JPS6065492A - 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 that prevents deterioration of insulation resistance value particularly at high temperatures and extends its life.

In general, in a 7-Z heater, as shown in Fig. 1, a coil-shaped heating wire 2 with terminal rods 1 at both ends is inserted into a metal pipe 3, and this metal vibro is filled with a magnetic material made of Magnenya. 4, and further a metal pipe 30
Both ends are completely sealed with low melting point glass 5 and heat resistant resin 6. The sheathed heater constructed in this way has extremely excellent performance, and it completely prevents a drop in insulation resistance due to moisture absorption, especially in hot and humid places such as Japan's climate, so it can prevent electric shock. It has the advantage of extremely reducing the risk of accidents such as electrical leakage and electrical leakage, and in recent years, production for home appliances and industrial products has been increasing. However, if the seal is completely sealed with glass or the like, the insulation resistance value during use will drop significantly if the temperature exceeds 700°C when using a sheathed heater.

As a result, a phenomenon was observed in which the durability was inferior. In particular, there was a drawback that this tendency became more pronounced as the surface temperature of the metal pipe 3 became higher.

The reason for this is that when the sheathed heater is completely sealed, most of the $1 of oxygen in the sheathed heater is consumed at the same time as the inner surface of the metal pipe 3 is oxidized, resulting in an oxygen-free state.

When heated to high temperatures under these conditions, changes occur in Magnenya's insulating powder. In particular, a small amount of iron oxide contained as an impurity reacts with metallic chromium among the constituent elements of the heating wire 2 and the metal pipe 3 to form a composite oxide in the magnesium oxide. Also.

Metallic chromium has a greater 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 these chromium-containing complex oxides and magnetite-based iron oxides can significantly reduce electrical insulation properties.

The present invention has been made in order to eliminate the above-mentioned drawbacks. 0.5 to 5% of a fine powder of a composite oxide sintered body sintered in an ambient atmosphere is added and mixed with electrical insulating powder, and the filling part is filled. The present invention provides a sheathed heater that can prevent deterioration of insulation resistance at high temperatures and extend its life.

An embodiment of the present invention will be described below. The oxide is nickel.
q oxide 90%wt, iron oxide 5%wt, silicon oxide 5e1
A composite oxide sintered body is synthesized at a ratio of 1,700° C. and heated and sintered in an oxidizing atmosphere at 1700° C., and the composite oxide sintered body is further ground into fine powder. It has been experimentally confirmed that the particles in this case are thick. This fine powder was added in an amount of 0.1 to 5% wt to Magnenya powder, which is a conventional electric insulating powder filling member 4, and was mixed well and adhered to the surface of the Magnenya particles, thereby forming a filling member 4. Next, after inserting the coiled heating wire 2 into the metal pipe 3 by connecting the terminal rod 1 to both ends, the filling member 4 made of electrical insulating powder and composite oxide sintered body is filled.
After performing the steps of rolling diameter reduction and annealing, both ends of the metal pipe filter are completely sealed with low melting point glass 5 and anti-alloy resin 6 to form a sheathed heater.

The operation of this embodiment based on the above-mentioned configuration will be explained below. By adding fine powder of composite oxide sintered body,
Before metallic chromium reacts with iron oxide, which is an impurity in magne/yellow, it reacts with the composite oxide sintered body, and even more complex composite [
An oxidized proboscis is produced.

Also, 1 oxygen in the composite oxide sintered body was slightly dissociated.

/- The oxygen inside the heater has the effect of increasing the seismic intensity,
1. Forms a dense oxide on the surface. Since this fine oxide has excellent thermal stability, it exhibits a protective effect against electric heat m2. As a result, the oxidation reaction inside the sheathed heater does not proceed any further, and a decrease in insulation resistance during heating and a decrease in disconnection life are prevented. Regarding this heater, the surface temperature of the metal pipe 3 is set to 900''C, and it is turned on for 60 minutes.
Intermittent current heating when OFF.

After conducting a cooling cycle test, the insulation resistance when heated at 800° CVc was measured. The results are shown in FIG.

The figure shows the data when approximately 1%wt of composite oxide sintered body is added, but the conventional filling member 4 made of Magnenya has 0.5 to 0.6 in the 100 cycle test as shown by the dotted line.
The resistance decreases to MΩ, and thereafter decreases to 0.3 to 0.4 MΩ, leading to disconnection in about 1,000 cycles. On the other hand, the sheathed heater made of the filling member 4 containing 1% wt of composite oxide sintered fine powder maintains the initial 2MΩ up to 750 cycles, as shown by the solid line, and a slight decrease is observed at +, 000 cycles. The wire does not break and maintains relatively high insulation resistance at high temperatures.

As described above, according to the present invention, the electrically insulating powder, which is one of the main components of the constituent materials of the sheathed heater, is filled with a complex oxide sintered body that does not lower the insulation resistance value even if it reacts with metal chromium. By.

This has the effect of preventing a drop in insulation resistance during heat and extending life.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional sheathed heater, and FIG. 2 is a characteristic diagram of insulation resistance during heat due to intermittent energization of a sheathed heater according to an embodiment of the present invention. 4-...Filling material applicant Hitachi Thermal Appliances Co., Ltd.

Claims (1)

[Claims] A sheathed heater having a filling member made of electrically insulating powder between a metal pipe and four hot wires. Nickel oxide 90-98 t Cod, iron oxide 0.5-5 t wt
, mixed powder at a ratio of 0.5 to 5% wt silicon oxide,
A filling member (4) is obtained by adding and mixing 0.1 to 5% wt of a composite oxide sintered body sintered in an oxidizing atmosphere into fine powder to the electrical insulating powder. Sheathed heater.