A sensor based on coupling of structure and liquid medium and a working method thereof

Abstract

The application provides a sensor based on structure and liquid medium coupling and a working method thereof, and belongs to the technical field of sensors. The sensor comprises an elastic element with an inner cavity, the side of the inner cavity of the elastic element is provided with a MEMS chip, one end of the MEMS chip is connected with a signal line, the other end of the signal line is connected with an external signal receiving device through the elastic element, the inner cavity is filled with a pressure guiding liquid, and the pressure guiding liquid is in contact with a pressure sensing diaphragm of the MEMS chip. The pressure guiding liquid is used for nearly lossless pressure transmission, the pressure acting on the pressure sensing diaphragm of the MEMS is highly consistent with the external pressure, the hysteresis and friction loss of traditional mechanical transmission are avoided, precise and rapid signal sensing is realized, a full-sealed unit is formed through welding and other processes, the internal pressure guiding liquid is not exchanged with the outside, and the stability of the sensor under harsh working conditions such as humidity, oil dirt and high temperature is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a sensor based on the coupling of structure and liquid medium and its working method. Background Technology

[0002] In modern automotive electronic control systems, real-time, high-precision monitoring of key parameters such as force and torque is crucial for ensuring vehicle performance, safety, and emissions. Among these, foil strain gauges, due to their high sensitivity and relatively simple structure, were once widely used for force monitoring in engine, chassis, and transmission systems. However, as automotive electronic systems evolve towards higher safety levels (such as ISO 26262 ASIL-D) and the actual operating environment of vehicles becomes increasingly harsh, foil strain gauges have revealed significant shortcomings in long-term reliability. Especially under conditions involving high temperature, vibration, and humid heat, their failure probability increases significantly, making them unable to meet the current requirements of automotive electronics for sensor lifespan, accuracy, and functional safety. Specific manifestations are as follows: 1. Structural failure mechanism of metal foil strain gauges A typical structure for a metal foil strain sensor includes a metal elastic substrate, strain gauge wires, an epoxy resin adhesive layer, and an external sealing layer. In automotive force monitoring scenarios, the sensor needs to operate continuously under high temperature and high vibration environments (such as the 50–100 Hz / 50 G acceleration vibration conditions specified in SAE J1455). Practical applications show that its main failure modes are concentrated in two aspects: thermal mismatch at the adhesive interface and failure of the sealing layer. 1) Interfacial delamination due to thermal expansion mismatch: The linear expansion coefficient of the metal substrate material is approximately α = 16.5 × 10⁻⁶. -6 / ℃, while the coefficient of linear expansion of the epoxy resin adhesive layer used to fix the strain gauge wire is as high as α=50×10 -6 / ℃. Under high-temperature conditions, the expansion difference between the two is significant, generating continuous thermal stress at the bonding interface. After repeated thermal cycling (e.g., 50℃–120℃, 3000 cycles, according to SAE J1455 Appendix D-3 test method), the interface delamination area can reach 63.2%, leading to decreased strain transfer efficiency and exacerbated zero-point drift. Statistical data shows that this failure mechanism results in the average service life of foil strain sensors in typical automotive environments not exceeding 1800 hours, far below the expected lifespan of critical sensors in ASIL-D level systems.

[0003] 2) Sealing Failure and Signal Drift under Environmental Coupling: Harsh environments such as automotive engine compartments involve multiple coupled factors including vibration, humidity, heat, and fuel vapor. Traditional epoxy or silicone sealants are prone to aging, hardening, or debonding from the substrate under the combined effects of high temperature (85℃) and dynamic loads. Experiments show that under the combined stress of vibration, thermal cycling, and moisture penetration, the debonding rate at the sealant interface can reach 78.4%. Sealing failure directly leads to the intrusion of external media, causing corrosion of the strain gauge wire and a decrease in insulation, manifested as follows: The monitoring signal accuracy fluctuation is ≥ ±8.2% (the industry safety threshold is generally ±3.0%). The signal drift rate exceeds 0.15% / h (safety requirement ≤0.05% / h).

[0004] Such signal anomalies can directly affect the closed-loop control accuracy of the engine electronic control unit (ECU), and may even cause misjudgment of the control strategy, threatening the functional safety of the system.

[0005] 2. Limitations of silicon piezoresistive sensors To improve packaging reliability and environmental adaptability, the industry is gradually introducing silicon piezoresistive sensors, which employ glass micro-fusion sealing technology to achieve hermetic sealing (sealing accuracy >99.9%) between the sensing element and the metal base. This technology achieves this by matching the coefficients of thermal expansion of glass and silicon (e.g., α = 3.5 × 10⁻⁶). -6 The glass exhibits good stability during thermal cycling (K < 0.7 MPa·m¹ / ²). However, the glass material itself has low fracture toughness (K < 0.7 MPa·m¹ / ²), making it susceptible to microcrack propagation in the glass sealing area under mechanical impact conditions encountered during vehicle operation (such as instantaneous acceleration of up to 1000 G from bumpy roads), leading to encapsulation cracking. Statistics show that the cracking rate of the glass micro-fusion encapsulation can reach 42.7% in mechanical impact tests, meaning the overall reliability of the sensor is still insufficient to meet the redundancy design and fail-safe objectives required by ASIL-D level.

[0006] Against this backdrop, in the current field of automotive force monitoring, foil strain gauges struggle to meet long-term stability requirements under high-temperature, vibration, and humid-heat coupling environments due to thermal mismatch in the adhesive layer and failure of the sealing protection. While silicon piezoresistive sensors improve airtightness, the brittleness of the glass seal makes them prone to cracking under mechanical impact. Both technologies suffer from reliability shortcomings, resulting in the overall sensor lifespan, accuracy, and functional safety level failing to fully meet ISO 26262 ASIL standards. The stringent requirements of D necessitate the development of a novel force sensor technology that exhibits high reliability under combined thermal, mechanical, and environmental stresses to ensure the monitoring accuracy and functional safety of automotive electronic control systems throughout their entire lifecycle. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a sensor based on the coupling of structure and liquid medium and its working method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a sensor based on structure and liquid medium coupling, comprising an elastic element having an inner cavity, wherein a MEMS chip is disposed on the side inside the inner cavity of the elastic element, one end of the MEMS chip is connected to a signal line, the other end of the signal line passes through the elastic element and is connected to an external signal receiving device, and the inner cavity is filled with a pressure-conducting liquid, which contacts the pressure-sensitive diaphragm of the MEMS chip.

[0009] It includes a sealing point, which is located at the outlet hole of the inner cavity and is used to lead out the signal line of the MEMS chip. The other end of the signal line passes through the sealing point of the elastic element and is connected to an external signal receiving device.

[0010] The elastic element, MEMS chip, and sealing point are formed into a completely airtight sensor unit through a sealing process.

[0011] The sealing process is a welding process, which seals and connects the elastic element, the MEMS chip, and the sealing point.

[0012] The welding process is laser welding, electron beam welding, or resistance welding.

[0013] The internal cavity structure of the elastic element is annular, circular, or polygonal.

[0014] The pressure-conducting liquid is silicone oil, fluorinated liquid, or inert grease.

[0015] The pressure-conducting liquid transmits the liquid pressure to the pressure-sensitive diaphragm of the MEMS chip through a hydrostatic transmission path, so as to convert the mechanical deformation signal into an electrical signal output.

[0016] The sensor is used for force or pressure monitoring in automotive powertrain systems.

[0017] Secondly, the present invention provides a method for operating a sensor based on the coupling of structure and liquid medium. When an external load is applied to the elastic element, the internal structure of the elastic element deforms, compressing the pressure-conducting liquid. The pressure-conducting liquid transmits the liquid pressure to the pressure-sensing diaphragm of the MEMS chip through a hydrostatic transmission path, so as to convert the mechanical deformation signal into an electrical signal output. The generated electrical signal is transmitted to an external signal receiving device through a signal line.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a sensor based on structure-liquid medium coupling and its operating method. It includes an elastic element with an inner cavity. A MEMS chip is disposed on the side of the inner cavity of the elastic element. One end of the MEMS chip is connected to a signal line, and the other end of the signal line passes through the elastic element and connects to an external signal receiving device. The inner cavity is filled with a pressure-conducting liquid, which contacts the pressure-sensing diaphragm of the MEMS chip. The elastic element directly isolates the core MEMS chip from the direct impact and contamination caused by harsh environmental factors such as complex external mechanical forces and corrosive media. Utilizing the near-lossless pressure transmission of the pressure-conducting liquid ensures that the pressure acting on the MEMS pressure-sensing diaphragm is highly consistent with the external pressure, avoiding the hysteresis and frictional loss of traditional mechanical transmission, and achieving accurate and rapid signal sensing. Through processes such as welding, a fully sealed unit is formed, preventing the internal pressure-conducting liquid from exchanging with the outside environment, completely solving problems such as chip moisture, condensation, and media corrosion, and greatly improving the stability of the sensor under harsh conditions such as humidity, oil, and high temperatures.

[0019] Furthermore, while effectively protecting the fragile MEMS chip, it eliminates the need for a complex, heavy-duty protective casing, inheriting the advantages of MEMS sensors such as small size and low cost, and facilitating easy integration and installation. This design is particularly suitable for force and pressure monitoring scenarios with high vibration, high pressure, and stringent reliability requirements, such as automotive powertrain systems. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 a is a cross-sectional view of the device structure of the present invention. Figure 2 b is a top view including two internal cavities; Figure 3 a is a cross-sectional view of the device structure of the present invention. Figure 3 b is a top view including two annular cavities and a square elastic body; Figure 4 a is a cross-sectional view of the device structure of the present invention. Figure 4 b is a top view including two circular cavities; Figure 5 a is a cross-sectional view of the device structure of the present invention. Figure 5 b is a top view including two circular cavities; Figure 6 a is a cross-sectional view of the device structure of the present invention. Figure 6 b is a top view including an inner cavity that is circular; Figure 7 a is a cross-sectional view of the device structure of the present invention. Figure 7 b is a top view including an inner cavity, and the inner cavity is square; The following are the labels in the attached diagram: 1. Elastic element; 2. MEMS chip; 3. Signal line; 4. Sealing point; 5. Pressure-conducting liquid. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0028] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0029] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0030] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0031] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] Example 1 A sensor based on the coupling of structure and liquid medium has the following structural components: like Figure 1As shown, a sensor based on structure and liquid medium coupling includes an elastic element 1 with an inner cavity. A MEMS chip 2 is disposed on the side inside the inner cavity of the elastic element 1. One end of the MEMS chip 2 is connected to a signal line 3, and the other end of the signal line 3 passes through the elastic element 1 and is connected to an external signal receiving device. The inner cavity is filled with a pressure-conducting liquid 5, which contacts the pressure-sensitive diaphragm of the MEMS chip 2.

[0033] The elastic element 1 is the mechanical sensing and load-bearing component of the entire sensor, and its interior is designed with a closed cavity. The structure of this cavity can be designed as cylindrical, annular, square, or other polygonal shapes, depending on the actual installation space and mechanical requirements. The elastic element 1 is used to receive external pressure or mechanical force.

[0034] MEMS chip 2 is the signal conversion core of the sensor, typically a silicon-based piezoresistive or capacitive pressure sensing chip. This chip is securely encapsulated and fixed to the sidewall of the inner cavity of the elastic element 1 using high-strength adhesives or welding processes. During installation, it is essential to ensure that the pressure-sensing diaphragm of MEMS chip 2 faces inwards towards the inner cavity, and that the surface of the pressure-sensing diaphragm is unobstructed from the inner cavity space. MEMS chip 2 integrates a sensitive element that converts mechanical deformation into electrical signals (such as changes in resistance or capacitance).

[0035] Signal line 3 is typically an extremely thin metal wire (such as gold wire or copper wire), one end of which is electrically connected to the pads of MEMS chip 2 by wire bonding or soldering to bring out electrical signals.

[0036] Sealing point 4 is a key sealing structure that ensures the long-term stable operation of the sensor. A precision exit hole is provided on the elastic element 1, through which the other end of the signal line 3 passes to connect to an external signal conditioning circuit or data acquisition device. Sealing point 4 is formed at this exit hole. Through special glass-metal sealing, ceramic-metal sealing, or polymer material encapsulation processes, it secures the signal line 3 while ensuring a complete airtight seal between it and the elastic element 1, preventing leakage of pressure-conducting liquid or intrusion of external media.

[0037] The pressure-conducting fluid 5 serves as the medium for pressure transmission, completely filling the entire cavity of the elastic element 1 and directly contacting the pressure-sensing diaphragm of the MEMS chip 2. This fluid must possess low viscosity, high bulk modulus, low coefficient of thermal expansion, good chemical stability, and insulation properties. Commonly used pressure-conducting fluids include silicone oil, fluorinated liquids, or inert greases. Preferably, in this embodiment, a vacuum process is performed after filling to eliminate air bubbles within the cavity, ensuring the immediacy and accuracy of pressure transmission.

[0038] Through the above design, the elastic element 1, the MEMS chip 2, and the sealing point 4 together form a rigidly connected whole. Preferably, a high-energy beam welding process (such as laser welding or electron beam welding) or resistance welding is used to finally weld and seal the packaging edge of the MEMS chip 2 and the interface of the sealing point 4, thereby forming a completely airtight sensor unit filled with pressure-conducting liquid 5. This fully sealed structure can effectively isolate the MEMS chip 2 from the influence of harsh external environments (such as humidity, corrosive gases, and particulate matter).

[0039] Preferably, the elastic element 1 and its inner cavity can be annular, circular, or polygonal in structure. One or two inner cavities can be provided. When two inner cavities are provided, signal transmission between the two cavities is achieved through signal lines 3 and pressure-conducting liquid 5. Figures 2-7 As shown.

[0040] Example 2 A sensor based on structure-liquid coupling operates as follows: When the sensor is installed at the location to be measured (such as a hydraulic line or a point of force application), external pressure or mechanical force acts on the force / pressure sensing surface of the elastic element 1. Under pressure, the force sensing surface of the elastic element 1 undergoes elastic deformation, causing a corresponding change in the volume of its inner cavity. This change in the inner cavity volume compresses the pressure-conducting liquid 5 filling it. Due to the incompressibility and fluidity of the liquid, this pressure change is transmitted almost instantaneously to every boundary surface of the inner cavity via the fluid medium and a hydrostatic transmission path. This transmission process has minimal energy loss and a transmission efficiency of over 99.5%, thus achieving distortion-free transmission of pressure from the elastic element to the internal sensitive point.

[0041] The liquid pressure transmitted to all parts of the internal cavity acts equally on the pressure-sensitive diaphragm of the MEMS chip 2. Under the action of liquid pressure, the diaphragm undergoes nanometer- to micrometer-level flexural deformation. This deformation causes a change in the resistance of the piezoresistive resistor fabricated on the diaphragm (for piezoresistive chips), or a change in the distance between the upper and lower electrodes, thus causing a change in capacitance (for capacitive chips). The MEMS chip 2 converts the above mechanical deformation into an electrical signal (such as a differential voltage signal or a frequency signal). This electrical signal is transmitted to the signal line 3 through the bonding point, and then led out to the outside of the sensor through the sealing point 4 via the signal line 3. After receiving this signal, the external signal receiving device (such as an amplifier, analog-to-digital converter, or controller) can accurately reconstruct the value of the applied external pressure or mechanical force through calibration and calculation.

[0042] Example 3 Taking high-pressure common rail fuel pressure monitoring in an automotive powertrain as an example, the pressure-sensing end face of the sensor's elastic element 1 is mounted on the common rail, allowing it to directly sense fuel pressure. Fuel pressure causes the elastic element 1 to deform, and this deformation is transmitted to the MEMS chip 2 via the pressure-conducting fluid 5. The chip's output signal is read by the engine control unit, achieving real-time, high-precision closed-loop feedback of injection pressure, thereby optimizing combustion efficiency and reducing emissions. The sensor's fully sealed structure can completely withstand the harsh environments of fuel, high temperatures, and vibration.

[0043] Finally, it should be noted that the above embodiments only describe the basic principles, main features, and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A sensor based on structural coupling with a liquid medium, characterized in that, The device includes an elastic element (1) with an inner cavity. A MEMS chip (2) is disposed on the side inside the inner cavity of the elastic element (1). One end of the MEMS chip (2) is connected to a signal line (3). The other end of the signal line (3) passes through the elastic element (1) and is connected to an external signal receiving device. The inner cavity is filled with a pressure-conducting liquid (5), which contacts the pressure-sensitive diaphragm of the MEMS chip (2).

2. The sensor based on structure-liquid medium coupling according to claim 1, characterized in that, It includes a sealing point (4), which is located at the outlet hole of the inner cavity and is used to lead out the signal line of the MEMS chip (2). The other end of the signal line (3) passes through the sealing point (4) of the elastic element and is connected to an external signal receiving device.

3. A sensor based on structure-liquid medium coupling according to claim 2, characterized in that, The elastic element (1), MEMS chip (2) and sealing point (4) are formed into a completely airtight sensor unit through a sealing process.

4. A sensor based on structure-liquid medium coupling according to claim 3, characterized in that, The sealing process is a welding process, which seals and connects the elastic element (1), the MEMS chip (2) and the sealing point (4).

5. A sensor based on structure-liquid medium coupling according to claim 4, characterized in that, The welding process is laser welding, electron beam welding, or resistance welding.

6. A sensor based on structure-liquid medium coupling according to claim 1, characterized in that, The inner cavity structure of the elastic element (1) is annular, circular, or polygonal.

7. A sensor based on structure-liquid medium coupling according to claim 1, characterized in that, The pressure-conducting liquid (5) is silicone oil, fluorinated liquid or inert grease.

8. A sensor based on structure-liquid medium coupling according to claim 1, characterized in that, The pressure-conducting liquid (5) transmits the liquid pressure to the pressure-sensitive diaphragm of the MEMS chip (2) through a hydrostatic transmission path, so as to convert the mechanical deformation signal into an electrical signal output.

9. A sensor based on structure-liquid medium coupling according to claim 1, characterized in that, The sensor is used for force or pressure monitoring in automotive powertrain systems.

10. A method for operating a sensor based on structure-liquid medium coupling, based on the sensor based on structure-liquid medium coupling according to any one of claims 1 to 9, characterized in that, When an external load is applied to the elastic element (1), the internal structure of the elastic element (1) deforms, compressing the pressure-conducting liquid (5). The pressure-conducting liquid (5) transmits the liquid pressure to the pressure-sensitive diaphragm of the MEMS chip (2) through the hydrostatic transmission path, so as to convert the mechanical deformation signal into an electrical signal output. The generated electrical signal is transmitted to the external signal receiving device through the signal line (3).

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