Sensor and method for measuring the quality of a urea solution

Abstract

The present invention discloses a sensor and method for measuring the quality of a urea solution, the sensor comprising a quality sensing element and a signal processing unit, the quality sensing element covered with a urea solution, the signal processing unit electrically connected to the quality sensing element, the quality sensing element receiving an excitation signal generated by the signal processing unit, generating a sensing signal, and transmitting the sensing signal to the signal processing unit, the signal processing unit generating the excitation signal and transmitting it to the quality sensing element, receiving the sensing signal transmitted from the quality sensing element, and calculating a quality sensing value of the urea solution based on the sensing signal, the quality sensing value of the urea solution including the urea concentration and the impurity ion concentration in the urea solution. The sensor can detect impurity ions and accurately measure the urea concentration, and can also diagnose so-called IR problems, where the sensor sensing value is within the normal range but is not accurate.

Description

[Technical Field]

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

[0002] In selective catalytic reduction (SCR) applications, urea solution is often added to the exhaust gas generated by the engine. Under the action of high-temperature exhaust gas, the urea solution generates ammonia (NH3) through thermal decomposition and hydrolysis of urea. The ammonia then reacts with nitrogen oxides (NOx) in the exhaust gas with the aid of an SCR catalyst to remove them. Due to the limited reaction ratio between ammonia and NOx, the amount of urea solution added must be precisely controlled while maintaining a constant urea concentration in the urea solution to avoid ammonia leakage and high NOx emissions. In diesel engine applications, according to the requirements of the ISO 22241 standard, a eutectic urea solution (32.5% wt) with a minimum freezing temperature, i.e., diesel exhaust treatment fluid (DEF), is typically used as the reductant carrier.

[0003] In urea metering control, non-compliant urea solutions (those that do not meet the requirements of the ISO 22241 standard) can lead to exhaust gas problems and system failure. For example, when diluting DEF, low-concentration urea in the solution can cause exhaust gas problems. Impurities in the solution, such as metal ions (calcium, zinc, magnesium, iron, chromium, nickel, sodium, potassium, etc.) found in tap water, or non-urea solutions (such as when fuel oil is accidentally added to the urea tank), can damage the SCR catalyst. To avoid exhaust gas problems, it is necessary to monitor the urea concentration in the DEF while also monitoring impurities in the DEF to prevent non-compliant solutions from entering the SCR system.

[0004] Most DEF sensors must be installed in the urea tank, which must have an opening to the ambient environment to allow air to contact the DEF to avoid vacuum-induced DEF supply problems. Under many conditions, including agitation, pressure changes, and agitation from the DEF pump's suction and return motion, air bubbles can form in the DEF. These bubbles can degrade the performance of the DEF sensor and even cause it to temporarily fail. If air bubbles adhere to the surface of the sensor probe (where they are difficult to dissipate on their own), these bubbles can cause the DEF sensor to fail for an extended period of time.

[0005] Additionally, the prior art allows for DEF sensor problems to trigger false DEF concentration alarms and does not provide a diagnostic for the DEF sensor itself. Summary of the Invention [Problem to be solved by the invention]

[0006] OBJECT OF THE INVENTION: In view of the deficiencies of the prior art, the technical problem that the present invention seeks to solve is to provide a sensor and a method for measuring the quality of a urea solution. [Means for solving the problem]

[0007] In order to solve the above technical problem, a first aspect provides a sensor for measuring the quality 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; The quality sensing element is used to receive an excitation signal generated by a signal processing unit, generate a sensing signal, and send the sensing signal to the signal processing unit; The signal processing unit is used to generate and send an excitation signal to the quality sensing element, receive the sensing signal sent from the quality sensing element, and calculate a quality sensing value of the urea solution based on the sensing signal, where the quality sensing value of the urea solution includes a urea concentration and an impurity ion concentration in the urea solution.

[0008] Further, the quality sensing element comprises an impedance sensing element and an ultrasonic sensing element, the impedance sensing element includes a first electrode and a second electrode, the urea solution between the first electrode and the second electrode is connected to the urea solution in the ultrasonic 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, the ultrasonic sensing element is electrically connected to the signal processing unit through a fifth signal line, and is used to generate ultrasonic waves according to an excitation signal sent from the signal processing unit, transmit and receive ultrasonic waves, and transmit the received ultrasonic signals to the signal processing unit.

[0009] Furthermore, the signal processing unit includes a central processing unit, an ultrasound signal processing subunit, and an impedance signal processing subunit; the central processing unit is used to send instructions to the ultrasonic signal processing subunit and the impedance signal processing subunit, receive the sensing signals processed by the ultrasonic signal processing subunit and the impedance signal processing subunit, and calculate the quality sensing value of the urea solution based on the sensing signals; the ultrasonic signal processing subunit is electrically connected to the ultrasonic sensing element through a fifth signal line, and is used to receive a first command sent from the central processing unit, generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent from the ultrasonic sensing element, and send it to the central processing unit after processing; the impedance signal processing subunit 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, and is used to receive a second command sent from a central processing unit, generate a second excitation signal, send the second excitation signal to the first electrode and the second electrode respectively, receive an impedance sensing signal sent from the first electrode, process the signal and send it to the central processing unit; 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 used to measure the resistance of the first electrode and transmit the resistance value to the central processing unit.

[0010] Further, the signal processing unit further includes a resistance measuring module, and the impedance sensing element further includes a first temperature sensing element, the first temperature sensing element is used to measure the urea solution temperature between the first electrode and the second electrode, and is electrically connected to the resistance measuring module through an eighth signal line, and 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.

[0011] A second aspect provides a method for measuring the quality of a urea solution, comprising the steps of: Step 1: the signal processing unit sends excitation signals to the quality sensing elements, the excitation signals including a first excitation signal sent to the ultrasonic sensing elements and a second excitation signal sent to the first electrode and the second electrode; 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, where the sensing signal includes an ultrasonic signal and an impedance sensing signal; Step 3: The signal processing unit receives the sensing signal sent from the quality sensing element, and calculates a quality sensing value of the urea solution based on the sensing signal, where 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.

[0012] Additionally, the calculation of the urea concentration of the urea solution in step 3 includes: Step 3.1, determine whether an ultrasound sensing element is available; Step 3.2, if an ultrasound sensing element is available, calculate the urea concentration of the urea solution using the ultrasound signal; Step 3.3: If an ultrasonic sensing element is not available, calculate the urea concentration of the urea solution using the impedance sensing signal.

[0013] Because ultrasonic signals are insensitive to impurity ions but sensitive to urea concentration, they can accurately measure the urea concentration in a urea solution. Impedance sensing signals are sensitive to impurity ions, but have low selectivity, and their resolution for urea concentration may be difficult to improve due to their high sensitivity to ionic impurities. If an ultrasonic sensing element is available, the ultrasonic signal can be used to calculate the urea concentration of the urea solution. If an ultrasonic sensing element is not available, for example, when a car is running, bubbles may form in the urea solution. These bubbles may reduce the performance of the ultrasonic sensing element and even cause it to temporarily malfunction. If bubbles adhere to the probe surface of the ultrasonic sensing element (these bubbles do not disappear on their own), they may cause the ultrasonic sensing element to malfunction for a long period of time. When impurities are not added during the car's running process, the urea concentration measured from the impedance sensing signal is not affected by ionic impurities. In this case, the impedance sensing signal can be used to calculate the urea concentration of the urea solution.

[0014] Furthermore, step 3.1 includes the following: assuming that the height value of the ultrasonic signal in the sensing signal is S_amp, comparing the height value S_amp of the ultrasonic signal with a first threshold value Thd_samp, and if S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable, which is indicated by a status flag Stat_QU=1; When the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound 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_sft. If T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable, which is indicated by the status flag Stat_QU=1. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available, which is indicated by the status flag Stat_QU=0.

[0015] By detecting distortions in the ultrasonic signal, such as changes in the height of the ultrasonic signal or shifts in the peak wave, it is possible to detect whether the ultrasonic sensing element is available, thereby avoiding the problem of the ultrasonic sensing element becoming non-functional and therefore being unable to accurately measure the urea concentration in the urea solution.

[0016] Further, calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2 includes: The propagation time of the ultrasonic wave in the urea solution is Tr, and the ultrasonic propagation distance is Ds. The propagation time Tr can be calculated based on the first excitation signal sent by the signal processing unit and the received ultrasonic signal. The relationship between the propagation time Tr value and the ultrasonic propagation velocity Cs satisfies the following formula: Cs=Ds / Tr (1) When ultrasonic waves propagate through a urea solution, the sound speed Cs is determined by the bulk modulus K and density ρ of the urea solution:

number

[0017] Further, calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3 includes: The impedance between the first electrode and the second electrode is Zs. The impedance Zs can be calculated by the signal processing unit based on the impedance sensing signal, and the urea solution temperature Ts and the urea concentration γ s It is also a function of: Zs=f(Ts,γ s ) (3) Therefore, the urea concentration of the urea solution γ s is obtained by calculating the impedance Zs and the urea solution temperature Ts.

[0018] Furthermore, when calculating the impurity ion concentration in the urea solution in step 3, the ultrasonic sensing element can be used, and calculating the impurity ion concentration in the urea solution using the impedance sensing signal includes: When the impedance between the first electrode and the second electrode is Zs, the impedance Zs is obtained by the signal processing unit through calculation based on the impedance sensing signal, and an impedance change value dZs of the impedance Zs is calculated, and the impedance change value dZs is defined as follows: dZs=(Zs(γ i ) - Zs(0)) / Zs(0) (5) Here, Zs(γ i ) is the impurity ion concentration i Zs(0) is the impedance between the first and second electrodes measured in a urea solution conforming to the ISO22241 standard, and the impurity ion concentration γ i Get: gamma i =Tbl(dZs).

[0019] In exhaust gas treatment systems, impurity ions remain and accumulate in the SCR catalyst, reducing its activity and denitration efficiency or even causing the catalyst to fail. When impurity ions are present in the urea solution, the ultrasonic signal is insensitive to the impurity ions and cannot detect their concentration, while the impedance sensing signal is sensitive to the impurity ions, and the high sensitivity of the impedance sensing element allows it to detect low concentrations of impurities in the urea solution.

[0020] Furthermore, when calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2, the urea solution temperature Ts is a function of the resistance Re of the first electrode, and the resistance Re of the first electrode is obtained by the measurement of the signal processing unit, and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qu=Tbl(Re,Tr) where Qu is the urea concentration of the urea solution obtained by calculating the ultrasonic s Shows.

[0021] Furthermore, when calculating the urea concentration of the urea solution using the ultrasonic signal in step 3.2, the urea solution temperature Ts is obtained by measurement of the first temperature sensing element, and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qu=Tbl(T135,Tr) where T135 denotes the urea solution temperature obtained by the measurement of the first temperature sensing element, and Qu is the urea concentration γ of the urea solution obtained by calculating the ultrasonic wave s Shows.

[0022] Furthermore, when calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is a function of the resistance Re of the first electrode, where the resistance Re of the first electrode is obtained by the measurement of the signal processing unit, and the impedance Zs is the function of the resistance Re of the first electrode and the urea concentration γ of the urea solution. s is a function of: Zs = g(Re,γ s ) (4) The urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qi=Tbl(Re,Zs) where Qi is the urea concentration of the urea solution obtained by calculating the impedance γ s Shows.

[0023] Furthermore, when calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is obtained by measurement of the first temperature sensing element, and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qi=Tbl(T135,Zs) where T135 denotes the urea solution temperature obtained by measuring the first temperature sensing element, Qi is the urea concentration γ of the urea solution obtained by calculating the impedance. s Shows.

[0024] A third aspect discloses a method for detecting a fault in a sensor for measuring the quality of a urea solution, comprising the steps of: Step 1: The signal processing unit receives the sensing signal transmitted from the quality sensing element and determines whether the ultrasonic sensing element and the impedance sensing element are available; Step 2: If both the ultrasonic sensing element and the impedance sensing element are available, calculate the urea concentration of the urea solution using the ultrasonic wave and the impedance respectively, and determine whether the IR failure of the sensor has occurred based on the difference between the two.

[0025] Additionally, step 1 includes: If the height value of the ultrasonic signal in the sensing signal is S_amp, the height value S_amp of the ultrasonic signal is compared with a first threshold value Thd_samp. If S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable. If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound 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 T_sft in the peak time of the ultrasonic signal is compared with a second threshold Thd_Tsft. If T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available. The condition for determining the availability of the impedance sensing element includes detecting whether the impedance sensing signal exceeds a maximum boundary or a minimum boundary measurement value: if the impedance sensing signal is higher than the maximum boundary measurement value or lower than the minimum boundary measurement value, the impedance sensor element is unavailable; otherwise, it is available.

[0026] Further, step 2 includes the following: if the urea concentration of the urea solution calculated using ultrasound is QU_conc and the urea concentration of the urea solution calculated using impedance is QI_conc, calculate the difference DEF_Diff between them: DEF_Diff=abs(QI_conc-QU_conc) abs() is a calculation of an absolute value, and if the DEF_Diff value is higher than the third threshold value Thd_Ddiff, it is determined that a sensor IR failure alarm has occurred, and if not, it is determined that a sensor IR failure has not occurred. [Effects of the Invention]

[0027] The present invention has the following beneficial effects.

[0028] The present application provides a sensor capable of detecting impurity ions and accurately measuring urea concentration, which is insensitive to the state of the urea solution, including being insensitive to air bubbles in the urea solution to avoid failure of the sensor under the action of air bubbles, and which is small and inexpensive.

[0029] To avoid triggering false alarms of urea concentration due to sensor problems, the sensor fault detection method provided by the present application can not only check for so-called OOR (Out-Of-Range) problems that result in readings outside the valid range, but also diagnose so-called IR (In-Range) problems that result in the sensor sensed value being within the normal range but not the accurate value. [Brief explanation of the drawings]

[0030] The advantages of these and / or other aspects of the present invention will become apparent as the present invention is more particularly described below in connection with the accompanying drawings and specific embodiments.

[0031] [Figure 1] FIG. 1 is a structural schematic diagram of a sensor for measuring the quality of a urea solution provided by an embodiment of the present application. [Figure 2]FIG. 1 is a structural schematic diagram of a quality sensing element in a sensor for measuring the quality of a urea solution provided by an embodiment of the present application. [Figure 3] FIG. 10 is another structural schematic diagram of a quality sensing element in a sensor for measuring the quality of a urea solution provided by an embodiment of the present application. [Figure 4] FIG. 1 shows the change curves of ultrasonic propagation time measurements and impedance measurements obtained using an ultrasonic sensing element and an impedance sensing element, respectively, with respect to the impurity ion concentration in the urea solution in a method for measuring the quality of a urea solution provided by an example of the present application. [Figure 5] FIG. 2 is a signal diagram of a first excitation signal received by an ultrasonic sensing element and a generated ultrasonic signal in a method for measuring the quality of a urea solution provided by an embodiment of the present application; [Figure 6] FIG. 1 is a structural schematic diagram of a signal processing unit in a sensor for measuring the quality of a urea solution provided by an embodiment of the present application. [Figure 7] 1 is a schematic flow chart of calculating the urea concentration of a urea solution in a method for measuring the quality of a urea solution provided by an example of the present application. [Figure 8] 1 is a schematic flowchart of a method for detecting a fault in a sensor for measuring the quality of a urea solution provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, embodiments of the present invention will be described in conjunction with the accompanying drawings.

[0033] The sensor and method for measuring the quality of a urea solution provided by the present application is applicable to selective catalytic reduction applications, where the sensor is used to measure the quality of the urea solution and to detect faults in the sensor itself when the urea solution is used as a diesel exhaust fluid (DEF).

[0034] The first embodiment of the present application discloses a sensor for measuring the quality of a urea solution, comprising: 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; The quality sensing element 100 is used to receive an excitation signal generated by a signal processing unit 120, generate a sensing signal, and send the sensing signal to the signal processing unit 120; The signal processing unit 120 is used to generate and send an excitation signal to the quality sensing element 100, receive the sensing signal sent from the quality sensing element 100, and calculate a quality sensing value of the urea solution based on the sensing signal, where the quality sensing value of the urea solution includes a urea concentration and an impurity ion concentration in the urea solution.

[0035] As shown in FIG. 1, when specifically implemented, the sensor for measuring the quality of the urea solution is provided with a rubber head 80 and a base 70, through which engine coolant flows through a coolant pipe 50 having an inlet 51 and an outlet 52 to heat the urea solution in the urea tank, a signal processing unit 120 is provided on the top of the rubber head 80 and connected to the base 70 via a cable tube 60, and a quality sensing element 100 is connected to the base 70.

[0036] In this embodiment, the quality sensing element 100 consists of 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 via a second signal line 123, one end of the first electrode 130 is electrically connected to the signal processing unit 120 via a first signal line 128, and the ultrasonic sensing element is electrically connected to the signal processing unit 120 via a fifth signal line 115, and is used to generate ultrasonic waves according to the excitation signal sent from the signal processing unit 120, transmit and receive ultrasonic waves, and transmit the received ultrasonic signals to the signal processing unit 120.

[0037] In an alternative embodiment, as shown in FIG. 2, the impedance of the first electrode 130 and the second electrode 125 varies with temperature, and specifically, the first electrode 130 and the second electrode 125 may be constructed of a material such as stainless steel (e.g., 304, 304L, 316, 316L), Hastelloy (nickel-molybdenum-chromium-tungsten alloy), or the like.

[0038] The second electrode 125 consists of a horizontal portion and a vertical portion, and one end of the horizontal portion away from the vertical portion is electrically connected to the signal processing unit 120 via a second signal line 123, the first electrode 130 and the second electrode 125 are not in contact with each other, and a urea solution is present between the horizontal portions of the first electrode 130 and the second electrode 125, and one 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 via a first signal line 128.

[0039] Optionally, the ultrasonic sensing element includes an ultrasonic transmitting and receiving unit 112, which is composed of an ultrasonic transmitter and a receiver, the transmitter and the receiver are parallel to each other, a urea solution is present between them, and the urea solution is in communication with the urea solution between the horizontal portion of the first electrode 130 and the horizontal portion of the second electrode 125, and both the transmitter and the receiver are electrically connected to the signal processing unit 120. Exemplarily, a mounting surface 110 is provided above one end of the horizontal portion of the second electrode 125, away from the vertical portion, and the ultrasonic transmitter is provided in close contact with the mounting surface 110, and the receiver is provided in close contact with the vertical portion of the second electrode 125.

[0040] Optionally, the ultrasonic sensing element comprises an ultrasonic transmitting / receiving unit 112 and a reflector 122, the ultrasonic transmitting / receiving unit 112 and the reflector 122 being parallel to each other, with a urea solution present between them, the urea solution being in communication with the urea solution between the horizontal portion of the first electrode 130 and the horizontal portion of the second electrode 125. For example, the ultrasonic transmitting / receiving unit 112 may be located above one end of the horizontal portion of the second electrode 125 away from the vertical portion, and the reflector 122 may be in close contact with the vertical portion of the second electrode 125, or for example, the vertical portion of the second electrode 125 may be directly used as the reflector 122. The ultrasonic transmitting / receiving unit 112 is used to transmit ultrasonic waves and receive ultrasonic echo signals reflected by the reflector 122. Optionally, the ultrasonic transmitting / receiving unit 112 comprises an ultrasonic transducer and a receiver (TR), and the ultrasonic transmitting / receiving unit 112 is electrically connected to the signal processing unit 120 via a fifth signal line 115.

[0041] In some other embodiments, the second electrode 125 may be designed in other shapes, for example, having the same shape as the first electrode 130 and arranged parallel to the first electrode 130. When the ultrasonic sensing element includes only the ultrasonic transmitting and receiving unit 112, and the ultrasonic transmitting and receiving unit 112 includes an ultrasonic transmitter and a receiver, the ultrasonic transmitter may be provided in close contact with the inside of one of the first electrode 130 or the second electrode 125, and the receiver may be provided in close contact with the inside of the other electrode, where the inside refers to the part where the first electrode 130 and the second electrode 125 face each other in parallel. When the ultrasonic sensing element includes the ultrasonic transmitting and receiving unit 112 and the reflector 122, the ultrasonic transmitting and receiving unit 112 may be provided in close contact with the inside of one of the first electrode 130 or the second electrode 125, and the reflector 122 may be provided in close contact with the inside of the other electrode, and for example, the inside of the other electrode may be directly used as the reflector 122.

[0042] In these above embodiments, by designing the second electrode 125 in an L-shape or by arranging the second electrode 125 and the first electrode 130 in parallel, the impedance sensing element is shared by all the ultrasonic sensing elements, and the quality sensing element 100 can be designed compactly and inexpensively.

[0043] In still other embodiments, regardless of whether the impedance sensing element and the ultrasonic sensing element are used in common, the positional relationship between the impedance sensing element and the ultrasonic sensing element is not limited to any other positional relationship as long as it is possible to ensure that the urea solution between the first electrode 130 and the second electrode 125 is in communication with the urea solution in the ultrasonic sensing element.

[0044] 3 , the impedance of the first electrode 130 does not change with temperature, and the structure and connection relationship of the impedance sensing element and the ultrasound sensing element are the same as those of any of the above embodiments, and the impedance sensing element 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 125, and is electrically connected to the signal processing unit 120 via an eighth signal line 127. Illustratively, the first temperature sensing element 135 is disposed adjacent to the first electrode 130.

[0045] In this embodiment, as shown in FIG. 6 , the signal processing unit 120 includes a central processing unit 230 (CPU, Central Processing Unit), an ultrasonic signal processing subunit 240 (USPSU, Ultrasonic Signal Processing Subunit), and an impedance signal processing subunit 250 (ISPSU, Impedance Signal Processing Subunit), The central processing unit 230 includes an MCU 231 (Microcontroller unit) and a memory 232, and is used to send instructions 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 is electrically connected to the ultrasonic sensing element via a fifth signal line 115, and is used to receive a first command sent from the central processing unit 230, generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent from the ultrasonic sensing element, and send it to the central processing unit 230 after processing; The ultrasonic signal processing subunit 240 includes a first waveform generation module 242 (WGM, Waveform Generation Module), a pulse generator 244 (PM, Pulse generator Module), a first amplifier 245, a rectifier 243 and an envelope detection module 241 (EDM, Envelope Detection Module), 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 based on the command and sends it to the pulse generator module 244, the pulse generator module 244 generates a first excitation signal based on the pulse signal and sends it to the ultrasonic transceiver unit 112 via a fifth signal line 115; The ultrasonic transceiver unit 112 generates an ultrasonic wave based on the first excitation signal and transmits the ultrasonic signal to a first amplifier 245; The first amplifier 245 amplifies the ultrasonic signal and sends the amplified ultrasonic signal to the rectifier 243, which filters out the negative voltage signal before sending it to the envelope detection module 241, which filters out the high frequency "carrier" signal and sends the pulse envelope signal to the central processing unit 230.

[0046] the impedance signal processing sub-unit 250 is electrically connected to one end of the first electrode 130 via a first signal line 128, and electrically connected to one end of the second electrode 125 via a second signal line 123, and is used to receive a second command sent from the central processing unit 230, generate a second excitation signal, send the second excitation signal to the first electrode 130 and the second electrode 125 respectively, receive the impedance sensing signal sent from the first electrode 130, process it and send it to the central processing unit 230; The impedance signal processing sub-unit 250 includes a second waveform generating module 251, a driver 253, a multiplex switch 255 (MUX, Multiplex switch), a second amplifier 254, and a signal processing module 252 (SPM, Signal Processing Module), wherein the central processing unit 230 generates a second command and sends it to the second waveform generating module 251, the second waveform generating module 251 generates an excitation signal (sine wave single excitation signal or swept frequency excitation signal) of a set frequency or frequency band based on 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, and the multiplex switch 255 selects whether to send the power excitation signal to the first electrode 130 via the first signal line 128 or to the second electrode 125 via the second signal line 123 based on a setting command sent from the MCU; The first electrode 130 transmits the impedance sensing signal to the second amplifier 254 via the first signal line 128, the second amplifier 254 amplifies the impedance sensing signal and transmits the amplified impedance sensing signal to the signal processing module 252, the signal processing module 252 processes the amplified impedance sensing signal and transmits the processed signal to the central processing unit 230.

[0047] In an alternative embodiment, 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 and is used to measure the resistance of the first electrode 130 and transmit the resistance value to the central processing unit 230.

[0048] In another alternative embodiment, the signal processing unit 120 further includes a resistance measurement module 260, and 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 transmit the resistance value to the central processing unit 230.

[0049] A second embodiment of the present application discloses a method for measuring the quality of a urea solution, comprising the following steps: Step 1: The signal processing unit 120 sends excitation signals to the quality sensing element 100, the excitation signals including a first excitation signal sent to the ultrasound 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 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, where the sensing signal includes an ultrasonic signal and an impedance sensing signal; Step 3: The signal processing unit 120 receives the sensing signal sent from the quality sensing element 100 and is used to calculate the quality sensing value of the urea solution based on the sensing signal, where 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.

[0050] In an alternative embodiment, step 2 includes: an ultrasonic transmitter in the ultrasonic transceiver unit 112 receives the first excitation signal, generates and transmits ultrasonic waves to a receiver, the receiver transmits the received ultrasonic signal to a signal processing unit 120, and the first electrode 130 transmits an impedance sensing signal to the signal processing unit 120.

[0051] In another alternative embodiment, step 2 includes: the ultrasonic transceiver unit 112 receives the first excitation signal and generates ultrasonic waves, the ultrasonic waves pass through the urea solution between the ultrasonic transceiver unit 112 and the vertical portion of the second electrode 125, are reflected by the vertical portion of the second electrode 125, generate ultrasonic echo signals and send them back to the ultrasonic transceiver unit 112, the ultrasonic transceiver unit 112 sends the ultrasonic echo signals to the signal processing unit 120, and the sensing signals in step 2 include the ultrasonic signals and the ultrasonic echo signals, which are the ultrasonic signals in an impedance sensing signal. The first electrode 130 sends the impedance sensing signal to the signal processing unit 120.

[0052] In this example, the calculation of the urea concentration of the urea solution in step 3 includes: Step 3.1, determine whether an ultrasound sensing element is available; Step 3.2, if an ultrasound sensing element is available, calculate the urea concentration of the urea solution using the ultrasound signal; Step 3.3: If an ultrasonic sensing element is not available, calculate the urea concentration of the urea solution using the impedance sensing signal.

[0053] As shown in Figures 5 and 7, for the first excitation signal 181 and the ultrasonic signal 182 in the sensing signal, step 3.1 includes: assuming that the height value of the ultrasonic signal in the sensing signal is S_amp, compare the height value S_amp of the ultrasonic signal with a first threshold value Thd_samp; if S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable, which is indicated by a status flag Stat_QU=1; and the first threshold value Thd_samp may be set slightly larger than the maximum value of S_amp in the operating temperature range (e.g., -11°C to -85°C).

[0054] When 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, where the normal value Tpk0 is determined by the pulse width of the ultrasonic excitation signal and may be set to half the excitation signal pulse width value.

[0055] The change in peak time of the ultrasonic signal, T_sft, is compared with a second threshold value, Thd_Tsft, and if T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable, which is indicated by a status flag, Stat_QU = 1. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available, which is indicated by a status flag, Stat_QU = 0. Here, the second threshold value, Thd_Tsft, may be set to the width of one or more carrier pulses.

[0056] Calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2 includes: When the propagation time of the ultrasonic wave in the urea solution is Tr and the ultrasonic propagation distance is Ds, the propagation time Tr is calculated based on the first excitation signal transmitted by the signal processing unit 120 and the received ultrasonic signal, In an alternative embodiment, 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 based on the time interval between the first excitation signal obtained by the ultrasonic transmitter and the ultrasonic signal received by the receiver.

[0057] In another alternative embodiment, the ultrasonic propagation distance Ds is twice the distance between the ultrasonic transmitting / receiving unit 112 and the reflector 122, and the propagation time Tr is calculated based on the time interval between the first excitation signal obtained by the ultrasonic transmitting / receiving unit 112 and the ultrasonic echo signal generated through the received ultrasonic reflector.

[0058] The relationship between the propagation time Tr and the ultrasonic propagation velocity Cs satisfies the following formula: Cs=Ds / Tr (1) When ultrasonic waves propagate through a urea solution, the sound speed Cs is determined by the bulk modulus K and density ρ of the urea solution:

number

[0059] Calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3 includes: Assuming that the impedance between the first electrode 130 and the second electrode 125 is Zs, the impedance Zs can be obtained by the signal processing unit 120 calculating based on the impedance sensing signal, i.e., the urea solution temperature Ts and the urea concentration γ s The function is: Zs=f(Ts,γ s ) (3) Therefore, the urea concentration of the urea solution γ s is obtained by calculation based on the impedance Zs and the urea solution temperature Ts.

[0060] In an alternative embodiment, the impedance of the first electrode 130 varies with temperature, and when calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2, the urea solution temperature Ts is a function of the resistance Re of the first electrode 130, which is obtained by measurement by the signal processing unit 120, and the urea concentration γ of the urea solution is calculated by a two-dimensional lookup. s Get: gamma s =Qu=Tbl(Re,Tr) where Qu is the urea concentration of the urea solution obtained by calculating the ultrasonic s Shows.

[0061] When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is a function of the resistance Re of the first electrode 130, where the resistance Re of the first electrode 130 is obtained by measurement by the signal processing unit 120, and the impedance Zs is a function of the resistance Re of the first electrode 130 and the urea concentration γ of the urea solution. s is a function of: Zs = g(Re,γ s ) (4) The urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qi=Tbl(Re,Zs) where Qi is the urea concentration of the urea solution obtained by calculating the impedance γ s Shows.

[0062] In another alternative embodiment, the impedance of the first electrode 130 does not change with temperature, and the impedance sensing element further includes a first temperature sensing element 135, and when calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2, the urea solution temperature Ts is obtained by measurement with the first temperature sensing element 135, and the urea concentration γ of the urea solution is calculated by a two-dimensional lookup. s Get: gamma s =Qu=Tbl(T135,Tr) where T135 denotes the temperature of the urea solution obtained by the measurement of the first temperature sensing element 135, which is obtained by the signal processing unit 120 acquiring and calculating the resistance of the first temperature sensing element 135, and Qu denotes the urea concentration γ of the urea solution obtained by calculating the ultrasonic wave s Shows.

[0063] When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, calculate the urea concentration γ of the urea solution by two-dimensional lookup. s Get: gamma s =Qi=Tbl(T135,Zs) where T135 denotes the urea solution temperature obtained by measurement of the first temperature sensing element 135, and Qi denotes the urea concentration γ of the urea solution obtained by calculating the impedance. s Shows.

[0064] In this embodiment, when calculating the impurity ion concentration in the urea solution in step 3, the ultrasonic sensing element is available, and calculating the impurity ion concentration in the urea solution using the impedance sensing signal includes: If the impedance between the first electrode 130 and the second electrode 125 is Zs, the impedance Zs is obtained by the signal processing unit 120 through calculation based on the impedance sensing signal, and an impedance change value dZs of the impedance Zs is calculated, and the impedance change value dZs is defined as follows: dZs=(Zs(γ i) - Zs(0)) / Zs(0) (5) Here, Zs(γ i ) is the impurity ion concentration γ i Zs(0) is the impedance between the first electrode 130 and the second electrode 125 measured in a urea solution conforming to the ISO 22241 standard, and the impurity ion concentration γ i Get: gamma i =Tbl(dZs).

[0065] As shown in Figure 4, the first curve 270 represents the change in impedance Zs measured in a urea solution after adding calcium chloride (CaCl2) impurity, and the second curve 271 represents the change in ultrasonic propagation time Tr obtained from the ultrasonic sensing element. As shown in the first and second curves 270 and 271, the impedance sensing signal is more sensitive to the ionic impurity concentration in the urea solution than 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 remain and accumulate in the SCR catalyst, reducing its activity and denitration efficiency, ultimately causing the catalyst to fail. This is why the ISO 22241 standard limits impurity ions to very low levels. Essentially, non-compliant urea solutions pose two problems: urea concentration issues that lead to exhaust gas rejection and impurity ion issues that lead to SCR damage. OBD (On-Board Diagnostics) standards require that only Type 1 problems, i.e. non-compliant urea concentrations that lead to exhaust gas problems, be detected, but OBD does not require detection of impurity ion concentrations if the urea solution concentration is within the acceptable range.

[0066] The impact of impurity ions on SCRs is long-term; that is, SCR degradation is due to the accumulation of impurity ions rather than their current concentration. Therefore, because ion impurities cannot be directly detected (detecting the emissions impact of impurity ions, rather than the impurity ions themselves), the detection of impurity ion effects can irreversibly deactivate the SCR, presenting SCR system manufacturers with significant maintenance issues. Urea solutions containing impurity ions are not uncommon. Purification, a costly step, is required during production, and additional costs are incurred for transporting and storing the solution to meet the requirements of ISO 22241. While avoidance measures, such as using low-purity solvents (e.g., tap water) or operating outside of specifications (e.g., using contaminated containers), can significantly reduce costs, resulting in the contamination of large amounts of impurity ions. Direct detection of impurity ion concentrations is necessary to reduce quality complaints.

[0067] In the present invention, as shown in Figures 2 and 3, the quality sensing unit detects the urea concentration of the urea solution and simultaneously detects the impurity ion concentration: the ultrasonic signal obtained from the ultrasonic sensing element detects the urea concentration of the urea solution to avoid exhaust gas problems caused by low urea concentration, and 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. At present, OBD does not require the detection of impurity ion concentration, so the measured impurity ion concentration is recorded in the signal processing unit 120 and can be used as the basis for further claims.

[0068] A third embodiment of the present application discloses a method for detecting a fault in a sensor for measuring the quality of a urea solution, comprising the following steps: Step 1: The signal processing unit 120 receives the sensing signal transmitted from the quality sensing element 100 and determines whether the ultrasonic sensing element and the impedance sensing element are available; As shown in Figures 5 and 7, step 1 includes: If the height value of the ultrasonic signal in the sensing signal is S_amp, the height value S_amp of the ultrasonic signal is compared with the first threshold value Thd_samp. If S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable, which is indicated by the status flag Stat_QU=1, and the urea concentration QU_conc of the urea solution calculated using the ultrasonic waves is unavailable. If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound 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 the second threshold value Thd_Tsft. If T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable, which is indicated by the status flag Stat_QU=1. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available, which is indicated by the status flag Stat_QU=0. The urea concentration QU_conc value of the urea solution calculated using ultrasonic waves is available. Then, the DEF report value DEF_conc value is set to QU_conc, and the DEF sensing flag DEF_flag is set to 0. This means that the DEF concentration value is the ultrasonic sensing value. The routine ends. The condition for determining the availability of the impedance sensing element includes detecting whether the impedance sensing signal exceeds a maximum or minimum boundary measurement value: if the impedance sensing signal is higher than the maximum boundary measurement value (such as the signal value measured in the case of an open circuit) or lower than the minimum boundary measurement value (such as the signal value measured in the case of a short circuit), the impedance sensor element is unavailable, as indicated by a status flag Stat_QI = 1; otherwise, the impedance sensor element is available, as indicated by a status flag Stat_QI = 0. If the status flag Stat_QI = 0, the urea concentration QI_conc of the urea solution calculated using the impedance is available, and the DEF report value DEF_conc is set to the urea concentration QI_conc of the urea solution calculated using the impedance. At the same time, the DEF sensing flag DEF_flag is set to 1, which means the DEF concentration sensing value is the impedance sensing value, and the routine ends. If the status flag Stat_QI = 1, the DEF sensing flag DEF_flag is set to 2, which means all DEF concentration sensing values ​​are unavailable, and the routine ends.

[0069] Step 2: If both the ultrasonic sensing element and the impedance sensing element are available, calculate the urea concentration of the urea solution using the ultrasonic wave and the impedance respectively, and determine whether the IR failure of the sensor has occurred based on the difference between the two.

[0070] Step 2 involves: Given that the urea concentration of the urea solution calculated using ultrasound is QU_conc and the urea concentration of the urea solution calculated using impedance is QI_conc, calculate the difference DEF_Diff between them: DEF_Diff=abs(QI_conc-QU_conc) abs() is the calculation of the absolute value, and as shown in Figure 8, if the DEF_Diff value is higher than the third threshold value Thd_Ddiff, it is determined that a sensor IR failure alarm has occurred, and the failure flag Fault_QR is indicated by 1; otherwise, it is determined that a sensor IR failure has not occurred, and the failure flag Fault_QR is indicated by 0.

[0071] In a specific embodiment, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, it can perform some or all of the steps in the inventive content and each embodiment of the method for measuring the quality of a urea solution and the method for detecting a fault in a sensor for measuring the quality of a urea solution provided by the present invention. The storage medium may be a magnetic disk, a compact disk, a read-only memory (ROM), a random access memory (RAM), etc.

[0072] It is clearly understood by those skilled in the art that the technical solutions in the embodiments of the present invention can be implemented by a computer program and a corresponding general-purpose hardware platform. Based on this understanding, the technical solutions in the embodiments of the present invention can be embodied in the form of a computer program, i.e., a software product, which can be stored in a storage medium and includes a number of instructions that enable a device including a data processing unit (which can be a personal computer, a server, a microcontroller, an MUU, or a network device, etc.) to perform the methods described in various embodiments or some parts of the embodiments of the present invention.

[0073] The present invention provides a sensor and method for measuring the quality of a urea solution, and there are many ways and means to realize this technical solution, and the above description is only a specific embodiment of the present invention, and those skilled in the art can make many improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered as part of the protection scope of the present invention. Components not specified in this embodiment can be realized by conventional technologies.

[0074] (Addendum) (Appendix 1) The apparatus comprises a quality sensing element (100) and a signal processing unit (120), wherein the quality sensing element (100) is completely covered with 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 an excitation signal generated by a signal processing unit (120), generate a 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 a sensing signal sent from the quality sensing element (100), and calculate a quality sensing value of the urea solution based on the sensing signal, and the quality sensing value of the urea solution includes a urea concentration and an impurity ion concentration in the urea solution.

[0075] (Appendix 2) 10. The sensor for measuring the quality of a urea solution according to claim 1, wherein the quality sensing element (100) comprises an impedance sensing element and an ultrasonic sensing element, the impedance sensing element including a first electrode (130) and a second electrode (125), the urea solution between the first electrode (130) and the second electrode (125) is in communication with the urea solution in the ultrasonic sensing element, one end of the second electrode (125) is electrically connected to the signal processing unit (120) via a second signal line (123), one end of the first electrode (130) is electrically connected to the signal processing unit (120) via a first signal line (128), and the ultrasonic sensing element is electrically connected to the signal processing unit (120) via a fifth signal line (115) and is used to generate ultrasonic waves based on an excitation signal sent from the signal processing unit (120), transmit and receive ultrasonic waves, and transmit received ultrasonic signals to the signal processing unit (120).

[0076] (Appendix 3) The signal processing unit (120) includes a central processing unit (230), an ultrasound signal processing subunit (240), and an impedance signal processing subunit (250); the central processing unit (230) is used to send instructions 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) is electrically connected to the ultrasonic sensing element via a fifth signal line (115), and is used to receive a first command sent from the central processing unit (230), generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent from the ultrasonic sensing element, process it, and send it to the central processing unit (230); The sensor for measuring the quality of a urea solution according to claim 2, 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 to one end of the second electrode (125) via a second signal line (123), and is used to receive a second command sent from a central processing unit (230), generate a second excitation signal, send the second excitation signal to the first electrode (130) and the second electrode (125), respectively, receive an impedance sensing signal sent from the first electrode (130), and send it to the central processing unit (230) after processing.

[0077] (Appendix 4) 4. The sensor for measuring the quality of a urea solution according to claim 3, wherein 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) and is used to measure the resistance of the first electrode (130) and transmit the resistance value to the central processing unit (230).

[0078] (Appendix 5) 4. The sensor for measuring the quality of a urea solution according to claim 3, wherein the signal processing unit (120) further comprises a resistance measurement module (260), and the impedance sensing element further comprises a first temperature sensing element (135), the first temperature sensing element (135) measuring the temperature of the urea solution between the first electrode (130) and the second electrode (125) and 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 transmit the resistance value to the central processing unit (230).

[0079] (Appendix 6) It includes the following steps: Step 1: The signal processing unit (120) sends excitation signals to the quality sensing element (100), the excitation signals 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), where the sensing signal includes an ultrasonic signal and an impedance sensing signal; Step 3: The signal processing unit (120) receives the sensing signal transmitted from the quality sensing element (100) and calculates a quality sensing value of the urea solution based on the sensing signal, and calculating 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.

[0080] (Appendix 7) The calculation of the urea concentration of the urea solution in step 3 includes the following steps: Step 3.1, determine whether an ultrasound sensing element is available; Step 3.2, if an ultrasound sensing element is available, calculate the urea concentration of the urea solution using the ultrasound signal; 7. The method for measuring the quality of a urea solution according to claim 6, characterized in that in step 3.3, if an ultrasonic sensing element is not available, the impedance sensing signal is used to calculate the urea concentration of the urea solution.

[0081] (Appendix 8) Step 3.1 includes: taking a height value of an ultrasonic signal in a sensing signal as S_amp, comparing the height value S_amp of the ultrasonic signal with a first threshold Thd_samp, and if S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable; When the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound signal, T_sft, is obtained by calculating the difference between the peak time, Tpk, and the normal value, Tpk0: T_sft=Tpk-Tpk0 8. A method for measuring the quality of a urea solution according to claim 7, characterized in that the change in peak time of the ultrasonic signal, T_sft, is compared with a second threshold value, Thd_Tsft, and if T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable, and if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available.

[0082] (Appendix 9) Calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2 includes: The propagation time of the ultrasonic wave in the urea solution is denoted as Tr, and the ultrasonic propagation distance is denoted as Ds. The propagation time Tr is calculated based on the first excitation signal transmitted by the signal processing unit 120 and the received ultrasonic signal, and the relationship between the propagation time Tr value and the ultrasonic propagation velocity Cs satisfies the following formula: Cs=Ds / Tr (1) When ultrasonic waves propagate through a urea solution, the sound speed Cs is determined by the bulk modulus K and density ρ of the urea solution:

number

[0083] (Appendix 10) Calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3 includes: The impedance between the first electrode (130) and the second electrode (125) is Zs, and the impedance Zs can be calculated by the signal processing unit (120) based on the impedance sensing signal, and the temperature Ts of the urea solution and the urea concentration γ of the urea solution can be calculated. s It is also a function of: Zs=f(Ts,γ s ) (3) Therefore, the urea concentration of the urea solution γ s 8. The method for measuring the quality of a urea solution according to claim 7, wherein Zs is obtained by calculating the impedance Zs and the urea solution temperature Ts.

[0084] (Appendix 11) When calculating the impurity ion concentration in the urea solution in step 3, an ultrasonic sensing element is available, and calculating the impurity ion concentration in the urea solution using the impedance sensing signal includes: If the impedance between the first electrode (130) and the second electrode (125) is Zs, the impedance Zs is obtained by calculation based on the impedance sensing signal by the signal processing unit (120), and an impedance change value dZs of the impedance Zs is calculated, and the impedance change value dZs is defined as follows: dZs=(Zs(γ i ) - Zs(0)) / Zs(0) (5) Here, Zs(γ i ) is the impurity ion concentration γ iZs(0) is the impedance between the first electrode (130) and the second electrode (125) measured in a urea solution conforming to the ISO22241 standard, and the impurity ion concentration γ i Get: gamma i 10. The method for measuring the quality of a urea solution according to claim 9, wherein Tbl(dZs) is the urea concentration.

[0085] (Appendix 12) When calculating the urea concentration of the urea solution using the ultrasonic signal in step 3.2, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130), and the resistance Re of the first electrode (130) is obtained by measurement by the signal processing unit (120), and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qu=Tbl(Re,Tr) where Qu is the urea concentration of the urea solution obtained by calculating the ultrasonic s 10. The method for measuring the quality of a urea solution according to claim 9, wherein the urea solution exhibits the following properties:

[0086] (Appendix 13) When calculating the urea concentration of the urea solution using the ultrasonic signal in step 3.2, the urea solution temperature Ts is obtained by measurement of the first temperature sensing element (135), and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qu=Tbl(T135,Tr) where T135 indicates the temperature of the urea solution obtained by measuring the first temperature sensing element (135), and Qu is the urea concentration γ of the urea solution obtained by calculating the ultrasonic wave. s 10. The method for measuring the quality of a urea solution according to claim 9, wherein the urea solution exhibits the following properties:

[0087] (Appendix 14) When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130), where the resistance Re of the first electrode (130) is obtained by measurement by the signal processing unit (120), and the impedance Zs is a function of the resistance Re of the first electrode (130) and the urea concentration γ of the urea solution. s is a function of: Zs = g(Re,γ s ) (4) The urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qi=Tbl(Re,Zs) where Qi is the urea concentration of the urea solution obtained by calculating the impedance γ s 11. The method for measuring the quality of a urea solution according to claim 10, wherein the urea solution exhibits the following properties:

[0088] (Appendix 15) When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is obtained by measuring the first temperature sensing element (135), and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. s Get: gamma s =Qi=Tbl(T135,Zs) where T135 indicates the temperature of the urea solution obtained by measuring the first temperature sensing element (135), and Qi is the urea concentration γ of the urea solution obtained by calculating the impedance. s 11. The method for measuring the quality of a urea solution according to claim 10, wherein the urea solution exhibits the following properties:

[0089] (Appendix 16) It includes the following steps: Step 1: The signal processing unit (120) receives the sensing signal transmitted from 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 sensing element and the impedance sensing element are available, calculate the urea concentration of the urea solution using the ultrasonic wave and the impedance, respectively, and determine whether an IR failure of the sensor has occurred based on the difference between the two.

[0090] (Appendix 17) Step 1 includes: If the height value of the ultrasonic signal in the sensing signal is S_amp, the height value S_amp of the ultrasonic signal is compared with a first threshold value Thd_samp. If S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable. If the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound 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 T_sft in the peak time of the ultrasonic signal is compared with a second threshold Thd_Tsft. If T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available. The method for detecting a failure of a sensor for measuring the quality of a urea solution described in Appendix 16, characterized in that the condition for determining the availability of the impedance sensing element includes detecting whether the impedance sensing signal exceeds a maximum boundary or a minimum boundary measurement value: if the impedance sensing signal is higher than the maximum boundary measurement value or lower than the minimum boundary measurement value, the impedance sensor element is unavailable, and if not, it is available.

[0091] (Appendix 18) Step 2 includes the following: Given that the urea concentration of the urea solution calculated using ultrasound is QU_conc and the urea concentration of the urea solution calculated using impedance is QI_conc, calculate the difference DEF_Diff between them: DEF_Diff=abs(QI_conc-QU_conc) abs() is a calculation of an absolute value, and if the DEF_Diff value is higher than the third threshold value Thd_Ddiff, it is determined that a sensor IR failure alarm has occurred, and if not, it is determined that a sensor IR failure has not occurred.

Claims

1. The method comprises a quality sensing element (100) and a signal processing unit (120), wherein the quality sensing element (100) is completely covered with 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 an excitation signal generated by a signal processing unit (120), generate a sensing signal, and transmit the sensing signal to the signal processing unit (120); The signal processing unit (120) is used to generate an excitation signal and transmit it to the quality sensing element (100), receive a sensing signal transmitted from the quality sensing element (100), and calculate a quality sensing value of the urea solution based on the sensing signal, wherein the quality sensing value of the urea solution includes a urea concentration and an impurity ion concentration in the urea solution.

2. 2. The sensor for measuring the quality of a urea solution according to claim 1, wherein the quality sensing element (100) comprises an impedance sensing element and an ultrasonic sensing element, the impedance sensing element including a first electrode (130) and a second electrode (125), the urea solution between the first electrode (130) and the second electrode (125) is in communication with the urea solution in the ultrasonic sensing element, one end of the second electrode (125) is electrically connected to a signal processing unit (120) via a second signal line (123), one end of the first electrode (130) is electrically connected to the signal processing unit (120) via a first signal line (128), and the ultrasonic sensing element is electrically connected to the signal processing unit (120) via a fifth signal line (115) and is used to generate ultrasonic waves based on an excitation signal sent from the signal processing unit (120), transmit and receive ultrasonic waves, and transmit received ultrasonic signals to the signal processing unit (120).

3. The signal processing unit (120) includes a central processing unit (230), an ultrasound signal processing subunit (240), and an impedance signal processing subunit (250); the central processing unit (230) is used to send instructions 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) is electrically connected to the ultrasonic sensing element via a fifth signal line (115), and is used to receive a first command sent from the central processing unit (230), generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, receive the ultrasonic signal sent from the ultrasonic sensing element, process it, and send it to the central processing unit (230); 3. The sensor for measuring the quality of a urea solution according to claim 2, wherein the impedance signal processing sub-unit (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), and is used to receive a second command sent from a central processing unit (230), generate a second excitation signal, send the second excitation signal to the first electrode (130) and the second electrode (125), respectively, receive an impedance sensing signal sent from the first electrode (130), and send the impedance sensing signal to the central processing unit (230) after processing.

4. 4. The sensor for measuring the quality of a urea solution according to claim 3, wherein the signal processing unit (120) further includes a resistance measurement module (260), which is electrically connected to the resistance measurement module (260) and 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 transmit the resistance value to the central processing unit (230).

5. 4. The sensor for measuring the quality of a urea solution according to claim 3, wherein the signal processing unit (120) further comprises a resistance measurement module (260), and the impedance sensing element further comprises a first temperature sensing element (135), which measures the urea solution temperature between the first electrode (130) and the second electrode (125) and 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 transmit the resistance value to the central processing unit (230).

6. It includes the following steps: Step 1: The signal processing unit (120) transmits excitation signals to the quality sensing element (100), the excitation signals including a first excitation signal transmitted to the ultrasound sensing element and a second excitation signal transmitted 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), where the sensing signal includes an ultrasonic signal and an impedance sensing signal; Step 3: The signal processing unit (120) receives the sensing signal transmitted from the quality sensing element (100) and calculates a quality sensing value of the urea solution based on the sensing signal, wherein calculating 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. The calculation of the urea concentration of the urea solution in step 3 includes the following steps: Step 3.1, determine whether an ultrasound sensing element is available; Step 3.2, if an ultrasonic sensing element is available, calculate the urea concentration of the urea solution using the ultrasonic signal; 7. The method for measuring the quality of a urea solution according to claim 6, wherein step 3.3, if an ultrasonic sensing element is not available, calculates the urea concentration of the urea solution using the impedance sensing signal.

8. Step 3.1 includes: taking 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 a first threshold value Thd_samp, and if S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable; When the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound signal, T_sft, is obtained by calculating the difference between the peak time, Tpk, and the normal value, Tpk0: T_sft = Tpk - Tpk0 8. The method for measuring the quality of a urea solution according to claim 7, further comprising: comparing a change in peak time T_sft of the ultrasonic signal with a second threshold Thd_Tsft; if T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable; and if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available.

9. Calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2 includes: The propagation time Tr of the ultrasonic wave in the urea solution is denoted as Tr, and the ultrasonic propagation distance is denoted as Ds. The propagation time Tr can be calculated based on the first excitation signal transmitted by the signal processing unit (120) and the received ultrasonic signal, and the relationship between the propagation time Tr value and the ultrasonic propagation velocity Cs satisfies the following formula: Cs=Ds / Tr (1) When ultrasonic waves propagate through a urea solution, the sound speed Cs is determined by the bulk modulus K and density ρ of the urea solution: [Equation 1] Here, the values ​​of the bulk modulus K and density ρ change depending on the urea solution concentration and temperature, Since the ultrasonic propagation distance Ds is a fixed value and the ultrasonic propagation velocity Cs is a function of the ultrasonic propagation time Tr, the urea concentration γ ｓ 8. The method for measuring the quality of a urea solution according to claim 7, characterized in that: Θ is obtained by calculating the ultrasonic propagation time Tr and the urea solution temperature Ts.

10. Calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3 includes: The impedance between the first electrode (130) and the second electrode (125) is Zs, and the impedance Zs can be calculated by the signal processing unit (120) based on the impedance sensing signal, and the urea solution temperature Ts and the urea concentration γ of the urea solution can be calculated. ｓ It is also a function of: Zs=f(Ts,γ) ｓ ) (3) Therefore, the urea concentration of the urea solution γ ｓ 8. The method for measuring the quality of a urea solution according to claim 7, wherein Zs is obtained by calculating the impedance Zs and the urea solution temperature Ts.

11. When calculating the impurity ion concentration in the urea solution in step 3, the ultrasonic sensing element is available, and calculating the impurity ion concentration in the urea solution using the impedance sensing signal includes: If the impedance between the first electrode 130 and the second electrode 125 is Zs, the impedance Zs can be obtained by the signal processing unit 120 through calculation based on the impedance sensing signal, and an impedance change value dZs of the impedance Zs can be calculated, and the impedance change value dZs can be defined as follows: $Zs=(Zs(γ ｉ ) - Zs(0) / Zs(0) (5) Here, Zs(γ ｉ ) is the impurity ion concentration γ ｉ Zs(0) is the impedance between the first electrode (130) and the second electrode (125) measured in a urea solution conforming to the ISO 22241 standard, and the impurity ion concentration γ ｉ Obtain: gamma ｉ 10. The method for determining the quality of a urea solution according to claim 9, characterized in that: = Tbl(dZs).

12. When calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130), and the resistance Re of the first electrode (130) is obtained by measurement by the signal processing unit (120), and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. ｓ Obtain: γ ｓ =Q=Tal(Re,Tr) where Qu is the urea concentration of the urea solution obtained by calculating the ultrasonic ｓ 10. The method for measuring the quality of a urea solution according to claim 9, characterized in that:

13. When calculating the urea concentration of the urea solution using the ultrasound signal in step 3.2, the urea solution temperature Ts is obtained by measurement of the first temperature sensing element (135), and the urea concentration γ of the urea solution is calculated by two-dimensional lookup. ｓ Obtain: γ ｓ =Q==D-(135,2) where T135 indicates the urea solution temperature obtained by measurement of the first temperature sensing element (135), and Qu is the urea concentration γ of the urea solution obtained by calculating the ultrasonic wave. ｓ 10. The method for measuring the quality of a urea solution according to claim 9, characterized in that:

14. When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is a function of the resistance Re of the first electrode (130), where the resistance Re of the first electrode (130) is obtained by measurement by the signal processing unit (120), and the impedance Zs is a function of the resistance Re of the first electrode (130) and the urea concentration γ of the urea solution. ｓ is a function of: Zs = g (Re, γ) ｓ ) (4) The urea concentration γ of the urea solution is calculated by two-dimensional lookup. ｓ Obtain: γ ｓ [#)(#) where Qi is the urea concentration γ of the urea solution obtained by calculating the impedance ｓ 11. The method for measuring the quality of a urea solution according to claim 10, characterized in that:

15. When calculating the urea concentration of the urea solution using the impedance sensing signal in step 3.3, the urea solution temperature Ts is obtained by measuring the first temperature sensing element (135), and the urea concentration γ of the urea solution is calculated by a two-dimensional lookup. ｓ Obtain: γ ｓ ake==n"b"b""""11cction of the where T135 indicates the urea solution temperature obtained by measurement of the first temperature sensing element (135), and Qi is the urea concentration γ of the urea solution obtained by calculating the impedance. ｓ 11. The method for measuring the quality of a urea solution according to claim 10, characterized in that:

16. It includes the following steps: Step 1: The signal processing unit (120) receives the sensing signal transmitted from 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 sensing element and the impedance sensing element are available, calculate the urea concentration of the urea solution using the ultrasonic wave and the impedance, respectively, and determine whether an IR failure of the sensor has occurred based on the difference between the two.

17. Step 1 includes: If the height value of the ultrasonic signal in the sensing signal is S_amp, the height value S_amp of the ultrasonic signal is compared with a first threshold value Thd_samp. If S_amp is less than Thd_samp, the ultrasonic sensing element is unavailable. When the S_amp value is higher than Thd_samp, the change in the peak time of the ultrasound 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 T_sft in the peak time of the ultrasonic signal is compared with a second threshold Thd_Tsft. If T_sft is less than Thd_Tsft, the ultrasonic sensing element is unavailable. If T_sft is higher than Thd_Tsft, the ultrasonic sensing element is available.

17. The method for detecting a failure of a sensor for measuring the quality of a urea solution according to claim 16, wherein the condition for determining the availability of the impedance sensing element includes detecting whether the impedance sensing signal exceeds a maximum boundary measurement value or a minimum boundary measurement value: if the impedance sensing signal is higher than the maximum boundary measurement value or lower than the minimum boundary measurement value, the impedance sensor element is unavailable; otherwise, the impedance sensor element is available.

18. Step 2 includes the following: If the urea concentration of the urea solution calculated using ultrasound is QU_conc and the urea concentration of the urea solution calculated using impedance is QI_conc, calculate the difference DEF_Diff between them: DEF_Diff=abs(QI_conc-QU_conc) abs() is an absolute value calculation, and if the DEF_Diff value is higher than the third threshold Thd_Ddiff, it is determined that a sensor IR failure alarm has occurred; otherwise, it is determined that a sensor IR failure has not occurred.

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