JPS59217985A - 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 The present invention relates to a sheathed heater, and particularly to a sheathed heater using a filler that prevents deterioration of insulation resistance value at high temperatures and extends its life.

Conventional 7-Z heaters have terminal rods 1 at both ends as shown in Figure 1.
A coiled heating wire 2 with 6 and is completely sealed. The D/-Z heater constructed in this way has excellent performance at operating temperatures below 700°C, and especially in hot and humid places like the climate of Japan, there is no reduction in insulation resistance due to moisture absorption, etc. Since it completely prevents electrical shock, it has the advantage of extremely reducing the risk of accidents such as electric shock and leakage, and in recent years, production efforts for home appliances and industrial products have been increasing.

However, when the seal is completely sealed with glass, etc., if the temperature exceeds 700°C when using a sheathed heater, the insulation resistance value during use will drop significantly, resulting in poor durability. Ta. In particular, there has been a drawback that the higher the surface temperature of the metal pipe 3, the more pronounced this direction becomes.

The reason for this is that when the sheathed heater is completely sealed, the inner surface of the metal pipe 3 oxidizes and almost all of the oxygen inside the metal pipe 3 is consumed and becomes oxygen-free. The change is wrapped in Magnenya 4, which is a filler that is an insulating powder.

In particular, a small amount of ejected iron contained as an impurity reacts with metallic chromium in the component elements of the heating wire 2 and the metal pipe 3 to form a composite/l oxide in the magnenoir oxide. In addition, metal chromium has a higher bonding energy with oxygen than iron, and in oxygen-free and high temperature conditions, iron oxide is reduced and changes to magnetite-based iron oxide. Even a small amount of the composite oxide or magnetite iron oxide significantly reduces the insulation properties.

The purpose of the present invention is to obtain a sheathed heater whose insulation resistance value does not decrease even at high temperatures, and as a filler for the sheathed heater, nickel oxide is mixed with magnesia powder at a stacking ratio of 01 to 5%, melted, and then pulverized.

It does not react with metal chromium and prevents the insulation resistance value from decreasing.

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

The oxide added is nickel oxide. Add 0.1 to 5 g of this nickel oxide to the magnesia powder.

It is melted at 2800°C to produce a spinel-based MgO-NiO composite oxide. After crushing this into a fine powder.

Use as a filler for electrical insulating powder.

By adding this nickel oxide to form a composite oxide with magnesia, the effect is to prevent iron oxide, which is an impurity contained in magnesia, from changing easily. This is because the metal chromium in the constituent material of the sheathed heater becomes MgO-NiO at high temperatures and in an oxygen-free atmosphere.
reacts with other complex oxides to produce even more complex oxides. Therefore, it is possible to prevent the formation of magnetite-based oxides by reacting with iron oxide in magnesia.

Hereinafter, they will be explained in more detail. Approximately 1 Ti nickel oxide is added to magnesia oxide powder having a purity of 98 Ti or higher, and the mixture is melted at approximately 2.800°C. Then crush it to 50~
The magnesia powder made in this way is used as the filler 4 for insulating magnetism.

Next, after inserting the coiled heating wire 2 into the metal pipe 3 with the terminal rod 1 connected to both ends, the filling material 4 is filled.
After the steps of rolling, diameter reduction and annealing are performed, both ends of the metal vibro are completely sealed with low melting point glass 5 and heat resistant resin 6 to form a sheathed heater.

The effect of this sheathed heater is to set the surface temperature of the metal pipe to 900°C and turn it on for 30 minutes.
.

After conducting intermittent heating and cooling cycle tests.

The insulation resistance value was measured at high temperature at 800°O.

As shown in FIG. 2, the conventional sheathed heater 7 (the figure shows data for the case where about 1 tre of nickel oxide is added).

After 100 cycles of testing, it decreased to 0.5-0.6 MΩ, and after that it decreased to 0.3-0.4 MΩ, and about 1.0
Disconnection occurs at 00 cycles. On the other hand, the /-Z heater 8 using the filler of the present invention maintained the initial 2MΩ up to 750 cycles, and although there was a slight decrease in the i,ooo cycles, there was no disconnection, and the insulation resistance value at high temperatures was maintained. can be kept.

As described above, according to the present invention, the insulation resistance value does not decrease even at high temperatures,
In addition, the intermittent life is extended, and since the corrugated nickel is applied directly to the magnesia powder as a filler, the process is simple.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional 7-Z heater and an embodiment of the present invention, and Fig. 2 is a change in insulation resistance at high temperatures due to intermittent energization of a sheathed heater according to an embodiment of the present invention (C). 2.・Heating wire. 3. Metal pipe. 4. Magnesia powder. 7./-Z heater filled with conventional filler. 8. Filled with filler mixed with composite oxide powder. Shida)-Zuhita. Applicant: Hitachi Nekki Shimei Ni Co., Ltd.

Claims (1)

[Claims] A sheathed heater made by inserting a heating wire into a metal pipe and filling it with a filler is characterized by adding nickel oxide to magnesia powder at a weight ratio of 0.1 to 5 g, mixing it, melting it, and then crushing it to make the filler. A sheathed heater.