JP2008210552A - Plate heater, heating device, image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a plate heater capable of obtaining more uniform heating in the longitudinal direction of an insulating substrate in a wide range from low resistance to high resistance by suppressing temperature differences in the longitudinal direction of the substrate. <P>SOLUTION: A wide heating resistor 16 having a length in the short side direction and a width in its longitudinal direction is formed on the long plate-like substrate 11, and electrodes 12, 13 for supplying power are formed at both ends of the heating resistor 16 through end part conductors 14, 15. An overcoat layer is formed on the end part conductors 14, 15 and the heating resistor 16. When the conductor length of the end part conductor 14 which is equivalent to one end and the width of the heating resistor 16 is defined as Lc, and the conductor width is defined as Wc, the resistance value R of the heating resistor 16 is made larger than 0.085 (Lc/Wc). Accordingly, uniformity of heating in the longitudinal direction of the insulating substrate 11 can be improved in a wide range from low resistance to high resistance by suppressing temperature differences in the longitudinal direction of the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin plate heater used in small equipment such as information equipment, home appliances, and manufacturing equipment, and a printer, a copying machine, a facsimile, a rewritable card reader / writer, etc. mounted with the plate heater. The present invention relates to an apparatus and an image forming apparatus using the heating apparatus.

A conventional plate heater using an insulating substrate such as ceramic forms a heating resistor having a positive temperature coefficient in the longitudinal direction on the insulating substrate, and supplies power to both ends of the heating resistor in the short direction. By connecting the electrodes, the temperature distribution in the longitudinal direction of the insulating substrate is made uniform (for example, Patent Document 1).
JP-A-7-94260

  In the technique of Patent Document 1 described above, since the end conductors formed at both ends in the longitudinal direction of the heat generating resistor have a conductor length Lc that is longer than the conductor width Wc, the resistance value of the end conductor tends to be high. Therefore, when power is supplied from the same end portion side of the heating resistor, current tends to flow to the power supply electrode side having a short conductive path, and the amount of heat generation tends to increase.

  In particular, if the conductor width is narrow or the resistance value of the heating resistor is low, it is difficult for the current to flow uniformly throughout the heating resistor, and the heating resistor cannot be heated uniformly. There has been a problem that the temperature is lowered, a uniform temperature distribution cannot be obtained in the longitudinal direction of the heater, and fixing defects such as uneven fixing occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a plate heater that can generate heat while suppressing a temperature difference in the longitudinal direction of an insulating substrate in a wide range from low resistance to high resistance, a heating device using the plate heater, and an image forming apparatus. It is to provide.

  In order to solve the above-described problems, a plate heater according to the present invention is formed along a long flat plate-like insulating substrate formed of a heat-resistant and insulating material and along both longitudinal sides of the insulating substrate surface. First and second end conductors, and first and second electrodes formed at one end of the first and second end conductors, respectively, to supply power to the first and second end conductors A heating resistor formed between and electrically connected to the first and second end conductors and formed widely in the longitudinal direction of the insulating substrate; the heating resistor and the first and second conductors; An overcoat layer covering and protecting the end conductor, and the conductor length of the first end conductor (or the second end conductor) connected to both ends of the heating resistor Lc, the first end conductor (or the first end conductor) ) Where the conductor width is Wc, the resistance value R of the heating resistor satisfies the relationship of 0.085 (Lc / Wc) <R.

  According to this invention, by setting the resistance value R of the heating resistor to a value larger than 0.085 (Lc / Wc), the temperature difference in the longitudinal direction of the insulating substrate can be set in a wide range from low resistance to high resistance. It becomes possible to suppress.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  1 and 2 are diagrams for explaining a first embodiment of the heater of the present invention. FIG. 1 is a top view and FIG. 2 is a cross-sectional view taken along line A-A 'of FIG.

In FIG. 1, reference numeral 11 denotes a heat-resistant and electrically insulating material having a thickness of about 0.5 mm to 1.0 mm, and has a high thermal conductivity such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or the like. It is a flat strip-like insulating substrate.

In FIG. 1, reference numeral 11 denotes a heat-resistant and electrically insulating material having a thickness of about 0.5 mm to 1.0 mm, and has a high thermal conductivity such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or the like. It is a flat strip-like insulating substrate. Reference numerals 12 and 13 denote power supply electrodes made of a good conductor film mainly composed of silver or the like.

  14 and 15 are formed of a material having a silver (Ag) content of, for example, 90 wt% or more in parallel with both sides of the insulating substrate 11 in a non-contact state with one end connected to the electrodes 12 and 13. End conductor. The electrode 12, the end conductor 14, the electrode 13, and the end conductor 15 are integrally formed by applying a conductive paste on the insulating substrate 11 and firing it, and are fixed to the insulating substrate 11. The opposite end conductor 14 formed integrally with the electrode 12 and the opposite end conductor 15 formed integrally with the electrode 13 are in an open state. That is, the electrodes 12 and 13 are integrally formed at one end of each of the end conductors 14 and 15 in the same direction.

16, after screen-printing a resistor paste such as ruthenium oxide (RuO ₂ ) having a relatively high resistance value formed in parallel along the longitudinal direction of the insulating substrate 11 between the end conductors 14 and 15, It is a wide heating resistor having a predetermined resistance value that is fired at a high temperature and has a film thickness of about 10 μm.

  17 is formed so as to cover the end conductors 14 and 15 and the heating resistor 16, and has excellent thermal conductivity such as alumina having a glass layer thickness of about 20 μm to 100 μm and a thermal conductivity of, for example, 2 W / m · K or more. It is an overcoat layer such as glass whose sliding property is improved by adding 25 to 35 wt% of an inorganic oxide filler. The overcoat layer 17 protects the end conductors 14 and 15 and the heating resistor 16 mechanically, chemically, and electrically.

Here, when the conductor length Lc of the end conductor 14 formed along both ends of the heating resistor 16 and the conductor width Wc of the end conductor 14 are set, the resistance value R of the heating resistor 16 is:
0.085 (Lc / Wc) <R (1)

To satisfy.

  In addition, although the expression (1) describes the conditions for the conductor length Lc and the conductor width Wc of the end conductor 14, the conductor length and the conductor width of the other end conductor 15 need not be the same conditions. . In other words, when the conductor length and the conductor width of the end conductor 15 are set to the conditions of the formula (1), the end conductor 14 may or may not satisfy the conditions of the formula (1). In short, any one of the end conductors 14 and 15 may be in a relationship satisfying the expression (1).

  As can be seen from the equation (1), when the resistance value of the end conductor 14 is large with respect to the resistance value R of the heating resistor 16, the current easily flows to the power feeding side with the short conductive path, and the long end of the conductive path It becomes difficult for current to flow through. For this reason, the amount of heat generated in the longitudinal direction of the insulating substrate 11 changes, so that a temperature difference is likely to occur.

  Here, the temperature difference with respect to the resistance value R of the heating resistor 16 when the conductor length Lc of the end conductor 14 is 220 mm and the conductor width Wc of the end conductor 14 is 1.1 mm is as shown in FIG. . When the resistance value becomes small, a temperature difference is likely to occur, so that it is difficult to produce a low resistance plate heater.

Therefore, it is necessary to reduce the resistance value Rc of the end conductor 14 to reduce the temperature difference. The resistance value Rc of the end conductor 14 can be reduced by increasing the thickness of the end conductor 14, but there are problems such as foaming at the contact portion with the heating resistor 16 and a decrease in withstand voltage characteristics. Therefore, it is desirable not to increase the thickness. Therefore, when the conductor length Lc, the conductor width Wc, and the sheet resistance value Sc (resistance value per unit area) are set, the resistance value Rc of the end conductor 14 is
Rc = Sc (Lc / Wc) (2)
Determined by

  Since the conductor length Lc of the end conductor 14 is determined by the size of the heating device, it is difficult to change. Further, the sheet resistance value Sc of a general Ag-based conductor is also 3 mΩ / □, and it is difficult to make it further smaller. Therefore, the resistance value of the conductor is generally changed depending on the conductor width Wc of the end conductor 14.

  Here, the temperature difference in the longitudinal direction with respect to the conductor width Wc of the end conductor 14 when the conductor length Lc of the end conductor 14 is 220 mm and the heater resistance value is 20Ω is as shown in FIG. It can be seen that the temperature difference increases as the conductor width Wc of the end conductor 14 decreases. The heater resistance value is the sum of the respective resistances of the electrode 12, the end conductor 14, the heating resistor 16, the end conductor 15, and the electrode 13. Strictly speaking, the resistance values of the conductors between the electrode 12 and the end conductor 14 and the electrode 13 and the end conductor 15 are also included.

From the experimental results, the resistance value Rc of the end conductor 14 and the resistance value R of the heating resistor 16 and the temperature difference ΔT in the longitudinal direction have the relationship of the following approximate expression.
(Rc2 + Rc × R) / (0.5 × R2 + Rc × R) ≈ΔT (3)
From this approximate expression, in order to make the temperature difference ΔT 7% or less, it is necessary to satisfy the expression (4) when the sheet resistance value Sc of the end conductor 14 is 3 mΩ / □.
0.085 (Lc / Wc) <R (4)
In this way, by setting the resistance value R of the heating resistor larger than the value obtained by 0.085 (Lc / Wc), the temperature difference ΔT in the heater length direction in a wide range from low resistance to high resistance. 7% or less can be realized, and the uniformity of heat generation in the longitudinal direction can be improved.

  FIG. 5 is a cross-sectional view for explaining an embodiment of the heating device of the present invention when the plate heater of the present invention is used for toner fixing.

  In FIG. 5, reference numeral 201 denotes a plate heater 100 fixed to the bottom of the support 202, an AC voltage is supplied to the plate heater 100, and pressure contact with the overcoat layer 17 that is a sliding layer of the heated plate heater 100. It is a cylindrical fixing film in which a heat-resistant sheet such as a polyimide resin that moves while being heated is rolled to be circulated. Reference numeral 203 denotes a pressure roller having a heat resistant elastic material, for example, a silicone rubber layer 204 fitted on the surface thereof. The plate heater 100 is opposed to the fixing film 201 so as to face the rotating shaft 205 of the pressure roller 203. They are mounted side by side in a base (not shown). The pressure roller 203 is brought into pressure contact with the fixing film 201 based on a means (not shown) to form a nip portion, and is rotated in the direction of the arrow during operation.

  At this time, the toner image To1 is first heated and melted by the plate heater 100 via the fixing film 201 between the surface of the fixing film 201 disposed on the overcoat layer 17 and the silicone rubber layer 204, and at least the surface portion thereof is It greatly exceeds the melting point and completely softens and melts. Thereafter, on the paper discharge side of the pressure roller 203, the copy paper P is separated from the plate heater 100, the toner image To2 is naturally radiated and cooled and solidified again, and the fixing film 201 is also separated from the copy paper P.

  In this embodiment, by improving the uniformity of the temperature distribution in the longitudinal direction of the plate heater 100, the fixability can be improved.

  Next, with reference to FIG. 6, an image forming apparatus according to the present invention will be described using a copying machine equipped with the heating device 200 according to the present invention as an example. In the figure, the part of the heating 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 heating 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 heating device 200 has an effective length according to the width (length) of the maximum size paper that can be copied by the copying machine 300 in the direction orthogonal to the moving direction of the copy paper P, that is, the width (length) of the maximum size paper. A plate heater 100 having a long heating resistor is provided in a state of being pressed by a silicone rubber layer 204 attached to the outer periphery of the pressure roller 203.

  The unfixed toner image T1 on the paper P sent between the plate heater 100 and the pressure roller 203 is melted by receiving heat from the heating resistor 12, and is printed with letters, alphanumeric characters, Copy images such as symbols and drawings are displayed.

  In this embodiment, an image forming apparatus having excellent fixability can be realized by using a heating device using the plate heater 100 having excellent plate heater slidability and thermal conductivity.

  The plate heater is used for fixing image forming apparatuses such as copying machines, but is not limited to this. For household appliances, precision equipment for business use and experiments, equipment for chemical reaction, etc. It can be used as a heat source for heating and heat retention.

The block diagram for demonstrating one Embodiment regarding the plate-shaped heater of this invention. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. Explanatory drawing for demonstrating the temperature difference with respect to the resistance value of a heating resistor. Explanatory drawing for demonstrating the temperature difference of the longitudinal direction with respect to the conductor width of an edge part conductor. Explanatory drawing for demonstrating one Embodiment regarding the heating apparatus of this 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

11 Insulating substrate 12, 13 Electrodes 14, 15 End conductor 16 Heating resistor 17 Overcoat layer 100 Flat plate heater 200 Heating device 300 Copying machine

Claims (3)

A long flat insulating substrate formed of a heat-resistant and insulating material;
First and second end conductors respectively formed along both longitudinal sides on the insulating substrate surface;
First and second electrodes respectively formed at one end of the first and second end conductors and supplying power to the first and second end conductors;
A heating resistor formed between and electrically connected to the first and second end conductors and formed widely in the longitudinal direction of the insulating substrate;
An overcoat layer covering and protecting the heating resistor and the first and second end conductors,
Lc is the conductor length of the first end conductor (or the second end conductor) connected to both ends of the heating resistor, and the first end conductor (or the first end conductor). ), The resistance value R of the heating resistor satisfies the relationship of 0.085 (Lc / Wc) <R. A heating roller;
The plate heater according to any one of claims 1 to 3, wherein a heating resistor disposed opposite to the heating roller is pressed against the heating roller;
A heating apparatus comprising: a fixing film movably provided between the plate heater and the pressure 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 heating apparatus according to claim 2, wherein the toner is fixed by passing a sheet on which an image is formed while being pressed against the heater via a fixing film by a pressure roller. Image forming apparatus.

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