JPS59104511A - Pressure sensor - Google Patents

Abstract

PURPOSE:To attain a pressure sensor which has a simple constitution and a small size and is difficult to break, by measuring the variance of the quantity of the light which passes through a distributed index lens from an optical fiber and is reflected by a diaphragm and is made incident to the optical fiber again. CONSTITUTION:When a pressure sensor 11 is so arranged that a bottom part 23b of the sensor 11 faces a position where pressure should be measured, a pressure 18 is applied to a diaphragm 22 through a round hole 23a. Then, the diaphragm 22, especially, the part near its center is displaced in the axial direction of a distributed index lens 17. Since the direction of the light which is emitted from an end face 17b and is reflected by the diaphragm 22 is changed, the quantity of the light which is made incident to the lens 17 again and is made incident to a light quantity measuring part through an optical fiber 12b is changed also. Consequently, the pressure 18 applied to the diaphragm 22 is measured by the variance of this quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensor for measuring pressure.

Figure 1 shows a force balance type pressure sensor, which is a type of pressure sensor that has been used conventionally.As shown in Figure 1, the force balance type pressure sensor (1) is attached to a fulcrum (2). It has a supported force bar (3), one end of which is connected to a diaphragm (5) via a rigid rod-shaped member (4), and the other end constitutes an electromagnet. A force coil (6) is provided. The diaphragm (5) includes a rigid thick plate portion (5a) and a rigid thick plate portion (5a).
It consists of a thin plate part (5b) formed integrally with this so as to extend around the outer periphery of the part a). This thin plate part (5b) is
It is wavy and has elasticity. And the thick plate part (
5a) is fixed to one end of the rod-shaped member (4), and is attached to the thin plate part (5a).
The periphery of b) is fixed to the housing of the sensor (1).

Approximately midway between the fulcrum (2) and the force coil (6), there is a detected member (n'a) provided on the force bar (3) and made of a magnetic material, and a detected member (7a) facing the detected member (7a). The detection member (
7b) is provided.

Displacement detector (force is measured by two opposing members (7aX7b)
The structure is such that as the distance between them becomes smaller, a larger value of current is output. - Also this displacement detector (7
) is connected to the amplifier (8) and force coil (6) via the conductor wire.
) are connected sequentially.

A permanent magnet (
A force smoke (9) equipped with a force coil (9a) is fixed to the housing of the sensor (1), and a force coil (9a), which is an electromagnet, is fixed to the housing of the sensor (1).
6) and the permanent magnet (9a) are configured to generate a magnetic field that causes repulsion to each other.

In the force-balanced pressure sensor (1) configured as described above, when a pressure uO) is applied to the diaphragm (5) from the direction of arrow P, the force bar (3) moves around the fulcrum (2). In FIG. 1, it rotates clockwise in multiple directions.

Then, since the member to be detected (7a) approaches the detection member (7b), the current output from the displacement detector (7) is increased by 1.

The amplifier (9) increases the current from the displacement detector (7)1]
7, t-scoi) v(6). The force coil (6) supplied with this amplified current generates a stronger magnetic field than before the pressure is applied to the diamond slam (5), so this magnetic field and the magnetic field caused by the permanent magnet (9a) are combined. The repulsive force also increases. Then, the pressure in the direction of arrow P (lO
The force bar ( 3) rotation stops.

Therefore, by measuring the current at that time or the voltage caused by this current using a current measuring section or a voltage measuring section not shown, the magnitude of the pressure 00) in the direction of arrow P can be measured.

Also, if the direction of arrow P is opposite, that is, the diaphragm (5)
Even when negative pressure is applied to the sensor, the pressure can be measured by the same operation as described above.

However, such a force-balance type pressure sensor (1) has a pressure detection section having a complicated structure, so that the sensor (1) as a whole is large-sized and easily damaged by impact or the like.

In addition, the force-balance type pressure sensor (1) has a complicated pressure detection section, so there is a lot of detection loss. It is not easy to obtain accurate measurement results because it is easily influenced by environmental changes such as environmental changes.

In addition, the force balance type pressure sensor (1) has a force coil (6
), displacement detector (7), amplification device (8), force smoke (9), and other electromagnetic components, they are easily affected by electromagnetic environmental changes, and this also makes it difficult to maintain accuracy. It is not easy to obtain accurate measurement results.

In addition, the force balance type pressure sensor (1) requires the sensor (1) to be placed at the pressure detection position, so it is often necessary to move this sensor (1) every time the pressure detection position is changed). Above is very inconvenient.

Furthermore, in addition to the force-balanced pressure sensor (1) described above, pressure sensors using pressure-sensitive diodes, for example, have also been used in the past. Since it is used, it is easily affected by electromagnetic environmental changes, making it difficult to obtain accurate measurement results.

The present invention comprises a gradient index lens, at least one optical fiber, and a diaphragm, and when the diaphragm receives pressure, the gradient index lens is displaced in the axial direction. and the amount of light that is emitted from the optical fiber, passes through the gradient index lens, is reflected by the diaphragm, passes through the gradient index lens again, and enters the optical fiber changes depending on the displacement. This relates to a pressure sensor configured in this way.By configuring it in this way, the pressure detection part has an extremely simple configuration, is extremely small, and is resistant to damage due to impact, etc., and is an optical type. Therefore, in addition to the above-mentioned features, the pressure detection part has an extremely simple structure, is extremely small, and is not easily damaged by shocks, etc., and is mechanically, thermally, and electromagnetically stable, and environmentally resistant. It has high performance and low detection loss, so accurate measurement results can always be obtained.Furthermore, by lengthening the optical fiber in the pressure section, the pressure detection position can be easily changed without moving the entire senna. , it is possible to provide a pressure sensor that is very convenient in practice.

Hereinafter, rust examples 1 to 6 of the present invention will be described with reference to FIGS. 2 to 7.

2 to 5 show a first embodiment of a pressure sensor according to the invention. As shown in FIGS. 2 to 5, the pressure sensor Uυ consists of two optical fins ((12a) (12
b) has an optical fiber guide insert inserted therein and made of stainless steel or the like. This guide (13) has a large diameter part (1
5a) and a small diameter part (13b), the inner diameter of the large diameter part (13a) is approximately twice the outer diameter of each of the optical fiber cords (14a) and (14b). The inner diameter of the 1 mm small diameter part (13b) is the same as the optical fiber (12a) (12b).
) is approximately twice the outer diameter of each.

The two optical fibers (12a) (12'b) are separated by removing coating waste from one end of the two optical fiber cords (14a) (14b).
(14b) One end of them is exposed from the force. The two optical fibers (12a) (12b) and the optical fiber cord (14a) (14b) are the original fiber (
12a) With the circumferential surfaces of the exposed portions of (12b) in close contact with each other, from the open end of the seven-diameter portion (13a) until the tip of this exposed portion is flush with the open end of the small diameter portion (13b). The cord (
The other end of the cord (14a) is connected to a conventionally known power source (not shown), and the other end of the cord (14b) is connected to a conventionally known light amount measuring section (not shown) incorporating a photovoltaic cell or the like. .

The small diameter part (15b) of the guide (]3) with the optical fibers (12a) and (12b) inserted and fixed therein is inserted into a cylindrical ferrule μ6) made of stainless steel or the like. A gradient index lens η made of glass or synthetic resin in a cylindrical shape is inserted in advance at one end of the ferrule (L6), and is fixed within the ferrule (L6) with adhesive or the like. Note that this refractive index distribution lens Iln has a refractive index distribution whose value is maximum at the axial center and decreases in the radial direction by a square division approximation,
It has a length of 1/4 pitch (n + 1/4 pitch where n is a natural number) of the meandering period of light.

The end face of the small diameter portion (13b) is brought into close contact with one end face (17a) of the lens (17), and the optical fiber (12a) (
A small hole (16
It is fixed within the ferrule α6) by a circle of adhesive such as epoxy resin injected from a). In addition, the lens (1
The wall surface near the opening end of the ferrule ([6) into which the ferrule 71 is inserted and fixed has a notch (16b) extending in the axial direction and connecting the notch (16b) with the inner circumferential surface of the ferrule (161). A communicating notch (16c) is formed, and the other end surface (17b) of the lens element is located slightly inside this opening end.

A diaphragm I24 made of stainless steel or the like and configured in a thin disc shape is brought into contact with the end face of the ferrule (161) on the notch (16b) (16c) side, and in this state, a cap X is attached to this end. The cap (23) is fixed to the outer circumferential surface of the ferrule θQ with an adhesive or the like. The notches (16b) (16c) made of stainless steel or the like serve as air vents in the space formed by the end face (17b) of the diaphragm (4) and the inner peripheral surface of the ferrule.

In order to measure pressure using the pressure sensor (111) configured as described above, first connect an optical fiber (121) from a light source (not shown).
Light is emitted into the lens t171 via a).

The lens Mη has a length of 174 pitches corresponding to the meandering period of light, but since the optical axis of the optical fiber (12a) is shifted from the axis of the lens surface by approximately the radius, the end face (1
7b), the element is ejected at an angle other than perpendicular to this end face (17b). A predetermined amount of the light emitted from the end surface (17b) and reflected by the diaphragm (2) enters the lens surface again from the end surface (17b), and a predetermined amount of the light that has entered the lens surface is reflected again. is optical fiber (12b)
and is guided to a light amount measuring section (not shown).

The pressure sensor IJ1) in this state is placed at the bottom (23b).
) is arranged to face the pressure gauge i1++i1 position, the pressure u81 is applied to the diaphragm (two) through the circular hole (25a), so the diaphragm (22
1 is displaced in the axial direction of the lens u7). Then, the direction of the light ray that was emitted from the end face (17b) and reflected by the diaphragm changes, so it enters the lens u7) again from the end face (17b) and passes through the optical fiber (12b) to the outside of the figure. The amount of light incident on the light amount measuring section also changes. Therefore, the pressure U mark applied to the diaphragm can be measured by this change in the amount of light.

In this first embodiment, the length of the lens aη is 1/4 pitch of the meandering period of the light, and the two optical fibers (12a) (12b) and the lens an transmit and receive light. At the end face (17a) where optical fibers (12aX12b
) are adjacent to each other with their optical axes being shifted from the axis of the lens (17) by approximately the radius thereof, but when using two optical fibers (12a) and (12b) for transmitting and receiving light,
By arranging the optical fibers in this way, the amount of light received by the optical fiber (12b) is the largest, and accurate measurement can be performed.

Also, the notches (16b) (16c) of the ferrule (16)
The distance between the end face (17b) in the diaphragm 2) and the end face (17b) in the ill is the distance between the diaphragm 2) and the end face (17b), but if this distance is too large, the original fiber (12b) ) will decrease the amount of light received, making accurate measurement difficult.On the other hand, if this distance is too short, there is a risk that this diaphragm (2) will come into contact with the end surface (17b) due to the displacement of the diaphragm 12. Therefore, this distance is normally desirably about 0.01 to 5.0 mm.

FIG. 6 shows a schematic structure of a second embodiment of the pressure sensor according to the invention. As shown in Figure 6, the bottom (2
4a) This second embodiment is different from the second embodiment except that the diaphragm t24), which has a substantially cylindrical shape, is directly attached to the outer peripheral surface of the refractive index gradient type lens using an adhesive or the like. The structure may be substantially the same as that of the first embodiment shown in FIGS. In addition, the peripheral wall (2) of the diaphragm ('14)
4b) has a bellows-like shape, and the peripheral wall (24b) and the bottom part (24a) have substantially the same thickness and are integrally formed with each other.

In order to measure pressure using the pressure sensor of the second embodiment having such a configuration, first, light is emitted from a light source (not shown) into the lens u7 via the optical fiber (12a). . The lens (1η) has a length of 1/4 pitch of the meandering period of light, but since the optical axis of the optical fiber (12a) is offset from the axis of the lens U force by approximately the radius of the optical fiber (12a), Light is emitted from the end face (17b) at an angle other than perpendicular to the end face (17b).The light is emitted from the end face (17b) and reflected by the bottom (24a) of the diaphragm (end). For quantitative determination, use lens 1 again from the end surface (17b).
A predetermined amount of the light that enters into the lens (L7) enters the optical fiber (12b) and is guided to a light amount measuring section (not shown).

The pressure sensor of the second embodiment in such a state is placed at the bottom (2
4a) is arranged so as to face the pressure measurement position, the pressure is applied to the bottom (24a), so the bellows-shaped peripheral wall (24b) is compressed in the axial direction, and the bottom (24a) is compressed in the axial direction.
4a), particularly near the center, is displaced in the axial direction of the lens u'D. Then, it is injected from the end face (17b) and the bottom part (24a
) changes the direction of the rays reflected by
It enters the lens tlL7) from the end surface (17b) again,
The scene when the light enters a light amount measuring section (not shown) via the optical fiber (12b) also changes. Therefore, by changing the amount of light, the pressure stamped on the bottom (24a) can be measured.

According to the second embodiment of the present invention, the bottom part of the diaphragm e/υ is removed by substantially the same operation as in the first embodiment, without using the ferrule uLi) or the cap (drying) in the first embodiment. The pressure (18) applied to (24a) can be measured optically.

FIG. 7 shows a schematic structure of a sixth embodiment of a pressure sensor according to the present invention. As shown in FIG. 7, there is only one optical fiber 0, which is closely connected to one end surface (17a) of the gradient index lens f1'0, and serves as both light emitting and receiving light. The source fiber (n 6) is connected to the optical fiber (31a) for light emission and light reception via a conventionally known light splitter (27) such as a light splitter using a graded index lens.
(51b), this sixth embodiment may have substantially the same configuration as the second embodiment shown in FIG.

In the pressure sensor of the sixth embodiment having such a configuration, the light emitted from the original fiber for light projection (31a) passes through the light distributor (27) and the optical fiber group and is then sent to the lens. (17) Injected into the interior. On the contrary, the light reflected by the bottom part (24a) and entering the lens (from l'D to the original fiber) is sent to the optical fiber (from the optical splitter t27).
31a) and (31b). Therefore,
From the optical fiber for light reception (31b), the bottom part (24a)
A predetermined amount of the light reflected by can be obtained.

According to the sixth embodiment of the present invention, the lens (1'D
and the optical fiber lever 6) can be closely opposed to each other so that their optical axes are substantially coaxial with each other.
If the amount of light received by the optical fiber (26) is maximized, accurate measurement results can be obtained.

The present invention has been explained above based on the first to sixth embodiments, but
The present invention is not limited to these examples, and various modifications are possible.

For example, in the first embodiment described above, the circular hole (23a
) to apply pressure (ta) to the diaphragm (2 hot water
Through holes communicating with each other are provided in the peripheral wall of the diaphragm (22) and the end surface (17b), and pressure is applied through the through hole to the space between the diaphragm (22) and the end surface (17b). It may also be displaced in the axial direction.

As described above, according to the pressure sensor according to the present invention, the pressure is detected using the diaphragm, the gradient index lens, and the optical fiber, so the pressure detection section has an extremely simple configuration and is extremely small and compact. Moreover, according to the pressure sensor according to the present invention, the pressure detection part has an extremely simple configuration, so there is little detection loss, and since it is an optical type, it can be used as described above. In addition, the pressure detection part has an extremely simple configuration, is extremely small, and is not easily damaged or damaged by shocks, etc. However, it is mechanically, thermally, and electrically stable and environmentally resistant. , it is possible to obtain accurate measurement results.

Furthermore, according to the pressure sensor according to the present invention, by lengthening the optical fiber of the pressure detection section, the pressure detection position can be easily changed without moving the light source, light amount measurement section, etc., which is very convenient in practice. be.

In addition, according to the pressure sensor based on "Unexploded Tsu," a refractive index gradient lens is placed closely at the tip of an optical fiber, and light can be emitted and received through the refractive index gradient lens in this state, so that the light beam is not diffused. Therefore, it is possible to obtain a large amount of light and improve detection accuracy.

In addition, according to the pressure sensor of the present invention, the end surface of the gradient index lens can be made flat, so the optical contact with the original fiber is ensured, and at the same time, the distance from the diaphragm can be minimized. It can be set as small as possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing a conventional example of a pressure sensor, FIG. 2 is a schematic cross-sectional view showing a first embodiment of a pressure sensor according to the present invention, and FIGS. The figures are a cross-sectional view taken along the lines I[-Ili, ■-■v, and V-V in FIG. 2, respectively, and FIGS. It is a schematic sectional view showing the second embodiment and the sixth embodiment. In addition, regarding the symbols used in the drawings, ■ ・
−・Pressure sensor t1′i) ・−・−・ −Refraction distribution type lens f
221t24) - diaphragm. agent souvenir bladder

Claims (1)

[Claims] a gradient index lens; at least one optical fiber disposed to face one end surface of the gradient index lens; and at least one optical fiber disposed to face the other end surface of the gradient index lens. a diaphragm provided therein, the diaphragm is displaced in the axial direction of the gradient index lens by receiving pressure, and the light emitted from the optical fiber passes through the gradient index lens and A pressure sensor 0 configured such that the amount of light that is reflected by a diaphragm, passes through the gradient index lens again, and enters the optical fiber changes depending on the displacement.