JP2014035373A - Image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device configured to reliably prevent temperature increase in a non-paper-passing part by properly setting the time when a magnetic flux blocking member moves toward a paper-passing part, and to provide an image forming device.SOLUTION: An image heating device includes an induction heating apparatus (100), and heat storage temperature detection means (TH2) for detecting temperature in a heat storage part (2) that stores heat generated by a heating rotary body (1). The induction heating apparatus includes: heating area setting means (71) that changes a magnetic flux density distribution along a conveyance width direction of a magnetic flux, to set a heating area according to a length of a recording material in the conveyance with direction; and a magnetic flux blocking means (11) arranged closer to the non-paper-passing part of the recording material than the heating area set by the heating area setting means, and movable toward the paper-passing part. The induction heating apparatus also includes control means (102) which sets the time to move the magnetic flux blocking member toward the paper-passing part on the basis of the temperature detected by the heat storage temperature detection means, to prevent temperature increase in the non-paper-passing part.

Description

  The present invention relates to an image heating apparatus such as a fixing device that heats an image formed on a recording material, and an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine including these image heating apparatuses. Relates to the device.

  Examples of the image heating device include a fixing device that fixes an unfixed image (toner image) formed on a recording material, and a gloss applying device that improves the glossiness of an image by heating the image fixed on the recording material. Is mentioned.

  2. Description of the Related Art Conventionally, in electrophotographic copying machines, toner (developer) of a toner image (unfixed image) transferred onto a recording material, which is a recording medium to be conveyed, is melted by heat and is applied to the recording material. An image heating device such as a fixing temperature to be fused is provided. In this image heating device, in order to increase the temperature at high speed, a fixing roller, which is a heating medium, has a small diameter, a resin film rotating body is pressed against the heating body from inside, and a thin metal rotating body is guided. What is heated by heating is known.

  These are all intended to reduce the heat capacity of the rotating body, which is a heating medium, and to heat it with a heat source with good heating efficiency. In addition, some non-contact heating sources are used, but from the viewpoint of cost and energy efficiency, in image forming apparatuses such as copying machines, a thin rotating body is brought into contact with the recording material, and the developer on the recording material is removed. Many image heating apparatuses of the type that are heated and melted have been proposed.

However, when a thin rotating body is used as a heating medium in order to reduce the heat capacity, the cross-sectional area of the cross section perpendicular to the axis is extremely small, and the heat transfer rate in the axial direction is not good. This tendency becomes more conspicuous as the wall becomes thinner, and is even lower for materials such as resins with low thermal conductivity. This means that when the thermal conductivity is λ, the temperature difference between two points is θ1-θ2, and the length is L, the amount of heat Q transmitted per unit time is
Q = λ · f (θ1-θ2) / L
It is clear from the Fourier law expressed by

  This is not a problem when a recording material having a full length in the rotation axis direction (longitudinal direction) of the rotating body, that is, a recording material having a maximum sheet passing width is passed and fixed. However, when a small-sized recording material having a small width is continuously passed, the temperature in the non-sheet passing area of the rotating body rises higher than the temperature control temperature, and the temperature in the sheet passing area and the non-sheet passing area There is a problem that the temperature difference from the temperature becomes extremely large.

  Therefore, there is a possibility that the heat-resistant life of the peripheral member made of the resin material may be reduced or thermally damaged due to such temperature unevenness in the longitudinal direction of the heating medium. Furthermore, there is a possibility that paper wrinkles, skew, fixing unevenness, etc. due to partial temperature unevenness may occur when a large size recording material is passed immediately after a small size recording material is passed continuously. There is also a problem.

  Such a temperature difference between the sheet passing area and the non-sheet passing area increases as the heat capacity of the recording material to be conveyed increases and the throughput (number of printed sheets per unit time) increases. For this reason, when an image heating apparatus is constituted by a thin rotating body having a low heat capacity, it has been difficult to apply it to a copying machine with high throughput.

  On the other hand, in an image heating apparatus using a halogen lamp or a heating resistor as a heating source, one that divides the heating source and selectively energizes so as to heat an area corresponding to the sheet passing width is known. Similarly, in some image heating apparatuses using an induction coil as a heating source, the heating source is divided and selectively energized.

  However, if a plurality of heating sources are provided or divided, the control circuit becomes complicated and the cost increases accordingly, and the number of divisions further increases when the recording material of various widths is handled. It will be even higher. Moreover, when a thin rotating body is used as a heating medium, the temperature distribution near the boundary when divided is discontinuous and non-uniform, which may affect the fixing performance.

  Therefore, a device provided with a displacement means for changing the position of the magnetic flux shielding means by arranging magnetic flux shielding means for shielding a part of the magnetic flux reaching the heating medium from the induction heating source between the heating medium and the induction heating source. Has been proposed (see Patent Document 1). In this apparatus, by moving the magnetic flux shielding means, the magnetic flux reaching from the induction heating source is shielded except for the necessary part to suppress the heat generation itself, and the heat distribution is controlled by controlling the heat generation range. Can be controlled.

  Further, in order to correspond to the size of each recording material, the magnetic core is divided in a direction orthogonal to the recording material conveyance direction and is movable by the moving means so that the moving distance varies depending on the size of the recording material. A configured apparatus is known (see Patent Document 2).

  In the apparatus described in Patent Document 2, since the distance between the induction heating source and the magnetic core is increased, the efficiency of the magnetic circuit formed of the magnetic core and the heating medium, which is formed around the induction heating source, is reduced and the heat generation amount is reduced. . Thereby, the temperature rise of the non-sheet passing portion is reduced, and as a result, the abnormal temperature rise of the magnetic core and the induction heating source is also reduced. Further, in order to correspond to the size of each recording material, the moving distance is made different depending on the size of the recording material, and it is possible to avoid the temperature rise of the non-sheet passing portion depending on the size of each recording material. .

JP 2005-321633 A JP 2001-194940 A

  However, in the electromagnetic induction heating type image heating apparatus described above, the positional relationship between the magnetic material core and the recording material divided in the direction orthogonal to the recording material conveyance direction does not match, and the heating area becomes wider than the recording material. There is a problem that the temperature rises in the non-sheet passing portion.

  Further, even if the positional relationship between the magnetic core divided in the direction orthogonal to the recording material conveyance direction and the recording material coincides, the temperature rises at both ends (edge portions) of the recording material. This requires a sufficient amount of heat to fix the toner even at the end of the recording material, but as the sheet passes, the amount of heat taken by the recording material at the end of the recording material relative to the sheet passing area is small. Caused by overheating.

  Therefore, control is performed to reduce the temperature rise by, for example, narrowing the heat generation width by moving the divided magnetic core during paper passing. In such a configuration in which the temperature rises partially, depending on the size of the recording material The temperature rise position changes. For this reason, it is difficult to accurately detect the temperature of the temperature raising portion, and it is difficult to perform control for changing the heat generation width at an appropriate timing in accordance with the temperature of the temperature raising portion.

  These phenomena appear more prominently in the fixing belt (heating belt) using a low heat capacity film, and the durability performance of the fixing belt is greatly deteriorated due to this excessive temperature rise. In addition, it is desired to reduce by a simpler configuration.

  Accordingly, the present invention provides an image heating apparatus that can reliably reduce the temperature rise of the non-sheet passing portion at the end of the recording material by appropriately setting the movement timing of the magnetic flux shielding member toward the sheet passing portion. An object of the present invention is to provide an image forming apparatus.

  The present invention provides a heating rotator that contacts and heats a recording material, and a heating region for induction heating by the heating rotator in a conveyance width direction perpendicular to the conveyance direction of the recording material. An image heating apparatus comprising: an induction heating apparatus that performs induction heating; and a heat storage temperature detection unit that detects a temperature in a heat storage unit in which heat generated by the heating rotating body is stored, and the induction heating apparatus includes the heating A heating area setting means for changing the magnetic flux density distribution along the conveyance width direction of the magnetic flux incident on the rotating body and setting the heating area according to the length of the recording material in the conveyance width direction, and the heating area setting The magnetic flux shielding member is arranged on the non-sheet passing portion side of the recording material with respect to the heating region set by the means and is movable to the sheet passing portion side, and the magnetic flux shielding based on the temperature detected by the heat storage temperature detecting means. Element Set the moving timing of moving in the sheet passing portion, and having a control means for reducing the non-sheet passing portion Atsushi Nobori.

  According to the present invention, the magnetic flux shielding member has a simple configuration for detecting the temperature of the heat storage section such as the pressure rotating body that stores the heat generated by the pressure rotating body, but based on the detected temperature of the heat storage section. It is possible to appropriately set the movement timing for moving the sheet passing side. Thereby, the temperature rise of the non-sheet passing portion at the end of the recording material in the heating region can be reliably reduced, and the durability of the heating rotator can be improved.

1 is an explanatory diagram of a configuration of an image forming apparatus equipped with a fixing device as an image heating device according to the present invention. 1 is an explanatory diagram of a fixing device according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram of a fixing device in the first embodiment. FIG. 3 is an explanatory diagram of a fixing belt in the first embodiment. FIG. 3 is an explanatory diagram of a fixing device in the first embodiment. FIG. 3 is an explanatory diagram of a fixing device in the first embodiment. FIG. 3 is an explanatory diagram of a fixing device in the first embodiment. (A), (b) is explanatory drawing of the core moving mechanism in 1st Embodiment. (A), (b) is explanatory drawing of the fixing device in 1st Embodiment. It is a disassembled perspective view which shows the relationship between the magnetic body core in 1st Embodiment, an exciting coil member, a fixing belt, and a pressure roller. It is a perspective view which shows the core moving mechanism in 1st Embodiment in the state seen from the inner surface side. (A), (b) is explanatory drawing in 1st Embodiment. It is a block diagram which shows the control system in 1st Embodiment. It is a flowchart figure in 1st Embodiment. (A), (b) is explanatory drawing in 1st Embodiment. It is explanatory drawing in 1st Embodiment. It is explanatory drawing in 1st Embodiment. It is explanatory drawing in 1st Embodiment. (A)-(c) is explanatory drawing in 1st Embodiment. It is a flowchart figure in 1st Embodiment. It is a timing chart figure in a 1st embodiment. (A), (b) is a perspective view of the fixing device in the first embodiment. It is a block diagram which shows the control system in 1st Embodiment. It is a flowchart figure in 1st Embodiment. (A)-(c) is explanatory drawing in 1st Embodiment. It is explanatory drawing of the fixing device in 2nd Embodiment which concerns on this invention. It is explanatory drawing in 2nd Embodiment.

  Hereinafter, the present invention will be described more specifically with reference to embodiments. The embodiment described below is an example of an embodiment according to the present invention, but the present invention is not limited to the embodiment.

  In the following embodiments, the image heating apparatus of the present invention will be described with respect to a fixing apparatus that fixes an unfixed toner image on a recording material. However, the present invention is directed to a recording material carrying a fixed image or a semi-fixed image. It can also be implemented as a heat treatment apparatus that adjusts the surface properties of an image by applying heat and pressure. A fixing belt (heating rotator) 1 to be described later can be constituted not only by a belt member but also by a roller member.

<First Embodiment>
An image forming apparatus equipped with an image heating apparatus can be equipped with the image heating apparatus of the present invention without distinction between monochrome / full color, sheet-fed type / recording material conveying type / intermediate transfer type, toner image forming system, and transfer system. In the present embodiment, only main parts relating to toner image formation / transfer / fixing will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, in addition to necessary equipment, equipment, and a housing structure. The image forming apparatus can be used in various applications such as a multifunction peripheral.

[Image forming apparatus]
FIG. 1 is an explanatory diagram of a configuration of an image forming apparatus 15 in which an image heating apparatus according to the present invention is mounted as a fixing device 16. As shown in FIG. 1, the image forming apparatus 15 includes a tandem type intermediate using an electrophotographic system in which yellow, magenta, cyan, and black image forming portions PY, PC, PM, and PK are arranged along an intermediate transfer belt 26. It is a transfer type full-color printer.

  The image forming portions PY, PC, PM, and PK arranged in order from the bottom to the top each have a photosensitive drum 21, a charging device 22, a developing device 23, a cleaning device 24, and the like.

  The developing device 23 provided in the yellow image forming unit PY stores yellow toner, and the developing device 23 provided in the cyan image forming unit PC stores cyan toner. Further, the developing device 23 provided in the magenta image forming unit PM contains magenta toner, and the developing device 23 provided in the black image forming unit PK contains black toner.

  An optical system 25 that forms an electrostatic latent image by exposing the photosensitive drum 21 is provided corresponding to the four color image forming portions PY, PC, PM, and PK. A laser scanning exposure optical system is used as the optical system.

  In each of the image forming units PY, PC, PM, and PK, the photosensitive drum 21 uniformly charged by the charging device 22 is subjected to scanning exposure based on image data from the optical system 25, whereby the photosensitive drum. An electrostatic latent image corresponding to the scanning exposure image pattern is formed on the surface.

  These electrostatic latent images are developed as toner images by the developing device 23. That is, a yellow toner image is formed on the photosensitive drum 21 of the yellow image forming unit PY, and a cyan toner image is formed on the photosensitive drum 21 of the cyan image forming unit PC. Further, a magenta toner image is formed on the photosensitive drum 21 of the magenta image forming unit PM, and a black toner image is formed on the photosensitive drum 21 of the black image forming unit PK.

  The color toner images formed on the photosensitive drums 21 of the image forming units PY, PC, PM, and PK are on the intermediate transfer belt 26 that rotates at a substantially constant speed in synchronization with the rotation of the photosensitive drums 21. In the predetermined alignment state, the images are superposed one after another and subjected to primary transfer. As a result, an unfixed full-color toner image is synthesized and formed on the intermediate transfer belt 26. In the present embodiment, an endless intermediate transfer belt 26 is used. The endless intermediate transfer belt 26 is wound around three rollers of a driving roller 27, a secondary transfer counter roller 28, and a tension roller 29, and is driven by the driving roller 27. Is done.

  A primary transfer roller 30 is used as a primary transfer unit of the toner image from the photosensitive drum 21 of each image forming unit PY, PC, PM, PK to the intermediate transfer belt 26. A primary transfer bias having a polarity opposite to that of the toner is applied to the primary transfer roller 30 from a bias power source (not shown).

  As a result, the toner images are primarily transferred from the photosensitive drums 21 of the image forming units PY, PC, PM, and PK to the intermediate transfer belt 26. After the primary transfer from the photosensitive drum 21 to the intermediate transfer belt 26 in each of the image forming units PY, PC, PM, and PK, toner remaining as a transfer residue on the photosensitive drum 21 is removed by the cleaning device 24.

  The above process is performed for each color of yellow, magenta, cyan, and black in synchronization with the rotation of the intermediate transfer belt 26, and the primary transfer toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 26. It should be noted that the above process is performed only for the target color during image formation of only a single color (monochromatic mode).

  On the other hand, the recording material P in the recording material cassette 31 is separated and fed one by one by a paper feed roller 32. Then, at a predetermined timing, the registration roller 33 conveys the intermediate transfer belt 26 wound around the secondary transfer counter roller 28 to the transfer fixing nip portion that is a pressure contact portion between the secondary transfer roller 34.

  The primary transfer composite toner image formed on the intermediate transfer belt 26 is collectively transferred onto the recording material by a bias having a polarity opposite to that of the toner applied to the secondary transfer roller 34 from a bias power source (not shown). The secondary transfer residual toner remaining on the intermediate transfer belt 26 after the secondary transfer is removed by the intermediate transfer belt cleaning device 35.

  The toner image secondarily transferred onto the recording material P is melt-mixed and fixed on the recording material P by the fixing device 16 that is an image heating device, and is sent out to the paper discharge tray 37 through the paper discharge path 36 as a full color print. .

[Fixing device]
FIG. 2 is an explanatory diagram (enlarged transverse side view) of a configuration of a main part of the fixing device 16 and a block diagram of a control system. FIG. 3 is a longitudinal sectional view of the fixing device 16 as seen from the secondary transfer portion side. FIG. 5 is a longitudinal front view for explaining the magnetic core moving mechanism and the fixing device 16.

  In the following description, the longitudinal direction of the fixing device 16 or a member constituting the fixing device 16 is a direction parallel to a direction orthogonal to the recording material conveyance direction in the recording material conveyance path surface. The short direction is a direction parallel to the recording material conveyance direction. The front surface of the fixing device 16 is a surface when the fixing device is viewed from the recording material inlet side, and the back surface is a surface when viewed from the recording material outlet side opposite to the recording material. The left and right sides of the fixing device 16 are left or right when the fixing device 16 is viewed from the front. The upstream side and the downstream side are the upstream side and the downstream side in the recording material conveyance direction.

  As shown in FIG. 2, a fixing device 16 as an image heating device includes a fixing belt 1, an induction heating device 100, and a pressure roller (pressure rotator) 2.

  That is, the fixing device 16 variably sets the heating area of induction heating by the fixing belt 1 as a heating rotating body that contacts and heats the recording material P and the fixing belt 1 in the conveyance width direction orthogonal to the conveyance direction of the recording material. And an induction heating device 100 for induction heating the fixing belt 1. Further, the fixing device 16 includes a pressure roller 2 as a heat storage unit in which heat generated by the fixing belt 1 is stored. The pressure roller 2 is also configured as a nip forming member that forms a fixing nip portion (heating nip portion) N of the recording material P in contact with the fixing belt 1.

  The fixing device 16 melts the toner (developer) of the toner image (unfixed image) transferred to the conveyed recording material by heat and fuses it onto the recording material P.

  The fixing belt 1 provided in the fixing device 16 is an endless belt member having a metal layer and an inner diameter of, for example, 30 mm. The pressure roller 2 is formed in a cylindrical shape having an outer diameter of, for example, 30 mm. The pressure roller 2 is in pressure contact with the outer surface of the fixing belt 1 supported on the inner surface by a pressure applying member 3 held by a metal stay 4, and the fixing nip of the recording material P between the fixing belt 1 and the pressure roller 2. Part N is formed.

  Further, a magnetic flux shielding core 5 as a magnetic shielding member for preventing a temperature rise due to induction heating is provided on the side of the exciting coil member 6 of the stay 4. The pressure applying member 3 constitutes a heat storage part in which the heat generated by the fixing belt 1 is stored, and is disposed in the fixing belt (heating rotator) 1 to form a fixing nip part (heating nip part) N. Thus, a contact member that contacts the inner surface of the fixing belt 1 is configured.

  As shown in FIG. 5, left and right fixing flanges 10 are disposed as restricting members that restrict the longitudinal movement and the circumferential shape of the fixing belt 1. A stay pressurizing spring 9b is contracted between both ends of the stay 4 that is inserted into the fixing flange 10 and the spring receiving member 9a on the apparatus chassis side, and a pressing force is applied to the stay 4. Yes. As a result, the lower surface of the fixing flange 10 and the upper surface of the pressure roller 2 are pressed across the fixing belt 1 to form the fixing nip portion N having a predetermined width.

  As shown in FIG. 2, the induction heating device 100 is disposed on the upper surface side of the outer peripheral surface of the fixing belt 1 so as to face the fixing belt 1 with a predetermined gap (gap). The induction heating device 100 is a heating source for induction heating the fixing belt 1.

  The induction heating apparatus 100 includes an exciting coil member 6 that is wound, for example, using a litz wire as an electric wire, which is horizontally long and shaped like a ship bottom, and is opposed to a part of the peripheral surface and side surface of the fixing belt 1. Yes. In addition, the induction heating device 100 includes magnetic cores 7a and 7b that cover the exciting coil member 6 so that the magnetic field generated by the exciting coil member 6 does not substantially leak outside the metal layer (conductive layer) of the fixing belt 1. doing. Further, the induction heating apparatus 100 includes a mold member 7c that supports the exciting coil member 6 and the magnetic cores 7a and 7b with an electrically insulating resin.

  The magnetic cores 7 a and 7 b serve to efficiently guide the alternating magnetic flux generated from the exciting coil member 6 to the fixing belt 1. It is used to increase the efficiency of the magnetic circuit of AC magnetic flux and to shield magnetic flux that avoids induction heating of the peripheral members by leaking magnetic flux to the surroundings. As the material for the magnetic cores 7a and 7b, a material having high magnetic permeability and low residual magnetic flux density such as ferrite may be used.

  When the magnetic cores 7a and 7b are separated from the exciting coil member 6 and the gap between them is widened in the non-sheet passing portion, the magnetic flux density passing through the fixing belt 1 is lowered, and the heat generation amount of the fixing belt 1 is reduced. Is done.

  In the rotating state of the fixing belt 1, a high frequency current of 20 to 50 kHz is applied from the power supply device (excitation circuit) 101 to the excitation coil member 6 of the induction heating device 100, and the fixing belt is caused by the magnetic field generated by the excitation coil member 6. One metal layer (conductive layer) generates induction heat.

  The temperature detection sensor TH1 includes a temperature detection sensor (temperature detection element) such as a thermistor, for example, and is disposed in contact with the position of the center inner surface in the width direction of the fixing belt 1 (see FIG. 16). Since the temperature detection sensor TH1 is attached to the pressure applying member 3 via an elastic support member, even if a positional variation such as a wave of the contact surface of the fixing belt 1 occurs, the temperature detection sensor TH1 is good to follow this. A good contact state is maintained. The temperature detection sensor TH1 is disposed at the position of the inner surface portion in the width direction of the sheet passing portion region of the fixing belt 1 when the recording material P is conveyed (see FIG. 16). The temperature detection sensor TH1 constitutes a heating temperature detection means for detecting the temperature corresponding to the sheet passing portion of the recording material P in the fixing belt (heating rotator) 1.

  The temperature detection sensor TH <b> 1 detects the temperature of a portion that is a sheet passing portion region in the fixing belt 1, and feeds back the detected temperature information to the control unit (CPU) 102. The control unit 102 controls the electric power input from the power supply device 101 to the exciting coil member 6 so that the detection temperature input from the temperature detection sensor TH1 is maintained at a predetermined target temperature (fixing temperature). The control unit 102 sets a movement timing for moving the magnetic flux shielding member (magnetic shielding plate) 11 to the paper portion side based on the temperature detected by the temperature detection sensor (heat storage temperature detection means) TH2, and sets the non-paper passing portion. A control means for reducing the temperature rise is configured.

  That is, when the detected temperature of the fixing belt 1 is raised to a predetermined temperature, the energization to the exciting coil member 6 is interrupted. In this embodiment, the electric power input to the exciting coil member 6 is controlled by changing the frequency of the high-frequency current based on the detection value of the temperature detection sensor TH1 so as to be constant at the target temperature of 180 ° C. that is the target temperature of the fixing belt 1. And adjust the temperature.

  Further, a non-contact type temperature detection sensor TH <b> 2 that measures the surface temperature of the pressure roller 2 is disposed in a state where a slight gap is left between the surface of the pressure roller 2. The temperature detection sensor TH2 is arranged in a state of facing the pressure roller 2 with a slight gap at the center of the sheet passing area when the recording material P is conveyed (see FIG. 16). The temperature detection sensor TH2 constitutes a heat storage temperature detection means for detecting the temperature corresponding to the sheet passing portion of the recording material P in the pressure roller 2 as the heat storage portion.

  At least when image formation is performed, the fixing belt 1 is rotationally driven (rotated) by the pressure roller 2 being rotationally driven by a motor (driving means) M1 controlled by the control unit 102. That is, the fixing belt 1 is rotationally driven at a substantially same peripheral speed as the conveying speed of the recording material P carrying the unfixed toner image conveyed from the secondary transfer portion (see FIG. 1) side. In the case of this embodiment, the surface rotation speed of the fixing belt 1 rotates at, for example, 300 mm / sec. In this case, it is possible to fix 80 full-color images in A4 size and 58 in A4R size in one minute. is there.

  Further, when the excitation coil member 6 of the induction heating device 100 is supplied with power from the power supply device 101 controlled by the control unit 102, the fixing belt 1 rises to a predetermined fixing temperature and the temperature is adjusted. In this state, the recording material P having an unfixed toner image is positioned between the fixing belt 1 and the pressure roller 2 in the fixing nip portion N with the toner image carrying surface side facing the fixing belt 1 side and a guide member (non-fixed). Guided and introduced in the figure). Then, the recording material P is in close contact with the outer peripheral surface of the fixing belt 1 at the fixing nip portion N, and is nipped and conveyed along the fixing nip portion N together with the fixing belt 1.

  As a result, heat of the fixing belt 1 is mainly applied, and an unfixed toner image is fixed to the surface of the recording material P by pressure under the pressure of the fixing nip N. The recording material P that has passed through the fixing nip portion N is deformed at the exit portion of the fixing nip portion N, is separated from the outer peripheral surface of the fixing belt, and is conveyed outside the fixing device 16.

[Fixing belt]
FIG. 4 is an explanatory diagram of the layer structure of the fixing belt (heating rotator) 1. The fixing belt 1 is supported by the support side plates 12 and 12 (see FIG. 5) in a state where the position in the longitudinal direction is regulated. The fixing belt 1 is an endless belt member having a base layer 1a which is a metal layer and having an inner diameter of, for example, 30 mm. The base layer 1a is made of nickel by electroforming and has a thickness of 40 μm, for example.

  On the outer periphery of the base layer 1a, a heat-resistant silicone rubber layer is provided as the elastic layer 1b. The thickness of the silicone rubber layer is preferably set within a range of 100 to 1000 μm, for example. In this embodiment, the thickness of the silicone rubber layer is set to, for example, 300 μm in consideration of reducing the heat capacity of the fixing belt 1 to shorten the warm-up time and obtaining a suitable fixed image when fixing a color image. ing. This silicone rubber has a hardness of JIS-A 20 degrees and a thermal conductivity of 0.8 W / mK. Further, on the outer periphery of the elastic layer 1b, a fluororesin layer (for example, PFA or PTFE) is provided as a surface release layer 1c with a thickness of 30 μm.

  In order to reduce the sliding friction between the inner surface of the fixing belt 1 and the temperature detection sensor TH1 (see FIG. 2) on the inner surface side of the base layer 1a, a resin layer (sliding layer) 1d such as a fluororesin or polyimide is 10 to 50 μm. It may be provided. In this embodiment, 20 μm of polyimide is provided as the resin layer 1d.

  For the base layer (metal layer) 1a of the fixing belt 1, iron alloy, copper, silver or the like can be appropriately selected in addition to nickel. Moreover, the structure of laminating | stacking these metals on a resin base layer may be sufficient. The thickness of the base layer 1a may be adjusted according to the frequency of the high-frequency current supplied to the exciting coil member 6 described later and the magnetic permeability / conductivity of the metal layer, and may be set within a range of, for example, about 5 to 200 μm. preferable.

[Pressure roller]
As shown in FIG. 2, the pressure roller 2 that forms the fixing nip portion N with the fixing belt 1 is formed in a cylindrical shape having an outer diameter of, for example, 30 mm, and the inner surface is supported by the pressure applying member 3. It is brought into pressure contact with the outer surface of the fixing belt 1. As a result, a fixing nip portion N of the recording material P is formed between the fixing belt 1 and the fixing belt 1.

  The pressure roller 2 is provided with a core rubber 2a made of iron alloy having a diameter in the center in the longitudinal direction of 20 mm and a diameter of both ends of 19 mm, for example, and a silicone rubber layer having a thickness of about 5 mm as the elastic layer 2b. ing. On the surface of the elastic layer 2b, a fluororesin layer (for example, PFA or PTFE) is provided as a release layer 2c with a thickness of, for example, 30 μm. The hardness at the center in the longitudinal direction of the pressure roller 2 is ASK-C70 ° C. The cored bar 2a is tapered (crown shape) because the pressure in the fixing nip N sandwiched between the fixing belt 1 and the pressure roller 2 is long even if the pressure applying member 3 is bent when pressed. It is because it can ensure uniformly over a direction.

  Since the thickness of the elastic layer 2b is different between the central portion and both end portions of the metal core 2a with a taper shape, the width in the rotation direction (the length in the conveying direction) of the fixing nip portion N is set when the fixing nip pressure is 600N. The length is about 9 mm at both ends in the longitudinal direction and about 8.5 mm at the center. As a result, the conveyance speed at both ends of the recording material P becomes faster than that at the center, and there is an advantage that paper wrinkles are less likely to occur.

[Pressure imparting member]
As shown in FIG. 5, the pressure applying member 3 is disposed in the fixing belt 1 (in the heating rotating body), the inner side surface is held by a metal stay 4, and the inner side surface of the fixing belt 1 is covered by the outer side surface. To support. The pressure applying member 3 applies a pressing force to the pressure roller 2 through the fixing belt 1 to form a fixing nip portion N between the fixing belt 1 and the pressure roller 2. The pressure applying member 3 is a heat resistant resin, and a magnetic flux shielding core 5 as a magnetic flux shielding member for preventing a temperature rise due to induction heating is provided on the exciting coil member 6 side of the stay 4 (see FIG. 2). ing.

  The stay 4 is made of iron in the present embodiment because it needs rigidity to apply pressure to the pressure contact portion. The stay 4 is particularly close to the exciting coil member 6 at both ends, and in order to prevent heat generation of the stay 4, the upper surface of the stay 4 extends in the longitudinal direction so as to shield the magnetic field generated by the exciting coil member 6. Thus, the above-described magnetic flux shielding core 5 is disposed.

  The fixing flange 10 is a right and left regulating member that regulates the longitudinal movement and the circumferential shape of the fixing belt 1. A stay pressing spring 9b is contracted between both end portions of the stay 4 that are inserted into the fixing flange 10 and the spring receiving member 9a on the apparatus chassis side. Yes. As a result, the lower surface of the pressure applying member 3 and the upper surface of the pressure roller 2 are pressed across the fixing belt 1 to form a fixing nip portion N of the recording material image. By doing so, it is possible to prevent the elastic layer of the pressure roller 2 and the fixing belt 1 from being deformed.

  Since the rotating fixing belt 1 has a base layer 1a made of metal, as a means for restricting the shift in the width direction even when in the rotating state, the end of the fixing belt 1 is simply received. It is sufficient to provide the fixing flange 10. Accordingly, there is an advantage that the configuration of the fixing device 16 can be simplified.

[Induction heating device]
In the present embodiment, the fixing belt 1 and the exciting coil member 6 of the induction heating device 100 are kept in an electrically insulated state by, for example, a 0.5 mm mold. The distance between the fixing belt 1 and the exciting coil member 6 is constant, for example, 1.5 mm (the distance between the mold surface and the fixing belt surface is 1.0 mm), and the fixing belt 1 is heated uniformly. .

  As described above, a high frequency current of 20 to 50 kHz is applied to the exciting coil member 6, and the base layer 1a of the fixing belt 1 generates induction heat. Then, the electric power input to the exciting coil member 6 is controlled by changing the frequency of the high-frequency current based on the detection value of the temperature detection sensor TH1 so as to be constant at 180 ° C. that is the target temperature of the fixing belt 1. Adjusted.

  In the present embodiment, since the induction heating device 100 including the exciting coil member 6 is arranged outside the fixing belt 1 that becomes high temperature, the temperature of the exciting coil member 6 does not easily become high. Further, the loss due to Joule heat generation can be reduced even when a high frequency current is passed without increasing the electrical resistance. Further, the arrangement of the exciting coil member 6 on the outside contributes to the reduction of the diameter (lower heat capacity) of the fixing belt 1, and it can be said that it is excellent in energy saving.

  Since the warming-up time of the fixing device 16 has a very low heat capacity, for example, when 1200 W is input to the exciting coil member 6, for example, the target temperature can be reached to 160 ° C. in about 15 seconds, and heating operation during standby is unnecessary. It is. Therefore, it is possible to keep power consumption very low.

[Movement mechanism of magnetic core]
As shown in FIG. 3, the exciting coil member 6 generates a magnetic flux incident on the fixing belt 1. The core moving mechanism 71 is configured to change the magnetic flux density distribution along the longitudinal direction of the magnetic flux incident on the fixing belt 1. The core moving mechanism 71 sets a heating area of the fixing belt 1 by the induction heating device 100 according to the length of the recording material P to be heated in the conveyance width direction. The core moving mechanism 71 changes the magnetic flux density distribution along the conveyance width direction of the magnetic flux incident on the fixing belt (heating rotator) 1 and sets the heating area according to the length of the recording material P in the conveyance width direction. The heating area setting means is configured.

  A plurality of magnetic cores 7a and 7b (see FIG. 16) are arranged in the longitudinal direction of the fixing belt 1 to guide the magnetic flux generated by the exciting coil member 6 to the fixing belt 1 in each region. The regulating member 73 (see also FIG. 16) moves the plurality of magnetic cores 7a and 7b in a direction in which they are in contact with and separated from the fixing belt 1. The regulating member 73 sets the heating region by bringing the number of magnetic cores 7a and 7b corresponding to the length in the width direction of the recording material closer to the fixing belt 1 than the other magnetic cores 7a and 7b.

  In the core moving mechanism (heating region setting means) 71, the magnetic cores 7 a and 7 b are held by the magnetic core holder 77 and housed in the housing 76. The magnetic core holder 77 is movable in the direction of the arrow P (P1, P2) that changes the gap between the magnetic cores 7a, 7b and the exciting coil member 6.

  The link member 75 is assembled so as to be rotatable around the rotation shaft 78, and the elongated hole portion 75 a at the end is connected to the connection protrusion 771 of the magnetic core holder 77. When the link member 75 rotates about the rotation shaft 78 in the direction of the arrow Q1, the magnetic core holder 77 and the magnetic cores 7a and 7b move in the P1 direction. When the link member 75 rotates in the arrow Q2 direction, the magnetic core holder 77 and the magnetic cores 7a and 7b move in the P2 direction. The link member 75 is biased in the direction of rotation in the arrow Q1 direction by the excitation coil spring 74, but the rotation of the link member 75 in the arrow Q1 direction is restricted by the restriction member 73.

  In a state where the link member 75 is pushed in by the restricting member 73, the link member 75 rotates in the arrow Q2 direction against the exciting coil spring 74. At this time, the magnetic core holder 77 moves in the direction of the arrow P <b> 2 and the magnetic cores 7 a and 7 b are approaching the exciting coil member 6.

  When the pushing by the restricting member 73 is released, the link member 75 is urged by the exciting coil spring 74, rotates in the direction of the arrow Q1, stops against the frame 79, and stops. As a result, the magnetic core holder 77 moves in the direction of the arrow P <b> 1, and the magnetic cores 7 a and 7 b move away from the exciting coil member 6. Reference numeral 761 denotes a guide portion of the housing 76 for moving and guiding the magnetic core holder 77.

[Core moving mechanism and magnetic flux shielding member moving mechanism]
6 and 7 are perspective views of the fixing device 16 in the present embodiment, FIG. 8A is a top view (plan view) of the fixing device 16 viewed from the direction of the arrow X in FIG. 6, and FIG. FIG. 8 is a top view (plan view) of the fixing device 16 as viewed from the direction of arrow X in FIG. 7. 9A and 9B are cross-sectional views of the fixing device 16, FIG. 10 is a perspective view showing the fixing device 16 and the induction heating device 100 partially disassembled, and FIG. 11 is induction heating viewed from the fixing belt 1 direction. 2 is a perspective view of the device 100. FIG.

  As shown in FIG. 10, in the induction heating apparatus 100, a plurality of magnetic cores 7 a and 7 b are arranged side by side in a direction orthogonal to the recording material conveyance direction, and surround the winding center portion and the periphery of the exciting coil member 6. It is configured as follows. The magnetic core 7 a is a core in the region E at the sheet passing end, and is configured to be movable by the core moving mechanism 71. Further, the magnetic core 7 b is a core in the region D at the center of paper passing and is supported by the housing 76. The area D has a sheet passing area width corresponding to the small size sheet width, and the combined width of the area D and the area E is a sheet passing area width corresponding to the large size sheet width.

  The magnetic cores 7a and 7b serve to efficiently guide the alternating magnetic flux generated from the exciting coil member 6 to the induction heating element of the fixing belt 1, and are used to increase the efficiency of the magnetic circuit (magnetic path). Used for. Ferrite is preferably used as the material for the magnetic cores 7a and 7b.

  As shown in FIG. 8 (a), the induction heating apparatus 100 is configured to cope with the temperature increase of the non-sheet passing portion of various paper sizes, for example, postcard, A5, B4, A4, and A3 size. . In other words, in the region E at the sheet passing end, the magnetic cores 7a and 7b are divided into a plurality in the direction orthogonal to the recording material conveyance direction, that is, the Y direction. The magnetic cores 7 a and 7 b are housed in the housing 76 by being thermally welded and held in the corresponding magnetic core holders 77.

  In this embodiment, the magnetic core holder 77 is provided. However, the magnetic core holder 77 is abolished, and the shapes of the magnetic cores 7a and 7b and the magnetic core holder 77 of the present embodiment are formed by using only the magnetic cores 7a and 7b. You may have.

  As shown in FIG. 9A, the magnetic core holder 77 that holds the magnetic cores 7a and 7b is configured to be movable by guidance by the guide portion 761 of the housing 76 as described above. This moving direction is the direction in which the gap between the magnetic cores 7a, 7b and the exciting coil member 6 is changed, that is, the direction of the arrows P (P1, P2).

  As described above, the link member 75 has the elongated hole portion 75 a connected to the connection protrusion 771 of the magnetic core holder 77, and is rotatable about the rotation shaft 78. By providing the link member 75 in this way, it is possible to increase the moving distance between the magnetic core holder 77 and the magnetic cores 7a and 7b.

  As described above, the link member 75 is urged to rotate in the direction of the arrow Q1 by the exciting coil spring 74, and the rotation in the direction of the arrow Q1 is restricted by the restriction member 73. In the present embodiment, the exciting coil spring 74 is attached to the link member 75. However, any configuration may be used as long as the magnetic cores 7a and 7b move in the direction of the arrow P1. Therefore, it is possible to attach the urging member to the magnetic cores 7a and 7b and the magnetic core holder 77, or to apply a moment in the Q1 direction by the weight of the link member 75.

  As shown in FIG. 8A, the restricting member 73 is connected to a pinion gear 80 supported at the center in the width direction orthogonal to the recording material conveyance direction, and the width direction is increased by the rotational movement of the pinion gear 80. That is, it is configured to be movable in the direction of the arrow Y (Y1, Y2).

  The pinion gear 80 is drivingly connected to the motor M, and is rotated by driving of the motor M controlled by the control unit 102. In the recording material conveyance direction (vertical direction in the figure) of the pinion gear 80, a pair of horizontally long regulating members 73 in a state where the rack gears 73c are engaged with each other with the pinion gear 80 interposed therebetween are arranged. A home position sensor 81 made of a photo interrupter is disposed at a position facing the pinion gear 80.

  The home position sensor 81 is configured to be shielded (light-shielded) / opened (light-transmitted) by a flag portion 73 a fixed to the end of one of the regulating members 73. The home position sensor 81 is in an ON state when shielded from light. In the state of FIG. 6 and FIG. 8A, all link members 75 are restricted by the restriction member 73.

  As shown in FIGS. 6 and 11, magnetic flux shielding members (magnetic shielding plates) 11 and 11 are integrally attached to the regulating members 73 and 73 located at both ends, respectively. Each of the pair of magnetic flux shielding members 11 is connected and fixed to a support portion 73b that is bent from the corresponding restriction member 73 and extends downward, and together with the corresponding restriction member 73, the width direction orthogonal to the recording material conveyance direction, that is, The movement in the direction of the arrow Y (Y1, Y2) is possible. The magnetic flux shielding member 11 is arranged closer to the non-sheet passing portion side of the recording material P than the heating region set by the core moving mechanism (heating region setting means) 71, and is configured to be movable to the sheet passing portion side.

  In this manner, the pair of magnetic flux shielding members 11 can be moved in conjunction with the core moving mechanism 71 that moves the magnetic cores 7 a and 7 b toward and away from the exciting coil member 6. In addition, the code | symbol 70 in FIG. 6 has shown the clearance gap formed between the upper part of the support side board 12, and the lower part.

  The magnetic flux shielding member 11 is configured using a curved (semi-cylindrical) copper plate, and is inserted into a space between the exciting coil member 6 and the fixing belt (heating belt) 1 (see FIGS. 2 and 10). ), The width of the magnetic cores 7a and 7b is specified. That is, as the magnetic flux shielding member 11, two copper plates having a thickness of, for example, 0.5 mm, which are equal to or greater than the skin depth, are inserted between the exciting coil member 6 and the fixing belt 1. Further, the magnetic flux shielding member 11 is configured to shield the width of the excitation coil member 6 facing the fixing belt 1 from the fixing belt 1 by, for example, 20 mm in the width direction (conveyance width direction) orthogonal to the recording material conveyance direction. Is done.

  As an effect of inserting the copper plate, there is a great effect of further reducing the heat generation amount of the base layer (metal layer) 1a which is a fixing belt heat generation layer whose magnetic flux is weakened by the movement of the magnetic cores 7a and 7b. Further, the magnetic flux shielding member 11 moves in conjunction with the core moving mechanism 71 of the magnetic cores 7a and 7b, so that the longitudinal heat generation distribution can be controlled more finely than the divided width of the magnetic cores 7a and 7b. The magnetic flux shielding member 11 moves in accordance with the size of various recording materials (for example, postcard, A5, B4, A4, A3 Nobi size, etc.) and weakens the magnetic flux density passing through the fixing belt 1 to thereby prevent the non-sheet passing portion. Suppresses the temperature rise.

  The magnetic flux shielding member (magnetic shielding plate) 11 is disposed not only between the exciting coil member 6 and the fixing belt 1, but also between the exciting coil member 6 and the magnetic cores 7a and 7b, or the fixing belt. 1 and the magnetic flux shielding core 5 are also conceivable. That is, the magnetic flux shielding member 11 is arranged between the exciting coil member 6 and the fixing belt 1, between the exciting coil member 6 and the magnetic cores 7a and 7b, between the fixing belt 1 and the magnetic flux shielding core 5, and the like. It is arranged on a magnetic circuit (magnetic path) generated from the member 6.

  As a result, a magnetic flux is generated in the magnetic flux shielding member 11 in a direction in which the magnetic flux from the exciting coil member 6 is canceled, and the heat generation range of the fixing belt 1 can be controlled. The magnetic flux shielding member 11 may be made of a nonmagnetic metal such as aluminum, copper, silver, gold, or brass, or an alloy thereof, or may be a material such as ferrite or permalloy that is a high magnetic permeability member.

  FIG. 12 is a layout diagram in the longitudinal direction when a maximum size sheet is passed. As shown in FIG. 12A, the magnetic flux shielding member 11 supports the fixing belt 1 and the end face of the inner diameter r in the longitudinal direction of the exciting coil member 6 when the maximum size paper is passed (A3 Nobi in this embodiment). A position corresponding to the support side plate 12 is arranged as an initial position A1. This initial position A1 is the home position. At this time, the home position sensor 81 is in an ON state (see FIG. 16).

  Accordingly, the home position is a state in which all the magnetic cores 7a and 7b are restricted in the direction of the arrow P2 (see FIG. 3), and the pair of magnetic flux shielding members 11 are respectively disposed at the initial position A1. Each R in FIG. 12 indicates the dimension obtained by adding the conveyance width direction size of the magnetic flux shielding member 11 to the inner diameter r in the longitudinal direction of the excitation coil member 6, and 2R indicates the conveyance width direction size of the excitation coil member 6. Yes.

  FIG. 13 is a block diagram showing a control system for controlling the motor M that rotationally drives the pinion gear 80 of the present embodiment. FIG. 14 is a flowchart for explaining each operation when the motor M is driven.

  As shown in FIG. 13, the control unit (CPU) 102 is connected to an operation unit (not shown) installed in the image forming apparatus 15, reads a signal from the recording material size input unit 111 in the computer, and performs a home position. The motor M is controlled based on the signal from the sensor 81.

  Next, the flow during the moving operation of the magnetic cores 7a and 7b will be described with reference to FIG.

  First, when a print job is started, in step S31, the control unit 102 reads an input value of the recording material size from the signal of the recording material size input unit 111. Then, a predetermined number of pulses C1 from the home position sensor 81 of the motor M such as a stepping motor is determined by calculation of the control unit 102 in accordance with the input value of the recording material size (S32).

  Subsequently, the control unit 102 reads the input signal of the home position sensor 81 (S33), and determines that the regulating member 73 is not located at the home position when it is in the OFF state. In this case, the regulating member 73 is close to the center side in the width direction (conveyance width direction) orthogonal to the recording material conveyance direction. Therefore, by rotating the motor M so as to move the regulating member 73 in the arrow Y2 direction (see FIG. 7), the regulating member 73 is returned until the home position sensor 81 is turned on (S35).

  When determining that the home position sensor 81 is in the ON state, the control unit 102 rotationally drives the motor M so as to move the regulating member 73 in the arrow Y1 direction (S34). When it is recognized that the home position sensor 81 has been switched off (S36), the motor M is moved by a predetermined number of pulses C1 (S37). Then, the movement operation of the magnetic cores 7a and 7b is completed, and printing is started.

  FIGS. 7, 8B, and 9B are a perspective view and a top view (plan view) of the fixing device 16 after the magnetic cores 7a and 7b are moved by the core moving mechanism 71 of the present embodiment. FIG.

  In FIG. 7, FIG. 8B and FIG. 9B, the non-sheet passing portion region C when the control unit 102 recognizes the recording material P as B4 size based on the signal from the recording material size input unit 111. The state after the magnetic cores 7a and 7b are moved (see FIG. 16) is shown. That is, three magnetic core holders 77 at both ends move in the direction of arrow P1 (FIG. 9B), and the gap between the magnetic core 7a and the exciting coil member 6 is widened (see FIG. 16).

  That is, when the restricting member 73 starts to move in the direction of arrow Y1 in FIG. 8, the restriction on the link member 75 on the end side in the width direction (conveyance width direction) perpendicular to the recording material conveyance direction is released. That is, when the regulating member 73 moves from the end side to the center side, the regulation is released in order from the magnetic core 7a on the end side. As described above, when the restricting member 73 is moved to the central portion when the small-size sheet is passed, the movable range of the restricting member 73 does not widen in the transport width direction, so that the space can be saved.

  Here, the state of the magnetic cores 7a and 7b whose restriction is released from the restriction member 73 will be described with reference to FIG.

  That is, the link member 75 deviated from the restriction of the restriction member 73 is rotated in the direction of the arrow Q1 about the rotation shaft 78 by the exciting coil spring 74 and comes into contact with the abutting portion A of the frame 79, thereby the link member 75. The position of is regulated. Accordingly, the magnetic core holder 77 and the magnetic cores 7a and 7b are moved in the direction of the arrow P1 by the guidance of the guide portion 761 of the housing 76, and the gap between the magnetic core 7a (7b) and the exciting coil member 6 is widened. It will be.

  On the other hand, as shown in FIG. 12B, the magnetic flux shielding member 11 moves to the proper position Z in the recording material end region as the regulating member 73 moves. Accordingly, in the states shown in FIGS. 7, 8B, 9B, and 12B, the distance between the exciting coil member 6 and the magnetic core 7a (7b) is large. Therefore, the efficiency of the magnetic circuit composed of the magnetic core 7a (7b) and the induction heating element (base layer 1a) formed around the exciting coil member 6 is reduced, and the amount of generated heat is reduced.

  Further, a magnetic circuit generated around the exciting coil member 6 in the recording material end region is shielded by the magnetic flux shielding member 11, and the heat generation of the fixing belt 1, that is, the induction heating element (base layer 1a) is suppressed. Therefore, the temperature rise of the non-sheet passing portion is avoided, and as a result, the abnormal temperature rise of the magnetic cores 7a and 7b and the exciting coil member 6 can be avoided.

  Conversely, when the restricting member 73 is moved in the direction of the arrow Y2, that is, when returning to the home position, the restricting member 73 comes into contact with the link member 75, and the contacted link member 75 is moved in the direction of the arrow Q2 in FIG. 9B. Rotate to At this time, the magnetic core holder 77 and the magnetic cores 7a and 7b move in the arrow P2 direction. That is, the state shown in the cross section of FIG. 9B shifts to the state shown in FIG.

  Hereinafter, the present invention will be described in more detail. FIGS. 15A and 15B are explanatory diagrams in the present embodiment. FIG. 16 is a longitudinal temperature distribution of the fixing belt 1 during A4 paper feeding, and FIGS. 17, 18, and 19A to 19C are explanatory diagrams in the present embodiment. FIG. 20 is a flowchart showing the operation of the present embodiment, and FIG. 21 is a timing chart thereof.

  As shown in FIG. 16, it can be seen that the temperature of the fixing belt 1 is greatly increased near the edge of the paper. The peak temperature of the fixing belt 1 in the vicinity of the paper edge is referred to as a non-sheet passing temperature. In order to reduce the non-sheet passing portion temperature, the magnetic flux shielding member 11 is moved toward the longitudinal central portion when a certain number of sheets are passed, and control is performed to narrow the longitudinal heat generation width. Note that C in FIG. 16 indicates a non-sheet passing portion area when the recording material P is conveyed.

  By narrowing the heat generation width, the heat generation amount of the non-sheet passing portion is reduced as shown in FIG. 17, and the non-sheet passing portion temperature is reduced. If the heat generation width is controlled to be narrowed before the sheet is passed, temperature sagging occurs at the end of the sheet passing area as shown in FIG.

  Since the temperature at the end of the sheet passing area increases as the non-sheet passing portion temperature increases, the control for narrowing the heat generation width is performed by referring to a table shown in FIG. Is prevented from exceeding the endurance failure temperature.

  When the number of sheets passing exceeds a predetermined number, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by one side x [mm]. The durability breakdown temperature is a temperature that significantly reduces the durability life of the fixing belt 1.

  FIG. 19B is a time transition of the sheet passing area of the fixing belt (heating belt) 1, the sheet passing area of the pressure roller 2, and the non-sheet passing area of the fixing belt 1 when starting up in the morning. It can be seen that the non-sheet passing portion temperature does not exceed the endurance failure temperature.

  On the other hand, after passing for a long time or after standby, the pressure roller 2 stores heat compared to when it is started up in the morning. For this reason, when there is no escape place for heat and the movement control of the magnetic flux shielding member 11 is performed in the same way as when it is started up in the morning, the non-sheet passing portion temperature exceeds the endurance failure temperature as shown in FIG.

  Therefore, after passing the paper for a long time, it is necessary to execute a control for narrowing the heat generation width by moving the magnetic flux shielding member 11 at an earlier timing than when it is started up in the morning. Note that “at the start in the morning” means a case where the induction heating apparatus 100 is cooled and the maximum power is required.

  In the configuration used in the above-described embodiment, since the fixing belt 1 is a thin belt, a partial temperature rise occurs near the end of the recording material as shown in FIG. Accordingly, since the longitudinal position of the temperature rise differs depending on the size of the recording material P, it is difficult to directly detect the temperature rise, and the temperature of the non-sheet passing portion must be predicted and controlled.

  Therefore, in the present embodiment, the surface temperature of the pressure roller 2 is measured, the heat storage state of the system is determined based on the measured temperature, and the control of the movement timing of the magnetic flux shielding member 11 is optimized.

  That is, in the present embodiment, the control is executed by detecting the temperature of the pressure roller 2 instead of the temperature of the fixing belt 1. This is because detecting the temperature of the pressure roller 2 having a large wall thickness and a large heat capacity than the thin fixing belt 1 having a small heat capacity can better understand the heat storage state of the system. Therefore, the movement timing of the magnetic flux shielding member 11 can be controlled more accurately.

  As shown in FIG. 20, the startup operation is performed according to the flowchart when starting up. In this embodiment, the movement timing of the magnetic flux shielding member 11 is detected by detecting the temperature of the pressure roller 2 when the target temperature is reached. To decide.

  That is, when the process of FIG. 20 starts, in step S11, the recording material size setting and the recording material size are set from an operation panel (not shown) provided in the image forming apparatus 15 or a personal computer (PC) connected to the image forming apparatus 15. Get job (JOB) start information.

  In step S <b> 12, the control unit 102 detects the home position of each member of the fixing device 16. In step S13, the magnetic cores 7a and 7b are moved up and down (advanced and retracted) with respect to the exciting coil member 6 according to the acquired recording material size by the movement of the regulating member 73 (t1 in FIG. 21). In conjunction with this, the magnetic flux shielding member 11 is moved together with the regulating member 73 in accordance with the recording material size (S14).

  In step S15, the control unit 102 causes the pressure roller 2 that has been separated by the operation of a drive mechanism (not shown) to contact the fixing belt 1 at a predetermined timing by operating the drive mechanism (see FIG. 21). t2). Then, the control unit 102 drives the motor M1 to rotate the pressure roller 2, and rotates the fixing belt 1 along with the pressure roller 2, so that the fixing belt 1 and the pressure roller 2 are rotated at a predetermined speed. The rotation is driven (S16) (t3 in FIG. 21).

  In step S17, when the temperature adjustment of the fixing device 16 is started, the fixing nip N reaches the target temperature at a certain time (S18).

  In step S <b> 19, the control unit 102 determines a movement timing for moving the magnetic flux shielding member 11 when the number of image forming sheets is x based on the temperature of the pressure roller 2 detected by the temperature detection sensor TH <b> 2. (T4 in FIG. 21).

  After image formation is started in step S20, it is determined in step S21 whether image formation for one job input this time has been completed. As a result, if the image formation is not completed, the process proceeds to step S26, and it is determined whether or not the number of formed images is the xth. If it is not the xth sheet, steps S20, 21, and 26 are repeated. When the xth sheet is reached, the process proceeds to step S27, and the magnetic flux shielding member 11 is moved.

  If it is determined in step S21 that the image formation has been completed, the control unit 102 stops the temperature adjustment and moves it to the home position (S22, S23).

  Subsequently, in step S24, the pressure roller 2 is separated (detached) from the fixing belt 1 by the operation of a driving mechanism (not shown) in the fixing device 16 (t5 in FIG. 21). Further, in step S25, a signal is output to the motor M, the pinion gear 80 is rotated in a predetermined direction, and the regulating member 73 is moved to the home position position detected by the home position sensor 81 (t6 in FIG. 21).

  As shown in FIG. 15A, the movement timing of the magnetic flux shielding member 11 in step S27 is determined in advance as a table table together with the movement amount of the magnetic flux shielding member 11 in the number of sheets to be passed.

In the table shown in FIG. 15A, the temperature of the pressure roller 2 when the target temperature of the fixing belt 1 is reached,
(1) Pressure roller temperature <120 ° C
(2) 120 ° C. ≦ pressure roller temperature <140 ° C.
(3) Three patterns are formed with 140 ° C. ≦ pressure roller temperature.

  Then, the number of sheets to be passed for each pattern and the insertion amount of the copper plate (magnetic flux shielding member 11) are set as different numbers.

That is, (1) When the pressure roller temperature <120 ° C,
(A) When the number of sheets to be passed is 10, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(B) When the number of sheets to be passed is 100, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(C) When the number of sheets to be passed is 300, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(D) When the number of sheets passed is 600, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

(2) When 120 ° C. ≦ pressure roller temperature <140 ° C.
(E) When the number of sheets to be passed is 8, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(F) When the number of sheets to be passed is 30, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(G) When the number of sheets to be passed is 100, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(H) When the number of sheets to be passed is 200, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

Furthermore, (3) 140 ° C. ≦ pressure roller temperature,
(I) When the number of sheets to be passed is 5, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(J) When the number of sheets to be passed is 10, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(K) When the number of sheets to be passed is 20, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(L) When the number of sheets to be passed is 30, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

  That is, the control unit 102 controls the magnetic flux shielding member so that the timing for narrowing the heat generation width is advanced when the pressure roller temperature is low. For example, at the start-up in the morning, the temperature of the pressure roller 2 when the target temperature of the fixing belt 1 is reached is less than 120 ° C. Therefore, from the above table, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width of 3 mm on one side at the timing of the tenth sheet passing, and the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width of 6 mm on the 100th sheet. . As a result, as shown in FIG. 15B, even when the system is in a heat storage state, the non-sheet passing portion temperature does not exceed the endurance failure temperature even if the number of sheets is stacked.

  When the temperature of the pressure roller 2 when the fixing belt 1 reaches the target temperature exceeds 160 ° C., the magnetic flux shielding member 11 is placed 3 mm on one side from the table in FIG. Move in the direction to reduce the heat generation width. Then, the magnetic flux shielding member 11 is moved to the tenth sheet in the direction of narrowing the heat generation width of 6 mm on one side. As a result, as shown in FIG. 15B, even when the pressure roller 2 is in a heat storage state, the non-sheet passing portion temperature does not exceed the endurance failure temperature during sheet passing.

  As a result, when the temperature of the pressure roller 2 when the temperature adjustment of the fixing belt 1 reaches 160 ° C., the durable life in the case of the same control as that when starting up in the morning was 100,000 sheets or less. On the other hand, the durability of over 300,000 sheets could be secured by executing the control of the present embodiment.

  If the temperature of the pressure roller 2 is lower than 140 ° C. and the same control as that at 160 ° C. or higher is performed, the temperature at the end of the sheet passing area of the fixing belt 1 is changed as shown in FIG. I'll be drunk. This is because the amount of heat transferred from the non-sheet passing portion to the end of the sheet passing region is reduced by narrowing the heat generation width before the non-sheet passing portion temperature exceeds the predetermined temperature. For this reason, it is extremely important to accurately grasp the heat storage state of the pressure roller 2 and to move the magnetic flux shielding member 11 at an appropriate timing.

  As described above, the control unit 102 as the control unit sets the movement timing of the magnetic flux shielding member 11 later as the temperature detected by the temperature detection sensor TH2 when the fixing belt 1 reaches the target temperature is lower. Further, the control unit 102 increases the movement amount of the magnetic flux shielding member 11 in accordance with the increase in the number of sheets of the recording material P to be passed.

  Thus, in the present embodiment, the non-contact temperature detection sensor TH2 is used to measure the surface temperature of the pressure roller 2 (see FIG. 2). By using such a non-contact temperature detection sensor TH2, the surface of the pressure roller 2 is not scratched or scraped, leading to a long life. A thermopile can be used as the non-contact temperature detection sensor TH2. The temperature information detected by the temperature detection sensor TH2 is fed back to the control unit 102.

  In the present embodiment, the temperature of the pressure roller 2 is detected while having a simple configuration for detecting the temperature corresponding to the paper passing portion of the pressure roller (heat storage portion) 2 that stores the heat generated by the fixing belt 1. Based on this, it is possible to appropriately set the movement timing for moving the magnetic flux shielding member 11 to the paper portion side. As a result, the temperature rise of the non-sheet passing portion at the end of the recording material in the heating region can be reliably reduced, and the durability of the fixing belt 1 can be improved.

  In the present embodiment, the movement of the magnetic cores 7a and 7b and the movement of the magnetic flux shielding member 11 are executed by controlling the motor M as a single drive source, and the regulating member 73 and the like. Since it is not necessary to enlarge the component parts in the longitudinal direction, the configuration is not complicated. Thereby, it is possible to avoid the non-sheet passing portion temperature rise corresponding to various types of recording material sizes with a space-saving configuration. In the present embodiment, the heat storage temperature detection means detects the pressure roller temperature corresponding to the sheet passing portion, but is not intended to be limited to this configuration. The heat storage temperature detecting means may be configured to detect the pressure roller temperature corresponding to the non-sheet passing portion.

<Second Embodiment>
Next, with reference to FIGS. 22A, 22B, 23, 24, and 25, a second embodiment in which the configuration is partially changed will be described. In addition, the same code | symbol is attached | subjected to the component which is common in 1st Embodiment mentioned above, and the description is abbreviate | omitted.

  In the present embodiment, the predetermined number of switching of the position detection sensor 89 is determined mainly based on the position detection sensor 89 and the plurality of flag portions 73d. Thereby, suppression of non-sheet passing portion temperature rise is executed. That is, on one of the pair of regulating members 73, a position detection sensor 89 made of a photo interrupter is disposed in the vicinity of the home position sensor 81 of the first embodiment. Further, the one restricting member 73 includes a plurality of comb-like flag portions 73d that sequentially pass through the position detection sensor 89 at the same pitch as the restricting member 73 moves, in addition to the flag portion 73a with respect to the flag portion 73a. Is formed.

  As shown in FIG. 23, the control unit 102 is connected to an operation unit installed in the image forming apparatus 15, reads a signal from the recording material size input unit 111 in the computer, and detects a signal from the home position sensor 81 and position detection. The motor M is controlled based on the signal from the sensor 89.

  Next, with reference to FIG. 24, the flow during operation in the present embodiment will be described. First, when a print job is started, in step S41, the control unit (CPU) 102 reads the input value of the recording material size from the signal of the recording material size input unit 111. Then, a predetermined switching number C2 of the position detection sensor 89 is determined by calculation of the control unit 102 in accordance with the input value of the recording material size (S42).

  In steps S43 and S45, the motor M is rotated so that the regulating member 73 is moved in the direction of arrow Y2 in FIG. 22 until the home position sensor 81 is turned on. When the home position sensor 81 is turned on and is in the home position in step S43, the motor M is rotated so as to move the regulating member 73 in the Y1 direction in step S44.

  Subsequently, the control unit 102 reads the input signal of the home position sensor 81 (S46), and determines that the regulating member 73 is not located at the home position when the control unit 102 is turned off. In this case, the regulating member 73 is close to the center side in the width direction (conveyance width direction) orthogonal to the recording material conveyance direction. Therefore, in order to rotate the motor M so as to move the regulating member 73 in the direction of the arrow Y2, the regulating member 73 is moved by the predetermined switching number C2 of the position detection sensor 89 determined in step S42 (S47). Thereby, the movement operation | movement of the magnetic body cores 7a and 7b is complete | finished.

  Subsequently, in step S48, paper feeding is started. FIG. 25A shows an initial state when the paper is passed. Further, in step S49, it is determined whether or not the predetermined number of continuous sheets has been reached. If so, the process proceeds to step S50. In step S50, as shown in FIG. 25 (b), the position detection sensor 89 performs reference taking while moving the regulating member 73. Then, the motor M is moved by a predetermined number of pulses C3, and the magnetic flux shielding member 11 is moved to the paper portion side by a predetermined amount (S51).

  Also according to this embodiment, substantially the same effect as that of the first embodiment can be obtained.

<Third Embodiment>
In the first and second embodiments described above, the temperature increase of the non-sheet passing portion is controlled based on the temperature of the pressure roller 2, but in this embodiment, the temperature of the pressure applying member 3 as the heat storage portion is detected. Based on this, the movement timing of the magnetic flux shielding member 11 is controlled to reduce the temperature rise of the non-sheet passing portion. 26 and 27 are explanatory diagrams in the present embodiment. Constituent parts common to the first and second embodiments described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 26, in order to measure the temperature of the pressure applying member 3 as a heat storage unit, a contact thermistor or the like is provided on the surface opposite to the surface facing the pressure roller 2 of the pressure applying member 3. A temperature detection sensor TH3 is disposed as a heat storage temperature detection means.

  Therefore, in this embodiment, the temperature of the pressure applying member 3 when the fixing belt 1 reaches the target temperature is detected, and the amount of movement of the magnetic flux shielding member 11 in the number of sheets to be passed is shown in FIG. Go to the table to show reading.

  As shown in FIG. 27, the movement timing of the magnetic flux shielding member 11 in this embodiment is determined in advance as a table table together with the movement amount of the magnetic flux shielding member 11 in the number of sheets to be passed.

In the table shown in FIG. 27, the temperature of the pressure applying member 3 when the target temperature of the fixing belt 1 is reached,
(I) Pressure applying member temperature <50 ° C
(Ii) 50 ° C. ≦ pressure applying member temperature <120 ° C.
(Iii) 120 ° C. ≦ pressure applying member temperature <160 ° C.
(Iv) Four patterns are formed as 160 ° C. ≦ pressure applying member temperature.

  Then, the number of sheets to be passed for each pattern and the insertion amount of the copper plate (magnetic flux shielding member 11) are set as different numbers.

That is, (i) when the pressure applying member temperature <50 ° C.,
(A) When the number of sheets passed is 10, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(B) When the number of sheets to be passed is 100, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(C) When the number of sheets to be passed is 300, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(D) When the number of sheets to be passed is 600, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

In the case of (ii) 50 ° C. ≦ pressure applying member temperature <120 ° C.
(E) When the number of sheets to be passed is 8, the magnetic flux shielding member 11 is moved in a direction to narrow the heat generation width by 3 mm on one side.
(F) When the number of sheets to be passed is 30, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(G) When the number of passing sheets is 100, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(H) When the number of sheets to be passed is 200, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

Furthermore, (iii) when 120 ° C. ≦ pressure applying member temperature <160 ° C.
(I) When the number of sheets to be passed is 6, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(J) When the number of sheets to be passed is 20, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(K) When the number of sheets to be passed is 50, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(L) When the number of sheets to be passed is 100, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

In the case of (iv) 160 ° C. ≦ pressure applying member temperature,
(M) When the number of sheets to be passed is 5, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 3 mm on one side.
(N) When the number of sheets to be passed is 10, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 6 mm on one side.
(O) When the number of sheets to be passed is 20, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 9 mm on one side.
(P) When the number of sheets to be passed is 30, the magnetic flux shielding member 11 is moved in the direction of narrowing the heat generation width by 12 mm on one side.

  According to this embodiment as described above, substantially the same effect as that of the first embodiment can be obtained. In other words, the heat storage state of the system including the pressure applying member 3 is determined and the movement timing of the magnetic flux shielding member 11 is controlled to prevent the temperature rise of the non-sheet passing portion of the fixing belt 1 from exceeding the durable breakdown temperature. , Durability life can be improved.

  Furthermore, in the present embodiment, the lower the temperature detected by the temperature detection sensor TH3 when the control unit 102 as the control means reaches the target temperature, the later the movement timing of the magnetic flux shielding member 11 is set. can do. Further, the control unit 102 can increase the movement amount of the magnetic flux shielding member 11 in accordance with an increase in the number of sheets of the recording material P to be passed.

  In addition, as a heat storage part which is a judgment material of a heat storage state, it can replace by not only the pressure roller 2 and the pressure provision member 3 which were mentioned above but detecting the temperature of the stay 4 grade | etc.,.

  DESCRIPTION OF SYMBOLS 1 ... Heating rotary body (fixing belt), 2 ... Heat storage part, nip formation member (pressure roller), 3 ... Heat storage part, contact member (pressure application member), 15 ... Image forming apparatus, 16 ... Image heating apparatus ( Fixing device), 11 ... Magnetic flux shielding member, 71 ... Heating area setting means (core moving mechanism), 100 ... Induction heating device, 102 ... Control means (control part), N ... Heating nip part (fixing nip part), P ... Recording material, PY, PC, PM, PK ... image forming unit, TH1 ... heating temperature detection means (temperature detection sensor), TH2, TH3 ... heat storage temperature detection means (temperature detection sensor)

Claims (6)

Induction for induction heating of the heating rotator by variably setting a heating area of the heating rotator that contacts and heats the recording material, and induction heating by the heating rotator in the conveyance width direction orthogonal to the recording material conveyance direction. In an image heating apparatus comprising a heating device,
Having a heat storage temperature detecting means for detecting a temperature in a heat storage section where heat generated by the heating rotating body is stored;
The induction heating device includes:
A heating area setting means for changing the magnetic flux density distribution along the conveyance width direction of the magnetic flux incident on the heating rotating body, and setting the heating area according to the length of the recording material in the conveyance width direction;
A magnetic flux shielding member that is disposed closer to the non-sheet passing portion side of the recording material than the heating region set by the heating region setting means and is movable to the sheet passing portion side;
Control means for setting a movement timing for moving the magnetic flux shielding member to the paper passing part side based on a temperature detected by the heat storage temperature detecting means and reducing a non-paper passing part temperature rise;
An image heating apparatus. A nip forming member that contacts the heating rotator to form a heating nip portion of the recording material;
The nip forming member is the heat storage part.
The image heating apparatus according to claim 1. A nip forming member that contacts the heating rotator to form a heating nip portion of the recording material;
An abutting member disposed in the heating rotator and abutting against an inner surface of the heating rotator so as to form the heating nip portion;
The contact member is the heat storage unit,
The image heating apparatus according to claim 1. Having a heating temperature detecting means for detecting the temperature in the heating rotating body;
The control means includes
The lower the temperature detected by the heat storage temperature detection means when the heating rotator reaches the target temperature, the slower the movement timing of the magnetic flux shielding member is set.
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. The control means includes
Increasing the amount of movement of the magnetic flux shielding member in accordance with an increase in the number of sheets of recording material passed,
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. An image forming apparatus comprising: an image forming unit that forms a toner image on a recording material; and a fixing device that fixes the toner image formed on the recording material by the image forming unit to the recording material.
The image fixing device according to claim 1, wherein the fixing device is an image heating device according to claim 1.
An image forming apparatus.

Images