A sensor and method for measuring urea solution quality and liquid level

Abstract

The present invention discloses a sensor and method for measuring the quality and level of urea solution. The sensor includes a quality sensing element and a signal processing unit. The quality sensing element is completely covered by urea solution and is electrically connected to the signal processing unit. The quality sensing element is configured to receive a first excitation signal generated by the signal processing unit, generate ultrasonic waves, transmit ultrasonic waves, receive ultrasonic echoes, and transmit the received ultrasonic echo signals to the signal processing unit. The signal processing unit is configured to generate the first excitation signal and transmit the first excitation signal to the quality sensing element, receive the ultrasonic echo signals transmitted by the quality sensing element, and calculate the quality and level of the urea solution based on the ultrasonic echo signals. The sensor can accurately measure the quality and level of urea solution and is unaffected by urea solution sloshing or abnormalities of the ultrasonic sensing element. It can also diagnose infrared (IR) problems where the sensor's sensed value is within the normal range but inaccurate.

Description

Technical Field

[0001] The present invention belongs to the field of urea solution detection, and in particular relates to a sensor and a method for measuring the quality and liquid level of a urea solution. Background Art

[0002] In the application of Selective Catalytic Reduction (SCR), urea solution is added to the exhaust gas produced by the engine. Under the action of high-temperature exhaust gas, the urea solution produces ammonia (NH3) through the thermal decomposition and hydrolysis of urea. Then, with the help of the SCR catalyst, the ammonia reacts with nitrogen oxides (NOx) in the exhaust gas and removes it. Due to the reaction ratio of ammonia to nitrogen oxides, in order to avoid ammonia leakage or high nitrogen oxide emissions, it is necessary to accurately control the dosage of urea solution and monitor the liquid level of urea solution. At the same time, the urea concentration in the urea solution also needs to be kept constant. For diesel engine applications, according to the requirements of ISO 22241 standard, a eutectic urea solution (32.5% wt) with the lowest freezing temperature, namely diesel exhaust fluid (DEF, Diesel Exhaust Fluid) is usually used as the reducing agent carrier.

[0003] In urea metering control, non-compliant urea solutions (those that do not meet the requirements of the ISO22241 standard) can cause emissions problems or system failures. For example, when the urea solution is diluted, low urea concentrations in the solution may cause emissions problems. To avoid emissions problems, the urea concentration in the DEF needs to be monitored. Simple impedance sensors have poor selectivity, and their resolution of urea concentration may be affected by their high sensitivity to ionic impurities and is difficult to improve. Furthermore, urea concentration and level sensors are typically separate sensors, resulting in a non-compact overall structure and high costs. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a sensor and method for measuring the quality and liquid level of urea solution in view of the shortcomings of the existing technology.

[0005] To solve the above technical problems, a first aspect discloses a sensor for measuring the quality and liquid level of a urea solution, comprising a quality sensing element and a signal processing unit, wherein the quality sensing element is completely covered by the urea solution, and the signal processing unit is electrically connected to the quality sensing element;

[0006] The quality sensing element is configured to receive the first excitation signal generated by the signal processing unit, generate ultrasonic waves, transmit ultrasonic waves, receive ultrasonic echoes, and send the received ultrasonic echo signals to the signal processing unit;

[0007] The signal processing unit is configured to generate a first excitation signal and send the first excitation signal to the quality sensing element, receive an ultrasonic echo signal sent by the quality sensing element, and calculate the quality and liquid level of the urea solution based on the ultrasonic echo signal, where the quality of the urea solution includes the urea concentration of the urea solution.

[0008] Furthermore, the quality sensing element includes a reflective assembly and an ultrasonic sensing element, the reflective assembly includes a vertical reflective plate and an inclined reflective plate, and there is an inclined angle between the vertical reflective plate and the inclined reflective plate;

[0009] The ultrasonic sensing element includes an ultrasonic transceiver unit, which is parallel to the vertical reflector, with a urea solution between the two. The ultrasonic transceiver unit is used to transmit ultrasonic waves to the vertical reflector and the inclined reflector. The vertical reflector reflects the ultrasonic waves transmitted by the ultrasonic transceiver unit to generate a first ultrasonic echo, which is received by the ultrasonic transceiver unit. The inclined reflector first reflects the ultrasonic waves transmitted by the ultrasonic transceiver unit to the surface of the urea solution, and then reflects them from the surface of the urea solution and then reflects them for a second time by the inclined reflector to form a second ultrasonic echo, which is received by the ultrasonic transceiver unit. The ultrasonic transceiver unit is electrically connected to the signal processing unit via a fifth signal line and transmits the received first and second ultrasonic echo signals to the signal processing unit.

[0010] Furthermore, the signal processing unit includes a central processing unit and an ultrasonic signal processing subunit, wherein the central processing unit is configured to send a first command to the ultrasonic signal processing subunit, receive an ultrasonic echo signal processed by the ultrasonic signal processing subunit, and calculate the quality and liquid level of the urea solution according to the ultrasonic echo signal; the ultrasonic echo signal includes a first ultrasonic echo and a second ultrasonic echo signal;

[0011] The ultrasonic signal processing subunit is used to receive a first command sent by the central processing unit, generate a first excitation signal, send the first excitation signal to the ultrasonic sensor element, receive the ultrasonic echo signal sent by the ultrasonic sensor element, and send it to the central processing unit after processing; the ultrasonic sensor element is electrically connected to the ultrasonic signal processing subunit through a fifth signal line.

[0012] The reflector assembly reflects ultrasonic waves transmitted by the same ultrasonic transceiver unit, generating a first ultrasonic echo and a second ultrasonic echo. This allows for simultaneous detection of both solution concentration and level without the need for a second ultrasonic transceiver unit, resulting in a more compact and economical sensor design. Furthermore, because ultrasonic sensing is insensitive to impurities in the urea solution, variations between components, and the urea solution's temperature, ultrasonic measurements of urea concentration and level are more accurate even in the presence of impurities, variations between components, and temperature fluctuations.

[0013] Furthermore, the quality sensing element further includes a first electrode and a second electrode, the second electrode may be included in the reflective assembly, a urea solution exists between the first electrode and the second electrode, and the urea solution is in communication with the urea solution between the ultrasonic transceiver unit and the reflective assembly;

[0014] The signal processing unit also includes an impedance signal processing subunit, which is electrically connected to one end of the first electrode through a first signal line and to one end of the second electrode through a second signal line. The quality of the urea solution also includes the impurity ion concentration of the urea solution. The central processing unit is further used to send a second command to the impedance signal processing subunit and receive the first impedance sensing signal processed by the impedance signal processing subunit, and calculate the impurity ion concentration of the urea solution according to the first impedance sensing signal. The impedance signal processing subunit is used to receive the second command sent by the central processing unit, generate a second excitation signal, and send the second excitation signal to the first electrode and the second electrode respectively, measure the first impedance sensing signal, and send it to the central processing unit after processing.

[0015] Ultrasonic signals are insensitive to impurity ions, while impedance sensing signals are sensitive to impurity ions. The high sensitivity of the impedance sensing element enables it to detect low-concentration impurities in the urea solution and avoid damage to the SCR catalyst.

[0016] Furthermore, the signal processing unit further includes a resistance measuring module, which is electrically connected to the other end of the first electrode via a sixth signal line and is configured to measure the resistance of the first electrode and send the resistance value to the central processing unit.

[0017] Furthermore, the signal processing unit also includes a resistance measuring module, and the quality sensing element also includes a first temperature sensing element. The first temperature sensing element is used to measure the temperature of the urea solution between the first electrode and the second electrode, and is electrically connected to the resistance measuring module through an eighth signal line. The resistance measuring module is used to measure the resistance of the first temperature sensing element and send the resistance value to the central processing unit.

[0018] Furthermore, the sensor also includes a liquid level sensing unit, which includes a third electrode and a fourth electrode. The urea solution between the third electrode and the fourth electrode is connected to the urea solution between the first electrode and the second electrode. The third electrode is electrically connected to the impedance signal processing subunit through a third signal line, and the fourth electrode is electrically connected to the impedance signal processing subunit through a fourth signal line. The central processing unit is also used to send a third command to the impedance signal processing subunit and receive a second impedance sensing signal processed by the impedance signal processing subunit, and calculate the urea solution level according to the second impedance sensing signal. The impedance signal processing subunit is also used to receive the third command sent by the central processing unit, generate a third excitation signal, and send the third excitation signal to the third electrode and the fourth electrode respectively, measure the second impedance sensing signal, and send it to the central processing unit after processing.

[0019] The liquid level sensing unit is insensitive to bubbles, fluid sloshing, local contamination, or even partially frozen urea solution in the urea solution. Therefore, when bubbles, sloshing, local contamination, or even partial freezing exist in the urea solution, the liquid level of the urea solution calculated using the liquid level sensing unit and the impedance sensing element in the quality sensing element is more accurate.

[0020] Furthermore, the liquid level sensing unit also includes a second temperature sensing element, which is used to measure the temperature of the urea solution between the third electrode and the fourth electrode and is electrically connected to the resistance measurement module through a seventh signal line; the resistance measurement module is also used to measure the resistance of the second temperature sensing element and send the resistance value to the central processing unit.

[0021] A second aspect discloses a method for measuring the quality and level of a urea solution, comprising the following steps:

[0022] Step 1: The signal processing unit sends a first excitation signal to the ultrasonic sensor element;

[0023] Step 2: The ultrasonic sensor element receives the first excitation signal, generates ultrasonic waves, transmits ultrasonic waves, receives ultrasonic echoes, and sends the received ultrasonic echo signals to a signal processing unit;

[0024] In step 3, the signal processing unit receives the ultrasonic echo signal sent by the quality sensor element, and calculates the quality and liquid level of the urea solution according to the ultrasonic echo signal. The quality of the urea solution includes the urea concentration of the urea solution.

[0025] Furthermore, the ultrasonic echo in step 2 includes a first ultrasonic echo and a second ultrasonic echo, and calculating the quality and liquid level of the urea solution according to the ultrasonic echo signal in step 3 includes:

[0026] The distance between the ultrasonic transceiver unit and the first vertical reflector is d177 , the distance between the ultrasonic transceiver unit and the inclined reflector is d 175 ,

[0027] The time interval T from the ultrasonic transceiver unit sending the ultrasonic wave to receiving the first ultrasonic echo q Expressed as:

[0028] T q =2*d 177 / Cs (1)

[0029] Where Cs represents the ultrasonic propagation velocity. When ultrasonic waves propagate in a urea solution, the ultrasonic propagation velocity Cs is determined by the bulk modulus K and density ρ of the urea solution:

[0030]

[0031] Among them, the values ​​of bulk modulus K and density ρ both change with the concentration and temperature of urea solution;

[0032] Since the ultrasonic wave propagation distance is 2*d 177 is a fixed value, and the ultrasonic propagation speed Cs is the time interval T q function of urea solution, so the urea concentration γ s By time interval T q and urea solution temperature Ts, the time interval T q Calculated by the signal processing unit based on the transmitted first excitation signal and the received first ultrasonic echo signal;

[0033] The time interval from the ultrasonic transceiver unit sending the ultrasonic wave to receiving the second ultrasonic echo is T l The height between the ultrasonic reflection point on the inclined reflector and the bottom of the urea tank is h 175 , then the urea solution level ld:

[0034] ld = (h 175 -d 175 )+d 177 *T l / T q (3).

[0035] Furthermore, the method further includes step 4, calculating the concentration of impurity ions in the urea solution, including:

[0036] The impedance between the first electrode and the second electrode is denoted as Zs. The impedance Zs is calculated by the signal processing unit according to the first impedance sensing signal. The impedance change value dZs of the impedance Zs is calculated. The impedance change value dZs is defined as follows:

[0037] dZs = (Zs(γ i) - Zs(0)) / Zs(0) (4)

[0038] Where Zs(γi) is the impedance between the first electrode and the second electrode measured in a urea solution with an impurity ion concentration of γi, and Zs(0) is the impedance between the first electrode and the second electrode measured in a urea solution that complies with the ISO 22241 standard. The impurity ion concentration γi is obtained by looking up the table:

[0039] γi=Tbl(dZs).

[0040] Furthermore, the method further includes step 5, when the ultrasonic sensor element is unavailable, calculating the urea concentration of the urea solution using the first impedance sensing signal, and calculating the liquid level of the urea solution using the first impedance sensing signal and the second impedance sensing signal.

[0041] Further, in step 5, the unavailability of the ultrasonic sensor element includes the presence of a first type of abnormality in the ultrasonic sensor element. Detecting whether the ultrasonic sensor element has the first type of abnormality includes: measuring the amplitude value Lvl of the second ultrasonic echo signal, and comparing the amplitude value with the fifth threshold value Thd_Lvll. If the amplitude value is higher than the fifth threshold value Thd_Lvll, it is determined that the ultrasonic sensor element does not have the first type of abnormality; otherwise, it is determined that the ultrasonic sensor element has the first type of abnormality.

[0042] Furthermore, in step 5, the ultrasonic sensor element being unavailable includes the ultrasonic sensor element having a second type of abnormality, and detecting whether the ultrasonic sensor element has the second type of abnormality includes: recording a height value of the first ultrasonic echo signal as S_amp, comparing the height value S_amp of the first ultrasonic echo signal with a first threshold value Thd_samp, and if S_amp is not higher than Thd_samp, determining that the ultrasonic sensor element has the second type of abnormality;

[0043] If the S_amp value is higher than Thd_samp, the change in the peak time T_sft of the first ultrasonic echo signal is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft = Tpk-Tpk0

[0044] The change T_sft of the peak moment of the first ultrasonic echo signal is compared with the second threshold Thd_Tsft. If T_sft is not higher than Thd_Tsft, it is determined that the ultrasonic sensor element has a second type of abnormality; if T_sft is higher than Thd_Tsft, it is determined that the ultrasonic sensor element does not have a second type of abnormality.

[0045] Furthermore, in step 5, the ultrasonic sensing element being unavailable includes the ultrasonic sensing element being unavailable due to shaking of the urea solution. Detecting whether the urea solution is shaking includes calculating a rate of change Zr of an impedance value Zs corresponding to the first impedance sensing signal. If the Zr value is higher than a fourth threshold Thd_zrl, determining that the urea solution is shaking; otherwise, determining that the urea solution is not shaking.

[0046] Furthermore, in step 5, the urea concentration of the urea solution is calculated using the first impedance sensing signal, including: the impedance Zs corresponding to the first impedance sensing signal is the product of the urea solution temperature Ts and the urea concentration γ of the urea solution. s Function:

[0047] Zs=f(Ts,γ s ) (5)

[0048] Therefore, the urea concentration of the urea solution is γ s Calculated from impedance Zs and urea solution temperature Ts.

[0049] Furthermore, in step 5, calculating the urea solution level using the first impedance sensing signal and the second impedance sensing signal includes calculating a ratio Rz between the two impedance values:

[0050] Rz=Zsl / Zs (6)

[0051] Wherein, Zsl represents the impedance value corresponding to the second impedance sensing signal.

[0052] Furthermore, in step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a table lookup calculation to compensate for nonlinear effects:

[0053] ld=Tbl(Rz) (7)

[0054] In formula (7), Tbl() represents a table lookup calculation, and the table value in the table lookup calculation is calibrated by test data obtained through experiments at different urea solution concentrations.

[0055] Furthermore, in step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a two-dimensional lookup table to compensate for the nonlinear effect caused by the urea solution temperature:

[0056] ld=Tbl(Rz,T227) (8)

[0057] Wherein, T227 is the urea solution temperature obtained by the second temperature sensing element, Tbl() represents a table lookup calculation, and the table value in the table lookup calculation is calibrated by test data obtained through experiments at different urea solution concentrations and temperatures.

[0058] Furthermore, the urea solution temperature Ts is obtained by measuring the resistance Re of the first electrode, or by measuring the first temperature sensing element.

[0059] Furthermore, the method further includes step 6 of determining whether an IR fault occurs in a sensor for measuring the quality and liquid level of the urea solution.

[0060] Furthermore, step 6 includes:

[0061] Step 6.1: The signal processing unit determines whether the quality sensor element and the liquid level sensor element have an OOR fault in the impedance detection, and whether the ultrasonic sensor element in the quality sensor element has a first type of abnormality and a second type of abnormality;

[0062] Step 6.2: If it is determined that the quality sensor element and the liquid level sensor unit do not have the OOR fault in the impedance detection, and the ultrasonic sensor element in the quality sensor element does not have the first type of abnormality and the second type of abnormality, determine whether the sensor has an IR fault based on the urea concentration or liquid level of the urea solution.

[0063] To prevent sensor problems from triggering false urea concentration alarms, the sensor itself requires diagnosis. In addition to detecting OOR (Out-of-Range) problems, where readings are outside the valid range, sensor diagnosis in step 6 can also diagnose IR (In-Range) problems, where sensor readings are within the normal range but inaccurate.

[0064] Furthermore, in step 6.2, judging whether an IR fault occurs in the sensor according to the urea concentration of the urea solution includes:

[0065] Calculating the absolute value DEF_Diff of the difference between the urea concentration obtained in step 3 based on the ultrasonic echo signal and the urea concentration obtained in step 5 using the first impedance sensing signal;

[0066] If the DEF_Diff value is higher than the third threshold Thd_Ddiff, it is determined that the sensor IR fault alarm occurs, otherwise it is determined that the sensor does not have an IR fault.

[0067] Furthermore, in step 6.2, judging whether an IR fault occurs in the sensor according to the liquid level of the urea solution includes:

[0068] Calculating an absolute value DLvl_Diff of a difference between the urea solution level obtained in step 3 according to the ultrasonic echo signal and the urea solution level obtained in step 5 using the first impedance sensing signal and the second impedance sensing signal;

[0069] If the DLvl_Diff value is higher than the sixth threshold Thd_Ldiff, it is determined that an IR fault occurs in the sensor; otherwise, it is determined that no IR fault occurs in the sensor.

[0070] Furthermore, in step 6.1, the signal processing unit determines whether there is an OOR fault in the impedance detection of the quality sensor element and the liquid level sensor unit, including:

[0071] Obtaining a first impedance sensing signal of the quality sensing element, and determining that an OOR fault exists in the quality sensing element if the first impedance sensing signal value is greater than a first maximum measurement value or less than a first minimum measurement value;

[0072] A second impedance sensing signal of the liquid level sensing unit is obtained. If the second impedance sensing signal value is greater than a second maximum measurement value or less than a second minimum measurement value, it is determined that an OOR fault exists in the liquid level sensing unit.

[0073] Beneficial effects: The present application provides a sensor that can simultaneously measure the quality and liquid level of urea solution using a single ultrasonic transmitting and receiving unit, and has a compact and economical design.

[0074] In exhaust gas treatment systems, impurity ions can accumulate in the SCR catalyst, reducing its activity and denitrification efficiency, and even rendering the catalyst ineffective. The sensor's quality sensing element incorporates an impedance sensor. Its high sensitivity enables it to detect low-concentration impurities in the urea solution, preventing damage to the SCR catalyst.

[0075] Since the ultrasonic sensor element in the quality sensor element is insensitive to impurities in the solution, changes between parts and the temperature of the urea solution, and the impedance sensor element in the quality sensor element and the liquid level sensor unit is insensitive to bubbles in the urea solution, fluid sloshing, local contamination and even partially frozen urea solution, the combination of the ultrasonic sensor element and the impedance sensor element can obtain accurate and reliable urea solution quality and liquid level.

[0076] The method for measuring the quality and level of urea solution of the present application can diagnose the IR problem that the sensor sensed value is within the normal range but is not an accurate value. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0078] Figure 1 A schematic diagram of the structure of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0079] Figure 2A schematic diagram of the structure of a quality sensing element of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0080] Figure 3 This is a schematic structural diagram of a second electrode in a quality sensing element of a sensor for measuring the quality and liquid level of a urea solution provided in an embodiment of the present application.

[0081] Figure 4 This is another structural schematic diagram of a quality sensing element of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0082] Figure 5 This is another structural schematic diagram of a quality sensing element of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0083] Figure 6 A schematic diagram of the structure of a signal processing unit of a sensor for measuring the quality and level of urea solution provided in an embodiment of the present application.

[0084] Figure 7 This is another structural schematic diagram of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0085] Figure 8 A schematic structural diagram of a liquid level sensing unit of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0086] Figure 9 This is another structural schematic diagram of a liquid level sensing unit of a sensor for measuring the quality and liquid level of urea solution provided in an embodiment of the present application.

[0087] Figure 10 A schematic diagram of an ultrasonic sensor element transmitting ultrasonic waves, and receiving a first ultrasonic echo and a second ultrasonic echo in a method for measuring the quality and liquid level of a urea solution provided in an embodiment of the present application. DETAILED DESCRIPTION

[0088] The embodiments of the present invention will be described below with reference to the accompanying drawings.

[0089] The present application provides a sensor and method for measuring the quality and level of a urea solution, which can be applied in a selective catalytic reduction scenario. When the urea solution is used as diesel exhaust fluid (DEF), the sensor is used to measure the quality and level of the urea solution and detect faults in the sensor itself.

[0090] The first embodiment of the present application discloses a sensor for measuring the quality and level of urea solution, such as Figure 1As shown, it includes a quality sensing element 100 and a signal processing unit 120, wherein the quality sensing element 100 is completely covered by the urea solution, and the signal processing unit 120 is electrically connected to the quality sensing element 100;

[0091] The quality sensing element 100 is configured to receive the first excitation signal generated by the signal processing unit 120, generate ultrasonic waves, transmit ultrasonic waves, receive ultrasonic echoes, and send the received ultrasonic echo signals to the signal processing unit 120;

[0092] The signal processing unit 120 is configured to generate a first excitation signal and send the first excitation signal to the quality sensing element 100 , receive an ultrasonic echo signal sent by the quality sensing element 100 , and calculate the quality and liquid level of the urea solution based on the ultrasonic echo signal. The urea solution quality includes the urea concentration of the urea solution.

[0093] like Figure 1 As shown, in a specific implementation, the sensor can be provided with a rubber head 80 and a base 70. Through the rubber head 80, the engine coolant flows through the coolant pipe 50 with an inlet 51 and an outlet 52 to heat the urea solution in the urea tank. The signal processing unit 120 can be provided on the top of the rubber head 80 and connected to the base 70 through the cable tube 60. The quality sensing element 100 is connected to the base 70.

[0094] In this embodiment, Figure 2 and Figure 3 As shown, the quality sensing element 100 includes a reflective assembly 125 and an ultrasonic sensor element. The reflective assembly 125 includes a vertical reflective plate 177 and an inclined reflective plate 175. There is an inclined angle between the vertical reflective plate 177 and the inclined reflective plate 175, and the inclined angle is preferably 45°.

[0095] The ultrasonic sensor element includes an ultrasonic transceiver unit 112, which is parallel to the vertical reflector 177, with a urea solution between the two. The ultrasonic transceiver unit 112 is used to transmit ultrasonic waves to the vertical reflector 177 and the inclined reflector 175. The surface of the vertical reflector 177 forms a first reflective surface 179 for receiving the ultrasonic waves transmitted by the ultrasonic transceiver unit 112, generating a first ultrasonic echo, and then reflecting the first ultrasonic echo to the ultrasonic transceiver unit 112. The surface of the inclined reflector 175 forms a second reflective surface 178 for receiving the ultrasonic waves transmitted by the ultrasonic transceiver unit 112 and reflecting them to the surface of the urea solution. The surface of the urea solution reflects the second ultrasonic echo to the second reflective surface 178, and the second reflective surface 178 then reflects the second ultrasonic echo to the ultrasonic transceiver unit 112. The ultrasonic transceiver unit 112 is electrically connected to the signal processing unit 120 via a fifth signal line 115, and transmits the received first and second ultrasonic echo signals to the signal processing unit 120.

[0096] In this embodiment, Figure 6 As shown, the signal processing unit 120 includes a central processing unit 230 and an ultrasonic signal processing subunit 240. The central processing unit 230 is used to send a first command to the ultrasonic signal processing subunit 240, receive the ultrasonic echo signal processed by the ultrasonic signal processing subunit 240, and calculate the quality and liquid level of the urea solution according to the ultrasonic echo signal; the ultrasonic echo signal includes a first ultrasonic echo and a second ultrasonic echo signal;

[0097] The ultrasonic signal processing subunit 240 is configured to receive a first command sent by the central processing unit 230, generate a first excitation signal, send the first excitation signal to the ultrasonic sensor element, receive an ultrasonic echo signal sent by the ultrasonic sensor element, process the echo signal, and send it to the central processing unit 230. The ultrasonic sensor element is electrically connected to the ultrasonic signal processing subunit 240 via a fifth signal line 115. The ultrasonic signal processing subunit 240 includes a first waveform generation module 242 (WGM), a pulse generator 244 (PM), a first amplifier 245, a rectifier 243, and an envelope detection module 241 (EDM). These components and the relationships between them are known in the art and are not limited in this embodiment.

[0098] In this embodiment, Figure 4As shown, the quality sensing element 100 further includes a first electrode 130, and the reflective assembly 125 further includes a second electrode 176. In one embodiment, a vertical reflective plate 177 is perpendicular to the second electrode 176, and the inclined reflective plate 175 is inclined toward an end away from the second electrode 176. A urea solution exists between the first electrode 130 and the second electrode 176, and the urea solution is in communication with the urea solution between the ultrasonic transceiver unit 112 and the reflective assembly 125.

[0099] like Figure 6 As shown, the signal processing unit 120 further includes an impedance signal processing subunit 250, and the impedance signal processing subunit 250 is electrically connected to one end of the first electrode 130 through the first signal line 128, and is electrically connected to one end of the second electrode 176 through the second signal line 123; the quality of the urea solution also includes the impurity ion concentration of the urea solution, and the central processing unit 230 is further used to send a second command to the impedance signal processing subunit 250 and receive the first impedance sensing signal processed by the impedance signal processing subunit 250, and calculate the impurity ion concentration of the urea solution according to the first impedance sensing signal; the impedance signal processing subunit 250 is used to receive the second command sent by the central processing unit 230, generate a second excitation signal, and send the second excitation signal to the first electrode 130 and the second electrode 176 respectively, receive the first impedance sensing signal sent by the first electrode 130, and send it to the central processing unit 230 after processing. The impedance signal processing subunit 250 includes a second waveform generating module 251, a driver 253, a multiplex switch 255 (MUX), a second amplifier 254 and a signal processing module 252. These components and the relationship between them belong to the prior art and are not limited in this embodiment.

[0100] In an optional implementation, the impedance of the first electrode 130 and the second electrode 176 changes with temperature. Specifically, the first electrode 130 and the second electrode 176 can be made of stainless steel (such as 304, 304L, 316, 316L), Hastelloy (nickel-molybdenum-chromium-tungsten alloy), and other materials. Figure 6 As shown, the signal processing unit 120 further includes a resistance measuring module 260 , which is electrically connected to the other end of the first electrode 130 via a sixth signal line 126 , for measuring the resistance of the first electrode 130 and sending the resistance value to the central processing unit 230 .

[0101] In another optional implementation, the signal processing unit 120 further includes a resistance measurement module 260, such as Figure 5As shown, the quality sensing element 100 further includes a first temperature sensing element 135 , which is used to measure the temperature of the urea solution between the first electrode 130 and the second electrode 176 . The first temperature sensing element 135 is electrically connected to the resistance measuring module 260 via the eighth signal line 127 . The resistance measuring module 260 is used to measure the resistance of the first temperature sensing element 135 and send the resistance value to the central processing unit 230 .

[0102] In this embodiment, Figure 7 As shown, the sensor further includes a liquid level sensing unit 200, as shown in FIG. Figure 8 As shown, the liquid level sensing unit 200 includes a third electrode 220 and a fourth electrode 205. The urea solution between the third electrode 220 and the fourth electrode 205 is in communication with the urea solution between the first electrode 130 and the second electrode 176. The third electrode 220 is electrically connected to the impedance signal processing subunit 250 via a third signal line 222, and the fourth electrode 205 is electrically connected to the impedance signal processing subunit 250 via a fourth signal line 223. The positions of the third electrode 220 and the fourth electrode 205 are not specifically limited in this embodiment; it is sufficient that the two electrodes are not electrically short-circuited. The impedance of the third electrode 220 and the fourth electrode 205 can vary with temperature. Specifically, the third electrode 220 and the fourth electrode 205 can be made of stainless steel (e.g., 304, 304L, 316, 316L), Hastelloy (nickel-molybdenum-chromium-tungsten alloy), or other materials. The fourth electrode 205 is grounded. The central processing unit 230 is further configured to send a third command to the impedance signal processing subunit 250 and receive the second impedance sensing signal processed by the impedance signal processing subunit 250, and calculate the urea solution level based on the second impedance sensing signal; the impedance signal processing subunit 250 is further configured to receive the third command sent by the central processing unit 230, generate a third excitation signal, and send the third excitation signal to the third electrode 220 and the fourth electrode 205 respectively, receive the second impedance sensing signal sent by the third electrode 220, and send the processed signal to the central processing unit 230.

[0103] like Figure 9 As shown, the liquid level sensing unit 200 further includes a second temperature sensing element 227, which is used to measure the temperature of the urea solution between the third electrode 220 and the fourth electrode 205, and is electrically connected to the resistance measurement module 260 via the seventh signal line 226; the resistance measurement module 260 is also used to measure the resistance of the second temperature sensing element 227 and send the resistance value to the central processing unit 230.

[0104] A second embodiment of the present application discloses a method for measuring the quality and liquid level of a urea solution, comprising the following steps:

[0105] Step 1: The signal processing unit 120 sends a first excitation signal to the ultrasonic sensor element;

[0106] Step 2: The ultrasonic sensor element receives the first excitation signal, generates ultrasonic waves, transmits ultrasonic waves, receives ultrasonic echoes, and sends the received ultrasonic echo signals to the signal processing unit 120;

[0107] In step 3, the signal processing unit 120 receives the ultrasonic echo signal sent by the quality sensing element 100 and calculates the quality and liquid level of the urea solution according to the ultrasonic echo signal. The quality of the urea solution includes the urea concentration of the urea solution.

[0108] In this embodiment, the ultrasonic echo in step 2 includes a first ultrasonic echo and a second ultrasonic echo, and calculating the quality and liquid level of the urea solution according to the ultrasonic echo signal in step 3 includes:

[0109] The distance between the ultrasonic transceiver unit 112 and the vertical reflector 177 is d 177 The distance between the ultrasonic transceiver unit 112 and the ultrasonic reflection point on the inclined reflector 175 is d 175 , the distance between the inclined reflector 175 and the urea solution surface is l 175 ,

[0110] The time interval T from the ultrasonic transceiver unit 112 sending the ultrasonic wave to receiving the first ultrasonic echo is q Expressed as:

[0111] T q =2*d 177 / Cs (1)

[0112] Where Cs represents the ultrasonic propagation velocity. When ultrasonic waves propagate in a urea solution, the ultrasonic propagation velocity Cs is determined by the bulk modulus K and density ρ of the urea solution:

[0113]

[0114] Among them, the values ​​of bulk modulus K and density ρ both change with the concentration and temperature of urea solution;

[0115] Since the ultrasonic wave propagation distance is 2*d 177 is a fixed value, and the ultrasonic propagation speed Cs is the time interval T q function of urea solution, so the urea concentration γ s By time interval T q and urea solution temperature Ts, the time interval T q Calculated by the signal processing unit 120 based on the transmitted first excitation signal and the received first ultrasonic echo signal;

[0116] The time interval from the ultrasonic transceiver unit 112 sending the ultrasonic wave to receiving the second ultrasonic echo is T l , which is calculated by the signal processing unit 120 according to the sent first excitation signal and the received second ultrasonic echo signal.

[0117] Expressed as:

[0118] T l =(2*d 175 +2*l 175 ) / Cs (3)

[0119] Then T l / T q =(d 175 +l 175 ) / d 177 , l 175 =d 177 *T l / T q -d 175

[0120] The height from the ultrasonic reflection point on the inclined reflector 175 to the bottom of the urea tank is h 175 , then the urea solution level ld is T l With T q The function of the ratio:

[0121] ld = h 175 +l 175 = (h 175 -d 175 )+d 177 *T l / T q (3).

[0122] In this embodiment, step 4 is further included, which is to calculate the concentration of impurity ions in the urea solution, including:

[0123] The impedance between the first electrode 130 and the second electrode 176 is denoted as Zs. The impedance Zs is calculated by the signal processing unit 120 according to the first impedance sensing signal. The impedance change value dZs of the impedance Zs is calculated. The impedance change value dZs is defined as follows:

[0124] dZs = (Zs(γ i ) - Zs(0)) / Zs(0) (4)

[0125] Wherein, Zs(γi) is the impedance between the first electrode 130 and the second electrode 176 measured in a urea solution with an impurity ion concentration of γi, and Zs(0) is the impedance between the first electrode 130 and the second electrode 176 measured in a urea solution that complies with the ISO 22241 standard. The impurity ion concentration γi is obtained by looking up the table:

[0126] γi=Tbl(dZs).

[0127] This embodiment further includes step 5, when the ultrasonic sensor element is unavailable, calculating the urea concentration of the urea solution using the first impedance sensing signal, and calculating the urea solution level using the first impedance sensing signal and the second impedance sensing signal.

[0128] In step 5, the ultrasonic sensor element being unavailable includes the ultrasonic sensor element having a first type of abnormality, and detecting whether the ultrasonic sensor element has the first type of abnormality includes: Figure 10 As shown, the amplitude value Lv1 of the second ultrasonic echo signal 183 is measured and compared with a fifth threshold value Thd_Lv11. If the amplitude value Lv11 is higher than the fifth threshold value Thd_Lv11, it is determined that the ultrasonic sensor element does not have a first-category abnormality. Otherwise, it is determined that the ultrasonic sensor element has a first-category abnormality. The fifth threshold value Thd_Lv11 can be set according to the signal amplitude range during normal use.

[0129] In step 5, the ultrasonic sensor element being unavailable includes the ultrasonic sensor element having a second type of abnormality, and detecting whether the ultrasonic sensor element has the second type of abnormality includes: Figure 10 As shown, the height value of the first ultrasonic echo signal 182 is recorded as S_amp, and the height value S_amp of the first ultrasonic echo signal is compared with the first threshold value Thd_samp. If S_amp is not higher than Thd_samp, it is determined that the ultrasonic sensor element has a second type of abnormality; the first threshold value Thd_samp can be set to be slightly higher than the maximum value of S_amp in the operating temperature range (for example, -11°C to -85°C).

[0130] If the S_amp value is higher than Thd_samp, the change in the peak time T_sft of the first ultrasonic echo signal is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft = Tpk-Tpk0

[0131] The change in the peak moment of the first ultrasonic echo signal, T_sft, is compared with a second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensor element is determined to have a second-category abnormality. If T_sft is higher than Thd_Tsft, the ultrasonic sensor element is determined not to have a second-category abnormality. Here, the normal value, Tpk0, is determined by the pulse width of the ultrasonic excitation signal and can be set to half the pulse width of the excitation signal. The second threshold, Thd_Tsft, can be set to the width of one or more carrier pulses.

[0132] In step 5, the ultrasonic sensor element being unavailable may be caused by the presence of sway in the urea solution. Detecting whether the urea solution is swaying includes calculating a rate of change Zr of an impedance value Zs corresponding to the first impedance sensing signal. If the Zr value is greater than a fourth threshold Thd_zrl, then it is determined that the urea solution is swaying; otherwise, it is determined that the urea solution is not swaying. The fourth threshold Thd_zrl can be set based on the signal amplitude range during normal use.

[0133] In step 5, the urea concentration of the urea solution is calculated using the first impedance sensing signal, including: the impedance Zs corresponding to the first impedance sensing signal is the product of the urea solution temperature Ts and the urea concentration γ of the urea solution s Function:

[0134] Zs=f(Ts,γ s ) (5)

[0135] Therefore, the urea concentration of the urea solution is γ s Calculated from impedance Zs and urea solution temperature Ts.

[0136] In step 5, calculating the urea solution level using the first impedance sensing signal and the second impedance sensing signal includes calculating the ratio Rz between the two impedance values:

[0137] Rz=Zsl / Zs (6)

[0138] Wherein, Zsl represents the impedance value corresponding to the second impedance sensing signal.

[0139] In an optional implementation, in step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a lookup table to compensate for nonlinear effects:

[0140] ld=Tbl(Rz) (7)

[0141] In formula (7), Tbl() represents a table lookup calculation, and the table value in the table lookup calculation is calibrated by test data obtained through experiments at different urea solution concentrations.

[0142] In another optional implementation, in step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a two-dimensional lookup table to compensate for the nonlinear effect caused by the urea solution temperature:

[0143] ld=Tbl(Rz,T227) (8)

[0144] Wherein, T227 is the urea solution temperature obtained by the second temperature sensing element 227, Tbl() represents a table lookup calculation, and the table value in the table lookup calculation is calibrated by test data obtained through experiments at different urea solution concentrations and temperatures.

[0145] In this embodiment, the urea solution temperature Ts is obtained by measuring the resistance Re of the first electrode 130 , or by measuring the first temperature sensing element 135 .

[0146] In this embodiment, step 6 is further included, which is to determine whether an IR fault occurs in the sensor for measuring the quality and level of the urea solution, including:

[0147] In step 6.1, the signal processing unit 120 determines whether the quality sensing element 100 and the liquid level sensing unit 200 have an Out-of-Order (OOR) fault during impedance testing, and whether the ultrasonic sensor element in the quality sensing element 100 has a first type of abnormality or a second type of abnormality. The signal processing unit 120 determines whether the quality sensing element 100 and the liquid level sensing unit 200 have an OOR fault during impedance testing, including:

[0148] Obtaining a first impedance sensing signal from the quality sensing element 100 , and determining that an OOR fault exists in the quality sensing element 100 if the first impedance sensing signal value is greater than a first maximum measurement value or less than a first minimum measurement value;

[0149] A second impedance sensing signal of the liquid level sensing unit 200 is obtained. If the second impedance sensing signal value is greater than the second maximum measurement value or less than the second minimum measurement value, it is determined that an OOR fault exists in the liquid level sensing unit 200.

[0150] In step 6.2, if it is determined that the quality sensing element 100 and the liquid level sensing unit 200 do not have the OOR fault in the impedance detection, and the ultrasonic sensor element in the quality sensing element 100 does not have the first type of abnormality and the second type of abnormality, it is determined whether the sensor has an IR fault based on the urea concentration or liquid level of the urea solution.

[0151] Judging whether the sensor has an IR fault based on the urea concentration of the urea solution includes:

[0152] Calculating the absolute value DEF_Diff of the difference between the urea concentration obtained in step 3 based on the ultrasonic echo signal and the urea concentration obtained in step 5 using the first impedance sensing signal;

[0153] If the DEF_Diff value is higher than the third threshold Thd_Ddiff, a sensor IR fault alarm is generated. Otherwise, the sensor is determined not to have an IR fault. The third threshold Thd_Ddiff can be set according to the error limit required by the OBD (On-Board Diagnostics) or design specifications.

[0154] Judging whether the sensor has an IR fault based on the urea solution level includes:

[0155] Calculating an absolute value DLvl_Diff of a difference between the urea solution level obtained in step 3 according to the ultrasonic echo signal and the urea solution level obtained in step 5 using the first impedance sensing signal and the second impedance sensing signal;

[0156] If the DLvl_Diff value is higher than the sixth threshold Thd_Ldiff, it is determined that the sensor has an IR fault, otherwise it is determined that the sensor has not an IR fault. The sixth threshold Thd_Ldiff can be set according to the error limit range required by the OBD or design specifications.

[0157] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program that, when executed by the data processing unit, executes the invention disclosure of a method for measuring urea solution quality and level, as well as some or all of the steps in various embodiments. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0158] 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 this understanding, the technical solutions in the embodiments of the present invention, in essence or in other words, the part that contributes to the prior art, can be embodied in the form of a computer program, i.e., a software product. The computer program software product can be stored in a storage medium and includes a number of instructions for enabling a device including a data processing unit (which can be a personal computer, server, single-chip microcomputer, MUU or network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0159] The present invention provides a sensor and method for measuring the quality and level of urea solution. Numerous methods and approaches exist for implementing this technical solution. The foregoing description is merely a specific embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of the present invention. Components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A sensor for measuring the quality and level of urea solution, characterized in that: It comprises a quality sensing element (100) and a signal processing unit (120), wherein the quality sensing element (100) is completely covered by a urea solution, and the signal processing unit (120) is electrically connected to the quality sensing element (100); The quality sensing element (100) is used to receive a first excitation signal generated by the signal processing unit (120), generate ultrasonic waves, transmit ultrasonic waves, receive ultrasonic echoes, and send the received ultrasonic echo signals to the signal processing unit (120); The signal processing unit (120) is used to generate a first excitation signal and send the first excitation signal to the quality sensing element (100), receive an ultrasonic echo signal sent by the quality sensing element (100), and calculate the quality and liquid level of the urea solution according to the ultrasonic echo signal, wherein the quality of the urea solution includes the urea concentration of the urea solution; The quality sensing element (100) includes a reflection assembly (125) and an ultrasonic sensing element, wherein the reflection assembly (125) includes a vertical reflection plate (177) and an inclined reflection plate (175), wherein the inclined reflection plate (175) and the vertical reflection plate (177) form a fracture structure, and an inclined angle exists between the inclined reflection plate (175) and the vertical reflection plate (177); the fracture structure formed by the inclined reflection plate (175) and the vertical reflection plate (177) means that when the inclined reflection plate (175) is projected onto the plane where the vertical reflection plate (177) is located, the projection edge of the inclined reflection plate (175) on the side close to the vertical reflection plate (177) is in contact with the edge of the vertical reflection plate (177); The ultrasonic sensor element comprises an ultrasonic transceiver unit (112), the ultrasonic transceiver unit (112) being parallel to the vertical reflector (177), with a urea solution present between the two. The ultrasonic transceiver unit (112) is used to transmit ultrasonic waves to the vertical reflector (177) and the inclined reflector (175), the vertical reflector (177) being used to receive the ultrasonic waves transmitted by the ultrasonic transceiver unit (112), generate a first ultrasonic echo, and then reflect the first ultrasonic echo to the ultrasonic transceiver unit (112); the inclined reflector (175) being used to receive the ultrasonic waves transmitted by the ultrasonic transceiver unit (112) and reflect them to the surface of the urea solution, the surface of the urea solution reflecting a second ultrasonic echo to the inclined reflector (175), and then reflecting the second ultrasonic echo to the ultrasonic transceiver unit (112); the ultrasonic transceiver unit (112) is electrically connected to the signal processing unit (120) via a fifth signal line (115), and transmits the received first ultrasonic echo and second ultrasonic echo signals to the signal processing unit (120).

2. A sensor for measuring the quality and liquid level of urea solution according to claim 1, characterized in that: The signal processing unit (120) comprises a central processing unit (230) and an ultrasonic signal processing subunit (240), wherein the central processing unit (230) is used to send a first command to the ultrasonic signal processing subunit (240), receive an ultrasonic echo signal processed by the ultrasonic signal processing subunit (240), and calculate the quality and liquid level of the urea solution according to the ultrasonic echo signal; the ultrasonic echo signal comprises a first ultrasonic echo and a second ultrasonic echo signal; The ultrasonic signal processing subunit (240) is used to receive a first command sent by the central processing unit (230), generate a first excitation signal, send the first excitation signal to the ultrasonic sensor element, receive the ultrasonic echo signal sent by the ultrasonic sensor element, and send it to the central processing unit (230) after processing; the ultrasonic sensor element is electrically connected to the ultrasonic signal processing subunit (240) via a fifth signal line (115).

3. The sensor for measuring the quality and liquid level of urea solution according to claim 2, characterized in that: The quality sensing element (100) further includes a first electrode (130), the reflective assembly (125) further includes a second electrode (176), and a urea solution exists between the first electrode (130) and the second electrode (176), and the urea solution is in communication with the urea solution between the ultrasonic transceiver unit (112) and the reflective assembly (125); The signal processing unit (120) further includes an impedance signal processing subunit (250), wherein the impedance signal processing subunit (250) is electrically connected to one end of the first electrode (130) via a first signal line (128), and is electrically connected to one end of the second electrode (176) via a second signal line (123); the quality of the urea solution also includes the impurity ion concentration of the urea solution; the central processing unit (230) is further used to send a second command to the impedance signal processing subunit (250) and receive the first impedance sensing signal processed by the impedance signal processing subunit (250), and calculate the impurity ion concentration of the urea solution according to the first impedance sensing signal; the impedance signal processing subunit (250) is used to receive the second command sent by the central processing unit (230), generate a second excitation signal, and send the second excitation signal to the first electrode (130) and the second electrode (176) respectively, measure the first impedance sensing signal, and send the processed first impedance sensing signal to the central processing unit (230).

4. The sensor for measuring the quality and liquid level of urea solution according to claim 3, characterized in that: The signal processing unit (120) further includes a resistance measuring module (260), wherein the resistance measuring module (260) is electrically connected to the other end of the first electrode (130) via a sixth signal line (126), and is used to measure the resistance of the first electrode (130) and send the resistance value to the central processing unit (230).

5. The sensor for measuring the quality and liquid level of urea solution according to claim 3, characterized in that: The signal processing unit (120) further includes a resistance measuring module (260), and the quality sensing element (100) further includes a first temperature sensing element (135). The first temperature sensing element (135) is used to measure the temperature of the urea solution between the first electrode (130) and the second electrode (176), and is electrically connected to the resistance measuring module (260) via an eighth signal line (127). The resistance measuring module (260) is used to measure the resistance of the first temperature sensing element (135) and send the resistance value to the central processing unit (230).

6. A sensor for measuring the quality and liquid level of urea solution according to claim 4 or 5, characterized in that: The liquid level sensing unit (200) is also included. The liquid level sensing unit (200) includes a third electrode (220) and a fourth electrode (205). The urea solution between the third electrode (220) and the fourth electrode (205) is in communication with the urea solution between the first electrode (130) and the second electrode (176). The third electrode (220) is electrically connected to the impedance signal processing subunit (250) via a third signal line (222). The fourth electrode (205) is electrically connected to the impedance signal processing subunit (250) via a fourth signal line (223). The processing unit (230) is further configured to send a third command to the impedance signal processing subunit (250) and receive a second impedance sensing signal processed by the impedance signal processing subunit (250), and calculate the urea solution level according to the second impedance sensing signal; the impedance signal processing subunit (250) is further configured to receive a third command sent by the central processing unit (230), generate a third excitation signal, and send the third excitation signal to the third electrode (220) and the fourth electrode (205), respectively, measure the second impedance sensing signal, and send the processed signal to the central processing unit (230).

7. The sensor for measuring the quality and liquid level of urea solution according to claim 6, characterized in that: The liquid level sensing unit (200) further includes a second temperature sensing element (227), the second temperature sensing element (227) being used to measure the temperature of the urea solution between the third electrode (220) and the fourth electrode (205), and being electrically connected to the resistance measuring module (260) via a seventh signal line (226); the resistance measuring module (260) is further used to measure the resistance of the second temperature sensing element (227) and transmit the resistance value to the central processing unit (230).

8. A method for measuring the quality and liquid level of a urea solution, applied to the sensor for measuring the quality and liquid level of a urea solution according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: the signal processing unit (120) sends a first excitation signal to the ultrasonic sensor element; Step 2, the ultrasonic sensor element receives the first excitation signal, generates ultrasonic waves, transmits ultrasonic waves, receives ultrasonic echoes, and sends the received ultrasonic echo signals to a signal processing unit (120); In step 3, the signal processing unit (120) receives the ultrasonic echo signal sent by the quality sensing element (100), and calculates the quality and liquid level of the urea solution according to the ultrasonic echo signal, wherein the quality of the urea solution includes the urea concentration of the urea solution.

9. The method for measuring the quality and liquid level of urea solution according to claim 8, characterized in that: The ultrasonic echo in step 2 includes a first ultrasonic echo and a second ultrasonic echo. Calculating the quality and liquid level of the urea solution according to the ultrasonic echo signal in step 3 includes: The distance between the ultrasonic transceiver unit (112) and the vertical reflector (177) is d 177 The distance between the ultrasonic transceiver unit (112) and the ultrasonic reflection point on the inclined reflection plate (175) is d 175 , The time interval T from the ultrasonic transceiver unit (112) sending the ultrasonic wave to receiving the first ultrasonic echo q Expressed as: T q =2*d 177 / Cs (1), Where Cs represents the ultrasonic propagation velocity. When ultrasonic waves propagate in a urea solution, the ultrasonic propagation velocity Cs is determined by the bulk modulus K and density 𝜌 of the urea solution: （2）， Among them, the values ​​of bulk modulus K and density 𝜌 vary with the concentration and temperature of urea solution; Since the ultrasonic wave propagation distance is 2*d 177 is a fixed value, and the ultrasonic propagation speed Cs is the time interval T q function of urea solution, so the urea concentration 𝛾 s By time interval T q and urea solution temperature Ts, the time interval T q Calculated and obtained by the signal processing unit (120) based on the transmitted first excitation signal and the received first ultrasonic echo signal; The time interval from the ultrasonic transceiver unit (112) sending the ultrasonic wave to receiving the second ultrasonic wave echo is T l The height of the ultrasonic reflection point on the inclined reflector (175) from the bottom of the urea tank is h 175 , then the urea solution level ld: ld = (h 175 -d 175 )+d 177 *T l / T q (3)。 10. The method for measuring the quality and liquid level of urea solution according to claim 9, characterized in that: The method further includes step 4, calculating the concentration of impurity ions in the urea solution, including: The impedance between the first electrode (130) and the second electrode (176) is denoted as Zs. The impedance Zs is calculated by the signal processing unit (120) based on the first impedance sensing signal. The impedance change value dZs of the impedance Zs is calculated. The impedance change value dZs is defined as follows: dZs = (Zs(𝛾 i ) - Zs(0)) / Zs(0) (4), Wherein, Zs(𝛾i) is the impedance between the first electrode (130) and the second electrode (176) measured in a urea solution with an impurity ion concentration of 𝛾i, and Zs(0) is the impedance between the first electrode (130) and the second electrode (176) measured in a urea solution conforming to the ISO 22241 standard; the impurity ion concentration 𝛾i is obtained by looking up the table: 𝛾i = Tbl(dZs).

11. The method for measuring the quality and liquid level of urea solution according to claim 10, characterized in that: The method further includes step 5, when the ultrasonic sensing element is unavailable, calculating the urea concentration of the urea solution using the first impedance sensing signal, and calculating the liquid level of the urea solution using the first impedance sensing signal and the second impedance sensing signal.

12. The method for measuring the quality and liquid level of urea solution according to claim 11, characterized in that: In step 5, the ultrasonic sensor element is unavailable, including the presence of a first type of abnormality in the ultrasonic sensor element. Detecting whether the ultrasonic sensor element has the first type of abnormality includes: measuring the amplitude value Lvl of the second ultrasonic echo signal, and comparing the amplitude value with the fifth threshold Thd_Lvll. If the amplitude value is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensor element does not have the first type of abnormality; otherwise, it is determined that the ultrasonic sensor element has the first type of abnormality.

13. The method for measuring the quality and liquid level of urea solution according to claim 11, characterized in that: In step 5, the ultrasonic sensor element being unavailable includes the ultrasonic sensor element having a second type of abnormality. Detecting whether the ultrasonic sensor element has the second type of abnormality includes: recording a height value of the first ultrasonic echo signal as S_amp, comparing the height value S_amp of the first ultrasonic echo signal with a first threshold value Thd_samp, and if S_amp is not higher than Thd_samp, determining that the ultrasonic sensor element has the second type of abnormality. If the S_amp value is higher than Thd_samp, the change in the peak time T_sft of the first ultrasonic echo signal is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft=Tpk-Tpk0 The change T_sft of the peak moment of the first ultrasonic echo signal is compared with the second threshold Thd_Tsft. If T_sft is not higher than Thd_Tsft, it is determined that the ultrasonic sensor element has a second type of abnormality; if T_sft is higher than Thd_Tsft, it is determined that the ultrasonic sensor element does not have a second type of abnormality.

14. The method for measuring the quality and liquid level of urea solution according to claim 11, characterized in that: In step 5, the ultrasonic sensing element being unavailable includes the ultrasonic sensing element being unavailable due to shaking of the urea solution. Detecting whether the urea solution is shaking includes calculating a rate of change Zr of an impedance value Zs corresponding to the first impedance sensing signal. If the Zr value is higher than a fourth threshold Thd_zrl, it is determined that the urea solution is shaking; otherwise, it is determined that the urea solution is not shaking.

15. A method for measuring the quality and liquid level of urea solution according to any one of claims 12, 13 or 14, characterized in that: In step 5, the urea concentration of the urea solution is calculated using the first impedance sensing signal, including: the impedance Zs corresponding to the first impedance sensing signal is the urea solution temperature Ts and the urea concentration 𝛾 of the urea solution s Function: （5）， Therefore, the urea concentration of the urea solution is s Calculated from impedance Zs and urea solution temperature Ts.

16. The method for measuring the quality and liquid level of urea solution according to claim 15, characterized in that: In step 5, calculating the urea solution level using the first impedance sensing signal and the second impedance sensing signal includes calculating the ratio Rz between the two impedance values: Rz=Zsl / Zs (6), Wherein, Zsl represents the impedance value corresponding to the second impedance sensing signal.

17. The method for measuring the quality and liquid level of urea solution according to claim 16, characterized in that: In step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a table lookup calculation to compensate for nonlinear effects: ld = Tbl(Rz) (7, In formula (7), Tbl() represents table lookup calculation, and the table value in the table lookup calculation is calibrated by the test data obtained by experiments under different urea solution concentrations.

18. The method for measuring the quality and liquid level of urea solution according to claim 16, characterized in that: In step 5, calculating the urea solution level ld using the first impedance sensing signal and the second impedance sensing signal includes using a two-dimensional lookup table to compensate for the nonlinear effect caused by the urea solution temperature: ld = Tbl(Rz, T227) (8), Wherein, T227 is the urea solution temperature obtained by the second temperature sensing element (227), and Tbl() represents a table lookup calculation, wherein the table value in the table lookup calculation is calibrated by test data obtained by experiments at different urea solution concentrations and temperatures.

19. The method for measuring the quality and liquid level of urea solution according to claim 15, characterized in that: The urea solution temperature Ts is obtained by measuring the resistance Re of the first electrode (130), or by measuring the first temperature sensing element (135).

20. The method for measuring the quality and liquid level of urea solution according to any one of claims 17 or 18, characterized in that: The method further includes step 6 of determining whether an IR fault occurs in a sensor for measuring the quality and level of the urea solution.

21. The method for measuring the quality and level of urea solution according to claim 20, characterized in that: Step 6 includes: Step 6.1, the signal processing unit (120) determines whether the quality sensing element (100) and the liquid level sensing unit (200) have an OOR fault during impedance detection, and whether the ultrasonic sensor element in the quality sensing element (100) has a first type of abnormality and a second type of abnormality; Step 6.2: If it is determined that the quality sensing element (100) and the liquid level sensing unit (200) do not have the OOR fault in the impedance detection, and the ultrasonic sensor element in the quality sensing element (100) does not have the first type of abnormality and the second type of abnormality, it is determined whether the sensor has an IR fault based on the urea concentration or liquid level of the urea solution.

22. The method for measuring the quality and liquid level of urea solution according to claim 21, characterized in that: In step 6.2, judging whether the sensor has an IR fault based on the urea concentration of the urea solution includes: Calculating the absolute value DEF_Diff of the difference between the urea concentration obtained in step 3 based on the ultrasonic echo signal and the urea concentration obtained in step 5 using the first impedance sensing signal; If the DEF_Diff value is higher than the third threshold Thd_Ddiff, it is determined that the sensor IR fault alarm occurs, otherwise it is determined that the sensor does not have an IR fault.

23. The method for measuring the quality and liquid level of urea solution according to claim 21, characterized in that: In step 6.2, judging whether the sensor has an IR fault based on the urea solution level includes: Calculating an absolute value DLvl_Diff of a difference between the urea solution level obtained in step 3 according to the ultrasonic echo signal and the urea solution level obtained in step 5 using the first impedance sensing signal and the second impedance sensing signal; If the DLvl_Diff value is higher than the sixth threshold Thd_Ldiff, it is determined that an IR fault occurs in the sensor; otherwise, it is determined that no IR fault occurs in the sensor.

24. A method for measuring the quality and liquid level of urea solution according to any one of claims 22 or 23, characterized in that: In step 6.1, the signal processing unit (120) determines whether an OOR fault exists in the quality sensing element (100) and the liquid level sensing unit (200) during impedance detection, including: Acquiring a first impedance sensing signal of the quality sensing element (100), and if the first impedance sensing signal value is greater than a first maximum measurement value, or less than a first minimum measurement value, determining that an OOR fault exists in the quality sensing element (100); A second impedance sensing signal of the liquid level sensing unit (200) is obtained, and if the second impedance sensing signal value is greater than a second maximum measurement value, or less than a second minimum measurement value, it is determined that an OOR fault exists in the liquid level sensing unit (200).

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