JPH03192682A - Sheathed heater - Google Patents

Abstract

PURPOSE:To improve heat efficiency by providing a flat surface on the upper surface of a spiral sheathed heater, and by providing unevenness coarser than the unevenness of the surfaces other than the flat surface. CONSTITUTION:The heat generated by a heating wire 2b is transmitted to a metal pipe 2a through electric insulating powder 2c. A pan 4 is heated by conduction heat from a flat surface 2d with unevenness thereon that is in contact at point or line with the pan, by radiation heat from the flat surface 2d that has a gap between the flat surface 2d and the pan 4, and by convective heat from the surface other than the flat surface 2d, and cooking is carried out in this way. The radiation heat that heats the pan is increased as the surface area of the flat surface 2d is increased for its unevenness. Heat efficiency is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a wax-wound sheathed heater for use in household cooking appliances.

BACKGROUND ART Conventionally, this type of sheathed heater has generally had a configuration as shown in Japanese Utility Model Publication No. 64-2086. The configuration will be described below with reference to FIGS. 5 and 6.

As shown in the figure, a 101-piece sheathed heater has two cross-sectional shapes, with the lower surface being substantially flat and the upper surface being spherical. Reference numeral 102 is a soup saucer with a concave cross section installed on the lower surface of the sheathed heater 101, which serves to catch boiling over from the pot 103 and also serves to reflect the radiant heat from the sheathed heater 1o1 toward the pot side. 104 is a box-shaped case.

In the above configuration, the pot 1031d is heated by heat conduction at the contact portion with the sheathed heater 1o1 and by radiant heat through the space. Since the sheathed heater 101 has a substantially flat lower surface and a spherical upper surface, the area of the sheathed heater near the bottom of the pot is small, and the amount of radiation is inversely proportional to the square of the distance.

This had the disadvantage of increasing heat loss due to radiation.

Problems to be Solved by the Invention With such conventional sheathed heaters for home cooking appliances, it was not possible to increase the surface area of the sheathed heater in the vicinity of the bottom of the pot, and there was a limit to the improvement of thermal efficiency. .

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a durable sheath heater that has excellent thermal efficiency and is less deformed due to repeated expansion and contraction due to cooling and heating.

Means for Solving the Problems In order to achieve the above object, the present invention provides a flat surface on the top surface of a spiral sheathed heater, and provides unevenness on the flat surface that is rougher than the surface roughness of the surface other than the flat surface. Alternatively, a thinly wound sheathed heater is provided with a groove in the axial direction of the sheathed heater in the flat part of the upper surface thereof.

Effect of the present invention With the above configuration, the unevenness or groove provided on the flat part of the upper surface of the sheathed heater on which the pot is placed and in contact has a large surface area of the sheathed heater that is closer to the bottom of the pot, increasing the amount of radiant heat to the bottom of the pot. This has the effect of increasing thermal efficiency, increasing the packing density of the insulating powder within the sheathed heater, improving heat transfer from the heating element within the sheathed heater, and further increasing thermal efficiency. In addition, the grooves provided in the axial direction on the top surface of the sheathed heater increase the rigidity of the sheathed heater, and the amount of deformation of the sheathed heater due to repeated expansion and contraction due to cooling and heating of the sheathed heater can be reduced, increasing durability. It is something that can be done.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4.

As shown in the figure, 1 is a box-shaped main body having an opening on the top surface, 2 is a sheath heater disposed in the opening of the main body 1, and a heating wire 2b formed into a coil shape is inserted into a metal pipe 2a. , the metal pipe is filled with electrically insulating powder 2G, and the openings at both ends of the metal pipe are sealed with a sealing material such as glass or silicone resin, and the cross-sectional shape is such that the upper surface side is flat 2d and the lower surface side is convex. Furthermore, the upper surface side plane 2d is provided with larger irregularities than the other surfaces.

3 is a saucer placed in the opening of the main body 1 below the sheathed heater 2. Reference numeral 4 denotes a pot which is an object to be heated and placed on the sheathed heater 2. 5 is a switch knob for turning on and off electricity to the sheathed heater.

In the above configuration, to explain the operation, the sheathed heater 2
Place the pot 4 on the flat surface 2d on the top side of the sheathed heater 2.
When the heating wire 2b inside is energized, the heat generated by the heating wire 2b is transmitted to the metal pipe 2a via the electrically insulating powder 2c, and the heat is transmitted to the metal pipe 2a through the electrically insulating powder 2c. The pot 4 is heated by heat, by radiant heat from the plane 2d where there is a gap between the plane 2d and the pot 4, and by convection heat from surfaces other than the upper plane 2d of the metal pipe 21L of the sheathed heater 2. Cooking is done.

As described above, according to the sheathed heater of the electric stove according to the embodiment of the present invention, most of the pot is heated by conductive heat and radiant heat from the uneven plane 2d on which the pot 4 is placed, so
As the surface area of the flat surface 2d increases due to the unevenness provided in the pot, the amount of radiant heat that heats the pot increases, increasing thermal efficiency.

Furthermore, by providing unevenness on the flat surface 2d by pressing or the like, the packing density of the electrically insulating powder is increased, and the heat generated from the heating wire 2b is better transferred to the metal pipe 2&~, so that the pot 4 can be heated smoothly. possible, start up and off
' Cooling speed is faster and heat loss can be reduced.

Furthermore, by providing grooves 2e on the flat surface 2d on the upper surface side of the sheathed heater 2, thermal efficiency is improved by increasing the surface area of the flat surface 2d close to the pot 4, similar to when the flat surface 2d is provided with unevenness, and the axial direction of the metal pipe 21L The provision of the groove 2e in the metal pipe 2a has the effect of increasing the rigidity of the metal pipe 2a, and the deformation caused by repeated expansion and contraction of the metal pipe 2 due to cooling and heating can be reduced. can be kept flat and prevent thermal efficiency from decreasing due to long-term use.

Effects of the Invention As is clear from the above embodiments, according to the present invention, the surface area of the sheathed heater in the vicinity of the bottom of the pot, which is the object to be heated, is increased by the unevenness or grooves provided on the flat part on the upper surface side of the sheathed heater. Therefore, more radiant heat is radiated to the pot, reducing heat loss and increasing thermal efficiency. In addition, by forming unevenness or grooves on the top surface of the sheathed heater by pressing, etc., the packing density of the electrical insulating powder inside the sheathed heater is increased, and the heat from the heating wire inside the sheathed heater is smoothly transferred. Since heat is transferred to the metal pipe that is the outer shell, the cooling speed becomes faster at startup or when the power is turned off, reducing unnecessary power supply time and reducing heat loss. In addition, by providing a groove on the upper plane of the sheathed heater, the rigidity of the metal pipe of the outer shell of the sheathed heater can be increased, and the deformation of the sheathed heater due to cooling and heating can be reduced, improving durability. can be achieved.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional perspective view of the essential parts of the sheathed heater of an electric stove according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view of the essential parts of the sheathed heater of the electric stove, and FIG. 3 is a perspective view of the electric stove. , FIG. 4 is a front sectional view of the electric stove, FIG. 5 is a front sectional view of the conventional electric stove, and FIG. 6 is an enlarged view of the same essential parts. 2...Sheathed heater, 2a...Metal pipe, 2b...Heating wire, 2d Plane, 2θ...Groove.

Claims (2)

[Claims] (1) A flat part is provided on the top surface of the spiral sheathed heater,
A sheathed heater in which the planar portion is provided with unevenness that is rougher than the surface roughness of the surface other than the planar portion. (2) The sheathed heater according to claim 1, wherein a groove is provided in the flat part of the upper surface of the spiral sheathed heater in the axial direction of the sheathed heater.