JP2006098931A - Endless belt, heater and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure durability and reliability of a heater of an endless belt, heating system/pressurized rotating body drive system, by preventing the endless belt from braking from its end part due to the frictional force in the direction of a rotary shaft, when using the endless belt. <P>SOLUTION: The part of an elastic layer only is arranged at an end part of the endless belt having a metal base layer and the elastic layer by making the elastic layer longer than the metal layer. The elastic layer of the endless belt comes into contact with an end flange (endless belt retaining member), so that the endless belt is in a light contact with an end flange, due to the elasticity of the elastic layer. Consequently, the end flange is prevented from wearing out by sliding on the endless belt and the length-direction end of the endless belt is prevented form breaking. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an endless belt (film) heating type / pressure rotating body driving type heating apparatus and an image forming apparatus such as an electrophotographic apparatus / electrostatic recording apparatus provided with the heating apparatus as an image heating apparatus.

  An endless belt heating method and pressure rotor drive type heating device sandwich an endless belt, an endless belt as a heating rotator, an endless belt internal member that is located inside the endless belt and that fits the endless belt loosely, and an endless belt A pressure rotator that is rotationally driven to form a nip portion by mutual pressure contact with the inner member of the endless belt, and the endless belt faces the surface of the endless belt inner member at the nip portion by the rotational drive of the pressure rotator. Is rotated while sliding, and the apparatus has a configuration in which the material to be heated is nipped and conveyed between the endless belt in the nip portion and the pressure rotator and heated.

  An electromagnetic induction heating method in which an endless belt as a heating rotator is made an electromagnetic induction heat generating member to generate heat by the action of the magnetic field generated by the magnetic field generating means, and the material to be heated is heated by the generated heat (Patent Document 1, etc.) In addition, a heater such as a ceramic heater or an electromagnetic induction heating element (a heating element or a heating element) is fixedly disposed at an inner position of the endless belt corresponding to the nip portion, and the heat of the heater is passed through the endless belt. (Patent Documents 2 and 3) and the like.

  Such a heating device of an endless belt heating method / pressure rotating body driving method is excellent in quick start property and energy saving in comparison with a heating device of a heat roller type.

  Further, the driving force of the endless belt as the heating rotator can be reduced, and the shifting force in the axial direction of the endless belt during rotation of the endless belt can be reduced. Can be configured with a simple means such as a flange member for receiving the end of the endless belt, and the apparatus configuration can be simplified, reduced in size, and reduced in cost.

  For this reason, in image forming apparatuses such as copying machines and printers, recording materials (transfer material sheets, electrofax sheets, electrostatic sheets, etc.) are used in appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. Unfixed image (toner image) of the target image information that is formed and supported on a recording paper, OHP sheet, printing paper, format paper, etc. by the transfer method or the direct method is heat-fixed as a permanently fixed image on the surface of the recording material. As the fixing device to be used, the above-described endless belt heating type / pressure rotating body driving type heating device has been put into practical use.

Japanese Patent Laid-Open No. 9-171889 JP-A-4-44075-44083 JP-A-9-139282

  However, in the heating device of the endless belt heating method / pressure rotating body driving method, the endless belt is likely to move toward one side or the other side in the direction of the rotation axis when rotating. This shift of the endless belt can be restricted by providing a member for receiving the end of the endless belt.

  However, when the base layer of the endless belt is made of metal, the end portion of the endless belt and the regulating member usually made of resin are worn by rubbing. Due to the wear part of the restricting member, the rotation of the endless belt becomes unstable, and the end in the longitudinal direction of the endless belt may be damaged.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned trouble of damaging the endless belt in the heating device of the endless belt heating method / pressure rotating body driving method, and to ensure the durability and reliability of the device.

  In order to achieve the above object, an invention according to claim 1 is an endless belt having a metal base layer and an elastic layer disposed outside the metal base layer, and the axial length of the elastic layer at the end of the endless belt. Is longer than the axial length of the metal base layer.

  The invention according to claim 2 is an endless belt having a metal base layer and an elastic layer disposed on the outer side of the metal base layer, and an endless belt inner member positioned inside the endless belt and externally fitting the endless belt loosely. The endless belt is pressed against the inner endless belt inner member to form a nip portion, and is a rotationally driven pressure member, disposed at the end of the endless belt, A substantially cylindrical endless belt holding member that regulates a shift in a rotation axis direction of the endless belt that is fitted and positioned in a radial direction, and the endless belt is moved to the nip portion by the rotational drive of the pressure rotating body; In the heating device that rotates while sliding on the surface of the endless belt inner member in order to sandwich and convey the material to be heated between the endless belt of the nip portion and the pressure rotating body, the endless belt The axial length of the elastic layer at the belt end being greater than the axial length of the metal base layer.

According to a third aspect of the present invention, in the second aspect of the invention, when the length of the metal base layer is LB, the length of the elastic layer is LE, and the pressurizing portion length of the first pressurizing member is LP. ,
LP <LB <LE
Is established.

  According to a fourth aspect of the present invention, in the invention of the second or third aspect, the endless belt is of an electromagnetic induction heat generating property and generates heat by the action of the magnetic field generated by the magnetic field generating means.

  The invention according to claim 5 is the invention according to claim 2 or 3, characterized in that the endless belt inner member includes at least a fixed heating element.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit that forms a single color or a plurality of color toner images on a recording material; and a fixing device that thermally fixes the toner image on the recording material. The fixing device is the heating device according to any one of claims 2 to 5.

  According to the present invention, by making the length of the elastic layer longer than the length of the metal layer of the endless belt having the metal base layer and the elastic layer, the elastic layer of the endless belt becomes the end flange (endless belt holding member). Therefore, the endless belt is in a light contact state with the end flange due to the elasticity of the elastic layer. Thereby, abrasion of the end flange due to sliding with the endless belt is prevented, and breakage of the endless belt can be prevented.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic color printer.

  Reference numeral 101 denotes a photosensitive drum (image carrier) made of an organic photosensitive member or an amorphous silicon photosensitive member, which is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined process speed (circumferential speed).

  The photosensitive drum 101 is uniformly charged with a predetermined polarity and potential by a charging device 102 such as a charging roller in the course of rotation.

  Next, the charged surface is subjected to a scanning exposure process of target image information by a laser beam 103 output from a laser optical box (laser scanner) 110. The laser optical box 110 outputs a laser beam 103 modulated (on / off) in response to a time-series electric digital pixel signal of target image information from an image signal generation device such as an image reading device (not shown), and is rotationally sensitized. An electrostatic latent image corresponding to target image information scanned and exposed on the surface of the body drum 101 is formed. Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

  In the case of full-color image formation, scanning exposure / latent image formation is performed on a first color separation component image of a target full-color image, for example, a yellow component image, and the latent image is subjected to yellow development in the four-color developing device 104. The yellow toner image is developed by the operation of the device 104Y.

  The yellow toner image is transferred to the surface of the intermediate transfer drum 105 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105.

  The surface of the rotating photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is cleaned by the cleaner 107 after removal of adhered residues such as transfer residual toner.

  The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above includes the second color separation component image of the target full-color image (for example, the magenta component image, the magenta developer 104M is activated), the third The color separation component images (for example, the cyan component image and the cyan developing device 104C are operated) and the fourth color separation component image (for example, the black component image and the black developing device 104BK are operated) are sequentially executed. The toner images of four colors, yellow toner image, magenta toner image, cyan toner image, and black toner image, are sequentially superimposed and transferred onto the surface of the intermediate transfer drum 105, and a color toner image corresponding to the target full-color image is synthesized and formed. Is done.

  The intermediate transfer drum 105 has a middle resistance elastic layer and a high resistance surface layer on a metal drum. The intermediate transfer drum 105 is in contact with or close to the photosensitive drum 101 at an approximately same peripheral speed as the photosensitive drum 101. The toner image on the side of the photosensitive drum 101 is transferred to the surface of the intermediate transfer drum 105 by a potential difference from the photosensitive drum 101 by applying a bias potential to the metal drum of the intermediate transfer drum 105. Let

  The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to the secondary transfer portion T2 in the secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106. The recording material P is transferred onto the surface of the recording material P fed from a paper feeding unit (not shown) at a predetermined timing. The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images from the surface of the intermediate transfer drum 105 to the recording material P side sequentially.

  The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105 and introduced into the image heating device (fixing device) 100, and undergoes a heat fixing process for an unfixed toner image to obtain a color image. The formed product is discharged to a discharge tray (not shown) outside the apparatus. The fixing device 100 will be described in detail in the next section (2).

  The rotary intermediate transfer drum 105 after the transfer of the color toner image onto the recording material P is cleaned by the cleaner 108 after removal of adhering residues such as residual toner and paper dust. The cleaner 108 is normally held in a non-contact state with the intermediate transfer drum 105, and contacts the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Kept in a state.

  Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and is transferred to the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The recording material P is held in contact.

  The apparatus according to the present embodiment can also execute a mono-color image print mode such as a monochrome image. Also, a double-sided image print mode or a multiple image print mode can be executed.

  In the double-sided image print mode, the recording material P on which the first-side image has been printed exiting the fixing device 100 is turned upside down through a recirculation conveyance mechanism (not shown) and sent again to the secondary transfer unit T2. The toner image is transferred to the two surfaces, and is again introduced into the fixing device 100, and the toner image is fixed to the two surfaces, whereby a double-sided image print is output.

In the multiple image print mode, the recording material P that has been printed on the first image and has exited the fixing device 100 is sent to the secondary transfer portion T2 again without being turned upside down via a recirculation conveyance mechanism (not shown). A second toner image transfer is received on the surface on which the first image has been printed, and the image is again introduced into the fixing device 100 and undergoes a second toner image fixing process, whereby a multiple image print is output.
(2) Fixing device 100
The fixing device 100 in the present embodiment is an electromagnetic induction heating type device. 2 is a partially cutaway front view of the fixing device 100, FIG. 3 is a longitudinal section view, and FIG. 4 is a transverse view view.

A) Overall schematic configuration of apparatus 10 is a fixing belt as an endless belt. As will be described later, the fixing belt 10 is a cylindrical member as an electromagnetic induction heat generating rotating body having an electromagnetic induction heat generating layer (conductor layer, magnetic layer, resistor layer).

  Reference numeral 16 denotes a substantially cylindrical belt guide member as an endless belt inner member. The fixing belt 10 is loosely fitted on the belt guide member 16. The lower surface portion of the belt guide member 16 is cut out as a flat surface along the longitudinal direction. Further, both end portions of the belt guide member 16 are formed as annular groove portions 16a and 16b having outer diameters slightly smaller than other portions.

  Reference numerals 23 a and 23 b denote a pair of left and right annular flange members as a substantially cylindrical endless belt holding member that regulates and holds the left and right ends of the fixing belt 10. Each has a sleeve portion and a saddle portion (flange portion), and the sleeve portions are fitted to the annular groove portions 16a and 16b on the left and right end portions of the belt guide member 16 so as to be freely rotatable.

  By fitting the left and right end portions of the fixing belt 10 to the sleeve portions of the left and right flange members 23a and 23b, the flange members 23a and 23b are attached to both ends of the fixing belt 10 so that the fixing belt cannot rotate. It is.

  Reference numeral 15 denotes a magnetic field generating means comprising magnetic cores 17a, 17b, 17c and an exciting coil 18, which is arranged on the right half side in FIG. 4 inside the belt guide member 16. Reference numeral 19 denotes an exciting coil holding member.

  Reference numeral 22 denotes a rigid pressure stay having a U-shaped cross section that is inserted into the belt guide member 16 and has a downward cross-sectional shape. The left and right end portions of the pressure stay 22 protrude outward from the left and right end portions of the belt guide member 16.

  Reference numerals 21a and 21b denote left and right pressure blocks which are fitted to both left and right ends of the pressure stay 22 and fixed by means such as screw tightening. FIG. 5 is a perspective view of the left pressure block 21a. The right pressure block 21b is also a member having the same shape.

  The above assemblies 16, 10, 23a, 23b, 22, 21a and 21b are heating assemblies.

  Reference numeral 30 denotes a pressure roller as a pressure rotator. The pressure roller 30 is composed of a cored bar 30a and a heat-resistant / elastic material layer 30b made of silicone rubber, fluororubber, fluororesin, or the like that is concentrically formed and coated around the cored bar. Yes.

  The pressure roller 30 is arranged such that both left and right end portions of the core metal 30a are rotatably held between the left and right side plates 70a and 70b of the apparatus chassis 70 via bearings 28a and 28b. Further, a drive gear G is fixed to the left end portion of the metal core 30a, and a rotational force is transmitted from the drive system M to the drive gear G so that the pressure roller has a predetermined peripheral speed and the arrow in FIG. It is rotationally driven in the clockwise direction (pressure roller drive system).

  The left and right side plates 70a and 70b of the device chassis 70 have longitudinal guide holes 70c and 70d whose upper ends are opened, and the above-described heating from the upper openings to the guide slots 70c and 70d. The left and right pressure blocks 21 a and 21 b of the assembly are dropped downward by engaging the vertical groove 21 c (FIG. 5) on the pressure block side with the vertical edge of the guide elongated hole, so that the heating assembly of the device chassis 70 is dropped. The pressure roller 30 is disposed between the left and right plates 70a and 70b. In this case, the lower surface of the belt guide member 16 has a notch flat surface 16 c facing downward, and faces the upper surface portion of the pressure roller 10 through the fixing belt 10.

  Reference numeral 24 denotes a fixing frame attached between upper end portions of the left and right side plates 70a and 70b of the apparatus chassis 70. Then, pressure springs 25a and 25b are contracted between the right and left end portions of the fixing frame 24 and the left and right pressure blocks 21a and 21b of the heating assembly, respectively. A pressing force is applied.

  As a result, the belt guide member 16 is pushed down against the heat resistance of the pressure roller 30 and the elasticity of the elastic material layer 30 b by the pressure stay 22, and the notched flat surface 16 c on the lower surface of the belt guide member 16 is fixed to the fixing belt 10. A fixing nip portion N having a predetermined width is formed by being pressed against the upper surface portion of the pressure roller 10 with a predetermined pressing force.

  When the pressure roller 30 is driven to rotate counterclockwise in FIG. 4 by the driving means M, a rotational force acts on the fixing belt 10 by the frictional force between the pressure roller 30 and the outer surface of the fixing belt 10 in the fixing nip portion N. The fixing belt 10 has an inner peripheral surface that closely slides on the notched flat surface 16c on the lower surface of the belt guide member 16 in the fixing nip portion N, and substantially corresponds to the rotational peripheral speed of the pressure roller 30. The outer periphery of the belt guide member 16 is rotated clockwise in FIG. That is, the fixing belt 10 rotates following the driving rotation of the pressure roller 30.

  In order to reduce the driving torque during the rotational driving, a sliding plate 41, which is another member having a low friction coefficient, may be attached to the cut-out flat surface 16c on the lower surface of the belt guide member 16 in the fixing nip portion N. Examples of the material of the sliding plate 41 include a fluororesin, glass, and a metal plate coated with molybdenum disulfide.

  As shown in FIG. 10, an excitation circuit 27 is connected to the power feeding portions 18a and 18b of the excitation coil 18 of the magnetic field generating means 15 disposed on the right half side inside the belt guide member 16. The excitation circuit 27 can generate a high frequency of 20 kHz to 500 kHz by a switching power supply. The exciting coil 18 generates an alternating magnetic flux by the alternating current (high-frequency current) supplied from the exciting circuit 27. In the electromagnetic induction heat generating layer of the fixing belt 10 that is an electromagnetic induction heat generating belt, an eddy current flows in a direction to cancel the alternating magnetic field, Joule heat is generated, and the fixing belt 10 generates heat.

  The temperature of the fixing nip portion N is predetermined by controlling the current supply to the exciting coil 18 by a temperature control system (not shown) including a temperature detecting means 26 provided on the outer surface of the belt guide member 16 in the vicinity of the fixing nip portion N. The temperature is adjusted so that the temperature is maintained.

  The temperature detection means 26 is a temperature sensor such as a thermistor for detecting the temperature of the fixing belt 10 disposed on the outer surface of the belt guide member in the vicinity of the fixing nip portion N in this example. The temperature of the fixing nip N is controlled based on the temperature information of the fixing belt 10.

  Thus, the pressure roller 30 is driven to rotate, and the fixing belt 10 is rotated accordingly, and the electromagnetic induction heat of the fixing belt 10 is generated as described above by supplying power from the exciting circuit 27 to the exciting coil 18, thereby fixing the fixing nip. In a state where the portion N rises to a predetermined temperature and is temperature-controlled, the recording material P on which the unfixed toner image t conveyed from the image forming unit is formed is guided to the fixing nip portion N, and the fixing nip portion N The image surface is introduced between the fixing belt 10 and the pressure roller 30 upward, that is, opposite to the fixing belt surface, and the image surface closely contacts the outer surface of the fixing belt 10 at the fixing nip portion N. The fixing nip portion N is nipped and conveyed together. In the process where the recording material P is nipped and conveyed together with the fixing belt 10 through the fixing nip N, the fixing belt 10 is heated by electromagnetic induction heat generation, and the unfixed toner image t on the recording material P is heated and fixed. The When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing belt 10 and discharged and conveyed. The heat-fixed toner image on the recording material is cooled to a permanently fixed image after passing through the fixing nip.

  In this example, a toner containing a low softening substance is used in the toner t. Therefore, an oil application mechanism for preventing offset is not provided in the fixing device, but when a toner containing no low softening substance is used. An oil application mechanism may be provided. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

B) Endless belt holding member At the left and right ends of the cylindrical fixing belt 10 which is an endless belt, as described above, a flange member 23a having a thickness of about 2 mm as an endless belt holding member for regulating and holding the end portion, 23 b is provided so as to cover the fixing belt 10. The flange members 23a and 23b are fixedly fitted to the annular groove portions 16a and 16b at the left and right end portions of the substantially cylindrical belt guide member 16, and are fitted. This flange member has good heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, fluororesin, liquid crystal polymer resin, mixed resin thereof, and metals such as aluminum and iron. Material is used.

  Positioning in the rotational axis direction (thrust direction, longitudinal direction) of the fixing belt 10 is performed by the flange members 23a and 23b, and the flange members 23a and 23b receive and fix the end portions of the fixing belt 10 when the fixing belt 10 rotates. It plays a role of restricting the movement of the belt 10 along the length of the belt guide member 16.

C) Fixing belt 10
FIG. 8 is a model diagram showing the layer structure of the electromagnetic induction heat-generating fixing belt 10 in the present embodiment.

  The fixing belt 10 of this example includes a metal base layer 1 made of a metal belt or the like as a base layer of an electromagnetic induction heat-generating fixing belt, an elastic layer 2 laminated on the outer surface, and a release layer 3 laminated on the outer surface. The composite structure.

  For adhesion between the metal base layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3, a primer layer (not shown) may be provided between the respective layers.

  In the fixing belt 10 having a substantially cylindrical shape, the metal base layer 1 is on the inner surface side, and the release layer 3 is on the outer surface side. As described above, when the alternating magnetic flux acts on the metal base layer 1, an eddy current is generated in the metal base layer 1 and the metal base layer 1 generates heat. The heat generated by induction in this layer heats the entire fixing belt 10 via the elastic layer 2 and the release layer 3, heats the recording material P that is passed through the fixing nip N, and heat-fixes the toner t image. Is made.

a. Metal base layer (electromagnetic induction heating layer) 1
The metal base layer 1 is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, or nickel-cobalt alloy.

  A nonmagnetic metal may be used, but a metal such as nickel, iron, magnetic stainless steel, cobalt-nickel alloy, etc., which absorbs magnetic flux more preferably is preferable.

The thickness is preferably thicker than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is the frequency f [Hz] of the excitation circuit, the magnetic permeability μ, and the specific resistance ρ [Ωm] σ = 503 × (ρ / fμ) ^1/2
It is expressed.

  This indicates the depth of absorption of the electromagnetic wave used for electromagnetic induction, and indicates that the intensity of the electromagnetic wave is 1 / e or less deeper than this. Conversely, most of the energy is absorbed up to this depth (Figure 9).

  The thickness of the metal base layer 1 is preferably 1 to 100 μm. If the thickness of the metal base layer 1 is less than 1 μm, most of the electromagnetic energy cannot be absorbed, resulting in poor efficiency. On the other hand, when the metal base layer 1 exceeds 100 μm, the rigidity becomes too high and the flexibility becomes poor, which is not practical for use as a rotating body. Therefore, the thickness of the metal base layer 1 is preferably 1 to 100 μm.

b. Elastic layer 2
The elastic layer 2 is a material having good heat resistance and thermal conductivity, such as silicone rubber, fluorine rubber, fluorosilicone rubber or the like.

  The thickness of the elastic layer 2 is preferably 10 to 500 μm. The elastic layer 2 has a thickness necessary for assuring the fixed image quality.

  When a color image is printed, a solid image is formed over a large area on the recording material P, particularly in a photographic image. In this case, if the heating surface (release layer 3) cannot follow the unevenness of the recording material P or the unevenness of the toner layer t, uneven heating will occur, and uneven gloss will occur in the image where the heat transfer is large and small. To do. A portion with a large amount of heat transfer has a high glossiness, and a portion with a small amount of heat transfer has a low glossiness.

  If the thickness of the elastic layer 2 is 10 μm or less, the unevenness of the recording material or the toner layer cannot follow the unevenness of the recording material and image gloss unevenness occurs. On the other hand, when the elastic layer 2 is 1000 μm or more, the thermal resistance of the elastic layer increases, making it difficult to realize a quick start. More preferably, the thickness of the elastic layer 2 is 50 to 500 μm.

  If the elastic layer 2 is too hard, it will not be able to follow the unevenness of the recording material P or the toner layer t, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 2 is preferably 60 ° or less (JIS-A: JIS-KA type tester), more preferably 45 ° or less.

Regarding the thermal conductivity λ of the elastic layer 2, 2.52 × 10 ^{−1 to} 8.4 × 10 ⁻¹ W / m · ° C. (6 × 10 ⁻⁴ to 2 × 10 ⁻³ cal / cm · sec · deg) ) Is good. When the thermal conductivity λ is smaller than 2.52 × 10 ⁻¹ W / m · ° C., the thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing belt 10 is slow. When the thermal conductivity λ is larger than 8.4 × 10 ⁻¹ W / m · ° C., the hardness becomes too high or the compression set is deteriorated. Therefore, the thermal conductivity λ is preferably 2.52 × 10 ^{−1 to} 8.4 × 10 ⁻¹ W / m · ° C. More preferably, it is 3.36 × 10 ^{−1 to} 3 × 10 ⁻¹ W / m · ° C. (8 × 10 ^{−4 to} 1.5 × 10 ⁻³ cal / cm · sec · deg).

c. Release layer 3
For the release layer 3, a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, and FEP can be selected.

  The thickness of the release layer 3 is preferably 1 to 100 μm. When the thickness of the release layer 3 is smaller than 1 μm, there arises a problem that a part having poor release property is formed due to coating unevenness of the coating film or durability is insufficient. Further, when the release layer exceeds 100 μm, there arises a problem that heat conduction is deteriorated. In particular, in the case of a resin release layer, the hardness becomes too high and the effect of the elastic layer 2 is lost.

d. In this embodiment, the length of the elastic layer at the end of the fixing belt is longer than the length of the base layer in the longitudinal direction. There is no base layer. The length of the difference in the length between the elastic layer and the base layer (the protruding portion) is related to the hardness and thickness of the elastic layer, and it is preferable that the elastic layer hardness is harder and that the longer the layer thickness, the longer. In the present embodiment, the length is 5 mm for an elastic layer thickness of 200 μm and a hardness of 20 °.

  FIG. 7 shows a case where the metal base layer is longer than the length of the elastic layer at the end of the fixing belt. In this case, when the fixing belt is shifted, the end portion of the belt comes into contact with the flange member. At this time, since the end portion of the base layer made of metal slides with the flange member, the base layer of the thin film may be damaged when the flange is made of metal. Further, when the flange member is made of resin, the flange member is worn by sliding with the base layer. Since the base layer is a thin metal, only a part of the flange member is scraped, and the flange can be deeply damaged. The fixing belt comes into the scratch, and the rotation is hindered to cause twisting and damage. This tendency was also observed when the length of the elastic layer at the end of the fixing belt and the length of the base layer were the same.

  In the present embodiment of FIG. 6, the elastic layer is longer than the length of the metal base layer at the end of the fixing belt. When the fixing belt moves and the belt end hits the flange member, the end of the elastic layer hits. Since the elastic layer has elasticity, it absorbs the shifting force after it hits the flange member. For this reason, the contact force to the flange member is alleviated and the flange member is hardly worn. Further, since the elastic layer is softer than the metal base layer, the flange member is not damaged. The sliding wear of the elastic layer itself is hardly generated because the shifting force is relaxed. Further, unlike a metal base layer, it is resistant to distortion and twisting, so that no crack or the like occurs. Furthermore, since the metal base layer does not directly contact the flange member, the occurrence of cracks in the fixing belt 10 can be prevented.

  Further, by using this belt, it is possible to simply hold the fixing belt against one end of the side plate, and it is possible to simplify the configuration.

D) Magnetic field generating means 15
The magnetic cores 17a, 17b, and 17c are members having high magnetic permeability, and materials used for the transformer core such as ferrite and permalloy are good, and it is more preferable to use ferrite with low loss even at 100 kHz or more.

  The exciting coil 18 is a conductive wire (electric wire) that constitutes a coil (wire ring) using a bundle (bundle) of a plurality of thin copper wires, each of which is covered with an insulation coating, and is wound a plurality of times. An exciting coil is formed. In this embodiment, the exciting coil 18 is formed by winding 10 turns.

  As the insulating coating, it is preferable to use a coating having heat resistance in consideration of heat conduction due to heat generation of the fixing belt 10. For example, a coating such as amideimide or polyimide may be used. The excitation coil 18 may improve the density by applying pressure from the outside.

  As shown in FIG. 4, the excitation coil 18 has a shape that follows the curved surface of the electromagnetic induction heat generating layer 1 of the fixing belt 10 that is an electromagnetic induction heat generating member. In this embodiment, the distance between the metal base layer 1 of the fixing belt 10 and the exciting coil 18 is set to be approximately 2 mm.

  When the distance between the magnetic cores 17a, 17b, 17c and the exciting coil 18 and the metal base layer 1 of the fixing belt 10 is as close as possible, the magnetic flux absorption efficiency is higher. If this distance exceeds 5 mm, this efficiency is increased. Is remarkably lowered, it is better to make it within 5 mm. If the distance is within 5 mm, the distance between the metal base layer 1 of the fixing belt 10 and the exciting coil 18 need not be constant.

  With respect to the lead wire from the exciting coil holding member 19 of the exciting coil 18, an insulating coating is applied to the outside of the bundle wire at a portion outside the exciting coil holding member 19.

  As the material of the exciting coil holding member 19, a material having excellent insulation and high heat resistance is preferable. For example, phenol resin, fluororesin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, FEP resin, LCP resin, or the like may be selected.

  As described above, the exciting coil 27 is connected to the power feeding portions 18a and 18b (FIG. 10). The excitation circuit 27 can generate a high-frequency current of about 20 kHz to 500 kHz by a switching power supply. The exciting coil 18 generates an alternating magnetic flux by the alternating current (high-frequency current) supplied from the exciting circuit 27. In the electromagnetic induction heating layer 1 of the fixing belt 10 which is an electromagnetic induction heat generating member, an eddy current flows in the direction to cancel the alternating magnetic flux, Joule heat is generated, and the fixing belt 10 generates heat.

  FIG. 11 schematically shows how the alternating magnetic flux is generated.

  A magnetic flux C represents a part of the generated alternating magnetic flux. The alternating magnetic flux C guided to the magnetic cores 17a, 17b, and 17c is vortexed in the electromagnetic induction heating layer 1 of the fixing belt 10 between the magnetic cores 17a and 17b and between the magnetic cores 17a and 17c. Generate current. This eddy current causes Joule heat (eddy current loss) to be generated in the electromagnetic induction heat generating layer 1 by the specific resistance of the electromagnetic induction heat generating layer 1.

  The calorific value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heat generating layer 1, and shows a distribution as shown in the graph of FIG. In the graph of FIG. 11, the vertical axis indicates the circumferential position of the fixing belt 10 represented by an angle θ with the center of the magnetic core 17 a being 0, and the horizontal axis is the heat generation in the electromagnetic induction heating layer 1 of the fixing belt 10. The quantity Q is indicated. Here, when the maximum heat generation amount is Q, the heat generation region H is defined as a region where the heat generation amount is Q / e or more. This is a region where the amount of heat generated for fixing can be obtained.

E) Safety circuit In the present embodiment, a thermo switch 50 (FIG. 2), which is a temperature detection element, is used to cut off the power supply to the exciting coil 18 at the time of runaway at a position opposite to the heat generating area H (FIG. 11) of the fixing belt 10. And FIG. 4).

  FIG. 10 is a circuit diagram of the safety circuit used in the present embodiment.

  The thermo switch 50 which is a temperature detecting element is connected in series with the +24 VDC power source and the relay switch 51. When the thermo switch 50 is turned off, the power supply to the relay switch 51 is cut off, the relay switch 51 operates, and the excitation circuit 27 The power supply to the exciting coil 18 is cut off by cutting off the power supply to the coil. The thermoswitch 50 was set to 220 ° C. OFF operation temperature.

  Further, the thermo switch 50 is disposed in a non-contact manner on the outer surface of the fixing belt 10 so as to face the heat generating area H of the fixing belt 10. The distance between the thermo switch 50 and the fixing belt 10 was about 2 mm. As a result, the fixing belt 10 is not damaged by the contact of the thermo switch 50, and deterioration of the fixed image due to durability can be prevented.

  According to the present embodiment, when the apparatus runs away due to an apparatus failure, the apparatus is stopped with the recording material P sandwiched in the fixing nip portion N, the power supply to the excitation coil 18 is continued, and the fixing belt 10 continues to generate heat. Even in this case, since the heat is not generated at the fixing nip portion N where the recording material P is sandwiched, the recording material P is not directly heated. Further, since the thermo switch 50 is disposed in the heat generating region H where the heat generation amount is large, when the thermo switch 50 senses 220 ° C. and the thermo switch 50 is turned off, the relay coil 51 causes the exciting coil 18 to be turned off. The power supply to is cut off.

  Therefore, since the ignition temperature of the paper as the recording material is about 400 ° C., the heat generation of the fixing belt 10 can be stopped without the paper igniting.

  In addition to the thermo switch 50, a temperature fuse can be used as the temperature detection element.

<Other embodiments>
1) The fixing belt end restricting / holding flange members 23a and 23b as endless belt holding members are not limited to the shape in which the abutting surface is perpendicular to the axial direction of the fixing belt, but from the outer surface of the belt as shown in FIG. The taper shape which contacts and becomes narrow toward the outer side may be comprised. Further, the fixing belt end regulating / holding flange member may have a tapered shape in which the outer diameter decreases toward the inner surface of the endless belt as shown in FIG. In this case, by making the end portion of the fixing belt into a shape that is obliquely cut, the elastic layer increases the ratio of surface contact with the end flange, so that the effect of absorbing the shifting force is increased.

  2) The fixing belt 10 which is an electromagnetic induction heat-generating member may have a form in which the elastic layer 2 is omitted in the case of heat fixing such as monochrome or one-pass multi-color image. The heat generating layer 1 can also be configured by mixing a metal filler into a resin. It can also be a member of a single heating layer.

  3) The magnetic field generating means 15 can be disposed outside the fixing belt 10.

  4) The pressure member 30 is not limited to a roller body, and may be a member of another form such as a rotating belt type.

  Also, in order to supply heat energy from the pressing member 30 side to the recording material, a heating unit such as electromagnetic induction heating is also provided on the pressing member 30 side to heat and adjust the temperature to a predetermined temperature. You can also

  5) FIG. 14 shows another apparatus configuration example. That is, this apparatus uses a fixing belt 10A as an endless belt as a heat-resistant member that does not have electromagnetic induction heat generation, and a heating element (heating element, heater) fixed on the inner surface side of the fixing belt 10A in the fixing nip N. ), An electromagnetic induction heat generating member 60 such as an iron plate is disposed. The electromagnetic induction heat generating member 60 is heated by electromagnetic induction by the magnetic field generating means 15 disposed inside the belt guide member 16, and the member 60 is formed in the fixing nip N. Heat is transferred to the recording material P through the fixing belt 10A. The present invention can also be applied to such an apparatus.

  6) FIG. 15 shows still another apparatus configuration example. That is, in this apparatus, the fixing belt 10A as an endless belt is made of a heat-resistant member made of a metal such as Ni or SUS, or a heat-resistant resin such as PI, and the heat generation fixed to the inner surface side of the fixing belt 10A in the fixing nip N. A ceramic heater 61 is disposed as a body (heating body, heater), the ceramic heater 61 generates heat, and the heat of the ceramic heater 61 is transferred to the recording material P through the fixing belt 10A in the fixing nip N. Is. The present invention can also be applied to such an apparatus.

  Further, the sliding property can be increased by applying a heat-resistant resin such as Teflon or polyimide to the sliding surface of the ceramic heater 61 which may be in direct contact with the elastic layer having poor sliding property.

  7) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but an image heating device that heats a recording material carrying an image to improve surface properties such as gloss, an image heating device that is supposed to be worn, In addition, it can be widely used as a means / device for heat-treating a material to be heated, such as a heating / drying device or a heating laminating device.

1 is a schematic configuration diagram of an example of an image forming apparatus. FIG. 3 is a partially cutaway front view of the fixing device. It is a longitudinal cross-sectional model figure of the same apparatus. It is a cross-sectional model figure of the same apparatus. It is a perspective view of a pressurization block. FIG. 6 is an explanatory diagram of a configuration that prevents flanging of the fixing belt. FIG. 6 is an explanatory diagram of a conventional configuration in which flange cutting occurs on the fixing belt. FIG. 3 is a layer configuration model diagram of a fixing belt. It is the graph which showed the relationship between the heat generating layer depth and electromagnetic wave intensity. It is the figure which showed the safety circuit. It is the figure which showed the relationship between a magnetic field generation means and the emitted-heat amount Q. It is explanatory drawing of another apparatus structure. It is explanatory drawing of another apparatus structure. It is a cross-sectional model figure of the fixing apparatus of another apparatus structure. It is a cross-sectional model diagram of a fixing device of still another device configuration.

Explanation of symbols

1 Metal base layer (heat generation layer)
2 Elastic layer 3 Release layer 10 Fixing belt (electromagnetic induction heat generating member)
DESCRIPTION OF SYMBOLS 15 Magnetic field generation | occurrence | production means assembly 16 Belt guide member 17 Magnetic core 18 Excitation coil 19 Excitation coil holding member 21a, 21b Pressing block 22 Pressing stay 23a, 23b Flanging member for fixing and holding fixing belt end 24 Fixing frame (stay)
25a, 25b Pressure spring 26 Temperature sensing element (thermistor)
30 Pressure roller 41 Sliding plate 50 Temperature sensing element for safety 51 Relay switch 10A Heat resistant belt (film)
60 Fixed heating element (electromagnetic induction heating member)
61 Fixed heating element (ceramic heater)

Claims (6)

In an endless belt having a metal base layer and an elastic layer disposed outside the metal base layer,
An endless belt, wherein an end of the endless belt has an axial length of the elastic layer larger than an axial length of the metal base layer. An endless belt having a metal base layer and an elastic layer disposed on the outer side of the metal base layer, an endless belt inner member positioned inside the endless belt and loosely fitting the endless belt, and the endless belt sandwiched between the endless belt A nip portion is formed by mutual pressure contact with the endless belt inner member, and is arranged at the end portion of the endless belt that is rotationally driven, and is fitted to the endless belt inner member to be positioned in the radial direction. A substantially cylindrical endless belt holding member that regulates a predetermined shift of the endless belt in the rotation axis direction, and the endless belt is driven by the rotation of the pressure rotator so that the endless belt faces the surface of the endless belt inner member at the nip portion. In the heating device that rotates while sliding, and heats the material to be heated between the endless belt of the nip portion and the pressure rotator,
The heating device according to claim 1, wherein an axial length of the elastic layer at an end portion of the endless belt is larger than an axial length of the metal base layer. When the length of the metal base layer is LB, the length of the elastic layer is LE, and the pressure part length of the first pressure member is LP,
LP <LB <LE
The heating apparatus according to claim 2, wherein:   The heating apparatus according to claim 2 or 3, wherein the endless belt is electromagnetic induction exothermic and generates heat by the action of a magnetic field generated by a magnetic field generating means.   4. The heating apparatus according to claim 2, wherein the endless belt inner member includes at least a fixed heating element. An image forming apparatus comprising: an image forming unit that forms a single color or a plurality of color toner images on a recording material; and a fixing device that thermally fixes the toner image on the recording material.
An image forming apparatus, wherein the fixing device is the heating device according to claim 2.

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