JPS58103638A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor which has excellent durability and good reproducibility and permits measurement of high pressure by providing electrodes on both surfaces of a film which is proeuced by dispersing fine particles of high dielectric inorg. materials in a polymer material and cold stretching or rolling the material and has voids of porosities in a specific range. CONSTITUTION:A film produced by dispersing high dielectric inorg. materials which are ferrodielectric ceramics such as barium titanate, lead titanate, lead zirconate of average particle sizes ranging 0.01-50mu in a fluorovinylidene resin so as to occupy about 5-50% volume ratio in the formed film is uniaxially or biaxially cold stretched or rolled to form a film having voids of about 1- 99.9vol% voids. Electrodes are provided on both surrfces of such film, whereby a pressure sensor which detects the change in electrostatic capacity according to pressure is obtained. Thus the sensor which permits measurement >=1,000kg/cm<2> pressure, of optional sizes and has excellent durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensor, and more particularly, to a pressure sensor that utilizes the fact that electrical capacitance decreases due to changes in pressure. Waniden sexless 4! ! ! When a molded product made of fine particles such as a sheet made of polyvinylidene fluoride and titanium-plated barium powder is cold stretched, the castability is lower than that of other stretched products. The reason for this is thought to be that voids are generated at the interface between the imitation particles and the polymeric material due to cold stretching, and the presence of such voids reduces the castability. When pressure is applied to such a cold-stretched product, the voids are temporarily crushed and the fermentation rate of the product increases. Furthermore, there is a certain relationship between pressure and electric capacity that is unique to the molded product, such as the relationship shown in FIGS. 2 and 3J. In particular, as can be seen from Figure 3, when appropriate stretching is applied, it is possible to measure pressures as large as 1000 #wt/d or more, and repeated use is possible.
- The pressure sensing portion of the pressure sensor according to the present invention is made of a polymeric substance and highly dielectric inorganic particles.

The polymer material that can be used in this invention is not particularly limited as long as it can form a hoid through molding after dispersing highly dielectric inorganic fine particles. It is preferable to use a thermoplastic resin, and among these, it is particularly preferable to use a vinylidene fluoride type resin having a high electrical coefficient. Such vinylidene fluoride thread side fat contains polyvinylidene fluoride homopolymer or more, preferably about 50 mole or more, and comonomers copolymerizable with dough, such as vinyl fluoride, trifluoroethylene, trifluoride, etc. These include co-remers with fluorine-containing comonomers such as ethylene chloride, ethylene tetrafluoride, and propylene hexafluoride.

In addition to such polymeric substances, highly dielectric inorganic fine particles constituting the pressure sensing portion of the pressure sensor according to the present invention include strongly fermented electric ceramics, for example, barium titanate, lead titanate, lead zirconate titanate, etc. It is particularly preferable to use fine particles of strong sieve electric porcelain having a perovskite crystal structure. In addition, crocodile electric fine particles other than strongly fermented electric ceramic image particles, for example cast electric bodies of titanium oxide thread, are also preferable.◎The average particle size of the highly dielectric inorganic particles used is:
It depends on the method of creating voids in the molded product, but
In general, the range of about 0.01 to 50 microns is preferred, and the range of about α5 to 5 microns is more preferred. It is also possible to form the film into an arbitrary shape after molding.However, if the molding is too slow, voids will be generated in the molded product. - Although cold stretching is preferable as a method for generating these voids, it is not limited to kneading, and any known method such as rolling or foaming may be used. The temperature during cold stretching or rolling is a temperature change below the softening point, preferably about 20C or more below the softening point.

Additionally, the stretching may be done in a uniaxial or biaxial direction.

In addition, the voids may be independent pores or continuous pores as long as the interface between the polymer material and the highly dielectric image particles is maintained. The snow under the gap may have any porosity in the formed film from about 1 to 999 volumes, preferably about 5% or more, more preferably about 10% porosity. It's more than a rice cake.

The amount of the highly dielectric inorganic fine particles in the molded product is preferably in the range of about 5 to 50 volume -1, and more preferably tL< about 10 to 40 volume -1.

If the amount of the highly dielectric inorganic material is too small, void formation will be insufficient, resulting in poor practicality as a pressure sensor. However, if the amount of the highly fermentable and electrically inert substances is too large, moldability is poor, resulting in the disadvantage that a special molding method such as a casting method must be used.

11 on both sides of the film formed as described above.
It is spread so that the L pole is in close contact with it. This allows pressure to be measured as an electrical property such as capacitance. The electrodes may be formed on the film by, for example, metal vapor deposition, or by other known methods such as adhering metal foil.

The pressure sensor according to the present invention is manufactured as described above, and the pressure t or the change in pressure is expressed as %#IK rate, change in cast W curtain, electric capacitance, electric capacitance such as change in electric capacity, electric capacity, etc. It is detected by changing the physical properties related to . Specifically, for example, a vI turtle bridge may be used, or the pressure sensor according to the present invention may be incorporated in advance as a capacitor in a high-frequency wave oscillation circuit, and a resonance frequency that is found according to the capacitance of the pressure sensor may be used. Methods such as measuring can be used.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example Polyvinylidene fluoride (manufactured by Kureha Chemical Industry ■: f#J Product name:
xF, 11000J) and barium titanate powder with an average particle size of t5-2sm (manufactured by Fuji Titanium Industries, Ltd.: Product name 1-B)
T-204J), the volume fraction after molding is 77
1G, and the latter was kneaded with a 180C hot roll so that the latter was 23-, and then formed into a sheet with a thickness of 130 microns by a 230C hot press. This sheet is 1
Uniaxially stretched 6.5 times at 60C to give a film thickness of 60 microns, and further stretched 3 times at 150C in a direction perpendicular to the uniaxial stretching direction to obtain a biaxially stretched film with a film thickness of 25 microns. The porosity of the film was 21.9 volumes, and the porosity of the 20 & Il pressed film was 397 volumes. The correlation between the pressure and the capacitance of the biaxially stretched film is shown in FIGS. 1, 2, and 3, respectively. These electromagnetic capacities were measured using an LOR meter (manufactured by Yokogawa-Hewlett Packard) at I KHz and an element electrode area of 2.6 cd. The table below shows the capacity cost conversion rate for pressure in a range where the correlation with pressure of each element is linear.

The uniaxially stretched film has linearity up to about 800 #l/(3f) and becomes an ambiguous pressure sensor within this range, while the biaxially stretched film shows some linearity in the pressure range. However, the rate of change with respect to pressurization is very large, so 100
It is also possible to measure 0Q weight/d or more.

As is known from the above embodiments, the pressure sensor according to the present invention can be manufactured in any size, such as small or large, has excellent durability, and can be used under a wide range of loads. It has many characteristics such as being able to measure

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 show the correlation between pressure and capacitance for an unstretched sheet, a -axially stretched film, and a biaxially stretched film, respectively. Agent Masaru Ueya

Claims (1)

[Claims] 1. The pressure sensing portion is a formed film made of a polymeric substance and highly castable amorphous particles, and the film has pores of about 1 volume to 999 volumes. 1. A pressure sensor characterized in that the film has a void of 100% and is provided with electrodes on both sides of the film, and detects pressure or In of pressure by converting it into a physical property value related to capacitance -ζ. 2. The pressure sensor according to claim 91, wherein the formed film is cold-stretched. 6. A pressure sensor according to claim 1 or 2, characterized in that the highly castable inorganic mold particles have an average particle diameter of about 0.01 to 50 microns. 4. Any one of claims 1 to 3, characterized in that the volume fraction of the t1611 torporic solid particles in the formed film is about 5 to 50 g6. pressure sensor. 5. The pressure sensor according to any one of claims 1 to 4, wherein the polymeric substance is vinylidene fluoride 1181. 6. The pressure sensor as set forth in claim 1 of claims 1 to 5, wherein the highly conductive inorganic fine particles are strongly conductive ceramics.