JP2534606B2 - pressure switch - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure switch which detects pressure and performs a switching operation.

[0002]

2. Description of the Related Art Generally, a sensor using a piezoelectric element is known as a sensor for detecting pressure. this is,
The pressure is detected by attaching a piezoelectric element, which is made thin enough not to affect the flexure of the pressure receiving film, on a thin film (called a pressure receiving film) that bends under pressure.

This sensor has a problem that the piezoelectric element is easily affected by the environment such as temperature and it is difficult to adjust the zero point. Further, since the piezoelectric element generates a voltage when receiving pressure, there is a possibility of sparking, and there is a problem that it should not be used in an environment requiring explosion protection.

[0004]

As described above, the conventional pressure sensor has a problem that its characteristics are influenced by environmental conditions, it is difficult to adjust the zero point, and it is not suitable in an explosion-proof environment.

Therefore, in order to eliminate such a problem, the present invention aims to provide a pressure switch whose characteristics are not influenced by environmental conditions, whose zero point is easily adjusted, and which is highly safe and reliable. And

[0006]

SUMMARY OF THE INVENTION According to the present invention, a pressure-receiving film having a first surface having a light-reflecting property, which is bent according to a difference between a force applied to a first surface and a force applied to a second surface, The tip contacted the first surface of this pressure-receiving film with almost no gap and was connected to the light-emitting part.
Optical fiber bundle connected to the light receiving part
And a bifurcated fiber bundle having
In a state where the pressure receiving membrane to the distal end comes close to Aiba bundle not introduced into the light receiving section light from the light emitting portion is shielded by the pressure receiving membrane, emission in a state in which the two branch fiber bundle pressure receiving film from the tip of the leaves The light from the section is reflected by the pressure receiving film and introduced into the light receiving section.

[0007]

The force applied to the second surface of the pressure receiving film is smaller than the force applied to the first surface of the pressure receiving film. Therefore, when the pressure receiving film is bent toward the second surface, the light from the light emitting portion The switch is turned on because it is reflected by the pressure receiving film and enters the light receiving portion. On the contrary, when the force applied to the second surface is larger than the force applied to the first surface, the pressure receiving film is in contact with the light emitting unit and the light receiving unit, so that the light from the light receiving unit is blocked by the pressure receiving film. The switch is turned off because it has not entered the light receiving part. In this way, switching can be performed by the deflection of the pressure receiving film according to the difference in the force applied to both sides of the pressure receiving film. Therefore, by applying a known force to one side surface of the pressure receiving membrane and an unknown force to the other side surface thereof, it is possible to detect the time point at which the unknown force reaches the known force.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. However, in this description, it is assumed that the effective areas of both side surfaces of the pressure receiving film to which pressure is applied are the same. That is, comparing the “force” applied to the entire surface is equivalent to comparing the “pressure” per unit area.

However, in the actual case, the effective areas of both surfaces may be different, and in that case, “pressure” and “force” need to be clearly discussed as different concepts. In order to avoid complication, this description will be made under the above assumptions.

FIG. 1 is a diagram showing the structure of a pressure switch according to an embodiment of the present invention. Reference numeral 1 is a pressure-receiving film made of a known suitable material and having light reflectivity. This pressure receiving membrane 1
Is sensitive to the pressure difference between the pressure P1 in the left side region A of the pressure receiving film 1 and the pressure P2 in the right side region B of the pressure receiving film 1 to bend.

The surface of the pressure receiving film 1 is processed flat so as not to diffusely reflect light. The pressure receiving film 1 completely separates the left side region A and the right side region B of the pressure receiving film 1.

A bifurcated fiber bundle 4 is arranged on the region B side of the pressure receiving film 1, and two kinds of optical fiber bundles 4a and 4b are bundled therein.

One is a fiber bundle 4a for sending light from the light emitting part 2 toward the pressure receiving film 1, and the other is a fiber bundle 4b for sending the light reflected by the pressure receiving film 1 to the light receiving part 3. . The fiber bundle 4a from the light emitting section 2 and the fiber bundle 4b to the light receiving section 3 are bundled into a single fiber bundle 4c by the joint section 5.
The tip surface of the bundled fiber bundle 4c on the pressure receiving film side is processed flat so that it can contact the pressure receiving film 1 without any gap.

Therefore, the light transmitted from the light emitting unit 2 and hitting the pressure receiving film 1 does not leak anywhere when the fiber bundle 4c and the pressure receiving film 1 are in contact with each other, so that the light receiving unit 3 is provided.
It is a mechanism that can not be sent to.

In such a structure, the operation in the case where the magnitude relationship between the pressures in the region A on the left side and the region B on the right side of the pressure receiving film 1 changes will be described. Here, for example, it is assumed that a known and certain fixed pressure is applied to the B side.

First, the pressure P1 on the A side is the pressure P on the B side.
It is assumed to be greater than 2. In this case, the pressure receiving film 1 is in contact with the tip surface of the fiber bundle 4c without any gap. Therefore, the light that has entered the pressure receiving film 1 from the light emitting unit 2 through the fiber bundles 4a and 4c does not leak from the fiber bundles 4a and 4c that have passed through even if the light is reflected by the pressure receiving film 1. Therefore, the reflected light from the pressure receiving film 1 does not reach the light receiving portion 3, and the switch remains off.

Next, the pressure P1 in the region A decreases and the pressure P1 in the region B decreases.
FIG. 2 shows a state in which the pressure P2 is lower than the pressure P2.

In this case, the pressure receiving film 1 is bent toward the area A due to the difference between the pressures P1 and P2. Then, the tip end surface of the fiber bundle 4c that has been in contact with the pressure receiving film 1 is separated from the pressure receiving film 1, and the light transmitted from the light emitting unit 2 is reflected by the pressure receiving film 1 in a direction different from the incident direction.

Therefore, the reflected light is reflected by the fiber bundle 4
It goes into the fiber leading to the light receiving part 3 in c,
It is detected by the light receiving unit 3.

In this way, the pressure switch performs an ON / OFF switching operation based on the known pressure P2, depending on whether or not the unknown pressure P1 reaches the reference pressure P2. Since this operation uses the reflection of light, it is accurate without being affected by environmental conditions such as temperature, and it can be used safely even in an explosion-proof environment. Also, it has a strong characteristic against electric noise.

Next, another embodiment of the present invention is shown in FIG.

One feature of this embodiment is that a light emitting / receiving element 8 integrally formed with a light emitting element for generating light and a light receiving element for receiving light is arranged directly opposite to the pressure receiving film 1. That is the point.

The light emitting / light receiving element 8 is connected to an external signal circuit through a light emitting element side lead wire 6 and a light receiving element side lead wire 7, respectively. The tip surface of the light emitting / receiving element 8 on the pressure receiving film 1 side is flattened so that when the pressure receiving film 1 is not bent, it can be brought into contact with it without any gap.

The light emitting / receiving element 8, the light emitting element side lead wire 6 and the light receiving element side lead wire 7 are surrounded by a protective tube 10 made of an appropriate material and protected from the surrounding environment.

Further, a spring 9 is arranged outside the protective tube 10, and an appropriate bias pressure is applied to the pressure receiving film 1. As a result, it is divided by the pressure receiving film 1.
When the pressure difference between the two regions is large, switching can be performed when the pressure difference between the two regions reaches this bias pressure.

It is desirable that the strength of the spring 9 can be adjusted to obtain a desired bias pressure.

In such a case, even if the unknown pressure to be detected does not change, this unknown pressure is added as the pressure P1, and the known pressure is changed to the pressure P, for example.
2, the bias pressure of the spring 9 is variably adjusted to detect the point where the switching operation is performed, and the unknown pressure P1 can be determined from the bias pressure at that point and the known pressure P2.

An application example of the pressure switch of the present invention will be described below.

First, FIG. 4 (A) shows the entire structure when applied to a pressure balance type indicator. Further, FIG. 2B shows an enlarged view of the main portion C of FIG.

In FIG. 1A, two pipes 21,
22 and the other pipe 22 is fitted into one pipe 21. The inner wall of the outer pipe 21 has a step portion, and the pressure receiving film 1 is supported between the step surface and the tip surface of the inner pipe 22 via a gap adjusting shim 11.

The bifurcated fiber 4 is inserted into the inner pipe 22 from the base end side of the pipe, and the tip end face of the fiber 4 faces the surface of the pressure receiving film 1 with a very small gap. The gap between the pressure receiving film 1 and the fiber 4 is adjusted by the gap adjusting shim 11 to an appropriate distance, that is, a minute distance suitable for satisfying both good responsiveness of switching operation and high measurement accuracy. It

Further, a groove is formed at an appropriate position on the outer circumference of the inner pipe 22 over the entire circumference thereof, and the O-ring 12 fitted in the groove seals the contact surface between the outer pipe 21 and the inner pipe 22.

The branch pipe 20 is connected to the inner pipe 22,
A known pressure P2 is introduced into the inner pipe 22 through the branch pipe 20. This known pressure P2 is transmitted to the chamber B on the right side of the pressure receiving membrane 1 through the gap between the fiber 4 and the inner wall of the inner pipe 22. On the other hand, an unknown pressure P1 is applied to the chamber A on the left side of the pressure receiving membrane 1 through the outer pipe 21.
Will be introduced.

In such a structure, if P1> P2, the pressure receiving film 1 is in close contact with the tip surface of the fiber 4 and the switch is in the OFF state. When P1 or P2 changes from this state and P1 = P2, the switch is turned on. In this way, the unknown pressure P1 becomes the known pressure P2.
Can be accurately detected.

Next, FIG. 5 shows a configuration when applied to a flow rate detector.

FIG. 3A shows the entire structure, and an enlarged view thereof is shown in FIG. In FIG. 5A, this type of flow rate detector has a throttle tube 13 for flowing a fluid,
This is a mechanism in which the pressure difference (proportional to the square of the flow velocity) between the upstream side and the downstream side of the throttle portion in the central portion is obtained, and then the flow rate is determined.

The pressure switch of the present invention is used to detect the pressure difference. Throttle tube 1 upstream and downstream of the throttle
Capillary tubes 14 and 15 for pressure pickup are provided perpendicularly to the flow path at the same distances from the center of 3, respectively. The upstream thin tube 14 and the downstream thin tube 15 are respectively connected to the pipes 23 and 24 that form the casing of the pressure switch.

In these two pipes 23 and 24,
One pipe 24 is fitted into the other pipe 23, and the pressure-receiving membrane 1 is provided between the tip end surface of the inner pipe 24 and the stepped surface of the inner wall of the outer pipe 23 via a gap adjusting shim 11. Is supported. The other end of the outer pipe 23 is closed to form a left side chamber A of the pressure receiving membrane 1, and upstream pressure is introduced into the chamber A from the upstream thin tube 14.

The inner pipe 24 constitutes the right side chamber B of the pressure receiving membrane 1, and the thin tube 15 is provided in this chamber B.
The downstream pressure is transmitted through. Further, the bifurcated fiber 4 is inserted from the base end side of the inner pipe 24, and the tip end surface of the fiber 4 faces the pressure receiving film 1 with a minute gap.

A groove is provided at a predetermined position on the outer surface of the inner pipe 24, and the O-ring 12 fitted in the groove seals the surfaces of the two pipes 23 and 24 in contact with each other. Furthermore, this bifurcated fiber 4
A spring 9 is arranged on the outer surface of the front end portion of the device, and a constant bias pressure is applied to the pressure receiving film 1 from the chamber B. The magnitude of the bias pressure applied by this spring 9 is
It is determined to give a pressure calculated back from the flow rate to be detected.

The operation in the case where the flow rate of the fluid flowing through the throttle tube 13 is increased in such a configuration will be described.

First, since the bias pressure is applied to the pressure receiving film 1 by the spring 9, the pressure receiving film 1 is separated from the bifurcated fiber 4 when the flow rate is small and the pressure difference is smaller than the bias pressure. Is in the ON state. From this state, the flow velocity of the fluid flowing through the throttle pipe 13 increases, and when the pressure difference reaches the bias pressure, the pressure receiving film 1 is discharged to 2
It comes into close contact with the branch fiber 4 and the switch is turned off. As a result, it can be seen that the flow velocity in the throttle tube 13 has reached a predetermined value.

Next, FIG. 6 shows a configuration when applied to a level detector. The figure (A) shows the whole structure, and the figure which expanded the part of E is shown in the figure (B). In this example, the pressure switch according to the present invention is attached to the bottom surface of the container 16.

When a fluid or powder is filled in the container 16, the density of the filling is ρ, the filled height is measured from the bottom surface of the container 16 to h, and the distance from the bottom surface to the pressure receiving membrane is d, When the area of the pressure receiving film 1 of the pressure switch according to the present invention is S, the pressure receiving film 1 receives a force of ρS (h−d) (1). That is, if a constant force due to the filler from the bottom surface to the pressure receiving membrane is subtracted from the force applied to the pressure receiving membrane 1, ρSh is obtained, and the pressure receiving membrane 1 receives a force proportional to the height h from the bottom surface of the filling material. . Therefore, if the pressure applied to the pressure receiving film 1 is known, the height h filled in the container 16 can be known.

Referring to FIG. 6 (A), the casing of the pressure switch is composed of two cylinders 25 and 26, and one cylinder 25
Is attached to the bottom of the container 16. The other cylinder 26 is fitted into this cylinder 25, and the pressure receiving film 1 is interposed between the tip end surface of the inner cylinder 26 and the step surface of the inner wall of the outer cylinder 25 via the gap adjusting shim 11. It is supported. The outer cylinder 25 constitutes a chamber A above the pressure receiving membrane 1, and the pressure P1 in the container is introduced into the chamber A.

On the other hand, the inner cylinder 26 constitutes the lower chamber B of the pressure receiving membrane 1, and the atmospheric pressure P2 is introduced into this chamber B through the side hole provided in the inner cylinder 26. Further, the bifurcated fiber 4 is fitted in the inner tube 26, and its tip end surface faces the pressure receiving film 1 with a minute gap.

Further, a spring 9 is arranged on the outer surface of the leading portion of the bifurcated fiber 4, and a constant bias pressure is applied to the pressure receiving film 1 from the chamber B side. The magnitude of the pressure applied by the spring 9 is determined so as to give the pressure difference calculated back from the level to be detected.

In such a structure, when the filling amount in the container is small and the downward pressure due to the filler is smaller than the bias pressure due to the spring 9, the pressure receiving film 1 is separated from the bifurcated fiber 4. , The switch is in the ON state. When the filling level rises and the filling pressure becomes equal to the bias pressure by the spring 9, the pressure receiving membrane 1
Is in close contact with the bifurcated fiber 4, and the switch is from ON to O
Switch to FF.

Finally, FIG. 7 shows the configuration when applied to a float type level detector.

FIG. 7A shows the entire structure, and FIG. 7B shows an enlarged view of the portion F. This detector is mounted on the upper part of the container to monitor the level of the filling amount of fluid or powder.

One of the two cylinders 27 and 28 constituting the casing of the pressure switch is the other cylinder 27.
The pressure-receiving membrane 1 is inserted between the tip end surface of the inner cylinder 28 and the stepped surface of the inner wall of the outer cylinder 27 via a gap adjusting shim 11.
Is supported. The lower and upper chambers A of the pressure-receiving membrane 1 constituted by the two cylinders 27 and 28, respectively.
Atmospheric pressure is introduced into B and B.

Further, from the lower end of the outer cylinder 27, the push rod 1 connected to the throat 19 placed in the container.
8 is inserted in a vertically movable state, and the length of the push rod 18 is adjusted so that the push rod contacts the pressure receiving film 1 at the filling level to be detected.

A stop ring 17 is attached to the push rod 18 to prevent the push rod 18 from falling off the cylinder 27 when the level is lowered. In addition, the inner cylinder 28 has 2
The branch fiber 4 is inserted, and the tip end surface thereof faces the pressure receiving film 1 with a minute gap.

A spring 9 is arranged on the outer surface of the leading portion of the bifurcated fiber 4 to apply a predetermined bias pressure to the pressure receiving film 1. The magnitude of the bias pressure applied by the spring 9 is such that the pressure receiving film 1 is appropriately separated from the tip surface of the fiber 4 in the state where the push rod 18 is not in contact with the pressure receiving film 1, and the push rod 18 is not in contact with the pressure receiving film 1. When it comes into contact with the
The size is set so as to be in close contact with the tip surface of the.

In such a structure, when the filling level in the container is still low and the push rod 18 is not in contact with the pressure receiving film 1, as shown in FIG.
Is away from the bifurcated fiber 4 and the switch is ON
Is in a state. When the filling level increases and the push rod 18 comes into contact with the pressure receiving membrane 1 and pushes it up, the pressure receiving membrane 1 comes into close contact with the bifurcated fiber 4, so the switch is switched from ON to OFF.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be implemented in various other states. For example,
It is also possible to measure the degree of force applied to the pressure receiving film from the output level of the light receiving unit by adopting an element or an amplifier that generates an electrical output that changes according to the amount of light received, in the light receiving unit.

[0057]

As described above, according to the pressure switch according to the present invention, a zero-adjustment is easy because a signal that is strong against disturbance such as light is used and the measurement is performed by the geometrical optical principle of reflection of light. In addition, since it has low resistance to the environment such as light receiving and light emitting elements, and elements that use electricity can be placed away from the detection environment, it is safe and reliable even in severe environments such as explosion proof environment and high temperature and humidity. High measurement can be performed. Further, according to the pressure switch of the present invention,
For example, attach the tip of the bifurcated fiber bundle to the first surface of the pressure-receiving membrane.
By adopting a configuration that makes contact with
Light is almost parallel light, so the optical axes of the light emitting part and the light receiving part
There is no need for alignment, and there are two branch
Since it is only necessary to bring the tip of the ive bundle into contact with the pressure receiving membrane,
Easy to assemble and highly accurate.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of a pressure switch according to the present invention.

FIG. 2 is a sectional view showing a state in which the pressure switch according to the present invention is turned on.

FIG. 3 is a sectional view showing the configuration of another embodiment of the pressure switch according to the present invention.

FIG. 4 is a cross-sectional view showing a configuration when the pressure switch according to the present invention is applied to a pressure balance type acupressure meter.

FIG. 5 is a cross-sectional view showing the configuration when the pressure switch according to the present invention is applied to a differential pressure type flow meter.

FIG. 6 is a cross-sectional view showing the configuration when the pressure switch according to the present invention is applied to a level detector.

FIG. 7 is a cross-sectional view showing the configuration when the pressure switch according to the present invention is applied to a float type level detector.

[Explanation of symbols]

 1 pressure receiving film 2 light emitting part 3 light receiving part 4 2 branched fiber

Claims (1)

(57) [Claims] 1. A pressure-receiving film, the first surface of which has a light-reflecting property, which bends according to a difference between a force applied to the first surface and a force applied to the second surface, and a first surface of the pressure-receiving film. The tip is almost open
Optical fiber bundle and light receiving part that are in close contact and connected to the light emitting part
Bifurcated fiber with optical fiber bundle connected to
And a flux is not introduced into the light receiving section light from the light emitting portion is shielded by the pressure receiving membrane is in a state where the pressure receiving membrane to the distal end of the bifurcated fiber bundle are close, the two branch fiber bundle
The pressure switch, wherein the light from the light emitting portion is reflected by the pressure receiving film and introduced into the light receiving portion when the pressure receiving film is separated from the tip of the pressure receiving film.