JP3204709B2 - Cord-shaped heating element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cord-shaped heating element having a positive temperature characteristic and used in a sheet heating device such as an electric carpet or an electric blanket, and a method of manufacturing the same.
In particular, the present invention relates to a device which is excellent in flexibility and is designed to reduce a change in resistance value due to bending.

[0002]

2. Description of the Related Art A cord-shaped heating element using a conductive resin composition having a positive temperature characteristic as a heating element is used for application to surface heating devices such as electric carpets, electric blankets, etc. for quick heating and self-temperature control. In recent years, it has attracted attention due to its characteristics, such as its ability to perform partial temperature control.

FIG. 4 is a partially cutaway perspective view showing an example of a conventional cord-shaped heating element. First, a conductive resin composition 14 having a positive temperature characteristic is extrusion-coated on the periphery of a pair of electrode wires 13 arranged in parallel, and an insulator layer 16 is further extruded on the periphery. Coated. When a voltage is applied to the cord-shaped heating element 17 configured as described above, the conductive resin composition 14 having a positive temperature characteristic starts to generate heat and performs self-temperature control at a certain temperature.

[0004]

However, the above-mentioned conventional cord-shaped heating element has the following problems.
First, the flexibility in the X direction (horizontal direction in the figure) is significantly inferior to the flexibility in the Y direction (vertical direction in the figure) in FIG.
When bent in the X direction, the adhesion between the electrode wires 13, 13 and the conductive resin composition 14 decreases, and the contact resistance increases. As a result, the resistance value of the cord-shaped heating element itself becomes high, so that necessary heat generation cannot be obtained, and the temperature of each part of the cord-shaped heating element varies. These problems may occur due to bending added during wiring in the manufacturing process when the cord-shaped heating element is used for a planar heating device such as an electric carpet, or when the heating device is used or stored.

The present invention has been made on the basis of the above points, and it is an object of the present invention to provide a cord-shaped heating element having excellent flexibility and exhibiting a stable resistance value even when stress is applied by bending. It is to provide a manufacturing method thereof.

[0006]

In order to achieve the above object, a cord-like heating element according to the present invention comprises a plurality of resin-coated wires formed by coating a conductive resin composition having a positive temperature characteristic on the outer periphery of an electrode wire. The resin-coated wires are twisted and fused and integrated with each other. In addition, at this time, the resin-coated wire has a length of 1.
It preferably has a major axis of 3 times or more and 4 times or less.

The method for producing a cord-shaped heating element according to the present invention comprises the steps of: twisting a plurality of resin-coated wires obtained by coating an outer periphery of an electrode wire with a conductive resin composition having a positive temperature characteristic; Are integrated by heat fusion. At this time, it is conceivable that the resin-coated wires are fused and integrated with each other at the same time as forming the insulator layer of the cord-shaped heating element.

The electrode wire used in the present invention includes a metal conductor as it is or a spiral wound around a fiber core.

The conductive resin composition having a positive temperature characteristic used in the present invention includes well-known thermoplastic resins, preferably crystalline thermoplastic resins such as polyolefins, fluororesins, polyurethanes, polyethers, and aliphatic polyesters. , Carbon black, graphite, nickel powder,
The main component is a mixture of a suitable amount of conductive powder such as silver powder by a known method. An organic peroxide such as dicumyl peroxide may be previously mixed with the composition so that when a plurality of resin-coated wires are fused and integrated with each other, crosslinking proceeds simultaneously.

The conductive resin composition having the positive temperature characteristic is coated on the above-mentioned electrode wire by a known method to obtain a resin-coated wire. The cross-sectional shape of the resin-coated wire includes a circle, an ellipse, a rectangle, and an oval shape. Of the resin-coated wires having these cross-sectional shapes, 1.3 with respect to the minor axis.
Those having a long diameter of not less than 2 times and not more than 4 times can be fused more reliably if they are twisted so that their long sides face each other and fused and integrated, so that the fused area increases,
Further, the effect is obtained that the distance between the electrode wires is hardly changed even when pressure is applied from the outside. Usually, two resin-coated wires are used as a pair, but more than two wires may be used.

In the present invention, as a method of heat-sealing a plurality of twisted resin-coated wires to integrate them, a method of continuously passing through a heating furnace, a method of passing through pressurized steam, A method using heat when forming an insulator layer, a method using heat generated by an electron beam, a microwave, and the like are exemplified. Particularly preferably, when forming the insulator layer on a resin-coated wire, the insulating layer is used. A method utilizing the heat of the body layer is used. According to this method, more reliable fusion is achieved by a synergistic effect with the pressure in the extruder. Further, the resin-coated wire may be crosslinked by an electron beam, an organic peroxide or the like after being integrated by heat fusion or simultaneously with heat fusion.

[0012] Here, it is generally preferred that the resin-coated wire is crosslinked to obtain good stability over time, but in the present invention, a resin-coated wire containing an organic peroxide in advance is used. After the resin-coated wires are twisted together, the resin-coated wires are fused by the heat of extruding the insulator layer crosslinked with organic peroxide in the next step of extruding the insulator layer, and then the whole is immediately heated. The method of cross-linking is particularly preferable because not only the reliability as a heating element but also the insulating layer becomes infusible, so that the overall reliability is excellent.

[0013]

According to the present invention, since a plurality of resin-coated wires each formed by coating the outer periphery of an electrode wire with a conductive resin composition having a positive temperature characteristic are twisted, stress caused by bending is reduced in a specific direction. It is possible to reduce the stress applied to the contact surface between the electrode wire and the conductive resin composition having the positive temperature characteristic even if the electrode wire is bent in any direction. Accordingly, it is possible to provide a cord-shaped heating element in which a change in resistance value due to bending is significantly reduced.

[0014]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. << Embodiment 1 >> A first embodiment of the present invention will be described with reference to FIGS. First, a conductive resin composition 4 having a positive temperature characteristic having an outer diameter of φ1 .0 is formed on the outer periphery of an electrode wire 3 formed by spirally winding a nickel-plated copper wire 2 of φ0.11 mm on a glass fiber core 1 of φ0.3 mm. The resin-coated wire 5 was formed by extrusion coating to a thickness of 2 mm. Next, the two resin-coated wires 5 are twisted (pitch: about 24 mm), and a polyethylene mixture 6 containing a peroxide as an insulator layer is extruded on the outer periphery thereof so as to have an outer diameter of 3.0 mm. The conductive resin composition 4 and the polyethylene mixture 6 were cross-linked in steam of 14 kg / cm ² for about 2 minutes. The cord-shaped heating element 7 manufactured in this manner is
As shown in FIG. 1, the two resin-coated wires were integrated by heat fusion.

The resistance value of the cord-shaped heating element 7 was measured at 25 points at 25 ° C. and found to be 150 Ω / m to 28
0 Ω / m (average value is 230 Ω / m).
The self-control heating temperature at the time of applying 0 V was in the range of 61 ° C to 64 ° C.

In Example 1, 35 parts by weight of conductive carbon black and 3 parts by weight of dicumyl peroxide as a cross-linking agent were used as a conductive resin composition having a positive temperature characteristic with respect to 100 parts by weight of low-density polyethylene. The composition obtained by blending parts was used. Extrusion of the conductive resin composition having the above-mentioned positive temperature characteristics was performed using a φ20 mm resin extruder with L / D = 20 and a compression ratio of 2.0 at a set temperature, cylinder: 100 ° C., and head: 120 ° C. I went in.

Example 2 In Example 2, a cord-like heating element 7 'as shown in FIG. 3 was manufactured in the same manner as in Example 1. However, the resin-coated wire used had an oval cross section in which the ratio of the major axis to the minor axis was 2: 1 (minor axis 1.2 mm). When the resistance value was measured in the same manner as in Example 1, the resistance value was 250 Ω / m to 340 Ω / m (average value 3
(00 Ω / m) and the variation was small. The self-control heating temperature at the time of applying 100 V is 60 ° C to 62 ° C.
° C range.

<< Comparative Example >> As a comparative example, a cord-like heating element having a conventional structure as shown in FIG. 4 is made of the same material as that of the present embodiment, and the distance between two electrode wires is the same as that of the present embodiment. Manufactured to be the same as In addition, the extrusion method and the crosslinking method were set to the same conditions.

Here, in order to compare the characteristics of the cord-like heating elements of Examples 1 and 2 and the cord-like heating element of the comparative example, the resistance change after bending was measured and evaluated. . As a test method, first, five pieces each of which was cut into 50 cm from each cord-shaped heating element were taken as a sample, and the sample was heated at 20 ° C.
Was measured. Then, as specified in the Electrical Appliance and Material Control Law [Attached Table 1, 1- (6) -H- (b): Bending strength], one end of the sample is sandwiched between two cylinders having a diameter of 5 mm, and the other end. The sample is bent 10 times per minute by suspending a 500 g weight on the sample and rotating the sample alternately left and right about 180 ° C. about the center line in the axial direction of the two cylinders without sliding the sample. The measurement was performed 100 times at a high speed, and the resistance value at 20 ° C. was measured again. The rate of change in resistance before and after the test was determined, and the results are shown in Table 1.

[0020]

[Table 1]

According to Table 1, the change in resistance value in each of the first and second embodiments is as small as + 30% or less. On the other hand, in the comparative example, the resistance value change was large, from + 60% to + 150%, and the variation was large, indicating that it was not practical.

[0022]

As described above in detail, according to the present invention, the resistance change due to bending is maintained while maintaining the excellent heating characteristics of the cord-shaped heating element using a conductive resin composition having a positive temperature characteristic as the heating element. Can be greatly reduced. This makes it possible to achieve excellent resistance value stability over a long period of time in applications to planar heating devices such as electric carpets and electric blankets that require bending.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, and is a partially cutaway perspective view of a cord-shaped heating element.

FIG. 2 is a view showing a first embodiment of the present invention and is a partially cutaway perspective view of a resin-coated wire.

FIG. 3 is a view showing a second embodiment of the present invention, and is a partially cutaway perspective view of a cord-shaped heating element.

FIG. 4 is a view showing a conventional example, and is a partially cutaway perspective view of a cord-shaped heating element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass fiber core 2 Nickel-plated copper wire 3 Electrode wire 4 Conductive resin composition having a positive temperature characteristic 5 Resin-coated wire 6 Polyethylene mixture (insulator layer) 7 Cord-shaped heating element 7 'Cord-shaped heating element

Claims (4)

(57) [Claims] 1. A plurality of resin-coated wires obtained by coating an outer periphery of an electrode wire with a conductive resin composition having a positive temperature characteristic are twisted together, and the resin-coated wires are fused and integrated with each other. A cord-like heating element characterized by the following. 2. The cord-shaped heating element according to claim 1, wherein the resin-coated wire has a major axis of 1.3 to 4 times a minor axis. . 3. A plurality of resin-coated wires obtained by coating an outer periphery of an electrode wire with a conductive resin composition having a positive temperature characteristic are twisted, and then the resin-coated wires are integrated by heat fusion. A method for producing a cord-like heating element, characterized in that: 4. The method of manufacturing a cord-shaped heating element according to claim 3, wherein the insulating layer of the cord-shaped heating element is formed and the resin-coated wires are fused and integrated with each other. How to make the body.