JPH0521144A - String-like heating element - Google Patents

Abstract

PURPOSE:To provide a heating element which maintains sensor properties and safe action features even when it is composed of a heat sensitizing material which does not have a rapid-melting property. CONSTITUTION:A heating element comprises core materials 3, 4, an electrode 1 wound thereto, a heat sensitizing layer 5 coated thereto, an electrode 2 wound thereto, and an enveloping insulating layer 6. The core materials 3, 4 are composed of a composite of materials with different heat deformation rates, for example, fiber threads 3 and metal wires which substantially deform within a certain range of temperatures (alias form memorization alloy wire). The heat sensitizing layer 5 consists of a material having a polyvinyl-chloride-group resin as a base resin, Therefore, this constitution allows, at abnormally high temperatures, the core materials 3, 4 to deform the entire heating element, causing short between the electrodes 1, 2 to operate a safety circuit. Thus, this constitution provides a very reliable heating element which allows its heat sensitizing material to be selected from a wide range of options, has sensor properties with a very variable impedance, and maintains a safe operation function at abnormally high temperatures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element used for an electric carpet, an electric blanket or the like, and more particularly to a material constitution of a core material of a string-shaped heating element.

[0002]

2. Description of the Related Art A heating element used for an electric carpet, an electric blanket, or the like, as shown in Japanese Patent Application Laid-Open No. 2-54885 and FIG. In general, the electrode 2 is spirally wound on top of this, and the jacket insulating layer 6 is covered from thereover. Here, the core yarn 3 is made of a yarn made of a single material such as polyester fiber or aromatic polyamide fiber, and the heat-sensitive layer 5 is mainly made of polyamide resin or polyvinyl chloride resin. Was used. A heating element of a type in which the heating element has both a heating resistor and a temperature sensor (also called a heater / sensor integrated type heating element)
When the heat sensitive layer is a material that causes impedance change in response to temperature change, the two electrodes 1 and 2 are short-circuited to operate the safety circuit when the heating element becomes abnormal temperature. In order to achieve this, it was also required at the same time that the material had a sharp melting characteristic in a certain temperature range.

[0003]

In the structure of the conventional heating element, and in the heating element of the above-mentioned heater / sensor integrated type, as described above, the heat sensitive layer has two characteristics, the impedance change characteristic and the steep melting characteristic. is necessary. When this heating element is used in a high capacity heater such as an electric carpet, a material having a high operating temperature of the heat sensitive layer and a high heat resistant temperature is required. However, regarding the current heat-sensitive layer material, the polyvinyl chloride-based material is excellent as a sensor material because the impedance change corresponding to the temperature change is large, but since it does not have a sharp melting property, it does not sandwich the heat-sensitive layer. However, since the two electrodes cannot be short-circuited and the safety circuit cannot be operated, there is an unsatisfactory aspect as a heater material. Also, although polyamide-based materials have steep melting characteristics, the impedance changes with temperature changes are relatively small, and the heat-resistant temperature is lower than that of polyvinyl chloride, which makes them unsuitable for high-capacity heaters. Had. That is, it has been difficult to obtain a material that is sufficiently satisfactory for the heat-sensitive layer of the heater / sensor integrated type heating element.

It is an object of the present invention to provide a heating element having a high heat resistant temperature, which has the structure of the heating element to make up for the drawbacks of the heat-sensitive layer material of the heating element and which has excellent sensor characteristics and also has the melting function.

[0005]

In order to achieve this object, a heating element according to the present invention comprises a core material, electrodes provided outside the core material, a heat sensitive layer provided outside the core material, and an outer insulation layer. The core material is composed of a plurality of materials having different thermal deformation rates.

[0006]

In the above structure, since the core material is composed of a plurality of materials having different thermal deformation rates, the core material itself becomes large due to the difference in thermal deformation rate (heat shrinkage rate) when the heating element rises to an abnormal temperature. Deform. On the other hand, even the heat-sensitive layer does not have a steep heat-melting property, but is softened because it is a thermoplastic resin. When the core material is largely deformed in the softened state of the heat-sensitive layer, the two electrodes sandwiching the heat-sensitive layer reach a short-circuited state. That is, the same effect as when the heat-sensitive layer has a steep heat-melting property is obtained.

[0007]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the structure of a string-shaped heating element, and a core material is a core thread 3 made of polyester fiber and an alloy material (commonly called shape memory alloy) 4 that largely changes in shape at a certain temperature. , A first electrode 1 made of copper or a copper alloy material is spirally wound around the first electrode 1, and from above,
A heat sensitive layer 5 made of a polyvinyl chloride resin as a main material and an organic electrolyte added thereto is coated, and a second electrode 2 also made of a copper or copper alloy material is spirally wound on the heat sensitive layer 5. It has a structure of covering the outer insulation layer 6 from above. Here, the shape memory alloy 4 is constituted by a thin metal wire set so as to have a linear shape in a normal use temperature range and a saw blade shape in a temperature range of 150 ° C. or higher. The shape memory alloy is generally Ni-Ti, Cu-Zn-Al, or the like, but Fe- is used as a material having a high deformation temperature range.
There is Pd. On the other hand, the heat-sensitive layer 5 is composed of a polyvinyl chloride resin as a main material, and an organic electrolyte which imparts ionic conductivity to the heat-sensitive layer 5, and a material to which an antioxidant, a stabilizer and a plasticizer are added. The electrodes 1 and 2 are made of copper or copper alloy wire in a foil shape and are spirally wound in a direction intersecting with each other. The electrode 1 is an electrode for detecting a temperature signal from the heat-sensitive layer 5 (hereinafter referred to as “electrode”). , And the electrode 2 is used as a heating resistor (hereinafter referred to as a heating line). When the electrical connection of the part related to the heating element is shown in FIG.
The (heat generating line) is connected to AC 100V via a relay contact, the electrode 1 is connected to the control circuit unit 9 at one end thereof, and at the same time, is connected to AC 100V via the diodes and the resistors 10a and 10b at both ends. As shown in this circuit diagram, when the signal line 1 and the heating line 2 are short-circuited, the resistance 10a
And 10b, a current can flow to generate heat, and if this resistance and the thermal fuse are thermally connected, the thermal fuse can be melted and the current to the heating wire 2 can be stopped when a short circuit occurs. Therefore, if this phenomenon is utilized to cause a short circuit between the signal line 1 and the heating line 2 when the temperature of the heater main body rises abnormally, it can function as a safety circuit. The above-mentioned material of the heat-sensitive layer 5 shows a large impedance change with respect to temperature change, and also has high heat resistance stability of impedance characteristics and is excellent as a sensor material, but since it uses polyvinyl chloride resin as a base material, It does not have a sharp melting characteristic in a certain temperature range. However, the core material of the present invention is a composite of the fibrous thread 3 and the shape memory alloy 4, so that the core material is greatly deformed as shown in FIG. 3 at a certain temperature or higher. At this time, since the heat-sensitive layer 5 is considerably softened at a high temperature, the signal line 1 and the heating line 2 are short-circuited due to the large deformation of the core material. Therefore, even if a material having no steep melting characteristics is used for the heat-sensitive layer, as a result of the large thermal deformation of the core portion, the same effect as the melting function can be obtained.

The case where the shape memory alloy wire is used as the core material has been described above. However, since it is sufficient to cause a large thermal deformation, a method of using a composite of yarns having different heat shrinkage rates in the core material is used. is there. The structure is shown in FIG. A core thread 3 made of polyester fiber and a core thread 4 made of aromatic polyamide fiber are twisted together and used as a core material. The other components are the same as those in the first embodiment. Here, the polyester fiber is a material having a relatively large heat shrinkage, which varies depending on the processing conditions at the time of wire production, but has a heat shrinkage of 5 to 8% in a temperature range of about 150 ° C, while the aromatic polyamide fiber has a small heat shrinkage. It is 1% or less even in the 150 ° C range. When such yarns having greatly different heat shrinkage rates are twisted together, the deformation as shown in FIG. 3 in the case of the above-mentioned Example 1 can be brought about in the temperature range of about 150 ° C. In the embodiment, the case where the yarns are twisted with each other has been described, but the same result can be obtained when the two yarns are simply bundled.

[0009]

As described above, the present invention comprises a core material, an electrode, a heat sensitive layer, an electrode, and an insulation layer, and the core material is made of two or more materials having different thermal deformation rates. Since it is configured, the heating element undergoes a large deformation when it reaches a high temperature range and can short-circuit between the two electrodes, and the material of the heat sensitive layer has a sharp melting characteristic in a certain temperature range. It is possible to operate the safety circuit in the abnormal temperature range even if there is no material. Therefore, in the heater / sensor integrated type heating element, the heat-sensitive layer material of the heating element can be selected relatively freely, and the heating element with excellent sensor characteristics as in the conventional example and having a high melting temperature is provided. can do.

[Brief description of drawings]

FIG. 1 is a structural diagram showing an embodiment of a heating element of the present invention.

FIG. 2 is a structural diagram of a second embodiment of the same heating element.

FIG. 3 is a structural diagram of the heating element in a high temperature state.

FIG. 4 is a circuit configuration diagram of a heater using the heating element.

FIG. 5 is a structural diagram of a conventional heating element.

[Explanation of symbols]

1, 2 electrodes 3 First core material 4 Second core material 5 heat sensitive layer 6 Insulation layer

Claims (4)

[Claims] 1. A core material, an electrode wound around the core material, a heat-sensitive layer covering the electrode, an electrode wound around the heat-sensitive layer, and an outer insulation layer. A string-shaped heating element composed of two or more materials having different thermal deformation rates. 2. The cord-shaped heating element according to claim 1, wherein the core material is composed of a fibrous material made of a single material or a composite material of polyester or polyamide, and an alloy material whose shape changes greatly at a certain temperature. . 3. The cord-shaped heating element according to claim 1, wherein the core material is composed of two fibers, a polyester fiber and an aromatic polyamide fiber. 4. The cord-shaped heating element according to claim 1, wherein the heat-sensitive layer is made of a material containing polyvinyl chloride resin as a main material and an organic electrolyte added thereto.