JPH04315789A - Electric heater - Google Patents

Abstract

PURPOSE:To increase safety, life, and the radiation energy from a heating wire in an electric heater used for an electric cooking apparatus of a radiation type. CONSTITUTION:A tape-like heating wire 9, which being an electric resistance heating body, is covered with a woven cloth 10, which is cylindrical shape and bears mesh, and is held with a heat insulator 11 and a holding material 12, further is armored with a supporting material 14, so that the radiation energy radiated from a heating wire 9 can be directly transmitted to a subject to be cooked.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heater with a large thermal power used in a radiant heater for an electric cooker or the like.

0002

[Prior Art] Electric heaters have traditionally been used in electric cooking appliances and electric heaters that transmit thermal energy (or infrared energy) emitted by an electric resistance heating element (hereinafter referred to as heating wire) to an object to be heated by means of hot air circulation or radiation. It is used for furnaces, etc.

Most of the electric heaters used in electric cooking appliances are sheathed heaters, quartz tube (or heat-resistant glass tube) heaters, or mica heaters.

A conventional electric heater will be explained below. As shown in FIG. 5, the sheathed heater has a rod-like configuration including a heating wire 1, an insulating material 2, a sealing material 3, and a protective tube 4. The length of an electric heater is usually several tens of cm and the diameter is 10 m.
m or less, the shape is mainly rod-like, ring-like, or a modified form of a ring. When energized, the surface temperature of the protective tube 4 becomes 700 to 800° C., and when placed inside the electric cooking device, the food to be cooked is heated.

The quartz tube heater uses a quartz tube as the protective tube 4, and the basic structure is the same as that of the sheathed heater, so a description thereof will be omitted.

As shown in FIG. 6, the mica heater is constructed by winding a heating wire 6 around a mica plate 5 and further forming two mica plates 7 and 8.
It has a structure in which it is fixed by sandwiching it between the two. A mica heater is fixed to the outside of the cavity that makes up the interior of the electric cooker and heats a part of the cavity (temperature is approximately 500 degrees Celsius).
The food is heated by secondary radiation.

The amount of heat generated by the heating wire 1 or 6 is determined by the electrical resistance of the heating wire 1 or 6 and the input, and the surface temperature of the electric heater is also roughly determined by this.

[0008]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, the heating wire 1 or 6 is coated with a suitable material to insulate or prevent disconnection due to corrosion. There is a problem in that the energy is impeded by the covering material and becomes small before it reaches the food to be cooked.Also, since the electric heater has a rod-like shape, the energy radiation area is small and the heating performance is low.

[0009] The present invention solves the above-mentioned conventional problems, and is highly safe, has a long life, and directly transmits the radiant energy of the heating wire to the food by holding the heating wire without interfering with the energy transfer. The purpose is to provide a high-power electric heater.

0010

[Means for Solving the Problems] In order to achieve this object, the electric heater of the present invention has a configuration including a tape-shaped heating wire covered with a cylindrical woven fabric having a mesh of ceramic fibers. are doing.

[0011]

[Operation] With this configuration, infrared rays generated by the heating wire are transmitted through the openings of the mesh of the ceramic fiber woven fabric.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, a heating wire 9 is covered with a cylindrical woven cloth 10 having a mesh of ceramic fibers containing silicon, carbon, oxygen, and titanium, and a heat insulating material 11
The heating wire 9 is held by the holder 12, the heat insulating material 11, the holder 12, and the heat insulating material 13 are fixed by the supporting material 14, and the heat insulating material 13 is exteriorized, so that the structure can be easily attached to the electric cooking appliance.

[0014] The heating wire 9 was made of an iron-chromium alloy or a nickel-chromium alloy, and the ceramic fiber woven fabric 10 was Tyranno Fiber (trade name, manufactured by Ube Industries, Ltd.).

The holder 12 and the heat insulating material 11 are ceramic sintered bodies, and the contact surfaces of the holder 12 and the heat insulating material 11 are fixed with a ceramic adhesive. The heating wire 9 is inserted into the through hole formed by both, preventing the heating wire 9 from shifting due to thermal expansion and contraction, and ensuring insulation. The heat insulating material 13 for blocking the heat of the heating wire 9 is formed into a mat shape of a material mainly composed of silica-alumina fibers.

The heating wire 9 is made of iron-chromium or nickel-based
In both chrome-based wires, the thickness of the wire is 50 μm, the width is 6 mm, and the length is set to give an output of 1.2 kW at an input of 100 V, taking into account the respective resistance values. When the output is 1.2 kW, the surface temperature of the heating wire 9 is about 800°C, and the infrared radiation at this time is about 2.
The distribution follows Planck's equation with a peak at 7 μm. Of course, it is necessary to multiply the distribution expressed by Planck's equation, which assumes an ideal blackbody, by the emissivity of the heating wire 9.

Furthermore, the length of the heating wire 9 is approximately 2 m due to the above-mentioned design, so the effective radiation area is 200×0.6=
It becomes 120cm2. Radiation area at 800℃ is 120cm
2 is also available, which is larger than conventional sheathed heaters that are about 40 cm2 or quartz tube heaters that are about 20 cm2 each.

The above-mentioned peak wavelength of 2.7 μm means that the infrared rays radiated from the electric heater of the present invention are well absorbed by the water contained in the food. Therefore, it is easier to evaporate moisture and burn the surface of the food, which is important in the heating operation, than in the past. The reason for this is that it has both the temperature needed to obtain the peak wavelength and a large radiating area that allows more energy to be obtained (mica heaters have a large area, but the temperature of the radiating surface is low).

As shown in FIG. 3, a tyranno fiber woven fabric 10
is a yarn with a cross section of 16 made by collecting a plurality of tyranno fibers 15, and the yarn usually has a size of several 100 to several 10.
It is often composed of 00 fibers. The tyranno fiber woven fabric 10 is made by knitting yarns in a mesh shape with an appropriate pitch. In the embodiment, a woven cloth 10 of Tyranno fiber is woven into a cylindrical shape, and the surface of the heating wire 9 is reliably covered. By covering the heating wire 9 with the woven fabric 10, it is possible to prevent corrosive substances from adhering to the surface of the heating wire 9. According to the inventors' experiments using saline water, it was found that this configuration resulted in a lifespan 4 to 5 times longer than when not covered with the woven fabric 10. In addition, as shown in FIG. 4, the tensile strength of Tyranno fibers hardly changes even at temperatures around 1000°C, so the heating wire 9 can be held and prevented from sagging or deforming. Suitable as a material that holds 9.

[0020] Tyranno fibers are thin and have a diameter of only a few micrometers, making the woven fabric 10 lightweight as a whole, and have a small heat capacity.Furthermore, the heating wire 9 has a mesh and has a large aperture ratio.
There is no major hindrance in the process of transmitting the infrared energy from the infrared rays to the food being cooked. Therefore, thermal energy can be effectively used to heat the food, and thermal efficiency is increased. Having a large opening ratio makes it possible to visually see the glowing state of the heater, and the infrared radiant energy transmitted through the openings directly heats the food, which has the effect of shortening the cooking time.

Next, an electric cooking device using an electric heater according to an embodiment will be explained. When we actually cooked grilled fish, meat, etc. with the electric heater of the above-mentioned example attached to the ceiling of a commercially available open range, the cooking time was approximately 1. /
The effect of being able to cook in 2 hours was obtained. For example 2
The 4 saury that used to take 0 minutes to roast now took just 10 minutes.

[0022]

As described above, the present invention has a configuration including a tape-shaped heating wire covered with a cylindrical woven fabric having a mesh of ceramic fibers, so that the heating wire can be heated without interfering with energy transmission. It is possible to realize an electric heater that is highly safe, has a long lifespan, and has high heating power by holding the heating wire and directly transmitting the radiant energy of the heating wire to the food being cooked.

[Brief explanation of the drawing]

[Fig. 1] A schematic cross-sectional view of essential parts of an electric heater according to an embodiment of the present invention.

[Figure 2] Partial plan schematic diagram of the electric heater

[Figure 3] Schematic partial slope diagram showing an enlarged view of the concept of the Tyranno fiber woven fabric of the electric heater

[Figure 4] Graph showing the relationship between temperature and tensile strength of Tyranno fiber in the same electric heater

[Figure 5] Schematic cross-sectional diagram of a conventional sheathed heater

[Figure 6] A schematic perspective view showing the concept of a conventional mica heater

[Explanation of symbols]

9 Heating wire 10 Woven fabric 11 Insulation material 12 Holder 14 Support material

Claims (1)

[Claims] 1. A tape-shaped electrical resistance heating element covered with a cylindrical woven fabric having a mesh of ceramic fibers, a holder for holding and fixing the electrical resistance heating element, a heat insulating material, and the A heater comprising a heat insulating material and a supporting material for fixing and sheathing the holder.