JPS62222124A - Liquid level detector - Google Patents

Abstract

PURPOSE:To enable even the detection of the liquid level of a liquid to be detected having strong corrosiveness and to dispense with the washing work of optical parts, by forming a hermetically sealed space between the mirror surface of a lens body and the liquid level in a holding cylinder when the liquid level to be detected reaches a predetermined value or more. CONSTITUTION:A lens body 25 is mounted in a holding cylinder 10 so that at least a part thereof is positioned above a liquid level 11 to be detected to arrange the holding cylinder 10 and one mirror surface thereof is faced to the liquid level 11. Next, an incident light introducing end part 27 and an emitted light introducing end part 8 are provided so as to be opposed to the other mirror surface of the lens body 25 and respectively connected to a light emitting element 16 and a light receiving element 17. The incident light from the end part 27 forms a focus on the liquid level 11 present at a reference position to be reflected from the liquid level 11 and almost all of the quantity of the reflected light is received by the light receiving element 17. Next, when the liquid level reaches a predetermined value or more, a hermetically sealed space is formed between one mirror surface of the lens body 25 and the liquid level 11 in the holding cylinder 10. Therefore, the liquid level does not rise further and the lens body 25 is not contacted with the liquid to be detected. As a result, the removal of the contaminant of the lens body or washing work becomes unnecessary and the liquid to be detected having strong corrosiveness can be also detected.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a liquid level detector that detects the position of a liquid level.

"Prior Art" Liquid level detectors are used that optically detect the position of the liquid level to be detected.

The structure of the main part shown in FIG. 2 is a conventionally used liquid level detector of this type, in which a prism 12 is disposed with a first prism surface 13 facing the liquid level 11 to be detected. Ru. A light emitting element 16 and a light receiving element 17 are arranged opposite to the second and third prism surfaces 14 and 15 of the prism 12, respectively.

The liquid level 11 to be detected is the first prism surface 13 of the prism 12
When the first prism surface 13 is in contact with the air layer without contacting the prism 1, the incident light from the light emitting element 16 is transmitted to the prism
The light is totally reflected by the first prism surface 13 of FIG. The liquid level 11 to be detected rises and the first prism surface 1 of the prism 12
3, the refractive index for the incident light at the position of the first prism surface 13 changes, and the incident light from the light emitting element 16 enters the liquid to be detected along the optical path shown by the dotted line in FIG. , does not reach the light receiving element 17.

Therefore, depending on whether or not light is received by the light receiving element 17, the liquid to be detected is placed at the reference position 1o on the first prism surface 13 of the prism 12.
It is detected whether or not it has been reached.

In FIG. 3, the same reference numerals are assigned to the same parts to show the structure of the main parts. This is another example of a conventionally used liquid level detector, and the prism 12 is a second and third prism. Surface 14.
15 is arranged to face the liquid surface 11 to be detected. In this case, the optical fibers 20 and 21 are arranged to face the first prism surface 12 of the prism 12, respectively, and the light emitting element 16 and the light receiving element 17 are arranged to face the extended end surfaces of the respective optical fibers 20 and 21. are arranged close to each other and facing each other. In the example shown in FIG. 3, the detected liquid level 11 is at the reference position 'fl
When lo is not reached, the second and third prisms 12
Since the prism surfaces 14 and 15 of are in contact with air, the incident light from the light emitting element 16 passes through the optical fiber 20 and enters the third
As shown in the optical path indicated by a solid line in the figure, the second and third prism surfaces 14. The light is totally reflected by the & 15, enters the optical fiber 21, and is received by the light receiving element 17.

When the detected liquid level 11 rises and reaches the reference position 10, parts of the second and third prism surfaces 14 and 15 of the prism 12 are immersed in the detected liquid. Therefore, the refractive index with respect to the incident light changes, and the incident light from the light emitting element 16 enters the liquid to be detected without being totally reflected on the second prism surface 14. Therefore, the detected liquid level 11 is at the reference position j! When the temperature reaches O, the light receiving element 17 does not receive light and the liquid to be detected is at the reference level.
flR.

Detection is made as to whether or not this has been reached.

“Problems to be Solved by the Invention” In conventional liquid level detectors, as mentioned above, the incident light is caused by the liquid level to be detected reaching the prism, which is an optical component that constitutes the liquid level detector. The presence or absence of light reception by the light receiving element 17 is detected based on changes in the refractive index of light in the optical path.

Therefore, during detection, optical components may be immersed in the liquid to be detected. For example, if the liquid to be detected is a highly corrosive liquid, the light receiving element 17 will be corroded, making it impossible to detect the liquid level. Met.

In addition, even if the liquid to be detected is not highly corrosive, the optical parts will be immersed in the liquid to be detected, so it is necessary to periodically wash the optical parts to remove the dirt. work was required.

Furthermore, conventionally used liquid level detectors can only determine whether the liquid level is at the reference position or not, and cannot quantitatively detect the liquid level position to be detected at all. do not have.

This invention was made in view of the current state of conventional liquid level detectors, and its purpose is to enable liquid level detection of highly corrosive liquids to be detected. It is an object of the present invention to provide a liquid level detector that does not require periodic cleaning of parts and can also perform quantitative detection of the liquid level of a liquid to be detected if necessary.

"Structure of the Invention" In the present invention, a holding cylinder is disposed with at least a portion thereof positioned above the liquid surface to be detected, and a lens body is attached within the holding cylinder with one mirror surface facing the liquid surface to be detected. . An incident light introduction end and an output light guide end are provided opposite to the other mirror surface of the lens body, and an incident light source and a light receiving element are connected to the incident light introduction end and the output light guide end, respectively. Ru.

In this invention, the incident light from the incident light introduction end is focused on the liquid surface to be detected at the reference position, is reflected by the liquid surface to be detected, and almost the total amount of reflected light is detected by the light receiving element. When the surface reaches a predetermined value or more, a sealed space is formed in the holding cylinder between one mirror surface of the lens body and the liquid surface to be detected.

Therefore, when the liquid level to be detected exceeds a predetermined value, a sealed space is formed between one mirror surface of the lens body and the liquid level to be detected in the holding cylinder, and the liquid level to be detected does not rise any further, and the lens body does not come into contact with the liquid to be detected. Therefore, there is no need to remove dirt from the lens body or to periodically wash the lens body, making maintenance easier, and it is also possible to detect a highly corrosive liquid to be detected. Furthermore, when a convex lens is used as the lens body, it is also possible to quantitatively measure the position of the liquid surface to be detected.

"Example" Hereinafter, the liquid level detector of this invention will be described in detail based on an example using the drawings.

FIG. 1 shows the configuration of the main parts of the first embodiment of the liquid level detector of this invention, in which a holding cylinder is disposed with at least a part of it above the liquid surface to be detected. .

In the first embodiment, a hollow cylindrical holding cylinder 10 is provided, and this holding cylinder 10 is fixedly attached by a fixture 23 to a tank 22 filled with the liquid to be detected. . The first embodiment is configured such that when the end surface of the holding cylinder 10 is on the liquid level of the liquid level 11 to be detected, the liquid level 11 to be detected is at the reference position 10.

A lens body 25 is attached within the holding cylinder IO with one mirror surface facing the liquid surface 11 to be detected.

In the first embodiment, a lens holder 26 has a gradient index lens fitted and held as a lens body 25 in a holding cylinder 10.
is fixed.

An incident light introduction end 27 and an output light guide end 28 are provided opposite the other mirror surface of the lens body. An incident light source and a light receiving element are connected to the incident light introduction end and the output light guide end, respectively. In the first embodiment, the incident light source 16 is optically connected to the incident light introduction end 27 via the optical fiber 31, and the output light guide end 28 is connected to the optical fiber 3.
A light receiving element 17 is optically connected via 2.

The incident light from the incident light tJ, 16 enters the lens body 25 from the incident light introducing end 27 via the optical fiber 31,
The optical characteristics of the lens body 25 are selected so that the light is emitted from the mirror surface of the lens body 25 facing the liquid surface 11 to be detected and is focused on the reference position ifo of the liquid surface 11 to be detected.

When the detected liquid level 11 coincides with this reference position 20 surface, the incident light is reflected by the detected liquid level 11 and enters the lens body 25 from the mirror surface of the lens body 25 facing the detected liquid level 11. do. This incident light is transmitted to the output light guide end 2 of the lens body 25.
8, the light is transmitted through the optical fiber 32 from the end face of the optical fiber 32 disposed opposite to the output light guide end 28, and almost the entire amount of reflected light is received by the light receiving element 17.

When the liquid level 11 to be detected is below the reference position lO, as shown in FIG.
The incident light transmitted through 1 takes an optical path as shown by the arrow in the figure, is reflected at the liquid surface 11 to be detected, and reaches the liquid surface 11 to be detected.
The light enters the lens body 25 from the mirror surface facing the , and is refracted within the lens body 25 as shown by the dotted line, so that it does not reach the output light guide end 28 .

Therefore, the reflected light from the liquid surface 11 to be detected does not enter the light receiving element 17, so that it is detected that the liquid surface 11 to be detected has deviated from the reference position β0.

The detected liquid level 11 is base 4I! As shown in FIG. 5, the reflected light reflected from the liquid surface 11 to be detected passes through the optical path shown by the dotted line and reaches the incident light introducing end 27 of the lens body 25. Then, it reaches the mirror surface where the emitted light guiding end 28 is provided, but it reaches a position away from the emitted light guiding end 28.

Therefore, in this case as well, the light reflected by the liquid surface 11 to be detected is not received by the light receiving element T-17, and it is detected that the liquid surface 11 to be detected has deviated from the reference position β0.

When the liquid level to be detected exceeds a predetermined value, inside the holding cylinder,
A sealed space is formed between one mirror surface of the lens body and the liquid surface to be detected.

That is, in the first embodiment, the circumferential surface of the holding cylinder 10 is formed in an airtight structure, and the lens body 25 is attached to the lens holder 26 in an airtight state with no gap at the opposing portion.
The lens holder 26 is also held and fixed to the holding cylinder 10 in an airtight manner with no gaps between them.

Therefore, when the detected liquid level 11 rises above the reference position β0, the air pressure in the sealed space surrounded by the mirror surface of the lens body 25 facing the detected liquid level 11, the detected liquid level 11, and the holding cylinder 1° increases. increases. Therefore, even if the liquid level 11 to be detected continues to rise, the rise will not exceed a predetermined position, and the liquid to be detected will not come into contact with the lens body 25.

The second embodiment of the present invention is shown in FIG. 6 by assigning the same reference numerals to the same parts, and in this embodiment, the end of the holding cylinder 10 is inserted into the liquid to be detected. A communication hole 40 is formed in the circumferential surface of the holding cylinder 10 located in the liquid to be detected. This communication hole 40 is located within the liquid to be detected when the liquid level 11 to be detected is at the y & position 10.
It is formed to

In the second embodiment shown in FIG. 6, a convex lens is used as the lens body 25, the convex lens is housed in a lens holder 26, and the lens holder 26 housing the convex lens is airtightly fixed to the holding cylinder 10. be done. The convex lens is housed in the lens holder 26 with one mirror surface facing the liquid surface 11 to be detected, and in this embodiment, a common lens including an incident light introduction end and an output light guide end is placed opposite the other mirror surface of the convex lens. An end 42 is provided. The optical fiber 4 is connected to this common end 42.
One end of the optical fiber 43 is optically connected, and the other end of the optical fiber 43 is connected to a directional coupler 45.

An input optical fiber 46 and an output optical fiber 47 are connected to this directional coupler 45.
6 and output optical fiber 47, respectively.
6 and the light receiving element 17 are optically connected.

In this case, the reflected light from the detected liquid surface 11 at the reference position is focused by the lens body 25, and the diameter of the focused light is made to be approximately the same as the diameter of the light receiving surface of the optical fiber 43 at the common end 42. It is configured. Therefore, almost the entire amount of the focused light at the common end portion 42 is incident on the optical fiber 43 which is disposed so as to face the lens body 25. Incident light emitted from the light emitting element 16 is transmitted via the input optical fiber 46, the directional coupler 45, and the optical fiber 43, and is focused on the reference position 10 by the lens body 25.

When the detected liquid level 11 matches the reference position TLIlo,
The incident light is reflected by the liquid surface 11 to be detected, and is focused by the lens body 25 onto the light receiving surface of the optical fiber 43.

For this reason, when the liquid surface 11 to be detected coincides with the reference position io, almost the entire amount of light reflected from the liquid surface 11 to be detected is incident on the optical fiber 43. The light incident on the optical fiber 43 is transmitted through the optical fiber 43, guided from the directional coupler 45 to the output optical fiber 47, and received by the light receiving element 17.

In the second embodiment shown in FIG. 6, the detected liquid level 11 is at the reference position! When the light falls below 0, as shown in FIG. 7, the light that passes from the optical fiber 43 through the lens body 25 and is projected onto the liquid surface to be detected 11 is reflected by the liquid surface to be detected 11, takes the optical path shown by the arrow, and passes through the lens. The light enters the body 25. The optical diameter of this incident light at the light receiving surface position of the optical fiber 43 is R, which is considerably larger than the diameter r of the light receiving surface of the optical fiber 43.

For this reason, the amount of light incident on the optical fiber 43 is transmitted to (-
) and 1G(-) via the optical fiber 43.
decreases to

In the second embodiment shown in FIG. 6, when the liquid level 11 to be detected rises above the reference position 10, the incident light from the optical fiber 43 is focused by the lens 25 and takes the optical path shown by the arrow in FIG. The light is projected onto the liquid surface 11 to be detected, is reflected by the liquid surface 11, and reaches the common end portion 42 along an optical path as shown by the arrow.

In this case, the diameter of the light beam at the common end portion 42 is R1, which is also larger than the diameter r of the light receiving surface of the optical fiber 43. In this case, if the amount of light received by the light receiving element 17 via the optical fiber 43 is ignored, the amount of light received by the light receiving element 17 is determined by the amount of light received by the light receiving element 17 via the optical fiber 43, if the attenuation within the transmission system is ignored. No. 812], the reference position
The deviation of the detected liquid level 11 from 11O and the common end 42
It is possible to quantitatively associate the luminous flux diameter R or R of the reflected light in . Therefore, in the second embodiment of the present invention shown in FIG. 6, the deviation of the liquid level 11 to be detected from the reference position 1o can be quantitatively detected.

In this second embodiment as well, a sealed space surrounded by the holding cylinder 10 is formed above the liquid level 11 to be detected, so that the liquid level 11 to be detected exceeds a predetermined value within the holding cylinder 10. It never rises. Therefore, in this second embodiment as well, the convex lens 25 and other optical parts of the liquid level detector do not come into contact with the liquid to be detected. Therefore, even if the liquid to be detected is a corrosive liquid, measurement is possible, and there is no need to remove dirt or periodically wash the optical parts.

The communication hole 40 formed in the holding cylinder 10 in the second embodiment shown in FIG. 6 can also be formed in the first embodiment shown in FIG. Cylindrical body 1 holding communication TL40
0, the connection of the liquid to be detected between the inside and outside of the holding cylinder 10 is made rough, and the communicating hole 40 has a damper effect, so that, for example, the influence of the ripples of the liquid to be detected outside the holding cylinder 10 is reduced. It can be shut off within 10 seconds.

It is also possible to modify this communication hole 40 to form a cut 50 in the holding cylinder 10, as shown in FIG.

Furthermore, as shown in FIG. 10 when applied to the second embodiment of FIG. 6, it is also possible to realize a configuration in which the open area of the open surface of the holding cylinder 10 that comes into contact with the liquid to be detected is narrowed. .

I! ll, as shown in FIG. 10, the outer diameter of the holding cylinder 10 is narrowed on the side opposite to the end surface to which the optical fiber 43 is connected to form a protruding cylindrical portion 51 with a narrowed outer diameter, and this protruding cylinder The protruding end surface of the portion 51 is an open surface. In this way, the inside of the holding cylinder lO is roughly connected to the liquid to be detected at the protruding cylinder part 51, and the protruding cylinder part 51 acts as a damper, causing the liquid to be detected to ripple outside the holding cylinder 10. The influence of can be removed within the holding cylinder 10. In this case, although not shown in FIG. 10, it is also possible to use the protruding cylindrical portion 51 and a connecting hole or a cutout.

In this way, according to the present invention, in any of the embodiments, it is possible to accurately measure whether or not the liquid level to be detected is at the reference position, and to do so without bringing the optical component into contact with the liquid to be detected. It is. Therefore, it is not necessary to remove dirt from the optical components of the liquid level detector or to periodically wash them, and the liquid level can also be detected even for corrosive liquids to be detected.

Furthermore, by using a predetermined lens as the lens body, it is also possible to quantitatively measure the deviation of the liquid level to be detected from the reference position. Therefore, the position of the liquid level to be detected can be continuously measured by detecting the change in the volume of the sealed space due to the liquid pressure to be detected.

"Effects of the Invention" As explained in detail above, according to the present invention, there is no need to remove dirt from optical parts or to periodically wash them, and the liquid level of corrosive liquids to be detected can be detected with high precision. It becomes possible to provide a surface detector.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a first embodiment of the present invention, FIGS. 2 and 3 are principle diagrams showing the configuration of a conventionally proposed liquid level detector, and FIG. Fig. 5 shows the operating principle when the liquid level to be detected falls below the reference position in the first embodiment shown in Fig. 1; FIG. 6 is a sectional view showing the structure of the second embodiment of the present invention, and FIG. 7 is a diagram showing the principle of operation when raised from the reference position. FIG. 8 is a diagram showing the principle of operation when the detected liquid level falls below the reference position. FIG. 8 is a diagram showing the principle of operation when the detected liquid level rises above the reference position in the second embodiment shown in FIG. , No. 9
The figure shows the configuration when a cut is formed in the holding tube in the second embodiment shown in FIG. 6, and FIG. It is a figure which shows the structure when a cylindrical part is formed. 10: Holding cylinder, 11: Detected liquid level, 12 Nibrism,
16: Light emitting element, 17: Light receiving element, 20° 21: Optical fiber, 22: Tank, 25: Lens body, 26: Lens holder, 27: Incident light introducing end, 28: Outgoing light guiding end,
31.32 + optical fiber, 40: communication hole, 42: common end, 43: optical fiber, 45 bidirectional coupler, 46: input optical fiber, 47: output optical fiber, 50: slit, 51: protruding cylindrical part .

Claims (1)

[Claims] A holding cylinder is disposed with at least a portion thereof positioned above the liquid surface to be detected, a lens body is attached within the holding cylinder with one mirror surface facing the liquid surface to be detected, and the other side of the lens body is mounted with one mirror surface facing the liquid surface to be detected. An incident light introduction end and an output light guide end are provided opposite to the mirror surface, and an incident light source and a light receiving element are connected to the incident light introduction end and the output light guide end, respectively, and the incident light introduction end The incident light is focused on the liquid surface to be detected at the reference position, is reflected by the liquid surface to be detected, and almost the entire amount of the reflected light is detected by the light receiving element, and the liquid surface to be detected is detected by the light receiving element. A liquid level detector characterized in that, when a predetermined value or more is exceeded, a sealed space is formed in the holding cylinder between one mirror surface of the lens body and the liquid level to be detected.