JPS63200485A - Sheathed heater with heat sensitive sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention directly heats liquids in water heaters, oil paths, etc.
This invention relates to a sheathed heater with a heat-sensitive sensor for controlling the temperature of a liquid and at the same time preventing abnormal heating due to inadvertent heating.

Conventional technology A sheathed heater has a structure in which a heater wire is inserted into a metal pipe, the heater wire is buried and filled with heat-resistant electrical insulating powder to hold it, and an outlet terminal is attached to the end of the metal pipe to connect to the heater wire. As a method to prevent abnormal heating, there is a method in which a material with a lower melting point than the heater wire is placed in a part of the sheathed heater. (For example, JP-A-59-56386
According to this, a metal with a low melting point is placed in series with the heater wire, and when abnormal heating occurs, the metal is melted to cut off the current.

Problems to be Solved by the Invention In a sheathed heater, in order to prolong the life of the heater wire, the metal pipe is filled with electrically insulating powder, and then the diameter is reduced by pressurizing the surrounding area in order to further increase the filling rate. At this time, the low melting point metal placed in series with the heater wire is completely fixed by the electrically insulating powder. If the heater causes abnormal heating and the temperature rises above the melting point of the low melting point metal, the low melting point metal will melt and become liquid, but because it is held by the electrically insulating powder, it will maintain its shape and melt. Never.

Tsu-! If a temperature fuse, which is widely used in home appliances, melts, it will flow out due to its own weight and cut off the current, but if a low melting point metal is placed inside the sheathed heater as described above, the insulation Because the metal is fixed and held in place, it may not be possible to interrupt the current even if the metal melts.

As a result, there is a drawback that abnormal heating cannot be prevented.

Means for Solving the Problems The present invention uses a resistor whose specific resistance increases as the temperature rises as a heater wire instead of the conventionally used iron chrome or nichrome wire heaters in order to prevent abnormal heating of sheathed heaters. A protective tube with a heat-sensitive sensor inserted into a part of the outer tube is connected.

Once the temperature reaches 90 degrees, a heat-sensitive sensor inside the sensor protection tube connected to a part of the exterior tube detects the sudden rise in temperature, activates a safety circuit, and cuts off the power supply. Thereafter, overheating occurs and a peak temperature occurs, but since the heater wire is made of a material whose specific resistance increases as the temperature rises, it is possible to keep the peak temperature low.

Embodiment An embodiment of the present invention will be described with reference to the drawings. A terminal rod 2 and a heater wire 6 are placed inside an exterior tube 1 made of metal such as stainless steel or copper.
Insert it in a joined state, and apply electrical insulating powder 4 around it.
Fill it with. Furthermore, it is sealed using a sealing material such as silicone, epoxy, or glass to prevent moisture. A sheathed heater is manufactured with such a configuration, and the heater wire 3 is made of nickel or iron as a resistor whose specific resistance changes greatly with temperature.

An iron-cobalt-nickel alloy or nickel-iron alloy wire is used. For all of these metals, the rate of increase in specific resistance is large as the temperature rises. The sensor protection tube 5f is joined to any part of the outer circumference of the exterior tube 1. A brazing material 7 such as nickel, silver, or phosphorous copper is used for the bonding. A thermal sensor 6 such as a thermistor is inserted into the joined sensor protection tube 5 and fixed.

In the above configuration, the heater wire 3 contains 70% Ni to Fe.
When used as a heater for heating liquids, especially when used underwater, heat conduction from the surface of the sheathed heater is good, so at the boundary between the metal pipe surface and water, 10%
The temperature becomes 0° C., and the resistance value of the heater wire 3 shows a constant value. The power value required at this time is set under these conditions. Furthermore, the temperature of the water is captured by a heat-sensitive sensor 6t'' and a signal is sent to the controller to control the water temperature.The water evaporates and the water level drops.

When the heater part is exposed and the temperature reaches 90 degrees, the surface of the heater rises rapidly, but the heat-sensitive sensor 6 detects an abnormal temperature, and the controller is activated to cut off the power.

In addition, even if the temperature is heated to 90 degrees without accidentally adding water, the temperature controller will operate to prevent abnormal heating. It became 9 years old.

It appears as a peak temperature. Here, the resistance value of the heater wire 3 increases as the temperature rises rapidly (resulting in a sudden decrease in power consumption. Since n decreases to about 1 when loaded underwater, the peak temperature due to overheating can be suppressed to a low level. This is an extremely convenient submersible heater for water heating compared to conventional iron chrome or nichrome heater wires.

Effect of light As described above, according to the present invention, a resistor whose electrical resistance increases as the temperature rises is used as the heater wire of the sheathed heater,
By joining a sensor protection tube to any part of the outer periphery of the exterior tube and inserting and fixing a heat-sensitive sensor therein, it is possible to control the water temperature to a predetermined level. Can keep temperature low. Compared to conventional heater wires using iron chrome or nichrome heater wires, this method has advantages such as being able to provide a sensor-equipped sheathed heater for heating liquids, which is extremely convenient.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of the present invention. 1... Exterior tube, 2... Terminal bar. 3... Heater wire, 4... Electrical insulation powder. 5...Sensor protection tube, 6...Heat-sensitive sensor.

Claims (1)

[Claims] In a sheathed heater in which a heater wire (3) is inserted into a metal sheathed tube (1) and further filled with electrical insulating powder (4), the heater wire (3) is equipped with a resistor whose electrical resistance increases as the temperature rises. A sensor protection tube (5) is joined to an arbitrary part of the outer circumference of the outer tube (1) using a material selected from nickel, an alloy of nickel and iron, or an alloy of iron and iron, cobalt and nickel as A sheathed heater with a heat-sensitive sensor, characterized in that a heat-sensitive sensor (6) is inserted and fixed in (5).