JPH0827293B2 - Liquid sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid sensor used as a water level sensor for detecting the presence or absence of liquid in a pipeline.

[0002]

2. Description of the Related Art A conventional liquid sensor used as a water level sensor has a conduit 33 as shown in FIGS. 3 (a) and 3 (b).
On the other hand, the light emitting element 34 and the light receiving element 35 are displaced from the center position and face each other. In this configuration, the pipeline
When the liquid 32 is in 33, the light 38 from the light emitting element 34 reaches the light receiving element 35 and is received, but when the liquid 32 is not in the conduit 33 as shown in FIGS. 4 (a) and 4 (b). , The light 38 from the light emitting element 34 does not reach the light receiving element 35 due to the difference in refractive index,
The presence or absence of the liquid 32 in the conduit 33 can be detected based on the change in the amount of light received by the light receiving element 35.

[0003]

However, in the above-described conventional liquid sensor, even when the liquid 32 is present in the conduit 33,
When the amount of light incident on the light receiving element 35 is small, or when there is no liquid 32 in the conduit 33, problems such as the inability to completely block the light reaching the light receiving element 35 side easily occur, and the liquid 32 in the conduit 33 is likely to occur. There is a problem in that the difference (on / off level) in the detection output of the light receiving element 35 cannot be made large with and without. Further, in the conventional liquid sensor, when the inner wall of the conduit 33 becomes dirty due to aging, the ON / OFF level of the detection output of the light receiving element 35 changes, and thus the presence or absence of the liquid 32 cannot be accurately detected. Further, in the conventional liquid sensor, since the sensor sensitivity is greatly affected by the variation of the elements 34 and 35 constituting the sensor, it is necessary to adjust each sensor.

As described above, the conventional liquid sensor has a problem that it cannot reliably detect the presence or absence of the liquid 32 in the conduit 33. The present invention has been proposed in order to solve such conventional problems, it is possible to take a large on-off level of the detection output, high reliability and accuracy without being affected by dirt in the pipeline. An object of the present invention is to provide a liquid sensor capable of detecting the presence / absence of liquid in a pipeline.

[0005]

Means for Solving the Problems A liquid sensor according to the invention to achieve this object, in the liquid sensor which detects whether the tube body formed of a material having a light transmitting liquid is passed, the On the outer peripheral surface of the pipe body, a notch-shaped part
Minutes, at least one plane is formed,
It is provided outside the tube and generates detection light and detects this
Light penetrates into the tube from the one plane of the outer peripheral surface of the tube
However, when liquid is passed through the pipe line of the pipe body,
From the boundary surface of the pipeline, it further penetrates into the pipeline, and liquid enters this pipeline.
When there is no light, the light emitting element arranged so as to totally reflect at the boundary surface and the detection light provided from the light emitting element, which is provided outside the tube, receives the detection light and It is composed of a light receiving element for detecting the presence or absence of liquid.

[0006]

According to the above-mentioned structure, when the light emitting element and the light receiving element are arranged with the tube sandwiched therebetween, for example, when liquid is present in the conduit, the detection light emitted from the light emitting element is emitted from the light receiving element side. Although light is received, when there is no liquid in the conduit, the detection light is totally reflected and does not reach the light receiving element side. Therefore, the presence or absence of liquid in the conduit can be detected based on the output of the light receiving element.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a liquid sensor according to the present invention will be described in detail below with reference to the drawings. In Figure 1. An example of this liquid sensor will be shown. In this figure, the light emitting element 4 and the light receiving element 5 are arranged on one side and the other side of the tube body 1 so as to face each other on a line obliquely connected to the tube 3 through which the liquid 2 passes. The light emitting element 4 and the light receiving element 5 are respectively housed in housing portions 6 and 7 cut out in the tube body 1, and these housing portions 6 and 7 have an incident surface and a light receiving surface orthogonal to the optical path. . In this figure, a tube 1 is made of a light-transmissive material such as glass or acrylic, and is passed through a conduit 3 by a light emitting element 4 and a light receiving element 5 which are arranged with the tube sandwiched therebetween. The presence or absence of the liquid 2 is detected. The light emitting element 4 and the light receiving element 5 are housed in the housing portions 6 and 7 which are notched in the tube body 1 and have an incident surface and a light receiving surface orthogonal to the optical path. The incident angle of the detection light from the light emitting element to the tube body is set to an angle such that total reflection is performed at the boundary surface with the tube path when there is no liquid 2 in the tube path 3. Therefore, when the liquid 2 is present in the conduit 3, the detection light 8 that has entered the tube at the incident angle A from the light emitting element 4 is transmitted through the conduit 3 while being refracted and reaches the light receiving element 5. The light is received by the light receiving element. Further, as shown in FIG. 2, when there is no liquid 2 in the pipe line 3,
The detection light 8 emitted from the light emitting element 4 is totally reflected by the boundary surface P between the material of the tube body 1 and the air layer 9 of the tube line 3 and is reflected back to one side of the tube body 1 and into the tube line 3. It is designed so that it does not transmit light. Here, the condition that the detection light 8 emitted from the light emitting element 4 is totally reflected is that the refractive index of the material forming the tube body 1 and the detection light 8
Is determined only by the angle of incidence A of the light on the tube 1. Next, the circuit configuration will be described. The light emitting element 4 is connected to the light emitting circuit 10 for supplying a light emitting current. The detection output of the light receiving element 5 is connected to one input terminal of the comparison circuit 12 via the amplification circuit 11. The reference voltage source 13 is connected to the other input terminal of the comparison circuit 12, and an output signal for detecting the presence or absence of the liquid 2 in the conduit 3 is taken out from the output terminal 14 of the comparison circuit 12.

In the liquid sensor having this structure, the conduit 3
When the liquid 2 is present, most of the detection light 8 emitted from the light emitting element 4 reaches the light receiving element 5 and is received, so that the output terminal 14 of the comparison circuit 12 detects the presence of the liquid at the high level. A (“H” level) detection signal is output. When there is no liquid 2 in the pipe 3, the detection light 8 emitted from the light emitting element 4 is totally reflected by the boundary surface P between the material of the pipe 1 and the air layer 9 of the pipe 3, and Since it is all folded back to one side and the detection light 8 does not reach the light receiving element 5,
From the output terminal 14 of the comparison circuit 12, a low level (“L” level) detection signal for detecting the absence of liquid is output. Therefore, with this liquid sensor, it is possible to make a large difference in the on / off level of the detection signal corresponding to the presence or absence of the liquid, and if the detection level in the presence of the liquid is appropriately determined, the liquid cannot be detected. , Dirt on pipe 3 or liquid 2
The presence / absence of the liquid 2 in the conduit 3 can be accurately detected without being affected by the color and turbidity of the liquid, and the variation of the elements 4 and 5 constituting the sensor.

[0009]

As described above, according to the present invention, light is transmitted from the outside of the tubular body to the tubular body, and when liquid is present in the tubular body, the light is passed through the tubular body, If there is no liquid in, the light is totally reflected at the boundary between the pipe and the pipe, so the detection level difference corresponding to the presence or absence of liquid in the pipe can be made large, and the detection result is It is not affected by the color or turbidity of the liquid, or the contamination of the pipeline due to aging.
Further, in the present invention, the tube body is used as a means for guiding the liquid, a means for guiding the light, or a means for refracting the light. That is, the tubular body is also used as an optical component. Therefore, according to the present invention, the presence or absence of the liquid in the conduit can be detected with high accuracy while having an extremely simple structure. In addition, the condition of total reflection when there is no liquid in the pipeline is the refractive index of the material of the tubular body that constitutes the pipeline.
Determined only by the incident angle of the detected light with respect to the longitudinal direction of the tube ,
Since it is not affected by variations in the elements that make up the sensor, it is not necessary to make fine adjustments for each sensor. Where
The angle of incidence is determined by the refractive index of the tube material.
Therefore, the detection light is incident in the direction of the incident surface on the outer peripheral surface of the tube.
In a predetermined direction, for example in the direction orthogonal to
It is possible to decide. And this incident surface of the tube
If it is formed by forming a notch on the outer peripheral surface,
At the manufacturing stage, the light emitting element
Easy designing because optical elements can be placed
Not only that, the installation work of these becomes easy and troublesome.
No need for rough optical path adjustment work.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a liquid sensor according to the present invention.

FIG. 2 is an explanatory diagram for explaining the operation when there is no liquid in the pipeline.

FIG. 3 is a configuration diagram showing a conventional liquid sensor.

FIG. 4 is an explanatory diagram for explaining the operation of the conventional liquid sensor.

[Explanation of symbols]

 1 tube 2 liquid 3 conduit 4 light emitting element 5 light receiving element 8 detection light 9 air layer 10 light emission circuit 11 amplification circuit 12 comparison circuit 13 reference voltage source

Claims (1)

[Claims] 1. A liquid sensor for detecting whether or not a liquid is passed through a tubular body made of a light-transmissive material, wherein a notched portion is provided on an outer peripheral surface of the tubular body.
At least one flat surface is formed and is provided outside the tubular body to generate detection light.
Light penetrates into the tube from the one plane of the outer peripheral surface of the tube
However, when liquid is passed through the pipe line of the pipe body,
From the boundary surface of the pipeline, it further penetrates into the pipeline, and liquid enters this pipeline.
When there is no light, the light emitting element arranged so as to totally reflect at the boundary surface, and the detection light emitted from the light emitting element, which is provided outside the tube body, is received and A liquid sensor including a light receiving element that detects the presence or absence of liquid.