JP2016136236A - Heater and image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the biased temperature rise of a heater in the short direction of a substrate.SOLUTION: A fixing device 40 includes a fixing belt (603), a pressure roller (70) which conveys a sheet (P) from an upstream side to a downstream side in a nip part (N), a substrate (610) which comes into contact with the inner surface of the fixing belt, electrodes (642, 652, 662) which are provided side by side at an interval in the longitudinal direction of the substrate, heating elements (620) which are connected to the electrodes, a wiring (640) which is provided on one end side (610d) to be connected to the heating elements (620a to 620l), a wiring (650) which is provided on the other end side (610e) to be connected to the heating elements (620c to 620j), a wiring (660a) which is provided on one end side (610d) to be connected to the heating elements (620a, 620b), and a power supply circuit (79) which feeds power to the heating elements, to make a heat generation width changeable. The heating elements are arranged to be offset with respect to the center of the substrate in the short direction of the substrate.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a heater and an image heating apparatus including the heater. This image heating apparatus is used in an image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine having a plurality of these functions.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a toner image is formed on a sheet, and this is fixed on the sheet by heating and pressurizing it with a fixing apparatus (image heating apparatus). As a fixing device used in this way, a fixing device of a type in which a heater is brought into contact with the inner surface of a thin flexible belt to apply heat to the belt has been proposed (Patent Document 1). Since such a fixing device has a low heat capacity, the start-up process can be performed in a short time.

  Patent Document 1 discloses changing the width of the heat generation area of the heater in accordance with the sheet width size. FIG. 10 is a circuit diagram of the fixing device described in Patent Document 1. In this fixing device, electrodes 1027 (1027a to 1027t) are arranged in the longitudinal direction of the substrate 1021. The resistance heating layer 1025 is heated by energizing the resistance heating layer 1025 (1025a to 1025s) disposed in the center of the short side of the substrate from each electrode.

  In this fixing device, each electrode is connected to a wiring layer 1029 (1029c, 1029d, 1029g, 1029h, 1029i, 1029j) formed on the substrate. Each wiring layer extends to the longitudinal end of the substrate and is connected to the power supply circuit by a wiring member. Specifically, a wiring layer 1029d connected to the plurality of electrodes, a wiring layer 1029h connected to the electrode 1027b, and a wiring layer 1029g connected to the electrode 1027d extend to one end in the longitudinal direction of the substrate. Note that the plurality of electrodes connected to the wiring layer 1029d are electrodes 1027a, 1027c, 1027e, 1027g, 1027i, 1027k, 1027m, and 1027o. A wiring layer 1029c connected to the plurality of electrodes, a wiring layer 1029i connected to the electrode 1027q, and a wiring layer 1029j connected to the electrode 1027s extend to the other longitudinal end of the substrate. Note that the plurality of electrodes connected to the wiring layer 1029c are electrodes 1027f, 1027h, 1027j, 1027l, 1027n, 1027p, 1027r, and 1027t.

  At one end in the longitudinal direction of the substrate, the electrode 1027a and the wiring layers 1029g and 1029h are each connected to a wiring member. At the other end in the longitudinal direction of the substrate, the electrode 1027t and the wiring layers 1029i and 1029j are each connected to a wiring member. Thus, the heating element 1006 is electrically connected to the power supply circuit.

  The power supply circuit includes an AC power supply and switches 1033 (1033e, 1033f, 1033g, 1033h, 1033i, 1033j, 1033k, 1033l), and changes the connection pattern of each wiring depending on the combination of ON / OFF of the switch 1033. That is, each wiring layer 1029 is connected to either the power supply terminal 1031a side or the power supply terminal 1031b side according to the connection pattern in the power supply circuit. With such a configuration, the width of the heat generation region of the resistance heat generation layer 1025 is changed according to the width size of the sheet.

JP 2012-37613 A

  According to the study by the present inventors, it has been found that there is room for improvement in the case of the heater configuration shown in FIG. Specifically, it has been found that the temperature of the heater is increased in the short direction of the substrate.

  Therefore, an object of the present invention is to provide a heater and an image heating apparatus that can suppress the temperature of the heater from being biased in the short direction of the substrate.

  Other objects of the present invention will become apparent upon reading the following detailed description with reference to the accompanying drawings.

According to a first aspect of the present invention, there is provided a heater for heating the endless belt, which is used in an image heating apparatus having a power supply unit having first and second terminals and an endless belt for heating a toner image on a sheet. And
A substrate,
A first electrical contact provided on the substrate and electrically connectable to the first terminal;
A plurality of second electrical contacts provided on the substrate and electrically connectable to the second terminal;
A plurality of first electrode portions that are alternately arranged at a predetermined distance in the longitudinal direction of the substrate and are electrically connected to the first electrical contacts, and electrically connected to the second electrical contacts. A plurality of electrode parts comprising a plurality of second electrode parts;
Each of the adjacent electrode portions is disposed so as to be electrically connected, and a plurality of heat generating portions that generate heat by power supply from the power supply portion;
A first wiring portion that electrically connects the first electrical contact and the plurality of first electrode portions;
A second wiring part that electrically connects a part of the plurality of second electrical contacts and a part of the plurality of second electrode parts;
The plurality of heat generating portions are arranged offset with respect to the center of the substrate in the short direction of the substrate.

According to a second aspect of the present invention, there is provided a power supply unit including first and second terminals,
An endless belt for heating the toner image on the sheet;
A substrate located inside the endless belt and extending along the width direction of the end level belt;
A first electrical contact provided on the substrate and electrically connectable to the first terminal;
A plurality of second electrical contacts provided on the substrate and electrically connectable to the second terminal;
A plurality of first electrode portions that are alternately arranged at a predetermined distance in the longitudinal direction of the substrate and are electrically connected to the first electrical contacts, and electrically connected to the second electrical contacts. A plurality of electrode parts comprising a plurality of second electrode parts;
Each of the adjacent electrode portions is disposed so as to be electrically connected, and a plurality of heat generating portions that generate heat by power supply from the power supply portion;
A first wiring portion that electrically connects the first electrical contact and the plurality of first electrode portions;
A second wiring part for electrically connecting a part of the plurality of second electrical contacts and a part of the plurality of second electrode parts;
A predetermined second electrical contact different from the part and a third wiring part for electrically connecting a predetermined second electrode part different from the part;
When the image heating process is performed on a sheet having a predetermined width that is narrower than the maximum width sheet that can be introduced into the apparatus, the power supply unit corresponds to a first heating region among the plurality of heating units. When supplying power through the first wiring portion and the second wiring portion and performing image heating processing on a sheet wider than the predetermined width, the first heating region of the plurality of heating portions And is configured to supply power through the second wiring portion and the third wiring portion to the heat generating portion corresponding to the second heating region adjacent thereto,
The plurality of heat generating portions are arranged offset with respect to the center of the substrate in the short direction of the substrate.

1 is a diagram illustrating a configuration of an image forming apparatus. FIG. 3 is a short cross-sectional view of the fixing device. FIG. 3 is a longitudinal sectional view of the fixing device. It is explanatory drawing of the electric power feeding structure of a heater. It is a block diagram of a heater. It is a figure explaining a connector. It is a figure which shows the structure of the heater of a comparative example. It is a figure which shows the structure of a heater. (A) is a figure explaining the electric power feeding system to a heater, (b) is a figure explaining the switching system of the heat_generation | fever area | region of a heater. (A) is a circuit diagram of the heater at the time of a large size, and (b) is a circuit diagram of the heater at the time of a small size.

  Hereinafter, embodiments of the present invention will be described in detail with reference to examples. In the following embodiments, an image forming apparatus will be described by taking a laser beam printer using an electrophotographic process as an example. In the following description, this laser beam printer is referred to as printer 1.

[Image forming unit]
FIG. 1 is a cross-sectional view of a printer 1 that is an image forming apparatus according to the present exemplary embodiment. The printer 1 is an image forming apparatus that transfers the toner image formed on the photosensitive drum 11 in the image forming unit 10 to the sheet P, fixes the image on the sheet P by the fixing device 40, and forms the image on the sheet P. . Hereinafter, the configuration will be described in detail with reference to FIG.

  As shown in FIG. 1, the printer 1 includes an image forming unit (image forming station) 10 that forms toner images of each color of Y (yellow), M (magenta), C (cyan), and Bk (black). Yes. The image forming unit 10 includes four photosensitive drums 11 (11Y, 11M, 11C, and 11Bk) corresponding to the colors Y, M, C, and Bk in order from the left side of FIG. The following is arranged around each photosensitive drum 11 as a similar configuration. Charger 12 (12Y, 12M, 12C, 12Bk). Exposure device 13 (13Y, 13M, 13C, 13Bk). Developing device 14 (14Y, 14M, 14C, 14Bk). Primary transfer blade 17 (17Y, 17M, 17C, 17Bk). Cleaner 15 (15Y, 15M, 15C, 15Bk). Hereinafter, a configuration for forming a Bk color toner image will be described as a representative, and configurations corresponding to other colors will be described using the same symbols, and description thereof will be omitted. Therefore, when there is no particular distinction, the above-described configuration is expressed as follows. That is, they are simply referred to as a photosensitive drum 11, a charger 12, an exposure device 13, a developing device 14, a primary transfer blade 17, and a cleaner 15.

  A photosensitive drum 11 as an electrophotographic photosensitive member is rotationally driven in a direction indicated by an arrow (counterclockwise in FIG. 1) by a driving source (not shown). Around the photosensitive drum 11, a charger 12, an exposure device 13, a developing device 14, a primary transfer blade 17, and a cleaner 15 are sequentially arranged along the rotation direction.

  The surface of the photosensitive drum 11 is charged in advance by a charger 12. Thereafter, the photosensitive drum 11 is exposed by an exposure device 13 that emits laser light in accordance with image information, and an electrostatic latent image is formed. The electrostatic latent image becomes a Bk color toner image by the developing device 14. At this time, the same process is performed for the other colors. The toner images on the respective photosensitive drums 11 are sequentially primary-transferred sequentially to the intermediate transfer belt 31 by the primary transfer blade 17. After the primary transfer, the toner remaining without being transferred to the photosensitive drum 11 is removed by the cleaner 15. In this way, the surface of the photosensitive drum 11 is cleaned, and the next image can be formed.

  On the other hand, the sheets P placed on the feeding cassette 20 or the multi-feed tray 25 are fed one by one by a feeding mechanism (not shown) and fed to the registration roller pair 23. The sheet P is a member on which an image is formed on the surface. Specific examples of the sheet P include plain paper, cardboard, resin sheet-like members, overhead projector films, and the like. The registration roller pair 23 temporarily stops the sheet P, and when the sheet P is skewed with respect to the conveyance direction, the direction is straightened. The registration roller pair 23 feeds the sheet P between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The roller 35 transfers the color toner image on the belt 31 to the sheet P. Thereafter, the sheet P is fed toward the fixing device (image heating device) 40. The fixing device 40 heats and presses the toner image T on the sheet P to perform a fixing process (image heating process) on the sheet P.

[Fixing device]
Next, the fixing device 40 that is an image heating device used in the printer 1 will be described. FIG. 2 is a short cross-sectional view of the fixing device 40. FIG. 3 is a longitudinal sectional view of the fixing device 40. FIG. 4 is a diagram of a power supply configuration of the heater 600. FIG. 5 is a diagram illustrating a configuration of the heater 600.

  The fixing device 40 is an image heating device that heats an image on a sheet by a heater unit 60 (hereinafter referred to as a unit 60). The unit 60 has a low heat capacity configuration in which a flexible thin fixing belt 603 (endless belt) is heated by a contacting heater 600 disposed inside the belt 603. Therefore, the belt 603 can be efficiently heated, and the start-up performance at the start of fixing is excellent. As shown in FIG. 2, when the belt 603 is sandwiched between the heater 600 and the pressure roller 70 (hereinafter referred to as the roller 70), a nip portion N is formed. The belt 603 rotates in the direction of the arrow (clockwise, FIG. 2), and the roller 70 rotates in the direction of the arrow (counterclockwise, FIG. 2), and the sheet P fed to the nip portion N is nipped and conveyed. . At this time, since the heat of the heater 600 is applied to the sheet P via the belt 603, the toner image T on the sheet P is heated and pressurized at the nip portion N and fixed to the sheet P. The sheet P that has passed through the fixing nip N is separated from the belt 603 and discharged. In this embodiment, the fixing process is performed as described above. Hereinafter, the configuration of the fixing device 40 will be described in detail with reference to the drawings.

  The unit 60 is a unit for heating and pressurizing the image on the sheet P. The unit 60 is provided such that its longitudinal direction is parallel to the longitudinal direction of the roller 70. The unit 60 includes a heater 600, a heater holder 601, a support stay 602, and a belt 603.

  The heater 600 is a heating member that slidably contacts the inner surface of the belt 603 and heats the belt 603. Further, the heater 600 presses the belt 603 from the inner surface side toward the roller 70 so that the width of the nip portion N becomes a desired width. The heater 600 is a plate having a width (length in the vertical direction in FIG. 5) of 5 to 20 mm, a length in the longitudinal direction along the width direction of the belt 603 (length in the horizontal direction in FIG. 5) 350 to 400 mm, and a thickness of 0.5 to 2 mm. Shaped member. The heater 600 includes a substrate 610 whose longitudinal direction is the direction orthogonal to the sheet P conveyance direction (the width direction of the sheet P), and a resistance heating element 620 (hereinafter referred to as a heating element 620) as a heating layer.

  The heater 600 is fixed to the lower surface of the heater holder 601 along the longitudinal direction of the heater holder 601. In this embodiment, the heating element 620 is provided on the back surface side (the surface side that does not slide with the belt 603) of the substrate 610, but this is provided on the front surface side (the surface side that slides with the belt 603) of the substrate 610. It may be provided. However, the heater 600 preferably has a configuration in which the heating element 620 is provided on the back surface side of the substrate 610 so that the heat uniformity effect of the substrate 610 can be obtained so that the heat applied to the belt 603 is not uneven. Details of the heater 600 will be described later.

  The belt 603 is a cylindrical (endless or endless) belt (film) that heats the image on the sheet at the nip portion N. As the belt 603, for example, a belt in which an elastic layer 603b is provided on a base material 603a and a release layer 603c is provided on the elastic layer 603b is used. As the base material 603a, a metal material such as stainless steel or nickel, a heat resistant resin such as polyimide, or the like is used. As the elastic layer 603b, a material having elasticity and heat resistance such as silicone rubber and fluororubber can be used. As the release layer 603c, a fluorine resin or a silicone resin can be used.

  The belt 603 of this embodiment uses a cylindrical nickel member having an outer diameter of 30 mm, a length in the longitudinal direction (width direction, the front side in FIG. 2) of 330 mm, and a thickness of 30 μm as the base material 603a. An elastic layer 603b of silicone rubber having a thickness of 400 μm is formed on the base material 603a, and a fluororesin tube (release layer 603c) having a thickness of 20 μm is further coated on the elastic layer 603b.

  Note that a polyimide layer having a thickness of 10 μm may be provided as the sliding layer 603 d on the substrate 610 on the contact surface side with the belt 603. In the case where the belt 603 is provided with a polyimide layer, the friction resistance between the fixing belt 603 and the heater 600 can be reduced, and wear on the inner surface of the belt 603 can be suppressed. In order to further improve the slidability, a lubricant such as grease may be applied to the inner surface of the belt.

  The heater holder 601 (hereinafter referred to as the holder 601) is a member that holds the heater 600 in a state of being pressed toward the inner surface of the belt 603. Further, the holder 601 has a curved contact surface with the belt, and has a function of regulating the rotation trajectory of the belt 603. For the holder 601, a heat-resistant resin or the like is used. In this example, Zenite 7755 (trade name) manufactured by DuPont was used.

  The support stay 602 supports the heater 600 through the holder 601. The support stay 602 is preferably made of a material that is not easily bent even when a high pressure is applied. In this embodiment, SUS304 (stainless steel) is used.

  As shown in FIG. 3, the support stay 602 is supported by left and right flanges 411a and 411b at both ends in the longitudinal direction. The flanges 411a and 411b are collectively referred to as a flange 411. The flange 411 regulates the movement of the belt 603 in the longitudinal direction and the shape in the circumferential direction. A heat resistant resin or the like is used for the flange 411. In this example, PPS (polyphenylene sulfide) was used.

  A pressure spring 415a is provided in a contracted state between the flange 411a and the pressure arm 414a. A pressure spring 415b is also provided in a contracted state between the flange 411b and the pressure arm 414b. Hereinafter, the pressure springs 415a and 415b are collectively referred to as a pressure spring 415. With such a configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 through the flange 411 and the support stay 602. The belt 603 is pressed against the upper surface of the roller 70 with a predetermined pressing force, and a nip portion N having a predetermined width is formed. In this embodiment, the applied pressure is 156.8 N (16 kgf) at one end, and the total applied pressure is 313.6 N (32 kgf).

  As shown in FIG. 3, the connector 700 is a power supply member that is electrically connected to the heater 600 in order to supply power to the heater 600. The connector 700 is detachably attached to one end in the longitudinal direction of the heater 600. Since the connector 700 is provided so as to be easily detachable from the heater 600, the fixing device 40 can be easily assembled and replaced when the belt 603 or the heater 600 is damaged, and the maintenance is excellent. Yes. Details of the connector 700 will be described later.

  As shown in FIG. 2, the roller 70 is a nip forming member that forms a nip portion N in cooperation with the belt 603 by contacting the outer surface of the belt 603. The roller 70 has a multilayer structure in which an elastic layer 72 is laminated on a metal core 71 and a release layer 73 is laminated on the elastic layer 72 in this order. Examples of the material of the core metal 71 include SUS (stainless steel), SUM (sulfur and sulfur composite free-cutting steel), Al (aluminum), and the like. Examples of the material of the elastic layer 72 include an elastic solid rubber layer, an elastic sponge rubber layer, and an elastic foam rubber layer. An example of the material of the release layer 73 is a fluororesin material.

  The roller 70 according to the present embodiment includes an iron cored bar 71, a foamed silicone rubber elastic layer 72 on the cored bar 71, and a fluororesin tube release layer 73 on the elastic layer 72. Yes. Further, the dimensions of the portion of the roller 70 having the elastic layer 72 and the release layer 73 are an outer diameter of 30 mm and a length of 330 mm.

  As shown in FIG. 3, the cored bar 71 of the roller 70 is rotatably held via bearings 42a and 42b on the back side and the near side of the side plate 41. A gear G is provided at one end of the core bar 71 in the axial direction, and the driving force of the motor M is transmitted to the core bar 71 of the roller 70. As shown in FIG. 2, the roller 70 to which the driving force from the motor M is transmitted is rotationally driven in the direction of the arrow (clockwise). Then, the driving force is transmitted to the belt 603 via the roller 70 at the nip portion N, so that the belt 603 is driven to rotate in the direction of the arrow (counterclockwise). The roller 70 functions as a transport rotating body that transports the sheet P sandwiched by the nip portion N from the upstream side to the downstream side.

  The control circuit 100 is a circuit that includes a CPU that performs operations associated with various controls, and a non-volatile medium such as a ROM that stores various programs. A program is stored in the ROM, and various controls are executed by the CPU reading and executing the program. The control circuit 100 may be an integrated circuit such as an ASIC as long as the same function is achieved.

  As shown in FIG. 4, the control circuit 100 is electrically connected to the power supply circuit 110 so as to control the energization content of the power supply circuit 110. The control circuit 100 is electrically connected to the main thermistor 630 so as to obtain the output of the main thermistor 630. The control circuit 100 is electrically connected to the main thermistor 630 so as to obtain the output of the sub thermistor 631. The control circuit 100 is electrically connected to the motor M in order to control energization of the motor M.

  The motor M is a driving unit that drives the roller 70 via the gear G. When energization is performed by the control circuit 100, the motor M starts to rotate (drive) the gear G. The control circuit 100 controls the rotation of the motor M. The control circuit 100 rotates the roller 70 and the belt 603 through the motor M at a predetermined speed. As the fixing process is executed, the speed of the sheet P nipped and conveyed at the nip portion N is adjusted to a predetermined process speed (for example, 200 [mm / sec]).

  The main thermistor 630 is a temperature sensor disposed in the vicinity of the longitudinal center on the back side (the side opposite to the sliding surface) of the heater 600. The main thermistor 630 is bonded to the heater 600 while being insulated from the heating element 620. The main thermistor 630 has a function of detecting the temperature of the heater 600. As shown in FIG. 4, the main thermistor 630 is connected to the control circuit 100 via an A / D converter (not shown), and transmits an output corresponding to the detected temperature to the control circuit 100.

  The control circuit 100 reflects the temperature information acquired from the main thermistor 630 in the energization control of the power supply circuit 110. That is, the control circuit 100 controls the power supplied to the heater 600 via the power supply circuit 110 based on the output of the main thermistor 630. In this embodiment, the control circuit 100 controls the wave number of the output of the power supply circuit 110 to adjust the heat generation amount of the heater 600. By performing such control, the heater 600 is kept constant at a predetermined temperature (for example, 200 degrees) for fixing.

  The sub-thermistor 631 is disposed on the back side of the heater 600 on the end side of the heat generation width A (FIG. 4). By arranging the sub-thermistor 631 in this way, the temperature of the region where the sheet P does not pass in the longitudinal direction of the heater 600 when the A4 size is vertically fed or the A5 size is horizontally fed as the sheet P is set. Can be detected. When the detected temperature of the sub-thermistor 631 exceeds a predetermined value (for example, 270 degrees), the sheet P feeding interval is lengthened to lower the throughput, thereby the temperature of the non-passing portion of the sheet P. Control to suppress the rise. That is, the control circuit 100 changes the printing speed based on the temperature information acquired from the sub-thermistor 631 and reflects it in each control of the printer 1.

[heater]
Next, the configuration of the heater 600 used in the fixing device 40 will be described in detail. FIG. 9B is an explanatory diagram for explaining a switching method of a heat generation region (heating region for a sheet) used for the heater 600. In the following description, regarding the fixing device 40 and the members constituting the fixing device 40, the longitudinal direction (width direction) is a direction (left-right direction, FIG. 3) orthogonal to the transport direction on the surface of the sheet P. The short side direction is a direction (vertical direction, FIG. 5) parallel to the conveyance direction on the surface of the sheet P. The front surface of the fixing device 40 is a surface of the fixing device 40 viewed from the sheet entrance side, and the back surface is a surface viewed from the opposite sheet exit side. The left and right sides of the fixing device 40 are left or right when the fixing device 40 is viewed from the front (FIG. 3). The upstream side and the downstream side are the upstream side and the downstream side in the sheet conveyance direction.

  The heater 600 of the present embodiment is a heater that uses the heat generation method shown in FIGS. As shown in FIG. 9A, the A electrode to the C electrode are connected to the A wiring, and the D electrode to the F electrode are connected to the B wiring (B1 wiring, B2 wiring, B3 wiring). These electrodes are provided at a predetermined distance in the longitudinal direction of the substrate. The electrodes connected to the A wiring and the electrodes connected to the B wiring are alternately arranged in the longitudinal direction (left-right direction, FIG. 9A), and a heating element (heating unit) that generates heat by energization between the electrodes. ) Is connected. The electrodes and the wiring are conductive patterns (conductive wire portions) formed in the same manner. In this embodiment, the conductive wire portion extending in the short direction of the substrate in order to be electrically connected to the heating element is called an electrode (electrode portion), and the substrate plays a role of connecting the electrode to which the voltage is applied. The conductive wire portion extending in the longitudinal direction is called wiring (feeding wire, wiring portion). When a voltage V is applied between the A wiring and the B wiring, a potential difference is generated between adjacent electrodes. Then, as indicated by the arrows in the figure, current flows through each heating element such that the directions of the currents flowing in adjacent heating elements are staggered. The heater of this system generates heat in this way.

  Further, as shown in FIG. 9B, when the switch 3 is provided in the wiring 3 and the connection between the B wiring and the F electrode is disconnected, the B electrode and the C electrode are at the same potential. No longer flows. In this method, since each of the heating elements arranged in the longitudinal direction is individually energized, by cutting a part of a plurality of B wirings (B1 wiring, B2 wiring, B3 wiring), Only a part of the plurality of heating elements can generate heat. In other words, in this method, the heat generation area can be switched by providing the switch 1, the switch 2, and the switch 3 for the B1, B2, and B3 wirings. The heater 600 is configured to be able to switch the heat generating area of the heat generating element 620 using the above-described method.

  By the way, a heating element that generates Joule heat generates heat regardless of the direction of current if energization is performed, but the heating element and electrodes are arranged so that current flows in the direction along the longitudinal direction as in this method. It is preferable. This is because, in this method, compared to the configuration in which the electrodes are arranged so that the current flowing through the heating element is oriented along the short direction (the direction perpendicular to the longitudinal direction, the vertical direction in FIG. 9A). This is because there are advantages such as When energizing the heating element to generate Joule heating, the heating element generates heat according to its resistance, so the size and material of the heating element are designed according to the direction of the current to flow so that the resistance becomes a desired value. The At this time, the dimension of the substrate on which the heating element is provided is very short in the lateral direction compared to the longitudinal direction. Therefore, when a current is passed in the short direction, it is difficult to give the heating element a desired resistance using a low resistance material. On the other hand, when a current is passed in the longitudinal direction, it is relatively easy to give the heating element a desired resistance using a low resistance material. In addition, when a high resistance material is used for the heating element, there is a risk of causing temperature unevenness during energization due to uneven thickness of the heating element.

  For example, when the heating element material is applied along the longitudinal direction of the substrate by screen printing or the like, a thickness unevenness of about 5% may occur in the short direction. This is because uneven heating of the heating element material is caused by a slight pressure difference in the short direction of the spatula-shaped member. Therefore, the structure which arrange | positions a heat generating body and an electrode so that it supplies with electricity to a longitudinal direction like this system is preferable.

  Further, when energizing each of the heating elements arranged in the longitudinal direction individually, it is preferable to arrange the heating elements and the electrodes so that the directions of currents flowing in adjacent heating elements are staggered as in this method. . As another arrangement method of the heating element and the electrode, a method in which a plurality of heating elements having both ends connected to the electrode are arranged in the longitudinal direction and energized in the same longitudinal direction can be considered. However, in this method, since two electrodes are disposed between adjacent heating elements, there is a risk of short circuit. In addition, the number of required electrodes increases, and a large non-heat generating portion is generated between the heating elements. For this reason, it is desirable to arrange the heating element and the electrode so as to also serve as an electrode positioned between adjacent heating elements as in this method. This arrangement method eliminates the possibility of a short circuit between the electrodes and eliminates the space between the electrodes.

  In this embodiment, the common power supply wiring 640 shown in FIG. 5 corresponds to the A wiring in FIG. 9A, and the counter power supply in FIG. 5 corresponds to the B wiring in FIG. 9A. Wirings 650, 660a, and 660b. Further, the electrodes corresponding to the A electrode to the C electrode in FIG. 9A are the common electrodes 642a to 642g in FIG. 5, respectively, and the electrodes corresponding to the D electrode to the F electrode are counter electrodes 652a to 652d, 662a, and 662b. It is. Further, heating elements 620a to 620l correspond to the heating elements in FIG. Hereinafter, the common electrodes 642a to 642g are collectively referred to as an electrode 642. The counter electrodes 652a to 652d are collectively referred to as an electrode 652. The counter electrodes 662a to 662b are collectively referred to as an electrode 662. The wirings 660a and 660b are collectively referred to as a wiring 660. The heating elements 620a to 620l are collectively referred to as a heating element 620. Hereinafter, the configuration of the heater 600 will be described in detail with reference to the drawings.

  As shown in FIG. 6, the heater 600 includes a substrate 610, a heating element 620 on the substrate 610, a conductor pattern (power supply wiring), and an insulating coat layer 680 covering the heating element 620 and the conductor pattern (power supply wiring). It has.

  The substrate 610 is a member that determines the size and shape of the heater 600 and is a member that contacts the inner surface of the belt 603 along the longitudinal direction so as to sandwich the belt 603 in cooperation with the roller 70. As the material of the substrate 610, a ceramic material such as alumina or aluminum nitride having excellent heat resistance, thermal conductivity, electrical insulation, and the like is used. In this embodiment, an aluminum nitride plate member having a length of 380 mm in the longitudinal direction (left and right direction, FIG. 5) and a length of 9 mm in the short direction (vertical direction, FIG. 5) is used. The thermal conductivity of the alumina plate is 30 [W / (m · K)].

  On the back surface of the substrate 610 (on the substrate), a heating element 620 and a conductor pattern (power supply wiring) are formed by a thick film printing method (screen printing method) using a conductive thick film paste. In this embodiment, a silver paste is used for the conductor pattern so that the resistivity is low, and a silver-palladium alloy paste is used for the heating element 620 so that the resistivity is high. As the paste for forming the heating element, a ruthenium oxide paste or the like may be used. Further, as shown in FIG. 6, the heating element 620 and the conductor pattern are covered with an insulating coating layer 680 made of heat-resistant glass, and are electrically protected so as not to cause a leak or a short circuit.

  As shown in FIG. 5, electrical contacts 641, 651, 661 a, and 661 b as part of the conductor pattern are provided on one end side 610 a in the longitudinal direction of the substrate 610. On the other end side 610c in the longitudinal direction of the substrate 610, a heating element 620, electrodes 642a to 642g and electrodes 652a to 652e and 662a to 662b as part of the conductor pattern are provided. An intermediate region 610b is provided between one end side 610a and the other end side 610c of the substrate.

  Further, as shown in FIG. 5, a wiring 640 composed of a single line as a part of the conductor pattern is provided on one end side 610 d of the substrate 610 in the short direction of the heating element 620. On the other end side 610e in the short direction of the substrate 610 relative to the heating element 620, wirings 650 and 660 made of a plurality of lines are provided as part of the conductor pattern. In the case where the above-described configuration is to be arranged in a limited space on the substrate 610, the heating element 620 is offset from the center toward the wiring 640 in the short direction of the substrate 610. This is because the wiring 640 is a single line, whereas the wirings 650 and 660 are a plurality of lines, and a wide arrangement space is required.

  In this embodiment, specifically, the width of the heating element 620 (length in the short direction) is 2 mm, the width of one end side 610d of the substrate 610 is 2 mm, and the width of the substrate 610 is 9 mm. The width of the other end side 610e was 5 mm. That is, the heating element 620 is offset toward the wiring 640 side by 1.5 mm from the center of the substrate 610 in the short direction (sheet conveyance direction).

  The heating element 620 (620a to 620l) is a resistor that generates Joule heat when energized. The heating element 620 is formed on the substrate 610 as one heating element along the longitudinal direction thereof. The heating element 620 is adjusted to have a width (length in the short direction) of 1 to 4 mm and a thickness of 5 to 20 μm so that the resistance value becomes a desired value. The heating element 620 of this example has a width of 2 mm and a thickness of 10 μm. Further, the total length of the heating elements 620 in the longitudinal direction is 320 mm, and has a length capable of heating the sheet P of A4 size (width 297 mm).

  On the heating element 620, seven electrodes 642a to 642g, which will be described later, are stacked side by side in the longitudinal direction. In other words, the heating element 620 is divided into six sections in the longitudinal direction by the electrodes 642a to 642g. Furthermore, one of six electrodes 652 and 662 (652a to 652d, 662a, and 662b) is laminated at the center of each section in the longitudinal direction of the heating element 620. Thus, the heating element 620 is divided into a total of 12 subsections. The heating element 620 divided into 12 subsections can be regarded as a plurality of heating elements 620a to 620l. From another viewpoint, it can be said that the plurality of heating elements 620a to 620l electrically connect the adjacent electrodes to each other. With such a configuration, the heater can partially generate heat in the longitudinal direction.

  The heating element 620 is formed so that the resistance value is substantially uniform in the longitudinal direction, and is 92.4Ω in this embodiment. The longitudinal dimensions of the heating elements 620a, 620b and 620k, 620l are 25 mm, and the longitudinal dimension of the heating elements 620c to 620j is 27.5 mm. This is because a sheet of a small size (width size: 210 mm) in which the longitudinal dimension (220 mm) of the heat generation width A (FIG. 4) composed of the heating elements 620 c to 620 j is narrower than the maximum width sheet that can be introduced into the apparatus. ) To a size suitable for heating. Furthermore, by making the dimensions of the heating elements 620a, 620b and 620k, 620l shorter than the dimensions of the heating elements 620c to 620j, the amount of heat generated at both ends of the heating element 620 is increased, so that the end of the heating element 620 It is also possible to prevent temperature sagging due to heat dissipation in the case. Note that the heating element 620 hardly generates heat at the position where the electrode 642 and the electrodes 652 and 662 are formed on the heating element 620. However, since the substrate 610 has a soaking action, the influence on the fixing process is negligible by limiting the thickness of the electrode to 1 mm or less. The thickness of each electrode in this example is 1 mm or less.

  The electrode 642 (642a to 642g) is a part of the conductor pattern described above. The electrode 642 is provided along the short direction of the substrate 610 so as to be orthogonal to the longitudinal direction of the heating element 620. In this embodiment, the electrode 642 is provided so as to be stacked on the heating element 620. In the present embodiment, the electrode 642 is each electrode located odd-numbered from one end in the longitudinal direction of the heating element 620 among the electrodes connected to the heating element 620. The electrode 642 is connected to a terminal 110a on one side of the power supply circuit 110 via a wiring 640 made of a single line to be described later.

  The electrodes 652 and 662 are part of the conductor pattern described above. The electrodes 652 and 662 are provided along the short direction of the substrate 610 so as to be orthogonal to the longitudinal direction of the heating element 620. The electrodes 652 and 662 are electrodes other than the electrode 642 described above among the electrodes connected to the heating element 620. In other words, in the present embodiment, the electrodes are located evenly from one end in the longitudinal direction of the heating element 620.

  That is, the electrodes 642 and the electrodes 662 and 652 are alternately arranged in the longitudinal direction of the heating element. The electrodes 652 and 662 are connected to the terminal 110b on the other side of the power supply circuit 110 via wirings 650 and 660 composed of a plurality of lines to be described later.

  The electrode 642 and the electrodes 652 and 662 function as electrode portions for supplying power to the heating element 620. Although the odd number from the longitudinal end of the heating element 620 is described as the electrode 642 and the even number from the longitudinal end of the heating element 620 is described as the electrodes 652 and 662 here, the heater 600 is not limited to this configuration. For example, the even number from the longitudinal end of the heating element 620 may be the electrode 642, and the odd number from the longitudinal end of the heating element 620 may be the electrodes 652 and 662.

  In this embodiment, four of all the electrodes connected to the heating element 620 are provided as the electrodes 652. Two of all the electrodes connected to the heating element 620 are provided as electrodes 662. However, the allocation of the electrodes is not limited to the configuration of this embodiment, and may be appropriately changed according to the heat generation width corresponding to the heater 600. For example, two electrodes 652 and four electrodes 662 may be provided.

The wiring 640 is a part of the conductor pattern described above. The wiring 640 extends to one end side 610a of the substrate along the longitudinal direction of the substrate 610 on one end side 610d in the short side direction of the substrate 610. The wiring 640 is connected to electrodes 642 (642a to 642g) connected to the heating elements 620 (620a to 620l). The wiring 640 is connected to an electrical contact 641 described later. In the present embodiment, in the region where the heating elements 620 and the wiring 640 are arranged, the width of the wiring 640 in the short direction of the substrate is 1 mm, and the insulating intervals are 0.5 mm each on both sides in the short direction. Is provided. Accordingly, one end side 610d in the short direction of the substrate 610 is 2 mm.
The wiring 650 is a part of the conductor pattern described above. The wiring 650 extends to the one end side 610a of the substrate along the longitudinal direction of the substrate 610 on the other end side 610e in the short side direction of the substrate 610. The wiring 650 is connected to electrodes 652 (652a to 652d) connected to the heating elements 620 (620c to 620j). The wiring 650 is connected to an electrical contact 651 described later.

  The wiring 660 (660a, 660b) is a part of the conductor pattern described above. The wiring 660a as the third wiring extends to the one end side 610a of the substrate along the longitudinal direction of the substrate 610 on the other side 610e in the short side direction of the substrate 610. The wiring 660a is connected to an electrode 662a connected to the heating element 620 (620a, 620b). The wiring 660a is connected to an electrical contact 661a described later. The wiring 660b extends to the one end side 610a of the substrate along the longitudinal direction of the substrate 610 on the other side 610e in the short side direction of the substrate 610. The wiring 660b is connected to an electrode 662b that is connected to the heating element 620. The wiring 660b is connected to an electrical contact 661b described later. In this embodiment, in the region where the heating element 620 and the wirings 650a, 660, and 660b are arranged, the widths of the wirings 650 and 660 in the short direction of the substrate 610 are each 1 mm. Further, an interval for insulation is provided by 0.5 mm on both sides of each wiring in the short direction. Therefore, the other end side 610e in the short direction of the substrate 610 is 5 mm.

  Note that the widths of the wiring 640 and the wirings 650, 660a, and 660b are not limited to the widths in this embodiment. For example, the wiring 640 in which the current flowing through each of the wirings 650, 660a, and 660b is concentrated may be provided wider than the wirings 650, 660a, and 660b in order to suppress unnecessary heat generation. At this time, even if the width of the wiring 640 is large, it is sufficient if the total width of the wirings 650, 660a, and 660b is sufficient. Therefore, even when the width of the wiring 640 is increased, the other end side 610e of the substrate where a plurality of insulating intervals are required by arranging a plurality of wirings is required to have a larger space than the one end side 610d of the substrate. does not change.

  The electrical contacts 641, 651, 661 (661a, 661b) are part of the above-described conductor pattern. The electrical contacts 641, 651, 661 desirably have an area of 2.5 mm × 2.5 mm or more so that power can be reliably received from the connector 700 described later. The electrical contacts 641, 651, 661 of the present embodiment have a length along the longitudinal direction of the substrate 610 of 3 mm and a length along the short direction of the substrate 610 of 2.5 mm or more that can be arranged. did. The electrical contacts 641, 651, 661 a, and 661 b are arranged side by side at a distance of 4 mm in the longitudinal direction of the substrate 610 on the one end side 610 a of the substrate with respect to the heating element 620. As shown in FIG. 6, the insulating coating layer 680 is not provided in a portion where the electrical contacts 641, 651, 661 a, and 661 b are present, and the electrical contacts 641, 651, 661 a, and 661 b are exposed. The electrical contacts 641, 651, 661 a, and 661 b are provided in a region 610 a that protrudes from the longitudinal end of the belt 603 of the substrate 610. Therefore, the electrical contacts 641, 651, 661 a, 661 b can be in contact with and electrically connected to the connector 700.

  When the connector 700 is connected to the heater 600 and a voltage is applied between the electrical contact 641 and the electrical contact 651, the electrode 642 (642b to 642f) and the electrode 652 (652a to 652d) are connected via the wiring 640 and the wiring 650. ) Between the two potentials. Therefore, in the heating elements 620c, 620d, 620e, 620f, 620g, 620h, 620i, and 620j, the current along the longitudinal direction of the substrate 610 flows in the alternate direction between the adjacent heating elements. Then, the heating elements 620c, 620d, 620e, 620f, 620g, 620h, 620i, and 620j as the first heat generation regions generate heat.

  When the connector 700 is connected to the heater 600 and a voltage is applied between the electrical contact 641 and the electrical contact 661a, a potential difference is generated between the electrode 642 and the electrode 662a through the wiring 640 and the wiring 660a. Therefore, in the heating elements 620a and 620b, the current along the longitudinal direction of the substrate 610 flows in an alternate direction between the adjacent heating elements. Then, the heating elements 620a and 620b as the second heat generation regions adjacent to the first heat generation region generate heat.

  When the connector 700 is connected to the heater 600 and a voltage is applied between the electrical contact 641 and the electrical contact 661b, a potential difference is generated between the electrode 642 and the electrode 662b through the wiring 640 and the wiring 660b. Therefore, in the heating elements 620k and 620l, the current along the longitudinal direction of the substrate 610 flows in the alternate direction between the adjacent heating elements. Then, the heating elements 620k and 620l as the third heat generation regions adjacent to the first heat generation region generate heat.

  As described above, the heater 600 can selectively energize the heating element to be heated from the heating elements 620a to 620l by selecting the electrical contact to which the voltage is applied.

  An intermediate region 610b is provided between one end side 610a and the other end side 610c of the substrate. Specifically, in this embodiment, the region between the electrode 642a and the electrical contact 651 of the substrate 610 is the intermediate region 610b. The intermediate region 610 b is a grace interval for allowing the connector 700 to be attached to the heater 600 disposed in the belt 603. In this embodiment, an interval of 26 mm is provided as an intermediate region.

[connector]
Next, the configuration of the connector 700 used in the fixing device 40 will be described in detail. FIG. 6 is a diagram for explaining the connector 700. The connector 700 of this embodiment functions as a power supply unit, and is electrically connected to the heater 600 by being attached to the heater 600. Specifically, the connector 700 includes a contact terminal 710 that can be electrically connected to the electrical contact 641 and a contact terminal 730 that can be electrically connected to the electrical contact 651. Further, a contact terminal 720a that can be electrically connected by contacting the electrical contact 661a and a contact terminal 720b that can be electrically connected by contacting the electrical contact 661b are provided. Each contact terminal is connected to each electrical contact by the connector 700 sandwiching the front and back of the region of the heater 600 protruding from the longitudinal direction of the belt 603 so that the connector 700 and the belt 603 do not contact each other. In the fixing device 40 of this embodiment having such a configuration, soldering or the like is not used for connection between the connector and the electrical contact. Therefore, the connection between the heater 600 and the connector 700 whose temperature rises as the fixing process is executed can be maintained with high reliability. Further, in the fixing device 40 of this embodiment, since the connector 700 is detachable from the heater 600, the belt 603 and the heater 600 can be easily replaced. Hereinafter, the configuration of the connector 700 will be described in detail with reference to the drawings.

  As shown in FIG. 6, a connector 700 having metal contact terminals 710, 720a, 720b, 730 is attached to the heater 600 from the short side direction of the substrate 610 on one end side 610a of the substrate. The contact terminals 710, 720a, 720b, and 730 will be described by taking the contact terminal 710 as an example. As shown in FIG. 6, the contact terminal 710 is a member that electrically connects an electrical contact 641 and a later-described SW 643. The contact terminal 710 includes an electrical contact 711 for contacting the electrical contact 641 and a cable 712 for connecting to the SW 643. The contact terminal 710 has a U-shape, and the heater 600 can be inserted into the gap of the U-shape by moving in the arrow direction in FIG. An electrical contact 711 is provided at a portion of the contact terminal 710 that contacts the electrical contact 641, and the electrical contact 641 and the contact terminal 710 are electrically connected when the electrical contact 711 comes into contact with the electrical contact 641. Since this electrical contact 711 has a leaf spring property, it comes into contact with the electrical contact 641 while being pressed. Therefore, the position of the contact terminal 710 can be fixed by sandwiching the front and back of the heater 600.

  Similarly, the contact terminal 720a is a member that electrically connects the electrical contact 661a and a later-described SW663. The contact terminal 720 a includes a portion that contacts the electrical contact 661 and a cable 722 a for connection to the SW 663. Similarly, the contact terminal 720b is a member that electrically connects the electrical contact 661b and a later-described SW663. The contact terminal 720 b includes a portion for contacting the electrical contact 661 and a cable 732 b for connecting to the SW 663. Similarly, the contact terminal 730 is a member that electrically connects the electrical contact 651 and a later-described SW 653. The contact terminal 730 includes a portion for contacting the electrical contact 651 and a cable 722 for connecting to the SW 653.

  As shown in FIG. 6, the metal contact terminals 710, 720 a, 720 b, and 730 are integrally held in a resin housing 750. The contact terminals 710, 720 a, 720 b, and 730 are arranged side by side in the housing 750 so as to be connectable to the electrical contacts 641, 661 a, 661 b, and 651 when the connector 700 is attached to the heater 600. A partition is provided between the contact terminals, and electrical insulation between the contact terminals is maintained.

  In the above description, the example in which the connector 700 is attached from the short-side end of the substrate 610 has been described. However, the method of attaching the connector 700 to the substrate 610 is not limited thereto. For example, the connector 700 may be configured to be attached from the end in the longitudinal direction of the substrate.

[Power supply to the heater]
Next, a method for supplying power to the heater 600 will be described. The fixing device 40 according to the present exemplary embodiment can change the width size of the heat generation region of the heater 600 by controlling the power supply to the heater 600 according to the width size of the sheet P. With such a configuration, heat can be efficiently supplied to the sheet P. Since the fixing device 40 according to the present exemplary embodiment conveys the sheet P based on the center, the heat generation area also expands based on the center. Hereinafter, power supply to the heater 600 will be described in detail with reference to the drawings.

  The power supply circuit 110 functions as a power supply unit and has a function of supplying power to the heater 600. In this embodiment, a commercial power supply (AC power supply) having an effective value of single-phase AC of 100 V is used. The power supply circuit 110 of this embodiment includes a power supply terminal 110a and a power supply terminal 110b having different potentials. Note that the power supply circuit 110 may be a DC circuit as long as it has a function of supplying power to the heater 600.

  As shown in FIG. 4, the control circuit 100 is electrically connected to SW643, SW653, and SW663, respectively, in order to control SW643, SW653, and SW663, respectively.

  The SW 643 is a switch (relay) provided between the power supply terminal 110a and the electrical contact 641. In accordance with an instruction from the control circuit 100, the SW 643 switches whether to connect the power terminal 110a and the electrical contact 641 (ON / OFF). The SW 653 is a switch provided between the power terminal 110b and the electrical contact 651. The SW 653 switches whether to connect the power supply terminal 110b and the electrical contact 651 in accordance with an instruction from the control circuit 100. The SW 663 is a switch provided between the power terminal 110b and the electrical contacts 661 (661a, 661b). In response to an instruction from the control circuit 100, the SW 663 switches whether to connect the power terminal 110b and the electrical contacts 661 (661a, 661b).

  The control circuit 100 acquires the width size information of the sheet P used for the fixing process in response to the reception of the job execution instruction. Then, the combination of ON / OFF of SW643, SW653, and SW663 is controlled according to the width size information of the sheet P so that the heat generation width of the heat generating element 620 becomes a heat generation width suitable for the heat treatment of the sheet P. To control. At this time, the control circuit 100, the power supply circuit 110, SW 643, SW 653, SW 663, and the connector 700 function as power supply means for supplying power to the heater 600.

  When the sheet P is a maximum size sheet (a sheet wider than the above-described small size), for example, when the A3 size is fed vertically or the A4 size is fed horizontally, the width size of the sheet P is 297 mm. Therefore, the control circuit 100 performs control to cause the heating element 620 to generate heat up to the heat generation width B (FIG. 4). Therefore, the control circuit 100 turns on all of SW643, SW653, and SW663. As a result, power is supplied to the heater 600 from the electrical contacts 641, 661a, 661b, 651, and the heating element 620 generates heat in all twelve small sections. At this time, since the heater 600 generates heat uniformly in the 320 mm region, it is suitable for heating the 297 mm sheet P.

  In the case where the size of the sheet P is a small sheet (a sheet narrower than the maximum width sheet that can be introduced into the apparatus), for example, when the A4 size is fed vertically or when the A5 size is fed horizontally, The width size is 210 mm. Therefore, the control circuit 100 performs control to cause the heating element 620 to generate heat up to the heat generation width A (FIG. 4). Therefore, the control circuit 100 turns on SW643 and SW653 and turns off SW663. As a result, power is supplied to the heater 600 from the electrical contacts 641 and 651, and the heating element 620 generates heat in 8 of the 12 small sections. At this time, since the heater 600 generates heat uniformly in the 213 mm region, it is suitable for heating the 210 mm sheet P.

  As described above, in the fixing device 40 of this embodiment, the single connector 700 is attached to one end in the longitudinal direction of the heater 600 to supply power to the heater 600. Therefore, an increase in the longitudinal length of the substrate 610 can be suppressed as compared with the case where connectors are attached to both ends of the substrate 610. Further, the heater is so arranged that one end side 610d in the short direction of the substrate is on the upstream side in the conveyance direction of the sheet P, and the other end side 610e in the short direction of the substrate is on the downstream side in the conveyance direction of the sheet P. 600 is held by a holder 601. Therefore, the heater 600 heats the upstream side of the nip portion N where the sheet P is easily deprived of heat. Therefore, the heater 600 can appropriately heat the nip portion N in a wide range in the transport direction. In this embodiment, since heat can be efficiently transferred from the heating element 620 to the low temperature portion of the belt 603, unnecessary heat accumulation on the substrate 610 is suppressed. Therefore, in this embodiment, partial overheating due to heat accumulation is suppressed in the heater 600.

(Comparative example)
For comparison with the present embodiment, a heater 800 having a conventional configuration will be described as a comparative example. FIG. 7 is a diagram illustrating a configuration of a heater of a comparative example. As shown in FIG. 7, the heater 800 includes a substrate 810, a heating element 820 on the substrate 810, a conductor pattern (840, 841, 842, 830, 831, 832) connected to the heating element 820, and these. An insulating coating layer (not shown). The material, dimensions, and manufacturing method of the substrate 810 and the heating element 820 are the same as in this embodiment.

  As shown in FIG. 7, electrical contacts 831 and 841 as a part of the conductive pattern are provided on one end side 810 a in the longitudinal direction of the substrate 810. On the other end side 810c in the longitudinal direction of the substrate 810, a heating element 820 and electrodes 832 and 842 as a part of the conductive pattern are provided. An intermediate region 810b is provided between one end side 810a and the other end side 810c of the substrate. In the intermediate region 810b, a wiring 840 as a part of the conductive pattern is provided. A wiring 830 as a part of the conductive pattern is provided on the other end side 810e of the substrate 810 in the short direction of the heating element 820.

The heating element 820 has a width of 2 mm and a thickness of 10 μm, as in this example. Further, the total length in the longitudinal direction of the heating element 820 is 320 mm, which is the length capable of heating the sheet P of A4 size (width 297 mm), as in this embodiment.
The resistance value of the heating element 820 is formed to be uniform in the longitudinal direction, and is adjusted so that the total heat generation amount in the entire longitudinal direction is the same as that of the present embodiment. Specifically, the resistance value of the heating element 820 is 7.7Ω.

  The heating element 820 is provided at the center position of the substrate 810 in the short direction. That is, the widths on the one end side 810d and the other end side 810 are equal to each other in the short direction of the substrate. Specifically, the width of one end side 810d and the other end side 810e is 3.0 mm with respect to the width 9 mm of the substrate 810 and the width 2 mm of the heating element 820. The heater 800 having such a configuration is used in the fixing device 40 in which the conveyance direction of the sheet P is as shown in FIG. That is, the heater 800 is arranged so that one end side 810d is on the upstream side and the other end side 810e is on the downstream side. As in this embodiment, the main thermistor 630 is provided at the center position in the longitudinal direction of the heating element 820 and at the center position in the short direction of the substrate 810. Similarly to the present embodiment, the sub-thermistor 631 is provided at one end portion in the longitudinal direction of the heating element 820 and at the center position in the lateral direction of the substrate 610.

  Next, Example 2 will be described. FIG. 8 is a diagram illustrating the configuration of the heater 900. In addition, since it is the same as that of Example 1 except the structure of a heater, detailed description is abbreviate | omitted. Hereinafter, the configuration of the heater 900 will be mainly described.

  In the heater 900, a heating element 920 extending in the longitudinal direction of the substrate 910 is divided into 12 heating elements 920a to 920l by seven electrodes 942a to 942g and six electrodes 952 and 962 (952a to 952d, 962a and 962b). It is the structure which was made. The difference from the first embodiment is that one end side 910 d of the substrate on which the wiring 940 corresponding to the wiring 640 is provided is provided on the downstream side in the conveyance direction of the sheet P. Details are as follows.

  As shown in FIG. 8, one end side 910a in the longitudinal direction of the substrate 910 is provided with electrical contacts 941, 9851, 961a, and 961b as a part of the conductor pattern. On the other end side 910c in the longitudinal direction of the substrate 910, a heating element 920, electrodes 942a to 942g, and electrodes 952a to 952e and 962a to 962b as part of the conductor pattern are provided. An intermediate region 910b is provided between one end side 910a and the other end side 910c of the substrate.

  Further, as shown in FIG. 8, a wiring 940 made of a single line as a part of the conductor pattern is provided on one end side 910 d of the substrate 910 in the short direction of the heating element 920. On the other end side 910e in the short direction of the substrate 910 relative to the heating element 920, wirings 950 and 960 made of a plurality of lines are provided as a part of the conductor pattern. When the above-described configuration is to be arranged in a limited space on the substrate 910, the heating element 920 is arranged offset from the center toward the wiring 940 in the short direction of the substrate 910. This is because the wiring 940 is a single line, whereas the wirings 950 and 960 are a plurality of lines, and a wide arrangement space is required. Specifically, the width of the heating element 920 (length in the short direction) is 2 mm, the width of one end side 910d of the substrate 910d is 2 mm, and the other end side 910e of the substrate is 9 mm in the short direction length of the substrate 910. The width was 5 mm. That is, the heating element 920 is offset to the wiring 940 side by 1.5 mm from the center of the substrate 910 in the short direction.

  The heater 900 having such a configuration is used in the fixing device 40 in which the conveyance direction of the sheet P is an arrow direction (FIG. 8). In other words, in the sheet P conveyance direction, the heater 900 is arranged such that the other end side 910e is the upstream side and the one end side 910d is the downstream side.

  As in the present embodiment, the main thermistor 630 is provided at the center position in the longitudinal direction of the heating element 920 and at the center position in the short direction of the substrate 910. Similarly to the present embodiment, the sub-thermistor 631 is provided at one end portion in the longitudinal direction of the heating element 920 and at the center position in the lateral direction of the substrate 910.

[Evaluation]
In order to verify the effects of Examples 1 and 2, an evaluation test was performed by mounting the heaters of Examples 1 and 2 and the comparative example on the fixing device 40. In the evaluation test, the sheet P is continuously fixed by the fixing device 40 in an environment of low temperature (about 15 degrees) and low humidity (about 10%), and the number of printed sheets until the throughput is reduced is measured. Do that. The maximum number of prints was 500. At this time, the sheet P is A4 size paper (trade name “CS-814”, manufactured by Canon Inc.) and is longitudinally fed (width 210 mm).

  In the evaluation test, the control circuit 100 of the fixing device 40 adjusts the amount of heat generated by the heater 600 so that the temperature detected by the main thermistor 630 is maintained at 200 degrees. The control circuit 100 performs continuous printing at a throughput of 40 sheets / minute when the detection temperature of the sub-thermistor 631 is less than 270 degrees, and 20 sheets / minute when the sub-thermistors 631, 831, and 931 are 270 degrees or more. Continuous printing with a throughput of 1 minute. That is, when the temperature detected by the sub-thermistors 631, 831, and 931 is changed from less than 270 degrees to 270 degrees or more, the fixing device 40 shifts to the throughput down state.

In the evaluation test, in Example 1 and Example 2, the heating elements 620 and 920 are heated to the heating width A (FIGS. 4 and 8). In other words, when the heater 600 is used, the fixing device 40 generates heat only in 8 sections (heat generating bodies 620c to 620j, width 220 mm) among the 12 small sections of the heat generating body 620 by power feeding from the electrical contacts 641 and 651. Further, when the heater 900 is used, the fixing device 40 generates heat only in 8 sections (heat generating bodies 920c to 920j, width 220 mm) among the 12 small sections of the heat generating body 920 by power feeding from the electrical contacts 941 and 951.
The results of the evaluation test under the above conditions are shown in Table 1.

  According to Table 1, in the heater 800 of the comparative example, it can be seen that the throughput is already reduced at the stage of the 18th sheet. This is because the structure of the heater 800 of the comparative example is a structure that generates heat in the entire area of the heating element 820 in the longitudinal direction. When the entire area of the heating element 820 generates heat, the belt 603 is heated by a width of 320 mm in the width direction, but the width of the region where heat is taken away by the sheet P of the belt 603 is 213 mm in the width direction of the belt. Therefore, an area as large as 107 mm in the width direction of the belt 603 is excessively heated, and heat is accumulated. Since it is difficult for the heater 800 to transmit heat to the heat storage region of the belt 603, the heater 800 stores heat similarly to the belt 603. Then, the heat storage of the heater 800 is detected by the sub-thermistor 631, and the fixing device 40 is in a reduced throughput state.

  On the other hand, in the heater 600 of Example 1, since only the heat generation width A (width 220 mm) can be generated, the width of the region heated excessively in the width direction of the belt 603 is 7 mm. Therefore, heat storage in the heater 600 can be suppressed. As a result, in Example 1, as shown in Table 1, the fixing device 40 did not go into a reduced throughput state even when 500 sheets were fixed.

  Further, in the heater 900 of the second embodiment that can generate heat only in the heat generation width A (width 220 mm) as in the first embodiment, although the result is different from the result of the first embodiment, the throughput is reduced until the 364th sheet. It is a practical level. Note that this difference is that the heater 600 of the first embodiment has a configuration in which the heating element 620 is offset on the upstream side in the conveyance direction of the sheet P, whereas the heater 900 of the second embodiment has a conveyance direction of the sheet P. This is due to the fact that the configuration is offset on the downstream side.

  As described above, the sheet P is fixed by passing through the nip portion N from the upstream side to the downstream side.

  At this time, the sheet P in the normal temperature state conveyed to the nip portion N absorbs heat at the upstream side of the nip portion N and reaches the fixing temperature, and thereafter, the downstream side of the nip portion N with the fixing temperature maintained. Going through. In other words, at the nip portion N, a large amount of heat is applied to the sheet P on the upstream side, and a small amount of heat is applied to the sheet P on the downstream side.

  In the heater 600 according to the first embodiment, since the heating element 620 is arranged close to the upstream side in the conveyance direction of the sheet P, the heat on the upstream side of the nip portion N taken away by the entry of the sheet P can be quickly compensated. Can do. Therefore, even when the throughput of the fixing process is high, the sheet P can be instantaneously raised to the fixing temperature on the upstream side of the nip portion N. By maintaining this state also on the downstream side of the nip portion N, Thus, the image T can be reliably fixed. That is, the heater 600 according to the first exemplary embodiment can heat the sheet P in a long region in the conveyance direction of the nip portion N, so that the fixing process can be stably performed. At this time, since the detected temperature of the main thermistor 630 is stabilized, unnecessary power supply to the heater 600 is suppressed. Therefore, the heater 600 can suppress heat generation and heat storage at the end in the longitudinal direction of the heating element 620. Therefore, the heater 600 was able to obtain good results in the evaluation test.

  On the other hand, in the heater 900 of the second embodiment, the heating element 920 is arranged close to the downstream side in the conveyance direction of the sheet P, so that the heat upstream of the nip portion N taken away by the entry of the sheet P is quickly compensated. Difficult to do. Therefore, when the throughput of the fixing process is high, it is difficult to raise the sheet P to the fixing temperature until the sheet P is conveyed to the downstream side of the nip portion N. That is, since the heater 900 according to the second embodiment heats the sheet P in a short region in the conveyance direction of the nip portion N, the fixing process becomes unstable. At this time, since the temperature detected by the main thermistor 630 becomes unstable, the heater 900 is excessively supplied with electric power. Therefore, the heater 900 generates heat unnecessarily at the longitudinal end portion of the heating element 920 and accumulates heat. Therefore, it can be said that the heater 600 of Example 1 is a more preferable configuration.

(Other examples)
As mentioned above, although the Example which can apply this invention was described, the numerical values, such as a dimension illustrated by each Example, are examples, Comprising: It is not limited to this numerical value. As long as the invention can be applied, numerical values can be selected as appropriate. Moreover, you may change suitably the structure as described in an Example in the range which can apply invention.

  In the first and second embodiments, the pattern of the heat generation area of the heater is not limited to the two patterns of the large size and the small size. For example, you may have the heat_generation | fever area | region of 3 or more patterns. That is, the number of electrical contacts is not limited to four and may have five or more electrical contacts. For example, in the first embodiment, an electrical contact different from the electrical contacts 641, 651, 661a, 661b may be provided.

  The electrical contacts 641, 651, 661 a, and 661 b are not necessarily arranged collectively on one end side in the longitudinal direction of the substrate 610. For example, the electrical contacts 641 and 661a may be disposed at one end of the substrate 610 in the longitudinal direction, and the electrical contacts 651 and 661b may be disposed at the other end of the substrate 610 in the longitudinal direction. However, the configurations of the first and second embodiments are preferable in that the increase in the size of the substrate in the longitudinal direction can be suppressed.

  The method for forming the heating element is not limited to the method described in the first embodiment. Specifically, in the first embodiment, the electrode 642 and the electrodes 652 and 662 are stacked on the heating element 620 extending along the longitudinal direction of the substrate 610. However, a configuration may be employed in which electrodes are formed side by side in the longitudinal direction of the substrate 610, and the heating elements 620a to 620l are formed between adjacent electrodes.

  The belt is not limited to a configuration in which the inner surface is supported by a heater and driven by a roller. For example, a belt unit system that is spanned by a plurality of rollers and driven by any of the plurality of rollers may be employed. However, the configurations as in the first and second embodiments are desirable from the viewpoint of reducing the heat capacity.

  The rotating body that forms the belt and the nip portion is not limited to the roller member. For example, a belt in which a belt is wound around a plurality of rollers may be used.

  The image forming apparatus described using the printer as an example is not limited to an image forming apparatus that forms a full-color image, and may be an image forming apparatus that forms a monochrome image. In addition, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multifunction machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

  In the above description, the fixing device that fixes an unfixed toner image on the sheet P has been described as an example. However, the image heating device is not limited thereto. For example, the image heating device may be a device that fixes a semi-fixed toner image on the sheet P, or a device that heats a fixed image. That is, the image heating device may be a surface heating device that adjusts the gloss and surface properties of an image.

Claims (5)

A heater for heating the endless belt, used in an image heating apparatus having a power supply unit having first and second terminals, and an endless belt for heating a toner image on a sheet,
A substrate,
A first electrical contact provided on the substrate and electrically connectable to the first terminal;
A plurality of second electrical contacts provided on the substrate and electrically connectable to the second terminal;
A plurality of first electrode portions that are alternately arranged at a predetermined distance in the longitudinal direction of the substrate and are electrically connected to the first electrical contacts, and electrically connected to the second electrical contacts. A plurality of electrode parts comprising a plurality of second electrode parts;
Each of the adjacent electrode portions is disposed so as to be electrically connected, and a plurality of heat generating portions that generate heat by power supply from the power supply portion;
A first wiring portion that electrically connects the first electrical contact and the plurality of first electrode portions;
A second wiring part that electrically connects a part of the plurality of second electrical contacts and a part of the plurality of second electrode parts;
The heater, wherein the plurality of heat generating portions are offset from a center of the substrate in a short direction of the substrate.   2. The heater according to claim 1, wherein the plurality of heat generating units are offset from the center of the substrate toward the upstream side in the sheet conveying direction.   2. A predetermined second electrical contact different from the part and a third wiring part for electrically connecting a predetermined second electrode part different from the part. Or 2 heaters. A power supply unit comprising first and second terminals;
An endless belt for heating the toner image on the sheet;
A substrate located inside the endless belt and extending along the width direction of the endless belt;
A first electrical contact provided on the substrate and electrically connectable to the first terminal;
A plurality of second electrical contacts provided on the substrate and electrically connectable to the second terminal;
A plurality of first electrode portions that are alternately arranged at a predetermined distance in the longitudinal direction of the substrate and are electrically connected to the first electrical contacts, and electrically connected to the second electrical contacts. A plurality of electrode parts comprising a plurality of second electrode parts;
Each of the adjacent electrode portions is disposed so as to be electrically connected, and a plurality of heat generating portions that generate heat by power supply from the power supply portion;
A first wiring portion that electrically connects the first electrical contact and the plurality of first electrode portions;
A second wiring part for electrically connecting a part of the plurality of second electrical contacts and a part of the plurality of second electrode parts;
A predetermined second electrical contact different from the part and a third wiring part for electrically connecting a predetermined second electrode part different from the part;
When the image heating process is performed on a sheet having a predetermined width that is narrower than the maximum width sheet that can be introduced into the apparatus, the power supply unit corresponds to a first heating region among the plurality of heating units. When supplying power through the first wiring portion and the second wiring portion and performing image heating processing on a sheet wider than the predetermined width, the first heating region of the plurality of heating portions And is configured to supply power through the second wiring portion and the third wiring portion to the heat generating portion corresponding to the second heating region adjacent thereto,
The image heating apparatus, wherein the plurality of heat generating portions are offset from a center of the substrate in a short direction of the substrate. 5. The image heating apparatus according to claim 4, wherein the plurality of heat generating units are offset from the center of the substrate toward the upstream side in the sheet conveying direction.