JP4110013B2 - Image heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is particularly suitable for use as an image heating and fixing apparatus for heating and pressure-fixing an unfixed image in an image information recording apparatus (image forming apparatus) such as a copying machine, a printer, and a facsimile machine. ) Induction heating methodImage heating deviceConcerningThe
[0002]
[Prior art]
  An image heating and fixing apparatus mounted on an image forming apparatus such as an electrophotographic copying machine, printer, or facsimile will be described as an example.
[0003]
  The image heating and fixing device in the image forming apparatus is an electrophotographic, electrostatic recording,MagneticUndecided, formed by the direct method or the indirect (transfer) method on the surface of the recording material as the material to be heated, using toner (developer) made of heat-meltable resin, etc., by appropriate image forming process means such as recording Wear toner image on recording materialHardThis is a device for heat fixing processing as a received image.
[0004]
  Conventionally, as such an image heating and fixing apparatus, there are various apparatuses such as a heat roller system, a film heating system, and an electromagnetic induction heating system.
[0005]
  a. Heat roller method
  This consists of a rotating roller pair of a fixing roller (heat roller) and a pressure roller that are heated and adjusted to a predetermined fixing temperature by incorporating a heat source such as a halogen lamp, and a pressure nip (fixing nip) of the roller pair. In this case, an unfixed toner image is heated and fixed on the surface of the recording material by introducing a recording material on which an unfixed toner image is formed and supported as a material to be heated.
[0006]
  However, this apparatus has problems such as a large heat capacity of the fixing roller, a large amount of electric power required for heating, and a long wait time (waiting time from when the apparatus is turned on until a print output is enabled). Further, since the heat capacity of the fixing roller is large, there is a problem that a large amount of power is required to raise the temperature of the fixing nip portion with limited power.
[0007]
  As a countermeasure, the thickness of the fixing roller is reduced to reduce the heat capacity of the fixing roller. However, if it is too thin, the strength will be insufficient. Further, similarly to the film fixing described later, a problem of non-sheet passing portion temperature rise occurs.
[0008]
  b. Film heating method
  This has a heating element and a film in which one surface slides on the heating element and the other surface moves in contact with the recording material. The heat of the heating element is applied to the recording material through the film to be determined. This is a device that heats and fixes a toner image on the recording material surface (see, for example, Patent Documents 1 to 16).
[0009]
  Such a film heating type apparatus can use a low heat capacity ceramic heater or the like as a heating body, and a heat resistant thin thin heat capacity apparatus as a film, and a heat roller type apparatus using a fixing roller having a large heat capacity. Compared to the above, there are advantages such as significantly reduced power consumption and shortened wait time, quick start performance, and suppression of temperature rise in the machine.
[0010]
  c. Electromagnetic induction heating method
  This is because an electromagnetic induction heating element is used as a heating element, and a magnetic field is applied to the electromagnetic induction heating element by a magnetic field generating means, and Joule heating based on eddy currents generated in the electromagnetic induction heating element is used as a recording material as a material to be heated. This is a device that heat-fixes an unfixed toner image on a recording material surface by applying heat.
[0011]
  As this type of device, for example, Patent Document 17 discloses a heat roller type device that electromagnetically heats a ferromagnetic fixing roller. The heat generation position can be close to the fixing nip portion. It achieves a more efficient fixing process than a heat roller type apparatus using a lamp as a heat source.
[0012]
  However, since the heat capacity of the fixing roller is large, there is a problem that a large amount of electric power is required to raise the temperature of the fixing nip portion with limited electric power. One solution to this problem is to reduce the heat capacity of the fixing roller. For example, reducing the thickness of the fixing roller.
[0013]
  For example, Patent Document 18 discloses an electromagnetic induction heating type fixing device using a film-like fixing roller (film) with a reduced heat capacity.
[0014]
  However, in a film-like fixing roller (film) with a reduced heat capacity, the heat flow in the long direction (the longitudinal direction of the fixing nip portion) is obstructed. Therefore, when a small-size recording material is passed, An excessive temperature rise (non-sheet passing portion temperature rise) has occurred, causing a problem of reducing the life of the film and the pressure roller. The problem of the temperature rise of the non-sheet passing portion is the same as in the case of the film heating type apparatus of the item b.
[0015]
  Further, for example, Patent Documents 19 and 20 disclose a heating apparatus having magnetic flux adjusting means for changing the density distribution of the acting magnetic flux with respect to the induction heating element from the magnetic flux generating means in the longitudinal direction of the fixing roller (film). Has been. One method for solving the non-sheet passing portion temperature rise by the electromagnetic induction heating type fixing device has been shown.
[0016]
  The above-mentioned Patent Documents 19 and 20 use a configuration in which a film-like induction heating element is heated as an example, but the problem of the temperature rise of the non-sheet-passing portion is also the case where a cylindrical induction heating element is used as a fixing roller. It is considered effective as a countermeasure.
[0017]
  As another method for solving the temperature increase in the non-sheet passing portion, there is a method in which the fixing speed is lowered when a small size recording material is passed (throughput reduction). By slowing down the fixing speed, the heat transfer time in the end direction (non-sheet passing portion) of the fixing roller is provided. However, this method reduces the productivity of the image forming apparatus.
[Patent Document 1]
          JP-A-63-313182
[Patent Document 2]
          Japanese Patent Laid-Open No. 2-157878
[Patent Document 3]
          JP-A-4-44075
[Patent Document 4]
          JP-A-4-44076
[Patent Document 5]
          JP-A-4-44077
[Patent Document 6]
          JP-A-4-44078
[Patent Document 7]
          JP-A-4-44079
[Patent Document 8]
          JP-A-4-44080
[Patent Document 9]
          JP-A-4-44081
[Patent Document 10]
          JP-A-4-44082
[Patent Document 11]
          JP-A-4-44083
[Patent Document 12]
          JP-A-4-204980
[Patent Document 13]
          JP-A-4-204981
[Patent Document 14]
          JP-A-4-204982
[Patent Document 15]
          JP-A-4-204983
[Patent Document 16]
          JP-A-4-204984
[Patent Document 17]
          Japanese Patent Publication No. 5-9027
[Patent Document 18]
          JP-A-4-166966
[Patent Document 19]
          Japanese Patent Laid-Open No. 9-171889
[Patent Document 20]
          JP-A-10-74009
[0018]
[Problems to be solved by the invention]
  Therefore, as the image heating and fixing device of the image forming apparatus, it is possible to save space for the standby space of the magnetic flux adjusting means used for measures for raising the temperature of the non-sheet passing portion and the installation space of the driving means for the magnetic flux adjusting means. Therefore, there is a demand for an image heating apparatus that has the same performance.
[0019]
  The present invention provides an electromagnetic induction heating system that can meet such demands.Image heating deviceIs to provide.
[0020]
[Means for Solving the Problems]
  The present invention is characterized by the following configurations.Image heating deviceIt is.
[0021]
  A coil that generates magnetic flux, a coil holder that supports the coil, a heat generating member that generates heat by induction and heats an image on the recording material, and a conveying direction of the recording material by shielding the magnetic flux from the coil A magnetic flux shielding member that changes a magnetic flux distribution in a direction orthogonal toA drive transmission member for transmitting a driving force to the magnetic flux shielding member;In the image heating apparatus, the coil holder is disposed inside the heating member,
  The heat generating member is supported by heat generating member support plates at both ends, and the coil holder maintains a gap with the heat generating member by a coil holder support plate outside the heat generating member support plate at the shaft portions at both ends. Both ends of the magnetic flux shielding member are respectively supported by a support shaft portion of a coil holder having an axis that coincides with the rotation axis of the heat generating member and the center line of the shaft portion.AndThe magnetic flux shielding member isAttached to the drive transmission member fitted to the support shaft portion of the coil holder and coincides with the rotational axis of the heat generating memberCentering on the axis of the support shaftSynchronously with the rotation of the drive transmission memberAn image heating apparatus that rotates between the coil holder and the heat generating member.
[0022]
  With such a configuration, it is possible to realize an induction heating type image heating apparatus using a magnetic flux shielding member that saves space and costs while improving power saving and productivity.
  Moreover, even if the support plate for the image heating device of the coil holder and the heat generating member is different, it is possible to maintain an interval such that the magnetic flux shielding member and the heat generating member do not rub against each other even if the magnetic flux shielding member rotates.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
  [First embodiment]
  1 to 4 show an example of an electromagnetic induction heating type fixing device as an image heating device according to the present invention.
[0024]
  FIG. 1 is a cross-sectional view showing a schematic configuration in the fixing roller longitudinal direction (fixing roller axial direction) of the fixing device of this example, and FIG. 2 is a cross-sectional view showing a schematic configuration of the fixing device in the radial direction of the fixing roller. FIG. 3 is an exploded perspective view for explaining the configuration of the magnetic flux shielding means and the magnetic flux generation means.
[0025]
  The fixing device of this example includes a magnetic flux adjustment heating assembly 1 and a fixing roller 7 as an induction heating element.(Heat generating member that heats the image on the recording material)The pressure roller 8 is mainly used.
[0026]
  The magnetic flux adjusting and heating assembly 1 includes an exciting coil 5 (Coil that generates magnetic flux:(Hereinafter referred to as coil) and magnetic core 6 (hereinafter referred to as core), coil 5 and holder for holding core 6(Coil holder)2 and both ends of the holder 2 are pivoted(Support shaft)Arc-shaped magnetic flux shield as magnetic flux adjusting means, which is freely arranged to rotate in the counterclockwise or clockwise direction indicated by arrows a and b.Element3 etc.
[0027]
  The magnetic flux generating means has a configuration in which the coil 5 and the T-shaped core 6 are arranged inside the fixing roller 7. The coil 5 and the core 6 are held by the holder 2 and covered with a holder lid 19.
[0028]
  The coil 5 has a substantially elliptical shape (horizontal boat shape) in the longitudinal direction of the fixing roller 7 and is disposed inside the holder 2 along the inner surface of the fixing roller. The core 6 includes a first core 6a (vertical portion) in the winding center portion of the coil 5 and a second core 6b (horizontal portion) disposed on the upper portion thereof to constitute a T-shaped core.
[0029]
  The coil 5 must generate an alternating magnetic flux sufficient for heating. For this purpose, it is necessary to make the resistance component low and the inductance component high. As a core wire of the coil, a litz wire in which about 80 to 160 fine wires having a diameter of 0.1 to 0.3 mm are bundled is used. Insulated coated wires are used for the thin wires. In this example, the coil 5 is configured to be wound 8 to 12 times around the first core 6a. An excitation circuit (not shown) is connected to the coil 5, and an alternating current can be supplied to the coil 5 through the circuit.
[0030]
  The core 6 may be made of a material having a high magnetic permeability and a low residual magnetic flux density such as ferrite and permalloy, but is not particularly limited as long as it can generate a magnetic flux. The shape and material of the core are not specified in the above. For example, the effect of the present invention can be obtained even if the first core 6a and the second core 6b are integrally formed to be T-shaped.
[0031]
  The cylindrical fixing roller 7 as the induction heating element is preferably made of a ferromagnetic metal such as iron, nickel, or cobalt. By using a ferromagnetic metal (a metal having a high magnetic permeability), the magnetic flux generated from the magnetic flux generating means 5 and 6 can be more restricted in the ferromagnetic metal. That is, the magnetic flux density can be increased. Thereby, an eddy current is efficiently generated on the surface of the ferromagnetic metal (fixing roller surface), and the surface can be heated.
[0032]
  The heat capacity is reduced by setting the thickness of the fixing roller 7 to about 0.3 to 2 mm. A toner release layer (not shown) is provided on the outer surface of the fixing roller 7. Generally, it is comprised by PTFE 10-50 micrometers or PFA 10-50 micrometers. Further, a rubber layer may be used inside the toner release layer.
[0033]
  The fixing roller 7 is rotatably supported at both ends by support plates (heating member support plates) 51 and 52.A fixing roller gear 18 is attached to one end of the fixing roller 7, and the gear is rotated by a drive motor (not shown).
[0034]
  The pressure roller 8 has a configuration in which a toner release layer is provided on the outer periphery of an iron core bar in the same manner as the silicone rubber layer and the fixing roller 7.
[0035]
  The magnetic flux adjusting means in the fixing roller longitudinal direction in the fixing device of this example is mainly composed of the magnetic flux shielding member 3, the holder 2, the shielding gear 11, and the bush 14. Among these components, the holder 2 and the magnetic flux shielding member 3 are disposed inside the fixing roller 7.
[0036]
  In the fixing device of this example, the support portions at both ends of the holder 2 holding the coil 5 and the core 6 are used as the rotation center of the magnetic flux shielding member 3.OctopusAnd features.
[0037]
  Both ends of the holder 2 are axially shaped to rotatably support the magnetic flux shielding member 3(Shaft)It is. The holder 2 has a function of holding the coil 5 and the core 6 and a function of rotatably supporting the magnetic flux shielding member 3.
[0038]
  The support shaft 2 a of the holder 2 has a shielding gear 11 for rotating the magnetic flux shielding member 3.(Drive transmission member that transmits driving force to rotate the magnetic flux shielding member)In order to improve the slidability of the magnetic flux shielding member 3, the support shaft 2b on the opposite side is provided with a bush 14, and the thrust direction is regulated by the thrust retaining rings 12 and 16, respectively.
[0039]
  The holder 2 is made of a non-magnetic, electrically insulating and high heat resistant material. For example, as the material of the holder 2, a material obtained by adding glass to a PPS resin having both heat resistance and mechanical strength is used. Of course, it is non-magnetic. When the holder is made of a magnetic material, the holder generates heat due to electromagnetic induction, and the heat generation efficiency of the fixing roller decreases.
[0040]
  Suitable materials for the holder include materials such as PPS resins, PEEK resins, polyimide resins, polyamide resins, polyamideimide resins, ceramics, liquid crystal polymers, and fluorine resins.
[0041]
  The material of the bush 14 and the shielding gear 11 is the same as that of the holder. Of these, it is preferable to select a material with particularly good sliding properties. For example, there are a polyamideimide resin, a PFA resin, a PEEK resin, and the like.
[0042]
  The magnetic flux shielding member 3 is composed of a non-magnetic and highly electrically conductive member. By using a non-magnetic member, there is an effect of blocking the magnetic flux. By using a good electrical conductive member, there is an effect of suppressing heat generation by electromagnetic induction of the magnetic flux shielding member itself. In this example, an aluminum alloy is used as the material of the magnetic flux shielding member 3, but an alloy such as copper, magnesium, or silver may be used.
[0043]
  The thickness of the magnetic flux shielding member 3 may be about 0.3 to 1.0 mm. If it is too thin, the magnetic flux shielding member itself generates electromagnetic induction heat. In addition, the strength is insufficient. On the other hand, if the thickness is too thick, the heat capacity of the magnetic flux shielding member increases, and when the fixing roller is heated, the heat is taken away, leading to an increase in the wait time.
[0044]
  As shown in FIG. 3, the magnetic flux shielding member 3 is provided with notches 3c and 3d having a shape that changes in stages corresponding to the paper size of the recording material (paper) as the material to be heated. In the figure, for example, in the longitudinal direction of the magnetic flux shielding member 3, the paper size width B that is smaller than the paper size width A is accommodated inside the paper size width A (maximum paper passing size) where the non-sheet passing portion temperature rise does not occur. The cutout portion 3c is provided, and the cutout portion 3d corresponding to the paper size width C smaller than the paper size width B is provided inside the paper size width B. Shielding portions (non-sheet passing portions) 3e and 3f corresponding to the paper size width B are formed at both inner ends of the paper size width A by the notches 3c, and both inner ends of the paper size width B are formed by the notches 3d. The shielding portions (non-sheet passing portions) 3g and 3h corresponding to the paper size width C are formed.
[0045]
  Therefore, the magnetic flux shielding member 3 of this example has a shape in which the shielding portions 3e, 3f and 3g, 3h corresponding to the paper size are changed in stages.
[0046]
  On the holder support shaft 2 a side, the modified hole 3 a having a notch provided at one end of the magnetic flux shielding member 3 and the cylindrical portion 11 b of the shielding gear 11 are fitted. The protrusion 11a formed on the cylindrical portion 11b of the shielding gear and the U-shaped hole 3a ′ of the magnetic flux shielding member 3 are fitted, so that when the shielding gear 11 is rotated, the magnetic flux shielding member 3 is shielded. It rotates in synchronization with. The shield gear 11 is rotationally driven by the driving means 20. The drive unit 20 may be any drive source such as a motor, and the present invention does not depend on the configuration of the drive unit. For example, the magnetic flux shielding member 3 may be rotated by an actuator such as a solenoid as a driving means and a motion transmission mechanism such as a link mechanism that converts the operation of the actuator into a rotational motion and transmits it to the shielding gear 11. .
[0047]
  The holder support shaft 2b side is a coil supply line that supplies power to the coil 5.(Excitation coil bundle)It has a shape that also serves as 15 guides. By making the holder support shaft 2b into a hollow pipe shape, the coil supply wire 15 is drawn through the inside. A holding hole 3b provided on the other end side of the magnetic flux shielding member 3 is rotatably fitted to the cylindrical portion 14a of the bush 14 on the holder support shaft 2b. A connector portion 15 a is provided at the end of the coil supply line 15 and is connected to the power control device 25. An alternating current is supplied to the coil 5 through the coil supply line 15 by controlling an excitation circuit (not shown) by the power control device 25.
[0048]
  The holder 2 has a support plate on the support shaft 2a side.(Coil holder support plate)13, the support shaft 2b side is a holder support member(Coil holder support plate)17 is supported.The holder support plates 13 and 17 are outside the support plates 51 and 52 of the fixing roller 7, respectively. As a result, the positions of the holder 3 and the fixing roller 7 with respect to the fixing device are determined, and the coil holder 3 is supported so as to maintain a gap with the fixing roller 7.The shape of the fitting portion between the support shaft 2a and the holder support plate 13 is a D-shaped shape (D cut). With the D-shape, the holder 2 is positioned in the circumferential direction of the fixing roller. As a result, the holder 2 has the support shaft 2a and the shaft center 2c of the support shaft 2b (see FIG. 3) as the rotation shaft of the fixing roller 7.LineIt is positioned so as to be coaxial with the center 7c (see FIG. 1).
[0049]
  In the fixing device of this example, the magnetic flux shielding member 3 is rotated by a predetermined angle in the predetermined direction by the driving means 20 by an angle corresponding to the paper size, and the shielding portion 3e having a shape that changes stepwise of the magnetic flux shielding member. 3f, 3g, and 3h are pivotally moved to the facing portion of the core 6a. By shielding the magnetic flux lines passing from the core 6a to the fixing roller 7 by this shielding portion, heat generation of the fixing roller is mitigated at the shielding portion, and an abnormal temperature rise is prevented.
[0050]
  In the magnetic flux shielding member 3 shown in this example, the two-stage magnetic flux adjustment of the paper size width B and the paper size width C which are smaller than the paper size width A (maximum paper passing size) where the temperature rise of the non-sheet passing portion does not occur is possible. . For example, for a metric paper size, the paper size width A is A4 width (297 mm), the paper size width B is B4 width (257 mm), and the paper size width C is A4R width (210 mm). In this case, the entire length of the notch is set to a notch width (paper size width) that changes stepwise corresponding to the respective paper size widths A, B, and C. The paper size is determined by the specifications of the image forming apparatus on which the fixing device is mounted. Further, the shielding part (or notch part) of the magnetic flux shielding member 3 is not limited to two stages, and the shielding part (stepping part) that changes step by step depending on the size at which the non-sheet passing part temperature rise occurs. Alternatively, the number of cutout portions) can be increased or decreased, and even if one or three or more are provided, a non-sheet-passing temperature rise prevention effect according to the paper size can be obtained.
[0051]
  In the fixing device of this example, as described above, in the holder 2 and the magnetic flux shielding member 3 that hold the coil 5 and the core 6, one end side of the magnetic flux shielding member 3 is held by the holder support shaft 2a, and the holder support shaft 2b Since the one end side of the magnetic flux shielding member 3 is held, the holder 2 and the magnetic flux shielding member 3 are configured as one compact assembly (unit).
[0052]
  Also, the shaft center 2c (see FIG. 3) of the support shaft 2a and the support shaft 2b of the holder 2 holding the magnetic flux shielding member 3 is arranged coaxially with the rotation shaft center 7c (see FIG. 1) of the fixing roller 7. ing. Thus, the magnetic flux shielding member 3 is disposed inside the fixing roller 7 via the shielding gear 11 and the bush 14 on the holder support shafts 2a and 2b coaxial with the rotation shaft center 7c of the fixing roller 7.That is, both ends of the magnetic flux shielding member 3 are respectively supported by the support shaft portions 2a and 2b of the holder 3 having an axis that coincides with the rotation axis of the fixing roller 7 and the center line of the shaft portion of the holder 2. The member 3 rotates between the holder 3 and the fixing roller 7 around the axis of the support shafts 2a and 2b.As a result, it is not necessary to provide a standby space for the magnetic flux shielding member outside the fixing roller, for example, outside the end of the fixing roller, thereby saving space.
[0053]
  Further, since the holder 2 for holding the magnetic flux generation means 5 and 6 and the magnetic flux shielding member 3 are compactly configured by one assembly (unit), the assembling property of the holder 2 and the magnetic flux shielding member 3 in the assembly process of the apparatus. In the maintenance, the exchangeability (serviceability) of the fixing roller 7 can be improved.
[0054]
  Further, since the magnetic flux shielding member 3 can be rotationally driven by the drive means 20 disposed on one side (the support shaft 2a side of the holder 2) at the rotation shaft center 7c of the fixing roller 7, the installation space of the drive means can be reduced. It only needs to be provided on the support shaft 2a side, and space saving in the fixing roller thrust direction is possible.
[0055]
  Therefore, conventionally, when a sheet as a recording material passes through the center in the longitudinal direction of the fixing roller (center reference paper transport system), the standby space for the magnetic flux shielding member and the drive means space for the magnetic flux shielding member are arranged on both sides in the longitudinal direction of the fixing roller. However, in this example, the magnetic flux shielding member 3 is made to stand by inside the fixing roller 7 and the driving means 20 can be arranged on one side of the fixing roller. The size of the image forming apparatus main body can be suppressed.
[0056]
  In the fixing device shown in this example, as shown in FIGS. 1 and 2, the fixing roller 7 and the pressure roller 8 that contain the assembly 1 are brought into pressure contact with each other up and down and assembled in a device housing (not shown). A fixing nip portion (heating nip portion) N having a predetermined width is formed between the two 7 and 8.
[0057]
  The fixing roller 7 is rotated in the clockwise direction indicated by the arrow P by the fixing roller gear 18, and the pressure roller 8 is also driven and rotated in the counterclockwise direction indicated by the arrow Q.
[0058]
  The coil 5 generates an alternating magnetic flux by an alternating current supplied from the power control device 25. The alternating magnetic flux is guided to the core 6 and acts on the fixing nip N, and an eddy current is generated on the surface of the fixing roller at the fixing nip N. Let The eddy current generates Joule heat due to the specific resistance of the roller surface. That is, by supplying an alternating current to the coil, the fixing roller 7 enters an electromagnetic induction heat generation state at the fixing nip portion N.
[0059]
  The temperature of the fixing nip N is controlled to a predetermined fixing temperature by controlling the alternating current supplied from the power control device 25 to the coil 5 by a temperature control system including a temperature detection sensor (not shown).
[0060]
  Accordingly, the fixing roller 7 is rotated by the rotation of the fixing roller gear 18, and an alternating current is supplied from the power control device 25 to the coil 6 so that the temperature of the fixing nip portion N rises to a predetermined temperature and is adjusted in temperature. A recording material (paper) S carrying a non-fixed toner image as a heated material between the fixing roller 7 and the pressure roller 8 in the fixing nip portion N follows a paper conveyance path (one-dot chain line) H along an arrow C. When the recording material is introduced from the direction, the recording material and the unfixed toner image are heated by the heat generated by the fixing roller 7 and the toner image is heated and fixed. The recording material that has passed through the fixing nip N is separated from the outer surface of the fixing roller by the separation claw 30 on the exit side of the fixing nip and conveyed.
[0061]
  Next, the operation and action of the magnetic flux shielding member in the fixing device of this example will be described with reference to FIG. 4 which is an image diagram of the magnetic circuit.
[0062]
  Magnetic field lines Ja (illustrated by a two-dot chain line) indicate a magnetic circuit of the generated magnetic field lines when electric power (alternating current) is input from the power control device to the magnetic flux generating means. The magnetic field lines Ja pass through the first core 6a (vertical portion), the fixing roller 7, and the second core 6b (horizontal portion). Actually, the lines of magnetic force pass through the inside of the fixing roller having a high magnetic permeability, but are shown as in FIG. 4 for easy understanding.
[0063]
  Here, let us consider a heat generation point due to electromagnetic induction heating in the fixing roller 7.
[0064]
  The heating point is particularly large at the fixing roller portion where the coil 5 faces. This is considered to be because the magnetic flux density is increased in the fixing roller portion opposed to the coil 5 because the first core 6a and the second core 6b are generated so that the lines of magnetic force go back and forth. Taking this into consideration, the magnetic flux generation means 5 and 6 of this example are arranged so as to be inclined so that the heating nip comes in front of the fixing nip N portion. Furthermore, the fixing roller 7 is rotated and heated without temperature unevenness.
[0065]
  The magnetic flux adjusting means is provided based on the above-described electromagnetic induction heating principle. In the magnetic flux adjusting means of this example, the magnetic flux shielding member 3 changes the path of the magnetic flux going back and forth inside the fixing roller. Thereby, the heat generation by electromagnetic induction in the longitudinal direction of the fixing roller is controlled.
[0066]
  That is, by placing the magnetic flux shielding member 3 between the core 6 and the fixing roller 7, the heat generation of the fixing roller can be efficiently reduced. In particular, in the case of the T-shaped core 6, it is efficient to shield the first core (vertical portion) 6a. As shown in FIG. 4 (a), the magnetic flux lines Ja have a higher density in the first core 6a than in the second core (horizontal portion) 6b, and are separated from the end of the first core to the end of the second core. Therefore, it is efficient to shield the magnetic flux line Ja at this magnetic circuit position.
[0067]
  As shown in FIG. 4A, the magnetic flux shielding member 3 stands by in a range where there is little influence on the magnetic circuit Ja when the paper size width A does not cause the non-sheet passing portion temperature rise. In the figure, the magnetic flux shielding member 3 stands by at a position where the magnetic circuit Ja does not exist. Since the magnetic flux shielding member 3 at this position does not affect the magnetic circuit Ja, fixing processing by electromagnetic induction heating is possible in the entire width of the paper size width A.
[0068]
  When the paper size width B where the temperature rise of the non-sheet passing portion occurs, the magnetic flux shielding member 3 rotates and moves on the magnetic circuit Ja shown in FIG. 4A as shown in FIG. Inhibit. In the figure, the shielding portions 3e and 3f of the magnetic flux shielding member 3 face the first core 6a and obstruct the flow of magnetic flux. The magnetic circuit Jb shown in the figure is a magnetic circuit when shielded by the width Ba (Bb) (see FIG. 3) of the shielding part 3e (3f). In the width Ba (Bb) of the shielding portion 3e (3f), which is a non-sheet passing portion when the paper size width is B, the magnetic flux passing through the inside of the fixing roller is smaller than that in the case of FIG. I understand. Thereby, in the range of width Ba * Bb of shielding part 3e * 3f, the heat_generation | fever by electromagnetic induction reduces and it can suppress non-sheet passing part temperature rising. At this time, the paper size width B (notch portion 3c) becomes a fixable region by electromagnetic induction heating.
[0069]
  The same applies to the paper size width C where the non-sheet passing portion temperature rise occurs. The magnetic flux shielding member 3 further rotates on the magnetic circuit Ja. In the figure, the shielding part 3g (3h) of the magnetic flux shielding member 3 faces the first core 6a and obstructs the flow of magnetic flux. The magnetic circuits Jc and Jc 'shown in the figure are magnetic circuits when shielded by the width Ca (Cb) (see FIG. 3) of the shielding part 3g (3h). With the added width (Ba + Ca) of the shielding portions 3e and 3g and the added width (Bb + Cb) of the shielding portions 3f and 3h, which are non-sheet passing portions when the paper size width is C, the magnetic flux passing through the fixing roller is as shown in FIG. ) And magnetic circuits Jb and Jc · Jc ′ shown in FIG. It can be seen that the magnetic flux passing through the inside of the fixing roller in the range of the width (Ba + Ca) · (Bb + Cb) is smaller than that in the case of FIG. Thereby, electromagnetic induction heat_generation | fever reduces in the range of a width | variety (Ba + Ca) and (Bb + Cb), and a non-sheet passing part temperature rising can be suppressed. At this time, the paper size width C (notch portion 3d) becomes a fixable region by electromagnetic induction heating.
  As described above, the magnetic flux shielding member 3 is a member that shields the magnetic flux from the coil 5 and changes the magnetic flux distribution in the direction orthogonal to the recording material conveyance direction. The magnetic flux shielding member 3 is rotated by an angle corresponding to the shielding position corresponding to the size of the recording material that needs to be shielded by the shielding gear 11, and the non-sheet passing portion of the size of the recording material that needs to be shielded is magnetic flux shielded. The member 3 is shielded between the holder 2 and the fixing roller 7 by the shape portions 3e, 3f, 3g, and 3h that are gradually changed.
[0070]
  [ Reference example 1 ]
  6, 7, and 8 show the fixing device of Reference Example 1. FIG.
[0071]
  Reference Example 1The fixing device shown in FIG. 1 is configured to adjust the magnetic flux by rotating the magnetic flux generating means with respect to the fixed magnetic flux adjusting means (magnetic flux shielding member). Magnetic flux generation means, fixing roller, pressure roller, etc.ofThe same reference numerals are used for the same functions as in the embodiment. The material of the holder and magnetic flux shielding member is also the firstofIt is the same as that of an Example.
[0072]
  The magnetic flux shielding member as the magnetic flux adjusting means is the firstofUnlike the magnetic flux shielding member of an Example, it is comprised from two member 3A * 3B (refer FIG. 6). The magnetic flux shielding members 3A and 3B have an arc shape with a notch that changes stepwise as shown in FIG. This notch will be described later. Of the two magnetic flux shielding members 3A and 3B, one magnetic flux shielding member 3A is a holder support plate 13 on the support shaft 2a side of the holder 2, and the other magnetic flux shielding member 3B is a holder support on the support shaft 2b side of the holder 2. Each plate 17 is fixed with screws (not shown).
[0073]
  Reference Example 1In this fixing device, the holder 2 holding the coil 5 and the core 6 as magnetic flux generating means is rotated by the shielding gear 11 with the support shafts 2a and 2b as the rotation center. The shielding gear 11 and the support shaft 2a are configured to transmit the drive by fitting in a D shape (D cut). Thereby, the holder 2 rotates in the directions of arrows a and b.
[0074]
  As shown in FIG. 8, the magnetic flux shielding members 3A and 3B are provided with shielding portions (non-sheet passing portions) 3p and 3q and 3r and 3s that change in stages corresponding to the paper size. These shields are the firstofIt is provided in a shape corresponding to the notched portions 3c and 3d that are changing stepwise as described in the embodiment.
[0075]
  Therefore, the magnetic flux shielding members 3A and 3B have shapes in which the shielding portions 3p and 3q and 3r and 3s corresponding to the paper size are changed in stages. In addition, the holder 2 has a core 6a integrated with the holder 2 in the shielding portions 3p, 3q and 3r, 3s of the shape of the magnetic flux shielding member which is changed in stages by the driving means 20 by an angle corresponding to the paper size. The opposing part is rotated. By shielding the magnetic flux lines passing from the core 6a to the fixing roller 7 by the shielding portion, heat generation of the fixing roller at the shielding portion (non-sheet passing portion) is alleviated and abnormal temperature rise is prevented.
[0076]
  In the magnetic flux shielding members 3A and 3B, the two-stage magnetic flux adjustment of the paper size width B and the paper size width C, which are smaller than the paper size width A (maximum paper passing size) where the temperature rise of the non-sheet passing portion does not occur, is possible. For example, for a metric paper size, the paper size width A is A4 width (297 mm), the paper size width B is B4 width (257 mm), and the paper size width C is A4R width (210 mm). In this case, the entire length of the notch is set to a notch width (paper size width) that changes stepwise corresponding to the respective paper size widths A, B, and C. The paper size is determined by the specifications of the image forming apparatus on which the fixing device is mounted. Further, the shielding part (or notch part) of the magnetic flux shielding member is not limited to two stages, and the shielding part (or the step part that changes step by step depending on the size at which the non-sheet passing part temperature rises) (Notch part) is provided by increasing or decreasing. However, when the paper size to be shielded is one, it is not a stepped shape.
[0077]
  The positional relationship between the magnetic flux shielding member 3A (or 3B) and the holder 2 holding the coil 5 / core 6 when the paper size width A does not cause the non-sheet passing portion temperature rise is as shown in FIG. It will be a positional relationship. That is, the holder 2 is in a position in a range where the magnetic circuit Ja is less affected. When the holder 2 is present at this position, the magnetic flux shielding member 3A (or 3B) does not affect the magnetic circuit Ja, so that fixing processing by electromagnetic induction heating is possible over the entire width of the paper size width A.
[0078]
  When the paper size width B where the temperature rise of the non-sheet passing portion occurs, the holder 2 holding the coil 5 and the core 6 rotates so that the magnetic flux shielding member comes on the magnetic circuit, and the magnetic flux shielding member Disturbs the flow of magnetic flux. In the figure, the first core 6a faces the shielding part 3p (3q) of the magnetic flux shielding member 3A (or 3B), and the shielding part inhibits the flow of magnetic flux. The magnetic circuits Jb and Jb 'shown in the figure are magnetic circuits when shielded by the width Ba (Bb) (see FIG. 8) of the shielding part 3q (3p). In the width Ba (Bb) of the shielding portion 3q (3p), which is a non-sheet passing portion when the paper size width is B, the magnetic flux passing through the inside of the fixing roller is smaller than that in the case of FIG. I understand. Thereby, in the range of width Ba * Bb of shielding part 3q * 3p, the heat_generation | fever by electromagnetic induction reduces and it can suppress non-sheet passing part temperature rising. At this time, the paper size width B (notch portion 3c) becomes a fixable region by electromagnetic induction heating.
[0079]
  The same applies to the paper size width C where the non-sheet passing portion temperature rise occurs. The holder 2 holding the coil 5 and the core 6 further rotates. In the figure, the first core 6a faces the shielding part 3r (3s) of the magnetic flux shielding member 3A (or 3B), and the shielding part inhibits the flow of magnetic flux. The magnetic circuits Jc and Jc ′ shown in the figure are magnetic circuits when shielded by the width Ca (Cb) (see FIG. 8) of the shielding part 3s (3r). In the added width (Ba + Ca) of the shielding parts 3r and 3p and the added width (Bb + Cb) of the shielding parts 3s and 3q (Bb + Cb) (see FIG. 7), the magnetic flux passing through the inside of the fixing roller is a non-sheet passing part when the paper size width is C. FIG. 7B and FIG. 7C show magnetic circuits Jb / Jb ′ and Jc / Jc ′. It can be seen that the magnetic flux passing through the inside of the fixing roller in the range of the width paper size width (Ba + Ca) · (Bb + Cb) is smaller than that in the case of FIG. Thereby, electromagnetic induction heat_generation | fever reduces in the range of a width | variety (Ba + Ca) and (Bb + Cb), and a non-sheet passing part temperature rising can be suppressed. At this time, the paper size width C (corresponding to the cutout portion 3d of the first embodiment) becomes a fixing possible region by electromagnetic induction heating.
[0080]
  [Reference example 2]
  Fixing deviceReference example 2Will be described with reference to FIG.
[0081]
  Reference Example 2The fixing device shown in FIG. 1 is an example in which the magnetic flux adjusting and heating assembly 1 of the first embodiment is applied to a fixing roller 7 having a radius r2 (r2 <r1) larger than the rotation radius r1 of the magnetic flux shielding member 3. In the fixing device of this example, the center of the fixing roller and the rotation center of the magnetic flux shielding member 3 are different. That is, the rotation center o 1 of the magnetic flux shielding member 3 is eccentric with respect to the rotation center o 2 of the fixing roller 7. The magnetic flux generating means 5, 6 and the pressure roller 8 are the first.ofThe same reference numerals are used for the same functions as in the embodiment. The materials of the holder 2 and the magnetic flux shielding member 3 are the same as in the first embodiment.
[0082]
  Reference Example 2In this fixing device, the magnetic flux shielding member 3 is rotated in the direction of arrows a and b with respect to the assembly 1 inside the fixing roller 7, therebyofThe same effect as the device of the example is obtained.
[0083]
  In this way, the large-diameter fixing roller 7 can also use the magnetic flux adjusting and heating assembly 1 that is used with a fixing roller having a smaller diameter, and can share parts and reduce the number of molds, thereby reducing costs. Leads to.
[0084]
  Further, it can be easily estimated from the third embodiment that a plurality of magnetic flux adjusting and heating assemblies can be provided on one fixing roller for a fixing roller having a large diameter.
[0085]
  [Reference example 3]
  Fixing deviceReference example 3Will be described with reference to FIGS.
[0086]
  Figure 10 shows the bookReference example 3FIG. FIG.Reference example 3It is an image figure of the magnetic circuit explaining the operation | movement and effect | action of this magnetic flux shielding member.
[0087]
  BookReference example 3The fixing device shown in FIG. 1 mainly includes a magnetic flux adjustment heating assembly 1, a fixing film 7, an arc-shaped film guide member 23, and a pressure roller 8 as a rotary pressure member. The magnetic flux adjustment heating assembly 1 has the same configuration as that of the first embodiment. The induction heating element uses a fixing film similar to the conventional example instead of the fixing roller.
[0088]
  A cylindrical (seamless) fixing film 7 as an induction heating element is loosely fitted on the cylindrical film guide member 23. firstofSimilar to the embodiment, the magnetic flux shielding member 3 is rotatably provided on the inner surface of the cylindrical film guide member 23.
[0089]
  The cylindrical film guide member 23 and the pressure roller 8 are brought into pressure contact with each other and assembled in an apparatus housing (not shown), and a fixing nip portion (heating nip portion) N having a predetermined width is formed between the both. Yes. In the fixing nip portion N, the inner surface of the fixing film 7 is in close contact with the lower surface of the arc-shaped film guide member 23.
[0090]
  The pressure roller 8 is rotationally driven in the direction of arrow Q by a driving means (not shown), and the fixing film is caused by the frictional force at the fixing nip N between the roller 8 and the outer surface of the fixing film 7 by the rotational driving of the pressure roller 8. A rotational force acts on 7. As a result, the fixing film 7 rotates in the direction of arrow P while the inner surface of the fixing film 7 slides in close contact with the lower surface of the cylindrical film guide member 23 at the fixing nip portion N.
[0091]
  The coil 5 generates an alternating magnetic flux by an alternating current supplied from an excitation circuit (not shown). The alternating magnetic flux is guided to the core 6 and acts on the fixing nip portion N, and an electromagnetic wave (described later) of the fixing film 7 in the fixing nip portion N. An eddy current is generated in the induction heating layer. The eddy current generates Joule heat by the specific resistance of the electromagnetic induction heating layer. That is, by supplying an alternating current to the coil 5, the fixing film 7 enters an electromagnetic induction heat generation state in the fixing nip portion N.
[0092]
  Also in the fixing film, the principle of electromagnetic induction heating and the image fixing method are the same as those of the fixing roller of the first embodiment.
[0093]
  In the fourth embodiment using the fixing film, the recording material S that has passed through the fixing nip N is separated from the outer surface of the fixing film 7 by the curvature of the cylindrical film guide member 23 on the exit side of the fixing nip N. As in the embodiment of the fixing roller, no separation claw is required.
[0094]
  The arc-shaped film guide member 23 is an insulating and heat-resistant member that does not hinder the passage of magnetic flux, and guides the inner surface of the cylindrical fixing film 7 that rotates outside the arc-shaped film guide member 23 to rotate the fixing film 7. The role of ensuring stability.
[0095]
  BookReference example 3The fixing film 7 is the same as the conventional one. It is a composite layer configuration of a three-layer laminate of an electromagnetic induction heat generating layer on the inner side (film guide member 23 side), an elastic layer on the outer side, and a release layer on the outer side (surface layer; pressure roller 8 side).
[0096]
  The arc-shaped magnetic flux shielding plate 3 can be rotated in the directions of arrows a and b inside the arc-shaped film guide member 23. When the paper size at which the temperature rise at the non-sheet passing portion is used for the magnetic flux shielding plate 3, the action density of the alternating magnetic flux with respect to the non-sheet passing region portion of the fixing nip portion N is passed through. It is the same as in the other embodiments that serves to prevent or alleviate the temperature rise phenomenon of the non-sheet passing portion.
[0097]
  BookReference example 3An image diagram of the magnetic circuit is shown in FIG. The change of the magnetic circuit by the magnetic flux shielding member 3 with the temperature rise at the non-sheet passing portion is the firstofIt is the same as the embodiment and is as follows.
[0098]
  FIG. 11A shows a magnetic circuit when the paper size width A does not cause the non-sheet passing portion temperature rise. The magnetic flux shielding member 3 stands by in a range where there is little influence on the magnetic circuit Ja. When the magnetic flux shielding member 3 is in the standby position, fixing is possible with the entire width of the paper size width A.
[0099]
  At the paper size width B where the temperature rise of the non-sheet passing portion occurs, as shown in FIG. 11B, the magnetic flux shielding member 3 rotates and moves on the magnetic circuit to obstruct the flow of magnetic flux. The magnetic circuit Jb shown in the figure is a magnetic circuit when shielded by the width Ba (Bb) (see FIG. 3) of the shielding part 3e (3f) of the magnetic flux shielding member 3. In the width Ba (Bb) of the shielding portion 3e (3f), which is a non-sheet passing portion when the paper size width is B, the magnetic flux passing through the inside of the fixing film is smaller than that in the case of FIG. I understand. As a result, heat generation due to electromagnetic induction is reduced in the range of the widths Ba and Bb of the shielding portions 3e and 3f, and the temperature rise of the non-sheet passing portion can be suppressed. At this time, the paper size width B (notch portion 3c) is a fixable region.
[0100]
  The same applies to the paper size width C where the non-sheet passing portion temperature rise occurs. The magnetic flux shielding member 3 further rotates on the magnetic circuit. In the figure, the shielding part 3g (3h) of the magnetic flux shielding member 3 faces the first core 6a and obstructs the flow of magnetic flux. The magnetic circuits Jc and Jc 'shown in the figure are magnetic circuits when shielded by the width Ca (Cb) (see FIG. 3) of the shielding part 3g (3h). With the addition width (Ba + Ca) of the shielding portions 3e and 3g and the addition width (Bb + Cb) of 3f and 3h, which are non-sheet-passing portions when the paper size width is C, the magnetic flux passing through the fixing roller is as shown in FIG. Magnetic circuits Jb and Jc · Jc ′ shown in FIG. It can be seen that the magnetic flux passing through the inside of the fixing roller in the range of the width (Ba + Ca) · (Bb + Cb) is smaller than that in the case of FIG. Thereby, electromagnetic induction heat_generation | fever reduces in the range of a width | variety (Ba + Ca) and (Bb + Cb), and a non-sheet passing part temperature rising can be suppressed. At this time, the paper size width C (notch portion 3d) becomes a fixable region by electromagnetic induction heating.
[0101]
  [Example of image forming apparatus]
  The fixing device of each embodiment is mounted on, for example, an electrophotographic image forming apparatus. Figure 5 is the firstof1 is an explanatory diagram of a schematic configuration illustrating an example of an image forming apparatus including a fixing device 10 according to an embodiment.
[0102]
  The image forming apparatus 100 reads an image of a document with the image reading unit 108, and exposes the surface of the photosensitive drum 101 from the image writing unit 109 according to a command from a controller (not shown) based on the read image data. Thus, an electrostatic latent image is formed on the photosensitive drum 101. Prior to exposure, the surface of the photosensitive drum 101 is uniformly charged to a predetermined potential by the charger 102, and laser light is emitted from the image writing unit 109 onto the uniformly charged photosensitive drum 101. Etc., an electrostatic latent image is formed on the photosensitive drum 101. The electrostatic latent image formed on the photosensitive drum 101 is developed with the toner of the developing device 103, and then the developed toner image is conveyed to a portion facing the transfer device 104 by the rotation of the photosensitive drum 101.
[0103]
  Corresponding to the conveyance of the developed toner image, the paper S is fed from the paper cassette one by one by the pickup roller 132 and the photosensitive drum 101 and the transfer device 104 are opposed to each other at a timing by the registration roller pair 135. It is conveyed to the part. Then, when the paper S passes through the facing portion between the photosensitive drum 101 and the transfer device 104, the developed toner image on the photosensitive drum 101 is transferred onto the paper S by the transfer device 104.
[0104]
  The sheet S on which the toner image has been transferred is conveyed to the position of the fixing roller 7 by a predetermined conveying device, pressed against the fixing roller 7 and the pressure roller 8, and electromagnetically generated by magnetic flux generation means provided in the fixing roller. The toner on the sheet S is melted and fixed on the sheet S by induction heating. Thereafter, the sheet S on which the toner image is fixed is stored in the tray 115 outside the apparatus main body by the paper discharge roller 111, and a series of image forming processes is completed.
[0105]
  In the fixing device of each embodiment, the holding member (holder 2) holds the magnetic flux generating means (the coil 5 and the core 6), and the support portions (support shafts 2a and 2b) at both ends in the longitudinal direction of the holding member are used as fulcrums. Since the magnetic flux shielding member 3 is rotated inside the fixing roller (fixing film) 7, contact between the coil 5 and the magnetic flux shielding member 3 in the magnetic flux generation means is avoided. Thereby, damage to the coil can be prevented.
[0106]
  Further, since the magnetic flux shielding member 3 is rotated with the support portions at both ends in the longitudinal direction of the holding member as fulcrums, the temperature rise of the non-sheet passing portion can be suppressed without reducing the fixing speed, leading to improvement in image formation productivity. .
[0107]
  In particular,ExampleThen, since the magnetic flux generating means (the coil 5 and the core 6), the holder 2, and the magnetic flux shielding member 3 are made into one assembly configuration, the assemblability and serviceability can be improved.
[0108]
  ExampleThus, by setting the rotation center of the magnetic flux shielding member 3 on the central axis of the fixing roller 7, the standby space of the magnetic flux shielding member and the drive means space of the magnetic flux shielding member can be saved.
[0109]
[0110]
[0111]
  As described above, it is possible to realize an induction heating type fixing device using a magnetic flux shielding means that saves space and costs while improving power saving and productivity.
[0112]
  [Other]
  Of the present inventionImage heating deviceIs not limited to the image heating and fixing device of the embodiment, but an image heating device that heats a recording material carrying an image to improve surface properties such as gloss, and an image heating device that is supposed to be worn.AndCan be used.
[0113]
  While various examples and embodiments of the present invention have been shown and described above, the spirit and scope of the present invention are not limited to the specific descriptions and figures in the present specification by those skilled in the art. It will be understood that various modifications and changes are set forth in all the claims that follow.
[0114]
[0115]
[0116]
[0117]
[0118]
[0119]
[0120]
[0121]
[0122]
[0123]
[0124]
[0125]
[0126]
[0127]
[0128]
[0129]
[0130]
[0131]
[0132]
[0133]
[0134]
[0135]
[0136]
[0137]
[0138]
【The invention's effect】
  As described above, according to the present invention, the electromagnetic induction heating methodImage heating deviceTherefore, it is possible to realize space saving of the standby space for the magnetic flux shielding member and the installation space for the driving means.
  Moreover, even if the support plate for the image heating device of the coil holder and the heat generating member is different, it is possible to maintain an interval such that the magnetic flux shielding member and the heat generating member do not rub against each other even if the magnetic flux shielding member rotates.
[Brief description of the drawings]
FIG. 1 shows a fixing device according to a first embodiment.SetFIG. 3 is a schematic cross-sectional view of the fixing roller in the longitudinal direction.
FIG. 2 is a schematic cross-sectional view of the fixing device according to the first embodiment in the fixing roller radial direction.
FIG. 3 is an exploded perspective view illustrating a configuration of a magnetic flux shielding member and magnetic flux generation means in the fixing device of the first embodiment.
FIG. 4 is an image diagram of a magnetic circuit when the magnetic flux is blocked by a magnetic flux shielding member in the fixing device of the first embodiment.
FIG. 5 is a schematic configuration diagram illustrating an example of an image forming apparatus equipped with the fixing device according to the first embodiment.
[Fig. 6]Reference example 1FIG. 3 is a schematic sectional view of the fixing roller in the longitudinal direction of the fixing device.
[Fig. 7]Reference example 1The image figure of a magnetic circuit when magnetic flux is interrupted | blocked with the magnetic flux shielding member in the fixing device of FIG.
[Fig. 8]Reference example 1The perspective view of the magnetic flux shielding member in the fixing device of FIG.
FIG. 9Reference example 2FIG. 3 is a schematic cross-sectional view of the fixing device in the radial direction of the fixing roller.
FIG. 10Reference example 3FIG. 3 is a schematic cross-sectional view of the fixing device in the radial direction of the fixing roller.
FIG. 11Reference example 3The image figure of a magnetic circuit when magnetic flux is interrupted | blocked with the magnetic flux shielding member in the fixing device of FIG.
[Explanation of symbols]
  1: Magnetic flux adjustment heating assembly, 2: Holder, 2a (2b): Holder support shaft, 3: Magnetic flux shielding member, 3e-3h, 3p-3q: Shielding part, 5: Excitation coil, 6: Magnetic core, 6a: First magnetic core, 6b: second magnetic core, 7: fixing roller, 8: pressure roller, N: fixing nip, Ja, Jb, Jc, Jc ′: magnetic field lines (magnetic circuit) of the magnetic flux generator )

Claims (3)

A coil that generates magnetic flux, a coil holder that supports the coil, a heat generating member that heats an image on the recording material by induction heat generation, and a conveyance direction of the recording material that shields the magnetic flux from the coil An image heating apparatus having a magnetic flux shielding member that changes a magnetic flux distribution in a direction perpendicular to the magnetic flux, a drive transmission member that transmits a driving force to the magnetic flux shielding member, and the coil holder disposed inside the heat generating member In
The heat generating member is supported by heat generating member support plates at both ends, and the coil holder is maintained at a gap from the heat generating member by a coil holder support plate outside the heat generating member support plate at the shaft portions at both ends. Both ends of the magnetic flux shielding member are supported by a support shaft portion of a coil holder having an axis that coincides with a rotation axis of the heat generating member and a center line of the shaft portion, and the magnetic flux shielding member is In synchronization with the rotation of the drive transmission member about the axis of the support shaft that is attached to the drive transmission member fitted to the support shaft of the coil holder and coincides with the rotation axis of the heat generating member An image heating apparatus that rotates between the coil holder and the heat generating member. The magnetic flux shielding member is pre hear dynamic by angle corresponding to the blocking position by rotating movement corresponding to the size of the recording material requiring shielding by the transmission member, wherein the non-sheet passing portion of the recording material size requiring shielding The image heating apparatus according to claim 1, wherein the magnetic flux shielding member is shielded between the coil holder and the heat generating member by a stepped shape portion.   3. The image heating apparatus according to claim 1, wherein at least one of the support shaft portions has a hollow pipe shape, and the bundle of the exciting coils is passed through the inside thereof.