JPH10239376A - Leak detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the surface temperature of a heater from undergoing dispersion and the heater from overheating with a simple construction and low cost by connecting a heat sensitive wire melted at above a fixed temperature for shorting a pair of conductors to an outside test terminal. SOLUTION: A heat sensitive wire 16 is fixedly wound around a heat generating part of a heat 12 immersed in a water tank 14 and the other end of the heat sensitive wire 16 has the inside conductor 22 and outside conductor 24 connected to the outside test terminal 19 of a leak detector body 1. For example, if the water tank 14 is turned down or broken by an earthquake or the like to expose the heater 12 to air, the temperature control by a controller 10 is disabled to overheat the heater 12 by continuous electrification. When the surface temperature of the heater 12 rises over about 180 deg.C, a macromolecular heat sensitive body inside the heat sensitive wire abruptly melts and the conductor 22 makes a contact with the conductor 24, so that the terminal 9 short- circuits. Thus, current flows to a zero phase current transformer 2 and a control circuit 3 electrifies an exciting coil 4 to open contacts 5 and interrupt an electric path to a controller body 10 for stopping the electrification of the heater 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric leakage detector, and more particularly, to an electric leakage detector having a function of preventing heating such as a heater.

[0002]

2. Description of the Related Art Generally, in an aquarium fish tank, a heater and a water temperature sensor are installed in the water tank, and these are connected to a controller installed outside the water tank so that the water temperature detected by the water temperature sensor becomes a set temperature. Turn on the power to the heater
/ OFF control. Here, since the heater is installed underwater, an electric shock accident due to electric leakage is likely to occur, and it is preferable that the controller is connected to a power supply via an electric leakage detector. In the above configuration, for example, when the water tank is overturned or damaged due to a disaster such as an earthquake and the heater is exposed to the air, the temperature control by the controller becomes impossible, so the heater is heated by continuous energization, and the surrounding combustibles are ignited. Secondary disaster such as fire may occur. For this reason,
In the conventional leak detector, an external test terminal is provided in parallel with the test switch of the leak detector, an external contact such as a thermostat is connected to the external test terminal, and the external contact is closed by heating the heater. Is configured to cut off the electric circuit.

FIG. 8 is a block diagram of a water temperature controller for an ornamental fish tank using the above-mentioned conventional leak detector, wherein 1 is a leak detector main body, 2 is a zero-phase current transformer, 3 is a control circuit, and 4 is a control circuit. Excitation coil, 5 is a contact for opening and closing an electric circuit to a load, 6 is a test switch for performing an operation test of a leakage detection function, 9 is an external test terminal connected in parallel with the test switch 6, 10
Is a temperature controller main body, 11 is a temperature control circuit, 12 is a heater, 13 is a water temperature sensor, 14 is a water tank, and 15 is a thermostat. The thermostat 15 connected in parallel with the test switch 6 is arranged in close contact with the heater 12. FIG. 9 shows an example of a temperature rise characteristic when the heater is energized in the air.
It has reached 50 ° C. On the other hand, when the heater is in water, the surface temperature is about 6 since the heater surface is cooled by water.
Keep below 0 ° C. Here, if the operating temperature of the thermostat 15 is set to, for example, about 100 ° C., the thermostat 15 does not operate when the heater 12 is underwater, and the contact of the thermostat 15 takes ten and several seconds when the heater 12 goes out into the air. Is closed and the test switch 6
By the operation equivalent to pressing, the control circuit 3 energizes the exciting coil 4, opens the contact 5 to cut off the electric path to the load, and stops energizing the heater 12 before a fire occurs.

[0004]

The conventional earth leakage detector is configured as described above. Since a mechanical contact such as a thermostat is used to detect the heating of the heater, the structure is complicated and the reliability is low. Cost increases.

Further, when a thermostat is attached to a heater, heating is detected at a limited temperature on the heater surface. However, in general, the temperature distribution on the heater surface is non-uniform, and if the temperature distribution is low, the heater surface may be located at a low temperature. When the thermostat is attached, there is a problem that the heating protection function does not operate effectively.

The present invention solves the above-mentioned problems, and has a heating protection function for a heater or the like which has a simple structure, is highly reliable, is inexpensive, and is not affected by variations in the surface temperature of the heater. The purpose is to obtain a leak detector.

[0007]

According to the present invention, in order to achieve the above-mentioned object, a leakage detecting section comprising a zero-phase current transformer for detecting a leakage current and a control circuit, and an electric circuit is cut off by a signal from the leakage detecting section. Opening / closing mechanism section, a power receiving terminal for obtaining commercial power, and a power supply terminal for supplying the power to an external device, and one of the electric circuits of the commercial power is branched and connected via the zero-phase current transformer. In a leakage detector provided with external test terminals to which the extracted electric circuit and the other electric circuit are connected, a heat-sensitive layer that rapidly melts at a certain temperature or higher is interposed between a pair of conductive wires, and at a certain temperature or higher, The external test terminal may be a heat-sensitive wire configured such that the heat-sensitive layer is melted and the pair of conductive wires is short-circuited, or a heat-sensitive wire configured by interposing a heat-sensitive layer whose impedance changes according to temperature between the pair of conductive wires. Connected to .

Further, at least a part of the heat-sensitive wire is formed into a coil shape.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment 1 in which an electric leakage detector according to the present invention is used for a water temperature controller for an ornamental fish tank, and FIG. Show. In FIG. 1, 1 is a leakage detector main body, 2 is a zero-phase current transformer, 3 is a control circuit, 4 is an exciting coil, 5 is a contact for opening and closing an electric circuit to a load, and 6 is an operation test of a leakage detection function. 9 is an external test terminal connected in parallel with the test switch 6, 10 is a temperature controller body, 11 is a temperature control circuit, 12 is a heater, 13 is a water temperature sensor, 14 is a water tank, 15 is a thermostat, 16 Is a heat ray. The heat-sensitive wire 16 has a structure as shown in FIG. 3, and an inner conductor 22, a polymer heat-sensitive body 23, an outer conductor 24, and a waterproof insulator 25 are sequentially provided on the outer periphery of a core 21. One end of the heat-sensitive wire 16 on the side that comes into contact with the heater 12 is subjected to a waterproof treatment so that water does not enter the inside. In the above configuration, the polymer thermosensitive body 23 is made of a nylon-based material and has a characteristic of rapidly melting at about 180 ° C., whereby the heat sensitive wire 16 short-circuits the inner conductor 22 and the outer conductor 24 at about 180 ° C. or more. Have the following characteristics. FIG. 4 is a diagram showing the tip shape of the heat-sensitive wire 16 alone, and the inner diameter D of the flexible coil-shaped portion is formed so as to be smaller than the diameter of the heater 12 having a cylindrical shape. The heat-sensitive wire 16 is fixed to the heater 12 with an appropriate pressing force by winding it around the heat-generating portion of the heater 12. At the other end of the heat-sensitive wire 16, the inner conductor 22 and the outer conductor 24 are connected to the external test terminal 9.

The operation of the leakage detector configured as described above will be described. For example, when the water tank is overturned or damaged due to a disaster such as an earthquake and the heater 12 is exposed to the air,
Since temperature control by the controller 10 becomes impossible, the heater 12 is heated by continuous energization. When the surface temperature of the heater 12 rises to about 180 ° C. or higher, the polymer thermosensitive body 23 inside the thermosensitive wire 16 wound around the outer periphery of the heater 12 is rapidly melted, and the inner conductor 22 and the outer conductor 24 come into contact with each other. Before the test terminals 9 are short-circuited, a current flows through the zero-phase current transformer 2, the control circuit 3 energizes the exciting coil 4, opens the contacts 5, cuts off the electric path to the controller main body 10, and before a fire occurs. The power supply to the heater 12 can be stopped.

Further, in the configuration of the first embodiment, a PVC-based material is used for the polymer
For example, even if the characteristic that the impedance between the inner conductor 22 and the outer conductor 24 is several hundred kΩ at 60 ° C. and several kΩ at 150 ° C. is given, as the surface temperature of the heater 12 increases, the inner conductor When the impedance between the outer conductor 22 and the outer conductor 24 decreases, a current flows through the zero-phase current transformer 2, the control circuit 3 energizes the exciting coil 4, opens the contact 5 and cuts off the electric path to the controller 10, The power supply to the heater 12 can be stopped before a fire occurs.

In the first embodiment, as shown in FIG. 2, the power supply terminal 8 and the external test terminal 9 are provided on the main body 1 of the electric leakage detector, but as in the second embodiment shown in FIG. You can attach a connection terminal to the terminal,
As in Embodiment 3 shown in FIG. 6, the leakage detector main body 1 and the temperature controller main body 10 may be connected by a three-core wire, and the temperature controller main body 10 may be provided with an external test terminal 9. Furthermore, it is preferable to integrate the leakage detector main body 1 and the temperature controller main body 10 because components such as a circuit board and a housing can be shared, and the cost can be reduced.

In the first embodiment, the heat-sensitive wire 16 is wound around the heater 12 as shown in FIG. 1. However, as in the fourth embodiment shown in FIG. Thus, the same effect can be obtained even when the heater 12 is attached in close contact with the binding band 17 or the like. Furthermore, if the tip of the heat-sensitive wire 16 is turned back and pulled out into the air,
This eliminates the need for waterproofing at the tip, further reducing the cost.
By manually lowering or short-circuiting the impedance between the inner conductor 22 and the outer conductor 24, it is possible to test whether the shut-off operation of the leakage detector functions normally.

In the above embodiment, the case where the present invention is applied to an aquarium fish tank temperature controller has been described. However, it goes without saying that the present invention can be used for other liquid temperature controllers and objects other than liquid.

[0015]

According to the present invention having the above-described structure, the heating detecting means is configured such that the pair of conductors is short-circuited at a certain temperature or higher, or the impedance between the pair of conductors changes according to the temperature. Using a hot wire and having no mechanical contacts simplifies the structure, improves reliability,
The effect that the manufacturing cost can be reduced can be obtained.

Further, by forming a part of the heat-sensitive wire in a coil shape in advance, it is easy to mount the heat-sensitive wire on the heater, and the heat-sensitive wire covers a wide area of the heater surface. The effect of being hardly affected by the variation can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an external view of a leakage detector according to Embodiment 1 of the present invention.

FIG. 3 is a structural diagram of a heat-sensitive wire according to Embodiment 1 of the present invention.

FIG. 4 is a front end view of a heat-sensitive wire according to Embodiment 1 of the present invention.

FIG. 5 is an external view of a leakage detector according to Embodiment 2 of the present invention.

FIG. 6 is a block diagram showing a third embodiment of the present invention.

FIG. 7 is a block diagram showing a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional leakage detector.

FIG. 9 is a graph showing a temperature rise characteristic of a heater in the air.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric leakage detector main body 2 Zero-phase current transformer 3 Control circuit 4 Excitation coil 5 Contact 6 Test switch 7 Power receiving terminal 8 Power supply terminal 9 External test terminal 10 Temperature controller main body 11 Temperature control circuit 12 Heater 13 Water temperature sensor 14 Water tank 15 Thermostat 16 Heat sensitive wire 17 Cable tie 18 External test switch 21 Core 22 Inner conductor 23 Polymer thermosensitive material 24 Outer conductor 25 Insulator

Claims (3)

[Claims] 1. A leakage detector comprising a zero-phase current transformer and a control circuit for detecting a leakage current, an opening / closing mechanism for interrupting an electric circuit by a signal from the leakage detector, and a power receiving terminal for obtaining commercial power. A power supply terminal for supplying the power to an external device, one of the electric circuits of the commercial power supply is branched, and the electric circuit taken out through the zero-phase current transformer and the other electric circuit are connected to each other. In a leakage detector provided with a test terminal, a heat-sensitive layer that melts at a certain temperature or higher is interposed between a pair of conductors, and the heat-sensitive layer melts at a certain temperature or higher and the pair of wires is configured to be short-circuited. An earth leakage detector, wherein a heat sensing wire is connected to the external test terminal. 2. The electric leakage detector according to claim 1, wherein the heat-sensitive wire is constituted by interposing a heat-sensitive layer whose impedance changes according to temperature between a pair of conductive wires. 3. The electric leakage detector according to claim 1, wherein at least a part of the heat-sensitive wire is formed in a coil shape.