JP5124134B2 - Heater, heating device, image forming apparatus - Google Patents

Description

  The present invention uses a plate-like heater used by being mounted on small equipment such as information equipment, home appliances and manufacturing equipment, a heating device such as a printer, a copier, a facsimile machine, and the like equipped with the heater, and the heating device. The present invention relates to an image forming apparatus.

In the conventional heater, a heating resistor is formed in the short direction of the insulating substrate in order to reduce the temperature change. (For example, Patent Document 1)
A plurality of heating resistors are formed in the short direction of the insulating substrate for the purpose of averaging the temperature distribution and improving the durability. (For example, Patent Document 2)
JP-A-7-94260 JP-A-5-29067

  When the heating resistor is formed in the longitudinal direction of the insulating substrate, the technique of Patent Document 1 described above can obtain a uniform temperature distribution in the longitudinal direction, but when the heated body is narrower than the longitudinal heating body width, The temperature at the end in the longitudinal direction where the heated body does not pass, the so-called non-sheet passing portion, is excessively increased.

  Further, in the technique of Patent Document 2, since there are intervals between a plurality of heating resistors, the temperature in the longitudinal direction of the insulating substrate is difficult to be uniform, and even if there is a partial defect, it operates with an abnormal temperature distribution. There is a problem.

  An object of the present invention is to obtain a uniform heat generation in the longitudinal direction of an insulating substrate constituting a ceramic heater, and to suppress a temperature rise of the heater in a non-sheet passing portion, a heating device using this heater, An object of the present invention is to provide an image processing apparatus using this heating apparatus.

In order to solve the above-described problems, a heater according to the present invention has a resistance temperature coefficient of 0 ppm / ° C. formed on a long plate-like heat-resistant insulating substrate and a graphite-based material. A first heating resistor having an electrical end so that the energization direction is perpendicular to the longitudinal direction of the insulating substrate, and the first heating resistor in the longitudinal direction of the insulating substrate. A second heating resistor formed on the insulating substrate alongside the heating resistor and having an electrical end so that the direction of energization is perpendicular to the longitudinal direction of the insulating substrate; The first heat generating resistor is formed on the insulating substrate using a graphite-based material in parallel with the second heat generating resistor in the longitudinal direction of the insulating substrate from the second heat generating resistor. In addition, the temperature coefficient of resistance is 0 ppm / A third heating resistor having an electrical end so that the energizing direction has a value less than that of the insulating substrate and is perpendicular to the longitudinal direction of the insulating substrate; A conductor that electrically connects the first, second, and third heating resistors in series so as to reach from the first heating resistor to the third heating resistor through the second heating resistor; A pair of power supply electrodes provided on an insulating substrate and serving as electrical ends of the entire first, second, and third heating resistors connected in series by the conductor, and the first and second electrodes And a third heating resistor and an overcoat layer for covering and protecting the conductor.

  According to the present invention, uniform heat generation can be obtained in the longitudinal direction of the insulating substrate, and a rapid temperature rise characteristic can be obtained, so that the temperature rise of the non-sheet passing portion can be suppressed.

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

  1 to 5 are for explaining a first embodiment relating to the heater of the present invention. FIG. 1 is a top view, FIG. 2 is a cross-sectional view along aa 'in FIG. 1, and FIG. 4 is a cross-sectional view taken along the line bb ′, FIG. 4 is a cross-sectional view taken along the line cc ′ of FIG. 1, and FIG.

11 is a heat-resistant and electrically insulating material having a thickness of about 0.5 mm to 1.0 mm, and has high thermal conductivity such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon carbide (SiC), and nitride. It is a flat strip-shaped insulating substrate formed of a highly rigid ceramic such as silicon (Si ₃ N ₄ ) or glass. At both ends in the longitudinal direction on the insulating substrate 11, electrodes 12 and 13 for good power feeding mainly composed of silver or the like are formed.

  In the longitudinal direction on the insulating substrate 11 between the electrode 12 and the electrode 13, a plurality of independent heating resistors 141 to 1 having a wide width and a short length in which the longitudinal direction of the insulating substrate 11 is a width and a short direction is a length. 143 is fixedly formed.

The conductor 151 having one end connected to the electrode 12 is integrally formed of the same material as the electrode 12 along one side edge in the longitudinal direction on the insulating substrate 11 and is superposed on one end of the heating resistor 141. Connect with. The other end of the heating resistor 141 and one end of the heating resistor 142 are connected in a state of being superimposed on the conductor 152 formed of the same material as the conductor 151 along the other side edge in the longitudinal direction on the insulating substrate 11. . The other end to one end of the heating resistor 143 of the heating resistor 142 is connected in a state of being superimposed on the conductors 153 formed by the same material as the conductor 151 along the longitudinal direction of the one side edge of the insulating substrate 11 To do. The other end of the heating resistor 143 is connected in a state of being overlapped with a conductor 154 formed integrally with the electrode 13 along the other side edge in the longitudinal direction on the insulating substrate 11.

  Reference numeral 16 denotes an overcoat layer made of glass or the like having a glass layer thickness of about 20 μm to 100 μm that covers the conductors 151 to 154 and the heating resistors 141 to 143 and performs mechanical, chemical, and electrical protection. The overcoat layer 16 improves thermal conductivity and slidability by adding about tens wt% of an inorganic oxide filler with excellent thermal conductivity such as alumina having a thermal conductivity of about 20 W / m · K, for example. I am trying. With the above configuration, the heater 100 is formed.

By the way, it is desirable to divide the pattern of the heating resistors 141 to 143 in accordance with the width of a sheet to be heated, for example, A4 size or A3 size paper. For example, the width of the heating resistor 142 is equivalent to A4 size, and the combined width of the heating resistors 141 to 143 is equivalent to A3 size. When A4 size paper is used, the heating resistors 141 and 143 corresponding to the position of the non-sheet passing portion outside the paper width are RuO ₂ (ruthenium oxide), graphite, Fe, Mn, Cr It is formed using a material having a resistance temperature coefficient of 100 ppm / ° C. or less using a transition metal oxide such as Ni, an Ag / Pd material, or the like.

  Since the heater temperature is detected by the thermistor 51, which is a kind of temperature detecting element shown in FIG. 5, on the back side of the insulating substrate 11 of the heating resistor 142 located at the center, the heating resistor 142 has a resistance temperature coefficient of 100 ppm / It is not limited to a material having a temperature of ℃ or less, and even if it is formed of the same material having the same resistance temperature coefficient as that of the heating resistors 141 and 143, it is formed using a material having a resistance temperature coefficient different from that of the heating resistors 141 and 143. It doesn't matter.

  As shown in FIG. 5, the thermistor 51 has one end connected to the detection terminal 53 via a pattern 52 formed on the insulating substrate 11 and the other end connected to a detection terminal 55 via a pattern 54.

  Here, the control in which the heat generation temperature is adjusted by the circuit configuration shown in FIG. 6 and the heat generation temperature is adjusted will be described with reference to FIG.

  That is, when the commercial power supply 61 is energized to the electrodes 12 and 13 of the heater 100 via the solid state relay 63 connected to the control terminal of the temperature control circuit 62, a current is supplied to the heating resistors 141 to 143 connected in series. It flows and generates heat. The temperature of the insulating substrate 11 also rises due to heat generated by the heating resistors 141-143. This heat is transmitted to the temperature sensing part of the thermistor 51 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 51 is output via a wiring conductor formed on the back side of the insulating substrate 11 in FIG. 1, and this is input to the temperature control circuit 62 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 63, and when the temperature is higher than the set temperature, an OFF signal is output to the solid state relay 63.

  Thus, the temperature adjustment of the heating resistors 141 to 143 is performed by controlling the power applied to the heating resistors 141 to 143. Although the temperature control circuit 62 has been described with respect to the on / off control of the solid state relay 63, temperature control by a pulse width modulation control method or the like may be used.

  When the heater 100 is supplied with power to the electrodes 12 and 13, current flows through the heating resistors 141 to 143, and the heating resistors 141 to 143 exhibit a substantially uniform heating temperature distribution in the longitudinal direction. In this embodiment, for example, the resistance value of the heating resistors 141 to 143 is set to 25Ω, and a current of 4 A flows when a voltage of 100 V is applied, resulting in a heating value of 400 W.

  Normally, as described above, the thermistor 51 provided on the back surface side of the insulating substrate 11 detects the temperature of the heater 100 and controls the solid state relay 63 on / off through the temperature control circuit 62 to control it to a predetermined temperature. .

  The temperature control of the heater 100 is performed by the thermistor 51 disposed on the back surface of the heating resistor 142 through which paper is passed regardless of the paper size, and detects the temperature of the heating resistor 142 and controls the power supplied. . The thermistor 51 is not necessarily attached to the insulating substrate 11, and may be attached to another fixed portion in a state where the thermistor 51 is in contact with the heating resistor to be detected. When there is a sheet passing, heat is not taken away by the sheet in the heating resistors 141 and 143 which are non-sheet passing portions depending on the sheet size.

  In the case of using a high resistance temperature coefficient of about 1000 ppm / ° C. of the heating resistor in the non-sheet passing portion as in the conventional case, the non-sheet passing portion when using a small size paper is temporarily 100 ° C. than the sheet passing portion. If it rises, the resistance value of the non-sheet passing portion will increase by 10% with respect to the resistance value of the sheet passing portion. As the resistance value of the non-sheet passing portion increases, the heat generation amount increases. When the heat generation amount increases, the resistance value further increases and the heat generation amount increases to repeat the vicious circle and increase the temperature of the non-sheet passing portion.

  However, if the resistance temperature coefficient is 100 ppm / ° C., even if the non-sheet passing portion is increased by 100 ° C., the resistance value is increased by 1%, and the vicious circle can be suppressed. If the resistance value is 0 ppm / ° C., the resistance value does not increase, and if it is −100 ppm / ° C., the resistance value decreases by 1%, and if it is −1000 ppm / ° C., the resistance value decreases by 10%. It can be kept small.

  7 to 9 are for explaining a second embodiment relating to the heater of the present invention. FIG. 7 is a top view, FIG. 8 is a sectional view taken along the line dd ′ of FIG. 7, and FIG. It is ee 'sectional drawing. The same components as those in the embodiment described above are denoted by the same reference numerals, and different portions will be described.

  This embodiment uses the short side of the heating resistor 142 located at the center as the width and the long side as the length, and the heating resistors 141 and 143 have the short side and the long side as in FIG. Connected. That is, the other end of the heating resistor 141 having one end connected to the conductor 151 is superimposed on a conductor 1521 formed of the same material as the electrode 12 along one side edge in the longitudinal direction of the insulating substrate 11. Connecting. The conductor 1521 is formed in an L shape extending from the portion connected to the heating resistor 141 to the vicinity of the other side edge so as to be orthogonal to the insulating substrate 11 in a non-contact state with the heating resistor 141. The insulating substrate 11 is connected to a portion of the conductor 1521 orthogonal to the insulating substrate 11 in a state where the short side direction of the heating resistor 142 formed in the longitudinal direction at the center of the insulating substrate 11 is overlapped with one end of the width.

  The other end of the heating resistor 143 having one end connected to the conductor 154 is connected in a state of being superimposed on a conductor 1531 formed of the same material as the electrode 13 along one side edge in the longitudinal direction of the insulating substrate 11. . The conductor 1531 is formed in an L shape by extending the other side edge of the insulating substrate 11 so as to be orthogonal to the heating resistor 143 from a portion connected to the heating resistor 143 in a non-contact state. The insulating substrate 11 is connected to a suitable conductor 1531 orthogonal to the heating resistor 142 in a state where the short side direction of the heating resistor 142 is overlapped with the other end of the width.

  Also in this embodiment, for example, when the A4 size is passed, the heating resistors 141 and 143 in the region where heat is not taken away by the paper is made of a material having a resistance temperature coefficient of 100 ppm / ° C. or less. . The resistance temperature coefficient of the heating resistor 143 is not necessarily set to 100 ppm / ° C. or less.

  10 to 13 are for explaining a third embodiment relating to the heater of the present invention. FIG. 10 is a top view, FIG. 11 is a sectional view taken along line ff ′ of FIG. 10, and FIG. FIG. 13 is a cross-sectional view along gg ′, and FIG. 13 is a cross-sectional view along hh ′ in FIG. The same components as those in the embodiment described above are denoted by the same reference numerals, and different portions will be described.

  In this embodiment, each of the heating resistors 141 and 143 uses a short side as a width and a long side as a length, and the heating resistor 142 uses a short side as a length and a long side as shown in FIG. It is.

  That is, in FIGS. 10 to 13, the other end side of the conductor 1511 whose one end is connected to the electrode 12 is formed in an L shape by extending the insulating substrate 11 from the vicinity of one side edge to the other side edge side in the orthogonal direction. Form. The insulating substrate 11 is connected to a portion of the conductor 1511 orthogonal to the insulating substrate 11 in a state where the short side direction of the heating resistor 141 formed in the longitudinal direction at the center of the insulating substrate 11 is overlapped with one end of the width. The other end of the width of the heat generating resistor 141 in the short direction is overlapped with a suitable portion perpendicular to the insulating substrate 11 of the conductor 1522 formed of the same material as the electrode 12 along the side edge in the longitudinal direction of the insulating substrate 11. Connect in the state where The conductor 1522 along the side edge of the insulating substrate 11 is connected in a state of being overlapped with one end of the heating resistor 142 having a width in the longitudinal direction.

  The other end of the heating resistor 142 having a width in the longitudinal direction is connected in a state of being superimposed on a conductor 1532 formed of the same material as the electrode 12 along the other side edge in the longitudinal direction of the insulating substrate 11. The conductor 1532 is formed in an L shape by extending the insulating substrate 11 from one side edge to the other side edge in a direction orthogonal to the heating resistor 143 from a portion connected to the heating resistor 143. The insulating substrate 11 is connected to a portion of the conductor 1532 perpendicular to the insulating substrate 11 in a state where the short side direction of the heating resistor 143 formed in the longitudinal direction at the center of the insulating substrate 11 is overlapped with one end of the width. The other end of the width of the heat generating resistor 143 in the short direction is overlapped with a suitable portion perpendicular to the insulating substrate 11 of the conductor 1541 formed of the same material as the electrode 13 along the side edge in the longitudinal direction of the insulating substrate 11. Connect in the state where

  Also in this embodiment, the heating resistor 142 is partitioned by a width corresponding to, for example, an A4 size sheet, and the heating resistors 141 to 143 are partitioned by a width corresponding to, for example, an A3 size sheet. In addition, at least the heating resistors 141 and 143 among the heating resistors 141 to 143 are formed of a material having a resistance temperature coefficient of 100 ppm / ° C. or less. Since the temperature of the heater 100 is detected by the thermistor 51, it is not always necessary to use the heating resistor 142 having a resistance temperature coefficient of 100 ppm / ° C. or less.

  In each of the first to third embodiments related to the heater of the present invention described above, the resistance temperature coefficient of the heating resistor of the portion that heats the paper having a size larger than the frequently used size is classified while the heating resistor is sized. By using the one of 100 ppm / ° C. or less, it is possible to suppress the temperature rise in the non-sheet passing state. Further, since the temperature adjustment is performed while viewing the temperature state of the heat generating resistor in the sheet passing state among the sized heat generating resistors with a thermistor, more accurate temperature control can be realized.

  14 to 17 are diagrams for explaining a fourth embodiment relating to the heater of the present invention. FIG. 14 is a top view, FIG. 15 is a cross-sectional view taken along line ii ′ of FIG. 14, and FIG. FIG. 17 is a cross-sectional view taken along the line j-j 'and FIG. 17 is a cross-sectional view taken along the line k-k' in FIG. The same components as those in the embodiment described above are denoted by the same reference numerals, and different portions will be described.

  In the above-described first to third embodiments relating to the heater described above, the position through which the A4 sheet passes is the center of the heater 100. However, in this embodiment, the object to be heated is used as the one-side reference. In other words, both the A4 and A3 sheets are passed through the heater 100 in the same position on one side.

  14 to 17, the other end of the conductor 1511 whose one end is connected to the electrode 12 is extended in the shape perpendicular to the longitudinal direction of the insulating substrate 11 from the vicinity of one side edge to the other side edge side to form an L shape. To form. The insulating substrate 11 is connected to a portion of the conductor 1511 perpendicular to the insulating substrate 11 in a state where the short side direction of the heating resistor 142 formed in the longitudinal direction of the insulating substrate 11 is overlapped with one end of the width. The other end of the width of the heating resistor 142 in the short direction is overlapped with a suitable portion perpendicular to the insulating substrate 11 of the conductor 1531 formed of the same material as the electrode 12 along the side edge in the longitudinal direction of the insulating substrate 11. Connect in the state where The conductor 1531 along the side edge of the insulating substrate 11 is connected in a state of being overlapped with one end of the heating resistor 1431 having a width in the longitudinal direction. The other end of the heating resistor 1431 having a width in the longitudinal direction is connected in a state of being superimposed on a conductor 154 formed of the same material as the electrode 13 along the other side edge in the longitudinal direction of the insulating substrate 11. Note that the width of the heating resistor 1431 is the combined width of the heating resistors 141 and 143 in FIG.

  The heating resistor 142 is divided by a width corresponding to, for example, an A4 size sheet, and the heating resistors 142 and 1431 are divided by a width corresponding to, for example, an A3 size sheet. Further, at least the heating resistor 1431 among the heating resistors 142 and 1431 is formed of a material having a resistance temperature coefficient of 100 ppm / ° C. or less. Since the temperature of the heater 100 is detected by the thermistor 51, it is not always necessary to use the heating resistor 142 having a resistance temperature coefficient of 100 ppm / ° C. or less.

  In the embodiment relating to the heater of the present invention, it is possible to suppress the temperature rise in the non-sheet passing state and to align one side of the paper with different dimensions at a specific position.

  In each of the above-described embodiments of the heater of the present invention, the paper size to be heated is described as A4 and A3. However, the position corresponding to A4 is a postcard and the position corresponding to A3 is A4. Etc., and can be appropriately changed based on the system.

  Next, with reference to FIG. 18, an embodiment of the heating device of the present invention when the above-described heater is mounted on the heating device 200 will be described. The heater 100 in the figure is the heater described with reference to FIGS. 1 to 5, and the same portions are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 18, reference numeral 201 denotes a pressure roller that 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 thereof. The heater 100 is mounted in parallel in a base (not shown) so as to face the rotating shaft 202 of the pressure roller 201.

  Around the heater 100, an endless roll-shaped fixing film 204 made of a heat-resistant sheet such as polyimide resin is circulated, and the overcoat of the insulating substrate 11 on which the heating resistors 141 to 143 are formed. The surface of the layer 16 is in elastic contact with the silicone rubber layer 203 of the pressure roller 201 through the fixing film 204.

  In the heating device 200 of FIG. 18, the heater 100 is energized to the electrodes 12 and 13 through a connector (not shown) in which the phosphor bronze plate or the like that is in contact with the electrodes 12 and 13 is subjected to silver plating, and is supplied with heat. Heat generated at 143 is transmitted to the insulating substrate 11 and the overcoat layer 16. The toner image To1 is first heated and melted by the heater 100 through the fixing film 204 between the surface of the fixing film 204 provided on the overcoat layer 16 and the silicone rubber layer 203, and at least the surface portion thereof greatly exceeds the melting point. It completely softens and melts. Thereafter, on the paper discharge side of the pressure roller 201, the copy paper P is separated from the heater 100, the toner image To2 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 To1 is once softened and melted completely, and then cooled again on the paper discharge side of the pressure roller 201. Therefore, the condensing force of the toner image To2 is very large.

  In the heating device 200, it is possible to suppress the temperature rise of the portions of the heating resistors 141 to 143 through which the sheet does not pass without switching the heating resistors 141 to 143 for different sheets. This eliminates the need for switching means for the heating resistors 141-143.

  Next, an image forming apparatus according to the present invention will be described with reference to FIG. 19, taking as an example a copier equipped with a heater according to the present invention and a heating device using the heater. 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. 19, 301 is a casing of the copying machine 300, 302 is a document placing table made of a transparent member such as glass provided on the upper surface of the casing 301, and scans the document P1 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 copy paper P 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 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 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. The pressure roller 201 of the heater 100 is provided by extending the heating resistors 141 to 143.

  Then, the unfixed toner image To1 on the copy paper P sent between the heater 100 and the pressure roller 201 is melted by the heat of the heating resistor 19, and the characters, alphanumeric characters and symbols on the copy paper P surface are melted. A copy image such as a drawing is displayed.

  In this embodiment, it is not necessary to switch a plurality of heating resistors, and the heater 100 that can be used even when different sheets are used that can obtain substantially the same temperature distribution over the entire heating portion of the heating resistors. Thus, the copying machine 300 using the heating device 200 can be realized.

  The heater is used for fixing image forming devices such as copiers, but is not limited to this, and is used for household electrical appliances, precision equipment for business use and experiments, equipment for chemical reactions, etc. It can also be used as a heat source for heating and heat insulation.

The top view for demonstrating 1st Embodiment regarding the heater of this invention. FIG. 2 is a cross-sectional view taken along the line a-a ′ in FIG. 1. B-b 'sectional drawing of FIG. C-c 'sectional drawing of FIG. The rear view of FIG. The circuit block diagram for demonstrating the temperature adjustment used for FIG. The top view for demonstrating 2nd Embodiment regarding the heater of this invention. D-d 'sectional drawing of FIG. E-e 'sectional drawing of FIG. The top view for demonstrating 3rd Embodiment regarding the heater of this invention. F-f 'sectional drawing of FIG. G-g 'sectional drawing of FIG. H-h 'sectional drawing of FIG. The top view for demonstrating 4th Embodiment regarding the heater of this invention. I-i 'sectional drawing of FIG. J-j 'sectional drawing of FIG. K-k 'sectional drawing of FIG. 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 141-143 Heating resistors 151-154, 1521, 1531 Conductor 16 Overcoat layer 51 Thermistor 100 Heater 200 Heating device 300 Copying machine

Claims (4)

A long flat heat-resistant insulating substrate;
Electrically formed on the insulating substrate using a graphite-based material, having a resistance temperature coefficient of less than 0 ppm / ° C., and the direction of energization being perpendicular to the longitudinal direction of the insulating substrate A first heating resistor having a flexible end;
An electrical end portion formed on the insulating substrate along with the first heating resistor in the longitudinal direction of the insulating substrate, and in such a manner that the direction of energization is perpendicular to the longitudinal direction of the insulating substrate. A second heating resistor having
The first heat generating resistor is formed on the insulating substrate using a graphite-based material in parallel with the second heat generating resistor in the longitudinal direction of the insulating substrate from the second heat generating resistor. A third heating resistor having an electrical end so that the temperature coefficient of resistance is less than 0 ppm / ° C. and the direction of energization is perpendicular to the longitudinal direction of the insulating substrate;
The first, second, and third heating resistors provided on the insulating substrate from the first heating resistor through the second heating resistor to the third heating resistor. A conductor electrically connected in series;
A pair of power supply electrodes provided on the insulating substrate and serving as electrical ends of the entire first, second, and third heating resistors connected in series by the conductor;
An overcoat layer that covers and protects the first, second, and third heating resistors and the conductor.   It further comprises a temperature detecting element provided on the insulating substrate on the side opposite to the side on which the second heating resistor is formed to detect the temperature of the second heating resistor. The heater according to claim 1. A pressure roller;
The heater according to claim 1 or 2, wherein the first, second, and third heating resistors are arranged to face the pressure roller.
A heating device, comprising: a fixing film movably provided between the heater and the pressure roller. Image forming means for forming an image by attaching toner to an electrostatic latent image formed on a medium and further transferring the toner to paper;
A heating device according to claim 3,
The image forming apparatus, wherein the paper on which the image is formed is passed through the fixing film while being pressed against the heater by the pressure roller, and the toner is fixed on the paper. .

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