Urea injection amount control method and system and automobile

Abstract

The invention discloses a urea injection amount control method and system and an automobile, and relates to the field of automobile tail gas treatment. The method comprises the steps that under the condition that an engine reaches a stable state, the NH3 leakage state is determined according to NOx data before and after urea injection, and the urea injection amount is adjusted according to the NH3 leakage state; the steady state means that steady state parameters related to the steady state of the engine meet steady state conditions. The urea spraying amount can be correspondingly adjusted and controlled according to the leakage state of NH3, so that the situation of over-spraying of urea is avoided or reduced, and then the use cost is reduced; and particularly for a vehicle which is in a high-speed operation scene for a long time and has a relatively stable engine state, the urea consumption can be effectively reduced.

Description

Technical Field

[0001] The present application relates to the field of automobile exhaust treatment, and specifically to a method and system for controlling the amount of urea injection, and an automobile. Background Art

[0002] Urea-SCR (Selective Catalytic Reduction) is a technology used to reduce NOx (nitrogen oxides) emissions from diesel vehicle exhaust. This technology injects a urea aqueous solution (usually 32.5% by mass) into the engine exhaust system (exhaust pipe) through a urea injection system. Urea decomposes at high temperatures to produce NH3 (ammonia), which reacts with NOx under the action of a catalyst to produce harmless nitrogen and water, thereby reducing NOx emissions.

[0003] At present, Urea-SCR technology is considered to be the most effective method to reduce NOx emissions from automotive diesel engines. Through the urea injection system, a 32.5% urea aqueous solution is sprayed into the exhaust pipe. It needs to go through the processes of wall impact, evaporation, hydrolysis, pyrolysis, etc. to convert into NH3, and then react with NO x reaction, reducing the exhaust NOx emissions of diesel engines.

[0004] At present, the treatment of diesel engine exhaust generally adopts the structure of DOC (Diesel Oxidation Catalyst) + DPF (Diesel Particulate Filter) + SCR + ASC (Ammonia Slip Catalyst), and Urea-SCR technology is still used to reduce NO x emission.

[0005] DOC has three main functions: reducing HC (hydrocarbon) emissions: oxidizing HC in the exhaust gas into H2O and CO2; oxidizing NO into NO2: NO2 oxidizes the carbon particles captured by the DPF into gaseous CO2; oxidizing the fuel sprayed into the exhaust pipe: the oxidation of diesel releases heat to increase the temperature of the DPF, and the carbon in the DPF reacts with oxygen to form CO2.

[0006] DPF is mainly used to capture particles in exhaust gas to meet the particle number (PN) requirements of exhaust gas.

[0007] ASC is mainly used to: eliminate excess or escaped NH3: oxidize excess NH3 into N2, N2O, NO x At the same time, catalyze NO x , NH3 reacts to produce nitrogen N2.

[0008] With the increasingly stringent emission regulations, NO x Emission limits are getting lower and lower, so more precise urea injection control strategies are needed to achieve the highest possible NO x Conversion efficiency and as low NH3 leakage as possible.

[0009] At the same time, the current engine development process generally adopts the prescribed WHTC / WHSC and vehicle PEMS cycles as standard development cycles. These operating conditions contain many dynamic conditions, and the operating conditions vary greatly, causing the catalyst temperature and air velocity to change rapidly, thus affecting the catalyst conversion efficiency.

[0010] On this basis, if you always follow NO x The 1:1 equivalent ratio of NH3 to urea injection may result in: x During the rapid increase, the actual urea injection rate cannot keep up with NO x The growth rate of emissions, resulting in NO x In the case of emissions exceeding the standard, therefore, in actual injection control, control is generally carried out according to over-injection.

[0011] According to the prescribed transient cycle WHTC working conditions, the actual injection amount is generally compared with the theoretical required urea injection amount calculated at an equivalent ratio of 1. The overspray coefficient is generally in the range of 1.05 to 1.1. The excess urea (NH3) is oxidized by ASC into N2, H2O, etc.

[0012] Therefore, urea is basically in an overspray state under various working conditions. Although the oversprayed part is oxidized by ASC, NO x It does not exceed the standard, but the urea consumption is high and the user cost is high. Summary of the invention

[0013] In view of the defects existing in the prior art, the technical problem solved by the present invention is: how to control the urea injection amount to avoid or reduce the occurrence of urea overspray, thereby reducing the use cost.

[0014] To achieve the above objectives, in a first aspect, an embodiment of the present application provides a method for controlling a urea injection amount, the method comprising the following steps: when the engine reaches a stable state, determining the leakage state of NH3 according to NOx data before and after urea injection, and adjusting the urea injection amount according to the leakage state of NH3; the stable state means that the steady-state parameters related to the engine stable state meet the steady-state conditions.

[0015] In combination with the first aspect, in one embodiment, the process of determining the leakage state of NH3 according to NOx data before and after urea injection, and adjusting the urea injection amount according to the leakage state of NH3 includes: determining the NH3 leakage value according to NOx data before urea injection and NOx data after urea injection at adjacent moments;

[0016] When the NH3 leakage value is non-zero, it means there is NH3 leakage, and the urea injection amount is reduced;

[0017] When the NH3 leakage value is 0, it means there is no NH3 leakage and the urea injection amount remains unchanged.

[0018] In combination with the first aspect, in one embodiment, the method further includes the following steps: under the condition that there is no NH3 leakage, determining the NOx specific emission based on the NOx emissions and the accumulated work within the NOx emission detection period; adjusting the urea injection amount based on the NOx specific emission; the NOx emission detection period is: when the accumulated work at a certain moment is less than the accumulated work threshold, and the accumulated work at the next moment is above the accumulated work threshold, the period between the start recording time of the accumulated work and the next moment when the accumulated work is above the accumulated work threshold.

[0019] In combination with the first aspect, in one embodiment, the NOx specific emission is obtained by dividing the NOx emission by the accumulated work.

[0020] In combination with the first aspect, in one implementation, the process of adjusting the urea injection amount according to the NOx emission ratio includes:

[0021] When the NOx emission ratio is less than the emission threshold range, reduce the urea injection amount;

[0022] When the NOx emission ratio is greater than the emission threshold range, the urea injection amount is increased.

[0023] In combination with the first aspect, in one implementation, the stable state determination process includes: under the enabling condition that the engine is in a steady state, determining that the engine is in a stable state; the enabling condition for the steady state is determined based on the engine speed, torque and environmental parameters.

[0024] In combination with the first aspect, in one embodiment, the process of determining whether the steady-state parameter meets the steady-state condition includes: determining that the value of the steady-state parameter meets the specified threshold; the process of determining the value of the steady-state parameter includes: determining the average value of the steady-state parameter within the specified period, and the actual value of the parameter at the next moment after the specified period; and taking the absolute value of the difference between the average value and the actual value as the value of the steady-state parameter.

[0025] In combination with the first aspect, in one implementation, the steady-state parameters include: a change in engine speed, a change in engine torque, and a change in vehicle speed.

[0026] In a second aspect, an embodiment of the present application provides a control system for urea injection amount, the system comprising: a controller, a stable state parameter sampling module and a urea injection module;

[0027] The controller is used to: execute the process provided in the first aspect of determining the leakage state of NH3 according to the NOx data before and after the injection of urea under the condition that the engine reaches a stable state, and adjusting the urea injection amount according to the leakage state of NH3;

[0028] The steady state parameter sampling module is used to: provide the controller with the parameters required to determine whether the engine reaches a steady state;

[0029] The urea injection module is used to inject urea according to the instructions of the controller.

[0030] In a third aspect, an embodiment of the present application provides a vehicle, which includes the urea injection amount control system provided in the second aspect.

[0031] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0032] (1) The present application can determine the NH3 leakage state according to the NOx data before and after urea injection when the engine reaches a stable state, and then adjust the urea injection amount according to the NH3 leakage state. Therefore, compared with the excessive urea injection in the prior art, the present application can adjust and control the urea injection amount according to the NH3 leakage state, thereby avoiding or reducing the occurrence of urea overspray, thereby reducing the use cost; especially for vehicles that are in a high-speed operation scenario for a long time and have a relatively stable engine state, it can effectively reduce urea consumption.

[0033] (2) In addition to adjusting and controlling the urea injection amount according to the leakage status of NH3, the present application further adjusts the urea injection amount according to the NOx ratio emission when the cumulative work exceeds the cumulative work threshold, thereby improving the adjustment accuracy of the urea injection amount and further reasonably controlling the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the flow of the method for controlling the urea injection amount in the embodiment of the present application;

[0035] Figure 2 Schematic diagram of the hardware structure of the urea injection amount control device involved in the embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] The research and development principle and concept of this application are as follows: After research, the applicant concluded that when the engine is in a steady-state condition, the urea injection amount can be appropriately reduced to reduce the oxidation effect of ASC on urea, thereby appropriately reducing urea consumption while meeting the NOx and NH3 emissions.

[0038] In a first aspect, an embodiment of the present application provides a method for controlling the injection amount of urea (urea aqueous solution), the method comprising the following steps: under the condition that the engine reaches a stable state, determining the leakage state of NH3 based on NOx data before and after urea injection, and adjusting the urea injection amount accordingly according to the leakage state of NH3; the above-mentioned stable state means that: the steady-state parameters related to the stable state of the engine meet the steady-state conditions.

[0039] It can be seen that the present application can determine the leakage state of NH3 according to the NOx data before and after urea injection when the engine reaches a stable state, and then adjust the urea injection amount according to the leakage state of NH3. Therefore, compared with the excessive injection of urea in the prior art, the present application can adjust and control the urea injection amount according to the leakage state of NH3, so as to avoid or reduce the occurrence of urea overspray, thereby reducing the use cost; especially for vehicles that are in a high-speed operation scenario for a long time and have a relatively stable engine state, it can effectively reduce urea consumption.

[0040] In one embodiment, the above-mentioned stable state determination process includes: under the enabling condition that the engine is in a steady state, determining that the engine is in a stable state; the enabling condition of the steady state is determined according to the engine speed, torque and environmental parameters.

[0041] Specifically, the enabling conditions for the engine to be in a steady state include:

[0042] (1) The engine speed, torque, cooling water temperature, ambient temperature, and ambient pressure are all above their respective set thresholds;

[0043] (2) NOx data can be collected normally (i.e., the front and rear NOx sensors work normally);

[0044] (3) Urea is injected normally (i.e. the urea injection system works normally).

[0045] Point (1) specifically includes:

[0046] The engine speed is above the speed setting threshold;

[0047] The engine torque is above the torque setting threshold;

[0048] The engine's cooling water temperature is above the torque setting threshold;

[0049] The ambient temperature of the engine is within the temperature threshold range (greater than or equal to the minimum temperature threshold and less than or equal to the maximum temperature threshold);

[0050] The ambient pressure of the engine is within a pressure threshold range (greater than or equal to a minimum pressure threshold and less than or equal to a maximum pressure threshold).

[0051] In one embodiment, the steady-state parameters include: a change in engine speed, a change in engine torque, and a change in vehicle speed.

[0052] Specifically, the above-mentioned steady-state parameter meets the steady-state condition. The determination process includes: determining that the value of the steady-state parameter meets the specified threshold (below the specified threshold). The steady-state parameter value determination process includes: determining the average value of the parameter within the specified period, and the actual value of the parameter at the next moment after the specified period (the accuracy of the next moment can be minutes and seconds, and the specific moment is not limited); the absolute value of the difference between the average value and the actual value of the parameter is used as the value of the parameter.

[0053] The following description will be made using the vehicle speed change as an example.

[0054] If the specified period is 10s and the time accuracy is 1s, statistics will be collected starting from time T0, and the average vehicle speed from T0 to T9 will be calculated. After comparing the actual vehicle speed at time T10 with the average vehicle speed, the absolute value of the difference between the two speeds will be calculated; if the absolute value is below the set speed change threshold, it means that the vehicle speed is stable.

[0055] It should be noted that the above process is a cyclic process, that is, the average vehicle speed in the range of T0 to T9 will be compared with the actual vehicle speed at time T10, and the average vehicle speed in the range of T1 to T10 will be compared with the actual vehicle speed at time T11, and so on.

[0056] The method for determining whether the remaining steady-state parameters (the engine speed change, the engine torque change) meet the specified threshold is the same as the method for determining the vehicle speed change described above.

[0057] In one embodiment, the above process of determining the NH3 leakage state according to the NOx data before and after the injection of urea and adjusting the urea injection amount according to the NH3 leakage state includes: obtaining the NH3 leakage value according to the NOx data before the injection of urea at adjacent moments (collected by the front NOx sensor) and the NOx data after the injection of urea (collected by the rear NOx sensor, that is, the NOx data before and after the injection of urea at the current moment and the previous moment, similar to the above, the time accuracy is not limited, generally in minutes or seconds) (based on the above information disclosure, the specific calculation method of the NH3 leakage result is common knowledge in the art and will not be repeated here).

[0058] When the NH3 leakage value is non-zero, it means that there is NH3 leakage, and the urea injection amount should be reduced;

[0059] When the NH3 leakage value is 0, it means there is no NH3 leakage, and the urea injection amount remains unchanged.

[0060] In one embodiment, the method further comprises the following steps: under the condition that there is no NH3 leakage, determining the NOx emission ratio according to the NOx emission and the accumulated work within the NOx emission detection period; and adjusting the urea injection amount according to the NOx emission ratio. The NOx emission detection period is: when the accumulated work at a certain moment is less than the accumulated work threshold, and the accumulated work at the next moment (similar to the above, the time accuracy is not limited, generally in minutes or seconds) is above the accumulated work threshold, the period between the start of recording the accumulated work and the next moment when the accumulated work is above the accumulated work threshold.

[0061] For example: starting from time T0, the cumulative work and NOx emissions are calculated in units of 1S. When the cumulative work at a certain moment is less than the work of the set work base window (the cumulative work threshold), but at the next moment it is greater than or equal to the work threshold of the set work base window, it is considered to be a work base window; the NOx emissions and cumulative work of the work base window are counted.

[0062] It should be noted that: similar to the determination process of steady-state parameters meeting steady-state conditions, after the above determination of NOx emission ratio, adjusting the urea injection amount according to the NOx emission ratio is also a polling process; that is, multiple work base windows with different time periods will be generated, such as T0~T10, T0 is the start recording time of cumulative work, T10 is the next moment when the cumulative work appears above the cumulative work threshold, T1~T11, T1 is the start recording time of cumulative work, T11 is the next moment when the cumulative work appears above the cumulative work threshold, and so on. The urea injection amount will be adjusted each time the NOx emission ratio is determined.

[0063] It can be seen from this that, in addition to adjusting and controlling the urea injection amount according to the leakage status of NH3, the present application will further adjust the urea injection amount according to the NOx ratio emission when the cumulative work exceeds the cumulative work threshold, thereby improving the adjustment accuracy of the urea injection amount and further reasonably controlling the cost.

[0064] Specifically, the NOx specific emission is the NOx emission divided by the accumulated work.

[0065] At the same time, the above-mentioned process of adjusting the urea injection amount according to the NOx specific emission includes:

[0066] When the NOx emission ratio is less than the emission threshold range (i.e., less than the emission lower limit threshold), it means that the urea injection amount is too much, and the urea injection amount should be reduced at this time;

[0067] When the NOx emission ratio is greater than the emission threshold range (i.e. greater than the emission upper limit threshold), it means that the urea injection amount is too small, and the urea injection amount should be increased at this time;

[0068] When the NOx emission ratio falls within the emission threshold range (ie, greater than or equal to the emission lower limit threshold and less than or equal to the emission upper limit threshold), it indicates that the urea injection amount is appropriate, and the urea injection amount is kept unchanged.

[0069] See below Figure 1 As shown, the above method is described from a timing perspective through an embodiment.

[0070] S1: Inject urea according to the initially calibrated urea injection quantity (ie, set the injection correction factor to 1).

[0071] S2: Determine whether the engine is in a steady-state enabling condition (see the corresponding part above for the specific method). If so, set the engine status judgment enable to TRUE and go to S3. Otherwise, set it to FALSE and end.

[0072] S3: Determine whether the engine is in a stable state (for specific methods, refer to the corresponding part above). If so, go to S4, otherwise end.

[0073] S4: Determine whether there is NH3 leakage (see the corresponding part above for the specific method). If so, reduce the urea injection amount and execute S4 again. Otherwise, go to S5.

[0074] S5: determining the NOx emission ratio according to the NOx emission and the accumulated work in the NOx emission detection cycle; and adjusting the urea injection amount according to the NOx emission ratio.

[0075] During the execution of S1 to S5, if the stable state of the engine changes (exits the stable state or regeneration occurs), the process returns to S1.

[0076] In a second aspect, an embodiment of the present application further provides a urea injection amount control system, comprising: a controller, a stable state parameter sampling module, and a urea injection module.

[0077] The controller is used to: determine the leakage state of NH3 according to the NOx data before and after the injection of urea after the engine reaches a stable state, and control the urea injection module to adjust the urea injection amount accordingly according to the leakage state of NH3; specifically:

[0078] The steady state determination process includes: determining that the engine is in a steady state under the enabling condition that the engine is in a steady state; the enabling condition that the engine is in a steady state is determined according to the engine speed, torque and environmental parameters.

[0079] Specifically, the enabling conditions for the engine to be in a steady state include:

[0080] (1) The engine speed, torque, cooling water temperature, ambient temperature, and ambient pressure are all above their respective set thresholds;

[0081] (2) NOx data can be collected normally (i.e., the front and rear NOx sensors work normally);

[0082] (3) Urea is injected normally (i.e. the urea injection system works normally).

[0083] The steady-state parameters include: the change in engine speed, the change in engine torque, and the change in vehicle speed.

[0084] The process of determining whether the steady-state parameter meets the steady-state condition includes: determining whether the value of the steady-state parameter meets the specified threshold (below the specified threshold). The process of determining the value of the steady-state parameter includes: determining the average value of the parameter within the specified period, and the actual value of the parameter at the next moment after the specified period (the accuracy of the next moment can be minutes and seconds, and the specific moment is not limited); the absolute value of the difference between the average value and the actual value of the parameter is used as the value of the parameter.

[0085] The leakage state of NH3 is determined according to the NOx data before and after urea injection. The process of adjusting the urea injection amount according to the leakage state of NH3 includes: obtaining the NH3 leakage value according to the NOx data before urea injection at adjacent moments (collected by the front NOx sensor) and the NOx data after urea injection (collected by the rear NOx sensor, that is, the NOx data before and after urea injection at the current moment and the previous moment, the same as above, the time accuracy is not limited, generally minutes or seconds).

[0086] When the NH3 leakage value is non-zero, it means that there is NH3 leakage, and the urea injection amount should be reduced;

[0087] When the NH3 leakage value is 0, it means there is no NH3 leakage, and the urea injection amount remains unchanged.

[0088] The controller is also used to: determine the NOx emission ratio according to the NOx emission and the accumulated work in the NOx emission detection period under the condition that there is no NH3 leakage; and adjust the urea injection amount according to the NOx emission ratio. The NOx emission detection period is: when the accumulated work at a certain moment is less than the accumulated work threshold, and the accumulated work at the next moment (similar to the above, the time accuracy is not limited, generally in minutes or seconds) is above the accumulated work threshold, the period between the start of the accumulated work recording and the next moment when the accumulated work is above the accumulated work threshold.

[0089] NOx specific emissions are the NOx emissions divided by the accumulated work.

[0090] The process of adjusting the urea injection amount according to NOx specific emissions includes:

[0091] When the NOx emission ratio is less than the emission threshold range (i.e., less than the emission lower limit threshold), it means that the urea injection amount is too much, and the urea injection amount should be reduced at this time;

[0092] When the NOx emission ratio is greater than the emission threshold range (i.e. greater than the emission upper limit threshold), it means that the urea injection amount is too small, and the urea injection amount should be increased at this time;

[0093] When the NOx emission ratio falls within the emission threshold range (ie, greater than or equal to the emission lower limit threshold and less than or equal to the emission upper limit threshold), it indicates that the urea injection amount is appropriate, and the urea injection amount is kept unchanged.

[0094] The steady-state parameter sampling module is used to provide the controller with the parameters required to determine whether the engine has reached a steady state. Specifically, the steady-state parameter sampling module includes a collection device for collecting the steady-state parameters mentioned above and the enabling conditions for the engine to be in a steady state, such as front and rear NOx sensors, vehicle speed sensors, rotational speed sensors, etc.

[0095] The urea injection module is used to inject urea according to the instructions of the controller.

[0096] In a third aspect, an embodiment of the present application provides a vehicle, which includes the urea injection amount control system mentioned in the second aspect.

[0097] In a fourth aspect, an embodiment of the present application provides a device for controlling the amount of urea injection. The device for controlling the amount of urea injection may be a device having a data processing function, such as a personal computer (PC), a laptop computer, or a server.

[0098] Reference Figure 2 , Figure 2The hardware structure diagram of the urea injection amount control device involved in the embodiment of the present application is shown in FIG. In the embodiment of the present application, the urea injection amount control device may include a processor, a memory, a communication interface, and a communication bus.

[0099] The communication bus may be of any type and is used to interconnect the processor, the memory, and the communication interface.

[0100] The communication interface includes an input / output (I / O) interface, a physical interface, and a logical interface, etc., which are used to interconnect the devices inside the urea injection amount control device, and an interface used to interconnect the urea injection amount control device with other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, an optical fiber interface, an ATM interface, etc.; the user device can be a display, a keyboard, etc.

[0101] The memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0102] The processor may be a general processor, and the general processor may call the control program of the urea injection amount stored in the memory, and execute the control method of the urea injection amount provided in the embodiment of the present application. For example, the general processor may be a central processing unit (CPU). The method executed when the control program of the urea injection amount is called may refer to the various embodiments of the control method of the urea injection amount of the present application, which will not be repeated here.

[0103] Those skilled in the art will understand that Figure 2 The hardware structure shown in the figure does not constitute a limitation on the present application, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0104] In a fifth aspect, an embodiment of the present application also provides a computer-readable storage medium.

[0105] The computer-readable storage medium of the present application stores a urea injection amount control program, wherein when the urea injection amount control program is executed by a processor, the steps of the urea injection amount control method as described above are implemented.

[0106] Among them, the method implemented when the urea injection amount control program is executed can refer to the various embodiments of the urea injection amount control method of the present application, and will not be repeated here.

[0107] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0108] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0109] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0110] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0111] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0112] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0113] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0114] The above are only specific implementations of the embodiments of the present invention, but the protection scope of the embodiments of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the embodiments of the present invention, and these modifications or replacements should be included in the protection scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for controlling the amount of urea injection, characterized in that: The method comprises the following steps: when the engine reaches a stable state, determining the leakage state of NH3 according to NOx data before and after urea injection, and adjusting the urea injection amount according to the leakage state of NH3; the stable state means that the steady-state parameters related to the engine stable state meet the steady-state conditions.

2. The method for controlling the urea injection amount according to claim 1, characterized in that: The process of determining the NH3 leakage state according to the NOx data before and after the injection of urea and adjusting the urea injection amount according to the NH3 leakage state includes: determining the NH3 leakage value according to the NOx data before the injection of urea and the NOx data after the injection of urea at adjacent moments; When the NH3 leakage value is non-zero, it means there is NH3 leakage, and the urea injection amount is reduced; When the NH3 leakage value is 0, it means there is no NH3 leakage and the urea injection amount remains unchanged.

3. The method for controlling the urea injection amount according to claim 2, characterized in that: The method also includes the following steps: under the condition that there is no NH3 leakage, determining the NOx specific emission according to the NOx emission and the accumulated work within the NOx emission detection period; adjusting the urea injection amount according to the NOx specific emission; the NOx emission detection period is: when the accumulated work at a certain moment is less than the accumulated work threshold value, and the accumulated work at the next moment is above the accumulated work threshold value, the period between the start recording time of the accumulated work and the next moment when the accumulated work is above the accumulated work threshold value.

4. The method for controlling the urea injection amount according to claim 3, characterized in that: The NOx specific emission is obtained by dividing the NOx emission by the accumulated work.

5. The method for controlling the urea injection amount according to claim 3, characterized in that: The process of adjusting the urea injection amount according to the NOx emission ratio includes: When the NOx emission ratio is less than the emission threshold range, reduce the urea injection amount; When the NOx emission ratio is greater than the emission threshold range, the urea injection amount is increased.

6. The method for controlling the urea injection amount according to any one of claims 1 to 5, characterized in that: The stable state determination process includes: under the enabling condition that the engine is in a stable state, determining that the engine is in a stable state; the enabling condition that the engine is in a stable state is determined according to the engine speed, torque and environmental parameters.

7. The method for controlling the urea injection amount according to any one of claims 1 to 5, characterized in that: The determination process of whether the steady-state parameter meets the steady-state condition includes: determining that the value of the steady-state parameter meets the specified threshold; the process of determining the value of the steady-state parameter includes: determining the average value of the steady-state parameter within the specified period, and the actual value of the parameter at the next moment after the specified period; and taking the absolute value of the difference between the average value and the actual value as the value of the steady-state parameter.

8. The method for controlling the urea injection amount according to any one of claims 1 to 5, characterized in that: The steady-state parameters include: a change in engine speed, a change in engine torque, and a change in vehicle speed.

9. A urea injection amount control system, characterized in that: The system comprises: a controller, a steady state parameter sampling module and a urea injection module; The controller is used to: execute the process of any one of claims 1 to 8, under the condition that the engine reaches a stable state, determining the leakage state of NH3 according to NOx data before and after urea injection, and adjusting the urea injection amount according to the leakage state of NH3; The steady state parameter sampling module is used to: provide the controller with the parameters required to determine whether the engine reaches a steady state; The urea injection module is used to inject urea according to the instructions of the controller.

10. An automobile, characterized in that: The vehicle comprises the urea injection amount control system according to claim 9.

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