WO2016052871A1

WO2016052871A1 - Device for controlling engine according to concentration of aqueous urea solution and method for controlling engine

Info

Publication number: WO2016052871A1
Application number: PCT/KR2015/009335
Authority: WO
Inventors: 김정호
Original assignee: 두산인프라코어 주식회사
Priority date: 2014-09-30
Filing date: 2015-09-04
Publication date: 2016-04-07
Also published as: KR20160038259A; KR102177356B1

Abstract

An engine control device comprises: a reducing agent concentration sensor for measuring the concentration of a reducing agent, which is supplied to a reducing agent ejection module installed on an engine exhaust tube; and a control unit for conducting a control for changing the engine combustion condition, when the measured concentration of the reducing agent is equal to or less than a reference concentration, such that the amount of nitrogen oxide discharged from the engine becomes less than the amount of current discharge.

Description

Engine Control System and Engine Control Method According to Urea Water Concentration

The present invention relates to an engine control apparatus and an engine control method, and more particularly, to an engine control apparatus and an engine control method using the same in an engine system having a selective catalytic reduction device.

The selective catalytic reduction device may be provided as an exhaust gas aftertreatment device for reducing pollutants contained in exhaust gas discharged from the engine. The selective catalytic reduction apparatus may reduce nitrogen oxide in the exhaust gas by spraying a reducing agent such as urea water in the flow direction of the exhaust gas.

Conventionally, when the concentration quality of the urea water is lower than the reference concentration, output restriction due to the exhaust gas regulation may occur together with a warning lamp, which may cause the exhaust gas regulation to be exceeded and the deterioration of merchandise.

One object of the present invention is to provide an engine control apparatus capable of controlling an engine according to an optimum engine control parameter suitable for the concentration of current urea water.

Another object of the present invention is to provide a method for controlling an engine using the engine control device.

In order to achieve the above object of the present invention, the engine control apparatus according to the exemplary embodiments of the present invention is a reducing agent concentration sensor for measuring the concentration of the reducing agent supplied to the reducing agent injection module installed in the engine exhaust pipe, and the measurement And a control unit configured to calculate an engine control parameter capable of improving exhaust gas treatment performance when the reduced reducing agent concentration is equal to or less than a reference concentration, and then perform reducing agent concentration based exhaust gas control using the calculated engine control parameter.

In example embodiments, the engine control parameter may include at least one of an EGR rate, a fuel injection timing, and a fuel injection pressure.

In example embodiments, the controller may calculate a concentration factor of the measured reducing agent concentration with respect to the reference concentration of the reducing agent and the threshold concentration of the reducing agent and control the engine using the calculated concentration factor. .

In exemplary embodiments, the optimum EGR rate at the measured reducing agent concentration is calculated by Equation 1 below, and the optimal injection timing at the measured reducing agent concentration is calculated by Equation 2 below: The optimum fuel injection pressure at the measured reducing agent concentration may be calculated by Equation 3 below.

[Equation 1]

(Where A is the normal EGR rate, B is the limit EGR rate, and Q is the concentration factor of the measured reducing agent concentration)

[Equation 2]

(Where C is the normal fuel injection time, D is the limit fuel injection time, and Q is the concentration factor of the measured reducing agent concentration)

[Equation 3]

Where E is the normal fuel injection pressure, F is the limit fuel injection pressure, and Q is the concentration factor of the measured reducing agent concentration.

In example embodiments, the controller may control the engine using the engine control parameter and the measured reducing agent concentration information.

In example embodiments, the controller may perform at least one of increasing the EGR rate of the engine, delaying the fuel injection timing, or increasing the fuel injection pressure.

In example embodiments, the engine control apparatus may further include an allowable threshold determination unit configured to determine whether the exhaust gas discharged to the atmosphere from the rear of the engine exhaust pipe exceeds an allowable threshold.

In example embodiments, when the exhaust gas exceeds the allowable limit value, the controller may perform a control to enter a regulation immediately without a warning light and without proceeding to the reducing agent concentration based control mode.

In example embodiments, the controller may output a warning signal to the user when the detected concentration of the reducing agent is equal to or less than a reference concentration.

In order to achieve the above object of the present invention, in the engine control method according to the exemplary embodiments of the present invention, the concentration of the reducing agent supplied to the reducing agent injection module is measured. It is determined whether the measured reducing agent concentration is less than or equal to the reference concentration. When the concentration of the reducing agent is below the reference concentration, the combustion conditions of the engine are changed so that nitrogen oxides emitted from the engine are discharged less than the current emission. The engine is controlled according to the changed combustion conditions.

In example embodiments, changing the combustion conditions of the engine includes performing at least one of increasing the engine's EGR rate, delaying fuel injection timing, or reducing fuel injection pressure. can do.

In example embodiments, the changing of the combustion condition may be performed within a range in which the emission of PM in the engine exhaust gas does not exceed the exhaust gas regulation.

In exemplary embodiments, the method may further comprise determining whether the exhaust gas discharged to the atmosphere when the combustion condition is changed exceeds an allowable limit value, and wherein the exhaust gas that is usually emitted is an allowable limit value. When exceeding may further comprise the step of reducing the engine power.

In example embodiments, the method may further include outputting a warning signal to a user when the detected reducing agent concentration is less than or equal to a reference concentration.

According to exemplary embodiments, when the concentration quality of the urea water is degraded, the engine control parameter may improve the exhaust gas treatment performance of the engine based on the measured urea water concentration without immediately entering into the regulation. The engine can be controlled based on the calculation. Therefore, even if the quality of the urea water concentration is slightly lowered, the merchandise can be improved by continuously operating the construction machine under the condition of maintaining the engine output or satisfying the exhaust gas regulation with the minimum output limit.

However, the effects of the present invention are not limited to the above-mentioned effects, and may be variously expanded within a range without departing from the spirit and scope of the present invention.

1 is a block diagram illustrating an engine system in accordance with example embodiments.

2 is a cross-sectional view illustrating an engine of the engine system of FIG. 1.

FIG. 3 is a block diagram illustrating an exhaust gas treatment system installed in the exhaust pipe of FIG. 1.

4 is a block diagram illustrating an engine control apparatus of the engine system of FIG. 1.

5A is a block diagram illustrating a first calculator of FIG. 4.

5B is a block diagram illustrating a second calculator of FIG. 4.

5C is a block diagram illustrating a third calculator of FIG. 4.

6 is a flowchart illustrating an engine control method according to exemplary embodiments.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, and the following examples can be modified in various other forms, and the scope of the present invention is It is not limited to an Example. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In addition, the thickness or size of each component in the drawings are exaggerated for convenience and clarity of description.

Throughout the specification, when referring to one component "located", "connected", or "coupled" to another component, the above-described one component directly on another component " It may be interpreted that there may be other components that are in contact with, or “in connection with,” or “coupled to”. On the other hand, when one component is said to be located on another component "directly on", "directly connected", or "directly coupled", it is interpreted that there are no other components intervening therebetween. do. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Although the terms first, second, etc. are used herein to describe various members, parts, regions, and / or parts, it is obvious that these members, parts, regions, and / or parts should not be limited by these terms. Do. These terms are only used to distinguish one member, part, region or part from another region or part. Thus, the first member, part, region, or portion, which will be described below, may refer to the second member, component, region, or portion without departing from the teachings of the present invention.

Also, relative terms such as "top" or "above" and "bottom" or "bottom" may be used herein to describe the relationship of certain elements to other elements as illustrated in the figures. It may be understood that relative terms are intended to include other directions of the device in addition to the direction depicted in the figures. For example, if the device is turned over in the figures, elements depicted as present on the face of the top of the other elements are oriented on the face of the bottom of the other elements described above. Thus, the exemplary term "top" may include both "bottom" and "top" directions depending on the particular direction of the figure. If the component faces in the other direction (rotated 90 degrees with respect to the other direction), the relative descriptions used herein may be interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

Embodiments of the present invention will now be described with reference to the drawings, which schematically illustrate ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, embodiments of the inventive concept should not be construed as limited to the specific shapes of the regions shown herein, but should include, for example, changes in shape resulting from manufacturing. The following embodiments may be configured by combining one or a plurality.

1 is a block diagram illustrating an engine system in accordance with example embodiments. 2 is a cross-sectional view illustrating an engine of the engine system of FIG. 1. FIG. 3 is a block diagram showing an exhaust gas treatment system engaged with the exhaust pipe of FIG. 1. 4 is a block diagram illustrating an engine control apparatus of the engine system of FIG. 1. FIG. 5A is a block diagram illustrating the first operation unit of FIG. 4, FIG. 5B is a block diagram illustrating the second operation unit of FIG. 4, and FIG. 5C is a block diagram illustrating the third operation unit of FIG. 4.

1 to 5C, the engine system discharges the exhaust gas from the engine 10 and the engine 10 to the outside, and compresses fresh air to supply the engine 10 to the turbocharger 30. ) And an EGR device 60 for recycling a portion of the exhaust gas at the front end of the turbocharger 30 to the engine 10.

In exemplary embodiments, the engine 10 may include a diesel engine as a driving source of construction machinery such as an excavator. The engine 10 may generate power required by combustion through compression ignition. As shown in FIGS. 1 and 2, the engine 10 has a plurality of cylinders having a combustion chamber 11 installed with an injector 18 for injecting fuel to burn fuel supplied from the injector 18. And (12). The intake air supplied from the intake pipe 40 is supplied into the combustion chamber 11 through the intake port 14, and after combustion in the combustion chamber 11, the exhaust gas is discharged through the exhaust port 16 to the exhaust pipe 50. Can be.

The turbocharger 30 may be connected to the exhaust manifold 24 of the engine 10 through the exhaust pipe 50 and to the intake manifold 20 of the engine 10 through the

intake pipes

40 and 42. . The turbocharger 30 may supply fresh air to the intake manifold 20 and discharge the exhaust gas to the outside through the exhaust pipe 70.

EGR device 60 may include an EGR line 62, an EGR valve 64, and an EGR cooler 66. The exhaust gas discharged from the exhaust manifold 24 of the engine 10 may be recycled to the intake manifold 20 of the engine 10 via the EGR line 62. The EGR valve 62 is installed in the EGR line 60 and can adjust the amount (EGR rate) of the recycle exhaust gas. An EGR cooler 66 may be installed in the EGR line 62 to cool the recycle exhaust gas.

As shown in FIG. 3, the exhaust gas treatment system includes a selective catalyst reduction comprising a reducing agent injection module 82 for injecting a reducing agent for reducing nitrogen oxides in the exhaust gas discharged from the engine 10. SCR) device 80 and diesel oxidation catalyst (DOC) 72 installed in exhaust pipe 70 in front of SCR device 80.

In exemplary embodiments, the SCR apparatus 80 includes a selective reduction catalyst (not shown) installed in the exhaust pipe 70 and a reducing agent for injecting a reducing agent into the exhaust pipe 70 in front of the selective reduction catalyst. May include an injection module 82. The reducing agent injection module 82 may inject a reducing agent such as urea water to reduce nitrogen oxides in the exhaust gas discharged from the engine. Since the temperature of the exhaust gas discharged from the engine is a high temperature of several hundred degrees ??, the reducing agent injected in the exhaust pipe 70 can be vaporized immediately. The vaporized reducing agent may be mixed with the exhaust gas, and the reducing agent and the nitrogen oxide may be catalytically reacted using the selective reduction catalyst to reduce the nitrogen oxide to nitrogen gas and water.

The reducing agent injection module 82 may be connected to the urea water supply module 92 through a pipe 84 to inject urea water into the exhaust pipe 70. In addition, the urea water supply module 92 may be connected to the urea water storage tank 90 through a supply line 94a and a recovery line 94b. The urea water storage tank 90 may store an aqueous solution of urea water called AdBlue or Diesel Exhaust Fluid (DEF) for ammonia generation. The urea water concentration tank 96 is installed in the urea water storage tank 90 to detect the concentration of urea water supplied to the urea water supply module 92 in real time. Alternatively, the urea water concentration sensor 96 may be installed in the pipe 84 or the supply line 94a connected to the reducing agent injection module 82.

In exemplary embodiments, the engine system models an engine control parameter as a combustion condition and calculates an optimal parameter value to improve exhaust gas treatment performance according to the detected concentration of urea water as a reducing agent, and calculates the calculated control parameter. It may include an engine control device for controlling the engine according to.

As shown in FIG. 4, the engine control apparatus selects any one of a normal engine control mode and a reducing agent concentration based control mode according to the measured reducing agent concentration and calculates an engine control parameter for the selected control mode. It may include a first control unit 100. In addition, the engine control device may further include a second control unit 200 for controlling the engine according to the calculated control parameter.

Specifically, the first control unit 100 determines whether the measured reducing agent concentration is less than or equal to the reference concentration, the engine control mode determination unit 110 and the reducing agent to select any one of the normal control mode and the reducing agent concentration-based control mode When the concentration-based control mode is selected, it may include a parameter calculation unit 120 for calculating the engine control parameters that can reduce the pollutants emitted from the engine to satisfy the exhaust gas regulation at the measured reducing agent concentration.

The urea water concentration sensor 96 may measure the concentration of urea water in the urea water storage tank 90 in real time using an ultrasonic method. For example, in consideration of the performance of the exhaust gas treatment system, exhaust gas regulation, and the like, a reference concentration of urea water (eg, 32.5%) and a limit concentration of urea (eg, 26%) may be set. have. However, if the user adds a diluent such as water to the urea water storage tank 90 or the concentration of urea water is not maintained smoothly, the concentration of urea water in the urea water storage tank 90 may drop below the reference concentration. have.

The engine control mode determiner 110 determines whether the detected concentration of urea is less than or equal to the reference concentration, and selects a normal engine control mode when the reference concentration is satisfied. have. For example, when the concentration of the detected urea water is less than the reference concentration (32.5%) and greater than the threshold concentration (26%), the exhaust gas regulation is performed at the detected urea concentration without immediately entering into regulation. It is possible to select to perform a control mode for calculating a control parameter that can be satisfied.

In example embodiments, the engine control mode determination unit 110 may output a warning signal to the user when the detected concentration of the urea water is equal to or less than a reference concentration. The engine control device may further include a warning display device for displaying a warning signal to a user. For example, the warning display device may include a warning light, a buzzer or a display device installed in the cab. When the warning display device is activated, the user may take measures to check the concentration of urea water and maintain the concentration of urea water at a reference concentration.

When the urea concentration concentration based control mode is selected, the parameter calculator 120 may calculate an engine control parameter that satisfies the exhaust gas regulation from the measured urea concentration. The parameter calculating unit 120 controls at least one of the optimal engine EGR rate, fuel injection timing and fuel injection pressure to reduce pollutants, for example, nitrogen oxides, emitted from the engine at the measured urea water concentration. Parameters can be calculated. When the urea concentration concentration-based control mode is selected, the parameter calculating unit 120 maintains a current engine output or reduces an engine control parameter that can reduce NOx in exhaust gas with a minimum torque reduction. Can be modeled and calculated The parameter calculator 120 may construct and store a control model for the urea water concentration based control mode based on the reducing agent concentration, the fuel injection timing and the exhaust gas treatment performance according to the injection pressure, the intake and exhaust dynamics of the engine, and the like. .

As shown in FIGS. 5A to 5C, the parameter calculating unit 120 calculates an EGR rate capable of reducing nitrogen oxides (NOx) in exhaust gas at the measured reducing agent concentration. A second calculation unit 124 for calculating a fuel injection timing capable of reducing nitrogen oxides in exhaust gas at the measured reducing agent concentration and a fuel injection pressure for reducing nitrogen oxides in exhaust gas at the measured reducing agent concentration; The third calculator 126 may be included.

When the urea solution concentration-based control mode is selected, the first calculator 122 may calculate an optimal EGR rate for reducing nitrogen oxides in the exhaust gas at the currently measured urea solution concentration. The first calculation unit 122 considers the normal EGR rate (A) at the urea water reference concentration and the limit EGR rate (B) at the urea water limit concentration according to the concentration factor (Q) of the urea water concentration currently measured. As the final control parameter, the optimal EGR rate can be calculated.

For example, if the urea water reference concentration is 30% and the urea water limit concentration is 25%, if the currently measured urea water concentration (X (%)) is 28.75%, the urea water concentration factor (Q) is 0.75, and If the measured urea water concentration (X (%)) is 27.5%, the urea water concentration factor (Q) is 0.5. If the currently measured urea water concentration (X (%)) is 26.25%, the urea water concentration factor (Q) is 0.25.

At normal urea water concentration (in normal control mode), the normal EGR rate (A) is determined according to engine rpm, and the engine rpm at which the dynamic characteristics of the engine, particulate matter (PM), etc. satisfy the exhaust gas regulation at the urea water limit concentration. The marginal EGR rate B can be determined accordingly. Therefore, the optimal EGR rate in the currently measured urea water concentration factor Q can be calculated by the following equation (1).

For example, if the urea water concentration factor Q is 0.5, the normal EGR rate is 20%, and the limit EGR rate is 30%, the optimal EGR rate (%) can be calculated by the following equation (2). .

Accordingly, the first calculator 122 may calculate an optimal EGR rate within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration. When the EGR rate is determined by the first calculator 122, an EGR rate control signal may be output, and the EGR rate control signal may be input to the EGR controller 210 of the second controller 200.

When the urea solution concentration-based control mode is selected, the second calculator 124 may calculate an optimal fuel injection timing for reducing nitrogen oxide in the exhaust gas at the currently measured urea solution concentration. The second calculation unit 124 determines the normal fuel injection timing (C) at the urea water reference concentration and the limit fuel injection timing (D) at the urea water limit concentration according to the concentration factor (Q) of the urea water concentration currently measured. In consideration, the optimum fuel injection timing can be calculated as the final control parameter.

The normal fuel injection timing (C) is determined according to the engine rpm at the urea water level concentration (in normal control mode), and the engine's dynamic characteristics, PM (particulate matters), etc. at the urea water limit concentration satisfy the emission regulations. The limit fuel injection timing D according to the rpm can be determined. Therefore, the optimum fuel injection timing in the currently measured urea water concentration factor Q can be calculated by the following equation (3).

For example, when the urea water concentration factor Q is 0.5, the normal fuel injection timing is BTDC (Before Top Dead Center) 3 and the limit fuel injection timing is ATDC (After Top Dead Center) 1, the optimum fuel injection timing is It can be calculated by the following equation (4).

Accordingly, the second calculator 124 may calculate the optimal fuel injection timing within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration. When the fuel injection timing is determined by the second calculator 124, a fuel injection timing control signal may be output, and the fuel injection timing control signal may be input to the fuel injection timing controller 220 of the second controller 200. .

When the urea solution concentration-based control mode is selected, the third calculator 126 may calculate an optimal fuel injection pressure for reducing nitrogen oxides in the exhaust gas at the currently measured urea solution concentration. The third calculation unit 126 calculates the normal fuel injection pressure E at the urea water reference concentration and the limit fuel injection pressure F at the urea water limit concentration according to the concentration factor Q of the currently measured urea water concentration. In consideration, the optimum fuel injection pressure can be calculated as the final control parameter.

In the urea water standard concentration (in the normal control mode), the normal fuel injection pressure (E) is determined according to the engine rpm, and at the urea water limit concentration, the dynamic characteristics of the engine, the PM (particulate matters), etc. satisfy the emission regulations. The limit fuel injection pressure F depending on the rpm can be determined. Therefore, the optimum fuel injection pressure in the currently measured urea water concentration factor Q can be calculated by the following equation (5).

For example, if the urea water concentration factor Q is 0.5, the normal fuel injection pressure is 1400 bar, and the limit fuel injection pressure is 1500 bar, the optimum fuel injection pressure bar can be calculated by the following equation (6). have.

Accordingly, the third calculator 126 may calculate an optimum fuel injection pressure within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration. When the fuel injection pressure is determined by the third calculator 126, a fuel injection pressure control signal may be output, and the fuel injection pressure control signal may be input to the fuel injection pressure controller 230 of the second controller 200. .

In example embodiments, when performing engine control according to the control parameter calculated by the parameter calculating unit 120, the first controller 100 may determine whether the exhaust gas discharged from the engine exceeds an allowable limit value. It may further include a tolerance threshold determination unit 130 for determining whether or not.

The allowable threshold value determination unit 130 satisfies the exhaust gas regulation when the engine control is performed according to the control parameters calculated by the parameter calculating unit 120 (engine EGR rate, fuel injection timing, fuel injection pressure). It is possible to determine whether NOx / PM is released.

The allowable threshold value determination unit 130 receives and analyzes the control signals output from the parameter calculating unit 120 and analyzes the control signals. When the engine control is performed according to the urea concentration concentration-based control mode, the exhaust gas (NOx / It is possible to predict whether the PM) exceeds the tolerance limit. Alternatively, the allowable threshold determination unit 130 measures the concentration of the pollutant in the exhaust gas discharged to the atmosphere from the rear end of the engine exhaust pipe 70, and determines whether the measured concentration exceeds the allowable threshold value. Can be.

If the allowable limit value is exceeded, torque reduction may be achieved by immediately entering the regulation without displaying a warning lamp and proceeding to the urea concentration concentration based control mode. In addition, when the measured urea concentration is less than the limit concentration, the allowable limit value determination unit 130 may output a control signal to raise a warning lamp and proceed to the normal control mode, and torque reduction in the normal control mode. This can be done.

The second control unit 200 may be included in an engine control unit (ECU) for controlling the engine system. For example, the second control unit may receive signals regarding engine rpm, engine torque, vehicle speed, throttle valve, air amount, and the like. In addition, the first control unit 100 may be installed as a separate controller or implemented in the form of control logic embedded in the engine control unit (ECU).

The EGR controller 210 of the second control unit 200 controls the rate (that is, the EGR rate) of recirculating the engine 10 as EGR gas by adjusting the EGR valve 64 based on the EGR rate control signal. Can be. The fuel injection timing controller 220 of the second controller 200 may control the fuel injection timing of the injector 18 based on the fuel injection timing control signal. The fuel injection pressure controller 230 of the second controller 200 may control the fuel injection pressure of the injector 18 based on the fuel injection pressure control signal.

In addition, the second controller 200 may control the engine system based on a control signal for the normal control mode from the first controller 100.

As described above, according to the engine control apparatus, when the concentration quality of urea water is lowered, it is possible to improve the exhaust gas treatment performance of the engine based on the measured urea water concentration without entering into regulation immediately. The engine control parameter can be calculated and the engine can be controlled based on this. Thus, even if the urea concentration concentration quality is slightly degraded, the construction machine can continue to operate under conditions that maintain engine output or meet emission regulations with minimum power limitations.

Hereinafter, a method of controlling the engine system using the engine control device of FIG. 3 will be described.

1, 2, 3, 4 and 6, the concentration of the reducing agent supplied to the reducing agent injection module 82 may be monitored in real time (S100).

In example embodiments, the concentration of urea water supplied to the urea water supply module 92 from the urea water concentration sensor 96 installed in the urea water storage tank 90 may be measured in real time.

Subsequently, it is determined whether the measured reducing agent concentration is less than or equal to the reference concentration, and selects one control mode among the normal control mode and the reducing agent concentration based control mode (S110).

In example embodiments, the normal engine control mode may be selected when the reference concentration is satisfied by determining whether the detected concentration of the urea water is less than or equal to the reference concentration, and if the concentration is less than or equal to the reference concentration, the urea concentration concentration based control mode may be selected. . For example, in consideration of the performance of the exhaust gas treatment system, exhaust gas regulation, and the like, a reference concentration of urea water (eg, 32.5%) and a limit concentration of urea (eg, 26%) may be set. have. However, if the user adds a diluent such as water to the urea water storage tank 90 or the concentration of urea water is not maintained smoothly, the concentration of urea water in the urea water storage tank 90 may drop below the reference concentration. have.

If the detected concentration of urea water is less than the reference concentration (eg, 32.5%) and greater than the threshold concentration (26%), the exhaust gas is not regulated immediately, but the exhaust gas regulation is performed at the detected urea concentration. It is possible to select to perform a control mode for calculating a control parameter that can be satisfied.

When the reducing agent concentration-based control mode is selected, calculates an engine control parameter that can improve the exhaust gas treatment performance at the measured reducing agent concentration and controls the engine based on this, and when the normal control mode is selected, normal control. The engine is controlled according to the parameter (S130).

In exemplary embodiments, when the urea concentration concentration-based control mode is selected, an optimum engine EGR rate, fuel injection timing, and fuel injection pressure may be used to improve exhaust gas treatment performance at the measured urea concentration. At least one control parameter may be calculated. Engine control parameters can be modeled and calculated to maintain current engine power or reduce NOx in the exhaust with minimal torque reduction.

For example, when the urea concentration concentration-based control mode is selected, an optimal EGR rate for reducing nitrogen oxides in the exhaust gas may be calculated at the currently measured urea concentration. An optimal EGR rate can be determined as the final control parameter between the normal EGR rate at the urea water reference concentration and the limit EGR rate at the urea water limit concentration based on the currently measured urea water concentration. Accordingly, the optimum EGR rate can be calculated within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration.

When the urea concentration concentration based control mode is selected, an optimal fuel injection timing for reducing nitrogen oxides in the exhaust gas at the currently measured urea concentration may be calculated. The optimal fuel injection timing can be determined as the final control parameter between the normal fuel injection timing at the urea water reference concentration and the limit fuel injection timing at the urea water limit concentration based on the currently measured urea water concentration. Accordingly, the optimum fuel injection timing may be calculated within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration.

When the urea concentration concentration based control mode is selected, an optimal fuel injection pressure for reducing nitrogen oxides in the exhaust gas may be calculated at the currently measured urea concentration. The optimal fuel injection pressure can be determined as the final control parameter between the normal fuel injection pressure at the urea water reference concentration and the limit fuel injection pressure at the urea water limit concentration based on the concentration of the urea water concentration currently measured. Accordingly, the optimum fuel injection pressure may be calculated within a range in which pollutants such as PM do not exceed the exhaust gas regulation at the currently measured urea water concentration.

In example embodiments, when performing engine control according to the calculated control parameter, it may be determined whether the exhaust gas discharged from the engine exceeds an allowable threshold value (S122).

When performing engine control according to the calculated control parameters (engine EGR rate, fuel injection timing, fuel injection pressure), it is possible to determine whether or not exhaust gas (NOx / PM) satisfying the exhaust gas regulation is discharged. have. That is, when engine control is performed according to the urea water concentration based control mode, it is possible to predict whether the exhaust gas (NOx / PM) discharged from the engine exceeds an allowable limit value. If the allowable limit value is exceeded, a warning lamp may be displayed to enter the regulation immediately without proceeding to the urea concentration concentration control mode. For example, when exceeding an allowable threshold, the engine can be controlled to drastically reduce the output of the engine or to reduce the engine rpm (idle running). In addition, if the detected concentration of urea is less than the reference concentration may output a warning signal to the user (S124). For example, the user is informed using a display device such as a warning light, buzzer or display device installed inside the cab, and the user checks the concentration of the urea water and maintains the concentration of the urea water at the reference concentration. Can be taken.

In addition, when the detected urea concentration is smaller than the threshold concentration, a warning lamp may be displayed to proceed to the normal control mode, and torque reduction may be achieved in the normal control mode.

Although the above has been described with reference to the embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be appreciated.

* Explanation of the sign

10: engine 11: combustion chamber

12: cylinder 14: intake port

16: exhaust port 18: injector

20: intake manifold 22: exhaust manifold

30: turbocharger 32: turbine

33: turbine wheel 34: compressor

35: compressor wheel 40: intake pipe

42: intake air supply pipe 50: exhaust pipe

60: EGR device 62: EGR line

64: EGR valve 66: EGR cooler

70: exhaust pipe 72: diesel oxidation catalyst

80: SCR device 82: reducing agent injection module

84: pipe 90: urea water storage tank

92: reducing agent injection module 96: urea water concentration sensor

100: first control unit 110: engine control mode determination unit

120: parameter calculator 122: first calculator

124: second calculator 126: third calculator

130: tolerance limit determination unit 200: second control unit

210: EGR controller 220: fuel injection timing controller

230: fuel injection pressure controller

Claims

Reductant concentration sensor for measuring the concentration of the reducing agent supplied to the reducing agent injection module installed in the engine exhaust pipe; And

An engine including a controller configured to calculate an engine control parameter for improving exhaust gas treatment performance when the measured concentration of the reducing agent is less than or equal to a reference concentration, and then perform a reducing agent concentration-based exhaust gas control using the calculated engine control parameter; controller.
The engine control apparatus of claim 1, wherein the engine control parameter comprises at least one of an EGR rate, a fuel injection timing, and a fuel injection pressure.
The engine control apparatus of claim 2, wherein the controller calculates a concentration factor of the measured reducing agent concentration with respect to the reference concentration of the reducing agent and the threshold concentration of the reducing agent, and controls the engine using the calculated concentration factor.
The method according to claim 3, wherein the optimum EGR rate at the measured reducing agent concentration is calculated by Equation 1 below, and the optimum injection timing at the measured reducing agent concentration is calculated by Equation 2 below. The optimum fuel injection pressure at the reduced reducing agent concentration is calculated by the following equation (3).

[Equation 1]

(Where A is the normal EGR rate, B is the limit EGR rate, and Q is the concentration factor of the measured reducing agent concentration)

[Equation 2]

(Where C is the normal fuel injection time, D is the limit fuel injection time, and Q is the concentration factor of the measured reducing agent concentration)

[Equation 3]

Where E is the normal fuel injection pressure, F is the limit fuel injection pressure, and Q is the concentration factor of the measured reducing agent concentration.
The engine control apparatus of claim 1, wherein the controller controls the engine using the engine control parameter and the measured reducing agent concentration information.
The method of claim 1, wherein the control unit controls to change the combustion condition of the engine when the measured concentration of the reducing agent is greater than the threshold concentration of the reducing agent, and controls to enter the regulation immediately when the concentration of the reducing agent is below the threshold concentration. Engine control unit.
The engine control apparatus of claim 1, wherein the controller performs at least one of increasing the EGR rate of the engine, delaying fuel injection timing, or increasing fuel injection pressure.
The engine control apparatus of claim 1, further comprising a tolerance limit determination unit configured to determine whether the exhaust gas discharged to the atmosphere from the rear of the engine exhaust pipe exceeds an allowable threshold.
The engine control apparatus of claim 8, wherein the controller is configured to perform a control to enter a regulation immediately without raising a warning lamp and proceeding to the reducing agent concentration based control mode when the exhaust gas exceeds the allowable limit value.
The engine control apparatus of claim 1, wherein the controller outputs a warning signal to a user when the detected concentration of the reducing agent is equal to or less than a reference concentration.
Measuring the concentration of the reducing agent supplied to the reducing agent injection module;

Determining whether the measured reducing agent concentration is equal to or less than a reference concentration;

Changing combustion conditions of the engine such that nitrogen oxides emitted from the engine are discharged less than current emissions when the concentration of the reducing agent is less than the reference concentration; And

And controlling the engine in accordance with the changed combustion conditions.
12. The engine of claim 11, wherein changing the combustion conditions of the engine comprises performing at least one of increasing the engine's EGR rate, delaying fuel injection timing, or reducing fuel injection pressure. Control method.
The engine control method of claim 11, wherein the changing of the combustion condition is performed within a range in which the emission of PM in the engine exhaust gas does not exceed the exhaust gas regulation.
12. The method of claim 11, further comprising: determining whether the exhaust gas discharged to the atmosphere when the combustion condition is changed exceeds an allowable limit value; And

Reducing the engine output when the exhaust gas discharged to the atmosphere exceeds an allowable threshold.
The engine control method of claim 11, further comprising outputting a warning signal to a user when the detected reducing agent concentration is less than or equal to a reference concentration.