JP2008166096A - Flat plate heater, fixing device, and image processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature rise in a region forming a paper non-passing part while using an inexpensive material having a TCR of negative characteristics for a heat generating resistor. <P>SOLUTION: Heat generating resistors 16, 18 having widths in the longitudinal direction of a long flat plate-like insulating substrate 11 made of ceramic and having lengths in its short direction are formed in the longitudinal direction on the substrate. The heat generating resistors 16, 18 are connected in series by a connecting conductor 17. One end of the heat generating resistor 16 is connected to the connecting conductor 17 while the other end is connected to an electrode 12 for power supply through a connecting conductor 14 and one end of the heat generating resistor 18 is connected to the connecting conductor 17 while the other end is connected to an electrode 13 for power supply through a connecting conductor 15. The heat generating resistor 16 has a negative temperature coefficient of resistance, and a narrowed width part 161 is formed in the center part of the longitudinal direction of the insulating substrate, and wide width parts 162, 163 made wider than the narrow width part 161 are formed at its both ends. The heat generating resistor 18 has a negative temperature coefficient of resistance, and a narrowed width part 181 is formed in the center part of the longitudinal direction of the insulating substrate, and wide width parts 182, 183 made wider than the narrow width part 181 are formed at its both ends. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin flat plate 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 copying machine, a facsimile, a rewritable card reader / writer, and the like mounted with the flat plate heater, The present invention relates to an image forming apparatus using the heating device.

Conventionally, a single wide heating resistor is formed in the short direction of a strip-shaped insulating substrate, and this heating resistor is a single wide heating resistor together with a flat plate heater having a positive temperature coefficient (PTC). When fixing a paper that is smaller than the heater size, the temperature at the end may be higher than the center of the heater where heat is taken away by the paper passing through the heater. If the value becomes high, the contact resistance with the power feeding connector increases, which may cause problems such as contact failure. For this reason, a PTC wide heating resistor is formed in the longitudinal direction of the substrate, a conductor is formed along both longitudinal ends of the PTC wide heating resistor, and the conductor is connected to the power feeding electrode. (For example, Patent Document 1)
JP-A-7-94260

The technique of the above-mentioned Patent Document 1 uses a high-priced noble metal such as an alloy of Ag (silver) / Pd (palladium) or RuO ₂ (ruthenium oxide) as a PTC heating resistor material, and the manufacturing cost is high. There is a problem of getting higher. Inexpensive heat generating resistors may be composed of graphite made of carbon or carbon as the main component. However, since the temperature coefficient of resistance (TCR) is a negative heat generating resistor, When the temperature difference occurs, there is a problem that the resistance value at the high temperature portion is lowered and the amount of heat generation is increased.

  An object of the present invention is to provide a flat plate heater capable of manufacturing a heater having a uniform temperature distribution in the longitudinal direction of an insulating substrate at a low cost, a fixing device using the flat plate heater, and an image forming apparatus using the fixing device.

  In order to solve the above-described problems, a flat plate heater according to the present invention is formed of a long flat plate insulating substrate made of a heat-resistant and insulating material, and formed along the longitudinal direction of the insulating substrate. First and second heating resistors having a width in the longitudinal direction and a length in the short direction, and a first connection conductor in which the first and second heating resistors are connected in series on the insulating substrate; A second connecting conductor connected to one end of the first heating resistor, a first electrode connected to the first connecting conductor, and a second electrode connected to the other end of the second heating resistor. A third connection conductor; and a second electrode connected to the second connection conductor, wherein the first heating resistor has a negative resistance temperature coefficient and has a longitudinal center portion. A wide portion with a wider width, and the width of both end portions in the longitudinal direction is narrower than the wide portion. The second heating resistor has a negative resistance temperature coefficient, is a narrow portion with a narrow central portion in the longitudinal direction, and has a width at both end portions in the longitudinal direction that is smaller than the narrow portion. It is characterized by a wide wide part.

  The flat plate heater according to the present invention includes a long flat insulating substrate formed of a heat-resistant / insulating material and a longitudinal direction of the insulating substrate. A first heating resistor having a length in a direction; a first connection conductor in which the first and second heating resistors are connected in series on the insulating substrate; and the first heating resistor. A second connection conductor connected to one end of the body, a first electrode connected to the first connection conductor, a third connection conductor connected to the other end of the second heating resistor, A second electrode connected to the second connection conductor, wherein the first heating resistor has a negative resistance temperature coefficient, widens the central portion in the longitudinal direction, The second heating resistor has a negative temperature coefficient of resistance and is long Narrowing the width of the center portion of the direction, characterized in that the gradually wide toward both ends in the longitudinal direction.

  According to the present invention, while using an inexpensive material having a negative TCR characteristic for the heating resistor, it is possible to suppress a temperature rise in a region corresponding to a non-sheet passing portion where heat dissipation due to sheet passing is small.

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

1 to 3 are diagrams for explaining a first embodiment of the flat plate heater according to the present invention. FIG. 1 is a configuration diagram, FIG. 2 is a cross-sectional view taken along the line aa 'in FIG. 1, and FIG. It is bb 'sectional drawing of.
In FIG. 1 to FIG. 3, reference numeral 11 denotes a heat-resistant, electrically insulating material such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), or other highly rigid material having electrical insulation. It is a strip-shaped insulating substrate having a high thermal conductivity and a base material such as ceramic.

  On both ends of the insulating substrate 11, electrodes 12 and 13 for feeding a good conductor film obtained by baking a silver-based conductor paste are formed. Reference numeral 14 denotes a connection conductor which is integrally formed of the same material as the electrode 12 and is formed up to the vicinity of the electrode 13 along one edge in the longitudinal direction of the insulating substrate 11. Reference numeral 15 denotes a connection conductor which is integrally formed of the same material as the electrode 13 and is formed up to the vicinity of the electrode 12 along the other edge in the longitudinal direction of the insulating substrate 11.

  Reference numeral 16 denotes a heating resistor formed along the longitudinal direction on the surface side of the insulating substrate 11 and formed in a state where one end having a short length and a wide width overlaps a part of the connection conductor 14. The heating resistor 16 includes a short central portion 161 and long ends 162 and 163 at both ends. The heating resistor 16 has a concave shape on the lower side in the figure.

  The other end of the heating resistor 16 is connected, for example, in a state where it overlaps with a part of the connection conductor 17 formed of the same material as that of the connection conductor 14 and having the substantially same width and protruding at the center.

  Reference numeral 18 denotes a heating resistor formed along the longitudinal direction on the surface side of the insulating substrate 11 and formed in a state where one end having a short length and a wide width overlaps a part of the connection conductor 15. The heating resistor 18 includes a long central portion 181 and short end portions 182 and 183 at both ends. The heating resistor 16 has a convex shape on the lower side in the figure.

  The heating resistors 16 and 18 are each formed by forming a thick film having a predetermined resistance value, for example, by baking a paste-like graphite resistor having a negative TCR characteristic at a high temperature. The heating resistors 16 and 18 have characteristics as shown in FIG. 4 because the TCR is formed of a material having negative characteristics. That is, the heating resistor made of graphite has a characteristic that the resistance value is large when the temperature is low and the resistance value is small when the temperature is high. TCR is negative, for example, -100 ppm / ° C. or less.

  The resistance value of the heating resistor 16 between the connection conductor 14 and the connection conductor 17 is set to the same value as the resistance value of the heating resistor 18 between the connection conductor 17 and the connection conductor 15.

  19 covers the connection conductors 14, 15, 17 and the heating resistors 16, 18, and is formed by applying and baking a glass paste, for example, by a thick film printing method in order to provide electrical, mechanical and chemical protection. Overcoat layer.

  In FIG. 1, t1 in the heating resistors 16 and 18 indicates an area corresponding to a width necessary for fixing, for example, an A4 size sheet, and the areas t2 and t3 include, for example, an A3 size area together with the area t1. The width of the region t4 (= t1 + t2 + t3) corresponding to the width of the size on which the sheet is fixed is provided.

  Here, when the electrodes 12 and 13 are energized and the heating resistors 16 and 18 start the temperature increase or when the effective heating area t4 of the heating resistors 16 and 18 is passed, the heating resistors 16 and 18 There is almost no temperature difference between the region t1 at the center of 18 and the regions t2 and t3 on both sides thereof. The resistance R1 in the region t1 of the heating resistors 16 and 18 connected in series is substantially equal to the resistance R2 of the heating resistors 16 and 18 in the regions t2 and t3. For this reason, the heat generation amount W1 in the region t1 and the heat generation amount W2 in the regions t2 and t3 are approximately the same. That is, R1≈R2 → W1≈W2.

  Therefore, as shown in FIG. 5, the heat generation amount W1 in the central region t1 of the insulating substrate 11 and the heat generation amount W2 in the end regions t2 and t3 of the insulating substrate 11 are approximately the same. The calorific value W obtained by synthesizing these calorific values W1 and W2 can obtain a substantially uniform temperature distribution in the longitudinal direction of the insulating substrate 11.

  As described above, since the TCR of the heating resistors 16 and 18 is formed of a negative material, the resistance value decreases as the temperature increases. When a sheet having a size smaller than the entire effective heating region of the heating resistors 16 and 18 is heated and fixed, the temperature of the end regions t2 and t3 tends to rise from the central portion t1, but the heating resistor 16 , 18 have negative characteristics, the decrease in resistance value on the regions t2 and t3 side is larger than that on the region t1.

  When the resistance value of the region t2 is R (t2), the resistance value of the region t2 is R (t1), and the difference is ΔR, ΔR = R (t1) −R (t2). The resistance value of the region t3 is the same value as that of the region t2, and the value of the difference ΔR is substantially the same. From this relationship, the temperature T (t2, t3) of the regions t2 and t3 and the temperature T (t1) of the region t1 are T (t2, t3)> T (t1), and ΔR (t2, t3 of the regions t2 and t3 ) And ΔR (t1) in the region t1 are ΔR (t2, t3) <ΔR (t1).

  The resistance values of the heating resistors 16 and 18 in the region t1 and the heating resistors 16 and 18 in the regions t2 and t3 are compared to the case where there is no temperature difference between the regions t2 and t3 which are the end portions and the region t1 which is the central portion. The resistance value of the end portion becomes small. For this reason, the heating resistor 18 having a large resistance at the end portion has a smaller resistance value than the heating resistor 16 having a large resistance at the center. That is, when the temperature has a relationship of T (t2, t3)> T (t1), the resistance is R16 (t2, t3) <R18 (t1).

  As shown in FIG. 6, since the heating resistors 16 and 18 are connected in series, the heat generation in the regions t2 and t3 having a lower resistance value than the heat generation amount W1 of the heating resistors 16 and 18 in the region t1 having a higher resistance value. The amount W2 is reduced. That is, when the temperature is in the relationship of T (t2, t3)> T (t1), the heat generation amount is W2 (t2, t3) <W1 (t1). Thereby, the calorific value in which the calorific value of the end portion having a high temperature is suppressed can be obtained.

  In this embodiment, while using a material having a negative TCR characteristic for the heating resistor, the temperature rise in the region corresponding to the non-sheet passing portion where heat dissipation due to the sheet passing is small is suppressed, and the entire effective region of the heating resistors 16 and 18 is reduced. A uniform temperature distribution can be obtained.

  7 to 9 are for explaining a second embodiment relating to the flat plate heater of the present invention. FIG. 7 is a structural view, FIG. 8 is a sectional view taken along the line cc 'of FIG. 7, and FIG. It is dd 'sectional drawing of. The same components as those in the above-described embodiments will be described with the same reference numerals.

  In FIG. 7, reference numeral 71 denotes a heating resistor formed along the longitudinal direction on the surface side of the insulating substrate 11 and formed in a state where one end having a short length and a wide width overlaps a part of the connection conductor 14. . The heating resistor 71 has a shape in which the length is short at the central portion in the longitudinal direction of the insulating substrate 11 and the length is gradually increased toward both ends thereof. Accordingly, the heating resistor 71 has a concave curved shape on the lower side in the drawing.

  The other end of the heating resistor 71 is connected in a state where it overlaps with a part of the connection conductor 73 having a curved shape, for example, made of the same material as the connection conductor 14 and having the same width.

  Reference numeral 72 denotes a heating resistor formed along the longitudinal direction on the surface side of the insulating substrate 11 and formed in a state where one end having a short length and a wide width overlaps a part of the connection conductor 73. The heating resistor 72 has a shape in which the length of the central portion is long and the length is gradually shortened toward both ends thereof. Therefore, the heating resistor 71 has a curved shape with a convex upper side in the drawing. The other end of the heating resistor 72 is connected in a state of being overlaid on a part of the connection conductor 15.

  The heating resistors 71 and 72 are each formed by forming a thick film having a predetermined resistance value, for example, by baking a paste-like graphite resistor having a negative TCR characteristic at a high temperature. Since the heating resistors 71 and 72 are made of a material having a negative TCR characteristic, they have characteristics as shown in FIG. That is, the heating resistor made of graphite has a characteristic that the resistance value is large when the temperature is low and the resistance value is small when the temperature is high.

  The resistance value of the heating resistor 71 between the conductor 14 and the connection conductor 73 is set to the same value as the resistance value of the heating resistor 72 between the connection conductor 73 and the conductor 15.

  In FIG. 7, t1 in the heating resistors 71 and 72 indicates an area corresponding to, for example, a width necessary for A4 size fixing, and areas t2 and t3 are fixed together with, for example, A3 size paper. The width of the region t4 (= t1 + t2 + t3) corresponding to the size width is provided.

  Here, when the electrodes 12 and 13 are energized and the heating resistors 71 and 72 start temperature rising or when A3 size paper is passed, the central region t1 of the heating resistors 71 and 72 and both sides thereof. There is almost no temperature difference between the regions t2 and t3. The resistance R1 in the region t1 of the heating resistors 71 and 72 connected in series is substantially equal to the resistance R2 of the heating resistors 71 and 72 in the regions t2 and t3. For this reason, the heat generation amount W1 in the region t1 and the heat generation amount W2 in the regions t2 and t3 are approximately the same. That is, R1≈R2 → W1≈W2.

  Therefore, as shown in FIG. 5, the calorific value W1 of the central region t1 and the calorific value W2 of the end regions t2 and t3 are approximately the same. The calorific value W obtained by synthesizing these calorific values W1 and W2 can obtain a substantially uniform temperature distribution in the longitudinal direction of the insulating substrate 11.

  The TCRs of the heating resistors 71 and 72 are made of a negative material, and the resistance value decreases as the temperature rises. When a sheet having a size smaller than the effective heating area of the heating resistors 71 and 72 is heated and fixed, the temperature of the areas t2 and t3 tends to rise from the area t1, but the TCR of the heating resistors 71 and 72 is increased. Is a negative characteristic, the decrease in the resistance value on the regions t2 and t3 side is larger than that on the region t1.

  When the resistance value of the region t2 is R (t2), the resistance value of the region t2 is R (t1), and the difference is ΔR, ΔR = R (t1) −R (t2). The resistance value of the region t3 is the same value as that of the region t2, and the value of the difference ΔR is substantially the same. From this relationship, the temperature T (t2, t3) of the regions t2 and t3 and the temperature T (t1) of the region t1 are T (t2, t3)> T (t1), and ΔR (t2, t3 of the regions t2 and t3 ) And ΔR (t1) in the region t1 are ΔR (t2, t3) <ΔR (t1).

  The resistance values of the heat generating resistors 71 and 72 in the region t1 and the heat generating resistors 71 and 72 in the regions t2 and t3 are compared to the case where there is no temperature difference between the regions t2 and t3 which are the end portions and the region t1 which is the central portion. The resistance value of the end portion becomes small. For this reason, the resistance values of the heating resistors 71 and 72 having a large resistance at the end are smaller than those of the heating resistors 71 and 72 having a large resistance at the center. That is, T (t2, t3)> T (t1) → R (t2, t3) <R (t1).

  As shown in FIG. 6, since the heat generating resistors 71 and 72 are connected in series, the heat generation in the regions t2 and t3 having a smaller resistance value than the heat generation amount W1 of the heat generating resistors 71 and 72 in the region t1 having a large resistance value. The amount W2 is reduced. That is, T (t2, t3)> T (t1) → W2 (t2, t3) <W1 (t1), and the amount of heat generated at the end portion having a high temperature can be suppressed.

  In this embodiment, the relationship described above is established at any position within the range of the region t4. Therefore, as long as the size of the paper is within the region t4, it is possible to suppress a temperature rise in other regions where the paper is not passed, regardless of the size of the paper that is passed.

  10 to 12 are for explaining a third embodiment relating to the flat plate heater of the present invention. FIG. 10 is a block diagram, FIG. 11 is a rear view of FIG. 10, and FIG. 'Cross section. The same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  That is, the connection conductor 141 is formed on the insulating substrate 11 in a state where a part of the connection conductor 141 is overlaid on the other end of the heating resistor 16 connected to the connection conductor 17 at one end. A through hole 101 is formed in the intermediate portion of the connecting conductor 141 in the longitudinal direction of the insulating substrate 11, and is electrically connected to one end of the connecting conductor 111 formed on the back side of the insulating substrate 11 shown in FIG. The other end of the connection conductor 111 is electrically connected to the electrode 12 through the through hole 102. The connection conductor 141 is made of, for example, an Ag-based material having a positive TCR characteristic. TCR is set to 1000 ppm / ° C. or higher.

  Further, the connection conductor 151 is formed on the insulating substrate 11 in a state where a part of the connection conductor 151 is layered on the other end of the heating resistor 18 connected to the connection conductor 17 at one end. A through hole 103 is formed in the intermediate portion of the connecting conductor 151 in the longitudinal direction of the insulating substrate 11, and is electrically connected to one end of the connecting conductor 112 formed on the back side of the insulating substrate 11 shown in FIG. The other end of the connection conductor 111 is electrically connected to the electrode 13 through the through hole 104. The connection conductor 151 is formed of, for example, an Ag-based material having a positive TCR characteristic.

  113 is an over-layer formed by coating and baking, for example, glass paste by a thick film printing method in order to cover the connection conductors 111 and 112 and the through holes 101 to 104 and perform electrical, mechanical and chemical protection. It is a coat layer.

  13 to 16 are for explaining a fourth embodiment relating to the flat plate heater of the present invention. FIG. 13 is a structural view, FIG. 14 is a sectional view taken along the line dd ′ of FIG. 13, and FIG. FIG. 16 is a sectional view taken along the line ef ′ of FIG.

  In this embodiment, the electrodes 12 and 13 are electrically connected to intermediate portions of the heating resistors 16 and 18 on the same surface of the insulating substrate 11 without using through holes.

  That is, the connection conductor 142 is formed on the insulating substrate 11 in a state where a part of the connection conductor 142 is overlapped with the other end of the heating resistor 16 connected to the connection conductor 17 at one end. The intermediate portion of the connecting conductor 142 in the longitudinal direction of the insulating substrate 11 and the electrode 12 are connected by the connecting conductor 143. The connection conductors 142 and 143 are made of, for example, an Ag-based material having a positive TCR characteristic.

  Further, the connection conductor 152 is formed on the insulating substrate 11 in a state where a part of the connection conductor 152 is overlapped with the other end of the heating resistor 18 connected at one end to the connection conductor 17. The intermediate portion of the connecting conductor 152 in the longitudinal direction of the insulating substrate 11 and the electrode 13 connect the connecting conductor 153 by connection. The connection conductors 152 and 153 are made of, for example, an Ag-based material having a positive TCR characteristic.

  In the third and fourth embodiments described above, since the connection conductors 14, 142, 143, 15, 152, and 153 are formed of conductors having a positive TCR characteristic, the resistance increases as the temperature increases. The value gets higher. That is, when the temperature has a relationship of T (t2, t3)> T (t1), the resistance is R (t2, t3) <R (t1).

  In addition, electrodes 12 and 13 to which electric power is supplied are connected to intermediate portions of the heating resistors 16 and 18 through connection conductors, respectively. When the temperatures of the flow areas t2 and t3, which are the ends in the longitudinal direction of the insulating substrate 11, increase, the resistance value of the conductors in the areas t2 and t3 becomes high, and the current hardly flows to the heating resistors 16 and 18. Therefore, it becomes difficult for current to flow through the heating resistors 16 and 18 at the ends in the longitudinal direction, and the amount of generated heat can be suppressed.

  As described above, in the case of the third and fourth embodiments, the temperature rise in the region corresponding to the non-sheet passing portion where the heat radiation due to the sheet passing is small is suppressed, and the uniform temperature distribution in the entire effective region of the heating resistors 16 and 18 is obtained. Obtainable.

  Next, fifth and sixth embodiments relating to the flat plate heater of the present invention will be described. FIGS. 17 to 19 are for explaining the fifth embodiment, and FIGS. 20 to 23 are for explaining the sixth embodiment.

  First, in FIGS. 17 to 19, FIG. 17 is a configuration diagram, FIG. 18 is a rear view of FIG. 17, and FIG. 19 is a cross-sectional view taken along line i-i ′ of FIG. The same components as those in FIGS. 7 to 9 of the second embodiment and FIGS. 10 to 12 of the third embodiment are denoted by the same reference numerals, and different portions will be mainly described here.

  In this embodiment, the portions corresponding to the connection conductors 14 and 15 having the configuration of FIG. 7 are the connection conductors 141 and 151 made of, for example, Ag-based material having a positive TCR characteristic as described with reference to FIG. Further, as described in FIGS. 10 and 11, the connection conductor 141 and the electrode 12 are connected through the through hole 101, the connection conductor 111, and the through hole 102. The connection conductor 151 and the electrode 13 are connected through the through hole 103, the connection conductor 112, and the through hole 104.

Next, in FIGS. 20 to 23, FIG. 20 is a configuration diagram, FIG. 21 is a cross-sectional view taken along line j ′ of FIG. 20, FIG. 22 is a cross-sectional view taken along line kk ′ of FIG. It is l 'sectional drawing. This embodiment is similar to the fifth embodiment shown in FIGS. 17 to 19 in that the electrodes 12 and 13 are formed on the same surface of the insulating substrate 11 without using through-holes and in the intermediate portions of the heating resistors 71 and 72. In the fifth and sixth embodiments described above, the intermediate portions of the connection conductors 141 and 142 and the electrode 12 are connected to each other, and the intermediate portions of the connection conductors 151 and 152 and the electrode 13 are connected to each other. In addition to being connected, these connection conductors are made of, for example, an Ag-based material having a positive TCR characteristic.

  Therefore, the resistance value increases as the temperature increases. That is, when the temperature has a relationship of T (t2, t3)> T (t1), the resistance is R (t2, t3) <R (t1).

  In addition, electrodes 12 and 13 to which electric power is supplied are connected to intermediate portions of the heating resistors 71 and 72 via connecting conductors, respectively. When the temperatures of the flow areas t2 and t3, which are the ends in the longitudinal direction of the insulating substrate 11, increase, the resistance value of the conductors in the areas t2 and t3 increases, and it becomes difficult for current to flow to the heating resistors 71 and 72. Therefore, it becomes difficult for current to flow through the heating resistors 71 and 72 at the ends in the longitudinal direction, and the amount of generated heat can be suppressed.

  FIG. 24 is a cross-sectional view for explaining an embodiment in which the plate heater of the present invention is a heating device 200 for toner fixing.

  In FIG. 24, reference numeral 201 denotes a plate heater 100 fixed to the bottom of a support 202, an AC voltage is supplied to the plate heater 100, and the plate heater 100 moves while being pressed against the overcoat layer 19 of the heated plate heater 100. This is a cylindrical fixing film in which a heat-resistant sheet of polyimide resin or the like 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, between the surface of the fixing film 201 disposed on the overcoat layer 28 and the silicone rubber layer 204, the toner image To1 is first heated and melted by the plate heater 100 via the fixing film 201, and at least the surface portion thereof. 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, since a low-priced material such as graphite having a negative TCR characteristic can be used for the heating resistor of the flat plate heater, the temperature rise in the region corresponding to the non-sheet passing portion with less heat dissipation due to sheet passing can be simplified. Can be suppressed.

  Next, with reference to FIG. 25, 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. 25, 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 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 long heating resistors 16 and 18 is provided in a state where it is pressed against 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 the heat of the heating resistor 16 and is printed on the surface of the copy paper P with characters, alphanumeric characters, Copy images such as symbols and drawings are displayed.

  In this embodiment, an image forming apparatus that suppresses a temperature rise in a non-sheet passing portion can be realized by using a heating device by the plate heater 100 using an inexpensive heating resistor such as graphite.

  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 1st Embodiment regarding the flat plate 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. Explanatory drawing for demonstrating the temperature characteristic of the heating resistor used for this invention. Explanatory drawing for demonstrating the effect of this invention. Explanatory drawing for demonstrating the effect of this invention. The block diagram for demonstrating 2nd Embodiment regarding the flat plate heater of this invention. C-c 'sectional drawing of FIG. D-d 'sectional drawing of FIG. The block diagram for demonstrating 3rd Embodiment regarding the flat heater of this invention. The rear view of FIG. E-e 'sectional drawing of FIG. The block diagram for demonstrating 4th Embodiment regarding the flat heater of this invention. F-f 'sectional drawing of FIG. FIG. 14 is a g-g ′ sectional view of FIG. 13. FIG. 14 is a cross-sectional view taken along the line h-h ′ in FIG. 13. The block diagram for demonstrating 5th Embodiment regarding the flat heater of this invention. The rear view of FIG. I-i 'sectional drawing of FIG. The block diagram for demonstrating 6th Embodiment regarding the flat plate heater of this invention. J-j 'sectional drawing of FIG. K-k 'sectional drawing of FIG. FIG. 21 is a cross-sectional view taken along the line l-l ′ of FIG. 20. 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, 17, 73, 111, 112, 141-143, 151-153 Connecting conductors 16, 18, 71, 72 Heating resistors 19, 113 Overcoat layers 101-104 Through hole 100 Flat plate heater 200 Heating device 300 Copying machine

Claims (8)

A long flat insulating substrate formed of a heat-resistant and insulating material;
First and second heating resistors formed along the longitudinal direction of the insulating substrate, each having a longitudinal direction as a width and a short direction as a length;
A first connecting conductor in which the first and second heating resistors are connected in series on the insulating substrate;
A second connection conductor connected to one end of the first heating resistor;
A first electrode connected to the first connection conductor;
A third connecting conductor connected to the other end of the second heating resistor;
A second electrode connected to the second connection conductor,
The first heating resistor has a negative resistance temperature coefficient, and has a wide portion in which the width of the central portion in the longitudinal direction of the insulating substrate is widened, and the width of both end portions in the longitudinal direction is narrower than that of the wide portion. A narrow part,
The second heating resistor has a negative temperature coefficient of resistance, and has a narrow portion with a narrow central portion in the longitudinal direction of the insulating substrate. The width of both end portions in the longitudinal direction is smaller than that of the narrow portion. A flat heater characterized by a wide and wide part. A long flat insulating substrate formed of a heat-resistant and insulating material;
First and second heating resistors formed along the longitudinal direction of the insulating substrate, each having a longitudinal direction as a width and a short direction as a length;
A first connecting conductor in which the first and second heating resistors are connected in series on the insulating substrate;
A second connection conductor connected to one end of the first heating resistor;
A first electrode connected to the first connection conductor;
A third connecting conductor connected to the other end of the second heating resistor;
A second electrode connected to the second connection conductor,
The first heating resistor has a negative resistance temperature coefficient, widens the width of the central portion in the longitudinal direction of the insulating substrate, and gradually narrows the width toward both ends in the longitudinal direction,
The flat plate heater, wherein the second heating resistor has a negative temperature coefficient of resistance, the width of the central portion in the longitudinal direction of the insulating substrate is narrowed, and gradually widened at both end portions in the longitudinal direction.   The flat plate heater according to claim 1 or 2, wherein a resistance value of the first and second heating resistors in the short direction of the insulating substrate is the same value as each portion in the longitudinal direction. .   The first electrode is connected to an intermediate portion of the second connection conductor, and the second electrode is connected to an intermediate portion of the third connection conductor, respectively. The flat plate heater described.   The connection between the first electrode and the second connection conductor and the connection between the second electrode and the third connection conductor are connected via different through-holes on different surfaces of the insulating substrate. The flat plate heater according to claim 4.   6. The flat plate heater according to claim 4, wherein the second and third connection conductors are made of a material having a positive resistance temperature coefficient. A heating roller;
The heating heater according to any one of claims 1 to 6, wherein a heating resistor disposed to face the heating roller is pressed against the heating roller.
A heating apparatus comprising a fixing film movably provided between the 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;
8. A heating apparatus according to claim 7, 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. An image forming apparatus.

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