JP2014219466A - Heating rotating body, image heating apparatus, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating rotating body 31 having a resistance heating layer 31b and power-supply rings 38L and 38R arranged at both ends for supplying electric power to the resistance heating layer 31b, and an image heating apparatus including the same, configured to prevent a power-supply ring adhesive surface from being separated due to thermal stress even after a long-time use with a simple configuration, thereby ensuring stable power supply.SOLUTION: A heating rotating body 31 is formed by laminating, in order from the inside to the outside, at least an insulating base material 31c, a resistance heating layer 31b which generates heat by electric power supplied, and an insulating layer 31a. On each of outer peripheral surfaces at both ends, there are provided an annular electrode layer 31d for supplying power to the resistance heating layer and power-supply rings 38L and 38R externally fitted to the electrode layer and having an inner circumferential surface adhered to the electrode layer in an electrically conductive manner. An edge part (a) of the electrode layer 31d closer to the center in a longitudinal direction of the heating rotating body is arranged inside of an edge part b of the power-supply rings 38L and 38R closer to the center in the longitudinal direction of the heating rotating body.

Description

  The present invention relates to a heating rotator used in an image heating apparatus that heats a sheet carrying an image by nipping and conveying it at a nip portion, an image heating apparatus incorporating the heating rotator, and an image forming apparatus equipped with the heating apparatus. .

  Examples of the image heating device include a fixing device that fixes an unfixed toner image formed on a sheet (recording material) such as paper as a fixed image. Further, a glossiness adjusting device (image modifying device) that adjusts the surface gloss of the image by reheating the toner image that has been semi-fixed or fixed on the sheet can be used.

  The image forming apparatus forms an image on a sheet using an image forming process such as an electrophotographic image forming system, an electrostatic recording image forming system, a magnetic recording image forming system, or the like. For example, a copying machine, a printer (laser beam printer, LED printer, etc.), a facsimile machine, a multi-function machine thereof, a word processor, and the like are included.

  The sheet is a member on which an image is formed by the image forming apparatus, and includes, for example, regular or irregular plain paper, cardboard, envelope, postcard, seal, resin sheet, OHT sheet, glossy paper, and the like.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image (developer image) is formed on a sheet, and the image is fixed by heating and pressurizing the toner image with a fixing apparatus as an image heating apparatus. Is going. Conventionally, as such a fixing device, there is an indirect heating method in which a fixing member is heated by a halogen heater which is a heating source provided inside a fixing member as a heating rotator, and the fixing member thermally fixes the toner image. It has been adopted.

  By the way, in recent years, from the viewpoint of energy saving, as a fixing method with high heat transfer efficiency and quick start-up of the apparatus, a method in which a resistance heating element is provided as a heating source on the fixing member itself and the resistance heating element is directly heated by energization has been adopted. Yes. By providing a resistance heating element in the vicinity of the surface of the fixing member, the startup time until the surface of the fixing member reaches the set temperature is shortened compared to the indirect heating method when a predetermined power is applied to the heating source. It is possible.

  In the fixing device described in Patent Document 1, a resistance heating layer as a heating source is formed on a cylindrical insulating substrate that is a first insulating layer, and both end portions in the longitudinal direction of the second insulating layer and the insulating layer are formed. An exothermic fixing belt having an electrode layer formed thereon is employed. The heat generating fixing belt feeds power from the power supply terminal to the electrode layer of the heat generating fixing belt, whereby the resistance heating element generates heat and the entire heat generating fixing belt is heated.

  In the nip portion formed between the heat fixing belt and the pressure roller by the heat fixing belt sandwiched between the belt support disposed inside the heat fixing belt and the pressure roller disposed outside the heat fixing belt. Then, the sheet on which the unfixed toner image is transferred is nipped and conveyed. Thus, the toner image can be fixed on the sheet by the heat of the heated heat generating fixing belt and the pressure of the nip portion.

  Such a fixing device of the heat fixing belt type has a thin heat generating fixing belt as a fixing member and has a small heat capacity, and is excellent in heat conversion efficiency of a heat generation amount with respect to input power, and generates heat up to a fixing possible temperature in a short time. It is possible to raise the temperature of the fixing belt. Therefore, the standby time after power-on is very short and a quick start is possible, and energy saving with reduced power consumption can be realized.

  By the way, in the configuration using the fixing member having the heat generating layer, the problem is that the power supply to the heat generating layer becomes unstable. FIG. 5 and FIG. 1 of Patent Document 2 each describe a heat-generating fixing roller having the following configuration as a method of supplying power to the resistance heat generator.

  5 has a configuration in which a part of the heating resistor is exposed from the protective film at the end of the heating fixing roller, and the inner surface of the power supply ring is bonded and fixed to the heating resistor. It is.

  In the heat fixing roller of FIG. 1, a part of the heat generating resistor is exposed from the protective film at the end of the heat fixing roller, and the inner peripheral surface of the power supply ring is bonded and fixed to the protective film. In this configuration, the exposed portion of the heating resistor is connected to the heating resistor via a power supply member.

  Since both of the above two configurations are configured to adhere and fix the power supply ring to the end of the heat fixing roller, the locus of the outer peripheral surface of the power supply during rotation is stable even with a low-rigidity member such as a heat fixing belt. In the initial stage of durability, stable power supply to the heating element can be easily achieved.

JP 2009-92785 A JP-A-9-283260

  However, as shown in FIG. 5 of Patent Document 2, the following problems occur in the fixing device in which the power supply ring is bonded and fixed immediately above the terminal electrode of the heating resistor with a conductive adhesive. That is, when the power supply ring is bonded and fixed immediately above the termination electrode of the heating resistor with a conductive adhesive, the temperature becomes high at 150 ° C. to 200 ° C. during use. Therefore, a part of the bonding surface is peeled off due to thermal stress, the effective bonding area is reduced, and there is a problem in that the power feeding ring and the termination electrode are finally disconnected.

  For this reason, in the heat fixing roller shown in FIG. 1 of Patent Document 2, the power supply ring is bonded and fixed to the protective film, and high-temperature solder or the like is used to ensure conduction between the resistance heating element and the power supply ring. As described above, when the power supply ring is bonded and fixed to the protective film and high temperature solder or the like is used to ensure conduction, there arises a problem that it becomes difficult to manufacture the belt. In addition, since it is necessary to extend the heating element to just below the power supply ring, there is a problem in that the heat generation area becomes longer than necessary and wasteful power is consumed.

  The present invention has been made to solve the problems of the prior art. The purpose is to provide stable power supply in this type of heating rotator and image heating device incorporating the same, even if it is used for a long time with a simple structure, and the peeling of the power ring adhesion surface due to thermal stress is suppressed. There is to do.

  A representative configuration of a heating rotator according to the present invention for solving the above-described problem is a heating rotator used in an image heating apparatus that heats a sheet carrying an image by nipping and conveying the sheet at a nip portion, A resistance heating layer and an insulating layer that are heated from at least the insulating base material and are heated in order from the inside to the outside are laminated, and annular electrode layers for supplying power to the resistance heating layer on the outer peripheral surfaces on both ends, respectively A feed ring externally fitted to the electrode layer and having an inner peripheral surface electrically connected to and bonded to the electrode layer, the edge of the electrode layer on the side near the center in the heating rotor longitudinal direction The portion is arranged inside the edge portion on the side close to the center of the feeding ring in the longitudinal direction of the heating rotator.

  In addition, a typical configuration of the image heating apparatus according to the present invention for solving the above-described problem is that the sheet carrying an image is sandwiched and conveyed between the heating rotator and the heating rotator and heated. A nip forming member for forming a nip portion to be formed, and a power supply member in contact with the power supply ring.

  According to the present invention, even if it is used for a long time with a simple configuration, peeling of the power feeding ring adhesion surface due to thermal stress is suppressed, and stable power feeding can be performed.

1 is a schematic configuration diagram of an example of an image forming apparatus. FIG. 6 is a schematic front view of a fixing device with a middle portion omitted. FIG. 3 is a schematic longitudinal sectional front view of the fixing device with a middle portion omitted. FIG. 4 is an enlarged transverse right side schematic view taken in the direction of arrows (4)-(4) in FIG. 2. It is a disassembled perspective view of a belt unit. FIG. 3 is an enlarged schematic cross-sectional view in a heat generation region of a belt. FIG. 3 is a schematic longitudinal sectional view of a main part for explaining a longitudinal positional relationship among a feeding ring, an electrode layer, and a resistance heating layer in Example 1. FIG. 6 is a schematic longitudinal sectional view of a main part for explaining the longitudinal positional relationship among a power feeding ring, an electrode layer, and a resistance heating layer in Example 2. It is a schematic diagram of the various variations of the layer structure of a belt.

[Example 1]
(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus 1 in which an image heating apparatus according to the present invention is mounted as a fixing device F. The image forming apparatus 1 is a color printer that can form an image corresponding to image information input from the host apparatus 200 (FIG. 2) to the control circuit unit 100 on a sheet P using electrophotographic technology.

  An image forming unit 2 forms four images for forming an image on the sheet P conveyed from the cassette 19 or 20 or the multi-feed tray 21 and conveyed by the conveyance mechanism 22 including the registration roller pair 22a. It has stations 3Y, 3M, 3C, 3K. Each station has a rotating drum type photoreceptor 4, a charging member 5, a laser scanner 6, a developing device 7, a transfer member 8, and a photoreceptor cleaner 9. Stations 3Y, 3M, 3C, and 3K form yellow, magenta, cyan, and black toner images, respectively.

  Further, the image forming unit 2 includes an intermediate transfer belt unit 10 and secondarily transfers the toner image primarily transferred from the stations 3Y, 3M, 3C, and 3K to the intermediate transfer belt 11 onto the sheet P by the secondary transfer roller 12. . Since the above-described operation of the image forming unit 2 and the image forming process are well known, detailed description thereof is omitted.

  The sheet P on which the unfixed toner image is transferred in the image forming unit 2 is sent to the fixing device F, and the toner image is heated and fixed on the sheet P. The sheet P exiting the fixing device F is route-switched to the first path 14 side or the second path 15 side by the flapper 13 according to the mode selection in advance. The sheet P introduced into the first path 14 is discharged to the face down tray 16 on the upper surface side of the apparatus. The sheet P introduced into the second path 14 is discharged to the face-up tray 17 on the side surface side of the apparatus.

  In the double-sided image forming mode, the sheet P on which the first-side image has been formed that has left the fixing device F is once introduced into the first path 14, then switched back and introduced into the third path 18. Then, the sheet is conveyed again through the conveyance mechanism 22 while being reversed with respect to the image forming unit 2.

(2) Fixing Device (2-1) Device Configuration The fixing device F according to this embodiment is a pressure roller driving type (tensionless type) heat generating fixing belt type fixing device. FIG. 2 is a schematic front view of the fixing device F with the middle portion omitted. However, the front cover plate 54 and the inlet side guide plate 55 in FIG. 4 are omitted. FIG. 3 is a schematic longitudinal sectional front view of the fixing device F with the middle portion omitted. FIG. 4 is an enlarged schematic cross-right side view taken along line (4)-(4) in FIG.

  Here, regarding the fixing device F or the constituent member of the present embodiment, the front side is the surface viewed from the sheet entrance side, the back side is the opposite surface (sheet exit side), and the left and right are the devices from the front side. Look left or right. The upstream side and the downstream side are the upstream side and the downstream side in the sheet conveying direction. The longitudinal direction (width direction) and the sheet width direction are directions substantially parallel to a direction orthogonal to the sheet conveyance direction on the sheet conveyance path surface. The short side direction is a direction substantially parallel to the sheet conveyance direction on the sheet conveyance path surface.

  The fixing device F includes a heat generating fixing belt (fixing member: hereinafter referred to as a belt) 31 as a heating rotator. Although details of the configuration of the belt 31 will be described later, the belt 31 includes a resistance heating layer 31b (FIGS. 6 to 9) that generates heat when energized. A cylindrical (endless belt-like) self-heating belt (tube heater) having a pair of power supply rings 38L and 38R for supplying power to the resistance heating layer 31b at both ends. In addition, a pressure roller 40 having elasticity as a nip forming member that forms a nip portion N that sandwiches and conveys and heats the sheet P carrying an image with the belt 31 is provided.

  In addition, a pressure pad (hereinafter referred to as a pad) 32 as a belt support (backup member) and a stay 33 as a pressure pad holding member are disposed inside the belt 31. The pad 32 is a heat insulating member having a substantially crescent cross section and long in the left-right direction. The stay 33 is a rigid member having a U-shaped transverse cross section and is long in the left-right direction, and is preferably a member that is not easily bent even when a high pressure is applied. For example, the stay 33 is a mold made of SUS304. The pad 32 and the stay 33 are arranged in parallel in the vertical direction, and the leg portion of the stay 33 and the flat surface side of the pad 32 are joined, and the pad 32 is held by the stay 33.

  The pad 32 is a member that faces the pressure roller 40 via the belt 31 and slides with the inner surface of the belt 31 in contact with the convex curved surface portion at the nip portion N as will be described later. It has a role as a guide that regulates the rotation trajectory of the belt 31 in the vicinity of the nip portion, and heat resistance and slidability with the belt inner surface are required. As a material, a heat-resistant resin such as a liquid crystal polymer, a metal such as ceramics or SUS can be used. Further, a material such as SUS having excellent slidability may be used for the nip portion, and a heat resistant resin such as liquid crystal polymer having excellent workability may be used for the guide portion. Further, heat-resistant grease may be applied to the sliding surface with the belt 31.

  A thermistor TH as a temperature sensor is disposed through an elastic support member 34 such as a leaf spring at a substantially central portion in the longitudinal direction of the stay 33. The belt 31 is loosely fitted to the assembly of the pressure pad 32, the stay 33, the elastic support member 34, and the thermistor TH. Terminal members 35L and 35R are attached to both ends of the belt 31, respectively.

  The terminal members 35L and 35R serve to guide movement of the belt 31 that is loosely fitted to the pad 32 and the stay 33 in the width direction and guide the inner peripheral surfaces of both ends of the rotating belt 31. do. The terminal members 35L and 35R are left and right shaped molded members made of heat-resistant and electrically insulating resin.

  Each of the terminal members 35L and 35R has a flange portion (seat portion) 35a for receiving the end face of the belt 31. A guide member 35b for guiding the inner peripheral surface of the end portion of the belt 31 is provided on the inner surface side of the flange portion 35a. The guide member 35b has a columnar shape having an outer diameter substantially corresponding to the inner diameter of the cylindrical belt 31. The guide member 35b has a hole 35c into which the end 33a of the stay 33 is inserted. Further, a pressure receiving block portion 35d is provided on the outer surface side of the flange portion 35a. And the longitudinal groove part 35e (FIG. 2, FIG. 5) exists in the junction part with the flange part 35a in the front side and back side of the pressure receiving block part 35d, respectively.

  In a state where the terminal members 35L and 35R are respectively attached to both end portions of the belt 31, the end portion 33a of the stay 33 is sufficiently fitted and engaged with the hole portion 35c of the guide member 35b. . Further, the guide member 35b is sufficiently fitted inside the end portion of the belt 31 and is fitted inside.

  Power supply members 37L and 37R are disposed on the tops of the flange portions 35a of the terminal members 35L and 35R via plate springs 36 such as SUS as conductive elastic support members, respectively. The power supply members 37L and 37R are in contact with the annular convex edge portions 38b of the pair of power supply rings 38L and 38R on both the left and right ends of the belt 31 while elastically sandwiching them from both sides inside the flange portion 35a.

  That is, the power supply members 37L and 37R are in stable contact with and electrically connected to the annular convex edge portions 38b of the left and right power supply rings 38L and 38R of the belt 31, respectively. The power feeding members 37L and 37R are preferably selected from those using metal brushes or carbon tips, or rotating roller types.

  The thermistor TH is elastically in contact with the inner surface of the belt 31 with a predetermined pressing force at substantially the center in the longitudinal direction of the belt 31 by the elastic force of the elastic support member 34.

  FIG. 5 shows the belt 31, the pad 32, the stay 33, the elastic support member 34, the thermistor TH, the left and right terminal members 35L and 35R, the left and right conductive elastic support members 36, the power supply, which are described above. It is a disassembled schematic view of members 37L and 37R. The pad 32, the stay 33, and the belt 31 are omitted in the middle. The assembly of these members is referred to as a belt unit 30.

  The pressure roller 40 includes an elastic layer 42 formed concentrically and integrally on the outer periphery of a metal core 41 made of a metal material, and an insulating layer 43 such as a fluororesin formed on the outer peripheral surface of the elastic layer 42. , An elastic roller. The material of the elastic layer 42 is preferably selected from heat-resistant rubber such as silicone rubber and fluorine rubber, or foam of silicone rubber. The elastic layer 42 of the pressure roller 40 has a reverse crown shape in order to stably convey the sheet P in the nip portion N without wrinkles or the like. Small-diameter shaft portions 41 a are provided concentrically and integrally with the core metal 41 at both left and right ends of the core metal 41.

  In the pressure roller 40, left and right small-diameter shaft portions 41a are rotatably held between the left and right side plates 51L and 51R of the apparatus frame 50 via bearing members 52L and 52R, respectively. A drive gear G is disposed concentrically and integrally at the end of the right small-diameter shaft portion 41a. The driving force of the motor M controlled by the control circuit unit 100 is transmitted to the gear G through a power transmission mechanism (not shown). As a result, the pressure roller 40 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction indicated by arrow R40 in FIG.

  On the other hand, the belt unit 30 is arranged between the left and right side plates 51L and 51R of the apparatus frame 50, with the pad 32 side facing downward and arranged in parallel with the pressure roller 35 above the pressure roller 35. . More specifically, vertical guide slits 51a (FIG. 3) in which vertical groove portions 35e (FIGS. 2 and 5) provided in the left and right terminal members 35L and 35R of the belt unit 30 are provided in the left and right side plates 51L and 51R, respectively. , FIG. 4) is engaged with the vertical edge portion. Accordingly, the left and right terminal members 35L and 35R are held so as to be slidable in the vertical direction with respect to the left and right side plates 51L and 51R, respectively.

  On both the left and right sides of the fixing device F, pressure mechanisms 60L and 60R having symmetrical configurations with respect to the left and right terminal members 35L and 35R are disposed. The pressure mechanisms 60L and 60R are mechanisms that press the belt 31 and the pressure roller 40 with a predetermined pressing force to form a nip portion (fixing nip portion) N having a predetermined width in the sheet conveyance direction X. Each of the mechanisms 60L and 60R includes a pressure lever 61 that contacts the upper surface of the pressure receiving block portion 35d of the terminal member 35L and 35R, a fixed spring receiving seat 63 above the pressure lever 61, and a pressure lever 61, respectively. And a pressurizing spring 62 that is contracted between the spring receiving seat 63.

  The pressure levers 61 of the pressure mechanisms 60L and 60R are in contact with the upper surfaces of the pressure receiving block portions 35d of the terminal members 35L and 35R in the free state, respectively, and press the terminal members 35L and 35R downward by the pressure of the pressure spring 62. (Pressurized state). As a result, the belt 31 is pressed against the upper surface of the pressure roller 40 with a predetermined pressing force against the elasticity of the elastic layer 42 via the stay 33 and the pad 32. By this pressure contact, a nip portion N having a predetermined width is formed between the belt 31 and the pressure roller 40 in the sheet conveying direction X.

  Moreover, it has the pressure release mechanism 64L * 64R which cancels | releases the pressurization state of said pressurization mechanism 60L * 60R, respectively. The pressure release mechanisms 64L and 64R are retracted by lifting the pressure levers 61 of the pressure mechanisms 60L and 60R from the upper surfaces of the pressure receiving block portions 35d of the terminal members 35L and 35R against the urging force of the pressure springs 62. It is a mechanism that moves to a position and holds it, and is controlled by the control circuit unit 100. The pressurization state of the pressurization mechanisms 60L and 60R is released by moving the pressurization lever 61 to the retracted position and holding it.

  This pressure release state may be a state where the belt 31 and the pressure roller 40 are separated from each other by a predetermined distance, or the belt 31 and the pressure roller 40 are in contact with each other, but the pressure is reduced more than a predetermined pressure. It may be in a state that has been done. Although a specific configuration of the pressure release mechanisms 64L and 64R is omitted in the drawing, for example, a mechanism using an electromagnetic solenoid, a mechanism using a cam and a motor, or the like can be adopted. The pressure release mechanism can also have a common mechanism configuration for the left and right pressure mechanisms 60L and 60R.

  2 and 3, W <b> 31 is the full width of the belt 31. W40 is the width of the pressure roller 40 (excluding the small-diameter shaft portion 41a). The length of the stay 33 is substantially the same as the full width W31 of the belt 31. The width of the pressure roller 40 is shorter than the entire width W31 of the belt 31 by a predetermined amount. The length of the pad 32 is substantially the same as the width W40 of the pressure roller 40. The width (longitudinal direction) of the nip portion N is the same as the width W40 of the pressure roller 40.

  The left and right power supply rings 38 </ b> L and 38 </ b> R of the belt 31 are positioned outside the end portion of the pressure roller 40. Wmax is a sheet conveyance area width (maximum sheet passing width) of the maximum width size that can be used in the fixing device F, and is smaller than the width W40 of the nip portion N by a predetermined value.

  In FIG. 4, 53 is a top cover plate of the fixing device F, 54 is a front cover plate, 55 is an entrance side guide plate, 56 is a back cover plate, 57 is an exit side guide plate, and 58 is a fixing discharge roller pair. The fixing discharge roller pair 58 is rotationally driven with a predetermined direction and a peripheral speed when the driving force of the pressure roller 40 is transmitted via an interlocking mechanism (not shown). The conductive elastic support members 36 of the left and right power supply members 37L and 37R are electrically connected to a power source unit (AC power source) 101 via wirings 102, respectively. The thermistor TH is electrically connected to the control circuit unit 100 via wiring (not shown).

(2-2) Fixing Operation In the fixing device F, in the standby state, the pressure mechanisms 60L and 60R are held in the pressure release state by the pressure release mechanisms 64L and 64R. That is, the pressure contact between the belt 31 and the pressure roller 40 is released. The rotation of the pressure roller 40 is stopped. Power supply to the left and right power supply members 37L and 37R is stopped.

  When a print job start signal is input to the control circuit unit 100, the control circuit unit 101 controls the power supply unit 101 to start energization of the resistance heating layer 31 b of the belt 31 with a predetermined energization control pattern. That is, a voltage is applied to the left and right power supply rings 38L and 38R via the left and right power supply members 37L and 37R. As a result, a resistance heating layer 31b between the left and right electrode layers 31d, which will be described later, generates heat by energization, and the belt 31 is heated all around. Then, electrical information related to the temperature of the belt 31 is input from the thermistor TH to the control circuit unit 100.

  The control circuit unit 100 determines an energization control pattern based on the detected temperature of the belt 31 input from the thermistor TH. Then, according to the determined energization control pattern, the power supply unit 101 is controlled by phase control / wave number control or the like to supply appropriate power to the resistance heating layer 31b.

  More specifically, when the thermistor TH detects the first predetermined temperature as the temperature of the belt 31, the control circuit unit 100 controls the pressure release mechanisms 64L and 64R to release the pressure mechanisms 60L and 60R from the pressure release state. Switch to the pressurized state. As a result, the belt 31 comes into pressure contact with the pressure roller 40, and a nip portion N having a predetermined width in the sheet conveyance direction X is formed therebetween. In addition, the control circuit unit 100 starts the motor M and starts to rotate the pressure roller 40 as a drive rotating body.

  The pressure roller 40 rotates at a predetermined peripheral speed in the counterclockwise direction of the arrow R40 in FIG. The rotational force acts on the belt 31 by the frictional force at the nip N between the pressure roller 40 and the outer surface of the belt 31 by the rotational driving of the pressure roller 40. As a result, the belt 31 has a circumferential surface substantially corresponding to the rotational peripheral speed of the pressure roller 40 in the clockwise direction indicated by the arrow R31 in FIG. Followed by speed.

  The flange portions 45a of the left and right terminal members 45L and 45R receive the belt end portion on the side of the shift side when the rotating belt 31 moves to the left or right side along the length of the pad 32, and restricts the shift movement. . Further, the guide member 35 b on the inner surface side of the flange portion 45 a guides the inner peripheral surfaces of both end portions of the belt 31.

  Thereafter, when the thermistor TH detects a second predetermined temperature higher than the first predetermined temperature, the control circuit unit 100 starts an image forming operation of the image forming unit. Then, the sheet P on which the toner image t is transferred is conveyed to the fixing device F. On the other hand, when the thermistor TH detects the third predetermined temperature (fixing temperature) higher than the second predetermined temperature, the control circuit unit 100 sets the energization to the resistance heating layer 31b of the belt 31 to the temperature control state. In the temperature control state, the energization control from the power supply unit 101 to the resistance heating layer 31b is performed using PI control or the like so that the temperature of the belt 31 is maintained substantially constant at the third predetermined temperature that is the fixing temperature. .

  When the sheet P to which the toner image t has been transferred is conveyed to the fixing device F, the sheet P is guided by the inlet side guide plate 55 and enters the nip portion N to be nipped and conveyed. As a result, the toner image t and the sheet P are heated and pressed to fix the toner image t to the sheet P as a fixed image. The introduction of the sheet P to the fixing device F is a so-called center reference based on the sheet width center in this embodiment. A so-called one-side reference may be used. The sheet P that has exited the nip portion N is separated from the belt 31, guided by the outlet side guide plate 57, enters the nip portion of the fixing discharge roller pair 58, and is discharged and conveyed.

  When a predetermined one or a plurality of continuous print jobs are completed, the control circuit unit 101 stops energization of the resistance heating layer 31b of the belt 31. Further, the driving of the motor M is stopped. Further, the pressure release mechanisms 64L and 64R are controlled to switch the pressure mechanisms 60L and 60R from the pressure state to the pressure release state. In this state, the control circuit unit 100 holds the fixing device F in a standby state until a start signal for the next print job is input.

(2-3) Configuration of Belt 31 FIG. 6 is an enlarged schematic cross-sectional view of the heat generation region of the belt 31. FIG. 7 is a schematic longitudinal cross-sectional view of the main part for explaining the longitudinal positional relationship of the feed ring, the electrode layer, and the resistance heating layer on the left side of the belt 31. The longitudinal positional relationship of the power supply ring, electrode layer, and resistance heating layer on the right side of the belt 31 is the same as that of FIG.

  The belt 31 in this embodiment is a cylindrical member having flexibility as a whole. In order from the outer side to the inner side of the belt 31, at least an insulating layer 31a, a resistance heating layer 31b that generates heat when supplied with power, and a cylindrical insulating base material 31c are laminated. Moreover, it has the cyclic | annular electrode layer 31d for electrically feeding to the resistance heating layer 31b along the periphery on the outer surface of both end parts side, respectively. The power feeding rings 38L and 38R are respectively fitted on the left and right electrode layers 31d by a conductive adhesive S having heat resistance.

  The cylindrical insulating base 31c maintains the strength of the belt 31 and has flexibility that allows deformation in the circumferential direction, while having insulation. If it is too thin, it is easily damaged, and if it is too thick, it is difficult to deform. Therefore, a heat-resistant resin material such as polyimide having a thickness of 20 μm to 100 μm can be used. In this example, a cylindrical polyimide belt having a thickness of 50 μm and a diameter of 30 mm was used.

  The resistance heating layer 31b is a layer that is formed on the outer peripheral surface of the cylindrical insulating substrate 31c and generates heat when energized. As the material, a material in which conductive carbon or metal powder is dispersed in a heat-resistant resin such as polyimide can be used. In this example, a coating layer of a resistance heating element made of carbon-dispersed polyimide and having a thickness of 25 μm is used so that the resistance value between the left and right electrode layers 31d on both ends of the belt is 10Ω at room temperature. The amount of carbon dispersion is adjusted. Thereby, the resistance heat generating layer 31b generates heat with about 1000 W of electric power when 100V is applied.

  The insulating layer 31a is formed on a part of the resistance heating layer 31b and the electrode layer 31d, and prevents current from flowing to other than the belt 31 and prevents contamination due to toner adhesion or the like. The insulating layer 31a is required to be releasable from the toner, and since it is in contact with the electrode layer 31d and the resistance heating layer 31b, the insulating layer 31a is also required to have an insulating property so that no current flows. Therefore, an insulating fluororesin material such as PFA PTFE or the like can be used.

  If the insulating layer 31a is too thin, it will have a short life due to wear due to friction with the sheet P and the pressure roller 40, and if it is too thick, the heat capacity will increase and the heat transfer will be reduced, thereby impairing energy saving. It is desirable to use a resin material. In this example, an insulating PFA resin tube having a thickness of 20 μm was used.

  The belt 31 does not necessarily have a three-layer structure. For example, in order to obtain a good image quality when forming a color image, it is preferable to make the surface of the belt 31 follow the surface shape of the sheet P easily. For this purpose, it is better to have an elastic layer 31e (FIG. 9A) made of silicone rubber or the like between the insulating layer 31a and the resistance heating layer 31b.

  Further, in order to prevent thermal degradation or the like due to the insulating layer 31a or the elastic layer 31e being directly heated by the resistance heating layer 31b, an intermediate layer 31f (between the insulating layer 31a or the elastic layer 31e and the resistance heating layer 31b). (B) and (c) of FIG. 9 may be provided. Further, in order to increase the adhesive strength between the layers of the belt 31, an adhesive layer 31g ((d) in FIG. 9) may be provided. Furthermore, a separate release layer 31h ((e) in FIG. 9) may be provided on the insulating layer 31a. In this case, a conductive material can be used for the release layer 31h. Further, various combinations of the layer configurations of (a) to (e) of FIG. 9 are possible.

  At both ends of the belt 42, electrode layers 31d for supplying power to the resistance heating layer 31b are formed. In this embodiment, as shown in FIG. 7, the resistance heating layer 31b is formed on the outer peripheral surface of the cylindrical insulating base 31c over the entire length of the cylindrical insulating base 31c. The electrode layer 31d is formed in an annular shape along the circumference on the outer surfaces on both end sides of the resistance heating layer 31b.

  The electrode layer 31d can be made of a material in which conductive particles are dispersed in a heat resistant resin such as polyimide. Further, by adjusting the resistance value so that the resistance is sufficiently smaller than that of the resistance heating layer 31b, heat generation in the electrode layer 31d can be suppressed. In this example, a polyimide having a conductive particle dispersed in a thickness of 75 μm was used.

  The power feeding rings 38L and 38R are respectively fitted on the left and right electrode layers 31d by a conductive adhesive S having heat resistance. That is, the outer peripheral surface of the electrode layer 31d and the inner peripheral surfaces of the power feeding rings 38L and 38R are bonded by the conductive heat-resistant adhesive layer S. For the adhesive layer S, a conductive heat resistant adhesive in which silver (filler) is filled in a silicone resin (binder component) is used. Although the conductive heat-resistant adhesive is used in this embodiment, other means such as high-temperature solder may be used.

  In the present embodiment, the feeding rings 38L and 38R are made of copper, and each has a circular short cylindrical portion 38a having an inner diameter of 30.4 mm, a thickness of 2 mm, and a width of 9 mm, and a circular protrusion of φ45 concentrically integrated with the short cylindrical portion 38a. It is a member which has the edge part 38b and is hard to deform | transform.

  Each of the feed rings 38L and 38R has a circular short cylindrical portion 38a fitted on the left and right electrode layers 31d of the cylindrical belt 31, and the outer peripheral surface of the electrode layer 31d is electrically conductive with the inner peripheral surface of the circular short cylindrical portion 38a. Bonded with the adhesive S. As a result, the left and right ends of the belt 31 are held in a cylindrical shape. The cylindrical guide members 35b of the left and right terminal members 35L and 35R are fitted into the left and right end portions of the belt 31 which is shaped like a cylinder. Thereby, the belt 31 can rotate stably.

  Power supply members 37L and 37R are in contact with the annular convex edge portions 38b of the power supply rings 38L and 38R, elastically sandwiching the annular convex edge portions 38b from both sides, respectively, and are stable with respect to the rotating annular convex edge portions 38b. It is in contact and electrically conducting.

  As shown in FIG. 7, the edge end a on the side near the center in the belt longitudinal direction (heating rotor longitudinal direction) of the electrode layer 31d is the edge end b on the side near the center in the belt longitudinal direction of the power feeding ring 38L. It is arranged inside. Since the resistance value of the electrode layer 31d is adjusted so that the resistance is sufficiently smaller than that of the resistance heating layer 31b, the resistance heating layer 31b generates heat inside the edge portion a where the electrode layer 31d is not formed.

  Therefore, as the edge a of the electrode layer 31d is arranged on the inner side and the distance between a and b is increased, the influence of heat on the adhesive S is reduced, and even if it is used for a long time with a simple configuration, it is caused by thermal stress. Peeling of the power supply ring bonding surface is suppressed and stable power supply can be achieved. The right side of the belt 31 is the same as FIG.

  However, since the heat generation area needs to be larger than the maximum image width used in the printer, the position of the edge portion a of the electrode layer 31d needs to be arranged so that the maximum image width is inside. Here, the maximum image width is the same width as the maximum passage width Wmax of the maximum size sort that can be used in the apparatus, or a predetermined smaller width.

  In order to show the effect of the present invention, the edge portion a near the center in the belt longitudinal direction of the electrode layer 31d is arranged inside the edge portion b near the center in the belt longitudinal direction of the power feeding rings 38L and 38R. Table 1 shows the results of the endurance print test in this case (this example). Table 1 also shows the results of the durability print test in the comparative example. In the comparative example, there is no electrode layer 31d, and the feed ring is bonded and fixed immediately above the terminal electrode of the resistance heating layer 31b with a conductive adhesive.

  In the case of the comparative example, when the number of durable prints was 100,000, the power feeding ring adhesive surface was peeled off due to thermal stress, and power feeding failure to the resistance heating layer 31b occurred, and the belt 31 became unusable.

  On the other hand, in the case of this example, since the distance from the heat generation area to the power supply ring bonding surface is large, the influence of thermal stress is small and the power supply ring bonding surface does not peel off, and the number of durable prints reaches 300,000. There were no problems such as poor power supply.

  As described above, according to this embodiment, in the fixing device in which the power supply ring is bonded to the end of the heat generating fixing belt, peeling of the power supply ring bonding surface due to thermal stress is suppressed even when used for a long time with a simple configuration. Power can be stably supplied.

[Example 2]
FIG. 8 is a schematic longitudinal sectional view of the main part for explaining the longitudinal positional relationship of the feeding ring, the electrode layer, and the resistance heating layer on the left side of the belt 31 in the second embodiment. The longitudinal positional relationship of the power supply ring, electrode layer, and resistance heating layer on the right side of the belt 31 is the same as that of FIG.

  In the second embodiment, the edge portion c of the resistance heating layer 31b is disposed inside the edge portion b on the side close to the center in the belt longitudinal direction (heating rotor longitudinal direction) of the power feeding ring 38L.

  In Example 1, the resistance heating layer 31b generates heat ideally inside the edge portion a where the electrode layer 31d is not formed, but from the edge portion a due to adhesion unevenness between the electrode layer 31d and the resistance heating layer 31b. There may be slight heat generation on the outside.

  By arranging the edge c of the resistance heating layer 31b inside the edge b near the center in the belt longitudinal direction of the power feeding ring 38L as in the second embodiment, the heat generating region can be more reliably arranged in the power feeding ring 38L. And the electrode ring 31d can be separated from the adhesion surface of the feeding ring. As a result, more stable power supply at the time of durability has become possible. The right side of the belt 31 is the same as FIG.

  Here, in the layer configuration of FIG. 7 (the heat generating layer 31b is provided below the adhesive layer S), the resistance values of the adhesive layer S and the electrode layer 31d are sufficiently small with respect to the heat generating layer 31b. The heat generation layer 31b hardly generates heat. However, depending on the bonding state of the heat generating layer 31b and the adhesive layer S (particularly between a and b in FIG. 7), there is a possibility of heat generation immediately below the electrode layer 31d. Therefore, in this embodiment 2 (FIG. 8), the electrode layer A distance is provided between 31d and the heat generating layer 31b.

[Other matters]
The embodiments according to the present invention have been described in detail above, but various known configurations can be substituted within the scope of the idea of the present invention.

  1) For example, in the embodiment, the apparatus using a cylindrical belt as the heating rotator 31 has been described. Without being limited thereto, the heating rotator 31 may be in the form of a roller.

  2) The nip forming member 40 that forms the nip portion N with the heating rotator 31 is not limited to a roller. It may be an endless belt that rotates or rotates. Moreover, it may not be a rotary body. That is, it can be in the form of a non-rotating member such as a pad or a plate-like member having a small friction coefficient on the surface which is a contact surface with the heating rotator or the sheet.

  3) The image heating apparatus of the present invention is not limited to use as a fixing apparatus that heats and presses an unfixed toner image carried on a sheet as in the embodiment and heat-fixes it as a fixed image. It is also effective as a heat treatment apparatus that adjusts the surface properties of an image such as improving the glossiness by heating and pressing an image (fixed image or semi-fixed image) once fixed or assumed on a sheet.

  4) The image forming unit of the image forming apparatus is not limited to the electrophotographic system. The image forming unit may be an electrostatic recording system or a magnetic recording service noble. Further, it is not limited to the transfer method, and a configuration in which an unfixed image is formed directly on a sheet may be used. A system in which an image is formed on a sheet by an ink jet method and heat-dried and fixed may be used.

  5) In the embodiment, the fixing device F may be implemented by an image forming apparatus other than the color electrophotographic printer of the embodiment, a monochrome copying machine, a facsimile, a monochrome printer, a composite machine thereof, or the like. That is, the fixing device and the color electrophotographic printer of the embodiment are not limited to the combination of the above-described constituent members, and may be realized in another embodiment in which some or all of the replacement members are replaced.

  F..Image heating device, 31..Heating rotator, 31a..Insulating layer, 31b..Resistance heating layer, 31c..Insulating substrate, 31d..Electrode layer, 38L.38R..Feeding ring, a. Edge edge of the electrode layer near the center in the longitudinal direction of the heating rotator, b. Edge edge of the feeding ring near the center in the longitudinal direction of the heating rotator, P. Sheet, t

Claims (14)

A heating rotator used in an image heating apparatus that heats a sheet carrying an image by nipping and conveying the sheet at a nip portion,
A resistance heating layer and an insulating layer that are heated from at least the insulating base material and are heated in order from the inside to the outside are laminated, and annular electrode layers for supplying power to the resistance heating layer on the outer peripheral surfaces on both ends, respectively A feed ring externally fitted to the electrode layer and having an inner peripheral surface electrically connected to and bonded to the electrode layer, the edge of the electrode layer on the side near the center in the heating rotor longitudinal direction The heating rotator is characterized in that the portion is disposed inside the edge portion on the side close to the center in the longitudinal direction of the heating rotator of the feeding ring.   2. The heating rotator according to claim 1, wherein an edge portion of the resistance heating layer is disposed on an inner side of an edge portion on a side closer to a center of the feeding ring in the longitudinal direction of the heating rotator.   The heating rotator according to claim 1 or 2, wherein the electrode layer and the power supply ring are bonded by a conductive adhesive.   The heating rotating body according to claim 1, wherein the electrode layer and the power supply ring are bonded by solder.   The heating rotator according to any one of claims 1 to 4, wherein the edge portion of the electrode layer is outside a region of a maximum sheet passing width in the nip portion.   The heating rotator according to any one of claims 1 to 5, wherein an elastic layer exists between the resistance heating layer and the insulating layer.   The heating rotating body according to any one of claims 1 to 6, wherein the insulating base is cylindrical. The heating rotator according to any one of claims 1 to 7,
A nip forming member for forming a nip portion for nipping and conveying a sheet carrying an image with the heating rotator and heating the sheet,
A power supply member in contact with the power supply ring;
An image heating apparatus comprising:   The image heating apparatus according to claim 8, wherein the nip forming member is a rotating body.   9. The image heating apparatus according to claim 8, wherein the nip forming member is a roller having an outer crown shape having an inverted crown shape.   The image heating apparatus according to claim 8, further comprising a backup member that is disposed inside an insulating base material of the heating rotator and faces the nip forming member.   The image heating apparatus according to any one of claims 8 to 11, wherein the nip forming member is a driving rotating body that rotationally drives the heating rotating body.   An inner peripheral surface of an end portion of the heating rotator that is disposed on both ends of the heating rotator and restricts movement of the heating rotator in the longitudinal direction when driven by the drive rotator and rotates. The image heating apparatus according to claim 12, further comprising a terminal member for guiding.   An image forming unit that forms a toner image on a sheet, and an image heating device according to any one of claims 8 to 13 that heats the toner image formed on the sheet by the image forming unit. An image forming apparatus.