JP2002005726A - Liquid detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid detector facilitating an optical axis adjustment and never performing a wrong detection even in the presence of a foreign matter in a liquid. SOLUTION: In this liquid detector, the light from a projection part 50 is made into a radial light in a cross sectional view of a pipe 30 by a projecting lens 80. The light receiving intensity of a light receiving part 51 is varied depending on the presence of the liquid L in the pipe 31, whereby the presence of the liquid L is detected. The light receiving intensity is varied depending on the presence of the liquid L even if the projection and light receiving parts 50 and 51 are slightly shifted in the cross sectional view of the pipe 31 without being linearly arranged. Accordingly, the detection of the liquid L can be performed without strictly performing the optical axis adjustment. Since the light from the projection part 50 is made to a parallel light in the vertical sectional view of the pipe 31, the shadow of a foreign matter, even if present in the liquid L, is never extended in a wide range on the light receiving part 51 side, and the wrong detection by the foreign matter can be thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid detecting apparatus for detecting whether or not a liquid level has reached a predetermined reference water level in a transparent or translucent pipe extending vertically.

[0002]

2. Description of the Related Art In general, a tank for storing a liquid is provided with a transparent pipe extending in a vertical direction communicating with the tank in order to make the level of the liquid in the tank visible from the outside. Then, a liquid detecting device is used to detect whether or not the liquid level in the pipe has reached a predetermined reference water level.

FIGS. 11 to 13 show a conventional example of this type of liquid detection apparatus disclosed in Japanese Utility Model Laid-Open Publication No. 55-112223. The light emitting device 1 and the light receiving device 2 are provided to face each other. As shown in FIG. 12, the light projector 1 includes a light emitting element 11.
The light emitted from the lens is converted into parallel light via the light projecting convex lens 12, and is further applied to the pipe 4 through the slit 61. On the other hand, the light receiver 2 includes a shielding plate 6 facing the slit 61.
2, a light receiving convex lens 22 and a light receiving element 21 are provided. When the liquid 5 reaches a predetermined level and the liquid 5 exists between the light emitting and receiving devices 1 and 2, the parallel light emitted from the light emitting device 1 is changed by the lens effect of the liquid 5 as shown in FIG. The light is condensed on the shielding plate 62, and no light is received by the light-receiving convex lens 22 and the light-receiving element 21 behind the light-shielding plate 62. On the other hand, when the liquid 5 disappears from between the light emitting and receiving devices 1 and 2, the light is not condensed, but is received by the light receiving element 21 via the light receiving convex lens 22, as shown in FIG. The liquid 5 is detected based on the output signal of 21.

[0004]

By the way, as shown in FIG. 12, the pipe 4 has a curved shape when viewed from the side, and has a lens effect when filled with liquid. Also, it can be seen that when the diameters of the pipes are different, the focal lengths due to the lens effect are different. That is, specifically, as shown in FIG. 14A, for example, the diameter d1 = φ
Assuming that the refractive index is 1.35 in a case where the liquid is filled in a 4 mm pipe, the focal length is a1 =
At 3.9 mm, its principal point is -2 mm. On the other hand, for example, in a pipe having a diameter d2 = φ10 mm, the focal length is a
2 = 9.6. From these, since d1 + a1 <d2, it is necessary to adjust the positional relationship between the light emitting and receiving light in the pipe having the diameter d1 = φ4 mm and the diameter d2 = φ10 mm. In other words, when the parallel light is incident on the pipe, the light receiving unit is set at a position (range a, range A) where the light receiving signal when there is liquid is larger than when there is no liquid as shown in the figure below. The position differs between the case of large diameter and the case of
Each time, the light receiving position has to be changed, which causes annoyance. The conditions that can be used without adjusting the positional relationship between the light emitting and receiving are d1 + a1> d2 and d
1 + a1 <d2 + a2. Satisfying this condition, d
In order to make 2-d1 as large as possible, it is preferable that the emitted light be diverged. Further, it is preferable that the light emitting section emits light from a position near the tube. In FIG. 15B, the ranges a and A in which a light receiving signal can be obtained larger when there is a liquid than when there is no liquid are shown in FIG.
(B) is wider and easier to adjust, and can be easily attached to pipes of different diameters without adjustment.

On the other hand, as shown in FIG. 11, the pipe 4 does not have a curved shape when viewed in a vertically divided plane, and does not have a lens effect. Therefore, when the light emitted from the light projector 1 is parallel light when viewed from the vertical split surface of the pipe 4, it is only necessary to match the optical axes of the two convex lenses 12, 22,
Optical axis adjustment is not difficult. However, if radiated light is given to the pipe 4 as viewed on the vertically divided surface of the pipe 4, for example, when bubbles are generated in the liquid, the projection of the bubbles over a wide range on the light receiver 2 side, and the received light intensity is reduced. This may cause an error detection that there is no liquid despite the presence of the liquid. Alternatively, even if there is no liquid in the pipe, when water droplets are attached to the pipe, the water drop has a convex lens effect,
The light receiving intensity can be increased over a wide range on the light receiver 2 side, which may cause erroneous detection if there is a liquid or the like even though there is no liquid.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and can be attached to pipes having different diameters, so that the optical axis can be easily adjusted and liquid detection that does not perform erroneous detection even when foreign substances exist in the liquid. The purpose is to provide the device.

[0007]

<Means for Solving the Problems and Functions / Effects><Invention of Claim 1> In order to achieve the above object, a liquid detecting device according to the invention of Claim 1 extends vertically and has a liquid level inside. A light-emitting unit and a light-receiving unit arranged with a translucent or translucent pipe that transitions therebetween, and a comparison unit that determines the magnitude relationship between a light-receiving signal output by the light-receiving unit and a predetermined reference value, In a liquid detection device that detects the presence or absence of a liquid between a light projecting unit and a light receiving unit based on a result of determination by the comparing unit, a light projecting lens is provided between the light projecting unit and the pipe, and the light projecting lens is provided. Lens for the light emitted from the light emitting unit,
It is characterized in that it is configured such that it is parallel light when viewed on the vertical split surface of the pipe, while it is emitted light when viewed on the horizontal split surface of the pipe.

[0008] According to this configuration, the light from the light projecting portion is viewed by the light projecting lens on the horizontal split surface of the pipe.
Synchrotron radiation. When there is a liquid in the pipe, the light is condensed by the lens effect and the light receiving intensity of the light receiving unit is increased. On the other hand, when there is no liquid, the light receiving unit does not exhibit the lens effect and the light receiving unit remains radiated light. Upon receiving the light, the received light intensity decreases. The presence or absence of the liquid can be detected based on the difference between the light receiving intensities. At this time, even if the size of the pipe differs from that of the light emitting and receiving unit, the light receiving intensity differs depending on the presence or absence of the liquid. Therefore, liquids can be detected without adjusting the optical axis or adjusting the positional relationship between the light emitting and receiving sections even for pipes with different sizes. No need to worry. In addition, since the light from the light emitting and receiving unit is collimated by the light projecting lens when viewed on the vertically split surface of the pipe, even if there is a foreign matter in the liquid, the projection of the foreign matter is directed to the light receiving unit side. It does not cover a wide range, and the influence on the received light intensity can be suppressed. This can prevent erroneous detection due to foreign matter in the liquid.

More specifically, the light projecting lens is constituted by a hexahedron having a pair of opposing surfaces in each of up, down, left, right and front, and of the six surfaces, the front end face of the light projecting lens facing the pipe. When viewed on the vertical split surface of the pipe, it has a convex structure in which the central portion protrudes toward the pipe, and when viewed on the horizontal split surface of the pipe, has a concave structure or flat surface in which the central portion is depressed toward the pipe. By having a configuration having a planar structure, the light projecting lens emits light emitted from the light emitting unit,
When viewed on the vertical split surface of the pipe, parallel light can be obtained, and when viewed on the horizontal split surface of the pipe, emitted light can be generated.

A liquid detecting device according to a second aspect of the present invention is a light projecting unit that is disposed with a transparent or translucent pipe extending vertically and in which the level of the liquid changes within the pipe. And a light receiving unit, and a comparing unit that determines a magnitude relationship between a light receiving signal output by the light receiving unit and a predetermined reference value, and based on a result of the determination by the comparing unit, a liquid between the light emitting unit and the light receiving unit. In the liquid detection device for detecting the presence or absence, the light projecting unit is characterized in that a plurality of light emitting units that emit emitted light are arranged along the longitudinal direction of the pipe.

According to this configuration, since the light from the plurality of light emitting units constituting the light projecting unit is radiated light, when there is a liquid in the pipe, when viewed from the horizontal split surface of the pipe, the lens effect is applied. The light is condensed, and the light receiving intensity of the light receiving unit increases. On the other hand, when there is no liquid, the light receiving portion receives light without emitting a lens effect and emits light, and the light receiving intensity is reduced. Then, from this difference, the presence or absence of the liquid can be detected. At this time, even if the size of the pipe differs from that of the light emitting and receiving unit, the light receiving intensity differs depending on the presence or absence of the liquid. Therefore, liquids can be detected without adjusting the optical axis or adjusting the positional relationship between the light emitting and receiving sections even for pipes with different sizes. No need to worry. Moreover, since a plurality of light emitting units are arranged along the longitudinal direction of the pipe,
In addition, even if a foreign substance occurs in the liquid and is located in front of one light emitting unit, light from another light emitting unit is given to the light receiving unit side,
The influence of the foreign matter on the light receiving intensity can be suppressed. This can prevent erroneous detection due to foreign matter in the liquid.

In the first and second aspects of the present invention, the comparing section may include a first reference value corresponding to a light receiving intensity when the liquid is present, and a light receiving signal output by the light receiving section. A first comparing unit that determines a magnitude relationship, and a second comparing unit that determines a magnitude relationship between a second reference value corresponding to the received light intensity when the liquid is not present and the received light signal,
When the light receiving signal falls below the second reference value based on the determination result by the first and second comparing units, an abnormality is detected, and the light receiving signal exceeds the second reference value and the first reference value is exceeded. When the value is below the value, it is possible to detect that there is no liquid, and when the light receiving signal exceeds the first reference value, there may be provided a determination means for detecting the presence of the liquid. This makes it possible to detect an abnormality in the liquid detection device in addition to the presence / absence of liquid, thereby increasing the accuracy of liquid detection.

<Invention of Claim 3> The liquid detecting device according to the invention of claim 3 is a projection device which is disposed with a transparent or translucent pipe extending vertically and in which the level of the liquid changes inside. An optical unit and a light receiving unit, and a comparison unit that determines a magnitude relationship between a light receiving signal output by the light receiving unit and a predetermined reference value,
In a liquid detection device that detects the presence or absence of liquid between the light projecting unit and the light receiving unit based on the determination result by the comparing unit, a light projecting lens is provided between the light projecting unit and the pipe, and the light projecting lens is provided. The lens for light is characterized in that the light emitted from the light emitting unit is configured to be parallel light when viewed on the vertical split surface of the pipe and when viewed on the horizontal split surface of the pipe. Have.

According to this configuration, when the light from the light projecting portion is viewed from the horizontal split surface of the pipe by the light projecting lens,
It is considered as parallel light. When there is a liquid in the pipe, the light is condensed by the lens effect and the light receiving intensity of the light receiving unit is increased. On the other hand, when there is no liquid, the light receiving unit does not have the lens effect and the light receiving unit remains in parallel light. Upon receiving the light, the received light intensity decreases. The presence or absence of the liquid can be detected based on the difference between the light receiving intensities. At this time, even if the size of the pipe differs from that of the light emitting and receiving unit, the light receiving intensity differs depending on the presence or absence of the liquid. Therefore, liquids can be detected without adjusting the optical axis or adjusting the positional relationship between the light emitting and receiving sections even for pipes with different sizes. No need to worry. In addition, since the light from the light emitting and receiving unit is collimated by the light projecting lens when viewed on the vertically split surface of the pipe, even if there is a foreign matter in the liquid, the projection of the foreign matter is directed to the light receiving unit side. It does not cover a wide range, and the influence on the received light intensity can be suppressed. This can prevent erroneous detection due to foreign matter in the liquid.

Specifically, the light projecting lens is composed of a hexahedron having a pair of opposing surfaces in each of up, down, left, right and front, and of the six surfaces, the front end face of the light projecting lens facing the pipe. When viewed in a vertically divided plane of the pipe, the light emitting lens of the pipe has a convex structure in which a central portion protrudes toward the pipe. Parallel light can be obtained when viewed on the vertical split surface and when viewed on the horizontal split surface of the pipe.

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 30 denotes a tank, and a transparent pipe 31 having a circular cross section communicates with the tank 30 on the side thereof so that the level of the liquid L in the tank 30 can be seen from the outside. And it is provided extending vertically. The liquid detection device according to the present embodiment is configured such that the liquid L
Is used to detect whether or not the level has reached a predetermined reference water level.

The liquid detecting device includes a sensor head section 40 (see FIG. 1) which is attached at an intermediate portion of a pipe 31, and an electric circuit section 70 (see FIG. 7) which is arranged apart from the pipe 31.
Are connected by a pair of optical fibers 55 and 56 (see FIG. 3).

The electric circuit section 70 is provided with a light projecting element and a light receiving element (not shown), and the light projecting element has one fiber 55 (hereinafter referred to as “light projecting optical fiber 55” as appropriate). ) Are abutted against each other.
The distal end of the light emitting optical fiber 55 constitutes the light emitting part 50 (see FIG. 3) of the present invention, and when the light emitting element is driven by the drive circuit, the light emitting part 50 (more specifically, The light is emitted from the front end face 55A) of the light projecting optical fiber 55. In addition, the base end face of the other optical fiber 56 (hereinafter, appropriately referred to as “optical fiber 56 for light reception”) is abutted on the light receiving element. The distal end of the light receiving optical fiber 56 constitutes the light receiving section 51 of the present invention, and the light received by the light receiving section 51 (more specifically, the distal end surface 56A of the light receiving optical fiber 56) is transmitted to the light receiving element. Given.

The optical fibers 55 and 56 have their distal ends fixed to the bracket 41. As shown in FIG. 3, the bracket 41 is formed by bridging one end of a pair of leg portions 42 and 43 that are opposed to each other with a predetermined space therebetween with a communication wall 44. The tip of one leg 42 (hereinafter, appropriately referred to as “light-projecting side leg 42”) opposes the other leg 43 (hereinafter, appropriately referred to as “light-receiving side leg 43”). A V-shaped groove 45 is formed on the surface. Also, as shown in FIG.
The winding walls 46, 46 extending vertically along are formed,
Further, the distal ends of the wound walls 46, 46 are reinforced by being connected to reinforcing walls 47, 47 which are bent and extend from the base end side of the light emitting side leg 42. Then, as shown in FIG. 3, the inner surface of the V-shaped groove 45 is pressed against the peripheral surface of the pipe 31, and FIG.
As shown in the figure, the wire W is wound around the outer surfaces of the wound walls 46, 46 together with the pipe 31, and the bracket 41 is fixed to the pipe 31. In addition, as shown by reference numerals 31X and 31Y in FIG.
Again press the inner surface of the V-shaped groove 45 against the peripheral surface of 1Y,
It can be fixed with the wire W.

A light projecting lens 80 is embedded in the light projecting side leg 42 as shown in FIG. The base end face 80B of the light projecting lens 80 is abutted against the light projecting portion 50 with a gap therebetween, and the front end face 80F is provided with the V-shaped groove 45.
Is exposed at the bottom. On the other hand, the light receiving side leg 43 has
A light receiving lens 90 is embedded, and its proximal end face 90B has
The front end face 90 </ b> F is exposed at a position facing the front end face 80 </ b> F of the light projecting lens 80 in the light receiving side leg 43.

The two lenses 80 and 90 are provided in the middle of each of them with prism portions 80A and 9 that change the direction of light by 90 degrees.
4A, for the sake of simplicity, FIG. 4 shows both lenses 8 simplified by omitting the prism portions 80A and 90A.
0,90 are shown. Hereinafter, a description will be given based on FIGS. First, as shown in FIG.
Numeral 90 is a hexahedron having a pair of opposing surfaces in each of the upper, lower, front, rear, right and left directions. In addition, the opposing surfaces facing each other in the up-down direction (longitudinal direction of the pipe 31) and in the left-right direction are parallel to each other. small.

As shown in FIG. 5, both lenses 80 and 90 have a front end face 80F and 90F facing the pipe 31 at a central portion toward the pipe 31 when viewed from a vertical split surface of the pipe 31. The base end faces 80B, 9 have a protruding convex structure.
0B has a planar structure extending straight in the up-down direction. As a result, as shown in the figure, when viewed from the vertical split surface of the pipe 31, the radiated light emitted from the light projecting unit 50 is converted into parallel light by the front end face 80F of the light projecting lens 80, and the pipe 31
, And the front end face 90 </ b> F of the light receiving lens 90 receives the light and condenses it on the light receiving unit 51.

On the other hand, as shown in FIG.
When 90 is viewed from the side of the pipe 31, the two lenses 80,
90 has a different structure. That is, the projection lens 80 is
The front end face 80F has a concave structure in which a central portion is depressed toward the pipe 31, and the base end face 80B has a convex structure in which a central portion protrudes toward the pipe 31. On the other hand, in the light receiving lens 90, both the front end face 90F and the base end face 90B
It is flat in the horizontal direction. As a result, as shown in FIG.
Radiation emitted from the light source 80 is projected onto the base end face 80 of the projection lens 80.
When the light is collimated at B and emitted from the projection lens 80, it is radiated and radiated to the pipe 31 by the concave shape of the front end face 80 </ b> F.

As shown in FIGS. 6A and 6B, the light emitted radially from the light projecting unit 50 through the light projecting lens 80 is formed by the liquid L in the pipe 31. Irrespective of the presence or absence, the light is received by the light receiving unit 51. Depending on the presence or absence of the lens effect by the liquid L, the light receiving intensity of the light receiving unit 51 is:
When there is no liquid L, it is smaller when there is no liquid L.

Next, the electrical configuration of the present embodiment will be described. The light received by the light receiving section 51 is supplied to a light receiving element (not shown) via an optical fiber 55, and the light receiving element receives a light receiving signal corresponding to a received light amount of the received light by the electric circuit section 70 shown in FIG. Output to the circuit 71. The light receiving circuit 71 has a built-in amplifier circuit, amplifies the light receiving signal received from the light receiving element, and supplies the amplified signal to the comparing circuit 72.

In this embodiment, the comparison circuit 72 includes a pair of comparators 1 and 2. Then, the comparator 1 determines the magnitude relationship between the first reference value and the received light signal, and outputs a binary signal corresponding to the magnitude relationship. The comparator 2 determines the magnitude relationship between the second reference value and the received light signal. The relationship is determined, and a binary signal corresponding to the magnitude relationship is output. Here, as described above, the first reference value is set to a potential corresponding to the received light intensity when the liquid L is present, and the second reference value is
The potential is set to a potential corresponding to the received light intensity when there is no liquid L. In FIG. 7, reference numeral 73 denotes an output circuit, which is based on the output results of the comparators 1 and 2.
It outputs ternary detection signals corresponding to "liquid present", "liquid not present" and "abnormal".

Next, the operation of this embodiment having the above configuration will be described. The liquid detection device of the present embodiment is attached to the pipe 31, and a start switch (not shown) is turned on. Then, radiated light is emitted from the light projecting unit 50, and when the radiated light enters the light projecting lens 80, when viewed from the horizontal split surface of the pipe 31, parallel light is emitted at the base end surface 80 B serving as a light incident surface. (See FIG. 6), and the front end face 80F of the projection lens 80.
Continue to. Here, the front end face 80F of the projection lens 80
Has a concave structure in the transverse direction of the pipe 31, the light emitted from the front end face 80F is converted into radiated light in the transverse direction of the pipe 31 and provided to the pipe 31. And
When the liquid L in the pipe 31 exists, as shown in FIG. 6B, the light is condensed by the lens effect, and the light receiving intensity of the light receiving unit 51 increases. On the other hand, when there is no liquid L, as shown in FIG. 6 (A), since the lens effect is not exhibited, the emitted light is not condensed, and the light receiving intensity is reduced.
At this time, the light emitting and receiving lenses 80 and 90 and the light emitting and receiving unit 5
Even when the diameter of the pipe 31 is different from that of the pipes 0 and 51, the light receiving intensity is different depending on the presence or absence of the liquid. Therefore, the liquid L can be detected without strictly adjusting the optical axis and strictly the positional relationship between the light emitting and receiving portions, and the application is expanded as compared with the conventional one, and there is no need to worry about the variation in the pipe size.

In the present embodiment, the light emitted from the light projecting unit 50 is once converted into parallel light on the base end face 80B, and then returned to the emitted light again. The emitted light can be emitted from the position, and the following operational effects can be obtained. That is, when radiated light is given from a position distant from the pipe 31, the radiated light passes through the pipe 31 due to the difference in the diameter of the pipe 31 as shown in comparison with FIGS. 8A and 8B. The light converging point P1 is different. For this reason, as shown in FIG.
In Y, the light-collecting point P1 is located in front of the light-receiving part 51, the light radiated from the light-collecting point P1 is given to the light-receiving part 51, and the light receiving intensity does not differ depending on the presence or absence of the liquid L,
The liquid L cannot be detected. Alternatively, in order to avoid this, it is necessary to change the arrangement of the light emitting and receiving units 50 and 51 one by one. However, this is not the case when the emitted light is emitted from a position close to the pipe 31. In the present embodiment, the emitted light from the light projecting unit 50 is once converted into parallel light at the base end face 80B. To return to the emitted light again.
Since the emitted light is emitted from a position close to, the presence or absence of the liquid L can be detected regardless of the diameter of the pipe 31.

As described above, when the light receiving intensity of the light receiving section 51 changes depending on the presence or absence of the liquid L, a light receiving signal having a magnitude corresponding to the light receiving intensity is output from the light receiving element. Then, the light receiving signal is taken into the comparators 1 and 2 via the light receiving circuit 71. Then, in each of the comparators 1 and 2, it is determined whether the light receiving signal is larger than the first and second reference values, and a detection signal corresponding to “liquid present” or “liquid not present” is output from the output circuit 73. Is output. Here, in the present embodiment, the light from the light projecting unit 50 is
When viewed from the vertical split surface of the pipe 31, the light emitting lens 80
As shown in FIG. 5, when a foreign substance Z such as a bubble or a solidified substance is generated in the liquid L, the foreign substance Z is not projected onto the light receiving unit 51 in a wide range as shown in FIG. ,
The effect on the received light intensity can be suppressed. This allows
Erroneous detection due to foreign matter Z in liquid L can be prevented.

Further, for example, when the optical fiber 55 is disconnected halfway, no light is emitted from the light projecting unit 50,
The light receiving unit 51 cannot receive light, and the level of the light receiving signal from the light receiving element becomes equal to or lower than a predetermined value (for example, 0 [V]). Then, this light receiving signal is taken into the comparator 2, it is determined that the light receiving signal has fallen below the second reference value, and an abnormality detection signal is output from the output circuit 73.

As described above, according to the liquid detection device of the present embodiment, the light passing through the pipe 31 is radiated when viewed from the horizontal split surface of the pipe 31, so that the pipe can be different. Also, the liquid can be detected without adjusting the optical axis or the positional relationship between the light emitting and receiving sections, and the application is expanded as compared with the conventional one, and there is no need to worry about the variation in the pipe size.
Since parallel light is used when viewed on the vertically split surface, even if there is foreign matter such as air bubbles in the liquid, even if water droplets adhere to the piping when there is no liquid, the effect is suppressed and false detection is eliminated. be able to. In addition, since the abnormality such as disconnection of the optical fibers 55 and 56 can be detected, the accuracy of liquid detection increases.

<Second Embodiment> This embodiment is shown in FIG. 9 and FIG. 10. Hereinafter, only the configuration different from the first embodiment will be described, and the same reference numerals will be given to the same configuration. Therefore, a duplicate description will be omitted.

The light projecting unit 50 in the liquid detecting apparatus of the present embodiment is configured such that each of the tips of the plurality of light projecting optical fibers 55 serves as a light emitting unit 100, and these light emitting units 100 are mutually connected along the longitudinal direction of the pipe 31. They are arranged at predetermined intervals. On the other hand, the light receiving section 51 is configured such that each of the distal ends of the plurality of light receiving optical fibers 56 serves as a small light receiving section 101, and the small light receiving sections 101 are sandwiched between the light emitting sections 100 with the pipe 31 interposed therebetween.
Facing.

Even with such a configuration, as shown in FIG. 10, the light from the light projecting portion 50 can be converted into radiation when viewed from the horizontal split surface of the pipe 31, so that the diameter of the pipe 31 is different. The light receiving intensity differs depending on the presence or absence of the liquid. Therefore, the liquid can be detected without strictly adjusting the optical axis or adjusting the positional relationship between the light emitting and receiving units,
Applications are wider than conventional ones, and there is no need to worry about variations in piping size. In addition, since the plurality of light emitting units 100 constituting the light projecting unit 50 are arranged along the longitudinal direction of the pipe 31, the liquid L is measured as shown in FIG.
Foreign matter such as air bubbles and coagulated matter is generated on the surface, or water droplets and the like adhere to the gas, and the foreign matter Z
Is located, the other light from the light emitting unit 100 is given to the light receiving unit 51 side, and the influence of the foreign matter Z on the light receiving intensity can be suppressed. Accordingly, even if foreign matter such as air bubbles is present in the liquid, or even if water droplets adhere to the pipe when there is no liquid, the influence thereof can be suppressed and erroneous detection can be prevented.

<Second Embodiment> This embodiment is shown in FIG. 16 and FIG. 17. Hereinafter, only the configuration different from the first embodiment will be described, and the same reference numerals will be given to the same configuration. Therefore, a duplicate description will be omitted.

When both the light projecting and light receiving lenses 81 and 91 of this embodiment are viewed from the vertical split surface of the pipe 31, both front end faces 81 F and 91 F facing the pipe 31 face toward the pipe 31. The central portion has a protruding surface structure, and the base end surface 8
1B and 91B form a planar structure extending straight in the vertical direction. Thereby, when viewed from the vertical split surface of the pipe 31, similarly to the first embodiment (see FIG. 5), the light emitting unit 5
The radiated light emitted from 0 is made parallel by the front end face 81F of the light projecting lens 81 and passes through the pipe 31, and the front end face 91F of the light receiving lens 91 receives the light and is condensed on the light receiving section 51. I do.

On the other hand, as shown in FIG.
When the first lens 91 and the first lens 91 are viewed from the horizontal split surface of the pipe 31, both lenses 8
1, 91 have different structures. That is, the light projecting lens 81
Has a flat front end face 81F and a base end face 81F.
B has a convex structure with a central portion protruding toward the pipe 31. On the other hand, in the light receiving lens 91, both the front end face 91F and the base end face 91B are flat in the lateral direction. As a result, as shown in the figure, when viewed on the horizontal split surface of the pipe 31, the radiated light emitted from the light projecting unit 50 is converted into parallel light by the base end surface 81 </ b> B of the light projecting lens 81. When the light is emitted from the lens 80, the light is radiated to the pipe 31 as parallel light by the flat surface of the front end face 81F.

As shown in FIGS. 17A and 17B, light emitted in parallel from the light projecting unit 50 through the light projecting lens 81 flows into the pipe 31 in the liquid L direction. Is received by the light receiving unit 51 regardless of the presence or absence of
The light receiving intensity of the light receiving unit 51 is smaller when there is no liquid L than when there is liquid L, depending on the presence or absence of the lens effect due to the above.

Next, the electrical configuration of this embodiment will be described. The light received by the light receiving section 51 is supplied to a light receiving element (not shown) via an optical fiber 55, and the light receiving element receives a light receiving signal corresponding to a received light amount of the received light by the electric circuit section 70 shown in FIG. Output to the circuit 71. The light receiving circuit 71 has a built-in amplifier circuit, amplifies the light receiving signal received from the light receiving element, and supplies the amplified signal to the comparing circuit 72.

In this embodiment, the comparison circuit 72 includes a pair of comparators 1 and 2. Then, the comparator 1 determines the magnitude relationship between the first reference value and the received light signal, and outputs a binary signal corresponding to the magnitude relationship. The comparator 2 determines the magnitude relationship between the second reference value and the received light signal. The relationship is determined, and a binary signal corresponding to the magnitude relationship is output. Here, as described above, the first reference value is set to a potential corresponding to the received light intensity when the liquid L is present, and the second reference value is
The potential is set to a potential corresponding to the received light intensity when there is no liquid L. In FIG. 7, reference numeral 73 denotes an output circuit, which is based on the output results of the comparators 1 and 2.
It outputs ternary detection signals corresponding to "liquid present", "liquid not present" and "abnormal".

Next, the operation of this embodiment having the above configuration will be described. The liquid detection device of the present embodiment is attached to the pipe 31, and a start switch (not shown) is turned on. Then, radiated light is emitted from the light projecting unit 50, and when the radiated light enters the light projecting lens 81, when viewed from the horizontal split surface of the pipe 31, parallel light is emitted at the base end surface 81 B serving as a light incident surface. (See FIG. 17), and the front end face 81 of the projection lens 81
Proceed to F. Here, the front end face 81F of the projection lens 81
Is flat in the horizontal split direction of the pipe 31,
The light emitted from the front end face 81F is converted into radiated light in the transverse direction of the pipe 31 and provided to the pipe 31. Then, when there is the liquid L in the pipe 31, FIG.
As shown in (2), light is condensed by the lens effect, and the light receiving intensity of the light receiving unit 51 is increased. On the other hand, the liquid L
When there is no light, as shown in FIG. 17 (A), since no lens effect is exhibited, parallel light is not condensed and the light receiving intensity is reduced. At this time, even if the diameter of the pipe 31 differs from the light emitting / receiving lenses 81, 91 and the light emitting / receiving sections 50, 51, the light receiving intensity also differs depending on the presence or absence of the liquid. Therefore, the liquid L can be detected without strictly adjusting the optical axis and strictly the positional relationship between the light emitting and receiving portions, and the application is expanded as compared with the conventional one, and there is no need to worry about the variation in the pipe size.

Further, in the present embodiment, the light emitted from the light projecting section 50 can be once converted into parallel light on the base end face 81B and emitted as parallel light from the front end face 81F. It works. That is, when the positional relationship between the light projecting unit 50 and the pipe 31 is fixed and the emitted light is given, as shown in FIGS. 8A and 8B, the size of the diameter of the pipe 31 is increased. , The light condensing point P1 of the light passing through the pipe 31 is different. For this reason, as shown in FIG. 8B, in the pipe 31Y having a small diameter, the focusing point P is located in front of the light receiving section 51.
At position 1, the light radiated from the light condensing point P <b> 1 is given to the light receiving unit 51, and the light receiving intensity does not differ depending on the presence or absence of the liquid L, and the liquid L cannot be detected. Alternatively, in order to avoid this, it is necessary to change the arrangement of the light emitting and receiving units 50 and 51 one by one. However, when the parallel light is emitted to the pipe 31 and the light receiving unit 51 is fixed at a predetermined position from the pipe 31, this is not the case. In the present embodiment, the parallel light is emitted from the light projecting unit 50. In addition, since the light receiving unit 51 is disposed at a position close to the pipe 31, the presence or absence of the liquid L can be detected regardless of the diameter of the pipe 31.

<Other Embodiments> The present invention is not limited to the above embodiments. For example, the following embodiments are also included in the technical scope of the present invention.
In addition to the following, various changes can be made without departing from the scope of the invention.

(1) In the above embodiments, the pipe 31 is transparent, but the pipe may be translucent.

(2) In the first embodiment, the distal ends of the optical fibers 55 and 56 are fixed to the bracket 41 as the light emitting and receiving portions 50 and 51. However, the light emitting element and the light receiving element are It is also possible to adopt a configuration in which the unit and the light receiving unit are fixed to a bracket, and wiring is extended from the light emitting and receiving elements and connected to the electric circuit unit.

(3) In the first embodiment, both lenses 8
0, 90 are bent and formed in the middle of the prism portions 80A, 90A.
, But as shown in simplified form in FIG.
A configuration without the prism unit may be used.

(4) In the first embodiment, as shown in FIG. 6, in the light projecting lens 80, the base end face 80B has a convex shape and the front end face 80F has a concave shape. The base end face 80B and the front end face 80F may both have a planar shape. This is because even in such a case, the emitted light can be emitted from the front end face 80F. However, the first
As in the embodiment, the base end face 80B has a convex shape, and the front end face 80B
If F has a concave shape, light can be emitted from a position close to the pipe 31 as described above.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a liquid detection device according to a first embodiment of the present invention.

FIG. 2 is a side view of the liquid detection device.

FIG. 3 is a cross-sectional plan view of the liquid detection device.

FIG. 4 is a perspective view of a projection lens.

FIG. 5 is a cross-sectional view of the pipe taken along a vertically divided plane.

FIG. 6 is a cross-sectional view of the pipe taken along a horizontal plane.

FIG. 7 is a block diagram showing an electrical configuration of the liquid detection device.

FIG. 8 is a conceptual diagram showing a problem due to a difference in pipe diameter.

FIG. 9 is a side sectional view of a liquid detection device according to a second embodiment.

FIG. 10 is a cross-sectional plan view of the liquid detection device.

FIG. 11 is a side sectional view of a conventional liquid detection device.

FIG. 12 is a conceptual diagram showing the principle of a liquid detection device.

FIG. 13 is a perspective view showing a bracket of the liquid detection device.

FIG. 14 is a conceptual diagram for explaining a conventional problem.

FIG. 15 is a conceptual diagram for explaining a conventional problem.

FIG. 16 is a perspective view of a light projecting lens according to a third embodiment.

FIG. 17 is a cross-sectional view of the pipe according to the third embodiment, taken along a vertical split plane.

[Description of Signs] 31, 31X, 31Y: Piping 41: Bracket 50: Light emitting unit 51: Light receiving unit 80: Light emitting lens 80B: Base end surface 80F: Front end surface 100: Light emitting unit L: Liquid

Claims (3)

[Claims] 1. A light projecting unit and a light receiving unit which are arranged vertically with a transparent or translucent pipe in which a liquid level changes inside, and a light receiving signal output by the light receiving unit and a predetermined A comparison unit that determines the magnitude relationship between the light projection unit and the reference value of the reference value, a liquid detection device that detects the presence or absence of liquid between the light projection unit and the light reception unit based on the determination result by the comparison unit; A light projecting lens is provided between the light emitting unit and the pipe, and the light projecting lens converts light emitted from the light emitting unit into parallel light when viewed from a vertically split surface of the pipe. A liquid detection device configured to emit radiation when viewed from a horizontal split surface of the pipe. 2. A light-transmitting unit and a light-receiving unit which are arranged vertically with a transparent or translucent pipe in which the level of a liquid changes within, and a light-receiving signal output from the light-receiving unit and a predetermined light-receiving unit. A comparison unit that determines the magnitude relationship between the light projection unit and the reference value of the reference value, a liquid detection device that detects the presence or absence of liquid between the light projection unit and the light reception unit based on the determination result by the comparison unit; The liquid detecting device according to claim 1, wherein a plurality of light emitting units for emitting radiation light are arranged along a longitudinal direction of the pipe. 3. A light projecting unit and a light receiving unit interposed with a transparent or translucent pipe extending vertically and in which a liquid level changes within, a light receiving signal output by the light receiving unit and a predetermined value. A comparison unit that determines the magnitude relationship between the light projection unit and the reference value of the reference value, a liquid detection device that detects the presence or absence of liquid between the light projection unit and the light reception unit based on the determination result by the comparison unit; A light-emitting lens is provided between the pipe and the pipe, and the light-emitting lens, when the light emitted from the light emitting unit is viewed on a vertically split surface of the pipe, and A liquid detection device, which is configured to make parallel light when viewed on a horizontal split surface.