JP2012068283A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of suitably reducing or shielding a magnetic flux passing through a heating rotator.SOLUTION: A fixing device comprises a heating rotating body 9a, a pressure rotating body 9b, an induction coil 71 and a magnetic core part 72. The magnetic core part 72 comprises one or a plurality of fixed core parts 74a and 74b facing to the outer circumferential surface of the heating rotating body 9a, a first movable core part 73 having a first magnetic flux shielding member 77 which is disposed to cover a first core member 739 arranged a predetermined distance apart from the outer circumferential surface of a heating rotating belt 93 above the heating rotating body 9a and a part of the outside surface of the first core member 739, and a second movable core part 75 having a second magnetic flux shielding member 78 which is disposed to cover a second core member 751 arranged a predetermined distance apart from the outer circumferential surface of the heating rotating belt 93 and a part of the outside surface of the second core member 751.

Description

  The present invention relates to a fixing device and an image forming apparatus including the same.

  Conventionally, as a fixing device for fixing an image on a sheet used in an image forming apparatus, a pressure is applied to form a fixing nip by sandwiching a sheet on which a toner image is transferred between the heating rotator and the heating rotator. A fixing device including a rotating body and a heater such as a halogen lamp for heating the heating rotating body is used.

  By the way, in recent years, as a method of heating the heating rotator in the fixing device, a method of heating by electromagnetic induction heating (IH; induction heating) using electromagnetic induction may be used. According to the fixing device using the electromagnetic induction heating (IH) method, there is an advantage that rapid heating is possible and heating efficiency is high as compared with a heating method using a halogen lamp.

  In the electromagnetic induction heating type fixing device, the paper when the paper is conveyed to the fixing nip of the fixing device in accordance with the width (paper passing width) of the paper as the transfer material conveyed (passed) to the fixing device. In order to suppress an excessive rise in the temperature of the heating rotator in the area outside the sheet passing area through which the paper passes (non-sheet passing area), the amount of heat generated by the heating rotator in the non-sheet passing area and the sheet passing area is reduced. A technique that can be adjusted has been proposed (see, for example, Patent Document 1).

  In the fixing device described in Patent Document 1, the magnetic core portion has a ferrite center core (first core member) that forms a magnetic path in the vicinity of the inner peripheral edge of the induction coil. The magnetic flux shielding member is disposed so as to cover a part of the outer peripheral surface of the center core, and is rotated integrally with the center core by the rotation of the first movable core portion.

  The fixing device described in Patent Document 1 rotates the center core and the magnetic flux shielding member integrally, thereby rotating the heating rotator in the non-sheet passing area and the sheet passing area according to the sheet passing width of each size of the sheet. Adjust the amount of heat generated.

JP 2010-26246 A

In the fixing device described in Patent Document 1, the magnetic flux shielding member arranged to cover a part of the outer peripheral surface of the center core may not be able to sufficiently shield the two magnetic fluxes passing through the center core. was there.
Accordingly, there is a demand for a fixing device that can appropriately reduce or shield the magnetic flux passing through the heating rotator in a non-sheet passing area outside the sheet passing area.

An object of the present invention is to provide a fixing device capable of appropriately reducing or shielding a magnetic flux passing through a heating rotator.
Another object of the present invention is to provide an image forming apparatus including the fixing device.

  The present invention forms a fixing nip between an annular heating rotator that generates heat by electromagnetic induction heating using electromagnetic induction and an annular arrangement that faces the heating rotator. A pressure rotator, an induction coil that is disposed along the outer surface at a predetermined distance from the outer surface of the heating rotator, is formed by winding a wire, and generates a magnetic flux for heating the heating rotator. A magnetic core portion that forms a magnetic path that passes around the inner periphery of the induction coil and the outer periphery of the induction coil so as to surround the induction coil. One or more fixed core portions facing the outer surface, and arranged in the vicinity of the inner peripheral edge of the induction coil along with the one or more fixed core portions in the circumferential direction of the magnetic path, without sandwiching the induction coil The heating time A first core member disposed at a predetermined distance from the outer surface of the body, and a first magnetic flux shielding member configured to reduce or shield magnetic flux disposed to cover a part of the outer surface of the first core member. A first movable core portion that is disposed in the vicinity of an outer peripheral edge of the induction coil along with the one or more fixed core portions in the circumferential direction of the magnetic path, and the heating rotating body without sandwiching the induction coil A second core member disposed at a predetermined distance from the outer surface; and a second magnetic flux shielding member configured to reduce or shield magnetic flux disposed so as to cover a part of the outer surface of the second core member. The present invention relates to a fixing device including a magnetic core portion having two movable core portions.

  In addition, a first shielding position where the first magnetic flux shielding member is opposed to the outer surface of the heating rotator to reduce or shield the magnetic flux, and the first magnetic flux shielding member is not opposed to the outer surface of the heating rotator. A first rotation driving unit configured to rotate the first movable core unit about a first movable core rotation axis so as to be disposed at a first non-shielding position where the magnetic flux is not reduced or shielded; and the second magnetic flux shielding member Facing the outer surface of the heating rotator to reduce or shield the magnetic flux, and the second magnetic flux shielding member does not face the outer surface of the heating rotator and does not reduce or shield the magnetic flux. A second rotation driving unit configured to rotate the second movable core unit about a second movable core rotation axis so that the second movable core unit can be disposed at a second non-shielding position; and the first magnetic flux shielding member of the first movable core unit. And controlling the first rotation drive unit to adjust the position. It is preferable to provide a drive control unit for controlling said second rotation driving unit to adjust the position of the second magnetic flux blocking member in the second movable core portion.

  Moreover, it is preferable that the said drive control part controls the said 1st rotation drive part and the said 2nd rotation drive part so that the magnetic flux density of the magnetic flux which passes along the said heating rotary body may be adjusted.

  The present invention also receives an image forming instruction information including an image forming unit that forms an image on the transfer material and size information that is information relating to the size of the transfer material on which the image is formed by the image forming unit. A first receiving unit configured to receive the first magnetic flux shielding member based on the size information of the transfer material received by the receiving unit. Controlling the first rotation driving unit to rotate the first movable core unit so as to be positioned at the position or the first non-shielding position, and the second magnetic flux shielding member is located at the second shielding position or the second The present invention relates to an image forming apparatus that controls the second rotation driving unit to rotate the second movable core unit so as to be positioned at a non-shielding position.

ADVANTAGE OF THE INVENTION According to this invention, the fixing device which can reduce or shield appropriately the magnetic flux which passes along a heating rotary body can be provided.
According to the present invention, an image forming apparatus including the fixing device can be provided.

FIG. 3 is a diagram for explaining an arrangement of each component of the printer according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view for explaining each component of the fixing device 9 of the printer 1 of the first embodiment. FIG. 3 is a view of the heating unit 70 shown in FIG. FIG. 5 is a schematic diagram showing a configuration related to a first magnetic flux shielding member 77, a second magnetic flux shielding member 78, and a third magnetic flux shielding member 79. It is a figure which shows the shape of the 1st magnetic flux shielding member 77, the 2nd magnetic flux shielding member 78, and the 3rd magnetic flux shielding member 79 in the printer 1 of this embodiment. It is a figure explaining the structure relevant to the 1st rotation drive part 155, the 2nd rotation drive part 154a, and the 3rd rotation drive part 154b in 1st Embodiment. It is sectional drawing for demonstrating the case where all of the 1st magnetic flux shielding member 77, the 2nd magnetic flux shielding member 78, and the 3rd magnetic flux shielding member 79 are located in a shielding position. It is sectional drawing for demonstrating the case where all of the 1st magnetic flux shielding member 77, the 2nd magnetic flux shielding member 78, and the 3rd magnetic flux shielding member 79 are located in a non-shielding position. FIG. 9 is a cross-sectional view for explaining each component of a fixing device 9 in a printer 1 of a second embodiment. FIG. 10 is a cross-sectional view for explaining each component of a fixing device 9 in a printer 1 according to a third embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The overall structure of a printer 1 as an image forming apparatus in the first embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining the arrangement of each component of the printer 1 according to the first embodiment of the present invention.

As shown in FIG. 1, the printer 1 as an image forming apparatus in the first embodiment forms a predetermined toner image on the apparatus body M and a sheet T as a sheet-like transfer material based on predetermined image information. An image forming unit GK that feeds the paper T toward the image forming unit GK, and a paper feed / discharge unit KH that discharges the paper T on which the toner image is formed.
The external shape of the apparatus main body M is comprised by case body BD as a housing | casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing device 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8 as a transfer unit, and a fixing device 9.

  As shown in FIG. 1, the paper supply / discharge unit KH includes a paper feed cassette 52, a transport path L for the paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side along the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8. Then, static elimination by the static eliminator 12 and cleaning by the drum cleaning unit 11 are performed.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of an arrow about a rotation axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2.
The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information input from an external device such as a PC (personal computer). By performing scanning exposure by the laser scanner unit 4, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 develops the electrostatic latent image formed on the photosensitive drum 2 using a single color (usually black) toner, and forms a single color toner image on the surface of the photosensitive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.
The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner contained in the toner cartridge 5 to the developing device 16.

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. The transfer roller 8 is configured to be rotatable while being in contact with the photosensitive drum 2.

A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.
The static eliminator 12 is disposed to face the surface of the photosensitive drum 2.
The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2.

The fixing device 9 melts and presses the toner constituting the toner image transferred onto the paper T and fixes the toner on the paper T.
Details of the fixing device 9 will be described later.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feeding unit 51. The cassette paper feed unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path L. Is provided.

  A paper discharge unit 50 is provided on the upper part of the apparatus main body M. The paper discharge unit 50 discharges the paper T to the outside of the apparatus main body M by the third roller pair 53. Details of the paper discharge unit 50 will be described later.

  The conveyance path L for conveying the paper T is a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer nip N, a second conveyance path L2 from the transfer nip N to the fixing device 9, and a discharge from the fixing device 9. A third conveyance path L3 up to the section 50, and a return conveyance path Lb for reversing the sheet conveying the third conveyance path L3 from the upstream side to the downstream side and returning it to the first conveyance path L1.

  Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.

  A sensor (not shown) for detecting the paper T and a skew of the paper T (oblique feeding) are in the middle of the first conveyance path L1 (specifically, between the second joining portion P2 and the transfer roller 8). ) A registration roller pair 80 for adjusting the timing of correction and toner image formation in the image forming unit GK and the conveyance timing of the paper T is disposed.

  A paper discharge unit 50 is disposed at the end of the third transport path L3. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1). The paper discharge unit 50 discharges the paper T conveyed on the third conveyance path L3 to the outside of the apparatus main body M by the third roller pair 53.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M.
A paper detection sensor (not shown) is disposed at a predetermined position on each conveyance path.

  Next, a configuration related to the fixing device 9 which is a characteristic part of the printer 1 of the present embodiment will be described in detail. FIG. 2 is a cross-sectional view for explaining each component of the fixing device 9 of the printer 1 of the first embodiment. 3 is a view of the heating unit 70 shown in FIG. FIG. 4 is a schematic diagram illustrating a configuration related to the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79. FIG. 5 is a diagram illustrating the shapes of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79 in the printer 1 of the present embodiment. FIG. 6 is a diagram illustrating a configuration related to the first rotation drive unit 155, the second rotation drive unit 154a, and the third rotation drive unit 154b in the first embodiment.

  FIG. 7A is a cross-sectional view for explaining a case where all of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79 are located at the shielding position. FIG. 7B is a cross-sectional view for explaining a case where all of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79 are located at the non-shielding position.

  As shown in FIG. 2, the fixing device 9 includes a heating rotator 9 a, a pressurizing rotator 9 b that is pressed against (contacted with) the heating rotator 9 a, a heating unit 70, and a plurality of temperature sensors 95. Prepare.

The heating rotator 9a is formed in an annular shape. The heating rotator 9a is configured to be rotatable in a first circumferential direction R1 that is the circumferential direction thereof. The heating rotator 9a generates heat by electromagnetic induction heating (IH; induction heating) using electromagnetic induction by using a heating unit 70 described later.
The heating rotator 9 a includes a fixing side roller 92 and a heating rotation belt 93 disposed so as to cover the outer peripheral surface of the fixing side roller 92.

  As shown in FIG. 2, the fixing side roller 92 is formed in a cylindrical shape. The fixing side roller 92 is configured to be rotatable in the first circumferential direction R1 around a first rotation axis J1 parallel to a direction D2 orthogonal to the first circumferential direction R1. The fixing side roller 92 is formed to extend in the direction of the first rotation axis J1. In the present embodiment, the orthogonal direction D2 orthogonal to the first circumferential direction R1 is also referred to as “paper width direction D2”.

  The fixing side roller 92 includes a fixing side roller main body 921 and a shaft member (not shown) coaxial with the first rotation axis J1. The fixing-side roller main body 921 includes a cylindrical metal member and an elastic layer formed on the outer peripheral surface of the metal member.

  A shaft member (not shown) of the fixing side roller 92 is formed so as to protrude from both ends of the fixing side roller main body 921 to the outside in the direction of the first rotation axis J1. A shaft member (not shown) of the fixing side roller 92 is rotatably supported by a case of the fixing device 9 and other members. Thereby, the fixing side roller 92 can rotate around the first rotation axis J1.

  As shown in FIG. 2, the heating rotary belt 93 is formed in an annular shape (endless belt shape). The heating rotary belt 93 is configured to be rotatable in the first circumferential direction R1. The heating rotation belt 93 is disposed along the outer peripheral surface of the fixing side roller 92 so as to cover the outer peripheral surface of the fixing side roller 92. The outer peripheral surface of the fixing side roller 92 is in contact with the inner peripheral surface of the heating rotating belt 93. The heating rotary belt 93 has heat resistance.

In the present embodiment, the heating rotary belt 93 is made of a ferromagnetic material such as nickel.
The heating rotating belt 93 is disposed in a region through which a magnetic flux generated by an induction coil 71 of the heating unit 70, which will be described later, passes, and the base material is made of a ferromagnetic material, whereby the induction coil 71 of the heating unit 70 is formed. This forms a magnetic path for the magnetic flux generated by. The magnetic flux generated by the induction coil 71 passes (is guided) along the heating rotating belt 93 that forms a magnetic path.

  In the heating rotary belt 93, an eddy current (induction current) is generated by electromagnetic induction by a magnetic flux passing through the heating rotary belt 93 generated by an induction coil 71 described later. Joule heat is generated by the electric resistance of the heating rotating belt 93 due to an eddy current flowing through the heating rotating belt 93.

  The pressure roller 9b as the pressure rotator is formed in a cylindrical shape. The pressure roller 9b is disposed on the lower side in the vertical direction of the heating rotator 9a so as to face the fixing side roller 92. The pressure roller 9b is configured to be rotatable in a second circumferential direction R2, which is the circumferential direction of the pressure roller 9b, around a second rotation axis J2 parallel to the paper width direction D2. The pressure roller 9b is formed to extend in the direction of the second rotation axis J2.

  The pressure roller 9 b is disposed so that the outer peripheral surface thereof is in contact with the outer peripheral surface (outer surface) of the heating rotary belt 93. The pressure roller 9 b is disposed so as to press the fixing side roller 92 through the heating rotating belt 93. The pressure roller 9 b sandwiches a part of the heating rotating belt 93 with the fixing side roller 92. The pressure roller 9 b sandwiches a part of the heating rotating belt 93 between the fixing roller 92 and forms the fixing nip F with the heating rotating belt 93. The fixing nip F sandwiches the paper T and conveys the paper T.

  The pressure roller 9b includes a pressure roller main body 941 and a shaft member (not shown) coaxial with the second rotation shaft J2. The pressure roller body 941 includes a cylindrical metal member, an elastic layer formed on the outer peripheral surface of the metal member, and a release layer formed on the outer peripheral surface of the elastic layer.

  A rotation drive unit (not shown) for rotating the pressure roller 9b is connected to a shaft member (not shown) of the pressure roller 9b. The rotation driving unit drives the pressure roller 9b to rotate in the second circumferential direction R2 at a predetermined speed, and is driven by the rotation of the pressure roller 9b to contact the outer peripheral surface of the pressure roller 9b. 93 is rotated. When the heating rotating belt 93 is rotated, the fixing side roller 92 that is in contact with the inner peripheral surface of the heating rotating belt 93 is rotated by the rotation of the heating rotating belt 93.

  When the sheet T conveyed to the fixing nip F is conveyed after passing through the sheet passing area in the fixing device 9, the toner image is fixed. The “paper passing area” is an area through which the paper T conveyed to the fixing nip F passes between the heating rotating belt 93 and the pressure roller 9b. An area outside the sheet passing area when the sheet T is conveyed to the fixing nip F is referred to as a “non-sheet passing area”.

  As shown in FIG. 3, a maximum sheet passing area 901 is set as a sheet passing area when the maximum length sheet T in the sheet width direction D2 is conveyed to the fixing nip F. The maximum sheet passing area 901 is set for each printer 1.

  Specifically, as shown in FIG. 3, a heating-side maximum sheet passing area 901 a is formed (set) on the outer peripheral surface of the heating rotating belt 93 as the maximum sheet passing area 901 in the heating rotating belt 93. On the outer peripheral surface of the pressure roller 9b, a pressure side maximum sheet passing area 901b is formed as a maximum sheet passing area 901 in the pressure rotating body 9b corresponding to the heating side maximum sheet passing area 901a of the heating rotating belt 93 ( Set). The length in the direction parallel to the sheet width direction D2 in the heating-side maximum sheet passing area 901a is referred to as “maximum sheet passing width W1”.

  Further, the minimum sheet passing area 903 is set as a sheet passing area through which the sheet T passes when the sheet T having the minimum length in the sheet width direction D2 is conveyed to the fixing nip F.

  Specifically, a heating-side minimum sheet passing area 903 a is formed (set) on the outer peripheral surface of the heating rotating belt 93 as the minimum sheet passing area 903 in the heating rotating belt 93. On the outer peripheral surface of the pressure roller 9b, a pressure side minimum sheet passing area 903b is formed (set) corresponding to the heating side minimum sheet passing area 903a of the heating rotating belt 93. The length in the direction parallel to the sheet width direction D2 in the heating-side minimum sheet passing area 903a is referred to as “minimum sheet passing width W3”.

Further, an intermediate sheet passing area 902 (heating-side intermediate sheet passing area 902a) is used as a sheet passing area for an intermediate length of paper T whose length in the sheet width direction D2 is shorter than the maximum length and longer than the minimum length. , Pressurization side intermediate sheet passing area 902b) is set. The length in the direction parallel to the sheet width direction D2 of the heating-side intermediate sheet passing region 902a is referred to as “intermediate sheet passing width W2.”
Note that the paper passing area of the paper T is not limited to this, and can be set as appropriate for the paper T of each size.

The heating unit 70 will be described. As shown in FIGS. 2 to 6, the heating unit 70 includes an induction coil 71, a magnetic core part 72, and a rotation driving part 770. The induction coil 71 is spaced from the outer peripheral surface of the heating rotary belt 93 by a predetermined distance and is disposed along the outer peripheral surface of the heating rotary belt 93. The induction coil 71 is formed by winding a wire in a long shape in the paper width direction D2 in plan view (when viewed from above in FIGS. 2 and 3).
The induction coil 71 is formed longer than the length of the heating rotary belt 93 in the paper width direction D2.

  The induction coil 71 is formed by winding a copper litz wire. The induction coil 71 is disposed so as to face a substantially half-circumferential outer peripheral surface on the upper side in the vertical direction of the heating rotary belt 93.

  As shown in FIGS. 2 and 3, the induction coil 71 is formed by winding a wire so as to surround a central region 718 formed so as to extend in the paper width direction D2.

  In the present embodiment, the induction coil 71 is fixed by winding a wire on a support member (not shown) formed of a heat-resistant resin material.

The induction coil 71 is connected to an induction heating circuit unit (not shown). An alternating current having a predetermined frequency is applied to the induction coil 71 from the circuit section for induction heating. The induction coil 71 generates a magnetic flux for causing the heating rotating belt 93 to generate heat when an alternating current is applied from the induction heating circuit unit.
The magnetic flux generated by the induction coil 71 is guided to a magnetic path that is a magnetic flux path formed by the heating rotating belt 93 and a magnetic core portion 72 (described later).

  The magnetic path is formed by the heating rotating belt 93 and the magnetic core portion 72 (described later) so that the magnetic flux generated by the induction coil 71 circulates in the first circulation direction R3a and the second circulation direction R3b. Each of the first circulation direction R3a and the second circulation direction R3b is a direction that circulates so as to surround the induction coil 71 through the inner side of the inner peripheral edge 711A and the outer side of the outer peripheral edge 711B of the induction coil 71. The magnetic flux generated by the induction coil 71 passes through the magnetic path.

  The magnetic flux generated by the induction coil 71 is applied with an alternating current of a predetermined frequency from an induction heating circuit unit (not shown), and therefore, the magnitude and direction of the magnetic flux generated by periodic fluctuation of the alternating current to plus or minus. Changes. An induction current (eddy current) is generated in the heating rotating belt 93 due to the change of the magnetic flux.

As shown in FIG. 2, the magnetic core portion 72 includes a center core portion 73 as a first movable core portion, an upstream arch core portion 74a and a downstream arch core portion 74b as a pair of fixed core portions, and a second movable core. It has the upstream side core part 75 as a core part, and the downstream side core part 76 as a 3rd movable core part.
The first core member 739 (described later) of the center core portion 73, the upstream arch core portion 74a, the downstream arch core portion 74b, the second core member 751 (described later) of the upstream side core portion 75, and the third core of the downstream side core portion 76. The member 761 (described later) is, for example, a ferrite magnetic core made of a ferromagnetic material formed by sintering ferrite powder.

  The center core portion 73, the upstream arch core portion 74a, the upstream side core portion 75, and the heating rotating belt 93 are arranged side by side in the first circulation direction R3a of the magnetic path. Further, the center core portion 73, the downstream arch core portion 74b, the downstream side core portion 76, and the heating rotary belt 93 are arranged side by side in the second circulation direction R3b of the magnetic path.

  Each of the upstream arch core portion 74 a and the downstream arch core portion 74 b is disposed to face the outer peripheral surface of the heating rotating belt 93 with the induction coil 71 interposed therebetween. Each of the upstream arch core portion 74a and the downstream arch core portion 74b is arranged in a pair on the upstream side and the downstream side in the transport direction D1 of the paper T so as to sandwich the center core portion 73 in the transport direction D1 of the paper T. Each of the upstream arch core portion 74 a and the downstream arch core portion 74 b is formed in an arch shape extending along the circumferential direction of the heating rotating belt 93.

  In the present embodiment, the upstream arch core portion 74a includes an upstream horizontal portion 746 and an upstream inclined portion 747, as shown in FIG. The downstream arch core portion 74 b includes a downstream horizontal portion 742 and a downstream inclined portion 743.

  Further, as shown in FIG. 3, a plurality of the upstream arch core part 74a and the downstream arch core part 74b are arranged apart from each other by a predetermined distance in the paper width direction D2. Each of the plurality of upstream arch core portions 74a and the plurality of downstream arch core portions 74b is spaced apart in the paper width direction D2 to form a plurality of magnetic paths that circulate in each of the first circulation direction R3a and the second rotation direction R3b.

As shown in FIG. 2, the center core portion 73 includes a magnetic path between the upstream arch core portion 74a and the heating rotary belt 93 in the first circulation direction R3a, and a downstream arch core portion 74b in the second circulation direction R3b. A magnetic path (see FIG. 7B) with the heating rotary belt 93 is formed. The center core portion 73 is configured as a common magnetic path of a pair of magnetic paths that circulate in the first circumferential direction R3a and the second circumferential direction R3b.
Center core portion 73 is disposed in the vicinity of central region 718 (in the vicinity of inner peripheral edge 711A of induction coil 71).

  The center core portion 73 is disposed so as to cover a first core member 739 disposed at a predetermined distance from the outer circumferential surface of the heating rotary belt 93 and a part of the outer circumferential surface of the first core member 739. Magnetic flux shielding member 77.

Further, as shown in FIGS. 2 to 4, the center core portion 73 is configured to be rotatable around a center core rotation axis J3 as a first movable core rotation axis parallel to the paper width direction D2.
As shown in FIGS. 3 and 4, the first core member 739 of the center core portion 73 has a cylindrical shape that is long in the direction of the center core rotation axis J <b> 3 and is longer than the maximum sheet passing width W <b> 1 of the maximum length paper T. The

  As shown in FIG. 2, the upstream side core part 75 and the downstream side core part 76 are respectively in a plurality of upstream arch core parts 74a and a plurality of downstream arch core parts 74b in the first circulation direction R3a and the second circulation direction R3b. A magnetic path (see FIG. 7B) with the heating rotary belt 93 is formed.

Each of the upstream side core portion 75 and the downstream side core portion 76 is disposed near the outside of the outer peripheral edge 711 </ b> B of the induction coil 71 on the upstream side and the downstream side with respect to the transport direction D <b> 1 of the paper T as viewed from the center core portion 73.
The upstream side core portion 75 is disposed so as to cover the second core member 751 disposed at a predetermined distance from the outer circumferential surface of the heating rotary belt 93 and a part of the outer circumferential surface of the second core member 751. 2 magnetic flux shielding member 78.

The downstream side core portion 76 is disposed so as to cover a part of the third core member 761 that is spaced apart from the outer peripheral surface of the heating rotary belt 93 by a predetermined distance and the outer peripheral surface (outer surface) of the third core member 761. A third magnetic flux shielding member 79.
Each of the upstream side core portion 75 and the downstream side core portion 76 faces the outer peripheral surface of the heating rotating belt 93 without sandwiching the induction coil 71.

As shown in FIGS. 2 to 4, the upstream side core portion 75 and the downstream side core portion 76 are respectively provided with an upstream side core rotational axis J4a and a third movable core rotational axis J4a that are parallel to the paper width direction D2. It is configured to be rotatable around a downstream side core rotation axis J4b as a movable core rotation axis.
As shown in FIGS. 3 and 4, the second core member 751 of the upstream side core portion 75 and the third core member 761 of the downstream side core portion 76 are arranged in the direction of the upstream side core rotational axis J4a and the downstream side core rotational axis J4b. The long cylindrical shape is formed longer than the area corresponding to the maximum sheet passing area 901.

  As shown in FIG. 4, each of the center core portion 73, the upstream side core portion 75, and the downstream side core portion 76 includes a maximum sheet passing area corresponding region 731 corresponding to the heating side maximum sheet passing area 901a in the sheet width direction D2. A minimum sheet passing area corresponding region 733 corresponding to the heating side minimum sheet passing area 903a, and an intermediate sheet passing area corresponding region 732 corresponding to the heating side intermediate sheet passing area 902a.

The first magnetic flux shielding member 77 is disposed so as to cover a part of the outer peripheral surface of the first core member 739 of the center core portion 73. The first magnetic flux shielding member 77 is attached along the outer peripheral surface of the first core member 739.
The first magnetic flux shielding member 77 is made of a nonmagnetic material and a conductive member having high conductivity. As the first magnetic flux shielding member 77, for example, oxygen-free copper is used.

  The first magnetic flux shielding member 77 is an induced current caused by the penetration of a magnetic flux perpendicular to the surface of the first magnetic flux shielding member 77, and generates a magnetic flux in a direction opposite to the penetrating magnetic flux. Then, the first magnetic flux shielding member 77 reduces or shields the magnetic flux passing through the magnetic path by generating a magnetic flux in a direction that cancels the complex magnetic flux (perpendicular penetrating magnetic flux).

As shown in FIG. 4, the first magnetic flux shielding member 77 has two first shielding plates 771 and 771 that are spaced apart from each other in the paper width direction D2.
In the following description, since the two first shielding plates 771 and 771 have the same configuration, the one first shielding plate 771 may be described.

As shown in FIG. 5, the 1st shielding board 771 is formed in step shape by planar view. The first shielding plate 771 includes a first maximum non-sheet passing area shielding portion 772, a first minimum non-sheet passing area shielding portion 773, and a first intermediate non-sheet passing area shielding portion 774. The first maximum non-sheet passing area shielding portion 772, the first minimum non-sheet passing area shielding portion 773, and the first intermediate non-sheet passing area shielding portion 774 are continuously arranged side by side in the circumferential direction of the first core member 739. The
The first magnetic flux shielding member 77 is configured to be rotatable about the center core rotation axis J3 integrally with the first core member 739.

  The second magnetic flux shielding member 78 and the third magnetic flux shielding member 79 are respectively an outer peripheral surface (outer surface) of the second core member 751 of the upstream side core portion 75 and an outer peripheral surface (outer surface) of the third core member 761 of the downstream side core portion 76. ) Is arranged so as to cover a part of.

  The description of the second magnetic flux shielding member 78 and the third magnetic flux shielding member 79 will be mainly focused on differences from the first magnetic flux shielding member 77, and the same configuration as the first magnetic flux shielding member 77 will be explained. Omitted.

  As shown in FIGS. 4 and 5, the second magnetic flux shielding member 78 includes two second shielding plates 781 and 781 that are spaced apart from each other in the paper width direction D <b> 2 of the upstream side core portion 75. The second shielding plate 781 has a second maximum non-sheet passing area shielding portion 782, a second minimum non-sheet passing area shielding portion 783, and a second intermediate non-sheet passing area shielding portion 784. The second magnetic flux shielding member 78 is configured to be rotatable integrally with the second core member 751 around the upstream side core rotation axis J4a.

  The third magnetic flux shielding member 79 includes two third shielding plates 791 and 791 that are spaced apart from each other in the paper width direction D2 of the downstream side core portion 76. The third shielding plate 791 includes a third maximum non-sheet passing area shielding portion 792, a third minimum non-sheet passing area shielding portion 793, and a third intermediate non-sheet passing area shielding portion 794. The third magnetic flux shielding member 79 is configured to be rotatable integrally with the third core member 761 about the downstream side core rotation axis J4b.

  As shown in FIG. 4, the rotation drive unit 770 includes a first rotation drive unit 155 that rotates the center core unit 73 about the center core rotation axis J3, and an upstream side core unit 75 that is centered on the upstream side core rotation axis J4a. And a third rotation drive unit 154b that rotates the downstream side core unit 76 about the downstream side core rotation axis J4b.

  As shown in FIG. 6, each of the first rotation drive unit 155, the second rotation drive unit 154 a, and the third rotation drive unit 154 b includes a rotation drive source 158 and a gear mechanism 156. For the gear mechanism 156, a worm gear configured by a first gear 156A connected to the output shaft 158A of the rotational drive source 158 and a second gear 156B meshing with the first gear 156A is used.

  Each of the first rotation drive unit 155, the second rotation drive unit 154a, and the third rotation drive unit 154b transmits the rotation drive force from the rotation drive source 158 to the gear mechanism 156, so that the center core shaft 735, the upstream side Each of the core shaft 785a and the downstream side core shaft 785b is rotationally driven.

  In addition, a rotational position detector 159 is disposed on one end side of each of the center core shaft 735, the upstream side core shaft 785a, and the downstream side core shaft 785b. The rotational position detection unit 159 includes a disk 159A with a slit and a rotational position detection sensor 159B.

  In the heating unit 70 configured as described above, the first magnetic flux shielding member 77 is opposed to the outer peripheral surface of the heating rotating belt 93 to reduce or shield the magnetic flux from the induction coil 71 by rotating the center core portion 73. The first shielding position (see FIG. 7A) to be performed, or the first non-shielding position (see FIG. 7B) that does not reduce or shield the magnetic flux from the induction coil 71 without facing the outer peripheral surface of the heating rotating belt 93. Can be made. Further, by rotating the upstream side core portion 75, the second magnetic flux shielding member 78 faces the outer peripheral surface of the heating rotary belt 93 to reduce or shield the magnetic flux from the induction coil 71 (FIG. 7A). Or a second non-shielding position (see FIG. 7B) that does not reduce or shield the magnetic flux from the induction coil 71 without facing the outer peripheral surface of the heating rotary belt 93. Further, by rotating the downstream side core portion 76, the third magnetic flux shielding member 79 faces the outer peripheral surface of the heating rotary belt 93 to reduce or shield the magnetic flux from the induction coil 71 (FIG. 7A). Or a third non-shielding position (see FIG. 7B) that does not reduce or shield the magnetic flux from the induction coil 71 without facing the outer peripheral surface of the heating rotary belt 93.

  The temperature sensor 95 detects the temperature of the heating rotary belt 93. As shown in FIG. 2, the temperature sensor 95 is disposed in contact with the outer peripheral surface of the heating rotary belt 93.

  Next, a configuration related to the control of the fixing device 9 will be described. As illustrated in FIG. 4, the printer 1 includes a receiving unit 101, a control unit 110, and a storage unit 120.

  The receiving unit 101 can receive image formation instruction information including size information regarding the size of the paper T.

  The control unit 110 includes a drive control unit 111. Based on the size information of the paper T received by the receiving unit 101, the drive control unit 111 refers to information stored in the storage unit 120 described later and adjusts the position of the first magnetic flux shielding member 77. The first rotation driving unit 155 is controlled, the second rotation driving unit 154a is controlled to adjust the position of the second magnetic flux shielding member 78, and the third rotation driving unit 154b is adjusted to adjust the position of the third magnetic flux shielding member 79. Control. The drive control unit 111 controls the first rotation drive unit 155, the second rotation drive unit 154a, and the third rotation drive unit 154b so as to adjust the magnetic flux density of the magnetic flux passing through the heating rotation belt 93.

  The storage unit 120 stores information on the operation amounts (rotation amounts) of the first rotation drive unit 155, the second rotation drive unit 154a, and the third rotation drive unit 154b.

Next, the operation of the printer 1 including the fixing device 9 of this embodiment will be described.
First, the accepting unit 101 accepts image formation instruction information generated when an operation unit (not shown) disposed outside the printer 1 is operated, for example, in a state where the printer 1 is powered on. .
For example, the accepting unit 101 accepts a print command for printing a minimum size paper T (for example, A5 size vertical paper T) having a minimum paper passing width W3.

  As a result, the drive control unit 111 corresponds to the minimum size paper T having the minimum sheet passing width W3 (for example, A5 size vertical paper T), the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 78. The center core portion 73, the upstream side core portion 75, and the downstream side core portion 76 are rotated so that the magnetic flux shielding member 79 is disposed.

Specifically, as shown in FIG. 7A, the drive control unit 111 sets the first magnetic flux shielding member 77 to the first shielding position in an area corresponding to the minimum sheet passing area 903 (minimum sheet passing area corresponding area 733). The first rotation driving unit 155 is controlled to be positioned, the second rotation driving unit 154a is controlled so that the second magnetic flux shielding member 78 is located at the second shielding position, and the third magnetic flux shielding member 79 is the third shielding. The third rotation drive unit 154b is controlled so as to be positioned.
Further, as shown in FIG. 7B, the drive control unit 111 includes the first non-shielding member for the first magnetic flux shielding member 77 in a region outside the region corresponding to the minimum sheet passing region 903 (minimum sheet passing region corresponding region 733). The first rotation driving unit 155 is controlled so as to be positioned, the second rotation driving unit 154a is controlled so that the second magnetic flux shielding member 78 is positioned at the second non-shielding position, and the third magnetic flux shielding member 79 is The third rotation driving unit 154b is controlled so as to be positioned at the third non-shielding position.

Next, the printer 1 starts a printing operation.
When the supply of power to the drive control unit is started, the pressure roller 9b is rotationally driven by a rotation drive unit (not shown). As the pressure roller 9b is driven to rotate, the heating rotary belt 93 is driven to rotate.

Next, the fixing device 9 starts a heat generating operation.
Thereby, an alternating current is applied to the induction coil 71 from an induction heating circuit section (not shown). The induction coil 71 generates a magnetic flux for causing the heating rotary belt 93 to generate heat. The magnitude and direction of the magnetic flux generated by the induction coil 71 changes.

  Here, in the sheet passing region of the A5 size vertical (minimum sheet passing width W3) sheet T, the size and direction of the magnetic flux passing through the magnetic path change, so that the upper part in the vertical direction of the heating rotary belt 93 is changed. Eddy current (induced current) is generated by electromagnetic induction. Joule heat is generated by the electric resistance of the heating rotating belt 93 due to an eddy current flowing through the heating rotating belt 93.

  Further, in the non-sheet passing region of the sheet T of A5 size vertical (minimum sheet passing width W3), as shown in FIG. 7A, the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79. All shields substantially all of the magnetic flux passing through the magnetic path by generating a magnetic flux that cancels the complex magnetic flux (perpendicular penetrating magnetic flux). That is, in the non-sheet passing region of the paper T, any one of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79 is positioned at the shielding position and shields the magnetic flux. The shielding effect is high, and the magnetic flux from the induction coil 71 can be shielded efficiently. Thereby, in the non-sheet passing region of the paper T, it is possible to efficiently suppress the temperature of the heating rotary belt 93 from being excessively increased.

Next, the heating rotary belt 93 is heated to a predetermined fixing temperature in the fixing nip F.
A portion of the heating rotary belt 93 that is heated by electromagnetic induction heating (IH) due to the rotation of the heating rotary belt 93 is directed toward the fixing nip F formed by the heating rotary belt 93 and the pressure roller 9 b of the fixing device 9. It is moved sequentially.
The fixing device 9 controls the induction heating circuit unit (not shown) so that the fixing nip F has a predetermined temperature.

  Then, the paper T on which the toner image is formed is introduced into the fixing nip F of the fixing device 9. In the fixing nip F, the toner melts and the toner is fixed on the paper T.

According to the printer 1 of the present embodiment, for example, the following effects are exhibited.
In the printer 1 of the present embodiment, the first rotation driving unit 155, the second rotation driving unit 154a, and the first rotation driving unit 155 are adjusted so that the positions of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79 are adjusted. By controlling the third rotation drive unit 154b, the magnetic flux density of the magnetic flux passing through the heating rotary belt 93 can be adjusted to appropriately reduce or shield the magnetic flux passing through the heating rotary belt 93. Thereby, it is possible to suppress the temperature of the heating rotary belt 93 from being excessively increased in the non-sheet passing region of the paper T.
In particular, when the magnetic flux is shielded by all of the first magnetic flux shielding member 77, the second magnetic flux shielding member 78, and the third magnetic flux shielding member 79, the shielding effect is high and the magnetic flux can be efficiently shielded.

  Further, the temperature of the heating rotary belt 93 is excessively increased in the non-sheet passing region of the paper T by a simple configuration that controls the rotation of the center core portion 73, the upstream side core portion 75, and the downstream side core portion 76. Can be suppressed.

  Next, a second embodiment and a third embodiment of the present invention will be described. The second embodiment and the third embodiment will be described mainly with respect to points different from the first embodiment, and the points not particularly described in the second embodiment and the third embodiment are about the first embodiment. The description is applied or incorporated as appropriate.

FIG. 8 is a cross-sectional view for explaining each component of the fixing device 9 of the printer 1 of the second embodiment.
In the second embodiment, a fixed side core 76 is arranged on the downstream side in the transport direction D1 of the paper T in the fixing device 9 instead of the downstream side core portion 76 described in the first embodiment, and third. The fixing device 9 is different from the fixing device 9 of the first embodiment in that the rotation driving unit 154b is not provided.

  As shown in FIG. 8, in the second embodiment, the fixed side core portion 76 </ b> A is disposed on the downstream side in the transport direction D <b> 1 of the paper T in the fixing device 9. The fixed side core portion 76A is formed in a substantially rectangular parallelepiped shape that is long in the paper width direction D2.

  The fixed side core portion 76A is, for example, a ferrite magnetic core. The fixed side core portion 76A, together with the downstream arch core portion 74b, forms a magnetic path that goes around in the second turning direction R3b.

  In addition, the drive control unit 111 in the second embodiment controls the first rotation driving unit 155 to adjust the position of the first magnetic flux shielding member 77 in the center core unit 73, and the second magnetic flux in the upstream side core unit 75. The second rotation drive unit 154a is controlled to adjust the position of the shielding member 78.

  In the printer 1 of the second embodiment, the operations and actions of the center core portion 73 and the upstream side core portion 75 are the same as those of the first embodiment, and thus the description of the operations and actions of the printer 1 of the first embodiment is incorporated. Therefore, the description is omitted.

According to the printer 1 of the second embodiment, the following effects can be obtained in addition to the effects shown in the first embodiment, in addition to the effects shown in the first embodiment.
In the printer 1 of the second embodiment, the configuration of the downstream side core 76 in the transport direction D1 of the paper T can be simplified while having the same effects as the first embodiment. Further, the cost required for the material of the third magnetic flux shielding member 79 can be reduced.

Next, a third embodiment of the present invention will be described. FIG. 9 is a cross-sectional view for explaining each component of the fixing device 9 of the printer 1 of the third embodiment.
In the third embodiment, the configuration of the heating rotator 9a is different from the fixing device 9 of the first embodiment.

  As shown in FIG. 9, the heating rotator 9 a of the third embodiment is arranged such that the heating side roller 91 and the fixing side roller 92 arranged to be separated from the heating side roller 91 by a predetermined distance (separated downward in the vertical direction). And a heating rotating belt 93 that is stretched between the heating side roller 91 and the fixing side roller 92.

Since the operation and action of the printer 1 of the third embodiment are the same as those of the first embodiment, the description of the operation and action of the printer 1 of the first embodiment is incorporated and the description is omitted.
According to the printer 1 of the third embodiment, the same effects as those shown in the first embodiment can be obtained.

  As mentioned above, although preferred embodiment was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.

  For example, in the above-described embodiment, the drive control unit 111 performs control so as to adjust the magnetic flux density of the magnetic flux passing through the heating rotary belt 93, but is not limited to this, and the temperature detected by the temperature sensor 95. You may control based on.

The type of the image forming apparatus of the present invention is not particularly limited, and may be a copier, a facsimile, or a complex machine of these in addition to a printer.
The sheet-shaped transfer material is not limited to paper, and may be a film sheet, for example.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum (image carrier), 8 ... Transfer roller (transfer part), 9 ... Fixing device, 9a ... Heating rotary body, 9b ... Pressure Rotating body (pressure roller), 16 ... developing device, 71 ... inductive coil, 72 ... magnetic core portion, 73 ... center core portion (first movable core portion), 74a ... upstream arch core portion ( Fixed core portion), 74b ...... Downstream arch core (fixed core portion), 75 ...... Upstream side core portion (second movable core portion), 76 ...... Downstream side core portion (third movable core portion), 77 ...... First magnetic flux shielding member, 78... Second magnetic flux shielding member, 79... Third magnetic flux shielding member, 101... Receiving portion, 111... Drive control portion, 154 a. 3 rotation drive part, 155 ... 1st rotation drive part, 739 ... 1st core member 751... Second core member, 761... Third core member, D2... Paper width direction (orthogonal direction), F... Fixing nip, J1... First rotation axis, J2. …… Center core rotation axis (first movable core rotation axis), J4a …… Upstream side core rotation axis (second movable core rotation axis), J4b …… Downstream side core rotation axis (third movable core rotation axis), T ...... Paper (Transfer material)

Claims (4)

An annular heating rotor that generates heat by electromagnetic induction heating using electromagnetic induction;
A pressure rotator that is annularly disposed opposite the heating rotator and forms a fixing nip with the heating rotator; and
An induction coil that is disposed along the outer surface at a predetermined distance from the outer surface of the heating rotator, is formed by winding a wire, and generates a magnetic flux for heating the heating rotator;
A magnetic core portion that forms a magnetic path that goes around the induction coil through the inside of the inner periphery and the outer periphery of the induction coil;
One or a plurality of fixed core portions facing the outer surface of the heating rotator across the induction coil;
Arranged in the vicinity of the inner peripheral edge of the induction coil along with the one or more fixed cores in the circumferential direction of the magnetic path, and spaced apart from the outer surface of the heating rotator without sandwiching the induction coil A first core member, and a first magnetic flux shielding member that reduces or shields a magnetic flux arranged to cover a part of the outer surface of the first core member;
Arranged in the vicinity of the outer peripheral edge of the induction coil along with the one or more fixed cores in the circumferential direction of the magnetic path, and spaced apart from the outer surface of the heating rotator without sandwiching the induction coil And a second movable core portion having a second magnetic flux shielding member that reduces or shields the magnetic flux arranged to cover a part of the outer surface of the second core member. And a magnetic core portion. A first shielding position where the first magnetic flux shielding member is opposed to the outer surface of the heating rotator to reduce or shield the magnetic flux; and the first magnetic flux shielding member is not opposed to the outer surface of the heating rotator and generates a magnetic flux. A first rotation driving unit configured to rotate the first movable core unit about a first movable core rotation axis so that the first movable core unit can be disposed at a first non-shielding position that is not reduced or shielded;
A second shielding position where the second magnetic flux shielding member opposes the outer surface of the heating rotator to reduce or shield the magnetic flux; and the second magnetic flux shielding member does not oppose the outer surface of the heating rotator and generates magnetic flux. A second rotation drive unit that rotates the second movable core unit about the second movable core rotation axis so as to be disposed at a second non-shielding position that is not reduced or shielded;
The first rotation driving unit is controlled to adjust the position of the first magnetic flux shielding member in the first movable core part, and the position of the second magnetic flux shielding member in the second movable core part is adjusted. The fixing device according to claim 1, further comprising: a drive control unit that controls the second rotation drive unit. The fixing device according to claim 2, wherein the drive control unit controls the first rotation drive unit and the second rotation drive unit so as to adjust a magnetic flux density of a magnetic flux passing through the heating rotator. An image forming unit for forming an image on a sheet-like transfer material;
A receiving unit capable of receiving image formation instruction information including size information which is information relating to a size of the transfer material on which an image is formed by the image forming unit;
A fixing device according to claim 2 or 3,
The drive control unit
Based on the size information of the transferred material received by the receiving unit, the first movable core unit is arranged such that the first magnetic flux shielding member is located at the first shielding position or the first non-shielding position. The first rotation driving unit is controlled to rotate, and the second movable core unit is rotated so that the second magnetic flux shielding member is positioned at the second shielding position or the second non-shielding position. An image forming apparatus that controls a two-rotation driving unit.

Images