Methanol-resistant fuel vehicle original vehicle adaptation type magnetic induction liquid level sensor and preparation method

Abstract

The application discloses a kind of methanol fuel resistant original vehicle adaptation type magnetic induction liquid level sensor and preparation method, belong to automobile fuel sensor technical field, the method includes: retaining original vehicle float ball, connecting rod, support mechanical assembly, at the original carbon film slide position assembly by magnet and magnetic sensitive element constitute non-contact sensing module;All metal contact points are treated with ≥1.0 μm pure gold plating, and electrochemical corrosion is blocked;Cable introduction end uses fluorosilicone glue to carry out capillary sealing;Overall is completely filled with methanol-resistant epoxy potting adhesive and is completely filled;Through the adjustable resistance calibration output resistance characteristics, so that it is matched with original vehicle ECU error ≤±2%;And 1000 hours methanol power immersion and 50V / m electromagnetic interference test verify reliability, finally form the full sealing module of "plug and play" replacement original sensor.The application solves the serious corrosion problem of methanol fuel to traditional carbon film sensor, without changing the whole vehicle circuit, installation time is less than 15 minutes, service life is increased by more than 10 times, is suitable for M85, M100 high proportion methanol fuel automobile, with high precision, low cost, high reliability advantage.

Description

Technical Field

[0001] This invention belongs to the field of automotive fuel level sensor technology, specifically relating to a magnetic induction level sensor and its manufacturing method that can directly reuse the original vehicle's mechanical structure, requires no modification to the vehicle's circuitry, possesses extreme resistance to methanol corrosion and strong anti-electromagnetic interference capabilities. Background Technology

[0002] With the promotion of methanol-fueled vehicles in the new energy field, the failure problem of traditional fuel vehicle liquid level sensors in methanol environments is becoming increasingly prominent. Most existing mainstream sensors use a carbon film sliding rheostat structure. The copper, iron, tin, and other metal components inside form a galvanic cell with methanol under a 12V / 24V supply voltage, causing severe electrochemical corrosion. This typically leads to resistance drift, open circuits, and signal loss within weeks to months. Current solutions use a complete replacement methanol-resistant sensor, but these generally have the following drawbacks: complex installation: requiring disassembly of the fuel tank and modification of the flange interface, resulting in poor compatibility and high after-sales costs; signal incompatibility: the output is voltage or digital, requiring the addition of a signal conversion module, which can disrupt the original vehicle ECU logic and cause false alarms or false alarms; low accuracy: using reed switches or infrared non-contact solutions results in large hysteresis and poor repeatability; unresolved penetration problem: methanol has strong permeability, and ordinary potting materials are prone to swelling and cracking, leading to continued internal corrosion.

[0003] Therefore, there is an urgent need for a new type of liquid level sensor solution that can reuse the original vehicle structure, fundamentally block the corrosion path, and has 100% signal compatibility with the original vehicle system. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for preparing a methanol-resistant, vehicle-compatible magnetic induction level sensor and, based on this method, to obtain a highly reliable sensor product, achieving the following objectives: In-situ replacement: Complete reuse of the original vehicle's float, connecting rod, and bracket, without disassembling the fuel tank; Zero corrosion: Multiple physical isolation is achieved through gold plating + capillary sealing + alcohol-resistant potting; Signal compatibility: Outputs an analog resistance signal, requiring no software or hardware changes to the ECU; Strong anti-interference: Signal fluctuation ≤ ±1%FS under strong electromagnetic environments such as fuel pump start-stop; Long lifespan: Functionally normal after 1000 hours of methanol immersion test; Low cost: Material costs are reduced by more than 80% compared to a complete replacement solution.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: A method for fabricating a methanol-fuel-resistant, original-vehicle-compatible magnetic induction liquid level sensor includes the following steps: S1. Retain and reuse original vehicle mechanical components: Retain the float, metal connecting rod, shaft and mounting bracket in the original vehicle fuel system as mechanical drive components for liquid level detection, without making any material or structural modifications. S2. Assemble a non-contact magnetic induction sensing module: Fix the magnet to the moving end of the original vehicle connecting rod, integrate the magnetic sensing element and signal conditioning circuit on the ceramic substrate, and install the module at the original carbon film slider position of the original vehicle bracket so that when the magnet moves up and down with the float, its magnetic field change is sensed by the magnetic sensing element without contact. S3. Full gold plating protection for key metal components: Electroplating is performed on the pins of magnetic sensitive elements, circuit board solder joints, connecting wire terminals and all metal conductors in contact with the external environment. The plating is pure gold with a thickness of ≥1.0μm to completely block the electrochemical corrosion path between methanol fuel and copper, iron and tin substrates. S4. Capillary sealing at the cable inlet: In the solder joint area between the sensor output cable and the circuit board, use methanol-resistant fluorosilicone or fluororubber potting compound for local potting to fill the gaps between the cable sheath and the circuit board, eliminating the channels for methanol to penetrate capillarily along the wires. S5. Overall potting protection: The assembled electronic module is placed into the protective shell and injected with high-density epoxy resin potting compound that is resistant to methanol corrosion. The volume change rate of the potting compound after immersion in M100 methanol fuel for 72 hours is ≤0.3%, and there is no cracking, no bubbling, and no change in conductivity. S6. External Resistor Matching and Characteristic Calibration: Before potting, the equivalent resistance value of the sensor output is adjusted by using an external adjustable resistor network to ensure that the fitting error between the resistance-liquid level curve and the original ECU preset characteristic curve is ≤±2% within the 0% to 100% liquid level range. S7. Composite environment aging and anti-interference verification: The finished sensor was subjected to an accelerated aging test of 1000 hours of continuous power supply (12V) and immersion in M100 methanol fuel. At the moment of oil pump start-up, a broadband electromagnetic interference of 50V / m and 100MHz~1GHz was applied. The output signal fluctuation did not exceed ±1%FS and there was no reset or signal loss. S8. Solidification and Encapsulation: After calibration and testing, the protective housing is finally sealed and solidified to form a completely sealed, non-removable, and non-repairable sensor unit, enabling "plug-and-play" replacement of the original vehicle.

[0006] As a preferred embodiment, the ceramic substrate in step S2 is alumina ceramic or aluminum nitride ceramic, and its coefficient of thermal expansion is matched with that of the gold plating layer within 5 ppm / ℃.

[0007] As a preferred embodiment, the methanol-resistant potting compound in step S4 is a two-component addition-type fluorosilicone with a dielectric constant ≤3.2 and a volume resistivity ≥1×10⁻⁶.14 Ω·cm.

[0008] As a preferred embodiment, the magnetic sensing element in step S2 is a Hall effect sensor or a magnetoresistive sensor with a response frequency ≥1kHz; the magnet is a sintered neodymium iron boron magnet with a magnetic energy product ≥40MGOe and its surface is treated with a three-layer electroplating process of nickel, copper, and nickel for corrosion protection; the signal conditioning circuit includes a low-pass filter circuit, a voltage follower, and a temperature compensation module to eliminate the influence of ambient temperature on the output of the magnetic sensing element.

[0009] As a preferred embodiment, the external adjustable resistor network in step S6 is a ten-turn precision potentiometer with an adjustment accuracy of 0.5Ω.

[0010] As a preferred embodiment, the electromagnetic interference simulation in step S7 conforms to the ISO 11452-2 standard.

[0011] As a preferred embodiment, the protective housing is made of methanol-resistant ABS or polyphenylene sulfide PPS material, with a wall thickness ≥1.5mm and an IP67 protection rating.

[0012] This invention also provides a methanol-resistant, vehicle-compatible magnetic induction level sensor prepared by the above-described process. It includes a mechanical drive component consisting of a float, connecting rod, and bracket, and an electronic module consisting of a ceramic substrate, magnetic sensitive element, magnet, steel wire magnetic circuit bracket, external adjustable resistor, gold-plated conductor, alcohol-resistant potting compound, and a sealed housing. The electronic module is directly mounted on the original carbon film slider position of the original vehicle bracket via a mechanical adaptation structure. Its output is a two-wire analog resistance signal with a resistance range consistent with the requirements of the original vehicle ECU.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: Completely solves corrosion problems and achieves ultra-long lifespan: Through triple isolation of "gold plating + capillary sealing + alcohol-resistant potting", physical isolation is achieved between methanol and all metal conductors, solder joints, and circuit boards, completely blocking the electrochemical corrosion path. After 1000 hours of methanol immersion test, there was no corrosion and no resistance drift.

[0014] Seamless compatibility with original vehicles: The output is a standard analog resistance signal (such as 0-90Ω, 0-240Ω, etc.), without the need to replace the ECU, instrument panel or add conversion module. The installation time is ≤15 minutes and it is applicable to more than 95% of original vehicle platforms.

[0015] High precision and high repeatability: Non-contact magnetic induction measurement, no mechanical wear, repeatability error <±1%, far superior to carbon film slider (±3%).

[0016] Strong anti-interference capability: The circuit adopts a low-pass filter + shielding design and has passed the ISO 11452-2 standard 50V / m electromagnetic interference test, ensuring signal stability.

[0017] Significant cost advantages: By reusing original vehicle mechanical parts and only replacing electronic modules, material costs are reduced by more than 80% and maintenance costs by 90%.

[0018] The process is highly replicable: the entire process is standardized, the parameters are clear, and it is easy to promote industrialization.

[0019] High reliability: Multiple sealing and anti-interference design ensure stable operation under vehicle vibration and complex electromagnetic environment.

[0020] The core innovations of this invention are as follows: A. Modular Reusable Structure: An electronic module adapted to the original vehicle bracket. This module can be directly fixed to the original vehicle bracket, replacing the original carbon film sliding plate assembly.

[0021] B. Multiple depth sealing processes To address the extremely high permeability and swelling properties of methanol, a "quadruple protection" system is employed: 1. Level 1 protection (substrate): Select a ceramic or a circuit board that cannot be swollen or corroded by methanol.

[0022] 2. Secondary protection (parts and solder joints): sensor (gold-plated), leg corners (gold-plated), lead wires (gold-plated), solder joints (silver).

[0023] 3. Level 3 protection (lead wire): The cable entry end is sealed with alcohol-resistant adhesive to prevent methanol from penetrating along the cable via capillary action.

[0024] 4. Overall potting: A type of adhesive resistant to methanol swelling and corrosion is used for overall potting.

[0025] C. Anti-interference magnetic induction circuit system 1. Magnetic sensing element (non-contact data readout) 2. Magnetic circuit design: The steel wire support, magnetic sensitive element, and magnet lead are used to form the circuit.

[0026] 3. Depending on the resistance value of the component, an external matching resistor is used to solve the problem of universal compatibility. D. Adjustable external resistor design: Given the wide variety of car models on the market and the inconsistent original resistance values, this design allows for adjustment and matching using an external adjustable resistor, making it highly versatile. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments thereof.

[0028] Example 1: Taking the original liquid level sensor of a certain M100 methanol fuel car as an example, its original carbon film rheostat specifications are: 240Ω resistance at 0% liquid level, 30Ω resistance at 100% liquid level, and 5V power supply voltage for ECU.

[0029] Step S1: Remove the original vehicle fuel tank cover, keeping the original float, connecting rod, and bracket.

[0030] Step S2: Fix a neodymium iron boron magnet with a diameter of 6mm and a magnetic energy product of ≥40MGOe at the bottom of the connecting rod; install a custom ceramic substrate module at the original carbon film slider position, integrate a Hall effect magnetic sensitive element (model: SS49E) on the substrate, and solder the signal conditioning circuit, including operational amplifier, filter capacitor and output buffer.

[0031] Step S3: Electroplating is performed on the magnetic sensitive element pins, circuit board pads, and copper wire terminals using a pulse electroplating process. The plating layer is 99.99% pure gold with a thickness of 1.2μm.

[0032] Step S4: Apply fluorosilicone (model: Dow Corning 1-4013) to the outside of the cable-to-substrate solder joint for localized potting, with a thickness ≥2mm. After curing, an elastic sealing layer is formed.

[0033] Step S5: Install the entire electronic module into the ABS protective housing, inject two-component epoxy potting compound (model: 3MScotch-Weld DP420), covering all components, and cure at room temperature for 24 hours; after a 72-hour M100 immersion test, the volume change rate is 0.18%, with no expansion or cracking.

[0034] Step S6: Connect the standard resistance box and adjust the external adjustable resistor so that the output resistance is 240Ω±2Ω at 0% liquid level and 30Ω±1Ω at 100% liquid level. After calibration, lock the resistance value.

[0035] Step S7: Immerse the entire sensor in M100 methanol solution and continuously power it at 12V for 1000 hours. During this period, measure the output resistance every 24 hours, with a maximum drift of ≤0.5Ω; then apply 50V / m electromagnetic interference (frequency band 100MHz-1GHz) at the moment of oil pump startup, with signal fluctuation ≤0.8%FS and no jumps.

[0036] Step S8: Apply adhesive to the top of the housing and seal it to complete the final encapsulation.

[0037] After installation in the vehicle, the instrument display accuracy was ±0.5%, and it ran continuously for 365 days without failure, far exceeding the average failure cycle of the original carbon film sensor, which was 3 months.

[0038] Example 2: Applicable to 24V systems in commercial vehicles, with original vehicle resistance ranging from 0-180Ω. The process steps are the same; only the magnet strength, the sensitivity of the magnetic element, and the resistance range of the external resistor need to be adjusted to achieve cross-platform compatibility.

[0039] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a methanol-fuel-resistant, original-vehicle-compatible magnetic induction liquid level sensor, characterized in that, The process includes the following steps: S1. Retain and reuse original vehicle mechanical components: Retain the float, metal connecting rod, shaft and mounting bracket in the original vehicle fuel system as mechanical drive components for liquid level detection, without material or structural modification; S2. Assemble a non-contact magnetic induction sensing module: Fix the magnet to the moving end of the original vehicle connecting rod, integrate the magnetic sensing element and signal conditioning circuit on the ceramic substrate, and install the module at the original carbon film slider position of the original vehicle bracket so that when the magnet moves up and down with the float, its magnetic field change is sensed by the magnetic sensing element without contact. S3. Full gold plating protection for key metal components: Electroplating is applied to the pins of the magnetic sensitive element, the solder joints of the circuit board, the terminals of the connecting wires, and all metal conductors that come into contact with the external environment to completely block the electrochemical corrosion path between methanol fuel and copper, iron, and tin substrates. S4. Capillary sealing at the cable inlet: In the solder joint area between the sensor output cable and the circuit board, use methanol-resistant fluorosilicone or fluororubber potting compound for local potting to fill the gaps between the cable sheath and the circuit board, eliminating the channels for methanol to penetrate capillarily along the wires. S5. Overall potting protection: The assembled electronic module is placed into the protective housing and injected with high-density epoxy resin potting compound that is resistant to methanol corrosion. S6. External Resistor Matching and Characteristic Calibration: Before potting, the equivalent resistance value of the sensor output is adjusted by an external adjustable resistor network so that the fitting error between the resistance-liquid level curve and the original ECU preset characteristic curve is ≤±2% within the 0% to 100% liquid level range. S7. Composite environment aging and anti-interference verification: The finished sensor was subjected to an accelerated aging test of 1000 hours of continuous immersion in M100 methanol fuel. At the moment of oil pump start-up, a broadband electromagnetic interference of 50V / m and 100MHz~1GHz was applied. The output signal fluctuation did not exceed ±1%FS and there was no reset or signal loss. S8. Solidification and Encapsulation: After calibration and testing, the protective housing is finally sealed and solidified to form a completely sealed, non-removable, and non-repairable sensor unit, enabling "plug-and-play" replacement of the original vehicle.

2. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The ceramic substrate in step S2 is alumina ceramic or aluminum nitride ceramic, and its coefficient of thermal expansion is within 5 ppm / ℃, matching that of the gold plating layer.

3. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The methanol-resistant potting compound used in step S4 is a two-component addition-curing fluorosilicone with a dielectric constant ≤3.2 and a volume resistivity ≥1×10⁻⁶. 14 Ω·cm.

4. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The electroplating layer in step 3 is pure gold, and the layer thickness is greater than 1.0 μm.

5. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, In step 5, the volume change rate of the potting compound after immersion in M100 methanol fuel for 72 hours is ≤0.3%, and there is no cracking, no bubbling, and no change in conductivity.

6. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The magnetic sensing element in step S2 is a Hall effect sensor or a magnetoresistive sensor with a response frequency ≥1kHz; the magnet is a sintered neodymium iron boron magnet with a magnetic energy product ≥40MGOe and its surface is treated with a three-layer electroplating process of nickel, copper, and nickel for corrosion protection; the signal conditioning circuit includes a low-pass filter circuit, a voltage follower, and a temperature compensation module to eliminate the influence of ambient temperature on the output of the magnetic sensing element.

7. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The external adjustable resistor network in step S6 is a ten-turn precision potentiometer with an adjustment accuracy of 0.5Ω.

8. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The electromagnetic interference simulation in step S7 conforms to the ISO 11452-2 standard.

9. The method for preparing the methanol-resistant, original vehicle-compatible magnetic induction liquid level sensor according to claim 1, characterized in that, The protective housing is made of methanol-resistant ABS or polyphenylene sulfide PPS material, with a wall thickness ≥1.5mm and an IP67 protection rating.

10. A methanol-resistant, vehicle-compatible magnetic induction liquid level sensor prepared by the method according to any one of claims 1-9, characterized in that, The system includes a mechanical drive component consisting of the original vehicle float, connecting rod, and bracket, and an electronic module consisting of a ceramic substrate, magnetic sensitive element, magnet, steel wire magnetic circuit bracket, external adjustable resistor, gold-plated conductor, alcohol-resistant potting compound, and sealed housing. The electronic module is directly installed on the original carbon film slider position of the original vehicle bracket through a mechanical adapter structure. The output terminal is a two-wire analog resistance signal with a resistance range consistent with the requirements of the original vehicle ECU.