JP2005140745A - Optical level sensor and liquid level detector using the same sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy-to-assemble optical level sensor for accurately detecting a liquid level, and to provide a liquid level detector using the same sensor. <P>SOLUTION: This optical level sensor 1 is equipped with: a a bar-like case 1A formed into a rectilinear shape and having a cutout space part formed in an intermediate portion thereof; a first hole 1c formed in one end part of the case along an axis line of the case; and a second hole 1d formed in the other end part of the case and formed on the same straight line as the axis line of the first hole. A wall surface 1e for demarcating the space part 1i on the first hole side is formed on an inclined surface in a direction widening the space part. A light emitting element 1a is disposed in the first hole 1c while a light receiving element 1b is disposed in the second hole 1d. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a level sensor and a liquid level detection device that are installed, for example, in a tank in which liquid is stored and detect the liquid level, and in particular, an optical level sensor that detects the presence or absence of stored liquid using optical means. And a liquid level detection apparatus using the sensor.

For example, an optical level sensor is used as a sensor that is installed in a tank in which liquid is stored and detects the liquid level.
This optical level sensor is configured to irradiate the liquid surface with laser light, detect the reflected light, and measure the distance to the liquid surface with its strength and time. In this optical level sensor, the sensor itself is complicated and expensive. For this reason, an optical level sensor that has a simple configuration and can be manufactured at low cost has been proposed in Japanese Patent Application Laid-Open No. 11-30549.

Next, the optical level sensor described in Patent Document 1 will be described with reference to FIG. 4A is a front view of a conventional optical level sensor, and FIG. 4B is a cross-sectional view taken along the line AA.
In FIG. 4, the optical level sensor 10 includes a transparent case 14 in which an optical prism portion 13 formed with a first reflecting surface 11 and a second reflecting surface 12 intersecting each other is integrally formed, and the inside of the case 14. The light-emitting element 15 and the light-receiving element 16 are respectively built in and opposed to the first reflection surface 11 and the second reflection surface 12.
As a result, an optical signal path 17 is formed between the light emitting element 15 and the light receiving element 16 via the optical prism portion 13, and an optical switch is configured by the light emitting element 15, the light receiving element 16, and the optical prism portion 13. ing.

  Here, the case 14 includes a tube 18 having a predetermined length. The tube 18 is formed in a quadrangular cross-sectional shape, and its tip is closed. Further, the proximal end portion of the tube 18 is formed in a conical shape. The optical prism portion 13 is formed at one corner portion at the distal end portion of the case tube 18.

  In this case, the first reflecting surface 11 and the second reflecting surface 12 are formed by two surfaces that are adjacent to each other at the corner and intersect each other. The light emitting element 15 and the light receiving element 16 that face the first reflecting surface 11 and the second reflecting surface 12 are arranged in parallel and mounted on the substrate 19. An electric wire (not shown) is connected to the light emitting element 15 and the light receiving element 16, and a tube 20 for covering the electric wire is provided.

  The operation will be described. When the optical switch is in the air, the light emitted from the light emitting element 15 connects the light emitting element 15, the first reflecting surface 11, the second reflecting surface 12, and the light receiving element 16. The light-receiving element 16 is reached via the optical signal path 17, whereby the optical switch is closed and turned on.

On the other hand, when the optical prism portion 13 of the optical switch touches the liquid surface, the light emitted from the light emitting element 15 proceeds to the liquid while being refracted by the first reflecting surface 11 and does not pass through the optical signal path 17. It does not reach the element 16, thereby opening the optical switch and turning it off.
Thus, the liquid level in the tank can be detected by detecting ON / OFF of the optical switch. The optical level sensor 10 is attached to a tank, a wall, or the like in which liquid is stored using the mounting flange portion.
JP-A-11-30549

  By the way, in the above-described conventional optical level sensor 10, the light from the light emitting element 15 is reflected by the first reflecting surface 11 and the second reflecting surface 12, and the reflected light is received by the light receiving element 16. Therefore, the light emitting element 15 and the light receiving element 16 must be attached to the first reflecting surface 11 and the second reflecting surface 12 with high accuracy, and assembly accuracy is required. It was. In particular, since the light emitting element 15 and the light receiving element 16 are attached to the substrate 19 and the substrate 19 is attached to the tube 18, not only the light emitting element 15 and the light receiving element 16 are attached to the substrate 19 with high precision, but also the substrate 19 Must be attached to the tube 18 with high accuracy, making assembly difficult.

  The present invention has been made to solve the above-described problems, and provides an optical level sensor that can be easily assembled and can accurately detect a liquid level, and a liquid level detection apparatus using the sensor. The purpose is to do.

  An optical level sensor according to the present invention, which has been made to achieve the above-mentioned object, is formed in a linear case and a rod-like case in which a notch space portion is formed in an intermediate portion thereof, and one end portion of the case. A first hole along the axis of the case, and a second hole formed at the other end of the case and collinear with the axis of the first hole. A wall surface defining a notch space on the hole side is formed on an inclined surface extending in the direction of expanding the notch space, a light emitting element is disposed in the first hole, and the second hole is provided with a light emitting element. A light receiving element is provided.

Thus, the first hole along the axis of the case is provided at one end of the case, and the second hole is provided at the other end of the case on the same straight line as the axis of the first hole. By arranging the light emitting element in one hole and the light receiving element in the second hole, a linear optical signal path is formed.
That is, when there is no liquid in the cutout space in the middle part of the case, the light emitted from the light emitting element 15 travels straight and is received by the light receiving element 16, thereby closing the optical switch and turning it on. Become. On the other hand, when there is a liquid in the notch space portion of the middle portion of the case, the light emitted from the light emitting element 15 is refracted at the slope portion, and therefore does not reach the light receiving element 16, thereby opening the optical switch, It is turned off.

  Moreover, this optical level sensor can be easily assembled by disposing the light emitting element and the light receiving element in the first hole and the second hole. That is, a linear optical signal path can be easily formed by housing the light emitting element and the light receiving element in the hole without adjusting the positional relationship between the light emitting element and the light receiving element.

The first hole and the second hole are through holes, the light transmitting member closes the through hole, the light transmitting member defines the notch space portion, and the first hole and the second hole are closed. A light transmissive member that defines a notch space portion on one hole side is formed on an inclined surface that expands the notch space portion, and a light transmissive property that defines a notch space portion on the second hole side. The member is preferably formed on a surface perpendicular to the axis of the case.
As described above, the first hole and the second hole may be formed as through holes, and the through holes may be closed by the light transmissive member.

  The optical level sensor, the light projecting control circuit for controlling the light emitting element, the light receiving control circuit for controlling the light receiving element, and the liquid level detection connected to the light projecting connection control circuit and the light receiving control circuit. A liquid level detection device is provided by including a circuit and a display device connected to the liquid level detection circuit.

  According to the present invention, it is possible to obtain an optical level sensor that can be easily assembled and can accurately detect a liquid level, and a liquid level detection apparatus using this sensor.

  An embodiment of an optical level sensor according to the present invention and a liquid level detection apparatus using the optical level sensor will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of an embodiment of a liquid level detection device according to the present invention, FIG. 2 is a diagram showing a case of an optical level sensor, (a) is a plan view, and (b) is a plan view. It is a front view. FIG. 3 is a diagram showing an optical path L of the optical level sensor, where (a) shows the optical path L when there is no liquid, and (b) shows the optical path L when there is liquid. FIG.

This optical level sensor 1 is characterized by a case 1A in which the light emitting element 1a and the light receiving element 1b are arranged and held facing each other.
The case 1A will be described in detail. The case 1A is formed in a linear bar shape, a notch space portion 1i is formed in an intermediate portion thereof, and a light emitting element 1a and a light receiving element 1b are formed at both ends thereof. The holding parts 1B and 1C to be attached are formed.
Through holes 1c and 1d are formed in the holding portions 1B and 1C of the case 1A on the same straight line along the axis of the case. That is, the through holes 1c and 1d are arranged in a straight line so as to oppose each other, and the through holes 1c and 1d are formed to have a size that can be accommodated without the light emitting element 1a and the light receiving element 1b shaking. Yes.

The through holes 1c and 1d formed in the case 1A may be formed using means such as a drill. However, if a forming means using a mold is used, the through holes 1c and 1d may be formed simultaneously when the case 1A is formed. Can do.
Further, the through holes 1c and 1d may be formed with a constant diameter from the end face of the case 1A, and the tip thereof may be the small diameter through holes 1c and 1d. That is, the mounting positions of the light emitting element 1a and the light receiving element 1b may be defined by forming the step portions 1j and 1k.

  Further, a wall surface 1e facing the notch space portion on the side of the through hole 1c (defining the notch space portion 1i) is formed as an inclined surface in the direction of expanding the notch space portion 1i. On the other hand, the wall surface 1f facing the notch space portion on the side of the through hole 1d (defining the notch space portion 1i) is a surface perpendicular to the axis of the case 1A (the straight line connecting the through holes 1c and 1d). It is formed as

Then, the side of the through holes 1c and 1d facing the notch space 1i is bonded with the light transmissive members 1g and 1h with an adhesive, and the light transmissive members 1g and 1h are used to pass through the through holes 1c and 1d. Is blocked.
Therefore, the light transmitting member 1g defines the notch space portion 1i, and the light transmitting member 1g is formed on an inclined surface that expands the notch space portion. Similarly, the light transmitting member 1h defines the notch space 1i, and the light transmitting member 1h is formed on a surface perpendicular to the axis of the case 1A.
The light transmissive members 1g and 1h are attached to the case 1A with an adhesive. However, the present invention is not limited to this, and the light transmissive members 1g and 1h are fused to the case 1A. You may make it do.

  Since the through holes 1c and 1d are closed as described above, the liquid A in the tank 2 can be prevented from coming into contact with the light emitting element 1a and the light receiving element 1b. The openings of the through holes 1c and 1d on the end face side of the case 1A are sealed with a sealing member such as a synthetic resin agent.

Further, the case 1A and the light transmissive members 1g and 1h can be formed of a transparent glass body or a transparent synthetic resin body, and it is determined whether the glass body or the synthetic resin material is selected in the tank 2. It is determined in consideration of the properties of the liquid A stored in the container.
Note that the case 1A itself does not necessarily need to be a light transmissive member, and at least a portion facing the through holes 1c and 1d among the members (light transmissive materials) closing the through holes 1c and 1d is light transmissive. It only has to have sex.

In the optical level sensor 1 configured in this way, the light emitting element 1a and the light receiving element 1b are provided in a straight line, and a linear optical signal path is formed.
As shown in FIG. 3A, when no liquid is present in the cutout space 1i in the middle part of the case, the light emitted from the light emitting element 1a goes straight and is received by the light receiving element 1b. As a result, the optical switch is closed and turned on. On the other hand, as shown in FIG. 3B, when a liquid is present in the cutout space portion 1i in the middle portion of the case, the light emitted from the light emitting element 1a is transmitted to the light transmissive member 1g that forms the slope portion. The light is refracted at the interface of the liquid and does not reach the light receiving element 1b, whereby the optical switch is opened and turned off.

  Thus, the presence or absence of the liquid can be detected by the light emitting element 1a and the light receiving element 1b. In addition, by housing the light emitting element 1a and the light receiving element 1b in the through holes 1c and 1d of the case 1A, they can be arranged on a straight line facing each other, can be easily assembled, and optical path adjustment and the like can be performed. There is no need to do it.

In addition, it is preferable to use an infrared LED as the light emitting element 1a from the viewpoint of stability, price, and a wavelength region having relatively less intensity than natural light.
On the other hand, the light receiving element 1b is preferably a phototransistor with a filter. The light intensity from the light emitting element 1a is received as analog data by a phototransistor, and the presence or absence of liquid is determined based on the light intensity based on a predetermined threshold. According to such a method, it is possible to appropriately determine even a viscous liquid such as oil.

  A liquid level detection apparatus using such an optical level sensor includes a light projection control circuit 3 that controls the light emitting element 1a, a light reception control circuit 4 that controls the light receiving element 1a, and the light projection connection control circuit 3 described above. And a liquid level detection circuit 5 connected to the light reception control circuit 4 and a display device 6 connected to the liquid level detection circuit 5.

  That is, as shown in FIG. 1, a plurality of optical level sensors 1A are arranged in the height direction of the tank 2 (two optical level sensors 1A are arranged in FIG. 1). The light emitting element 1a and the light projection control circuit 3 are electrically connected. On the other hand, each light receiving element 1b and the light receiving control circuit 4 are electrically connected. The liquid level is detected by the liquid level detection circuit 5 in which the light projection control circuit 3 and the light reception control circuit 4 are electrically connected, and the display device 6 is electrically connected to the liquid level detection circuit 5. Is displayed.

In the liquid level detection device configured as described above, when both the lower optical level sensor 1A and the upper optical level sensor 1A receive light from the light emitting element 1a, the light receiving element 1b receives the light. The liquid level in the tank 2 is recognized to be located below the lower optical level sensor 1A (or the liquid A does not exist in the tank 2), and this is indicated in the display device 6. Is displayed.
Further, when the light receiving element 1b does not receive the light from the light emitting element 1a in the lower optical level sensor 1A, and the light receiving element 1b receives the light from the light emitting element 1a in the upper optical level sensor 1A. It is recognized that the liquid level in the tank 2 is above the lower optical level sensor 1A, and that the liquid level is located below the upper optical level sensor 1A. Is displayed.
Furthermore, when both the lower optical level sensor 1A and the upper optical level sensor 1A do not receive the light from the light emitting element 1a, the liquid level in the tank 2 is at the upper optical level. It is recognized that the liquid level is located above the sensor, and that effect is displayed on the display device 6.

  In the above embodiment, two optical level sensors are used. However, by providing a large number in the tank, the liquid level can be detected with high accuracy. Moreover, in the said embodiment, although the case where the light emitting element 1a and the light receiving element 1b were accommodated in the through-holes 1c and 1d was demonstrated, it is not necessarily a through-hole and a simple hole may be sufficient. In this case, the slope portion is formed on the case 1A itself, and the case 1A needs to be formed of a light transmitting member.

  The present invention can be used to detect the level of any liquid (including viscous liquids).

FIG. 1 is a schematic configuration diagram of an embodiment of a liquid level detection device according to the present invention. 2A and 2B are diagrams showing a case of the optical level sensor, where FIG. 2A is a plan view and FIG. 2B is a front view. 3A and 3B are diagrams showing an optical path of the optical level sensor, where FIG. 3A is a diagram showing an optical path when there is no liquid, and FIG. 3B is a diagram showing an optical path when there is a liquid. 4A and 4B are diagrams showing a conventional optical level sensor, in which FIG. 4A is a side view and FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical level sensor 1A Case 1a Light emitting element 1b Light receiving element 1c Through hole 1d Through hole 1e Wall surface 1f Wall surface 1g Light transmitting member 1h Light transmitting member 1i Notch space part 1j Step part 1k Step part 2 Tank 3 Light projection control circuit 4 Light reception control circuit 5 Liquid level detection circuit 6 Display circuit L Optical path

Claims (3)

A rod-like case formed in a straight line and having a notch space portion formed in the middle portion thereof, a first hole along the axis of the case formed in one end portion of the case, and the other end portion of the case A second hole formed on the same straight line as the axis of the first hole,
A wall surface defining a notch space portion on the first hole side is formed on an inclined surface in a direction of expanding the notch space portion,
2. The optical level sensor according to claim 1, wherein a light emitting element is disposed in the first hole, and a light receiving element is disposed in the second hole. The first hole and the second hole are through holes, the light transmitting member closes the through hole, the light transmitting member defines the notch space,
The light transmissive member that defines the notch space portion on the first hole side is formed on an inclined surface that expands the notch space portion, and the light that defines the notch space portion on the second hole side. The optical level sensor according to claim 1, wherein the transparent member is formed on a surface perpendicular to the axis of the case.   The optical level sensor according to claim 1, a light projecting control circuit for controlling the light emitting element, a light receiving control circuit for controlling the light receiving element, and the light projecting connection control circuit. And a liquid level detection circuit connected to the light reception control circuit, and a display device connected to the liquid level detection circuit.

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