JPS6164093A - Sheathed heater - 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 Field of the Invention The present invention relates to a nose heater whose heater wire is protected by a metal pipe.

This sheathed heater is more suitable for contact heating with metals and heating of liquids than bare heaters, so it is widely used in home appliances and industrial products. In particular, when heating liquids, it has high thermal efficiency and excellent electrical insulation properties, so it is used as a heater for water heaters and oil baths.

Conventional technology 7-Z heaters have 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. One way to prevent abnormal heating is to place a substance with a lower melting point than the heater wire 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.

Problem to be Solved by the Invention 7- In a heater, in order to prolong the life of the heater wire, a metal pipe is filled with electrically insulating powder, and then the surrounding area is pressurized to reduce f4 in order to further increase the filling rate. At this time, low melting point gold 1. placed in series with the heater wire.・The electricity is completely fixed by the color border decoration. If the heater experiences abnormal heating and the temperature rises above the melting point of the low melting point metal,
The low-melting point metal melts and becomes liquid, but because it is held in place by electrically insulating powder, it maintains its shape and does not melt. In other words, when a temperature heater, which is widely used in home appliances, melts, it flows out due to its own weight and can cut off the current, but when a low junction metal is placed inside the 7-Z heater as described above, is fixed and held by insulating material q, so even if the metal melts, it may not be possible to interrupt the current.

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 in place of the conventionally used iron chrome or nichrome wire heaters in order to prevent abnormal heating of sheathed heaters. It is used as a.

The fact that the specific resistance increases as the operating temperature increases means that when the voltage is constant, the power decreases as the temperature of the sheathed heater increases, which reduces the surface power density of a sheathed heater with a fixed shape. If you set it as a 7-Z heater with a power density within a certain range, even if an abnormality occurs and the heater temperature suddenly rises, it will be saturated at a certain temperature, and even if an abnormality occurs, the heater surface will burn out at 411 degrees. It can be designed within the temperature range.

Embodiment An embodiment of the present invention will be described with reference to the drawings. A terminal rod 2 and a heater wire tube are inserted into a metal pipe 1 made of stainless steel or copper in a state in which they are joined, and the surrounding area is filled with electrical insulating powder 4. do. In addition, it is moisture-proof.
, and is sealed using a sealing material 5 such as glass. A sheathed heater is manufactured with such a configuration, and here the heater wire 6 is made of nickel, nickel, etc. as a resistor whose specific resistance changes greatly with temperature.
iron.

An iron-cobalt-nickel alloy, aluminum or nickel-iron alloy wire is used. For all of these metals, the rate of increase in resistivity increases with temperature.

In the above configuration, the heater wire 5 is made of Ni 70%-Fe.
When using 30% as a heater for heating liquids, especially when used underwater, the heat conduction from the surface of the heater is good, so the boundary between the metal pipe surface and the water is 1.
00° C., and the resistance value of the heater wire 6 shows a constant value.

If the power value required at this time is set under these conditions, the water evaporates and the water level drops, exposing the heater section and creating a vacant state, when the heater surface rises rapidly. However, as the resistance value increases as the temperature rises, the power consumption suddenly decreases. This is an actual value that is reduced to 172 to 1/6 of the value when loaded underwater.

Therefore, if the surface power density of the 7-Z heater used underwater is set to 10 W/crl or less when loaded underwater, the surface power density can be kept below 600'C at 5 w/cA or less even when the heater is idle. This makes it possible to prevent burnout and disconnection due to abnormal heating, making it an extremely convenient sheathed heater for liquid heating compared to conventional iron-chrome or nichrome heater wires.

Furthermore, when used in conjunction with a commonly used abnormal heating prevention circuit, it becomes possible to significantly lower the Lanonyu temperature immediately after the sensor detects an abnormal temperature and the power is turned off.

The same holds true even when other resistors shown in the embodiments described in L are used.

Effects of the Invention] 2. According to Komei, burnout and disconnection due to abnormal heating can be reliably prevented by using a low antibody whose electrical resistance increases as the temperature rises as the heater wire of the sheathed heater. This has the advantage that it can be used as a very convenient liquid heating heater wire compared to conventional iron chrome or nichrome heater wires.

[Brief explanation of the drawing]

Line 11 is a longitudinal sectional view of the present invention. In the figure, 1 gold 10,000 pipe, 6 is heater wire. 4 is an electrically insulating powder.

Claims (1)

[Claims] 1.) In a sheathed heater in which a heater wire (3) is inserted into a metal pipe (1) and further filled with electrical insulating powder (4), the temperature rise in the heater wire (3) A sheathed heater characterized in that it uses a resistor whose electrical resistance increases. 2.) The resistor whose electrical resistance increases as the temperature rises is selected from a nickel-iron alloy, an iron-cobalt-nickel alloy, nickel, and iron, as described in claim 1). Sheathed heater.