JP2012247760A - Image heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating apparatus of an electromagnetic induction heating system that can sufficiently prevent temperature increase at paper non-passing portions when a small-sized recording material is made to pass and that does not cause stain on images of recording materials, even if a heating member whose heat capacity is low is used.SOLUTION: An image heating apparatus comprises control means that alternatively executes: a first control mode that controls to change the number of divided movable cores to be moved according to a width size of a recording material introduced into the apparatus, moves the divided movable cores according to a basis weight of the recording material introduced into the apparatus and the number of passed sheets per unit of time, and makes a soaking member having a releasing resin layer bring into contact with a heating member or a pressurizing member; and a second control mode that moves the divided movable cores, but does not make the soaking member bring into contact with the heating member or the pressurizing member. After a job for heating a small-sized recording material is completed, a predetermined post-rotation soaking control is executed.

Description

  The present invention relates to an electromagnetic induction heating type image heating apparatus for heating an image on a recording material. Examples of the image heating device include a fixing device that fixes an unfixed image formed on a recording material, and a gloss imparting device that improves the glossiness of an image by heating the image fixed on the recording material.

  In an image forming apparatus such as an electrophotographic copying machine, image heating is performed such that a toner image (unfixed image) formed on a recording material that is a recording medium to be conveyed is melted by heat and fused onto the recording material. A fixing device as a device is provided.

  One of the configuration methods of the image heating apparatus is an electromagnetic induction heating method. This apparatus forms a magnetic field generating means having a magnetic field generating coil and a magnetic core, a rotatable heating member that generates electromagnetic induction heat by the action of a magnetic field generated from the magnetic field generating means, and a nip portion with the heating member. A pressure member that can rotate. Then, the recording material carrying the image at the nip portion is nipped and conveyed and heated.

  In such an apparatus, there is an apparatus having a configuration described in Patent Document 1 in order to suppress a so-called non-sheet passing portion temperature rise phenomenon. In this apparatus, the magnetic core of the magnetic field generating means is divided into a plurality of longitudinal directions along the heating member, and the individual movable cores can be independently moved in the direction in which the distance from the heating member is changed by the core moving means. . Then, control is performed to change the number of the movable movable cores to be moved according to the width size of the recording material introduced into the apparatus.

  Further, Patent Document 2 proposes a fixing device that controls contact / separation of a heat equalizing member having substantially the same longitudinal dimension as that of the heating member in order to suppress the temperature rise of the non-sheet passing portion. Yes.

JP 2011-053597 A JP 2000-137399 A

  It is conceivable to further suppress the temperature rise of the non-sheet passing portion by applying the heat equalizing member method of Patent Document 2 to the apparatus of Patent Document 1. However, in actual trials, when the heat equalizing member is provided with a fluororesin layer as a toner release layer, the wear of the fluororesin layer portions corresponding to both ends (edge portions) in the width direction of the recording material is remarkable. become. For this reason, there has been a problem that the toner adhering to the heat equalizing member due to the lowering of the releasability due to the wear of the release layer returns to the recording material and causes image contamination.

  This requires a sufficient amount of heat generation to fix the toner even at the end of the recording material. However, as the sheet passes, the heating member corresponding to the end of the recording material has a larger area than the sheet passing area of the heating member. The amount of heat lost to the recording material is small. As a result, the temperature of the heating member near the end of the recording material in the non-sheet-passing region is excessively increased, and as a result, the toner release resin layer of the heat equalizing member is worn. Such a phenomenon appears more remarkably in a fixing belt using a low heat capacity film as a heating member.

  The present invention solves this problem, and even when a heating member having a low heat capacity is used, the temperature rise at the non-sheet passing portion when a small size recording material is passed can be sufficiently suppressed, and an image of the recording material can be obtained. An object of the present invention is to provide an image heating apparatus of an electromagnetic induction heating system that does not cause dirt.

  In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention includes a magnetic field generation unit including a magnetic field generation coil and a magnetic core, and a region where a magnetic field generated from the magnetic field generation unit exists. Rotating heating member composed of a magnetic member that generates electromagnetic induction heat when passing through, a rotatable pressing member that forms a nip portion with the heating member, and a temperature of a sheet passing area of the heating member are detected. And temperature control means for controlling power supplied to the magnetic field generating coil so that information on the temperature detected by the temperature detection means is maintained at information corresponding to a predetermined temperature, An image heating apparatus that sandwiches and conveys a recording material carrying an image at the nip portion, and heats the magnetic core when the direction perpendicular to the recording material conveyance direction is a longitudinal direction. Long A split movable core that is arranged along a direction and is divided into a plurality in the longitudinal direction and individually movable in a direction in which the distance from the heating member is individually changed. Core moving means for moving the split movable core to a first distance position with respect to the heating member and a second distance position farther from the heating member than the first distance position; and a toner release resin layer on the surface A soaking member having the same longitudinal dimension as the pressurizing member, a first position where the soaking member abuts against the pressurizing member, and a second position spaced apart from the pressurizing member. The soaking member moving means for moving to a position and the recording material passed through the apparatus are small size recording materials having a width smaller than the maximum width large size recording material capable of passing through the apparatus, Passing small-size recording material that is passed among the split movable cores The core moving means is controlled so that the split movable core corresponding to is positioned at the first distance position, and the other split movable cores are positioned at the second distance position, and the paper is passed. A first control mode for controlling the heat equalizing member moving means to move the heat equalizing member to the first position according to the basis weight of the small size recording material and the number of passing sheets per unit time; Control means for selecting and executing a second control mode for controlling the soaking member moving means so as to move the member to the second position, and the control means comprises the small size recording When the job for heating the material is completed, the power supplied to the magnetic field generating coil is stopped, and in the first control mode, the pressure member is rotated while the heat equalizing member is moved to the first position. For a predetermined time In the second control mode, the heat equalizing member is moved from the second position to the first position, and the rotation of the pressure member is continued for a predetermined time. It is characterized in that post-rotation soaking control is performed.

  According to the present invention, even when a heating member having a low heat capacity is used, the temperature rise at the non-sheet passing portion when a small size recording material is passed can be sufficiently suppressed, and image staining of the recording material can occur. It is possible to provide an image heating apparatus of an electromagnetic induction heating system without any problem.

1 is a schematic configuration of an example of an image forming apparatus. It is a front schematic diagram of the principal part of the mounted fixing device. It is a vertical front schematic diagram of the principal part of the apparatus. FIG. 3 is an enlarged right side view taken along line (4)-(4) in FIG. 2. It is a figure at the time of the state which the division | segmentation movable core of a coil unit has moved to the 2nd distance position. FIG. 3 is a layer configuration model diagram of a fixing belt. It is a disassembled perspective view of the coil and core of a coil unit. It is a schematic diagram of the relationship between the longitudinal position of the paper width of the split movable core when passing 80 g paper in <Experiment 1>, and the relationship between the longitudinal temperature distribution of the fixing belt when passing paper. FIG. 10 is a diagram illustrating a temperature transition of a sheet passing portion and a non-sheet passing portion of the fixing belt with respect to time when 80 g paper is passed in <Experiment 1>. It is a schematic diagram of the relationship between the longitudinal position of the width of the split movable core paper when passing 300 g paper in <Experiment 1> and the relationship of the longitudinal temperature distribution of the fixing belt when passing paper. FIG. 10 is a diagram illustrating a temperature transition of a sheet passing portion and a non-sheet passing portion of the fixing belt with respect to time when 300 g paper is passed in <Experiment 1>. FIG. 6 is a schematic diagram of the relationship between the longitudinal position of the width of the split movable core paper when passing 300 g paper in <Experiment 2>, and the relationship between the longitudinal temperature distribution of the fixing belt when passing paper. FIG. 9 is a diagram illustrating a state of temperature transition of a fixing belt sheet passing portion and a non-sheet passing portion with respect to time when 300 g paper is passed in <Experiment 2>. It is a flowchart figure of control mode selection.

  Examples of the present invention will be described below.

[Example]
(1) Image Forming Apparatus FIG. 1 is a structural model diagram of an example of an image forming apparatus in which an image heating device according to the present invention is mounted as a fixing device. This image forming apparatus is a color image forming apparatus (printer) using an electrophotographic system. Y, C, M, and K are four image forming portions that form yellow, cyan, magenta, and black color toner images, respectively, and are arranged in order from the bottom to the top. Each of the image forming units Y, C, M, and K includes a photosensitive drum 1, a charging device 2, a developing device 3, a cleaning device 4, and the like.

  Yellow toner is used for the developing device 3 of the image forming unit Y, cyan toner is used for the developing device 3 of the image forming unit C, magenta toner is used for the developing device 3 of the image forming unit M, and the developing device 3 of the image forming unit K. Each contains black toner.

  An optical system 5 for forming an electrostatic latent image by exposing the drum 1 is provided corresponding to the four color image forming portions Y, C, M, and K. A laser scanning exposure optical system is used as the optical system. In each of the image forming units Y, C, M, and K, the drum 1 uniformly charged by the charging device 2 is subjected to scanning exposure based on image data from the optical system 5, thereby scanning exposure on the drum surface. An electrostatic latent image corresponding to the image pattern is formed.

  These electrostatic latent images are developed as toner images by the developing device 3. That is, the yellow toner image is stored on the drum 1 of the image forming unit Y, the cyan toner image is stored on the drum 1 of the image forming unit C, the magenta toner image is stored on the drum 1 of the image forming unit M, and the drum of the image forming unit K is displayed. 1 is formed with a black toner image.

  The color toner images formed on the drums 1 of the image forming units Y, C, M, and K are in a predetermined position on the intermediate transfer member 6 that rotates at a substantially constant speed in synchronization with the rotation of the drums 1. In the combined state, the images are sequentially superimposed and transferred primarily. As a result, an unfixed full-color toner image is synthesized and formed on the intermediate transfer member 6. In this embodiment, an endless intermediate transfer belt is used as the intermediate transfer member 6, and is wound around three rollers of a driving roller 7, a secondary transfer roller opposing roller 8, and a tension roller 9. Yes, driven by the drive roller 7.

  A primary transfer roller 10 is used as a primary transfer unit of the toner image from the drum 1 to the belt 6 in each of the image forming units Y, C, M, and K. A primary transfer bias having a polarity opposite to that of the toner is applied to the roller 10 from a bias power source (not shown). As a result, the toner image is primarily transferred from the drum 1 of each image forming unit Y, C, M, K to the belt 6. After the primary transfer from the drum 1 to the belt 6 in each of the image forming units Y, C, M, and K, the toner remaining as a transfer residue on the drum 1 is removed by the cleaning device 4.

  The above process is performed for each color of yellow, cyan, magenta, and black in synchronization with the rotation of the belt 6, and the primary transfer toner images of the respective colors are sequentially superimposed on the belt 6. 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 11 is separated and fed by the feeding roller 12, and the belt 6 and the secondary transfer roller wound around the roller 8 at a predetermined timing by the registration roller 13. 14 is transported to a secondary transfer nip portion which is a pressure contact portion with. The primary transfer composite toner image formed on the belt 6 is collectively transferred (secondary) onto the recording material P by a bias having a polarity opposite to that of the toner applied to the roller 14 from a bias power source (not shown). The secondary transfer residual toner remaining on the belt 6 after the secondary transfer is removed by the intermediate transfer belt cleaning device 15. Arrow a is the recording material conveyance direction.

  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 which is an image heating device, and is sent out to the paper discharge tray 18 through the paper discharge path 17 as a full color print. .

(2) Fixing device 16
2 is a schematic front view of a main part of the fixing device 16, FIG. 3 is a schematic front view of the main part of the device 16, and FIG. 4 is an enlarged right side view taken along line (4)-(4) of FIG. is there. In the following description, the longitudinal direction of the fixing device 16 or a member constituting the fixing device 16 is the axial direction (thrust direction) of the rotating body, the direction orthogonal to the recording material conveyance direction a in the recording material conveyance path surface, or the direction thereof. The direction is parallel to the direction. The short direction is a direction parallel to the recording material conveyance direction a.

  Regarding the fixing device 16, the front means the surface of the device 16 viewed from the recording material inlet side, the back surface the opposite surface (recording material outlet side), and the left and right are the left or right when the device is viewed from the front. . Up or down is up or down in the direction of gravity. The upstream side and the downstream side are the upstream side and the downstream side in the recording material conveyance direction. The recording material size or the sheet passing width of the recording material is a recording material dimension (width size) in a direction orthogonal to the recording material conveyance direction a on the recording material surface.

  The fixing device 16 is an external heating type electromagnetic induction heating type image heating device in which a magnetic field generating means is provided outside the heating member. The apparatus 16 is roughly divided between the left and right side plates 30L and 30R of the apparatus chassis 30, a heating assembly 40, a pressure roller 50 having elasticity as a pressure member (pressure rotating body), and a coil unit as magnetic field generating means. 60 and a soaking unit 70. Further, a pressurization / pressure release mechanism 80 of the heating assembly 40 with respect to the pressure roller 50 and a shift mechanism 90 of the soaking unit 70 are provided.

(2-1) Heating assembly 40
The heating assembly 40 is a rotatable heating member (heating rotator) composed of a magnetic member (metal layer, conductive member) that generates electromagnetic induction heat when passing through a region where a magnetic field generated from a coil unit 60 described later is present. ) As a cylindrical fixing belt 41. Further, a metal stay 42 inserted into the belt 41 is provided. A pressure pad 43 as a pressure applying member is attached to the lower surface of the stay 42 along the length of the stay.

  The pad 43 is a member that forms a fixing nip portion N by applying a pressing force between the belt 41 and the pressure roller 50, and is made of a heat resistant resin. Since the stay 42 needs rigidity to apply pressure to the nip portion N, it is made of iron in this embodiment. Also, on the upper surface side of the stay 42, a magnetic shielding core 44 as a magnetic shielding member for preventing the stay 42 from being heated by induction heating due to the action of a magnetic field generated from the coil unit 60 extends over the length of the stay. It is arranged.

  Extending arm portions 42 a are provided at the left and right ends of the stay 42, respectively, and the extending arm portions 42 a protrude outward from the left and right ends of the belt 41, respectively. The left and right extending arm portions 42a are fitted with symmetrical flange members 45L and 45R, respectively. The belt 41 is loosely fitted to the stay 42, the pad 43, and the core 44, and the movement in the longitudinal direction (left and right direction) is restricted by the flange portions 45a of the left and right flange members 45L and 45R. The

  A temperature sensor TH such as a thermistor as a temperature detecting means (temperature detecting element) for detecting the temperature of the belt 41 is disposed through the elastic support member 46 in the longitudinal center portion of the pad 43. The sensor TH is in elastic contact with the inner surface of the belt 41 by a member 46. As a result, even if a position variation occurs such as the sensor contact surface of the belt 41 undulates, the sensor TH follows this and a good contact state is maintained.

  The heating assembly 40 is disposed between the left and right side plates 30L and 30R by engaging the pressure receiving portions 45b of the left and right flange members 45L and 45R with the vertical guide slit portions 31 disposed on the side plates 30L and 30R, respectively. ing. Therefore, the heating assembly 40 has a degree of freedom of movement in the vertical direction along the vertical guide slit portion 31 between the left and right side plates 30L and 30R.

  FIG. 6 is a model diagram showing the layer structure of the belt 41. In this embodiment, the belt 41 has a nickel base layer (magnetic member, metal layer) 41a having an inner diameter of 30 mm and manufactured by electroforming. The thickness of the base layer 41a is 40 μm. A heat-resistant silicone rubber layer is provided as an elastic layer 41b on the outer periphery of the base layer 41a. The thickness of the silicone rubber layer is preferably set within a range of 100 to 1000 μm.

  In the present embodiment, the thickness of the silicone rubber layer 41b is set to 300 μm in consideration of reducing the heat capacity of the belt 41 to shorten the warm-up time and obtaining a suitable fixed image when fixing a color image. Yes. 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 41b, a fluororesin layer (for example, PFA or PTFE) is provided as a surface release layer 41c with a thickness of 30 μm.

  Further, on the inner surface side of the base layer 41a, a resin layer (sliding layer) 1d such as fluororesin or polyimide is provided in an amount of 10 to 50 μm in order to reduce sliding friction between the inner surface of the belt and the temperature sensor TH1 as temperature detecting means. May be. In this example, 20 μm of polyimide was provided as the layer 1d.

  The belt 41 has a low heat capacity and flexibility (elasticity) as a whole, and maintains a cylindrical shape in a free state. For the metal layer 41a of the belt 41, a metal such as iron alloy, copper, or silver can be selected as appropriate in addition to nickel. Moreover, the structure of laminating | stacking these metals on a resin base layer may be sufficient. The thickness of the metal layer 41a may be adjusted according to the frequency of a high-frequency current flowing in an excitation coil (magnetic field generating coil) 62, which will be described later, and the permeability / conductivity of the metal layer 41a. good.

(2-2) Pressure roller 50
The pressure roller 50 is rotatably disposed between the left and right side plates 30 </ b> L and 30 </ b> R via a bearing 51 with the axial direction being substantially parallel to the longitudinal direction of the assembly 40 below the heating assembly 40.

  In this embodiment, the roller 50 has an outer diameter in which a core rubber 50a made of an iron alloy having a diameter of 20 mm in the longitudinal direction and a diameter of both ends of 19 mm is provided with a silicone rubber layer as the elastic layer 50b. It is a 30 mm elastic roller. On the surface, a fluororesin layer (for example, PFA or PTFE) is provided as a release layer 50c with a thickness of 30 μm. The hardness of the roller 50 at the center in the longitudinal direction is ASK-C70 ° C. The metal core 50a is tapered so that the pressure in the fixing nip N formed by the pressure contact between the belt 41 and the roller 50 is uniform in the longitudinal direction even if the pad 43 is bent when pressed. It is to make it.

  A drive gear 52 is fixedly disposed at the right end of the cored bar 50a. The driving force of the fixing motor 53 controlled by the control circuit unit 100 is transmitted to the gear 52 via a transmission means (not shown), and the roller 50 is rotated at a predetermined speed in the counterclockwise direction of the arrow in FIG. Driven by rotation.

(2-3) Pressure / pressure release mechanism 80
Cam shafts 81 are rotatably disposed on the left and right side plates 30L and 30R via bearings 82 and 82, respectively. On the left and right ends of the cam shaft 81, eccentric cams 83 that are symmetrical and have the same shape are arranged in the same phase on the outside of the side plates 30L and 30R. A pressure lever 84 that engages with the cam 83 is disposed outside the side plates 30L and 30R.

  Further, a pressure spring (elastic member) 85 is disposed between the lower surface of each lever 84 and the upper surface of the pressure receiving portion 45b of the flange member 45L / 45R on each side. A cam shaft driving means 86 controlled by the control circuit section 100 is connected to the right end portion of the cam shaft 81 via a transmission means (not shown). As the cam shaft driving means 86, for example, a stepping motor, a solenoid, or the like can be used.

  The assembly 40 is pressed (loaded) against the roller 50 by rotating the cam shaft 81 by the driving means 86 so that the large raised portions of the left and right cams 83 are in the downward rotation angle posture. The pressurized state is maintained.

  That is, the left and right levers 84 are pushed down by the left and right cams 83, respectively, and the left and right springs 85 are compressed between the lever 84 and the upper surface of the pressure receiving portion 45b of the flange members 45L and 45R. The stay 42 is pushed down together with the left and right flange members 45L and 45R by the compression reaction force of the spring 85, and the pad 43 presses against the roller 50 against the elasticity of the elastic layer 50b across the belt 41. As a result, a fixing nip N having a predetermined width is formed between the belt 41 and the roller 50 in the recording material conveyance direction. The pad 43 assists in forming the pressure profile of the nip N.

  The width of the nip portion N in this embodiment is about 9 mm at both ends in the longitudinal direction and about 8.5 mm at the center when the nip pressure is 600N. This has the advantage that paper wrinkles are less likely to occur because the conveyance speed at both ends of the recording material P is faster than the central portion.

  Further, the cam shaft 81 is rotated by the driving means 86 so that the small raised portions of the left and right cams 83 are in the downward rotation angle posture, so that the assembly 40 is released from pressure (extracted) from the roller 50. Become. That is, the compression of the left and right springs 85 is released. As a result, the pressure applied to the roller 50 by the pad 43 is released.

  The above-described members 81 to 86 constitute a pressure / pressure release mechanism 80 of the assembly 40 with respect to the roller 50. The control circuit unit 100 controls and holds the mechanism 80 in a pressurized state at least during the fixing operation of the apparatus. In the standby state, the mechanism 80 is controlled and held in a pressure release state. By doing so, it is possible to prevent the elastic layer 50b of the roller 50 and the belt 41 from being plastically deformed.

(2-4) Coil unit 60
The coil unit 60 is a heating source (induction heating means) for inductively heating the belt 41, and on the upper surface side of the assembly 40, that is, on the side opposite to the roller 50 side of the assembly 40 by 180 °, the left and right side plates 30L and 30R. The position is fixed. The unit 60 is obtained by assembling an exciting coil 62, a magnetic core 63, and the like to a long housing 61 along the belt 41.

  The housing 61 is a horizontally-long box-shaped heat-resistant resin molded product (molded member of an electrically insulating resin) having a longitudinal direction in the left-right direction. The bottom plate 61 a side of the housing 61 is a surface facing the belt 41. The bottom plate 61a is curved inward of the housing 61 so as to be along a substantially semicircular range of the outer peripheral surface of the belt 41 in the cross section. The housing 61 is open as an opening on the side opposite to the bottom plate 61a side. The housing 61 is arranged such that the bottom plate 61a faces the upper surface of the belt 41 with a predetermined gap (gap) α, and the left and right end portions are fixed to the left and right side plates 30L and 30R by brackets 66. Established.

  The coil 62 uses, for example, a litz wire as an electric wire, and is wound so that it is horizontally long and has a bottom shape and is opposed to a part of the peripheral surface and side surface of the belt 41 as shown in FIG. And it is applied to the inner surface of the housing bottom plate 61a that is curved toward the inside of the housing, and is housed inside the housing. A high frequency current of 20 to 50 kHz is applied to the coil 62 from a power supply device (excitation circuit) 64 controlled by the control circuit unit 100.

  The core 63 is an outer magnetic core that covers the coil 62 so that the magnetic field generated by the coil 62 does not substantially leak outside the metal layer (conductive layer) of the belt 41. The core 63 is disposed along the longitudinal direction of the belt 41, and is divided into a plurality of lines in a direction perpendicular to the recording material conveyance direction, and is arranged around the winding center portion of the coil 62 and the periphery thereof. It is comprised so that it may surround.

  That is, the core 63 is disposed along the longitudinal direction of the belt 41 when the direction orthogonal to the recording material conveyance direction a is the longitudinal direction. In addition, as shown in FIG. 7, it has a split movable core 63a that is divided into a plurality of parts in the longitudinal direction and can be moved independently in a direction in which the distance from the belt 41 is individually changed. The first distance position D (FIG. 4) in which the individual cores 63a are close to the belt 41 by a predetermined distance is controlled by the control circuit unit 100, and the second distance is further away from the belt 41 than the position D. A core moving means (core moving mechanism) 65 for moving to the distance position E (FIG. 5) is provided.

  Although the specific configuration of the core moving unit 65 is omitted in order to avoid complication of the drawing, for example, the core moving unit described in Patent Document 1 can be applied.

(2-5) Soaking unit 70
The soaking unit 70 abuts on the belt 41 that is a heating member or the roller 50 that is a pressure member, and uniformizes the temperature in the longitudinal direction (axial direction) of the belt 41 or the roller 50 to raise the non-sheet passing portion. It has a soaking member that relaxes the temperature. In this embodiment, the unit 70 is disposed below the roller 50 between the left and right side plates 30L and 30R.

  The unit 70 is provided with a toner release resin monk 2b on the surface as a heat equalizing member that can be contacted and separated (removable) with respect to the lower surface of the roller 50 in a housing 71 that is long along the roller 50. It has a soaking roller 72. Further, a cleaning roller 73 (cleaning roller) as a toner cleaning member for cleaning the roller 72 is provided.

  The roller 72 is made of a member having a good thermal conductivity and a small heat capacity. In this embodiment, the roller 72 is a solid 22φ aluminum cored bar (metal cored bar) 72a provided with a 12 μm PFA coating layer as a toner release resin layer 72b. The roller 72 has substantially the same longitudinal dimension as that of the roller 50 (including the same dimension, including a slightly longer or shorter dimension: the same applies hereinafter). The roller 72 is disposed in the housing with shaft portions at both ends being rotatably supported between the left and right side plates of the housing 71. The upper surface side of the housing 71 is opened as an opening, and the upper surface of the roller 72 faces the opening.

  In this embodiment, the roller 73 is a roller having a hardness of 30 ° (Asker-C 1 kgf) in which a silicon sponge layer having a thickness of 5 mm is provided as a cleaning layer 73b on a solid 8φ metal core 73a. Further, it has substantially the same longitudinal dimension as the roller 72. The roller 73 is pressed against the roller 72 at 20 N and arranged in parallel, and the shafts on both ends are rotatably supported between the left and right side plates of the housing 71.

  The unit 70 is moved up by a predetermined amount by the shift mechanism 90. As a result, the roller 72 is held in a state of being moved to the first position F (a position indicated by a solid line in FIG. 4) in a state where the roller 72 is in a predetermined contact with the roller 50. Further, the unit 70 is moved down by the shift mechanism 90 in a predetermined manner. As a result, the roller 72 is moved to and held at the second position G (a position indicated by a two-dot chain line in FIG. 4) in a state of being separated from the roller 50.

  That is, the unit 70 is arranged such that the guided portions 71a on the left and right sides of the housing 71 are engaged with the vertical guide slit portions 32 provided on the left and right side plates 30L and 30R, respectively. Accordingly, the unit 70 has a degree of freedom of movement in the vertical direction along the vertical guide slit portion 32 between the left and right side plates 30L and 30R.

  Below the unit 70, cam shafts 91 are rotatably disposed on the left and right side plates 30L and 30R via bearings 92 and 92, respectively. On the left and right sides of the cam shaft 91, eccentric cams 93 that are symmetrical and have the same shape are fixed in the same phase inside the side plates 30L and 30R. A cam shaft drive means 94 controlled by the control circuit section 100 is connected to the right end of the cam shaft 81 via a transmission means (not shown). As the driving means 94, for example, a stepping motor, a solenoid or the like can be used.

  The above members 91 to 94 constitute a soaking member moving means 90 for moving the roller 73 in the contact direction and the separation direction with respect to the roller 50. The cam shaft 91 is rotated by the drive means 94 so that the large raised portions of the left and right cams 93 are in the upward rotation angle posture, whereby the unit 70 is moved up in a predetermined manner. Accordingly, the roller 72 is held at the first position F in a state where the roller 72 is in contact with the roller 50 with a load of 100 N in this embodiment.

  Further, the cam shaft 91 is rotated by the driving means 94 so that the small raised portions of the left and right cams 93 are in the upward rotation angle posture, whereby the unit 70 is moved downward by a predetermined amount. As a result, the roller 72 is held at the second position G in a state of being separated from the roller 50.

  In the present embodiment, the roller 72 rotates following the rotation of the roller 50 in a state where it is in contact with the roller 50. By causing the roller 72 to come into contact with the roller 50 under a situation where the non-sheet passing portion temperature rise occurs in the fixing device 16, it is possible to suppress the non-sheet passing portion temperature rise of the roller 50 and the belt 41. The roller 73 is rotated by the rotation of the roller 72, and the toner adhering to the roller 72 is taken into the sponge layer 73 and removed.

  Here, the roller 72 may be configured to be driven by a drive mechanism (not shown) so that the peripheral speed is the same as that of the roller 50 in the forward direction of the rotation of the roller 50 at the contact portion with the roller 50. The roller 73 can also be configured to be driven by a drive mechanism (not shown) so as to rotate (sliding and rotate) in the same direction or in the opposite direction with a circumferential speed difference from the roller 72 at the contact portion with the roller 72. Further, a recleaning member such as a blade or a brush for recleaning the roller 73 can be provided.

(2-6) Fixing Operation In the standby state of the image forming apparatus, the fixing device 16 has the fixing motor 53 turned off and the rotation of the roller 50 is stopped. The mechanism 80 is in a pressure release state, and the pressurization of the nip portion N is released. Power supply to the coil 62 of the unit 60 is turned off. The unit 70 is moved downward, and the roller 72 is held at the first position G in a state of being separated from the roller 50.

  The control circuit unit 100 places the mechanism 80 in a pressurized state at a predetermined control timing based on the input of the image formation start signal. As a result, the nip portion N is in a pressurized state. Also, the motor 53 is turned on. Thereby, the roller 50 is rotationally driven at a predetermined speed in the counterclockwise direction of the arrow in FIG.

  Due to the rotation of the roller 50, a rotational force acts on the belt 41 by the frictional force between the surface of the roller 50 and the surface of the belt 41 in the nip portion N. While the inner surface of the belt 41 slides in close contact with the lower surface of the pad 43, the outer periphery of the stay 42, the pad 43, and the core 44 is driven to rotate in the clockwise direction of the arrow at the same speed as the rotation speed of the pressure roller 50. Movement in the thrust direction accompanying the rotation of the belt 41 is restricted by the flange portions 45a of the left and right flange members 45L and 45R.

  The belt 41 is driven and rotated as described above by rotating the roller 50 by the motor 53 controlled by the control circuit unit 100 at least during execution of image formation. This rotation is performed at substantially the same peripheral speed as the conveyance speed of the recording material P carrying the unfixed toner image t conveyed from the secondary transfer nip portion side. In this embodiment, the belt 41 rotates at a surface rotation speed of 321 mm / sec, and a full-color image can be fixed at 80 sheets of A4 size and 58 sheets of A4R size per minute.

  The control circuit unit 100 supplies an alternating current (high-frequency current) of, for example, 20 kHz to 500 kHz to the coil 62 from the power supply device 64. The coil 62 generates an alternating magnetic flux (magnetic field) by supplying an alternating current. The alternating magnetic flux is guided to the metal layer 1 a of the belt 41 on the upper surface side of the belt 41 rotating by the core 63. Then, an eddy current is generated in the metal layer 1a, and the metal layer 1a is self-heated (electromagnetic induction heat) by Joule heat due to the eddy current, and the belt 41 is heated.

  That is, when the rotating belt 41 passes through the region where the magnetic field generated from the coil unit 60 is present, the metal layer 1a generates heat by electromagnetic induction and is heated all around. In this embodiment, the belt 41 and the coil 62 of the unit 60 are kept electrically insulated by a housing bottom plate (mold) 61a having a thickness of 0.5 mm. The distance between the belt 41 and the coil 62 is constant at 1.5 mm (the distance (gap α) between the surface of the housing bottom plate 61a and the belt surface is 1.0 mm), and the belt 41 is heated uniformly.

  The temperature of the belt 41 is detected by the temperature sensor TH. The temperature sensor TH detects the temperature of the portion of the belt 41 that is the paper passing area, and the detected temperature information is fed back to the control circuit unit 100. The control circuit unit (temperature control means) 100 maintains the detected temperature (information regarding the detected temperature) input from the temperature sensor TH at a predetermined target temperature (fixing temperature: information corresponding to the predetermined temperature). The power supplied from the power supply device 64 to the coil 62 is controlled.

  That is, when the detected temperature of the belt 41 rises to a predetermined temperature, the energization to the coil 62 is interrupted. In the present embodiment, the temperature is adjusted by controlling the power input to the coil 62 by changing the frequency of the high-frequency current based on the detected value of the temperature sensor TH so that the belt 41 becomes constant at the target temperature of 180 ° C. It is carried out.

  In the state where the roller 50 is driven and the belt 41 rises to a predetermined fixing temperature and is adjusted in temperature as described above, the recording material P having the unfixed toner image t in the nip portion N faces the toner image carrying surface side of the belt. It is guided and guided by the guide member 33 toward the 41 side. The recording material P is in close contact with the outer peripheral surface of the belt 41 at the nip portion N, and is nipped and conveyed along the nip portion N together with the belt 41.

  As a result, mainly the heat of the belt 41 is applied, and the unfixed toner image t is fixed to the surface of the recording material P by heat and pressure under the pressure of the nip portion N. The recording material P that has passed through the nip portion N is conveyed from the outer peripheral surface of the belt 41 to the outside of the fixing device due to self-separation (curvature separation) due to deformation of the exit portion of the nip portion N.

  Since the coil unit 60 is disposed not inside the belt 41 that is at a high temperature but outside the coil 41, the temperature of the coil 62 is unlikely to be high, the electrical resistance does not increase, and the loss due to Joule heat generation is reduced even when a high-frequency current flows. It becomes possible to do. Further, the arrangement of the coil 62 outside contributes to the reduction in the diameter (reduction in heat capacity) of the belt 41, and thus it can be said that it is excellent in energy saving.

  Since the warm-up time of the fixing device 16 of this embodiment has a very low heat capacity, for example, when 1200 W is input to the coil 62, the target temperature of 180 ° C. can be reached in about 15 seconds. Since the heating operation during standby is unnecessary, it is possible to keep the power consumption very low.

(2-7) Suppression of temperature rise at non-sheet passing portion In FIG. 2, Wmax is the width size (sheet passing area) of a large size recording material having the maximum width that can be passed through the apparatus 16. In this embodiment, the large-size recording material is 13 inch × 19 inch paper and is longitudinally fed. Therefore, Wmax is 13 inches (330 mm).

  Area A is a paper passing area for a small size recording material having a width smaller than Wmax. In the apparatus of this embodiment, it is assumed that the recording material P is fed by center reference conveyance. O is the central reference conveyance. A region B is a non-sheet passing region in the belt 41 and the roller 50 generated when the small size recording material is passed. This is a difference area ((Wmax−A) / 2) between the paper passing area Wmax of the large size recording material and the paper passing area A of the small size recording material that has passed, and occurs on both sides of the paper passing area A.

  When the small-size recording material is continuously fed, the non-sheet passing area B of the belt 41 has the same unit length as the portion corresponding to the sheet passing area A, although no heat energy is consumed for heating the recording material P. Since heat is generated with a predetermined calorific value per unit, heat is stored. Therefore, a so-called non-sheet passing portion temperature rise phenomenon occurs in which the temperature of the belt 41 corresponding to the non-sheet passing area B is higher than that corresponding to the sheet passing area A. The pressure roller 50 in contact with the belt 41 due to the temperature increase of the non-sheet passing portion of the belt 41 also raises the temperature of the non-sheet passing portion corresponding portion than the sheet passing portion corresponding portion.

  If the thickness of the heating member is reduced to reduce the heat capacity in order to increase the temperature of the heating member at a high speed, the cross-sectional area of the heating member at a right angle to the axis is extremely small, so that the heat conduction 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. Assuming that 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 Fourier's law that it is expressed.

  This is not a problem when a recording material full of the length in the longitudinal direction of the heating member, that is, a recording material having a maximum sheet passing width (large size recording material) is passed and fixed. However, when continuously passing a small-sized recording material having a smaller width than that, the temperature in the non-sheet passing area of the heating member rises above the temperature control temperature, and the temperature in the sheet passing area and the non-sheet passing area The temperature difference from the temperature in the area becomes extremely large (temperature rise at the non-sheet passing portion).

  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 the temperature increase of the non-sheet passing portion of the heating member. Furthermore, when a recording material having a larger width is passed immediately after passing a small size recording material continuously, paper wrinkles due to partial temperature unevenness or fixing unevenness may occur. is there.

  Such a temperature difference between the sheet passing area and the non-sheet passing area increases as the heat capacity of the recording material conveyed increases and the throughput (number of printed sheets per unit time) increases. For this reason, when the heating device is constituted by a thin-walled and low heat capacity heating member, it has been difficult to apply to a high-throughput copying machine or the like.

  In this embodiment, when a small-size recording material is passed, the selective movement control of the split movable core 63a of the unit 60 and the attachment / detachment control of the heat equalizing roller 72 with respect to the pressure roller 50 are combined for non-passage. The temperature rise of the paper section is appropriately suppressed. This will be described below.

a) Suppression of non-sheet passing portion temperature rise by movement control of divided movable core 63a As described above, the core 63 of the unit 60 is disposed along the longitudinal direction of the belt 41, and as shown in FIG. And a split movable core 63a which is divided into a plurality of parts in the longitudinal direction and can be moved independently in a direction in which the distance from the bell is individually changed. And it has the core moving mechanism 65 controlled by the control circuit part 100 and moving each division | segmentation movable core 63a.

  When the recording material to be passed through the apparatus is a small size recording material, the control circuit unit 100 corresponds to the paper passing area A of the small size recording material to be passed among the split movable cores 63a. The split movable core to be performed is positioned at the first distance position D. The core moving mechanism 65 is controlled so that the other movable movable cores are positioned at the second distance position E.

  In the present embodiment, the individual cores 63a are moved by the mechanism 65 to the first distance position D approaching the coil 41 with an interval of 0.5 mm as shown in FIG. 4, and as shown in FIG. 41 can be moved to a second distance position E which is 10 mm apart from the distance 41. When the core 63a is at the first distance position D, the heat generation efficiency of the belt 41 portion to which the core corresponds is very high. On the other hand, when the core 63a is at the second distance position E, the heat generation efficiency of the portion of the belt 41 corresponding to the core decreases.

  When the print job is started, the control circuit unit 100 reads the size input value of the recording material to be passed. When the recording material to be passed is a large size recording material, the mechanism 65 is controlled so that all of the split movable cores 63a are positioned at the first distance position D. In the case of a small size recording material, among the split movable core 63a, the split movable core corresponding to the paper passing area A of the small size recording material to be passed is positioned at the first distance position D, and the others The mechanism 65 is controlled so that the split movable core is positioned at the second distance position E.

  As a result, the heat generation efficiency of the portion corresponding to the non-sheet passing area B of the belt 41 is lower than that corresponding to the sheet passing portion A, so that the temperature rise of the non-sheet passing portion of the belt 41 and the roller 50 is suppressed. .

b) Suppression of temperature rise of non-sheet passing portion by desorption control of heat equalizing roller 72 When the print job starts, the control circuit portion 100 reads the size input value of the recording material to be passed. When the recording material is a large size recording material, the mechanism 90 is controlled so as to move the roller 72 to the second position G separated from the roller 50.

  When the recording material is a small size recording material, the mechanism 90 is controlled to move the roller 72 to the first position F in contact with the roller 50. The roller 72 in contact with the roller 50 promotes the uniform temperature in the longitudinal direction of the roller 50, and the temperature rise of the belt 41 and the non-sheet passing portion of the roller 50 is suppressed.

c) Selection of Control Mode In the present invention, when the recording material to be passed through the apparatus is a small small size recording material, the control circuit unit 100 determines the basis weight of the small size recording material to be passed and The next first control mode and the second control mode are selected and executed according to the number of passing sheets per unit time.

  In the first control mode, as shown in a) above, the temperature rise of the non-sheet passing portion is suppressed by the movement control of the split movable core 63a, and the roller 72 is moved to the first position F where the roller 50 is in contact with the roller 50. Thus, the mechanism 90 is controlled. That is, the control is performed to suppress the temperature rise of the non-sheet passing portion by the core 63a and the temperature rise of the non-sheet passing portion by the soaking roller 72 together.

  In the second control mode, the temperature rise of the non-sheet passing portion is suppressed by the movement control of the split movable core 63a as in the above a), but the roller 72 is moved to the second position G separated from the roller 50. Thus, the mechanism 90 is controlled. That is, the temperature control roller 72 does not suppress the temperature rise of the non-sheet passing portion.

Here, let C be the longitudinal length (core width) of each split movable core 63a. In this embodiment, C = 15 mm. The basis weight of the recording material is 80 g / m ² , the fixable belt temperature is 160 ° C., and the fixing belt heat limit temperature is 220 ° C.

  Further, it is known that the belt surface temperature is −10 ° C. when the paper is not passed and −15 ° C. when the paper is continuously fed, rather than the temperature of the temperature sensor TH disposed inside the belt 41. In the following description, the fixing belt surface temperature is used for easy understanding. However, the actual fixing belt temperature adjustment temperature uses the temperature sensor TH disposed in the longitudinal central portion inside the fixing belt. The temperature control temperature may be determined by offsetting the value of.

(2-8) Post-rotation soaking control When the job for continuously passing a small-size recording material is executed and finished, the apparatus is in a non-sheet passing portion temperature rise state. Therefore, if a recording material having a width larger than the recording material that has been continuously passed in the previous job is passed as the next job to the device in the non-passing portion temperature rise state, In some cases, the temperature is excessively increased in a portion where the temperature is increased, and an image defect such as hot offset may occur. In the present invention, in order to suppress the occurrence of such image defects, the following post-rotation soaking control is executed.

That is, the control circuit unit 100 stops the power supplied to the coil 62 when the job for heating the small size recording material is completed. When the previous job is in the first control mode, the rotation speed equalization control is performed after the rotation of the pressure roller 50 is continued for a predetermined time while the heat equalization roller 72 is moved to the first position F and then stopped. Execute. Further, in the second control mode, the soaking roller 72 is moved from the second position G to the first position F, and the rotation of the pressure roller 50 is continued for a predetermined time and then stopped, and then the soaking rotation soaking control is performed. That is, after the previous job and the next job, the soaking roller 72 is brought into contact with the pressure roller 50 to perform the idling rotation after a certain period of time so as to perform the rotating soaking control. By making the pressure-uniforming roller 72 abut and the pressure roller 50 rotate idly, it is possible to accelerate the temperature-uniformization of the temperature of the excessive temperature rising portion.

  Further, when the soaking roller 72 is brought into contact with the pressure roller 50 by the post-rotation soaking control, the control circuit unit 100 pressurizing / pressing release mechanism 80 is changed to the pressurizing release state, and the belt 41 and the pressing roller 50 It is desirable to release the pressure. At this time, although there is little demerit with respect to the soaking effect by separating the belt 41 having a small heat capacity and little longitudinal soaking effect, the pressure pad 43 and the belt 41 rubbed against the inner surface of the belt 41 can thereby be reduced. Rubbing with the inner surface can be reduced.

In the following, the large-size recording material is 13 inch × 19 inch paper and is longitudinally fed. Accordingly, the width of the paper passing area Wmax is 330 mm. The small size recording material is an A4 size recording material and is laterally fed. Accordingly, the width of the paper passing area A is 297 mm. The basis weight of the recording material is 80 g / m ² (80 g paper) and 300 g / m ² (300 g paper). Then, an experiment is performed to compare the number of sheets until the image smears when 80 g paper and 300 g paper are passed at a ratio of 2: 1.

<Experiment 1>
1) Recording material of 80 g paper In Experiment 1, a recording material P having a basis weight of 80 g is passed at a passing number of 80 ppm per unit time. In this case, the rotation speed of the belt 41 is set to 321 mm / s. FIG. 8 is a schematic diagram showing the relationship between the longitudinal position and the paper width of each divided movable core 63a and the fixing belt temperature distribution when the paper is passed in this case. FIG. 8 is a schematic diagram, and the ratio of the width of the sheet passing area A and the non-sheet passing area B and the number of the split movable cores 63a in the sheet passing area A and the non-sheet passing area B are consistent with the actual. It is not a thing. The same applies to FIGS. 10 and 12.

  In Experiment 1, the soaking roller 72 is in contact with the pressure roller 50 during the sheet passing. Further, the core 63a corresponding to the sheet passing area A is moved to the first distance position D, and the core 63a corresponding to the non-sheet passing area B is moved to the second distance position E. . That is, the temperature increase of the non-sheet passing portion is suppressed by the first control mode. The individual split movable cores 63a are moved to an appropriate positional relationship with respect to the paper width of the recording material to be passed.

  As a result, the temperature of the non-sheet-passing portion (temperature 2) is kept at a heat-resistant limit temperature of 220 ° C. or lower while keeping the sheet-passing portion temperature (temperature 1) at 165 ° C. which is 5 ° C. higher than the fixable belt temperature 160 ° C. It can be suppressed to 210 ° C. The transition of the fixing belt temperature with respect to the elapsed time is as shown in FIG.

2) Recording material of 300 g paper In this experiment 1, a recording material having a basis weight of 300 g is passed through at 26 ppm. In this case, the rotation speed of the belt 41 is set to 107 mm / s. FIG. 10 is a schematic diagram showing the relationship between the longitudinal position and the paper width of each divided movable core 63a and the fixing belt temperature distribution when the paper is passed in this case.

  In Experiment 1, the soaking roller 72 is in contact with the pressure roller 50 during the sheet passing. Further, the core 63a corresponding to the sheet passing area A is moved to the first distance position D, and the core 63a corresponding to the non-sheet passing area B is moved to the second distance position E. . That is, also in this case, the temperature rise of the non-sheet passing portion is suppressed by the first control mode. The individual movable movable cores 63a and the outer magnetic cores are moved to an appropriate positional relationship with respect to the paper width.

  As a result, the temperature of the non-sheet-passing portion (temperature 2) is kept at a heat-resistant limit temperature of 220 ° C. or lower while keeping the sheet-passing portion temperature (temperature 1) at 165 ° C. which is 5 ° C. higher than the fixable belt temperature 160 ° C. It can be suppressed to 190 ° C. or lower. The transition of the fixing belt temperature with respect to the elapsed time is as shown in FIG.

  In this experiment 1, as described above, the soaking roller 73 was brought into contact with the pressure roller 50 for both 80 g paper and 300 g paper, and 2000 sheets of 80 g paper and 1000 sheets of 300 g paper were alternately flowed. As a result, the surface of the fluororesin layer 73b of the soaking roller 73 was abraded, causing image smearing on 200,000 sheets.

  As described above, a sufficient amount of heat generation is required to fix the toner even at the end of the small size recording material. However, as the paper is passed, the recording material is moved with respect to the paper passing area A of the belt 41 as a heating member. In the belt portion corresponding to the end portion, the amount of heat taken by the recording material P is small. Therefore, the temperature of the belt portion near the end of the recording material in the non-sheet passing area B is raised (temperature 2) than the sheet passing area A. And the abrasion of the fluororesin layer part of the soaking roller part corresponding to a temperature rising part becomes remarkable. For this reason, the toner adhering to the soaking member due to the lowering of the releasability due to the wear of the release layer returns to the recording material and causes image contamination.

<Experiment 2>
In Experiment 2, the recording material P having a basis weight of 80 g is passed through at 80 ppm, the soaking roller 73 is brought into contact with the pressure roller 50, the divided movable core 63a is moved, and the recording material P is passed through. This is the same as in Experiment 1. That is, the temperature increase of the non-sheet passing portion is suppressed by the first control mode.

  In contrast, when 300 g paper is passed at 26 ppm, the split movable core 63a is moved, but the soaking roller 73 is not brought into contact with the pressure roller 50. That is, the temperature increase of the non-sheet passing portion is suppressed by the second control mode.

  FIG. 12 shows a schematic diagram of the relationship between the longitudinal position and paper width of each divided movable core and the fixing belt temperature distribution when paper is passed in this case. In this case, each divided movable core 63a is moved to an appropriate positional relationship with respect to the paper width. As a result, even if the soaking roller 73 is not brought into contact with the pressure roller 50, the sheet passing portion temperature (temperature 1) is maintained at 165 ° C., which is 5 ° C. higher than the fixable belt temperature 160 ° C. (Temperature 2) of the part heating portion can be suppressed to 200 ° C. or less, which is 220 ° C. or less. The change in the fixing belt temperature with respect to the elapsed time is as shown in FIG.

  Compared to the case where 80 g paper is passed at 80 ppm, the belt temperature of the non-sheet passing portion B is heat resistant even if the soaking roller 73 is not brought into contact with the pressure roller 50 because 300 g paper is allowed to flow slowly at 26 ppm. The limit temperature of 220 ° C is not exceeded.

  In Experiment 2, as described above, the soaking roller 73 is brought into contact with the pressure roller 50 in the 80 g paper (first control mode). For 300 g paper, the soaking roller 73 is not brought into contact with the pressure roller 50 (second control mode). Then, 2000 sheets of 80 g paper and 1000 sheets of 300 g paper were alternately flowed. As a result, the fluororesin layer 73b on the surface of the soaking roller 73 is worn out. However, compared with Experiment 1, the time during which the soaking roller 73 is in contact with the pressure roller 50 is short. It was found that dirt was generated.

  Accordingly, the control circuit unit 100 determines whether the soaking roller 73 is in contact with the pressure roller 50 according to the basis weight of the recording material and the number of passing sheets per unit time according to the flowchart shown in FIG. (Selection of control mode and second control mode). As a result, it has been found that it is possible to suppress wear on the surface layer of the soaking roller and to prevent image smearing for a longer time.

  The flowchart of FIG. 14 will be described. In step S1, it is determined whether the recording material to be passed is A4 paper which is a small size recording material or [13 "× 19"] paper which is a large size recording material. If it is A4 paper, then in S2, it is determined whether the basis weight of the recording material is 80 g paper or 300 g paper. Information on the size and basis weight of the recording material to be passed is input in advance by the user to the control circuit unit 100 from an operation unit (not shown) or a host device (not shown) of the image forming apparatus.

  In the case of 80g paper, the passing number of ppm per unit time in S3 is set to 80 ppm. In S3, the control mode is set to the first control mode. That is, the split movable core 63a corresponding to the non-sheet passing portion B is moved to the second distance position E. Further, the soaking roller 72 is brought into contact with the roller 50. In this state, the set predetermined image forming jub is executed (S5 to S7).

  When the image forming operation is completed (S7), post-rotation soaking control is executed (S8 to S11). That is, the power supply to the coil 41 is turned off, and the mechanism 80 is changed to the pressure release state, and the pressurization of the nip portion N is released (S8). The rotation of the pressure roller 9 is continued for a predetermined time while the soaking roller 72 is in contact (S9 to S11). Thereby, it is possible to speed up the soaking | uniform-heating of the temperature of the overheating part of an apparatus. Then, after a predetermined time has elapsed, the driving of the pressure roller 50 is turned off, and the soaking roller 72 is moved to the second position G (S12). In this state, the next job is waited.

  In S2, in the case of 300 g paper, ppm is set to 26 ppm in S14. In S15, the control mode is set to the second control mode. That is, the split movable core 63 a corresponding to the non-sheet passing portion B is moved to the second distance position E, but the heat equalizing roller 72 is held in a state of being separated from the roller 50. In this state, the set predetermined image forming jub is executed, and the image forming operation ends (S5 to S7).

  When the image forming operation is completed (S7), the post-rotation soaking control is executed (S8 to S11) as in the case of 80g paper. In this case, the soaking roller 72 is changed from the second position G to the first position F (S13). After a predetermined time has elapsed, the driving of the pressure roller 50 is turned off, and the soaking roller 72 is moved to the second position G (S12). In this state, the next job is waited.

  In the case of [13 "× 19"] paper in S1, it is determined in S16 whether the basis weight of the recording material is 80g paper or 300g paper. In the case of 80 g paper, ppm is set to 80 ppm in S17. In the case of 300 g paper, ppm is set to 26 ppm in S18.

  In both cases of 80g paper and 300g paper, all the split movable cores 63a are moved to the first distance position D. The soaking roller 72 is held away from the roller 50 (S19). In this state, the set predetermined image forming jub is executed, and the image forming operation is finished (S20 to S22).

  When the recording material is [13 "× 19"] paper, which is a large size recording material, the apparatus is not in the non-sheet passing portion temperature rising state when the job is executed and terminated. Therefore, in this case, the post-rotation soaking control is not executed, and after the image forming operation is completed, the power supply to the coil 62 is turned off, the mechanism 80 is switched to the pressure release state, and the nip portion N is applied. The pressure is released and the driving of the pressure roller 50 is turned off (S23). In this state, the next job is waited.

In the flowchart of FIG. 14, the large size recording material is [13 "× 19"] paper, and the small size recording material is A4 paper. Further, in this example, the basis weight is 80 g / cm ² and 300 g / cm ² , and the number of passing sheets per unit time is 80 ppm and 26 ppm. This is an example, and the present invention is not limited to this. That is, the size, basis weight, and ppm of the recording material serving as the control standard can be stored in advance in a memory (not shown) of the control circuit unit 100 as an arbitrarily set reference table, and the apparatus control can be executed.

[Other device configurations]
1) The heating member 41 may be a roller body. Moreover, it can also be set as the endless belt body which has the flexibility which hangs around between several stretching members, and is circulated and moved.

  2) A configuration in which the magnetic field generating means 60 is disposed inside the heating member 41 may be employed. Further, it is possible to adopt a configuration in which one of the coil 62 and the core 63 of the magnetic field generating means 60 is disposed outside the heating member 41 and the other is disposed inside.

  3) The pressure member 50 may be configured as an endless belt body.

  4) The image heating device according to the present invention is not limited to use as the fixing device 16 of the embodiment. It can also be effectively used as a gloss increasing device (image modifying device) that increases the gloss of the image by heating the image fixed on the recording material.

  16. Image heating device, 41 ... Heating member, 41a ... Magnetic member, 50 ... Pressure member, N ... Nip part, 60 ... Magnetic field generating means, 62 ... Magnetic field generating coil, 63 ... Magnetic Body core, 63a ... Divided movable core, 65 ... Core moving means, 72 ... Heat equalizing member, 90 ... Heat equalizing member moving means, TH ... Temperature detecting means, 100 ... Control means, Temperature control means, P ... Recording material, t ... Toner image

Claims (5)

A rotatable heating member composed of a magnetic member that includes a magnetic field generating coil and a magnetic core, and a magnetic member that generates electromagnetic induction heat when passing through a region where a magnetic field generated from the magnetic field generating unit exists; A rotatable pressure member that forms a nip portion with the heating member, a temperature detection unit that detects a temperature of a sheet passing area of the heating member, and information about a temperature detected by the temperature detection unit is a predetermined temperature. Temperature control means for controlling the power supplied to the magnetic field generating coil so that the corresponding information is maintained, and an image heating apparatus that holds and conveys a recording material carrying an image at the nip portion and heats it. And
When the direction perpendicular to the recording material conveyance direction is the longitudinal direction, the magnetic core is disposed along the longitudinal direction of the heating member, and is divided into a plurality of portions in the longitudinal direction and individually It has a split movable core that can move independently in the direction of changing the distance to the heating member,
A core moving means for moving the individual divided movable cores to a first distance position with respect to the heating member and a second distance position farther from the heating member than the first distance position;
A soaking member having a toner release resin layer on the surface and having the same longitudinal dimension as the pressure member;
A soaking member moving means for moving the soaking member to a first position contacting the pressing member and a second position spaced from the pressing member;
When the recording material to be passed through the apparatus is a small size recording material whose width is smaller than the maximum size large size recording material that can be passed through the apparatus, among the divided movable cores, The core moving means is controlled so that the split movable core corresponding to the sheet passing area of the size recording material is positioned at the first distance position, and the other split movable cores are positioned at the second distance position. At the same time, the first heat equalizing member moving means is controlled to move the heat equalizing member to the first position in accordance with the basis weight of the small size recording material to be passed and the number of passing sheets per unit time. Control means for selecting and executing a control mode and a second control mode for controlling the soaking member moving means so as to move the soaking member to the second position;
And when the job for heating the small-size recording material is completed, the control means stops the power supplied to the magnetic field generating coil, and in the first control mode, the control member is moved to the first temperature equalizing member. The rotation of the pressurizing member is continued for a predetermined time while being moved to the position, and then stopped. In the second control mode, the heat equalizing member is moved from the second position to the first position. An image heating apparatus that performs post-rotation soaking control in which the rotation of the pressure member is continued for a predetermined time and then stopped.   Pressurizing / pressurizing releasing means for switching the heating member and the pressurizing member to a state in which the heating member and the pressure member are pressurized with a predetermined pressure and a pressure releasing state in which the pressure is released; The image heating apparatus according to claim 1, wherein the rotation soaking control is executed in a state in which the pressurizing / pressurizing release means is changed to a pressurizing release state.   When the recording material passed through the apparatus is the large size recording material, the control means controls the core moving means so that all of the split movable cores are positioned at the first distance position. 2. The image heating apparatus according to claim 1, wherein the heat equalizing member moving unit is controlled to move the heat equalizing member to the second position.   4. The image heating apparatus according to claim 1, wherein a toner release resin layer is provided on the surface of the metal core bar. 5.   The image heating apparatus according to claim 1, wherein a toner cleaning member is in contact with the heat equalizing member.