JP2013108407A - Combustion injection method for internal combustion engine and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection method for an internal combustion engine, the method capable of correcting a difference between an actual fuel injection amount and an indicated fuel injection amount due to deterioration of an injector using a NOx sensor provided downstream of an exhaust gas treatment device, and to provide the internal combustion engine.SOLUTION: A difference value Δλ is calculated between an actual air excess ratio λ1 calculated from an oxygen concentration value O2_exh of a NOx sensor 21 provided downstream of an exhaust gas purification device 15 provided at an exhaust passage 7 and a target air excess ratio λ2 calculated from a currently indicated fuel injection amount Q_fin and a fresh air amount m_air detected by an MAF sensor 22 provided at an intake passage 5. A current learning value L(i, j) stored in a learning region map M1 using a common rail pressure and an indicated fuel injection amount as a base and corresponding to a current common rail pressure P and the currently indicated fuel injection amount Q_fin is corrected so that the difference value Δλ becomes zero, and a new learning value L(I, J) is calculated. When performing the fuel injection from an injector 3, the currently indicated fuel injection amount Q_fin is corrected by the learning value L(I, J) to perform the fuel injection.

Description

  The present invention uses the oxygen concentration of a NOx sensor provided downstream of the exhaust gas purification device, and corrects the fuel injection of the internal combustion engine that can be corrected so as to eliminate the difference between the actual fuel injection amount and the commanded fuel injection amount. The present invention relates to a method and an internal combustion engine.

  Conventionally, in an engine (internal combustion engine), an ECU (control device) controls an injector (fuel injection valve) to adjust the fuel injection amount from the injector to an appropriate amount. The command fuel injection amount adjusted to an appropriate amount is determined so as to improve fuel consumption, reduce harmful components of exhaust gas, and reduce noise.

  However, various problems occur when the indicated fuel injection amount and the amount actually injected by the injector deviate due to deterioration or failure of the fuel supply system including the injector. For example, when the actual injection amount is smaller than the commanded fuel injection amount, the required torque is not obtained and the travel is hindered. On the other hand, when the actual injection amount is larger than the commanded fuel injection amount, Problems such as an increase in fuel pressure, engine failure, fuel consumption deterioration, and an increase in the concentration of harmful components in exhaust gas occur.

  Therefore, an excess air ratio sensor or an excess air ratio sensor (such as an oxygen sensor also called a lambda sensor or an A / F sensor called an A / F sensor) that can measure the excess air ratio or the air / fuel ratio is used to measure the exhaust gas from the target air / fuel ratio. An apparatus that corrects the deviation amount of the air-fuel ratio (for example, see Patent Document 1) and an apparatus that compares and corrects the excess air ratio in the exhaust gas, the command injection quantity, and the excess air ratio calculated from the fresh air quantity Yes (see, for example, Patent Document 2).

  These devices detect an excess air ratio in the exhaust gas or an air-fuel ratio of the exhaust gas by an excess air ratio sensor provided upstream of the exhaust gas treatment device or upstream and downstream of the exhaust gas treatment device. The detected excess air ratio or air / fuel ratio depends on the actual fuel injection amount. By correcting the deviation between this and the target value obtained from the indicated fuel injection amount, or comparing the deviations, abnormal fuel injection is detected. By detecting this, the injector is monitored and controlled so that the actual fuel injection amount and the command fuel injection amount do not deviate.

The excess air ratio sensor provided in the above apparatus is, for example, ZrO ₂ (zirconia) or TiO ₂ (titania) which is provided upstream of the exhaust gas processing apparatus and has electrodes with Pt (platinum) coating on the inner and outer surfaces. It is formed with a solid electrolyte tube formed by, for example.

  The principle of this excess air ratio sensor is that oxygen ions flow from the atmosphere side where the oxygen partial pressure is high toward the exhaust gas side where the oxygen partial pressure is low, thereby generating an electromotive force proportional to the logarithm of the oxygen partial pressure ratio between the electrodes. The oxygen concentration in the exhaust gas is detected from the electromotive force.

By using the above-described device equipped with this excess air ratio sensor, it is possible to correct the deviation between the actual fuel injection amount and the commanded fuel injection amount, or to detect an abnormality in fuel injection by comparing the deviations. However, since the excess air ratio sensor uses Pt or ZrO ₂ , the sensor is expensive. Therefore, since the manufacturing cost increases, only a few engines are equipped with an excess air ratio sensor.

On the other hand, many recent engines are equipped with an exhaust gas purification device to clean the exhaust gas. This engine is provided with a NOx sensor for measuring the content of NOx (nitrogen oxide) in the exhaust gas downstream of the exhaust gas purification device.

  This NOx sensor is, for example, a sensor that is provided downstream of an exhaust gas treatment device and is made of a ceramic solid electrolyte (oxygen ion conductor) that is excellent in durability and heat resistance, and has at least two compartments. The exhaust gas is exhausted by the first oxygen pump by using a first oxygen pump that removes oxygen other than NOx in one compartment and a second oxygen pump that decomposes NOx and removes the generated oxygen in the other compartment. The oxygen concentration in the exhaust gas is detected, and the NOx concentration in the exhaust gas is detected by the second oxygen pump.

Similar to the above-described excess air ratio sensor, the NOx sensor uses oxygen ion conductors (SnO ₂ , ITO, YBCO, WO ₃ , TiO ₂ , ZrO ₂ , Zn ₂ SnO _4, etc.), and Pt, Rh on the surface thereof. Since it is processed by applying (rhodium) or the like, the sensor is expensive.

  However, this NOx sensor is a method for directly detecting the NOx occlusion state of the NOx occlusion reduction catalyst in the exhaust gas purification device and giving an optimum timing for reducing agent charging control, or a method for diagnosing deterioration of the catalyst on the vehicle. It is a sensor that is indispensable for providing an exhaust gas purifying device in an engine.

JP-A-11-82117 JP 10-141125 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to use a NOx sensor provided downstream of an exhaust gas purification device without adding an expensive excess air ratio sensor to deteriorate the injector. A fuel injection method for an internal combustion engine and an internal combustion engine capable of correcting the next commanded fuel injection amount so that the deviation between the actual fuel injection amount generated by the above and the commanded fuel injection amount becomes zero It is.

  The fuel injection method for an internal combustion engine according to the present invention for solving the above-described object is a fuel injection method for an internal combustion engine in which an exhaust gas purification device is provided in an exhaust passage, and a NOx sensor provided downstream of the exhaust gas purification device. A deviation value between the actual excess air ratio λ1 calculated from the oxygen concentration value and the target excess air ratio λ2 calculated from the fresh air amount detected by the intake air amount sensor provided in the intake passage and the current commanded fuel injection amount is calculated. The deviation value is zero for the current injection time correction value stored in the injection time correction value map based on the common rail pressure and the commanded fuel injection amount and corresponding to the current common rail pressure and the current commanded fuel injection amount. The injection time correction value is calculated as described above, and the fuel is injected by correcting the current command fuel injection amount with the injection time correction value when fuel is injected from the fuel injection valve. Method It is.

  According to this method, using the NOx sensor provided downstream of the exhaust gas purification device including the SCR device (selective catalytic reduction device), the indicated fuel injection amount of the injector (fuel injection valve) is changed to the actual fuel injection amount. Therefore, the difference between the actual fuel injection amount and the command fuel injection amount can be eliminated. As a result, it is possible to correct the deviation between the actual fuel injection amount and the commanded fuel injection amount due to the deterioration of the injector without adding an excess air ratio sensor conventionally required for correcting the fuel injection amount. Accordingly, the number of parts can be reduced, and the manufacturing cost can be reduced.

In the fuel injection method for the internal combustion engine, the injection time correction value is expressed by the following equation (1) using the actual excess air ratio λ1, the target excess air ratio λ2, and the current injection time correction value. The commanded fuel injection amount is determined by the following equation (2) using the injection time correction value and the current commanded fuel injection amount.
However, L (i, j): current injection time correction value, L (I, J): injection time correction value, W_cor: weighting factor, Q_fin: current command fuel injection amount, Q_corr: command fuel injection amount, α: injection A coefficient for converting the time correction value into the injection amount correction value is used.

  According to this method, the actual fuel injection amount is corrected by correcting the injection amount of the injector using the injection time correction value that is corrected so that the deviation between the actual excess air ratio λ1 and the ideal excess air ratio λ2 becomes zero. Based on the above, the next commanded fuel injection amount can be corrected. As a result, without adding an excess air sensor, the fuel consumption deteriorates, the smoke emission increases, and the exhaust gas that occurs when the deviation between the actual fuel injection amount and the commanded fuel injection amount becomes large due to deterioration of the injector or the like. Heat damage such as exhaust pipes and turbochargers due to high gas temperatures can be prevented.

  An internal combustion engine for solving the above problem is an internal combustion engine provided with an exhaust gas purification device in an exhaust passage, and an actual excess air ratio λ1 calculated from an oxygen concentration value of a NOx sensor provided downstream of the exhaust gas purification device. Means for calculating a deviation value between the fresh air amount detected by the intake air amount sensor provided in the intake passage and the target excess air ratio λ2 calculated from the current indicated fuel injection amount, and the common rail pressure and the indicated fuel injection amount. The injection time correction is performed by correcting the current injection time correction value stored in the base injection time correction value map and corresponding to the current common rail pressure and the current commanded fuel injection amount so that the deviation value becomes zero. A control device comprising: means for calculating a value; and means for performing fuel injection by correcting the current command fuel injection amount with the injection time correction value when fuel is injected from the fuel injection valve .

In the above internal combustion engine, the control device uses the actual air excess rate λ1, the target air excess rate λ2, and the current injection time correction value as the injection time correction value, as shown in the equation (3). ) And a means for obtaining the commanded fuel injection amount by the equation (4) shown above using the injection time correction value and the current commanded fuel injection amount.
However, L (i, j): Current injection time correction value, L (I, J): Injection time correction value, W_cor
: Weight coefficient, Q_fin: current command fuel injection amount, Q_corr: command fuel injection amount, α: coefficient for converting the injection time correction value to the injection amount correction value.

  According to this configuration, the actual excess air ratio λ1 can be calculated from the output of the NOx sensor, and the indicated fuel injection amount can be corrected from the actual fuel injection amount using the actual excess air ratio λ1. As a result, it is not necessary to add an excess air ratio sensor that is conventionally required to eliminate the difference between the actual fuel injection amount and the command fuel injection amount, and thus the cost can be reduced.

  According to the present invention, it is possible to use the NOx sensor provided downstream of the exhaust gas processing device without adding an expensive excess air ratio sensor, and to indicate the actual fuel injection amount generated due to deterioration of the injector and the indicated fuel. The next command fuel injection amount can be corrected so that the deviation from the injection amount is zero.

It is the figure which showed the intake and exhaust system of the internal combustion engine of embodiment which concerns on this invention. It is the schematic which showed control of the internal combustion engine of embodiment which concerns on this invention. It is a learning area | region map used for the fuel-injection method of the internal combustion engine of embodiment which concerns on this invention. 3 is a flowchart showing a fuel injection method for an internal combustion engine according to an embodiment of the present invention.

  Hereinafter, a fuel injection method for an internal combustion engine and an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, an in-line four-cylinder diesel engine will be described as an example. However, the present invention is not limited to this and may be applied to any internal combustion engine provided with a NOx sensor.

  First, the configuration of an internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, an engine (internal combustion engine) 1 includes a fuel supply system 4 including an injector (fuel injection valve) 3 for injecting fuel into each cylinder 2, an intake system 6 including an intake passage 5, and an exhaust passage. An exhaust system 8 including 7 is provided.

  The fuel intake system 4 is a system that injects high-pressure fuel from an injector 3 connected to a common rail 9 that stores pressurized fuel, and includes a fuel tank and a supply pump (not shown). The intake system 6 includes an intake filter 10, an intercooler 11, and an intake throttle 12, and the exhaust system 8 is an exhaust gas treatment including a DPF (diesel particulate collection filter) 13 and an SCR device (selective catalytic reduction device) 14. A device 15 is provided.

  Further, the intake system 6 and the exhaust system 8 can send the compressed air into the engine by rotating the turbine at high speed using the energy of the exhaust gas and driving the centrifugal compressor with the rotational force. The turbocharger 16, the EGR cooler 17, and the EGR valve 18 are provided with an EGR device (exhaust gas recirculation device) 19 that takes out a part of the exhaust gas after combustion, guides it to the intake side, and sucks it again.

The configuration of the engine 1 is a well-known configuration, and each device can use a well-known technique. In this embodiment, the exhaust gas treatment device 1 including at least the SCR device 14.
As long as 5 is provided in the exhaust system 8, the other configuration is not limited to the above configuration.

  In addition, an ECU (control device) 20 that controls the above-described device and system, a NOx sensor 21, a MAF sensor (fresh air amount sensor) 22, and a pressure sensor 23 connected to the ECU 20 are provided. In addition, although the sensor which is not illustrated is provided in the engine 1, in this embodiment, it is sufficient that at least the sensors 21 to 23 are provided.

  The ECU 20 is a control device called an engine control unit, and is a microcontroller that comprehensively performs electrical control in charge of control of the engine 1 by an electric circuit. As shown in FIG. Then, the fuel injection amount of the injector 3 is controlled based on the command fuel injection amount Q_corr.

  The ECU 20 includes an actual excess air ratio calculating means 24, a target excess air ratio calculating means 25, a learned value calculating means 26, and an indicated fuel injection amount calculating means 27, and also includes a learning region map M1 and a current indicated fuel injection amount Q_fin. Is remembered. Each of these means 24 to 27 is stored in the ECU 20 as a program and sequentially executed when correcting the fuel injection amount.

  The NOx sensor 21 provided downstream of the SCR device 14 is a sensor that measures the concentration value of NOx (nitrogen oxide) in the exhaust gas, and is a sensor that can measure the oxygen concentration value O2_exh in the exhaust gas. is there. The NOx sensor 21 is used in a method for directly detecting the NOx occlusion state of the NOx occlusion reduction catalyst in the SCR device 14 to give an optimum timing for reducing agent charging control, and a method for diagnosing deterioration of the catalyst on the vehicle. This sensor is necessary when the exhaust system 8 includes the SCR device 14.

  The NOx sensor 21 is excellent in durability and heat resistance, and a known NOx sensor can be used as long as it can measure the NOx concentration in the exhaust gas and can measure the oxygen concentration value O2_exh in the exhaust gas. In addition, the MAF sensor 22 and the pressure sensor 23 may be well-known sensors if the MAF sensor 22 detects the fresh air amount m_air and the pressure sensor 23 can detect the common rail pressure (common rail pressure) P. it can.

Next, the operation of the engine 1 will be described with reference to FIGS. The engine 1 performs this operation every time a predetermined crank angle (for example, every 360 °) is reached. First, as shown in FIG. 2, using the oxygen concentration value O2_exh detected by the NOx sensor 21, the actual excess air ratio calculating means 24 provided in the ECU 20 calculates the actual excess air ratio λ1 from the following equation (5). calculate. Here, the oxygen concentration in the atmosphere is O2_air.

  The actual excess air ratio calculating means 24 can calculate the actual excess air ratio λ1 derived from the actual fuel injection amount from the oxygen concentration value O2_exh detected by the NOx sensor 21. Thereby, in order to calculate the actual excess air ratio λ1, by using the NOx sensor 21 that needs to be provided in the engine 1 including the SCR device 14, it is not necessary to separately add an excess air ratio sensor. Therefore, the number of parts can be reduced, and the manufacturing cost can be reduced.

Next, using the current command fuel injection amount Q_fin stored in the ECU 20, the fresh air amount m_air detected by the MAF sensor 22, and the ideal air-fuel ratio AFR, the target excess air ratio calculating means 25 is calculated.
However, the target excess air ratio λ2 is calculated from the following formula (6).
Here, the ideal air-fuel ratio AFR takes various values depending on the properties of the fuel. For example, when the fuel is light oil, the value is about 14.5.

  Next, the current learning value (current injection time correction value) L (i, j) stored in the learning region map (injection time correction value map) M1 is corrected. The learning region map M1 will now be described. As shown in FIG. 3, the learning region map M1 is a map based on the common rail pressure P_area and the fuel flow rate (indicated fuel injection amount) Q_area stored in advance in the ECU 20.

  The learning value (injection time correction value) L (i, j) stored in the learning region map M1 is a correction value for the injection time of the injector 3. In addition, the numerical value described in the learning area map M1 shown in FIG. 3 is a numerical value for explanation, and the actual numerical value is not limited to this. Further, the number of cells is not limited, and actually, a numerical value may be set finely to increase the number of cells.

Next, as shown in FIG. 2, the actual learning value (current injection time correction value) L (i, j) stored in the learning region map M1 is set to the actual excess air ratio λ1 and the target excess air ratio λ2. Using the deviation value Δλ and the weighting coefficient w_cor, the learning value calculation means 26 corrects the value from the following equation (7) to calculate the learning value (injection time correction value) L (I, J). .

  Then, the learning value L (I, J) corrected so that the deviation value Δλ between the actual excess air ratio λ1 and the target excess air ratio λ2 becomes zero by the learned value calculating means 26 is learned as a new learned value. Store in the area map M1.

Next, using the current commanded fuel injection amount Q_fin and the learned value L (I, J), the commanded fuel injection amount calculating means 27 calculates the next commanded fuel injection amount Q_corr from the following equation (8). . Here, α is a coefficient for converting the learning value L (I, J) into an injection amount correction value.

  Then, the ECU 20 controls the injector 3 to inject at the calculated command fuel injection amount Q_corr.

  According to the above operation, the current learning value L (i, j) stored in the learning area map M1 is corrected so that the deviation value Δλ between the actual excess air ratio λ1 and the target excess air ratio λ2 is zero. By updating the learned value L (I, J), the deviation between the actual fuel injection amount and the commanded fuel injection amount Q_corr due to deterioration of the fuel supply system 4 including the injector 3 can be corrected. Further, since the corrected learning value L (I, J) is stored in the learning region map M1, it is possible to always calculate the command fuel injection amount Q_corr corrected in accordance with the actual fuel injection amount.

  Further, the engine 1 can calculate the actual excess air ratio λ1 using the oxygen concentration value O2_exh of the NOx sensor 21 provided downstream of the SCR device 14 when the injector 3 injects fuel. Since the next command fuel injection amount Q_corr can be corrected so that the deviation value Δλ between the excess air ratio λ1 and the target excess air ratio λ2 becomes zero, the deterioration of the injector 3 without adding an excess air ratio sensor. The deviation between the commanded fuel injection amount Q_corr and the actual fuel injection amount can be eliminated.

  Next, the fuel injection method of the engine 1 will be described with reference to the flowchart of FIG. This fuel injection method is performed for each predetermined crank angle of the engine 1 and is corrected so as to be the indicated fuel injection amount Q_corr based on the actual fuel injection amount of the injector 3.

  First, step S11 for calculating the actual excess air ratio λ1 in the exhaust gas is performed using the oxygen concentration value O2_exh of the NOx sensor 21 provided downstream of the SCR device 14. In this step S11, the actual excess air ratio λ1 is calculated using the above equation (5), but it is only necessary to be able to determine the excess air ratio based on the actual fuel injection amount, and is not limited to the above method.

  Next, step S12 for calculating the target excess air ratio λ2 is performed using the MAF sensor 16 and the current command fuel injection amount Q_fin. In this step S12, the target excess air ratio λ2 is calculated using the above formula (6), but it is sufficient if the target excess air ratio λ2 obtained from the current command fuel injection amount Q_fin can be calculated. Not limited.

  Next, step S13 for comparing the calculated actual excess air ratio λ1 with the target excess air ratio λ2 is performed. If λ1 = λ2 in step S13, the actual fuel injection amount and the current command fuel injection amount Q_fin coincide with each other, and the process proceeds to step S17 without correction. On the other hand, if λ1 ≠ λ2 in step S13, the actual fuel injection amount is deviated from the current commanded fuel injection amount Q_fin, so the process proceeds to step S14 and correction is performed.

  If it is determined in step S13 that λ1 ≠ λ2, then step S14 for calling the current learning value L (i, j) from the learning region map M1 is performed. In step S14, the current learning value L (i, j) corresponding to the current common rail pressure P detected by the pressure sensor 23 and the current commanded fuel injection amount Q_fin is called. The learning value L (i, j) is a learning value used when the current command fuel injection amount Q_fin is corrected.

  Next, using the deviation value Δλ between the actual excess air ratio λ1 and the target excess air ratio λ2, the current learning value L (i, j) is corrected to calculate the learning value L (I, J). I do. In this step S15, the learning value L (I, J) is calculated using the above mathematical formula (7). Next, step S16 of writing the learning value L (I, J) to the learning area map M1 is performed. At this time, the location of the cell written in the learning area map M1 is specified by the current common rail pressure P and the current commanded fuel injection amount Q_fin.

  Next, step S18 for calculating the next commanded fuel injection amount Q_corr using the learned value L (I, J) and the current commanded fuel injection amount Q_fin is performed. In step S18, the command fuel injection amount Q_corr is calculated using the above equation (8). When the next commanded fuel injection amount Q_corr is calculated, the process returns to the start, and the above steps are repeated until the engine 1 stops. When the engine 1 is stopped, this fuel injection method is completed.

If it is determined in step S13 that λ1 = λ2, the current learning value L (i, j) is changed to the learning value L (
I, J) is performed, step S17 is performed, the process proceeds to step S18, the next commanded fuel injection amount Q_corr is calculated, and the process returns to the start.

  According to the fuel injection method described above, the next commanded fuel injection amount Q_corr is corrected using the oxygen concentration O2_exh of the NOx sensor 21 so as to eliminate the deviation between the actual fuel injection amount and the current commanded fuel injection amount Q_fin. Can do. Thus, without adding an excess air ratio sensor, deterioration of fuel consumption, increase in smoke emission, and the like, when the deviation between the actual fuel injection amount and the commanded fuel injection amount Q_corr becomes large due to deterioration of the injector, etc., and Thermal damage to the exhaust pipe 7 and the turbocharger 16 due to the high temperature of the exhaust gas can be prevented.

  Further, the learning value L (I, J) obtained by correcting the current learning value L (i, j) of the learning region map M1 so that the deviation value Δλ between the actual excess air ratio λ1 and the target excess air ratio λ2 becomes zero. By updating with the above, it is always possible to eliminate the difference between the actual fuel injection amount and the commanded fuel injection amount Q_corr. According to this, even if the fuel injection amount actually decreases with respect to the instructed injection amount due to the deterioration of the injector 3, the decrease is corrected. Can be injected. Therefore, it is possible to prevent a problem that occurs when the deviation between the actual fuel injection amount and the command fuel injection amount Q_coor is large.

  In this embodiment, an in-line four-cylinder diesel engine has been described as an example. However, by setting an ideal air-fuel ratio or the like to a value suitable for gasoline, it can also be applied to a gasoline engine equipped with an exhaust gas processing device. .

  The internal combustion engine of the present invention can correct the deviation between the actual fuel injection amount and the commanded fuel injection amount by using a NOx sensor provided downstream of the exhaust gas processing device, so that it is particularly necessary to process the exhaust gas. It can be used for vehicles equipped with a diesel engine.

1 engine (internal combustion engine)
2 Cylinder block 3 Cylinder 4 Injector (fuel injection valve)
5 Intake pipe (intake passage)
6 Intake system 7 Exhaust pipe (exhaust passage)
8 Exhaust System 9 Common Rail 10 Intake Filter 11 Intercooler 12 Intake Throttle 13 DPF (Diesel Particulate Filter)
14 SCR device (selective catalytic reduction device)
15 Exhaust gas treatment device 16 Turbocharger 17 EGR device (exhaust gas recirculation device)
18 EGR cooler 19 EGR valve 20 ECU (control device)
21 NOx sensor 22 MAF sensor (fresh air sensor)
23 pressure sensor λ1 actual excess air ratio λ2 target excess air ratio M1 learning region map (injection time correction value map)
L (i, j) Current learning value (current injection time correction value)
L (I, J) Learning value (injection time correction value)
Q_fin Current commanded fuel injection amount Q_corr Commanded fuel injection amount O2_exh Oxygen concentration O2_air Atmospheric oxygen concentration m_air Fresh air intake amount AFR Ideal air-fuel ratio

Claims (4)

In a fuel injection method for an internal combustion engine provided with an exhaust gas purification device in an exhaust passage,
Calculated from the actual excess air ratio λ1 calculated from the oxygen concentration value of the NOx sensor provided downstream of the exhaust gas purifying device, the fresh air amount detected by the intake air amount sensor provided in the intake passage, and the current commanded fuel injection amount The deviation value from the target excess air ratio λ2 is calculated,
The current injection time correction value stored in the injection time correction value map based on the common rail pressure and the commanded fuel injection amount and corresponding to the current common rail pressure and the current commanded fuel injection amount is set so that the deviation value becomes zero. To calculate the injection time correction value,
A fuel injection method for an internal combustion engine, wherein fuel injection is performed by correcting the current instruction fuel injection amount with the injection time correction value when fuel is injected from a fuel injection valve. The injection time correction value is obtained by the following equation (1) using the actual excess air ratio λ1, the target excess air ratio λ2, and the current injection time correction value.
2. The fuel injection method for an internal combustion engine according to claim 1, wherein the command fuel injection amount is obtained by the following equation (2) using the injection time correction value and the current command fuel injection amount.
However,
L (i, j): Current injection time correction value L (I, J): Injection time correction value W_cor: Weight coefficient Q_fin: Current command fuel injection amount Q_corr: Command fuel injection amount α: Injection time correction value is corrected for injection amount Factor to convert to value In an internal combustion engine provided with an exhaust gas purification device in the exhaust passage,
Calculated from the actual excess air ratio λ1 calculated from the oxygen concentration value of the NOx sensor provided downstream of the exhaust gas purifying device, the fresh air amount detected by the intake air amount sensor provided in the intake passage, and the current commanded fuel injection amount Means for calculating a deviation value from the target excess air ratio λ2;
The current injection time correction value stored in the injection time correction value map based on the common rail pressure and the commanded fuel injection amount and corresponding to the current common rail pressure and the current commanded fuel injection amount is set so that the deviation value becomes zero. Means for calculating the injection time correction value,
An internal combustion engine comprising: a control device including means for performing fuel injection by correcting the current instruction fuel injection amount with the injection time correction value when fuel is injected from a fuel injection valve. Means for obtaining the injection time correction value by the following equation (3) using the actual excess air ratio λ1, the target excess air ratio λ2, and the current injection time correction value;
4. The internal combustion engine according to claim 3, further comprising means for obtaining the command fuel injection amount by the following equation (4) using the injection time correction value and the current command fuel injection amount.
However,
L (i, j): Current injection time correction value L (I, J): Injection time correction value W_cor: Weight coefficient Q_fin: Current command fuel injection amount Q_corr: Command fuel injection amount α: Injection time correction value is corrected for injection amount Factor to convert to value