Urea spraying quality sensor

Abstract

The invention discloses a urea injection quality sensor, and belongs to the technical field of urea solution detection, the urea injection quality sensor comprises a floater, an inner column, a Hall magnetic sensitive device, a quality sensing module and a signal processing unit, the Hall magnetic sensitive device is arranged in the inner column and is connected with the signal processing unit; the Hall magneto-sensitive device can interact with a magneton installed in the floater to generate a liquid level sensing signal, when the floater moves up and down, the liquid level sensing signal changes to form a pulse sequence, and the signal processing unit can obtain a continuous urea liquid level according to the pulse sequence and the position of the Hall magneto-sensitive device; the quality sensing module is connected with the signal processing unit to generate a urea quality sensing signal; the urea injection quality sensor detects a failure of the urea nozzle based on the urea quality sensing signal and the continuous urea liquid level. According to the sensor, the accurate urea liquid level can be obtained, multiple functions are provided, and meanwhile estimation is more reliable through a urea crystallization and ammonia storage amount calculation method based on high-precision liquid level information.

Description

Technical Field

[0001] The invention belongs to the technical field of urea solution detection, and in particular relates to a urea injection quality sensor. Background Art

[0002] Urea level sensors are a key component in the Selective Catalytic Reduction (SCR) system, used to monitor and control the amount of urea solution (commonly known as Diesel Exhaust Fluid or DEF) in the system. This sensor ensures that the SCR system can continue to operate effectively, thereby reducing nitrogen oxides (NOx) emitted by diesel engines.

[0003] Urea level sensors are usually installed in urea tanks and can monitor the liquid level in real time, helping the vehicle management system determine when the urea solution needs to be replenished. The working principle of the sensor is based on technologies such as reed switches, capacitors, ultrasound or optics, which can accurately measure the liquid level in the tank. When the urea level is lower than the set threshold, the sensor will send a signal to the vehicle's control system to prompt the driver or maintenance personnel to replenish it to ensure the normal operation of the SCR system. In addition, urea level sensors can also help detect possible problems in the system, such as urea crystallization or failure of the sensor itself, to ensure efficient operation of the system and compliance with emission control. This is of great significance for complying with strict environmental regulations and reducing environmental pollution.

[0004] Urea level sensors based on reed switches are the most widely used. Reed switches are a type of magnetic switch. In urea level sensors using reed switches, a float moves up and down with the liquid level. The float contains a magnet. When the distance between the magnet and the reed switch is less than the operating distance, the reed switch closes. The urea level can be detected by detecting the resistance change caused by the closure of the reed switch and the position of the reed switch.

[0005] However, the reed switch is a switch tube that can only provide discrete liquid level data. In order to increase the accuracy of liquid level sensing, the number of reed switches needs to be increased. Too many reed switches not only make the layout difficult, but also increase the risk of failure. Hall magnetic sensors can also be used together with magnets to measure urea liquid levels. Hall magnetic sensors can be non-switch devices, but the distance between the magnets and the device is measured by the signal they generate. However, the signal generated by the Hall magnetic sensor itself will change due to other factors, resulting in inaccurate measurements, which limits the application of Hall magnetic sensors in urea liquid level sensors.

[0006] In the SCR system, urea is decomposed into ammonia through pyrolysis and hydrolysis, and then reacts with nitrogen oxides in the catalyst. The overall reaction of urea pyrolysis and hydrolysis is endothermic, which means that the decomposition of urea requires the absorption of exhaust gas energy. When the energy transferred from exhaust gas to urea solution is not enough to decompose urea, the undecomposed urea will form crystals in the SCR system. Factors that affect exhaust gas energy transmission include improper handling of urea solution and changes in environmental conditions. When the urea injection system cannot effectively atomize the solution (for example, the urea injection angle or atomization degree does not match the mixer, resulting in the urea solution not being evenly distributed, or the urea solution not being fully atomized due to nozzle blockage or unstable injection pressure), the urea solution droplet size and distribution will change, resulting in changes in the heat transfer effect; when the temperature distribution in the SCR decomposition tube is uneven, the temperature in some areas is too low, or when the ambient temperature is too low, the heat will be insufficient to support the thermal decomposition and hydrolysis of urea; in addition, when there are problems with the concentration or purity of the solution (such as too high concentration or too high impurities), the energy required for the thermal decomposition and hydrolysis of urea will also change. All these factors may form urea crystals, which are usually formed on the nozzle, exhaust pipe or catalyst surface, and are mostly in the form of hard crystal deposition. The presence of urea crystals will hinder the normal injection of the solution, affect the contact area and activity of the catalyst, thereby reducing the efficiency of the SCR system, increasing the maintenance requirements of the system, and may lead to failure to meet strict environmental emission standards.

[0007] By sensing the conditions that cause urea crystallization, the amount of crystallization can also be calculated through the crystallization model in SCR control, and the urea injection amount can be controlled according to the amount of crystallization or the DPF (Diesel Particulate Filter) regeneration (heating the exhaust gas) can be triggered to reduce or eliminate urea crystallization. However, the accuracy of the crystallization model depends on the control accuracy of urea injection. At the same time, the urea crystallization model needs to accumulate the urea injection rate to calculate the number of crystals, and the accuracy of urea injection also has an accumulation effect. In addition, according to the status of the SCR system and the history of urea injection, the amount of ammonia stored in the SCR carrier can also be estimated, but again, this estimate is also very dependent on the control accuracy of urea injection. Summary of the invention

[0008] Purpose of the invention: The technical problem to be solved by the present invention is to provide a urea injection quality sensor in view of the deficiencies in the prior art.

[0009] In order to solve the above technical problems, in a first aspect, a urea injection quality sensor is disclosed, comprising a float, an inner column, a Hall magnetic sensor, a quality sensing module and a signal processing unit, wherein a magnetic particle is installed in the float and can move up and down along the inner column; a Hall magnetic sensor is arranged in the inner column and connected to the signal processing unit; the Hall magnetic sensor can interact with the magnetic particle to generate a liquid level sensing signal, and the liquid level sensing signal is received and processed by the signal processing unit; when the float moves up and down, the liquid level sensing signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and its amplitude is analogically related to the position of the magnetic particle; the signal processing unit can obtain a continuous urea liquid level determined by the accuracy of the Hall magnetic sensor according to the pulse sequence and the position of the Hall magnetic sensor; the quality sensing module is connected to the signal processing unit, and the quality sensing module generates a urea quality sensing signal; the urea injection quality sensor detects the urea quality according to the urea quality sensing signal, and detects a urea nozzle fault according to the urea quality sensing signal and the continuous urea liquid level.

[0010] Furthermore, the float is restricted from rotating around the inner column, the signal processing unit includes a marking resistor, and at least one of the pulse sequences is a marking pulse signal, the pulse voltage of which is related to the resistance value of the marking resistor.

[0011] Furthermore, at least two closely arranged Hall magneto-sensitive devices are provided in the inner column.

[0012] Further, the continuous urea liquid level determined by the accuracy of the Hall magnetic sensor device can be obtained according to the pulse sequence and the position of the Hall magnetic sensor device, including:

[0013] Step 1-1, finding the mark pulse signal generated by the mark resistor by checking the pulse voltage, and marking it as the initial pulse;

[0014] Step 1-2, finding the pulse generated by the Hall magneto-sensitive device by checking the pulse voltage after the initial pulse, and measuring its pulse voltage;

[0015] Step 1-3, calculating the urea liquid level height according to the measured pulse voltage generated by another adjacent Hall magnetic sensor arranged closely.

[0016] In one implementation, steps 1-3 include: when the magnet moves from bottom to top, two Hall magneto-sensitive devices generate voltage signals, the voltage generated by the Hall magneto-sensitive device at the bottom is V301, the voltage generated by the Hall magneto-sensitive device at the top is V302, and V303 is the difference between V301 and V302:

[0017] V303 = V301 - V302 (F2)

[0018] Calculate the urea liquid level height h based on the measured voltages V301, V302, and V303:

[0019] When V303>0 & V302 = Vo & V301>Vo, dh = Tbl1(V301), h = H0 - dh;

[0020] When V303>0 & V302>Vo & V301>Vo, dh = Tbl2(V302), h = H1 - dh;

[0021] When V303<0 & V302>V2, dh = Tbl3(V301), h = H0 + dh;

[0022] When V303<0 & V302<V2, dh = Tbl4(V302), h = H1 + dh;

[0023] When V303>0 & V301<Vo & V302<Vo, dh = Tbl5(V301), h = H2 + dh;

[0024] When V303>0 & V301 = Vo & V302<Vo, dh = Tbl6(V302), h = H3 + dh (F3)

[0025] Where V2 is the calibration threshold, Vo is the voltage generated by the Hall magnetosensitive device when the magnet is far from the Hall magnetosensitive device, and V2 and Vo are calibrated through experiments; Tbl1(), Tbl2(), bl3(), Tbl4(), Tbl5(), and Tbl6() are look-up table calculations, and the table values are calibrated through experiments; dh is the relative height, H0 and H1 are the liquid level heights when the north magnetic pole of the magnet in the float is closest to the lower Hall magnetosensitive device and the upper Hall magnetosensitive device respectively, while H2 and H3 are the liquid level heights when the south magnetic pole of the magnet is closest to the lower Hall magnetosensitive device and the upper Hall magnetosensitive device respectively.

[0026] Furthermore, at least three equidistantly arranged Hall magnetosensitive devices are provided in the inner column.

[0027] Furthermore, the continuous urea liquid level determined by the accuracy of the Hall magnetosensitive device can be obtained according to the pulse sequence and the position of the Hall magnetosensitive device, including:

[0028] Step 1-1, find the marker pulse signal generated by the marker resistor by checking the pulse voltage, and mark it as the initial pulse;

[0029] Step 1-2: Search for the pulses generated by the Hall magneto-sensitive device by checking the pulse voltages after the initial pulse, and measure their pulse voltages.

[0030] Step 1-3: Calculate the urea liquid level height based on the pulse voltages generated by two adjacent Hall magneto-sensitive devices arranged at equal intervals.

[0031] In one implementation, Step 1-3 includes: For the nth device among multiple Hall magneto-sensitive devices, n ≥ 2, calculate the urea liquid level height h:

[0032] When V(n - 1) < Vo & V(n) > Vo, dh = Tbl7(V(n)), h = H(k) - dh;

[0033] When (V(n) > Vo or V(n) < Vo) & V(n + 1) = Vo, dh = Tbl8(V(n)), h = H(k) + dh (F5)

[0034] Wherein, V(n - 1), V(n), and V(n + 1) are the voltage signals generated by the (n - 1)th, nth, and (n + 1)th Hall magneto-sensitive devices respectively, Vo is the voltage generated by the Hall magneto-sensitive device when the magnetic element is far from it; Tbl7() and Tbl8() are calculations by looking up tables, and their table values are calibrated through experiments; dh is the relative height, and H(k) is the liquid level when the north pole of the magnetic element is closest to the nth Hall magneto-sensitive device.

[0035] Further, the detection of urea nozzle failure includes:

[0036] Step 2-1-1: Calculate the measured urea volume change dUV through the change in the float liquid level:

[0037] dUV = Tbl_LV(L0) - Tbl_LV(L0 - dL) (F6)

[0038] Where L0 is the starting liquid level for calculation, dL is the amount of liquid level decrease, both L0 and dL are obtained through Step 1-3 calculation, Tbl_LV() is a calculation by looking up tables for calculating the urea volume corresponding to the liquid level, and the table values in the look-up table calculation are calibrated for the used urea tank in the experiment;

[0039] Step 2-1-2: Calculate the expected urea volume change Tu through the urea injection amount:

[0040] Tu = sigma(Dc * T) (F7)

[0041] Where Dc is the urea injection rate command, T is the calculation period, and sigma() is an accumulation calculation;

[0042] Step 2-1-3, detecting a urea nozzle fault by comparing the measured urea volume change dUV with the expected urea volume change Tu and according to the urea quality sensing signal:

[0043] Calculate the absolute value DisJV of the difference between Tu and dUV:

[0044] DisJV = Abs(Tu-dUV)(F8)

[0045] Among them, Abs() is calculated by taking the absolute value. If DisJV is greater than the first error judgment threshold Thd_ErUp, it is detected that there is a fault in the urea nozzle; if DisJV is not greater than the first error judgment threshold Thd_ErUp, it is determined whether DisJV is less than the second error judgment threshold Thd_ErLow. If DisJV is less than the second error judgment threshold Thd_ErLow, it is detected that the urea nozzle is not faulty; the first calculation threshold Thd_Jmin, the first error judgment threshold Thd_ErUp, and the second error judgment threshold Thd_ErLow are all calibrable quantities and are calibrated through experiments.

[0046] Furthermore, the urea injection quality sensor further detects a urea pump failure including:

[0047] Step 2-2-1, empty the urea pump;

[0048] Step 2-2-2, record the float liquid level 1;

[0049] Step 2-2-3, fill the urea pump;

[0050] Step 2-2-4, record float level 2;

[0051] Step 2-2-5, diagnosing urea pump fault according to the difference between the float liquid level 1 and the float liquid level 2 and the urea quality sensing signal.

[0052] In one implementation, step 2-2-5 includes:

[0053] The difference is compared with the third error judgment threshold Thd_LdLow. If the difference is less than the third error judgment threshold Thd_LdLow, it is detected that the urea pump body has a fault; if the difference is not less than the third error judgment threshold Thd_LdLow, the difference is compared with the fourth error judgment threshold Thd_LdUp. If the difference is greater than the fourth error judgment threshold Thd_LdUp, it is detected that the urea pump body has no fault; the third error judgment threshold Thd_LdLow and the fourth error judgment threshold Thd_LdUp are both calibrable quantities and are calibrated through experiments.

[0054] Furthermore, the urea injection quality sensor further calculates urea crystals including:

[0055] Step 3-1-1, calculating the first crystallization amount dV2a based on the urea injection rate, the exhaust gas temperature and the exhaust gas mass flow rate:

[0056] dV2a = sigma(Tbl_Crystal(Mf*Tin, Dc)*T) (F11)

[0057] Wherein, Mf is the mass flow rate of exhaust gas, Tin is the exhaust gas temperature measured upstream of the urea nozzle, Tbl_Crystal() is a table lookup calculation, and its table value is calibrated by experiment;

[0058] Step 3-1-2, calculate the second crystallization amount dV2b by the urea volume change dUV, tail gas temperature and tail gas mass flow rate:

[0059] dV2b = Tbl_Crystal(sigma(Mf*Tin, T), dUV) (F12)

[0060] Where dUV is the volume change of urea, calculated by formula (F6);

[0061] Step 3-1-3, calculating the urea crystal amount dV2 according to the first crystal amount dV2a and the second crystal amount dV2b:

[0062] Calculate the difference Abs (dV2a-dV2b) between dV2a and dV2b, where Abs() is an absolute value calculation. If the difference is greater than the first judgment threshold Thd_Cmax, dV2 = dV2a, otherwise dV2 = dV2b. The first judgment threshold Thd_Cmax is a calibrable quantity and is obtained by calibration in the experiment.

[0063] Furthermore, the urea injection quality sensor further calculates the ammonia storage amount including:

[0064] Step 3-2-1, calculate the urea consumption value dV1 according to the exhaust mass flow Mf and the difference in nitrogen and oxygen concentration deltaNOx between the outlet and inlet of the post-treatment system:

[0065] dV1 = Sigma(Mf*deltaNOx*C1*T) (F9)

[0066] deltaNOx = NOx_out - NOx_in (F10)

[0067] Where NOx_out is the nitrogen oxide concentration at the outlet of the aftertreatment system, NOx_in is the nitrogen oxide concentration at the inlet of the aftertreatment system, and C1 is a constant;

[0068] Step 3-2-2, calculating the ammonia storage amount dV3 according to the urea volume change dUV, the urea consumption value dV1 and the urea crystal amount dV2:

[0069] dV3 = dV - dV1 - dV2 (F16).

[0070] In a second aspect, a urea injection quality sensor is disclosed, comprising a float, an inner column, a Hall magnetic sensor, a quality sensing module and a signal processing unit, wherein a magnetic particle is installed in the float and can move up and down along the inner column; a Hall magnetic sensor is arranged in the inner column and connected to the signal processing unit; the Hall magnetic sensor can interact with the magnetic particle to generate a liquid level sensing signal, and the liquid level sensing signal is received and processed by the signal processing unit; when the float moves up and down, the liquid level sensing signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and its amplitude is analogically related to the position of the magnetic particle; the signal processing unit can obtain a continuous urea liquid level determined by the accuracy of the Hall magnetic sensor according to the pulse sequence and the position of the Hall magnetic sensor; the quality sensing module is connected to the signal processing unit, and the quality sensing module generates a urea quality sensing signal; the urea injection quality sensor detects the urea quality according to the urea quality sensing signal, and calculates the urea crystal according to the urea quality sensing signal and the continuous urea liquid level.

[0071] Beneficial effects: The present invention proposes a multifunctional urea injection quality sensor with high-precision liquid level detection capability. While detecting urea quality and urea liquid level, the sensor uses the sensed urea quality and high-precision urea liquid level information as well as engine exhaust flow, exhaust temperature, urea injection rate, and sensing values ​​obtained from the NOx sensor to diagnose the faults of the urea nozzle and the urea pump body, and calculate the urea crystal amount and ammonia storage amount in the SCR system. While providing multiple functions, the urea crystal and ammonia storage amount calculation method based on high-precision liquid level information also makes the estimation more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] 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.

[0073] Figure 1 A schematic diagram of the structure of a urea injection quality sensor provided in an embodiment of the present application Figure 1 .

[0074] Figure 2 A schematic diagram of the structure of a urea injection quality sensor provided in an embodiment of the present application Figure 2 .

[0075] Figure 3 This is a schematic diagram of the structure of a Hall magnetic sensor and a signal processing unit in a urea injection quality sensor provided in an embodiment of the present application.

[0076] Figure 4 A schematic diagram of a pulse signal generated by a signal processing unit in a urea injection quality sensor provided in an embodiment of the present application.

[0077] Figure 5 This is a signal characteristic diagram of a Hall magnetosensitive device in a urea injection quality sensor provided in an embodiment of the present application.

[0078] Figure 6 A schematic diagram of a flow chart of calculating urea liquid level height in a urea injection quality sensor provided in an embodiment of the present application.

[0079] Figure 7 A cross-sectional view of a urea injection quality sensor provided in an embodiment of the present application along the horizontal direction of the float and a cross-sectional view along the vertical direction of the float.

[0080] Figure 8 A schematic diagram of two closely arranged Hall magnetosensitive devices and a schematic diagram of voltage generation are provided in an inner column of a urea injection quality sensor provided in an embodiment of the present application.

[0081] Fig. 9 A schematic diagram of a urea injection quality sensor provided in an embodiment of the present application, wherein three or more equidistantly arranged Hall magnetic sensors are arranged in an inner column, and a schematic diagram of voltage generation is provided.

[0082] Fig.10 A schematic diagram of a flow chart of detecting a urea nozzle fault in a urea injection quality sensor provided in an embodiment of the present application.

[0083] Fig.11 A schematic diagram of a flow chart of detecting a urea pump failure in a urea injection quality sensor provided in an embodiment of the present application.

[0084] Fig.12 A schematic diagram of a flow chart for calculating urea crystals and ammonia storage amounts in a urea injection quality sensor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0085] The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0086] The present invention proposes a urea injection quality sensor, which can provide continuous and accurate liquid level readings through a Hall magnetic sensor. The liquid level readings can provide comprehensive information of the urea solution itself together with the urea quality and liquid temperature. On this basis, the continuous and accurate liquid level readings are further used to diagnose the urea nozzle and the urea pump body, and calculate the urea crystal and ammonia storage amount based on the urea quality detection. The calculation of the urea crystal amount and the ammonia storage amount enables the urea injection quality sensor to not only detect the characteristics of the urea itself, but also further reveal the information of the urea injection system including the urea nozzle, the urea pump body, the crystal and the ammonia storage, thus becoming a urea injection quality sensor.

[0087] The first embodiment of the present application discloses a urea injection quality sensor, comprising a float 150, an inner column 155, a Hall magnetic sensor 161, a quality sensing module 40 and a signal processing unit 140. The float 150 is provided with a magnet 151 and can move up and down along the inner column 155; the inner column 155 is provided with a Hall magnetic sensor 161 connected to the signal processing unit 140; the Hall magnetic sensor 161 can interact with the magnet 151 to generate a liquid level sensing signal, and the liquid level sensing signal is received and processed by the signal processing unit 140; when the float 150 moves up and down, the liquid level sensing signal The signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and its amplitude is analogically related to the position of the magneton 151; the signal processing unit 140 can obtain the continuous urea liquid level determined by the accuracy of the Hall magnetic sensor 161 according to the pulse sequence and the position of the Hall magnetic sensor 161; the quality sensing module 40 is connected to the signal processing unit 140, and the quality sensing module 40 generates a urea quality sensing signal; the urea injection quality sensor detects the urea quality according to the urea quality sensing signal, and detects the urea nozzle fault according to the urea quality sensing signal and the continuous urea liquid level.

[0088] The float 150 is restricted from rotating around the inner column 155 . The signal processing unit 140 includes a marker resistor 204 . At least one of the pulse sequences is a marker pulse signal, and its pulse voltage is related to the resistance value of the marker resistor 204 .

[0089] In an optional implementation, at least two closely arranged Hall magneto-sensitive devices 161 are provided in the inner column 155 .

[0090] In another optional implementation, at least three Hall magnetic sensors 161 arranged equidistantly are provided in the inner column 155 .

[0091] The signal characteristics of the Hall magnetosensitive device 161 are as follows:

[0092] The signal amplitude generated by the Hall magnetic sensor 161 is related to the distance between the magneton 151 and the device: when the north and south poles of the magneton 151 are less than the working distance of the Hall magnetic sensor 161, the signal amplitude is related to the distance, and when the north and south poles of the magneton 151 are more than the working distance of the Hall magnetic sensor 161, the signal changes to a certain value and loses the distance correlation. The voltage signal generated by the Hall magnetic sensor 161 is an analog signal related to the position of the magneton, so the high-precision liquid level ("continuous" liquid level) determined by its accuracy can be obtained through the device.

[0093] Example 1

[0094] like Figure 1 and Figure 2 As shown, the urea injection quality sensor includes a float 150, an inner column 155, a Hall magnetic sensor 161, a quality sensing module 40 and a signal processing unit 140. The inner column 155 is arranged between the base 70 and the glue head module 80. The support column 60 is placed parallel to the inner column 155. At the same time, a heating pipeline 50 is also arranged between the base 70 and the glue head module 80. The heating pipeline 50 is connected to the inlet end 51 and the outlet end 52. After the heating control valve (not shown) is opened, the engine coolant flows into the heating pipeline from the inlet end 51, and flows out from the outlet end 52 after passing through the heating pipeline 50. The coolant takes away heat from the engine and transfers it to the urea solution through the heating pipeline, which is used to thaw the urea solution and keep its temperature higher than the freezing temperature when the system is running. The quality sensing module 40 is arranged at the bottom of the sensor to detect abnormalities in the urea solution, including low or high urea concentration and the addition of non-urea solution.

[0095] A magnet 151 is installed in the float 150, and the magnet 151 is magnetic. The float 150 surrounds the inner column 155 and moves up and down along the inner column 155 according to the liquid level. A sensing unit 90 including a Hall magnetic sensor 161, a liquid temperature sensor 152 and a reed switch 162 is placed in the inner column 155. The Hall magnetic sensor 161 and the reed switch 162 are arranged on the substrate 160. The Hall magnetic sensor 161, the liquid temperature sensor 152 and the reed switch 162 are connected to the signal processing unit 140 through signal lines 142, 143 and 141 respectively, and the quality sensing module 40 is connected to the signal processing unit 140 through the signal line 146.

[0096] The urea injection quality sensor is arranged in the urea tank (not shown). Under the buoyancy of the urea liquid, as the float 150 moves up and down, the distance between the magnet 151 and the reed switch 162 and the Hall magnetic sensor 161 arranged in the inner column 155 also changes. When the distance from the magnet 151 to a certain reed switch 162 is less than the magnetic force action distance, the reed switch 162 will be closed, resulting in a change in the detection signal. Through the change in the detection signal caused by a certain reed switch 162 and the position of the reed switch 162 in the inner column, the position of the float 150 relative to the inner column can be measured, thereby measuring the height of the liquid. Similarly, when the distance from the magnet 151 to a certain Hall magnetic sensor 161 causes the signal generated by the Hall magnetic sensor 161 to change, the height of the liquid can also be measured through the signal change and the position of the Hall magnetic sensor 161 in the inner column 155.

[0097] The sensing unit 90 and the signal processing unit 140 may be used as Figure 3 The circuit shown in FIG. 1 is implemented. In the circuit, the signal processing unit 140 includes a multi-channel analog switch circuit 210 and a counter 205. One end of the sensing unit 90 is connected to the multi-channel terminal D of the multi-channel analog switch circuit 210. The multi-channel terminal D of the multi-channel analog switch circuit 210 is also connected to a marking resistor 204. The control end of the multi-channel analog switch circuit 210 is connected to the counter 205. The counter 205 generates a counting signal. The counting signal sequentially connects the multi-channel terminal D of the multi-channel analog switch circuit 210 to the single-channel terminal Y to generate the pulse sequence. The pulse voltage of at least one pulse signal in the pulse sequence is related to the resistance value of the marking resistor 204. The signal processing unit 140 also includes a pulse generating circuit 200. The pulse generating circuit 200 is connected to the counter 205 and is used to generate a clock signal. The signal processing unit 140 also includes a CPU 100. The CPU 100 is connected to the single-channel terminal Y of the multi-channel analog switch circuit 210 and is used to process the sensing signal.

[0098] One end of the reed switch 162 is connected to the ground GND, and the other end is connected to the multi-way end (D end) of the multi-way analog switch circuit 210. The Hall magnetic sensor 161 has three terminals: power supply end, ground end, and signal end. The power supply end is connected to the power supply Vcc, the ground end is connected to the ground GND, and the signal end is connected to the D end of the multi-way analog switch circuit 210. One end of the liquid temperature sensor 152 is connected to the ground GND, and the other end is connected to the D end of the multi-way analog switch circuit 210. In addition, the input end of the multi-way analog switch circuit 210 is also connected to a marking resistor 204, and the other end is connected to the ground GND. The control end of the multi-way analog switch circuit 210 is connected to a counter 205, and its clock is generated by a pulse generating circuit 200. The single end (Y end) of the multi-way analog switch circuit 210 is connected to the power supply Vcc through a pull-up resistor 207, and is connected to the CPU 100 through a signal line 145. The CPU 100 includes a microprocessor, which processes and calculates the signal generated by the signal processing unit 140 to obtain the liquid level and sensor status information, and sends it to the engine control unit ECU (Engine Control Unit, not shown) through a data bus (not shown).

[0099] exist Figure 3 In the circuit, the pulse generated by the pulse generating circuit 200 triggers the counter 205 to generate a sequential counting signal, which in turn sequentially connects the D terminal of the multi-way analog switch circuit 210 to the Y terminal, and the signal generated thereby is received by the CPU 100 through the signal line 145. Figure 4 is a Figure 3 Graphs of signals generated by the circuit. Curve 201 is the pulse signal generated by the pulse generating circuit 200, and curve 202 is the signal generated by the multi-channel analog switch circuit 210 on the signal line 145. Voltage Vr is the signal generated when the connected reed switch 162 is disconnected, Vt is the signal generated when the liquid temperature sensor 152 is connected, Vs is the signal generated when the marking resistor 204 is connected, Vh is the signal generated when the Hall magnetic sensor 161 is connected, and the signal with a pulse voltage close to zero is the signal generated when the reed switch 162 is closed.

[0100] The Hall magnetosensitive device 161 is a device that generates a voltage output signal, and its signal characteristics are as follows: Figure 5As shown. In the figure, the horizontal axis is the liquid level height, and the vertical axis is the voltage value generated by the Hall magnetic sensor 161. The north and south poles of the magneton 151 are arranged parallel to the Hall magnetic sensor 161. When the magneton 151 approaches the Hall magnetic sensor 161 from top to bottom, the south pole points to the Hall magnetic sensor 161, and when the magneton 151 approaches the Hall magnetic sensor 161 from bottom to top, the north pole points to the Hall magnetic sensor 161. When the magneton 151 is far away from the Hall magnetic sensor 161, the voltage output is a constant value Vo. When the liquid level rises, the north pole approaches the Hall magnetic sensor 161. When the liquid level exceeds the height Hb, the output voltage rises. When the north pole is closest to the Hall magnetic sensor 161 and the liquid level reaches the height Hn, the voltage rises to the first extreme value (highest extreme value) Vn. Then the North Pole begins to move away from the Hall magnetic sensor 161, the voltage decreases, and the South Pole begins to approach the Hall magnetic sensor 161. When the South Pole is closest to the Hall magnetic sensor 161 and the liquid level reaches Hs, the voltage drops to the second extreme value (the minimum extreme value). After the liquid level is higher than Hs, the South Pole also begins to move away from the Hall magnetic sensor 161, and the voltage rises. When the liquid level reaches Hu, the magneton leaves the sensitive area of ​​the Hall magnetic sensor, and the voltage rises to Vo. The liquid level heights Hb, Hn, Hs, and Hu can be calibrated through experiments, and the voltages Vo and Vn can be calibrated through experiments.

[0101] exist Figure 1 and Figure 2 In the system shown, the following can be used: Figure 7 The sensing unit 90 and the float 150 are shown. In the figure, there is a square opening in the middle of the float 150, and the square inner column 155 passes through the hole, which contains the sensing unit 90. The square opening and the square inner column prevent the float 150 from rotating around the inner column 155.

[0102] In an optional implementation, when at least two closely arranged Hall magnetic sensors 161 are provided in the inner column 155, the continuous urea liquid level determined by the accuracy of the Hall magnetic sensor 161 can be obtained according to the pulse sequence and the position of the Hall magnetic sensor 161, including:

[0103] Step 1-1, finding the mark pulse signal generated by the mark resistor by checking the pulse voltage, and marking it as the initial pulse;

[0104] Step 1-2, searching for the pulse generated by the Hall magneto-sensitive device (161) by checking the pulse voltage after the initial pulse, and measuring the pulse voltage;

[0105] Step 1-3, calculating the urea liquid level height according to the measured pulse voltage generated by another adjacent Hall magnetic sensor (161) arranged closely.

[0106] In another optional implementation, when at least three equally spaced Hall magnetic sensors 161 are provided in the inner column 155, the continuous urea liquid level determined by the accuracy of the Hall magnetic sensor 161 can be obtained according to the pulse sequence and the position of the Hall magnetic sensor 161, including:

[0107] Step 1-1, finding the mark pulse signal generated by the mark resistor by checking the pulse voltage, and marking it as the initial pulse;

[0108] Step 1-2, searching for the pulse generated by the Hall magneto-sensitive device (161) by checking the pulse voltage after the initial pulse, and measuring the pulse voltage;

[0109] Step 1-3, calculating the urea liquid level height according to the measured pulse voltage generated by two adjacent equally spaced Hall magnetic sensors (161).

[0110] The urea nozzle fault detection includes:

[0111] Step 2-1-1, calculating the measured urea volume change dUV through the float liquid level change;

[0112] Step 2-1-2, obtaining the expected urea volume change Tu by calculating the urea injection rate;

[0113] Step 2-1-3, detecting urea nozzle failure by comparing the measured urea volume change dUV with the expected urea volume change Tu and according to the urea quality sensing signal.

[0114] The urea injection quality sensor further detects urea pump failure, including:

[0115] Step 2-2-1, empty the urea pump;

[0116] Step 2-2-2, record the float liquid level 1;

[0117] Step 2-2-3, fill the urea pump;

[0118] Step 2-2-4, record float level 2;

[0119] Step 2-2-5, diagnosing urea pump fault according to the difference between the float liquid level 1 and the float liquid level 2 and the urea quality sensing signal.

[0120] The urea injection quality sensor further calculates urea crystallization, including:

[0121] Step 3-1-1, calculating the first crystallization amount dV2a based on the urea injection rate, the exhaust gas temperature and the exhaust gas mass flow rate;

[0122] Step 3-1-2, calculating the second crystallization amount dV2b by the urea volume change dUV, the tail gas temperature and the tail gas mass flow rate;

[0123] Step 3-1-3, calculating the urea crystal amount dV2 according to the first crystal amount dV2a and the second crystal amount dV2b.

[0124] The urea injection quality sensor further calculates the ammonia storage amount including:

[0125] Step 3-2-1, calculating the urea consumption value dV1 according to the exhaust mass flow rate and the difference in nitrogen and oxygen concentrations at the outlet and inlet of the post-treatment system;

[0126] Step 3-2-2, calculating the ammonia storage amount dV3 according to the urea volume change dUV, the urea consumption value dV1 and the urea crystal amount dV2.

[0127] Example 2

[0128] Use features such as Figure 5 The Hall magnetic sensor device shown, Figure 2 CPU 100 can run as follows Figure 6 The program shown in the figure processes the signal. This program can be run as an interrupt service program with a period of T (calculation period), and T can be set according to the required sampling frequency. After the program starts, it first detects whether there is a pulse rising edge (pulse signal such as Figure 4 As shown in curve 202), if the rising edge is not detected, the program stops and exits. Otherwise, the pulse voltage Vp is measured. If the voltage is within the range of Vs-R_lo to Vs+R_up, the two variables ID and i are cleared, then ID is increased by 1, and it is determined whether the position corresponding to the pulse ID is a reed switch. If it is a reed switch, the reed switch signal is processed. In the signal processing, Vp can be compared with the first voltage threshold Thd_lo. If Vp is less than the first voltage threshold Thd_lo, it means that the reed switch is closed, otherwise the reed switch is disconnected. If it is determined that the position corresponding to the pulse ID is not a reed switch, the program determines whether the position corresponding to the pulse ID is a Hall magnetic sensor. If not, it determines whether it is a thermistor (liquid temperature sensor). If not, the program stops and exits. Otherwise, the liquid temperature resistor calculates the liquid temperature

[0129] UT=Tbl_T(Vp)(F1)

[0130] Where UT is the liquid temperature, Tbl_T() is a table lookup calculation for calculating the liquid temperature, and the table value can be calibrated through experiments. Return to the judgment of whether the position corresponding to ID is a Hall magnetic sensor. If the corresponding position is a Hall magnetic sensor, enter the Hall magnetic sensor signal processing, and then jump to the judgment of whether the ID position is a thermistor. In this program, each threshold R_lo, R_up, and Thd_lo can be calibrated through experiments.

[0131] like Figure 8 As shown, two Hall magneto-sensitive devices 161 (A1, A2) are arranged closely on the substrate 160. When the magnet 151 moves from bottom to top, the voltage signals generated by the two Hall magneto-sensitive devices are shown in curves 301 and 302, where curve 301 is the voltage V301 generated by the Hall magneto-sensitive device A1 at the bottom, and curve 302 is the voltage V302 generated by the Hall magneto-sensitive device A2 at the top. Curve 303 is the difference between V301 and V302:

[0132] V303 = V301 - V302 (F2)

[0133] The liquid level h can be further calculated by measuring the voltages V301, V302 and V303:

[0134] If (V303>0&V302=Vo&V301>Vo), then dh=Tbl1(V301), and h=H0-dh;

[0135] else if (V303>0&V302>Vo&V301>Vo), then dh=Tbl2(V302), and h=H1-dh;

[0136] else if (V303<0&V302>V2), then dh=Tbl3(V301), and h=H0+dh;

[0137] else if (V303<0&V302 <V2), then dh=Tbl4(V302), and h=H1+dh;

[0138] else if (V303>0&V301 <Vo&V302<Vo), then dh=Tbl5(V301), and h=H2+dh;

[0139] else if (V303>0&V301=Vo&V302 <Vo), then dh=Tbl6(V302), and h=H3+dh.(F3)

[0140] Where V2 is the calibration threshold value, which can be calibrated by experiment; Tbl1(), Tbl2(), Tbl3(), Tbl4(), Tbl5(), and Tbl6() are table calculations, and the table values ​​can be calibrated by experiment; dh is the relative height, H0 and H1 are the liquid level heights when the north magnetic pole of the magnet 151 in the float 150 is closest to the Hall magnetic sensor A1 and A2, respectively, and H2 and H3 are the liquid level heights when the south magnetic pole of the magnet 151 is closest to the Hall magnetic sensor A1 and A2, respectively. If none of the conditions in formula (F3) are met, the h value is not calculated.

[0141] Fig. 9 The second arrangement of the Hall magnetic sensors 161 (B1, B2, B3, B4) is shown. In this way, the Hall magnetic sensors are arranged equidistantly on the substrate 160. When the magnet 151 moves from bottom to top, the generated voltage curves are shown as curves 310, 311, 312 and 313. Among them, curve 310 is the voltage V(310) generated by the Hall magnetic sensor B1 arranged at the bottom, 311 is the voltage V(311) generated by the Hall magnetic sensor B2, and 312 and 313 are the voltages V(312) and V(313) generated by the Hall magnetic sensors B3 and B4, respectively. Through the voltages V(310), V(311), V(312), and V(313), the liquid level height h can be further calculated:

[0142] If (V(310)<Vo&V(311)> Vo), then dh=Tbl7(V(311)), and h=H(4)-dh;

[0143] else if((V(311)>Vo or V(311) <Vo)&V(312)=Vo), then dh=Tbl8(V(311)),and h=H(4)+dh;

[0144] else if(V(311)<Vo&V(312)> Vo), then dh=Tbl7(V(312)), and h=H(5)-dh;

[0145] else if((V(312)>Vo or V(312) <Vo)&V(313)=Vo), then dh=Tbl8(V(312)),and h=H(5)+dh.(F4)

[0146] Among them, Tbl7() and Tbl8() are table lookup calculations, and their table values ​​can be calibrated by experiments; H(4) and H(5) are the liquid levels when the north magnetic pole of the magneton 151 is closest to the Hall magnetic sensor devices B2 and B3, respectively. If the condition in (F4) is not met, the height h is not calculated. By extension, for the nth device among multiple Hall magnetic sensors, (F4) can be expanded to:

[0147] If(V(n-1)<Vo&V(n)> Vo), then dh=Tbl7(V(n)), and h=H(k)-dh;

[0148] else if((V(n)>Vo or V(n) <Vo)&V(n+1)=Vo), then dh=Tbl8(V(n)), and h=H(k)+dh(F5)

[0149] V(n-1), V(n), V(n+1) are the voltage signals generated by the n-1th, nth and n+1th Hall magnetic sensors respectively, and H(k) is the liquid level when the north pole of the magneton 151 is closest to the nth Hall magnetic sensor.

[0150] High-precision and continuous liquid level detection can be further used to detect urea nozzle and urea pump failures in the SCR system. Fault detection of urea nozzles can be implemented by a program running in the CPU 100. A flowchart of an example fault detection program is shown below. Fig.10 As shown. After the program starts, it first determines whether the urea injection system is in working condition. If it is not in working condition, the program stops and exits. In an SCR system, the operation of the urea injection system generally includes 4 states: initialization state, working state, cleaning state and standby state. In the initialization state, the urea pump establishes a stable injection pressure and clears the air in the urea injection system; then the urea injection system enters the working state, in which the urea pump maintains a stable pressure while controlling the injection amount of urea by periodically opening the urea nozzle; when the injection task is completed, the urea injection system enters the cleaning state, in which the urea residue in the urea injection system is emptied; then the urea injection system enters the standby state until it is shut down. Return Fig.10 The program determines the working state of the urea injection system. If the system is in working state, the change of urea volume dUV in the urea tank is calculated:

[0151] dUV = Tbl_LV(L0)-Tbl_LV(L0-dL) (F6)

[0152] Where L0 is the starting liquid level, dL is the amount of liquid level reduction, and Tbl_LV() is a table lookup calculation used to calculate the urea volume corresponding to the liquid level. The table value in the table lookup calculation can be calibrated for the urea tank used in the experiment. Then calculate the total urea injection volume Tu when the urea liquid level changes from L0 to L0-dL:

[0153] Tu = Sigma(Dc*T)(F7)

[0154] Where Dc is the urea injection rate command, T is the calculation period, and Sigma() is the cumulative calculation. After calculating Tu, determine whether the Tu value is greater than the first calculation threshold Thd_Jmin. If Tu is not greater than the first calculation threshold Thd_Jmin, the program stops and exits. Otherwise, calculate the absolute value DisJV of the difference between Tu and dUV:

[0155] DisJV = Abs(Tu-dUV)(F8)

[0156] Where Abs() is calculated by taking the absolute value. Then the program determines the size of DisJV and the first error threshold Thd_ErUp. If DisJV is greater than the first error threshold Thd_ErUp, the error flag INJ_Err is set. The setting of the error flag will trigger the urea nozzle fault alarm; if DisJV is not greater than the first error threshold Thd_ErUp, it is determined whether DisJV is less than the second error threshold Thd_ErLow. If DisJV is not less than the second error threshold Thd_ErLow, the program stops and exits, otherwise the program clears the flag INJ_Err, and the clearing of the flag will stop the urea fault alarm. The program stops and exits after clearing the flag INJ_Err. The program can also further confirm the fault type. For example, if Tu is greater than dUV, it means that the actual urea injection amount is lower than the command value, and the urea nozzle may be blocked. If Tu is less than dUV, it means that the actual urea injection amount is higher than the command value, and the urea nozzle may have a control failure. In the program, the first calculation threshold Thd_Jmin, the first error judgment threshold Thd_ErUp, and the second error judgment threshold Thd_ErLow are all calibrable quantities and can be calibrated through experiments.

[0157] Similarly, the fault detection of the urea pump body can also be realized by the program running in the CPU 100. The working state of the urea injection system also includes the pump body detection state, such as Fig.11As shown, after an example program starts, it is first determined whether the urea injection system is in the pump detection state. If not, the program stops and exits. If the urea injection system is in the pump detection state, the urea injection system cleaning state is first triggered, in which the urea injection system empties the urea solution retained therein. After the cleaning is completed, the program records the urea liquid level and assigns it to the variable Lp2. Then, the program triggers the urea injection system initialization state, in which the urea injection system establishes injection pressure and discharges the air therein. After the initialization is completed, the program records the liquid level and assigns it to the variable Lp1. Thereafter, the difference between Lp2 and Lp1 is calculated and compared with the third error judgment threshold Thd_LdLow. If the difference is less than the third error judgment threshold Thd_LdLow, the error flag UPV_Err is set and the program stops and exits. The error flag UPV_Err will trigger a urea pump fault alarm. Possible causes of urea pump failure include buffer chamber blockage, buffer chamber detachment, and urea pipeline problems. If the difference between Lp2 and Lp1 is not less than the third error threshold Thd_LdLow, the difference is compared with the fourth error threshold Thd_LdUp. If the difference is greater than the fourth error threshold Thd_LdUp, the error flag UPV_Err is cleared and then the program stops and exits. Otherwise, the program stops and exits directly. Clearing the error flag UPV_Err will stop the urea pump body fault alarm. Similarly, the third error threshold Thd_LdLow and the fourth error threshold Thd_LdUp in the program are both calibrable quantities and can be calibrated through experiments.

[0158] Based on the above detection of urea nozzle and urea pump body, the amount of urea crystals and the amount of ammonia stored in the SCR system can be further calculated. The calculation method can be as follows: Fig.12 The program shown in the figure is implemented. This program can be used as an interrupt service program to run in a cycle T. Fig.12 As shown, after the program starts, it is first determined whether the detection condition of urea liquid level change dV is met. The detection condition may include the following 5 items:

[0159] Condition 1: No urea addition or discharge (urea addition or discharge can be detected by rapid changes in the liquid level).

[0160] Condition 2: The urea pump is in working condition.

[0161] Condition 3: Eliminate the influence of urea shaking (the influence of urea shaking on liquid level detection can be eliminated by taking the average value or filtering calculation).

[0162] Condition 4: Urea quality is normal (urea quality sensor (such as Figure 1-2 The quality sensing module 40) works normally, and its reading value is within the allowable normal range, such as 30%-34%).

[0163] Condition 5: There is no fault in the urea nozzle and urea pump body (the INJ_Err and UPV_Err error flags are not set).

[0164] If these five conditions are met, the urea volume change dUV is detected (the detection of dUV can be calculated using formula (F6)), otherwise dUV is set to 0, and then the program stops and exits. After dUV detection, the program determines whether the dUV value is greater than or equal to the second calculation threshold Calc_Min. If dUV is less than the second calculation threshold Calc_Min, the program stops and exits, otherwise the total urea consumption value dV1 and the crystallization estimated value dV2a based on the urea injection amount and the crystallization estimated value dV2b based on the urea consumption are calculated. The calculation of dV1 can be done using the following formula:

[0165] dV1 = sigma(Mf*deltaNOx*C1*T) (F9)

[0166] deltaNOx = NOx_out – NOx_in (F10)

[0167] Where Mf is the mass flow rate of exhaust gas, NOx_out is the nitrogen oxide concentration at the outlet of the after-treatment system, and NOx_in is the nitrogen oxide concentration at the inlet of the after-treatment system. DeltaNOx represents the difference between the nitrogen oxide concentration at the outlet of the after-treatment system and the nitrogen oxide concentration at the inlet. C1 is a constant. When the units of nitrogen oxide concentrations NOx_out and NOx_in are ppm, and the unit of Mf is g / s, the unit of T is s, and the unit of dV1 is ml, C1= 2.93*10 -6 , and dV2a can be calculated using the following formula:

[0168] dV2a = sigma(Tbl_Crystal(Mf * Tin , Dc)*T) (F11)

[0169] Where Tin is the exhaust gas temperature measured upstream of the urea nozzle. Tbl_Crystal() is a table lookup calculation, and its table value can be calibrated through experiments.

[0170] The calculation formula for dV2b is:

[0171] dV2b = Tbl_Crystal(sigma(Mf * Tin*T), dV) (F12)

[0172] The urea crystal amount dV2 can be further calculated based on dV2a and dV2b: the program first calculates the difference between dV2a and dV2b, Abs(dV2a-dV2b), where Abs() is an absolute value calculation. If the difference is greater than the first judgment threshold Thd_Cmax, then dV2 = dv2a, otherwise dV2 = dv2b, where dV2 is the estimated urea crystal amount (the volume of crystallized urea, not the crystal grams itself). After calculating dV2, the program further calculates the ammonia storage amount dV3, and the calculation formula is as follows:

[0173] dV3 = dV - dV1 - dV2 (F13)

[0174] Like dV2, dV3 is not the grams of ammonia stored, but the volume of urea solution converted to ammonia storage. After calculating dV3, the program stops and exits. The ammonia storage amount calculated by the program can be used to further control urea injection, and the calculated crystallization amount can further trigger de-crystallization regeneration to remove urea crystals by heating the exhaust gas. Fig.12 In the program shown, the second calculation threshold Calc_Min and the first judgment threshold Thd_Cmax are both calibrable quantities and can be calibrated in experiments.

[0175] The second embodiment of the present application discloses a urea injection quality sensor, comprising a float 150, an inner column 155, a Hall magnetic sensor 161, a quality sensing module 40 and a signal processing unit 140. The float 150 is provided with a magnet 151 and can move up and down along the inner column 155; the inner column 155 is provided with a Hall magnetic sensor 161 connected to the signal processing unit 140; the Hall magnetic sensor 161 can interact with the magnet 151 to generate a liquid level sensing signal, and the liquid level sensing signal is received and processed by the signal processing unit 140; when the float 150 moves up and down, the liquid level sensing signal The signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and the amplitude of the pulse is analogically related to the position of the magneton 151; the signal processing unit 140 can obtain the continuous urea liquid level determined by the accuracy of the Hall magnetic sensor 161 according to the pulse sequence and the position of the Hall magnetic sensor 161; the quality sensing module 40 is connected to the signal processing unit 140, and the quality sensing module 40 generates a urea quality sensing signal; the urea injection quality sensor detects the urea quality according to the urea quality sensing signal, and calculates the urea crystals according to the urea quality sensing signal and the continuous urea liquid level.

[0176] The manner of obtaining the continuous urea liquid level and calculating the urea crystals is the same as that in the first embodiment, and will not be described in detail here.

[0177] The present invention provides a concept and method of a urea injection quality sensor. 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 quality sensor, characterized in that: The invention comprises a float (150), an inner column (155), a Hall magnetic sensor (161), a quality sensing module (40) and a signal processing unit (140); the float (150) is provided with a magnet (151) and is capable of moving up and down along the inner column (155); the inner column (155) is provided with a Hall magnetic sensor (161) and is connected to the signal processing unit (140); the Hall magnetic sensor (161) is capable of interacting with the magnet (151) to generate liquid level sensing. signal, the liquid level sensing signal is received and processed by the signal processing unit (140); when the float (150) moves up and down, the liquid level sensing signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and its amplitude is analogically related to the position of the magneton (151); the signal processing unit (140) can obtain a continuous urea liquid level determined by the accuracy of the Hall magnetic sensor (161) according to the pulse sequence and the position of the Hall magnetic sensor (161); The quality sensing module (40) is connected to the signal processing unit (140), and the quality sensing module (40) generates a urea quality sensing signal; the urea injection quality sensor detects urea quality according to the urea quality sensing signal, and detects urea nozzle fault according to the urea quality sensing signal and the continuous urea liquid level.

2. The urea injection quality sensor according to claim 1, characterized in that: The float (150) is restricted from rotating around the inner column (155), and the signal processing unit (140) includes a marker resistor (204). At least one of the pulse sequences is a marker pulse signal, and its pulse voltage is related to the resistance value of the marker resistor (204).

3. The urea injection quality sensor according to claim 2, characterized in that: At least two closely arranged Hall magneto-sensitive devices (161) are provided in the inner column (155).

4. The urea injection quality sensor according to claim 3, characterized in that: The continuous urea liquid level determined by the accuracy of the Hall magnetic sensor (161) can be obtained according to the pulse sequence and the position of the Hall magnetic sensor (161), including: Step 1-1, finding the mark pulse signal generated by the mark resistor by checking the pulse voltage, and marking it as the initial pulse; Step 1-2, searching for the pulse generated by the Hall magneto-sensitive device (161) by checking the pulse voltage after the initial pulse, and measuring the pulse voltage; Step 1-3, calculating the urea liquid level height according to the measured pulse voltage generated by another adjacent Hall magnetic sensor (161) arranged closely.

5. The urea injection quality sensor according to claim 2, characterized in that: At least three Hall magneto-sensitive devices (161) are arranged at equal intervals in the inner column (155).

6. The urea injection quality sensor according to claim 5, characterized in that: The continuous urea liquid level determined by the accuracy of the Hall magnetic sensor (161) can be obtained according to the pulse sequence and the position of the Hall magnetic sensor (161), including: Step 1-1, finding the mark pulse signal generated by the mark resistor by checking the pulse voltage, and marking it as the initial pulse; Step 1-2, searching for the pulse generated by the Hall magneto-sensitive device (161) by checking the pulse voltage after the initial pulse, and measuring the pulse voltage; Step 1-3, calculating the urea liquid level height according to the measured pulse voltage generated by two adjacent equally spaced Hall magnetic sensors (161).

7. A urea injection quality sensor according to any one of claims 1-6, characterized in that: The urea nozzle fault detection includes: Step 2-1-1, calculating the measured urea volume change dUV through the float liquid level change; Step 2-1-2, obtaining the expected urea volume change Tu by calculating the urea injection rate; Step 2-1-3, detecting urea nozzle failure by comparing the measured urea volume change dUV with the expected urea volume change Tu and according to the urea quality sensing signal.

8. A urea injection quality sensor according to any one of claims 1-6, characterized in that: The urea injection quality sensor further detects urea pump failure, including: Step 2-2-1, empty the urea pump; Step 2-2-2, record the float liquid level 1; Step 2-2-3, fill the urea pump; Step 2-2-4, record float level 2; Step 2-2-5, diagnosing urea pump fault according to the difference between the float liquid level 1 and the float liquid level 2 and the urea quality sensing signal.

9. The urea injection quality sensor according to claim 7, characterized in that: The urea injection quality sensor further calculates urea crystallization, including: Step 3-1-1, calculating the first crystallization amount dV2a based on the urea injection rate, the exhaust gas temperature and the exhaust gas mass flow rate; Step 3-1-2, calculating the second crystallization amount dV2b according to the urea volume change dUV, the tail gas temperature and the tail gas mass flow rate; Step 3-1-3, calculating the urea crystal amount dV2 according to the first crystal amount dV2a and the second crystal amount dV2b.

10. The urea injection quality sensor according to claim 9, characterized in that: The urea injection quality sensor further calculates the ammonia storage amount including: Step 3-2-1, calculating the urea consumption value dV1 according to the exhaust mass flow rate and the difference in nitrogen and oxygen concentrations at the outlet and inlet of the post-treatment system; Step 3-2-2, calculating the ammonia storage amount dV3 according to the urea volume change dUV, the urea consumption value dV1 and the urea crystal amount dV2.

11. A urea injection quality sensor, characterized in that: The invention comprises a float (150), an inner column (155), a Hall magnetic sensor (161), a quality sensing module (40) and a signal processing unit (140); the float (150) is provided with a magnet (151) and is capable of moving up and down along the inner column (155); the inner column (155) is provided with a Hall magnetic sensor (161) and is connected to the signal processing unit (140); the Hall magnetic sensor (161) is capable of interacting with the magnet (151) to generate liquid level sensing. signal, the liquid level sensing signal is received and processed by the signal processing unit (140); when the float (150) moves up and down, the liquid level sensing signal changes to form a pulse sequence, wherein there is at least one pulse in the pulse sequence, and its amplitude is analogically related to the position of the magneton (151); the signal processing unit (140) can obtain a continuous urea liquid level determined by the accuracy of the Hall magnetic sensor (161) according to the pulse sequence and the position of the Hall magnetic sensor (161); The quality sensing module (40) is connected to the signal processing unit (140), and the quality sensing module (40) generates a urea quality sensing signal; the urea injection quality sensor detects urea quality according to the urea quality sensing signal, and calculates urea crystals according to the urea quality sensing signal and the continuous urea liquid level.

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