A method for protecting a urea nozzle

Abstract

The present invention discloses a method for protecting a urea nozzle, comprising: obtaining an enable control signal for the urea nozzle; determining the fault state of the urea nozzle based on the enable control signal; obtaining a high-temperature protection signal for the urea nozzle when the urea nozzle is not faulty; controlling the urea nozzle to spray at a first preset spray volume based on the high-temperature protection signal; obtaining a crystallization corrosion signal for the urea nozzle when the urea nozzle is not faulty; and controlling the urea nozzle to spray at a first preset spray condition based on the crystallization corrosion signal. Using this method, when the urea nozzle is not faulty, the urea nozzle is protected from high temperature, crystallization, and corrosion, ensuring that the urea nozzle is not damaged and improving its reliability and service life.

Description

Technical Field

[0001] The present 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 for 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. It passes through the urea pipeline and is controlled by the urea nozzle to inject urea, causing the urea to decompose 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, and has a significant 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. The head of the urea nozzle is directly exposed to high-temperature exhaust gas. When not spraying, the urea at the urea nozzle is not updated, which brings two problems: on the one hand, the high temperature may directly damage the urea nozzle; on the other hand, the high temperature will cause the urea inside the nozzle to decompose due to heat, forming urea crystals that block the nozzle, or produce acidic substances that corrode the internal structure of the nozzle. Summary of the Invention

[0004] The present 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] Obtain the enable control signal of the urea nozzle;

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

[0008] Obtaining a high temperature protection signal of the urea nozzle when there is no fault in the urea nozzle;

[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 crystallization corrosion signal of the urea nozzle when there is no fault in the urea nozzle;

[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 conditions 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 nitrogen oxides is greater than the second preset temperature, the urea nozzle is controlled to perform an 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 nitrogen oxides is greater than the second preset temperature, before controlling the urea nozzle to perform the injection action at the first preset injection amount, the method further includes:

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

[0020] Optionally, the crystallization 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 timing device is controlled to start 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 a 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 an enable control signal from the urea nozzle; determines the fault status of the urea nozzle based on the enable control signal; obtains a high-temperature protection signal for the urea nozzle when the urea nozzle is fault-free; controls the urea nozzle to spray at a first preset spray volume based on the high-temperature protection signal; and obtains a crystallization corrosion signal for the urea nozzle when the urea nozzle is fault-free; controls the urea nozzle to spray at the first preset spray condition based on the crystallization corrosion signal. This method, while ensuring the urea nozzle itself is fault-free, prevents damage to the urea nozzle caused by high temperature, crystallization, and corrosion, thereby improving the reliability and service life of the urea nozzle.

[0029] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily 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 flowchart of a urea nozzle protection method provided in an embodiment of the present invention;

[0032] Figure 2 This is a flow chart of a second urea nozzle protection method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions 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 embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the description 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 numbers 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 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 This is a flow chart of a urea nozzle protection method provided by an embodiment of the present invention. This embodiment is applicable to the situation where the urea nozzle is exposed to high temperature, crystallization and corrosion to protect the urea nozzle, such as Figure 1 As shown, the method includes:

[0036] S110 : Acquire an enable control signal of a urea nozzle.

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

[0038] Specifically, the enabling control signal may be obtained in a manner including but not limited to obtaining it through 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 for the urea nozzle, if the enable control signal satisfies corresponding preset conditions, the urea nozzle can be determined to be in a normal state, and the urea nozzle itself is capable of spraying. If 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 requirements, and the urea nozzle may have a certain fault. The urea nozzle is then determined to be in a faulty state. In this faulty state, the urea nozzle should not be controlled to spray, 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 exposed to 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 to ensure that the urea nozzle is in a fault-free state. Therefore, this step performs the fault state of the urea nozzle in advance.

[0042] S130: When the urea nozzle is not faulty, 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 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 gas temperature of nitrogen oxides is excessively high, the urea nozzle's internal cooling capacity alone may be unable to maintain the temperature within the safe operating range. In this case, excessively high exhaust temperatures may directly damage the urea nozzle, causing changes in urea nozzle injection accuracy or even damage. To address this issue, this embodiment provides a solution for detecting a high-temperature protection signal for the urea nozzle when the urea nozzle is determined to be fault-free. Based on the high-temperature protection signal, and when all corresponding preset conditions are met, the urea nozzle is controlled to inject at a first preset injection amount, ensuring urea nozzle injection. This allows the urea nozzle to remove the high temperature of nitrogen oxides during injection, thereby reducing the internal temperature of the urea nozzle and preventing damage to the urea nozzle caused by high temperatures, thereby protecting the urea nozzle. The first preset injection amount may be a minimum injection amount, which can be determined based on actual conditions. For example, the first preset injection amount may be the minimum injection amount corresponding to the exhaust gas temperature determined by a table lookup.

[0046] S150: When the urea nozzle is not faulty, a crystallization 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 : Control the urea nozzle to perform an injection action under a first preset injection condition according to the crystal corrosion signal.

[0049] Specifically, when the urea nozzle meets the injection conditions and is controlled to perform injection, if the urea nozzle does not spray for an extended period, the urea solution inside the nozzle will not flow. The high temperature within the exhaust pipe can then cause the urea inside the nozzle to decompose, forming urea crystals that can clog the nozzle. Alternatively, the urea can react chemically with the sulfides in the nitrogen oxide exhaust, producing acidic substances that can corrode the internal structure of the urea nozzle and damage it. Therefore, this step protects the urea nozzle from crystallization corrosion. Specifically, when the urea nozzle is confirmed to be fault-free, a crystallization corrosion signal is obtained. When the crystallization corrosion signal meets the corresponding preset conditions, indicating a risk of crystallization corrosion, the nozzle is controlled to perform injection under the first preset injection condition to refresh the urea at the nozzle, ensuring that no reactants are generated in the urea at the nozzle, thereby protecting the nozzle from damage.

[0050] The technical solution of the embodiment of the present invention obtains an enable control signal for the urea nozzle; determines the fault status of the urea nozzle based on the enable control signal; obtains a high-temperature protection signal for the urea nozzle when the urea nozzle is fault-free; controls the urea nozzle to spray at a first preset injection volume based on the high-temperature protection signal; obtains a crystallization corrosion signal for the urea nozzle when the urea nozzle is fault-free; and controls the urea nozzle to spray at the first preset injection condition based on the crystallization corrosion signal. This method, while ensuring the urea nozzle itself is fault-free, prevents damage to the urea nozzle caused by high temperature, crystallization, and corrosion, thereby improving the reliability and service life of the urea nozzle.

[0051] In another alternative embodiment, Figure 2 This is a flow chart of a second urea nozzle protection method provided by 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, obtaining the urea solution temperature signal may include, but is not limited to, obtaining it via a urea temperature sensor. The urea solution temperature signal can reflect the thawing status of the urea. When the urea solution temperature signal is greater than or equal to a first preset temperature, it indicates that the urea has been successfully thawed. When the urea solution temperature signal is less than the first preset temperature, it indicates that the urea has not been successfully thawed. Obtaining the urea solution pressure signal may include, but is not limited to, obtaining it via a urea pressure sensor. Obtaining the SCR inlet temperature signal may include, but is not limited to, obtaining it via an SCR front exhaust temperature sensor. Since the SCR front exhaust temperature sensor is located very close to the urea nozzle, the SCR inlet temperature signal can be considered to be the temperature of the urea nozzle. Obtaining the engine exhaust flow signal may include, but is not limited to, obtaining the intake flow rate using a flow sensor installed at the engine intake, determining the engine exhaust flow rate based on a certain correspondence, and obtaining the engine exhaust flow rate. Alternatively, a flow sensor may be installed directly at the engine exhaust port for acquisition. The specific method can be determined based on actual circumstances and is not limited here. The electrical fault signal of the urea nozzle can be transmitted through the urea nozzle electrical fault communication to determine the electrical fault signal.

[0055] S220: 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 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 persist for a first preset time, it is determined that the urea nozzle is fault-free.

[0056] Specifically, after receiving the enable control signal, if it is determined based on the enable control signal that the temperature signal of the urea solution is greater than a first preset temperature, i.e., the urea is successfully thawed, 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 engine exhaust flow signal is greater than a first preset exhaust flow, and the urea nozzle is not faulty, and if the time during which the above conditions are met and the corresponding relationships are maintained for a first preset time, indicating that the urea nozzle remains in the above state during the time period, the urea nozzle is determined to be faulty. If any of the above conditions is not met, such as if the urea is not successfully thawed, the urea nozzle is determined to be in a faulty state, and the control is exited, i.e., control of subsequent urea nozzles is stopped.

[0057] It is understood that the first preset temperature can be determined based on actual conditions, the first preset pressure can be 700 kPa absolute, the first preset inlet temperature can be a commonly used temperature threshold of 170°C, and the first preset exhaust flow rate can be determined based on the engine displacement and rated engine speed, without limitation. The first preset time can be an anti-shake time, which can be determined based on actual conditions and without limitation.

[0058] S230: When the urea nozzle is not faulty, 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, obtaining the urea solution injection flow rate signal may include, but is not limited to, obtaining the high-temperature protection signal by a certain calculation method based on the design value of the injection flow rate. Obtaining the exhaust gas 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, determine a first preset injection amount according to the exhaust temperature signal of nitrogen oxides using a preset correspondence, and control the urea nozzle 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 obtaining a urea solution injection flow rate signal and a NOx exhaust temperature signal, based on the urea solution injection flow rate signal and the NOx exhaust temperature signal, if it is determined that the urea solution injection flow rate signal is less than a first preset injection flow rate and the NOx exhaust temperature signal is greater than a second preset temperature (where the first preset injection flow rate may be an injection flow rate threshold of 300 mg / s and the second preset temperature may be a commonly used hysteresis temperature threshold of 450°C), this indicates that the urea nozzle injection amount is too low and the NOx exhaust temperature is too high. Prolonged operation in these conditions may damage the urea nozzle, thus requiring protection of the urea nozzle. The urea nozzle is then controlled to inject at the first preset injection rate to continuously cool the urea nozzle. In this embodiment, the first preset injection rate is determined based on a preset, calibrated correspondence between the NOx exhaust temperature signal and the first preset injection rate. That is, when determining the NOx exhaust temperature, the exhaust temperature is substituted into the preset correspondence, and the first preset injection rate corresponding to the exhaust temperature is obtained by a table lookup or other method.

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

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

[0066] Specifically, the acquisition of the crystallization 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 a 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, 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, controlling the urea nozzle to perform the injection action under the first preset injection condition.

[0069] The urea nozzle drive duty cycle refers to the ratio of the time the urea nozzle is open to the total injection cycle during urea injection. Specifically, the drive duty cycle is a key parameter describing the pulse width modulation (PWM) signal, which determines how long the urea nozzle is open within a certain period of time. In a urea injection system, by adjusting the duty cycle of the PWM signal, the injection volume of the urea nozzle can be controlled, thereby precisely controlling the injection volume of the urea solution to meet exhaust gas treatment requirements. The first preset injection condition is that the injection volume of the urea nozzle is the second preset injection volume and lasts for a fourth preset time, where the fourth preset time is greater than the third preset time.

[0070] Specifically, after obtaining the urea nozzle drive duty cycle, based on the urea nozzle drive duty cycle, if the drive duty cycle is less than a first preset duty cycle (e.g., 1%), indicating that the urea nozzle has injected too little urea or has not injected as required, the timing device is controlled to start timing. When the timing reaches a second preset time (e.g., 300 seconds), indicating that the urea nozzle has not injected or has injected too little urea for an extended period of time, possibly causing clogging or corrosion, the urea nozzle is controlled to inject according to the first preset injection condition. Furthermore, if it is determined that the urea nozzle drive duty cycle signal is greater than the first preset duty cycle and persists for a third preset time (e.g., 2 seconds), indicating that the urea nozzle's injection capacity has met the injection requirement, the timing device is controlled to stop timing and reset the timer. If it is determined that the drive duty cycle is less than the first preset duty cycle, the timing device is restarted, and the urea nozzle is controlled to inject.

[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. The fourth preset time is greater than the third preset time. In this embodiment, the fourth preset time may be 5s.

[0072] The technical solution of the embodiment of the present invention comprises: obtaining 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, a temperature signal of an SCR inlet 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 persist for a first preset time; obtaining a high-temperature protection signal of the urea nozzle when the urea nozzle is fault-free; determining a first preset injection amount based on a preset correspondence relationship according to the exhaust temperature signal of nitrogen oxides when the injection flow signal of the urea solution is less than the first preset injection flow and the exhaust temperature signal of nitrogen oxides is greater than a second preset temperature, and controlling the urea nozzle to perform an injection action at the first preset injection amount; obtaining 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 at the first preset injection condition when a driving duty cycle signal of the urea nozzle is less than the first preset duty cycle and persists for a second preset time. By using 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 the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0074] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for protecting a urea nozzle, characterized in that: include: obtaining an enabling control signal of the urea nozzle; determining a fault state of the urea nozzle according to the enable control signal; obtaining 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; obtaining a crystallization corrosion signal of the urea nozzle when the urea nozzle is not faulty; controlling the urea nozzle to perform an injection action under a first preset injection condition according to the crystal corrosion signal; The crystallization corrosion signal includes a driving duty cycle signal of the urea nozzle; The step of controlling the urea nozzle to perform an injection action under a first preset injection condition according to the crystal corrosion signal 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, controlling the urea nozzle to perform an injection action under the first preset injection condition; 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: 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 the time to zero; When the timing reaches the second preset time, controlling the urea nozzle to perform the injection action according to the first preset injection condition; 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.

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 a 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 conditions persist 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 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 a first preset injection flow rate and the exhaust temperature signal of nitrogen oxides is greater than a second preset temperature, before controlling the urea nozzle to perform an injection action at the first preset injection amount, the method further includes: The first preset injection amount is determined according to the exhaust gas temperature signal of nitrogen oxides using a preset corresponding relationship; the preset corresponding relationship is a preset calibrated corresponding relationship between the exhaust gas temperature signal of nitrogen oxides and the first preset injection amount.

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