Planar Heating Element With Improved Temperature Distribution Uniformity

Abstract

The present invention relates to a planar heating element, and more specifically to an electrode structure for maintaining a uniform temperature distribution across the entire surface of a heating layer. The planar heating element of the present invention comprises first and second bus electrodes arranged oppositely on both sides of a heating layer, and a plurality of branch electrodes that alternately branch from the bus electrodes into the interior of the heating layer. In particular, the branch electrodes are formed such that the gap between two adjacent branch electrodes is largest at the center of the heating layer and gradually narrows from the center toward the edge. Accordingly, the electric field is relatively increased in the edge region of the heating layer to reinforce the local current density, while excessive heating is suppressed in the center, thereby maintaining a uniform temperature distribution across the entire heating layer. Therefore, the present invention has the effect of improving heating performance in a vehicle heater, preventing local thermal stress or material degradation, and providing stable and reliable heating characteristics over a long period.

Description

Technology Field

[0001] The present invention relates to a radiant heat type surface heating heater used for indoor heating in the automotive field, including electric vehicles, and more specifically, to a surface heating heater that improves the uniformity of temperature distribution across the entire heating element. Background Technology

[0002] In the automotive sector, including electric vehicles, auxiliary heating devices using surface heating that utilizes radiant heat are being utilized to heat the interior, in addition to air circulation heaters. Surface heating elements used as radiant heaters have the advantage of reaching a target temperature within a short time once power is applied, and their use is expanding with the recent proliferation of electric vehicles.

[0003] Meanwhile, in conventional planar heating element structures, temperature imbalances frequently occurred where the central part overheated while the edge parts remained at a relatively low temperature. As a result, there were issues with product performance variation and reduced reliability due to localized thermal stress concentration. The problem to be solved

[0004] The present invention aims to solve the problems of the aforementioned prior art and has the main purpose of making the temperature distribution of the entire heating element uniform by improving the electrode structure of the heating element of a planar heating heater.

[0005] Furthermore, the objectives of the present invention are not limited to those mentioned above, and other unmentioned objectives will be clearly understood from the description below. means of solving the problem

[0006] The present invention relates to a planar heating heater comprising a base film, a heating layer, and a pair of electrodes, wherein the pair of electrodes comprises a first electrode and a second electrode, and each of the first electrode and the second electrode comprises a terminal portion disposed on one side of the base film, a bus electrode portion extending from the terminal portion, and a plurality of branch electrodes formed by branching from the bus electrode portion, wherein the first bus electrode portion of the first electrode and the second bus electrode portion of the second electrode are disposed oppositely with the heating layer in between, and each of the plurality of first branch electrodes branched from the first bus electrode portion and the plurality of second branch electrodes branched from the second bus electrode portion are disposed across the heating layer, wherein the first branch electrode and the second branch electrode are alternately disposed spaced apart from each other, and the spacing between the first branch electrode and the second branch electrode adjacent to each other is formed to decrease monotonically from the center of the heating portion to both ends.

[0007] In one aspect, the planar heating element according to the present invention is preferably formed such that the spacing between adjacent first branch electrodes and second branch electrodes decreases as the distance from the center of the heating element increases, and is formed symmetrically at both ends with respect to the central part.

[0008] In addition, it is preferable that the first bus electrode part and the second bus electrode part are formed symmetrically with respect to each other.

[0009] In addition, it is preferable that the first terminal portion of the first electrode and the second terminal portion of the second electrode are spaced apart from each other on one side of the base film.

[0010] In addition, it is preferable that each of the first electrode and the second electrode is formed such that the edge region of the electrode extending from the bus electrode portion to the terminal portion has a curved profile.

[0011] Furthermore, the heating layer may be formed of a plurality of heating layers spaced apart from each other and disposed between the first bus electrode portion and the second bus electrode portion. Here, each of the plurality of heating layers is electrically connected to at least one of the plurality of first branch electrodes and at least one of the plurality of second branch electrodes, respectively.

[0012] In another aspect, the present invention provides a transport device comprising the above-described planar heating element. In addition, the present invention provides a heating device comprising the above-described planar heating element. Effects of the invention

[0013] According to the present invention, by forming the spacing of branch electrodes wide at the center of the heating layer and narrow at the edges, overheating in the center is suppressed and heating at the edges is reinforced, thereby maintaining a uniform temperature distribution across the entire surface of the heating layer. This improves the heating performance of a vehicle heater and prevents local thermal stress or material degradation, thereby increasing stability and reliability. Furthermore, since the temperature distribution is uniformized solely through shape design, uniform heating is possible without complex control circuits or sensors, and stable performance is achieved even under external conditions or wind conditions during vehicle operation, thereby simultaneously improving energy efficiency and safety. Brief explanation of the drawing

[0014] FIG. 1 is a schematic plan view showing the overall configuration of a planar heating heater according to the present invention. FIG. 2 shows a cross-section of a planar heating heater according to the present invention, and is a cross-sectional view taken along the cutting line II of FIG. 1. FIG. 3 shows a cross-section of a planar heating heater according to the present invention, and is a cross-sectional view taken along the line II-II of FIG. 1. Specific details for implementing the invention

[0015] In describing the present invention, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the invention, such detailed description is omitted.

[0016] Furthermore, when it is stated that one component is 'connected,' 'supported,' 'connected,' 'supplied,' 'transmitted,' or 'contacted' with another component, it should be understood that the connection, support, connection, transmission, or contact may be direct to that other component, or that other components may exist in between.

[0017] Furthermore, it should be noted in advance that expressions such as upper side, lower side, side, top, bottom, bottom, and side in this specification are described based on what is shown in the drawings, and may be expressed differently if the orientation of the object changes. For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted, and the size of each component does not entirely reflect its actual size.

[0018] Furthermore, terms including ordinal numbers such as first, second, etc., used in the description of this specification may be used to describe various components, but are used solely for the purpose of distinguishing said components from other components.

[0019] And, the meaning of 'comprising' as used in the specification specifies certain characteristics, regions, integers, steps, actions, elements, and / or components, and does not exclude the existence or addition of other specific characteristics, regions, integers, steps, actions, elements, components, and / or groups.

[0020] The inventor of the present invention discovered that conventional planar heating heaters suffer from significant heat loss at the edges due to convection, radiation, and contact with a support compared to the center, and are prone to the formation of cold spots. Furthermore, due to the line resistance (IR) and potential boosting of the electrode itself, current injection is uneven, resulting in a temperature imbalance of overheating in the center and low temperatures at the edges. The present invention proposes a new electrode structure to equalize the temperature distribution of the heating layer in a planar heating heater for vehicles. The following describes specific details for implementing the present invention with reference to the attached drawings.

[0021] Referring to FIGS. 1 to 3, the planar heating element according to the present invention is composed of a planar heating element in the form of a thin film and can basically be composed of a base film (10), a heating layer (20), a pair of electrodes (30, 40), and a protective layer (50).

[0022] The base film (10) is formed from a material that is flexible, electrically insulating, and heat resistant, and may use a polymer film such as polyethylene terephthalate (PET), polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), or cycloolefin copolymer (COC).

[0023] A heating layer (20) that generates heat through electrical resistance is applied to the base film, and can be formed by printing a paste mixed with conductive carbon components and additives. For example, a conductive paste can be made by mixing carbon components such as carbon nanotubes (CNT), graphene, and carbon black with additives such as surfactants in a solvent, and a heating layer can be formed on the surface of the base film using a printing method such as screen printing or offset printing. The composition and thickness of the heating layer and the content of the conductive carbon components are adjusted to suit the desired heating characteristics. In addition, the heating layer (20) may be formed as a single continuous film, or it may be divided into multiple narrow strips and formed into multiple heating cells spaced apart from each other. If the heating layer (20) is divided into multiple cells, it can disperse the heat concentrated in the center to reduce temperature variations and contribute to minimizing power consumption by controlling the overall resistance through the parallel connection effect.

[0024] The heating portion (20a) refers to a portion formed to generate heat by electrical resistance when current is applied, and the heating layer (20) is arranged between the bus electrode portions (30, 40) and between a plurality of branch electrodes (33, 43) branched from them, so that current flows. That is, the heating portion refers to a portion that generates Joule heat when current is applied and acts as a heat source for a vehicle heater, and can be implemented as the entire heating layer or as a part thereof.

[0025] A pair of electrodes consists of a first electrode (30) and a second electrode (40) formed on a base film, and these electrodes are arranged facing each other with a heating layer (20) in between. Each of the first electrode (30) and the second electrode (40) has a structure including a terminal portion (31, 41) for applying power, a bus electrode portion (32, 42) for supplying current, and a plurality of branch electrodes (33, 43) extending from the bus electrode portion toward the heating layer to distribute current to the heating layer.

[0026] The terminal portions (31, 41) of the two electrodes are formed side by side on one edge of the base film (10) and are positioned at a certain distance from each other. By arranging the terminal portions (31, 41) of the electrodes together on the same side edge, it is possible to facilitate connection with a direct current (DC) power source in vehicles, etc., and increase the freedom of wiring design. The connecting corner portion (R) leading from the terminal portion (31, 41) of each electrode to the bus electrode portion (32, 42) is formed to have a gentle curved profile instead of a sharp corner. This rounding treatment of the corner area (R) alleviates stagnation or concentration caused by a sudden change in the direction of current flow and induces the current to flow more smoothly. That is, the local width around the terminal portion (31, 41) is gradually increased to provide curvature when necessary, which alleviates current crowding in the section adjacent to the terminal portion, thereby improving the reliability of the connection part. Through this, local overheating or thermal shock can be reduced.

[0027] The bus electrode portion (32) of the first electrode (30) and the bus electrode portion (42) of the second electrode (40) are formed in a long shape facing each other on the base film (10) with the heating layer (20) in between. In particular, the bus electrode portions (32, 42) of the first electrode (30) and the second electrode (40) are manufactured in a symmetrical shape to balance the amount of current flowing in and out from the (+) electrode side and the (-) electrode side. From each bus electrode portion (32, 42), a plurality of branch electrodes (33, 43) are formed branching out in a direction facing each other, and these branch electrodes (33, 43) extend across the heating layer (20) area. The plurality of branch electrodes (first branch electrodes) (33) of the first electrode (30) and the plurality of branch electrodes (second branch electrodes) (43) of the second electrode (40) are arranged alternately and staggeredly on the heating layer. That is, the branch electrode (43 or 33) of the opposite electrode (40 or 30) is positioned adjacent to the branch electrode (33 or 43) of one electrode (30 or 40), and the branch electrodes (33, 43) of the two electrodes are arranged offset from each other, thereby providing a structure in which current can be supplied evenly to the entire area of ​​the heating layer (20). If the heating layer (20) is divided into a plurality of heating layer cells, at least one first branch electrode (33) and at least one second branch electrode (43) are connected to each heating cell, so that all heating layer cells are electrically connected between the first electrode (30) and the second electrode (40).

[0028] In the planar heating heater according to the present invention, it is preferable that the spacing between adjacent first branch electrodes (33) and second branch electrodes (43) is formed differently at the central part (C) and both ends (P1, P2) of the heating part. Specifically, the spacing (G) between adjacent first and second branch electrodes (33, 43) is formed largest in the central region (C) and has a shape in which the spacing decreases monotonically as it goes toward both ends (P1, P2). For example, the spacing (G1) at both ends (adjacent first and second branch electrodes at the outermost part of the heating part) is formed narrower than the spacing (G2) at the central part (first and second branch electrodes located at the center of the heating part) of adjacent first and second branch electrodes (33, 43). For example, when the width of the branch electrodes (33, 43) is 2 mm, the width of the bus electrode section (32, 42) is 15 mm, and the heating layer cell (20) is 6, the branch electrode spacing (G2) at the central section (C) can be formed in a shape that gradually decreases from 15 mm to 10 mm at both ends (P1, P2). In this way, by designing the spacing between two adjacent branch electrodes (33, 43) to vary by position, the distribution of current flowing along the branch electrodes (33, 43) can be adjusted to control the local current density between the branch electrodes (33, 43). In this way, by introducing pitch grading that gradually and continuously reduces the spacing between adjacent branch electrodes (33, 43) from the center of the heating part to the edge (G2->G1), and by reconstructing the local electric field / current density distribution through position-dependent control of only the spacing (G), the electric field and injection current in the edge region are relatively increased, thereby structurally compensating for heat loss at the edge. As a result, the temperature variation across the front of the heating part can be reduced and uniformity maintained.

[0029] To explain further, the spacing (G) between adjacent branch electrodes (33, 43) is formed to decrease as the distance (d) from the center of the heating part increases. At this time, it can be formed symmetrically at both ends (P1, P2) with respect to the center (C) of the heating part (20a), and the spacing between the branch electrodes can be designed as a function G(d) of the distance (d). Here, the function G(d) is a monotonically increasing function, and linear, polynomial, exponential, and step functions are all possible. Such pitch grading (G2>G1) of adjacent branch electrodes can achieve temperature uniformity throughout the heating part by eliminating the edge low-temperature phenomenon and suppressing central overheating through an increase in the local electric field E(d) and local current density as it approaches the edge region. By increasing the density of branch electrodes (number of electrodes per single length) in the edge regions (P1, P2), the effective boundary admittance Y(d) is increased, and the bus-heating layer coupling is strengthened, thereby maintaining the boundary potential and inducing flattening of the heating layer potential. In particular, the effect of the terminal potential drop caused by the distributed resistance (IR) of the bus-branch electrodes is reduced, and the power deviation between heating layer cells can be reduced. Therefore, by suppressing unnecessary overheating and compensating for the necessary edge regions, an effect of increasing the average temperature relative to the same power consumption (or reducing power consumption relative to the same average temperature) can be obtained.

[0030] The protective layer (50) is laminated to cover the front surface of the base film (10) on which the electrodes (30, 40) and the heating layer (20) are formed, thereby providing electrical insulation from the external environment and preventing thermal and mechanical damage. The material of the protective layer (50) is a material having excellent electrical insulation and heat resistance, and, for example, a heat-resistant resin can be spray-coated to form it uniformly on the front surface of the film. The protective layer (50) is integrated with the heating layer (20) so that insulation performance is maintained even at high temperatures, and is designed to ensure stable insulation performance and durability even when the heating layer is heated to a high temperature of about 300°C, especially when used as a vehicle heater.

[0031] The planar heating heater of the present invention, configured as described above, can actively control the distribution of the current applied to the entire heating layer by forming the spacing between a plurality of branch electrodes to be widest in the central part of the heating layer and gradually narrowing from the center to the edge part. Accordingly, at the edge part, the spacing between neighboring branch electrodes decreases, causing the local electric field to increase relatively; thus, the current density at the edge of the heating layer increases, thereby reinforcing the heating of the edge part where heat loss is high. Conversely, at the central part, the spacing between branch electrodes widens, causing the current density to decrease relatively, thereby suppressing excessive heating in the central part. Due to this variable spacing structure, the overall temperature distribution of the heating layer is maintained uniformly, and the phenomena of overheating in the center and low temperature at the edge are simultaneously resolved. As a result, comfortable and uniform heating performance can be achieved across the entire surface of the heater, and since heat is not concentrated in a specific area, local thermal stress and deterioration of the heating element are suppressed, enabling stable use for a long period. Furthermore, since these effects are achieved solely through the shape control of the electrode pattern, uniform heat generation can be realized without complex control circuits or additional sensors. Additionally, stable performance can be maintained even under external conditions or wind conditions during vehicle operation, significantly improving energy efficiency and reliability.

[0032] An electrode structure in which multiple branch electrodes are arranged alternately allows current to flow evenly across the entire width of the heating layer, thereby preventing heat concentrated in specific areas and ensuring uniform heat output across the entire surface. Furthermore, when the heating layer is formed with multiple separate heating cells, heat that might otherwise be concentrated in the center is dispersed, and since current is supplied to each cell in parallel, overall heating efficiency can be increased. This configuration is also advantageous for controlling the heating of only specific areas as needed, and by dispersing the heating area, local thermal stress is reduced, thereby improving the durability of the product. A structure in which the corners connecting the bus electrode and the terminal are treated with curves facilitates the smooth flow of current, preventing localized overheating at the electrode area and enhancing the reliability of the electrode. Additionally, thanks to the placement of the terminals of the two electrodes on the same side edge, the arrangement of the power connection is simplified, and wiring and assembly are facilitated when applied to vehicles. Overall, the surface heating heater of the present invention can improve the uniformity of temperature distribution, energy efficiency, and reliability through structural improvements.

[0033] The planar heating element according to the present invention can be advantageously utilized as an auxiliary indoor heating device for eco-friendly vehicles, such as electric vehicles, hybrid vehicles, and hydrogen vehicles. Furthermore, it can be applied as an indoor heating panel for railway vehicles, aircraft, ships, etc. In addition, beyond these transportation devices, it can be used as a heating panel installed on the walls, floors, and ceilings of buildings, and since it can be utilized in various fields such as medical heating devices, household electric mats, electric blankets, and industrial defrosting devices, its industrial applicability is very high.

[0034] Although preferred embodiments of the present invention have been described so far, those skilled in the art may implement the invention in modified forms without departing from the essential characteristics of the invention. Therefore, the embodiments of the present invention described herein should be considered in an illustrative rather than a restrictive sense, and the scope of the present invention is defined by the claims rather than the description above, and should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the present invention.

Claims

Claim 1 A planar heating heater comprising a base film, a heating layer, and a pair of electrodes, wherein the pair of electrodes comprises a first electrode and a second electrode, and each of the first electrode and the second electrode comprises a terminal portion disposed on one side of the base film, a bus electrode portion extending from the terminal portion, and a plurality of branch electrodes formed by branching from the bus electrode portion, wherein the first bus electrode portion of the first electrode and the second bus electrode portion of the second electrode are disposed oppositely with the heating layer in between, and each of the plurality of first branch electrodes branched from the first bus electrode portion and the plurality of second branch electrodes branched from the second bus electrode portion are disposed across the heating layer, wherein the first branch electrode and the second branch electrode are alternately disposed spaced apart from each other, and the spacing between the first branch electrode and the second branch electrode adjacent to each other is formed to decrease monotonically from the center of the heating portion to both ends. Claim 2 A planar heating heater according to claim 1, wherein the gap (G) between the adjacent first branch electrode and the second branch electrode is formed to decrease as the distance (d) in the direction from the center of the heating part toward the two ends increases, and the gap (G) is formed symmetrically at the two ends with respect to the center. Claim 3 A planar heating heater according to claim 1, characterized in that the first bus electrode portion and the second bus electrode portion are formed symmetrically with respect to each other. Claim 4 A planar heating heater according to claim 1, characterized in that the first terminal portion of the first electrode and the second terminal portion of the second electrode are spaced apart from each other on one side of the base film. Claim 5 A planar heating heater according to claim 1, wherein each of the first electrode and the second electrode is formed such that the edge region of the electrode extending from the bus electrode portion to the terminal portion has a curved profile. Claim 6 A planar heating heater according to claim 1, wherein the heating layer is formed of a plurality of heating layers spaced apart from each other and disposed between the first bus electrode portion and the second bus electrode portion. Claim 7 A planar heating heater according to claim 6, wherein each of the plurality of heating layers is electrically connected to at least one of the plurality of first branch electrodes and at least one of the plurality of second branch electrodes. Claim 8 A transport device comprising a surface heating heater according to any one of claims 1 to 7. Claim 9 A heating device comprising a surface heating heater according to any one of claims 1 to 7.

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