JP4779150B2 - Diaphragm type pressure sensor - Google Patents

Description

  The present invention relates to a diaphragm type pressure sensor using a stress luminescent material as a material of the diaphragm, and more specifically, by measuring the amount of light emitted from the diaphragm when the diaphragm is deformed by the applied pressure. The present invention relates to a diaphragm type pressure sensor for calculating pressure.

  Conventionally, pressure sensors that measure the amount of diaphragm displacement using light are known (see, for example, Patent Documents 1 to 3).

Japanese Patent Publication No. 63-271975 JP-A-8-184514 JP-A-8-63164

However, the conventional diaphragm type pressure sensor requires a light source, which has been an obstacle to downsizing the sensor.
This is because providing a light source requires not only a light emitting element but also wiring, a power source, and the like related thereto.
In addition, this complicates the sensor structure itself and increases the number of parts, resulting in failure.

The present invention has been made on the basis of such background technology, and has been made to overcome the above-described problems of the background technology.
That is, an object of the present invention is to provide a diaphragm type pressure sensor that has a simple structure and is miniaturized.

  Thus, as a result of intensive research on the background of such problems, the inventor unexpectedly uses a stress luminescent material as the diaphragm material itself, thereby eliminating the need for a light source and simplifying the structure. The present invention has been completed based on this finding.

That is, the present invention includes (1) a box, a diaphragm including a stress-stimulated luminescent material provided in an opening of the box, and a light receiving unit provided at a position facing the diaphragm and receiving light emitted from the diaphragm. A diaphragm type pressure sensor, wherein the diaphragm is a flexible ceramic or glass base material mixed with SrAl ₂ O ₄ : Eu which is a stress luminescent material , and the thickness of the diaphragm is 1 μm to 1000 μm, the light receiving portion is the end face of the optical fiber, the optical fiber is a light transmission path, a cladding having a refractive index smaller than that of the core to confine light in the core, and the core and the cladding are covered consists of a coating material, the inner wall of the box body made of polycarbonate or aluminum is formed a reflective film, and the diaphragm It consists in a diaphragm-type pressure sensor reflecting film is provided on the surface.

The present invention also provides: (2) consists in a diaphragm-type pressure sensor according to (1) further is disposed a condenser lens between the diaphragm and the light receiver.

The present invention also relates to (3), consists in a diaphragm-type pressure sensor according to (1) or (2) converted into pressure by measuring the light received by the light receiving portion.

In addition, as long as the objective of this invention is met, the structure which combined said (1) to ( 3 ) suitably is also employable.

  According to the present invention, since the diaphragm is a material containing a stress-stimulated luminescent material, a light source is not required, and a diaphragm type pressure sensor with a simple structure and reduced size can be provided.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a diaphragm type pressure sensor according to an embodiment of the present invention.
The diaphragm type pressure sensor of this embodiment has a cylindrical box 1 having a bottom 1a.
The box 1 is made of a synthetic resin material (for example, polycarbonate) or a metal material (for example, aluminum) so that light from the outside does not enter or light does not leak from the inside to the outside.

  In addition, a reflection film is formed on the inner wall of the box 1 so that light can be efficiently reflected.

A condensing lens 3 is disposed via a lens holding part 2 in the middle of the box 1 in the longitudinal direction, that is, between a diaphragm and a light receiving part described later.
The lens holder 2 and the condenser lens 3 divide the space of the cylindrical box 1 into a first space 4 and a second space 5.
A diaphragm 6 is provided at the opening of the box 1 that is the end of the first space 4.

This diaphragm 6 is obtained by adding an appropriate amount of a stress luminescent material to a material to be a base material.
Here, the stress light-emitting material refers to a material that emits light by energy mechanically applied by stress, frictional force, impact force, vibration, or the like.

Moreover, as a material used as a base material, a polymer material, flexible ceramics, glass, or the like can be used. Examples of the polymer material include polyimide (PI), polymethyl methacrylate (PMMA), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), Polyvinylidene chloride (PVDC), polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), polyphenyl sulfide (PPS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene It is preferable to include at least one of phthalate (PEN), polyetherimide (PEI) or polyetheretherketone (PEEK).
In particular, polyimide, polyethylene terephthalate, polymethyl methacrylate and the like are suitable for the deformation characteristics as a diaphragm.
In addition, when flexible ceramics or glass is used as a base material, it is superior in heat resistance as compared with a polymer material, so that it can be used under high temperature conditions.

As the stress luminescent material, an inorganic material and an organic material can be used. From the viewpoint of light emission intensity, it is desirable to use an inorganic material.
The stress-stimulated inorganic material is obtained by doping a crystal serving as a base material with an element serving as a luminescent center. Examples of the material of the inorganic base material constituting the stress-stimulated luminescent material include oxides, sulfides, carbides, and nitrides having a melilite structure, FeS ₂ structure, wurtz structure, spinel structure, corundum structure, or β-alumina structure. .

  As an element serving as a light emission center doped in this inorganic base material, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu It is preferable to use one or more of rare earth ions such as Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, and W.

For example, when a strontium and aluminum-containing composite oxide is used as the base material, xSrO · yAl ₂ O ₃ · zMO (M is a divalent metal, Mg, Ca, Ba, x, y, and z are integers), xSrO · yAl ₂ O ₃ .zSiO ₂ (x, y, z are integers) may be used.
Among these, SrMgAl ₁₀ O ₁₇ : Eu, (Sr _x Ba _1-x ) Al ₂ O ₄ : Eu (0 <x <1), SrAl ₂ SiO ₇ : Eu, and the like are desirable.
Examples of the form of the diaphragm include a film formed by mixing a stress luminescent material into a polymer material as a base material, and a film in which a luminescent material layer is formed on the surface of the film as a base material. Any film that can be deformed can be used.

In addition, a reflective film 7 is provided on the upper surface of the diaphragm 6 so that light emitted from the diaphragm 6 can efficiently reach a light receiving portion described later.
The material of the reflective film 7 is not particularly limited as long as it does not inhibit the deformation of the diaphragm. For example, a metal film such as aluminum, gold, platinum, nickel, titanium, etc. is used. It is formed.

In addition, an optical fiber 8 is provided in the center of the bottom portion 1 a and is disposed so as to face the diaphragm 6.
The optical fiber 8 includes a core 9 which is a light transmission path, a clad 10 having a refractive index smaller than that of the core 9 in order to confine light in the core 9, and a covering material 11 which covers the core 9 and the clad 10. It is comprised by.
The optical fiber 8 is arranged so that the center of its end face is on the central axis of the condenser lens 3.
By using the end face of the optical fiber 8 as a light receiving part, the structure of the light receiving part itself becomes simple, and the structure of the pressure sensor can be further simplified.

As shown in FIG. 2, when pressure p is applied to the upper surface of the diaphragm 6, the diaphragm 6 bends and light is emitted from the stress-stimulated luminescent material.
Since the emitted light is totally reflected by the reflection film 7 and the inner wall of the box 1, the intermediate position between the diaphragm 6 and the end face of the optical fiber 8, more specifically between the opening and the bottom of the box 1. Is efficiently guided to the condensing lens 3 provided in the lens.
A part of the light guided to the condensing lens 3 is condensed by the condensing lens 3, and illuminates the end surface of the optical fiber 8 as a light receiving unit, specifically the end surface of the core 9. Will invade.

The light that has entered the core 9 is totally reflected without entering the cladding 10 having a lower refractive index than the core 9 surrounding the core 9, and enters the photodetector 12 shown in FIG.
That is, the light emitted by the deformation of the diaphragm 6 is received by the photodetector 12 from the box 1 via the optical fiber 8.
A photodiode is provided in the photodetector 12. The photodiode converts light energy into an electrical signal and sends the signal to an information processing apparatus such as a personal computer 13 via a cable.
In place of the photodiode, for example, a photomultiplier tube, a phototransistor, a CCD, or the like can be employed.
In this personal computer 13, an electrical signal is converted into a pressure value and displayed using a program created in advance.
Thus, the light measured by the light receiving unit is finally converted into pressure.

In calculating the pressure, a conversion formula may be obtained in advance by measuring the correspondence between the pressure applied to the diaphragm 6 and the voltage value of the electric signal transmitted from the photodiode by the pressure. is necessary.
By storing the conversion formula in the program in this way, an accurate pressure can be converted and displayed as appropriate.
In addition, since the light emission intensity of the stress luminescent material varies depending on the temperature, the calibration of the conversion formula is performed with the temperature condition also included in the variable.

  Also, when measuring the pressure, it should be noted that since the diaphragm 6 emits light after the diaphragm 6 starts to deform due to the pressure, the pressure change monotonously increases or decreases monotonously. It is necessary to measure the light.

The diaphragm 6 in the present invention preferably has a thickness in the range of 1 μm to 1000 μm so as to be easily deformed by pressure (see FIG. 4).
The smaller the degree of deformation caused by the pressure of the diaphragm 6, the smaller the pressure is measured.

According to the above-described embodiment, the diaphragm 6 is a material including a stress-stimulated luminescent material, so that a light source is not required, and a diaphragm type pressure sensor that has a simple structure and is miniaturized can be provided.
[Other Embodiments]
Although FIG. 1 described above is a diaphragm type pressure sensor having a condensing lens, the present invention does not necessarily require a condensing lens.
That is, as the diaphragm type pressure sensor, it is possible to omit the condensing lens arranged between the diaphragm and the light receiving unit.
Also in this case, the light receiving unit and the like adopt the same configuration as that of the above-described embodiment.

FIG. 5 shows an example in which the pressure in the pipe is measured using the diaphragm type pressure sensor of the present invention.
As described above, the diaphragm is disposed on the pipe surface and the pressure in the pipe is measured. This is very useful because the sensor itself is simple and downsized.
Although the present invention has been described above, the present invention is not limited to the above-described embodiment, and it is needless to say that various other modifications are possible without departing from the essence thereof.
For example, although the stress-stimulated luminescent material has been described as an inorganic material, any organic material that has a light-emitting phenomenon due to stress can be applied as a diaphragm.
Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Using the apparatus shown in FIG. 6, a performance evaluation test of a diaphragm type pressure sensor was performed.
Here, the size of the box was such that the inner diameter of the opening was 25 mm, and the distance from the diaphragm 6 to the end of the optical fiber 8 was 15 mm.
As the optical fiber, a plastic optical fiber having a fiber diameter of 3 mm, a core diameter of 2.94 mm, and a maximum attenuation of 0.19 dB / m was used.
The diaphragm 6 was formed into a film shape (thickness: 250 μm) by mixing SrAl ₂ O ₄ : Eu (SAO-E), which is a luminescent particle, with polymethyl methacrylate (PMMA), which is a base material, (weight ratio 10: 1).
Incidentally, the strength of functioning with the diaphragm can be sufficiently maintained with this weight ratio example.
With respect to such a diaphragm type pressure sensor, various pressure fluctuations were applied to the diaphragm from the pressure application unit by gas pressure, and the emission intensity was measured.
FIG. 7 shows a graph of the experimental results.
The vertical axis indicates the emission intensity (cps) and the horizontal axis indicates the applied pressure (MPa), and the unit of the emission intensity, cps, indicates the number of photons detected per second.
As can be seen from this graph, the emission intensity shows excellent linearity with respect to the applied pressure fluctuation in the range of pressure fluctuation from 0 to 0.1 MPa.
For this reason, a sufficient effect as a pressure sensor can be exhibited.

  The present invention relates to a diaphragm type pressure sensor that calculates the pressure by measuring the amount of light radiated from the diaphragm when the diaphragm is deformed by the applied pressure. The diaphragm emits light by deformation. As long as it is used, the principle can be applied to other than the pressure sensor, and the field of application is wide.

FIG. 1 is an explanatory view showing a diaphragm type pressure sensor according to an embodiment of the present invention. FIG. 2 is an explanatory view showing a state when a load is applied to the diaphragm of the diaphragm type pressure sensor of FIG. FIG. 3 is a block diagram showing the overall configuration of the diaphragm type pressure sensor of FIG. FIG. 4 is a diagram illustrating a state where the diaphragm is vibrating. FIG. 5 shows an example in which the pressure in the pipe is measured using the diaphragm type pressure sensor of the present invention. FIG. 6 shows an apparatus used for a performance evaluation test of a diaphragm type pressure sensor. FIG. 7 is a graph showing a result of an experiment relating to a performance evaluation test of a diaphragm type pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor main body 1a Bottom part 2 Lens holding part 3 Condensing lens 4 1st space 5 2nd space 6 Diaphragm 7 Reflective film 8 Optical fiber 9 Core 10 Clad 11 Coating material p Pressure

Claims (3)

Box and
A diaphragm including a stress-stimulated luminescent material provided in the opening of the box;
A diaphragm-type pressure sensor having a light receiving portion provided at a position facing the diaphragm and receiving light emitted by the diaphragm,
The diaphragm is obtained by mixing SrAl ₂ O ₄ : Eu, which is a stress luminescent material, with a base material made of flexible ceramics or glass ,
The diaphragm has a thickness of 1 μm to 1000 μm,
The light receiving part is an end face of an optical fiber,
The optical fiber comprises a core that is a light transmission path, a clad having a refractive index smaller than that of the core to confine light in the core, and a coating material that covers the core and the clad,
A diaphragm type pressure sensor, wherein a reflection film is formed on an inner wall of the box made of polycarbonate or aluminum , and a reflection film is provided on an upper surface of the diaphragm.   2. The diaphragm type pressure sensor according to claim 1, further comprising a condensing lens disposed between the diaphragm and the light receiving unit. The diaphragm type pressure sensor according to claim 1 or 2 , wherein light received by the light receiving unit is measured and converted into pressure.

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