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WO2006065063A1 - Electrophotographic image forming apparatus - Google Patents

Electrophotographic image forming apparatus Download PDF

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Publication number
WO2006065063A1
WO2006065063A1 PCT/KR2005/004277 KR2005004277W WO2006065063A1 WO 2006065063 A1 WO2006065063 A1 WO 2006065063A1 KR 2005004277 W KR2005004277 W KR 2005004277W WO 2006065063 A1 WO2006065063 A1 WO 2006065063A1
Authority
WO
WIPO (PCT)
Prior art keywords
thin film
film heater
metal
fixing device
tube
Prior art date
Application number
PCT/KR2005/004277
Other languages
French (fr)
Inventor
Hyung Woo Kim
Original Assignee
Hyung Woo Kim
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hyung Woo Kim filed Critical Hyung Woo Kim
Publication of WO2006065063A1 publication Critical patent/WO2006065063A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
    • G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
    • G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
    • G03G15/2053—Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/20—Fixing, e.g. by using heat
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
    • G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
    • G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
    • G03G15/2064—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat combined with pressure
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/0095—Heating devices in the form of rollers

Definitions

  • the present invention relates to a fixing device of an image forming apparatus, which has a structure in which a thin film heater with a heating property is formed on an inner or outer surface of a cylindrical metal tube in a state where an insulation film is interposed therebetween, or a structure in which a thin film heater is formed directly on an inner or outer surface of a cylindrical nonmetal tube, thereby shortening the rising time of the surface temperature of a fixing roller and lowering power consumption.
  • a fixing device for use in fixing toner particles transferred to a printing medium in a laser printer, a digital copy machine, or the like has a structure shown in Fig. 1.
  • Fig. 1 is a sectional view illustrating the structure of a conventional fixing device of an electrophotographic image forming apparatus, using a halogen lamp as a heating source.
  • the conventional fixing device has a cylindrical metal tube 12, a halogen lamp 11 as a heat generation unit installed at the center in the metal tube, and a coating layer 13 made of
  • a pressing roller 15 is positioned below the cylindrical metal tube 12 with a printing sheet 14 interposed therebetween. The pressing roller 15 presses the printing sheet 14 with a constant force by means of an urging spring 16. Accordingly, powder type toner 17 for forming an image on the printing sheet is fixed due to the heat generated by the heat generation unit so that the image can be formed on the printing sheet.
  • An object of the present invention is to provide a fixing device of an image forming apparatus, which has a structure in which a thin film heater with a heating property is formed on an inner or outer surface of a cylindrical metal tube in a state where an insulation film is interposed therebetween, or a structure in which a thin film heater is formed directly on an inner or outer surface of a cylindrical nonmetal tube, thereby shortening the rising time of the surface temperature of a fixing roller and lowering power consumption as compared with a conventional halogen lamp heating type device.
  • a fixing device may use a conductive pattern formed on one side of the thin film heater 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 upon supply of electric power, and metal pads defining a pattern such that a plurality of heating thin film cells are formed.
  • the thin film heater attached to the cylindrical metal or nonmetal tube according to the present invention described above there are advantages in that it is possible to shorten time required for a temperature rise from room temperature to the fixing temperature to a range of several seconds, to simplify the process of manufacturing the fixing device and reduce the number of parts so as to lower production costs, to maintain temperature constant so as to prevent overheating in the fixing device, and to lower power consumption.
  • an image heating apparatus using the fixing device of the present invention may be used as an apparatus for improving surface properties (e.g., gloss) of a recording medium containing an image by heating the recording medium or as a temporary fixing device.
  • surface properties e.g., gloss
  • FIG. 1 is a sectional view of a conventional fixing device.
  • Figs. 2 to 5 are views showing the structures of fixing devices using metal tubes, according to embodiments of the present invention.
  • Figs. 6 to 9 are views showing the structures of fixing devices using nonmetal tubes, according to embodiments of the present invention.
  • Figs. 10 to 12 are exemplary views of a thin film heater with a conductive pattern formed thereon.
  • Figs. 13 to 14 are exemplary views of a thin film heater with metal pads formed thereon.
  • Figs. 15 to 17 are a view showing a fixing device to which the present invention is applied, and graphs showing measured surface temperature values of the fixing device, respectively.
  • the present invention relates to a fixing device for fixing an image on a printing sheet in a laser printer, a laser multifunctional imaging apparatus, a digital copy machine or the like to which an electrophotographic scheme is applied.
  • a thin film heater 22, 32, 42 or 52 enabling instantaneous heating is formed to be in direct contact with a cylindrical metal tube 23 or 33 or a cylindrical nonmetal tube 43 or 53 in order to change a conventional indirect heating scheme to a direct heating scheme.
  • An insulation film 24 or 34 is interposed between the thin film heater 22, 32, 42 or 52 and the cylindrical metal tube 23 or 33 in order to achieve electrical insulation between the two metal layers.
  • a conductive pattern 29, 39, 49 or 59 may be further formed on one side of the thin film heater 22, 32, 42 or 52 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.
  • Figs. 2 and 3 are views showing the structure of a fixing device using a metal tube, according to an embodiment of the present invention
  • Figs. 4 and 5 are views showing the structure of a fixing device using a metal tube, according to another embodiment of the present invention.
  • 2 and 3 comprises a cylindrical metal tube 23, an insulation film 24 formed on an outer surface of the cylindrical metal tube 23, a thin film heater 22 formed to be in contact with the cylindrical metal tube 23 with the insulation coating 24 interposed therebetween, a conductive pattern 29 formed at one side of the thin film heater 22, a protecting layer 21 formed on the thin film heater 22, metal pads 25 formed at one side end of the thin film heater 22, and power connection terminals 26 for use in supplying electric power to the metal pads 25.
  • the fixing device according to another embodiment of the present invention shown in Figs. 4 and 5 comprises a cylindrical metal tube 33, an insulation film 34 formed on an inner surface of the cylindrical metal tube 33, a thin film heater 32 formed to be in contact with the cylindrical metal tube 33 with the insulation film 34 interposed therebetween, a conductive pattern 39 formed at one side of the thin film heater 32, a protecting layer 31 formed on the cylindrical metal tube 33, metal pads 35 formed at one side end of the thin film heater 32, and power connection terminals 36 for use in supplying electric power to the metal pads 35.
  • Figs. 6 and 7 are views showing the structure of a fixing device using a nonmetal tube, according to an embodiment of the present invention
  • Figs. 8 and 9 are views showing the structure of a fixing device using a nonmetal tube, according to another embodiment of the present invention.
  • the fixing device according to an embodiment of the present invention shown in Figs. 6 and 7 comprises a cylindrical nonmetal tube 43, a thin film heater 42 formed on an outer surface of the cylindrical nonmetal tube without an insulator therebetween, a conductive pattern 49 formed at one side of the thin film heater 42, a protecting layer 51 formed on the thin film heater 42, metal pads 45 formed at one side end of the thin film heater 42, and power connection terminals 46 for use in supplying electric power to the metal pads 45.
  • the fixing device according to another embodiment of the present invention shown in Figs. 8 and 9 comprises a cylindrical nonmetal tube 53, a thin film heater 52 formed on an inner surface of the cylindrical nonmetal tube without an insulator therebetween, a conductive pattern 59 formed at one side of the thin film heater 52, a protecting layer 61 formed on the cylindrical nonmetal tube 53, metal pads 55 formed at one side end of the thin film heater 52, and power connection terminals 56 for use in supplying electric power to the metal pads 55.
  • reference numerals 27, 37, 47 and 57 designate gears
  • reference numerals 28, 38, 48 and 58 designate bearings.
  • Gears 27, 37, 47 and 57 are provided at both ends of each of the cylindrical metal tubes 23 and 33 and the cylindrical nonmetal tubes 43 and 53, while the power connection terminals 26, 36, 46 and 56 are coupled with the gears 27, 37, 47 and 57 and come into contact with the meal pads 25, 35, 45 and 55, respectively.
  • Figs. 2, 4, 6 and 8 shows that a pressing roller for pressing a printing sheet with a constant force is conventionally placed below the fixing device.
  • each of the fixing devices according to the embodiments of the present invention shown in Figs. 4 and 8 further comprises a heater protecting layer 41 or 71 for protecting the thin film heater 32 or 52 formed inside the heater protecting layer from foreign substances.
  • the heater protecting layers 41 and 71 may be formed of inorganic heater protecting layer materials (SiNx, SiOx) and organic heater protecting layer materials (polyimide, polyamide, Teflon, PET, etc.).
  • the insulation film 24 is formed on the outer surface of the cylindrical metal tube 22, and the thin film heater with the conductive pattern 29 formed thereon is disposed on the insulation film 24.
  • the metal pads 25 are formed at the both ends of the thin film heater and the power connection terminals 26 are in contact with the metal pads 25.
  • the protecting layer 21 is formed on the surface of the thin film heater so that the thin film heater cannot be stained with foreign substances.
  • the cylindrical metal tubes 23 and 33 in the present invention may be made of a metal with superior thermal conductivity such as aluminum or stainless steel, or thermally enhanced plastics (PET) capable of resisting to a temperature of at least 250 ° C or heat-resistant glass or earthenware. It is preferred that the thickness of the cylindrical metal tube 23 or 33 be generally in a range of 0.3mm to 2.0mm.
  • a metal with superior thermal conductivity such as aluminum or stainless steel, or thermally enhanced plastics (PET) capable of resisting to a temperature of at least 250 ° C or heat-resistant glass or earthenware. It is preferred that the thickness of the cylindrical metal tube 23 or 33 be generally in a range of 0.3mm to 2.0mm.
  • the insulation film 24 or 34 is the insulation film 24 or 34.
  • the insulation film should not produce dielectric breakdown and should maintain a leakage current below 20/zA upon application of a voltage of about 100V to the thin film heater.
  • the insulation film should have superior contact properties with the substrate and the thin film heater such that the insulation film is not physically delaminated from the cylindrical metal tube when the thin film heater generates heat at a high temperature.
  • the insulation film should not chemically react with the thin film heater or the substrate. Since bad surface roughness of the insulation film affects electrical resistivity of the thin film heater, it is preferred that the insulation film have surface roughness enough not to affect the electrical resistivity of the thin film heater.
  • the insulation films 24 and 34 may be one or a combination of two or more selected among an oxidized insulation film formed by oxidizing the surface of the substrate made of aluminum or stainless steel using an arc; a polymer insulation film using a polymer-based material (polyimide, polyamide, Teflon or PET) or the like; and an insulation film formed by coating ceramic, glass, ceramic glaze or the like.
  • 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 metallic surface of the metal substrate so that an electrochemical reaction can occur between metal atoms of the surface of the metal plate and external oxygen to convert properties of the metallic surface into an oxidized film.
  • A1203, ZrO3, Y2O3 or the like is used as the oxide insulation film, and the oxide insulation film may be formed on a metal plate, a metal tube, a nonmetal plate or a nonmetal tube through a plasma spray coating method.
  • An embodiment of a process of forming an oxide insulation film on a metal plate, a metal tube, a nonmetal plate or a nonmetal tube will be described below.
  • the concentration of an alkaline electrolyte filled in a bath is evaluated, a metal plate 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 made of aluminum so that external power can be supplied to the metal plate made of aluminum, and the external power is supplied to the metal plate made of aluminum so as to oxidize the surface of the metal plate made of aluminum.
  • radio frequency AC power is strongly applied to the metal plate made of aluminum through the process of forming an oxidized insulation film, an arc is instantaneously generated on the surface of the metal plate made of aluminum.
  • 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 made of aluminum.
  • an aluminum oxide can be formed on the surface of a metal plate made of aluminum
  • a titanium oxide can be formed on the surface of a metal plate made of titanium
  • a beryllium oxide can be formed on the surface of a metal plate made of beryllium.
  • an electrical insulation film using a polymer material may be obtained by applying a polymer material capable of securing electrical insulation with a uniform thickness on a substrate, so as to achieve electrical insulation between two layers, i.e., the metal substrate and the thin film heater.
  • a polymer insulation film is formed using a liquid organic polymer material that is to be uniformly coated on the surface of a metal plate (or metal tube) made of a metal.
  • coating methods include a spin coating method, a spray coating method, a dipping coating method, and a screen printing method.
  • 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.
  • One embodiment of a process of coating a polyimide-based material on a metal plate by means of the spray coating method is as follows.
  • the metal plate is cleaned with acetone, EPA (isopropyl alcohol) or the like, the polyimide-based material is sprayed onto the metal plate while the cleaned metal plate is rotated at a high speed (e.g., 2 5 000rpm or more), and the polyimide-based material coated on the surface of the metal plate is subjected to heat treatment.
  • a high speed e.g., 2 5 000rpm or more
  • a polymer insulation film having superior thermal stability and a glassy temperature (GT) of 300 ° C or more is formed on the surface of the metal plate 21.
  • a method of forming both an oxidized insulation film and a polymer insulation film may be performed by first forming an oxidized insulation film on a metal substrate and a polymer insulation film on the oxidized insulation film, or otherwise, by coating a polymer-based material on the surface of a metal substrate made of a metal and forming an oxidized insulation film thereon.
  • the thickness of each of the insulation films can be reduced and dielectric breakdown can be minimized, as compared with a case where only one of the insulation films is applied.
  • the thickness of the insulation film 24 or 34 preferably ranges from 0.5 ⁇ m to 500/an, more preferably 0.5[m to 200/iin for efficient heat conduction (the thickness of the insulation film varies according to the material of the insulation film).
  • the insulation film 24 or 34 has a dielectric breakdown voltage of 1,000V or more, and a leakage current of 20/zA or less upon application of a voltage of 100V.
  • the insulation film 24 or 34 should be formed such that it is not delaminated respectively from the metal tube 23 or 33 and the thin film heater 22 or 32 when the thin film heater 22 or 32 generates heat (in a thermal cycle).
  • the thin film heater 22, 32, 42 or 52 generates heat in a resistive heat generation manner by means of application of a DC or AC voltage to the metal pads connected to the thin film heater so that a predetermined amount of current can flow through the thin film heater.
  • Temperature obtained through heat generation due to the its own resistance of the thin film heater may exceed 500 0 C and may rapidly rise contrary to a bulk heater. This is because the thin film heater has a very small volume as a thin film.
  • the thin film heater 22, 32, 42 or 52 in the form of a thin film has a very large current flux, the thin film heater itself is required to have electrically, thermally and chemically resistant properties.
  • the thin film heater should electrically have high heater strength, have high resistance to continuously applied energy and maintain a long life span.
  • the thin film heater 22, 32, 42 or 52 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-silicide (e.g., TaSi, WSi, etc.) combined with a metal-silicide, or a thick conductive paste such as Ag/Pd.
  • a single metal e.g., Ta, W, Pt, Ru, Hf, Mo, Zr, Ti, etc.
  • a binary metal alloy e.g., TaW, etc.
  • a binary metal-nitride e.g., WN, MoN, ZrN, etc.
  • the thin film heater 22, 32, 42 or 52 has a thickness of several tens ⁇ m or less (e.g., 0.05/im to 30 ⁇ m, wherein the thickness of the thin film heater varies according to the material of the thin film heater).
  • the heat capacity of the thin film heater 22, 32, 42 or 52 is expressed as a function with a parameter of thickness.
  • the present invention can deduce an optimum thickness range of the thin film heater through various simulations and experiments to satisfy two requirements for the instantaneous rise of the temperature of the thin film heater 22, 32, 42 or 52 and the extension of the lifespan of the thin film heater. Although there is a slight difference in thickness according to the material of the thin film heater, the difference is merely a minute difference.
  • the optimum thickness of the thin film heater 22 or 32 is deduced based on the following formula.
  • Methods for forming a thin film heater using vacuum evaporation include a thick film screen printing method, 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.
  • the thin film heater in the present invention may be used in a state where a conductive pattern is formed thereon or in a state where a conductive pattern is not formed thereon.
  • a protecting layer may be formed on one side of the thin film heater to protect the thin film heater.
  • the heater protecting layer may be 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.
  • 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.
  • a conductive pattern 29, 39, 49 or 59 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 22, 32, 42 or 52.
  • 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.
  • conductive patterns 29, 39, 49 or 59 with various shapes and configurations on one side of the thin film heater, as illustrated in Figs. 10 to 12. Furthermore, the formation of the conductive pattern 29, 39, 49 or 59 on the thin film heater 22, 32, 42 or 52 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.
  • 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 to a portion of the entire thin film heater, resulting in drop in the production yield of the thin film heater.
  • the metal pads 25, 35, 45 or 55 are formed on the both ends of the thin film heater to secure a uniform current density in the thin film heater, so that the metal pads can be responsible for electrical connection between the thin film heater and an external power supply. It is preferred that the width of the metal pads be identical with or larger than that of the thin film heater to provide a constant current density to the thin film heater. Meanwhile, the metal pads 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. 13 and 14.
  • the metal pads should have temperature stability during heat generation of the thin film heater and should not produce resistance increase or physical delamination due to oxidation of the metal pads.
  • the metal pads in the present invention can be made of Al, Au, W, Pt, Ag, Ta, Mo, Ti or the like.
  • the thin film heater is provided inside the cylindrical metal tube.
  • the protecting layer 31 is formed on the outer surface of the cylindrical metal tube 33.
  • the thin film heater 32 with the conductive pattern 39 formed thereon is disposed on the inner surface of the cylindrical metal tube 33 with the insulation film 34 interposed therebetween.
  • the metal pads 35 for use in supplying electric power are formed on the both ends of the thin film heater 32. At this time, a thin film heater without a conductive pattern may be used.
  • the power connection terminals 26 that will come into contact with the metal pads 35 are inserted into the cylindrical metal tube 33.
  • a second protecting layer 42 may be formed below the thin film heater 32 to protect the thin film heater from foreign substances.
  • the cylindrical nonmetal tube 43 is used instead of the cylindrical metal tube.
  • an insulation film is not needed to be provided between the cylindrical nonmetal tube 43 and the thin film heater 42.
  • the thin film heater 42 with the conductive pattern 49 formed thereon is disposed on the outer surface of the cylindrical nonmetal tube 43 without an insulator therebetween, and the protecting layer 51 is provided on the thin film heater. At this time, the thin film heater without a conductive pattern may be used.
  • the cylindrical nonmetal tube 43 may be made of thermally enhanced plastics, heat resistant resins, ceramics, glass and earthenware capable of resisting to a temperature of at least 250 ° C . hi the fixing apparatus according to the still further embodiment of the present invention shown in Figs. 8 and 9, the thin film heater 52 with the conductive pattern 59 formed thereon is disposed on the inner surface of the cylindrical nonmetal tube 53. At this time, a thin film heater without a conductive pattern may be used.
  • the protecting layer 61 for protecting contamination due to foreign substances is formed on the cylindrical nonmetal tube, and the second protecting layer 71 for protecting the inner thin film heater 52 is also formed inside the nonmetal tube.
  • Fig. 15 shows a fixing device to which the present invention is applied
  • Fig. 16 illustrates a graph showing measured changes in the surface temperature of the fixing device with time when an electric power of 80 watts is applied to the fixing device shown in Fig. 15,
  • Fig. 17 illustrates a graph showing measured changes in the surface temperature when varying power is applied for 10 seconds to the fixing device shown in Fig. 15.
  • Figs. 15 to 17 are numerical values obtained in one embodiment of a fixing 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 insulation film, the metal pads and the metal tube (or nonmetal tube).
  • a saturation characteristic is represented at 223 ° C after passage of a predetermined period of time when an electric power of 80 watts is applied.
  • 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 fixing device so as to reduce time required to reach a surface temperature and power consumption corresponding to product characteristics.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Resistance Heating (AREA)
  • Fixing For Electrophotography (AREA)
  • Control Of Resistance Heating (AREA)

Abstract

The present invention relates to a fixing device of an image forming apparatus, which has a structure in which a thin film heater with a heating property is formed on an inner or outer surface of a cylindrical metal tube in a state where an insulation film is interposed therebetween, or a structure in which a thin film heater is formed directly on an inner or outer surface of a cylindrical nonmetal tube, thereby shortening the rising time of the surface temperature of a fixing roller and lowering power consumption. More particularly, the present invention provides a fixing device of an electrophotographic image forming apparatus, comprising a cylindrical metal or nonmetal tube; an insulation film formed on an outer or inner surface of the cylindrical metal tube to provide electrical insulation; a thin film heater for generating heat by means of resistive heat generation upon application of electric power thereto so that the generated heat can be transferred to the cylindrical metal or nonmetal tube; a conductive pattern formed on one side of the thin film heater 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 upon supply of electric power; metal pads formed at at least one side end of the thin film heater to uniformly supply the electric power to a side of the thin film heater; a protecting layer formed on one side of the thin film heater to prevent adhesion of foreign substances or toner to the thin film heater; and power connection terminals brought into contact with the metal pads.

Description

[DESCRIPTION] [Invention Title]
ELECTROPHOTOGRAPHIC IMAGE FORMING APPARATUS [Technical Field] The present invention relates to a fixing device of an image forming apparatus, which has a structure in which a thin film heater with a heating property is formed on an inner or outer surface of a cylindrical metal tube in a state where an insulation film is interposed therebetween, or a structure in which a thin film heater is formed directly on an inner or outer surface of a cylindrical nonmetal tube, thereby shortening the rising time of the surface temperature of a fixing roller and lowering power consumption. [Background Art]
Generally, a fixing device for use in fixing toner particles transferred to a printing medium in a laser printer, a digital copy machine, or the like has a structure shown in Fig. 1.
Fig. 1 is a sectional view illustrating the structure of a conventional fixing device of an electrophotographic image forming apparatus, using a halogen lamp as a heating source.
The conventional fixing device has a cylindrical metal tube 12, a halogen lamp 11 as a heat generation unit installed at the center in the metal tube, and a coating layer 13 made of
Teflon or the like formed on a surface of the cylindrical metal tube 12. Radiant heat is generated by the halogen lamp 11 as the heat generation unit inside the cylindrical metal tube 12 so that the cylindrical metal tube 12 can be indirectly heated. A pressing roller 15 is positioned below the cylindrical metal tube 12 with a printing sheet 14 interposed therebetween. The pressing roller 15 presses the printing sheet 14 with a constant force by means of an urging spring 16. Accordingly, powder type toner 17 for forming an image on the printing sheet is fixed due to the heat generated by the heat generation unit so that the image can be formed on the printing sheet.
When a printer, a digital copying machine or the like is turned on/off, such a conventional fixing device requires considerable warm-up time greater than several tens of seconds in order to raise the temperature of the cylindrical metal tube 12 from room temperature to a toner fixing temperature at which the toner 17 can be fixed. As such, the heat generated by the heat generation unit is transferred as radiant heat through air or the cylindrical metal tube 12 to the printing sheet in an indirect heat-generation manner, and additional time greater than several tens of seconds is required for a temperature rise up to the fixing temperature when a standby mode is switched to an operation mode for printing. This causes a problem of user's long waiting time. Further, since a high power of 1. OkW to 3.OkW should be used as initial power for operating the halogen lamp in the conventional fixing device, there is a problem of high power consumption.
[Disclosure] [Technical Problem]
The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a fixing device of an image forming apparatus, which has a structure in which a thin film heater with a heating property is formed on an inner or outer surface of a cylindrical metal tube in a state where an insulation film is interposed therebetween, or a structure in which a thin film heater is formed directly on an inner or outer surface of a cylindrical nonmetal tube, thereby shortening the rising time of the surface temperature of a fixing roller and lowering power consumption as compared with a conventional halogen lamp heating type device.
[Technical Solution]
A fixing device of an electrophotographic image forming apparatus according to an aspect of the present invention for achieving the object comprises a cylindrical metal tube; an insulation film formed on an outer surface of the cylindrical metal tube to provide electrical insulation; a thin film heater formed as a thin film on the outer surface of the cylindrical metal tube with the insulation film interposed therebetween so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical metal tube through the insulation film; a protecting layer formed on an outer surface of the thin film heater to prevent adhesion of foreign substances or toner to the thin film heater; metal pads formed at at least one side end of the thin film heater to uniformly supply the electric power to a side of the thin film heater; and power connection terminals brought into contact with the metal pads.
A fixing device of an electrophotographic image forming apparatus according to another aspect of the present invention for achieving the object comprises a cylindrical metal tube; an insulation film formed on an inner surface of the cylindrical metal tube to provide electrical insulation; a thin film heater formed as a thin film on the inner surface of the cylindrical metal tube with the insulation film interposed therebetween so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical metal tube through the insulation film; a protecting layer formed on an outer surface of the cylindrical metal tube to prevent adhesion of foreign substances or toner to the cylindrical metal tube; metal pads formed at at least one side end of the thin film heater to uniformly supply the electric power to a side of the thin film heater; and power connection terminals brought into contact with the metal pads.
A fixing device of an electrophotographic image forming apparatus according to a further aspect of the present invention for achieving the object comprises a cylindrical nonmetal tube; a thin film heater formed as a thin film on an outer surface of the cylindrical nonmetal tube so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical nonmetal tube; a protecting layer formed on an outer surface of the thin film heater to prevent adhesion of foreign substances or toner to the thin film heater; metal pads formed at at least one side end of the thin film heater to uniformly supply the electric power to a side of the thin film heater; and power connection terminals brought into contact with the metal pads.
A fixing device of an electrophotographic image forming apparatus according to a still further aspect of the present invention for achieving the object comprises a cylindrical nonmetal tube; a thin film heater formed as a thin film on an inner surface of the cylindrical nonmetal tube so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred directly to the cylindrical nonmetal tube; a protecting layer formed on an outer surface of the cylindrical nonmetal tube to prevent adhesion of foreign substances or toner to the thin film heater; metal pads formed at at least one side end of the thin film heater to uniformly supply the electric power to a side of the thin film heater; and power connection terminals brought into contact with the metal pads.
Further, a fixing device according to a still further aspect of the present invention may use a conductive pattern formed on one side of the thin film heater 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 upon supply of electric power, and metal pads defining a pattern such that a plurality of heating thin film cells are formed.
[Advantageous Effects]
By using the thin film heater attached to the cylindrical metal or nonmetal tube according to the present invention described above, there are advantages in that it is possible to shorten time required for a temperature rise from room temperature to the fixing temperature to a range of several seconds, to simplify the process of manufacturing the fixing device and reduce the number of parts so as to lower production costs, to maintain temperature constant so as to prevent overheating in the fixing device, and to lower power consumption.
Further, an image heating apparatus using the fixing device of the present invention may be used as an apparatus for improving surface properties (e.g., gloss) of a recording medium containing an image by heating the recording medium or as a temporary fixing device.
[Description of Drawings] Fig. 1 is a sectional view of a conventional fixing device.
Figs. 2 to 5 are views showing the structures of fixing devices using metal tubes, according to embodiments of the present invention.
Figs. 6 to 9 are views showing the structures of fixing devices using nonmetal tubes, according to embodiments of the present invention.
Figs. 10 to 12 are exemplary views of a thin film heater with a conductive pattern formed thereon.
Figs. 13 to 14 are exemplary views of a thin film heater with metal pads formed thereon.
Figs. 15 to 17 are a view showing a fixing device to which the present invention is applied, and graphs showing measured surface temperature values of the fixing device, respectively.
* Explanation of Reference Numerals for Main Portions in the Drawings* 21, 31, 41, 51, 61, 71: Teflon protecting layer 22, 32, 42, 52: Thin film heater 23, 33 : Cylindrical metal tube
43, 53: Cylindrical nonmetal tube 24, 34: Insulation film
25, 35, 45, 55: Metal pad
26, 36, 46, 56: Power connection terminal
27, 37, 47, 57: Gear 28, 38, 48, 58: Bearing 29, 39, 49, 59: Conductive pattern
[Best Mode]
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.
The present invention relates to a fixing device for fixing an image on a printing sheet in a laser printer, a laser multifunctional imaging apparatus, a digital copy machine or the like to which an electrophotographic scheme is applied. In the fixing device of the present invention, a thin film heater 22, 32, 42 or 52 enabling instantaneous heating is formed to be in direct contact with a cylindrical metal tube 23 or 33 or a cylindrical nonmetal tube 43 or 53 in order to change a conventional indirect heating scheme to a direct heating scheme. An insulation film 24 or 34 is interposed between the thin film heater 22, 32, 42 or 52 and the cylindrical metal tube 23 or 33 in order to achieve electrical insulation between the two metal layers. Moreover, a conductive pattern 29, 39, 49 or 59 may be further formed on one side of the thin film heater 22, 32, 42 or 52 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. The constitution of the present invention will be described in detail with reference to the accompanying drawings.
Figs. 2 and 3 are views showing the structure of a fixing device using a metal tube, according to an embodiment of the present invention, and Figs. 4 and 5 are views showing the structure of a fixing device using a metal tube, according to another embodiment of the present invention. The fixing device according to an embodiment of the present invention shown in Figs. 2 and 3 comprises a cylindrical metal tube 23, an insulation film 24 formed on an outer surface of the cylindrical metal tube 23, a thin film heater 22 formed to be in contact with the cylindrical metal tube 23 with the insulation coating 24 interposed therebetween, a conductive pattern 29 formed at one side of the thin film heater 22, a protecting layer 21 formed on the thin film heater 22, metal pads 25 formed at one side end of the thin film heater 22, and power connection terminals 26 for use in supplying electric power to the metal pads 25.
The fixing device according to another embodiment of the present invention shown in Figs. 4 and 5 comprises a cylindrical metal tube 33, an insulation film 34 formed on an inner surface of the cylindrical metal tube 33, a thin film heater 32 formed to be in contact with the cylindrical metal tube 33 with the insulation film 34 interposed therebetween, a conductive pattern 39 formed at one side of the thin film heater 32, a protecting layer 31 formed on the cylindrical metal tube 33, metal pads 35 formed at one side end of the thin film heater 32, and power connection terminals 36 for use in supplying electric power to the metal pads 35.
Figs. 6 and 7 are views showing the structure of a fixing device using a nonmetal tube, according to an embodiment of the present invention, and Figs. 8 and 9 are views showing the structure of a fixing device using a nonmetal tube, according to another embodiment of the present invention.
The fixing device according to an embodiment of the present invention shown in Figs. 6 and 7 comprises a cylindrical nonmetal tube 43, a thin film heater 42 formed on an outer surface of the cylindrical nonmetal tube without an insulator therebetween, a conductive pattern 49 formed at one side of the thin film heater 42, a protecting layer 51 formed on the thin film heater 42, metal pads 45 formed at one side end of the thin film heater 42, and power connection terminals 46 for use in supplying electric power to the metal pads 45.
The fixing device according to another embodiment of the present invention shown in Figs. 8 and 9 comprises a cylindrical nonmetal tube 53, a thin film heater 52 formed on an inner surface of the cylindrical nonmetal tube without an insulator therebetween, a conductive pattern 59 formed at one side of the thin film heater 52, a protecting layer 61 formed on the cylindrical nonmetal tube 53, metal pads 55 formed at one side end of the thin film heater 52, and power connection terminals 56 for use in supplying electric power to the metal pads 55.
In the figures, reference numerals 27, 37, 47 and 57 designate gears, while reference numerals 28, 38, 48 and 58 designate bearings. Gears 27, 37, 47 and 57 are provided at both ends of each of the cylindrical metal tubes 23 and 33 and the cylindrical nonmetal tubes 43 and 53, while the power connection terminals 26, 36, 46 and 56 are coupled with the gears 27, 37, 47 and 57 and come into contact with the meal pads 25, 35, 45 and 55, respectively. Each of Figs. 2, 4, 6 and 8 shows that a pressing roller for pressing a printing sheet with a constant force is conventionally placed below the fixing device.
Moreover, each of the fixing devices according to the embodiments of the present invention shown in Figs. 4 and 8 further comprises a heater protecting layer 41 or 71 for protecting the thin film heater 32 or 52 formed inside the heater protecting layer from foreign substances. Here, the heater protecting layers 41 and 71 may be formed of inorganic heater protecting layer materials (SiNx, SiOx) and organic heater protecting layer materials (polyimide, polyamide, Teflon, PET, etc.).
The respective components of the present invention constructed above will be specifically described below. First, the structure of the embodiment of the present invention shown in Figs. 2 and 3 will be summarized as follows.
The insulation film 24 is formed on the outer surface of the cylindrical metal tube 22, and the thin film heater with the conductive pattern 29 formed thereon is disposed on the insulation film 24. In order to apply electric power to the thin film heater, the metal pads 25 are formed at the both ends of the thin film heater and the power connection terminals 26 are in contact with the metal pads 25. The protecting layer 21 is formed on the surface of the thin film heater so that the thin film heater cannot be stained with foreign substances.
The cylindrical metal tubes 23 and 33 in the present invention may be made of a metal with superior thermal conductivity such as aluminum or stainless steel, or thermally enhanced plastics (PET) capable of resisting to a temperature of at least 250 °C or heat-resistant glass or earthenware. It is preferred that the thickness of the cylindrical metal tube 23 or 33 be generally in a range of 0.3mm to 2.0mm.
Generally, in a case where a thin film heater and its heater material for generating heat by means of application of electric power thereto are formed on a substrate such as a metal plate or a cylindrical metal tube, there is a need for a functional layer capable of performing electrical insulation between the thin film heater and the substrate. The functional layer is the insulation film 24 or 34. To achieve the electrical isolation of the thin film heater, the insulation film should not produce dielectric breakdown and should maintain a leakage current below 20/zA upon application of a voltage of about 100V to the thin film heater. The insulation film should have superior contact properties with the substrate and the thin film heater such that the insulation film is not physically delaminated from the cylindrical metal tube when the thin film heater generates heat at a high temperature. When the thin film heater generates heat at a high temperature, the insulation film should not chemically react with the thin film heater or the substrate. Since bad surface roughness of the insulation film affects electrical resistivity of the thin film heater, it is preferred that the insulation film have surface roughness enough not to affect the electrical resistivity of the thin film heater.
The insulation films 24 and 34 may be one or a combination of two or more selected among an oxidized insulation film formed by oxidizing the surface of the substrate made of aluminum or stainless steel using an arc; a polymer insulation film using a polymer-based material (polyimide, polyamide, Teflon or PET) or the like; and an insulation film formed by coating ceramic, glass, ceramic glaze or the like.
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 metallic surface of the metal substrate so that an electrochemical reaction can occur between metal atoms of the surface of the metal plate and external oxygen to convert properties of the metallic surface into an oxidized film.
A1203, ZrO3, Y2O3 or the like is used as the oxide insulation film, and the oxide insulation film may be formed on a metal plate, a metal tube, a nonmetal plate or a nonmetal tube through a plasma spray coating method. An embodiment of a process of forming an oxide insulation film on a metal plate, a metal tube, a nonmetal plate or a nonmetal tube will be described below.
The concentration of an alkaline electrolyte filled in a bath is evaluated, a metal plate 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 made of aluminum so that external power can be supplied to the metal plate made of aluminum, and the external power is supplied to the metal plate made of aluminum so as to oxidize the surface of the metal plate made of aluminum. As radio frequency AC power is strongly applied to the metal plate made of aluminum through the process of forming an oxidized insulation film, an arc is instantaneously generated on the surface of the metal plate 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 made of aluminum. Through such a process of forming an oxidized insulation film, an aluminum oxide can be formed on the surface of a metal plate made of aluminum, a titanium oxide can be formed on the surface of a metal plate made of titanium, and a beryllium oxide can be formed on the surface of a metal plate made of beryllium.
In the meantime, an electrical insulation film using a polymer material may be obtained by applying a polymer material capable of securing electrical insulation with a uniform thickness on a substrate, so as to achieve electrical insulation between two layers, i.e., the metal substrate and the thin film heater.
A polymer insulation film is formed using a liquid organic polymer material that is to be uniformly coated on the surface of a metal plate (or metal tube) made of a metal. Here, coating methods include a spin coating method, a spray coating method, a dipping coating method, and a screen printing method.
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. One embodiment of a process of coating a polyimide-based material on a metal plate by means of the spray coating method is as follows.
The metal plate is cleaned with acetone, EPA (isopropyl alcohol) or the like, the polyimide-based material is sprayed onto the metal plate while the cleaned metal plate is rotated at a high speed (e.g., 25000rpm or more), and the polyimide-based material coated on the surface of the metal plate is subjected to heat treatment.
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 300 °C or more is formed on the surface of the metal plate 21.
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 is improved. By coating the polymer-based material on the surface of the metal plate 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.
A method of forming both an oxidized insulation film and a polymer insulation film may be performed by first forming an oxidized insulation film on a metal substrate and a polymer insulation film on the oxidized insulation film, or otherwise, by coating a polymer-based material on the surface of a metal substrate made of a metal and forming an oxidized insulation film thereon.
If both the oxidation insulation film and the polymer insulation film are formed, the thickness of each of the insulation films can be reduced and dielectric breakdown can be minimized, as compared with a case where only one of the insulation films is applied.
The thickness of the insulation film 24 or 34 preferably ranges from 0.5μm to 500/an, more preferably 0.5[m to 200/iin for efficient heat conduction (the thickness of the insulation film varies according to the material of the insulation film). The insulation film 24 or 34 has a dielectric breakdown voltage of 1,000V or more, and a leakage current of 20/zA or less upon application of a voltage of 100V. The insulation film 24 or 34 should be formed such that it is not delaminated respectively from the metal tube 23 or 33 and the thin film heater 22 or 32 when the thin film heater 22 or 32 generates heat (in a thermal cycle).
The thin film heater 22, 32, 42 or 52 generates heat in a resistive heat generation manner by means of application of a DC or AC voltage to the metal pads connected to the thin film heater so that a predetermined amount of current can flow through the thin film heater. Temperature obtained through heat generation due to the its own resistance of the thin film heater may exceed 5000C and may rapidly rise contrary to a bulk heater. This is because the thin film heater has a very small volume as a thin film.
Since the thin film heater 22, 32, 42 or 52 in the form of a thin film has a very large current flux, the thin film heater itself is required to have electrically, thermally and chemically resistant properties. The thin film heater should electrically have high heater strength, have high resistance to continuously applied energy and maintain a long life span.
Physical delamination between and cracking in the metal substrate and the insulation film should not occur when the thin film heater 22, 32, 42 or 52 generates heat. Furthermore, in 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. As for chemical properties, since the thin film heater may be exposed directly to oxygen or undergoes high temperature, substantial increases in the resistance value of the thin film heater due to oxidation should be prevented.
The thin film heater 22, 32, 42 or 52 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-silicide (e.g., TaSi, WSi, etc.) combined with a metal-silicide, or a thick conductive paste such as Ag/Pd.
The thin film heater 22, 32, 42 or 52 has a thickness of several tens μm or less (e.g., 0.05/im to 30μm, wherein the thickness of the thin film heater varies according to the material of the thin film heater).
To ensure that the temperature of the thin film heater 22, 32, 42 or 52 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 itself very low.
That is, the heat capacity of the thin film heater 22, 32, 42 or 52 is expressed as a function with a parameter of thickness. The thinner the thin film heater is, the smaller the heat capacity thereof is. On the other hand, the thinner the thin film heater 22 or 32 is, the shorter the lifespan of the thin film heater may be.
Therefore, the present invention can deduce an optimum thickness range of the thin film heater through various simulations and experiments to satisfy two requirements for the instantaneous rise of the temperature of the thin film heater 22, 32, 42 or 52 and the extension of the lifespan of the thin film heater. Although there is a slight difference in thickness according to the material of the thin film heater, the difference is merely a minute difference.
That is, the optimum thickness of the thin film heater 22 or 32 is deduced based on the following formula.
[Formula 1] p=Rsχt where p (resistivity) is a specific resistivity value of the material of the thin film heater 22 or 32, Rs (sheet resistance) is a surface resistance value of the thin film heater 22 or 32, and t (thickness of film) is the thickness of the thin film heater 22 or 32. Meanwhile, it can be seen that the thickness and specific resistivity value have a proportional relationship therebetween. Therefore, the optimum thickness range of the thin film heater 22, 32, 42 or 52 (e.g.,
0.05/im to 30μm) is deduced according to the material of the thin film heater 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.
Methods for forming a thin film heater using vacuum evaporation include a thick film screen printing method, 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. As shown in Figs. 2 to 9, the thin film heater in the present invention may be used in a state where a conductive pattern is formed thereon or in a state where a conductive pattern is not formed thereon. A protecting layer may be formed on one side of the thin film heater to protect the thin film heater. Here, the heater protecting layer may be 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.
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.
Meanwhile, as illustrated in Figs. 10 to 12, a conductive pattern 29, 39, 49 or 59 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 22, 32, 42 or 52.
In a case where the thin film heater 22, 32, 42 or 52 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. In order to prevent the overheating phenomenon and induce uniform heat generation on the entire surface of the thin film heater 22, 32, 42 or 52 within a shorter period of time at the early stage of supply of electric power, it is possible to form conductive patterns 29, 39, 49 or 59 with various shapes and configurations on one side of the thin film heater, as illustrated in Figs. 10 to 12. Furthermore, the formation of the conductive pattern 29, 39, 49 or 59 on the thin film heater 22, 32, 42 or 52 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 to a portion of the entire thin film heater, resulting in drop in the production yield of the thin film heater. The metal pads 25, 35, 45 or 55 are formed on the both ends of the thin film heater to secure a uniform current density in the thin film heater, so that the metal pads can be responsible for electrical connection between the thin film heater and an external power supply. It is preferred that the width of the metal pads be identical with or larger than that of the thin film heater to provide a constant current density to the thin film heater. Meanwhile, the metal pads 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. 13 and 14.
Additionally, the metal pads should have temperature stability during heat generation of the thin film heater and should not produce resistance increase or physical delamination due to oxidation of the metal pads. Considering the required properties of the metal pads, the metal pads in the present invention can be made of Al, Au, W, Pt, Ag, Ta, Mo, Ti or the like.
In the fixing device according to the other embodiment of the present invention shown in Figs. 4 and 5, the thin film heater is provided inside the cylindrical metal tube.
As shown in Fig. 4, the protecting layer 31 is formed on the outer surface of the cylindrical metal tube 33. The thin film heater 32 with the conductive pattern 39 formed thereon is disposed on the inner surface of the cylindrical metal tube 33 with the insulation film 34 interposed therebetween. The metal pads 35 for use in supplying electric power are formed on the both ends of the thin film heater 32. At this time, a thin film heater without a conductive pattern may be used. The power connection terminals 26 that will come into contact with the metal pads 35 are inserted into the cylindrical metal tube 33.
At this time, a second protecting layer 42 may be formed below the thin film heater 32 to protect the thin film heater from foreign substances. In the fixing device according to the further embodiment of the present invention shown in Figs. 6 and 7, the cylindrical nonmetal tube 43 is used instead of the cylindrical metal tube. In case of using the cylindrical nonmetal tube 43, an insulation film is not needed to be provided between the cylindrical nonmetal tube 43 and the thin film heater 42. The thin film heater 42 with the conductive pattern 49 formed thereon is disposed on the outer surface of the cylindrical nonmetal tube 43 without an insulator therebetween, and the protecting layer 51 is provided on the thin film heater. At this time, the thin film heater without a conductive pattern may be used.
The cylindrical nonmetal tube 43 may be made of thermally enhanced plastics, heat resistant resins, ceramics, glass and earthenware capable of resisting to a temperature of at least 250°C . hi the fixing apparatus according to the still further embodiment of the present invention shown in Figs. 8 and 9, the thin film heater 52 with the conductive pattern 59 formed thereon is disposed on the inner surface of the cylindrical nonmetal tube 53. At this time, a thin film heater without a conductive pattern may be used. The protecting layer 61 for protecting contamination due to foreign substances is formed on the cylindrical nonmetal tube, and the second protecting layer 71 for protecting the inner thin film heater 52 is also formed inside the nonmetal tube.
Fig. 15 shows a fixing device to which the present invention is applied, Fig. 16 illustrates a graph showing measured changes in the surface temperature of the fixing device with time when an electric power of 80 watts is applied to the fixing device shown in Fig. 15, and Fig. 17 illustrates a graph showing measured changes in the surface temperature when varying power is applied for 10 seconds to the fixing device shown in Fig. 15.
Meanwhile, it should be noted that numerical values illustrated in Figs. 15 to 17 are numerical values obtained in one embodiment of a fixing 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 insulation film, the metal pads and the metal tube (or nonmetal tube). As illustrated in Fig. 16, it can be seen that a saturation characteristic is represented at 223 °C after passage of a predetermined period of time when an electric power of 80 watts is applied.
As illustrated in Fig. 17, it can be seen that the surface temperature linearly increases for 10 seconds with varying electric power.
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 fixing device so as to reduce time required to reach a surface temperature and power consumption corresponding to product characteristics.
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

[CLAIMS] [Claim 1 ]
A fixing device of an electrophotographic image forming apparatus, comprising: a cylindrical metal tube (23); an insulation film (24) formed on an outer surface of the cylindrical metal tube to provide electrical insulation; a thin film heater (22) formed as a thin film on the outer surface of the cylindrical metal tube with the insulation film interposed therebetween so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical metal tube through the insulation film; a protecting layer (21) formed on an outer surface of the thin film heater (22) to prevent adhesion of foreign substances or toner to the thin film heater; metal pads (25) formed at at least one side end of the thin film heater (22) to uniformly supply the electric power to a side of the thin film heater; and power connection terminals (26) brought into contact with the metal pads.
[Claim 2]
The fixing device as claimed in claim 1, wherein a conductive pattern (29) 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.
[Claim 3]
A fixing device of an electrophotographic image forming apparatus, comprising: a cylindrical metal tube (33); an insulation film (34) formed on an inner surface of the cylindrical metal tube to provide electrical insulation; a thin film heater (32) formed as a thin film on the inner surface of the cylindrical metal tube with the insulation film interposed therebetween so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical metal tube through the insulation film; a protecting layer (31) formed on an outer surface of the cylindrical metal tube (33) to prevent adhesion of foreign substances or toner to the cylindrical metal tube; metal pads (35) formed at at least one side end of the thin film heater (32) to uniformly supply the electric power to a side of the thin film heater; and power connection terminals (36) brought into contact with the metal pads.
[Claim 4]
The fixing device as claimed in claim 3, wherein a conductive pattern (29) 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.
[Claim 5]
The fixing device as claimed in claim 3, further comprising a protecting layer (41) formed on an inner surface of the thin film heater (32) to protect the thin film heater from the foreign substances.
[Claim 6]
A fixing device of an electrophotographic image forming apparatus, comprising: a cylindrical nonmetal tube (43); a thin film heater (42) formed as a thin film on an outer surface of the cylindrical nonmetal tube so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred to the cylindrical nonmetal tube; a protecting layer (51) formed on an outer surface of the thin film heater (42) to prevent adhesion of foreign substances or toner to the thin film heater; metal pads (45) formed at at least one side end of the thin film heater (42) to uniformly supply the electric power to a side of the thin film heater; and power connection terminals (46) brought into contact with the metal pads.
[Claim 7]
The fixing device as claimed in claim 6, wherein a conductive pattern (49) 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.
[Claim 8]
A fixing device of an electrophotographic image forming apparatus, comprising: a cylindrical nonmetal tube (53); a thin film heater (52) formed as a thin film on an inner surface of the cylindrical nonmetal tube so as to generate heat by means of resistive heat generation upon application of electric power to the thin film heater so that the generated heat can be transferred directly to the cylindrical nonmetal tube; a protecting layer (51) formed on an outer surface of the cylindrical nonmetal tube (53) to prevent adhesion of foreign substances or toner to the thin film heater; metal pads (55) formed at at least one side end of the thin film heater (52) to uniformly supply the electric power to a side of the thin film heater; and power connection terminals (56) brought into contact with the metal pads.
[Claim 9]
The fixing device as claimed in claim 8, wherein a conductive pattern (59) 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.
[Claim 10]
The fixing device as claimed in claim 8, further comprising a protecting layer (71) formed on an inner surface of the thin film heater (52) to protect the thin film heater (52) from the foreign substances.
[Claim 11]
The heating apparatus as claimed in any one of claims 1 to 10, wherein the metal pads (25; 35; 45; 55) define a pattern such that a plurality of heating thin film cells are formed.
[Claim 12]
The fixing device as claimed in any one of claims 1 to 10, wherein the thin film heater (22; 32; 42; 52) 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.
[Claim 13]
The fixing device as claimed in any one of claims 1 to 10, wherein the metal pads (25; 35; 45; 55) are configured such that the width of the metal pads is identical with or larger than that of the thin film heater (22; 32; 42; 52) to supply electric power of a uniform current density to the thin film heater, 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.
[Claim 14] The fixing device as claimed in any one of claims 1 to 10, wherein the insulation film
(24; 34) is formed on the surface of the metal tube (23; 33) by forming at least one insulation film selected among an oxidized insulation film formed by oxidizing the surface of the metal tube (23; 33) using an arc, an insulation film formed by coating ceramic, glass, ceramic glaze or the like on the surface of the metal tube (23; 33), and a polymer insulation film formed by coating a polymer on the surface of the metal tube (23; 33). [Claim 15]
The fixing device as claimed in claim 14, wherein the insulation film has a dielectric breakdown voltage of 1,000V or more and has a leakage current of 20M or less when a voltage of 100V is applied thereto. [Claim 16]
The fixing device as claimed in claim 14, 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. [Claim 17]
The fixing device as claimed in claim 16, 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.
PCT/KR2005/004277 2004-12-14 2005-12-13 Electrophotographic image forming apparatus WO2006065063A1 (en)

Applications Claiming Priority (2)

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KR1020040105729A KR100476298B1 (en) 2004-12-14 2004-12-14 Fusing roller apparatus of electrophotographic image forming apparatus
KR10-2004-0105729 2004-12-14

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DE102009015942B3 (en) * 2009-04-02 2010-11-25 OCé PRINTING SYSTEMS GMBH Fixing roller for fixing device in electrographic printer for fixing toner image on printing substrate, has infrared heat radiator foil comprising metallic heating foil circularly guided around surface and attached to electric power source
JP2017142471A (en) * 2016-02-13 2017-08-17 キヤノン株式会社 Heating body, method for manufacturing heating body, and image heating device including heating body

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Publication number Priority date Publication date Assignee Title
KR100810734B1 (en) 2006-06-14 2008-03-07 김형우 Electrophotographic image forming apparatus
KR101164189B1 (en) * 2010-07-20 2012-07-10 (주)우리정도 A seamless blackening metal sleeve for fuser fixing unit

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JP2001125415A (en) * 1999-10-27 2001-05-11 Daiken Kagaku Kogyo Kk Both high- and low-voltage power source type quick heat roller and device using same

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JPH06156778A (en) * 1992-11-30 1994-06-03 Mita Ind Co Ltd Image forming device
JPH0962129A (en) * 1995-08-22 1997-03-07 Mitsui Toatsu Chem Inc Fixing roller for copying machine
JP2001125415A (en) * 1999-10-27 2001-05-11 Daiken Kagaku Kogyo Kk Both high- and low-voltage power source type quick heat roller and device using same

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009015942B3 (en) * 2009-04-02 2010-11-25 OCé PRINTING SYSTEMS GMBH Fixing roller for fixing device in electrographic printer for fixing toner image on printing substrate, has infrared heat radiator foil comprising metallic heating foil circularly guided around surface and attached to electric power source
JP2017142471A (en) * 2016-02-13 2017-08-17 キヤノン株式会社 Heating body, method for manufacturing heating body, and image heating device including heating body

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