JP4971621B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus for heating an image on a recording material by an electromagnetic induction heating method. For example, the present invention relates to a gloss applying device on a recording material and a fixing device for fixing an image on the recording material.

  Conventionally, there is an electromagnetic induction heating method as an image heating and fixing device for heating an image on a recording material.

  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.

For example, an apparatus for electromagnetically heating a ferromagnetic fixing roller by the action of magnetic flux generated from a coil is disclosed. The heat generation position where the magnetic flux acts can be close to the fixing nip portion, and a higher-efficiency fixing process is achieved than a heat roller type apparatus using a halogen lamp as a heat source. (For example, see Patent Document 1)
Further, there is disclosed a heating apparatus characterized by having a magnetic flux shielding means for changing the density distribution of the acting magnetic flux in the longitudinal direction of the fixing roller (film). With this electromagnetic induction heating type fixing device, when a recording material having a size smaller than the maximum size is continuously heated, an abnormal temperature rise in the difference area between the maximum size and the conveyance area of the small size, so-called non-sheet passing portion rising One way to solve the temperature was shown. (For example, see Patent Document 2)
Japanese Patent Publication No. 5-9027 JP 2004-265670 A

  However, Patent Document 2 has the following problems. That is, when the control unit or the drive unit that controls the movement of the magnetic flux suppression member fails during rotation of the magnetic flux suppression member, the position of the magnetic flux suppression member becomes unknown. Similarly, regarding the rotation restriction by the position sensor, if the position sensor fails, the position of the magnetic flux suppression member becomes unknown. In such a case, the magnetic shielding member is connected to the magnetic flux adjusting region (the region facing the end surface of the center core disposed at the center of the T-core around which the coil is wound) facing the heat generating region where the magnetic flux generated from the coil is concentrated. There is a possibility of covering with a part. If the end surface of the center core remains covered with the magnetic shielding member, there arises a problem that the temperature of the magnetic shielding member or coil is abnormally increased. In addition, when the magnetic flux adjustment region covers the entire longitudinal direction with the magnetic flux suppression member, the apparent impedance L value from the coil rapidly decreases, a large current flows, and the power supply is destroyed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent inconvenience due to the movement of the connecting portion of the magnetic flux suppression means to a predetermined magnetic flux suppression position.

In order to achieve the above object, an image heating apparatus according to the present invention includes a magnetic flux generation unit that generates magnetic flux, a heating element that generates heat by the magnetic flux from the magnetic flux generation unit, and a magnetic flux that travels from the magnetic flux generation unit toward the heating element. And a moving means for moving the magnetic flux suppressing member to a magnetic flux suppressing position for suppressing the magnetic flux from the magnetic flux generating means toward the heating element and a retracted position retracted from the magnetic flux suppressing position; An image heating apparatus for heating an image on a recording material by heat of the heating element, and a moving unit that moves integrally with the movement of the magnetic flux suppression member as the magnetic flux suppression member moves, and the magnetic flux suppression member wherein a control unit for controlling the operation of the moving means, the magnetic flux suppressing the magnetic flux suppressing member from the retracted position in order to stop at a predetermined position including the magnetic flux suppression position and the retracted position When moving in the direction of the location, without stopping in the flux suppressing member by the control unit is the magnetic flux suppression position, when the magnetic flux suppressing member has moved beyond the magnetic flux suppression position, said moving portion And a restricting portion that restricts movement in the direction by contact.

The image heating apparatus according to the present invention includes a magnetic flux generation unit that generates magnetic flux, a heating element that generates heat by the magnetic flux from the magnetic flux generation unit, and a magnetic flux suppression member that suppresses the magnetic flux from the magnetic flux generation unit toward the heating element. And a moving means for moving the magnetic flux suppressing member to a magnetic flux suppressing position for suppressing the magnetic flux from the magnetic flux generating means to the heating element and a retracted position retracted from the magnetic flux suppressing position. In the image heating apparatus that heats an image on a recording material by the heat of the body, a moving unit that moves integrally with the movement of the magnetic flux suppression member as the magnetic flux suppression member moves, and the magnetic flux suppression member that moves the retracted position and the moving a control unit for controlling the operation of said moving means in order to stop at a predetermined position including the magnetic flux suppression position, the magnetic flux suppressing member from said magnetic flux suppression position in the direction to the retracted position When that mobile magnetic flux suppressing member by the control unit without stopping at the retracted position, when the magnetic flux suppressing member has moved beyond the retracted position, the direction by contact with the moving part And a restricting section for restricting the above.

  It is possible to prevent problems caused by the connecting portion of the magnetic flux suppression means moving to a predetermined magnetic flux suppression position.

(Example)
(1) Example of Image Forming Apparatus FIG. 1 is a schematic model diagram of an example of an image forming apparatus in which an electromagnetic induction heating type heating apparatus according to the present invention is mounted as an image heating fixing apparatus (hereinafter referred to as a fixing apparatus). The image forming apparatus of this example is a laser printer using a transfer type electrophotographic process.
Reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. It is rotationally driven at a predetermined peripheral speed in the clockwise direction of the arrow.

  Reference numeral 102 denotes a contact charging roller as charging means. The outer peripheral surface of the rotating photosensitive drum 101 is uniformly charged to a predetermined polarity and potential.

  Reference numeral 103 denotes a laser scanner as exposure means. Laser light modulated in accordance with the time-series electric digital pixel signal of the image information is output, and the uniformly charged surface of the rotating photosensitive drum 101 is subjected to scanning exposure L. As a result, an electrostatic latent image corresponding to the scanning exposure pattern is formed on the photosensitive drum surface.

  Reference numeral 104 denotes a developing device. The electrostatic latent image on the surface of the photosensitive drum is reversely developed or normally developed as a toner image.

  Reference numeral 105 denotes a transfer roller as transfer means. A transfer nip T is formed by contacting the photosensitive drum 101 with a predetermined pressing force. A recording material P as a material to be heated is fed to the transfer nip T from a sheet feeding mechanism (not shown) at a predetermined control timing, and is nipped and conveyed through the transfer nip T. A predetermined transfer bias is applied to the transfer roller 105 at a predetermined control timing. As a result, the toner images on the photosensitive drum 101 surface side are sequentially electrostatically transferred onto the surface of the recording material P that is nipped and conveyed through the transfer nip T.

  The recording material P exiting the transfer nip T is separated from the surface of the photosensitive drum 101 and introduced into the fixing device 100. The fixing device 100 heats and presses and fixes the unfixed toner image on the introduced recording material P as a permanently fixed image. The recording material P is discharged and conveyed.

  A photosensitive drum cleaner 106 removes transfer residual toner on the photosensitive drum after separation of the recording material. The photosensitive drum surface, from which the transfer residual toner has been removed and cleaned, is repeatedly used for image formation.

  a is the conveyance direction of the recording material P. In the image forming apparatus of the present embodiment, the recording material P is fed and conveyed on the basis of the central sheet passing center of the recording material.

(2) Fixing device 100
FIG. 2 is a front model view of a main part of a fixing device as an image heating device, and FIG. 3 is an enlarged cross-sectional model diagram. FIG. 4 is a schematic longitudinal sectional view of the fixing roller assembly portion.

<Fixing roller>
Reference numeral 1 denotes a fixing roller as an induction heating element. It is a cylindrical roller formed of an induction heating element (conductive magnetic material) such as iron, nickel, and SUS430 and having a thickness of, for example, about 0.1 mm to 1.5 mm. In general, a release layer such as a fluororesin or an elastic layer and a release layer is formed on the outer peripheral surface. By using a ferromagnetic metal such as iron (a metal with high permeability), the magnetic flux generated from the magnetic flux generating means can be more restrained inside the metal. That is, since the magnetic flux density can be increased, an eddy current can be efficiently generated on the metal surface.

  The fixing roller 1 has a front end and a rear end on the outside of the front fixing plate 21 and the fixing rear plate 22, respectively, and a first support member 26a and a rear support member (core) of a front support member (centering plate) 26, respectively. The first support member 27a of the determination plate) 27 is attached. Between the fixing roller 1 and the first support member 26a of the front support member (centering plate) 26 or the first support member 27a of the rear support member (centering plate) 27, heat insulating bushes 23a and 23b and bearings 24a The bearing is supported rotatably through 24b.

  The heat insulating bushes 23a and 23b are used to reduce heat transfer from the fixing roller 1 to the bearings 24a and 24b. G1 is a fixing roller driving gear that is externally fitted and fixed to the front end portion of the fixing roller 1. When the rotational force of the first motor M1 is transmitted to the gear G1 via a power transmission system (not shown), the fixing roller 1 is rotationally driven at a predetermined speed in the clockwise direction of the arrow in FIG. FIG. 7 is an external perspective view of the fixing roller 1 with the heat insulating bushes 23a and 23b and the fixing roller gear G1 attached thereto.

  Reference numeral 2 denotes a pressure roller as a pressure member. It is an elastic roller comprising a cored bar 2a and an elastic layer 2b formed concentrically and integrally around the cored bar 2a. The elastic layer 2b is, for example, a silicone rubber layer which is a surface releasable heat resistant rubber layer. The pressure roller 2 is arranged in parallel to the lower side of the fixing roller 1, and the front end and the rear end of the cored bar 2a are respectively connected between the front fixing plate 21 and the fixing rear plate 22 with bearings 25a. The bearing is supported rotatably through 25b. The bearings 25a and 25b are arranged on the front fixing plate 21 and the fixing rear plate 22 so as to be slidable in the direction of the fixing roller 1, respectively. The bearings 25a and 25b are pushed up and biased toward the fixing roller by biasing means (not shown). By doing so, the pressure roller 2 is brought into pressure contact with the lower surface of the fixing roller 1 against the elasticity of the elastic layer 2 b with a predetermined pressing force F and heated between the fixing roller 1 and the pressure roller 2. A fixing nip portion N having a predetermined width as a nip portion is formed. The pressure roller 2 is driven and rotated by receiving a frictional rotational force at the fixing nip portion N when the fixing roller 1 is rotationally driven.

<Coil assembly>
Reference numeral 3 denotes an exciting coil assembly as a magnetic flux generating means. The exciting coil assembly 3 is inserted and disposed in the inner space of the cylindrical fixing roller 1 described above. The exciting coil assembly 3 includes an exciting coil (hereinafter abbreviated as a coil) 4, a magnetic core (hereinafter abbreviated as a core) 5a and 5b arranged in a T-shaped cross section, and the coil 4 and the core 5a. -It has a holder 6 in which 5b is incorporated and held. Further, the exciting coil assembly 3 is an assembly having a magnetic flux suppressing member 7 as a magnetic flux suppressing means (magnetic flux adjusting means) disposed on the outer side of the holder 6 so as to be freely rotatable coaxially with the holder 6. FIG. 8 is an external perspective view of the exciting coil assembly 3 and the magnetic flux suppression member moving means M2, 28, G4, and G5. FIG. 9 is an exploded perspective view of the holder 6 and the magnetic flux suppressing member 7. FIG. 10 is an exploded perspective view of the inside of the holder 6.

  Here, in the following, regarding the constituent members and portions of the fixing device, the longitudinal direction is a direction orthogonal (crossing) to the recording material conveyance direction a on the recording material conveyance path surface.

  The holder 6 has a substantially cylindrical cross section in the entire longitudinal direction. As the material, a material obtained by adding glass to a PPS resin having both heat resistance and mechanical strength is used. For the holder 6, materials such as PPS resin, PEEK resin, polyimide resin, polyamide resin, polyamideimide resin, ceramic, liquid crystal polymer, and fluorine resin are suitable.

  As shown in FIG. 10, the holder 6 is molded in the form of a first half 6a and a second half 6b that are divided into two vertically along the longitudinal axis. The first half body 6a and the second half body 6b are overlapped and joined together with an adhesive, or joined together at a fitting structure, so that the cross-sectional shape is a substantially cylindrical member in the entire longitudinal direction. . The coil 4 and the cores 5a and 5b are incorporated into the first half 6a. The holder 6 holding the coil 4 and the cores 5a and 5b incorporated therein is assembled by superimposing and integrally joining the second half 6b so as to cover the first half 6a. Reference numerals 4a and 4b denote lead wires (lead wires) of the coil 4. The lead wires 4 a and 4 b are led out of the holder 6 through a hole 6 c provided in the front end surface of the holder 6.

  As shown in FIG. 10, the coil 4 has a substantially oval shape (horizontal boat shape) that is long in the longitudinal direction of the fixing roller 1, and is disposed inside the first half 6 a of the holder 6 along the inner surface of the fixing roller 1. Has been placed. The coil 4 generates 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 the core wire of the coil 4, a litz wire in which about 80 to 160 fine wires having a diameter of 0.1 to 0.3 are bundled is used. Insulated coated wires are used for the thin wires. In addition, a coil 1 that is wound 6 to 12 times around the first core 5a is used.

  The core 5 a is a first core (vertical portion) in the winding center portion of the coil 4. The core 5b is a second core (horizontal portion) at the top thereof. These two cores 5a and 5b constitute a T-shaped core in cross section. The cores 5a and 5b are preferably made of ferrite or the like having a low high magnetic permeability residual magnetic flux density, but are not particularly limited as long as they can generate magnetic flux. Further, the shape and material of the cores 5a and 5b are not defined, and the first core 5a and the second core 5b may be integrally formed into a T-shape.

  The holder 6 of the exciting coil assembly 3 is configured to be supported as shown in FIGS. That is, the end of the cylindrical holder 6 protrudes outward from the front end opening of the fixing roller 1, and the fitting round hole 26c provided in the second support member 26b attached to the outside of the front fixing plate 21. It is fitted and supported. Further, the rear end is protruded outward from the rear end opening of the fixing roller 1, and the D-shaped portion 6 d provided at the rear end is attached to the outside of the fixing rear plate 22. The member 27 is fixedly supported in a non-rotatable manner by being D-fitted in a fitting D-hole 27c provided in the second support member 27b. As a result, the holder 6 is placed in the fixing roller 1 so that the holder 6 and the fixing roller 1 are substantially coaxial, and a predetermined gap is maintained between the outer surface of the holder and the inner surface of the fixing roller, and in the circumferential direction. It is positioned and positioned non-rotating in an angular orientation. The coil lead wires 4 a and 4 b that are extended to the outside of the holder from a hole 6 c provided on the front end surface of the holder 6 are connected to the excitation circuit 51. In this embodiment, the holder 6 is positioned in the circumferential direction by D fitting, but is not limited to D fitting. If the position of the holder 6 in the circumferential direction is determined, any means can be configured.

<Magnetic flux suppression means>
As shown in FIG. 9, the magnetic flux suppressing member 7 basically forms a circular cross section in the entire longitudinal direction, and has an arcuate shutter portion (magnetic flux suppressing portion) 7 a that is wide in the circumferential direction on both longitudinal sides. 7a and a narrow arc-shaped connecting plate portion (connecting portion) 7b between the two 7a and 7a. The connecting portion 7b is engaged and supported by shutter gears disposed at both ends, and is supported so as to be rotatable in the longitudinal direction (rotating shaft direction) of the fixing roller 1, and an arcuate shutter portion (magnetic flux suppressing portion) 7a. It is a support part which supports 7a. In general, non-ferrous metals such as aluminum and copper-based metals are used as the material, and among them, materials having low electrical resistivity are preferably used. The magnetic flux suppressing member 7 is formed with bending portions 7c and 7c at both ends thereof, and the bending portions 7c and 7c are respectively fitted on the front end portion and the rear end portion of the holder 6 so as to be freely rotatable. The shutter gear G2 and the second shutter gear G3 are engaged. In this way, the magnetic flux suppressing member 7 is supported by both ends between the first and second shutter gears G2 and G3. That is, the first shutter gear G2 and the first shutter gear G2 in which bending overs 7c and 7c (FIGS. 8 and 9) provided at both longitudinal ends are rotatably fitted to the front end and the rear end of the holder 6 respectively. The second shutter gear G3 is engaged with and supported. The magnetic flux suppressing member 7 is configured such that the first and second shutter gears G2 and G3 are rotated by the magnetic flux suppressing member moving means M2, 28, G4, and G5, so that the outer surface of the holder and the inner surface of the fixing roller are fixed inside the fixing roller 1. In the circumferential gap between the holder 6 and the holder 6.

  In M2, 28, G4, and G5 as moving means for moving the magnetic flux suppressing member 7 in FIG. 8, M2 is a second motor, 28 is a shaft, G4 is a first output gear, and G5 is a second output gear. The shaft 28 is arranged outside the fixing roller 1 in parallel with the fixing roller 1 and is rotatably supported between the front plate 21 and the rear plate 22 via a bearing member (not shown). The second motor M2 is a drive source that rotates the shaft 28, and uses a stepping motor. The first output gear G4 and the second output gear G5 are coaxially fixed to the shaft 28, respectively. The first output gear G4 is connected to the first shutter gear G2 of the exciting coil assembly 3 and the second output gear. The gear G5 is meshed with the second shutter gear G3. As the second motor M2 is rotationally driven, a rotational force is transmitted to the first and second shutter gears G2 and G3. As a result, the magnetic flux suppressing member 7 rotates around the holder 6 so as to be substantially coaxial with the holder 6. As the material of the gear, various resin materials can be selected depending on the ambient temperature and torque.

  In FIG. 2, reference numeral 50 denotes a control circuit unit (CPU) as control means. The control circuit unit 50 activates the first motor M1 via the driver 52 at a predetermined control timing of the image forming sequence control. As a result, a rotational force is applied to the fixing roller driving gear G1, and the fixing roller 1 is rotationally driven in a predetermined area in the clockwise direction of the arrow in FIG. The pressure roller 2 is driven to rotate.

  Further, the control circuit unit 50 activates the excitation circuit 51 to supply an alternating current to the coil 4 at a predetermined control timing. Due to the action of the alternating magnetic flux (alternating magnetic field) generated by this, the fixing roller 1 heats up due to induction heat generation.

  FIG. 6 shows a heat generation state of the fixing roller 1 in the system as described above in a cross-sectional side view of the fixing roller 1. The main magnetic flux generation region of the magnetic flux generating means and the circumference of the fixing roller portion corresponding thereto. It is explanatory drawing of direction calorific value distribution. The coil 4 generates an alternating magnetic flux when an alternating current flows. The fixing roller 1 uses magnetic metal or magnetic material as described above, and an induced current (eddy current) is generated within the thickness of the fixing roller 1 so as to cancel the magnetic field. The fixing roller 1 itself generates heat due to the Joule heat generated by the induced current, and the temperature rises.

  In the configuration of this embodiment, the outer surface side of the first half 6a incorporating the coil 4 and the cores 5a and 5b of the holder 6 is a main magnetic flux generation region, and the magnetic flux acts on the fixing roller 1 in this magnetic flux generation region. Then, the fixing roller 1 is heated. Then, in the circumferential direction of the fixing roller 1, the distribution of heat generation amount generated by the fixing roller portion corresponding to the main magnetic flux generation region, as shown in the schematic diagram, there are portions H and H where the heat generation amount is large at two locations. To do. In the present embodiment, the holder 6 is positioned so that the one portion H is positioned corresponding to the fixing nip portion N and the other one portion H is positioned upstream of the fixing nip portion N in the rotation direction of the fixing roller. Is positioned so as to be fixedly supported in a non-rotating manner by positioning its circumferential angular posture.

  As shown in FIGS. 3 and 6, the magnetic flux suppressing member 7 is normally in the circumferential gap between the outer surface of the holder 6 and the inner surface of the fixing roller 1. The position is moved and held in the gap portion on the opposite side. The opposite gap portion is a portion where the magnetic flux does not substantially act on the fixing roller 1 from the magnetic flux generating means, or a portion where the amount of applied magnetic flux is small. The holding position of the magnetic flux suppression member 7 in FIGS. 3 and 6 is defined as a first switching position.

  Then, the temperature rise temperature of the fixing roller 1 is detected and controlled by a central thermistor TH1, which is a temperature detecting means disposed in contact with or in non-contact with the fixing roller 1 at a substantially central position in the longitudinal direction of the fixing roller 1. Input to the circuit 50. The control circuit 50 controls the power supplied from the excitation circuit 51 to the coil 4 so that the fixing roller detection temperature input from the central thermistor TH1 is maintained at a predetermined target temperature (fixing temperature), thereby controlling the temperature of the fixing roller 1. Take control. In the state where the magnetic flux suppressing member 7 is held at the first switching position in FIGS. 3 and 6, the fixing roller 1 is maintained at a predetermined target temperature in the effective heating full length region in the longitudinal direction.

  In a state where the temperature of the fixing roller 1 rises to a predetermined fixing temperature and is adjusted in temperature, the recording material P carrying the unfixed toner image t is introduced into the fixing nip portion N, and is nipped and conveyed through the fixing nip portion N. Go. As a result, the unfixed toner image t is heated and pressure-fixed on the surface of the recording material P by the heat of the fixing roller 1 and the pressing force of the fixing nip N.

  Here, the paper width is a recording material dimension in a direction orthogonal to the recording material conveyance direction a on the plane of the recording material P. As described above, in the present embodiment, the recording material passing is a central paper passing reference centered on the recording material. 2 and 4, O is the recording material center paper passing reference line (virtual line). A is a sheet passing area width of a recording material having a maximum sheet width that can be used for the apparatus. A recording material having a paper width corresponding to the paper passing area width A is a large size recording material. B is a paper passing area width of a recording material having a paper width smaller than the paper width of the large size recording material. A recording material having a paper width smaller than that of the large size recording material is defined as a small size recording material. C is the difference area width between the large size recording material sheet passing area width A and the small size recording material sheet passing area width B. That is, the non-sheet passing area width generated in the recording material conveyance path when the small size recording material is passed. Since the recording material passing is based on the central reference, the non-sheet passing region when the small size recording material is passed occurs on both the left and right sides of the small size recording material passing region width B. The non-sheet passing area width C varies depending on the size of the sheet width of the small size recording material that has been passed.

  The central thermistor TH1 is used for controlling the temperature of the fixing roller 1 and corresponds to a small size recording material passing area width B which becomes a recording material passing area even if a recording material having a large or small paper width is passed. Are arranged.

  TH2 is an end thermistor which is a temperature detection means for monitoring the temperature rise of the non-sheet-passing portion, which is disposed in contact or non-contact with a position corresponding to the non-sheet-passing region width C. The detected temperature information of the end thermistor TH2 is also input to the control circuit unit 50.

  When the small-size recording material is continuously fed, the temperature of the non-sheet-passing area width C of the fixing roller 1 is increased. The temperature rise state is input to the control circuit unit 50 from the end thermistor TH2. When the temperature rise temperature of the non-sheet passing portion input from the end portion thermistor TH2 becomes higher than a predetermined allowable temperature, the control circuit portion 50 starts the second motor M2 via the driver 53 and causes the magnetic flux suppressing member 7 to move. The first switching position shown in FIGS. 3 and 6 is rotated to the second switching position shown in FIG.

  The second switching position of the magnetic flux suppressing member 7 is a position where the wide arc-shaped shutter portions (magnetic flux suppressing portions) 7a and 7a on both longitudinal sides of the magnetic flux suppressing member 7 have entered the following positions. That is, in the circumferential gap between the outer surface of the holder 6 and the inner surface of the fixing roller 1, the gap portion corresponding to the main magnetic flux generation region and the gap portion corresponding to the non-sheet passing region width C · C. It is the position that entered.

  As a result, the amount of magnetic flux applied from the magnetic flux generation means to the fixing roller portion corresponding to the non-sheet passing region width C / C is reduced, and the heat generation of the fixing roller portion corresponding to the non-sheet passing region width C / C is suppressed. . That is, the non-sheet passing portion temperature rise is suppressed.

  The shutter portions 7a and 7a may be configured to enter the entire gap portion corresponding to the main magnetic flux generation region and corresponding to the non-sheet passing region width C · C. It can also be configured to enter a part of. FIG. 5 shows a configuration in which it enters a substantially half region of the gap portion.

  After the magnetic flux suppressing member 7 is pivotally moved to the second switching position, the control circuit unit 50, when the non-sheet passing region temperature input from the end thermistor TH2 becomes lower than a predetermined allowable temperature, the magnetic flux suppressing member 7 Is moved back to the first switching position. In this way, it is possible to prevent the temperature of the non-sheet passing region portion from being excessively lowered.

  Further, after the magnetic flux suppressing member 7 is pivoted to the second switching position, the control circuit unit 50 moves the magnetic flux suppressing member 7 to the first when the recording material used for passing paper is switched from the small size recording material to the large size recording material. Return to 1 switching position and rotate.

  As a method of ensuring the relative distance (gap) between the fixing roller 1 and the magnetic flux suppressing member 7, there is a method of widening the distance between the magnetic flux suppressing member 7 and the fixing roller 1. However, along with this, if the distance between the cores 5a and 5b and the fixing roller 1 is increased more than necessary, the heat exchange efficiency deteriorates, and it is not used today. The magnetic flux suppressing member 7 and the holder 6 are extended to the opposite side where the coil 4 is disposed, so that the cross-sectional shape of the holder 6 is substantially circular in the entire longitudinal direction. By adopting this shape, the relative position accuracy can be improved by matching the cross-sectional centers of the holder 6, the fixing roller 1, and the magnetic flux suppressing member 7.

  As described above, the first shutter gear G2 and the second shutter gear G3 are rotatably arranged at the front end portion and the rear end portion of the holder 6 as drive transmission means for driving the magnetic flux suppressing member 7, respectively. . Both ends of the magnetic flux suppressing member 7 are formed with bending over 6c, and are engaged with the first shutter gear G2 and the second shutter gear G3, respectively, so that the magnetic flux suppressing member 7 is connected to the first and second shutter gears G2,. Both sides are supported between G3. The first shutter gear G2 and the second shutter gear G3 are fitted to the holder 6 in a region not engaged with the bending over 7c of the magnetic flux suppressing member 7. For this reason, the magnetic flux suppressing member 7 is supported and rotated by the entire surface of the holder 6 and the inner diameter portions of the gears G2 and G3. In the region where the gears G2 and G3 and the holder 6 are fitted, the maximum outer diameter portion of the holder 6 forms a straight shape. Here, the expression “maximum outer diameter portion” means that a rib may be provided on the holder 6 in the fitting region so that the shape of the rib may be a straight shape. As a result, the relative position accuracy can be improved by fitting the holder 6 and the magnetic flux suppression member 7 so that the center of the cross section is accurately aligned.

  The magnetic flux suppression member 7 basically forms an arc shape in the entire lengthwise direction of the fixing roller, and the length of the arc portion changes from both ends to the center. When a small size recording material is fed, the temperature rise at the end of the fixing roller is suppressed by moving the shutter portions 7a and 7a at both ends of the magnetic flux suppression member corresponding to the non-sheet passing region to the magnetic flux generation region. In the present embodiment, the shutter part 7a, 7a, which is a magnetic flux shielding area, is provided in the non-sheet passing area and the magnetic flux is suppressed by moving the shutter part to the magnetic flux generation area. Absent. For example, a magnetic flux suppressing member (shutter portion) is provided at the central portion corresponding to the paper passing portion of the magnetic flux generation region, and the shutter portion is moved to the magnetic flux generation region. In this way, even if the temperature of the fixing roller is adjusted by changing the magnetic flux distribution in the sheet passing area with respect to the non-sheet passing portion, the heat generation distribution of the sheet passing portion and the non-sheet passing portion in the longitudinal direction of the fixing roller is changed. Good.

(Driving method of magnetic flux suppressing member)
A method for driving the magnetic flux suppression member 7 will be described with reference to FIGS. 11 and 12. FIG. 11 is a perspective view showing the drive mechanism of the magnetic flux suppressing member 7 of this embodiment, and the magnetic flux suppressing member in which the magnetic flux suppressing portion of the magnetic flux suppressing member 7 corresponds to three types of recording material paper widths of large, medium and small. 7 is a perspective view of FIG. FIG. 12 is an enlarged view of the driving means of the magnetic flux suppressing member 7 for explaining the movement restricting portion of the magnetic flux suppressing member of this embodiment. In FIG. 11 and FIG. 12, some members are omitted for easy explanation.

  As a first drive transmission means (moving means) for driving the magnetic flux suppression member, a magnetic flux suppression member drive gear G2 is provided on the front side of the image forming apparatus main body, and G3 is disposed as that on the rear side as the second drive transmission means.

  Both ends of the magnetic flux suppressing member 7 form a bending over 7c, and gears G2 and G3 which are the first and second drive transmission means are engaged.

  Further, the gears G2 and G3 as the first and second drive transmission means are fitted to the holder in a region not engaged with the magnetic flux suppressing member.

  For this reason, the magnetic flux suppressing member 7 is surface-supported along the entire surface of the holder and the inner diameter portion of the gear, and since it rotates, there is no local wear of the holder.

  A shaft 28 is provided in parallel with the fixing roller as third drive transmission means for distributing power to the gears G2 and G3.

  The power generation means for driving the bundle shielding member uses a stepping motor M2.

  The power obtained from the stepping motor M2 is transmitted from the front and rear of the magnetic flux suppression member 7 via the output gear and further via the shaft 28 and the first and second magnetic flux suppression member drive gears G2, G3.

  The magnetic flux suppressing member drive gear G2 is provided with a first notch G2a, a second notch G2b, and a third notch G2c.

  The rotation of the magnetic flux suppression member drive gear G2 is controlled by ON and OFF signals detected when the first, second, and third cutout portions G2a, G2b, and G2c pass the position detection sensor 210. The cutout positions of the first, second, and third cutout portions G2a, G2b, and G2c correspond to positions where the non-sheet passing portion magnetic flux adjustment of various paper sizes is possible.

  FIG. 12 is a diagram illustrating a case where the position detection sensor 210 cannot detect the notches G2a, G2b, and G2c of the magnetic flux suppression member drive gear G2. The magnetic flux suppression member drive gear G2 continues to rotate because the rotational position is unknown, but a restriction member is provided so that the movement region of the magnetic flux suppression member does not move beyond a predetermined region. Specifically, the movement of the magnetic flux suppressing member is restricted by the rotation restricting portion G2d as the restricting member of the magnetic flux suppressing member drive gear G2 coming into contact with the rotation restricting member 220a. In this way, the driving torque of the stepping motor M2 becomes a load, motor step-out occurs, and rotation stops. The rotation restricting portion G2d and the rotation restricting member 220a are similarly provided on the rear side (220b), and the magnetic flux suppressing member driving gear G3 is also restricted in rotation at the same time. At this time, as shown in FIG. 12, even when the magnetic flux suppressing member 7 is most rotated, the first core 5a is not covered with the magnetic flux suppressing member 7 in the central portion. That is, the movement of the connecting portion 7a of the magnetic flux suppression member 7 to a predetermined magnetic flux suppression position is restricted. In this embodiment, the magnetic flux suppressing portion 7a and the arc-shaped connecting plate portion (connecting portion) 7b are the same member, and the material is generally made of a non-ferrous metal such as aluminum or a copper-based metal. Used.

  Here, the magnetic flux suppression position is a position corresponding to the winding center of the coil (end core center of the first core), and corresponds to the position where the working magnetic flux from the coil to the heating element is maximum.

  As described above, the rotation restricting member 220a and the rotation restricting portion G2d are provided at positions where the first core 5a is not covered by the magnetic flux suppressing member 7 in the entire longitudinal direction even when the magnetic flux suppressing member 7 is most rotated. It has been.

  Although not shown, the magnetic flux suppressing member drive gear G2 is provided with a rotation restricting portion similar to the rotation restricting portion G2d even when it is turned toward the third notch G2c. The rotation is restricted by the rotation restricting member 220a so that the magnetic flux suppressing member 7 does not cover the entire first core 5a.

  By adopting the configuration as described above, the end surface of the first core 5a generated by concentration of magnetic flux is not covered by the magnetic shielding member throughout the entire length, so that the magnetic shielding member or coil prevents abnormal temperature rise. It becomes possible to do. It is also possible to prevent the impedance L value from rapidly decreasing and the power supply from being destroyed.

  In this embodiment, the rotation restricting members are provided on both sides of the magnetic flux suppressing member, but the present invention is not limited to this. For example, the restriction member may be provided on one side or in the center for restriction. In this case, the position of the regulating member is preferably regulated at the end on the power generation means (drive source) side in order to move the magnetic flux suppression means. By carrying out like this, the twist of the magnetic flux suppression member at the time of regulation of a regulating member can be reduced.

(3) Others 1) The apparatus according to the embodiment switches the movement of the magnetic flux suppressing member 7 between the first switching position and the second switching position in accordance with two types of recording materials, a large size recording material and a small size recording material. Although it is a thing, it is not necessarily limited to this. Of course, it is possible to adopt a configuration in which the position is switched in multiple stages corresponding to three or more types of recording material paper widths. FIG. 13 is a schematic perspective view of the magnetic flux suppressing member 7 corresponding to three types of recording material paper widths of large, medium and small.

  2) Although the apparatus of the embodiment has an apparatus configuration in which the recording material is conveyed on the basis of the central sheet passing, the present invention can be effectively applied to an apparatus configuration based on the one-side sheet passing. FIG. 14 and FIG. 15 each show an example of a magnetic flux suppressing member in the case of a one-side paper-passing reference device. O ′ is a one-side paper passing reference line.

  3) The electromagnetic induction heating type image heating apparatus according to the present invention is not limited to the image heating and fixing apparatus of the embodiment, but is a hypothetical fixing apparatus that presupposes an unfixed image on a recording material, and reheats a recording material carrying a fixed image. Therefore, it is also effective as an image heating apparatus such as a surface modification apparatus for modifying the image surface properties such as gloss. In addition, heating that heats the sheet-like material to be heated, such as a heat press device for removing wrinkles from the sheet-like material to be heated, a heat laminating device, a heat-drying device that evaporates the moisture content of the material to be heated such as paper Of course, it is effective even when used as an apparatus.

Schematic model diagram of an example of an image forming apparatus Front model diagram of the main part of the fixing device Expanded cross-sectional model view of the main part of the fixing device Longitudinal cross section model of the fuser roller assembly Enlarged cross-sectional model view of the main part of the fixing device when the magnetic flux adjusting member is pivotally moved to the second switching position. Illustration of the heat generation distribution in the circumferential direction of the main magnetic flux generation area and the fixing roller part corresponding to it External perspective view of fixing roller with heat insulation bush and fixing roller gear attached External perspective view of exciting coil assembly and magnetic flux adjusting member moving means Exploded perspective view of holder and magnetic flux adjusting member Disassembled perspective view of the inside of the holder The perspective view of the control part and drive gear which control the movement of the magnetic flux suppression member of a present Example Enlarged view of the restricting portion and the drive gear for restricting the movement of the magnetic flux suppressing member of this embodiment Perspective model view of magnetic flux adjusting member corresponding to three types of recording material paper width: large, medium and small The perspective model figure of the magnetic flux adjustment member form example in the case of the apparatus of the one-side paper passing reference | standard Perspective model view of another magnetic flux adjusting member configuration example in the case of a one-side paper passing reference device

Claims (6)

Magnetic flux generating means for generating magnetic flux, a heating element that generates heat by the magnetic flux from the magnetic flux generating means, a magnetic flux suppressing member that suppresses magnetic flux from the magnetic flux generating means to the heating element, and from the magnetic flux generating means to the heating element Moving means for moving the magnetic flux suppression member to a magnetic flux suppression position for suppressing the magnetic flux toward and a retracted position retracted from the magnetic flux suppression position, and an image on the recording material by the heat of the heating element In an image heating apparatus for heating,
A moving part that moves integrally with the movement of the magnetic flux suppression member as the magnetic flux suppression member moves, and the moving means for stopping the magnetic flux suppression member at a predetermined position including the retracted position and the magnetic flux suppression position. When the control unit that controls the movement of the magnetic flux suppression member moves in the direction from the retracted position to the magnetic flux suppression position, the control unit does not stop the magnetic flux suppression member at the magnetic flux suppression position. An image heating apparatus comprising: a restricting portion that restricts movement in the direction by contacting the moving portion when the magnetic flux suppressing member moves beyond the magnetic flux suppressing position . Magnetic flux generating means for generating magnetic flux, a heating element that generates heat by the magnetic flux from the magnetic flux generating means, a magnetic flux suppressing member that suppresses magnetic flux from the magnetic flux generating means to the heating element, and from the magnetic flux generating means to the heating element Moving means for moving the magnetic flux suppression member to a magnetic flux suppression position for suppressing the magnetic flux toward and a retracted position retracted from the magnetic flux suppression position, and an image on the recording material by the heat of the heating element In an image heating apparatus for heating,
A moving part that moves integrally with the movement of the magnetic flux suppression member as the magnetic flux suppression member moves, and the moving means for stopping the magnetic flux suppression member at a predetermined position including the retracted position and the magnetic flux suppression position. And when the magnetic flux suppressing member moves in the direction from the magnetic flux suppressing position to the retracted position, the control unit does not stop the magnetic flux suppressing member at the retracted position. An image heating apparatus comprising: a restricting portion that restricts movement in the direction by contacting the moving portion when the magnetic flux suppressing member moves beyond the retracted position .   The magnetic flux generating means has an exciting coil, and the exciting coil is extended and wound along the direction of the rotation axis of the heating element. The magnetic flux suppression position is the winding center of the coil and the heating element. The image heating apparatus according to claim 1, wherein the image heating apparatus is between.   When the magnetic flux suppressing member moves in the direction from the magnetic flux suppressing position to the retracted position, the restriction that restricts the movement of the magnetic flux suppressing member in the direction beyond the predetermined position by contacting the moving portion. 4. The image heating apparatus according to claim 1, wherein the heating unit is provided at both ends of the heating element to restrict movement of the magnetic flux suppressing member from both sides. 5.   The image heating apparatus according to claim 1, wherein the magnetic flux suppressing member is a non-magnetic metal. The moving means includes a drive transmission member that engages with the magnetic flux suppression member and transmits a driving force for moving the magnetic flux suppression member, and the moving portion is provided to move integrally with the drive transmission member. The image heating apparatus according to claim 1, wherein the restricting portion is provided in a movement region of the drive transmission member.

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