A piezoelectric film pressure sensor suitable for different temperatures

Abstract

The present invention discloses a piezoelectric film pressure sensor suitable for different temperatures, comprising an upper insulation layer, an upper heating layer, a piezoelectric material film layer, a lower heating layer and a lower insulation layer stacked in sequence from top to bottom, the piezoelectric material film layer is encapsulated between the upper heating layer and the lower heating layer and the piezoelectric signal is led out through a signal line; the upper insulation layer and the lower insulation layer are both composed of a hard support skeleton and a flexible insulation filling material, the hard support skeleton is a hollow grid support frame, the thickness of the hard support skeleton is the thickness of the upper insulation layer and the lower insulation layer, and the flexible insulation filling material is filled in the grid of the hard support skeleton. The present invention eliminates the problem of the piezoelectric film pressure sensor being affected by the external temperature by setting the insulation layer, ensures the sensitivity of the piezoelectric film pressure sensor, and improves the accuracy of piezoelectric data acquisition.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric thin film pressure sensors, and specifically to a piezoelectric thin film pressure sensor applicable to different temperatures. Background Art

[0002] A piezoelectric thin film pressure sensor is a dynamic strain sensor, mainly composed of a thin film made of a piezoelectric material (polyvinylidene fluoride PVDF or lead zirconate titanate piezoelectric ceramic PZT). The piezoelectric constant reflects the ability of the piezoelectric material to generate charge under stress, and is one of the important indicators to measure the performance of piezoelectric materials. The temperature at which the piezoelectric material begins to lose its piezoelectric properties is called the Curie point temperature. The Curie point is an important characteristic parameter of the piezoelectric material, which determines the operating temperature range of the piezoelectric material. When the temperature rises to the Curie point, the piezoelectric properties of the piezoelectric material will gradually be lost. When PVDF is actually used, its piezoelectric constant varies greatly at different temperatures, and the sensitivity of the device changes accordingly. Especially at high temperatures, PVDF will show the depolarization characteristic. In actual engineering applications, the external environmental temperature is constantly changing, the piezoelectric coefficient of the material is also constantly changing, the force-electric relationship is always in a fluctuating state, and the sensitivity of the device also changes continuously, resulting in errors in the data acquisition accuracy of the piezoelectric thin film pressure sensor in actual engineering applications. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a piezoelectric thin film pressure sensor applicable to different temperatures. By setting a heat preservation layer, the problem that the piezoelectric thin film pressure sensor is affected by the external temperature is eliminated, and while ensuring the sensitivity of the piezoelectric thin film pressure sensor, the accuracy of piezoelectric data acquisition is improved.

[0004] The technical solution of the present invention is as follows:

[0005] A piezoelectric thin film pressure sensor applicable to different temperatures includes an upper heat preservation layer, an upper heating layer, a piezoelectric material thin film layer, a lower heating layer, and a lower heat preservation layer stacked in sequence from top to bottom. The piezoelectric material thin film layer is encapsulated between the upper heating layer and the lower heating layer and the piezoelectric signal is led out through a signal wire;

[0006] Both the upper heat preservation layer and the lower heat preservation layer are composed of a rigid support framework and a flexible heat insulation filling material. The rigid support framework is a hollow grid support frame, and the thickness of the rigid support framework is the thickness of the upper heat preservation layer and the lower heat preservation layer. The flexible heat insulation filling material is filled in the grid of the rigid support framework.

[0007] A flexible temperature sensor is arranged on the piezoelectric material thin film layer, and the electrode wire of the flexible temperature sensor, the power supply wires of the upper heating layer and the lower heating layer are all connected to an external temperature controller.

[0008] Both the upper heating layer and the lower heating layer described above are made of self - controlled temperature PTC electrothermal films, and the self - controlled temperature PTC electrothermal films are encapsulated with polyimide layers.

[0009] The described flexible temperature sensor is printed on the top or bottom surface of the piezoelectric material thin film layer and is arranged in an annular structure along the edge of the piezoelectric material thin film layer. A high - thermal - conductivity insulating isolation layer is provided between the flexible temperature sensor and the piezoelectric material thin film layer.

[0010] The described high - thermal - conductivity insulating isolation layer is made of silicon dioxide thin film or aluminum oxide thin film.

[0011] The grid of the described rigid support framework is a rhombic grid with X - shaped intersections. The thickness of the rigid support framework is 0.8 - 1 mm, and the length and width of each rhombic grid are both 1 - 1.5 mm.

[0012] The described rigid support framework is made of polylactic acid or acrylonitrile - butadiene - styrene copolymer by 3D printing method.

[0013] The described flexible heat - insulating filling material is made of aerogel heat - insulating material and is filled into the rigid support framework by 3D printing method.

[0014] Advantages of the present invention:

[0015] (1). The upper heat - insulating layer and the lower heat - insulating layer provided in the present invention can effectively prevent the damage of the piezoelectric material thin film layer caused by extremely high or extremely low temperatures in the external environment, and can also reduce the heat transfer effect of the upper heating layer and the lower heating layer on the external environment. Most of the existing heat - insulating layer materials have a loose and porous structure, and the deformation formed after being impacted externally cannot be completely restored. Moreover, when under external pressure, the porous structure will absorb part of the energy of the external pressure, affecting the accuracy of data acquisition of the piezoelectric material thin film layer. The upper heat - insulating layer and the lower heat - insulating layer of the present invention both adopt a rigid support framework filled with a flexible heat - insulating filling material, making the upper heat - insulating layer and the lower heat - insulating layer have a certain stiffness, not easily deformed after being impacted externally. And the grid of the rigid support framework is a rhombic grid with X - shaped intersections, and through the design of the grid size parameters, the torsional strength is greatly improved, further enhancing the anti - deformability of the upper heat - insulating layer and the lower heat - insulating layer.

[0016] (2). The present invention is provided with an upper heating layer and a lower heating layer, which can perform double - sided heating on the piezoelectric material thin film layer in a low - temperature environment to ensure that the temperature of the piezoelectric material thin film layer is in a certain constant state. And both the upper heating layer and the lower heating layer are made of self - controlled temperature PTC (positive temperature coefficient thermistor) electrothermal films. When the self - controlled temperature PTC electrothermal film reaches the set maximum temperature, the resistance value increases, the current drops, the heating power decreases, and the temperature tends to be stable, avoiding the problem of depolarization of the piezoelectric material thin film layer caused by high temperature.

[0017] (3) In the present invention, a flexible temperature sensor with an annular structure is arranged on the piezoelectric material thin film layer. Since the temperature distribution on the piezoelectric material thin film layer is uneven, the flexible temperature sensor with an annular arrangement structure can comprehensively cover the edge area of the piezoelectric material thin film layer to achieve all-round temperature monitoring. Moreover, a highly thermally conductive insulating isolation layer is provided between the flexible temperature sensor and the piezoelectric material thin film layer. The highly thermally conductive insulating isolation layer has the characteristics of high thermal conductivity and low dielectric constant. While quickly conducting the temperature on the piezoelectric material thin film layer to the flexible temperature sensor, the highly thermally conductive insulating isolation layer can also isolate the electromagnetic interference of the flexible temperature sensor to the piezoelectric material thin film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is an exploded view of the present invention.

[0019] Figure 2 is a plan view of the upper thermal insulation layer of the present invention.

[0020] Figure 3 is a schematic structural view of the flexible temperature sensor printed on the piezoelectric material thin film layer of the present invention.

[0021] Figure 4 is a schematic structural view of the present invention placed on the high-speed railway foundation for stress monitoring.

[0022] Reference numerals: 1 - upper thermal insulation layer, 2 - upper heating layer, 3 - piezoelectric material thin film layer, 4 - lower heating layer, 5 - lower thermal insulation layer, 6 - signal line, 7 - flexible temperature sensor, 8 - highly thermally conductive insulating isolation layer, 9 - electrode line, 10 - power supply and power line, 11 - rigid support framework, 12 - flexible heat insulation filling material, 13 - piezoelectric thin film pressure sensor, 14 - high-speed railway foundation, 15 - temperature controller, 16 - stress monitor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] See Figures 1-3 , a piezoelectric thin film pressure sensor applicable to different temperatures, including an upper thermal insulation layer 1, an upper heating layer 2, a piezoelectric material thin film layer 3, a lower heating layer 4, and a lower thermal insulation layer 5 stacked in sequence from top to bottom. The piezoelectric material thin film layer 3 is encapsulated between the upper heating layer 2 and the lower heating layer 4 and the piezoelectric signal is led out through a signal line 6;

[0025] The upper thermal insulation layer 1 and the lower thermal insulation layer 5 are both composed of a rigid support framework and a flexible heat insulation filling material 12. The rigid support framework 11 is a hollow grid support frame, and the grid is a rhombic grid with an X-shaped intersection. The thickness of the rigid support framework 11 is the thickness of the upper thermal insulation layer 1 and the lower thermal insulation layer 5. The thickness of the rigid support framework 11 is 0.8 - 1 mm. The length and width of each rhombic grid are both 1 - 1.5 mm. The flexible heat insulation filling material 12 is filled in the rhombic grid of the rigid support framework 11. The rigid support framework 11 is made of polylactic acid (PLA) or acrylonitrile-butadiene-styrene copolymer (ABS) by using a 3D printing method. The flexible heat insulation filling material 12 is selected as an aerogel heat insulation material and is filled in the rigid support framework 11 by using a 3D printing method;

[0026] A flexible temperature sensor 7 is printed on the top or bottom surface of the piezoelectric material thin film layer 3 and is arranged in an annular structure along the edge of the piezoelectric material thin film layer 3. A high thermal conductivity insulating layer 8 is arranged between the flexible temperature sensor 7 and the piezoelectric material thin film layer 3. The electrode wire 9 of the flexible temperature sensor 7, the power supply wires 10 of the upper heating layer 2 and the lower heating layer 4 are all connected to an external temperature controller. The upper heating layer 2 and the lower heating layer 4 are both selected as self-regulating PTC electric heating films, and the self-regulating PTC electric heating films are encapsulated with a polyimide (PI) layer outside.

[0027] In the northern part of our country, the problem of foundation settlement of high-speed railways in our country is particularly obvious. In order to prevent accidents of railway foundations, stress monitoring of high-speed railway foundations is particularly important. Since high-speed railway foundations have extremely high requirements for railway smoothness, the monitoring devices cannot be too large, and the influence of freeze-thaw cycles on the sensitivity of sensors needs to be considered during long-term monitoring. Therefore, the piezoelectric thin film pressure sensor 13 of the present invention is placed in the high-speed railway foundation 14. The electrode wire 9 of the flexible temperature sensor 7, the power supply wires 10 of the upper heating layer 2 and the lower heating layer 4 are all connected to an external temperature controller 15 and are powered by a solar cell. The piezoelectric material thin film layer 3 is connected to a stress monitor 16.

[0028] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A piezoelectric film pressure sensor suitable for use at different temperatures, characterized in that: It includes an upper insulation layer, an upper heating layer, a piezoelectric material film layer, a lower heating layer and a lower insulation layer stacked in sequence from top to bottom, wherein the piezoelectric material film layer is encapsulated between the upper heating layer and the lower heating layer and the piezoelectric signal is led out through a signal line; The upper insulation layer and the lower insulation layer are both composed of a hard support frame and a flexible insulation filling material. The hard support frame is a hollow grid support frame. The thickness of the hard support frame is the thickness of the upper insulation layer and the lower insulation layer. The flexible insulation filling material is filled in the grid of the hard support frame. A flexible temperature sensor is arranged on the piezoelectric material film layer, and the electrode wires of the flexible temperature sensor, the power supply wires of the upper heating layer and the lower heating layer are all connected to an external temperature controller; The upper heating layer and the lower heating layer are both made of self-temperature-controlled PTC electric heating film, and the self-temperature-controlled PTC electric heating film is encapsulated with a polyimide layer; The flexible temperature sensor is printed on the top surface or bottom surface of the piezoelectric material film layer and arranged in a ring structure along the edge of the piezoelectric material film layer. A high thermal conductivity insulating isolation layer is arranged between the flexible temperature sensor and the piezoelectric material film layer. The high thermal conductivity insulating isolation layer is made of silicon dioxide film or aluminum oxide film.

2. The piezoelectric film pressure sensor suitable for different temperatures according to claim 1, characterized in that: The grid of the rigid support frame is an X-shaped crossed prismatic grid, the thickness of the rigid support frame is 0.8-1 mm, and the length and width of each prismatic grid are both 1-1.5 mm.

3. The piezoelectric film pressure sensor suitable for different temperatures according to claim 1, characterized in that: The rigid support frame is made of polylactic acid or acrylonitrile-butadiene-styrene copolymer using a 3D printing method.

4. The piezoelectric film pressure sensor suitable for different temperatures according to claim 1, characterized in that: The flexible heat-insulating filling material is aerogel heat-insulating material, and is filled into the hard supporting frame by a 3D printing method.

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