JP2002148102A - Detector and method for detecting liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect a liquid in a container even when the container is made of a light diffusible material such as a milk white one. SOLUTION: Light is emitted from a light projecting part 22 toward a wall part of the container 10, diffused light from a portion distant from a light emitting area of the light is received by a photoreceiving part 23, and the presence of the liquid is detected based on a change in a received light quantity of the diffused light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid detecting device for optically detecting the liquid level and the presence or absence of a liquid.

[0002]

2. Description of the Related Art An example of this type of liquid detecting device is disclosed in Japanese Patent Application Laid-Open No. H8-320248. The basic principle of the device is as shown in FIG. Light is emitted from the light projecting unit 2 to the side wall 1 of the
In this configuration, the light receiving unit 3 is provided at a position where the light reflected inside the light receiving unit is received. As shown in FIG. 2A, when the liquid is not present in the irradiation area of the light from the light projecting unit 2, the light is specularly reflected inside the side wall 1 and reaches the light receiving unit 3, but the liquid is If present, the specular reflectance is greatly reduced.
Most of the light from the light source penetrates the side wall 1 and does not reach the light receiving portion 3. Therefore, the presence or absence of the liquid can be determined by measuring the amount of light incident on the light receiving unit 3.

In the conventional liquid detecting device, the light receiving unit 3 is installed in a direction in which the light receiving unit 3 can receive the regular reflection light from the light projecting unit 1 because of such a principle.

[0004]

However, the container is not always made of a transparent material. For example, when accommodating a corrosive liquid, a material having high corrosion resistance is required for the container, and a fluororesin may be selected. Although it is translucent, it has high light diffusion and exhibits milky white. In the case of containers made of such materials,
In the conventional photoelectric type liquid detection device, since the light emitted from the light projecting portion diffuses so as to spread to the surroundings on the side wall, almost no regular reflection light is obtained, and the problem that the presence or absence of the liquid cannot be accurately determined. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid detecting apparatus capable of reliably detecting a liquid in a container made of a material into which light is diffused.

[0006]

As a means for achieving the above object, the present invention provides a method of irradiating light toward a wall of a container, and irradiating the light from a location distant from the light irradiation area. And the presence or absence of liquid is detected based on a change in the amount of the diffused light received. When light is applied to a wall having a property of transmitting light and diffusing light inside, the light enters inside and diffuses in all directions.
Some of the light is reflected to enter the wall at an angle that can be reflected, and travels further away. Light traveling toward the wall at an angle that cannot be reflected passes through the wall and penetrates to the outside.
In order to repeat this, light appears to radiate radially around the light irradiation area from the outside. Here, when the liquid comes into contact with the wall of the container on the side opposite to the light irradiation side, the amount of light that penetrates into the liquid from the wall increases due to a sharp decrease in reflection on the wall and the amount of light penetrating from the outside. The observed light bleed is reduced.

Accordingly, the light projecting unit irradiates the wall of the container with light, and the light receiving unit receives the diffused light that is reflected by the inner wall of the container into the wall and diffusely reflected from a location away from the light irradiation area. If the change in the amount of light received and the amount of diffused light received is detected by the amount-of-light-receiving change means, the presence or absence of liquid on the back side of the wall can be reliably detected.

It is necessary that the area to be observed by the light receiving section is farther away from the irradiation area of the light from the light emitting section itself. This is because, in the irradiation area itself, the amount of diffused light not reflected on the inner surface of the wall increases and the S / N ratio decreases. Conversely, diffused light from a location that is too far from the irradiation area is too weak and not appropriate. The preferred distance depends on specific conditions such as the material and thickness of the container wall, but the amount of diffused light incident upon the contact of the liquid with the wall at the position where the light emitting and receiving unit is located It is needless to say that the portion where the decrease rate is the largest is preferable.

A first light receiving section for receiving diffused light from a light irradiation area or a place close thereto, and a diffused light from a place farther from the light irradiation area than the first light receiving section. A second light receiving unit may be provided, and a difference or a change in a ratio between respective light receiving amounts of the diffused light by the first and second light receiving units may be detected by a light receiving amount change detecting unit. Invention). According to this configuration, the diffused light received by the first light receiving unit contains a large amount of information on the state of the wall of the container, that is, color, dirt, and the like. Includes information on the state of the wall and information on the presence or absence of liquid. Therefore, if the difference or ratio is observed based on the amount of light received by the first light receiving unit as a reference, a change in the state of the wall of the container (discoloration, adhesion of dirt), etc., can be canceled out to determine the presence or absence of liquid. Can extract only the information about and can make a more accurate judgment.

One of the light projecting portion and the first light receiving portion is composed of an optical fiber arranged at the center of the optical fiber cable, and the other is composed of a plurality of optical fibers arranged annularly around the optical fiber. It may be configured (the invention of claim 4). This makes it possible to reduce the size of the entire device, and even when using an optical element such as a lens, the number of components of the optical element can be reduced and the optical element can be manufactured at low cost.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. <First Embodiment> A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a container 10 formed of a material having a light transmitting property and a light diffusing property such as a fluororesin.
2 shows a state where the liquid detection device 20 is attached. As shown in FIG.
A light projecting element 22 constituting a light projecting section and a light receiving element 23 constituting a light receiving section are housed in the interior of the container at a predetermined distance from each other. The elements 22 and 23 are substantially perpendicular to the wall surface of the container 10 and are arranged side by side in the direction along the liquid surface in the container 10.

The light emitting element 22 is pulse-lit by a light emitting drive circuit 24 as shown in FIG. 3, and an output signal from the light receiving element 23 is amplified by a light receiving circuit 25 and compared with a predetermined level Vref by a comparator 26. The output circuit 27 is driven based on the comparison result.

Now, the operation of the above configuration will be described.
When the liquid level of the liquid contained in the container 10 has not reached the mounting position of the liquid detection device 20, the light emitted from the light projecting element 22 enters the wall of the container 10 and is directed in all directions therein. To spread. Some of the light is reflected to enter the wall at an angle that can be reflected, and travels further away. Light traveling toward the wall at an angle that cannot be reflected passes through the wall and penetrates to the outside. In order to repeat this, the light bleeds radially from the outside with the light irradiation area as the center (in the drawing, diagonal lines are crossed to represent the bleeding part of the light). For this reason, a part of the diffused light from a position distant from the irradiation area of the light from the light projecting element 22 enters the light receiving element 23, and a light receiving signal corresponding to the amount of received light is amplified by the light receiving circuit 25 and Is compared with the reference voltage Vref. Here, the reference voltage Vref is set to a voltage slightly lower than the level of the light receiving signal when the liquid level does not reach the installation height of the light emitting and receiving elements 22 and 23, and the output circuit 27 does not operate.

However, when the liquid level in the container 10 rises and reaches the installation height of the light emitting and receiving elements 22, 23, the container 1
Since the back side of the light irradiation area of the light projecting element 22 in the 0 wall comes into contact with the liquid, as shown in FIG.
Reflection inside the wall is drastically reduced, and the amount of light that penetrates into the liquid from the wall increases. As a result, the range of bleeding of light observed from the outside becomes smaller, the amount of diffused light received by the light receiving element 23 decreases, the light receiving signal level falls below the reference voltage Vref, and the comparator 26 and the output circuit 27 Will work. As described above, in the present embodiment, the light receiving element 23 is set so as to receive the diffused light instead of the specularly reflected light in which the light from the light projecting element 22 is reflected on the inner surface of the wall. Liquid in a container made of the above material can be reliably detected.

<Second Embodiment> FIGS. 4 and 5 show a second embodiment of the present invention. In this embodiment, the first and second two light receiving elements 32 and 3 are provided for one light emitting element 31.
3 are arranged. These light emitting and receiving elements 31 to 33 are mounted in the housing recesses 35 to 37 of the housing 34 and mounted on the container 10 so as to be aligned with the liquid surface.

The optical axes of the light projecting element 31 and the second light receiving element 33 are substantially perpendicular to the wall surface.
The light receiving element 33 receives the diffused light from a location distant from the irradiation area of the light from the light projecting element 31.
On the other hand, the first light receiving element 32 has
6, an optical path limiting portion 36A is formed so as to receive the direct diffused light from the light irradiation area of the light projecting element 31.

The electrical configuration is as shown in FIG. 5. The light emitting element 31 is pulse-lit by the light emitting drive circuit 38, and the output signals from the first light receiving element 32 and the first light receiving element 33 are differential. The signal is input to the amplifier circuit 39, where both light receiving elements 3
The difference between the light receiving signals from the light receiving signals 2 and 33 is amplified and compared with a predetermined level Vref by the comparator 40, and the output circuit 41 is driven based on the comparison result.

According to this configuration, the diffused light received by the first light receiving element 32 contains a large amount of information due to the diffusion rate, color, dirt, and the like of the wall of the container 10. on the other hand,
The second light receiving element 33 also includes such information,
Further, similarly to the above-described embodiment, when the liquid level in the container 10 has not reached the installation height of the light emitting and receiving elements 31 to 33, and when it has reached, the level greatly changes.
Therefore, since the light receiving signals from the light receiving elements 32 and 33 are differentially amplified, information due to the diffusion rate, color, dirt, and the like of the wall of the container 10 is canceled, and only information about the liquid level is extracted. Will be. As a result, it is possible to stably detect the liquid level over a long period of time even under a situation where the inner surface of the container 10 is gradually becoming dirty or under a condition where the container 10 itself is gradually discolored. Can be.

<Third Embodiment> FIG. 6 shows a third embodiment of the present invention. This is one in which the light projecting unit and the light receiving unit are configured using an optical fiber. A threaded base 52 is attached to the end of each of the three optical fiber cables 51,
The base 52 is screwed into the mounting hole 53A of the base 53 and fixed. A nozzle 52A is formed at the tip end of the base 52 toward the wall surface of the container 10.
A core wire (not shown) of the optical fiber cable 51 is fixed in 2A. These three optical fiber cables 51
Of the core wires, the one located on the left side in the figure constitutes the light projecting unit, and the one next to it constitutes the first light receiving unit and directly receives the diffused light from the irradiation area of the light projecting unit. The light receiving unit located a short distance away on the right side constitutes a second light receiving unit, and receives diffused light from a location distant from the irradiation area of the light from the light emitting unit. ing. Although not shown, a light projecting element and two light receiving elements are provided on the other end side of each optical fiber cable 51, and the electrical configuration is the same as that of the second embodiment shown in FIG.

According to such a configuration, the same effect as that of the second embodiment can be obtained, and the electric circuit can be removed only by arranging the optical fiber cable 51 in the vicinity of the container 10, so that the flammability can be reduced. It is safe even if a liquid of a certain nature is contained in the container 10.

<Other Embodiments>

The present invention is not limited to the embodiment described above with reference to the drawings. For example, the following embodiment is also included in the technical scope of the present invention, and further departs from the gist other than the following. Various changes can be made without departing from the scope of the present invention.

(1) In each of the above embodiments, the case where the entire container 10 is formed of a material having a light transmitting property and a light diffusing property has been described. However, the present invention is not limited to this. For example, most of the container is made of metal. It can be used for detecting the liquid level in the window even if the window is made of a light-transmitting and light-diffusing material.

(2) In the second and third embodiments,
Although the light emitting section, the first light receiving section, and the second light receiving section are arranged in this order, the arrangement order is not limited to this. For example, as shown in FIG. 61 may be arranged, and the second light receiving unit 62 may be arranged on the opposite side.
Further, as shown in FIG. 8, the light projecting unit 60 and the first light receiving unit 6
1 are arranged side by side, and the second light receiving section 62 is
May be placed away from the camera. As described above, regardless of the arrangement of the light emitting and receiving unit, the first light receiving unit 61 is provided with the light emitting unit 6.
A second light receiving unit 62 receives diffused light from a location farther from the light irradiation area than the first light receiving unit 61, It is good to do.

(3) When the light emitting and receiving unit is formed using an optical fiber cable, for example, the structure shown in FIG. 9 is possible. Here, a large-diameter optical fiber 71 is arranged at the center of the optical fiber cable 70, a large number of thin optical fibers 72 are annularly arranged on the outer periphery thereof, and the outermost periphery is covered with a protective jacket 73. A light projecting element 74 is disposed at the end of the center fiber 71 so as to face the end of the center fiber 71, and the other end of the outer fiber 72 is bundled to form a light receiving element 7.
5 are opposed to each other, so that the tip of the fiber 72 is used as a light receiving section. In this case, the electrical configuration is the same as that of the first embodiment shown in FIG. With such a configuration, the light emitting and receiving unit can be configured with one optical fiber cable 70, the structure of the detecting unit is extremely simplified, and even when an optical system such as a lens is used, the optical system can be used. Extremely simple.
The relationship between the light emitting and receiving light of the above configuration may be reversed, that is, the light receiving element 75 is opposed to the central optical fiber 71,
The light projecting element 74 may be made to face the optical fiber 72 around it.

(4) Furthermore, in order to realize the configuration of the second embodiment using one optical fiber cable, for example, the structure shown in FIG. 10 is possible. Here, a large-diameter optical fiber 81 is arranged at the center of the optical fiber cable 80,
A number of thin optical fibers 82 are arranged in an annular shape on the outer periphery,
A large number of thin optical fibers 84 are also arranged on the outer periphery of the protective layer 85 via a spacer layer 83, and the outermost periphery is covered with a protective jacket 85. A light projecting element 86 is provided at the end of the center fiber 81, and the fiber 81 is used as a light projecting section.
And the outermost group of fibers 84 is bundled and the second light receiving element 88 is arranged to face the second light receiving unit. In this case, the electrical configuration is the same as that of the second embodiment shown in FIG. With such a configuration, the light emitting unit and the first and second optical fibers are connected by one optical fiber cable 80.
, And the structure of the detection unit is extremely simplified. In addition, the second light receiving section is destined to have a weak diffused light as the distance from the light projecting section is increased in order to increase the S / N ratio. If the light is received by the annular region surrounding the region, there is an advantage that a relatively large amount of light can be obtained.

When light is transmitted and received using the optical fiber cable 80, a lens may be provided at the end of the optical fiber cable 80. In that case, if a toroidal lens in which three lens portions are arranged concentrically is used, FIG.
A light projecting area 90, a first light receiving area 91, and a second light receiving area 92 as shown in FIG. In order to obtain the light projecting area 93, the first light receiving area 94, and the second light receiving area 95 as shown in FIG. 7B, two lens portions are formed concentrically on the center side and minute What is necessary is just to use the integral type lens which arrange | positioned the lens annularly. Further, in this embodiment, the light projecting unit and the first light receiving unit may of course be reversed.

(5) In each of the above embodiments, the light emitting element and the light receiving element are individually provided in the light emitting section and each light receiving section. However, for example, the first light receiving section and the second light receiving section in the second embodiment are provided. The two light receiving units may be configured using a two-divided photoelectric element having two photoelectric conversion units integrally. In addition, the light receiving unit in the first embodiment uses a light receiving element such as a PSD or a CCD to observe a wide range of diffused light. When there is liquid, the intensity center of gravity of the diffused light is larger than when there is no liquid. Detection can also be performed by utilizing the shift to the light emitting unit side.

(6) The light projecting portion and the light receiving portion may be in close contact with the wall surface of the container or may be separated from each other. However, the close contact is less likely to be affected by dirt on the outer surface of the container and reflected light. preferable.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a main part of the first embodiment.

FIG. 3 is a block diagram showing an electrical configuration of the first embodiment.

FIG. 4 is a cross-sectional view showing a main part of the second embodiment.

FIG. 5 is a block diagram showing an electrical configuration of a second embodiment.

FIG. 6 is a cross-sectional view showing a main part of a third embodiment.

FIG. 7 is a plan view showing a main part of a different embodiment.

FIG. 8 is a plan view showing a main part of a different embodiment.

FIG. 9 is a perspective view showing an optical fiber cable according to another embodiment.

FIG. 10 is a perspective view showing an optical fiber cable according to another embodiment.

FIG. 11 is a plan view showing a light irradiation area.

FIG. 12 is a sectional view showing the principle of a conventional liquid detection device.

[Explanation of symbols]

 10 Container 20 Liquid detecting device 22, 31 Light emitting element (light emitting part) 23, 32, 33 Light receiving element (light receiving part) 39 Differential amplifier circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F014 AB02 AB03 FA01 FA02 2G051 AA48 AB15 BA00 BB17 CA02 CA07 CB05 CC17 EA08 EA25 EB01 EB02

Claims (4)

[Claims] 1. A liquid detecting method for detecting a liquid in a container, at least a part of which is a material having a light diffusing property and a light transmitting property, wherein the liquid is irradiated onto a wall of the container. Receiving diffused light that is diffused and reflected from a location distant from the light irradiation area while being reflected into the wall by the inner wall of the container, and detecting the presence or absence of liquid based on a change in the amount of the diffused light received. A liquid detection method characterized by the above-mentioned. 2. A container for detecting a liquid in a container having a light diffusing property and a light transmitting property, comprising: a light projecting unit for irradiating light toward a wall of the container; and an inner wall of the container. A light-receiving unit that receives diffused light that is diffusely reflected from a location distant from the light irradiation area by the light-emitting unit while being reflected into the wall, and a light-receiving amount that detects a change in the amount of diffused light received by the light-receiving unit A liquid detection device comprising: a change detection unit. 3. A light-projecting unit for detecting a liquid in a container made of a material having a light-diffusing property and a light-transmitting property, wherein the light-projecting unit irradiates light toward a wall of the container, and The first to receive diffused light from or near the light irradiation area
And a second light receiving portion that receives diffused light that is diffusely reflected from a location farther from a light irradiation area by the light emitting portion than the first light receiving portion while being reflected into the wall portion by the inner wall of the container.
And a light-receiving-amount change detecting means for detecting a difference or a change in a ratio between respective light-receiving amounts of the diffused light by the first and second light-receiving units. 4. A plurality of light sources, one of which comprises an optical fiber arranged at the center of an optical fiber cable, and the other of which comprises an annularly arranged optical fiber around the optical fiber. 4. The liquid detecting device according to claim 3, comprising a fiber.