JP2014052454A - Image heating device - Google Patents

Abstract

Even when a large-sized recording material is designed to be capable of heat treatment using a magnetic flux shielding plate having a long length in the rotational axis direction, image formation is performed while keeping the length in the rotational axis direction of the heating rotator short. An image heating apparatus capable of avoiding an increase in size of the apparatus or the like is provided.
An upper portion of an elliptical abutting surface of a fixing flange is lowered so that only a protruding portion of a magnetic flux shielding member can pass. For this reason, the magnetic flux shielding member 11 moves to the outer side in the rotation axis direction from the position where the fixing flange 10 regulates the end of the fixing belt 1, and the fixing belt by the magnetic flux is moved to the center side in the rotation axis direction of the fixing belt 1. The uniform heating range of 1 can be formed widely.
[Selection] Figure 2

Description

  The present invention relates to an image heating apparatus of an induction heating method in which both ends of a heating rotator are regulated in the rotation axis direction by a non-rotation regulating part, and more specifically, for suppressing a temperature rise in a non-sheet passing part of the heating rotator. The present invention relates to a structure for extending a moving range of a magnetic flux shielding member.

  A toner image is formed on an image carrier and transferred to a recording material directly or via an intermediate transfer member, and the recording material onto which the toner image has been transferred is heated and pressed at a nip portion of a fixing device which is an example of an image heating device. Therefore, an image forming apparatus that fixes an image on a recording material is widely used. A pressure rotator (belt member or roller member) is pressed against the heating rotator to form a nip portion of the recording material. An induction heating device is arranged opposite the heating rotator provided with a metal layer, and induction heating is performed by alternating magnetic flux. Inductive heating type image heating apparatuses have been put into practical use. In the image heating apparatus of the induction heating method, since large heating by the induction heating apparatus concentrates on the heating rotator with a small mass, a temperature rise in a region not in contact with the recording material at both ends in the width direction of the heating rotator, so-called non-transmission. The temperature rise of the paper section becomes a problem (Patent Document 1).

  Patent Document 2 discloses an image heating apparatus of a belt induction heating system that heats a belt member using an induction heating apparatus. Then, a large number of magnetic cores movable in the contact / separation direction with respect to the belt member and a pair of magnetic flux shielding plates movable in the rotation axis direction of the belt member are controlled so that the temperature of the non-sheet passing portion is increased. The magnetic flux incident on the end region of the belt member located outside is reduced.

JP 2001-194940 A JP2012-128312A

  As shown in Patent Document 2, when adjusting the induction heating range of the heating rotator by moving the pair of magnetic flux shielding plates in the rotation axis direction of the heating rotator, the end of the heating rotator is restricted in the rotation axis direction. The restricting portion to be a restriction of the moving range of the pair of magnetic flux shielding plates. The distance between the inner edges of the pair of magnetic flux shielding plates with the outer edges of the pair of magnetic flux shielding plates abutting against the regulating portion is the maximum range in which the magnetic flux can be incident and heated in the heating rotor. Because it becomes.

  Therefore, when designing an image heating apparatus that can heat-treat a recording material having a length of 400 mm in the rotation axis direction using a pair of magnetic flux shielding plates having a length in the rotation axis direction of 30 mm, the required length of the heating rotator is 460 mm.

  However, as shown in Patent Document 2, even when the induction heating range of the belt member can be set finely by controlling a pair of movable magnetic flux shielding plates, uniform heating is applied to both ends in the width direction of the recording material. Therefore, it is necessary to apply heat to the outside of the recording material. Necessary for heating the toner image due to a delay in the rise of the temperature of the heating member in contact with both ends of the width of the recording material in the heat treatment of the first and second recording materials before the temperature rise at the non-sheet passing portion. This is because it may not reach a certain temperature.

  Therefore, the required length of the heating rotator is further increased to reach nearly 500 mm, and the image heating apparatus is increased in size. When a magnetic flux shielding plate having a long length in the rotation axis direction is used, the length of the required heating rotating body is further increased, and the image heating apparatus is further increased in size. Increasing the size of the image heating device is not preferable against energy saving, resource saving, and saving installation space.

  The present invention maintains the length of the heating rotator in the direction of the rotational axis while keeping the length of the heating rotator short even if the magnetic shielding plate having a long length in the direction of the rotational axis is used to allow heat treatment of a large size recording material. An object of the present invention is to provide an image heating apparatus capable of avoiding an increase in size of a forming apparatus or the like.

  An image heating apparatus according to the present invention includes a heating rotator that is heated by incidence of an alternating magnetic flux, a regulating portion that is arranged non-rotatingly and restricts an end portion of the heating rotator in a rotation axis direction, and the heating rotator. An induction heating means that is arranged oppositely to generate an alternating magnetic flux, a magnetic flux shielding member that is arranged to be movable in the direction of the rotation axis of the heating rotator between the heating rotator and the induction heating means, and the magnetic flux shielding And a moving mechanism capable of adjusting the heating range in the rotation axis direction of the heating rotator by moving the member. The moving mechanism can move the magnetic flux shielding member to the outside in the rotation axis direction from the position where the restricting portion restricts the end of the heating rotator, and the restricting portion includes the restricting portion. It has an external shape that does not interfere with the magnetic flux shielding member that moves outward in the rotational axis direction from the position where the end of the heating rotator is regulated.

  In the image heating apparatus of the present invention, the outer shape is rotated more than the position where the end of the heating rotator is regulated while the regulating portion as a whole retains the function of regulating the end of the heating rotator in the rotation axis direction. It does not interfere with the magnetic flux shielding member that moves outward in the axial direction. The magnetic flux shielding member can move outward in the rotation axis direction from the position where the end of the heating rotator is regulated without being obstructed by the regulating part. Therefore, even if the magnetic shielding plate having a long length in the rotation axis direction is used and heat treatment of a large size recording material is designed, the length of the heating rotator in the rotation axis direction can be kept short. Etc. can be avoided.

1 is an explanatory diagram of a configuration of an image forming apparatus. FIG. 3 is an explanatory diagram of a cross-sectional configuration perpendicular to the rotation axis of the fixing device. 3 is an explanatory diagram of a cross-sectional structure of a fixing belt. FIG. FIG. 4 is an explanatory diagram of a vertical cross-sectional configuration parallel to the rotation axis direction of the fixing device. It is explanatory drawing of arrangement | positioning of an outer side magnetic body core. It is explanatory drawing of a movement of an outer side magnetic body core. It is explanatory drawing of a movement of a magnetic flux shielding member. It is explanatory drawing of the effect of a movement of a magnetic flux shielding member. It is a block diagram of heating control of the fixing belt. 5 is a flowchart of fixing belt heating control. 6 is an explanatory diagram of a heat treatment of a maximum size recording material in Example 1. FIG. 3 is an explanatory diagram of a heat treatment of a small size recording material in Example 1. FIG. 6 is an explanatory diagram of a heat treatment of a maximum size recording material in Comparative Example 1. FIG. 10 is an explanatory diagram of a heat treatment of a maximum size recording material in Comparative Example 2. FIG. 10 is an explanatory diagram of a heat treatment of a small size recording material in Comparative Example 2. FIG. FIG. 10 is an explanatory diagram of a relationship between a magnetic flux shielding member and a fixing flange in Embodiment 2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, as long as the magnetic flux shielding member can move beyond the restricting portion that restricts the heating rotator in the rotation axis direction, a part or all of the configuration of the embodiment is replaced with the alternative configuration. This embodiment can also be implemented.

  Accordingly, the image heating apparatus heats the recording material to which the toner image has been transferred to fix the toner image on the recording material, and also heats the semi-fixed or fixed toner image to a desired image. It includes an image heating device that imparts surface properties. The heating rotator and the pressure rotator are not limited to the belt member, and may be roller members.

  The image forming apparatus can be mounted 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 method, and transfer method. 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.

(1) Example of Image Forming Apparatus FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 200 is a tandem intermediate transfer type full-color printer in which yellow, magenta, cyan, and black image forming portions PY, PM, PC, and PK are arranged along an intermediate transfer belt 26. is there.

  In the image forming unit PY, a yellow toner image is formed on the photosensitive drum 21 (Y) and transferred to the intermediate transfer belt 26. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 21 (M) and transferred to the intermediate transfer belt 26. In the image forming units PC and PK, a cyan toner image and a black toner image are formed on the photosensitive drums 21 (C) and 21 (K), respectively, and transferred to the intermediate transfer belt 26.

  The intermediate transfer belt 26 is composed of an endless resin belt, is stretched around a driving roller 27, a secondary transfer counter roller 28, and a tension roller 29, and is driven by the driving roller 27. The recording material P is taken out from the recording material cassette 31 one by one by the paper feed roller 32 and waits at the registration roller 33. The recording material P is fed to the secondary transfer portion T2 by the registration roller 33, and the toner image is transferred from the intermediate transfer belt 26 in the process of being conveyed through the secondary transfer portion T2. The recording material P to which the four color toner images have been transferred is conveyed to the fixing device A, and is heated and pressed by the fixing device A to fix the toner image on the surface. The recording material on which the image is fixed is discharged to the external tray 37 through the discharge conveyance path 36.

  The image forming units PY, PM, PC, and PK are different except that the toner colors used in the developing devices 23 (Y), 23 (M), 23 (C), and 23 (K) are different from yellow, magenta, cyan, and black. The configuration is substantially the same. In the following, the image forming unit PY will be described, and redundant description regarding the image forming units PM, PC, and PK will be omitted.

  In the image forming unit PY, a charging roller 22, an exposure device 25, a developing device 23, a transfer roller 30, and a drum cleaning device 24 are arranged around the photosensitive drum 21. The charging roller 22 charges the surface of the photosensitive drum 21 to a uniform potential. The exposure device 25 scans the laser beam and writes an electrostatic image of the image on the photosensitive drum 21. The developing device 23 supplies toner to the electrostatic image and develops the toner image on the photosensitive drum 21. The transfer roller 30 is applied with a DC voltage to transfer the toner image on the photosensitive drum 21 to the intermediate transfer belt 26.

<Example 1>
(2) Image Heating Device Example FIG. 2 is an explanatory diagram of a cross-sectional configuration perpendicular to the rotation axis of the fixing device. FIG. 3 is an explanatory diagram of a cross-sectional structure of the fixing belt. FIG. 4 is an explanatory diagram of a vertical cross-sectional configuration parallel to the rotation axis direction of the fixing device. FIG. 5 is an explanatory view of the arrangement of the outer magnetic core. In the following description, regarding the fixing device and the members constituting the fixing device, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material, and the length is a dimension in the longitudinal direction. The short direction is a direction parallel to the recording material conveyance direction on the surface of the recording material, and the width is a dimension in the short direction.

  As shown in FIG. 2, during the heat treatment of the recording material, the control unit 150 operates the fixing motor 104 to rotationally drive the pressure roller 2. The fixing belt 1 is driven to rotate by the pressure roller 2 and is driven to rotate at a circumferential speed substantially the same as the conveyance speed of the recording material P carrying the unfixed toner image T. Here, the surface rotation speed of the fixing belt 1 is set to 300 mm / sec, and an A4 size laterally fed full-color image can be fixed on 80 plain papers per minute. In the case of A4 size vertical feeding, fixing processing can be performed on 58 sheets of plain paper.

  During the heat treatment of the recording material, the recording material P having the unfixed toner image T is introduced into the nip portion N in a state where the temperature of the fixing belt 1 is adjusted to a predetermined fixing temperature. The toner image carrying surface of the recording material P is brought into close contact with the outer peripheral surface of the fixing belt 1 and is nipped and conveyed together with the fixing belt 1 through the nip portion N. As a result, heat is applied to the fixing belt 1, and the unfixed toner image T is fixed to the surface of the recording material P by receiving pressure from the nip portion N. The recording material P that has passed through the nip N is separated from the fixing belt 1 by the curvature and is conveyed from the fixing device A to the outside.

  The fixing belt 1 is a cylindrical endless belt having a longitudinal length of 390 mm, an inner diameter of 30 mm, and a thickness of 360 μm. The fixing belt 1 has a metal layer for enabling induction heating.

  As shown in FIG. 3, the base layer 1 a is a nickel metal layer manufactured by an electroforming method and has a thickness of 40 μm. In addition to nickel, an iron alloy, copper, silver, or the like can be appropriately selected for the metal layer. The metal layer may be formed by laminating a metal on the resin base layer. The thickness of the metal layer needs to be adjusted according to the frequency of the high-frequency current flowing through the exciting coil 6 and the permeability / conductivity of the metal layer. The thickness of the metal layer is preferably set between about 5 and 200 μm.

  The elastic layer 1b is a heat-resistant silicon rubber layer provided on the outer periphery of the base layer 1a. The silicon rubber layer has a hardness of JIS-A 20 degrees and a thermal conductivity of 0.8 W / mK. The thickness of the silicon rubber layer is preferably set within a range of 100 to 1000 μm. Here, 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, the thickness of the silicon rubber layer is set to 300 μm.

  The surface release layer 1c is a fluororesin layer (for example, PFA or PTFE) provided on the outer periphery of the elastic layer 1b, and has a thickness of 30 μm here. The resin layer 1d is a slippery layer such as a fluororesin or polyimide provided on the inner surface side of the base layer 1a. Here, the resin layer 1d is polyimide having a thickness of 20 μm. The resin layer 1d preferably has a thickness of 10 to 50 μm in order to reduce sliding friction between the inner surface of the fixing belt and the temperature sensor TH1.

  The pressure roller 2 is disposed in contact with the outer periphery of the fixing belt 1. The pressure roller 2 has a cylindrical shape with an outer diameter of 30 mm and a length in the longitudinal direction of 350 mm, and forms a nip portion N with the fixing belt 1. The hardness at the center in the longitudinal direction of the pressure roller 2 is ASK-C70 ° C. The pressure roller 2 is provided with an elastic layer 2b of a silicon rubber layer on the peripheral surface of an iron alloy cored bar 2a, and the outer peripheral surface of the elastic layer 2b is covered with a release layer 2c of a fluororesin layer (for example, PFA or PTFE). ing. The cored bar 2a has a diameter of 20 mm in the center in the longitudinal direction so that the pressure distribution in the longitudinal direction of the nip portion N between the fixing belt 1 and the pressure roller 2 is uniform even when the pressing member 3 is bent during pressing. The diameter of both ends is 19 mm. The elastic layer 2b has a thickness of 5 mm, and the release layer 2c has a thickness of 30 μm. In order to make the conveyance speed at both ends of the recording material P faster than that at the central portion and to prevent the occurrence of paper wrinkles, the width of the nip portion N in the rotational direction is the width at both ends in the longitudinal direction when the nip pressure is 600N. About 9 mm and about 8.5 mm in the center.

  As shown in FIG. 4, the support side plate 12 supports the pressure roller 2 in a rotatable manner while holding the fixing flange 10 in a non-rotatable manner and capable of slight vertical movement. The flange surface 10 b of the fixing flange 10 regulates the position of the fixing belt 1 in the longitudinal direction. The fixing flange 10 is a right and left restricting member that restricts the longitudinal movement and the circumferential shape of the fixing belt 1. Since the base layer of the fixing belt 1 is made of metal, a fixing flange 10 that simply receives the end of the fixing belt 1 as a means for restricting the shift in the width direction even when the fixing belt 1 is in a rotating state. Is sufficient.

  Both ends of the stay 4 are disposed through the fixing flange 10. The stay 4 applies pressure evenly to the pressure applying member 3 along the longitudinal direction of the nip portion. The stay 4 is made of iron because it needs rigidity. Since the stay 4 is close to the exciting coil 6, a magnetic shielding core 5 is arranged on the upper surface of the stay 4 in the longitudinal direction so as to shield the magnetic field generated by the exciting coil 6 to avoid induction heating of the stay 4. Yes. The magnetic shielding core 5 is a magnetic shielding member for preventing temperature rise due to induction heating of the stay 4.

  The stay pressurizing spring 9b is contracted between both ends of the stay 4 and the stay-side spring receiving member 9a on the chassis side of the fixing device A, and applies a pressing force to both ends of the stay 4 to apply pressure. The nip portion N between the fixing belt 1 and the pressure roller 2 supported by the member 3 is pressurized. The pressure applying member 3 is formed of a heat resistant resin and is held by a metal stay 4. The pressure applying member 3 applies a pressing force to the pressure roller 2 via the fixing belt 1 to pressurize the nip portion N, and applies a pressing force to the fixing belt 1 and the pressure roller 2. The nip portion N is formed.

  The contact / separation mechanism 105 shown in FIG. 2 can release the urging force of the stay pressurizing spring 9b against the stay 4 by rotating a cam (not shown) to release the pressurization of the nip portion N. When the fixing device A is stopped, the pressure of the nip portion N is released to prevent the elastic layer of the pressure roller 2 and the fixing belt 1 from being permanently deformed.

  As shown in FIG. 2, the induction heating device 100 is a heating source for induction heating the fixing belt 1. 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 fixing belt 1 and the exciting coil 6 of the induction heating device 100 are kept electrically insulated by a 0.5 mm mold. The distance between the mold surface and the fixing belt surface is 1.0 mm, and the distance between the fixing belt 1 and the exciting coil 6 is constant at 1.5 mm.

  As shown in FIG. 5, the exciting coil 6 uses, for example, a litz wire as an electric wire, and is wound so that the electric wire is horizontally long and has a bottom shape and faces a part of the peripheral surface and side surface of the fixing belt 1. The outer magnetic core 7 a covers the excitation coil 6 so that the magnetic field generated by the excitation coil 6 does not substantially leak to other than the metal layer (conductive layer) of the fixing belt 1. The outer magnetic core 7a is arranged side by side in a direction perpendicular to the recording material conveyance direction, and is configured to surround the winding center portion and the periphery of the exciting coil 6. The outer magnetic core 7a is arranged for increasing the efficiency of the magnetic circuit of the exciting coil 6 and for magnetic shielding, and efficiently guides the alternating magnetic flux generated from the exciting coil 6 to the fixing belt 1. The outer magnetic core 7a is made of a material having a high magnetic permeability and a low residual magnetic flux density such as ferrite. The mold member 7c supports the exciting coil 6 and the outer magnetic core 7a with an electrically insulating resin.

  As shown in FIG. 2, the temperature sensor TH <b> 1 is a temperature detection element such as a thermistor, and detects the temperature of the fixing belt 1 in contact with the inner surface of the central portion in the longitudinal direction of the fixing belt 1. Since the temperature sensor TH1 is attached to the pressure applying member 3 via an elastic support member, even if a positional variation such as the contact surface of the fixing belt 1 undulates, a good contact state follows the positional variation. To maintain.

  The power supply device 101 applies a high frequency current of 20 kHz to 50 kHz to the exciting coil 6 while the fixing belt 1 is rotating during the heat treatment of the recording material. The alternating magnetic field generated by the exciting coil 6 to which the high-frequency current is applied generates an induction current in the metal layer (conductive layer) of the fixing belt 1 to induce heat generation in the fixing belt 1.

  The temperature control circuit 102 controls the induction heating device 100 based on the output of the temperature sensor TH1 so that the temperature of the central portion in the rotation axis direction of the fixing belt 1 maintains a predetermined temperature. The temperature control circuit 102 controls the electric power input to the exciting coil 6 by changing the frequency of the high-frequency current based on the detected value of the temperature sensor TH1 so that the detected temperature of the temperature sensor TH1 is constant at 180 ° C., for example. To do. When the temperature detected by the temperature sensor TH1 reaches, for example, 220 ° C., the temperature control circuit 102 cuts off the energization to the exciting coil 6.

  In the fixing device A, since the induction heating device 100 is disposed outside the fixing belt 1 instead of inside the fixing belt 1 that becomes high in temperature, the temperature of the exciting coil 6 is not easily increased. Therefore, the electrical resistance of the exciting coil 6 does not increase, and loss due to Joule heat generation can be reduced even when a high-frequency current is passed. Since the exciting coil 6 is arranged outside the fixing belt 1, it contributes to the reduction of the diameter and the heat capacity of the fixing belt 1, and the energy saving is improved. Since the warming-up time of the fixing device A has a very low heat capacity, when the power of 1500 W is input to the exciting coil 6, the surface temperature of the fixing belt 1 reaches the target temperature of 180 ° C. in about 15 seconds. For this reason, the heating operation during standby is not required, and the power consumption can be kept very low.

(3) Control of heating range of fixing belt FIG. 6 is an explanatory view of the movement of the outer magnetic core. FIG. 7 is an explanatory view of the movement of the magnetic flux shielding member. FIG. 8 is an explanatory diagram of the effect of movement of the magnetic flux shielding member. FIG. 9 is a block diagram of heating control of the fixing belt. FIG. 10 is a flowchart of fixing belt heating control.

  As shown in FIG. 5, the outer magnetic cores 7 a and 92 are arranged side by side in a direction orthogonal to the recording material conveyance direction, and are configured to surround the winding center portion and the periphery of the exciting coil 6. The outer magnetic core 7a is a core located in the region E of the sheet passing end, and can be moved by the core moving mechanism 106 shown in FIG. On the other hand, the outer magnetic core 92 is a core located in the region D at the center of paper passing, and is fixed to the housing of the induction heating device 100.

  In the region E, the outer magnetic core 7a is arranged in the longitudinal direction so that the recording material of various sizes up to various recording material sizes, for example, postcards, A5, B4, A4, and A3 It is divided into multiple parts. The area D is a paper passing area corresponding to the paper width of the small size recording material, and the total length of the area D and the area E combined corresponds to the paper width of the large size recording material (A3 Nobi size). It has become.

  As shown in FIG. 4, the width of the outer magnetic core 7 a is 10 mm, and two of the outer magnetic cores 7 a are combined into one movement unit. The moving unit of the outer magnetic core 7a is preferably wide in order to reduce the number of components. The outer magnetic body core 7a is moved up and down with an amplitude of 15 mm by a core moving mechanism 106 using a cam row whose phases are gradually changed.

  The control unit 150 operates the core moving mechanism 106 according to the size of the recording material to be heat-treated, and either the position close to the excitation coil 6 or the position far from the excitation coil 6 for each moving unit of the outer magnetic core 7a. Set The controller 150 discriminates the type of the recording material and moves the outer magnetic core 7a located in the non-sheet passing area in a direction away from the exciting coil 6. By moving the outer magnetic core 7a corresponding to the size of the recording material, the temperature rise of the non-sheet passing portion is suppressed. The effect of moving the outer magnetic core 7 a is to adjust the heat generation amount in a wide range in the longitudinal direction of the fixing belt 1.

  As shown in FIG. 6A, the outer magnetic core 7a moves in the direction approaching the excitation coil 6 in the sheet passing region of the recording material to increase the magnetic flux density incident on the fixing belt 1. As shown in FIG. 6B, the outer magnetic core 7a moves away from the exciting coil 6 in the non-sheet passing region of the recording material, and the gap between the exciting coil 6 and the outer magnetic core 7a is increased. The magnetic flux density that spreads and enters the fixing belt 1 is reduced, and the heat generation amount of the fixing belt 1 is reduced.

  As shown in FIG. 4, since the outer magnetic core 7a has a set of two moving units, a magnetic flux is incident on the fixing belt 1 in the non-sheet passing portion in a range of maximum 10 mm × 2 = 20 mm. There is a possibility that the temperature rise in the non-sheet passing portion may occur. Therefore, in the first embodiment, the magnetic flux shielding member 11 is provided so that the range in which the magnetic flux enters the fixing belt 1 can be finely adjusted. The drive mechanism 107 moves the magnetic flux shielding member 11 to a position corresponding to the size of the recording material to be passed. The effect of moving the magnetic flux shielding member 11 is to control the heat generation distribution in the longitudinal direction of the fixing belt 1 more finely than the moving unit width of the outer magnetic core 7a.

  The pair of magnetic flux shielding members 11 is maintained in the longitudinal direction of the fixing belt 1 while maintaining a symmetrical positional relationship in the longitudinal direction of the fixing belt 1 by a drive mechanism 107 using a resin lead screw mechanism arranged in parallel with the fixing belt 1. Moving. The magnetic flux shielding member 11 has a greater effect of weakening the magnetic flux incident on the fixing belt 1 than the movement of the outer magnetic core 7a, and moves in conjunction with the moving mechanism of the outer magnetic core 7a. The longitudinal heat generation distribution can be controlled more finely than the division width of the core 7a.

  As shown in FIG. 7A, the magnetic flux shielding member 11 is disposed between the exciting coil 6 and the fixing belt 1 at both ends in the longitudinal direction of the fixing belt 1. The magnetic flux shielding member 11 is a copper plate, and the thickness of the copper plate is set to 0.5 mm in consideration of the skin depth at 20 kHz to 50 kHz. The magnetic flux shielding member 11 may be 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.

  As shown in FIG. 7B, in FIG. 7A, when the induction heating device 100 is removed and viewed from the A direction, the width of the magnetic flux shielding member 11 in the direction intersecting the recording material conveyance direction is 20 mm. The width is set to 20 mm in consideration of having a sufficient width to exhibit the magnetic flux shielding effect, not reducing the maximum heat generation width corresponding to the maximum size recording material, and not increasing the width in the longitudinal direction of the fixing device A. . The magnetic flux shielding member 11 has a protruding portion 11a that partially protrudes outward in the longitudinal direction. The width in the longitudinal direction of the magnetic flux shielding member 11 including the protruding portion 11a is 23 mm, which is wider than the moving unit of the outer magnetic core 7a.

  As shown in FIG. 8A, the outer magnetic core 7 a is positioned closer to the exciting coil 6 on the center side than the end surface on the center side of the magnetic flux shielding member 11 in the longitudinal direction of the fixing belt 1. . As a result, a uniform temperature distribution with a uniform magnetic flux density is obtained in a region sandwiched between the pair of magnetic flux shielding members 11 in the longitudinal direction of the fixing belt 1.

  In the longitudinal direction of the fixing belt 1, the outer magnetic core 7 a is positioned so as to move away from the exciting coil 6 outside the outer end face of the magnetic flux shielding member 11. As a result, the heat generation amount can be efficiently reduced in the region outside the pair of magnetic flux shielding members 11 in the longitudinal direction of the fixing belt 1.

As shown in FIG. 8 (a), 500 sheets of A4 size plain paper having a basis weight of 105 [g / m ² ] in a 15 ° C. environment are fed at a productivity of 80 sheets per minute by lateral feed. The temperature rise at the non-sheet passing portion was measured. The target temperature for temperature adjustment in the experiment is 180 ° C. at the center of the fixing belt 1. The design upper limit temperature of the fixing belt 1 is 230 ° C. on the inner surface of the fixing belt 1.

  The four outer magnetic cores 7a outside the recording material are raised with respect to the recording material P of A4 size lateral feed, and the lowered outer magnetic core 7a located outside the recording material P and the fixing belt 1 The magnetic flux shielding member 11 was positioned between and stopped.

  As indicated by a dotted line in FIG. 8B, the magnetic flux incident on the fixing belt 1 in the non-sheet passing region is limited by the magnetic flux shielding effect of the magnetic flux shielding member 11, and thus the temperature rise of the non-sheet passing portion is suppressed. The temperature of the non-sheet passing portion of the fixing belt 1 did not reach the designed upper limit temperature.

  As shown by a solid line in FIG. 8B, when the same experiment was performed by moving the magnetic flux shielding member 11 to the outermost position in the longitudinal direction, the non-sheet passing portion temperature of the fixing belt 1 was The maximum temperature has been exceeded. This is because the magnetic flux emitted from one lowered outer magnetic core 7a located outside the recording material P is incident on the fixing belt 1 and the temperature rise of the non-sheet passing portion has greatly advanced.

  As shown in FIG. 9 with reference to FIG. 4, the control unit 150 controls the operation of the image forming apparatus 200. The control unit 150 reads the signals from the operation unit 202 of the image forming apparatus 200 and the recording size input unit 201 such as the recording material size detection unit in the recording material cassette 31, and then the size of the recording material P to be heated next. The heating width of the fixing belt 1 corresponding to is determined. The controller 150 controls the core moving mechanism 106 to set up and down the outer magnetic core 7a, and controls the drive mechanism 107 to set the longitudinal position of the magnetic flux shielding member 11. The controller 150 sets the desired heating width according to the recording material size by interlocking the outer magnetic core 7a and the magnetic flux shielding member 11.

  As shown in FIG. 10 with reference to FIG. 9, when the power of the image forming apparatus 200 is turned on, the control unit 150 rotates the pressure roller 2 to rotate the fixing belt 1 to supply power to the power supply apparatus 101. Then, the fixing belt 1 is heated by the induction heating device 100 (S1001).

  When the temperature detected by the temperature sensor TH1 reaches 180 ° C. (Yes in S1002), the control unit 150 shifts to a standby standby state in which heating rotation is performed while maintaining 180 ° C. until a print job is started (S1003).

  When receiving a print job (Yes in S1004), the control unit 150 reads the recording material size input to the recording material size input unit 201 when a print signal is input. For example, A4 size, A4 vertical size, A5 size, postcard size, and the like.

  The control unit 150 controls the core moving mechanism 106 and the driving mechanism 107 to shift the outer magnetic core 7a up and down and the longitudinal position of the magnetic flux shielding member 11 to a state corresponding to the recording material size of the print job (S1005). ).

  When the print job is completed (Yes in S1006), the controller 150 stops the heating rotation of the fixing belt 1 (S1007) and shifts to the OFF state. Alternatively, the state shifts to a standby standby state in which heating rotation is performed while maintaining 180 ° C., and the next print job is waited.

(4) Experimental result of magnetic flux shielding member FIG. FIG. 12 is an explanatory diagram of the heat treatment of the small size recording material in the first embodiment. FIG. 13 is an explanatory diagram of the heat treatment of the maximum size recording material in Comparative Example 1. FIG. 14 is an explanatory diagram of the heat treatment of the maximum size recording material in Comparative Example 2. FIG. 15 is an explanatory diagram of the heat treatment of the small size recording material in Comparative Example 2.

  As shown in FIG. 2, the fixing belt 1, which is an example of a heating rotator, is heated with an alternating magnetic flux incident thereon. An induction heating device 100, which is an example of induction heating means, is arranged opposite to the fixing belt 1 to generate an alternating magnetic flux.

  As shown in FIG. 4, the fixing flange 10, which is an example of a restricting portion, is disposed non-rotatingly and restricts the end portion of the fixing belt 1 in the rotation axis direction. The abutting surface 10b of the fixing flange 10 is fixed to a cylindrical portion of the fixing flange 10 which is an example of a support member that guides the inner peripheral surface of the end portion of the fixing belt 1 and supports it rotatably.

  The magnetic flux shielding member 11, which is an example of the magnetic flux shielding member, is disposed so as to be movable in the rotation axis direction of the fixing belt 1 at the interval between the fixing belt 1 and the induction heating device 100. The drive mechanism 107, which is an example of a moving mechanism, can adjust the heating range in the rotation axis direction of the fixing belt 1 by moving the magnetic flux shielding member 11. The drive mechanism 107 moves the pair of magnetic flux shielding members 11 in conjunction with a screw mechanism in a boundary region at both ends of a region where the alternating magnetic flux density is high along the rotation axis direction of the fixing belt 1.

  In the induction heating apparatus 100, the length of the region where the alternating magnetic flux density is high along the rotation axis direction of the fixing belt 1 can be changed stepwise by the core moving mechanism 106. The length of the magnetic flux shielding member 11 along the rotational axis direction of the fixing belt 1 is slightly longer than the length of the change unit that changes the length of the region where the alternating magnetic flux density is high in a stepwise manner. The magnetic flux shielding member 11 has a length along the rotational axis direction of the fixing belt 1 that is twice the length of the change unit that changes the length of the alternating magnetic flux density region in the induction heating device 100 in a stepwise manner. Also short.

  As shown in FIG. 11B, the drive mechanism (107: FIG. 4) can move the magnetic flux shielding member 11 outward in the rotational axis direction from the position where the fixing flange 10 regulates the end of the fixing belt 1. It is. The fixing flange 10 has an external shape that does not interfere with the magnetic flux shielding member 11 that moves outward in the rotational axis direction from the position where the fixing flange 10 regulates the end of the fixing belt 1. As shown in FIG. 11A, the upper portion of the elliptical abutting surface 10b of the fixing flange 10 is lowered to allow the protruding portion 11a of the magnetic flux shielding member 11 to pass therethrough.

  The protrusion 11 a, which is an example of a portion on the end side along the fixing belt rotation axis direction in the magnetic flux shielding member 11, has a circumferential length which is an example of the length in the rotational direction of the fixing belt 1. 11 is shorter than the central portion along the fixing belt rotation axis direction. The elliptical abutting surface 10 b of the fixing flange 10 has an appearance shape that interferes with the central portion of the magnetic flux shielding member 11 but does not interfere with the end portion of the magnetic flux shielding member 11.

  For this reason, the protruding portion 11a of the magnetic flux shielding member 11 can pass outward through the lower upper position of the elliptical abutting surface 10b of the fixing flange 10. However, the central portion of the magnetic flux shielding member 11 along the rotation axis direction of the fixing belt 1 does not fall within the lower range of the elliptical abutting surface 10b of the fixing flange 10, and is thus restricted by the abutting surface 10b. .

  As shown in FIG. 4, since the fixing belt 1 is loosely inserted into the cylindrical portion of the fixing flange 10, the fixing belt 1 flutters during the rotation of the heat treatment. For this reason, the abutting surface 10b of the fixing flange 10 needs to be formed high so that the fixing belt 1 does not run over due to flapping during rotation.

  Although exaggerated in FIG. 4, in order to reduce the magnetic resistance of the magnetic circuit of the exciting coil 6, the distance between the fixing belt 1 and the exciting coil 6 is 1.5 mm (the distance between the mold surface and the fixing belt surface). Is 1.0 mm). Therefore, if the abutting surface 10b of the fixing flange 10 is formed high, the abutting surface 10b of the fixing flange 10 interferes with the magnetic flux shielding member 11, and the movement to the outside position beyond the abutting surface 10b is prevented.

  However, in the electromagnetic induction heating type fixing device A, it is desired to further increase the maximum possible sheet passing width in order to meet various market demands. In recent years, the size of the image forming apparatus 200 and the fixing device A has been further reduced, and the maximum size can be achieved without increasing the size of the apparatus and satisfying measures for increasing the temperature of the non-sheet-passing portion without countering space saving. It is desired to increase the width of paper passing.

  However, in the fixing device A, the end of the fixing belt 1 is regulated to shift the fixing belt 1 by using the abutting surface 10 b of the fixing flange 10, so that the magnetic flux shielding member 11 has a relationship with the fixing flange 10. The escape position is limited.

  Therefore, in the first embodiment, the abutting surface 10b of the fixing flange 10 is partially formed low, and the magnetic flux shielding member 11 can move outward beyond the abutting surface 10b without impairing the function of the abutting surface 10b. I did it. As a result, the length of the fixing device A having the fixing flange 10 is not increased, and the fixing device A is not enlarged. The temperature can be reduced.

  As shown in FIG. 7B, in the magnetic flux shielding member 11 of Example 1, the length in the longitudinal direction of the fixing belt 1 was 20 mm including the protruding portion 11a having a length of 8 mm. The protruding portion 11 a having a length of 8 mm has a circumferential length that covers 60 ° of the outer periphery of the fixing belt 1, and the remaining 12 mm of the inner portion 11 b has a circumferential length that covers 120 ° of the outer periphery of the fixing belt 1. did.

  As shown in FIG. 11B, the diameter of the abutting surface 10b of the fixing flange 10 is formed to be small so as to overlap the protruding portion 11a of the magnetic flux shielding member 11, and the inner portion 11b of the magnetic flux shielding member 11 abuts. The magnetic flux shielding member 11 can be moved outward until it hits the surface 10b.

  For this reason, when a recording material of A3 size (330 mm width), which is the maximum sheet passing size, is passed, the magnetic flux shielding member 11 moves outward to a position partially overlapping the fixing flange 10. The protruding portion 11a protrudes outward from the part of the fixing flange 10 in the longitudinal direction.

  As shown in FIG. 11C, when the magnetic flux shielding member 11 of Example 1 is used, the temperature drop at both ends of the recording material P having the maximum sheet passing size is not observed, and the image is caused by the temperature drop. It is possible to prevent the occurrence of defects.

As shown in FIG. 12 (a), 500 sheets of A4 size plain paper having a basis weight of 105 [g / m ² ] under an environmental condition of 15 ° C. are fed continuously at a productivity of 58 sheets per minute by vertical feed. Then, the fixing process was performed, and the temperature rise of the non-sheet passing portion of the fixing belt 1 was evaluated. The same process speed as in the case of productivity of 80 sheets per minute for A4 size side feed. The target temperature for adjusting the temperature of the fixing belt 1 is 180 ° C. at the center of the fixing belt 1, and the upper limit design temperature of the fixing belt 1 is 230 ° C. on the inner surface. In the case of the magnetic flux shielding member 11 according to the first embodiment, the magnetic flux of the two outer magnetic cores 7a, which are units of movement, can be sufficiently shielded in the A4 size longitudinally fed recording material P. For this reason, in the continuous heating process for the recording material P of A4 size longitudinally fed, a portion that exceeds the design upper limit temperature does not occur in the entire longitudinal direction of the fixing belt 1.

  Referring to FIG. 7B, the magnetic flux shielding member 11 of Comparative Example 1 does not have the protrusion 11 a and has a circumferential length that covers the entire outer circumference of the fixing belt 1 at 120 °. Thus, the total length was set to 20 mm, which was the same as in Example 1.

  As shown in FIG. 13A, in the magnetic flux shielding member 11 of Comparative Example 1, the magnetic flux shielding member 11 is placed on the abutting surface 10b of the fixing flange 10 when the recording material having the maximum paper passing size is passed. The magnetic flux shielding member 11 can be retracted only to the position where it abuts. The magnetic flux shielding member 11 of Comparative Example 1 interferes with the abutting surface 10b of the fixing flange 10 and is located on the inner side in the longitudinal direction from the position of the magnetic flux shielding member 11 of Example 1. In the magnetic flux shielding member 11 of the comparative example 1, the heating region in the longitudinal direction of the fixing belt 1 is shorter by about 20 mm than in the first embodiment.

  As shown in FIG. 13B, in the magnetic flux shielding member 11 of Comparative Example 1, the longitudinal temperature distribution of the fixing belt 1 15 seconds after the power supply of the fixing device A is compared with that of Example 1 at both ends. It was found that the temperature of was greatly reduced. In the magnetic flux shielding member 11 of Comparative Example 1, the temperature is 30 ° C. lower than the central portion at the end of the recording material (330 mm width) of the maximum sheet passing size, and the unevenness of gloss does not occur and fixing failure occurs. did.

  Referring to FIG. 7B, the magnetic flux shielding member 11 of Comparative Example 2 does not have the protrusion 11 a and has a circumferential length that covers the entire 120 ° of the outer periphery of the fixing belt 1. Thus, the total length was 15 mm shorter than that of Example 1.

  As shown in FIG. 14A, the magnetic flux shielding member 11 of Comparative Example 2 interferes with the abutting surface 10 b of the fixing flange 10, but has a shorter overall length than that of Example 1, and thus the longitudinal direction of the fixing belt 1. The maximum heating area can be secured in substantially the same manner as in the first embodiment. For this reason, in the magnetic flux shielding member 11 of Comparative Example 2, the longitudinal temperature distribution of the fixing belt 1 15 seconds after power-on of the fixing device A is not much lower than the temperature at both ends as compared with Example 1. . In the magnetic flux shielding member 11 of Comparative Example 1, the temperature did not become lower than the central portion at the end of the recording material (330 mm width) of the maximum sheet passing size, and neither gloss unevenness nor poor fixing occurred. .

  As shown in FIG. 15A, as in the case of Example 1, in the magnetic flux shielding member 11 of Comparative Example 2, A4 size plain paper is continuously fed at a productivity of 58 sheets per minute by vertical feeding. The sheet was passed, and the temperature rise at the non-sheet passing portion of the fixing belt 1 was evaluated. The magnetic flux shielding member 11 of Comparative Example 2 has a shorter length in the longitudinal direction than that of Example 1, and therefore cannot sufficiently shield the magnetic flux of the outer magnetic core 7a, and on the outer side of the magnetic flux shielding member 11 in the longitudinal direction. The fixing belt 1 is heated. The magnetic flux shielding member 11 of the comparative example 2 is not able to shield a part of the magnetic flux of the outer magnetic core 7a close to the exciting coil 6, and causes the non-sheet passing portion temperature increase to be involved. Therefore, in the case of the magnetic flux shielding member 11 of Comparative Example 2, the temperature distribution in the longitudinal direction of the fixing belt 1 has exceeded the designed upper limit temperature outside the longitudinal direction of the magnetic flux shielding member 11.

<Example 2>
FIG. 16 is an explanatory diagram of the relationship between the magnetic flux shielding member and the fixing flange in the second embodiment. In FIG. 16, (a) is Example 2, (b) is Comparative Example 3, and (c) is Comparative Example 4.

  As shown in FIG. 16A, in the second embodiment, the abutting surface 10b of the fixing flange 10 has a partly lower angular range corresponding to the protruding portion 11a in the circumferential direction of the fixing belt 1. For this reason, as shown in FIG. 11B, the protruding portion 11 a of the magnetic flux shielding member 11 protrudes to the outside of the fixing flange 10, and a wide heating region can be formed on the inner side in the rotation axis direction of the fixing belt 1.

  As shown in FIG. 16B, in Comparative Example 3, the protruding portion 11a of the magnetic flux shielding member 11 protrudes outside the fixing flange 10 and widens in the direction of the rotation axis of the fixing belt 1 in the same manner as in Example 2. A heating region can be formed. However, since the angle range (magnetic flux shielding range) of the protruding portion 11a of the magnetic flux shielding member 11 in the circumferential direction of the fixing belt 1 is narrow, a sufficient magnetic flux shielding effect cannot be exhibited, and the temperature rise of the non-sheet passing portion is likely to occur. Become.

  As shown in FIG. 16C, in Comparative Example 4, the angular range of the protruding portion 11a of the magnetic flux shielding member 11 in the circumferential direction of the fixing belt 1 is widened in order to increase the effect of suppressing the temperature increase of the non-sheet passing portion. doing. However, since the width is increased, in Comparative Example 4, the angle range in which the abutting surface 10b of the fixing flange 10 is formed low is too large. When the angle range for lowering the abutting surface 10b of the fixing flange 10 is increased, the fixing belt 1 rides on the abutting surface 10b or collides with the edge due to flapping while the fixing belt 1 is rotating. Guide failure is likely to occur in the part.

  Therefore, the endurance test of the fixing belt 1 and the evaluation of the temperature rise of the non-sheet passing portion were performed by varying the angular range (the length in the circumferential direction of the fixing belt 1) of the protrusion 11a of the magnetic flux shielding member 11. In the durability test of the fixing belt 1, the heat treatment by longitudinal feeding of the A4 size recording material described in Example 1 was performed for 500,000 sheets, and the belt edge of the fixing belt 1 was observed with a microscope. Table 1 shows the experimental results of the temperature rise of the non-sheet passing portion and the occurrence of guide failure.

  As shown in Table 1, when the length of the protruding portion 11a in the circumferential direction of the fixing belt 1 is 10 mm or less, the temperature rise of the non-sheet passing portion cannot be sufficiently suppressed. In addition, when the length of the protruding portion 11a in the circumferential direction of the fixing belt 1 is 23 mm or more, a low portion of the abutting surface 10b of the fixing flange 10 becomes too wide and a guide defect is likely to occur. From this result, in the fixing device A, the length of the protruding portion 11a in the circumferential direction of the fixing belt 1 is desirably 13 mm or more and 20 mm or less.

  In Examples 1 and 2, the magnetic flux shielding member 11 is disposed between the exciting coil 6 and the fixing belt 1. However, the magnetic flux shielding member may be arranged between the exciting coil 6 and the outer magnetic core 7a, between the fixing belt 1 and the magnetic shielding core 5, or the like. In this case, an opening or notch through which the protrusion provided on the magnetic flux shielding member passes is provided at a corresponding position of the fixing flange 10 so that the magnetic flux shielding member can be moved in the longitudinal direction to a position overlapping the fixing flange 10. it can.

  Further, in Examples 1 and 2, the predetermined range in the circumferential direction of the abutting surface 10b is formed low so that the contour shape in the circumferential direction of the abutting surface 10b of the fixing flange 10 is a continuous curve. However, the contour shape in the circumferential direction of the abutting surface 10b of the fixing flange 10 need not be a continuous curve. The abutting surface 10b is provided with a height sufficient for regulating the fixing belt 1, and a circumferential groove or opening is formed only in a portion corresponding to the protruding portion 11a of the magnetic flux shielding member 11, so that the protruding portion 11a is formed. You may let it pass.

<Effect of Example>
In the fixing device A, since the magnetic flux generated by the exciting coil 6 generates an eddy current in the induction heating element provided on the fixing belt 1 and generates heat by Joule heat, the heat generation source can be placed very close to the toner. For this reason, the time required for the surface temperature of the fixing belt 1 to be an appropriate temperature for fixing is shortened when the fixing device is activated, as compared with a conventional heat roller system using a halogen lamp. Further, since the heat transfer path from the heat generation source to the toner is short and simple, the heat efficiency is high.

  In the fixing device A, when a small amount of recording material is continuously fed and a large amount of fixing processing is performed, the sheet passing area in contact with the recording material of the fixing belt 1 is removed by the recording material. In the non-sheet passing area that does not come into contact with the heat, heat is accumulated and the non-sheet passing portion temperature rises. In the fixing device A, the outer magnetic core 7a is divided in the longitudinal direction of the fixing belt 1 and can be moved by the core moving mechanism 106 in order to prevent the temperature increase of the non-sheet passing portion. It is different depending on. Since the distance between the exciting coil 6 and the outer magnetic core 7a is increased, the efficiency of the magnetic circuit made of the outer magnetic core 7a and the induction heating element formed around the exciting coil 6 is reduced, and the heat generation amount is reduced. Non-sheet passing portion temperature rise corresponding to the size of the recording material is avoided.

  In the fixing device A, a magnetic flux shielding member 11 that shields a part of the magnetic flux reaching the fixing belt 1 is disposed between the fixing belt 1 and the induction heating device 100, and the position of the magnetic flux shielding member 11 is moved by the driving mechanism 107. Change according to the size of the recording material. By moving the magnetic flux shielding member 11, the magnetic flux reaching from the induction heating device 100 is shielded except for the necessary part, and the heat generation itself is suppressed, so that the heat generation range is controlled and the heat distribution of the fixing belt 1 is heated. Can be controlled. By defining the relationship between the length of the outer magnetic core 7a and the length of the magnetic flux shielding member 11 in the longitudinal direction of the fixing belt 1, it is possible to suppress the temperature rise of the non-sheet passing portion in various sizes of recording materials.

DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Pressure roller 3 Pressure giving member 4 Stay 5 Magnetic shielding core 6 Excitation coil 7a Outer magnetic body core 10 Fixing flange 11 Magnetic flux shielding member 11a Protruding part 11b Inner part 100 Induction heating device 106 Core moving mechanism 107 Drive mechanism 150 Control unit TH1 Temperature sensor

Claims (5)

A rotating heating body that is heated by the incidence of alternating magnetic flux;
A restricting portion arranged in a non-rotating manner to restrict the end of the heating rotating body in the direction of the rotation axis;
An induction heating means arranged to face the heating rotator to generate an alternating magnetic flux;
A magnetic flux shielding member disposed so as to be movable in the direction of the rotation axis of the heating rotator between the heating rotator and the induction heating means;
In the image heating apparatus comprising: a moving mechanism capable of moving the magnetic flux shielding member and adjusting a heating range in a rotation axis direction of the heating rotating body,
The moving mechanism is capable of moving the magnetic flux shielding member to the outer side in the rotation axis direction than the position where the restricting portion restricts the end of the heating rotator,
The image heating apparatus according to claim 1, wherein the restricting portion has an appearance shape that does not interfere with the magnetic flux shielding member that moves outward in a rotation axis direction from a position where the restricting portion restricts an end of the heating rotating body. The induction heating means can stepwise change the length of a region where the density of alternating magnetic flux along the rotation axis direction of the heating rotator is high,
The magnetic flux shielding member has a length along the rotational axis direction of the heating rotator that is longer than the length of the change unit that changes the length of the alternating magnetic flux in a stepwise manner,
2. The moving mechanism according to claim 1, wherein the moving mechanism moves the magnetic flux shielding member in conjunction with each other in a boundary region at both ends of a region where an alternating magnetic flux density is high along a rotation axis direction of the heating rotator. Image heating device.   In the magnetic flux shielding member, the length along the rotation axis direction of the heating rotating body is shorter than twice the length of the change unit that changes the length of the alternating magnetic flux density stepwise. The image heating apparatus according to claim 2. In the magnetic flux shielding member, the length of the central portion along the rotation axis direction of the heating rotator has a length in the rotation direction of the heating rotator, and the portion on the end side along the rotation axis direction of the heating rotator. Longer than the length of the heating rotator in the rotational direction,
The said restriction | limiting part has the external appearance shape which does not interfere in the part by the side of the said magnetic flux shielding member but interferes in the part by the side of the said edge part of the said magnetic flux shielding member. The image heating apparatus according to any one of the above.   The said restriction | limiting part is being fixed to the supporting member which supports the inner peripheral surface of the edge part of the said heating rotary body, and supports it rotatably, The one of Claim 1 thru | or 4 characterized by the above-mentioned. Image heating device.

Images