JP2006079969A - Sheath heater and heating device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheath heater and a heating device using the same friendly to environment. <P>SOLUTION: A coil-shaped heating wire 2 is arranged at the center of a metal pipe 1, electric insulation powder 3 of magnesium oxide as main component is filled between the heating wire 2 and the metal pipe 1, and both ends of the metal pipe 1 are sealed by a sealant 5 made of glass with a low melting point in which, lead is contained by 1,000 ppm or less. A safe heating source not using lead which has a problem as a harmful substance nowadays, is thereby provided. Especially, by restraining a content of lead to 1,000 ppm or less, a legal regulation such as the European RoHS order is met. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheathed heater used as a heat source and a heating device using the sheathed heater as a heating source.

  In the conventional sheathed heater, a coiled heating wire is arranged in the center of the metal pipe, and between the heating wire and the metal pipe, an electrically insulating powder mainly composed of magnesium oxide is filled, and both ends of the metal pipe are oxidized. It was sealed with a sealant made of low melting point glass containing lead as a main component (for example, see Patent Document 1).

  In a sheathed heater with such a configuration, if there is a defect such as cracks or voids in the sealant, moisture in the atmosphere will enter through the cracks or gaps in the sealant during use, and the electrical insulation between the metal pipe and the heating wire will be improved. Problems such as direct contact with a sheathed heater or indirect contact with a metal member cause an electric shock or a breaker falls, making it impossible to use a heating device that uses the sheathed heater as a heating source. Occurs. For these reasons, low-melting glass mainly composed of lead oxide, which has excellent airtightness and workability so that moisture does not enter, has been used at both ends of the metal pipe.

And the sheathed heater of the said structure has been used as a heat source for various heating apparatuses, such as induction heating cooking with a roaster, a home bakery, a hot plate, and a fish roaster.
Japanese Patent Publication No.57-18308

  However, the lead glass used for the sealing agent of the conventional sheathed heater contains a lot of lead, which has been considered a problem as a harmful substance, and has a problem of adversely affecting the environment.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an environment-friendly sheathed heater and a heating device.

  In order to solve the above-described conventional problems, the sheathed heater according to the present invention has a coil-shaped heating wire disposed in the center of a metal pipe, and an electric power mainly composed of magnesium oxide between the heating wire and the metal pipe. Fill with insulating powder and seal both ends of the metal pipe with a sealant made of low melting point glass with lead content of 1000ppm or less, and use lead which has been regarded as a harmful substance in recent years. In addition, a sheathed heater excellent in electrical insulation and durability can be provided. In particular, by limiting the lead content to 1000 ppm or less, it becomes possible to comply with European and RoHS regulations.

  Moreover, the heating device of the present invention uses the sheathed heater according to any one of claims 1 to 5 as a heating source, while ensuring the same characteristics as those of a conventional sheathed heater using lead glass. It is possible to provide an environmentally friendly heating device that does not contain harmful substances.

  The sheathed heater of the present invention and a heating device using the sheathed heater are environmentally friendly heating sources and heating devices because they do not contain harmful substances.

  1st invention arrange | positions a coil-shaped heating wire in the center of a metal pipe, is filled with the electrically insulating powder which has a magnesium oxide as a main component between the said heating wire and the said metal pipe, and both ends of the said metal pipe Is sealed with a sealant made of low melting point glass with a lead content of 1000 ppm or less, and it has excellent electrical insulation and durability without using lead, which has recently been regarded as a problem as a harmful substance. A sheathed heater can be provided. In particular, by limiting the lead content to 1000 ppm or less, it becomes possible to comply with European and RoHS regulations.

  In particular, the second invention uses a low-melting glass mainly composed of bismuth oxide as the sealing agent of the first invention, and can suppress the distortion remaining in the glass at the time of sealing, Since the water resistance also increases, it is possible to provide a sheathed heater excellent in electrical insulation and durability while ensuring sealing properties excellent in mechanical strength and moisture resistance.

  The third invention uses a low-melting glass mainly composed of zinc oxide and boron oxide as the sealing agent of the first invention, while ensuring the same electrical insulation and durability as in the prior art. Lead-free can be achieved, and since no heavy metal is contained at all, a more environmentally friendly sheathed heater can be provided.

In the fourth invention, the linear expansion coefficient of the sealing agent according to any one of the first to third inventions is set to 100 × 10 ^{−7 to} 130 × 10 ⁻⁷ / ° C. Adhesiveness with the welded electrical extraction terminal can be secured, and a sheathed heater excellent in mechanical strength and moisture resistance can be secured.

  In particular, the fifth invention is the one in which the outside of the sealing agent of any one of the first to fourth inventions is sealed with at least a silicon resin or an insulator, and the mechanical strength of the sealing agent is improved and the electrical insulation property is increased. And reliability related to durability can be remarkably improved.

  A sixth invention uses the sheathed heater according to any one of claims 1 to 5 as a heating source, and maintains a property equivalent to that of a conventional sheathed heater using lead glass, It is possible to provide an environmentally friendly heating device that does not contain any of them.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a sheathed heater according to the first embodiment of the present invention.

In FIG. 1, 1 is a metal pipe, 2 is a coiled heating wire, and 3 is an electrically insulating powder made of magnesium oxide filled in a gap between the metal pipe 1 and the heating wire 2. Reference numeral 4 denotes an electrical lead terminal integrated by spot welding at both ends of the heating wire 2. 5 is a sealing agent made of a low-melting glass having a lead content of 1000 PPM or less and having a so-called lead-free bismuth oxide as a main component and a linear expansion coefficient of 110 × 10 ⁻⁷ / ° C.

  In addition, as a sealant made of lead-free low-melting glass, a sheath heater is used for each of those containing bismuth oxide as a main component, those containing zinc oxide and boron oxide as main components, and those containing lead oxide as a main component. Table 1 shows the results of measuring the time-dependent change in the insulation resistance value between the metal pipe 1 and the electrical extraction terminal 4 when the product is prototyped and left in a high humidity of 40 ° C. and a relative humidity of 95%.

  As is apparent from the results in Table 1, both the main component of bismuth oxide of the present invention and the main component of zinc oxide and boron oxide exhibited excellent insulating properties equivalent to those of the prior art.

  Table 2 shows the results of measuring the change in the insulation resistance value after applying a constant load to the electrical extraction terminal 4 in the horizontal direction and leaving it for one month in the same manner as described above.

  As shown in Table 2, the insulation resistance value after applying a mechanical load to the electrical extraction terminal 4 showed the same characteristics as the conventional ones mainly composed of zinc oxide and boron oxide. The main component showed better characteristics than the conventional sheathed heater.

  Thus, by using lead-free low-melting glass mainly composed of bismuth oxide or zinc oxide and boron oxide as the sealing agent 5, a conventional sheathed heater using low-melting glass mainly composed of lead oxide. It is possible to provide a sheathed heater that can ensure excellent electrical insulation properties as well as the environment and is environmentally friendly.

  In particular, those using bismuth oxide as the sealant 5 can provide a highly reliable sheathed heater with excellent mechanical properties. Furthermore, since zinc oxide and boron oxide do not contain any heavy metal, a more environmentally friendly sheathed heater can be provided.

  The low-melting glass mainly composed of bismuth oxide contains about 70% bismuth oxide, contains other components such as boron oxide, silicon oxide, and zinc oxide, and has a working temperature of 500 ° C. to 900 ° C. The one in the range of ℃ is good. Further, the low melting point glass mainly composed of zinc oxide and boron oxide contains 30 to 70% zinc oxide and 10 to 40% boron oxide, and the working temperature is the same as that mainly composed of bismuth oxide. In the range of 500 ° C. to 900 ° C.

In addition, a sheathed heater having a low coefficient of linear expansion of 80 × 10 ^{−7 to} 140 × 10 ⁻⁷ / ° C. in a low melting point glass containing bismuth oxide as a main component was prototyped, and a high humidity was obtained by the same method described above. Table 3 shows the measured insulation resistance values after being left in the atmosphere for one month.

As is apparent from Table 3, the linear expansion coefficient of 100 × 10 ^{−7 to} 130 × 10 ⁻⁷ / ° C. shows stable electrical insulation characteristics. Use a good one.

  Furthermore, a highly reliable sheathed heater with improved electrical insulation and mechanical strength can be provided by sealing with an insulator or silicon resin in addition to the sealing agent 5 made of low melting point glass.

  FIG. 2 is a perspective view showing a schematic configuration of an induction heating cooker that is one of the heating devices using the sheathed heater in the embodiment, and FIG. 3 is a longitudinal front sectional view of the induction heating cooker.

  11 is a cooker body, 12 is a top plate located at the top of the cooker body 11, 13 and 14 are located below the top plate 12, a heating coil for generating induction heating, and 15 for cooking fish and the like. In the roaster heating chamber to be performed, 16 is a roaster door. Reference numeral 17 denotes an operation unit that controls the heating coil 13, the roaster heating chamber 15, and the like. Reference numeral 15a denotes a saucer installed in the roaster heating chamber 15, reference numeral 15b denotes a grill, and reference numerals 15c and 15d denote an upper heater and a lower heater made of the sheathed heaters described in the above embodiment.

  As described above, it is possible to provide an environment-friendly induction heating cooker by using the upper heater 15c and the lower heater 15d made of a sheathed heater using low melting point glass mainly composed of bismuth oxide as the sealing agent 5. it can.

  In the above embodiment, an induction heating cooker has been described as an example of a heating device that uses a sheathed heater. However, the sheathed heater of the present invention is also used in a home bakery, a hot plate, a fish roaster, and the like. Can provide environmentally friendly products.

  Further, by using a sealing agent made of low-melting glass mainly composed of zinc oxide and boron oxide instead of bismuth oxide, it is possible to provide a more environmentally friendly product which does not contain any heavy metal.

  As described above, the sheathed heater according to the present invention and the heating device using the sheathed heater become an environment-friendly heating source and heating device. Of course, the heating device used in general households has a heating source for business and industrial use. It can also be applied to heating equipment and devices.

Sectional drawing of the sheathed heater in Embodiment 1 of this invention Perspective view showing schematic configuration of induction heating cooker using the same sheathed heater Vertical front sectional view of the induction heating cooker

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal pipe 2 Heating wire 3 Electrical insulation powder 4 Electrical extraction terminal 5 Sealing agent 11 Cooking unit body 12 Top plate 13, 14 Heating coil 15c Upper heater 15d Lower heater

Claims (6)

A coiled heating wire is placed in the center of the metal pipe, and an electric insulating powder mainly composed of magnesium oxide is filled between the heating wire and the metal pipe, and both ends of the metal pipe have lead content. Is a sheathed heater sealed with a sealant made of low melting point glass of 1000 ppm or less. The sheathed heater according to claim 1, wherein a low melting point glass mainly composed of bismuth oxide is used as the sealing agent. The sheathed heater according to claim 1, wherein a low-melting glass mainly composed of zinc oxide and boron oxide is used as the sealing agent. The sheathed heater according to claim 1, wherein the sealant has a linear expansion coefficient of 100 × 10 ^{−7 to} 130 × 10 ⁻⁷ / ° C. The sheathed heater according to any one of claims 1 to 4, wherein the outside of the sealing agent is sealed with at least a silicon resin or an insulator. The heating apparatus which used the sheathed heater of any one of Claims 1-5 as a heating source.

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