KR102474612B1 - Method of nitrogen oxide in engine reflecting travel distance - Google Patents

Abstract

The present invention predicts the actual emission of nitrogen oxides as the driving distance increases after starting and compares the accumulated nitrogen oxides with a reference value to control combustion of the engine, thereby reducing the emission of nitrogen oxides. It's about control methods.
In the method of controlling nitrogen oxides of an engine reflecting the driving distance according to the present invention, when the engine 10 is started (S10) or the key is turned ON, the nitrogen oxide emission (NOx_mass) and the driving distance of the vehicle are each set to 0. an initial reset step (S20) of performing an initial reset step (S20) and a nitrogen oxide emission amount obtaining step (S100) of calculating the combustion temperature and nitrogen oxide concentration from the combustion pressure of the engine 10 and obtaining the amount of nitrogen oxide discharged from the engine 10 (S100). ) And, by accumulating the amount of nitrogen oxide discharged from the engine 10 and accumulating the travel distance of the vehicle, the EGR ratio according to the travel distance or the concentration of oxygen flowing into the cylinder of the engine. The correction value acquired step (S200) and the correction value obtained in the correction value acquisition step (S200) are applied to the initial EGR ratio or the oxygen concentration of the initial intake manifold to obtain the final EGR valve control value (EGR valve Final). and an EGR correction control step (S300) of obtaining and controlling the EGR valve 33 with the final EGR valve control value (EGR valve Final).

Description

Engine nitrogen oxide control method reflecting driving distance {METHOD OF NITROGEN OXIDE IN ENGINE REFLECTING TRAVEL DISTANCE}

The present invention relates to a nitrogen oxide control method for reducing nitrogen oxides (NOx) emitted from a vehicle, and more particularly, as the driving distance increases after starting, the actual emission of nitrogen oxides is predicted and the accumulated nitrogen oxides are calculated as a reference value. It relates to a method for controlling nitrogen oxides of an engine reflecting a travel distance so that emissions of nitrogen oxides are reduced by controlling combustion of the engine compared to the above.

In a conventional engine, the engine is developed and mass-produced in an unpredictable state of nitrogen oxides discharged from the engine.

However, in accordance with gradually tightening exhaust gas regulations, it is determined whether the regulations are satisfied by measuring the amount of nitrogen oxides (NOx) discharged under various operating conditions and environmental conditions.

In order to meet these exhaust gas regulations, there has recently been an increasing trend of installing post-processing devices such as SCR (Selective Catalytic Reduction) or LNT (Lean NOx Trap).

However, nitrogen oxides discharged from the engine vary in the amount of nitrogen oxides discharged from the engine due to variations between engines, environmental factors, deterioration of parts, etc., or are discharged beyond the predicted amount, which is finally emitted from the vehicle. It also affects the nitrogen oxides emitted, which may cause the exhaust gas not to meet the existing requirements.

As such, if there is a deviation in the amount of nitrogen oxide discharged from the engine or it is out of the predicted range, there is a problem that the performance of the post-processing device such as the SCR or the LNT is not properly displayed or fuel efficiency is lowered. . For example, in the SCR, when the emission of nitrogen oxides increases, the purification efficiency of the nitrogen oxides decreases, and the injection amount of urea is increased to compensate for this. The increase in the amount of urea injection shortens the replenishment cycle of the urea. The LNT has a problem in that fuel efficiency is lowered due to frequent regeneration since a regeneration cycle is shortened to reduce the stored nitrogen oxide when the emission of the nitrogen oxide increases.

Meanwhile, the following prior art documents disclose a technology related to 'a device for estimating a state quantity of an internal combustion engine, a control device for an internal combustion engine, and a method for estimating a state quantity of an internal combustion engine'.

JP 2007-127004 A

The present invention was invented to solve the above problems, and when the driving distance increases after starting, the accumulated amount of nitrogen oxides emitted according to the combustion state of the engine is calculated, and the result is compared with a reference value to reduce engine combustion. By controlling, an object of the present invention is to provide a method for controlling nitrogen oxides of an engine reflecting a travel distance capable of controlling the emission of nitrogen oxides according to the travel distance.

In order to achieve the above object, the method for controlling nitrogen oxides of an engine reflecting the driving distance according to the present invention sets the nitrogen oxide emissions and the driving distance of the vehicle to zero, respectively, when the engine is started or turned ON. A reset step, a nitrogen oxide emission amount obtaining step of obtaining an amount of nitrogen oxide discharged from the engine by calculating a combustion temperature and a nitrogen oxide concentration from the combustion pressure of the engine, and accumulating the amount of nitrogen oxide discharged from the engine. and accumulating the driving distance of the vehicle to obtain a correction value of either the EGR ratio according to the driving distance or the concentration of oxygen flowing into the cylinder of the engine, and the initial EGR ratio or the initial intake manifold and an EGR correction control step of obtaining a final EGR valve control value by applying the correction value obtained in the correction value acquisition step to the oxygen concentration, and controlling the EGR valve with the final EGR valve control value.

The nitrogen oxide emission obtaining step, the correction value obtaining step, and the EGR correction control step are performed simultaneously after the initial resetting step is performed until the engine is stopped or the key is turned off.

The nitrogen oxide emission obtaining step may include a combustion pressure measuring step of collecting in real time combustion pressure output to the ECU from combustion pressure sensors installed in each cylinder of the engine, combustion pressure at the time of starting combustion in the cylinder, and maximum combustion. The maximum combustion temperature calculation step of calculating the maximum combustion temperature, which is the maximum combustion temperature in the cylinder, based on pressure, oxygen concentration, and air-fuel ratio; The nitrogen oxide concentration calculation step of calculating the concentration of nitrogen oxide discharged from the cylinder based on the pilot injection amount, and the nitrogen oxide concentration calculated in the nitrogen oxide concentration calculation step, the amount of air, and the engine load. It is characterized in that it includes a real-time nitrogen oxide emission calculation step of calculating the emission amount.

In the step of calculating the concentration of nitrogen oxides, the concentration of nitrogen oxides discharged from each cylinder is calculated based on the zeldovich mechanism.

After the real-time nitrogen oxide emission calculating step is performed, an engine operation determining step of determining whether the engine is operating is further included, and if the engine is operating, the combustion pressure measuring step is returned.

In the engine operation determination step, if the engine is not operating, it is characterized in that it is terminated.

The correction value obtaining step may include a correction control region satisfaction determination step of determining whether the engine is operating in a correction control region in which the EGR ratio of the engine or the oxygen concentration of the intake manifold should be corrected according to the driving distance of the vehicle; If the engine is operating in the correction control region, a correction control entry step in which the amount of nitrogen oxides discharged from the engine and the driving distance of the vehicle start to accumulate, and the amount of nitrogen oxide accumulated according to the driving distance of the vehicle A target nitrogen oxide emission calculation step of calculating a target cumulative nitrogen oxide emission amount of phosphorus; a target ratio calculation step of calculating a ratio between an accumulated value of nitrogen oxides emitted during the operation of the vehicle and the target cumulative nitrogen oxide emission amount; A correction application determination step of determining whether the driving distance of the vehicle is greater than a correction value application reference value preset for applying the correction value of the EGR ratio or the oxygen concentration of the intake manifold; and and a correction value calculation step of calculating a correction value of the EGR ratio or a correction value of the oxygen concentration of the intake manifold when the value is greater than the reference value.

In the correction value calculation step, a correction value of the EGR ratio or a correction value of the oxygen concentration of the intake manifold is calculated from different correction maps according to the target ratio.

The correction control region satisfaction determination step includes an environmental condition satisfaction determination step of determining whether external environmental conditions of the engine satisfy a preset correction control range, and whether or not the engine operating condition satisfies a preset correction control range. It is characterized in that it includes a driving condition satisfaction determination step of determining.

The environmental condition satisfaction determination step may include determining whether intake air temperature of the air flowing into the engine, atmospheric pressure of the air flowing into the engine, and temperature of the cooling water of the engine all satisfy a preset correction control range. .

In the environmental condition satisfaction determination step, if any one of the intake air temperature of the air flowing into the engine, the atmospheric pressure of the air flowing into the engine, and the temperature of the cooling water of the engine does not satisfy a preset correction control range, the correction control It is characterized in that the region satisfaction determination step is re-performed.

The driving condition satisfaction determination step may include determining whether the speed of the vehicle and the acceleration of the vehicle satisfy a preset correction control range.

In the driving condition satisfaction determination step, if at least one of the vehicle speed and the vehicle acceleration does not satisfy a preset correction control range, the correction control region satisfaction determination step is re-performed.

In the correction application determination step, if the driving distance of the vehicle is not greater than the correction value application reference value, a correction value non-application step of not applying the correction value of the EGR ratio or the oxygen concentration of the intake manifold. do.

After the correction value calculation step or the correction value non-application step is performed, an engine operation determination step of determining whether the engine is operating is further included, and if the engine is operating, the correction control region satisfaction determination step is returned. characterized by

In the engine operation determination step, if the engine is not operating, it is characterized in that it is terminated.

In the environmental condition satisfaction determination step and the driving condition satisfaction determination step, the environmental condition satisfaction determination step is performed after the driving condition satisfaction determination step is performed.

In the EGR correction control step, an initial engine control setting an initial EGR target value, which is an initial control value of the EGR valve, or an initial intake manifold target oxygen concentration, which is an initial oxygen concentration in the intake manifold, according to an operating region of the engine. or obtaining a corrected EGR target value obtained by correcting the initial EGR target value by adding the correction value of the EGR ratio obtained in the step of obtaining the correction value to the initial EGR target value. Correction in which a corrected intake manifold target oxygen concentration in which the initial intake manifold target oxygen concentration is corrected is obtained by adding the oxygen concentration correction value of the intake manifold obtained in the correction value obtaining step to the initial intake manifold target oxygen concentration. An engine control condition setting step, and an engine operating deviation calculation step of obtaining an EGR deviation, which is the difference between the corrected EGR target value and the actual EGR ratio, or an oxygen concentration deviation, which is the difference between the corrected intake manifold target oxygen concentration and the actual intake manifold oxygen concentration. In addition, an EGR valve control initiation step of calculating a control amount of the EGR valve reflecting the EGR deviation or the oxygen concentration deviation and starting control of the EGR valve, and the EGR valve control amount calculated in the EGR valve control initiation step a final EGR valve control value calculation step of adding the opening amount of the EGR valve set according to the current operating range of the engine and calculating the final EGR valve control value, which is the final control amount of the EGR valve; and an EGR valve opening control step of controlling the opening of the EGR valve.

The step of starting the EGR valve control is characterized in that the closed-loop control is performed by PID control.

In the EGR valve control starting step, a control value is determined according to a deviation of an actual amount of oxygen according to the EGR deviation or the oxygen concentration deviation.

After the EGR valve opening control step is performed, an engine operation determination step of determining whether the engine is operating is further included, and if the engine is operating, the initial engine control condition setting step is returned.

In the engine operation determination step, if the engine is not operating, it is characterized in that it is terminated.

According to the nitrogen oxide control method of the engine reflecting the travel distance of the present invention having the configuration as described above, it is possible to control the amount of nitrogen oxide discharged from the engine in real time according to the increase in the travel distance.

Accordingly, it is possible to reduce the emission deviation of nitrogen oxides generated from the difference between the development environment of the engine and actual vehicle driving conditions.

1 is a schematic diagram of an engine to which a method for controlling nitrogen oxides of an engine reflecting a travel distance according to the present invention is applied.
Figure 2 is a flow chart showing a method for controlling nitrogen oxides of an engine reflecting a travel distance according to the present invention.
FIG. 3 is a flowchart showing S100 of FIG. 2 in detail;
FIG. 4 is a flowchart illustrating S200 of FIG. 2 in detail;
FIG. 5 is a flowchart illustrating S300 of FIG. 2 in detail;

Hereinafter, a method for controlling nitrogen oxides of an engine reflecting a travel distance according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, when the engine 10 is started (S10), the nitrogen oxide emission (NOx_mass) and the vehicle's travel distance are each set to zero. An initial reset step (S20) of setting, and a nitrogen oxide emission amount obtaining step of calculating the combustion temperature and nitrogen oxide concentration from the combustion pressure of the engine 10 to obtain the amount of nitrogen oxide discharged from the engine 10 ( S100), the amount of nitrogen oxide discharged from the engine 10 is accumulated and the travel distance of the vehicle is accumulated, and either the EGR ratio according to the travel distance or the concentration of oxygen flowing into the cylinder of the engine is corrected. A correction value acquisition step (S200) for obtaining a final EGR valve control value (EGR valve final) by applying the correction value obtained in the correction value acquisition step (S200) to the initial EGR ratio or the initial intake manifold oxygen concentration and an EGR correction control step (S300) of obtaining and controlling the EGR valve 33 with the final EGR valve control value (EGR valve Final).

1 shows an engine system in which a method for controlling nitrogen oxides of an engine reflecting a travel distance according to the present invention is performed.

The engine 10 includes a plurality of cylinders 11, and each cylinder 11 is provided with a combustion pressure sensor 12 capable of measuring combustion pressure inside the cylinder 11. The combustion pressure sensor 12 may be installed integrally with the glow plug or may be installed independently.

The air introduced through the intake line 21 is supplied to the inside of each of the cylinders 11 through the intake manifold 15, and after being combusted inside the cylinder 11, the air flows through the exhaust manifold 16. and is discharged through the exhaust line 22. A turbine 31a and a compressor 31b of the turbo charger 31 are installed in the exhaust line 22 and the intake line 21, respectively, and an intercooler for cooling the air intake into the engine is installed in the intake line 21. (32) is installed. A post-processing device 41 for purifying harmful substances contained in the exhaust gas is installed in the exhaust line 22 . At least one post-processing device 41 is installed to purify harmful substances included in the exhaust gas. In addition, an EGR line 23 is installed to connect the exhaust line 22 and the intake line 21, and an EGR valve 33 for controlling the amount of recirculated EGR gas is installed in the EGR line 23. do.

The combustion pressure of each cylinder 11 measured by the combustion pressure sensor 12 is transmitted to the ECU 50 in real time. The ECU 50 includes the combustion pressure sensor 12 as well. An algorithm for a method for controlling nitrogen oxides of an engine reflecting a travel distance, which will be described later, is stored using existing various sensors and values controlled for combustion of the engine 10, and this is actually performed.

The ECU 50 predicts the amount of nitrogen oxides (NOx) emitted from the engine 10 using combustion pressure and various control conditions in real time according to the driving distance, and controls the EGR valve 33 to , The nitrogen oxide is controlled to be discharged only within a predetermined range.

The ECU 50 is connected to the memory 51, or the memory 51 is provided inside the ECU 50 to store the accumulated amount of nitrogen oxide emissions, or to store other values such as the distance traveled by the vehicle. used to store

In the initial reset step (S20), the amount of nitrogen oxides (NOx) emitted and the driving distance of the vehicle are respectively initialized. When the engine 10 is started (S10), the ECU 50 sets the amount of nitrogen oxides emitted (NOx_mass) to 0, and also sets the driving distance of the vehicle to 0.

Meanwhile, the initial reset (S20) may be performed when the engine 10 is started, or may be performed when the key is turned on.

In the nitrogen oxide emission obtaining step (S100), the ECU 50 uses the combustion pressure of each cylinder 11 of the engine 10 output to the combustion pressure sensor 12 to determine the inside of each cylinder 11. Combustion temperature and nitrogen oxide temperature are calculated to obtain the amount of nitrogen oxide (NOx_mass) discharged from the engine 10 . The obtained emission amount of nitrogen oxide (NOx_mass) is stored in real time.

In the step of obtaining a correction value (S200), the emission amount (NOx_mass) of the nitrogen oxide discharged from the engine 10 is accumulated and the travel distance of the vehicle is accumulated, and the EGR ratio according to the travel distance or the A correction value of any one of the concentrations of oxygen is acquired. In the correction value acquisition step (S200), an EGR ratio correction value (EGR_cor) or an intake manifold oxygen concentration correction value (Inmani-O_cor) is calculated to control intake air of the engine 10. In the correction value acquisition step (S200), the deviation between the amount of nitrogen oxides (Nox) discharged from the engine 10 and the predicted amount increases as the driving distance of the vehicle increases. A correction value (EGR_cor) or a correction value (Inmani-O_cor) of the oxygen concentration of the intake manifold is calculated and used for control.

The EGR correction control step (S300) applies the correction value obtained in the correction value acquisition step (S200) to the initially set initial EGR target value (EGR_des) or the initial intake manifold oxygen concentration (Inmani-O_des), A final EGR valve control value (EGR valve Final) to control the EGR valve 33 is obtained, and the EGR valve 33 is controlled with the final EGR valve control value (EGR valve Final).

The nitrogen oxide emission step (S100), the correction value acquisition step (S200), and the EGR correction control step (S300) are performed when the engine 10 is stopped after the initial reset step (S20) is performed or when the engine 10 is stopped. It is performed simultaneously until OFF.

The nitrogen oxide emission amount obtained in real time in the nitrogen oxide emission obtaining step (S100) is accumulated in the correction value obtaining step (S200), and the EGR ratio or the oxygen concentration of the intake manifold in the correction value obtaining step (S200) used to correct In addition, the correction value (EGR_cor) of the EGR ratio or the correction value (Inmani-O_cor) of the intake manifold oxygen concentration obtained in the correction value acquisition step (S200) is the final EGR valve control value in the EGR correction control step (S300). (EGR valve Final).

Hereinafter, the nitrogen oxide emission step (S100), the correction value acquisition step (S200), and the EGR correction control step (S300) will be described in detail.

As shown in FIG. 3 , in the step of acquiring nitrogen oxide emissions (S100), the combustion pressure output to the ECU 50 from the combustion pressure sensor 12 installed in each cylinder 11 of the engine 10 is measured in real time. Combustion pressure measuring step (S110) collected in the cylinder 11 based on the combustion pressure (Psoc), maximum combustion pressure (Pmax), oxygen concentration, and air-fuel ratio (AF) at the time of combustion start in the cylinder 11 The maximum combustion temperature calculation step (S120) of calculating the maximum combustion temperature (Temp), which is the maximum combustion temperature within In the nitrogen oxide concentration calculation step (S130) of calculating the concentration of nitrogen oxide discharged from the cylinder 11 based on the rail pressure (RAIL) and the pilot injection amount (Pilot), and the nitrogen oxide concentration calculation step (S130) A real-time nitrogen oxides amount calculation step (S140) of calculating the amount of nitrogen oxides discharged from the cylinder 11 (NOx_mass) based on the obtained concentration of nitrogen oxides, air amount, and engine load.

In the combustion pressure measuring step (S110), the combustion pressure in each cylinder 11 is measured by the combustion pressure sensor 12 installed in each cylinder 11 of the engine 10, and the result is output to the ECU 50. . While continuously measuring the combustion pressure in each cylinder 11 measured from the combustion pressure sensor 12 in real time, it is collected in the memory 51 .

In the maximum combustion temperature calculation step ( S120 ), the ECU 50 calculates the maximum combustion temperature Temp in the cylinder 11 . The ECU 50 controls the maximum combustion temperature in the cylinder 11 based on the combustion pressure Psoc at the start of combustion, the maximum combustion pressure Pmax, the oxygen concentration in the cylinder 11, and the air-fuel ratio AF. Calculate the maximum phosphorus combustion temperature (Temp). The maximum combustion temperature (Temp) is determined according to the combustion pressure (Psoc) at the time of combustion start, the maximum combustion pressure (Pmax), the oxygen concentration in the cylinder 11, and the air-fuel ratio (AF), and is in the form of a map. etc. may be stored in the ECU 50, and the ECU 50 may calculate the maximum combustion temperature Temp as an input condition.

The nitrogen oxide concentration calculation step (S130) is based on the maximum combustion temperature (Temp), the oxygen concentration of the cylinder 11, the fuel injection timing (SOI), the rail pressure (RAIL), and the pilot injection amount (Pilot), The concentration of nitrogen oxides produced in the cylinder 11 is calculated. The ECU 50 determines the maximum combustion temperature Temp obtained in the calculation of the maximum combustion temperature (S120) and the control conditions used by the ECU 50 for combustion of the engine 10, for example, the fuel injection. The concentration of nitrogen oxide in each cylinder 11 is calculated using the timing (SOI), the rail pressure (RAIL), and the pilot injection amount (Pilot).

At this time, the concentration of nitrogen oxide can be calculated using the Zeldovich mechanism.

The Zeldovich mechanism describes the generation of nitrogen oxides by the heat generated in the combustion process of fuel, and can be expressed by the following reaction equation.

N ₂ + O ↔ NO + N

N + O ₂ ↔ NO + O

N + OH ↔ NO + H

Here, the nitrogen oxide concentration ([NOx]) is the maximum combustion temperature (Temp), the oxygen concentration of the cylinder 11, the fuel injection timing (SOI), the rail pressure (RAIL), and the pilot injection amount (Pilot) It can be stored in the ECU 50 in the form of a map, etc., and the ECU 50 can calculate the concentration of nitrogen oxides ([NOx]) under input conditions.

In the real-time nitrogen oxide amount calculation step (S140), the amount of nitrogen oxide discharged from the cylinder 11 (NOx_mass) is calculated based on the nitrogen oxide concentration, air amount, and engine load obtained in the nitrogen oxide concentration calculation step (S130). . Here, the engine load may be replaced by the total amount of fuel Q injected to operate with the engine load.

The nitrogen oxide emission NOx_mass is determined by the nitrogen oxide concentration, the air amount, and the engine load Q, and may be stored in the ECU 50 in the form of a map, etc., and the ECU 50 The nitrogen oxide emission amount (NOx_mass) is calculated according to the input value.

The engine operation determination step (S150) determines whether the engine 10 is operating after the real-time nitrogen oxide emission calculation step (S140) is performed.

If the engine 10 is operating in the engine operation determination step S150, the process is repeated by returning to the combustion pressure measurement step S110, and if the engine 10 is not operating, ends (30).

As shown in FIG. 4 , in the correction value acquisition step (S200), the engine ( 10) a correction control range satisfaction determination step (S210) for determining whether or not the engine is operating, and if the engine 10 is operating in the correction control range, the amount of nitrogen oxides discharged from the engine 10 and the operation of the vehicle A correction control entry step (S220) of starting to accumulate the distance, and a target nitrogen oxide emission calculation step (S230) of calculating a target accumulated nitrogen oxide emission amount (Target_NOx_mass_distance), which is the accumulated nitrogen oxide emission amount according to the driving distance of the vehicle; , a target ratio calculation step (S240) of calculating an accumulated value (NOx_mass_acc) of nitrogen oxides emitted according to the operation of the vehicle and a ratio (NOx_ratio) with the target cumulative nitrogen oxide emission (Target_NOx_mass_distance), and the driving distance of the vehicle A correction application determination step (S250) of determining whether is greater than a correction value application reference value preset to apply the correction value of the EGR ratio or the oxygen concentration of the intake manifold, and the vehicle travel distance is the correction value application reference value If it is greater than the EGR ratio correction value (EGR_cor) or the intake manifold oxygen concentration correction value (Inmani-O_cor), a correction value calculation step (S260) is included.

In the correction control region satisfaction determination step (S210), it is determined whether the engine 10 is operating in a correction control region in which the control condition of the engine 10 should be corrected according to the travel distance.

The control condition of the engine 10 may be the EGR ratio or the oxygen concentration of air introduced from the intake manifold 15 to the cylinder 11 .

If the engine 10 is operating in the correction control region in the correction control region satisfaction determination step (S210), a correction control entry step (S220), which will be described later, is performed. If the engine 10 is operating outside the correction control area, the correction control area satisfaction determination step (S210) is repeatedly performed.

The correction control region satisfaction determination step (S210) includes the environmental condition satisfaction determination step (S211) of determining whether the external environmental conditions of the engine 10 satisfy a preset correction control range, and the engine 10 is operated and a driving condition satisfaction determination step (S212) of determining whether the condition satisfies a preset correction control range.

In the environmental condition satisfaction determination step (S211), the intake air temperature of the air flowing into the engine 10, the atmospheric pressure of the air flowing into the engine 10, and the temperature of the cooling water of the engine 10 are all set in advance and the correction control is performed. Determine whether the range is satisfied. When the intake air temperature, the atmospheric pressure, and the coolant temperature are within preset ranges in the environmental condition satisfaction determination step (S211), the driving condition satisfaction determination step (S212) is performed. If any one of the above three is not within the preset range, the environmental condition satisfaction determination step (S211) is performed again.

In the driving condition satisfaction determination step (S212), it is determined whether the speed of the vehicle and the acceleration of the vehicle satisfy a preset correction control range. In the driving condition satisfaction determination step (S212), when both the speed and acceleration of the vehicle are within a preset range, a correction control entry step (S220), which will be described later, is performed. If any of the speed or acceleration is not within the preset range, the process returns to the environmental condition satisfaction determination step (S211) repeatedly.

Meanwhile, the environmental condition satisfaction determination step (S211) and the driving condition satisfaction determination step (S212) may be performed in a reverse order. That is, after the driving condition satisfaction determination step (S212) is performed, the environmental condition satisfaction determination step (S211) may be performed.

This is because the correction control region satisfaction determination step (S210) is a step of determining whether both the external environmental conditions and the operating conditions of the engine 10 satisfy both preset conditions, and will be described later only when both conditions are satisfied. Since the correction control entry step (S220) is performed, the order may be changed and performed.

The correction control entry step (S220) is performed when the engine 10 is operating in the correction control region in the correction control region satisfaction determination step (S210). In the correction control entry step (S220), the amount of nitrogen oxides emitted is accumulated, and the driving distance of the vehicle is also accumulated.

The emission of nitrogen oxides accumulated in the correction control entry step (S220) and the driving distance of the vehicle are performed after the initial resetting step, and the amount of nitrogen oxides emitted after the engine 10 is started (NOx_mass) and the running distance are accumulated.

In the target nitrogen oxide emission calculation step (S230), a target cumulative nitrogen oxide emission amount (Target_NOx_mass_distance), which is an accumulated emission amount of nitrogen oxide predicted as the driving distance of the vehicle is accumulated, is calculated. This increases as the driving distance increases, and is pre-stored in the ECU 50 as a map or the like.

In the target ratio calculation step (S240), a value (NOx_mass_acc) of accumulated nitrogen oxides emitted according to the driving of the vehicle, the target cumulative nitrogen oxide emission amount (Target_NOx_mass_distance), and a ratio (NOx_ratio) are calculated.

The accumulated value (NOx_mass_acc) of nitrogen oxides emitted according to the operation of the vehicle is a value obtained by accumulating the amount of nitrogen oxides (NOx_mass) obtained in the step of obtaining the amount of nitrogen oxides (NOx_mass) during the driving distance after starting the vehicle, which is the target value. A target ratio (NOx_ratio) is calculated by dividing the target cumulative nitrogen oxide emission (Target_NOx_mass_distance) obtained in the step of calculating the amount of nitrogen oxides (S230).

In the correction application determination step ( S250 ), it is determined whether the driving distance after starting the vehicle is greater than a preset correction value application reference value to correct and apply the control condition of the engine 10 . Correcting and applying the control condition of the engine 10 means applying a value corrected for the EGR ratio or the oxygen concentration of the intake manifold.

To this end, in the correction application determination step (S250), the travel distance after starting the vehicle is compared with a reference value, and if the travel distance is greater than the reference value, a correction value calculation step (S260) described later is performed. Otherwise, The correction value non-applying step (S270), which will be described later, is performed.

The correction value calculation step (S260) is performed when the vehicle travel distance is greater than the vehicle travel distance compared to the preset correction value application reference value in the correction application determination step (S250), and the engine 10 The control conditions, that is, the corrected EGR ratio (EGR_cor) obtained by correcting the EGR ratio and the oxygen concentration of the intake manifold and the corrected intake manifold oxygen concentration (Inmani-O_cor) are calculated.

In the correction value calculation step (S260), the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen according to the target ratio (NOx_ratio) obtained in the target ratio calculation step (S240), engine speed (N), and engine load. Calculate the concentration (Inmani-O_cor).

Here, when calculating the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor), the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor) are calculated from the map stored in the ECU (50). -O_cor) is calculated, it is preferable to calculate the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor) by applying different maps according to the target ratio.

By correcting and controlling the opening degree of the EGR valve to a value considering the travel distance of the vehicle, even if the travel distance of the vehicle increases, by controlling the amount of nitrogen oxides actually discharged from the engine 10, the post-processing device Do not lower the purification efficiency.

The correction value non-application step (S270) is performed when the driving distance of the vehicle is not greater than the reference value in the correction application determination step (S250). In the step of not applying the correction values (S270), both the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor) are set to zero. That is, since the correction value is 0, correction is not applied. When the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor) are 0, it is not necessary to consider the driving distance of the vehicle, so that the EGR valve 33 adjusts the EGR ratio determined by other conditions. control the opening

The engine operation determination step (S280) determines whether the engine 10 is operating after the correction value calculation step (S260) or the correction value non-application step (S270) is performed.

If the engine 10 is operating in the engine operation determination step (S280), the correction control region satisfaction determination step (S210) is returned to the correction control region satisfaction determination step (S210) to the correction value calculation step. (S260) is repeatedly performed, and if the engine 10 is not operating, it ends (30).

5 shows an EGR correction control step (S300). In the EGR correction control step (S300), the initial EGR target value (EGR_des), which is the initial control value of the EGR valve 33, or the initial intake manifold, which is the oxygen concentration in the initial intake manifold, according to the operating region of the engine 10 The correction value of the EGR ratio obtained in the initial engine control condition setting step (S310) of setting the manifold target oxygen concentration (Inmani-O2_des) and the correction value acquisition step (S200) of the initial EGR target value (EGR_des) (EGR_COR) is added to obtain a corrected EGR target value (EGR_NEW) obtained by correcting the initial EGR target value (EGR_des). The initial intake manifold target oxygen concentration (Inmani-O2_des) by adding the intake manifold oxygen concentration correction value (Inmani-O_cor) obtained in the correction value acquisition step (S200) to the initial intake manifold target oxygen concentration (Inmani-O2_des) Corrected engine control condition setting step (S320) in which Inmani-O2_des) acquires the corrected intake manifold target oxygen concentration (Inmani-O2_NEW), and the difference between the corrected EGR target value (EGR_NEW) and the actual EGR ratio (EGR_act) An engine operation deviation calculation step for obtaining the EGR deviation (EGR_DVT) or the oxygen concentration deviation (Inmani-O2_dvt), which is the difference between the corrected intake manifold target oxygen concentration (Inmani-O2_NEW) and the actual intake manifold oxygen concentration (Inmani-O2_act) (S330) and an EGR valve control start step of starting control of the EGR valve 33 by calculating a control amount of the EGR valve 33 reflecting the EGR deviation (EGR_dvt) or the oxygen concentration deviation (Inmani-O2_dvt). (S340) and the control amount of the EGR valve 33 calculated in the EGR valve control start step (S340) by adding the opening amount of the EGR valve set according to the current operating range of the engine 10 to the EGR valve ( 33), a final EGR valve control value calculation step (S350) calculated with the final EGR valve control value (EGR valve Final), which is the final control amount, and the EGR valve 33 with the final EGR valve control value (EGR valve Final). and an EGR valve opening control step (S360) for controlling the opening degree of.

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In the initial engine control condition setting step (S310), an initial engine control condition is set using the driving state of the vehicle, the driving state of the engine 10, and the like. In the correction value acquisition step (S200), the EGR ratio or the oxygen concentration in the intake manifold is set as the initial EGR target value (EGR_des) or the initial EGR target value (EGR_des) according to the operating range of the engine 10 as the control condition of the engine 10. The ECU 50 sets the intake manifold target oxygen concentration (Inmani-O2_des). The initial EGR target value (EGR_des) and the initial intake manifold target oxygen concentration (Inmani-O2_des) may be obtained from a preset map according to an operating region of the engine 10 .

The correction engine control condition setting step (S320) adds the correction value obtained in the correction value acquisition step (S200) to the initial EGR target value (EGR_des) or the initial intake manifold target oxygen concentration (Inmani-O2_des), thereby correcting the correction. set the engine control conditions.

The correction values for correction of the control conditions of the engine 10 obtained in the correction value acquisition step (S200), that is, the corrected EGR ratio (EGR_cor) and the corrected intake manifold oxygen concentration (Inmani-O_cor) are the initial EGR target values. In addition to (EGR_des) and the initial intake manifold target oxygen concentration (Inmani-O2_des), a corrected target value is calculated.

For example, the corrected EGR target value is obtained by adding the corrected EGR ratio (EGR_cor) to the initial EGR target value (EGR_des), and the corrected intake manifold oxygen concentration (Inmani-O2_des) is added to the initial intake manifold target oxygen concentration (Inmani-O2_des). -O_cor) is added to obtain the corrected intake manifold target oxygen concentration (Inmani-O2_NEW).

In the engine driving deviation calculation step (S330), a difference between a target value of a condition for controlling the engine 10 and an actually measured value is obtained. That is, the EGR deviation (EGR_dvt), which is the difference between the corrected EGR target value (EGR_NEW) and the actual EGR ratio (EGR_act), is obtained, or the corrected intake manifold target oxygen concentration (Inmani-O2_NEW) and the actual intake manifold oxygen concentration ( The oxygen concentration deviation (Inmani-O2_dvt), which is the difference between Inmani-O2_act), is calculated. The actual EGR ratio (EGR_act) and the actual intake manifold oxygen concentration (Inmani-O2_act) are determined by a value used by the ECU 50 to control the EGR valve 33 or a sensor installed in the intake manifold. can be saved

The EGR deviation (EGR_dvt) and the oxygen concentration deviation (Inmani-O2_dvt) obtained in the engine operation deviation calculation step (S330) are used for PID control.

In the EGR valve control start step (S340), the control amount of the EGR valve 33 is calculated according to the EGR deviation (EGR_dvt) or the oxygen concentration deviation (Inmani-O2_dvt), and control of the EGR valve 33 is started.

The EGR valve control start step (S340) is preferably closed-loop controlled by PID (Proportional Integral Differential) control. The reason why PID control is used in the EGR valve control starting step (S340) is for precise control.

In addition, in the EGR valve control starting step (S340), a control value may be determined according to the actual oxygen amount deviation (Air_dvt) according to the EGR deviation (EGR_dvt) or the oxygen concentration deviation (Inmani-O2_dvt).

The final EGR valve control value calculation step (S350) is a preliminary EGR control value ( EGR valve pre_control) is added to calculate the final EGR valve control value (EGR valve Final), which is the final control amount of the EGR valve 33. The pre-EGR control value (EGR valve pre_control) is stored in advance as a map or the like according to the operating range of the engine 10, which is to use the existing map-based control for fast behavior of the EGR valve 33. It is for

The EGR valve opening control step (S360) is a step of controlling the EGR valve 33 with the final EGR valve control value calculated in the final EGR valve control value calculation step (S350). The ECU 50 controls the driving distance of the vehicle by reflecting the final EGR valve control value (EGR valve final).

The engine operation determination step (S370) determines whether the engine 10 is operating after the EGR valve opening control step (S360) is performed.

If the engine 10 is operating in the engine operation determination step S370, it returns to the initial engine control condition setting step S310, the above process is repeated, and the engine 10 operates. If not, it ends (30).

10: engine 11: cylinder
12: combustion pressure sensor 15: intake manifold
16: exhaust manifold 21: intake line
22: exhaust line 23: EGR line
31: turbo charger 31a: turbine
31b: compressor 32: intercooler
33: EGR valve 41: post-processing device
50: ECU 51: memory
S10: engine start phase
S20: initial reset step
S30: end stage
S100: Nitrogen Oxide Emission Acquisition Step
S110: combustion pressure measurement step
S120: Calculation of maximum combustion temperature
S130: Nitrogen Oxide Concentration Calculation Step
S140: Real-time nitrogen oxide emission calculation step
S150: engine operation judgment step
S200: correction value acquisition step
S210: Compensation Control Area Satisfaction Determination Step
S211: Environmental condition satisfaction determination step
S212: Operation condition satisfaction determination step
S220: calibration control entry step
S230: Step of Calculating Target Nitrogen Oxide Emissions
S240: Target ratio calculation step
S250: correction application judgment step
S260: Compensation value calculation step
S270: correction value non-apply step
S280: engine operation judgment step
S300: EGR correction control step
S310: initial engine control condition setting step
S320: Compensation engine control condition setting step
S330: engine operation deviation calculation step
S340: EGR valve control start step
S350: final EGR valve control value calculation step
S360: EGR valve opening control step
S370: engine operation judgment step
NOx_mass: Nitrogen oxide emissions
NOx_mass_acc: cumulative value of nitrogen oxide emissions
Target_NOx_mass_distance : Target cumulative NOx emissions
AF: air-fuel ratio
EGR valve Final: Final EGR valve control value
EGR_NEW: Corrected EGR target value
EGR_des: Initial EGR target value
EGR_act: Actual EGR rate
EGR_dvt: EGR Deviation
EGR_cor: correction value of EGR ratio
Air_dvt: Oxygen amount deviation
Inmani-O2: Oxygen concentration entering the cylinder
Inmani-O2_NEW: Corrected intake manifold target oxygen concentration
Inmani-O2_des: Initial intake manifold target oxygen concentration
Inmani-O2_act : Actual intake manifold oxygen concentration
Inmani-O2_dvt: Oxygen concentration deviation
Inmani-O_cor: correction value of intake manifold oxygen concentration
N: engine rotational speed
Pilot: Pilot injection amount
Pmax: maximum combustion pressure
Psoc: Combustion pressure at the start of combustion
Q: Engine load (total fuel amount)

Claims (22)

When the engine is started or the key is turned on, an initial reset step of setting the amount of nitrogen oxides emitted and the driving distance of the vehicle to zero, respectively;
A nitrogen oxide emission amount obtaining step of obtaining an emission amount of nitrogen oxide discharged from the engine by calculating a combustion temperature and a nitrogen oxide concentration from the combustion pressure of the engine;
A correction value acquisition step of acquiring a correction value of either the EGR ratio according to the travel distance or the concentration of oxygen flowing into the cylinder of the engine by accumulating the amount of nitrogen oxide discharged from the engine and the travel distance of the vehicle. Wow,
An EGR correction control step of obtaining a final EGR valve control value by applying the correction value obtained in the correction value acquisition step to the initial EGR ratio or the oxygen concentration of the initial intake manifold, and controlling the EGR valve with the final EGR valve control value. including,
The step of obtaining nitrogen oxide emissions,
A combustion pressure measuring step of collecting combustion pressure output to the ECU from combustion pressure sensors installed in each cylinder of the engine in real time;
A maximum combustion temperature calculation step of calculating a maximum combustion temperature, which is a maximum combustion temperature in the cylinder, based on the combustion pressure, maximum combustion pressure, oxygen concentration, and air-fuel ratio at the time of combustion start in the cylinder;
A nitrogen oxide concentration calculation step of calculating the concentration of nitrogen oxide discharged from the cylinder based on the maximum combustion temperature, the oxygen concentration of the cylinder, the fuel injection timing, the rail pressure, and the pilot injection amount;
A real-time nitrogen oxide emission calculation step of calculating the amount of nitrogen oxide discharged from the cylinder based on the nitrogen oxide concentration, air amount, and engine load obtained in the nitrogen oxide concentration calculation step. Nitrogen oxide control method. According to claim 1,
The nitrogen oxide emission step, the correction value acquisition step, and the EGR correction control step are simultaneously performed after the initial reset step is performed until the engine is stopped or the key is turned off. The nitrogen oxide control method of the reflected engine. delete According to claim 1,
In the nitrogen oxide concentration calculation step, based on the zeldovich mechanism, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that for calculating the concentration of nitrogen oxide discharged from each cylinder. According to claim 1,
Further comprising an engine operation determination step of determining whether the engine is operating after the nitrogen oxide real-time nitrogen oxide emission calculation step is performed,
If the engine is operating, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the return to the combustion pressure measuring step. According to claim 5,
In the engine operation determination step, if the engine is not operating, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the end. According to claim 1,
The correction value acquisition step,
A correction control region satisfaction determination step of determining whether the engine is operating in a correction control region in which an EGR ratio of the engine or an oxygen concentration of an intake manifold should be corrected according to the driving distance of the vehicle;
When the engine is operating in a correction control region, a correction control entry step of accumulating the amount of nitrogen oxide discharged from the engine and the driving distance of the vehicle;
A target nitrogen oxide emission calculation step of calculating a target cumulative nitrogen oxide emission amount, which is the accumulated emission amount of nitrogen oxide according to the driving distance of the vehicle;
A target ratio calculation step of calculating a ratio between an accumulated value of nitrogen oxides emitted according to the operation of the vehicle and the target cumulative nitrogen oxide emission rate;
A correction application determination step of determining whether the driving distance of the vehicle is greater than a preset correction value application reference value for applying the correction value of the EGR ratio or the oxygen concentration of the intake manifold;
and a correction value calculation step of calculating a correction value of the EGR ratio or an oxygen concentration correction value of the intake manifold when the driving distance of the vehicle is greater than the reference value for applying the correction value. Nitrogen oxide control method. According to claim 7,
In the calculation of the correction value, a correction value of the EGR ratio or a correction value of the oxygen concentration of the intake manifold is calculated from different correction maps according to the target ratio. . According to claim 7,
In the step of determining the satisfaction of the correction control region,
An environmental condition satisfaction determination step of determining whether external environmental conditions of the engine satisfy a preset correction control range;
A method for controlling nitrogen oxides of an engine reflecting a driving distance, comprising a step of determining whether the operating condition of the engine satisfies a preset correction control range. According to claim 9,
In the step of determining whether the environmental conditions are satisfied,
It is determined whether the intake air temperature of the air flowing into the engine, the atmospheric pressure of the air flowing into the engine, and the temperature of the cooling water of the engine all satisfy a preset correction control range. control method. According to claim 10,
In the step of determining the satisfaction of the environmental conditions,
If any one of the intake air temperature of the air flowing into the engine, the atmospheric pressure of the air flowing into the engine, and the temperature of the cooling water of the engine does not satisfy a preset correction control range,
The nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the step of determining the satisfaction of the correction control region is re-performed. According to claim 9,
In the step of determining whether the driving conditions are satisfied,
A method for controlling nitrogen oxides of an engine reflecting a travel distance, characterized in that determining whether the speed of the vehicle and the acceleration of the vehicle satisfy a preset correction control range. According to claim 12,
In the driving condition satisfaction determination step,
When at least one of the speed of the vehicle and the acceleration of the vehicle does not satisfy a preset correction control range, the step of determining the satisfaction of the correction control range is re-performed. . According to claim 7,
In the step of determining application of correction,
and a correction value non-application step of not applying the correction value of the EGR ratio or the oxygen concentration of the intake manifold if the driving distance of the vehicle is not greater than the reference value for applying the correction value. Nitrogen oxide control method. According to claim 14,
Further comprising an engine operation determination step of determining whether the engine is operating after the correction value calculation step or the correction value non-application step is performed,
If the engine is operating, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the return to the correction control region satisfaction determination step. According to claim 15,
In the engine operation determination step, if the engine is not operating, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the end. According to claim 9,
The environmental condition satisfaction determination step and the driving condition satisfaction determination step,
The nitrogen oxide control method of the engine reflecting the driving distance, characterized in that the environmental condition satisfaction determination step is performed after the driving condition satisfaction determination step is performed. According to claim 1,
The EGR correction control step,
An initial engine control condition setting step of setting an initial EGR target value, which is an initial control value of the EGR valve, or an initial intake manifold target oxygen concentration, which is an initial oxygen concentration in the intake manifold, according to an operating region of the engine;
or adding a correction value of the EGR ratio obtained in the correction value obtaining step to the initial EGR target value to obtain a corrected EGR target value obtained by correcting the initial EGR target value. Correction in which a corrected intake manifold target oxygen concentration in which the initial intake manifold target oxygen concentration is corrected is obtained by adding the oxygen concentration correction value of the intake manifold obtained in the correction value obtaining step to the initial intake manifold target oxygen concentration. An engine control condition setting step;
An engine operation deviation calculation step of obtaining an EGR deviation, which is a difference between the corrected EGR target value and an actual EGR ratio, or an oxygen concentration deviation, which is a difference between the corrected intake manifold target oxygen concentration and the actual intake manifold oxygen concentration;
An EGR valve control starting step of calculating a control amount of the EGR valve reflecting the EGR deviation or the oxygen concentration deviation and starting control of the EGR valve;
The final EGR valve control value (EGR valve final), which is the final control amount of the EGR valve, by adding the opening amount of the EGR valve set according to the current operating range of the engine to the control amount of the EGR valve calculated in the EGR valve control start step A step of calculating the final EGR valve control value calculated by
An EGR valve opening control step of controlling the opening of the EGR valve with the final EGR valve control value (EGR valve Final). According to claim 18,
The EGR valve control starting step is a method of controlling nitrogen oxides of an engine reflecting a travel distance, characterized in that closed-loop control by PID (Proportional Integral Differential) control. According to claim 19,
The EGR valve control initiation step,
A method of controlling nitrogen oxides of an engine reflecting a running distance, characterized in that the control value is determined according to the deviation of the actual amount of oxygen according to the deviation of the EGR or the deviation of the oxygen concentration. According to claim 18,
After the EGR valve opening control step is performed, an engine operation determining step of determining whether the engine is operating is further included,
If the engine is operating, the method of controlling nitrogen oxides of the engine reflecting the travel distance, characterized in that the return to the initial engine control condition setting step. According to claim 21,
In the engine operation determination step, if the engine is not operating, the nitrogen oxide control method of the engine reflecting the travel distance, characterized in that the end.

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