A high sensitivity sensor

Abstract

The application discloses a high-sensitivity sensor, which comprises a protective cover, an upper bearing plate, an elastic element, a transmission top rod, a sensing unit crack module, a lower limit plate and a displacement input base, the transmission top rod penetrates through the center of the elastic element, one end of the transmission top rod is connected with the lower limit plate, the other end of the transmission top rod extends out of the upper bearing plate and is connected with the sensing unit crack module, the lower limit plate is connected with the displacement input base, the bottom of the displacement input base is provided with a first sharp end and a second sharp end, and the line connecting the first sharp end and the second sharp end is obliquely arranged relative to the mounting reference surface of the displacement input base; and the sensing unit crack module is arranged in the protective cover. The application realizes first-level mechanical conversion of initial displacement through the inclined surface mechanism, and realizes second-level signal amplification in combination with stress concentration of the crack sharp end, so that the response accuracy of weak mechanical signals is greatly improved, and the signal gain is more than 300%.

Description

Technical Field

[0001] This invention pertains to sensors, specifically a high-sensitivity sensor. Background Technology

[0002] In the fields of industrial inspection and structural health monitoring, early detection of microcracks in high-rigidity bodies (such as precision machine tools, high-stability test benches, and critical load-bearing structural components) is particularly essential. However, due to their high elastic modulus and strong resistance to deformation, the strain and physical displacement signals on the surface of high-rigidity bodies are extremely weak when microcracks occur or when they are damaged by initial stress. These signals are easily masked by high-frequency mechanical vibrations and electromagnetic noise in industrial environments. Existing micro-signal detection sensors often suffer from insufficient sensitivity, significant environmental interference, and difficulty in effectively capturing micro-strain on the surface of high-rigidity bodies. To achieve high-precision capture of high-frequency, minute physical quantity changes caused by microcracks in high-rigidity bodies, there is an urgent need for a sensing structure that can effectively transmit, physically amplify, and highly sensitively convert the minute deformation and mechanical signals of high-rigidity solids into observable electrical signals. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a high-sensitivity sensor.

[0004] Technical Solution: The high-sensitivity sensor of the present invention includes a protective cover, an upper support plate, an elastic element, a transmission push rod, a sensing unit crack module, a lower limit plate, and a displacement input base. The transmission push rod passes through the center of the elastic element, one end of which is connected to the lower limit plate, and the other end extends out of the upper support plate and is connected to the sensing unit crack module. The lower limit plate is connected to the displacement input base, and the bottom of the displacement input base has a first tip and a second tip. The line connecting the first tip and the second tip is inclined relative to the mounting reference surface of the displacement input base. The sensing unit crack module is disposed inside the protective cover.

[0005] Furthermore, the elastic element is a spring. The spring constant is selected and designed according to the expected range to ensure that the drive shaft does not disengage or idle during dynamic displacement.

[0006] Furthermore, the spring is initially in a pre-compressed state, and its elastic force is in the same direction as the axis of the transmission push rod, always pointing towards the displacement input base.

[0007] Furthermore, the sensing unit crack module includes an epoxy resin layer, electrodes, and a sensitive layer. The electrodes and the sensitive layer are disposed within the epoxy resin layer. The sensitive layer is crack-shaped and made of piezoresistive material. The sensing unit crack module is connected to an external circuit via a signal transmission line to output an electrical signal that changes linearly with the multiplication of stress concentration.

[0008] Furthermore, the sensitive layer is fabricated by physical vapor deposition, flexible printing, or photolithography.

[0009] Furthermore, the axial displacement of the transmission push rod and the horizontal displacement of the displacement input base satisfy the following formula:

[0010]

[0011] in, H is the angle between the guide slope of the displacement input base and the horizontal reference plane, H is the axial displacement of the transmission push rod, and L is the horizontal displacement of the displacement input base.

[0012] Furthermore, the guide slope of the displacement input base is a plane, a logarithmic curve surface, or a quadratic curve surface to achieve nonlinear compensation signal output.

[0013] Furthermore, α ranges from 5° to 60°. If α is greater than 60°, the resistance of the inclined plane transmission will increase sharply, which may easily lead to mechanical self-locking or lateral jamming, causing the transmission push rod to be subjected to excessive lateral shear stress and wear, resulting in a significant decrease in transmission efficiency. If α is less than 5°, the displacement amplification conversion rate will be extremely low, the effective mechanical strain in the vertical direction will be insufficient to trigger the stress concentration effect of the crack in the sensitive layer, and it will be overly sensitive to the substrate machining tolerance and surface roughness, which may easily cause measurement distortion.

[0014] Furthermore, the transmission push rod and displacement input base are made of hard aluminum alloy, stainless steel or engineering plastic to reduce self-deformation loss during mechanical transmission.

[0015] Furthermore, the bottom of the transmission push rod is provided with a friction-reducing coating or rolling elements, which helps to reduce frictional lag between the push rod and the inclined surface of the base.

[0016] Furthermore, the high-sensitivity sensor is encapsulated in a sealed housing to isolate the external environment from the mechanical transmission accuracy and the crack module.

[0017] Working Principle: Using a base with a guiding inclined surface as the displacement input source, and a sensing module containing a pre-fabricated crack structure as the core sensing unit, a transmission mechanism with a pre-tightened elastic element converts horizontal micro-displacement into vertical axial stress acting on the crack sensing module. The contact part at the bottom of the transmission mechanism forms a kinematic pair with the inclined surface of the base. When the base undergoes horizontal displacement, the inclined surface forces the transmission mechanism to generate axial displacement and compress the elastic element, resulting in a high concentration of axial load at the crack tip inside the sensing module. When changes in external load cause fluctuations in the stress field at the crack tip, the sensitive layer inside the sensing module generates changes in resistance or charge signals, achieving precise detection of mechanical displacement. Furthermore, by adjusting the tilt angle α of the inclined surface of the base, the mapping ratio between horizontal and vertical displacement can be changed, thereby achieving modular control of the sensor's detection sensitivity and range.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0019] 1. By utilizing the dual cascade amplification mechanism of inclined plane amplification and stress concentration at the crack tip, the sensitivity coefficient (GF) of the sensor is increased to 150~350, which is more than 75 times higher than that of the traditional resistive strain gauge (GF is about 2).

[0020] 2. It features modular adjustable sensitivity, high mechanical stability, and wide measurement range, solving the problem that traditional strain sensors cannot simultaneously achieve both sensitivity and measurement range in the detection of minute displacements.

[0021] 3. Combining the pre-tightening and buffering effects of the elastic element, the sensor, after experiencing 10... 6 After one cycle of loading, the zero-point drift rate is less than 0.5%, and the hysteresis error is less than 1.2%. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the model of the crack sensing unit 5 of the present invention;

[0024] Figure 3 This is a physical image of the crack module 5 of the sensing unit of the present invention. Detailed Implementation

[0025] Unless otherwise specified, all materials and reagents used in the following embodiments are commercially available.

[0026] like Figure 1The high-sensitivity sensor based on mechanical displacement conversion and stress concentration at the crack tip includes a protective cover 1, an upper support plate 2, an elastic element 3, a transmission rod 4, a sensing unit crack module 5, a lower limit plate 6, and a displacement input base 7. The transmission rod 4 passes through the center of the elastic element 3, and its lower end is fixedly connected to the top center of the lower limit plate 6 via a threaded connection. Specifically, the lower end of the transmission rod 4 is machined with an external thread, screwed into the internal threaded hole at the top of the lower limit plate 6, and coated with thread-fastening adhesive. The middle part of the transmission rod 4 slides through the guide hole on the upper support plate 2, forming a guide sliding fit with the upper support plate 2. The preferred fit tolerance is H7 / f6 clearance fit. To further reduce lateral friction, a self-lubricating brass bushing or a polytetrafluoroethylene (PTFE) guide sleeve is fixedly embedded in the inner wall of the guide hole. After the upper end of the transmission rod 4 extends out of the upper support plate 2, it is fixedly connected to the base of the sensing unit crack module 5 via a threaded fastening connection (or fixedly connected by high-strength epoxy resin adhesive). The bottom surface of the lower limit plate 6 is slidably connected to the inclined surface of the displacement input base 7. When the displacement input base 7 is subjected to external forces and undergoes a horizontal linear displacement, its inclined surface pushes against the lower limit plate 6 and the transmission push rod 4 to overcome the preload of the elastic element 3, and slides vertically. The bottom of the displacement input base 7 has a first tip 71 and a second tip 72, and the line connecting the first tip 71 and the second tip 72 is inclined relative to the mounting reference surface of the displacement input base 7. The sensing unit crack module 5 is housed inside the protective cover 1. The elastic element 3 is a spring, with the following specific structural parameters: material: 304 stainless steel / 65Mn spring steel / beryllium bronze (QBe2); wire diameter d: 0.3~0.8 mm (preferably 0.5 mm); spring outer diameter D: 3.0~6.0 mm (preferably 4.0 mm); free length L: 8.0~15.0 mm (preferably 10.0 mm); elastic coefficient k: 100~800 N / m (preferably 350 N / m); pre-compression: 0.5~2.0 mm. The spring is initially in a pre-compressed state, and its elastic force direction is consistent with the axial direction of the transmission push rod 4, always pointing towards the displacement input base 7. The axial displacement of the transmission push rod 4 and the horizontal displacement of the displacement input base 7 satisfy the following formula:

[0027]

[0028] in, H is the angle between the guide slope of the displacement input base 7 and the horizontal reference plane, H is the axial displacement of the transmission push rod 4, and L is the horizontal displacement of the displacement input base 7. The angle is 5° to 60°, preferably 10° to 45°.

[0029] The guide slope of the displacement input base 7 is a plane, a logarithmic curve, or a quadratic curve. The transmission push rod 4 and the displacement input base 7 are made of hard aluminum alloy, stainless steel, or engineering plastic. The bottom of the transmission push rod 4 is equipped with an anti-friction coating or rolling elements. The coating material is selected from one or more combinations of diamond-like carbon (DLC), polytetrafluoroethylene (PTFE), or molybdenum disulfide. The thickness of the DLC coating is 0.5~3.0 μm (friction coefficient μ≤0.05); the thickness of the PTFE or molybdenum disulfide coating is 5.0~15.0 μm (friction coefficient μ≤0.08); the rolling elements are miniature balls embedded in the bottom of the transmission push rod 4, made of silicon nitride ceramic, zirconia ceramic, or 440C stainless steel, with a ball diameter of 1.0~2.5 mm and a surface roughness Ra≤0.01 μm.

[0030] like Figures 2-3 The sensing unit crack module 5 includes an epoxy resin layer 51, an electrode 52, and a sensitive layer 53. The electrode 52 and the sensitive layer 53 are disposed within the epoxy resin layer 51. The sensitive layer 53 is crack-shaped and made of piezoresistive materials, such as carbon-based nanomaterials (single-walled / multi-walled carbon nanotubes (CNTs), graphene, reduced graphene oxide), and conductive polymers (polyaniline (PANI), polypyrrole (PPy)). The sensitive layer 53 is fabricated by physical vapor deposition, flexible printing, or photolithography.

[0031] The specific working process and principle of the sensor in this embodiment are as follows:

[0032] (1) Static initial state:

[0033] When the system is in its initial state without external excitation, the elastic element 3 is in a pre-compressed state, and the downward axial pressure it generates acts on the transmission push rod 4 through the lower limit plate 6. This causes the double-support structure at the bottom of the transmission push rod 4 to fit tightly against the lower end of the guide slope of the displacement input base 7. At this time, the initial stress sensed by the crack module 5 at the top is zero or a constant pre-tightening reference value, and the circuit outputs a stable static initial signal.

[0034] (2) Signal input and mechanical conversion stage:

[0035] When the displacement input base 7 is subjected to an external load and generates a horizontal relative displacement L (as shown by the horizontal arrow in the figure), since the top surface of the base 7 is provided with a guide slope that forms an angle α with the horizontal plane, the transmission push rod 4 is squeezed by the slope, forcing it to overcome the elastic force of the elastic element 3 and move upward along the vertical guide path.

[0036] According to trigonometric geometric relations, the horizontal displacement L is linearly transformed into the vertical axial displacement H, and the transformation relationship satisfies:

[0037]

[0038] This process achieves the direction conversion of physical quantities and preliminary mechanical magnification.

[0039] (3) Load transfer and stress concentration stage:

[0040] As the transmission push rod 4 generates a vertical displacement H upwards, its tip directly acts on the crack module 5. The displacement H causes further compression of the elastic element 3, generating an incremental load ΔF. This load is precisely transmitted to the interior of the crack module 5. Because the crack module 5 contains a pre-fabricated biomimetic crack structure, an extremely high stress concentration field is generated in the localized area at the crack tip, causing the minute axial displacement to be converted into severe localized stress fluctuations.

[0041] (4) Signal output and detection stage:

[0042] Under the influence of the stress field at the crack tip, the sensitive layer (such as a piezoelectric film or a piezoresistive conductive layer) inside the crack module 5 undergoes a sudden change in its physical properties (such as resistivity or charge density). This change is output to the external processing circuit via an electrical signal lead. By analyzing the amplitude or frequency of the output electrical signal, the value of the initial horizontal displacement L can be deduced, thus enabling highly sensitive detection of minute deformations or displacements in large structures.

[0043] (5) Dynamic reset process:

[0044] When the external horizontal excitation is removed, the elastic element 3 releases the stored elastic potential energy, driving the transmission push rod 4 to quickly return to the initial low position along the guide slope, so that the sensor re-enters the test state, ensuring the continuity and repeatability of the detection process.

Claims

1. A high-sensitivity sensor, characterized in that: The device includes a protective cover (1), an upper support plate (2), an elastic element (3), a transmission rod (4), a sensing unit crack module (5), a lower limit plate (6), and a displacement input base (7). The transmission rod (4) passes through the center of the elastic element (3). One end of the transmission rod (4) is connected to the lower limit plate (6), and the other end extends out of the upper support plate (2) and is connected to the sensing unit crack module (5). The lower limit plate (6) is connected to the displacement input base (7). The bottom of the displacement input base (7) has a first tip (71) and a second tip (72). The line connecting the first tip (71) and the second tip (72) is inclined relative to the mounting reference surface of the displacement input base (7). The sensing unit crack module (5) is disposed inside the protective cover (1).

2. The high-sensitivity sensor according to claim 1, characterized in that: The elastic element (3) is a spring.

3. A high-sensitivity sensor according to claim 2, characterized in that: The spring is initially in a pre-compressed state, and its elastic force direction is consistent with the axial direction of the transmission push rod (4), and always points to the displacement input base (7).

4. A high-sensitivity sensor according to claim 1, characterized in that: The sensing unit crack module (5) includes an epoxy resin layer (51), an electrode (52) and a sensitive layer (53). The electrode (52) and the sensitive layer (53) are disposed in the epoxy resin layer (51). The sensitive layer (53) is crack-shaped and made of piezoresistive material.

5. A high-sensitivity sensor according to claim 4, characterized in that: The sensitive layer (53) is prepared by physical vapor deposition, flexible printing or photolithography.

6. A high-sensitivity sensor according to claim 1, characterized in that: The axial displacement of the transmission push rod (4) and the horizontal displacement of the displacement input base (7) satisfy the following formula: in, H is the angle between the guide slope of the displacement input base (7) and the horizontal reference plane, H is the axial displacement of the transmission push rod (4), and L is the horizontal displacement of the displacement input base (7).

7. A high-sensitivity sensor according to claim 6, characterized in that: The guide slope of the displacement input base (7) is a plane, a logarithmic curve surface, or a quadratic curve surface.

8. A high-sensitivity sensor according to claim 6, characterized in that: The The range is 5° to 60°.

9. A high-sensitivity sensor according to claim 1, characterized in that: The transmission push rod (4) and displacement input base (7) are made of hard aluminum alloy, stainless steel or engineering plastic.

10. A high-sensitivity sensor according to claim 1, characterized in that: The bottom of the transmission push rod (4) is provided with a friction-reducing coating or a rolling element.

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