Urea injection system provided with frost crack prevention device and detection method of urea injection system

Abstract

The invention provides a urea injection system provided with a frost crack prevention device and a detection method thereof.The frost crack prevention device is arranged in the urea injection system and used for preventing a pipeline in the urea injection system from frost crack and comprises a first pipeline (110) arranged on the upstream of a urea pump (120) in the urea injection system, and a second pipeline (120) arranged on the upstream of the urea pump (120) in the urea injection system; an area higher than a liquid level line (106) is arranged in the first pipeline (110); the liquid level line (106) is the height of a urea solution (104) in a container for storing the urea solution (104) in the urea injection system; according to the method, the system is used for system detection.

Description

Technical Field

[0001] The invention relates to a urea injection system and a detection method thereof, in particular to a urea injection system provided with an anti-freezing cracking device and a detection method thereof. Background Art

[0002] This section merely provides background information related to the present disclosure and is not necessarily prior art.

[0003] The SCR (Selective Catalytic Reduction) system is an important exhaust treatment technology in modern diesel engines, and its main purpose is to reduce the emission of nitrogen oxides (NOx). The urea injection system is a key component of the SCR system, which mainly includes several parts such as the urea solution storage tank, the urea solution delivery system, the urea injection unit, and the control system. The function of the urea solution storage tank is to store the urea solution. The urea solution is usually a mixture of 32.5% urea and 67.5% deionized water, called automotive urea solution or DEF (Diesel Exhaust Fluid). The urea solution storage tank is usually equipped with a heating device to prevent the urea solution from crystallizing in a low temperature environment. The urea solution delivery system includes a urea pump, a delivery pipeline, and a filter, etc., which are used to transport the urea solution from the storage tank to the injection system. The urea pump is usually an electric pump that can provide a stable urea solution flow and pressure. Urea injection unit: responsible for injecting the urea solution into the exhaust pipe. Its design ensures that the urea solution evaporates quickly and decomposes into ammonia in the high-temperature exhaust gas. The control system includes a CU (control unit) and sensors to monitor engine operating conditions and exhaust composition and calculate the urea injection amount.

[0004] In addition to the urea injection system, the SCR system also includes sensors, such as NOx sensors, temperature sensors, pressure sensors, etc., and SCR catalysts. The SCR catalyst is located in the exhaust pipe and is used to react the injected ammonia with the nitrogen oxides in the exhaust gas under the action of the catalyst to generate harmless nitrogen and water. The catalyst is usually vanadium-based, copper-based, or iron-based.

[0005] In the SCR system, the CU first detects the nitrogen oxide content in the exhaust gas through the NOx sensor, and obtains the engine's operating status data (such as speed, load, etc.), and then calculates the amount of urea solution to be injected based on the detected NOx content and the engine's operating status. According to the calculation results, the CU controls the urea pump to deliver the urea solution to the nozzle and controls it to inject urea into the exhaust pipe. In the exhaust pipe, the urea solution quickly decomposes in the high-temperature exhaust gas to generate ammonia, which reacts with the NOx in the exhaust gas in the SCR catalyst to remove it.

[0006] The SCR system can significantly reduce the NOx emissions of diesel engines, meet strict emission standards, and is suitable for various types of diesel engines and working conditions. However, the SCR system also needs to regularly check the urea solution storage, the working status of the urea delivery system, and the injection status of the nozzles, so as to regularly replenish the urea solution and ensure the normal operation of the system. In addition, in low temperature environments, it is necessary to ensure that the heating devices of the urea storage tank and pipelines are working properly to melt the frozen urea and prevent the urea from freezing again during operation.

[0007] In the urea tank, freezing of urea will affect the components. After freezing, the volume of urea expands by about 1.1 times. When urea is sealed in a closed cavity, its volume expansion after freezing will produce a very large pressure on the cavity wall. If the cavity is not elastic enough or not strong enough, this stress may cause it to crack. Therefore, when designing the urea system, it is generally necessary to avoid the urea solution filling the closed cavity after the urea pump stops running.

[0008] In some applications, especially in light-duty engine applications, a structure in which the urea pump is placed in the urea tank is used, which is the so-called In-Tank design. This structure takes up little space, is compact, and is low-cost and easy to heat (heats up quickly). However, this design also has inherent shortcomings, especially when using an electric pump. It is difficult to keep the urea inlet pipeline from being filled with urea. Even if it is cleaned during shutdown, the urea pump itself may leak and expand and contract due to heat, so the urea will still fill the inlet pipeline. And this part of the urea expands in volume when frozen, which can easily rupture this part of the pipeline.

[0009] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0010] Purpose of the invention: The technical problem to be solved by the present invention is to provide a urea injection system with an anti-freezing cracking device and a detection method thereof in view of the deficiencies in the prior art.

[0011] In order to solve the above technical problems, the present invention discloses a urea injection system provided with an anti-freezing cracking device and a detection method thereof, wherein the anti-freezing cracking device is in the urea injection system and is used to prevent the pipeline in the urea injection system from freezing and cracking, and the anti-freezing cracking device comprises:

[0012] A first pipeline is arranged upstream of a urea pump in the urea injection system, wherein the first pipeline has an area above a liquid level line;

[0013] The liquid level line is the height of the urea solution in the container storing the urea solution in the urea injection system.

[0014] Furthermore, the system comprises:

[0015] A urea tank for storing a urea solution, wherein the urea tank is provided with the urea pump for pumping the urea solution;

[0016] The first port of the urea pump is connected to the first pipeline, and the second port is connected to the second pipeline;

[0017] The second pipe is communicated with the urea nozzle.

[0018] Furthermore, a vent hole is provided on the top of the urea tank, and a liquid inlet is provided on the side wall, and the position of the liquid inlet determines the position of the liquid level line.

[0019] Furthermore, the second pipeline is connected to a pressure sensor.

[0020] Furthermore, the second pipeline is communicated with a liquid return pipeline, and a one-way valve is provided on the liquid return pipeline to control the flow direction of the urea solution to flow out only from the liquid return pipeline.

[0021] Furthermore, the urea pump is provided with three control states, specifically including:

[0022] In a first control state, the urea solution flows in from the first port and flows out from the second port after being pressurized;

[0023] In a second control state, the urea solution flows in from the second port and flows out from the first port after being pressurized;

[0024] In a third control state, the urea solution does not pass through the urea pump.

[0025] Furthermore, the system also includes:

[0026] The controller is electrically connected to the urea pump, the pressure sensor and the urea nozzle respectively, and is used for acquiring the pressure value and controlling the urea pump and the urea nozzle.

[0027] Furthermore, the system has four operating states according to the control instructions of the controller, specifically including:

[0028] The first operating state is an initialization state, the urea pump operates in a first control state, the urea nozzle is closed, and injection pressure is established in the second pipeline, while the air therein is exhausted;

[0029] The second operation state is the injection state, the urea pump operates in the first control state, and the urea nozzle is periodically opened to control the urea injection amount;

[0030] The third operating state is an emptying state, the urea pump enters a second control state, the urea nozzle is turned on, and air is used to empty the urea solution in the second pipeline, the urea pump and the first pipeline;

[0031] The fourth operating state is a shutdown state, and the urea pump enters a third control state.

[0032] Furthermore, a box cover is provided at the entrance of the liquid inlet;

[0033] A filter screen is provided at the inlet of the first pipeline.

[0034] The present invention also proposes a method for detecting a urea injection system provided with an anti-freezing cracking device, and the method uses the aforementioned system to perform system detection, comprising the following steps:

[0035] Step 1, closing the urea nozzle;

[0036] Step 2, operating the urea pump to the second control state;

[0037] Step 3, using the pressure sensor to obtain a pressure value, and making a judgment, if the pressure value is higher than a first threshold, it is judged that the second pipeline is faulty or the urea pump is faulty;

[0038] Step 4, opening the urea nozzle;

[0039] Step 5, using the pressure sensor to obtain a pressure value, and making a judgment, if the pressure value is not higher than a second threshold, it is judged that the urea nozzle is faulty;

[0040] Step 6, closing the urea nozzle;

[0041] Step 7, operating the urea pump to the first control state;

[0042] Step 8: Use the pressure sensor to obtain a pressure value, and calculate the time required for the pressure value to reach a third threshold value. If the time is less than a fourth threshold value, it is determined that the first pipeline is faulty.

[0043] Beneficial effects:

[0044] 1. The present invention proposes a urea injection system using an "X"-shaped curved pipe as a liquid inlet pipe. The special shape of the pipe makes it impossible for the system to be filled with urea after cleaning, so there is enough expansion space to prevent the liquid inlet pipe from freezing and cracking.

[0045] 2. The present invention also proposes a detection method, which can diagnose the integrity and performance of the injection pipeline, urea pump, urea nozzle, and the "J" curved pipe by comprehensively controlling the urea pump and the urea nozzle and measuring the impact of their actions on the pressure sensor signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0047] Figure 1 It is a schematic diagram of the overall structure and injection state in an embodiment.

[0048] Figure 2 Schematic diagram of the clearing state in an embodiment.

[0049] Figure 3 Schematic diagram of shutdown state in an embodiment.

[0050] Figure 4 The figure is a flow chart of diagnosing the system in one embodiment.

[0051] Figure 5 The figure is a flow chart of diagnosing the anti-freeze crack device in one embodiment. DETAILED DESCRIPTION

[0052] The present invention proposes a urea injection system using a 'X' shaped curved pipe as a liquid inlet pipe. The special shape of the pipe makes it impossible for the system to be filled with urea after cleaning, so there is enough expansion space to prevent the liquid inlet pipe from freezing and cracking. At the same time, in the present invention, the integrity and performance of the injection pipe, urea pump, urea nozzle, and 'X' shaped curved pipe can also be diagnosed by comprehensively controlling the urea pump and the urea nozzle and measuring the influence of their actions on the pressure sensor signal.

[0053] like Figure 1 As shown, the urea injection system includes a urea tank 105, in which a urea pump 120, a urea nozzle 135, and a controller 130 are arranged. The urea tank has a liquid inlet 101 and a tank cover 102, and the liquid inlet 101 includes a liquid inlet filter (not shown). There are inlet and outlet holes 103 at the upper end of the urea tank, and urea solution 104 is stored in the urea tank.

[0054] Restricted by the liquid inlet 101 and the air inlet and outlet holes 103, the highest liquid level does not exceed the liquid level line 106. The urea tank 105 may also be provided with a liquid level line 106 in other ways.

[0055] The liquid inlet end of the urea pump 120 is connected to the filter 115 through a "X"-shaped curved pipe 110, and the highest position of the curved pipe 110 is higher than the liquid level line 106. The urea pump 120 is connected to the urea nozzle 135 through the injection pipeline 112, and there is a return hole in the middle of the injection pipeline 112 leading to the inside of the urea tank. A one-way valve 111 is arranged in the return hole. Under the action of the valve, urea can only flow out of the return hole and cannot flow in from the return hole. The urea injection system also includes a pressure sensor 125, which is used to measure the pressure in the downstream pipeline of the urea pump. The urea pump 120, the pressure sensor 125, and the urea nozzle 135 are connected to the controller 130 through signal lines 121, 122, and 123 respectively.

[0056] In the SCR system, the urea injection system generally has four working states: 1. Initialization (Prime), 2. Injection (Working), 3. Purge (Purge), 4. Halt (Halt), and the urea pump 120 has three working states: 1. Forward working state, 2. Reverse working state, and 3. Halt state.

[0057] In the initialization state, the urea pump 120 is in a forward working state, the urea solution enters the urea pump through the filter 115 and the X-shaped curved pipe 110 for pressurization, and then enters the injection pipeline 112 to establish a stable injection pressure, and then the nozzle 135 is opened to exhaust the air in the urea pipeline.

[0058] Then the system enters the injection state, in which the controller 130 sends an injection command to the urea nozzle 135, opens the urea nozzle at a fixed time, and controls the urea injection amount by controlling the duty cycle or the opening interval;

[0059] When the SCR system stops working, the urea injection system enters an emptying state, in which the urea pump 120 enters a reverse working state (reversed or with the help of a reverse control valve), evacuates the urea in the urea nozzle 135 and the injection line 112 and flows back to the urea tank 105 .

[0060] When the urea injection system is emptied, it enters the shutdown state, and the urea pump 120 is in the shutdown state, and the system stops operating until the next system is started. After the urea injection system is emptied, some pipes may still have urea residue or some urea formed by urea reflux. This part of urea must be controlled below a certain amount to prevent freezing and cracking of the pipes.

[0061] Figure 1The system shown is in the initialization state and the injection state, at which the urea pump 120 is started, and the urea in the urea tank 105 passes through the filter 115 and the X-shaped curved pipe 110 and flows into the urea pump 120. After flowing out of the urea pump 120, a part of the urea solution flows back to the urea tank through the one-way valve 111, and the other part enters the urea nozzle 135 and is sprayed out of the system after it is turned on. Figure 1 When the system is in the clear state, Figure 2 As shown, at this time, the urea pump 120 pumps liquid in the reverse direction. At the same time, due to the effect of the one-way valve 111 (the urea solution in the urea tank cannot flow back to the urea pump 120 through the one-way valve 111), after the nozzle 135 is opened, air flows into the urea pump through the nozzle 135 and the injection pipeline 112, and flows out through the "X"-shaped curved pipe 110 and the filter 115, emptying the urea solution therein. The air flowing into the urea pump eventually flows out of the urea tank through the inlet and outlet holes 103. After shutdown, the system is as follows Figure 3 As shown, at this time, with the leakage of air in the pipeline 112, the one-way valve 111, the pump 120, and the "J"-shaped curved pipe 110 and the dissolution in the urea solution, and the influence of the contraction of the pipeline and the curved pipe, the urea solution in the urea tank 105 will flow back to the "J"-shaped curved pipe 110 through the filter 115. However, since the highest point of the curved pipe is higher than the liquid level 106, the urea flowing back into the "J"-shaped curved pipe 110 can only enter the left side of the curved pipe, but cannot fill it (its liquid level will be slightly lower than the urea liquid level in the urea tank). In this way, a large expansion space is reserved, so that the pipeline and the pump will not be damaged when the urea freezes and expands.

[0062] The curved pipe 110 may also be in other forms, for example, it may have multiple points exceeding the liquid level 106, and it does not have to be in the shape of a triangle.

[0063] exist Figure 1-3 In the system shown, the controller 130 has a microprocessor, which can comprehensively control the urea pump 120 and the urea nozzle 135 by running the program in the microprocessor, and diagnose the integrity and performance of the injection pipeline, urea pump, urea nozzle, and the "X" curved pipe by measuring the impact of their actions on the signal of the pressure sensor 125. The diagnostic program can be combined with the normal operation of the urea injection system without increasing the system burden.

[0064] exist Figure 1 In the system shown, the diagnosis of the urea pipeline 112, the one-way valve 111, the urea pump 120, and the urea nozzle 135 can be performed during the emptying process. The diagnostic method can be implemented by a diagnostic program, and the diagnostic program can be run in the microprocessor of the controller. Figure 4As shown, after a diagnostic example program starts, the urea nozzle 135 is first closed, and then the urea pump 120 is reversed to allow the urea to flow back, and wait for Ts seconds. Then, the pressure measurement value P125 obtained from the pressure sensor 125 is checked. If P125 is greater than a threshold Thd_maxP, it means that the injection pipeline is leaking or there is a problem with the pump 120. The fault flags LK_Err and Pump_Err are set to 1. LK_Err is 1, which will trigger the injection pipeline leakage fault, and Pump_Err is 1, which will trigger the urea pump fault. After setting the fault flag, the program stops and exits. Going back to the comparison between P125 and Thd maxP, if P125 is not greater than Thd maxP, P125 is compared with Thd_maxP-Thd_db1, where Thd_db1 is a debounce threshold. If P125 is less than Thd_MaxP-Thd_db1, the error flags LK_Err and Pump_Err are cleared to 0. LK_Err and Pump_Err being 0 will clear the injection line leakage fault and urea pump fault. The program then turns on the urea nozzle 135 and waits for Tw seconds, then determines whether P125 is greater than the threshold Thd_minP. If P125 is not greater than Thd_minP, the nozzle fault flag NZ_Err is set to 1. The flag NZ_Err being 1 will trigger the urea nozzle fault, and then the program stops and exits. Otherwise, check whether P125 is greater than Thd_minP+Thd_db2, where Thd_db2 is another debounce threshold. If P125 is greater than Thd_minP+Thd_db2, the error flag NZ_err is cleared to 0. NZ_err being 0 will clear the urea nozzle fault. The program then turns off the urea nozzle 135, stops, and exits. Figure 4 In the program shown, the thresholds Thd_maxP, Thd_db1, Thd_minP, Thd_db2, and the constants Ts and Tw are calibration constants and can be calibrated in experiments.

[0065] The diagnosis of the zigzag curved pipe 110 can be performed during the initialization process. Similarly, the diagnosis method can be implemented through a diagnosis program. Figure 5As shown, after the diagnosis routine starts, the urea nozzle 135 is first closed, and then the urea pump 120 is turned on in the forward direction. After that, it is determined whether the time T_Pa when P125 reaches the pressure Pa is greater than or equal to a threshold value Thd_TPamin. If T_Pa is greater than or equal to Thd_TPamin, it is determined that the 9-shaped curved pipe 110 and the filter are not separated from the urea pump 120, and the error flag Filt_Err is cleared to 0. Filt_Err is 0 to clear the 9-shaped curved pipe fault. Otherwise, if T_Pa is less than Thd_TPamin-Thd_db3, where Thd_db3 is a debounce threshold, the error flag Filt_Err is set to 1. Filt_Err is 1 to trigger the 9-shaped curved pipe fault. The program stops and exits after completing the above steps. Figure 5 In the program shown, the thresholds Thd_TPamin and Thd_db3 are calibration constants and can be calibrated in experiments.

[0066] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, the invention content of a urea injection system with an anti-freeze cracking device and a detection method thereof provided by the present invention and some or all steps in each embodiment can be run. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0067] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on such an understanding, the technical solutions in the embodiments of the present invention can be essentially or partly contributed to the prior art in the form of computer programs, i.e., software products, which can be stored in a storage medium and include several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, an MCU or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0068] The present invention provides a urea injection system with an anti-freeze cracking device and a method for detecting the same. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A urea injection system provided with an anti-freezing cracking device, characterized in that: The anti-freezing and cracking device is in the urea injection system and is used to prevent the pipeline in the urea injection system from freezing and cracking. The anti-freezing and cracking device includes: A first pipeline (110) disposed upstream of a urea pump (120) in the urea injection system, wherein the first pipeline (110) has an area above a liquid level line (106); The liquid level line (106) is the height of the urea solution (104) in the container storing the urea solution (104) in the urea injection system.

2. A urea injection system with an anti-freezing cracking device according to claim 1, characterized in that: The system comprises: A urea tank (105) for storing a urea solution (104), wherein the urea tank (105) is provided with a urea pump (120) for pumping the urea solution (104); The first port of the urea pump (120) is connected to the first pipeline (110), and the second port is connected to the second pipeline (112); The second pipe (112) is in communication with a urea nozzle (135).

3. A urea injection system with an anti-freezing cracking device according to claim 2, characterized in that: The top of the urea tank (105) is provided with a vent hole (103), and the side wall is provided with a liquid inlet (101), and the position of the liquid inlet (101) determines the position of the liquid level line (106).

4. A urea injection system with an anti-freezing cracking device according to claim 3, characterized in that: The second pipe (112) is in communication with a pressure sensor (125).

5. A urea injection system with an anti-freezing cracking device according to claim 4, characterized in that: The second pipe (112) is in communication with a liquid return pipe, and a one-way valve (111) is provided on the liquid return pipe for controlling the flow direction of the urea solution (104) to flow out only from the liquid return pipe.

6. A urea injection system with an anti-freezing cracking device according to claim 5, characterized in that: The urea pump (120) is provided with three control states, specifically including: In a first control state, the urea solution (104) flows in from the first port and flows out from the second port after being pressurized; In a second control state, the urea solution (104) flows in from the second port and flows out from the first port after being pressurized; In a third control state, the urea solution (104) does not pass through the urea pump (120).

7. A urea injection system with an anti-freezing cracking device according to claim 6, characterized in that: The system further comprises: The controller (130) is electrically connected to the urea pump (120), the pressure sensor (125) and the urea nozzle (135) respectively, and is used to obtain a pressure value and control the urea pump (120) and the urea nozzle (135).

8. A urea injection system with an anti-freezing cracking device according to claim 7, characterized in that: The system has four operating states according to the control instructions of the controller (130), specifically including: The first operating state is an initialization state, the urea pump (120) operates in a first control state, the urea nozzle (135) is closed, and injection pressure is established in the second pipe (112), while the air therein is exhausted; The second operating state is an injection state, the urea pump (120) operates in a first control state, and the urea nozzle (135) is periodically opened to control the urea injection amount; The third operating state is an emptying state, the urea pump (120) enters a second control state, the urea nozzle (135) is turned on, and air is used to empty the urea solution (104) in the second pipeline (112), the urea pump (120) and the first pipeline (110); The fourth operating state is a shutdown state, and the urea pump (120) enters a third control state.

9. A urea injection system with an anti-freezing cracking device according to claim 8, characterized in that: A box cover (102) is provided at the entrance of the liquid inlet (101); A filter screen (115) is provided at the inlet of the first pipeline (110).

10. A method for detecting a urea injection system provided with an anti-freezing cracking device, using the system according to any one of claims 6 to 9 for system detection, characterized in that: The following steps are involved: Step 1, closing the urea nozzle (135); Step 2, operating the urea pump (120) to the second control state; Step 3, using the pressure sensor (125) to obtain a pressure value, and making a judgment, if the pressure value is higher than a first threshold, it is judged that the second pipeline (112) is faulty or the urea pump (120) is faulty; Step 4, opening the urea nozzle (135); Step 5, using the pressure sensor (125) to obtain a pressure value, and making a judgment, if the pressure value is not higher than a second threshold value, it is judged that the urea nozzle (135) is faulty; Step 6, closing the urea nozzle (135); Step 7, operating the urea pump (120) to the first control state; Step 8: using the pressure sensor (125) to obtain a pressure value, and calculating the time required for the pressure value to reach a third threshold value; if the time is less than a fourth threshold value, it is determined that the first pipeline (110) is faulty.

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