controller 20 learns a sensitivity of a change rate of cylinder internal pressure with respect to a change of intake air temperature. When intake air temperature changes, the controller 20 controls fuel injection so that the change of combustion parameter caused by the change of intake air temperature is compensated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to fuel injection control for compensating for variations in combustion caused by intake air temperature of an internal combustion engine.

The prior art in Patent Document 1 discloses that a heat generation parameter of an internal combustion engine is calculated from a combustion chamber pressure and a crank angle detected by a cylinder pressure sensor, and a pilot injection amount is controlled based on the heat generation parameter.
JP 2003-207488 A

  In internal combustion engines, variations in combustion occur due to various factors such as temperature, fuel injection amount, and air amount. The prior art of Patent Literature 1 detects the actual injection timing using an in-cylinder pressure sensor, thereby enabling feedback control of the actual injection timing to the target injection timing.

  Such feedback control is effective in compensating for variations in combustion, but compensation specific to a specific variation factor cannot be performed. For example, the intake air temperature is a factor that varies greatly depending on the air temperature and causes a large variation in combustion. However, correction of combustion specifically for the variation in combustion caused by the intake air temperature is not performed.

  In view of the above situation of the prior art, an object of the present invention is to realize fuel injection control specialized for correction of variation in combustion caused by intake air temperature.

  In order to achieve the above object, according to the present invention, in a fuel injection control device for an internal combustion engine, a means for detecting an intake air temperature, a means for detecting a change in a combustion parameter due to a difference in intake air temperature, An intake air temperature change means forcibly changing, a learning means for learning the sensitivity of the combustion parameter to the intake air temperature change from the intake air temperature difference before and after the intake air temperature change by the intake air temperature change means and the change in the combustion parameter, and the intake air temperature And a fuel injection control means for controlling fuel injection based on the learned sensitivity of the combustion parameter to the intake air temperature change.

  In the fuel injection control method for an internal combustion engine, the present invention also detects an intake air temperature, detects a change in a combustion parameter due to a difference in the intake air temperature, forcibly changes the intake air temperature, and forcibly changes the intake air temperature. The sensitivity of the combustion parameter to the intake air temperature change is learned from the difference in the intake air temperature before and after the change and the change of the combustion parameter, and the fuel injection is controlled based on the intake air temperature and the sensitivity of the learned combustion parameter to the intake air temperature change. Yes.

  The sensitivity of the combustion parameter to the intake air temperature change is learned, and when the intake air temperature changes, the fuel injection control is performed based on the change of the combustion parameter, so that it is possible to make a correction specifically for the variation in combustion caused by the intake air temperature.

  A first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a fuel injection control device for an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is a flowchart for explaining a fuel injection learning control routine executed by a controller provided in the fuel injection control device. FIG. 3 is a diagram showing the relationship between the intake air temperature and the combustion noise according to the cooling capacity of the EGR cooler. FIG. 4 is a diagram showing the relationship between the intake air temperature and the discharge amount of nitrogen dioxide (NOx) according to the cooling capacity of the EGR cooler.

  Referring to FIG. 1, a compression ignition type multi-cylinder internal combustion engine 1 for a vehicle includes an intake passage 3 and an exhaust passage 11. The intake air sucked into the intake passage 3 via the air cleaner 2 is supercharged by the compressor 4 of the turbocharger, cooled by the intercooler 5, and then supplied from the intake collector 6 to the combustion chamber 8 of each cylinder via the intake manifold 7. Is done.

  A fuel injection nozzle 9 is provided in the combustion chamber 8 of each cylinder. The fuel injection nozzle 9 generates an air-fuel mixture in the combustion chamber 8 by injecting fuel into the intake air.

  The reciprocating piston 10 compresses and ignites the air-fuel mixture by compressing the air-fuel mixture and burns the air-fuel mixture in the combustion chamber 8. The combustion gas is discharged into the exhaust passage 11 and is released into the atmosphere after rotationally driving the turbine 12 of the turbocharger.

  The internal combustion engine 1 includes an exhaust gas recirculation (EGR) passage 13 that recirculates part of the exhaust gas in the exhaust passage 11 to the intake collector 6. The EGR passage 13 is provided with an EGR cooler 14 for cooling the reflux exhaust, a bypass passage 15 for bypassing the EGR cooler 14, and an EGR valve 16 for adjusting the flow rate of the reflux exhaust. The EGR cooler 14 and the bypass passage 15 are switched by operating the bypass valve 19. The EGR passage 13, the EGR cooler 14, the bypass passage 15, and the bypass valve 19 constitute intake air forced change means.

  Fuel is supplied from the common rail 17 to the fuel injection nozzle 9. A fuel pump 18 that rotates integrally with the internal combustion engine 1 pressurizes the fuel in the fuel tank and supplies it to the common rail 17. The fuel injection timing and the fuel injection period of the fuel injection nozzle 9 are controlled by a pulse width modulation signal output from the controller 20 as learning means and fuel injection control means.

  The controller 20 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 20 with a plurality of microcomputers.

  The controller 20 includes an in-cylinder pressure sensor 22 as parameter detecting means for detecting the pressure in the combustion chamber 8, an accelerator pedal depression amount sensor 23 for detecting an accelerator pedal depression amount APO provided in the vehicle, and a crank angle θ of the internal combustion engine 1. Detection signals from a crank angle sensor 24 that detects the engine rotational speed Ne, a vehicle speed sensor 25 that detects the traveling speed V of the vehicle, and an intake air temperature sensor 26 that detects the intake air temperature in the intake air collector 6 are respectively detected. A signal is input.

  Based on these input signals, the controller 20 calculates the maximum value dP / dθMax1 of the in-cylinder pressure change rate dP / dθ under a combination of a certain engine speed Ne and the fuel injection amount Qf as a parameter indicating the change in combustion. To do. Next, the EGR cooler 14 and the bypass passage 15 are switched by operating the bypass valve 19. Then, the maximum value dP / dθMax2 of the in-cylinder pressure change rate dP / dθ is calculated under the same combination of the engine speed Ne and the fuel injection amount Qf. The difference dP / dθMax1-dP / dθMax2 between the maximum values of the two in-cylinder pressure change rates dP / dθ is the difference in combustion parameters caused by the difference in the intake air temperature of the internal combustion engine 1 due to the switching between the EGR cooler 14 and the bypass passage 15. . The controller 20 learns the sensitivity of the combustion parameter with respect to the intake air temperature from these values, and controls the fuel injection so that the combustion parameter is kept optimal according to the difference in the intake air temperature thereafter.

  A fuel injection learning control routine executed by the controller 20 for the above control process will be described with reference to FIG. This routine is executed every time the internal combustion engine 1 is operated.

  In step S1, the controller 20 determines whether or not the accelerator pedal depression amount APO is zero and the rate of change ΔV of the vehicle speed V, that is, whether the vehicle acceleration is equal to or less than zero. In other words, it is determined whether or not the condition that the accelerator pedal is not depressed, the internal combustion engine 1 is in an idle operation state, and the vehicle is not accelerating is satisfied.

  If this condition is not satisfied, the controller 20 waits until the condition is satisfied.

  When the condition of step S1 is established, the controller 20 determines the maximum value dP / dθMax1 of the in-cylinder pressure change rate dP / dθ under the engine rotation speed Ne and the fuel injection amount Qf at that time in step S2. Calculate based on the input signal from 22. The calculation result is stored in the RAM together with the intake air temperature detected by the intake air temperature sensor 26 before switching the bypass valve 19.

  In step S3, the controller 20 switches the bypass valve 19 to switch the cooling of the recirculated exhaust gas by the EGR cooler 14 from on to off or from off to on.

  In step S4, the controller 20 determines whether the accelerator pedal depression amount APO is zero and whether the change rate ΔV of the vehicle speed V, that is, the acceleration of the vehicle is equal to or less than zero, as in step S1. If these conditions are not satisfied, the controller 20 waits until the conditions are satisfied.

  When the condition of step S4 is satisfied, the controller 20 determines the maximum value dP / dθMax2 of the in-cylinder pressure change rate dP / dθMax2 under the same engine rotation speed Ne and fuel injection amount Qf as in step S2 in step S5. Calculation is performed based on the input signal from the sensor 22. Further, the intake air temperature after switching of the bypass valve 19 detected by the intake air temperature sensor 26 is read.

  The controller 20 calculates the EGR cooler 14 and the bypass passage 15 based on the calculated dP / dθMax2 and the intake air temperature after the bypass valve 19 is switched, and the dP / dθMax1 stored in the RAM and the intake air temperature before the bypass valve 19 is switched. A combustion parameter difference dP / dθMax1−dP / dθMax2 caused by the difference in intake air temperature of the internal combustion engine 1 due to switching is calculated, and the sensitivity of the combustion parameter to the intake air temperature is calculated from the calculated result and the actually measured intake air temperature difference.

  In step S <b> 6, the controller 20 determines a correction amount for the pilot injection amount by the fuel injection nozzle 9 and a correction amount for the rail pressure of the common rail 17 for correcting the change in the combustion parameter due to the intake air temperature.

  In step S7, the controller 20 controls the pilot injection amount and the rail pressure of the common rail 17 based on the correction amount based on the intake air temperature based on the intake air temperature detected by the intake air temperature sensor 22, thereby changing the combustion parameter. to correct.

  In the above routine, steps up to step S6 constitute a learning process, and step S7 constitutes a fuel injection control process based on learning. After the internal combustion engine 1 starts operation in time series, the controller 20 executes a learning process from steps S1 to S6. Thereafter, the fuel injection control process in step S7 is performed using the learned correction amount. Continue until the end of operation.

  The contents of the fuel injection control in step S7 will be described next.

  FIG. 3 shows the relationship between the intake air temperature in the intake air collector 6 and the combustion noise AVL according to the cooling capacity of the EGR cooler 14. As shown in the figure, the combustion noise increases as the intake air temperature decreases. Further, this tendency appears more prominently as the cooling capacity of the EGR cooler 14 is smaller.

  FIG. 4 shows the relationship between the intake air temperature in the intake collector 6 and the discharge amount of nitrogen dioxide (NOx) according to the cooling capacity of the EGR cooler 14. As shown in the figure, the NOx emission increases as the intake air temperature decreases. In addition, this tendency becomes more prominent as the cooling capacity of the EGR cooler 14 is smaller. Since the cooling capacity of the EGR cooler 14 is known, the relationship between the intake air temperature and the combustion noise in the internal combustion engine 1 and the relationship between the intake air temperature and the NOx emission amount may be stored in advance in the ROM of the controller 20 as a map. it can.

  Based on the detected intake air temperature, the controller 20 calculates combustion noise with reference to a map stored in the ROM, and corrects the rail pressure of the common rail 17 in a decreasing direction when the combustion noise is larger than a predetermined region. Or increase the pilot injection amount.

  The controller 20 also calculates the NOx emission amount with reference to the map stored in the ROM based on the calculated intake air temperature. If the NOx emission amount is larger than a predetermined area, the rail pressure of the common rail 17 is reduced. Correct in the direction or increase the pilot injection amount.

  In this way, by performing fuel injection control based on the intake air temperature using the maximum value dP / dθMax of the in-cylinder pressure change rate dP / dθ as a combustion parameter, changes in the intake air temperature cause combustion noise and NOx generation in the internal combustion engine 1. The unfavorable influence on the quantity can be corrected appropriately.

    A second embodiment of the present invention will be described with reference to FIG.

  FIG. 5 shows a fuel injection learning control routine executed by the controller 20 instead of the fuel injection learning control routine of FIG. The difference between this routine and the routine of FIG. 2 is that the maximum value Pmax of the in-cylinder pressure P detected by the in-cylinder pressure sensor 22 is used as a parameter indicating the change in combustion instead of the maximum value dP / dθMax of the in-cylinder pressure change rate. Use.

  Steps S1, S3, S4 and S7 are the same as the routine of FIG. In this routine, steps S12, S15, and S16 are provided instead of steps S2, S5, and S6.

  In step S12, the controller 20 reads the in-cylinder pressure maximum value Pmax1 at the engine speed Ne and the fuel injection amount Qf under the conditions in step S1 from the value of the in-cylinder pressure P detected by the in-cylinder pressure sensor 22, and the calculation result Is stored in the RAM.

  In step S15, the in-cylinder pressure maximum value Pmax2 at the same engine speed Ne and fuel injection amount Qf after switching the bypass valve 19 is read from the value of the in-cylinder pressure P detected by the in-cylinder pressure sensor 22.

  The controller 20 calculates a combustion parameter difference Pmax1-Pmax2 caused by a difference in intake air temperature of the internal combustion engine 1 due to switching between the EGR cooler 14 and the bypass passage 15 from the read Pmax2 and Pmax1 stored in the RAM, and further, Calculate the sensitivity of the combustion parameter to temperature.

  In step S <b> 16, the controller 20 determines a correction amount for the pilot injection amount by the fuel injection nozzle 9 and a correction amount for the rail pressure of the common rail 17 with respect to changes in the combustion parameters.

  As described above, even when the in-cylinder pressure maximum value Pmax is used as the combustion parameter instead of the in-cylinder pressure change rate maximum value dP / dθMax, it is possible to accurately correct the intake air temperature change.

  A third embodiment of the present invention will be described with reference to FIG.

  FIG. 6 shows a fuel injection learning control routine executed by the controller 20 instead of the fuel injection learning control routine of FIG. The difference between this routine and the routine of FIG. 2 is that the actual ignition timing IGT is used instead of the maximum value dP / dθMax of the in-cylinder pressure change rate as a parameter indicating the change in combustion. The actual ignition timing IGT can be detected by the in-cylinder pressure sensor 22.

  Steps S1, S3, S4 and S7 are the same as the routine of FIG. In this routine, steps S22, S25, and S26 are provided instead of steps S2, S5, and S6.

  In step S22, the controller 20 detects the actual ignition timing IGT1 at the engine speed Ne and the fuel injection amount Qf under the conditions of step S1, and stores the calculation result in the RAM.

  In step S25, the controller 20 detects the actual ignition timing IGT2 at the same engine rotational speed Ne and fuel injection amount Qf after the bypass valve 19 is switched.

  The controller 20 calculates a combustion parameter difference IGT1-IGT2 caused by a difference in intake air temperature of the internal combustion engine 1 due to switching of the EGR cooler 14 and the bypass passage 15 from the detected actual ignition timing IGT2 and IGT1 stored in the ROM, Calculate the sensitivity of the combustion parameter to the intake air temperature.

  In step S <b> 26, the controller 20 determines a correction amount for the pilot injection amount by the fuel injection nozzle 9 and a correction amount for the rail pressure of the common rail 17 with respect to changes in the combustion parameters.

  As described above, even when the actual ignition timing IGT is used as the combustion parameter instead of the maximum value dP / dθMax of the in-cylinder pressure change rate, it is possible to accurately correct the intake air temperature change.

  As mentioned above, although this invention has been demonstrated through some specific embodiment, this invention is not limited to these embodiment. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.

  For example, an ignition delay period can be used as a parameter indicating a change in combustion instead of the maximum value dP / dθMax of the in-cylinder pressure change rate.

  In each of the embodiments described above, the intake air temperature forcibly changing means includes the EGR passage 13, the EGR cooler 14, the bypass passage 15, and the bypass valve 19, but the intake air temperature forcibly changing means forcibly changes the intake air temperature. Any device having a function of changing to the above may be used. For example, a bypass passage 30 that bypasses the intercooler 5 and a bypass valve 31 that switches the intercooler 5 and the bypass passage 30 are provided as intake temperature forced change means, and the intake air temperature can be forcibly changed by switching the bypass valve 31. It is.

1 is a schematic configuration diagram of a fuel injection control device for an internal combustion engine according to a first embodiment of the present invention. It is a flowchart explaining the learning control routine of the fuel injection which the controller with which a fuel injection control apparatus is provided performs. It is a diagram which shows the relationship between intake temperature and combustion noise according to the cooling capacity of an EGR cooler. It is a diagram which shows the relationship between the intake temperature and the discharge amount of nitrogen dioxide (NOx) according to the cooling capacity of the EGR cooler. It is a flowchart explaining the learning control routine of the fuel injection by 2nd Embodiment of this invention. It is a flowchart explaining the learning control routine of the fuel injection by 3rd Embodiment of this invention.

Explanation of symbols

1 Internal combustion engine 3 Intake passage 6 Intake collector 7 Intake manifold 8 Combustion chamber 9 Fuel injection nozzle 11 Exhaust passage 13 Exhaust gas recirculation (EGR) passage 14 EGR cooler 15 Bypass passage 16 EGR valve 17 Common rail 18 Fuel pump 19 Bypass valve 20 Controller 22 Tube Internal pressure sensor 23 Accelerator pedal depression sensor 24 Crank angle sensor 25 Vehicle speed sensor 26 Intake air temperature sensor

Claims (7)

In a fuel injection control device for an internal combustion engine,
Means for detecting the intake air temperature;
Means for detecting changes in combustion parameters due to differences in intake air temperature;
Intake air temperature forcibly changing means for forcibly changing the intake air temperature;
Learning means for learning the sensitivity of the combustion parameter to the intake air temperature change from the intake air temperature difference before and after the intake air temperature change by the intake air temperature forced change means and the change of the combustion parameter;
Fuel injection control means for controlling fuel injection based on the intake air temperature and the sensitivity of the learned combustion parameter to the intake air temperature change;
A fuel injection control device for an internal combustion engine, comprising:   The internal combustion engine is for a vehicle, the vehicle includes an accelerator pedal, and further includes means for preventing learning by the learning means when the amount of depression of the accelerator pedal is zero and the change in the vehicle speed is not less than zero. The fuel injection control device for an internal combustion engine according to claim 1.   3. The fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the combustion parameter is a maximum rate of change of the in-cylinder pressure.   3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the combustion parameter is a maximum in-cylinder combustion pressure.   3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the combustion parameter is an actual ignition timing of the injected fuel.   The intake air temperature forcibly changing means includes an exhaust gas recirculation passage that recirculates part of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine, a cooler that cools the recirculated exhaust gas in the exhaust gas recirculation passage, a bypass passage that bypasses the cooler, and a cooler and a bypass 6. A fuel injection control device for an internal combustion engine according to claim 1, further comprising a bypass valve for switching the passage.   The internal combustion engine includes a fuel injection nozzle and a common rail that supplies fuel to the fuel injection nozzle, and the fuel injection control means is configured to control at least one of a pilot injection amount of the fuel injection nozzle and a rail pressure of the common rail. A fuel injection control device for an internal combustion engine according to any one of claims 1 to 6.

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