Film pressure sensor and insole

Abstract

The present invention relates to a film pressure sensor and insole in the field of sensor technology, comprising a flexible pressure-sensitive film material, an insulating substrate and an electrode assembly, wherein the electrode assembly is arranged on one end surface of the insulating substrate, and the flexible pressure-sensitive film material is also fixedly mounted on the end surface of the insulating substrate on which the electrode assembly is arranged, wherein the conductivity of the flexible pressure-sensitive film material is between that of a conductor and an insulator, and the flexible pressure-sensitive film material is used to turn on the electrode assembly when the film pressure sensor is subjected to pressure so that the film pressure sensor exhibits a resistance value corresponding to the pressure it is subjected to, and an adsorption elimination assembly is provided between the electrode assembly and the flexible pressure-sensitive film material, and the adsorption elimination assembly is used to eliminate the adsorption and adhesion phenomenon between the flexible pressure-sensitive film material and the electrode assembly, thereby solving the problem of slow response speed of existing film pressure sensors.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a film pressure sensor and a shoe insole. Background Art

[0002] Pressure sensors are one of the important components of modern electronic technology. When meeting certain technical requirements, film pressure sensors made of rubber or silicone have the highest cost-effectiveness.

[0003] The film pressure sensor is a piezoresistive film with a conductivity ρ between that of a conductor and an insulator formed by fully mixing and curing a certain proportion of graphite carbon element or other conductive material powder with insulating materials such as rubber or silicone. The piezoresistive film has a certain degree of elasticity.

[0004] When pressure is applied to a varistor film, its internal microstructure changes, causing its volume resistance to decrease. The rate of change in volume resistance is roughly proportional to the applied pressure. Simply measuring the resistance of the varistor film can convert the applied pressure to the film. When the applied pressure is removed, the film returns to its original state.

[0005] The film pressure sensor in the prior art generally adopts a so-called sandwich structure in which a metal electrode is connected to the upper and lower surfaces of the piezoresistive film under pressure. However, the film pressure sensor with this structure has the following defects: first, the upper and lower electrode plates and the piezoresistive film cannot be accurately aligned during installation, which affects the change in the contact area of the three, and in turn affects the resistance change rate of the sensor after being pressurized; second, during installation, the film pressure sensor with a sandwich structure is difficult to install and position on the firmware, and the installation process of the piezoresistive film is required to be high, which reduces the installation efficiency of the sensor; third, the response speed is slow, especially after the piezoresistive film removes the applied pressure, a local vacuum is generated between the film and the smooth metal electrode, and adsorption and adhesion occur, resulting in the resistance change of the piezoresistive film being out of sync with the pressure.

[0006] On the other hand, due to the influence of various factors such as the mixing uniformity of the glue and graphite carbon elements before the film is cured, the temperature of the curing process, the curing time, etc., the electrical characteristics of the film pressure sensor are highly discrete, which will cause the risk of reduced finished product qualification rate of firmware containing multiple film pressure sensors. Summary of the Invention

[0007] Aiming at the shortcomings of the prior art, the present invention provides a film pressure sensor and an insole, which solves the problem of slow response speed of the prior film pressure sensor.

[0008] In order to solve the above technical problems, the present invention is solved by the following technical solutions:

[0009] A film pressure sensor includes a flexible pressure-sensitive film material, an insulating substrate and an electrode assembly, wherein the electrode assembly is arranged on one end surface of the insulating substrate, and a flexible pressure-sensitive film material is also fixedly mounted on the end surface of the insulating substrate on which the electrode assembly is arranged. The conductivity of the flexible pressure-sensitive film material is between that of a conductor and an insulator, and the flexible pressure-sensitive film material is used to turn on the electrode assembly when the film pressure sensor is subjected to pressure so that the film pressure sensor presents a resistance value corresponding to the pressure it is subjected to. An adsorption elimination component is provided between the electrode assembly and the flexible pressure-sensitive film material, and the adsorption elimination component is used to eliminate the adsorption and adhesion phenomenon between the flexible pressure-sensitive film material and the electrode assembly.

[0010] Optionally, the adsorption elimination component includes a frosted layer and a graphite carbon layer, the graphite carbon layer is arranged on one end surface of the electrode component close to the flexible pressure-sensitive film material, the frosted layer is arranged on one end surface of the flexible pressure-sensitive film material close to the electrode component, and the frosted layer at least covers the area opposite to the graphite carbon layer and the flexible pressure-sensitive film material, and the frosted layer is not arranged in contact with the graphite carbon layer.

[0011] Optionally, the electrode assembly includes a first metal electrode and a second metal electrode, the first metal electrode and the second metal electrode are both arranged on the same surface of the insulating substrate, and the first metal electrode and the second metal electrode are arranged separately.

[0012] Optionally, a positioning component is provided between the electrode component and the flexible pressure-sensitive film material, and the positioning component is provided in contact with only one group of the first metal electrode and the second metal electrode.

[0013] Optionally, a support assembly is further provided on one end surface of the flexible pressure-sensitive adhesive material close to the electrode assembly.

[0014] Optionally, the positioning assembly and the supporting assembly are spaced apart, and the height of the positioning assembly is higher than the height of the supporting assembly.

[0015] Optionally, the supporting component is configured as a ring structure, and the positioning component is disposed on an end surface of the supporting component away from the flexible pressure-sensitive film material.

[0016] Optionally, the materials of the positioning component and the supporting component are the same as the flexible pressure-sensitive film material.

[0017] A shoe insole comprises any one of the above-mentioned film pressure sensors.

[0018] Optionally, before the plurality of film pressure sensors are arranged inside the insole, a binning test is required for the plurality of film pressure sensors, which specifically includes the following steps:

[0019] Performing a pressure test on the film pressure sensor, and classifying the plurality of film pressure sensors into different grades based on the gain resistor values required by the signal amplification circuit;

[0020] Based on the grading result, film pressure sensors with the same gain resistance value are arranged in the same insole.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] The surface of the flexible pressure-sensitive film material adopts a frosted surface structure, i.e., a frosted layer, and the contact surface of the electrode assembly with the flexible pressure-sensitive film material is coated with a conductive frosted graphite carbon layer. The combined effect of the two avoids the problem of "local vacuum between the film and the smooth metal electrode after the pressure is removed from the varistor film, resulting in adsorption and adhesion" in the sandwich-structured varistor film sensor, thereby solving the defects of slow response speed caused by adsorption and the varistor film resistance change being out of sync with the pressure; by setting a support component, the flexible pressure-sensitive film material and the electrode assembly can be in a slightly separated state when there is no pressure, solving the defect that the flexible pressure-sensitive film material also exhibits a certain resistance when not under pressure; by setting a positioning component, the position of the flexible pressure-sensitive film material and the electrode assembly can be precisely aligned, thereby improving the electrical parameter stability of the flexible pressure-sensitive film material, simplifying the installation process of the film pressure sensor, and improving the installation efficiency of the film pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a structural diagram of the flexible pressure-sensitive film material proposed in the first embodiment;

[0025] Figure 2 This is a diagram showing the position structure of the electrode assembly and the graphite carbon layer proposed in the first embodiment;

[0026] Figure 3 This is an installation diagram of a film pressure sensor proposed in the first embodiment;

[0027] Figure 4This is a structural diagram of the flexible pressure-sensitive film material proposed in the second embodiment;

[0028] Figure 5 This is a diagram showing the position structure of the electrode assembly and the graphite carbon layer proposed in the second embodiment;

[0029] Figure 6 This is an installation diagram of a film pressure sensor proposed in the second embodiment;

[0030] Figure 7 This is a schematic diagram of the electrical connections of metal electrodes with four groups of varistor films installed on a firmware proposed in the third embodiment;

[0031] Figure 8 This is a circuit for measuring the resistance value of the R11 varistor film when 16 groups of varistor films are connected in a 4*4 matrix proposed in the third embodiment;

[0032] Figure 9 This is a circuit schematic diagram for grading all film pressure sensors proposed in the third embodiment.

[0033] Figure numerals: 1. flexible pressure-sensitive film material; 2. insulating substrate; 3. frosted layer; 4. graphite carbon layer; 5. first metal electrode; 6. second metal electrode; 7. positioning column; 8. positioning hole; 9. support assembly; 10. electrical connection line. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0035] Example 1

[0036] like Figure 1 、 Figure 2 and Figure 3 As shown, a film pressure sensor includes a flexible pressure-sensitive film material 1, an insulating substrate 2 and an electrode assembly, wherein the electrode assembly is arranged on one end surface of the insulating substrate 2, and the flexible pressure-sensitive film material 1 is also fixedly mounted on the end surface of the insulating substrate 2 where the electrode assembly is arranged. The conductivity of the flexible pressure-sensitive film material 1 is between that of a conductor and an insulator, and the flexible pressure-sensitive film material 1 is used to turn on the electrode assembly when the film pressure sensor is subjected to pressure so that the film pressure sensor presents a resistance value corresponding to the pressure it is subjected to. An adsorption elimination component is provided between the electrode assembly and the flexible pressure-sensitive film material 1, and the adsorption elimination component is used to eliminate the adsorption and adhesion phenomenon between the flexible pressure-sensitive film material 1 and the electrode assembly.

[0037] It should be noted that the flexible pressure-sensitive film material 1 of this embodiment can be a varistor film, which is made by fully mixing rubber or silicone with a conductive material such as graphite carbon powder and then curing it by injection molding or other methods. The shape of the formed varistor film is not limited, and can be a square, a quadrilateral with arc-shaped corners, a circle or an ellipse, or a special shape according to the requirements of the firmware stress test.

[0038] Among them, the adsorption elimination component includes a frosted layer 3 and a graphite carbon layer 4. The graphite carbon layer 4 is arranged on one end surface of the electrode assembly close to the flexible pressure-sensitive film material 1, and the frosted layer 3 is arranged on one end surface of the flexible pressure-sensitive film material 1 close to the electrode assembly, and the frosted layer 3 at least covers the area where the graphite carbon layer 4 and the flexible pressure-sensitive film material 1 are opposite to each other. The frosted layer 3 and the graphite carbon layer 4 are not arranged in contact. In this embodiment, the frosted layer 3 is a rough surface formed by sandblasting or etching on the die-casting mold before the flexible pressure-sensitive film material 1 is die-cast through the die-casting mold.

[0039] Therefore, in this embodiment, the surface of the flexible pressure-sensitive film material 1 adopts a frosted rough surface structure, namely, a frosted layer 3, and at the same time, the contact surface of the electrode assembly with the flexible pressure-sensitive film material 1 is coated with a conductive rough surface graphite carbon layer 4. The combined effect of the two avoids the problem of "local vacuum generated between the piezoresistive film and the smooth metal electrode after the piezoresistive film is removed and pressure is applied, thereby causing adsorption and adhesion" in the sandwich-structured piezoresistive film sensor, thereby solving the defects of slow response speed caused by adsorption and the asynchronous change of the piezoresistive film resistance and pressure.

[0040] Further, if Figure 2 and Figure 3 As shown, the electrode assembly includes a first metal electrode 5 and a second metal electrode 6. The first metal electrode 5 and the second metal electrode 6 are both arranged on the same surface of the insulating substrate 2, and the first metal electrode 5 and the second metal electrode 6 are separately arranged. A positioning component is arranged between the electrode assembly and the flexible pressure-sensitive film material 1, and the positioning component is only arranged in contact with one group of the first metal electrode 5 and the second metal electrode 6. A supporting component 9 is also provided on one end surface of the flexible pressure-sensitive film material 1 close to the electrode assembly.

[0041] Among them, such as Figure 3As shown, the positioning component and the support component 9 are spaced apart, and the height of the positioning component is higher than the height of the support component 9. The materials of the positioning component and the support component 9 are the same as the flexible pressure-sensitive film material 1. More specifically, the positioning component includes positioning posts 7 and positioning holes 8. The number of positioning posts 7 is the same as the number of positioning holes 8, and the positioning posts 7 are fixed on the flexible pressure-sensitive film material 1. The positioning holes 8 are arranged through the insulating substrate 2. There are more than two groups of positioning posts 7 on the flexible pressure-sensitive film material 1. During installation, the positioning posts 7 are fixed in the positioning holes 8 to achieve relative position fixation between the flexible pressure-sensitive film material 1 and the first metal electrode 5 and the second metal electrode 6.

[0042] On the other hand, the support component 9 can be a support column, and the number of support columns is set in two or more groups according to the area of the flexible pressure-sensitive film material 1. The height of the support component 9 is related to the area of the flexible pressure-sensitive film material 1. When the area of the flexible pressure-sensitive film material 1 is 80 square millimeters, the height of the support component 9 is between 20 and 30 microns.

[0043] By providing the support assembly 9, the flexible pressure-sensitive film material 1 is slightly separated from the rough graphite carbon layer 4 when not under pressure, thereby further eliminating the adsorption of the varistor film with the first metal electrode 5 and the second metal electrode 6 on the smooth surface after being under pressure. This ensures that a high resistance state is present between the first metal electrode 5 and the second metal electrode 6 when the flexible pressure-sensitive film material 1 is not under pressure, thereby solving the defect that varistor films with a sandwich structure or printed circuit process also exhibit a certain resistance when not under pressure.

[0044] In this embodiment, the positioning column 7, the supporting component 9 and the flexible pressure-sensitive film material 1 can be made of the same material so that they can be formed simultaneously when the flexible pressure-sensitive film material 1 is injection molded or cured by other methods, which simplifies the film process. At the same time, due to the provision of the positioning column 7, the position of the flexible pressure-sensitive film material 1 and the electrode assembly can be precisely aligned, which improves the electrical parameter stability of the flexible pressure-sensitive film material 1, simplifies the installation process of the film pressure sensor, and improves the installation efficiency of the film pressure sensor.

[0045] The first metal electrode 5 and the second metal electrode 6 are manufactured on the insulating substrate 2 by an electroplating process. The first metal electrode 5 and the second metal electrode 6 are led out by an electrical connection line 10. The frosted layer 3 covers at least the area opposite to the graphite carbon layer 4 and the flexible pressure-sensitive film material 1, and at most one group of graphite carbon layers 4 and the corresponding first metal electrode 5 or second metal electrode 6 are arranged in contact with the positioning post 7 to ensure that the positioning post 7 and the support assembly 9 are insulated from the electrode assembly when the flexible pressure-sensitive film material 1 is not under pressure and when it is under pressure.

[0046] Example 2

[0047] like Figure 4 、 Figure 5 and Figure 6 As shown, the difference between this embodiment and embodiment 1 is that the support component 9 of this embodiment is set as an annular structure, and the positioning component is set at an end surface of the support component 9 away from the flexible pressure-sensitive film material 1. Specifically, multiple support components 9 on the flexible pressure-sensitive film material 1 are connected to form a support ring, and its height can be set to 20 to 30 microns. More than two groups of positioning columns 7 are provided on the support ring. At this time, the shape of the electrode assembly matches the varistor film, the shape of the first metal electrode 5 is set to an annular shape, and the shape of the second metal electrode 6 is set to a circle located within the first metal electrode 5.

[0048] Therefore, even when the supporting component 9 on the flexible pressure-sensitive film material 1 is connected to the first metal electrode 5 via the graphite carbon layer 4, due to the provision of the supporting component 9, when the flexible pressure-sensitive film material 1 is not under pressure, the flexible pressure-sensitive film material 1 and the second metal electrode 6 are in an insulating state.

[0049] Example 3

[0050] A shoe insole, comprising the film pressure sensor according to any one of the first embodiment or the second embodiment, such as Figure 7 The figure shows a schematic diagram of the electrical connections of metal electrodes with four groups of piezoresistive films installed on a fixture. In actual applications, the number of piezoresistive films required for each fixture is determined by the pressure measurement requirements. In this embodiment, when the fixture is an insole, 16 groups of piezoresistive films can be installed to measure the pressure distribution at 16 locations on the sole of the foot during exercise.

[0051] On the other hand, due to the reasons of the film raw materials themselves, rubber or silicone and graphite carbon powder are not easy to mix evenly. Even the microstructures of each varistor film of the same batch of rubber will be different, resulting in the electrical characteristics of the batch-produced varistor film products having greater discreteness.

[0052] Since the linearity of the pressure and resistance value changes of the varistor film and the consistency of electrical parameters such as the body resistance are relatively poor, in order to reasonably use the finished varistor film, this embodiment applies a certain pressure to the finished varistor film and then divides the finished varistor film into grades according to the resistance value of the gain resistor required by the signal amplification circuit.

[0053] In this application, multiple varistor films with the same gain resistor value are placed in the same firmware. In this way, only one gain resistor is needed to obtain the actual pressure value borne by each varistor film. This has the advantage of a simple correction circuit when there are many varistor films in one firmware and the varistor films are connected in a matrix.

[0054] Specifically, if Figure 8The figure shows a circuit for measuring the resistance value of the R11 varistor film when 16 groups of film pressure sensors are connected in a 4*4 matrix. During measurement, the row switch HK1 is connected to the power supply V-, the remaining row switches HK2 to HK4 are grounded, the column switch LK1 is closed, and the remaining column switches LK2 to LK4 are open. V- is connected to the ground line through HK1, R11, LK1, and the operational amplifier. Because of the virtual ground of the operational amplifier, the output voltage of the operational amplifier is:

[0055] Vout / Rf=-(V- / R11), that is, Vout=-(V- / R11)*Rf. From this formula, we can know that when the rated pressure is applied to the varistor, adjusting the resistance value of the gain resistor Rf can change the output voltage Vout of the operational amplifier.

[0056] Therefore, it is only necessary to divide the varistor films with the same gain resistor Rf value into grades, and use an operational amplifier and a gain resistor Rf in the same firmware to perform gain calibration on the varistor film, so as to facilitate the subsequent circuit to calculate the pressure value that each varistor film is subjected to, thereby achieving the purpose of simplifying the production process and improving product production efficiency.

[0057] like Figure 9 As shown in the figure, it is a circuit schematic diagram for grading all film pressure sensors. The working principle of grading is: when the rated pressure is applied to the piezoresistive film RF of the film pressure sensor, the resistance of the piezoresistive film RF becomes smaller, and the output voltage Vout of the operational amplifier IC is proportional to the change in the resistance value of the piezoresistive film RF before and after being pressurized, that is, Vout = -(V- / RF)*Rf. From this formula, it can be seen that when V- and RF are constant, adjusting the value of the gain resistor Rf can change the output voltage Vout of the operational amplifier.

[0058] The specific method of grading the finished varistor film is: Figure 9 Apply rated pressure to the varistor film RF, adjust the resistance of the gain resistor Rf so that the output voltage Vout of the operational amplifier is a predetermined voltage value. At this time, the resistance of the resistor Rf is the appropriate gain resistance value of the varistor film.

[0059] In order to ensure that each finished product of the varistor film can be matched with an Rf resistor of appropriate resistance value, this embodiment normalizes the resistance value of the gain resistor Rf that the varistor film needs to match and divides it into grades according to the national standard fixed resistor nominal value. In this way, the gain resistor Rf can be selected from a resistor with a limited number of ordinary nominal resistance values within a reasonable error range.

[0060] On the other hand, taking into account the power consumption and anti-interference performance of the pressure / voltage conversion circuit of the varistor film, it is preferred that the varistor film with a resistance value of less than 1K and a resistance value of more than 100K when a pressure of 1kg is applied be considered as unusable waste film, the gain resistance of the varistor film within the usable range is classified according to the international E24 fixed resistance nominal value, and the varistor film with an Rf resistance value between the two nominal values is classified to the nominal value according to the principle of proximity.

[0061] More specifically, when a pressure of 1kg is applied to the varistor film, the varistor film with an Rf resistance value between 1K and 100K is divided into grades according to the intervals of the international E24 fixed resistance nominal value, with a total of 48 nominal values of 1K, 1.1K, 1.2K to 91K.

[0062] The varistor film whose Rf resistance value is not the nominal value during the varistor film grading test is filed according to the principle of proximity. For example, when a pressure of 1kg is applied to the varistor film, the gain resistor Rf is adjusted to make Vout reach a predetermined voltage value. If the gain resistor Rf value is between 1K and 1.1K during the test, the nominal resistance middle value is calculated as (1K+1.1K) / 2=1.05K. The varistor film with a gain resistor Rf value ≤1.05K during the test is classified as Rf=1K, and the varistor film with a gain resistor Rf value >1.05K during the test is classified as Rf=1.1K.

[0063] When there are higher requirements for pressure resolution and accuracy, the varistor film can be divided into grades according to the intervals of the international E48 or international E96 fixed resistance nominal values.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A film pressure sensor, characterized in that: The invention comprises a flexible pressure-sensitive film material, an insulating substrate and an electrode assembly, wherein the electrode assembly is arranged on one end surface of the insulating substrate, and the flexible pressure-sensitive film material is fixedly mounted on the end surface of the insulating substrate provided with the electrode assembly. The conductivity of the flexible pressure-sensitive film material is between that of a conductor and an insulator, and the flexible pressure-sensitive film material is used to conduct the electrode assembly when the film pressure sensor is subjected to pressure so that the film pressure sensor exhibits a resistance value corresponding to the pressure applied to the film pressure sensor. An adsorption elimination component is provided between the electrode assembly and the flexible pressure-sensitive film material, and the adsorption elimination component is used to eliminate adsorption and adhesion between the flexible pressure-sensitive film material and the electrode assembly. The adsorption elimination component includes a frosted layer and a graphite carbon layer, wherein the graphite carbon layer is arranged on one end surface of the electrode assembly close to the flexible pressure-sensitive film material, and the frosted layer is arranged on one end surface of the flexible pressure-sensitive film material close to the electrode assembly, and the frosted layer at least covers the area where the graphite carbon layer and the flexible pressure-sensitive film material are opposite, and the frosted layer and the graphite carbon layer are not in contact; The electrode assembly includes a first metal electrode and a second metal electrode, wherein the first metal electrode and the second metal electrode are both arranged on the same surface of the insulating substrate, and the first metal electrode and the second metal electrode are arranged separately; A positioning component is provided between the electrode component and the flexible pressure-sensitive film material, and the positioning component is provided in contact with only one of the first metal electrode and the second metal electrode; A support assembly is also provided on one end surface of the flexible pressure-sensitive adhesive material close to the electrode assembly; The positioning assembly is spaced apart from the supporting assembly, and the height of the positioning assembly is higher than the height of the supporting assembly; The support component is configured as a ring structure, and the positioning component is configured on an end surface of the support component away from the flexible pressure-sensitive film material; The materials of the positioning component and the supporting component are the same as the flexible pressure-sensitive film material.

2. A shoe insole, characterized in that: The device comprises several groups of film pressure sensors as claimed in claim 1.

3. The insole according to claim 2, characterized in that: Before the plurality of film pressure sensors are arranged inside the insole, a bin test is required for the plurality of film pressure sensors, which specifically includes the following steps: Performing a pressure test on the film pressure sensor, and classifying the plurality of film pressure sensors into different grades based on the gain resistor values required by the signal amplification circuit; Based on the grading result, film pressure sensors with the same gain resistance value are arranged in the same insole.

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