JP2019091003A - Heater and fixing device and image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide a heater capable of suppressing heat generation spots in a first direction with a simple configuration.
[Solution means]
The heater 23 is provided on a plurality of heat generating portions 40A to 40J provided in a state of being axially aligned on one surface of the heat insulating layer 31, and on one surface of the heat insulating layer 31, and supplies power to the heat generating portions 40A to 40J. The plurality of wiring portions 41 to 45 electrically connecting to the power supply 17 are provided, and the wiring portions 41 to 45 are electrically connected to the power supply 17 at the axially outer side of the plurality of heat generating portions 40A to 40J. The dimension of the passing direction of the plurality of heat generating parts 40A to 40J including the electrode terminal parts 41A to 45A is set to be gradually smaller as the electrode terminal parts 41A to 45A are separated in the axial direction.
[Selected figure] Figure 3

Description

  The present invention relates to a heater, a fixing device, and an image forming apparatus.

  The electrophotographic image forming apparatus includes a fixing device that thermally fixes the toner on the medium.

  For example, the heater of the fixing device described in Patent Document 1 is provided along the longitudinal direction, and includes a heat generating portion generating heat by energization and a plurality of heat generating portions arranged in a row at predetermined intervals in the longitudinal direction to supply power. And a branch road. The plurality of branch paths are a first branch path branched from a conductor path extending from an electrical contact connected to one end of the power supply, and a second branch path branched from the conductive path at a position farther from the electrical contact than the first branch path And a branch line of This heater suppresses the decrease in the amount of heat generation as it gets farther from the electrical contact due to the voltage drop due to the electrical resistance of the conductor path by making the resistance of the first branch wire larger than the resistance of the second branch wire. Was. That is, the heat generation spots in the longitudinal direction of the heater were suppressed by changing the resistance of each branch line.

JP, 2016-62024, A

  In the above-described heater, the resistances are different by changing the widths and materials of the first branch line and the second branch line which are the conductor patterns on the substrate. However, changing the width of the conductor pattern or the material requires a large specification change on the manufacturing apparatus side, which often makes it difficult to manufacture. Moreover, it is general to select a low resistance material as a feed branch, and it is difficult to adjust the resistance with a branch with a small resistance.

  The present invention provides a heater, a fixing device, and an image forming apparatus capable of suppressing heat generation spots in the first direction with a simple configuration in order to solve the above-mentioned problems.

  In order to achieve the above object, the heater of the present invention is provided on a substrate, a plurality of heat generating parts provided in a state of being arranged in a first direction on one surface of the substrate, and one surface of the substrate And a plurality of wiring portions for electrically connecting the heat generating portion and a power supply for supplying power to the heat generating portion, wherein the plurality of wiring portions are respectively provided on the power supply outside the plurality of heat generating portions in the first direction. And the dimension of the second direction orthogonal to the first direction of the plurality of heat generating portions is gradually or stepwise as it is separated from the electrode end portion in the first direction It is set to be small.

  In this case, the electrode terminal portions of the plurality of wiring portions are provided on both sides in the first direction across the plurality of heat generating portions, and the dimensions of the plurality of heat generating portions in the second direction are from both end sides in the first direction It is preferable that the first direction is set to be gradually or stepwise smaller toward the center.

  In this case, the plurality of wiring portions are a common wiring portion commonly connected to the plurality of heat generation portions from one side in the second direction of the heat generation portion, and the plurality of heat generation from the other in the second direction of the heat generation portion. A plurality of individual wiring parts individually connected to the part, and the common wiring part and each of the individual wiring parts respectively extend in a second direction and are connected to the branch part on the heating part The plurality of branch paths of the common wiring portion and the individual wiring portions of the common wiring portion and the individual wiring portion are alternately disposed to divide the plurality of heat generating portions, and include conductor paths connecting the electrode terminal portions. It is preferable that currents flow in opposite directions in the heat generating portions adjacent to each other across the branch paths due to the potential difference generated between the branch paths.

  In other cases, each of the heat generating portions is constituted by a plurality of resistance heating elements arranged in the first direction, and the plurality of wiring portions are commonly connected to one end of the plurality of heat generating portions in the second direction. The common wiring portion and the plurality of individual wiring portions individually connected to the other ends of the plurality of heat generating portions in the second direction, and the common wiring portion and each of the individual wiring portions are respectively A conductive path connecting the heat generating portion and the electrode terminal portion is included, and each of the resistance heat generating members generates heat by flowing a current in a second direction between the common wiring portion and each of the individual wiring portions. Is preferred.

  In order to achieve the above object, the fixing device of the present invention forms a pressure area between a fixing member which heats the toner on the medium while rotating around an axis, and the fixing member while rotating around an axis. A pressure member for pressing the toner on the medium passing through the pressure area, and a pressure member provided opposite to the pressure member with the fixing member interposed therebetween, and heating the fixing member. And a heater.

  Further, according to the fixing device of the present invention, a pressure area is formed between the fixing member for heating the toner on the medium while rotating around the axis, and the fixing member while rotating around the axis, and the pressure area 3. A heater according to claim 2, further comprising: a pressure member for pressing the toner on the medium passing through; and a heater according to claim 2 disposed opposite to the pressure member with the fixing member interposed therebetween to heat the fixing member. The diameter of the pressure member may be set to be gradually smaller from the axial ends toward the center.

  Further, according to the fixing device of the present invention, a pressure area is formed between the fixing member for heating the toner on the medium while rotating around the axis, and the fixing member while rotating around the axis, and the pressure area A pressure member for pressing the toner on the medium passing through, and a heater provided opposite to the pressure member with the fixing member interposed therebetween, and heating the fixing member, the pressure member The diameter of the heater is set so as to gradually decrease from both axial ends toward the center, and the heater is provided on the substrate and on one surface of the substrate so as to be aligned in the axial direction of the fixing member. A plurality of heat generating parts, and a plurality of wiring parts provided on one surface of the substrate and electrically connecting the heat generating parts and a power supply for supplying power to the heat generating parts, the plurality of wiring parts are respectively In front of one of the plurality of heat generating parts in the axial direction The dimension of the passing direction orthogonal to the axial direction of the plurality of heat generating portions includes an electrode end portion electrically connected to the power supply, and the dimension in the axial direction decreases gradually or stepwise from the axial direction both ends The dimension in the passage direction of the heat generating portion arranged at the other end in the axial direction is set smaller than the dimension in the passage direction of the heat generating portion arranged at the one end in the axial direction.

  In this case, the plurality of wiring portions are connected to the common wiring portion commonly connected to the plurality of heat generating portions from one side in the passing direction of the heat generating portion, and to the plurality of heat generating portions from the other passing direction of the heat generating portion. A branch path and the electrode terminal each including a plurality of individual wiring parts connected individually, the common wiring part and the individual wiring parts of each extending in the passing direction and being connected on the heat generating part A plurality of branch paths of the common wiring portion and each of the individual wiring portions are alternately disposed to divide the plurality of heat generating portions, and the plurality of branch paths of the plurality of branch paths are included. It is preferable that currents flow in opposite directions in the heat generating portions adjacent to each other across the branch paths due to the potential difference generated therebetween.

  In other cases, each of the heat generating parts is constituted by a plurality of resistance heating elements arranged in the axial direction, and the plurality of wiring parts are commonly connected to one end of the plurality of heat generating parts in the passage direction. The common wiring portion, and the plurality of individual wiring portions individually connected to the other end of the plurality of heat generation portions in the passage direction, the common wiring portion and each of the individual wiring portions are respectively the heat generation portion It is preferable that each of the resistance heating elements generate heat by flowing a current in a passing direction between the common wiring portion and each of the individual wiring portions.

  In order to achieve the above object, an image forming apparatus of the present invention is provided with the fixing device described in any of the above.

  According to the present invention, exothermic spots in the first direction (axial direction) of the heater can be suppressed with a simple configuration.

FIG. 1 is a schematic view (front view) showing a printer according to a first embodiment of the present invention. FIG. 1 is a cross-sectional view schematically showing a fixing device according to a first embodiment of the present invention. It is a bottom view which shows the heater concerning a 1st embodiment of the present invention typically. It is IV-IV sectional drawing of FIG. It is a graph which shows the relationship between the temperature of a heater, and the position of the axial direction. It is a bottom view which shows the heater concerning a 2nd embodiment of the present invention typically. It is a top view which shows typically the pressure roller of the fixing device concerning a 3rd embodiment of the present invention. It is a bottom view which shows the heater concerning a 4th embodiment of the present invention typically. It is a bottom view showing typically the heater concerning the modification of a 1st embodiment of the present invention. It is a bottom view which shows the heater concerning a 5th embodiment of the present invention typically. It is a bottom view which shows the heater concerning the modification of a 5th embodiment of the present invention typically. It is a bottom view which shows the heater concerning a 6th embodiment of the present invention typically.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. Note that "Fr" shown in each figure indicates "front", "Rr" indicates "rear", "L" indicates "left", "R" indicates "right", and "U" indicates "Up" is shown, "D" is showing "down." In addition, each drawing shows the characteristics of each configuration with some emphasis, and does not necessarily show exact dimensions.

[General configuration of the printer]
A printer 1 as an example of an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic view (front view) showing the printer 1.

  The printer 1 is provided with an apparatus main body 2 that forms an external appearance of a substantially rectangular parallelepiped. At a lower portion of the apparatus main body 2, for example, a sheet feeding cassette 3 for storing a sheet S (medium) such as plain paper is provided. A sheet discharge tray 4 is provided on the top surface of the apparatus body 2. The sheet S is not limited to paper, and may be resin or the like.

  The printer 1 further includes a sheet feeding device 5, an image forming device 6, and a fixing device 7. The sheet feeding device 5 is provided at the upstream end of the conveyance path P extending from the sheet feeding cassette 3 to the sheet discharge tray 4. The image forming device 6 is provided at an intermediate portion of the conveyance path P, and the fixing device 7 is provided on the downstream side of the conveyance path P.

  The imaging device 6 includes a toner container 10, a drum unit 11, and an optical scanning device 12. The toner container 10 contains, for example, a black toner (developer). The drum unit 11 includes a photosensitive drum 13, a charging device 14, a developing device 15, and a transfer roller 16. The transfer roller 16 contacts the photosensitive drum 13 from the lower side to form a transfer nip. The toner may be a two-component developer in which a toner and a carrier are mixed, or may be a one-component developer composed of a magnetic toner.

  A control device (not shown) of the printer 1 appropriately controls each device and executes an image forming process as follows. The charging device 14 charges the surface of the photosensitive drum 13. The photosensitive drum 13 receives the scanning light emitted from the light scanning device 12 and carries an electrostatic latent image. The developing device 15 uses the toner supplied from the toner container 10 to develop the electrostatic latent image on the photosensitive drum 13 into a toner image. The sheet S is fed from the sheet feeding cassette 3 to the conveyance path P by the sheet feeding device 5, and the toner image on the photosensitive drum 13 is transferred to the sheet S passing through the transfer nip. The fixing device 7 fixes the toner image on the sheet S. Thereafter, the sheet S is discharged to the discharge tray 4.

First Embodiment: Fixing Device
Next, the fixing device 7 according to the first embodiment will be described with reference to FIGS. 2 to 5. FIG. 2 is a cross-sectional view schematically showing the fixing device 7. FIG. 3 is a bottom view schematically showing the heater 23. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. FIG. 5 is a graph showing the relationship between the temperature of the heater 23 and the position in the axial direction.

  As shown in FIG. 2, the fixing device 7 includes a fixing belt 21, a pressure roller 22, and a heater 23. The fixing belt 21 and the pressure roller 22 are provided inside the housing 20 (see FIG. 1). The heater 23 is a heat source for heating the fixing belt 21.

<Fixing belt>
The fixing belt 21 as an example of the fixing member is an endless belt, and is formed in a substantially cylindrical shape that is long in the front-rear direction (axial direction). The surface layer of the fixing belt 21 is made of, for example, a synthetic resin material having heat resistance and elasticity, such as polyimide resin. The fixing belt 21 is disposed above the inside of the housing 20. A pair of substantially cylindrical caps (not shown) are attached to both axial ends of the fixing belt 21. A belt guide (not shown) for holding the substantially cylindrical shape of the fixing belt 21 may be provided inside the fixing belt 21.

  A pressing member 24 is provided inside the fixing belt 21. The pressing member 24 is formed of, for example, a metal material in a substantially rectangular shape elongated in the axial direction. The pressing member 24 is supported by the housing 20 through the fixing belt 21 (and the cap) in the axial direction. The fixing belt 21 described above is rotatably supported by the pressing member 24.

<Pressing roller>
The pressure roller 22 as an example of the pressure member is formed in a substantially cylindrical shape that is long in the front-rear direction (axial direction). The diameter (outer diameter) of the pressure roller 22 is set to be substantially uniform (substantially the same) in the axial direction. The pressure roller 22 is disposed below the inside of the housing 20. The pressure roller 22 includes a metal cored bar 22A and an elastic layer 22B such as silicone sponge laminated on the outer peripheral surface thereof. Both axial ends of the cored bar 22 </ b> A are rotatably supported by the housing 20. A drive motor (not shown) is connected to the cored bar 22A via a gear train or the like, and the pressure roller 22 is rotationally driven by the drive motor. The fixing device 7 includes a pressure adjusting unit (not shown) that adjusts the contact pressure of the pressure roller 22 with the fixing belt 21 by moving the pressure roller 22 up and down. By pressing the pressure roller 22 against the fixing belt 21, a pressure area N is formed between the fixing belt 21 and the pressure roller 22. Further, the pressure area N is from the position on the upstream side of the sheet S in the conveyance direction at a pressure of 0 Pa to the position on the downstream side in the conveyance direction of the sheet S at a pressure of 0 Pa again via the position of maximum pressure. It points to the area.

<Heater>
The heater 23 as an example of a heater is formed in a substantially rectangular plate shape long in the front-rear direction (axial direction) (see FIG. 3). The heater 23 is fixed to the lower surface of the pressing member 24 via the holding member 25. The holding member 25 is formed of, for example, a heat-resistant resin material in a substantially semi-cylindrical shape which is long in the axial direction. The holding member 25 is curved along the lower inner surface of the fixing belt 21.

  As shown in FIGS. 3 and 4, the heater 23 includes a base 30, a heat insulating layer 31, and a heat generating contact portion 32. The substrate 30 is fixed to the lower surface of the holding member 25. The heat insulating layer 31 is formed on the lower surface of the base 30 and integrally with the base 30 to constitute a substrate. The heat generating contact portion 32 is formed on the lower surface of the heat insulating layer 31. In the present specification, the “passing direction (second direction)” is a direction orthogonal to the axial direction (first direction) and a direction in which the sheet S passes through the pressure area N of the fixing device 7 ( Direction). Also, in the following description, the terms "upstream" and "downstream" and the like refer to the terms "upstream" and "downstream" and the like in the passing direction.

  As shown in FIG. 4, the heater 23 is held on the lower surface of the holding member 25 in a posture in which the heat generating contact portion 32 is directed to the pressure roller 22 and brings the heat generating contact portion 32 into contact with the inner surface of the fixing belt 21. When the heater 23 receives the fixing belt 21 pressed against the pressure roller 22, a pressure area N is formed at the contact portion between the fixing belt 21 and the pressure roller 22. That is, the heater 23 is provided to face the pressure roller 22 with the fixing belt 21 interposed therebetween (see also FIG. 2), and has a function of heating the fixing belt 21. The housing 20 is provided with a temperature sensor (not shown) for detecting the surface temperature of the fixing belt 21 or the temperature of the heater 23.

<Base material>
As shown in FIG. 3 and FIG. 4, the base material 30 is formed in a substantially rectangular plate shape which is long in the axial direction, for example, of a material having electrical insulation such as ceramic. Both upper and lower surfaces of the base 30 are formed to be substantially smooth.

<Adiabatic layer>
The heat insulating layer 31 is laminated (deposited) on one surface (the entire lower surface) of the substrate 30. The heat insulating layer 31 is formed on the base material 30 of a material having electrical insulation such as ceramic (glass) and low thermal conductivity. The heat insulating layer 31 has a function of restricting the transfer of the heat generated at the heat generating contact portion 32 to the substrate 30 side.

<Heat contact portion>
The heat generating contact portion 32 is laminated on the lower surface of the heat insulating layer 31. The heat generating contact portion 32 includes a heat generating layer portion 40, a plurality of (for example, five) wiring portions 41 to 45, and a coating layer 46.

(Heating layer)
The heat generating layer portion 40 is an electric resistor that generates heat by energization and is stacked on the lower surface of the heat insulating layer 31 (see FIG. 4). The heat generating layer portion 40 is formed of a conductive material such as a metal having a resistance value higher than that of the wiring portions 41 to 45. As shown in FIG. 3, the heat generating layer portion 40 has a shape in which the width in the passing direction is gradually narrowed from both axial end portions toward the center. The heat generating layer portion 40 is formed to be symmetrical in the front-rear direction about the narrowest portion in the axial center. The heat generating layer portion 40 has an axial length capable of heating the entire area of the sheet S of A4 size (width 297 mm), for example. Although details will be described later, the heat generating layer portion 40 is divided into a plurality of heat generating portions 40A to 40J arranged at substantially equal intervals in the axial direction.

(Wiring section)
The plurality of wiring portions 41 to 45 are provided on the lower surface of the heat insulating layer 31 (see FIG. 4). The plurality of wiring portions 41 to 45 are formed of a conductive material such as metal (a material having a lower resistance value than the heat generating layer portion 40). The plurality of wiring portions 41 to 45 are formed of the same metal material.

  Specifically, as shown in FIG. 3, the plurality of wiring parts 41 to 45 include a common wiring part 41 and four individual wiring parts 42 to 45. The common wiring portion 41 is mainly disposed on the upstream side (left side (one side in the second direction)) of the heat generating layer portion 40, and the plurality of heat generating portions 40A to 40J from the upstream side of the heat generating layer 40 (heat generating portions 40A to 40J). Commonly connected to. The four individual wiring portions 42 to 45 are mainly disposed on the downstream side (the right side (the second direction)) of the heat generating layer portion 40, and individually from the downstream side of the heat generating layer portion 40 to the plurality of heat generating portions 40A to 40J. It is connected. In the present specification, in the description common to the common wiring portion 41 and the individual wiring portions 42 to 45, the wiring portions 41 to 45 are simply referred to as “wiring portions 41 to 45”.

  The common wiring portion 41 includes a pair of electrode terminal portions 41A, a conductor path 41B, and five branch paths 41C. The individual wiring portions 42 and 43 include electrode terminal portions 42A and 43A, conductor paths 42B and 43B, and two opposing branch paths 42C and 43C. The individual wiring portions 44 and 45 include electrode terminal portions 44A and 45A, conductor paths 44B and 45B, and opposing branch paths 44C and 45C. The common wiring portion 41 is formed to be symmetrical in the back and forth direction with the narrowed portion at the center in the axial direction of the heat generating layer portion 40 as an axis. Similarly to this, the individual wiring portion 42 and the individual wiring portion 43 are formed symmetrically in the front-rear direction, and the individual wiring portion 44 and the individual wiring portion 45 are also formed symmetrically in the front-rear direction.

  Each of the electrode terminal portions 41A to 45A is provided on both axial outer sides of the heat generating layer portion 40 (the plurality of heat generating portions 40A to 40J) with respect to the heat generating layer portion 40. The pair of electrode terminal portions 41A, the electrode terminal portions 42A and 43A, and the electrode terminal portions 44A and 45A are provided in this order in the order from the heat generating layer 40 side toward the axial direction outer side at substantially equal intervals. . The electrode end portions 42A and 44A are disposed forward of the heat generating layer portion 40, and the electrode end portions 43A and 45A are disposed rearward of the heat generating layer portion 40. The electrode terminal portion 41A is electrically connected to one terminal of the power source 17, and the electrode terminal portions 42A to 45A are electrically connected to the other terminal of the power source 17. A drive motor or the like is electrically connected to the power supply 17 via various drive circuits (not shown). Further, the power supply 17, the drive motor, the temperature sensor, and the like are electrically connected to the control device of the printer 1 via various circuits, and appropriately controlled by the control device.

  The conductor paths 41B to 45B connect the branch paths 41C to 45C and the electrode terminal portions 41A to 45A which extend in the passing direction and are connected to the heating layer portion 40 (heating portions 40A to 40J). In detail, the conductor path 41B is provided on the upstream side (left side) of the heat generating layer portion 40 so as to connect the pair of electrode terminal portions 41A. The conductor paths 42B to 45B are provided on the downstream side (right side) of the heat generating layer portion 40 so as to extend from the electrode terminal portions 42A to 45A toward the axial center (inner side). The conductor paths 44B and 45B are disposed to the right of the conductor paths 42B and 43B, and extend inward from the conductor paths 42B and 43B.

  The five branch paths 41C are arranged at substantially equal intervals in the axial direction, and extend from the conductor path 41B onto the heating layer portion 40. The two opposing branch paths 42C and 43C extend from the axially intermediate portion and the axial tip end of the conductor paths 42B and 43B onto the heat generating layer portion 40. The opposing branch paths 44C and 45C extend on the heat generating layer portion 40 from the axial direction end portions of the conductor paths 44B and 45B.

  The five branch paths 41C and the six opposing branch paths 42C to 45C are stacked (arranged) on the heat generating layer portion 40 alternately and at substantially equal intervals to define ten heat generating portions 40A to 40J. . That is, by electrically connecting the five branch paths 41C and the six opposing branch paths 42C to 45C to the heating layer portion 40, the heating layer portion 40 is divided into ten heating portions 40A to 40J. There is. The plurality of wiring portions 41 to 45 are provided corresponding to the ten heat generating portions 40A to 40J, and have a function of electrically connecting the heat generating portions 40A to 40J and the power supply 17 supplying power thereto. There is.

(Heating part)
The ten heat generating portions 40A to 40J are provided on the lower surface of the heat insulating layer 31 with the same metal material. The ten heat generating portions 40A to 40J are provided in a line from the front to the rear (axially) in this order. The dimensions in the passage direction (left and right direction) of the ten heat generating portions 40A to 40J are gradually reduced in the axial direction from the respective electrode terminal portions 41A to 45A (both axial end sides) It is set to become. That is, each heat generating part 40A-40J is formed in the substantially trapezoidal shape which becomes thin toward a center from axial direction both sides. For example, assuming that the maximum length of the heat generating portions 40A and 40J in the passage direction is 100%, the length of the axial center of the heat generating layer portion 40 in the passage direction is set to about 98%. The heat generating portions 40D to 40G arranged near the axial center are provided in a range corresponding to the sheet S of small size (for example, A5 size). All the heat generating parts 40A to 40J are provided in a range corresponding to the sheet S of normal size (for example, A4 size).

  As shown in FIG. 4, the coating layer 46 covers the wiring portions 41 to 45 and the heat generating portions 40A to 40J. The coat layer 46 is formed of, for example, a material such as ceramic or the like which has an electrical insulation property and a small sliding friction with the fixing belt 21. The coat layer 46 has a function of electrically protecting the wiring portions 41 to 45 and the like to prevent a leak and a short. The coat layer 46 constitutes a surface in contact with the inner surface of the fixing belt 21. In addition, the material which has electrical insulation, such as the heat insulation layer 31 and the coating layer 46, is laminated | stacked on the part to which the heat-generating layer part 40 and the wiring parts 41-45 are not laminated | stacked.

  For the manufacture of the heater 23 described above, for example, a film forming technique such as sputtering, a printed substrate manufacturing technique, a screen printing technique, or a combination of these techniques can be used. For example, the heat insulating layer 31 and the heat generating contact portion 32 (the heat generating layer portion 40, the wiring portions 41 to 45, the coat layer 46) may be formed on the substrate 30 by sputtering. Further, for example, the heat insulating layer 31 and the heat generating contact portion 32 are formed on the substrate 30 by repeating steps of exposure using a photomask which is a manufacturing technique of a printed circuit, development, etching, peeling, lamination, and the like. It is also good. Also, for example, the heat insulating layer 31 and the heat generating contact portion 32 may be formed by applying (screen printing) an electrically insulating paint or a conductive paint on the substrate 30. According to these manufacturing methods, the heat insulating layer 31 and the heat generating contact portion 32 can be formed with high accuracy.

[Function of fixing device]
Here, the operation (fixing process) of the fixing device 7 will be described with reference to FIGS. 1 to 3 and 5. Here, as an example, the case of using the sheet S of A4 size will be described.

  First, the control device controls driving of the drive motor and the power supply 17 (heater 23). The pressure roller 22 is rotated by receiving a driving force of a drive motor, and the fixing belt 21 is rotated by being driven by the pressure roller 22 (see a solid arrow in FIG. 2). The power supply 17 applies a voltage between the common wiring portion 41 and the individual wiring portions 42 to 45. Then, a potential difference is generated between the branch path 41C and the opposing branch path 42C-45C, and the potential difference causes currents to flow in opposite directions in the heat generating portions 40A to 40J adjacent to each other with the branch paths 41C to 45C interposed therebetween (see FIG. See arrow 3). Accordingly, the heat generating portions 40A to 40J generate heat, and the range corresponding to the normal size of the fixing belt 21 can be heated.

  By the way, since the electric resistances of the conductor paths 42B to 45B increase with distance from the electrode end portions 42A to 45A, the voltage applied to the heat generating portions 40A to 40J decreases with distance from the electrode end portions 42A to 45A (a voltage drop occurs ). Therefore, assuming that all the heat generating parts 40A to 40J have the same size, the calorific value of each of the heat generating parts 40A to 40J gradually decreases as they are separated from the electrode terminal parts 41A to 45A. Become. That is, the amount of heat generation of the heat generating portions 40A and 40J located closest to the electrode end portions 41A to 45A is the largest, and the heat generating portions 40E and 40F located at the farthest position (near the axial center) from the electrode end portions 41A to 45A. The calorific value is the smallest. Therefore, the axial direction both ends of heater 23 become high temperature, and the center vicinity becomes low temperature (refer the dashed-dotted line of FIG. 5). As described above, there are cases where the temperature of the fixing belt 21 becomes nonuniform over the axial direction due to the heat generation spots of the heater 23, and appropriate fixing processing can not be performed.

  Therefore, the heater 23 of the fixing device 7 according to the first embodiment sets the size in the passing direction of the heat generating portions 40A to 40J gradually smaller as it separates from each of the electrode terminal portions 41A to 45A (see FIG. 3). That is, the sum of the electrical resistances of the electrode terminal portions 41A to 45A and the heat generating portions 40A to 40J is adjusted to be substantially the same regardless of the route. Thus, the amount of heat generation of each of the heat generating portions 40A to 40J, that is, the temperature of the heater 23 becomes substantially uniform in the axial direction, and the fixing belt 21 can be substantially uniformly heated in the axial direction (FIG. 5). See the solid line of).

  Subsequently, the temperature sensor detects the surface temperature of the fixing belt 21 and transmits a detection signal to the control device through the input circuit. When the control device receives a detection signal indicating that the set temperature (for example, 150 to 200 ° C.) is reached from the temperature sensor, the control device controls the heater 23 to maintain the set temperature, and the image forming process already described Start execution The sheet S on which the toner image has been transferred enters into the housing 20, and the fixing belt 21 heats the toner (toner image) on the sheet S passing through the pressure area N while rotating forward around the axis. The pressure roller 22 presses the toner on the sheet S passing through the pressure area N while rotating around the axis. Then, the toner image is fixed to the sheet S. Then, the sheet S on which the toner image is fixed is delivered to the outside of the housing 20 and discharged to the paper discharge tray 4 (see FIG. 1). The sheet S is conveyed in a state in which the center of the axial direction (longitudinal width) is aligned with the axial center of the fixing belt 21.

  A switch (not shown) is provided in the circuit around the power supply 17. When the connection between the power supply 17 and the individual wiring parts 42 and 43 is disconnected by this switch, the heating parts 40A to 40C and the heating parts 40H to No current flows to 40 J (no heat generation). As a result, only the heat generating parts 40D to 40G can generate heat, and only the range (near the axial center) corresponding to the small size can be heated.

  In the heater 23 of the fixing device 7 according to the first embodiment described above, the dimension in the passing direction (second direction) of the ten heat generating portions 40A to 40J gradually decreases as the distance from the electrode terminal portions 41A to 45A increases. (See Figure 3). According to this configuration, the resistance values of the heat generating portions 40E and 40F far from the electrode terminal portions 41A to 45A can be made smaller than the resistance values of the heat generating portions 40A and 40J close to the electrode terminal portions 41A to 45A. Thereby, it can suppress that the emitted-heat amount (temperature) of heat-emitting part 40A-40J falls so as to be far from electrode terminal part 41A-45A by the influence of the voltage drop in the wiring parts 41-45. As a result, it is not necessary to adjust the electrical resistance in the wiring parts 41 to 45 where the change in manufacture is difficult, etc., and the axial direction (first direction) with a simple configuration of adjusting the dimensions of the heat generating parts 40A to 40J in the passing direction. Can suppress fever spots.

  Moreover, according to the heater 23 which concerns on 1st Embodiment, it can electrically feed only all the heat-emitting part 40A-40J or heat-emitting part 40D-40G. As a result, the fixing belt 21 can be heated in the range corresponding to the size of the sheet S, so that the power consumption can be reduced. Further, since only the range (near the center in the axial direction) corresponding to the small size sheet S can be heated in the fixing belt 21, it is possible to suppress the excessive temperature rise of both axial ends of the fixing belt 21.

  Further, according to the heater 23 according to the first embodiment, since the wiring portions 41 to 45 extend from both sides in the axial direction toward the center, wiring is more than when the wiring portions 41 to 45 are extended from one side in the axial direction The lengths of the portions 41 to 45 (conductor paths 41B to 45B) can be formed short. Thereby, the voltage drop in the wiring parts 41-45 can be suppressed.

Second Embodiment
Next, the heater 26 of the fixing device 7 according to the second embodiment will be described with reference to FIG. FIG. 6 is a bottom view schematically showing the heater 26. As shown in FIG. In the following description, the same components as those of the heater 23 (the fixing device 7) according to the first embodiment are denoted by the same reference numerals, and the description of the same or corresponding components as the heater 23 is omitted.

  In the fixing device 7 according to the first embodiment, the heater 23 of the double-feeding type in which the electrode terminal portions 41A to 45A are disposed on both sides in the axial direction is employed. However, in the fixing device 7 according to the second embodiment It differs in the point by which the heater 26 of the one-side feed type which arrange | positioned the electrode terminal parts 51A-53A on the other hand is employ | adopted. That is, the heater 26 has such a shape that the heater 23 is halved at the axial center.

<Heat contact portion>
The heat generating contact portion 33 of the heater 26 includes a heat generating layer portion 50, a common wiring portion 51, two individual wiring portions 52 and 53, and a coat layer 46 (see FIG. 4).

(Heating layer)
The heat generating layer portion 50 has a shape in which the width in the passing direction is gradually narrowed from one (front) to the other (rear) in the axial direction. The heat generating layer portion 50 has, for example, an axial length capable of heating the entire area of the sheet S of A4 size.

(Wiring section)
The common wiring portion 51 is mainly disposed on the upstream side (left side) of the heat generating layer portion 50, and the individual wiring portions 52 and 53 are mainly arranged on the downstream side (right side) of the heat generating layer portion 50.

  The common wiring portion 51 includes an electrode terminal portion 51A, a conductor path 51B, and five branch paths 51C. The individual wiring portion 52 includes an electrode terminal portion 52A, a conductor path 52B, and four opposing branch paths 52C. The individual wiring portion 53 includes an electrode terminal portion 53A, a conductor path 53B, and two opposing branch paths 53C.

  Each of the electrode terminal portions 51A to 53A is provided on one side (forward side) of the heat generating layer portion 50 in the axial direction. The electrode terminal portions 51A to 53A are provided in this order in a substantially equal interval from the heat generating layer portion 50 side toward the axially outer side. The electrode terminal portion 51A is electrically connected to one terminal of the power source 17, and the electrode terminal portions 52A and 53A are electrically connected to the other terminal of the power source 17.

  The conductor path 51B is provided on the upstream side (left side) of the heat generating layer portion 50 so as to extend from the electrode terminal portion 51A toward the other side (rearward) in the axial direction. The conductor paths 52B and 53B are provided on the downstream side (right side) of the heat generating layer portion 50 so as to extend rearward from the electrode terminal portions 52A and 53A. The conductor path 53B is disposed on the right side of the conductor path 52B and extends rearward beyond the conductor path 52B.

  The five branch paths 51 </ b> C are arranged at substantially equal intervals in the axial direction, extend downstream from the conductor path 51 </ b> B, and are connected onto the heat generating layer portion 50. The four opposing branch paths 52 </ b> C are arranged at substantially equal intervals in the axial direction, extend upstream from the conductor path 52 </ b> B, and are connected onto the heat generating layer portion 50. The opposing branch paths 53C are arranged at substantially equal intervals in the axial direction at the rear of the opposing branch path 52C at the rearmost end, extend upstream from the conductor path 53B, and are connected on the heat generating layer portion 50. The five branch paths 51C and the six opposing branch paths 52C and 53C are stacked on the heat generating layer portion 50 alternately and at substantially equal intervals, and the heat generating layer portion 50 is divided into ten heat generating portions 50A to 50J. ing.

(Heating part)
The ten heat generating parts 50A to 50J are provided in a line from the front to the rear in this order. The dimensions in the passage direction of the ten heat generating portions 50A to 50J are set so as to gradually decrease as they are separated from the electrode terminal portions 51A to 53A in the axial direction. For example, assuming that the maximum length of the heat generating portion 50A in the passage direction is 100%, the length of the axial center of the heat generating layer portion 50 (between the heat generating portion 50E and the heat generating portion 50F) is set to about 98%. The minimum length of the heat generating portion 50J in the passage direction is set to about 97%. The heat generating portions 50A to 50G arranged in one axial direction (forward) are provided in a range corresponding to the small size sheet S, and all the heat generation portions 50A to 50J are provided in a range corresponding to the normal size sheet S It is done. The sheet S is conveyed with its front end aligned with the front side of the fixing belt 21.

  Here, assuming that all the heat generating parts 50A to 50J have the same size, the calorific value of each of the heat generating parts 50A to 50J gradually decreases with distance from the electrode terminal parts 51A to 53A. Become. Therefore, one axial end (front) of the heater 26 becomes high temperature, and the other axial end (rear) becomes low temperature (see the two-dot chain line in FIG. 5). In that respect, according to the heater 26 of the fixing device 7 according to the second embodiment described above, it is possible to suppress the heat generation spots in the axial direction with a simple configuration of adjusting the dimension of the heat generation portions 50A to 50J in the passage direction. The same operation and effect as the heater 23 according to the above-described first embodiment can be obtained, etc. (see the solid line in FIG. 5).

Third Embodiment
Next, the fixing device 8 according to the third embodiment will be described with reference to FIG. FIG. 7 is a plan view schematically showing the pressure roller 55 and the like of the fixing device 8. In the following description, the same components as those of the fixing device 7 according to the first embodiment are denoted by the same reference numerals, and the description of the same or corresponding components as the fixing device 7 is omitted.

  In the fixing device 8 according to the third embodiment, the heater 23 has a plurality of (ten) heat generating portions 40A to 40J, and the dimensions in the passage direction of the plurality of heat generating portions 40A to 40J are from the axial direction toward the center It is set to be gradually shorter (see FIG. 3).

  In this fixing device 8, the fixing device 7 according to the first embodiment is that the pressure roller 55 has a shape (hereinafter, also referred to as “reverse crown shape”) that is narrowed near the approximate center in the axial direction. It is different from. The diameter (outer diameter) of the pressure roller 55 is set so as to gradually decrease from both axial ends toward the center. The difference (the amount of necking) of the radius between the axial direction both ends of the pressure roller 55 and the center is set to, for example, about 0.1 to 0.2 mm. By using the pressure roller 55 having a reverse crown shape, a force of pulling outward in the axial direction acts on the sheet S passing through the pressure area N. Accordingly, it is possible to suppress that the sheet S passing through the pressure area N is wrinkled.

  By the way, in the fixing device 8 using the pressure roller 55 of the reverse crown shape, the pressure width (length in the passing direction) of the pressure area N gradually narrows (shortens) from both ends in the axial direction toward the center. In addition, the pressure in the pressure area N becomes smaller near the axial center than on both sides in the axial direction. For this reason, the temperature on both sides in the axial direction of the fixing belt 21 becomes higher than the temperature in the vicinity of the axial center.

  In that respect, in the heater 23 of the fixing device 8 according to the third embodiment, the dimension in the passing direction of the heat generating portions 40A to 40J is set to be gradually smaller as it is separated from each of the electrode terminal portions 41A to 45A (see FIG. 3) . For example, when the maximum length of the heat generating portions 40A and 40J in the passage direction is 100%, the length in the axial direction center of the heat generating layer portion 40 in the passage direction is set to about 92 to 95%. In addition, it is preferable to enlarge the dimensional difference of the passing direction of the heat generating parts 40A to 40J as the amount of contraction of the pressure roller 55 is larger.

  According to the heater 23 of the fixing device 8 according to the third embodiment, the dimensions in the passage direction of the ten heat generating portions 40A to 40J are gradually shortened from the both sides in the axial direction toward the center. A temperature drop near the axial center of the layer portion 40 can be suppressed. As a result, even in the fixing device 8 using the pressure roller 55 in the reverse crown shape, it is possible to reduce the temperature difference between the axial direction both sides of the pressure area N and the vicinity of the center. As a result, heat generation spots in the axial direction of the heater 23 can be suppressed, and the fixing belt 21 can be substantially uniformly heated in the axial direction.

Fourth Embodiment
Next, a fixing device 8 according to a fourth embodiment will be described with reference to FIG. FIG. 8 is a bottom view schematically showing the heater 27. As shown in FIG. In the following description, the same components as those of the heaters 23 and 26 (fixing devices 7 and 8) according to the first to third embodiments are denoted by the same reference numerals, and are the same as or correspond to those of the fixing devices 7 and 8. Description of the configuration is omitted.

  In the fixing device 8 according to the third embodiment, the heater 23 of the both-side power feeding type is adopted, but the fixing device 8 according to the fourth embodiment is different in that the heater 27 of the one-side power feeding type is adopted. . Further, since the pressure roller 55 having the reverse crown shape is adopted in the fixing device 8, the heater 26 of the one-side power feeding type according to the second embodiment can not be applied to the fixing device 8. Therefore, in the fixing device 8 according to the fourth embodiment, a single-sided power supply type heater 27 different from the heater 26 is employed.

<Heat contact portion>
The heat generating contact portion 34 of the heater 27 includes a heat generating layer portion 60, a common wiring portion 61, two individual wiring portions 62 and 63, and a coat layer 46 (see FIG. 4).

(Heating layer)
The heat generating layer portion 60 has a shape in which the width in the passing direction is gradually narrowed from both axial end portions toward the center. Further, one axial end (front end) of the heat generating layer portion 60 is formed slightly longer in the passing direction than the other axial end (rear end). The heat generating layer portion 60 has, for example, an axial length capable of heating the entire area of the sheet S of A4 size.

(Wiring section)
The common wiring portion 61 is mainly disposed on the upstream side (left side) of the heat generating layer portion 60, and the individual wiring portions 62 and 63 are mainly disposed on the downstream side (right side) of the heat generating layer portion 60.

  The common wiring portion 61 includes an electrode terminal portion 61A, a conductor path 61B, and five branch paths 61C. The individual wiring portion 62 includes an electrode terminal portion 62A, two conductor paths 62B, and four opposing branch paths 62C. The individual wiring portion 63 includes an electrode terminal portion 63A, a conductor path 63B, and two opposing branch paths 63C.

  Each of the electrode terminal portions 61A to 63A is provided on one side (forward side) of the heat generating layer portion 60 in the axial direction. The electrode terminal portions 61A to 63A are provided in this order in a substantially equal interval from the heat generating layer portion 60 side toward the axially outer side. The electrode terminal portion 61A is electrically connected to one terminal of the power source 17, and the electrode terminal portions 62A and 63A are electrically connected to the other terminal of the power source 17 (not shown in FIG. 8).

  The conductor path 61B is provided on the upstream side (left side) of the heat generating layer portion 60 so as to extend from the electrode terminal portion 61A toward the other axial direction (rearward). The two conductor paths 62B bifurcated from the electrode end portion 62A are provided on the downstream side (right side) of the heat generating layer portion 60 so as to extend from the front to the rear. The conductor path 63B is provided on the downstream side of the heat generating layer portion 60 so as to extend rearward from the electrode terminal portion 63A. The conductor path 63B is disposed between the two conductor paths 62B.

  The five branch paths 61 </ b> C are arranged at substantially equal intervals in the axial direction, extend downstream from the conductor path 61 </ b> B, and are connected onto the heat generating layer portion 60. The four opposing branch paths 62 </ b> C extend upstream from the two conductor paths 62 </ b> B and are connected to the heating layer portion 60. The two opposing branch paths 63 </ b> C extend upstream from the conductor path 63 </ b> B and are connected on the heat generating layer portion 60. The five branch paths 61C and the six opposite branch paths 62C and 63C are stacked on the heat generating layer portion 60 alternately and at substantially equal intervals, and the heat generating layer portion 60 is divided into ten heat generating portions 60A to 60J. ing.

(Heating part)
The ten heat generating parts 60A to 60J are provided in a line from the front to the rear in this order. The dimensions in the passage direction of the ten heat generating portions 60A to 60J are set so as to gradually decrease in the axial center from both axial end sides. The heat generating portions 60D to 60G arranged near the axial center are provided in the range corresponding to the small size sheet S, and all the heat generating portions 40A to 40J are provided in the range corresponding to the normal size (for example, A4 size) It is done. The sheet S is conveyed in a state in which the center of the axial direction (longitudinal width) is aligned with the axial center of the fixing belt 21.

  The dimension (maximum dimension M2) of the heat generating portion 60J disposed at the other axial end (rear end) is the dimension (maximum dimension) of the heat generating portion 60A disposed at the axial end (front end) M1) is set smaller than M1) (M1-M2 is smaller by ΔM). For example, assuming that the maximum length of the heat generating portion 60A in the passage direction is 100%, the length in the passage direction of the axial center (between the heat generating portion 60E and the heat generating portion 60F) of the heat generating layer portion 60 is about 92 to 95%. The minimum length of the heat generating part 60J in the passage direction is set to about 97%. In addition, it is preferable to enlarge the dimensional difference of the passing direction between the axial direction both ends and the center of the heat generating layer portion 60 as the amount of contraction of the pressure roller 55 is larger.

  In the heater 27 of the fixing device 8 according to the fourth embodiment described above, the dimensions in the passage direction of the ten heat generating portions 60A to 60J are set to be gradually shorter from both axial ends to the center, and the axial rear end The dimension of the heat generating portion 60J in the passage direction is set to be smaller than that of one axial end (60A). According to this configuration, it is possible to suppress the temperature drop near the axial center of the heat generating layer portion 60 due to the influence of the voltage drop. As a result, even in the fixing device 8 using the pressure roller 55 in the reverse crown shape, it is possible to reduce the temperature difference between one axial direction (front) of the pressure area N and the vicinity of the center. Although the heat generation amount is reduced at the rear of the heat generating layer portion 60 due to the voltage drop, the temperature at the rear of the pressure area N can be increased by the influence of the reverse crown shape of the pressure roller 55. As a result, even in the fixing device 8 using the reverse crown-shaped pressure roller 55 and the one-sided power supply heater 27, it is possible to make the pressure area N substantially uniform in the axial direction.

  In the heaters 23, 26 and 27 according to the first to fourth embodiments, the dimensions in the passage direction of the plurality of heat generating portions 40A to 40J, 50A to 50J, 60A to 60J are the electrode terminal portions 41A to 45A, 51A to Although it was set as it becomes small gradually as it separates from 53A and 61A-63A, the present invention is not limited to this. For example, as shown in FIG. 9, the dimensions of the plurality of heat generating portions 40A to 40J, etc. in the passage direction become smaller stepwise (stepwise) as they are axially separated from the electrode end portions 41A to 45A, etc. It may be set.

  Further, in the heaters 23, 26 and 27 according to the first to fourth embodiments, ten heat generating portions 40A to 40J and the like are formed, but the present invention is not limited to this. For example, the branch path may be formed to form two or more heat generating parts (not shown).

Fifth Embodiment
Next, the heater 28 of the fixing device 7 according to the fifth embodiment will be described with reference to FIG. FIG. 10 is a bottom view schematically showing the heater 28. As shown in FIG. In the following description, the same components as those of the heaters 23, 26 and 27 (fixing devices 7 and 8) according to the first to fourth embodiments are designated by the same reference numerals, and correspond to or correspond to the heaters 23 and the like. Description of the configuration is omitted.

  In the heaters 23, 26 and 27 according to the first to fourth embodiments, a plurality of heating portions 40A to 40J and the like are formed by dividing the heating layer portions 40, 50 and 60 by a plurality of branch paths 41C to 45C. However, the heater 28 according to the fifth embodiment is different in that each of the heat generating portions 70A to 70E is configured by a plurality of resistance heating elements 77 arranged in the axial direction (first direction).

<Heat contact portion>
The heat generating contact portion 35 of the heater 28 includes five heat generating portions 70A to 70E, a common wiring portion 71, five individual wiring portions 72 to 76, and a coat layer 46 (see FIG. 4).

(Heating part)
The five heat generating parts 70A to 70E are formed in line in the axial direction. Each of the heat generating parts 70A to 70E is composed of a plurality of resistance heat generating members 77 aligned in a line in the axial direction. In detail, the heat generating portion 70A disposed at the center in the axial direction includes a plurality of resistance heat generating members 77 arranged in a range corresponding to the front and rear width of the small size (for example, A5 size) sheet S passing the pressure area N. It is composed of The two heat generating portions 70B and 70C arranged on both sides in the axial direction of the heat generating portion 70A are arranged in a range corresponding to the front and rear width of the medium size (for example, B5 size) sheet S passing through the pressure area N. It is constituted by a resistance heating element 77. The two heat generating portions 70D and 70E disposed on both sides in the axial direction of the heat generating portions 70B and 70C are arranged in a range corresponding to the front-rear width of the sheet S of normal size (for example, A4 size) passing through the pressure area N. A plurality of resistance heating elements 77 are formed.

  The five heat generating portions 70A to 70E have a shape in which the width in the passing direction is gradually narrowed from both axial end portions toward the center. Each of the resistance heating elements 77 constituting the heating portions 70A to 70E is formed in a substantially trapezoidal shape elongated in the passing direction and narrower at the center side in the passing direction than the axially outer side. The resistance heating elements 77 disposed on the axial center side are formed in a substantially trapezoidal shape shorter in the passing direction than the resistance heating elements 77 disposed on both axial sides. In detail, for example, assuming that the maximum length of the resistance heating elements 77 located at both axial ends in the passing direction is 100%, the length of the resistance heating elements 77 located at the axial center is 98% The degree is set. Each resistance heating element 77 is formed to have the same dimension in the axial direction. In the present specification, "same size" does not require completely the same size, but means that a slight error in manufacturing is allowed.

  Each resistance heating element 77 is formed such that the dimensional ratio (L / W) of the dimension in the passage direction to the dimension in the axial direction is 1 or more and 100 or less. Specifically, the length (L) of the resistance heating element 77 in the passage direction can be set in the range of 3 mm or more and 20 mm or less in consideration of the easiness of manufacture, the maximum length of the pressure area N, and the like. . The axial width (W) of the resistance heating element 77 can be set in the range of 0.2 mm or more and 5 mm or less in consideration of manufacturability, dimension ratio (L / W), and the like.

(Wiring section)
The common wiring portion 71 is connected in common to the upstream end (one end in the passage direction) of the five heat generating portions 70A to 70E. The five individual wiring parts 72 to 76 are individually connected to the downstream ends (the other ends in the passing direction) of the five heat generating parts 70A to 70E. Each of the wiring portions 71 to 76 extends from the portion connected to the heat generating portions 70A to 70E to a position outside the heat generating portions 70A to 70E in the axial direction and a tip end portion of the conductor paths 71B to 76B. And electrode terminal portions 71A to 76A. The electrode terminal portions 71A to 76A are provided axially outside the heat generating portions 70A to 70E. Each of the conductor paths 71B to 76B connects the heat generating portions 70A to 70E and the electrode terminal portions 71A to 76A.

  In detail, the conductor path 71B of the common wiring portion 71 extends in the axial direction from the connecting portion with the heat generating portions 70A to 70E. The pair of electrode terminal portions 71A is bent to the downstream side (right side) from both ends of the conductor path 71B. On the other hand, the conductor paths 72B of the individual wiring portion 72 extend on both sides in the axial direction from the connection portion with the heat generating portion 70A. The pair of electrode terminal portions 72A is bent upstream (left side) from both ends of the pair of conductor paths 72B. The conductor paths 73B and 75B of the individual wiring portions 73 and 75 and the conductor paths 74B and 76B of the individual wiring portions 74 and 76 extend axially outward so as to be separated from the connection portions with the heat generating portions 70B to 70E. The electrode terminal portions 73A to 76A are bent upstream from the tip end portions of the conductor paths 73B to 76B. The electrode terminal portions 73A and 74A are disposed axially inward of the pair of electrode terminal portions 72A, and the electrode terminal portions 75A and 76A are disposed axially inward of the electrode terminal portions 73A and 74A. The pair of electrode terminal portions 71A is disposed axially inward of the electrode terminal portions 75A and 76A.

  In this heater 28, each resistance heating element 77 generates heat by flowing current in the passing direction between the common wiring portion 71 and the individual wiring portions 72 to 76.

  According to the heater 28 according to the fifth embodiment described above, the same operation and effect as the heater 23 and the like according to the first embodiment can be obtained.

  In the heater 28 according to the fifth embodiment, one common wiring portion 71 and one individual wiring portion 72 are connected to one heat generating portion 70A, but the present invention is not limited to this. For example, as shown in FIG. 11, even if the heating portion 70A is set as an area divided into two, the common wiring portion 71 and the individual wiring portion 72 are divided into two each and connected to the divided heating portion 70A. Good.

  The heater 28 according to the fifth embodiment is employed in the fixing device 7 using the cylindrical pressure roller 22. However, instead of this, the fixing device using the pressure roller 55 having a reverse crown shape is used. 8 may be adopted.

Sixth Embodiment
Next, the heater 29 of the fixing device 7 according to the sixth embodiment will be described with reference to FIG. FIG. 12 is a bottom view schematically showing the heater 29. As shown in FIG. In the following description, the same components as those of the heater 28 according to the fifth embodiment are denoted by the same reference numerals, and the description of the same or corresponding components as the heater 28 is omitted.

  The heater 28 according to the fifth embodiment is a both-side feed type, but the heater 29 according to the sixth embodiment is different in that it is a one-side feed type. That is, the heater 29 has such a shape that the heater 28 is halved at the axial center.

  Heat generating contact portion 36 of heater 29 includes three heat generating portions 70A, 70B and 70D, common wiring portion 71, three individual wiring portions 72, 73 and 75, and coating layer 46 (see FIG. 4). It is. That is, in the heat generating contact portion 36 of the heater 29, the heat generating portions 70C and 70E and the two individual wiring portions 74 and 76 are omitted. According to this configuration, since the connection between the electrode terminal portions 71A, 72A, 73A, 75A and the external device such as the power source can be concentrated in one place, the heater 29 can be miniaturized.

  Note that the heater 29 of the one-side power supply type according to the sixth embodiment can not be applied to the fixing device 8 using the pressure roller 55 in the reverse crown shape. Therefore, the same technical concept as the heater 27 (see FIG. 8) according to the fourth embodiment described above is adopted, and the heater 28 according to the fifth embodiment is changed to a single-feed type, and a pressure roller of reverse crown shape The present invention may be applied to the fixing device 8 using the 55 (the seventh embodiment: not shown).

  In the heaters 28 and 29 according to the fifth to seventh embodiments, the dimensions in the passing direction of the plurality of heat generating portions 70A to 70E (resistance heat generating members 77) gradually increase with distance from the electrode terminal portions 71A to 76A. Although the configuration is made smaller, the present invention is not limited to this, and may be set so as to be reduced stepwise (stepwise) (not shown).

  In the heaters 23, 26 and 27 according to the first to fourth embodiments, the heat generating parts 40A to 40J and the like are arranged to correspond to the sheet S of two types of sizes, and the fifth to seventh embodiments. In the heaters 28 and 29, the heat generating portions 70A to 70E and the like are arranged to correspond to the sheet S of three types of sizes, but the present invention is not limited to this. The wiring portion and the plurality of heat generating portions (heat generating layer portions) may be provided to correspond to the sheet S of one size, or provided to correspond to the sheet S of three or more sizes. May be

  Further, in the fixing devices 7 and 8 according to the first to fourth embodiments, the pressure rollers 22 and 55 are rotationally driven, and the fixing belt 21 is driven to rotate, but the present invention is not limited thereto. The pressure rollers 22 and 55 may be driven to rotate.

  Further, in the fixing devices 7 and 8 according to the first to fourth embodiments, the pressure rollers 22 and 55 are moved up and down (moved in a direction to approach or move away) with respect to the fixing belt 21. It is not limited to. For example, the fixing belt 21 may be moved toward or away from the pressure rollers 22 and 55.

  In the description of the present embodiment, the present invention is applied to a monochrome printer 1 as an example, but the present invention is not limited to this. For example, the present invention may be applied to a color printer, a copier, a facsimile or a multifunction machine. It may apply.

  The description of the above embodiment shows one aspect of the heater, the fixing device, and the image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above embodiment.

1 Printer (image forming device)
7, 8 Fixing Device 17 Power Supply 21 Fixing Belt (Fixing Member)
22, 55 Pressure roller (pressure member)
23, 26-29 heater (heater)
30 substrate (substrate)
31 Thermal insulation layer (substrate)
41, 51, 61 Common wiring area (wiring area)
42 to 45, 52, 53, 62, 63, 72 to 76 Individual wiring part (wiring part)
40A to 40J, 50A to 50J, 60A to 60J, 70A to 70E Heating part 41A to 45A, 51A to 53A, 61A to 63A, 71A to 76A Electrode end part N Pressure area S sheet (medium)

Claims (10)

A substrate,
A plurality of heat generating portions provided in a state of being arranged in a first direction on one surface of the substrate;
And a plurality of wiring portions provided on one surface of the substrate and electrically connecting the heat generating portion and a power source for supplying power to the heat generating portion.
Each of the plurality of wiring portions includes an electrode terminal portion electrically connected to the power supply in the first direction outside of the plurality of heat generation portions,
The dimension of the second direction orthogonal to the first direction of the plurality of heat generating portions is set to be gradually or stepwise smaller as it is separated from the electrode terminal portion in the first direction. Heater. The electrode terminal portions of the plurality of wiring portions are provided on both sides in the first direction across the plurality of heat generating portions,
The dimension in the second direction of the plurality of heat generating portions is set to be gradually or stepwise reduced from the both ends in the first direction toward the center in the first direction. Heater. The plurality of wiring portions are
A common wiring portion commonly connected to the plurality of heat generating portions from one side in the second direction of the heat generating portion;
A plurality of individual wiring portions individually connected to the plurality of heat generating portions from the other in the second direction of the heat generating portion;
Each of the common wiring portion and each of the individual wiring portions includes a conductor path extending in a second direction and connecting a branch path connected on the heat generating portion and the electrode terminal portion.
The plurality of branch paths between the common wiring portion and each of the individual wiring portions are alternately arranged to divide the plurality of heat generating portions,
3. The heater according to claim 1, wherein currents flow in opposite directions to each other in the heat generating portions adjacent to each other across the branch paths due to the potential difference generated between the plurality of branch paths. Each of the heat generating portions is constituted by a plurality of resistance heat generating members arranged in the first direction,
The plurality of wiring portions are
A common wiring portion commonly connected to one end of the plurality of heat generating portions in the second direction;
And a plurality of individual wiring parts individually connected to the other ends of the plurality of heat generating parts in the second direction,
Each of the common wiring portion and each of the individual wiring portions includes a conductor path connecting the heat generating portion and the electrode terminal portion.
3. The device according to claim 1, wherein each of the resistance heating elements generates heat when a current flows in a second direction between the common wiring portion and each of the individual wiring portions. Heater. A fixing member that heats toner on the medium while rotating about an axis;
A pressure member that forms a pressure area between the fixing member and the fixing member while rotating about an axis, and presses the toner on the medium passing through the pressure area;
5. A fixing device comprising: a heater according to any one of claims 1 to 4, which is provided to face the pressure member with the fixing member interposed therebetween and which heats the fixing member. A fixing member that heats toner on the medium while rotating about an axis;
A pressure member that forms a pressure area between the fixing member and the fixing member while rotating about an axis, and presses the toner on the medium passing through the pressure area;
The heater according to claim 2, provided opposite to the pressure member with the fixing member interposed therebetween, and heating the fixing member.
The fixing device is characterized in that the diameter of the pressure member is set so as to gradually decrease toward the center from both axial ends. A fixing member that heats toner on the medium while rotating about an axis;
A pressure member that forms a pressure area between the fixing member and the fixing member while rotating about an axis, and presses the toner on the medium passing through the pressure area;
And a heater provided to face the pressure member with the fixing member interposed therebetween, and heating the fixing member.
The diameter of the pressure member is set to be gradually smaller from the axial ends toward the center,
The heater is
A substrate,
A plurality of heat generating portions provided on one surface of the substrate in a state of being arranged in the axial direction of the fixing member;
And a plurality of wiring portions provided on one surface of the substrate and electrically connecting the heat generating portion and a power source for supplying power to the heat generating portion.
Each of the plurality of wiring portions includes an electrode terminal portion electrically connected to the power supply on the outer side in the axial direction with respect to the plurality of heat generating portions,
The dimension of the passage direction orthogonal to the axial direction of the plurality of heat generating portions is set so as to gradually or stepwise decrease in the axial center from both axial end sides,
A fixing device characterized in that the dimension in the passage direction of the heat generating portion disposed at the other axial end is smaller than the dimension in the passage direction of the heat generating portion disposed at the one axial end. The plurality of wiring portions are
A common wiring portion commonly connected to the plurality of heat generating portions from one side in the passage direction of the heat generating portion;
And a plurality of individual wiring parts individually connected to the plurality of heat generating parts from the other of the passing direction of the heat generating parts,
Each of the common wiring portion and each of the individual wiring portions includes a conductive path extending in the passing direction and connecting a branch path connected on the heat generating portion and the electrode terminal portion.
The plurality of branch paths between the common wiring portion and each of the individual wiring portions are alternately arranged to divide the plurality of heat generating portions,
8. The fixing device according to claim 6, wherein currents flow in opposite directions in the heat generating portions adjacent to each other across the respective branch paths due to a potential difference generated between the plurality of branch paths. Each of the heat generating parts is constituted by a plurality of resistance heating elements arranged in an axial direction;
The plurality of wiring portions are
A common wiring portion connected in common to one end of the plurality of heat generating portions in the passage direction;
And a plurality of individual wiring portions individually connected to the other end of the plurality of heat generating portions in the passage direction,
Each of the common wiring portion and each of the individual wiring portions includes a conductor path connecting the heat generating portion and the electrode terminal portion.
8. The device according to claim 6, wherein each of the resistance heating elements generates heat when a current flows in a passing direction between the common wiring portion and each of the individual wiring portions. Fixing device.   An image forming apparatus comprising the fixing device according to any one of claims 5 to 9.

Images