A flexible tubular capacitive pressure sensor

Abstract

The present invention relates to the technical field of pressure sensors, and specifically to a flexible tubular capacitive pressure sensor. The flexible tubular capacitive pressure sensor includes: a protective layer sheath; pressure-sensitive film deformation capacitive electrodes, which are uniformly and staggeredly distributed on the inner side wall of the protective layer sheath, and the included angle between adjacent pressure-sensitive film deformation capacitive electrodes is 120°; a conductor common capacitive electrode, which is disposed through the protective layer sheath and forms a capacitor with the pressure-sensitive film deformation capacitive electrodes; and a detection auxiliary module, which is respectively installed in cooperation with the conductor common capacitive electrode and the protective layer sheath and is electrically connected to the pressure-sensitive film deformation capacitive electrodes. The flexible tubular capacitive pressure sensor of the present invention can convert and calculate the three-dimensional direction of the pressure, improving the accuracy, practicability and flexibility of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and specifically to a flexible tubular capacitive pressure sensor. Background Art

[0002] A pressure sensor is one of the most widely used sensors in the current sensor field. In recent years, with the development of aerospace, automotive, marine environment, intelligent robots, consumer, portable electronic products, wearable electronic products, bionics and biomedical fields, the demand for flexible pressure sensors has been increasing, and at the same time, higher requirements have been put forward for the design and manufacturing of flexible pressure sensors. Similar to traditional pressure sensors, flexible pressure sensors can also be classified into piezoresistive flexible sensors, capacitive flexible sensors, and piezoelectric flexible sensors according to their principles.

[0003] Currently, for flexible pressure sensors applied in bionics and biomedicine, there are extremely high precision requirements, and there is also a need to measure the three-dimensional direction of force. Ordinary capacitive pressure sensors do not have the ability to measure the three-dimensional direction of force, and at the same time, the accuracy is often affected by factors such as temperature, static pressure, edge effect, and parasitic capacitance. Therefore, in view of the above current situation, there is an urgent need to develop a flexible tubular capacitive pressure sensor to overcome the deficiencies in current practical applications. Summary of the Invention

[0004] The purpose of the present invention is to provide a flexible tubular capacitive pressure sensor to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A flexible tubular capacitive pressure sensor, the flexible tubular capacitive pressure sensor includes:

[0007] A protective layer sleeve;

[0008] A pressure-sensitive film deformation capacitance electrode, the pressure-sensitive film deformation capacitance electrodes are evenly distributed in a staggered manner on the inner side wall of the protective layer sleeve, and the number of the pressure-sensitive film deformation capacitance electrodes is three sets, and the three sets of pressure-sensitive film deformation capacitance electrodes are mutually at an angle of 120°;

[0009] A conductor common capacitance electrode, the conductor common capacitance electrode penetrates through the protective layer sleeve and forms a capacitor with the pressure-sensitive film deformation capacitance electrode, and the capacitance value of the capacitor is between 6 - 30 pf; and

[0010] A detection auxiliary module, the detection auxiliary module is respectively installed in cooperation with the conductor common capacitance electrode and the protective layer sleeve, and is electrically connected to the pressure-sensitive film deformation capacitance electrode.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] (1) Through three piezoresistive film deformation capacitance electrodes that are mutually at an angle of 120°, it is possible to measure the change in capacitance caused by the deformation of the capacitance electrode due to external force, and the magnitudes of the forces in different directions measured are different, so that the three-dimensional direction of the pressure can be transformed and calculated, improving the accuracy, practicability and flexibility of the device;

[0013] (2) Through frequency detection and amplification, the frequency change amount can be correlated with the force change amount, so that the product has ultra-high precision in measuring capacitance values at the aF level, realizing ultra-high precision measurement of capacitance sensors, and can be applied to pressure measurement of bionic flexible joints, flexible bionic attitude recognition, heart pulse monitoring, blood vessel clearance, liquid level and air pressure measurement, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a three-dimensional structural schematic diagram of the whole of the present invention.

[0015] Figure 2 It is a front view sectional structural schematic diagram of the protective layer and sleeve part in the present invention.

[0016] Figure 3 It is a distribution schematic diagram of the piezoresistive film deformation capacitance electrode part in the present invention.

[0017] Figure 4 It is a schematic diagram of the working principle of the whole of the present invention.

[0018] In the figure: 1 - piezoresistive film deformation capacitance electrode, 2 - insulating isolation layer, 3 - conductor common capacitance electrode, 4 - thin film capacitance wire, 5 - protective layer and sleeve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] The following describes in detail the specific implementation of the present invention with reference to specific embodiments.

[0021] Please refer to Figures 1-4 , a flexible tubular capacitive pressure sensor provided by an embodiment of the present invention, the flexible tubular capacitive pressure sensor includes:

[0022] A protective layer and sleeve 5;

[0023] The pressure-sensitive film deformation capacitance electrode 1 is misaligned and distributed on the inner side wall of the protective layer sleeve 5, and the included angle between adjacent pressure-sensitive film deformation capacitance electrodes 1 is an obtuse angle;

[0024] The conductor common capacitance electrode 3 is disposed through the protective layer sleeve 5 and forms a capacitor with the pressure-sensitive film deformation capacitance electrode 1; and

[0025] The detection auxiliary module is respectively installed in cooperation with the conductor common capacitance electrode 3 and the protective layer sleeve 5 and is electrically connected to the pressure-sensitive film deformation capacitance electrode 1.

[0026] The detection auxiliary module includes: an insulating isolation layer 2, which is uniformly distributed in the protective layer sleeve 5 and is respectively installed in cooperation with the pressure-sensitive film deformation capacitance electrode 1 and the conductor common capacitance electrode 3; and

[0027] The thin film capacitance wire 4 has one end passing through the insulating isolation layer 2 and is electrically connected to the pressure-sensitive film deformation capacitance electrode 1, and the number of the thin film capacitance wires 4 is the same as the number of the pressure-sensitive film deformation capacitance electrodes 1.

[0028] The conductor common capacitance electrode 3 is a triangular prism structure, which uses a base material with good insulation and strength. The base material is a material such as ceramic or glass, and a material with good conductivity is coated or plated on the surface of the base material. The material with good conductivity is a material such as aluminum, silver or copper.

[0029] The insulating isolation layer 2 is a hollow thin disc structure, which uses a composite fiber prepared by doping ceramic in polyester resin and then by the spinning method and has good insulation.

[0030] Please refer to Figure 1 and Figure 2 The protective layer sleeve 5 is a capsule-like structure and uses a highly flexible material.

[0031] The protective layer sleeve 5 is a hollow tube made of a highly flexible material such as polytetrafluoroethylene or polyethylene.

[0032] When the capacitor is working, first, through the provided protective layer sheath 5, where the protective layer sheath 5 is a polytetrafluoroethylene hollow tube with a certain thickness, its diameter is 1 mm, length is 3 mm, and thickness is 0.3 mm. And because the protective layer sheath 5 is a highly flexible material, the volume of a single sensor is small and can be divided into multiple levels to simulate peristaltic changes, thus realizing the flexibility of the sensor. Then, through the provided insulating isolation layer 2, where the insulating isolation layer 2 is a composite fiber prepared by doping ceramic in polyester resin and then by the spinning method, which has good insulation. The insulating isolation layer 2 can also be a simple ceramic material. A very thin layer of metallic aluminum with a thickness of 5 μm is vacuum-evaporated on the ceramic rod. After evaporating aluminum, the conductive ceramic rod is cut into a triangular prism-shaped round rod with a length of 0.1 mm and a height of 3 mm as the conductor common capacitance electrode 3. And the conductor common capacitance electrode 3 is encapsulated into the insulating isolation layer 2 by UV-curing resin dispensing and curing, and then dispensed and cured on the inner surface of the protective layer sheath 5 to complete the encapsulation. Among them, the conductor common capacitance electrode 3 can also be a simple metallic material. And through the provided pressure-sensitive film deformation capacitance electrode 1, where the pressure-sensitive film deformation capacitance electrode 1 is encapsulated on the inner surface of the protective layer sheath 5 by UV-curing resin dispensing and curing, and several pressure-sensitive film deformation capacitance electrodes 1 are evenly distributed in a staggered manner. A silver electrode thin film wire is screen-printed at one end of each pressure-sensitive film deformation capacitance electrode 1 as the thin film capacitance wire 4, which is encapsulated on the inner surface of the protective layer sheath 5 by UV-curing resin dispensing and curing. Among them, the other end of the thin film capacitance wire 4 is connected to an external detection circuit. When the protective layer sheath 5 is subjected to pressure, according to the capacitance determinant formula: C = εS / (4πkd), it can be known that for a capacitance pressure sensor with a certain area, different pressure ranges will design thin film electrodes with different areas according to the range. But for a pressure sensor with a determined range, it is a capacitance sensor of the same material and with the same area of the induction electrode. The size of the capacitance is related to the distance between the two capacitance poles. When the strain electrode is stressed and the substrate approaches or is squeezed and deformed, the capacitance value will change. Therefore, there is a quantitative relationship between the pressure and the capacitance value. Therefore, through several pressure-sensitive film deformation capacitance electrodes 1 evenly distributed in a staggered manner, the change in capacitance caused by the deformation of the capacitance electrode due to external force can be measured, and the magnitudes of the forces in different directions measured are different, so that the three-dimensional direction of the pressure can be calculated and transformed, improving the accuracy, practicability and flexibility of the device, which is worthy of promotion.

[0033] In an embodiment of the present invention, please refer to Figure 3 , the pressure-sensitive film deformation capacitance electrode 1 is a square small block of 10 μm×10 μm, which is made by vacuum-evaporating a layer of metallic aluminum on a polypropylene plastic film.

[0034] The number of the pressure-sensitive film deformation capacitance electrodes 1 is three sets, and the three sets of the pressure-sensitive film deformation capacitance electrodes 1 are mutually at an angle of 120°.

[0035] A very thin layer of metallic aluminum with a thickness of 5 μm is vacuum-evaporated onto a polypropylene plastic film. The polypropylene plastic film after aluminum evaporation is cut into 10 μm×10 μm square small pieces as the pressure-sensitive film deformation capacitance electrode 1, which is encapsulated by UV-curing resin dispensing and curing on the inner surface of the protective layer sleeve 5. There are three pressure-sensitive film deformation capacitance electrodes 1 evenly distributed at 120° to each other on the inner surface of the protective layer sleeve 5, and they are also evenly distributed in the radial direction of the protective layer sleeve 5. When the small electrode is extruded in different directions, the internal variable capacitance electrode deforms itself, changing the output capacitance of the sensor. At the same time, the change in the distance between the variable capacitance electrode and the middle common electrode will also change the output capacitance. Therefore, it is possible to measure the change in capacitance caused by the deformation of the capacitance electrode due to external force, and the magnitudes of the forces in different directions measured are different, so that the three-dimensional direction of the force can be calculated by conversion.

[0036] In an embodiment of the present invention, please refer to Figures 1-4 , the capacitance value of the capacitor is between 6 - 30 pf.

[0037] During the use of the sensor, it is connected to an external detection circuit through the thin film capacitance wire 4. The detection circuit is used to detect the capacitance of the capacitor. Among them, the sensing capacitance value of the capacitance sensor is designed within the resonant frequency band of the detection circuit. The center resonant frequency of the detection circuit is designed at the MHz level. The capacitance value of the capacitance sensor is counted between 6 - 30 pf. From the capacitance determinant formula: C = εS / (4πkd), it can be seen that by changing the capacitance value of the capacitance sensor, and then changing the frequency of the resonant circuit. Through the above method, the pressure causes the deformation of the capacitance sensor, changing the capacitance value, and converting the change amount of the capacitance value into the frequency of MHz. By collecting the high-precision frequency change through a digital processor, the quantization relationship is 30 pf / MHz, that is, theoretically, a precision of 0.03 aF can be recognized through a frequency change amount of 1 Hz. That is to say, through this frequency detection and amplification, the relationship between the frequency change amount and the force change amount can be deduced and associated, so that the product has ultra-high precision in measuring capacitance values at the aF level, realizing ultra-high precision measurement of the capacitance sensor, and can be applied to pressure measurement of bionic flexible joints, flexible bionic attitude recognition, heart pulse monitoring, blood vessel clearance, liquid level and air pressure measurement, etc.

[0038] It should be noted that in the present invention, unless otherwise clearly specified and limited, terms such as "sliding", "rotating", "fixing", "provided with" should be understood in a broad sense. For example, it can be a welded connection, a bolt connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A flexible tubular capacitive pressure sensor, characterized in that, The flexible tubular capacitive pressure sensor includes: A protective layer sleeve; A pressure-sensitive film deformation capacitive electrode, which is evenly distributed in a staggered manner on the inner side wall of the protective layer sleeve, and the number of the pressure-sensitive film deformation capacitive electrodes is three sets, and the three sets of the pressure-sensitive film deformation capacitive electrodes form an angle of 120° with each other; A conductor common capacitive electrode, which is disposed through the protective layer sleeve and forms a capacitor with the pressure-sensitive film deformation capacitive electrode, and the capacitance value of the capacitor is between 6-30 pf; and A detection auxiliary module, which is respectively installed in cooperation with the conductor common capacitive electrode and the protective layer sleeve and is electrically connected to the pressure-sensitive film deformation capacitive electrode; The detection auxiliary module includes: an insulating isolation layer, which is evenly distributed in the protective layer sleeve and is respectively installed in cooperation with the pressure-sensitive film deformation capacitive electrode and the conductor common capacitive electrode; and A thin film capacitor wire, one end of which penetrates through the insulating isolation layer and is electrically connected to the pressure-sensitive film deformation capacitive electrode, and the number of the thin film capacitor wires is the same as the number of the pressure-sensitive film deformation capacitive electrodes; The insulating isolation layer is a hollow thin disc structure and is made of a material with good insulation and strength.

2. The flexible tubular capacitive pressure sensor according to claim 1, wherein The conductor common capacitive electrode is a triangular prism structure and is made of a substrate with good insulation and strength, and a material with good conductivity is coated or plated on the surface of the conductor common capacitive electrode.

3. The flexible tubular capacitive pressure sensor according to claim 2, wherein The conductor common capacitive electrode is made of ceramic or glass material, and aluminum, silver or copper material is plated on the surface of the conductor common capacitive electrode.

4. The flexible tubular capacitive pressure sensor according to any one of claims 1-3, characterized in that, The protective layer sleeve is a capsule-like structure and is made of a highly flexible material.

5. The flexible tubular capacitive pressure sensor according to claim 4, wherein, The protective layer sleeve is a hollow tube made of polytetrafluoroethylene or polyethylene material.

6. The flexible tubular capacitive pressure sensor according to claim 1, wherein, The pressure-sensitive film deformation capacitive electrode is a 10μm×10μm square small piece, which is made by vacuum evaporating a layer of aluminum metal on a polypropylene plastic film.

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