Piezoelectric film pressure sensor suitable for different temperatures

Abstract

The invention discloses a piezoelectric film pressure sensor suitable for different temperatures, which comprises an upper thermal insulation layer, an upper heating layer, a piezoelectric material film layer, a lower heating layer and a lower thermal insulation layer which are sequentially stacked from top to bottom, and is characterized in that the piezoelectric material film layer is packaged between the upper heating layer and the lower heating layer and leads out piezoelectric signals through a signal line; the upper heat preservation layer and the lower heat preservation layer are each composed of a hard supporting framework and a flexible heat insulation filling material, the hard supporting frameworks are hollowed-out grid supporting frames, the thickness of the hard supporting frameworks is equal to the thickness of the upper heat preservation layer and the thickness of the lower heat preservation layer, and grids of the hard supporting frameworks are filled with the flexible heat insulation filling materials. By arranging the thermal insulation layer, the problem that the piezoelectric film pressure sensor is influenced by external temperature is solved, and the accuracy of piezoelectric data acquisition is improved while the sensitivity of the piezoelectric film pressure sensor is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of piezoelectric film pressure sensors, in particular to a piezoelectric film pressure sensor suitable for use at different temperatures. Background Art

[0002] Piezoelectric film pressure sensor is a dynamic strain sensor, mainly composed of a film made of piezoelectric material (polyvinylidene fluoride PVDF or lead zirconate titanate piezoelectric ceramic PZT). The piezoelectric constant reflects the ability of piezoelectric materials to generate charge under stress and is one of the important indicators for measuring the performance of piezoelectric materials. The temperature at which piezoelectric materials begin to lose their piezoelectric properties is called the Curie point temperature. The Curie point is an important characteristic parameter of piezoelectric materials, which determines the operating temperature range of piezoelectric materials. When the temperature rises to the Curie point, the piezoelectric properties of piezoelectric materials will gradually be lost. When PVDF is actually used, its piezoelectric constant at different temperatures will vary greatly, and the sensitivity of the device will change accordingly. Especially at high temperatures, PVDF will show depolarization characteristics. In actual engineering applications, the external environment temperature is constantly changing, the piezoelectric coefficient of the material is also constantly changing, the electromechanical relationship is always in a fluctuating state, and the sensitivity of the device is constantly changing, which makes the data acquisition accuracy of piezoelectric film pressure sensors in actual engineering applications have errors. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a piezoelectric film pressure sensor suitable for different temperatures. By setting a thermal insulation layer, the problem of the piezoelectric film pressure sensor being affected by external temperature is eliminated, and the sensitivity of the piezoelectric film pressure sensor is ensured while improving the accuracy of piezoelectric data acquisition.

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

[0005] A piezoelectric film pressure sensor suitable for use at 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, 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;

[0006] 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.

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

[0008] The upper heating layer and the lower heating layer are both made of self-temperature-controlling PTC electric heating film, and the self-temperature-controlling PTC electric heating film is encapsulated with a polyimide layer.

[0009] The flexible temperature sensor is printed on the top 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 provided between the flexible temperature sensor and the piezoelectric material film layer.

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

[0011] 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.

[0012] The rigid support frame is made of polylactic acid or acrylonitrile-butadiene-styrene copolymer using a 3D printing method.

[0013] The flexible heat-insulating filling material is aerogel heat-insulating material, and is filled into the hard supporting frame by a 3D printing method.

[0014] Advantages of the present invention:

[0015] (1) The upper insulation layer and the lower insulation layer provided in the present invention can effectively prevent the extremely high temperature or extremely low temperature of the external environment from damaging the piezoelectric material film layer, and can also reduce the heat transfer effect of the upper heating layer and the lower heating layer to the external environment. Most of the existing insulation layer materials are loose porous structures. The deformation formed after being subjected to external impact cannot be completely restored. When subjected to external pressure, the porous structure will absorb part of the energy of the external pressure, affecting the accuracy of data collection of the piezoelectric material film layer. The upper insulation layer and the lower insulation layer of the present invention are both filled with flexible thermal insulation filling materials using a hard support skeleton, so that the upper insulation layer and the lower insulation layer have a certain rigidity and are not easily deformed after being subjected to external impact. The grid of the hard support skeleton is an X-shaped cross-prism grid, and the torsional strength is greatly improved through the design of the grid size parameters, and the deformation resistance of the upper insulation layer and the lower insulation layer is further improved.

[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 film layer in a low-temperature environment to ensure that the temperature of the piezoelectric material film layer is in a certain constant state, and both the upper heating layer and the lower heating layer are made of self-controlling PTC (positive temperature coefficient thermistor) electric heating film. When the self-controlling PTC electric heating film reaches the set maximum temperature, the resistance value increases, the current decreases, the heating power decreases, and the temperature tends to stabilize, thereby avoiding the problem of depolarization of the piezoelectric material film layer due to high temperature.

[0017] (3) The present invention arranges a flexible temperature sensor with an annular structure on the piezoelectric material film layer. The temperature distribution on the piezoelectric material film layer is uneven. The flexible temperature sensor with an annular arrangement structure can fully cover the edge area of ​​the piezoelectric material film layer to achieve all-round monitoring of the temperature. In addition, 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 has the characteristics of high thermal conductivity and low dielectric constant. The high thermal conductivity insulating isolation layer can quickly transfer the temperature on the piezoelectric material film layer to the flexible temperature sensor, while isolating the flexible temperature sensor from electromagnetic interference to the piezoelectric material film layer. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0020] Figure 3 It is a schematic diagram of the structure of the flexible temperature sensor of the present invention printed on a piezoelectric material film layer.

[0021] Figure 4 It is a schematic diagram of the structure of the present invention placed in a high-speed railway foundation for stress monitoring.

[0022] Figure markings: 1-upper insulation layer, 2-upper heating layer, 3-piezoelectric material film layer, 4-lower heating layer, 5-lower insulation layer, 6-signal line, 7-flexible temperature sensor, 8-high thermal conductivity insulation isolation layer, 9-electrode line, 10-power supply line, 11-rigid support skeleton, 12-flexible insulation filling material, 13-piezoelectric film pressure sensor, 14-high-speed railway foundation, 15-thermostat, 16-stress monitor. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See Figure 1-Figure 3 , a piezoelectric film pressure sensor suitable for different temperatures, comprising an upper insulation layer 1, an upper heating layer 2, a piezoelectric material film layer 3, a lower heating layer 4 and a lower insulation layer 5 stacked in sequence from top to bottom, the piezoelectric material 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 insulation layer 1 and the lower insulation layer 5 are both composed of a hard support frame and 11 flexible insulation filling materials 12. The hard support frame 11 is a hollow grid support frame, and the grid is an X-shaped cross-prism grid. The thickness of the hard support frame 11 is the thickness of the upper insulation layer 1 and the lower insulation layer 5. The thickness of the hard support frame 11 is 0.8-1 mm, and the length and width of each prism grid are 1-1.5 mm. The flexible insulation filling material 12 is filled in the prism grid of the hard support frame 11. The hard support frame 11 is made of polylactic acid PLA or acrylonitrile-butadiene-styrene copolymer ABS by 3D printing method. The flexible insulation filling material 12 uses aerogel insulation material and is filled in the hard support frame 11 by 3D printing method.

[0026] A flexible temperature sensor 7 is printed on the top or bottom surface of the piezoelectric material film layer 3 and is arranged in a ring structure along the edge of the piezoelectric material film layer 3. A high thermal conductivity insulating isolation layer 8 is arranged between the flexible temperature sensor 7 and the piezoelectric material film layer 3. The electrode wire 9 of the flexible temperature sensor 7 and the power supply wire 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 both use self-temperature controlling PTC electric heating film, and the self-temperature controlling PTC electric heating film is encapsulated with a polyimide PI layer.

[0027] In northern my country, the problem of thawing settlement of the foundation of our country's high-speed railway is particularly obvious. In order to prevent accidents of the railway foundation, stress monitoring of the high-speed railway foundation is particularly important. Since the high-speed railway foundation has extremely high requirements for the smoothness of the railway, the monitoring device cannot be too large, and long-term monitoring needs to take into account the impact of the freeze-thaw cycle on the sensitivity of the sensor. Therefore, the piezoelectric 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 line 10 of the upper heating layer 2 and the lower heating layer 4 are all connected to the external temperature controller 15, and powered by solar cells, and the piezoelectric material film layer 3 is connected to the stress monitor 16.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that 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.

2. The piezoelectric film pressure sensor suitable for different temperatures according to claim 1, characterized in that: A flexible temperature sensor is arranged on the piezoelectric material film layer, and the electrode wires of the flexible temperature sensor, and the power supply wires of the upper heating layer and the lower heating layer are all connected to an external temperature controller.

3. The piezoelectric film pressure sensor suitable for different temperatures according to claim 2, characterized in that: The upper heating layer and the lower heating layer are both made of self-temperature-controlling PTC electric heating film, and the self-temperature-controlling PTC electric heating film is encapsulated with a polyimide layer.

4. The piezoelectric film pressure sensor suitable for different temperatures according to claim 2, characterized in that: The flexible temperature sensor is printed on the top 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 provided between the flexible temperature sensor and the piezoelectric material film layer.

5. The piezoelectric film pressure sensor suitable for different temperatures according to claim 4, characterized in that: The high thermal conductivity insulating isolation layer is made of silicon dioxide film or aluminum oxide film.

6. 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.

7. 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.

8. 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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