JPS63133482A - Electric heating unit - 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 Industrial Application The present invention relates to an electric heating unit used mainly for cooking in ordinary households.

Conventional technology Traditionally, electric heating units for cooking used in general households include electric stoves with heating wires wound spirally on ceramics, and units made by winding sheathed heaters in a spiral shape. There is also an electric range.

In addition to these, in Europe and the United States, there is an electric heating system called smooth top, in which a spirally wound heating wire is placed in a groove in the insulation material, and a ceramic glass plate is placed on top of the heating wire, and the ceramic glass plate is used as the heating surface. units are widely used.

In Japan, electric stoves made of ceramic are still in strong demand because they are inexpensive and have superior thermal efficiency compared to electric heating units such as smooth tops.

However, electric stoves that use traditional ceramics are dangerous because the heating wires are directly exposed to the outside, and the contents of the cooking material may boil over, significantly shortening the lifespan of the heating wires. It had drawbacks.

Furthermore, since ceramics have a large heat capacity, they are heavy and difficult to cool down, so they cannot be moved or stored immediately after use, and have disadvantages in terms of usability.

For this reason, the present inventors have already developed a top plate made of a metal plate,
A heat insulating base consisting of a spirally wound heating wire, a groove in which the heating wire is arranged in a meandering manner, and a heat insulating material mainly composed of silica or alumina fiber, and a metal housing the heat insulating base. The present invention proposes an electric heating unit having a storage case made of a plate, a radiation layer formed on the side of the object to be heated of the top plate, and an insulating layer formed on the side of the heating wire.

Problems to be Solved by the Invention However, in conventional electric heating units that use a heat insulating material mainly composed of silica or alumina fiber as a heat insulating base, the strength of the heat insulating base rapidly decreases when used at high temperatures for a long time. However, there were problems in actual use. This phenomenon can be seen where the insulation material and the heating wire come into contact, for example, after using the heating unit for a long time.
If the product is dropped, the insulation material may fall off at the above locations, creating a very dangerous situation.

The present invention solves these problems and aims to provide an electric heating unit that has excellent strength even when used at high temperatures for long periods of time.

Means for Solving the Problems In order to solve the above problems, the present invention includes a top plate made of a metal plate, a spirally wound heating wire, and a groove in which the heating wire is arranged in a meandering manner. It is composed of a heat insulating base made of a heat insulating material containing silica and alumina fibers as main components and clay and silica sol as binders, and a storage case made of a metal plate that houses this heat insulating base.

Function: The heat insulating material mainly composed of silica or alumina fibers used in conventional electric heating units is manufactured by using silica sol as the main binding material and vacuum forming the silica sol.

This is because silica sol is inexpensive, and
This is because it has excellent moldability during vacuum forming.

However, when insulation materials that use silica sol as a binder are used at high temperatures for long periods of time, the amorphous silica changes to crystallization, and the bonding force that binds the silica and alumina fibers due to hydrogen bonds is lost. As a result, a remarkable decrease in strength can be seen.

However, in the present invention, since silica sol and clay are used as binding materials, the moldability during conventional vacuum forming can be ensured with the conventional silica sol, and the decrease in strength at high temperatures can be ensured by the clay. can.

When used at high temperatures, clay, silica, and alumina fibers react, resulting in mullite (3M 1205/2Si).
It is thought that because the crystal phase of O2) is precipitated and chemically bonded, the decrease in strength is suppressed.

For this reason, by using silica sol and clay as binding materials for conventional insulation materials mainly composed of silica and alumina fibers, it is possible to obtain insulation materials with excellent strength even when used at high temperatures for long periods of time. By using this heat insulating material as a heat insulating base, an electric heating unit with excellent strength can be obtained.

Embodiments Hereinafter, specific embodiments of the present invention will be described based on the drawings. In the figure, reference numeral 1 denotes a top plate made of 5 pcc, and both sides of the top plate 1 are coated with a heat-resistant paint that is excellent in absorbing and radiating heat. Reference numeral 2 denotes a heat insulating base made of a heat insulating material containing silica and alumina fibers as main components and clay and silica sol as binders, and this heat insulating base 2 is provided with meandering grooves 21L. 3 is a spirally wound heating wire, and this heating wire 3 is disposed in a groove 2a provided in the heat insulating base 2. Reference numeral 4 denotes a storage case made of a stainless steel plate that stores the heat insulating base 2 on which the heating wire 3 is arranged. I'm letting you do it. In addition, the top plate 1
and the heat insulating base 2 are integrated with each other with a slight gap.

6 is an insulator, and 6 is an electrical outlet terminal, which are provided on the lower side of the storage case 4.

The electric heating unit of the present invention having such a configuration and the conventional electric heating unit using a heat insulating material containing conventional silica or alumina fiber as the main component and silica sol as a binder as the heat insulating base 2 are heated to high temperatures. We conducted a comparative evaluation of the strength when used for a long time.

In this comparative evaluation, after adjusting the voltage so that the surface temperature of the heating wire 3 was 1000°C and 1100°C, intermittent energization was performed with 30 minutes of energization and 10 minutes of rest as one cycle, and 100 cycles, 1000 cycles, and 500
After 0 cycles had passed, the test was performed by dropping the heat insulating base 2 from a height of 1 m and checking the damage state of the heat insulating base 2.

The results are shown in the table below. In this table, the O mark indicates that there is no damage at all, the Δ mark indicates that there is some damage but there is no problem in actual use, and the X mark indicates that the damage is severe and there is no problem in actual use. Each indicates that it cannot withstand use.

(Left below) As is clear from the table, in an electric heating unit using a conventional heat insulating material using silica sol as a binding material, t100
After 500 cycles at 0'C, the strength began to decrease, and at 1100C, the strength decreased significantly, causing problems in actual use. On the other hand, an electric heating unit using a heat insulating material containing silica sol and clay as a binder showed excellent strength with no decrease in strength even after 5000 cycles at 1000°C.

Effects of the Invention As is clear from the above description, the present invention has a top plate made of a metal plate, a spirally wound heating wire, and a groove in which the heating wire is arranged in a meandering manner. It is composed of a heat insulating base made of a heat insulating material mainly composed of silica and alumina fibers and binders of clay and silica sol, and a storage case made of a metal plate that houses this heat insulating base, so it can withstand high temperatures for long periods of time. It is possible to provide an electric heating unit that has excellent strength even when used.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an electric heating unit showing an embodiment of the present invention. 1...Top plate, 2...Insulation base, 2a.
...Groove, 3...Heating wire, 4...Storage case.

Claims (1)

[Claims] It has a top plate made of a metal plate, a spirally wound heating wire, and a groove in which the heating wire is arranged in a meandering manner, and the main components are silica and alumina fibers, and clay and silica sol are used as binding materials. An electric heating unit characterized by comprising a heat insulating base made of a heat insulating material and a storage case made of a metal plate for storing the heat insulating base.