JP2006293133A - Fixing heater, fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the temperature control of a fixing heater using a thermistor for detecting temperature. <P>SOLUTION: A heating resistor 12 and electrodes 13 and 14 for supplying power to the heating resistor are formed in the longitudinal direction of a long plate-like insulating substrate 11 formed of heat resistant/insulating material. An overcoat layer 17 is applied onto the heating resistor 12, and the thermistor 24 for controlling temperature is electrically connected to wiring conductors 22 and 23 connected to terminal parts 20 and 21 on an opposite side to the side of the insulating substrate 11 where the heating resistor 12 is formed through conductive adhesives 25 and 26. The conductive adhesives 25 and 26 are organic resin containing the conductive particles of Ag and the volume resistance value is set to ≤2×10<SP>-4</SP>Ωcm. Thus, the true value of the resistance value of the thermistor 24 detecting the temperature of the fixing heater is detected, and heat conductivity to the thermistor is made high to improve the accuracy of the temperature control of the heater. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin heater used in information equipment, home appliances, manufacturing equipment, and the like, a heating device such as a printer, a copier, a facsimile machine, and a rewritable paper mounted with the heater, and an image forming apparatus using the heating device.

Conventional fixing heaters use a thermistor for temperature detection, a conductive material using Ag (silver) / Pd (palladium) alloy or Ag as the conductive particles on the back side where the heating resistor of the insulating substrate constituting the fixing heater is formed. It is attached using an adhesive. (For example, Patent Document 1)
Japanese Patent Laid-Open No. 10-48978

  The technique of Patent Document 1 described above is that the Ag / Pd alloy or the conductive adhesive using Ag as a conductive particle is a specific resistance (electric resistance × cross-sectional area ÷ length) of the conductive particle itself in the Ag / Pd alloy. Because the volume resistivity of the conductive adhesive is large, and some common Ag-based adhesives do not have a low volumetric efficiency. Therefore, when thermistor resistance is used in a small temperature range, the conductive adhesive The connection resistance of the agent may be affected. In addition, the Ag / Pd alloy or the adhesive using Ag is not high in the thermal conductivity of the conductive particles per se in the Ag / Pd alloy, and in some general Ag-based adhesives, the thermal conductivity is not high. Therefore, it takes time to transmit the heat of the heater to the thermistor element. As described above, when rapid startup of heater temperature and accurate temperature control for higher speed are required, it is not sufficient.

  An object of the present invention is to provide a fixing heater capable of improving the accuracy of temperature control of a fixing heater using a thermistor for temperature detection, a fixing device using the fixing heater, and an image forming apparatus using the fixing device. It is to provide.

In order to solve the above-described problems, a fixing heater according to the present invention is a heater for supplying heat to a heating resistor and the heating resistor in the longitudinal direction of a long plate-like substrate formed of a heat-resistant and insulating material. An electrode is formed, an overcoat layer is applied on the heating resistor, and a thermistor for temperature control is mounted on the opposite substrate on which the heating resistor is formed, and the thermistor is a conductive particle The organic resin containing Ag is electrically connected to the electrode with a conductive adhesive having a volume resistance of 2 × 10 ⁻⁴ Ω · cm or less or a thermal conductivity of 5 W / m · K or more. It is characterized by.

  According to the present invention, it is possible to improve the accuracy of temperature control of the fixing heater.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view for explaining the configuration of an embodiment relating to the heater of the present invention, FIG. 2 is a rear view of FIG. 1, and FIG. 3 is a sectional view taken along line xx ′ of FIG.
In FIG. 1, 11 is formed in a long shape with a heat-resistant and insulating material such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ) or the like. Insulating substrate. A heating resistor 12 is formed on the insulating substrate 11 by thick film printing using a resistor paste whose conductive component is composed of Ag / Pd, RuO ₂ or the like. Reference numerals 13 and 14 are formed on the insulating substrate 11 by thick film printing using a conductive paste composed of Ag, Ag / Pt (platinum), Ag / Pd, or the like, and supplied with electric power. Electrode.

  13 is an electrode electrically connected to one end of the heating resistor 12, and 14 is formed by thick film printing using a conductor paste made of Ag, Ag / Pt, Ag / Pd, etc. on the insulating substrate 11. The electrode is electrically connected to one end of the conductive wiring pattern 15 formed. The other end of the wiring pattern 15 is electrically connected to one end of a connection conductor 16 formed on the insulating substrate 11 by thick film printing using a conductive paste. The other end of the connection conductor 16 is electrically connected to the other end of the heating resistor 12.

Reference numeral 17 denotes an overcoat layer formed by covering the heating resistor 12 and the connection conductor 16 with a glass paste by printing using a thick film printing method and firing the glass paste. The overcoat layer 17 is made by adding, for example, lead-free amorphous SiO, borosilicate glass mainly composed of B ₂ O ₃ and alumina having higher thermal conductivity than glass.

  Next, the back surface side of the insulating substrate 11 will be described together with FIG. 2 showing the back surface of FIG. 1 and FIG. 3 showing the x-x ′ cross section of FIG.

  In FIG. 2, reference numerals 20 and 21 denote terminal portions, which are formed by the same method as the electrodes 14 and 15. One end of a pair of wiring conductors 22 and 23 made of a material mainly composed of Ag / Pd or the like is coupled to the terminal portions 20 and 21, respectively. The other ends of the wiring conductors 22 and 23 are electrically connected by conductive adhesives 25 and 26 on the electrodes 241 and 242 of the chip-shaped thermistor 24 for temperature control as shown in FIG.

  The thermistor 24 uses an electrical resistor having a large negative temperature coefficient. The thermistor 24 is a sensor composed of a heat detection element that changes its resistance value to a large or small resistance value when the temperature rises. is there.

  As the conductive adhesives 25 and 26, a conductive adhesive made of an organic resin such as an epoxy resin, a polyimide resin, or a phenol resin mixed with Ag as conductive particles is applied by printing, stamping, or dipping. A thermistor 24 is mounted thereon and pressurized to thermally cure the conductive adhesives 25 and 26 in a thin state. Thereby, the thermistor 24 can be electrically connected to the electrodes 14 and 15.

Reference numerals 271 and 272 denote insulating particles Al mainly composed of an organic resin such as an epoxy resin or a polyimide resin, in order to efficiently conduct heat transfer to the thermistor through a temperature change caused by adhesion reinforcement between the thermistor 24 and the electrodes 22 and 23 and heat generation. It is an adhesive containing ₂ O ₃ , SiO ₂ or the like.

Here, the conductive adhesives 25 and 26 are set to have a volume resistance value of 2 × 10 ⁻⁴ Ω · cm or less after the adhesive is cured. In order to set the volume resistance value, the conductive particles are made of Ag particles having a small specific resistance, large particles having a large particle diameter, particles having a scaly shape, or increasing the content of the conductive particles. There is a way. The volume resistance value can also be lowered by selecting an organic resin having a large volumetric shrinkage rate, an organic resin having good wettability with respect to the conductive particles, or an additive. By these methods, the volume resistance value can be set to 2 × 10 ⁻⁴ Ω · cm or less.

Thus, by setting the volume resistance value of the conductive adhesives 25 and 26 to 2 × 10 ⁻⁴ Ω · cm or less, the connection resistance to the thermistor for detecting the temperature of the fixing heater can be reduced. Even in a region where the thermistor resistance value near the operating temperature of the heater is low, the influence of the connection resistance of the adhesive can be ignored, and the accuracy of temperature control can be improved.

Next, another embodiment of the fixing heater of the present invention will be described. This embodiment is different from the above embodiment in that the conductive adhesive adhesives 25 and 26 have a thermal conductivity of 5 W / m · K or more after the adhesive is cured.
In order to set the thermal conductivity of the conductive adhesives 25 and 26 to 5 W / m · K or more, the conductive particles are Ag particles having a high thermal conductivity and containing a large amount of particles having a large particle diameter. There are methods such as mixing a plurality of particles having different diameters and shapes, and increasing the content of conductive particles. In addition, the thermal conductivity can be increased by using an organic resin having a large volumetric shrinkage ratio or improving the wettability of the organic resin with respect to the conductive particles.
The thermal conductivity can be set to 5 W / m · K or more by these methods.

  Thus, by setting the thermal conductivity of the conductive adhesives 25 and 26 to 5 W / m · K or more, the thermal conductivity to the thermistor for detecting the temperature of the fixing heater can be improved, and the heater temperature It is possible to improve the accuracy of temperature control with less overshoot and quick response speed.

  The fixing heater 100 having the above-described configuration is incorporated in the fixing device and is energized by, for example, the circuit configuration shown in FIG.

  That is, when the commercial power supply 41 is energized to the electrodes 13 and 14 of the fixing heater 100 via the solid state relay 43 connected to the control terminal of the temperature control circuit 42, a current flows through the heating resistor 12 connected in series. Fever. The insulating substrate 11 also rises in temperature due to heat generated by the heating resistor 12. This heat is transmitted to the temperature sensing part of the thermistor 24 attached to the back side of the insulating substrate 11 and changes the resistance value of the temperature sensing part. A change in the resistance value of the thermistor 24 is output and input to the temperature control circuit 42 to determine whether the temperature is at the set temperature. When the temperature is lower than the set temperature, an ON signal is output to the solid state relay 43, and when the temperature is higher than the set temperature, an OFF signal is output to the solid state relay 43.

  In this way, the temperature of the heating resistor 12 is adjusted by controlling the power applied to the heating resistor 12. Although the temperature control circuit 42 has been described with respect to the on / off control of the solid state relay 43, other temperature adjustments such as a pulse width modulation control method may be used.

  When electric power is supplied to the electrodes 13 and 14 in the fixing heater 100, current flows through the heating resistor 12, and the heating resistor 12 exhibits a substantially uniform heating temperature distribution in the longitudinal direction. In this embodiment, for example, when the resistance value of the heating resistor 12 is 25Ω and a voltage of 100 V is applied, a current of 4 A flows and a heating value of 400 W can be obtained.

  Normally, as described above, the thermistor 24 provided on the back side of the insulating substrate 11 detects the temperature of the fixing heater 100 and controls the solid state relay 43 on / off through the temperature control circuit 42 to control it to a predetermined temperature. Yes.

  Next, with reference to FIG. 5, an embodiment of the fixing device of the present invention when the embodiment of the fixing heater described above is mounted on the fixing device 200 will be described. The fixing heater 100 in the figure is the same as that shown in FIGS. 1 to 3, and the same portions are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 5, reference numeral 201 denotes a pressure roller which is rotated by a rotating shaft 202, and a heat resistant elastic material such as a silicone rubber layer 203 is fitted on the surface of the pressure roller. The fixing heater 100 is juxtaposed with the rotating shaft 202 of the pressure roller 201 and attached to a base (not shown).

  Around the fixing heater 100, an endless roll-shaped fixing film 204 made of a heat-resistant sheet such as a polyimide resin is wound in a circulating manner, and an overcoat just above the insulating substrate 11 with the heating resistor 12 interposed therebetween. The surface of the layer 18 is in elastic contact with the silicone rubber layer 203 of the pressure roller 201 through the fixing film 204.

  In the fixing device 200, the fixing heater 100 is energized through a connector (not shown) in which a phosphor bronze plate or the like in contact with the electrodes 13, 14 is subjected to silver plating, and the heat is applied to the heat generating resistor 12 over the overcoat layer 17. The toner image T1 is first heated and melted by the fixing heater 100 via the fixing film 204 between the surface of the fixing film 204 provided and the silicone rubber layer 203, and at least its surface portion greatly exceeds the melting point and is completely softened and melted. . Thereafter, on the paper discharge side of the pressure roller 201, the copy paper P is separated from the fixing heater 100, the toner image T2 is naturally radiated and cooled and solidified again, and the fixing film 204 is also separated from the copy paper P.

As described above, the toner image T1 is once completely softened and melted and then cooled again on the paper discharge side of the pressure roller 201, so that the condensing force of the toner image T2 is very large.
In this embodiment, it is possible to realize a fixing device using a fixing heater with high thermal efficiency obtained from high withstand voltage characteristics.

  Next, with reference to FIG. 6, an image forming apparatus according to the present invention will be described, taking as an example a copier equipped with a fixing heater according to the present invention and a fixing device using the fixing heater. In the figure, the part of the fixing device 200 is the same as described above, and the same reference numerals are given to the same parts, and the description thereof is omitted.

  In FIG. 6, reference numeral 301 denotes a casing of the copying machine 300, and 302 an original placing table made of a transparent member such as glass provided on the upper surface of the casing 301, which scans the original P <b> 1 by reciprocating in the arrow Y direction.

  An illuminating device 302 including a light irradiation lamp and a reflecting mirror is provided in the upper direction in the housing 301, and a reflected light source from the document P1 irradiated by the illuminating device 302 is a short focus small diameter imaging element. A slit exposure is performed on the photosensitive drum 304 by the array 303. The photosensitive drum 304 rotates in the direction of the arrow.

  Reference numeral 305 denotes a charger that uniformly charges, for example, a photosensitive drum 304 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. An electrostatic image subjected to image exposure by the imaging element array 303 is formed on the photosensitive drum 304 charged by the charger 305. This electrostatic image is visualized using toner made of a resin that softens and melts when heated by the developing device 306.

  The copy paper P stored in the cassette 307 is rotated by a pair of conveying rollers 309 that are rotated in pressure contact with each other in synchronization with the feeding roller 308 and the image on the photosensitive drum 304. Sent to the top. The toner image formed on the photosensitive drum 304 is transferred onto the copy paper P by the transfer discharger 310.

  Thereafter, the paper P that is separated from the photosensitive drum 304 is guided to the fixing device 200 by the conveyance guide 311 and subjected to a heat fixing process, and then is discharged into the tray 312. After the toner image is transferred, residual toner on the photosensitive drum 304 is removed using a cleaner 313.

  The fixing device 200 is longer in the direction orthogonal to the moving direction of the copy paper P than the effective length corresponding to the width (length) of the maximum size paper that can be copied by the copier 300, that is, longer than the width (length) of the maximum size paper. A pressure roller 201 of the fixing heater 100 is provided by extending the heating resistors 121 and 122.

  Then, the unfixed toner image T1 on the paper P sent between the fixing heater 100 and the pressure roller 201 is melted by receiving heat from the heating resistors 121 and 122, and characters and alphanumeric characters on the copy paper P surface. A copy image such as a symbol or a drawing is displayed.

  In this embodiment, it is possible to realize a copying machine 300 using the fixing device 200 using a fixing heater with high thermal efficiency obtained from high withstand voltage characteristics.

  The present invention is not limited to the embodiment described above. For example, the overcoat layer material cannot be specified because it needs to be changed depending on the material of the opposing fixing film and other conditions. However, when the fixing film is a resin, the overcoat layer is an overcoat layer when glass or the fixing film is a metal. It is desirable to combine resins. As this resin, polyamide (PA), polyacetal (POM), polytetrafluoroethylene (PTFE), polyphenylene sulfide, elastomer, polyolefin, fluorine, etc., which are generally considered to be excellent in slidability, are used. Conceivable. Basically, any of them may be used, but imides such as PI (polyimide) and PAI (polyamideimide), which are heat-resistant and elastic, are preferable, but if the hardness is too low, the resin coating will be scraped off. Therefore, for example, a hardness of 3H or more is necessary.

  Further, the shape and width of the heating resistor, the combination of multiple pieces, the arrangement, and the like are not limited to the above-described embodiment. The same applies to the mounting arrangement of the thermistor.

  Furthermore, the fixing heater is used for fixing an image forming apparatus such as a copying machine, but is not limited to this, and is not limited to a household electrical product, a precision device for business use or experiment, a device for chemical reaction, etc. It can also be used as a heat source for heating and heat retention.

The front view for demonstrating the structure of one Embodiment regarding the fixing heater of this invention. The rear view of FIG. X-x 'sectional drawing of FIG. The circuit block diagram for demonstrating the temperature adjustment used for FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram for explaining an embodiment of a fixing device according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram for explaining an embodiment of an image forming apparatus according to the present invention;

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Insulation board | substrate 12 Heating resistor 13,14 Electrode 16 Connection conductor 17 Overcoat layer 20,21 Terminal part 22,23 Wiring conductor 24 Thermistor 25,26 Conductive adhesive 100 Fixing heater 200 Fixing apparatus 300 Copying machine

Claims (3)

A heating resistor and an electrode for supplying power to the heating resistor are formed in the longitudinal direction of a long flat substrate formed of a heat-resistant and insulating material, and an overcoat layer is applied on the heating resistor. In the fixing heater in which a thermistor for temperature control is mounted on the opposite substrate on which the heating resistor is formed,
The thermistor is formed of a conductive adhesive having an organic resin containing Ag as conductive particles and having a volume resistance of 2 × 10 ⁻⁴ Ω · cm or less or a thermal conductivity of 5 W / m · K or more. A fixing heater which is electrically connected. A heating roller;
The fixing heater according to claim 1, wherein a heating resistor disposed opposite to the heating roller is pressed against the heating roller.
A fixing device comprising: a fixing film movably provided between the fixing heater and the heating roller. Forming means for attaching a toner to an electrostatic latent image formed on a medium and transferring the toner to a sheet to form a predetermined image;
3. A fixing device according to claim 2, wherein the toner is fixed by passing a sheet on which an image is formed through a fixing film through a fixing film while being pressed against the fixing heater. Image forming apparatus.

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