JPH0533509B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a positive resistance temperature coefficient heating element (hereinafter referred to as a PTC heating element) useful as a warming appliance, a general heating device, etc.

Prior Art It has been known that a resistor composition in which conductive fine powder is dispersed in a crystalline polymer exhibits remarkable PTC characteristics, and a heating element with self-temperature control using this composition has been developed. Attempts have been made to construct a The advantages of this method are that the shape of the resistor is excellent and any shape can be easily obtained, it has excellent flexibility, and the resistance value can be adjusted over a wide range. It has been used as a low power density sheet heating element and a long flexible heating element.

However, when a large power density is required, a heat equalizing plate is essential to make the temperature distribution of the heating element itself uniform, and as shown in Figure 6, the conventional PTC heating element A PTC resistor 2 whose main component is a material in which conductive fine powder is dispersed in a crystalline polymer is closely attached to an electrically insulating substrate 1 made of an alumina sintered body with good quality. Countermeasures such as providing a pair of electrodes 3 and 4 were taken. (Japanese Patent Publication No. 55-40161) Problems to be Solved by the Invention In such conventional high power density PTC heating elements, a heat equalizing plate is indispensable, and without a heat equalizing plate, local abnormal heat generation due to voltage concentration occurs. phenomenon occurs, and normal heat generation characteristics cannot be obtained. Further, even if a heat equalizing plate is provided, there is a limit to the thermal conductivity of an electrically insulating material such as an alumina sintered body, and there is not enough margin to prevent voltage concentration from occurring. Furthermore, ceramic materials such as alumina sintered bodies are not flexible and do not have sufficient adhesion to the heated object, and may not be suitable for the size and shape of an integral heating element due to restrictions on maximum processing dimensions. I've reached my limit. As an alternative material to ceramic-based heat equalizer plates, heat equalizer plates made by laminating high thermal conductivity metal plates such as aluminum and electrically insulating plates such as polyester film have been devised; If the thickness of the electrically insulating plate is set to , it is difficult to obtain a heat equalization effect superior to that of the alumina sintered body, and it is not possible to obtain a large power density. Thus, traditional high power density
PTC heating elements had a lot of problems caused by the heat equalizing plate, and there was no room for further development.

In order to solve the problems all at once, it was important to introduce a PTC heating element that did not need to rely on a heat equalizing plate. As a result of our studies focusing on this point, we found that the width of the area where the voltage concentration phenomenon occurs is several millimeters or less, and if we install a pair of electrodes within that area, we can reduce the voltage gradient between the electrodes. It was estimated that the heat distribution would be almost uniform. As a result of further investigation, it was found that if fine comb-shaped electrodes were provided on the surface of the PTC resistor, the area occupied by the electrodes would become considerably large, and there would be almost no effective heat generating area, making it impossible to obtain as high a power density. Ta. As a solution to this problem, we introduced a method of applying voltage in the thickness direction of the PTC resistor, and as a result of repeated experiments, no extreme voltage concentration phenomenon was observed if the thickness of the resistor was 5 mm or less. Also, the thickness is 1
mm or less, 2W/cm ² for large heat dissipation loads
No abnormalities were observed even when the temperature increased by 60 degrees. From this result, thin-walled PTC with a thickness of 5 mm or less
It was concluded that a heating element in which electrodes are provided on both sides of the resistor has a high heat diffusion ability between the electrodes, and essentially no voltage concentration phenomenon can occur. However, although the phenomenon of resistor destruction due to voltage concentration does not occur,
For large heat loads, unexpectedly large voltage gradient distribution and temperature distribution exist between the electrodes of the heating element, causing local thermal deterioration of the resistor composition and heat transfer loss. Body thickness is at least 3
It has been found that it is less than mm, preferably less than 1 mm. The heating element with this structure has a very simple configuration and is free from the various constraints imposed by heat soaking plates, so it was expected to make a big leap forward in terms of performance, structure, and construction method.

Based on this conclusion, we begin a concrete study.
PTC resistor compositions were far from being practical due to numerous problems related to their withstand voltage characteristics, ensuring insulation distance, terminal processing methods, mounting structure, heat extraction methods, etc. As an alternative, ceramic-based PTC resistors such as barium titanate sintered bodies were investigated, and the results showed that they have excellent power density, heat resistance, withstand voltage characteristics, and thermal conductivity, and are ideal for constructing small heating units. It was determined that there were no major problems. However, since it is a sintered body, it has no flexibility, making it extremely difficult to process large areas or long lengths. Large area, uniform heat generation, flexibility,
It was difficult to satisfy the functions required for continuous long length processing. Judging from these points, ceramic-based
We abandoned the PTC resistor and confirmed that the only way was to solve the problems that would arise when using an organic PTC resistor. Hereinafter, specific problems to be solved by the present invention will be explained.

A heating element that applies a voltage in the thickness direction of a thin PTC resistor that is mainly composed of organic material and has a thickness of 3 mm or less, preferably 1 mm or less, has a unit area of It has the advantage of being able to set a large amount of output per hit. However, on the other hand, if the state of heat transfer to the heated object is incomplete or unstable, sufficient output may not be obtained, or
There were problems such as unstable output. The reason for this is the self-temperature control function, which is a phenomenon unique to PTC heating elements set to high output; if the amount of heat taken from the heating element is small, the output is extremely limited, and if the amount of heat taken from the heating element is large, the output increases significantly. However, this is due to the disadvantage that the variable band is very large. Overcoming these shortcomings,
In order to obtain stable high output, it is necessary to remove as much heat from the PTC heating element as possible, lower the temperature of the PTC resistor as much as possible, and obtain more heat generation. It was necessary to have a sturdy structure and prevent the temperature of the heating element from fluctuating. However, the higher the output, the smaller the heating element, so even if you try to make it fit into the slight unevenness of the surface of the object to be heated, it will not be completed due to the small deformation span. Only close contact was possible. And furthermore,
Due to thermal distortion due to heat generation and cooling of the heating element and deformation of shape over time due to long-term use, the adhesion becomes even more imperfect, and not only will the desired output not be obtained, but the output will be insufficient. It was stable and had a large fluctuation range. As a countermeasure for this, a method such as wrapping a heating element around the object to be heated and tightening it with a band from the outside may be considered, but if the object to be heated is flexible, or has a recessed or flat surface, This method cannot be used in cases of heat, and there is no effective countermeasure.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a thin strip-shaped positive electrode with a thickness of 1 mm or less, the main component of which is a composition in which conductive fine powder is dispersed in a crystalline polymer. A heating element consisting of a resistance temperature coefficient resistor, a pair of electrode bodies provided to apply a voltage in the thickness direction of the resistor, and the heating element is hermetically covered with a heat-adhesive layer. Consists of a thin exterior material with an adhesive run-up part that widens from the covering part in the width direction,
The heat transfer surface side of the exterior material is formed into a shape that follows a plane, and the other side is molded into a shape that follows the outer surface of the heat generating element, and the adhesion run-up part of the exterior material is more flexible than the central part of the heat generating element. It is much more sexual.

Effect The effect of this technical means is as follows.
In other words, a PTC heating element that applies voltage in the thickness direction of a thin PTC resistor has a large output per unit area, and the heating element itself can be made smaller, but the amount of heat it handles is extremely large, and it is not stable enough to compensate for that amount of heat. It is necessary to form a transmission path for the heat generated.
In order to form the transmission passage, the periphery of the heating element is hermetically covered with a heat-sealing layer, and a thin exterior material having a close contact run-up portion that widely extends in the width direction from the covering portion is provided. The effect is that the part that is hermetically sealed around the heating element via a heat-adhesive layer has been miniaturized, so the span has become smaller, and it takes a considerable amount of pressure to bring it into close contact with the heated surface by itself. Although necessary, the flexible portion as a whole, including the adhesion run-up portion, serves as a guide plate and can be brought into close contact with a relatively weak force. In addition, as an additional benefit, this adhesion run-up part greatly contributes to heat diffusion and can reduce the thermal resistance of the part that is in close contact with the heated object, and it can greatly improve the adhesion and strength when fixing with adhesive etc. It can also be improved. These synergistic effects form a stable heat transfer path with low thermal resistance, and as a result, high output can be stably obtained.

Example Embodiments will be described below based on the accompanying drawings.

(Example 1) Fig. 1 is a comprehensive explanation of the present invention. In Fig. 1, 5 has a thickness of 0.3 mm and a width of 5 mm.
The PTC resistors 6 and 7 are a pair of copper plate electrodes configured to be in close contact with both surfaces of the PTC resistor 5. Reference numeral 8 denotes a soft vinyl chloride sheathing material surrounding the PTC heating element consisting of the PTC resistor 5 and electrodes 6 and 7, and numeral 9 denotes a 15 mm wide flat surface made of a soft vinyl chloride sheet integrally bonded to the sheathing material 8. It is a member. Since the planar member 9 has a larger bending rigidity than the exterior material 8, the deformed shape of the planar member 9 can be reflected on the exterior material 8. On the other hand, since the width dimension of the planar member 9 is set to 15 mm, the load required to give a certain amount of deflection is small, and while the distortion of the planar member 9 itself is corrected, the flat member 9 is substantially flat with a slight curvature. It can be easily placed along the surface of the object to be heated. As a result, the portion of the sheathing material 8 also deforms following the sheathing material 9, so that it comes into close contact with the surface of the object to be heated. The flat member 9 also functions as a heat diffusion plate, reducing the thermal resistance of the contact surface with the object to be heated, which tends to cause unstable heat transfer. Furthermore, when fixing with an adhesive or the like, not only the adhesive strength but also the adhesive strength overcomes the stress caused by the spring back of the exterior material 8, and has the function of preventing air spaces from forming and floating. Due to the synergistic effect of these functions, the thermal resistance of the heat transfer path from the PTC resistor 5 to the heated object can be significantly reduced, and fluctuations due to installation conditions etc. are eliminated, resulting in a stable thermal connection state. can be obtained.

FIG. 2 also provides supplementary explanation of the present invention. In FIG. 2, the heating element portion consisting of the PTC resistor 5 and electrodes 6 and 7 is the same as in FIG. 1, and 10 is the same as in FIG. Exterior material 8 and planar member 9
It is a planar member that has the following functions and is made by extrusion molding of semi-rigid vinyl chloride. The planar member 10 has a tapered cross-sectional shape in order to ensure flexibility and to transmit the deformation state at the end face to the heating element portion. This configuration is characterized by its simple structure and excellent workability.

FIG. 3 also provides a supplementary explanation of the present invention. In FIG. 3, the PTC resistor 5, electrodes 6 and 7 are the same as in FIG. 1, and 11 is an exterior material made of resin film. It is processed to cover the side and top surfaces of the PTC resistor 5. Reference numeral 12 denotes a flat member made of a resin film, and the resin films 11 and 12 are integrally formed by heat-sealing the joining portion thereof. Further, the thickness of the resin film 12 is the same as that of the resin film 11.
The bending stiffness ratio is set to 1.5, and flatness is maintained with a bending stiffness ratio of 3 or more. By using a resin film, this structure enables thin wall processing, which is not easy with extrusion processing. Note that the planar member 12 can be made of not only a resin film but also a highly rigid inorganic material such as mica.

FIG. 4 also explains an embodiment of the present invention. In FIG. 4, the PTC resistor 5 and the electrode portions 6 and 7 are the same as those in FIG. It is a thin-walled exterior material that is sealed and covered and has an adhesion run-up part that widens widely from the covering part in the width direction, and the lower surface is a flat member, and has the same structure as shown in FIG. 2. A heat-sealing layer 13 made of a resin with a low melting temperature is filled between the electrodes 6 and 7 and the flat member 10. The effect of the thermal adhesive layer 13 is that it acts as a cushion material during processing;
Even if priority is given to finishing the flat member 10 into a flat surface, processing distortion can be prevented from remaining in other parts. Furthermore, an air layer between the PTC resistor 5 and the planar member 10 is eliminated, which has the effect of reducing thermal resistance. Furthermore, in addition to filling, the heating element can be completely integrated by providing adhesive properties.

Example 2 In FIG. 5, the PTC resistor 5 and electrodes 6 and 7 are the same as in FIG. 14 is a heat-sealing layer bonded to the resin film exterior material 15;
It is processed to cover the side and top surfaces of the PTC resistor 5. Reference numeral 16 denotes a heat sealing layer bonded to the resin film flat member 17, and the exterior material 15 and the plane member 17 are integrally constructed via the heat sealing layers 14 and 16. The planar member 17 maintains a planar shape with twice the wall thickness and eight times the bending rigidity of the exterior material 15. The features of this configuration are the thin exterior material 15 and the flat member 1, which were difficult to extrude.
7, and at the same time, the heat-sealing layers 14 and 16 allow the resistor 5 to be processed.
The advantage is that the exterior material 15 and the planar member 17 can be integrated.

Effects of the Invention As described above, according to the present invention,
This makes it possible to significantly improve the heat transfer characteristics when a PTC heating element is attached to an object to be heated, and to reduce the variable factors as much as possible. The PTC heating element itself, which applies voltage in the thickness direction of the thin PTC resistor, has a structure that can withstand high output, but in order to extract the output effectively and stably,
The present invention is extremely effective and indispensable.

As a result, the following effects are achieved.

(1) The adhesion when bonded to the object to be heated is dramatically stabilized, which improves heat transfer characteristics and allows stable output of high output.

(2) There is no unbalanced point between the heat generation and heat radiation of the heating element when it is attached to the object to be heated, so there are no discontinuous points in the resistance value, resulting in extremely long life and highly reliable positive resistance temperature coefficient heat generation. Can form a body.

(3) Although the flexibility of the heat generating element is small, the blank area is sufficiently large and flexible so that it can flexibly respond to slight irregularities on the mounting surface, resulting in good adhesion processability. . PTC has much higher output even when mounted, and has excellent flexibility and workability.
A heating element can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view supplementary explanation of the PTC heating element of the first embodiment of the present invention, FIG. 2 is a partial perspective view supplementary explanation of the PTC heating element of the first embodiment of the present invention, and FIG. The figure is a partial perspective view for supplementary explanation of the PTC heating element according to the first embodiment of the present invention, FIG. 4 is a partial perspective view of the PTC heating element according to the first embodiment of the present invention, and FIG. FIG. 6 is a partial perspective view of a PTC heating element of the second embodiment, and FIG. 6 is a partial perspective view of a conventional PTC heating element. 5...PTC resistor, 6,7...electrode, 8,1
1, 15... Exterior material, 9, 10, 12, 17...
Planar member, 3, 14, 16...thermal adhesive layer.

Claims (1)

[Claims] 1. A thin band-shaped positive resistance temperature coefficient resistor with a thickness of 1 mm or less whose main component is a composition in which conductive fine powder is dispersed in a crystalline polymer, and a voltage is applied in the thickness direction of the resistor. A thin-walled exterior material having a heat generating element consisting of a pair of electrode bodies provided to protect the heat generating element, and an adhesive run-up part that seals and covers the circumference of the heat generating element through a heat-adhesive layer and widely spreads in the width direction from the covering part. The heat transfer surface side of the exterior material is shaped so that it follows a plane, and the other side is shaped so that it follows the outer surface of the heat generating element, and the adhesion run-up part of the exterior material is formed so that it is smaller than the central part of the heat generating element. A positive resistance temperature coefficient heating element with much greater flexibility.