Nitrogen oxide reducing agent injection method and program product thereof

Abstract

The invention provides a nitrogen oxide reducing agent injection method, which is used for a diesel engine post-processing system, works in a first injection step after an engine is started, and simultaneously carries out a starting temperature verification step to compare whether the temperature of a peripheral verification point of a nitrogen oxide sensor is greater than a preset temperature or not; if the result in the temperature verification step is no, entering a dew elimination step and then starting a nitrogen oxide sensor; if the result in the temperature checking step is yes, directly entering the sensor starting step; after the sensor starting step is completed, whether the nitrogen oxide sensor meets the standard injection condition or not is judged, and when the nitrogen oxide sensor meets the standard injection condition, the reducing agent injector is controlled to inject the reducing agent according to the nitrogen oxide amount obtained based on the measurement data of the nitrogen oxide sensor.

Description

Technical Field

[0001] The invention relates to the field of tail gas post-treatment, in particular to a method for injecting a nitrogen oxide reducing agent after a diesel engine is started. Background Art

[0002] In the after-treatment system of diesel vehicles, removing nitrogen oxides from exhaust gas is an important issue. Now one method of removing nitrogen oxides is to inject a reducing agent into the tailpipe to reduce harmful nitrogen oxides into harmless nitrogen. How to accurately measure the content of nitrogen oxides in the tailpipe is the premise of accurately controlling the injection of the reducing agent. An important method for measuring the nitrogen oxide content in the tailpipe is to use a nitrogen oxide sensor arranged in the tailpipe. However, there are many limitations on the effective operation of the nitrogen oxide sensor, including that the data measured by the nitrogen oxide sensor is only sufficiently reliable after reaching the standard working conditions, and the data before this is not reliable. In addition, if the vehicle engine is turned off and does not enter the working state for a long time, the temperature of the nitrogen oxide sensor will decrease, so that dew will form on the surface of the nitrogen oxide sensor. Before the dew is eliminated, if the nitrogen oxide sensor is heated, it is easy to damage the material on the surface of the nitrogen oxide sensor. Therefore, before the nitrogen oxide sensor reaches the standard working conditions, the dew elimination work on the surface of the nitrogen oxide sensor must be completed.

[0003] However, not all cases will have dew on the surface of the NOx sensor. For example, if the engine is restarted within a short period of time after being turned off, no dew will form on the surface of the NOx sensor. In this case, it is a waste of time to remove the dew on the surface of the NOx sensor. As a result, the vehicle cannot inject the reducing agent based on the accurate measurement value of the NOx sensor for a longer period of time, so as to reduce the NOx more effectively. Summary of the invention

[0004] The object of the present invention is to provide a reducing agent injection method for a nitrogen oxide sensor, which can accurately control the injection of the reducing agent as early as possible.

[0005] In order to achieve the above-mentioned purpose of the invention, the present invention provides a method for injecting a nitrogen oxide reducing agent, which is used in a diesel engine aftertreatment system. The diesel engine aftertreatment system includes a nitrogen oxide sensor, a reducing agent injector and a controller. The controller collects information from the nitrogen oxide sensor and controls the injection of the reducing agent injector, which includes the following steps:

[0006] An engine starting step, after starting the engine, entering a first injection step and a temperature verification step;

[0007] a temperature verification step, comparing whether the temperature of the inspection point around the nitrogen oxide sensor is greater than a preset temperature, if the result in the temperature verification step is no, then entering the dew elimination step and the first injection step; if the result in the temperature verification step is yes, then entering the sensor startup step and the first injection step;

[0008] a dew removing step for removing dew on the nitrogen oxide sensor;

[0009] a dew judging step, judging whether the dew eliminating step is completed, and entering the sensor starting step after completion;

[0010] In the first injection step, the controller controls the reductant injector to inject the reductant in a preset amount;

[0011] A sensor starting step, starting the nitrogen oxide sensor;

[0012] a nitrogen oxide determination step, determining whether the nitrogen oxide sensor satisfies a standard injection condition, and entering a second injection step and terminating the first injection step when the nitrogen oxide sensor satisfies the standard injection condition;

[0013] In the second injection step, the controller controls the reductant injector to inject the reductant in an amount of nitrogen oxides obtained based on measurement data of the nitrogen oxide sensor.

[0014] To achieve the above invention objectives, the present invention also provides a nitrogen oxide reductant injection system, including a nitrogen oxide sensor, a reductant injector and a controller, wherein the controller can collect signals from the nitrogen oxide sensor and control the reductant injector to complete the injection in the manner described above.

[0015] In order to achieve the above invention objectives, the present invention also provides a computer executable program product, and the computer executable program can implement the above method when executed.

[0016] By using the technical solution provided by the present invention, the dew elimination step is omitted under certain conditions, so that the exhaust gas after-treatment system can inject the reducing agent based on the measurement data of the nitrogen oxide sensor, and the reducing agent injection can be accurately controlled as early as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The exemplary embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are only used to explain the present application but not to limit the scope of the present application. In the attached drawings:

[0018] Figure 1 is a structural block diagram of a nitrogen oxide reducing agent injection system according to the present invention.

[0019] Figure 2 is a flow chart of a nitrogen oxide reducing agent injection method according to the present invention. DETAILED DESCRIPTION

[0020] It should be understood that the drawings are only used to illustrate the present application.

[0021] See also Figure 1 As shown, it is a structural block diagram of the nitrogen oxide reducing agent injection system according to the present invention. The nitrogen oxide reducing agent injection system of the present invention is arranged on the exhaust gas after-treatment system of the diesel engine, and includes a nitrogen oxide sensor 1, a reducing agent injector 2 and a controller 3. The nitrogen oxide sensor 1 is generally arranged at the front end of the exhaust pipe in the exhaust gas after-treatment system to measure the content of nitrogen oxides in the exhaust gas passing through the exhaust pipe. The reducing agent injector 2 is used to inject the nitrogen oxide reducing agent, so that the nitrogen oxides in the exhaust gas can react with the ammonia in the nitrogen oxide reducing agent to generate harmless nitrogen gas, which is discharged into the atmosphere. The reducing agent generally uses urea aqueous solution. The controller 3 can collect the signal generated in the nitrogen oxide sensor 1 and control the injection timing and injection amount of the reducing agent injector 2. In some embodiments including this embodiment, the controller 3 is part of the control center that controls the overall exhaust gas after-treatment system. In other embodiments, the controller can be set separately.

[0022] Figure 2 The method for injecting a nitrogen oxide reducing agent according to the present invention is used in a diesel engine aftertreatment system, especially as Figure 1 In the nitrogen oxide reducing agent injection system shown. In some implementations including this embodiment, the nitrogen oxide reducing agent injection method of the present invention first includes an engine starting step S000, starting the diesel engine, and then performing a temperature verification step S001 and a first injection step S003. In the first injection step S003, the controller 3 controls the reducing agent injector 2 to inject the reducing agent, but since the nitrogen oxide sensor 1 does not meet the standard injection conditions at this time, the measured value of the nitrogen oxide sensor 1 is not credible at this time, so in the first injection step S003, the measured value of the nitrogen oxide sensor 1 is not used as the basis for calculating the reducing agent injection amount, but the reducing agent is injected based on the preset injection amount. In this embodiment, the first injection step S003 starts directly after the engine starting step S000 and continues to the second injection step S007. Because the first injection step and the second injection step are both injected using the same reducing agent injector, the first injection step naturally ends when the second injection step starts.

[0023] In the temperature verification step S001, firstly, the temperature of the inspection point around the nitrogen oxide sensor 1 is compared to see whether it is greater than the preset temperature. If the result in the temperature verification step S001 is no, then the dew elimination step S002 is entered; if the result in the temperature verification step S001 is yes, then the sensor start step S005 is entered. In the temperature verification step S001, it is necessary to set a temperature verification point. The setting of the temperature verification point is based on experience. The technicians in this profession can determine the preferred position of setting the temperature verification point around the nitrogen oxide sensor. The so-called periphery in this application means that the temperature of the position can be linked with the temperature of the nitrogen oxide sensor, so that the temperature of the nitrogen oxide sensor can be judged to a certain extent. In this embodiment, firstly, taking the upper engine verification point set on the engine as an example, the engine verification temperature can be set to 30 degrees to 100 degrees, such as 40, 50, and 60 degrees through experiments. Of course, the tailpipe verification point on the tailpipe can also be set as an example. The tailpipe verification temperature can be set to 30 degrees to 200 degrees, such as 40, 60, and 80 degrees through experiments. For the setting of the temperature check point, only one point may be set, or both the engine check point and the tailpipe check point may be set, and when the check temperature results of the two check points are both yes, the result of the temperature check step is considered to be yes. Of course, in some other embodiments, any check temperature result may be considered to be yes, and the result of the temperature check step is considered to be yes.

[0024] In summary, in the temperature verification step, if the judgment result is "no", the dew elimination step S002 is entered. In the dew elimination step S002, the dew on the nitrogen oxide sensor 1 is eliminated by heating. In the following dew determination step S004, it is determined whether the dew elimination step is completed by the size of the exhaust gas calorific value. If the overall calorific value of the heated nitrogen oxide sensor exceeds the preset value, it is considered that the dew elimination step is completed, and after completion, the sensor start step S005 is entered.

[0025] From the above, it can be seen that in the temperature verification step, if the judgment result is yes, the first spraying step S003 and the sensor activation step S005 are entered. The spraying condition in the first spraying step S003 is no different from the above. That is, if the judgment result is yes, it is considered that dew elimination is not needed at this time, and the dew elimination step S002 is skipped and the sensor activation step S005 is directly performed.

[0026] In the sensor start-up step S005, the nitrogen oxide sensor is heated by heating, and a series of tests are performed to make the nitrogen oxide sensor reach a predetermined temperature, generally reaching more than 700 degrees. During the sensor start-up step, the nitrogen oxide judgment step S006 is performed to judge whether the nitrogen oxide sensor 1 meets the standard injection condition, and when the nitrogen oxide sensor 1 meets the standard injection condition, the second injection step S007 is entered and the first injection step S003 is terminated. Whether the nitrogen oxide sensor 1 meets the standard injection condition in this embodiment includes the following judgments: whether the voltage is within a preset range, whether the temperature is within a preset range, whether the oxygen signal is normal, and whether the nitrogen oxide sensor signal is normal. At this point, it is considered that the nitrogen oxide sensor meets the standard injection condition. Then, in the second injection step S007, the controller 3 controls the reductant injector 2 to inject the reductant with the amount of nitrogen oxide obtained based on the measurement data of the nitrogen oxide sensor 1. At this time, because the calculation basis of the reductant is the nitrogen oxide content measured in real time by the nitrogen oxide sensor, the injection of the reductant is accurate.

[0027] Using the above method, when the temperature of the temperature check point is within the preset temperature range, it is reasonably judged that there is no dew on the nitrogen oxide sensor at this time, so the dew elimination step is directly skipped and the sensor startup step is performed, so as to make the nitrogen oxide sensor signal reliable as soon as possible, thereby accurately controlling the injection of the reducing agent.

[0028] In addition, the present invention also provides a computer executable program product, which implements the above method when executed.

[0029] The present application has been described in detail above in conjunction with specific embodiments. Obviously, the above description and the embodiments shown in the accompanying drawings should be understood as exemplary and do not constitute a limitation to the present application. For those skilled in the art, various modifications or changes can be made to the present application without departing from the spirit of the present application, and these modifications or changes do not depart from the scope of the present application.

Claims

1. A method for injecting a nitrogen oxide reducing agent, used in a diesel engine aftertreatment system, the diesel engine aftertreatment system comprising a nitrogen oxide sensor (1), a reducing agent injector (2) and a controller (3), the controller (3) collecting information from the nitrogen oxide sensor (1) and controlling the injection of the reducing agent injector (2), characterized in that The following steps are involved: An engine starting step (S000), after starting the engine, entering a first injection step (S003) and a temperature verification step (S001); A temperature verification step (S001), comparing whether the temperature of the inspection point around the nitrogen oxide sensor (1) is greater than a preset temperature, if the result in the temperature verification step (S001) is no, then entering a dew elimination step (S002); if the result in the temperature verification step (S001) is yes, then entering a sensor start-up step (S005); A dew removal step (S002) for removing dew on the nitrogen oxide sensor (1); Dew determination step (S004), determining whether the dew elimination step is completed, and entering the sensor activation step (S005) after completion; In the first injection step (S003), the controller (3) controls the reducing agent injector (2) to inject the reducing agent in a preset amount; A sensor starting step (S005), starting the nitrogen oxide sensor (1); a nitrogen oxide determination step (S006), determining whether the nitrogen oxide sensor (1) satisfies a standard injection condition, and when the nitrogen oxide sensor (1) satisfies the standard injection condition, entering a second injection step (S007) and terminating the first injection step (S003); In the second injection step (S007), the controller (3) controls the reducing agent injector (2) to inject the reducing agent in an amount of nitrogen oxides obtained based on the measurement data of the nitrogen oxide sensor (1).

2. The nitrogen oxide reducing agent injection method according to claim 1, wherein: The peripheral inspection point is an engine verification point set on the engine. When the engine verification point is selected for verification, the preset temperature is the engine verification temperature.

3. The nitrogen oxide reducing agent injection method according to claim 2, wherein: The engine calibration temperature is 30 to 100 degrees, for example, 40, 50 or 60 degrees.

4. The method for injecting a nitrogen oxide reducing agent according to claim 1, wherein: The peripheral inspection point is an exhaust pipe verification point arranged on the engine exhaust pipe. When the exhaust pipe verification point is selected for verification, the preset temperature is the exhaust pipe verification temperature.

5. The nitrogen oxide reducing agent injection method according to claim 4, wherein: The tailpipe calibration temperature is 30 degrees to 200 degrees, for example, 40, 60 or 80 degrees.

6. The nitrogen oxide reducing agent injection method according to claim 1, wherein: The peripheral check points are selected from both an engine check point set on the engine and an exhaust pipe check point set on the engine exhaust pipe (4); when the engine check point is selected for check, the preset temperature is the engine check temperature; when the exhaust pipe check point is selected for check, the preset temperature is the exhaust pipe check temperature.

7. The nitrogen oxide reducing agent injection method according to claim 6, wherein: The engine calibration temperature is 30 to 100 degrees, such as 40, 50 or 60 degrees, and the exhaust pipe calibration temperature is 30 to 200 degrees, such as 40, 60 or 80 degrees.

8. The nitrogen oxide reducing agent injection method according to any one of claims 1 to 7, wherein: The standard injection condition includes one or more of a voltage being within a preset range, a temperature being within a preset range, an oxygen signal being valid, and a nitrogen oxide signal being valid.

9. A nitrogen oxide reducing agent injection system, comprising a nitrogen oxide sensor (1), a reducing agent injector (2) and a controller (3), characterized in that: The controller (3) can collect the signal of the nitrogen oxide sensor (1) and control the reducing agent injector (2) to inject in a manner to complete the method according to any one of claims 1 to 8.

10. A computer executable program product, characterized in that: The computer executable program performs the method according to any one of claims 1 to 8 when executed.

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