A sensor and method for measuring the quality of urea solution

Abstract

This invention discloses a sensor and method for measuring the quality of urea solution, comprising a quality sensing element and a signal processing unit. The quality sensing element is covered by the urea solution, and the signal processing unit is electrically connected to the quality sensing element. The quality sensing element receives an excitation signal generated by the signal processing unit, generates a sensing signal, and sends the sensing signal to the signal processing unit. The signal processing unit generates an excitation signal and sends it to the quality sensing element, receives the sensing signal sent by the quality sensing element, and calculates a urea solution quality sensing value based on the sensing signal. The urea solution quality sensing value includes the urea concentration and impurity ion concentration in the urea solution. The sensor can detect impurity ions and accurately measure the urea concentration, and can also diagnose the so-called IR problem where the sensor sensing value is within the normal range but inaccurate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of urea solution quality detection, and particularly relates to a sensor and method for measuring urea solution quality. BACKGROUND

[0002] In selective catalytic reduction (SCR) applications, 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 pyrolysis and hydrolysis of urea, and then ammonia reacts with nitrogen oxides (NOx) in the exhaust gas with the help of an SCR catalyst and removes them. Limited by the reaction ratio of ammonia to nitrogen oxides, in order to avoid ammonia leakage or high nitrogen oxide emissions, the addition amount of urea solution needs to be accurately controlled, and 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, eutectic urea solution with the lowest freezing temperature (32.5%wt), i.e. diesel exhaust fluid (DEF), is usually used as a reducing agent carrier.

[0003] In urea metering control, non-compliant urea solution (urea solution that does not meet the requirements of ISO 22241 standard) can cause emission problems or system failure. For example, when DEF is diluted, low-concentration urea in the solution can cause emission problems, and impurities in the solution, such as some metal ions (calcium, zinc, magnesium, iron, chromium, nickel, sodium and potassium, etc.) contained in tap water, or non-urea solution (such as fuel mistakenly added into the urea tank), can damage the SCR catalyst. In order to avoid causing emission problems, it is necessary to monitor the urea concentration in DEF, and also to monitor the impurities in DEF to prevent non-compliant solution from entering the SCR system.

[0004] Most DEF sensors need to be installed in the urea tank, but in order to avoid vacuum causing DEF supply problems, the urea tank must have an opening to the surrounding environment and through which air comes into contact with DEF. Under many conditions, such as shaking, pressure changes, agitation caused by suction or return movement of the DEF pump, etc., bubbles can be generated in the DEF. These bubbles can reduce the performance of the DEF sensor, and even temporarily disable it. When the bubbles adhere to the surface of the sensor probe (these bubbles are difficult to disappear on their own), these bubbles can cause the DEF sensor to be disabled for a long time.

[0005] In addition, the prior art has triggered false alarms of DEF concentration due to DEF sensor problems, and cannot diagnose the DEF sensor itself. SUMMARY

[0006] The technical problem solved by the present application is to provide a sensor and method for measuring the quality of urea solution.

[0007] To solve the above technical problem, the first aspect discloses a sensor for measuring the quality of urea solution, comprising a quality sensing element and a signal processing unit, the quality sensing element is completely covered by the urea solution, and the signal processing unit is electrically connected with the quality sensing element.

[0008] The quality sensing element is used for receiving an excitation signal generated by the signal processing unit, generating a sensing signal, and sending the sensing signal to the signal processing unit.

[0009] The signal processing unit is used for generating an excitation signal and sending it to the quality sensing element, receiving the sensing signal sent by the quality sensing element, and calculating a urea solution quality sensing value according to the sensing signal, wherein the urea solution quality sensing value includes the urea concentration and the impurity ion concentration in the urea solution.

[0010] Further, the quality sensing element comprises an impedance sensing element and an ultrasonic wave sensing element, the impedance sensing element comprises a first electrode and a second electrode, the urea solution between the first electrode and the second electrode is in communication with the urea solution in the ultrasonic wave sensing element, one end of the second electrode is electrically connected to the signal processing unit through a second signal line, one end of the first electrode is electrically connected to the signal processing unit through a first signal line, and the ultrasonic wave sensing element is electrically connected to the signal processing unit through a fifth signal line, and is used for generating ultrasonic waves according to the excitation signal sent by the signal processing unit, emitting and receiving the ultrasonic waves, and sending the received ultrasonic wave signal to the signal processing unit.

[0011] Further, the signal processing unit comprises a central processing unit, an ultrasonic signal processing subunit, and an impedance signal processing subunit,

[0012] The central processing unit is used for sending a command to the ultrasonic signal processing subunit and the impedance signal processing subunit, receiving the sensing signal processed by the ultrasonic signal processing subunit and the impedance signal processing subunit, and calculating a urea solution quality sensing value according to the sensing signal.

[0013] The ultrasonic signal processing subunit is electrically connected with the ultrasonic wave sensing element through the fifth signal line, is used for receiving a first command sent by the central processing unit, generating a first excitation signal, sending the first excitation signal to the ultrasonic wave sensing element, receiving the ultrasonic wave signal sent by the ultrasonic wave sensing element, and sending the processed ultrasonic wave signal to the central processing unit.

[0014] The impedance signal processing subunit is electrically connected with one end of the first electrode through a first signal line, and electrically connected with one end of the second electrode through a second signal line, used for receiving a second command sent by the central processing unit, generating a second excitation signal, and sending the second excitation signal to the first electrode and the second electrode respectively, receiving an impedance sensing signal sent by the first electrode, and sending the impedance sensing signal to the central processing unit after processing.

[0015] Further, the signal processing unit further comprises a resistance measuring module, the resistance measuring module is electrically connected with the other end of the first electrode through a sixth signal line, and used for measuring the resistance of the first electrode and sending the resistance value to the central processing unit.

[0016] Further, the signal processing unit further comprises a resistance measuring module, the impedance sensing element further comprises a first temperature sensing element, the first temperature sensing element is used for measuring the temperature of the urea solution between the first electrode and the second electrode, and is electrically connected with the resistance measuring module through an eighth signal line, the resistance measuring module is used for measuring the resistance of the first temperature sensing element and sending the resistance value to the central processing unit.

[0017] The second aspect discloses a method for measuring the quality of urea solution, comprising the following steps:

[0018] Step 1, the signal processing unit sends an excitation signal to the quality sensing element, the excitation signal comprises a first excitation signal sent to the ultrasonic wave sensing element, and a second excitation signal sent to the first electrode and the second electrode;

[0019] Step 2, the quality sensing element receives the excitation signal generated by the signal processing unit, generates a sensing signal, and sends the sensing signal to the signal processing unit; the sensing signal comprises an ultrasonic wave signal and an impedance sensing signal;

[0020] Step 3, the signal processing unit receives the sensing signal sent by the quality sensing element, calculates a urea solution quality sensing value according to the sensing signal, and the calculation of the urea solution quality sensing value comprises calculation of urea concentration in the urea solution and calculation of impurity ion concentration in the urea solution.

[0021] Further, the calculation of the urea concentration in the urea solution in step 3 comprises:

[0022] Step 3.1, judging whether the ultrasonic wave sensing element is available;

[0023] Step 3.2, when the ultrasonic wave sensing element is available, the urea concentration in the urea solution is calculated using the ultrasonic wave signal;

[0024] Step 3.3, when the ultrasonic wave sensing element is unavailable, the urea concentration in the urea solution is calculated using the impedance sensing signal.

[0025] Ultrasonic signals are insensitive to impurity ions but sensitive to urea concentration, thus enabling accurate measurement of urea concentration in urea solutions. Impedance sensing signals, on the other hand, are sensitive to impurity ions but have poor selectivity; their resolution for urea concentration may be limited by their high sensitivity to ionic impurities. When an ultrasonic sensor is available, the urea concentration of the solution is calculated using the ultrasonic signal. However, when the ultrasonic sensor is unavailable, such as during vehicle operation when bubbles may form in the urea solution, these bubbles can degrade the performance of the ultrasonic sensor or even temporarily disable it. When bubbles adhere to the probe surface of the ultrasonic sensor (which is difficult to dissipate on its own), they can cause prolonged malfunction. Since no impurities are introduced during vehicle operation, the urea concentration measured using impedance sensing signals is unaffected by ionic impurities, allowing for the calculation of the urea concentration in the solution using impedance sensing signals.

[0026] Further, step 3.1 includes: recording the height value of the ultrasonic signal in the sensing signal as S_amp, comparing the height value of the ultrasonic signal S_amp with the first threshold Thd_samp, and if S_amp is not higher than Thd_samp, the ultrasonic sensing element is unusable, indicated by the status flag Stat_QU=1.

[0027] If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft = Tpk - Tpk0

[0028] The change in the peak time of the ultrasonic signal, T_sft, is compared with the second threshold, Thd_sft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensor is unavailable, indicated by the status flag Stat_QU = 1; if T_sft is higher than Thd_Tsft, the ultrasonic sensor is available, indicated by the status flag Stat_QU = 0.

[0029] By detecting distortions in ultrasonic signals, including changes in ultrasonic signal height and shifts in peak waves, the usability of ultrasonic sensing elements can be determined, thus avoiding the problem of inaccurate measurement of urea concentration in urea solution due to the malfunction of ultrasonic sensing elements.

[0030] Further, step 3.2, which uses ultrasonic signals to calculate the urea concentration of the urea solution, includes:

[0031] Let Tr be the propagation time of ultrasound in urea solution, and Ds be the propagation distance of ultrasound. The propagation time Tr is calculated by the signal processing unit based on the transmitted first excitation signal and the received ultrasound signal. The relationship between the propagation time Tr and the ultrasound propagation speed Cs satisfies the following formula:

[0032] Cs=Ds / Tr (1)

[0033] When ultrasound propagates in a urea solution, the sound velocity Cs is determined by the bulk modulus K and density ρ of the urea solution:

[0034]

[0035] Among them, the values ​​of bulk modulus K and density ρ both change with the concentration and temperature of urea solution;

[0036] Since the ultrasonic wave propagation distance Ds is a fixed value, and the ultrasonic wave propagation speed Cs is a function of the ultrasonic wave propagation time Tr, the urea concentration γ of the urea solution... s It was calculated from the ultrasonic wave propagation time Tr and the urea solution temperature Ts.

[0037] Further, step 3.3, which uses impedance sensing signals to calculate the urea concentration of the urea solution, includes:

[0038] Let Zs be the impedance between the first and second electrodes. The impedance Zs is calculated by the signal processing unit based on the impedance sensing signal, and it is also the urea solution temperature Ts and the urea concentration γ of the urea solution. s Functions:

[0039] Zs=f(Ts,γ s (3)

[0040] Therefore, the urea concentration γ of the urea solution s It was calculated from the impedance Zs and the urea solution temperature Ts.

[0041] Furthermore, in step 3, when calculating the concentration of impurity ions in the urea solution, an ultrasonic sensing element can be used. The concentration of impurity ions in the urea solution is calculated using an impedance sensing signal, including:

[0042] Let Zs be the impedance between the first electrode and the second electrode. The impedance Zs is calculated by the signal processing unit based on the impedance sensing signal. The impedance change value dZs is calculated, and the impedance change value dZs is defined as follows:

[0043] dZs=(Zs(γ i )-Zs(0)) / Zs(0) (5)

[0044] Where Zs(γi) is the impedance between the first and second electrodes measured in a urea solution with an impurity ion concentration of γi, and Zs(0) is the impedance between the first and second electrodes measured in a urea solution conforming to ISO 22241 standard; the impurity ion concentration γi is obtained by looking up a table:

[0045] γi=Tbl(dZs).

[0046] In exhaust gas treatment systems, impurity ions can remain and accumulate in the SCR catalyst, reducing its activity and denitrification efficiency, and even causing catalyst failure. When impurity ions are present in the urea solution, ultrasonic signals are not sensitive to impurity ions and cannot detect their concentration; however, impedance sensing signals are sensitive to impurity ions, and the high sensitivity of impedance sensing elements enables them to detect low concentrations of impurities in the urea solution.

[0047] Furthermore, in step 3.2, when calculating the urea concentration of the urea solution using ultrasonic signals, the urea solution temperature Ts is a function of the resistance Re of the first electrode. The resistance Re of the first electrode is measured by the signal processing unit, and the urea concentration γ of the urea solution is obtained through a two-dimensional lookup table. s :

[0048] γ s =Qu=Tbl(Re,Tr)

[0049] Where Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

[0050] Furthermore, in step 3.2, when calculating the urea concentration of the urea solution using ultrasonic signals, the urea solution temperature Ts is measured by the first temperature sensing element, and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s :

[0051] γ s =Qu=Tbl(T135,Tr)

[0052] Wherein, T135 represents the temperature of the urea solution measured by the first temperature sensing element, and Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

[0053] Furthermore, in step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea solution temperature Ts is a function of the resistance Re of the first electrode, which is measured by the signal processing unit; the impedance Zs is the sum of the resistance Re of the first electrode and the urea concentration γ of the urea solution. s Functions:

[0054] Zs=g(Re,γs (4)

[0055] The urea concentration γ of the urea solution was obtained by looking up a two-dimensional table. s :

[0056] γ s =Qi=Tbl(Re,Zs)

[0057] Where Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

[0058] Furthermore, in step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea solution temperature Ts is measured by the first temperature sensing element, and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s :

[0059] γ s =Qi=Tbl(T135,Zs)

[0060] Wherein, T135 represents the temperature of the urea solution measured by the first temperature sensing element, and Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

[0061] The third aspect discloses a fault detection method for a sensor used to measure the quality of urea solution, comprising the following steps:

[0062] Step 1: The signal processing unit receives the sensing signal sent by the quality sensing element and determines whether the ultrasonic sensing element and the impedance sensing element are available.

[0063] Step 2: If both the ultrasonic sensor and the impedance sensor are available, calculate the urea concentration of the urea solution using both ultrasonic and impedance sensors. Determine whether the sensor has an IR malfunction based on the difference between the two values.

[0064] Further, step 1 includes:

[0065] The height value of the ultrasonic signal in the sensing signal is S_amp. The height value of the ultrasonic signal S_amp is compared with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, the ultrasonic sensing element is unusable.

[0066] If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0:

[0067] T_sft=Tpk-Tpk0

[0068] The change in the peak time of the ultrasonic signal, T_sft, is compared with a second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensing element is unusable; if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is usable.

[0069] The criteria for determining the availability of an impedance sensing element include detecting whether the impedance sensing signal exceeds its maximum or minimum boundary measurement value: if the impedance sensing signal is greater than the maximum boundary measurement value or less than the minimum boundary measurement value, the impedance sensor element is unavailable; otherwise, it is available.

[0070] Further, step 2 includes: Let QU_conc be the urea concentration of the urea solution calculated using ultrasound, and QI_conc be the urea concentration of the urea solution calculated using impedance; calculate the difference between the two, DEF_Diff.

[0071] DEF_Diff=abs(QI_conc-QU_conc)

[0072] abs() calculates the absolute value. If the DEF_Diff value is higher than the third threshold Thd_Ddiff, the sensor is determined to have an IR fault alarm; otherwise, the sensor is determined not to have an IR fault.

[0073] Beneficial effects:

[0074] This application provides a sensor capable of detecting impurity ions and accurately measuring urea concentration. The sensor is insensitive to the state of the urea solution, including insensitivity to air bubbles in the urea solution, to avoid sensor failure due to the action of air bubbles. The sensor is compact and inexpensive.

[0075] To avoid false alarms about urea concentration caused by sensor problems, the sensor fault detection method provided in this application can not only detect the so-called OOR (Out-Of-Range) problem that causes the reading value to be outside the effective range, but also diagnose the so-called IR (In-Range) problem where the sensor's sensed value is within the normal range but is inaccurate. Attached Figure Description

[0076] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0077] Figure 1 This is a schematic diagram of the structure of a sensor for measuring the quality of urea solution, provided in an embodiment of this application.

[0078] Figure 2This is a schematic diagram of the quality sensing element in a sensor for measuring the quality of urea solution, provided in an embodiment of this application.

[0079] Figure 3 This is another structural schematic diagram of a quality sensing element in a sensor for measuring the quality of urea solution, provided in an embodiment of this application.

[0080] Figure 4 The curves showing the changes in ultrasonic propagation time and impedance measurement values ​​as a function of impurity ion concentration in a urea solution obtained using an ultrasonic sensing element and an impedance sensing element, respectively, in a method for measuring the quality of urea solution provided in this application embodiment.

[0081] Figure 5 This is a signal diagram of the first excitation signal received and the generated ultrasonic signal in a method for measuring the quality of urea solution provided in an embodiment of this application.

[0082] Figure 6 This is a schematic diagram of the signal processing unit in a sensor for measuring the quality of urea solution, provided in an embodiment of this application.

[0083] Figure 7 This is a schematic flowchart illustrating the calculation of urea concentration in a method for measuring the quality of urea solution, provided in an embodiment of this application.

[0084] Figure 8 This is a flowchart illustrating a fault detection method for a sensor used to measure the quality of urea solution, as provided in an embodiment of this application. Detailed Implementation

[0085] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0086] The sensor and method provided in this application for measuring the quality of urea solution can be applied in selective catalytic reduction scenarios. When urea solution is used as diesel exhaust fluid (DEF), the sensor is used to measure the quality of urea solution and detect faults in the sensor itself.

[0087] The first embodiment of this application discloses a sensor for measuring the quality of urea solution, including a quality sensing element 100 and a signal processing unit 120. 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.

[0088] The quality sensing element 100 is used to receive the excitation signal generated by the signal processing unit 120, generate a sensing signal, and send the sensing signal to the signal processing unit 120.

[0089] The signal processing unit 120 is used to generate an excitation signal and send it to the quality sensing element 100, receive the sensing signal sent by the quality sensing element 100, and calculate the urea solution quality sensing value based on the sensing signal. The urea solution quality sensing value includes the urea concentration and impurity ion concentration in the urea solution.

[0090] like Figure 1 As shown, in a specific implementation, the sensor used to measure the quality of urea solution can be equipped with a rubber head 80 and a base 70. Through the rubber head 80, engine coolant flows through a 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 set on the top of the rubber head 80 and connected to the base 70 through a cable pipe 60. The quality sensing element 100 is connected to the base 70.

[0091] In this embodiment, the quality sensing element 100 includes an impedance sensing element and an ultrasonic sensing element. The impedance sensing element includes a first electrode 130 and a second electrode 125. The urea solution between the first electrode 130 and the second electrode 125 is connected to the urea solution in the ultrasonic sensing element. One end of the second electrode 125 is electrically connected to the signal processing unit 120 through a second signal line 123. One end of the first electrode 130 is electrically connected to the signal processing unit 120 through a first signal line 128. The ultrasonic sensing element is electrically connected to the signal processing unit 120 through a fifth signal line 115, and is used to generate ultrasonic waves according to the excitation signal sent by the signal processing unit 120, emit and receive ultrasonic waves, and send the received ultrasonic wave signal to the signal processing unit 120.

[0092] In one alternative implementation, such as Figure 2 As shown, the impedance of the first electrode 130 and the second electrode 125 changes with temperature. Specifically, the first electrode 130 and the second electrode 125 can be made of materials such as stainless steel (e.g., 304, 304L, 316, 316L) and Hastelloy (nickel-molybdenum-chromium-tungsten alloy).

[0093] The second electrode 125 includes a horizontal portion and a vertical portion. The end of the horizontal portion away from the vertical portion is electrically connected to the signal processing unit 120 through the second signal line 123. The first electrode 130 is not in contact with the second electrode 125, and there is a urea solution between the horizontal portions of the first electrode 130 and the second electrode 125. The end of the first electrode 130 away from the vertical portion of the second electrode 125 is electrically connected to the signal processing unit 120 through the first signal line 128.

[0094] Optionally, the ultrasonic sensing element includes an ultrasonic transceiver unit 112, which includes an ultrasonic transmitter and a receiver. The transmitter and receiver are parallel to each other, and a urea solution exists between them. This urea solution is in communication with the urea solution between the horizontal portions of the first electrode 130 and the second electrode 125. Both the transmitter and the receiver are electrically connected to a signal processing unit 120. For example, a mounting surface 110 is provided above the end of the horizontal portion of the second electrode 125 away from the vertical portion. The ultrasonic transmitter is disposed close to the mounting surface 110, and the receiver is disposed close to the vertical portion of the second electrode 125.

[0095] Optionally, the ultrasonic sensing element includes an ultrasonic transceiver unit 112 and a reflector 122. The ultrasonic transceiver unit 112 is parallel to the reflector 122, and a urea solution exists between them. This urea solution is connected to the urea solution between the horizontal portions of the first electrode 130 and the second electrode 125. For example, the ultrasonic transceiver unit 112 may be located above the end of the horizontal portion of the second electrode 125 away from the vertical portion, with the reflector 122 in close contact with the vertical portion of the second electrode 125. Alternatively, for example, the vertical portion of the second electrode 125 may be used directly as the reflector 122. The ultrasonic transceiver unit 112 is used to transmit ultrasonic waves and receive ultrasonic echo signals reflected by the reflector 122. Optionally, the ultrasonic transceiver unit 112 includes an ultrasonic transducer and a receiver (TR). The ultrasonic transceiver unit 112 is electrically connected to the signal processing unit 120 via a fifth signal line 115.

[0096] In other embodiments, the second electrode 125 can also be designed in other shapes, such as having the same shape as the first electrode 130 and being placed parallel to the first electrode 130. When the ultrasonic sensing element only includes an ultrasonic transceiver unit 112, which includes an ultrasonic transmitter and a receiver, the ultrasonic transmitter can be placed close to the inner side of either the first electrode 130 or the second electrode 125, and the receiver can be placed close to the inner side of the other electrode. The inner side refers to the parallel and opposite parts of the first electrode 130 and the second electrode 125. When the ultrasonic sensing element includes an ultrasonic transceiver unit 112 and a reflector 122, the ultrasonic transceiver unit 112 can be placed close to the inner side of either the first electrode 130 or the second electrode 125, and the reflector 122 can be placed close to the inner side of the other electrode. For example, the inner side of the other electrode can also be directly used as the reflector 122.

[0097] In these embodiments, the second electrode 125 is designed in an L-shape, or the second electrode 125 is parallel to the first electrode 130. The impedance sensing elements can all be shared by the ultrasonic sensing elements, making the design of the quality sensing element 100 compact and inexpensive.

[0098] In some other embodiments, the shared use of the impedance sensing element and the ultrasonic sensing element is not considered. As long as the urea solution between the first electrode 130 and the second electrode 125 and the urea solution in the ultrasonic sensing element are connected, the positional relationship between the impedance sensing element and the ultrasonic sensing element does not need to be otherwise limited.

[0099] In another alternative implementation, such as Figure 3 As shown, the impedance of the first electrode 130 does not change with temperature. The structure and connection relationship of the impedance sensing element and the ultrasonic sensing element are similar to the optional implementation described above. The impedance sensing element also 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 125. It is electrically connected to the signal processing unit 120 via the eighth signal line 127. For example, the first temperature sensing element 135 can be placed adjacent to the first electrode 130.

[0100] In this embodiment, as Figure 6 As shown, the signal processing unit 120 includes a central processing unit 230 (CPU), an ultrasonic signal processing subunit 240 (USPSU), and an impedance signal processing subunit 250 (ISPSU).

[0101] The central processing unit 230 includes an MCU 231 (microcontroller unit) and a memory 232, which is used to send commands to the ultrasonic signal processing subunit 240 and the impedance signal processing subunit 250, receive the sensing signals processed by the ultrasonic signal processing subunit 240 and the impedance signal processing subunit 250, and calculate the quality sensing value of the urea solution based on the sensing signals.

[0102] The ultrasonic signal processing subunit 240 and the ultrasonic sensing element are electrically connected via the fifth signal line 115. The subunit is used to receive the first command sent by the central processing unit 230, generate the first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent by the ultrasonic sensing element, process it, and send it to the central processing unit 230.

[0103] The ultrasonic signal processing subunit 240 includes a first waveform generation module 242 (WGM), a pulse generator module 244 (PM), a first amplifier 245, a rectifier 243, and an envelope detection module 241 (EDM). The central processing unit 230 generates a first command and sends it to the first waveform generation module 242. The first waveform generation module 242 generates a pulse signal according to these commands and sends it to the pulse generator module 244. The pulse generator module 244 generates a first excitation signal according to the pulse signal and sends it to the ultrasonic transceiver unit 112 through the fifth signal line 115.

[0104] The ultrasonic transceiver unit 112 generates ultrasonic waves according to the first excitation signal and sends the ultrasonic signal to the first amplifier 245;

[0105] The first amplifier 245 amplifies the ultrasonic signal and sends the amplified ultrasonic signal to the rectifier 243; the rectifier 243 removes the negative voltage signal and sends it to the envelope detection module 241; the envelope detection module 241 filters out the high-frequency "carrier" signal and sends the pulse envelope signal to the central processing unit 230.

[0106] The impedance signal processing subunit 250 is electrically connected to one end of the first electrode 130 via a first signal line 128 and to one end of the second electrode 125 via a second signal line 123. It is used to receive a 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 125 respectively. It also receives the impedance sensing signal sent by the first electrode 130, processes it, and sends it to the central processing unit 230.

[0107] The impedance signal processing subunit 250 includes a second waveform generation module 251, a driver 253, a multiplex switch 255 (MUX), a second amplifier 254, and a signal processing module 252 (SPM). The central processing unit 230 generates a second command and sends it to the second waveform generation module 251. The second waveform generation module 251 generates an excitation signal (sinusoidal single-frequency excitation signal or sweep frequency excitation signal) of a set frequency or frequency band according to the second command and sends it to the driver 253. The driver 253 generates a power excitation signal and sends it to the multiplex switch 255. The multiplex switch 255 selects to send the power excitation signal to the first electrode 130 through the first signal line 128 or to the second electrode 125 through the second signal line 123 according to the setting instruction issued by the MCU.

[0108] The first electrode 130 sends an impedance sensing signal to the second amplifier 254 through the first signal line 128; the second amplifier 254 amplifies the impedance sensing signal and sends the amplified impedance sensing signal to the signal processing module 252; the signal processing module 252 processes the amplified impedance sensing signal and sends the processed signal to the central processing unit 230.

[0109] In an alternative implementation, the signal processing unit 120 further includes a resistance measurement module 260 (RMM), which is electrically connected to the other end of the first electrode 130 via a sixth signal line 126. The resistance measurement module 260 is used to measure the resistance of the first electrode 130 and send the resistance value to the central processing unit 230.

[0110] In another alternative implementation, the signal processing unit 120 further includes a resistance measurement module 260, wherein the first temperature sensing element 135 is electrically connected to the resistance measurement module 260 via an eighth signal line 127, and the resistance measurement 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.

[0111] The second embodiment of this application discloses a method for measuring the quality of urea solution, comprising the following steps:

[0112] Step 1: The signal processing unit 120 sends an excitation signal to the quality sensing element 100. The excitation signal includes a first excitation signal sent to the ultrasonic sensing element and a second excitation signal sent to the first electrode 130 and the second electrode 125.

[0113] Step 2: The quality sensing element 100 receives the excitation signal generated by the signal processing unit 120, generates a sensing signal, and sends the sensing signal to the signal processing unit 120; the sensing signal includes an ultrasonic signal and an impedance sensing signal.

[0114] Step 3: The signal processing unit 120 receives the sensing signal sent by the quality sensing element 100 and calculates the quality sensing value of the urea solution based on the sensing signal. The calculation of the quality sensing value of the urea solution includes calculating the urea concentration in the urea solution and calculating the impurity ion concentration in the urea solution.

[0115] In one optional implementation, step 2 includes: the ultrasonic transmitter in the ultrasonic transceiver unit 112 receives the first excitation signal, generates ultrasonic waves, and sends them to the receiver; the receiver sends the received ultrasonic signal to the signal processing unit 120; and the first electrode 130 sends an impedance sensing signal to the signal processing unit 120.

[0116] In another optional implementation, step 2 includes: the ultrasonic transceiver unit 112 receiving the first excitation signal and generating ultrasonic waves; the ultrasonic waves passing through the urea solution between the ultrasonic transceiver unit 112 and the vertical portion of the second electrode 125, reflecting at the vertical portion of the second electrode 125 to generate an ultrasonic echo signal, which is then transmitted back to the ultrasonic transceiver unit 112; the ultrasonic transceiver unit 112 sending the ultrasonic echo signal to the signal processing unit 120; the sensing signal in step 2 includes the ultrasonic signal, i.e., the ultrasonic echo signal, in the impedance sensing signal. The first electrode 130 sends an impedance sensing signal to the signal processing unit 120.

[0117] In this embodiment, step 3, calculating the urea concentration of the urea solution, includes:

[0118] Step 3.1: Determine if the ultrasonic sensing element is usable;

[0119] Step 3.2: When the ultrasonic sensing element is available, the urea concentration of the urea solution is calculated using the ultrasonic signal.

[0120] Step 3.3: When the ultrasonic sensing element is unavailable, the urea concentration of the urea solution is calculated using the impedance sensing signal.

[0121] like Figure 5 and Figure 7 As shown, the first excitation signal 181 and the ultrasonic signal 182 in the sensing signal, step 3.1 includes: recording the height value of the ultrasonic signal in the sensing signal as S_amp, comparing the height value of the ultrasonic signal S_amp with the first threshold Thd_samp, if S_amp is not higher than Thd_samp, the ultrasonic sensing element is unusable, indicated by the status flag Stat_QU=1; the first threshold Thd_samp can be set to be slightly higher than the maximum value of S_amp in the operating temperature range (e.g., -11℃ to -85℃).

[0122] If the value of S_amp is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft = Tpk - Tpk0, where the normal value Tpk0 is determined by the pulse width of the ultrasonic excitation signal and can be set to half of the pulse width value of the excitation signal.

[0123] The change in the peak time of the ultrasonic signal, T_sft, is compared with a second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensor is unavailable, indicated by the status flag Stat_QU = 1; if T_sft is higher than Thd_Tsft, the ultrasonic sensor is available, indicated by the status flag Stat_QU = 0. The second threshold, Thd_Tsft, can be set to the width of one or several carrier pulses.

[0124] Step 3.2, which uses ultrasonic signals to calculate the urea concentration of the urea solution, includes:

[0125] Let Tr be the propagation time of ultrasound in urea solution, and Ds be the propagation distance of ultrasound. The propagation time Tr is calculated by the signal processing unit 120 based on the transmitted first excitation signal and the received ultrasound signal.

[0126] In one alternative implementation, the ultrasonic propagation distance Ds is the distance between the ultrasonic transmitter and receiver in the ultrasonic transceiver unit 112, and the propagation time Tr is calculated as the time interval between the first excitation signal obtained by the ultrasonic transmitter and the ultrasonic signal received by the receiver.

[0127] In another alternative implementation, the ultrasonic propagation distance Ds is twice the distance between the ultrasonic transceiver unit 112 and the reflector 122, and the propagation time Tr is calculated as the time interval between the first excitation signal obtained by the ultrasonic transceiver unit 112 and the ultrasonic echo signal generated by the ultrasonic reflector.

[0128] The relationship between the propagation time Tr and the ultrasonic wave propagation speed Cs satisfies the following formula:

[0129] Cs=Ds / Tr (1)

[0130] When ultrasound propagates in a urea solution, the sound velocity Cs is determined by the bulk modulus K and density ρ of the urea solution:

[0131]

[0132] Among them, the values ​​of bulk modulus K and density ρ both change with the concentration and temperature of urea solution;

[0133] Since the ultrasonic wave propagation distance Ds is a fixed value, and the ultrasonic wave propagation speed Cs is a function of the ultrasonic wave propagation time Tr, the urea concentration γ of the urea solution... s It was calculated from the ultrasonic wave propagation time Tr and the urea solution temperature Ts.

[0134] Step 3.3, which uses impedance sensing signals to calculate the urea concentration of the urea solution, includes:

[0135] Let Zs be the impedance between the first electrode 130 and the second electrode 125. The impedance Zs is calculated by the signal processing unit 120 based on the impedance sensing signal, and is also the urea solution temperature Ts and the urea concentration γ of the urea solution. s Functions:

[0136] Zs=f(Ts,γ s (3)

[0137] Therefore, the urea concentration γ of the urea solution s It was calculated from the impedance Zs and the urea solution temperature Ts.

[0138] In one alternative implementation, the impedance of the first electrode 130 varies with temperature. In step 3.2, when calculating the urea concentration of the urea solution using ultrasonic signals, the urea solution temperature Ts is a function of the resistance Re of the first electrode 130. The resistance Re of the first electrode 130 is measured by the signal processing unit 120, and the urea concentration γ of the urea solution is obtained through a two-dimensional lookup table. s :

[0139] γ s =Qu=Tbl(Re,Tr)

[0140] Where Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

[0141] In step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea solution temperature Ts is a function of the resistance Re of the first electrode 130, which is measured by the signal processing unit 120; the impedance Zs is the sum of the resistance Re of the first electrode 130 and the urea concentration γ of the urea solution. s Functions:

[0142] Zs=g(Re,γ s (4)

[0143] The urea concentration γ of the urea solution was obtained by looking up a two-dimensional table. s :

[0144] γ s =Qi=Tbl(Re,Zs)

[0145] Where Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

[0146] In another alternative implementation, the impedance of the first electrode 130 does not change with temperature. The impedance sensing element also includes a first temperature sensing element 135. In step 3.2, when the urea concentration of the urea solution is calculated using the ultrasonic signal, the urea solution temperature Ts is measured by the first temperature sensing element 135, and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s :

[0147] γ s =Qu=Tbl(T135,Tr)

[0148] Wherein, T135 represents the urea solution temperature measured by the first temperature sensing element 135, which is calculated by the signal processing unit 120 by obtaining the resistance of the first temperature sensing element 135; Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

[0149] In step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea concentration γ of the urea solution is obtained through a two-dimensional lookup table. s :

[0150] γ s =Qi=Tbl(T135,Zs)

[0151] Wherein, T135 represents the temperature of the urea solution measured by the first temperature sensing element 135, and Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

[0152] In this embodiment, when calculating the concentration of impurity ions in the urea solution in step 3, an ultrasonic sensing element can be used. The calculation of the impurity ion concentration in the urea solution using an impedance sensing signal includes:

[0153] Let Zs be the impedance between the first electrode 130 and the second electrode 125. The impedance Zs is calculated by the signal processing unit 120 based on the impedance sensing signal. The impedance change value dZs is calculated, and the impedance change value dZs is defined as follows:

[0154] dZs=(Zs(γ i )-Zs(0)) / Zs(0) (5)

[0155] Wherein, Zs(γi) is the impedance between the first electrode 130 and the second electrode 125 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 125 measured in a urea solution conforming to ISO 22241 standard; the impurity ion concentration γi is obtained by looking up a table:

[0156] γi=Tbl(dZs).

[0157] Depend on Figure 4 As shown, curve 270 represents the change in impedance value Zs in the urea solution after the addition of calcium chloride (CaCl2) impurity, and curve 271 represents the change in ultrasonic wave propagation time Tr obtained from the ultrasonic sensing element. As shown in curves 270 and 271, the impedance sensing signal is more sensitive to the concentration of ionic impurities in the urea solution compared to the ultrasonic signal. The high sensitivity of the impedance sensing element allows it to detect low concentrations of impurities in the urea solution. In exhaust gas treatment systems, impurity ions can remain in the SCR catalyst and accumulate there, reducing its activity and denitrification efficiency, and even causing catalyst failure. This is why standard ISO 22241 limits impurity ions to very low levels. In fact, non-compliant urea solutions present two types of problems: one is an incorrect urea concentration, which may lead to non-compliance with emissions standards; the other is impurity ions that can damage the SCR. The OBD (On-Board Diagnostics) standard only requires the detection of the first type of problem, i.e., incorrect urea concentrations that cause emission problems. However, if the urea solution concentration is within the permissible range, OBD does not require the detection of impurity ion concentrations.

[0158] Because the effect of impurity ions on SCR is a long-term effect—that is, SCR degradation is caused by the accumulation of impurity ions rather than their current concentration—the lack of direct detection of ionic impurities (detecting the emission consequences of impurity ions rather than the impurity ions themselves) can lead to irreversible SCR failure by the time the effects of impurity ions are detected. This can result in serious warranty issues for SCR system manufacturers. Urea solutions containing impurity ions are not uncommon. Purification is a costly step in the manufacture of urea solutions, and transporting and storing solutions to meet the requirements of standard ISO 22241 incurs additional costs. Workarounds, such as using lower-purity solvents (e.g., tap water) and non-compliant operations (e.g., using contaminated containers), can significantly reduce costs but introduce large amounts of impurity ions. Direct detection of impurity ion concentration is essential to reduce quality claims.

[0159] In this invention, such as Figure 2 and Figure 3 As shown, the quality sensing unit detects both the urea concentration and the impurity ion concentration in the urea solution: the ultrasonic signal obtained from the ultrasonic sensing element is used to detect the urea concentration in the urea solution to avoid emission problems caused by low urea concentration; simultaneously, the impedance sensing signal generated by the first electrode 130 and the second electrode 125 is used to further detect the impurity ion concentration in the urea solution. Since OBD currently does not require the detection of impurity ion concentration, the measured impurity ion concentration can be recorded in the signal processing unit 120 as a basis for future claims.

[0160] The third embodiment of this application discloses a fault detection method for a sensor used to measure the quality of urea solution, comprising the following steps:

[0161] Step 1: The signal processing unit 120 receives the sensing signal sent by the quality sensing element 100 and determines whether the ultrasonic sensing element and the impedance sensing element are available.

[0162] like Figure 5 and Figure 7 As shown, step 1 includes:

[0163] Record the height value of the ultrasonic signal in the sensing signal as S_amp. Compare the height value of the ultrasonic signal S_amp with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, the ultrasonic sensing element is unavailable. Use the status flag Stat_QU=1 to indicate that the urea concentration QU_conc of the urea solution cannot be calculated using ultrasound.

[0164] If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0:

[0165] T_sft=Tpk-Tpk0

[0166] The change in the peak time of the ultrasonic signal, T_sft, is compared with the second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensor is unavailable, indicated by the status flag Stat_QU = 1. If T_sft is higher than Thd_Tsft, the ultrasonic sensor is available, indicated by the status flag Stat_QU = 0. This indicates that the urea concentration QU_conc value of the urea solution can be calculated using ultrasound. Then, the DEF reporting value DEF_conc is set to QU_conc, and the DEF sensing flag DEF_flag is set to 0, indicating that the DEF concentration value is the ultrasonic sensing value, and the routine ends.

[0167] The availability criteria for impedance sensing elements include detecting whether the impedance sensing signal exceeds its maximum or minimum boundary measurement value: if the impedance sensing signal is greater than the maximum boundary measurement value (e.g., the signal value measured during an open circuit) or less than the minimum boundary measurement value (e.g., the signal value measured during a short circuit), the impedance sensor element is unavailable, indicated by the status flag Stat_QI = 1; otherwise, it is available, indicated by the status flag Stat_QI = 0. When the status flag Stat_QI = 0, it indicates that the urea concentration QI_conc of the urea solution can be calculated using impedance, and the DEF reporting value DEF_conc is set to the urea concentration QI_conc calculated using impedance. Simultaneously, the DEF sensing flag DEF_flag is set to 1, indicating that the DEF concentration sensing value is an impedance sensing value, and the routine ends. When the status flag Stat_QI = 1, the DEF sensing flag DEF_flag is set to 2, indicating that all DEF concentration sensing values ​​are unavailable, and the routine ends.

[0168] Step 2: If both the ultrasonic sensor and the impedance sensor are available, calculate the urea concentration of the urea solution using both ultrasonic and impedance sensors. Determine whether the sensor has an IR malfunction based on the difference between the two values.

[0169] Step 2 includes: Let QU_conc be the urea concentration of the urea solution calculated using ultrasound, and QI_conc be the urea concentration of the urea solution calculated using impedance. Calculate the difference between the two, DEF_Diff.

[0170] DEF_Diff=abs(QI_conc-QU_conc)

[0171] abs() is used to calculate absolute values, such as Figure 8 As shown, if the DEF_Diff value is higher than the third threshold Thd_Ddiff, then the sensor is determined to have an IR fault alarm, indicated by the fault flag Fault_QR=1; otherwise, the sensor is determined not to have an IR fault, indicated by the fault flag Fault_QR=0.

[0172] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention's content regarding a method for measuring the quality of urea solution and a fault detection method for a sensor used to measure the quality of urea solution, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0173] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MUU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0174] This invention provides a sensor and method for measuring the quality of urea solution. Many methods and approaches exist for implementing this technical solution; the above description is merely a specific embodiment of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A sensor for measuring the quality of urea solution, characterized in that, It includes 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 the excitation signal generated by the signal processing unit (120), generate the sensing signal, and send the sensing signal to the signal processing unit (120). The signal processing unit (120) is used to generate an excitation signal and send it to the quality sensing element (100), receive the sensing signal sent by the quality sensing element (100), and calculate the quality sensing value of the urea solution based on the sensing signal. The quality sensing value of the urea solution includes the urea concentration and the impurity ion concentration in the urea solution. The quality sensing element (100) includes an impedance sensing element and an ultrasonic sensing element. The ultrasonic sensing element is used to detect the urea concentration, and the impedance sensing element is used to detect the urea concentration and the impurity ion concentration. If both the ultrasonic sensing element and the impedance sensing element are available, the urea concentration of the urea solution is calculated using ultrasound and impedance respectively. The sensor is judged to have an IR fault based on the absolute value of the difference between the two and the relative size of the third threshold. The IR fault is that the sensor's sensing value is within the normal range but inaccurate.

2. The sensor for measuring the quality of urea solution according to claim 1, characterized in that, The impedance sensing element includes a first electrode (130) and a second electrode (125). The urea solution between the first electrode (130) and the second electrode (125) is connected to the urea solution in the ultrasonic sensing element. One end of the second electrode (125) is electrically connected to the signal processing unit (120) through a second signal line (123). One end of the first electrode (130) is electrically connected to the signal processing unit (120) through a first signal line (128). The ultrasonic sensing element is electrically connected to the signal processing unit (120) through a fifth signal line (115) for generating ultrasonic waves according to the excitation signal sent by the signal processing unit (120), transmitting and receiving ultrasonic waves, and sending the received ultrasonic wave signal to the signal processing unit (120).

3. A sensor for measuring the quality of urea solution according to claim 2, characterized in that, The signal processing unit (120) includes a central processing unit (230), an ultrasonic signal processing subunit (240), and an impedance signal processing subunit (250). The central processing unit (230) is used to send commands to the ultrasonic signal processing subunit (240) and the impedance signal processing subunit (250), receive the sensing signals processed by the ultrasonic signal processing subunit (240) and the impedance signal processing subunit (250), and calculate the quality sensing value of the urea solution based on the sensing signals. The ultrasonic signal processing subunit (240) and the ultrasonic sensing element are electrically connected through the fifth signal line (115). The subunit is used to receive the first command sent by the central processing unit (230), generate the first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent by the ultrasonic sensing element, process it and send it to the central processing unit (230). The impedance signal processing subunit (250) is electrically connected to one end of the first electrode (130) via a first signal line (128) and to one end of the second electrode (125) via a second signal line (123). It is used to receive a 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 (125) respectively. It also receives the impedance sensing signal sent by the first electrode (130), processes it, and sends it to the central processing unit (230).

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

5. A sensor for measuring the quality of urea solution according to claim 3, characterized in that, The signal processing unit (120) further includes a resistance measurement module (260), and the impedance sensing element 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 (125), and is electrically connected to the resistance measurement module (260) through an eighth signal line (127). The resistance measurement 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 method for measuring the quality of a urea solution, applied to a sensor for measuring the quality of a urea solution as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1, the signal processing unit (120) sends an excitation signal to the quality sensing element (100), the excitation signal including a first excitation signal sent to the ultrasonic sensing element and a second excitation signal sent to the first electrode (130) and the second electrode (125). Step 2: The quality sensing element (100) receives the excitation signal generated by the signal processing unit (120), generates a sensing signal, and sends the sensing signal to the signal processing unit (120); the sensing signal includes an ultrasonic signal and an impedance sensing signal. Step 3: The signal processing unit (120) receives the sensing signal sent by the quality sensing element (100) and calculates the quality sensing value of the urea solution based on the sensing signal. The calculation of the quality sensing value of the urea solution includes calculating the urea concentration in the urea solution and calculating the impurity ion concentration in the urea solution.

7. A method for measuring the quality of a urea solution according to claim 6, characterized in that, Step 3 involves calculating the urea concentration of the urea solution, including: Step 3.1: Determine if the ultrasonic sensing element is usable; Step 3.2: When the ultrasonic sensing element is available, the urea concentration of the urea solution is calculated using the ultrasonic signal. Step 3.3: When the ultrasonic sensing element is unavailable, the urea concentration of the urea solution is calculated using the impedance sensing signal.

8. A method for measuring the quality of urea solution according to claim 7, characterized in that, Step 3.1 includes: recording the height value of the ultrasonic signal in the sensing signal as S_amp, comparing the height value of the ultrasonic signal S_amp with the first threshold Thd_samp, and if S_amp is not higher than Thd_samp, the ultrasonic sensing element is unusable. If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft = Tpk - Tpk0 The change in the peak time of the ultrasonic signal, T_sft, is compared with a second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensing element is unusable; if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is usable.

9. A method for measuring the quality of a urea solution according to claim 7, characterized in that, Step 3.2, which uses ultrasonic signals to calculate the urea concentration of the urea solution, includes: Let Tr be the propagation time of ultrasound in urea solution, and Ds be the propagation distance of ultrasound. The propagation time Tr is calculated by the signal processing unit (120) based on the first excitation signal sent and the received ultrasound signal. The relationship between the propagation time Tr and the ultrasound propagation speed Cs satisfies the following formula: Cs=Ds / Tr (1) When ultrasound propagates in a urea solution, the speed of ultrasound propagation 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 both change with the concentration and temperature of urea solution; Since the ultrasonic wave propagation distance Ds is a fixed value, and the ultrasonic wave propagation speed Cs is a function of the ultrasonic wave propagation time Tr, the urea concentration γ of the urea solution... s It was calculated from the ultrasonic wave propagation time Tr and the urea solution temperature Ts.

10. A method for measuring the quality of a urea solution according to claim 7, characterized in that, Step 3.3, which uses impedance sensing signals to calculate the urea concentration of the urea solution, includes: Let Zs be the impedance between the first electrode (130) and the second electrode (125). The impedance Zs is calculated by the signal processing unit (120) based on the impedance sensing signal, and is also the urea solution temperature Ts and the urea concentration γ of the urea solution. s Functions: Zs=f(Ts,γ s ) (3) Therefore, the urea concentration γ of the urea solution s It was calculated from the impedance Zs and the urea solution temperature Ts.

11. A method for measuring the quality of a urea solution according to claim 10, characterized in that, In step 3, when calculating the concentration of impurity ions in the urea solution, an ultrasonic sensing element can be used. The concentration of impurity ions in the urea solution is calculated using impedance sensing signals, including: Let Zs be the impedance between the first electrode (130) and the second electrode (125). The impedance Zs is calculated by the signal processing unit (120) based on the impedance sensing signal. The impedance change value dZs is calculated, and the impedance change value dZs is defined as follows: dZs=(Zs(γ i )-Zs(0)) / Zs(0) (5) Wherein, Zs(γi) is the impedance between the first electrode (130) and the second electrode (125) 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 (125) measured in a urea solution conforming to ISO 22241 standard; the impurity ion concentration γi is obtained by looking up a table: γi=Tbl(dZs).

12. A method for measuring the quality of a urea solution according to claim 9, characterized in that, In step 3.2, when calculating the urea concentration of the urea solution using ultrasonic signals, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130). The resistance Re of the first electrode (130) is measured by the signal processing unit (120), and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s : γ s =Qu=Tbl(Re,Tr) Where Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

13. A method for measuring the quality of a urea solution according to claim 9, characterized in that, In step 3.2, when the urea concentration of the urea solution is calculated using ultrasonic signals, the urea solution temperature Ts is measured by the first temperature sensing element (135), and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s : γ s =Qu=Tbl(T135,Tr) Wherein, T135 represents the urea solution temperature between the first electrode (130) and the second electrode (125) as measured by the first temperature sensing element (135), and Qu represents the urea concentration γ of the urea solution. s Obtained by ultrasonic calculations.

14. A method for measuring the quality of a urea solution according to claim 10, characterized in that, In step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130), which is measured by the signal processing unit (120); the impedance Zs is the sum of the resistance Re of the first electrode (130) and the urea concentration γ of the urea solution. s Functions: Zs=g(Re,γ) s ) (4) The urea concentration γ of the urea solution was obtained by looking up a two-dimensional table. s : γ s =Qi=Tbl(K,Zs) Where Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

15. A method for measuring the quality of a urea solution according to claim 10, characterized in that, In step 3.3, when calculating the urea concentration of the urea solution using the impedance sensing signal, the urea solution temperature Ts is measured by the first temperature sensing element (135), and the urea concentration γ of the urea solution is obtained by looking up a two-dimensional table. s : γ s =Qi=Tbl(T135,Zs) Wherein, T135 represents the urea solution temperature between the first electrode (130) and the second electrode (125) as measured by the first temperature sensing element (135), and Qi represents the urea concentration γ of the urea solution. s Obtained from impedance calculations.

16. A fault detection method for a sensor used to measure the quality of a urea solution, applied to the sensor for measuring the quality of a urea solution as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: The signal processing unit (120) receives the sensing signal sent by the quality sensing element (100) and determines whether the ultrasonic sensing element and the impedance sensing element are available. Step 2: If both the ultrasonic sensor and the impedance sensor are available, calculate the urea concentration of the urea solution using both ultrasonic and impedance sensors. Determine whether the sensor has an IR fault based on the difference between the two values.

17. A fault detection method for a sensor used to measure the quality of urea solution according to claim 16, characterized in that, Step 1 includes: The height value of the ultrasonic signal in the sensing signal is S_amp. The height value of the ultrasonic signal S_amp is compared with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, the ultrasonic sensing element is unusable. If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasonic signal, T_sft, is obtained by calculating the difference between the peak time Tpk and the normal value Tpk0: T_sft=Tpk-Tpk0 The change in the peak time of the ultrasonic signal, T_sft, is compared with a second threshold, Thd_Tsft. If T_sft is not higher than Thd_Tsft, the ultrasonic sensing element is unusable; if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is usable. The criteria for determining the availability of an impedance sensing element include detecting whether the impedance sensing signal exceeds its maximum or minimum boundary measurement value: if the impedance sensing signal is greater than the maximum boundary measurement value or less than the minimum boundary measurement value, the impedance sensing element is unavailable; otherwise, it is available.

18. A fault detection method for a sensor used to measure the quality of urea solution according to claim 16, characterized in that, Step 2 includes: Let QU_conc be the urea concentration of the urea solution calculated using ultrasound, and QI_conc be the urea concentration of the urea solution calculated using impedance. Calculate the difference between the two, DEF_Diff. DEF_Diff=abs(QI_conc-QU_conc) abs() calculates the absolute value. If the DEF_Diff value is higher than the third threshold Thd_Ddiff, the sensor is determined to have an IR fault alarm; otherwise, the sensor is determined not to have an IR fault.

Images