WO2006065064A1

WO2006065064A1 - A sterilizing apparatus

Info

Publication number: WO2006065064A1
Application number: PCT/KR2005/004278
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: KR100472871B1

Abstract

The present invention relates to a hot water supplying apparatus for heating water in sterilizers, rapid water heaters, steam cleaners, boilers, water purifiers, washing machines, dishwashers and the like, and/or to a sterilizing apparatus for killing bacteria propagating in water, and provides an instantaneous heating type water heating/sterilizing apparatus for supplying hot water or killing bacteria propagating in water by instantaneously heating the water to a high temperature with heat generated by a thin film heater mounted inside or outside a tube. According to the present invention, there are advantages in that time and electric power required for heating water can be reduced, time to reach a bacteria-killing temperature can be shortened and power consumption can be lowered, high resistant bacteria can be killed due to generation of hot bubbles in water, the water heating/sterilizing apparatus can be prevented from being overheated, and the process of manufacturing the water heating/sterilizing apparatus can be simplified and the number of parts can be reduced so that production costs of a water purifier, a sterilizer, a boiler or the like can be lowered.

Description

A STERILIZING APPARATUS

Technical Field

[1] The present invention relates to a hot water supplying apparatus for heating water in sterilizers, rapid water heaters, steam cleaners, boilers, water purifiers, washing machines, dishwashers and the like, and/or to a sterilizing apparatus for killing bacteria propagating in water (hereinafter, the hot water supplying apparatus and the sterilizing apparatus will be collectively referred to as a "water heating/sterilizing apparatus"). More particularly, the present invention relates to an instantaneous heating type water heating/sterilizing apparatus for killing bacteria propagating in water by instantaneously heating the water to a high temperature with heat generated by a thin film heater mounted inside or outside a tube. Background Art

[2] Generally, a water heating/sterilizing apparatus is used to heat water as well as to kill bacteria propagating in the water, and is installed in water purifiers, sterilizers, boilers and the like.

[3] Fig. 1 is a sectional view showing an embodiment of a conventional water heating/ sterilizing apparatus.

[4] As shown in Fig. 1, in the conventional water heating/sterilizing apparatus, a sheath heater (or a C-G heater) 11 is mounted around an outer wall of a tube (heating tube) 10, and a power connection terminal 12 for use in supplying external electric power to the sheath heater 11 is mounted.

[5] In the conventional apparatus described above, when electric power is supplied to the power connection terminal 12, the sheath heater 11 generates heat by means of its own electrical resistance and heats the tube 10, thereby indirectly heating water that flows through a flow passage inside the tube 10. Accordingly, hot water can be provided or bacteria propagating in the water can be killed to some extent.

[6] However, the aforementioned prior art has problems due to structural characteristics of the sheath heater 11. That is, since the sheath heater is not compact but bulky and accordingly the apparatus is also bulky, there are problems in that the large volume of the sheath heater 11 causes a great deal of time to be consumed in reaching a temperature at which water can be indirectly heated, high electric power is consumed to raise the temperature of the bulky sheath heater 11 to a high temperature, and a cooling rate of the sheath heater 11 is low after the supply of electric power to the water heating/sterilizing apparatus is cut off.

[7] Meanwhile, instead of the sheath heater 11, a halogen lamp may be mounted as a heat generating means of the water heating/sterilizing apparatus. However, in this case, there is a disadvantage in that heat loss becomes large due to indirect heating by means of radiation from the halogen lamp. Disclosure of Invention

Technical Problem

[8] The present invention is conceived to solve the aforementioned problems and to meet the aforementioned needs. An object of the present invention is to provide an instantaneous heating type water heating/sterilizing apparatus for killing bacteria propagating in water by instantaneously heating the water to a high temperature with heat generated by a thin film heater mounted inside or outside a tube. Technical Solution

[9] An instantaneous heating type water heating/sterilizing apparatus according to an aspect of the present invention for achieving the object comprises a heat generating device mounted within a tube to rapidly heat or sterilize a liquid by instantaneously applying heat to the liquid in a flow passage defined in the tube, wherein the heat generating device includes a lowermost substrate for mounting a heater thereon; an insulation film formed around the substrate to provide electrical insulation; a thin film heater formed as a thin film on the insulation film to instantaneously generate heat by means of resistive heat generation when external electric power is supplied to a side of the thin film heater, so that the heat can be transferred directly to the liquid in the flow passage; a metal pad mounted at an end of the thin film heater to uniformly supply the external electric power to the side of the thin film heater; and a protecting layer formed around the thin film heater and the metal pad to protect the thin film heater and the metal pad from the liquid flowing through the flow passage.

[10] An instantaneous heating type water heating/sterilizing apparatus according to another aspect of the present invention for achieving the object comprises a heat generating device mounted within a tube to rapidly heat or sterilize a liquid by instantaneously applying heat to the liquid in a flow passage defined in the tube, wherein the heat generating device includes an insulation film formed around an outer surface of the tube to provide electrical insulation between the tube and the heat generating device; a thin film heater formed as a thin film on the outer surface of the tube with the insulation film interposed therebeween to instantaneously generate heat by means of resistive heat generation when electric power is supplied to a side of the thin film heater, so that the generated heat can be transferred directly to the tube through the insulation film; a conductive pattern having lower electric resistance and higher thermal conductivity than thin film heater and formed on the one side of the thin film heater to induce uniform heat generation throughout 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; and a metal pad mounted at an end of the thin film heater to uniformly supply the external electric power to the side of the thin film heater.

[11] In a still further aspect of the present invention, the apparatus may employ a conductive pattern, which has lower electric resistance and higher thermal conductivity than thin film heater and is formed on one side of the thin film heater, for inducing uniform heat generation of an entire surface of the thin film heater and reducing 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 upon supply of electric power; and metal pads defining 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 for a water heating/ sterilizing apparatus 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 water can be heated with low electric power within a shorter period of time, time to reach a bacteria-killing temperature can be shortened, and power consumption can be lowered.

[13] Furthermore, since the present invention employs the thin film heater with a uniform thickness and the conductive pattern for inducing uniform heat generation of the entire surface of the thin film heater and preventing the occurrence of an overheating phenomenon at a portion of the thin film heater at an early stage of supply of electric power, so that the entire surface of the thin film heater can generate heat with a minute temperature difference, there are advantages in that monitoring only a portion of the thin film heater using a temperature sensor can prevent the water heating/sterilizing apparatus from being overheated and thus damage to the water heating/sterilizing apparatus can be prevented.

[14] Further, with the formation of the insulation film on the substrate and the formation of the thin film heater on the insulation film in the present invention, there are advantages in that the process of manufacturing a water heating/sterilizing apparatus can be simplified and the number of parts can be reduced and accordingly it is possible to lower production costs for a water purifier, a sterilizer, a boiler or the like.

[15] Furthermore, since the volume of the thin film heater is small in the present invention, there are advantages in that a temperature rise and drop can be achieved for a shorter period of time and heat loss can be simultaneously reduced. Brief Description of the Drawings

[16] Fig. 1 is a sectional view showing an embodiment of a conventional water heating/ sterilizing apparatus.

[17] Figs. 2 and 3 are sectional views showing various embodiments of an instantaneous heating type water heating/sterilizing apparatus according to the present invention.

[18] Fig. 4 is a view showing the structure of an embodiment of a heat generating device in Figs. 2 and 3.

[19] Fig. 5 is a sectional view showing another embodiment of the instantaneous heating type water heating/sterilizing apparatus.

[20] Figs. 6 to 8 are exemplary views of thin film heaters with conductive patterns formed thereon.

[21] Figs. 9 and 10 are exemplary views of thin film heaters with metal pads formed thereon.

[22] Figs. 11 to 13 are a view showing an embodiment of a water heating/sterilizing apparatus to which the present invention is applied, and graphs showing measured surface temperature values of the water heating/sterilizing apparatus, respectively.

[23] Figs. 14 to 16 are a view showing another embodiment of a water heating/sterilizing apparatus to which the present invention is applied, and graphs showing measured surface temperature values of the water heating/sterilizing apparatus, respectively.

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

[25] 20: Tube 31: Substrate

[26] 32: Insulation film 33: Thin film heater

[27] 34: Metal pad 35: Heater protecting layer

[28] 36: Conductive pattern 37: Protecting layer

Best Mode for Carrying Out the Invention

[29] 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.

[30] Figs. 2 and 3 are sectional views showing various embodiments of an instantaneous heating type water heating/sterilizing apparatus according to the present invention, wherein a heat generating device is mouned inside a tube. In other embodiments of the present invention, the tube with a thin film heater mounted therein may be variously configured as a cylindrical tube, a rectangular tube or the like depending on characteristics of a product.

[31] Fig. 2 shows an instantaneous heating type water heating/sterilizing apparatus with a structure in which a heat generating device 21 is mounted on an inner wall surface at a side of a tube (heating tube) 20, and Fig. 3 shows an instantaneous heating type water heating/sterilizing apparatus with a structure in which heat generating devices 21 are mounted on inner wall surfaces at one and the other sides of a tube 20, respectively.

[32] Alternatively, a plurality of heat generating devices 21 may be mounted on an inner wall surface at a side of the tube (heating tube) 20, and a plurality of heat generating devices 21 may be mounted on each of inner wall surfaces at one and the other sides of the tube 20.

[33] Meanwhile, Figs. 2 and 3 show that bubbles are generated in water when the heat generating device 21 instantaneously generates heat to a high temperature (e.g., under 400⁰C to 500⁰C).

[34] A single heat generating device or a plurality of heat generating devices 21 may be mounted inside the tube 20 in the present invention. However, since a certain portion of water (liquid) flowing through a flow passage may be delivered in a state where heat for sterilizing the water at high temperature has not been applied thereto, it is preferred that the size, number and arrangement of the heat generating devices 21 be determined in consideration of the inner volume of the tube 20 so that the heat can be transferred throughout the interior of the tube 20.

[35] In the meantime, even though Figs. 2 and 3 show various embodiments of the mounting positions of the heat generating devices 21, the mounting positions of the heat generating devices 21 may be changed by combining these embodiments in different manners. For example, the mounting positions of the heat generating devices may be determined such that one heat generating device 21 is mounted at a water inflow portion, i.e., on an upper and inner wall surface at a side of the tube 20, while another heat generating device 21 is mounted on a lower and inner wall surface at the other side of the tube 20.

[36] Further, it is preferred that the heat generating devices 21 mounted on the inner wall surfaces at one and the other sides of the tube 20 have a structure capable of generating heat toward a central portion of the tube 20.

[37] Fig. 4 is a view showing the structure of an embodiment of the heat generating device in Figs. 2 and 3. A direction (a direction designated by arrows in Figs. 2 and 3) in which heat generated by the heat generating device 21 is radiated toward the interior of the tube is generally referred to as an "upward direction of the heat generating device 21."

[38] As shown in Fig. 4, the heat generating device 21 comprises a lowermost substrate 31 for mounting a thin film heater 33 thereon; an insulation film 32 formed around the substrate 31 to provide electrical insulation between the substrate 31 and the thin film heater 33; a thin film heater 33 formed as a thin film on the insulation film 32 to instantaneously generate heat by means of its own electrical resistance by recieving external electric power through metal pads 34; a conductive pattern 36 formed on one side of the thin film heater 33 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 upon supply of electric power; metal pads (so-called metal electrodes) 34 mounted respectively on one side and the other side of the thin film heater 33 so as to uniformly supply the external electric power to the thin film heater 33 through power connection lines (not shown); and a protecting layer 35 for protecting the thin film heater 33 from the water (liquid) flowing through the inner flow passage of the tube 20.

[39] When external low electric power (e.g., 500W) is supplied through the metal pads

34 to the thin film heater 33 in the present invention, the thin film heater 33 generates heat (undergoes a temperature rise) at a very high rate (i.e., a rise up to a temperature at which bacteria in water can be killed), and the water in the tube 20 is heated.

[40] Specifically, when the thin film heater 33 instantaneously generates heat at a high temperature (e.g., 400⁰C to 500⁰C), bubbles can be generated in the water existing within the tube 20 in the upward direction of the heat generating device 21, so that the bubbles at high temperature can kill the bacteria propagating in the water (sterilization action through a superheating phenomenon).

[41] The substrate 30 serves as a base. The insulation film 32, the thin film heater 33, the conductive pattern 36, the metal pads 34, the heater protecting layer 35 and the like may be formed on the substrate 30. The substrate 30 may be made of Si, a metal, ceramic, an insulator or the like.

[42] The heater protecting layer 35 is mounted around the outside of the thin film heater

33 and the metal pads 34 to electrically/chemically protect the thin film hater 33 and the metal pads 34 from the water (liquid) flowing through the inner flow passage of the tube 20. The heater protecting layer 35 may be made of SiNx, SiOx, AlOx, a polymer, polyimide, Teflon or the like. The optimum thickness of the heater protecting layer 35 capable of exhibiting thermal conductivity and a protective function is determined according to the material thereof, and preferably ranges from about 0.1D to about 20 D.

[43] The protecting layer may be formed on both a thin film heater with a conductive pattern formed thereon and a conductive pattern without a conductive pattern.

[44] The insulation film 32 is made of a ceramic material such as alumina (aluminum oxide, Al O ) or magnesia (magnesium oxide, MgO), a polymer, polyimide, or Teflon so as to provide electrical insulation between the substrate 31 and the thin film heater 33. The thickness of the insulation film 32 capable of providing the electrical insulation between the substrate 31 and the thin film heater 33 is prefeably in a range of 0.5D to 500D, more preferably 0.5D to 200D, and may vary according to the material of the insulation film.

[45] Requirements for the insulation film 32 are as follows.

[46] The insulation film 32 should achieve electrical insulation between the substrate 31 and the thin film heater 33. To achieve the electrical isolation of the thin film heater 33 supplied with external electric power, the insulation film 32 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 33.

[47] Additionally, the insulation film should have superior contact properties with the substrate 31 and the thin film heater 33 such that the insulation film 32 is not physically delaminated from the substrate 31 and the thin film heater 33 when the thin film heater 33 generates heat at a high temperature.

[48] Furthermore, the insulation film 22 should have superior surface roughness and should not chemically react with the substrate 31 and the thin film heater 33 when the thin film heater 33 generates heat at a high temperature. That is, since bad surface roughness of the insulation film 32 affects electrical resistivity of the thin film heater 33, it is preferred that the insulation film 32 have surface roughness enough not to affect the electrical resistivity of the thin film heater 33.

[49] As for the insulation film 32 capable of satisfying the aforementioned requirements, the surface of the substrate 31 may be formed with one selected among an oxidized insulation film formed by oxidizing the surface of the substrate 31 made of a metal such as aluminum or stainless steel using an arc; a polymer insulation film formed by coating a polymer-based material such as polyimide, polyamide, Teflon or PET on the surface of the substrate 31; and an insulation film formed by coating ceramic, glass, ceramic glaze or the like, or may be formed with a double insulation film comprising two or more of the aforementioned insulation films.

[50] As an embodiment of the formation of an oxidized insulation film, a metal substrate made of aluminum (Al), beryllium (Be), titanium (Ti), stainless steel or the like is dipped in an alkaline electrolyte, and external electrical energy such as an arc is applied to the surface of the substrate 31 made of a metal so that an electrochemical reaction can occur between metal atoms of the surface of the substrate 31 and external oxygen to convert properties of the surface of the substrate 31 into an oxidized film.

[51] Al 0 , ZrO , Y O or the like is used as the oxide insulation film, and the oxide insulation film may be formed on a metal plate or a metal tube through a plasma spray coating method.

[52] An embodiment of a process of forming an oxide insulation film on a metal plate or a metal tube will be described below.

[53] The concentration of an alkaline electrolyte filled in a bath is evaluated, a substrate

(i.e., a metal plate or a metal tube) made of aluminum is dipped into the alkaline electrolyte filled in the bath in a state where a lead wire is connected to the substrate 31 made of aluminum so that external power can be supplied to the substrate 31 made of aluminum, and the external power is supplied to the substrate 31 made of aluminum so as to oxidize the surface of the substrate 31 made of aluminum.

[54] As radio frequency AC power is strongly applied to the substrate 31 made of aluminum through the process of forming an oxidized insulation film, an arc is instantaneously generated on the surface of the substrate 31 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 substrate 31 made of aluminum.

[55] Through such a process of forming an oxidized insulation film, an aluminum oxide can be formed on the surface of a substrate 31 made of aluminum, a titanium oxide can be formed on the surface of a substrate 31 made of titanium, and a beryllium oxide can be formed on the surface of a substrate 31 made of beryllium.

[56] In the meantime, the 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 substrate 31 made of a metal.

[57] Particularly, such a polymer insulation film should not produce thermal deformation when heat is generated by the thin film heater 33. Further, when the thin film heater 33 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 substrate 31 and the thin film heater 33, and also have superior surface roughness such that the polymer insulation film does not chemically react with the substrate 31 and the thin film heater 33.

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

[59] A polymer insulation film is formed using a liquid organic polymer material that is to be uniformly coated on the surface of the substrate 31 made of a metal.

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

[61] 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.

[62] One embodiment of a process of coating a polyimide-based material on the substrate 31 by means of the spray coating method is as follows.

[63] The substrate 31 is cleaned with acetone, IPA (isopropyl alcohol) or the like, the polyimide-based material is sprayed onto the substrate 31 while the cleaned substrate 31 is rotated at a high speed (e.g., 2,000rpm or more), and the polyimide-based material coated on the surface of the substrate 31 is subjected to heat treatment.

[64] 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 substrate 31.

[65] 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 substrate 31 is improved. By coating the polymer-based material on the surface of the substrate 31 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.

[66] 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 substrate 31 made of a metal and uniformly coating a polymer-based material on the oxidized insulation film.

[67] 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 substrate 31 and the thickness of a resulting polymer insulation film solely formed on the surface of the substrate 31, 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.

[68] 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 33 is transmitted into the pin holes.

[69] 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.

[70] 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.

[71] The thickness of the insulation film 32 preferably ranges from 0.5D to 500D, more preferably 0.5D to 200D for optimum heat conduction (the thickness of the insulation film varies according to the material of the insulation film). The insulation film 32 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 32 should be formed such that it is not delaminated respectively from the substrate 31 and the thin film heater 33 when the thin film heater 33 generates heat (in a thermal cycle).

[72] The thin film heater 33 is mounted on the insulation film 32 in a form of a thin film with a thickness of 0.05D to several tens D. When external electric power (DC or AC power) is supplied to the thin film heater 33 through the metal pads 34, the thin film heater 33 performs joule heating by means of its own electrical resistance.

[73] Here, due to thin film characteristics of the thin film heater 33, i.e., a small volume of the thin film heater 33, a heating rate and cooling rate of the thin film heater 33 are very high, temperature obtainable by the heat generation of the thin film heater 33 due to its own electrical resistance can exceed 800⁰C, and the thin film heater 33 enables a very fast temperature rise contrary to a conventional sheath heater.

[74] Requirements for the thin film heater 33 are as follows.

[75] Although the thin film heater 33 enables a rapid temperature rise due to the thin film characteristics as compared with a conventional sheath heater, the thin film heater 33 may have a very large current flux due to the thin film characteristics. Thus, the thin film heater 33 is required to have electrically, thermally and chemically resistant properties.

[76] That is, the thin film heater 33 should electrically have high heater strength. Only when the thin film heater 33 has high resistance to energy continuously applied through the metal pads 34, it can maintain a long life span.

[77] Furthermore, the thin film heater 33 should be mounted on the insulation film 32 such that separation of the insulation film 32 or delamination between the substrate 31 and the insulation film 32 due to the heat generation of the thin film heater 33 does not occur.

[78] Moreover, in the thin film heater 33 that is a device subjected to continuous thermal shocks, changes in a resistance value of the thin film heater due to the thermal shocks should occur within an allowable numerical value range.

[79] Further, the thin film heater 33 may generate heat at a high temperature if it is exposed directly to air (oxygen). At this time, substantial increases in the resistance value of the thin film heater due to oxidation should not be produced.

[80] To satisfy the aforementioned requirements, the thin film heater 33 is 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.

[81] Further, the thin film heater 33 has a thickness of several tens D or less (e.g., 0.05D to

30D, wherein the thickness of the thin film heater varies according to the material of the thin film heater).

[82] Particularly, to ensure that the temperature of the thin film heater 33 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 33 itself very low.

[83] Further, in order to maintain the surface temperature of the thin film heater 33 at

500⁰C or more to generate superheating of liquid, a heating rate of the thin film heater 33 should be very high and generally meet the condition of "dT/dt > 10⁶°C(lM°C)/sec."

[84] Here, the heat capacity of the thin film heater 33 is expressed as a function with a parameter of thickness. The thinner the thin film heater 33 is, the smaller the heat capacity thereof is. On the other hand, the thinner the thin film heater 33 is, the shorter the lifespan of the thin film heater may be.

[85] Therefore, the present invention can deduce an optimum thickness range of the thin film heater 33 suitable to characteristics of each product through various simulations and experiments to satisfy two requirements for the instantaneous rise of the temperature of the thin film heater 33 and the extension of the lifespan of the thin film heater 33. On the other hand, there may be a slight difference in thickness according to the material of the thin film heater 33.

[86] That is, the optimum thickness of the thin film heater 33 is deduced based on the following formula.

[87] [Formula 1]

[88] p=Rsxt

[89] where p (resistivity) is a specific resistivity value of the material of the thin film heater 33, Rs (sheet resistance) is a surface resistance value of the thin film heater 33, and t (thickness of film) is the thickness of the thin film heater 33. Meanwhile, it can be seen that the thickness and specific resistivity value have a proportional relationship therebetween.

[90] Therefore, the optimum thickness range of the thin film heater 33 (e.g., 0.05D to 30D) is deduced according to the material of the thin film heater 33 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 33.

[91] The thin film heater 33 is formed on the insulation film 32 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.

[92] In the present invention, the thin film heater may be used in a state where the conductive pattern is formed thereon as shown in Figs. 4 and 5, or in a state where a conductive pattern is not formed thereon.

[93] Meanwhile, as illustrated in Figs. 6 to 8, a conductive pattern 36 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.

[94] 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.

[95] In order to prevent the overheating phenomenon and induce uniform heat generation on the entire surface of the thin film heater 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. 6 to 8.

[96] 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.

[97] The metal pads 34 are mounted respectively 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 33. Here, since the metal pads 34 are formed on the one side and the other side of the thin film heater 33, respectively, a uniform (constant) current density can be achieved on the entire surfaces of the thin film heater 33.

[98] Particularly, the width of the metal pads 34 is caused to be identical with or larger than that of the thin film heater 33 to provide a uniform current density on the entire surfaces of the thin film heater 33.

[99] Meanwhile, as illustrated in Figs. 9 and 10, the metal pads in the present invention can have a variety of sizes, numbers and positions on the thin film heater.

[100] Additionally, the metal pads 34 are made of a metal such as Al, Au, W, Pt, Ag, Ta, Mo or Ti to secure temperature stability of the metal pads 34, to prevent resistance increase due to oxidation, and to prevent separation thereof from the thin film heater 33 when the thin film heater 33 generates heat.

[101] Fig. 5 is a sectional view showing another embodiment of an instantaneous heating type water heating/sterilizing apparatus.

[102] As shown in Fig. 4, an insulation film 32 is formed around an outer wall surface of a tube (heating tube) 20, a thin film heater 33 is formed on the insulation coating 32, a conductive pattern 36 is formed on one side of the thin film heater, and metal pads 34 are mounted respectively on a lower side of the thin film heater 33 and on the other lower side thereof. At this time, a thin film heater without a conductive pattern may be used.

[103] In this case, heat generated by the thin film heater 33 is used to heat the tube 20, thereby heating water flowing through an inner flow passage of the tube 20 or killing bacteria existing in the water.

[104] In another embodiment, heating is made outside a metal plate to raise the temperature of water, thereby obtaining hot water within a shorter period of time. This is preferably applied to piping of a boiler, and the like.

[105] Fig. 11 shows a water heating/sterilizing apparatus to which an embodiment of the present invention is applied, Fig. 12 illustrates a graph showing measured changes in the surface temperature of the water heating/sterilizing apparatus with time when an electric power of 80 watts is applied to the water heating/sterilizing apparatus shown in Fig. 11, and Fig. 13 illustrates a graph showing measured changes in the surface temperature when varying power is applied for 10 seconds to the water heating/ sterilizing apparatus shown in Fig. 11.

[106] As illustrated in Fig. 12, it can be seen that a saturation characteristic is represented at 223⁰C after passage of a predetermined period of time when an electric power of 80 watts is applied. As illustrated in Fig. 13, it can be seen that the surface temperature linearly increases for 10 seconds with varying electric power.

[107] Fig. 14 shows a water heating/sterilizing apparatus to which another embodiment of the present invention is applied, Fig. 15 illustrates a graph showing measured changes in the surface temperature of the water heating/sterilizing apparatus with time when an electric power of 50 watts is applied to the water heating/sterilizing apparatus 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 water heating/ sterilizing apparatus shown in Fig. 14.

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

[109] Meanwhile, it should be noted that numerical values illustrated in Figs. 11 to 13 and

14 to 16 are numerical values obtained in various embodiments of a water heating/ sterilizing apparatus, 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 insulation film, the metal pads and the metal tube (or nonmetal tube).

[110] 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 insulation film, the metal pads and the metal tube (or nonmetal tube) in consideration of product requirements for a water heating/sterilizing apparatus so as to reduce time required to reach a surface temperature and power consumption corresponding to product characteristics.

[I l l] 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 water heating/sterilizing apparatus, comprising: a heat generating device (21) mounted within a tube to rapidly heat or sterilize a liquid by instantaneously applying heat to the liquid in a flow passage defined in the tube, wherein the heat generating device (21) includes: a lowermost substrate (31) for mounting a heater thereon; an insulation film (32) formed around the substrate to provide electrical insulation; a thin film heater (33) formed as a thin film on the insulation film to instantaneously generate heat by means of resistive heat generation when external electric power is supplied to a side of the thin film heater, so that the heat can be transferred directly to the liquid in the flow passage; a metal pad (34) mounted at an end of the thin film heater to uniformly supply the external electric power to the side of the thin film heater; and a protecting layer (35) formed around the thin film heater and the metal pad to protect the thin film heater and the metal pad from the liquid flowing through the flow passage.

[2] The water heating/sterilizing apparatus as claimed in claim 1, wherein a conductive pattern (36) 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 water heating/sterilizing apparatus as claimed in claim 1, wherein the tube comprises: a tube cooling portion (20a) for reducing conduction of the generated heat to the outside of the tube; and a tube insulating film (20b) for providing electrical insulation between the tube cooling portion and the heat generating device.

[4] The water heating/sterilizing apparatus as claimed in claim 1, wherein one or more heat generating devices are mounted inside the tube, and each of the heat generating devices is mounted on an inner wall surface at a side of the tube or an inner wall surface at the other side of the tube.

[5] The water heating/sterilizing apparatus as claimed in claim 1, wherein the protecting layer is made of any one of SiNx, SiOx, AlOx, a polymer, polyimide and Teflon.

[6] An instantaneous heating type water heating/sterilizing apparatus, comprising: a heat generating device (21) mounted within a tube to rapidly heat or sterilize a liquid by instantaneously applying heat to the liquid in a flow passage defined in the tube, wherein the heat generating device (21) includes: an insulation film (32) formed around an outer surface of the tube to provide electrical insulation between the tube and the heat generating device; a thin film heater (33) formed as a thin film on the outer surface of the tube with the insulation film interposed therebeween to instantaneously generate heat by means of resistive heat generation when electric power is supplied to a side of the thin film heater, so that the generated heat can be transferred directly to the tube through the insulation film; and a metal pad (34) mounted at an end of the thin film heater to uniformly supply the external electric power to the side of the thin film heater.

[7] The water heating/sterilizing apparatus as claimed in claim 6, wherein a conductive pattern (36) 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.

[8] The water heating/sterilizing apparatus as claimed in any one of claims 1 to 7, wherein the metal pad (34) defines a pattern such that a plurality of heating thin film cells are formed.

[9] The water heating/sterilizing apparatus as claimed in any one of claims 1 to 7, wherein the thin film heater 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-silicide combined with a metal-silicide, and a thick conductive paste.

[10] The water heating/sterilizing apparatus as claimed in any one of claims 1 to 7, wherein the metal pad is configured such that the width of the metal pad 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, and the metal pad is 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.

[11] The water heating/sterilizing apparatus as claimed in any one of claims 1 to 7, wherein the insulation film is formed on the surface of the substrate by forming at least one insulation film selected among an oxidized insulation film formed by oxidizing the surface of the substrate using an arc, an insulation film formed by coating ceramic, glass, ceramic glaze or the like on the surface of the substrate, and a polymer insulation film formed by coating a polymer on the surface of the substrate.

[12] The water heating/sterilizing apparatus as claimed in claim 11, 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.

[13] The water heating/sterilizing apparatus as claimed in claim 11, 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.

[14] The water heating/sterilizing apparatus as claimed in claim 13, 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.