JPS6137751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating coil with improved tracking resistance.

FIG. 1 shows an example of a cross section of an induction heating furnace. In the figure, 1 is a current-carrying coil wrapped around a copper tube, 2 is a cooling coil wrapped around a copper tube, and 3 is a coil wrapped around a copper tube.
is an insulator inserted between the turns of each coil 1 and 2 (hereinafter referred to as an insulating spacer), 4 is the main insulator, and 5 is the structure of the inner and outer surfaces of the coil, which is composed of a refractory material, a heat insulating material, an insulator, etc. 6 is a furnace structure which is normally at ground potential, and 7 is an adhesive applied to the insulating spacer 3.

Induction heating furnaces require the use of high voltage as they increase in capacity and power, and the withstand voltage and voltage per turn of the coil tend to increase, but due to the nature of induction heating furnaces, copper tube coils 1, The area near No. 2 often becomes wet or has a corrosive atmosphere due to volatile components from the furnace material and the melted material in the furnace. In order to dissipate these, a dispersion hole is provided by single-overlapping the insulating spacers 3 as shown in FIG. 2, but this does not mean that the volatile components can be completely dissipated.

These volatile components may directly stain the insulating spacer 3 and the main insulator 4, or over time they may contaminate the copper tube coils 1, 2.
Conductive products (including those that become conductive when wet) adhere or accumulate on the insulating spacer 3 or main insulator 4 when they peel off or melt and flow out.
contamination and cause insulation breakdown.

Furthermore, although the copper tube coils 1 and 2 undergo thermal expansion during operation of the induction heating furnace, the insulating spacer 3 and each of the copper tube coils 1 and 2 have different coefficients of expansion. Therefore, when a strong adhesive is used to bond between the insulating spacers 3 and 3 or between the insulating spacer 3 and the copper tube coils 1 and 2, the thermal expansion of the insulating spacer 3 and the copper tube coils 1 and 2 The insulating spacer 3, which is weak in strength and unable to follow the behavior, often breaks, resulting in a short circuit between layers.

The present invention was made to solve the above-mentioned drawbacks, and uses an adhesive that has corrosion resistance, electrical insulation or tracking resistance, and flexibility to bond between insulating spacers and between insulating spacers and copper tube coils. To provide an induction heating coil.

Examples will be described below. Adhesive 7 is an epoxy resin composition consisting of a cycloaliphatic epoxy resin having two or more oxirane rings in the molecule as a main component and a polyamide having an active hydrogen equivalent of 50 to 700 as a curing agent.

The polyamide contained in the above curing agent forms a stable complex salt through coordination bonds with copper, increasing the anticorrosive effect. Uses an alicyclic epoxy that does not have Therefore, it has excellent tracking resistance. Furthermore, among cycloaliphatic epoxies, diglycidyl ester type epoxy resins and hydantoin type epoxy resins have excellent curability with polyamides, and the cured products obtained from these epoxy resins and polyamides with an active hydrogen equivalent of 50 to 700 are , has a low crosslinking density, is rubber-like, and has high flexibility and adhesive properties, so it is suitable because it can follow the thermal expansion behavior of the coil. It is also possible to add fillers, colorants, flexibility-imparting agents, and other components to these epoxy resin compositions, if necessary.

Although the above embodiment describes an induction heating coil, the same effects as the above embodiment can be expected if applied to a coil with large thermal expansion behavior.

According to this invention, the main agent of the adhesive for bonding between each insulating spacer and the copper tube coil is a cycloaliphatic epoxy resin having two or more oxirane rings in the molecule, or a diglycidyl ester type cycloaliphatic epoxy resin. Epoxy resin or cycloaliphatic hydantoin epoxy resin, and the curing agent has an active hydrogen equivalent of 50
~700 polyamide epoxy resin composition has excellent tracking resistance,
An induction heating coil having flexibility at the bonded portion can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view of the induction heating furnace, and FIG. 2 is a sectional view showing the portion shown in FIG. 1. In the figure, 1, 2
3 is a coil, 3 is an insulating spacer, and 7 is an adhesive. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A coil having a copper tube wound thereon, in which a plurality of insulating spacers coated with adhesive are arranged between the turns of the coil, where the adhesive has two or more oxiranes in its molecules. An induction heating coil characterized in that it is an epoxy resin composition, which is a cycloaliphatic epoxy resin having a ring, and a curing agent is a polyamide having an active hydrogen equivalent of 50 to 700. 2. The induction heating coil according to claim 1, wherein the main ingredient of the adhesive is a diglycidyl ester type cycloaliphatic epoxy resin. 3. The induction heating coil according to claim 1, wherein the main ingredient of the adhesive is a cycloaliphatic hydantoin epoxy resin.