JPS586891B2 - temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature detector using an optical fiber, which is suitable for use in detecting the temperature of a place where a strong electromagnetic field is generated, such as inside a generator or a motor.

Thermistors are mainly used as temperature sensing elements in conventional temperature detectors.

However, thermistors detect temperature by detecting changes in electrical resistance due to temperature, so in strong electromagnetic fields the S/M ratio decreases due to noise generated, and since the signal is extracted using electric wires, sufficient insulation measures must be taken. .

Temperature detectors using thermocouples also have similar drawbacks.

Recently, temperature detectors using optical fibers with good insulation and unaffected by electromagnetic fields, such as the one shown in FIG. 1, have been considered.

In FIG. 1, light from a light source 1 is guided through an optical fiber 2 to a temperature detection section.

A shutter 4 is attached to the other end of the bimetal 3, one end of which is fixed, and the shutter 4 is interposed in the optical path between the optical fiber 2 and the optical fiber 5 provided opposite to it to block light. .

When the bimetal 3 reaches a certain temperature and bends, the shutter 4 is removed from the optical path, and the light guided from the light source 1 by the optical fiber 2 passes through the optical fiber 5 and reaches the light receiving element 6.
Can detect temperature.

In this temperature sensor, the mechanical part, that is, the bimetal 3
Since the shutter 4 is equipped with a
It requires a space for movement, and if that space is filled with dirt or dust, it has the disadvantage of causing malfunction detection.

It is an object of the present invention to eliminate the above-mentioned drawbacks and to obtain a temperature sensor using an optical fiber that is not affected by electromagnetic fields, has high dielectric strength, is not easily affected by vibrations, is free from wear, and has a long life.

The present invention is characterized in that temperature is detected by utilizing the expansion and contraction of fluid due to temperature changes and by intermittent light guided by an optical fiber.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention. 7 is a temperature sensor in which a liquid 7a that does not allow light to pass through is placed in a transparent container 7b that allows light to pass through, and the liquid level of the liquid 7a changes upward or downward depending on changes in the surrounding temperature. For example, a mercury thermometer.

A light source 1 is provided on one side of the temperature sensor 7, and light from the light source 1 enters one end of an optical fiber 2 and is guided to one side of the temperature sensor 7 placed on the temperature detection section.

One end of another optical fiber 5 is provided on the opposite side of the optical fiber 2 across the temperature sensor 7.

A light receiving element 6 is attached to the other end of the optical fiber 5.
It is arranged to receive light from the

Next, the operation of the present invention will be explained. Light from the light source 1 enters one end of the optical fiber 2 and is guided to the temperature sensor 7 by the optical fiber 2.

When the temperature around the thermosensor 7 is low, the liquid level inside the thermosensor T does not block light that is lower than the optical fiber 2 position.

Therefore, the light emitted from the other end of the optical fiber 2 is transmitted to the transparent container 7b.
The light passes through the optical fiber 5, enters one end of the optical fiber 5, and reaches the light receiving element 6.

Therefore, the arrival of light can be detected as an electrical signal based on the output of the light receiving element 6.

When the surrounding temperature exceeds the set temperature, the liquid 7 in the temperature sensor 7
Since a is expanded and its liquid level rises to block the light from the optical fiber 2, the optical signal to the light receiving element 6 stops and there is no output, making it possible to detect an increase in the power level.

Since the temperature sensor 7 has a structure in which the liquid 7a is sealed in a transparent container 7b, the ends of the optical fibers 2 and 5 can be directly bonded to the transparent container 7b.

This prevents the optical fibers 2 and 5 from shaking due to vibrations, and also prevents sensitivity from decreasing due to dust or the like.

Figure 2 shows the case of temperature detection at one point, but by arranging a plurality of optical fibers 2 and 5 in line along the direction of movement of the liquid 7a, one thermosensor 7 can detect temperature at multiple points. is possible.

This will be explained using the example shown in FIG.

Light from a light source 1 is guided through a plurality of optical fibers 2, divided by an optical distributor 8, and the optical fibers 2 are fixed at positions of a thermosensor 7 corresponding to a plurality of set temperatures.

By arranging a plurality of optical fibers 5 to face the optical fibers and detecting whether or not light is transmitted by the corresponding light receiving elements 6, a plurality of points can be detected by one temperature detector.

It is also possible to use a material that reflects light, such as mercury, in the liquid 7a of the temperature sensor 7, and detect the temperature by reflection.

FIG. 4 shows an example of this, in which light from a light source 1 is guided to a temperature sensor 7 by an optical fiber 2.

When the liquid level is low, the light passes through the transparent container 7b, but when the liquid level rises above the position of the optical fiber 2, the light is reflected by the liquid 7a and returns to the optical fiber 2.

The light travels in the opposite direction through the optical fiber 2 and is split into two parts by the optical splitter 8, with one part hitting the light-receiving element 6, and a temperature rise can be detected in the same manner as described above.

Although not shown in the drawings, lenses may be used in the light receiving section and the light projecting section of the optical fiber in order to improve efficiency.

Further, the transparent container 7b may not be entirely transparent, but only the portion where the optical fiber is provided is transparent.

Furthermore, the liquid used in the thermosensor is not limited to mercury, but other liquids or fluids, or a combination thereof may be used.

As described above, according to the temperature detector of the present invention, since light is used as the detection medium, the signal is extracted using an optical fiber (insulator) without being affected by electromagnetic fields, so insulation is good.

In addition, the temperature sensor utilizes the expansion and contraction of the fluid and has a structure in which the fluid is sealed in a container with a transparent part, making it resistant to vibration and free from abrasion.The optical fiber can be tightly attached to the temperature sensor container, making it less susceptible to contamination due to dust, etc. strong against

Furthermore, since the outer surface of the temperature sensor can be made of an insulating material, it has a high withstand voltage, and since the structure is simple, it can be made compact and inexpensive.

[Brief explanation of drawings]

Fig. 1 is a front view showing a conventional temperature detector using optical fiber and bimetal, Fig. 2 is a front view showing one embodiment of the present invention, and Figs. 3 and 4 are other embodiments of the present invention. FIG. 1...Light source, 2...Optical fiber, 5
...Optical fiber, 6... Light receiving element,
7...Temperature sensor, 7a...Liquid, 7b.
...Transparent container, 8...Light distributor.

Claims (1)

[Claims] 1 Consists of a light source, a temperature sensor that is housed in a container with a transparent part and is equipped with a fluid that expands and contracts due to temperature changes and does not allow light to pass through, a light receiving element, and an optical fiber, and the light from the light source is transmitted to the temperature sensor. A temperature sensor characterized by detecting temperature based on the presence or absence of light that is transmitted through an optical fiber to a transparent part of a container and is reflected or intermittent due to the expansion and contraction of a fluid within the temperature sensor.