WO2006065061A1

WO2006065061A1 - A heating apparatus of cooking device

Info

Publication number: WO2006065061A1
Application number: PCT/KR2005/004275
Authority: WO
Inventors: Hyung Woo Kim
Original assignee: Hyung Woo Kim
Priority date: 2004-12-14
Filing date: 2005-12-13
Publication date: 2006-06-22
Also published as: KR20060067860A

Abstract

The present invention relates to a heating apparatus for a cooking device for use in cooking a food, and provides an instantaneous heating type heating apparatus for a cooking device, wherein an insulation film is mounted at a rear side of a metal plate on which a food is to be put and a thin film heater is mounted at a lower side of the insulation film, or a thin film heater is mounted at a lower side of a nonmetal plate, and low electric power is supplied to the thin film heater through metal pads so that the temperature of a surface of the metal plate can be instantaneously raised by means of heat generation of the thin film heater. According to the present invention, there are advantages in that the temperature of the thin film heater can be instantaneously raised to a high temperature with low electric power to shorten user's waiting time for cooking and to lower power consumption, the entire surface of the thin film heater with a uniform thickness generates heat at a constant temperature to prevent overheating in the heating apparatus for a cooking device and accordingly to prevent damage to a food, and the insulation film is formed on the surface of the metal plate and the thin film heater is formed on the insulation film to simplify the process of manufacturing the heating apparatus for a cooking device and to reduce the number of parts.

Description

A HEATING APPARATUS FOR COOKING DEVICE

Technical Field

[1] The present invention relates to a heating apparatus for a cooking device for use in cooking a food, and more particularly, to an instantaneous heating type heating apparatus for a cooking device, wherein an insulation film is mounted at a rear side of a metal plate on which a food is to be put and a thin film heater is mounted at a lower side of the insulation film, or a thin film heater is mounted at a rear side of a nonmetal plate (e.g., ceramic, glass), and low electric power is supplied to the thin film heater through metal pads so that the temperature of a surface of the metal plate can be instantaneously raised by means of heat generation of the thin film heater. Background Art

[2] Generally, heating apparatuses for cooking include a gas roaster, a gas oven, a convection oven, a toaster, and the like.

[3] Fig. 1 is a view illustrating an embodiment of a conventional gas roaster, Fig. 2 is a view illustrating an embodiment of a conventional gas oven, Fig. 3 is a view illustrating an embodiment of a conventional convection oven, and Fig. 4 is a view illustrating an embodiment of a conventional toaster.

[4] The gas roaster illustrated in Fig. 1 and the gas oven illustrated in Fig. 2 are used to cook a food put on a metal plate using light and heat generated by combustion of a gas, which is supplied from the outside, by means of an ignition spark; the convection oven illustrated in Fig. 3 is used to cook a food put into the oven using heat generated by a C-G heater or a halogen lamp; and a toaster illustrated in Fig. 4 is used to cook bread using heat generated by a coil by applying electricity to the coil mounted around a slot into which the bread is to be inserted.

[5] However, these prior arts have problems in that it takes a great deal of time to reach a food-cooking temperature, high electric power of several kilowatts or a large amount of gas is consumed, and a cooling rate of a heating apparatus for a cooking device is low after the supply of electric power or gas is cut off.

[6] That is, in order to cook a food by means of a gas roaster or a gas oven, a large amount of gas is needed, there is a risk of gas explosion, and it takes a great deal of time to cook a food using weak flames.

[7] In order to cook a food by means of a convection oven, a toaster or the like, it takes a great deal of time to cause a halogen lamp or a coil to generate heat. Particularly, since the halogen lamp and the coil are bulky, a heat generating rate is very slow, it takes a great deal of time to reach a food-cooking temperature, high electric power is consumed, and cooling rates of the halogen lamp and the coil are low after the supply of electric power is cut off. Disclosure of Invention

Technical Problem

[8] The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide an instantaneous heating type heating apparatus for a cooking device, wherein an insulation film is mounted at a rear side of a metal plate on which a food is to be put and a thin film heater is mounted at a lower side of the insulation film, or a thin film heater is mounted at a rear side of a nonmetal plate, and low electric power is supplied to the thin film heater through metal pads so that the temperature of a surface of the metal plate can be instantaneously raised by means of heat generation of the thin film heater. Technical Solution

[9] A heating apparatus according to an embodiment of the present invention comprises a metal plate for heating a food; an insulation film mounted at a rear surface of the metal plate to electrically insulate the metal plate and to conduct generated heat to the metal plate; a thin film heater mounted as a thin film at a lower side of the insulation film to instantaneously generate heat at a high temperature by means of its own electrical resistance of the thin film heater by receiving external electric power; metal pads mounted on one side and the other side of the thin film heater to uniformly supply the external electric power to the thin film heater; and electrical connection terminals that are in contact with the metal pads to supply the electric power to the metal pads.

[10] A heating apparatus according to another embodiment of the present invention comprises a nonmetal plate for heating a food; a thin film heater mounted as a thin film at a lower side of the nonmetal plate to instantaneously generate heat at a high temperature by means of its own electrical resistance of the thin film heater by receiving external electric power; metal pads mounted on one side and the other side of the thin film heater to uniformly supply the external electric power to the thin film heater; and electrical connection terminals that are in contact with the metal pads to supply the electric power to the metal pads.

[11] A conductive pattern may be formed on one side of the thin film heater of the heating apparatus to induce uniform heat generation of an entire surface of the thin film heater and to reduce a difference in temperature between an electrode lead-in portion of the thin film heater and a central portion of the thin film heater within a shorter period of time at an early stage of supply of electric power, and the metal pads may define a pattern such that a plurality of heating thin film cells are formed.

Advantageous Effects [12] By mounting the thin film heater as a heat generating means in a heating apparatus for a cooking device in accordance with the present invention, the temperature of the thin film heater can be instantaneously raised to a high temperature even with low electric power. Thus, there are advantages in that user's waiting time for food cooking can be shortened and power consumption can be lowered. [13] Furthermore, since the entire surface of the thin film heater with a uniform thickness generates heat at a constant temperature in the present invention, there is an advantage in that overheating can be prevented in a heating apparatus for a cooking device and thus damage to a food can be prevented. [14] Further, with the formation of the insulation film on the surface of the metal plate and the formation of the thin film heater on the insulation film, or with the formation of the thin film heater on the nonmetal plate, there are advantages in that the process of manufacturing a heating apparatus for a cooking device can be simplified and the number of parts can be reduced.

Brief Description of the Drawings [15] Figs. 1 to 4 are views showing embodiments of conventional heating apparatuses for cooking devices. [16] Figs. 5 and 6 are views showing the structures of embodiments of an instantaneous heating type heating apparatus for a cooking device using a metal plate, according to the present invention. [17] Figs. 7 and 8 are views showing the structures of embodiments of an instantaneous heating type heating apparatus for a cooking device using a nonmetal plate, according to the present invention. [18] Figs. 9 to 11 are exemplary views showing embodiments of a conductive pattern formed on one side of a thin film heater. [19] Figs. 12 to 13 are exemplary views showing embodiments of a metal pad defining a pattern on a thin film heater. [20] Figs. 14 to 16 are a view showing a heating apparatus for a cooking device to which the present invention is applied, and graphs showing measured surface temperature values of the heating apparatus, respectively.

[21] *Explanation of Reference Numerals for Main Portions in the Drawings*

[22] 21 : Metal plate 22: Insulation film

[23] 23: Thin film heater 24: Metal pad

[24] 25: Temperature sensor 26: Electrical connection terminal

[25] 27: Support 28: Conductive pattern

[26] 29: Protecting layer 30: Nonmetal plate

Best Mode for Carrying Out the Invention [27] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, details on well- known functions or constitutions relevant to the present invention will be omitted if they would make the gist of the present invention unnecessarily obscure. The terms used in the description are defined considering the functions of the present invention and may vary depending on the intention or usual practice of a user or operator. Therefore, the definitions should be made based on the entire contents of the description.

[28] Fig. 5 is a view showing the structure of an embodiment of an instantaneous heating type heating apparatus for a cooking device using a metal plate, according to the present invention. Reference numerals 21, 22, 23, 24, 25, 26 and 27 designate a metal plate, an insulation film, a thin film heater, a metal pad, a temperature sensor, an electrical connection terminal and a support, respectively. Fig. 6 is a view showing the structure of an embodiment of an instantaneous heating type heating apparatus for a cooking device using a metal plate and a thin film heater with a conductive pattern formed thereon, according to the present invention. Reference numerals 28 and 29 designate a conductive pattern and a protecting layer, respectively.

[29] Fig. 7 is a view illustrating an embodiment of the structure of a heating apparatus using a nonmetal plate, according to the present invention, wherein reference numeral 30 designates a nonmetal plate.

[30] Fig. 8 is a view illustrating another embodiment of the structure of a heating apparatus for a cooking device using a nonmetal plate and a thin film heater with a conductive pattern formed thereon, according to the present invention, wherein reference numerals 28 and 29 designate a conductive pattern and a protecting layer, respectively.

[31] In a heating apparatus for a cooking device according to the present invention, when external low electric power (e.g., 500W) is supplied to a thin film heater 23 through electrical connection terminals 26 and metal pads 24 by a user's operation for putting a power plug into an outlet in a house, the thin film heater 23 generates heat (undergoes a temperature rise) at a very high rate (i.e., a rise up to a food-cooking temperature, for example, 200⁰C), and the heat is conducted to a metal plate 21. In such a state, a user cooks a food or the like by putting the food on the metal plate 21.

[32] Furthermore, in the present invention, when the supply of the external electric power to the thin film heater 23 is cut off by a user' operation for pulling out the power plug of the heating apparatus from the outlet in the house, the thin film heater 23 is cooled (undergoes a temperature drop) at a very fast rate (i.e., a drop within a shorter period of time to a temperature value at which the user does not get burned due to the metal plate 21 of the heating apparatus), and heat is not transferred to the metal plate 21.

[33] The thickness of the metal plate 21 ranges from 0.3mm to 3mm, and the metal plate

21 is made of a metal such as aluminum or stainless steel.

[34] An insulation film 22 has a smallest thickness such that heat generated by the thin film heater 23 is conducted to a metal plate 21 at a high rate, and the insulation film is an insulation film made of ceramic materials such as alumina (aluminum oxide, Al O ) and magnesia (magnesium oxide, MgO), an insulation film made of a polymer, or an insulation film formed of a combination of the two insulation films to achieve electrical insulation between the metal plate 21 and the thin film heater 23.

[35] The insulation film 22 preferably has a small thickness enough to allow heat generated by the thin film heater 23 to be conducted to the metal plate 21 at a high rate, and the thickness of the insulation film 22 is preferably in a range of 0.5D to 500D to achieve electrical insulation between the metal plate 21 and the thin film heater 23. More preferably, the thickness of the insulation film 22 is in a range of 0.5D to 200D. The thickness of the insulation film may vary according to the material of the insulation film.

[36] Requirements for the insulation film 22 are as follows.

[37] The insulation film 22 should achieve electrical insulation between the metal plate

21 and the thin film heater 23. To achieve the electrical isolation of the thin film heater 23 supplied with external electric power, the insulation film 22 should not produce dielectric breakdown and should maintain a leakage current below 2OD when a voltage of about 100V is applied to the thin film heater 23.

[38] Additionally, the insulation film should have superior contact properties with the metal plate 21 and the thin film heater 23 such that the insulation film 22 is not physically delaminated from the metal plate 21 and the thin film heater 23 when the thin film heater 23 generates heat at a high temperature.

[39] Furthermore, the insulation film 22 should have superior surface roughness and should not chemically react with the metal plate 21 and the thin film heater 23 when the thin film heater 23 generates heat at a high temperature. That is, since bad surface roughness of the insulation film 22 affects electrical resistivity of the thin film heater 23, it is preferred that the insulation film 22 have surface roughness enough not to affect the electrical resistivity of the thin film heater 23.

[40] To satisfy the aforementioned requirements, as for the insulation film 22, the surface of the metal plate 21 may be formed with one or two or more insulation films selected among an oxidized insulation film formed by oxidizing the surface of the metal plate 21 made of a metal such as aluminum or stainless steel using an arc, an insulation film formed by coating ceramic, glass, ceramic glaze or the like on the surface of the metal plate, and a polymer insulation film formed by coating a polymer- based material such as polyimide, polyamide, Teflon or PET on the surface of the metal plate 21.

[41] An embodiment of a method for forming an oxidized insulation film will be described below.

[42] The oxidized insulation film is formed by applying external electrical energy such as an arc to the metallic surface of a metal plate 21, which is made of a metal such as aluminum (Al), beryllium (Be), titanium (Ti) or stainless steel and dipped in an alkaline electrolyte, so that an electrochemical reaction occurs between metal atoms of the surface of the metal plate 21 and external oxygen to convert properties of the surface of the metal plate 21 into an oxidized film.

[43] Al O , ZrO , Y O or the like is used for the oxidized insulation film, and the

2 3 3 2 3 oxidized insulation film may be formed on the metal plate by means of plasma spray coating and the like. Hereinafter, one embodiment of a process of forming the oxidized insulation film on the metal plate will be described below.

[44] The concentration of an alkaline electrolyte filled in a bath is evaluated, a metal plate 21 made of aluminum is dipped into the alkaline electrolyte filled in the bath in a state where a lead wire is connected to the metal plate 21 made of aluminum so that external power can be supplied to the metal plate 21 made of aluminum, and the external power is supplied to the metal plate 21 made of aluminum so as to oxidize the surface of the metal plate 11 made of aluminum.

[45] As radio frequency AC power is strongly applied to the metal plate 21 made of aluminum through the process of forming an oxidized insulation film, an arc is instantaneously generated on the surface of the metal plate 21 made of aluminum. Thus, an oxidized insulation film that is a dense oxidized film having a very low pinhole concentration is formed on the surface of the metal plate 21 made of aluminum.

[46] Through such a process of forming an oxidized insulation film, an aluminum oxide can be formed on the surface of a metal plate 21 made of aluminum, a titanium oxide can be formed on the surface of a metal plate 21 made of titanium, and a beryllium oxide can be formed on the surface of a metal plate 21 made of beryllium.

[47] In the meantime, a polymer insulation film is formed by coating a polymer-based material capable of securing electrical insulation with a uniform thickness on the surface of the metal plate 21 made of a metal.

[48] Particularly, such a polymer insulation film should not produce thermal deformation when heat is generated by the thin film heater 23. Further, when the thin film heater 23 generates heat at a high temperature, the polymer insulation film should have a superior contact property such that the polymer insulation film is not physically de- laminated from the metal plate 21 and the thin film heater 23, and also have superior surface roughness such that the polymer insulation film does not chemically react with the metal plate 21 and the thin film heater 23.

[49] One embodiment of a process of forming a polymer insulation film will be described below.

[50] A polymer insulation film is formed using a liquid organic polymer material that is to be uniformly coated on the surface of the metal plate 21 made of a metal.

[51] Here, coating methods include a spin coating method, a spray coating method, a dipping coating method, and a screen printing method.

[52] Furthermore, polymer materials include polyimide-based materials, polyamide- based materials, Teflon-based materials, paint-based materials, silver-ston, Tefzel-s, epoxy, rubber, and UV-sensitive materials.

[53] For example, one embodiment of a process of coating a polyimide-based material on the metal plate 21 by means of the spray coating method is as follows.

[54] The metal plate 21 is cleaned with acetone, IPA (isopropyl alcohol) or the like, the polyimide-based material is sprayed onto the metal plate 21 while the cleaned metal plate 21 is rotated at a high speed (e.g., 2,000rpm or more), and the polyimide-based material coated on the surface of the metal plate 21 is subjected to heat treatment.

[55] Through the process of forming a polymer insulation film by means of the spray coating method, a polymer insulation film having superior thermal stability and a glassy temperature (GT) of 300⁰C or more is formed on the surface of the metal plate 21.

[56] Furthermore, by slowly cooling the polyimide-based material during the process of heat treatment of the polyimide-based material, adhesiveness of the polymer insulation film to the metal plate 21 is improved. By coating the polymer-based material on the surface of the metal plate 21 during the spray coating process, thickness uniformity of the polymer insulation film is enhanced and the polymer insulation film has a very low pinhole concentration, thereby preventing the occurrence of current leakage.

[57] Meanwhile, a double insulation film comprising an oxidized insulation film and a polymer insulation film can be formed by forming the oxidized insulation film on the surface of a metal plate 21 made of a metal and uniformly coating a polymer-based material on the oxidized insulation film, or by coating the polymer-based material on the surface of the metal plate made of a metal and forming the oxidized insulation film on the coated polymer-based material.

[58] The total thickness of the double insulation film comprising the oxidized insulation film and the polymer insulation film is smaller than the sum of the thickness of a resulting oxidized insulation film solely formed on the surface of the metal plate 21 and the thickness of a resulting polymer insulation film 21 solely formed on the surface of the metal plate 21, and the double insulation film can minimize dielectric breakdown as compared with each of the single oxidized insulation film and the single polymer insulation film.

[59] Here, the dielectric breakdown in the oxidized insulation film is mainly caused by pin holes formed in the oxidized insulation film, and the dielectric breakdown of the oxidized insulation film may be produced when external electric power supplied to the thin film heater 23 is transmitted into the pin holes.

[60] The dielectric breakdown in the polymer insulation film is mainly caused by generation of air bubbles due to application of a liquid PR upon formation of the polymer insulation film, and the dielectric breakdown may be produced in portions of the polymer insulation film where the air bubbles existed after the polymer insulation film is solidified.

[61] Therefore, it is preferred that the occurrence of dielectric breakdown, which is inherent in the oxidized insulation film or the polymer insulation film, be complemented by the double insulation film comprising the oxidized insulation film and the polymer insulation film.

[62] The thickness of the insulation film 22 preferably ranges from 0.5D to 500D, more preferably 0.5D to 200D for efficient heat conduction (the thickness of the insulation film varies according to the material of the insulation film). The insulation film 22 has a dielectric breakdown voltage of 1,000V or more, and a leakage current of 2OD or less upon application of a voltage of 100V. The insulation film 22 should be formed such that it is not delaminated respectively from the metal plate 21 and the thin film heater 23 when the thin film heater 23 generates heat (in a thermal cycle).

[63] The thin film heater 23 is mounted on the insulation film 22 in a form of a thin film with a thickness of 0.05D to several tens D (e.g., 0.05D to 30D). When external electric power (DC or AC power) is supplied to the thin film heater 23 through the metal pads 24, the thin film heater 23 performs joule heating by means of its own electrical resistance.

[64] Here, due to thin film characteristics of the thin film heater 23, i.e., a small volume of the thin film heater 23, a heating rate and cooling rate of the thin film heater 23 are very high, temperature obtainable by the heat generation of the thin film heater 23 due to its own electrical resistance can exceed 500⁰C, and the thin film heater 23 enables a very fast temperature rise contrary to a conventional sheath heater.

[65] Requirements for the thin film heater 23 are as follows.

[66] Although the thin film heater 23 enables a rapid temperature rise due to the thin film characteristics as compared with a conventional sheath heater, the thin film heater 23 may have a very large current flux due to the thin film characteristics. Thus, the thin film heater 23 is required to have electrically, thermally and chemically resistant properties.

[67] That is, the thin film heater 23 should electrically have high heater strength. Only when the thin film heater has high resistance to continuously applied energy, it can maintain a long life span.

[68] Furthermore, the thin film heater 23 should be mounted on the insulation film 22 such that separation of the insulation film 22 or delamination between the metal plate 21 and the insulation film 22 due to the heat generation of the thin film heater 23 does not occur.

[69] Moreover, in the thin film heater 23 that is a device subjected to continuous thermal shocks, substantial changes in a resistance value of the thin film heater due to the thermal shocks should not be produced.

[70] Further, since there may be a case where the thin film heater 23 generates heat at a high temperature if it is exposed directly to air (oxygen), substantial increases in the resistance value of the thin film heater due to oxidation should not be produced.

[71] To satisfy the aforementioned requirements, the thin film heater 23 may be made of a single metal (e.g., Ta, W, Pt, Ru, Hf, Mo, Zr, Ti, etc.) with a high melting point, a binary metal alloy (e.g., TaW, etc.) with a combination of the above metals, a binary metal-nitride (e.g., WN, MoN, ZrN, etc.) combined with a metal-nitride, a binary metal- suicide (e.g., TaSi, WSi, etc.) combined with a metal-silicide, or a thick conductive paste such as Ag/Pd.

[72] Further, the thin film heater 23 has a thickness of several tens D or less (e.g., 0.05D to

3OD, wherein the thickness of the thin film heater varies according to the material of the thin film heater).

[73] Particularly, to ensure that the temperature of the thin film heater 23 rises instantaneously, i.e., to minimize time taken until the thin film heater itself is heated to a high temperature, it is necessary to make the heat capacity of the thin film heater 23 itself very low.

[74] That is, the heat capacity of the thin film heater 23 is expressed as a function with a parameter of thickness. The thinner the thin film heater 23 is, the smaller the heat capacity thereof is. On the other hand, the thinner the thin film heater 23 is, the shorter the lifespan of the thin film heater may be.

[75] Therefore, the present invention can deduce an optimum thickness range of the thin film heater 23 through various simulations and experiments to satisfy two requirements for the instantaneous rise of the temperature of the thin film heater 23 and the extension of the lifespan of the thin film heater 12. On the other hand, although there is a slight difference in thickness according to the material of the thin film heater 23, the difference is merely a minute difference.

[76] That is, the optimum thickness of the thin film heater 23 is deduced based on the following formula.

[77] [Formula 1] [78] p=Rsxt

[79] where p (resistivity) is a specific resistivity value of the material of the thin film heater 23, Rs (sheet resistance) is a surface resistance value of the thin film heater 23, and t (thickness of film) is the thickness of the thin film heater 23. Meanwhile, it can be seen that the thickness and specific resistivity value have a proportional relationship therebetween.

[80] Therefore, the optimum thickness range of the thin film heater 23 (e.g., 0.05D to 30D) is deduced according to the material of the thin film heater 23 corresponding to characteristics of each product by performing simulation with the aforementioned parameters as input data considering the resistivity value range of the material of the thin film heater 23.

[81] The thin film heater 23 is formed on the insulation film 22 by means of vacuum evaporation methods, thick film screen printing methods, or the like. The vacuum evaporation methods include physical vapor deposition (sputtering, reactive sputtering, co-sputtering, evaporation and E-beam) methods, and chemical vapor deposition (low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD)) methods.

[82] A protecting layer 29 is preferably formed at a lower side (surface) of the thin film heater 23 to protect the thin film heater 23 from external foreign substances (e.g., moisture, etc.). Here, the heater protecting layer is formed of inorganic heater protecting layer materials such as SiNx and SiOx and organic heater protecting layer materials such as polyimide, polyamide, Teflon and PET.

[83] The protecting layer may be formed on a thin film heater with a conductive pattern formed thereon as well as a thin film heater with no conductive pattern formed thereon.

[84] Meanwhile, as illustrated in Figs. 9 to 11, a conductive pattern 28 having lower electric resistance and higher thermal conductivity than thin film heaters with various shapes and configurations can be formed on one side of the thin film heater.

[85] In a case where a thin film heater on which a conductive pattern is not formed is used, uniform temperature distribution may not be achieved on the entire surface of the thin film heater or the thin film or the insulation film may be damaged by means of an overheating phenomenon occurring at a portion of the thin film heater, due to a temperature difference generated between an electrode lead-in portion of the thin film heater and a central portion of the thin film heater at an early stage of supply of electric power.

[86] In order to prevent the overheating phenomenon and induce uniform heat generation on the entire surface of the thin film heater within a shorter period of time at the early stage of supply of electric power, it is possible to form conductive patterns with various shapes and configurations on one side of the thin film heater, as illustrated in Figs. 9 to 11.

[87] Furthermore, the formation of the conductive pattern on the thin film heater can improve a production yield over a single thin film heater on which a conductive pattern is not formed upon production of the thin film heater. This is because the single thin film heater on which a conductive pattern is not formed may suffer from degradation in the quality of the entire resistor even due to a minute thickness difference in or damage such as a scratch to a portion of the entire thin film heater, resulting in drop in the production yield of the thin film heater.

[88] The metal pads 24 are mounted on one side and the other side of the thin film heater so as to uniformly supply the external electric power to the thin film heater 23. Here, since the metal pads 24 are formed on the one side and the other side of the thin film heater 23, respectively, a uniform (constant) current density can be achieved on the entire surfaces of the thin film heater 23.

[89] Particularly, it is preferred that the width of the metal pads 24 be identical with or larger than that of the thin film heater 23 to provide a uniform current density on the entire surfaces of the thin film heater 23.

[90] Meanwhile, the metal pads 15 in the present invention can define patterns at different positions with a variety of configurations, sizes and numbers such that a plurality of heating thin film cells are formed as illustrated in Figs. 12 and 13.

[91] Additionally, the metal pads 24 are made of a metal such as Al, Au, W, Pt, Ag, Ta,

Mo or Ti to secure temperature stability of the metal pads 24, to prevent resistance increase due to oxidation, and to prevent separation thereof from the thin film heater 23 when the thin film heater 23 generates heat.

[92] A temperature sensor 25 performs a well-known function of sensing temperature resulting from heat generated by the thin film heater 23.

[93] Electrical connection terminals 26 are preferably formed on a circuit board (not shown in the figure) in the heating apparatus for a cooking device.

[94] A heating apparatus for a cooking device according to another embodiment of the present invention comprises a nonmetal plate 30 for heating a food; a thin film heater 23 mounted as a thin film at a lower side of the nonmetal plate to instantaneously generate heat at a high temperature by means of its own electrical resistance of the thin film heater by receiving external electric power; metal pads 24 mounted on one side and the other side of the thin film heater to uniformly supply the external electric power to the thin film heater; and electrical connection terminals 26 that are in contact with the metal pads to supply the electric power to the metal pads.

[95] As illustrated in Figs. 7 and 8, in the case where the nonmetal plate 30 is used instead of the metal plate, it is not necessary to provide an insulation film between the nonmetal plate and the thin film heater. [96] Similarly to the case where the metal plate is used, the one side of the thin film heater 23 may be formed with a conductive pattern 28 for ensuring uniform heat generation on the entire surface of the thin film heater within a shorter period of time at an early stage of supply of electric power and for preventing the occurrence of an overheating phenomenon at an electrode lead-in portion of the thin film heater as well as a heater protecting layer 29 for protecting the thin film heater 23 from external foreign substances.

[97] Furthermore, the metal pads 24 can define a pattern such that a plurality of heating thin film cells are formed in the same manner as the case where the metal plate is used.

[98] A nonmetal plate is made of thermally enhanced plastics, heat resistant resins, ceramics, glass and earthenware capable of resisting to a temperature of at least 25O⁰C.

[99] Fig. 14 shows a heating apparatus for a cooking device to which the present invention is applied, Fig. 15 illustrates a graph showing measured changes in the surface temperature of the heating apparatus with time when an electric power of 50 watts is applied to the heating apparatus for the cooking device shown in Fig. 14, and Fig. 16 illustrates a graph showing measured changes in the surface temperature when varying power is applied for 10 seconds to the heating apparatus for the cooking device shown in Fig. 14. Meanwhile, it should be noted that numerical values illustrated in Figs. 14 to 16 are numerical values obtained in one embodiment of a heating apparatus for a cooking device, and the numerical values may be deduced as different results according to resistance values, thicknesses and materials of respective components such as the thin film heater, the conductive pattern formed on the thin film heater, the insulation film, the metal pads and the metal plate.

[100] As illustrated in Fig. 15, it can be seen that a saturation characteristic is represented at 287⁰C after passage of a predetermined period of time when an electric power of 50 watts is applied.

[101] As illustrated in Fig. 16, it can be seen that the surface temperature linearly increases for 10 seconds with varying electric power.

[102] Additionally, an optimum product can be produced by differently applying resistance values, thicknesses, materials and the like of respective components such as the thin film heater, the conductive pattern, the insulation film, the metal pads and the metal plate in consideration of product requirements for a heating apparatus for a cooking device so as to reduce time required to reach a surface temperature and power consumption corresponding to product characteristics.

[103] As other embodiments of the present invention, the aforementioned instantaneous heating type heating apparatus for a cooking device can be mounted on a gas roaster, a gas oven, a convection oven, a toaster and the like as well as cooking equipment such as a pot, a frying pan and an electronic pot. Although the present invention has been described in connection with the preferred embodiments, the embodiments of the present invention are only for illustrative purposes and should not be construed as limiting the scope of the present invention. It will be understood by those skilled in the art that various changes and modifications can be made thereto within the technical spirit and scope defined by the appended claims.

Claims

[1] An instantaneous heating type heating apparatus for a cooking device, comprising: a metal plate (21) for heating a food; an insulation film (22) mounted at a rear surface of the metal plate to electrically insulate the metal plate and to conduct generated heat to the metal plate; a thin film heater (23) mounted as a thin film at a lower side of the insulation film to instantaneously generate heat at a high temperature by means of its own electrical resistance of the thin film heater by receiving external electric power; metal pads (24) mounted on one side and the other side of the thin film heater to uniformly supply the external electric power to the thin film heater; and electrical connection terminals (26) that are in contact with the metal pads to supply the electric power to the metal pads.

[2] The heating apparatus as claimed in claim 1, wherein a conductive pattern (28) is formed on the one side of the thin film heater to induce uniform heat generation throughout an entire surface of the thin film heater.

[3] The heating apparatus as claimed in claim 1, wherein the metal pads (24) define a pattern such that a plurality of heating thin film cells are formed.

[4] An instantaneous heating type heating apparatus for a cooking device, comprising: a nonmetal plate (30) for heating a food; a thin film heater (23) mounted as a thin film at a lower side of the nonmetal plate to instantaneously generate heat at a high temperature by means of its own electrical resistance of the thin film heater by receiving external electric power; metal pads (24) mounted on one side and the other side of the thin film heater to uniformly supply the external electric power to the thin film heater; and electrical connection terminals (26) that are in contact with the metal pads to supply the electric power to the metal pads.

[5] The heating apparatus as claimed in claim 4, wherein a conductive pattern (28) is formed on the one side of the thin film heater to induce uniform heat generation throughout an entire surface of the thin film heater.

[6] The heating apparatus as claimed in claim 4, wherein the metal pads (24) define a pattern such that a plurality of heating thin film cells are formed.

[7] The heating apparatus as claimed in any one of claims 1 to 6, wherein a protecting layer (29) is formed at a lower side of the thin film heater (23) to protect the thin film heater from foreign substances.

[8] The heating apparatus as claimed in any one of claims 1 to 6, wherein the thin film heater (23) is made of any one of a single metal, a binary metal alloy combined with the single metal, a binary metal-nitride combined with a metal- nitride, a binary metal- suicide combined with a metal-silicide, and a thick conductive paste.

[9] The heating apparatus as claimed in any one of claims 1 to 6, wherein the metal pads (24) are configured such that the width of the metal pads is identical with or larger than that of the thin film heater to supply electric power of a uniform current density to the thin film heater (23), and the metal pads are made of any one of Al, Au, W, Pt, Ag, Ta, Mo and Ti that have temperature stability during heat generation and avoid resistance increase and physical delamination due to oxidation.

[10] The heating apparatus as claimed in any one of claims 1 to 6, wherein the insulation film (22) is at least one selected among an oxidized insulation film formed by oxidizing the surface of the metal plate (21) using an arc, a polymer insulation film formed by coating a polymer on the surface of the metal plate (21), and a double insulation film formed by forming the oxidized insulation film and the polymer insulation film on the surface of the metal plate (21).

[11] The heating apparatus as claimed in claim 10, wherein the insulation film has a dielectric breakdown voltage of 1,000V or more and has a leakage current of 2OD or less when a voltage of 100V is applied thereto.

[12] The heating apparatus as claimed in claim 10, wherein the oxidized insulation film is formed of any one of an aluminum oxide, a beryllium oxide or a titanium oxide, and the polymer of the polymer insulation film is any one of polyimide, polyamide, Teflon, paint, silver-ston, tefzel-s, epoxy and rubber.

[13] The heating apparatus as claimed in claim 12, wherein the polymer is coated on the surface of the metal plate by means of any one of a spin coating method, a spray coating method, a dipping coating method and a screen printing method.