Urea nozzle protection method

Abstract

The invention discloses a protection method for a urea nozzle. The protection method comprises the steps that an enabling control signal of the urea nozzle is obtained; determining the fault state of the urea nozzle according to the enabling control signal; acquiring a high-temperature protection signal of the urea nozzle when the urea nozzle has no fault; according to the high-temperature protection signal, a urea nozzle is controlled to execute the spraying action with the first preset spraying amount; obtaining a crystallization corrosion signal of the urea nozzle when the urea nozzle has no fault; and according to the crystallization corrosion signal, a urea nozzle is controlled to execute injection action under a first preset injection condition. By means of the method, the urea nozzle is protected when the urea nozzle has no fault and has the phenomena of high temperature, crystallization, corrosion and the like, it is guaranteed that the urea nozzle is not damaged, the reliability of the urea nozzle is improved, and the service life of the urea nozzle is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of urea nozzles, and in particular to a protection method for a urea nozzle. Background Art

[0002] Diesel engine exhaust NOx emissions are relatively high. NOx is harmful to human health and the environment. Therefore, emission regulations have strict requirements on diesel engine exhaust NOx emissions. The National VI commercial vehicle after-treatment layout generally uses selective catalytic reduction technology (SCR) to treat NOx emissions. The urea solution is affected by the air pressure in the urea tank, passes through the urea pipeline, and is controlled by the urea nozzle to spray urea, so that urea decomposes into NH3, which reacts with NOx to reduce NOx emissions. The urea nozzle is a key component of the National VI emission standard diesel engine after-treatment system, which has a great impact on engine emissions and the crystallization of the after-treatment SCR system. The urea nozzle is the most critical actuator and requires high reliability to ensure that the set reductant injection amount is accurately executed.

[0003] In the existing SCR control structure, the urea nozzle is directly installed on the exhaust pipe, and the head of the urea nozzle is directly in contact with the high-temperature exhaust gas. When not spraying, the urea at the urea nozzle will not be updated, which brings two problems: on the one hand, the high temperature may directly damage the urea nozzle, and on the other hand, the high temperature will cause the urea inside the nozzle to decompose due to heat, generate urea crystals to block the nozzle, or generate acidic substances to corrode the internal structure of the nozzle. Summary of the invention

[0004] The invention provides a urea nozzle protection method, which can avoid damage to the urea nozzle caused by high temperature, crystallization and corrosion while ensuring that the urea nozzle itself is fault-free, thereby improving the reliability and service life of the urea nozzle.

[0005] The present invention provides a urea nozzle protection method, comprising:

[0006] Obtaining the enabling control signal of the urea nozzle;

[0007] Determine the fault status of the urea nozzle according to the enable control signal;

[0008] When the urea nozzle has no fault, a high temperature protection signal of the urea nozzle is obtained;

[0009] According to the high temperature protection signal and the enable control signal, the urea nozzle is controlled to perform an injection action with a first preset injection amount;

[0010] Acquire the crystal corrosion signal of the urea nozzle when the urea nozzle is not faulty;

[0011] According to the crystal corrosion signal and the enable control signal, the urea nozzle is controlled to perform an injection action under a first preset injection condition.

[0012] Optionally, the enabling control signal includes a temperature signal of the urea solution, a pressure signal of the urea solution, an SCR inlet temperature signal, an exhaust flow signal of the engine, and an electrical fault signal of the urea nozzle.

[0013] Optionally, determining the fault state of the urea nozzle according to the enable control signal includes:

[0014] When the temperature signal of the urea solution is greater than the first preset temperature, the pressure signal of the urea solution is greater than the first preset pressure, the SCR inlet temperature signal is greater than the first preset inlet temperature, the exhaust flow signal of the engine is greater than the first preset exhaust flow, and the urea nozzle is fault-free, and all of these last for the first preset time, it is determined that the urea nozzle is fault-free.

[0015] Optionally, the high temperature protection signal includes an injection flow signal of a urea solution and an exhaust temperature signal of nitrogen oxides.

[0016] Optionally, according to the high temperature protection signal, controlling the urea nozzle to perform an injection action with a first preset injection amount includes:

[0017] When the injection flow rate signal of the urea solution is less than the first preset injection flow rate and the exhaust temperature signal of the nitrogen oxide is greater than the second preset temperature, the urea nozzle is controlled to perform the injection action with the first preset injection amount.

[0018] Optionally, after the injection flow rate signal of the urea solution is less than the first preset injection flow rate and the exhaust temperature signal of the nitrogen oxide is greater than the second preset temperature, before controlling the urea nozzle to perform the injection action with the first preset injection amount, the method further includes:

[0019] According to the exhaust temperature signal of nitrogen oxides, a first preset injection amount is determined using a preset corresponding relationship; the preset corresponding relationship is a preset calibrated corresponding relationship between the exhaust temperature signal of nitrogen oxides and the first preset injection amount.

[0020] Optionally, the crystal corrosion signal includes a driving duty cycle signal of the urea nozzle.

[0021] Optionally, according to the crystal corrosion signal, controlling the urea nozzle to perform the injection action under the first preset injection condition includes:

[0022] When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and lasts for a second preset time, the urea nozzle is controlled to perform an injection action under the first preset injection condition.

[0023] Optionally, when the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and lasts for a second preset time, controlling the urea nozzle to perform the injection action under the first preset injection condition includes:

[0024] When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle, the control timing device starts timing;

[0025] When the driving duty cycle signal of the urea nozzle is greater than the first preset duty cycle and lasts for a third preset time, the timing device is controlled to stop timing and reset to zero;

[0026] When the timing reaches the second preset time, the urea nozzle is controlled to perform the injection action under the first preset injection condition.

[0027] Optionally, the first preset injection condition is that the injection amount of the urea nozzle is the second preset injection amount and lasts for a fourth preset time, and the fourth preset time is greater than the third preset time.

[0028] The technical solution of the present invention obtains the enable control signal of the urea nozzle; determines the fault state of the urea nozzle according to the enable control signal; obtains the high temperature protection signal of the urea nozzle when the urea nozzle is not faulty; controls the urea nozzle to perform the injection action with a first preset injection amount according to the high temperature protection signal; obtains the crystallization corrosion signal of the urea nozzle when the urea nozzle is not faulty; controls the urea nozzle to perform the injection action with a first preset injection condition according to the crystallization corrosion signal. By using the above method, while ensuring that the urea nozzle itself is fault-free, damage to the urea nozzle caused by high temperature, crystallization and corrosion is avoided, thereby improving the reliability and service life of the urea nozzle.

[0029] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A flow chart of a urea nozzle protection method provided by an embodiment of the present invention;

[0032] Figure 2 The present invention provides a flowchart of a second urea nozzle protection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof 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 necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] In one embodiment, Figure 1 A flow chart of a urea nozzle protection method provided in an embodiment of the present invention is provided. This embodiment is applicable to the case where a urea nozzle is protected under high temperature, crystallization and corrosion. Figure 1 As shown, the method includes:

[0036] S110, obtaining an enable control signal of a urea nozzle.

[0037] The enabling control signal is a signal related to whether the urea nozzle is faulty or not. The enabling control signal includes at least but is not limited to a temperature signal of the urea solution, a pressure signal of the urea solution, an SCR inlet temperature signal, an exhaust flow signal of the engine, and an electrical fault signal of the urea nozzle.

[0038] Specifically, the method for acquiring the enabling control signal may include, but is not limited to, acquiring it according to a corresponding sensor or the like.

[0039] S120: Determine the fault state of the urea nozzle according to the enable control signal.

[0040] Specifically, after obtaining the enable control signal of the urea nozzle, according to the enable control signal of the urea nozzle, when the enable control signal meets the corresponding preset conditions, it can be determined that the urea nozzle is in a non-fault state, and the urea nozzle itself has an injection function. When one of the enable control signals does not meet the corresponding preset conditions, it indicates that some parameters of the urea nozzle do not meet the requirements, and the urea nozzle may have a certain fault, then it is determined that the urea nozzle is in a fault state, and the urea nozzle should not be controlled to inject in the fault state, and the protection control action should not be triggered.

[0041] It can be understood that this embodiment is mainly used to solve the problem of controlling the urea nozzle when the urea nozzle is at high temperature, corrosion and crystallization. That is to say, the premise for the urea nozzle to be damaged by high temperature, corrosion and crystallization is that the urea nozzle needs to be in a fault-free state. Therefore, this step performs the fault state of the urea nozzle in advance.

[0042] S130: When the urea nozzle has no fault, a high temperature protection signal of the urea nozzle is obtained.

[0043] The high temperature protection signal includes the injection flow signal of the urea solution and the exhaust temperature of the nitrogen oxides.

[0044] S140: According to the high temperature protection signal, control the urea nozzle to perform an injection action with a first preset injection amount.

[0045] Specifically, when the exhaust temperature of nitrogen oxides is too high, the cooling capacity of the urea nozzle itself may not be able to maintain the temperature inside the urea nozzle within a safe working range. At this time, the excessively high exhaust temperature may directly damage the urea nozzle, causing the injection accuracy of the urea nozzle to change or even damage the urea nozzle. To this end, in view of the phenomenon that the urea nozzle may be damaged by excessively high exhaust temperature, this embodiment provides a solution to obtain a high temperature protection signal of the urea nozzle when it is determined that the urea nozzle is not faulty. According to the high temperature protection signal, when the high temperature protection signals all meet the corresponding preset conditions, the urea nozzle is controlled to perform the injection action with the first preset injection amount to ensure the injection of the urea nozzle, so that the urea nozzle takes away the high temperature of nitrogen oxides during injection, thereby reducing the temperature inside the urea nozzle, preventing the urea nozzle from being damaged by high temperature, and protecting the urea nozzle. Among them, the first preset injection amount can be the minimum injection amount, which can be determined according to actual conditions. For example, the first preset injection amount can be the minimum injection amount corresponding to the exhaust temperature determined by looking up the table.

[0046] S150: When the urea nozzle is not faulty, a crystal corrosion signal of the urea nozzle is obtained.

[0047] The crystallization corrosion signal may include but is not limited to a driving duty cycle signal of the urea nozzle.

[0048] S160: According to the crystal corrosion signal, control the urea nozzle to perform an injection action under a first preset injection condition.

[0049] Specifically, when the urea nozzle meets the injection condition, the urea nozzle is controlled to perform the injection action. However, when the urea nozzle does not spray for a long time, the urea solution inside the urea nozzle does not flow. At this time, the high temperature in the exhaust pipe will cause the urea inside the urea nozzle to be thermally decomposed to generate urea crystals, thereby blocking the urea nozzle, or the urea reacts chemically with the sulfide in the nitrogen oxide tail gas to produce acidic substances, thereby corroding the internal structure of the urea nozzle and causing damage to the urea nozzle. For this reason, this step protects the urea nozzle from the crystallization corrosion problem. Specifically, when it is confirmed that the urea nozzle is not faulty, the crystallization corrosion signal of the urea nozzle is obtained, and when the crystallization corrosion signal meets the corresponding preset condition, indicating that the urea nozzle has a crystallization corrosion risk at this time, the urea nozzle is controlled to perform the injection action under the first preset injection condition to update the urea at the urea nozzle, to ensure that no reactants are generated in the urea at the urea nozzle, and then to ensure that the urea nozzle is not damaged.

[0050] The technical solution of the embodiment of the present invention is to obtain the enable control signal of the urea nozzle; determine the fault state of the urea nozzle according to the enable control signal; obtain the high temperature protection signal of the urea nozzle when the urea nozzle is not faulty; control the urea nozzle to perform the injection action with a first preset injection amount according to the high temperature protection signal; obtain the crystallization corrosion signal of the urea nozzle when the urea nozzle is not faulty; control the urea nozzle to perform the injection action with a first preset injection condition according to the crystallization corrosion signal. By using the above method, while ensuring that the urea nozzle itself is fault-free, the damage of the urea nozzle caused by high temperature, crystallization and corrosion is avoided, and the reliability and service life of the urea nozzle are improved.

[0051] In another alternative embodiment, Figure 2 This is a flow chart of a second urea nozzle protection method provided in an embodiment of the present invention. This embodiment refines the specific implementation method of how to protect the urea nozzle in the above embodiment. Figure 2 As shown, the method includes:

[0052] S210: Acquire an enable control signal of a urea nozzle.

[0053] The enabling control signal includes a temperature signal of the urea solution, a pressure signal of the urea solution, an SCR inlet temperature signal, an exhaust flow signal of the engine, and an electrical fault signal of the urea nozzle.

[0054] Specifically, the acquisition of the temperature signal of the urea solution may include but is not limited to acquisition through a urea temperature sensor. The temperature signal of the urea solution can reflect the thawing of the urea. When the temperature signal of the urea solution is greater than or equal to the first preset temperature, it means that the urea is successfully thawed. When the temperature signal of the urea solution is less than the first preset temperature, it means that the urea is not successfully thawed. The acquisition of the pressure signal of the urea solution may include but is not limited to acquisition through a urea pressure sensor. The acquisition of the SCR inlet temperature signal may include but is not limited to acquisition through an SCR front row temperature sensor, and the SCR front row temperature sensor is very close to the location of the urea nozzle, so the SCR inlet temperature signal can be considered as the temperature of the urea nozzle. The acquisition of the exhaust flow signal of the engine may include but is not limited to obtaining the intake flow through a flow sensor installed at the engine intake port, determining the exhaust flow of the engine according to a certain corresponding relationship, and obtaining the exhaust flow of the engine; of course, a flow sensor can also be directly set at the exhaust port of the engine to obtain, which can be determined according to actual conditions and is not limited here. The electrical fault signal of the urea nozzle can be determined by the electrical fault communication transmission of the urea nozzle.

[0055] S220: When the temperature signal of the urea solution is greater than the first preset temperature, the pressure signal of the urea solution is greater than the first preset pressure, the SCR inlet temperature signal is greater than the first preset inlet temperature, the exhaust flow signal of the engine is greater than the first preset exhaust flow, and the urea nozzle is fault-free, and all of these conditions last for a first preset time, it is determined that the urea nozzle is fault-free.

[0056] Specifically, after obtaining the enable control signal, when it is determined according to the enable control signal that the temperature signal of the urea solution is greater than the first preset temperature, that is, the urea is successfully thawed, the pressure signal of the urea solution is greater than the first preset pressure, the SCR inlet temperature signal is greater than the first preset inlet temperature, the exhaust flow signal of the engine is greater than the first preset exhaust flow, and the urea nozzle is not faulty, and the time when the above conditions all meet the corresponding corresponding relationship lasts for the first preset time, it indicates that the urea nozzle is always in the above state during the time period, and it can be determined that the urea nozzle is not faulty. When any of the above conditions is not met, for example, when the urea is not successfully thawed, it can be determined that the urea nozzle is in a faulty state, and then exit, that is, stop controlling the subsequent urea nozzles.

[0057] It is understandable that the first preset temperature can be determined according to actual conditions, the first preset pressure can be an absolute pressure of 700 kPa, the first preset inlet temperature can be a common temperature threshold of 170°C, and the first preset exhaust flow rate can be actually determined according to the engine displacement and the rated speed of the engine, and no limitation is made here. The first preset time can be an anti-shake time, which can be specifically determined according to actual conditions, and no limitation is made here.

[0058] S230: When the urea nozzle has no fault, a high temperature protection signal of the urea nozzle is obtained.

[0059] The high temperature protection signal includes an injection flow signal of a urea solution and an exhaust temperature signal of nitrogen oxides.

[0060] Specifically, the acquisition of the injection flow rate signal of the urea solution may include but is not limited to obtaining the high temperature protection signal by a certain calculation method according to the design value of the injection flow rate. The acquisition of the exhaust temperature signal of nitrogen oxides may include but is not limited to obtaining it through a temperature sensor.

[0061] S240: When the injection flow rate signal of the urea solution is less than the first preset injection flow rate and the exhaust temperature signal of nitrogen oxides is greater than the second preset temperature, a first preset injection amount is determined according to the exhaust temperature signal of nitrogen oxides by using a preset corresponding relationship, and the urea nozzle is controlled to perform an injection action with the first preset injection amount.

[0062] The preset corresponding relationship is a preset calibrated corresponding relationship between the exhaust temperature signal of nitrogen oxides and the first preset injection quantity.

[0063] Specifically, after the injection flow rate signal of the urea solution and the exhaust temperature signal of the nitrogen oxide are obtained, according to the injection flow rate signal of the urea solution and the exhaust temperature signal of the nitrogen oxide, when it is determined that the injection flow rate signal of the urea solution is less than the first preset injection flow rate and the exhaust temperature signal of the nitrogen oxide is greater than the second preset temperature, wherein the first preset injection flow rate may be the injection flow rate threshold of 300 mg / s and the second preset temperature may be the common hysteresis temperature threshold of 450°C, it indicates that the injection amount of the urea nozzle is too small and the exhaust temperature of the nitrogen oxide is too high. If the urea nozzle is in the above state for a long time, it may cause damage to the urea nozzle. Therefore, the urea nozzle needs to be protected, and the urea nozzle is controlled to perform the injection action with the first preset injection amount to continuously cool the urea nozzle. In this embodiment, the first preset injection amount is determined by a preset calibrated preset corresponding relationship between the exhaust temperature signal of the nitrogen oxide and the first preset injection amount. That is, when determining the exhaust temperature of the nitrogen oxide, the exhaust temperature is substituted into the preset corresponding relationship, and the first preset injection amount corresponding to the exhaust temperature can be obtained by looking up a table or the like.

[0064] S250: When the urea nozzle is not faulty, a crystal corrosion signal of the urea nozzle is obtained.

[0065] The crystal corrosion signal includes a driving duty cycle signal of the urea nozzle.

[0066] Specifically, the acquisition of the crystal corrosion signal may include but is not limited to calculating the injection flow rate of the urea nozzle.

[0067] S260: When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and lasts for a second preset time, control the urea nozzle to perform an injection action under the first preset injection condition.

[0068] Among them, this step can be refined as follows: when the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle, the timing device is controlled to start timing; when the driving duty cycle signal of the urea nozzle is greater than the first preset duty cycle and lasts for a third preset time, the timing device is controlled to stop timing and reset to zero; when the timing reaches the second preset time, the urea nozzle is controlled to perform the injection action under the first preset injection condition.

[0069] Among them, the driving duty cycle of the urea nozzle refers to the ratio of the time the urea nozzle is open to the entire injection cycle time during the urea injection process. Specifically, the driving duty cycle is an important parameter that describes the pulse width modulation (PWM) signal, which determines the length of time the urea nozzle is open within a certain period of time. In the urea injection system, by adjusting the duty cycle of the PWM signal, the injection amount of the urea nozzle can be controlled, and then the injection amount of the urea solution can be accurately controlled to meet the needs of exhaust gas treatment. The first preset injection condition is that the injection amount of the urea nozzle is the second preset injection amount, and it lasts for a fourth preset time, and the fourth preset time is greater than the third preset time.

[0070] Specifically, after the driving duty cycle of the urea nozzle is obtained, according to the driving duty cycle of the urea nozzle, when the driving duty cycle is less than the first preset duty cycle, for example, the first preset duty cycle may be 1%, indicating that the urea nozzle sprayed too little urea or did not spray according to the spraying requirements, the timing device is controlled to start timing, and when the timing time reaches the second preset time, the second preset time may be 300s, indicating that the urea nozzle has not performed the spraying action for a long time or the spraying amount is too small for a long time, and the urea nozzle may be blocked or corroded, etc., the urea nozzle is controlled to perform the spraying action under the first preset spraying condition. In addition, when it is determined that the driving duty cycle signal of the urea nozzle is greater than the first preset duty cycle and lasts for a third preset time, the third preset time is 2s, indicating that the spraying capacity of the urea nozzle meets the spraying requirements, the timing device is controlled to stop timing, and the above timing is reset to zero, and when it is determined that the driving duty cycle is less than the first preset duty cycle, the timing is restarted, and the urea nozzle is controlled to perform the spraying action.

[0071] It should be noted that when the urea nozzle is controlled to perform the injection action under the first preset injection condition, the first preset injection condition is that the injection amount of the urea nozzle is the second preset injection amount and lasts for a fourth preset time, and the fourth preset time is greater than the third preset time. In this embodiment, the fourth preset time can be 5s.

[0072] The technical solution of the embodiment of the present invention is as follows: by acquiring an enable control signal of a urea nozzle; determining that the urea nozzle is fault-free when a temperature signal of a urea solution is greater than a first preset temperature, a pressure signal of a urea solution is greater than a first preset pressure, an SCR inlet temperature signal is greater than a first preset inlet temperature, an exhaust flow signal of an engine is greater than a first preset exhaust flow, and the urea nozzle is fault-free and all of these conditions last for a first preset time; acquiring a high temperature protection signal of the urea nozzle when the urea nozzle is fault-free; determining a first preset injection amount according to the exhaust temperature signal of nitrogen oxides by using a preset corresponding relationship when an injection flow signal of the urea solution is less than a first preset injection flow and an exhaust temperature signal of nitrogen oxides is greater than a second preset temperature, and controlling the urea nozzle to perform an injection action with the first preset injection amount; acquiring a crystallization corrosion signal of the urea nozzle when the urea nozzle is fault-free; and controlling the urea nozzle to perform an injection action with the first preset injection condition when a driving duty cycle signal of the urea nozzle is less than a first preset duty cycle and lasts for a second preset time. By utilizing the above method, while ensuring that the urea nozzle itself is fault-free, the urea nozzle is controlled to perform different injection actions under high temperature and crystallization corrosion conditions to protect the urea nozzle, avoid damage to the urea nozzle caused by high temperature, crystallization and corrosion, and improve the reliability and service life of the urea nozzle.

[0073] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0074] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for protecting a urea nozzle, characterized in that: include: Acquiring an enabling control signal of the urea nozzle; determining a fault state of the urea nozzle according to the enable control signal; acquiring a high temperature protection signal of the urea nozzle when the urea nozzle has no fault; According to the high temperature protection signal, controlling the urea nozzle to perform an injection action with a first preset injection amount; acquiring a crystal corrosion signal of the urea nozzle when the urea nozzle has no fault; According to the crystal corrosion signal, the urea nozzle is controlled to perform an injection action under a first preset injection condition.

2. The protection method according to claim 1, characterized in that: The enabling control signal includes a temperature signal of a urea solution, a pressure signal of the urea solution, an SCR inlet temperature signal, an exhaust flow signal of an engine, and an electrical fault signal of the urea nozzle.

3. The protection method according to claim 2, characterized in that: Determining the fault state of the urea nozzle according to the enable control signal includes: When the temperature signal of the urea solution is greater than a first preset temperature, the pressure signal of the urea solution is greater than a first preset pressure, the SCR inlet temperature signal is greater than a first preset inlet temperature, the exhaust flow signal of the engine is greater than a first preset exhaust flow, and the urea nozzle is fault-free, and all of these last for a first preset time, it is determined that the urea nozzle is fault-free.

4. The protection method according to claim 2, characterized in that: The high temperature protection signal includes an injection flow rate signal of a urea solution and an exhaust temperature signal of nitrogen oxides.

5. The protection method according to claim 4, characterized in that: According to the high temperature protection signal, controlling the urea nozzle to perform an injection action with a first preset injection amount includes: When the injection flow rate signal of the urea solution is less than a first preset injection flow rate and the exhaust temperature signal of nitrogen oxides is greater than a second preset temperature, the urea nozzle is controlled to perform an injection action with the first preset injection amount.

6. The protection method according to claim 5, characterized in that: After the injection flow rate signal of the urea solution is less than the first preset injection flow rate and the exhaust temperature signal of the nitrogen oxide is greater than the second preset temperature, before controlling the urea nozzle to perform the injection action with the first preset injection amount, the method further includes: The first preset injection amount is determined according to the exhaust temperature signal of nitrogen oxides using a preset corresponding relationship; the preset corresponding relationship is a preset calibrated corresponding relationship between the exhaust temperature signal of nitrogen oxides and the first preset injection amount.

7. The protection method according to claim 2, characterized in that: The crystal corrosion signal includes a driving duty cycle signal of the urea nozzle.

8. The protection method according to claim 7, characterized in that: According to the crystal corrosion signal, controlling the urea nozzle to perform an injection action under a first preset injection condition includes: When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and lasts for a second preset time, the urea nozzle is controlled to perform an injection action under the first preset injection condition.

9. The protection method according to claim 8, characterized in that: When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and lasts for a second preset time, controlling the urea nozzle to perform an injection action under the first preset injection condition, including: When the driving duty cycle signal of the urea nozzle is less than the first preset duty cycle, controlling the timing device to start timing; When the driving duty cycle signal of the urea nozzle is greater than the first preset duty cycle and lasts for a third preset time, controlling the timing device to stop timing and reset to zero; When the timing reaches the second preset time, the urea nozzle is controlled to perform the injection action under the first preset injection condition.

10. The protection method according to claim 9, characterized in that: The first preset injection condition is that the injection amount of the urea nozzle is a second preset injection amount and lasts for a fourth preset time, and the fourth preset time is greater than the third preset time.

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