JP2003036958A - Method for manufacturing cord type heater coated with metal tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method by which manufacturing cost is remarkedly reduced, for example, by continuously producing a cord type heater coated with metal tube which can be suitably used as a defrosting heater of a refrigerator. SOLUTION: At the outer periphery of that in which one or plural cord type heaters are bundled wherein insulation coating is applied on a heater wire, after the metal shell is continuously coated using a metal tube tubulation machine, a reducing work is applied so that the metal shell immediately comes to a bellows state or spiral state in succession.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cord-shaped heater covered with a metal tube, which is preferably used as, for example, a defrosting heater for a refrigerator, and more particularly to a metal skin having a spiral structure or a bellows structure. The present invention relates to a product in which a manufacturing cost is significantly reduced by continuously producing a coated long cord-shaped heater.

[0002]

2. Description of the Related Art Conventionally, cord-shaped heaters having various configurations have been known as heaters for keeping heat of various devices, heaters for heating, heaters for preventing freezing, etc. Among them, for example, a heater for defrosting a refrigerator. As an example of a cord-shaped heater used as, for example, a cord-shaped heater in which a heating wire is spirally wound around a core fiber made of glass fiber, and an insulating layer formed by braiding or horizontal winding of glass fiber is formed on the heating wire. But,
There is a configuration in which the metal tube is housed and arranged.

In this type of cord-shaped heater, since the outermost metal tube functions as a mechanical protection member, a thermal protection member and a heat conduction member, the heater wire of the cord-shaped heater housed inside is improved. By appropriately changing the type and the type of the insulating coating, it is possible to use in a wide range of applications other than the defrosting heater of the refrigerator.

When this kind of cord-shaped heater is used as a defrosting heater for a refrigerator, it is arranged at a predetermined position in a state of being bent into a meandering shape or the like.

[0005]

However, the above conventional cord-shaped heater has the following problems. First, the conventional cord-shaped heater is manufactured by inserting the prepared cord-shaped heater into a metal tube that has been cut into a predetermined length in advance. However, there is a problem in that the manufacturing cost is increased because it cannot be manufactured.

Further, in this type of cord-shaped heater, the inner diameter of the metal pipe is designed to be larger than the outer diameter of the cord-shaped heater in order to improve the workability of inserting the cord-shaped heater into the metal pipe. Therefore, there is a problem that a void is partially generated between the inner wall of the metal tube and the cord-shaped heater, and the heating efficiency is reduced. Here, for such a problem, for example, a method of inserting a cord-shaped heater into a metal pipe and then subjecting the metal pipe to a drawing process to reduce the gap between the metal pipe and the cord-shaped heater is considered. To be
However, in this case, the number of manufacturing steps is further increased and the manufacturing cost is significantly increased, and the total length of the metal tube changes depending on the type of drawing and the degree of drawing, and the size of the metal tube is reduced. There was a risk of causing problems such as instability.

As a result of various studies to solve the problems of the prior art, the inventors of the present invention did not insert a cord-shaped heater into a preformed metal tube as in the prior art, but If the outer surface of the cord-shaped heater is covered by welding using a metal pipe forming machine while welding, and then immediately drawn continuously, the inner surface of the metal outer sheath and the surface of the cord-shaped heater are close to or close to each other. It has been found that a long heater having the above structure can be continuously produced. In addition, when performing drawing processing, by designing the shape of the metal skin to be a spiral shape or a bellows shape that satisfies certain specific conditions, the heat dissipation area of the metal skin is increased and heating of the object to be heated is performed. It has also been found that the efficiency is significantly improved.

[0008]

That is, a method of manufacturing a metal tube-covered cord-shaped heater according to the present invention is such that one or a plurality of cord-shaped heaters having an insulating coating on a heater wire are bundled together with a metal The present invention is characterized in that the metal outer coat is continuously coated by using a pipe forming machine, and then the metal outer coat is immediately and continuously drawn so as to have a spiral or bellows shape.

At this time, it is considered that the metal skin has a spiral structure or a bellows structure satisfying the condition of the expression (1).

[0010]

[Formula 1]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The cord-shaped heater used in the present invention is not particularly limited as long as it has a structure in which an insulating coating is applied on the heater wire. The number of pieces used is not particularly limited, and one piece or a plurality of pieces may be aligned or twisted and bundled.

As the heater wire, a single wire or a stranded wire of a metal resistance wire such as a nickel chrome alloy wire, an iron chrome alloy wire, a copper nickel alloy wire, and a stainless wire is used as it is, or those metal resistance wires are made of polyester fiber, Glass fiber,
Heater core made of fiber material such as alumina fiber, aromatic polyamide fiber, wholly aromatic polyester fiber, or
It is possible to use, for example, one wound around a heater core provided with an elastic coating such as silicone rubber on the circumference of the above fiber material. These may be appropriately selected in consideration of the usage conditions of the metal tube covered cord-shaped heater obtained according to the present invention. For example, a spirally wound metal resistance wire is used on the heater core. In this case, a high watt density cord-shaped heater can be easily obtained by adjusting the type of metal resistance wire and the winding pitch.

The insulating coating may be formed by a known method using a known insulating material. As an insulating material,
Examples thereof include electrical insulating compositions such as silicone rubber, fluororubber, and fluororesin, and fiber materials such as glass fiber, alumina fiber, silica fiber, and alumina / silica fiber. When an electrically insulating composition is used as the insulating material, it may be formed by extrusion or the like,
When a fiber material is used, it may be formed by braiding or horizontal winding. These insulating coatings may be formed in a single layer on the heater wire, or may be formed in a multilayer of two or more layers.

The outer periphery of the cord-shaped heater having the above-mentioned structure is provided with a metal jacket for the purpose of mechanical protection and thermal protection of the cord-shaped heater and good conduction of heat generated from the cord-shaped heater to the side of the object to be heated. Are coated. The present invention is characterized in that the metal outer cover is continuously coated in the longitudinal direction of the cord-shaped heater, whereby the intended effect of drastically reducing the manufacturing cost is realized.

As a means for continuously coating the metal outer cover in the longitudinal direction of the cord-shaped heater, the present invention employs a metal pipe forming machine capable of continuously forming a tubular product while welding a metal ribbon. is doing. By using this metal pipe forming machine, it is possible to continuously coat the metal skin in the state of being close to or in close contact with the outer periphery of the cord-shaped heater.

The metal material forming the metal shell may be a metal material that can be formed into a tubular product by the metal pipe forming machine described above, that is, a metal material that can be formed into a tubular product by welding. Anything can be used without particular limitation. As an example, stainless steel, a nickel alloy, a copper alloy, an aluminum alloy, etc. can be illustrated. Among these metal materials, the aluminum alloy is a metal material having excellent heat resistance and corrosion resistance, is easy to draw, and further has excellent thermal conductivity, and thus, for example, is obtained by the present invention. It is particularly preferable when the cord-shaped heater is used as a defrosting heater for a refrigerator.

In the present invention, the outer circumference of the cord-shaped heater is coated with the metal outer cover, and immediately thereafter, the metal outer cover is continuously drawn so as to have a spiral or bellows shape. Examples of means for performing the drawing include swaging, drawing, pressing, rolling, and caulking, but are not particularly limited. The drawing process may be performed on a part of the length of the metal skin or on the entire length.

By performing the drawing process, the inner surface of the metal skin and the surface of the cord-shaped heater are brought into close proximity or in close contact with each other, and by making the shape spiral or bellows, the heat dissipation area of the metal skin is increased. To do. Therefore, the heating efficiency for the object to be heated is significantly improved. In addition, since the flexibility of the obtained cord-shaped heater is improved by forming the metal skin in a spiral shape or a bellows shape, for example, an arbitrary shape (for example, a meandering shape) according to the intended use during actual use.
Improves workability when bending into Further, unlike the conventional case, it is not necessary to perform the drawing process in a separate step, so that the number of manufacturing steps is reduced and the manufacturing cost is significantly reduced.

In the present invention, when the drawing process is performed, the spiral structure or the bellows structure of the metal shell has a groove depth of the spiral or the bellows of a, the spiral or bellows average as shown in FIGS. When the inner diameter is b, the wall thickness of the spiral or the bellows is c, and the pitch of the spiral or the bellows is d, it is desirable to perform molding so as to satisfy the condition of the following expression 1.

[0020]

[Formula 1]

Here, (a × b) / (c × in the equation 1
When the value of d) is less than 2, the shape of the metal shell approaches the shape of a cylindrical tube, so that the heat dissipation area of the metal shell is reduced and the heating efficiency for the object to be heated is reduced. The flexibility decreases. On the other hand, when the value of (a × b) / (c × d) in the formula 1 is 30 or more, the spiral or bellows groove protrudes into the inside (cord-shaped heater side), so that the metal skin Although the area for radiating heat is increased, the close contact between the inner surface of the metal skin and the surface of the cord-shaped heater is reduced, which in turn reduces the heating efficiency for the object to be heated.

[0022]

EXAMPLES The contents of the present invention will be described in detail below with reference to examples.

Example 1 First, a nickel-chromium alloy wire having an outer diameter of 0.05 mm was placed on a heater core made of an E glass fiber bundle having an outer diameter of 0.7 mm.
A quadruple horizontal line consisting of a bundle of glass fibers in which six 75-count E glass yarns are aligned as an insulating coating on a heater wire wound spirally at a predetermined pitch so as to have 100Ω per 1 m of the heater core. A wound layer, a braided layer made of glass fibers, and a braided layer made of 130-long alumina long fibers were sequentially formed to obtain a cord-shaped heater having an outer diameter of 2.8 mm.

Next, a commercially available metal pipe making machine (made by Kanthal) was used on the outer circumference of the cord-shaped heater to have a width of 12 mm.
A metal ribbon made of SUS304 having a thickness of 0.2 mm is continuously coated while being welded to form a metal outer cover, and continuously, using a rotary swaging machine, the entire length of the metal outer cover is measured. Was drawn to form a spiral shape, and a metal tube-coated cord-shaped heater having a finished outer diameter of 3.2 mm was manufactured. The drawing process was set so that the spiral structure of the metal skin was (a × b) / (c × d) = 5.

Comparative Example 1 The spiral structure of the metal skin is (a × b) / (c × d) = 1.8.
A metal tube-covered cord-shaped heater was manufactured by using the same material and the same construction method as in Example 1 except that the above setting was made.

Comparative Example 2 A metal tube-coated cord made of the same material and the same construction method as in Example 1, except that the spiral structure of the metal shell was set to (a × b) / (c × d) = 32. Shaped heater was manufactured.

Here, the following three kinds of evaluation tests were carried out using the thus obtained three kinds of metal tube covered cord-shaped heaters as samples.

Flexibility In order to evaluate the flexibility, the minimum bending radius of the metal tube coated cord-shaped heater was measured and compared. The maximum bending stress at that time was also measured.

Heating Efficiency In order to evaluate the heating efficiency, the heating time was measured and compared by the following method. First, as the object to be heated, SUS30
A plate having a length of 4 mm and a length of 300 mm and a thickness of 2 mm was prepared. Next, after disposing the sample on the surface on one side, a thermocouple was installed at the center position of the back surface on which the sample was not disposed. Then, a voltage was applied to the cord-shaped heater covered with a metal tube and the time until the thermocouple reached 100 ° C. was measured.

The obtained results are shown in Table 1.

[Table 1]

According to Table 1, first, regarding flexibility, the metal tube covered cord-shaped heater of Example 1 having a spiral structure of (axb) / (cxd) = 5 and the spiral structure ( ax
In Comparative Example 2 in which b) / (c × d) = 32, the minimum bending radius was 3 mm, which was a small value, while the helical structure was (a × b) / (c × d) = 1.8. The cord-shaped heater coated with metal tube of Comparative Example 1 had a large value of 11 mm. Further, the maximum bending stress has the same tendency as the minimum bending radius, and Example 1 and Comparative Example 2 are excellent in flexibility, and Comparative Example 1 is inferior in flexibility.

Regarding the heating efficiency, the temperature rising time became longer in the order of Example 1, Comparative Example 2, and Comparative Example 1, and the result was that Example 1 had the best heating efficiency.

As described above, the metal-tube-coated cord-shaped heater having both sufficient flexibility and heating efficiency has a spiral structure or a bellows structure satisfying 2 ≦ (a × b) / (c × d) <30. It was confirmed that only the present example satisfying the above condition was satisfied.

[0034]

As described above in detail, in the manufacturing method of the present invention, the outer periphery of the cord-shaped heater is continuously coated with the metal outer coat by using the metal pipe forming machine, and immediately thereafter, the metal outer coat is continuously coated. It is characterized by being drawn so as to have a spiral or bellows shape. By adopting this method, continuous production in a long length is possible, and the inner surface of the metal skin and the surface of the cord-shaped heater are close to or close to each other without the need for drawing in a separate process as in the past. It will be in the state of doing. Therefore, the manufacturing cost is significantly reduced as compared with the conventional one, and the heating efficiency is remarkably improved in terms of its characteristics. Therefore, it can be suitably used in a wide range of fields such as a defrosting heater for refrigerators, a heat retention heater for various devices, a heating heater, an antifreezing heater, and the like.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention and is a view for explaining a spiral structure of a metal outer cover.

FIG. 2 is a diagram showing an example of the present invention, and is a diagram for explaining a bellows structure of a metal skin.

[Explanation of symbols]

a Groove depth b Average wall thickness c wall thickness d pitch

Claims (2)

[Claims] 1. A metal wire-making machine is used to continuously coat the outer circumference of one or more cord-shaped heaters having an insulating coating on the heater wire with a metal shell, and immediately thereafter. A method of manufacturing a metal tube-covered cord-shaped heater, characterized in that the metal outer cover is drawn so as to have a spiral shape or a bellows shape. 2. The method for producing a metal-tube-covered cord-shaped heater according to claim 1, wherein the metal skin has a spiral structure or a bellows structure satisfying the condition of Expression 1. [Formula 1]