Urea pressure sensor

Abstract

The invention provides a urea pressure sensor, which relates to the technical field of pressure sensors and comprises a signal processing module, a pressure sensitive assembly, a sealing ring assembly, a pouring sealant layer, a cover plate and a shell. According to the pressure sensitive assembly, a silicon strain gauge and an elastic body are integrated through the glass micro-melting technology, and multiple sealing is formed through cooperation of a sealing ring, a pouring sealant layer and an annular glue groove in a shell. And the signal processing module is provided with an integrated circuit which is integrated with a sectional temperature compensation circuit with adaptive parameter updating and error closed-loop correction, and a signal processing chip which realizes resistance and voltage conversion, low-noise amplification and standardized output with signal type adaptive switching. The urea corrosion resistance and stability are improved through multiple sealing, the wide temperature range detection precision is guaranteed through temperature compensation and signal self-adaptive switching of an integrated circuit, external equipment is adapted, and the pressure monitoring requirement of a selective catalytic reduction system is met.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, and more particularly to a urea pressure sensor. Background Technology

[0002] With the full implementation of vehicle emission regulations, commercial vehicles such as diesel and hybrid vehicles are generally equipped with selective catalytic reduction (SCR) systems to control nitrogen oxide emissions. As a core sensing component of the SCR system, the urea pressure sensor needs to collect real-time working pressure data within the urea pipeline. On one hand, this sensor works with the electronic control unit to precisely adjust the urea injection quantity, avoiding urea waste due to over-injection or excessive emissions due to under-injection. On the other hand, it provides diagnostic signals for abnormal operating conditions such as urea passage blockage and pump malfunction, directly determining the emission reduction efficiency of the SCR system and the vehicle's operational compliance.

[0003] However, existing urea pressure sensors have significant technical shortcomings: First, the design of the fixing and sealing structure between the pressure-sensitive element and the housing is unreasonable. Traditional sensors often rely on a single sealing ring, which is prone to aging and failure during long-term use, leading to urea residue clogging the interface. Insufficient potting process can also allow moisture to enter the internal circuitry, severely affecting the sensor's corrosion resistance and sealing performance, making it difficult to adapt to the highly corrosive conditions of urea solutions. Second, the integrated circuit performance of the signal processing module is insufficient, the temperature compensation logic is simple, and it cannot effectively counteract temperature interference with the pressure signal over a wide temperature range. Furthermore, the signal output lacks an adaptive switching mechanism. Therefore, it is necessary to provide a urea pressure sensor that solves the above technical problems. Summary of the Invention

[0004] This invention provides a urea pressure sensor to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides a urea pressure sensor, including a signal processing module, a pressure-sensitive component, a sealing ring assembly, a potting compound layer, a cover plate, and a housing;

[0006] The pressure-sensitive component is centrally located within the housing cavity. The pressure-sensitive component consists of a hollow elastomer and a silicon strain gauge within the cavity, with a sealing ring from the sealing ring assembly fitted onto the lower end of the elastomer.

[0007] The potting compound layer is placed between the pressure-sensitive component and the inner wall of the housing, and is lower than the upper end face of the elastomer, forming a secondary seal between the pressure-sensitive component and the housing;

[0008] The cover is located on the top of the housing. Another sealing ring of the sealing ring assembly is located near the port at the lower end of the housing. The inner cavity of the cover is hollowed out and has a PIN pin placement port and a power interface. A PIN pin is configured in the PIN pin placement port, and one end of the PIN pin is in contact with the power interface.

[0009] The signal processing module is located above the pressure-sensitive component, with its lower surface facing the upper end of the pressure-sensitive component. The signal processing module has a hollow center, and its upper surface has a solder pad. A connecting wire is soldered to this solder pad, which is electrically connected to the pressure-sensitive component on the bottom surface. A protective cover is attached to the hollow part of the upper surface. The signal processing module has an integrated circuit and a fisheye-shaped power input terminal. The integrated circuit has a signal processing chip and a temperature compensation circuit, which are used to convert the original pressure signal into an electrical signal and to compensate for the influence of ambient temperature on accuracy, respectively.

[0010] Preferably, the temperature compensation circuit on the integrated circuit adopts segmented dynamic temperature compensation logic, as follows:

[0011] The circuit has multiple preset temperature ranges covering the sensor's operating temperature range. Each temperature range corresponds to a unique linear compensation parameter and a nonlinear compensation parameter. The temperature compensation circuit also has a built-in ambient temperature acquisition component to obtain the sensor's operating temperature in real time.

[0012] When the temperature compensation circuit is working, the real-time temperature is first acquired through the ambient temperature acquisition component. Then, the temperature-urea pressure sensor-urea pressure sensor compensation parameter mapping relationship pre-stored in the integrated circuit is called to determine the temperature range to which the real-time temperature belongs and the corresponding linear compensation parameters and nonlinear compensation parameters. Subsequently, based on the pre-processed electrical signal output by the signal processing chip, the temperature-compensated electrical signal is obtained through the compensation calculation logic containing linear correction terms and nonlinear correction terms. The pre-processed electrical signal is the electrical signal formed after the signal processing chip performs a preliminary conversion on the original pressure signal output by the pressure-sensitive component. The compensation calculation logic is used to offset the influence of environmental factors on the accuracy of the electrical signal at different temperatures.

[0013] As a preferred embodiment, the signal processing chip on the integrated circuit performs the following specific steps to convert the raw pressure signal into an electrical signal:

[0014] Step 1, Resistance Change to Voltage Signal Conversion: Receive the resistance change of the silicon strain gauge in the pressure-sensitive component due to the pressure of the urea medium. Based on the bridge structure formed by the silicon strain gauge, convert the resistance change into the original voltage signal according to the bridge signal conversion rules. The bridge structure is specifically a circuit structure that can realize the conversion of resistance change into voltage signal, and the bridge signal conversion rules are matched to the signal output characteristics of the bridge structure.

[0015] Step 2, Voltage Signal Amplification: The original voltage signal is amplified by the low-noise amplification component built into the signal processing chip to obtain the amplified electrical signal;

[0016] Step 3, Voltage signal to standardized output signal conversion: The amplified electrical signal is filtered and standardized sequentially to obtain a standardized electrical signal that can be output. The standardization conversion is based on two sets of parameters: one set is the extreme value range of the amplified electrical signal, where the extreme value range corresponds to the signal change interval from the lower limit to the upper limit of the pressure sensitive component; the other set is the preset output voltage range of the sensor. The amplified electrical signal is converted into a standardized electrical signal that matches the output voltage range through signal amplitude mapping logic.

[0017] Preferably, the integrated circuit also includes a non-volatile memory component for storing linear compensation parameters and nonlinear compensation parameters of the temperature compensation circuit, as well as bridge power supply parameters of the signal processing chip, reference resistance parameters of the silicon strain gauge, amplification parameters of the low-noise amplification component, extreme parameters of the amplified electrical signal, and extreme parameters of the sensor output voltage range. The above parameters can be updated by external configuration commands.

[0018] Preferably, the inner wall of the housing is provided with an annular step at the mating point with the pressure-sensitive component, the radial dimension of which is adapted to the outer wall of the elastic body of the pressure-sensitive component; the inner wall of the housing is provided with an annular adhesive groove, which surrounds the outer periphery of the elastic body, and the adhesive injected into the groove forms a continuous circumferential bond with the outer wall of the elastic body; and the lower end of the housing is provided with a through hole adapted to the external urea pump pipeline, which communicates with the inner cavity of the housing.

[0019] Preferably, the circuit board protective coating of the signal processing module is a composite coating that is both moisture-proof and urea-resistant; the hollow structure in the middle of the signal processing module is sized to match the bonding area of ​​the connection line between the pressure-sensitive component and the signal processing module; and the bonding area of ​​the pads on the upper surface of the signal processing module is also coated with protective adhesive.

[0020] Preferably, the cover plate is integrally molded from a high-molecular polymer; the PIN pin placement port inside the cover plate cavity is interconnected with the power interface, the PIN pin is housed in the PIN pin placement port in a contact connection manner, and the axis of the PIN pin is aligned with the axis of the fisheye-shaped power input terminal on the signal processing module.

[0021] Preferably, the segmented dynamic temperature compensation logic of the temperature compensation circuit also integrates an adaptive parameter update mechanism and an error closed-loop correction unit, as detailed below:

[0022] The adaptive parameter update mechanism has a preset calibration cycle, and updates the mapping relationship between temperature and compensation parameters according to the following logic within each calibration cycle:

[0023] The sensor is triggered to enter a preset standard operating condition that includes standard temperature and standard pressure. The pre-processed electrical signal output by the signal processing chip and the compensated electrical signal output by the temperature compensation circuit are collected. The current compensation deviation is obtained by comparing the compensated electrical signal with the preset theoretical standard electrical signal under the standard operating condition. If the compensation deviation exceeds the preset allowable deviation threshold, the linear compensation parameters and nonlinear compensation parameters of the corresponding temperature range are updated according to the preset rules of the adjustment range of the adaptation parameters.

[0024] The error closed-loop correction unit is electrically connected to the output of the temperature compensation circuit. It collects the compensated electrical signal at continuous intervals in real time and calculates the degree of signal fluctuation. If the degree of signal fluctuation exceeds the preset fluctuation allowable threshold, the compensation parameter reloading process is triggered. The newly generated linear compensation parameters and nonlinear compensation parameters are called by the adaptive parameter update mechanism to recalculate the compensated electrical signal.

[0025] Preferably, in the step of converting the voltage signal to a standardized output signal in the signal processing chip, an adaptive switching logic for the output signal type is adopted, as follows:

[0026] The output signal type adaptive switching logic includes: identifying the external device installed on the sensor through signal interaction, and obtaining the signal type identification information sent by the external device during the initial connection;

[0027] The preset output signal type configuration parameters determine the target signal type required by the external device, including analog or digital signals, based on the matching of the signal type identification information of the external device with the preset output signal type configuration parameters.

[0028] If the target signal type is an analog signal, the amplified electrical signal range corresponding to the lower and upper detection limits of the pressure-sensitive component is compared with the preset standard analog output voltage range. The filtered amplified electrical signal is then converted into a standard analog voltage signal compatible with the external device through linear mapping logic. If the target signal type is a digital signal, the filtered amplified electrical signal is encoded according to the preset standard digital communication protocol and converted into a standard digital signal compatible with the external device.

[0029] Compared with related technologies, the urea pressure sensor provided by the present invention has the following advantages:

[0030] 1. This solution achieves integrated molding of silicon strain gauges and stainless steel elastomers through glass micro-fusion technology, reducing potential interface sealing risks. Combined with structural adhesive in the housing annular groove, elastic potting compound in the component gaps, and sealing rings at both ends, multiple sealing protections are formed, effectively isolating urea medium corrosion and external moisture ingress. It is suitable for the highly corrosive conditions of urea solution, significantly improving the long-term working stability of the sensor and solving the problem of sensor failure due to urea residue blockage and moisture intrusion caused by a single sealing structure.

[0031] 2. The integrated circuit in this solution incorporates segmented temperature dynamic compensation logic with adaptive parameter updates and error closed-loop correction, which can effectively offset the influence of temperature on pressure signals over a wide temperature range. At the same time, the three-level conversion steps of its signal processing chip and the adaptive switching logic of output signal type can accurately process pressure signals and adapt to the signal reception requirements of different external devices, ensuring high accuracy and multi-scenario adaptability of pressure detection, and solving the problem that sensor signal processing is easily affected by temperature interference and is difficult to adapt to different external devices. Attached Figure Description

[0032] Figure 1 An exploded view of the structure of a urea pressure sensor provided by the present invention;

[0033] Figure 2 A cross-sectional view of the housing provided for this invention;

[0034] Figure 3 The cover plate structure diagram provided by the present invention;

[0035] Figure 4 The structural diagram of the pressure-sensitive component provided by the present invention;

[0036] Figure 5 A schematic diagram of the sealing structure of the pressure-sensitive component provided by the present invention;

[0037] Figure 6 This is a schematic diagram of the structure of the upper surface of the signal processing module provided by the present invention;

[0038] Figure 7 This is a schematic diagram of the lower surface of the signal processing module provided by the present invention;

[0039] Figure 8 This is a schematic block diagram of the signal processing module provided by the present invention.

[0040] The following are the labeling elements in the diagram: 1. Housing; 2. Encapsulating layer; 3. Sealing ring assembly; 4. Pressure sensitive component; 41. Silicon strain gauge; 5. Signal processing module; 51. Integrated circuit; 52. Solder pad; 53. Connecting wire; 54. Protective cover; 55. Power input terminal; 6. Cover plate; 7. Annular groove; 8. Elastomer; 9. Annular step; 10. PIN pin placement port; 11. Power interface. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “group,” “class,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0043] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0044] Please refer to the following: Figures 1-8 A urea pressure sensor includes a signal processing module 5, a pressure-sensitive component 4, a sealing ring assembly 3, a potting compound layer 2, a cover plate 6, and a housing 1;

[0045] The pressure-sensitive component 4 is centrally located in the inner cavity of the housing 1. The pressure-sensitive component 4 consists of a hollow elastomer 8 and a silicon strain gauge 41. A sealing ring of the sealing ring component 3 is fitted onto the lower end of the elastomer 8. The housing is integrally molded from PPE PA GF30 material, which is resistant to urea solution corrosion and is not prone to solution adhesion causing blockage.

[0046] The potting compound layer 2 is located between the pressure-sensitive component 4 and the inner wall of the housing 1, and is lower than the upper end face of the elastomer 8, forming a secondary seal between the pressure-sensitive component 4 and the housing 1; wherein the pressure-sensitive component 4 adopts a glass micro-fusion pressure sensor (MSG), which is formed by sintering a silicon strain gauge onto a stainless steel sensitive elastomer 8 under high temperature conditions, and has the characteristics of high pressure detection accuracy, wide operating temperature range, stable structure, and wide media compatibility.

[0047] The cover plate 6 is located on the top of the housing 1. Another sealing ring of the sealing ring assembly 3 is located near the port at the lower end of the housing 1. The inner cavity of the cover plate 6 is hollowed out and has a PIN pin placement port 10 and a power interface 11. A PIN pin is configured in the PIN pin placement port 10, and one end of the PIN pin is in contact with the power interface 11.

[0048] The signal processing module 5 is located above the pressure-sensitive component 4, with its lower surface facing the upper end of the pressure-sensitive component 4. The signal processing module 5 has a hollow center, and its upper surface has a pad 52. The pad 52 is soldered to the pressure-sensitive component 4 via a connecting wire 53 and is electrically connected to the pressure-sensitive component 4 on the bottom surface. A protective cover 54 is attached to the hollow center of the upper surface. The signal processing module 5 has an integrated circuit 51 and a fisheye-shaped power input terminal 55. The integrated circuit 51 has a signal processing chip and a temperature compensation circuit, which are used to convert the original pressure signal into an electrical signal and to compensate for the influence of ambient temperature on accuracy, respectively.

[0049] Specifically, the temperature compensation circuit on the 51 microcontroller employs segmented dynamic temperature compensation logic, as detailed below:

[0050] Multiple temperature ranges are preset to cover the sensor's operating temperature range, and each temperature range corresponds to a unique linear compensation parameter. With nonlinear compensation parameters Furthermore, the temperature compensation circuit has a built-in ambient temperature acquisition component to obtain the sensor's operating temperature T in real time.

[0051] When the temperature compensation circuit is working, it first acquires the real-time temperature T through the ambient temperature acquisition component, and then calls the temperature-compensation parameter mapping relationship pre-stored in the integrated circuit 51 to determine the temperature range to which the real-time temperature T belongs and the corresponding linear compensation parameters for that range. Nonlinear compensation parameters Subsequently, based on the preprocessed electrical signal output by the signal processing chip The temperature-compensated electrical signal is obtained through a compensation calculation logic that includes linear and nonlinear correction terms. The compensation formula is ;in, The preset temperature calibration reference value, This is the electrical signal obtained after the signal processing chip performs a preliminary conversion on the original pressure signal output by the pressure-sensitive component 4; the compensation calculation logic is used to offset the influence of environmental factors on the accuracy of the electrical signal at different temperatures.

[0052] Specifically, the signal processing chip on the 51 microcontroller converts the raw pressure signal into an electrical signal using the following steps:

[0053] Step 1, Resistance Change to Voltage Signal Conversion: Receive the resistance change of the silicon strain gauge 41 in the pressure-sensitive component 4 due to the pressure of the urea medium. Based on the bridge structure composed of silicon strain gauges 41, the resistance change is converted into the original voltage signal through the bridge signal conversion rule. The bridge signal conversion formula is: ;in, The supply voltage for the Wheatstone bridge, This is the reference resistance value of silicon strain gauge 41 when no pressure is applied;

[0054] The bridge circuit structure is specifically a circuit structure that can convert resistance changes into voltage signals, and the bridge signal conversion rules are matched to the signal output characteristics of the bridge circuit structure.

[0055] Step 2, Voltage Signal Amplification: The original voltage signal is amplified using the low-noise amplification component built into the signal processing chip. Amplification is performed to obtain the amplified electrical signal. The formula is A is the preset gain of the low-noise operational amplifier;

[0056] It should be noted that the low-noise amplifier has the function of suppressing signal interference, and the amplification process follows the preset amplification factor rules;

[0057] Step 3, voltage signal to standardized output signal conversion: This involves converting the amplified electrical signal... The signal is then filtered and normalized sequentially to obtain a standardized electrical signal that can be output. The standardized transformation satisfies the following formula ,in This represents the minimum amplified electrical signal value corresponding to when pressure-sensitive component 4 is at the detection lower limit (minimum urea pressure). This represents the maximum amplified electrical signal value corresponding to when pressure-sensitive component 4 is at its detection limit (maximum urea pressure). These are the preset maximum and minimum output voltages for the sensor.

[0058] Specifically, integrated circuit 51 also includes a non-volatile memory component for storing linear compensation parameters and nonlinear compensation parameters of the temperature compensation circuit, as well as bridge power supply parameters of the signal processing chip, reference resistance parameters of the silicon strain gauge 41, amplification parameters of the low-noise amplification component, extreme value parameters of the amplified electrical signal, and extreme value parameters of the sensor output voltage range. The above parameters can be updated by external configuration commands.

[0059] An annular step 9 is provided at the mating point between the inner wall of the housing 1 and the pressure-sensitive component 4. Its radial dimension is adapted to the outer wall of the elastomer 8 of the pressure-sensitive component 4. This step is used to prevent the adhesive from overflowing to the lower end of the elastomer 8 when the potting layer 2 is injected, ensuring that the gap between the lower end of the elastomer 8 and the inner cavity of the housing 1 is not blocked by the potting layer 2. An annular groove 7 is provided on the inner wall of the housing 1. The annular groove 7 surrounds the outer circumference of the elastomer 8. The adhesive injected into the groove forms a continuous circumferential bond with the outer wall of the elastomer 8, thereby achieving axial fixation of the pressure-sensitive component 4 in the inner cavity of the housing 1. Furthermore, a through hole adapted to the external urea pump pipeline is provided at the lower end of the housing 1. This through hole communicates with the inner cavity of the housing 1, allowing the urea medium to enter the inner cavity of the housing 1 through the through hole and act on the elastomer 8 of the pressure-sensitive component 4.

[0060] Specifically, the circuit board protective coating of the signal processing module 5 is a composite coating that is both moisture-proof and urea-resistant, used to isolate moisture and urea vapor that may seep into the inner cavity of the housing 1, preventing the internal circuitry of the signal processing module 5 from getting damp or corroded. The hollow structure in the middle of the signal processing module 5 is sized to fit the bonding area of ​​the connection line 53 between the pressure-sensitive component 4 and the signal processing module 5, used to accommodate the bonding area and prevent the connection line 53 from interfering with other structures of the signal processing module 5. Furthermore, the bonding area of ​​the pads 52 on the upper surface of the signal processing module 5 is also coated with protective adhesive, which, together with the protective cover 54 of the hollow area, forms a double protection for the connection line 53, further enhancing the stability of the connection line 53 bonding and preventing vibration from causing the connection line 53 to fall off or break.

[0061] Specifically, the cover plate 6 is integrally molded from a high-molecular polymer, which has the characteristics of being lightweight and resistant to urea media corrosion. The PIN pin placement port 10 inside the cover plate 6 is interconnected with the power interface 11. The PIN pin is housed in the PIN pin placement port 10 in a contact connection manner, and the axis of the PIN pin is aligned with the axis of the fisheye-shaped power input terminal 55 on the signal processing module 5, ensuring that one end of the PIN pin is in stable contact with the power interface 11 and the other end is tightly fitted with the fisheye terminal. When the cover plate 6 is mated with the housing 1, the positioning port on the inner wall of the cover plate 6 cooperates with the positioning structure on the upper end of the housing 1 to achieve precise alignment. Then, the adhesive injected along the mating gap between the two forms a fixation, so that the cover plate 6 forms an axial limit on the signal processing module 5, preventing the signal processing module 5 from shifting inside the housing 1.

[0062] Specifically, the segmented dynamic temperature compensation logic of the temperature compensation circuit also integrates an adaptive parameter update mechanism and an error closed-loop correction unit, as detailed below:

[0063] The adaptive parameter update mechanism presets a fixed calibration period, and updates the temperature-compensation parameter mapping relationship according to the following logic within each calibration period:

[0064] The sensor is triggered to enter a preset standard operating condition, including standard temperature and standard pressure values; the pre-processed electrical signal output by the current signal processing chip is acquired. And the compensated electrical signal currently output by the temperature compensation circuit. ;

[0065] Preset theoretical standard electrical signal under preset standard operating conditions The current compensation deviation value is calculated based on the theoretical standard electrical signal and the compensated electrical signal. The formula is ;

[0066] A preset allowable deviation threshold is set. If the current compensation deviation value is greater than the allowable deviation threshold, the linear compensation parameters and nonlinear compensation parameters for the corresponding temperature range are updated using the following parameter adjustment formula: , In the formula, , These are the updated linear compensation parameters and nonlinear compensation parameters, respectively. , These are the corresponding parameters before the update. The temperature value is under standard operating conditions. The preset temperature calibration reference value, , A preset coefficient to accommodate the adjustment range of parameters;

[0067] The error closed-loop correction unit is electrically connected to the output of the temperature compensation circuit, and the compensated electrical signals at two consecutive adjacent time points are acquired in real time. and Calculate signal fluctuation The formula is A preset fluctuation tolerance threshold is set. If the signal fluctuation exceeds the preset threshold, the compensation parameter reloading process is triggered, and the adaptive parameter update sub-mechanism is invoked to update the latest generated parameter. , The compensated electrical signal is recalculated to ensure the stability of the compensated signal across the entire operating temperature range;

[0068] It should be noted that the calibration cycle, standard operating condition parameters, allowable deviation threshold, allowable fluctuation threshold, and parameter adjustment rules are all pre-stored in the non-volatile memory component of integrated circuit 51 and can be updated through external configuration commands to adapt to the temperature compensation requirements of different usage scenarios.

[0069] Specifically, in the step of converting voltage signals to standardized output signals in the signal processing chip, adaptive switching logic for output signal types is adopted, as follows:

[0070] The output signal type adaptive switching logic includes: identifying the external device installed on the sensor (i.e., the signal receiving device of the selective catalytic reduction system (SCR), such as the SCR system control unit or monitoring module) through signal interaction, and obtaining the signal type identification information sent by the external device at the time of initial connection;

[0071] The preset output signal type configuration parameters determine the target signal type required by the external device, including analog or digital signals, based on the matching of the signal type identification information of the external device with the preset output signal type configuration parameters.

[0072] If the target signal type is an analog signal, the amplified electrical signal range corresponding to the detection lower limit to detection upper limit of the pressure-sensitive component 4 is compared with the preset standard analog output voltage range. The filtered amplified electrical signal is then converted into a standard analog voltage signal adapted to the external device through linear mapping logic. If the target signal type is a digital signal, the filtered amplified electrical signal is encoded according to the preset standard digital communication protocol and converted into a standard digital signal adapted to the external device. It should be noted that the output signal type configuration parameters, standard analog output voltage range, and preset standard digital communication protocol are all pre-stored in the non-volatile storage component of integrated circuit 51 and can be updated through external configuration commands to adapt to the needs of different SCR system signal receiving devices.

[0073] The present invention provides a method for preparing a urea pressure sensor as follows:

[0074] Pressure-sensitive component fabrication: Using glass micro-melting (MSG) technology, silicon strain gauge 41 and hollow stainless steel elastomer 8 are sintered together with a glass medium at high temperature to form an integrated pressure-sensitive component 4. Subsequently, a sealing ring of sealing ring component 3 is fitted onto the lower end of the elastomer 8.

[0075] Housing assembly and sealing: The prepared pressure-sensitive component 4 is placed in the inner cavity of the housing 1, which is integrally molded from PPEPAGF30 material, so that the component is adapted to the annular step 9 on the inner wall of the housing; urea-resistant structural adhesive is injected into the annular groove 7 on the inner wall of the housing 1, and at the same time, elastic potting adhesive is injected into the gap between the pressure-sensitive component 4 and the inner wall of the housing 1, and the height of the potting adhesive is controlled to be lower than the upper end face of the elastomer 8 to form a potting adhesive layer 2. After the adhesive layer cures, the component is fixed and a secondary seal is achieved.

[0076] Signal processing module assembly: The signal processing module 5, which has an integrated circuit 51 and a fisheye-shaped power input terminal 55, is placed above the pressure-sensitive component 4. The silicon strain gauge 41 of the pressure-sensitive component 4 is bonded to the pad 52 of the signal processing module 5 through the connecting wire 53 (such as gold wire or aluminum wire). Protective glue is applied to the bonding area, and a protective cover 54 is attached to the hollowed-out part in the middle of the signal processing module 5.

[0077] Cover plate fixing and circuit conduction: The cover plate 6, which is integrally molded from a high-molecular polymer, is adapted to the upper positioning structure of the housing 1 through the positioning port on the inner wall, so that one end of the PIN pin in the PIN pin placement port 10 on the cover plate 6 contacts the power interface 11 and the other end is aligned with the fisheye-shaped power input terminal 55 of the signal processing module 5; adhesive is injected along the joint between the cover plate 6 and the housing 1, and the fixation is achieved after the adhesive cures. At the same time, another sealing ring of the sealing ring assembly 3 is fitted at the lower end of the housing 1 near the port, thus completing the overall fabrication of the urea pressure sensor.

[0078] The working principle of the urea pressure sensor provided by this invention is as follows:

[0079] First, place the PIN pin inside the cover plate 6 into the PIN pin inside the port 10. One end of the PIN pin is in contact with the external power interface 11 and connected. The other end is precisely connected to the fisheye-shaped power input terminal 55 on the signal processing module 5 (the axis of the PIN pin is aligned with the axis of the fisheye terminal). This sequentially forms a complete power supply path for the external power supply, power interface 11, PIN pin, fisheye terminal 55, and integrated circuit 51, providing a stable operating voltage for the integrated circuit 51 of the signal processing module 5 and the silicon strain gauge 41 bridge of the pressure sensitive component 4, ensuring that each component is in an operational state.

[0080] The through hole at the lower end of the housing 1 is connected to the external urea pump pipeline. The urea medium enters the inner cavity of the housing 1 through the through hole and directly acts on the elastic body 8 of the pressure sensitive component 4.

[0081] Since the pressure-sensitive component 4 adopts glass micro-fusion (MSG) technology, the silicon strain gauge 41 is sintered onto the upper surface of the elastomer 8 through high-temperature glass sintering. When urea pressure is applied to the elastomer 8, the elastomer 8 produces a deformation proportional to the pressure, which drives the silicon strain gauge 41 on the surface to deform synchronously. The resistance value of the silicon strain gauge 41 changes with the deformation. The greater the pressure, the greater the change in resistance, thus realizing the physical signal conversion of urea pressure, elastomer deformation, and silicon strain gauge resistance change.

[0082] In the integrated circuit 51 of the signal processing module 5, the silicon strain gauge 41 forms a bridge structure, such as a Wheatstone bridge, that can realize resistance-to-voltage conversion. The output characteristics of this bridge are adapted to the resistance change of the silicon strain gauge 41.

[0083] Resistance to voltage conversion: The change in resistance of silicon strain gauge 41 causes the bridge circuit to become unbalanced, and the output is the original voltage signal that is proportional to the change in resistance.

[0084] Low-noise amplification: The signal processing chip of the integrated circuit 51 has a built-in low-noise amplification component, which amplifies the weak original voltage signal to obtain an amplified electrical signal with a larger amplitude that is easier to process later. At the same time, it suppresses electromagnetic interference in the vehicle environment to ensure signal purity.

[0085] The temperature compensation circuit of the integrated circuit 51 acquires the sensor's operating temperature in real time through a built-in ambient temperature acquisition component, and optimizes the signal by combining it with segmented dynamic temperature compensation logic.

[0086] The temperature compensation circuit calls the temperature and compensation parameter mapping relationship pre-stored in the non-volatile storage component, and determines the temperature range and corresponding linear / nonlinear compensation parameters based on the real-time temperature.

[0087] Based on the preprocessed electrical signal (amplified but uncompensated electrical signal) output by the signal processing chip, temperature correction is performed on the electrical signal through calculation logic that includes linear correction terms and nonlinear correction terms to obtain a compensated electrical signal that cancels out the temperature effect.

[0088] If the fluctuation of the compensated electrical signal exceeds the preset threshold, the error closed-loop correction unit triggers the reloading of the compensation parameters to ensure stable signal accuracy over a wide temperature range.

[0089] The amplified and compensated electrical signal then enters the voltage signal to standardized output signal conversion stage of the signal processing chip.

[0090] Filtering: The compensated electrical signal is filtered to further remove residual noise and ensure signal stability;

[0091] Standardization conversion: Based on two sets of preset parameters (the range of amplified electrical signals corresponding to the extreme values ​​detected by the pressure-sensitive component 4 and the preset output voltage range of the sensor), the filtered electrical signal is converted into a standardized electrical signal through signal amplitude mapping logic.

[0092] Signal type adaptive switching: If an external device (such as an SCR system control unit) sends signal type identification information during initial connection, the output signal type adaptive switching logic will match the preset configuration parameters and convert the standardized electrical signal into an appropriate analog or digital signal, which will then be output to the external device to provide accurate pressure data for urea injection control and fault diagnosis of the SCR system.

[0093] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0094] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A urea pressure sensor, characterized by The signal processing module (5), the pressure sensitive component (4), the sealing ring assembly (3), the potting adhesive layer (2), the cover plate (6) and the shell (1) are included. The pressure sensitive component (4) is centrally arranged in the inner cavity of the shell (1), and the pressure sensitive component (4) is composed of an elastic body (8) with a hollow inner cavity and a silicon strain gauge (41), and the elastic body (8) is sleeved with one sealing ring of the sealing ring assembly (3) at the lower end. The potting adhesive layer (2) is arranged between the pressure sensitive component (4) and the inner wall of the shell (1) and is lower than the upper end surface of the elastic body (8), thereby forming a secondary seal between the pressure sensitive component (4) and the shell (1). The cover plate (6) is arranged at the top of the shell (1), and the other sealing ring of the sealing ring assembly (3) is arranged at the lower end of the shell (1) near the port, and the inner cavity of the cover plate (6) is hollow and provided with a PIN needle placement port (10) and a power supply interface (11), and the PIN needle placement port (10) is provided with a PIN needle, and one end of the PIN needle is in contact with the power supply interface (11). The signal processing module (5) is arranged above the pressure sensitive component (4), and the lower surface of the signal processing module (5) is arranged opposite to the upper end of the pressure sensitive component (4), and the middle part of the signal processing module (5) is hollow, and the upper surface of the signal processing module (5) is provided with a solder pad (52), and the solder pad (52) is welded on the solder pad (52) through a connecting line (53), and the pressure sensitive component (4) at the bottom is electrically connected, and a protective cover (54) is attached to the upper surface of the signal processing module (5); the signal processing module (5) is provided with an integrated circuit (51) and a fisheye-shaped power input terminal (55), and a signal processing chip and a temperature compensation circuit are arranged on the integrated circuit (51), which are used for converting the pressure original signal into an electric signal and offsetting the influence of environmental temperature on the accuracy.

2. A urea pressure sensor according to claim 1, characterised in that The temperature compensation circuit on the integrated circuit (51) adopts a segmented temperature dynamic compensation logic, which is as follows: A plurality of temperature intervals covering the working temperature range of the sensor are preset, each temperature interval corresponds to a unique linear compensation parameter and a nonlinear compensation parameter, and the temperature compensation circuit is provided with an environmental temperature acquisition component for acquiring the working temperature of the sensor in real time; During the operation of the temperature compensation circuit, the real-time temperature is collected by the environmental temperature acquisition component, and the temperature compensation parameter mapping relationship pre-stored in the integrated circuit (51) is called to determine the temperature interval to which the real-time temperature belongs and the linear compensation parameter and the nonlinear compensation parameter corresponding to the interval, and then based on the pre-processed electric signal output by the signal processing chip, the compensation calculation logic containing the linear correction term and the nonlinear correction term is used to obtain the temperature-compensated electric signal; wherein the pre-processed electric signal is the electric signal formed after the signal processing chip converts the pressure original signal output by the pressure sensitive component (4), and the compensation calculation logic is used to offset the influence of environmental factors on the accuracy of the electric signal at different temperatures.

3. A urea pressure sensor according to claim 1, characterised in that The specific steps of converting the pressure original signal into an electric signal by the signal processing chip on the integrated circuit (51) are as follows: Step one, resistance change to voltage signal conversion: receive the resistance change amount of the silicon strain gauge (41) in the pressure sensitive assembly (4) due to the bearing of the urea medium pressure, based on the bridge circuit structure composed of the silicon strain gauge (41), the resistance change amount is converted into the original voltage signal through the bridge signal conversion rule; the bridge circuit structure is a circuit structure that can realize the conversion of resistance change to voltage signal, and the bridge signal conversion rule matches the signal output characteristics of the bridge circuit structure; Step two, voltage signal amplification: the original voltage signal is amplified by the low-noise amplification component built-in the signal processing chip to obtain the amplified electric signal; Step three, voltage signal to standardized output signal conversion: the amplified electric signal is sequentially filtered and standardized to obtain the standardized electric signal which can be output externally; the standardization conversion is realized based on two groups of parameters: one group is the extreme value range of the amplified electric signal, wherein the extreme value range corresponds to the signal change interval from the lower limit to the upper limit of the pressure sensitive assembly (4) detection, and the other group is the output voltage range preset by the sensor, and the amplified electric signal is converted into the standardized electric signal matching the output voltage range through the signal amplitude mapping logic.

4. A urea pressure sensor according to claims 2-3, characterised in that The integrated circuit (51) further comprises a non-volatile storage component for storing the linear compensation parameters and the nonlinear compensation parameters of the temperature compensation circuit, and the bridge power supply parameters, the silicon strain gauge (41) reference resistance parameters, the amplification parameters of the low-noise amplification component, the extreme value parameters of the amplified electric signal, and the extreme value parameters of the sensor output voltage range of the signal processing chip, and the above-mentioned parameters can be updated through external configuration instructions.

5. A urea pressure sensor according to claim 1, wherein The inner wall of the shell (1) is provided with an annular step (9) at the joint with the pressure sensitive assembly (4), and the radial dimension of the annular step (9) is matched with the outer wall of the elastomer (8) of the pressure sensitive assembly (4); the inner wall of the shell (1) is provided with an annular glue groove (7), and the annular glue groove (7) surrounds the outer periphery of the elastomer (8); the adhesive glue injected in the groove forms a circumferential continuous bonding with the outer wall of the elastomer (8); and the lower end of the shell (1) is provided with a through hole matched with the external urea pump pipeline, and the through hole is in communication with the inner cavity of the shell (1).

6. A urea pressure sensor according to claim 1, wherein The protective coating of the circuit board of the signal processing module (5) is a composite coating that is resistant to moisture and urea chemical corrosion; the size of the hollow structure in the middle of the signal processing module (5) is matched with the bonding part of the connecting line (53) between the pressure sensitive assembly (4) and the signal processing module (5); and the bonding part of the solder pad (52) on the upper surface of the signal processing module (5) is also coated with protective glue.

7. A urea pressure sensor according to claim 1, wherein The cover plate (6) is integrally formed by a high molecular polymer; the PIN needle placement port (10) and the power supply interface (11) in the inner cavity of the cover plate (6) are in mutual conduction, the PIN needle is accommodated in the PIN needle placement port (10) in a contact connection mode, and the axis of the PIN needle is aligned with the axis of the fisheye-shaped power input terminal (55) of the signal processing module (5).

8. A urea pressure sensor according to claim 2, wherein The segmented temperature dynamic compensation logic of the temperature compensation circuit also integrates an adaptive parameter updating mechanism and an error closed-loop correction unit, and the specific content is as follows: The adaptive parameter updating mechanism presets a calibration period, and updates the mapping relationship between the temperature and the compensation parameters in each calibration period according to the following logic: The sensor is triggered to enter a preset standard working condition containing a standard temperature and a standard pressure, and the preprocessed electrical signal output by the signal processing chip and the compensated electrical signal output by the temperature compensation circuit at this time are collected; By comparing the compensated electrical signal with the preset theoretical standard electrical signal under the standard working condition, the current compensation deviation is obtained; If the compensation deviation exceeds the preset deviation allowable threshold, the linear compensation parameters and the nonlinear compensation parameters corresponding to the temperature interval are updated according to the preset rule of adaptive parameter adjustment amplitude; The error closed-loop correction unit is electrically connected with the output end of the temperature compensation circuit, and the compensated electrical signal at continuous time is collected in real time, and the signal fluctuation degree is calculated; If the signal fluctuation degree exceeds the preset fluctuation allowable threshold, the compensation parameter reloading process is triggered, the linear compensation parameters and the nonlinear compensation parameters generated by the adaptive parameter updating mechanism are called, and the compensated electrical signal is recalculated.

9. A urea pressure sensor according to claim 3, characterised in that In the step of converting the voltage signal to the standardized output signal in the signal processing chip, the output signal type adaptive switching logic is adopted, and the specific implementation is as follows: The output signal type adaptive switching logic includes: recognizing the external device installed by the sensor through signal interaction, and obtaining the signal type identification information sent by the external device at the initial connection; Preset output signal type configuration parameters are matched with the signal type identification information of the external device to determine the target signal type required by the external device, including an analog signal or a digital signal; If the target signal type is an analog signal, the amplified electrical signal corresponding to the detection lower limit to the detection upper limit of the pressure sensitive component (4) is converted into a standard analog voltage signal adaptive to the external device through linear mapping logic based on the preset standard analog output voltage range; if the target signal type is a digital signal, the filtered amplified electrical signal is encoded according to the preset standard digital communication protocol to convert it into a standard digital signal adaptive to the external device.

Images