JP2014089798A - Planar heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-safety planar heating element superior in durability free from heating unevenness with a simple structure.SOLUTION: The planar heating element includes: a sheet-like polymer resistor 11; at least a pair or more of electrodes 12 disposed on one side of the polymer resistor 11 for supplying the power to the polymer resistor 11; electrical insulation base materials 13a and 13b that cover the polymer resistor 11 and the electrode 12 at both sides thereof; connection sections connecting a heating part of the polymer resistor 11, the polymer resistor 11 and the electrodes 12; and heat-conductive noncombustible materials 14a and 14b covering the outsides of the electrical insulation base materials 13a and 13b at both sides. Thus, the planar heating element 9 which is superior in the durability with high safety free from heating unevenness is achieved.

Description

  The present invention relates to a planar heating element that heats a battery of an automobile or the like mainly in a cold region.

  Conventionally, in an environment where, for example, a battery mounted on an automobile is -30 ° C or lower, the engine can be started due to a significant decrease in the battery's electric capacity even when the battery liquid freezes or the battery liquid does not freeze. Therefore, there is considered a means for heating the battery itself with an auxiliary heat source to prevent a decrease in battery capacity.

  As shown in FIGS. 5 to 6, this type of planar heating element includes a radiator plate 103 on which ceramic PTC heating elements 101 and 102 are mounted and a heat insulating heat insulating material 104 arranged on the outer periphery of the battery 105. The battery 105 is heated as a power source (see Patent Document 1).

  Also, a configuration using a PTC heating element made of a flexible substrate coated with a resin-based PTC heating element in which conductive powder and resin are mixed instead of a ceramic PTC heating element has been proposed (Patent Document 2). reference).

  Furthermore, in a planar heating element composed of a resin-based PTC heating element, a proposal for improving the practicality by devising an electrode configuration for supplying electric power to a polymer resistor (see Patent Document 3) and heat conduction to an unheated object Proposals for improvement (see Patent Document 4) have also been made.

Japanese Patent Laid-Open No. 9-190841 Japanese Patent Laid-Open No. 9-213459 JP 2008-213661 A Japanese Utility Model Publication No. 4-74893

  In recent years, in order to cope with energy saving and CO2 reduction, automobiles are increasingly interested in hybrid cars that combine an engine and a motor, electric cars that use only a motor as a power source, and the like. The batteries installed in these automobiles require a large electric capacity in order to drive the motor, and the battery is also housed in a case as a battery module in which several battery cells are connected in series. By connecting a large number of battery units in series (and connecting them in parallel if necessary), a high-voltage and large-capacity battery is realized.

Even in these batteries, reduction of the electric capacity becomes a problem in a severe low-temperature environment as in the past, and it is conceivable to heat the batteries by means as described in Patent Document 1 and Patent Document 2. However, in the configuration in which the ceramic PTC heating elements 101 and 102 are arranged as the heating elements on the heat radiating plate 3 as shown in FIGS. When heating a battery consisting of a battery unit having a multi-layer unit structure used in a hybrid vehicle or an electric vehicle, a temperature difference occurs between the battery units, so that the electrical capacity of the battery as a whole may be insufficiently restored. There was sex. Further, in the configuration shown in Patent Document 2, a planar heating element type PTC heater is used as a heating source. However, since the PTC heating element on the comb-shaped electrode part is a non-heating part, Due to the positional relationship with each battery unit, heating unevenness occurs between the battery units, so that the same problem as described above remains. In addition, in a planar heating element type PTC heater, when temperature unevenness occurs in the planar heating element itself, a portion where the temperature of the heating element is high has a high resistance value. Abnormal overheating (hot spot phenomenon) may occur, and the life of the planar heating element may be impaired due to temperature unevenness.

  In addition, the planar heating element described in Patent Document 3 has a configuration in which electrodes are disposed on both surfaces of a sheet-like thin film resistor, and the electrode itself acts as a soaking plate, so that the soaking effect of the planar heating element. Although the electrode spacing is very narrow, there is a concern about short-circuiting between electrodes for high voltage power supplies such as hybrid cars and electric cars, even though this is not a problem with low voltage power supplies such as 12V systems. The

  On the other hand, the heater for heat insulation described in Patent Document 4 has a heat conductive material attached to one surface of an insulating material that covers the planar heating element from both sides, thereby improving the thermal conductivity of the surface in contact with the object to be heated. However, since the heat conduction material is provided only on one side, if the heating value of the heater is large, it is easy to keep warm by the insulating material, and the resistance value rises due to the self-temperature rise of the planar heating element, resulting in resistance The calorific value per unit area of the body is limited and it is difficult to increase the output.

  In addition, the planar heating element having the PTC characteristic has a positive temperature coefficient in which the resistance value increases as the temperature rises. As a result, self-temperature control works, and safety can be achieved without using other temperature control means. Although it is often used as a high heater, in the sheet heating element in which electrodes are patterned as in Patent Document 4, if a break occurs in the electrode part in contact with the resistor, the resistor near the broken electrode is There was a problem that it acted as a substitute for the electrode and caused abnormal overheating by concentrating current on a part of the resistor.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to provide a planar heating element that has an easy configuration, has little heating unevenness, has excellent durability, and high safety.

  In order to solve the above problems, a sheet-like polymer resistor, at least a pair of electrodes disposed on one side of the polymer resistor and supplying power to the polymer resistor, the polymer resistor, and the polymer resistor An electrically insulating substrate covering the electrode from both sides, a heat generating portion of the polymer resistor, and a connecting portion between the polymer resistor and the electrode are thermally conductive from both sides of the electrically insulating substrate. The structure is covered with non-combustible material. As a result, it is possible to provide a planar heating element with less unevenness in heating and excellent durability and high safety.

  According to the planar heating element of the present invention, the heat conductive incombustible material provided on both surfaces of the polymer resistor can enhance the soaking effect of the planar heating element, thereby suppressing heating unevenness. Further, since heat exchange can be performed from both sides of the sheet heating element, it is possible to suppress the temperature rise of the sheet heating element itself, and the amount of heat generated per unit area of the sheet heating element can be improved. Furthermore, the outer surface of the polymer resistor is covered with a thermally conductive incombustible material from both sides, so that the possibility of ignition is extremely low even if the polymer resistor is abnormally heated, and a highly safe planar heating element. Can be provided.

The perspective view of the planar heating element in Embodiment 1 of this invention Battery cell connection diagram in the battery module on which the sheet heating element according to Embodiment 1 of the present invention is mounted 1 is an exploded perspective view of a sheet heating element according to Embodiment 1 of the present invention. Sectional drawing of the principal part of the planar heating element in Embodiment 1 of this invention Side view of a conventional sheet heating element Sectional view of the main part of a conventional sheet heating element

  The present invention provides a sheet-like polymer resistor, at least a pair of electrodes disposed on one side of the polymer resistor and supplying power to the polymer resistor, and the polymer resistor and the electrode on both sides. The electrically insulating base material covered from the heat generating portion of the polymer resistor and the connecting portion between the polymer resistor and the electrode are covered with a thermally conductive non-combustible material from both outside surfaces of the electrically insulating base material. A heat conductive non-combustible material provided on both surfaces of the polymer resistor, because both the surfaces of the polymer resistor are covered with a heat conductive non-combustible material from the outside of the electrically insulating substrate. Increases the soaking effect of the sheet heating element and allows more efficient heat exchange, making it possible to increase the output of the sheet heating element per unit area and making the outer surface of the sheet heating element nonflammable from both sides. By doing so, even in the unlikely event of abnormal heat generation, surface heat generation is highly safe But it is possible to provide.

  In addition, it is preferable that a metal sheet is used for the thermally conductive noncombustible material of the planar heating element. Thereby, since a soaking effect and a nonflammable effect can be obtained with a thin material, a planar heating element that is thin, inexpensive, and excellent in safety can be provided.

  Further, it is more preferable that one of the heat conductive non-combustible materials of the planar heating element is thicker than the thickness of the heat conductive non-combustible material on the other surface. As a result, when the thickness and material of the electrically insulating base material provided on both sides of the polymer resistor are different, the thermal conductivity efficiency imbalance to the thermally conductive incombustible material is different from the thickness of the thermally conductive incombustible material. By providing this, it becomes possible to correct the balance of the heat dissipation effect from both sides of the planar heating element.

  Further, in the planar heating element, one outer surface of the electrically insulating substrate is configured to be flat, the thermally conductive noncombustible material in contact with the flat surface of the electrically insulating substrate is a rigid metal sheet, and the other heat More preferably, the conductive incombustible material is composed of a metal foil. As a result, even in a planar heating element having a curved surface, it is possible to provide a planar heating element that is excellent in the soaking effect and is less likely to be deformed by an external force and excellent in reliability.

(Embodiment 1)
A planar heating element according to an embodiment of the present invention will be described with reference to FIGS.

  1 is a perspective view of the heating element, FIG. 2 is a connection diagram of battery cells in a battery module in which the heating element is mounted, FIG. 3 is an exploded perspective view of the heating element, and FIG. FIG. A battery 6 that is an object to be heated is configured by stacking battery modules 8 in which a plurality of battery cells 7 are connected in series. A planar heating element 9 is fixed to the battery 6 so as to face one surface of the battery 6 with a gap provided between the battery 6 and the support member 10.

The sheet heating element 9 is a thin film (about 100 μm) polymer resistor 11, which is arranged in parallel on one side of the polymer resistor 11 and is electrically connected to the polymer resistor 11. The pair of electrodes 12, the polymer resistor 11 and the electrode 12 are covered from both sides, the electrically insulating bases 13a and 13b made of a material such as polyethylene terephthalate, and the heat generating region of the polymer resistor 11 as well as the entire polymer. Thermally conductive incombustible materials 14a and 14b are disposed outside the electrically insulating base materials 13a and 13b so as to cover the connection portion between the resistor 11 and the electrode 12. The polymer resistor 11 is made of a material having PTC (Positive Temperature Coefficient) characteristics, and the resistance value of the polymer resistor 11 increases as the temperature rises, and has a self-temperature adjusting function that stabilizes at a predetermined temperature. ing. The electrically insulating bases 13a and 13b are coated with a hot melt material on the joint surface with the polymer resistor 11, and are bonded to the polymer resistor 11 and the electrode 12 by laminating. The heat conductive incombustible materials 14a and 14b are made of a metal material having excellent heat conductivity. On one surface side where the polymer resistor 11 and the electrode 12 are joined and have a convex portion, a flexible metal foil (such as an aluminum tape) is attached as a heat conductive non-combustible material 14a, and the other surface. A metal sheet (a thin plate such as aluminum) is attached to the side (that is, the flat surface side) as the heat conductive non-combustible material 14b. The battery 6 is provided with a temperature detection means 15, and the power supplied to the planar heating element 9 is controlled by the control means 16 in response to temperature information from the temperature detection means 15. Further, a battery storage box 17 is disposed so as to surround the periphery of the battery 6 and the planar heating element 9.

  In the planar heating element configured as described above, the operation and action will be described below.

  The control means 16 starts energization of the sheet heating element 9 when the battery temperature monitored by the temperature detection means 15 falls below a preset temperature condition, and the sheet heating element when the battery 6 reaches a predetermined temperature. Shut off the power to 9.

  The heat generated in the polymer resistor 11 is transmitted to the heat conductive non-combustible materials 14a and 14b through the electrically insulating base materials 13a and 13b. Here, since the polymer resistor 11 and the electrode 12 are joined to each other and the electrically insulating base material 13a forms a convex portion, a flexible metal foil is attached to the surface, so that the electrically insulating base material is attached. Adhesiveness with 13a is ensured. Further, in the planar heating element, not only one surface side but also the other flat surface side is provided with a rigid metal sheet, so that soaking is promoted from both sides of the planar heating element 9. Therefore, local power concentration (hot spot phenomenon) generated due to temperature unevenness of the planar heating element 9 is less likely to occur, and the reliability and durability of the planar heating element 9 can be improved. The heat transmitted to the heat conductive non-combustible materials 14a and 14b is indirectly heated by directly heating the battery 6 by radiation or convection from the surfaces of the heat conductive non-combustible materials 14a and 14b or by heating the air in the battery storage box 17. Thus, the battery 6 can be warmed.

  Further, by imparting rigidity to the thickness of the heat conductive non-combustible material 14b (metal sheet) to such an extent that deformation does not occur when handling parts, a deformation stress is applied to the junction with the polymer resistor 11 and the electrode 12. Therefore, it is possible to provide a highly reliable planar heating element with increased resistance to handling stress during assembly. In addition, since the distance between the electrodes 12 can be set widely, the risk of short-circuit between electrodes can be eliminated even when used as a high-voltage-specific planar heating element, and a safe and easy-to-use planar heating element is provided. I can do it. Furthermore, since the heat conductive incombustible materials 14a and 14b are disposed so as to cover both surfaces of the polymer resistor 11, in the unlikely event, a part of the electrode 12 in contact with the polymer resistor 11 is disconnected, Even if current concentration occurs in the polymer resistor 11, the planar heating element 9 does not burn, so that a highly safe planar heating element can be provided.

  As described above, in the planar heating element according to the present invention, the temperature unevenness of the planar heating element is improved and the cooling efficiency of the planar heating element is improved, and the heat generation amount per unit area of the planar heating element is improved. In addition, it is possible to provide a safe and reliable planar heating element even with a high-voltage power supply, so that it can be widely applied as a heater for other heating as well as battery heating in hybrid cars and electric cars for cold regions. be able to.

6 Battery 8 Battery Module 9 Planar Heating Element 11 Polymer Resistor 12 Electrode 13a, 13b Electrical Insulating Base Material 14a, 14b Thermal Conductive Nonflammable Material

Claims (4)

Sheet-like polymer resistor, at least one pair of electrodes disposed on one side of the polymer resistor and supplying power to the polymer resistor, and electrical insulation covering the polymer resistor and the electrode from both sides A surface configured to cover the conductive substrate, the heat generating portion of the polymer resistor, and the connection portion between the polymer resistor and the electrode with a thermally conductive non-combustible material from both outer surfaces of the electrically insulating substrate Heating element. The planar heating element according to claim 1, wherein the heat conductor non-combustible material uses a metal sheet. 3. The planar heating element according to claim 1, wherein one of the heat conductive incombustible materials is configured to be thicker than the thickness of the heat conductive incombustible material on the other surface. One outer surface of the electrically insulating substrate is configured to be flat, the thermally conductive noncombustible material in contact with the flat surface of the electrically insulating substrate is provided with a rigid metal sheet, and the other thermally conductive noncombustible material is The planar heating element according to claim 1, which is made of a metal foil.