JPH0774764B2 - Overheat detector - Google Patents

Description

The present invention relates to an overheat detection device. For more details,
The present invention relates to an overheat detection device suitable for detection of local overheat that may occur in various electrical devices, particularly closed switchboards, GIS, and other electrical devices that incorporate high-voltage circuits.

(B) Conventional technology In electrical equipment such as a closed switchboard that has a built-in high-voltage circuit, a local heating phenomenon occurs due to defective assembly of the circuit, defective connection, or deterioration of insulation in the circuit system. May cause electrical troubles or short circuit accidents.

In order to prevent such electrical troubles and short circuit accidents, it is necessary to quickly detect the occurrence of the local heating phenomenon,
Various thermal sensors, such as infrared sensors, thermo cameras,
It is possible to monitor the presence or absence of local heating (overheating) using a thermocouple, thermistor, or the like.

However, the infrared sensor and the thermo camera are not suitable from the economical point of view, and the thermocouple, thermistor, etc. are electric detection devices themselves, so it is necessary to consider the insulation of the infrared sensor or the dedicated wiring. It is not preferable to install it in the switchboard because it is necessary.

Therefore, as a non-electrical detection device, a gas such as a halogenated hydrocarbon is enclosed in a container that is melted or opened at the time of overheating and placed in a switchboard, and the gas released from the container at the time of overheating is A method of indirectly detecting overheating by detecting with a gas sensor is also under study.

(C) Problems to be Solved by the Invention However, when the above detection method is applied, it is necessary to miniaturize the gas-enclosed container as much as possible due to space limitations in the switchboard. Therefore, in order to release the gas having the optimum concentration for detection into the switchboard space, it is necessary to enclose the gas in the container at a considerably high pressure, and the enclosing operation is extremely difficult. Further, since the gas such as the above-mentioned halogenated hydrocarbon is a harmful substance in itself, its use is not preferable from the viewpoint of pollution.

In this regard, the inventors of the present invention have proposed a carbon dioxide gas generation type detection device in which a thermofusible plastic container in which an organic acid is sealed instead of gas is arranged in a box in which alkali carbonate powder is laid, and a carbon dioxide gas sensor. In combination with the above, we have previously proposed a system that detects the overheating phenomenon by detecting carbon dioxide gas generated by the reaction between an organic acid and an alkali metal carbonate during the overheating decay.

However, in such a system, it is difficult to obtain a quick response because the generation rate of carbon dioxide is relatively slow. In addition, carbon dioxide is present in the air at 300 to 400 ppm and indoors at 600 to 800 ppm, which becomes a large background, and at least 500 p for clear detection.
It is necessary to generate carbon dioxide gas that corresponds to an increase in concentration of pm or more, and a large amount of organic acid or carbonate is used, which makes it difficult to downsize the detection device. In addition, since the alkali carbonate used as the reaction agent itself has a large bulk specific gravity, there is also a disadvantage that the box itself for storing it has a relatively large capacity.

The present invention has been made under such circumstances, and an object thereof is to provide an overheat detection device which is suitable for downsizing, can perform overheat detection safely and quickly, and is excellent in economy.

(D) Means for Solving the Problems Thus, according to the present invention, in a breathable box body having a metal powder having an ionization tendency larger than hydrogen introduced at the bottom, a sealed container storing an inorganic acid aqueous solution, A container destruction means capable of self-deforming at a predetermined temperature or higher and applying stress to the sealed container to destroy it, and discharging the internal inorganic acid aqueous solution onto the metal powder, the inorganic acid aqueous solution and the metal powder are provided. There is provided an overheat detecting device for generating hydrogen gas by the reaction of.

Various metal powders having an ionization tendency larger than that of hydrogen can be applied, but powders of aluminum, zinc, iron, nickel, tin, etc. are suitable in terms of stability, easiness of handling, and the like. The particle size of the powder is not particularly limited, and granular particles may be used, and a combination of granular particles and powder is also possible.

On the other hand, as the breathable box used in the present invention, those having a space capable of accommodating the metal powder and the hermetically sealed container, and having breathability are usually used, and a main body having an upper opening,
It is suitable to be configured in combination with a lid having one or more vent holes. However, a filter for preventing the scattering of inorganic acid mist may be stretched over the vent,
As this filter, paper, membrane filter,
Nonwoven fabric is suitable. Incidentally, such a box body is suitable to be composed of a material having heat resistance and impact resistance, and
Suitably it is composed of metal or heat-resistant plastic.

The inorganic acid aqueous solution used in this invention includes hydrochloric acid, sulfuric acid,
Nitric acid and a mixed acid aqueous solution thereof are suitable, and in addition thereto, an aqueous solution of phosphoric acid, chromic acid, silicic acid or the like can also be used. The acid concentration of these aqueous solutions is not particularly limited, but especially when an oxidizing acid such as sulfuric acid is used,
It is suitable to use the one of 18 regulations. In addition, an additive capable of promoting a hydrogen generating reaction with a metal, for example, copper sulfate may be blended in these aqueous solutions.

The container that encloses the inorganic acid aqueous solution is composed of a member having a material and a thickness that can be easily destroyed by the container destruction means described later, and specifically, a glass container, a synthetic resin container, or a metal container is applied. You can Usually, it is suitable to use a glass container or a synthetic resin container from the viewpoint of ease of enclosing operation and breakage. Further, the shape of the container is not particularly limited, but a cylindrical shape is suitable from the viewpoint of destructiveness, and in particular, a container having a stress concentration portion such as a constriction, a groove, or a cut at the fracture center position may be used.

As the container destruction means in the present invention, a means which operates at a predetermined temperature to destroy the sealed container is used.
As such a container destruction means, it is preferable to use an accidentally deformable material that can directly or indirectly destroy the container based on thermal deformation of the member itself, not by operation by electrical control.
For example, a destruction means using a shape memory alloy or bimetal is suitable. In particular, the shape memory alloy is integrated with or placed close to the above-mentioned enclosure, and the container is destroyed by the deformation of the shape memory alloy at a predetermined temperature in order to simplify the structure and further downsize the device. preferable. For example, in the case of using a cylindrical sealed container, a flat shape that bends when heated, a rod-shaped shape memory alloy is arranged in the longitudinal direction of the container,
It can be configured by inserting and arranging a container into a ring-shaped shape memory alloy that contracts when heated, or by fixing an expandable rod-shaped shape memory alloy adjacent to the container. Various shape memory alloys can be applied, but Ni-Ti alloy type and Cu-Zn-Al alloy type are suitable.

When such a self-deforming material is used as a container destruction means, an appropriate projecting member is provided on the inner wall of the box opposite to the side surface provided with the self-deforming material in order to facilitate the destruction of the container. It is preferable to form or dispose. The protrusion may be any of a protrusion, a ridge, and a rod,
Further, it may have a sharp tip, a smooth tip, or a curved tip, as long as it constitutes a fulcrum structure capable of concentrating stress on at least a part of the side surface of the container. When such a protrusion is used as a part of the container destruction means, the entire container can be efficiently destroyed without providing a stress concentration portion such as a neck in the container, which is one preferred embodiment of the present invention. It is a mode.

In the overheat detecting device of the present invention, the capacity of the sealed container is not particularly limited, but, for example, a container having an inner capacity of about 3 ml can be applied. Also, the amount of metal powder introduced into the box can be increased or decreased as necessary, but normally
It is suitable to use about 1g.

The overheat detecting device of the present invention is arranged, for example, in the vicinity of a conductor member in the switchboard which may be overheated, and a plurality of the overheat detecting devices are arranged and used as necessary. Then, the detection of hydrogen gas generated at the time of overheating is performed by using a suitable hydrogen gas detector, for example, a semiconductor hydrogen gas sensor. Since hydrogen gas is a lightweight gas itself, it diffuses upward after being generated. Therefore, it is suitable to dispose the hydrogen gas detector above the disposition position of the overheat detection device and separately from the high-voltage circuit or the conductor where overheat may occur.

FIG. 1 shows a specific example of the overheat detecting device of the present invention. Here, the overheat detection device 1 is a cylindrical glass in which a box body (2; made of stainless steel) having an open upper part in which zinc powder 3 is introduced into the bottom has a constriction in the center and an aqueous solution of an inorganic acid is sealed inside. An ampoule (5; glass container) is housed sideways, and the box lid 4 having a large number of vent holes 41 closes the upper part by adhesion. A rectangular shape memory alloy 6 is fixed to the upper surface of the glass ampoule 5 by a fixing band 7 made of wire. This shape memory alloy plate
It is made of a Ni-Ti alloy processed to bend in a V shape at a temperature of 100 ° C or higher. The bending temperature is Ni-
By adjusting the alloy composition of Ti and the heat treatment temperature,
It can be appropriately determined between 150 ° C. In addition, 71 shows the sealing end which melt-sealed the glass ampoule.
Although not shown, the void in the box body 2 is filled with a nonwoven fabric for allowing the glass ampoule to stand still and for preventing the acid mist from scattering when the glass ampoule is broken.

In such an overheat detecting device 1, when the temperature of the shape memory alloy plate 6 exceeds 100 ° C. due to external overheating, the alloy plate 6
Rapidly bends into a V shape, but the stress due to this causes the glass ampoule to be constricted and the glass ampoule is broken at the center as shown in Fig. 2, and the aqueous inorganic acid solution is released into the box. And reacts with zinc powder to generate hydrogen gas. Since this hydrogen gas dissipates upward through the ventilation port 41, by detecting this hydrogen gas, overheating will be detected.

When the shape memory alloy plate that bends in a V shape as described above is used, the arrangement position can be various modes such as above, below, and side of the glass ampoule. From the viewpoint that the aqueous acid solution can be released efficiently, it is preferable to dispose the aqueous solution above or to the side.

When a shape memory alloy is used as the container destruction means, it can be integrated with the container by a fixing band such as a wire as described above, but it is stably fixed in terms of mechanical strength and surface smoothness of the container. Can be difficult. In such a case, it is desirable to fix the container and the shape memory alloy using an appropriate jig. An example of such a jig is shown in FIG. 3, an example in which a glass ampoule and a shape memory alloy plate are fixed by this jig is shown in FIG. 4, and an overheat detecting device constituted by using such a jig-fixed glass ampoule is shown in FIG. It is shown in FIG. As shown in FIGS. 3 (a) and 3 (b), the jig used here is the end insertion space of the glass ampoule 5 and the shape memory alloy 6.
It is composed of two kinds of jigs 8 and 9 having different outer dimensions each having an end insertion space. Here, the jig 9 having a large external dimension is used.
Is inserted into the box body and acts not only to fix the glass ampoule 5 and the shape memory alloy plate 6 but also to the box body. On the other hand, the jig 8 having a small outer dimension is the shape memory alloy plate 6
A movable jig that moves in the box according to the bending of the.

When the shape memory alloy 6 is bent due to overheating in the overheat detecting device 1'in which the glass ampoule 5 is housed in the box using such a jig, the jig 8 as shown in FIG. Tilts upward, and the glass ampoule 5 is broken by the stress associated therewith, and hydrogen gas is generated in the same manner as described above.

Further, FIG. 7 (a) shows another overheat detecting device of the present invention, and FIG. 7 (b) is a sectional view taken along the line AA. As shown in the figure, this overheat detecting device has a cylindrical glass ampoule 5 containing an aqueous solution of an inorganic acid having no constriction, which is housed in a box body composed of a box body 2 and a box lid 4 and has a bottom portion made of zinc. Powder 3 is introduced. A rectangular shape memory alloy plate 6 processed to be bent in a V shape is disposed on one side surface of the box body so as to be in contact with the glass ampoule 5, and the other side surface is centered. A ridge 10 made of a metal rod is arranged vertically. In the overheat detecting device 1, the shape memory alloy plate 6 by heating is used as described above.
The bending of the glass ampoule 5 breaks it and the inorganic acid aqueous solution is released to the bottom of the container. However, the presence of the ridges 10 makes the glass ampoule 5 break more smoothly and over the whole area, which makes it possible to detect overheat more. It will be done quickly.

In addition, in the above-mentioned specific example, an example using a stainless steel box is shown, but a synthetic resin box can also be suitably used.
In particular, when combining with the shape memory alloy plate as described above, it is preferable to use a synthetic resin box with good heat conductivity,
It is preferable in that the temperature of the shape memory alloy plate is rapidly raised at the time of overheating, and thus the rapid overheating is detected. As such a synthetic resin material, a material having heat resistance up to 150 to 170 ° C. is suitable from a normal use environment, and for example, polyamide, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polysulfone, etc. are suitable. However, a material obtained by further crosslinking these by irradiation treatment or a glass fiber reinforced material may be used. Boron nitride (BN) and aluminum oxide (Al ₂ O ₃ ) are added to the synthetic resin material.
It is preferable to use a composite resin material mixed with such a filler (usually 20 to 50% by weight) because the thermal conductivity can be further improved and the insulating property of the container can be further improved. The changes in insulation resistance and thermal conductivity due to the mixing of such fillers are shown in the table below. The addition amount of the filler in each table is 45% by weight.

For example, a nylon box reinforced with 30% by weight of glass fiber is applied, and a shape memory alloy plate having a displacement temperature of 105 ° C. is combined to form a device as shown in FIG. 1, which is placed on a hot plate and overheated. If the hot plate is 171 ℃
While the glass ampoule is destroyed when the temperature is shown, when the nylon container containing 15% by weight of glass fiber and 40% by weight of boron nitride is applied, the hot plate becomes 145%.
It has also been confirmed that the glass ampoule is broken when the temperature reaches ℃ and the overheat can be detected more quickly.

(E) Example Example 1 An overheat detection test was conducted using the overheat detector of the present invention.
The overheat detector uses a jig as shown in Fig. 3, and the specific dimensions are l ₁ = 14mm, l ₂ = 17.0mm, m ₁ = 17mm,
m ₂ = 19.0 mm. And, a glass ampoule with a constricted concave portion in the center between these jigs, 38 mm in length and 14 mm in outer diameter (1.2 ml of 6N-H ₂ SO ₄ containing a saturated amount of copper ions was enclosed).
And a shape memory alloy plate having a thickness of 1.5 mm, a width of 10 mm, and a length of 38 mm (memory shape is V-shaped; displacement temperature 105 ° C.), and 1.5 g of zinc powder (manufactured by Wako Pure Chemical Industries) was sprayed on the plate. An apparatus as shown in FIG. 5 (a) was used, which was constructed by mounting it in the upper open box body, and then closing the upper part (using an adhesive) with a lid having a vent having a diameter of about 2 mm.

Such an overheat detection device is placed on a hot plate, and this is introduced near the bottom of a test box (2600 x 2300 x 1200 mm) assuming a switchboard, and a semiconductor hydrogen gas sensor (model number TG-821; Figaro Giken The hot plate was overheated and the output of the hydrogen gas sensor was monitored with the detection unit of (Ltd.) fixed.

About 10 seconds after the temperature of the hot plate was raised to 130 ° C., the glass ampoule was broken by the bending of the shape memory alloy (see FIG. 5B), and the output of the hydrogen gas sensor was significantly increased. The sensor output at this time (performed three times)
As shown in the figure.

As described above, according to the overheat detecting device of the present invention, it is possible to quickly detect overheat based on the generation of hydrogen gas.

Example 2 A shape memory alloy plate (displacement temperature 105 ° C.) similar to that of Example 1 was placed in a glass ampoule (inner diameter 12 mm, length 50 mm) in which 6N—H ₂ SO ₄ 3.3 ml (containing a saturated amount of copper ions) was enclosed. The overheat detecting device of the present invention as shown in FIG. 1 was obtained by fixing with a wire and mounting it in a box containing 5 g of zinc powder.

When this was tested in the same manner as in Example 1, it was confirmed that the glass ampoule was broken and hydrogen gas was detected when the hot plate reached 140 ° C.

Example 3 6N-H ₂ SO ₄ 1.2ml glass ampoule (inner diameter 12 mm, length 32 mm) encapsulating (copper ion content of the saturated amount) and thickness 1.5 mm, width 1
By attaching a shape memory alloy plate (displacement temperature 105 ° C) of 2 mm and length of 32 mm and zinc powder of 1.5 g, Fig. 7 (a)
An overheat detecting device of the present invention as shown in (b) was obtained.

When this was tested in the same manner as in Example 1, it was confirmed that when the hot plate reached 132 ° C., the glass ampoule was broken and hydrogen gas was detected as shown in FIG. 7 (C). .

(F) Effect of the Invention According to the overheat detecting device of the present invention, overheat in an electric device, particularly an electric device such as a switchboard having a built-in high-voltage circuit, can be quickly detected.

Especially, since it is a device that detects overheating using hydrogen gas generated by the reaction of an inorganic acid and a metal as an index, the background is smaller than that of a device that uses carbon dioxide gas as an index (hydrogen is in the air It is highly sensitive because it exists only in trace amounts. Since it is not a gas for directly enclosing an index, it is very useful in that it can be easily manufactured and has high sensitivity, and can be easily made compact and lightweight.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of an overheat detecting device of the present invention, and FIG. 2 is a structural explanatory view showing an overheat detecting state of the overheat detecting device of FIG. 1, and FIG. 3 (a). , (B) is
FIG. 4 is a perspective view illustrating a jig used in an overheat detecting device according to an embodiment of the present invention, and FIG. 4 shows a state in which a glass ampoule and a shape memory alloy plate are sandwiched by the jigs of FIGS. 3 (a) and 3 (b). FIG. 5 (a) is a diagram showing an overheat detecting device of the present invention constructed by using the jigs of FIGS. 3 (a) and 3 (b).
FIG. 5 (B) is a structural explanatory view showing the overheat detection state of the apparatus of FIG. 5 (A), and FIG. 6 is a detection output when hydrogen gas generation from the overheat detection apparatus of the present invention is detected by a sensor. FIG. 7 (a) is a cross-sectional view showing another overheat detecting device of the present invention, and FIG. 7 (b) is A in FIG. 7 (a).
A cross-sectional view taken along the line A and FIG. 7C are views corresponding to FIG. 7A similarly showing the overheat detection state. 1 ... Overheat detection device, 2 ... Box body, 3 ... Zinc powder, 4 ... Box lid, 41 ... Vent, 5 ... Glass ampoule, 6 ... Shape memory alloy plate, 7 ... Fixed Bands, 8, 9 ... jigs, 10 ... ridges.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihisa Tanaka, 47 Umezu Takaunecho, Ukyo-ku, Kyoto City, Kyoto Prefecture Nissin Electric Co., Ltd. Co., Ltd. (56) References Showa Sho 62-4845 (JP, U)

Claims (3)

[Claims] 1. A sealed container in which an aqueous solution of an inorganic acid is stored in a breathable box having a metal powder having an ionization tendency larger than hydrogen introduced at the bottom, and the sealed container self-deforming at a predetermined temperature or higher. It is characterized by applying a stress to and destroying it, and providing a container destruction means capable of releasing the internal inorganic acid aqueous solution onto the metal powder, and generating hydrogen gas by the reaction between the inorganic acid aqueous solution and the metal powder. Overheat detection device. 2. The overheat detecting device according to claim 1, wherein the container breaking means is made of a shape memory alloy. 3. The overheat detecting device according to claim 1, which is used in combination with a hydrogen gas detector.