JP2011180176A - Fixing device and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of achieving uniform heat generation of a heating member, and to provide an image forming apparatus with the same. <P>SOLUTION: The fixing device (14) for fixing an image on a recording medium includes a coil (52) which is arranged along an outer surface of a heating member (46) to generate the magnetic field for executing the induction heating of the heating member, a coil holder (53) for holding the coil, and a core (58) which is arranged on the side opposite to the heating member across the coil holder, and forms a magnetic path around the coil, and is rotated around the axis extending in the width direction of the recording medium to be conveyed. The core has a plurality of core bodies (58a-58d) which are divided in the direction across the axis of rotation and constituted of a magnetic material so as to form the magnetic path. The coil holder has a distance adjusting mechanism (80) which is abutted on an outer circumferential surface of the core body to keep the distance between the outer circumferential surface of the core body and the surface of the heating member at a substantially constant value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device that heats and melts unfixed toner on a sheet while passing a recording medium carrying a toner image between a nip between a fixing roller pair or a heating belt and a roller, and an image forming apparatus equipped with the fixing device. It relates to the device.

  In recent years, in this type of image forming apparatus, a belt system capable of setting a small heat capacity has attracted attention due to demands for shortening the warm-up time and energy saving in the fixing device (for example, see Patent Document 1). In recent years, the electromagnetic induction heating method (IH) that has the potential for rapid heating and high-efficiency heating has attracted attention. From the viewpoint of energy saving when fixing color images, electromagnetic induction heating is combined with the belt method. Many products have been commercialized. When combining the belt method and electromagnetic induction heating, there is a configuration in which a device for generating a magnetic field for electromagnetic induction is arranged outside the belt because of the coil layout and ease of cooling, and the advantage that the belt can be directly heated. Many have been adopted (so-called outer packaging IH).

  In the above-mentioned electromagnetic induction heating method, various technologies have been developed to prevent excessive temperature rise in the non-sheet passing area according to the width of the sheet size (sheet passing width) passed through the fixing device. In particular, a technique for switching the size of the outer packet IH is disclosed. Specifically, it has a ferrite center core that forms a magnetic path around the coil. By rotating the center core, the heat roller is induction-heated or interrupted by the magnetic flux generated by the coil. It is possible to select whether to suppress induction heating, and it is possible to provide a difference in the heat generation amount of the heat roller between the non-sheet passing area and the sheet passing area.

  The center core is formed in an elongated shape along its rotation axis so as to form a magnetic path in the maximum sheet area. In other words, if the center core is configured as a single elongated body, unless the center core is manufactured with high accuracy, the rotational runout becomes large, and a uniform gap cannot be obtained between the center core and the heat roller. Uneven heat generation occurs in the axial direction. On the other hand, if the center core is cut and manufactured, the manufacturing cost cannot be reduced, and dimensional accuracy is difficult to obtain by molding using a mold. Therefore, it is conceivable to divide the center core into a plurality of core bodies and arrange the center core on the shaft member (for example, see Patent Document 2).

JP-A-6-31801 JP 2006-171273 A

However, the conventional technique has a problem that the positions of the outer peripheral surfaces of the center core do not match.
This is because, when the center core is composed of a plurality of core bodies, the dimensional variation in manufacturing each core body, specifically, the shrinkage ratio (diameter direction and axial direction) when the powder is pressed and sintered. This is because each core body is different.

More specifically, there are core bodies with different inner and outer diameters due to the difference in shrinkage ratio in the radial direction. In particular, the core body with a large inner diameter has a large backlash with respect to the shaft member and is difficult to fix. When the inner diameter is fixed by contacting at one point of the shaft member, the deflection of the core body with respect to the shaft member becomes large.
In addition, when these core bodies having different inner diameters are simply arranged on the shaft member, the distance between each core body and the heat roller is different, and uniform heat generation of the heat roller cannot be realized.

Further, the center core is disposed not on the heat roller side but on the coil side. That is, the attachment position of the coil bobbin that holds the coil also affects the distance between each core body and the heat roller.
As described above, since the distance between each core body and the heat roller is affected by the position of the coil bobbin in addition to the relationship between the shaft member and the core body, measures to define the positions of the coil bobbin and the center core are required. In the above-mentioned conventional technology, no special consideration is given in this regard.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device capable of solving the above-described problems and realizing uniform heat generation of a heating member and an image forming apparatus equipped with the fixing device.

  A first invention for achieving the above object is a fixing device for fixing an image on a recording medium, which is disposed along an outer surface of a heating member and generates a magnetic field for induction heating the heating member. Coil, a coil holding part for holding the coil, and a width of the recording medium which is disposed on the opposite side of the heating member across the coil holding part, forms a magnetic path around the coil, and is conveyed A plurality of core bodies made of a magnetic material that is divided and arranged in a direction intersecting with the rotation axis, and that forms a magnetic path. On the other hand, the coil holding part includes a distance adjustment mechanism that abuts on the outer peripheral surface of the core body and holds the distance between the outer peripheral surface of the core body and the surface of the heating member substantially constant.

  This invention pays attention to the point which makes the outer peripheral surface of the divided | segmented core main body correspond. And according to 1st invention, the system (outer packaging IH) which heat-melts a toner image by induction-heating a heating member with the magnetic field generated with the coil is employ | adopted. If the rotating core is divided into individual core bodies, each core body can have a simple shape that facilitates processing accuracy and dimensional accuracy.

  Further, according to the present invention, the coil holding portion is provided with a distance adjusting mechanism, and abuts on the outer peripheral surface of the core body to hold the distance between the outer peripheral surface of the core body and the surface of the heating member substantially constant. Specifically, when the distance between the coil holding part and the heating member is ensured to be constant, if the distance between the coil holding part and the outer peripheral surface of the core main body is kept constant, the outer peripheral surface of the core main body This is because it is possible to ensure a constant distance from the surface of the heating member.

And according to this distance adjustment mechanism, the outer peripheral surfaces of the divided core bodies can be easily aligned, heat generation unevenness in the axial direction can be prevented, and uniform heating of the heating member can be realized. As a result, the manufacturing cost is reduced, and the warm-up time is reduced and the energy is saved.
According to a second aspect of the present invention, in the configuration of the first aspect, the distance adjusting mechanism is a contact portion that is integrally formed with the coil holding portion and abuts against all the outer peripheral surfaces of the core bodies.

According to the second invention, in addition to the action of the first invention, if the contact part is provided in the coil holding part, the core abuts on all the outer peripheral surfaces of the core body divided into a plurality of parts. The outer peripheral surfaces of the main bodies are flush with each other, and the distance between the outer peripheral surface of the core main body and the surface of the heating member can be reliably maintained.
According to a third invention, in the configuration of the first invention, the distance adjusting mechanism is provided in the coil holding portion, and rotates while contacting both the surface of the coil holding portion and all the outer peripheral surfaces of the core bodies. It is a positioning rotator which performs.

According to the third invention, in addition to the operation of the first invention, if the positioning rotating body is provided in the coil holding portion, each of the core main bodies divided into a plurality is brought into contact with the outer peripheral surface. The outer peripheral surfaces of the core main bodies are flush with each other, and the distance between the outer peripheral surface of the core main body and the surface of the heating member can be reliably maintained.
Further, since the friction between the core body and the distance adjusting mechanism can be reduced, it is possible to prevent an increase in torque generated during the rotation of the core body, and wear and noise of the core body and the distance adjusting mechanism due to the friction.

According to a fourth aspect of the present invention, in the configuration of the first aspect, the distance adjusting mechanism is rotatably supported by the bearing of the coil holding portion, or the bearing of the coil holding portion and the shaft rotatably supported by the bearing. It is a positioning rotator that is provided through the core body and rotates while being in contact with all the outer peripheral surfaces of the core bodies.
According to the fourth invention, in addition to the operation of the first invention, if the positioning rotating body is provided in the coil holding portion, it comes into contact with all the outer peripheral surfaces of the core body divided into a plurality of parts. The outer peripheral surfaces of the core main bodies are flush with each other, and the distance between the outer peripheral surface of the core main body and the surface of the heating member can be reliably maintained. Further, since the friction between the core body and the distance adjusting mechanism can be reduced, it is possible to prevent an increase in torque generated during the rotation of the core body, and wear and noise of the core body and the distance adjusting mechanism due to the friction.

Furthermore, when the positioning rotating body is provided via a bearing or a bearing and a shaft, the friction between the distance adjusting mechanism and the coil holding part can be reduced. In particular, it can be prevented.
According to a fifth invention, in the configuration of the fourth invention, the positioning rotator is provided on the outer peripheral surface of the shaft, and is divided and arranged in a direction intersecting the axis.

According to the fifth aspect of the invention, in addition to the effects of the fourth aspect of the invention, if the rotating positioning rotating bodies are also divided and configured individually, each positioning rotating body is easy to obtain machining accuracy and dimensional accuracy. It only takes shape.
According to a sixth invention, in the configurations of the third to fifth inventions, the coil holding portion is provided with a concave groove capable of receiving the positioning rotating body.

According to the sixth invention, in addition to the actions of the third to fifth inventions, if the coil holding part has a concave groove, the positioning rotating body can be prevented from moving with respect to the coil holding part, and divided into a plurality of parts. It is possible to reliably contact all the outer peripheral surfaces of the core body.
According to a seventh aspect, in the configurations of the second to sixth aspects, the contact portion or the positioning rotator is in contact with the outer peripheral surface of the core body at a plurality of points as viewed in the circumferential direction of the core portion. Features.

According to the seventh invention, in addition to the operations of the second to sixth inventions, if the contact portion or the positioning rotating body abuts the core body at a plurality of points, the outer peripheral surface of the core body and the surface of the heating member The distance can be maintained more reliably.
An eighth invention is characterized in that, in the configurations of the first to seventh inventions, the coil holding part has a positioning part for holding the distance from the heating member substantially constant.

According to the eighth invention, in addition to the effects of the first to seventh inventions, if a positioning part is further provided, the distance between the coil holding part and the heating member can be reliably maintained. In combination with the mechanism, the distance between the outer peripheral surface of the core body and the surface of the heating member is extremely constant.
According to a ninth aspect of the invention, in the configuration of the first to eighth aspects of the invention, the shaft member includes a shaft member that extends along the rotation axis of the core portion and that has a plurality of core bodies disposed on the outer peripheral surface thereof. The surface and the inner peripheral surface of each core body are loosely fitted so that the core body can move in the radial direction of the shaft member.

According to the ninth invention, in addition to the operations of the first to eighth inventions, when each core main body and the shaft member are separately configured and each core main body is disposed on the outer peripheral surface of the shaft member, If a gap is provided between the outer peripheral surface of the shaft member and the inner peripheral surface of each core body, the outer peripheral surfaces of the divided core bodies are more easily aligned.
A tenth invention is characterized in that, in the configuration of the ninth invention, the outer peripheral surface of the shaft member and the inner peripheral surface of each core body are connected by fitting of irregularities.

According to the tenth invention, in addition to the action of the ninth invention, each core body can be easily rotated by connecting the shaft member and each core body by fitting the concaves and convexes. The rotation direction of the main body and the shaft member can be easily regulated, and the assemblability of the core portion is improved.
An eleventh invention is characterized in that, in the configurations of the first to tenth inventions, the core portion is disposed above the distance adjusting mechanism as viewed in the direction of the action of gravity.

According to the eleventh aspect of the invention, in addition to the actions of the first to tenth aspects, if the core portion is disposed above the distance adjusting mechanism as viewed in the direction of the action of gravity, the distance is adjusted by the weight of each core body. It is possible to easily contact the mechanism.
According to a twelfth aspect, in the configurations of the first to eleventh aspects, a pressing member that presses the outer peripheral surface of each core body toward the distance adjusting mechanism is arranged on the opposite side of the distance adjusting mechanism across the core portion. It is characterized by being.

According to the twelfth invention, in addition to the actions of the first to eleventh inventions, if the core portion is pressed toward the distance adjusting mechanism by the pressing member, the outer peripheral surface of each core body and the distance adjusting mechanism are A more uniform contact is possible.
In a thirteenth aspect based on the twelfth aspect, the pressing member has a shaft extending in the axial direction, and an elastic layer formed on the surface thereof and in contact with the outer peripheral surface of each core body. It can be driven and rotated.

According to the thirteenth invention, in addition to the action of the twelfth invention, when the pressing member is further provided, the pressing member is in contact with the outer peripheral surface of each core body. Thus, the core portion can be driven and rotated. Thus, even if the pressing member is used, the drive source is only required at one place, and the structure of the apparatus is not complicated.
A fourteenth aspect of the present invention is the configuration of the first to thirteenth aspects of the present invention, comprising a shielding member that is provided on the outer peripheral surface of the core portion and can shield magnetism within a magnetic field generated by the coil, and the rotation direction of the core portion The step portion between the shielding member and the core portion viewed in FIG. 5 is characterized in that the downstream side in the rotational direction of the core portion of the shielding member and the core portion is formed higher than the upstream side in the rotational direction.

  According to the fourteenth invention, in addition to the effects of the first to thirteenth inventions, when viewed in the rotational direction of the core portion, for example, the distance adjusting mechanism that has been in contact with the outer peripheral surface of the core body is a shielding member. After that, the distance adjusting mechanism that has been in contact with the shielding member comes into contact with the outer peripheral surface of the core body. In other words, there is a step at a position where it abuts against a different member, and there is a concern that this step portion will scrape the distance adjustment mechanism, but the distance adjustment mechanism first contacts the higher one of the shielding member and the core part. There is no such concern because it comes into contact with the lower one.

According to a fifteenth aspect of the present invention, in the configurations of the second to fourteenth aspects, the contact portion or the positioning rotator is composed of a member made of a fluororesin having a good slip property, or the contact portion or the positioning rotator has a slip property. It is characterized by being coated with a good fluororesin.
According to the fifteenth invention, in addition to the effects of the second to fourteenth inventions, the friction can be reduced if the contact portion or the positioning rotating body is configured to be slippery. The distance to the surface can be kept constant over a long period of time.

A sixteenth aspect of the invention is an image forming apparatus in which first to fifteenth fixing devices are mounted and a toner image formed by an image forming unit is fixed to a recording medium using the fixing devices.
According to the sixteenth aspect, in addition to the effects of the first to fifteenth aspects, the heat generation performance of the heating member is ensured and a good toner image is formed. As a result, the reliability of the image forming apparatus is improved. .

  According to the present invention, the distance adjusting mechanism of the coil holding portion is in contact with the outer peripheral surface of each core main body, the outer peripheral surface of each core main body can be matched, and the fixing device that realizes uniform heat generation of the heating member and An image forming apparatus equipped with this can be provided.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. FIG. 3 is a longitudinal sectional view showing a structural example (first embodiment) of the fixing unit. It is a side view which shows the structure of a center core periphery in detail. It is the top view and sectional drawing of a center core. It is a figure which shows the operation example accompanying rotation of a center core. It is a figure which shows the structural example of a center core and a distance adjustment mechanism. It is a front view of a center core and a distance adjustment mechanism. FIG. 6 is a longitudinal sectional view showing a structural example (second embodiment) of a fixing unit. (A) is a side view showing the configuration around the center core in detail, and (B) is a diagram showing a structural example of the center core and the distance adjusting mechanism. It is a front view of a center core and a distance adjustment mechanism. It is a figure which shows the structural example (3rd Example) of a center core and a distance adjustment mechanism. It is a front view of a center core and a distance adjustment mechanism. It is a figure which shows the structural example (4th Example) of a center core and a distance adjustment mechanism. It is a front view of a center core and a distance adjustment mechanism.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 1 according to an embodiment. The image forming apparatus 1 includes, for example, a printer, a copier, and a facsimile apparatus that perform printing by transferring a toner image onto the surface of a sheet as an example of a recording medium based on image information input from the outside, and a composite having these functions. It can take the form of a machine or the like. In the following embodiments, the recording medium is not limited to a sheet, and can be implemented even if the recording medium is other than a sheet (such as an OHP sheet).

An image forming apparatus 1 shown in FIG. 1 is, for example, a tandem color printer. The image forming apparatus 1 includes a square box-shaped apparatus main body 2 that forms (prints) a color image on a sheet therein, and discharges the sheet on which the color image is printed on the upper surface of the apparatus main body 2. The discharge tray 3 is provided.
In the lower part of the apparatus main body 2, a paper feed cassette 5 for storing paper is disposed. In addition, a stack tray 6 is provided in the central portion of the apparatus main body 2 for supplying paper of a type not stored in the paper feed cassette 5 to the apparatus main body 2. An image forming unit 7 is provided on the upper part of the apparatus main body 2, and the image forming unit 7 transmits image data such as characters and patterns transmitted from a host device such as a PC connected to the image forming apparatus 1. The image is formed on the paper based on the above.

  As shown in FIG. 1, a first transport path 9 for transporting a sheet fed from the sheet feeding cassette 5 to a secondary transfer unit 23 described later is disposed on the left side of the apparatus body 2. From the right part to the left part, a second transport path 10 for transporting the sheet fed from the stack tray 6 to the secondary transfer unit 23 is provided. Further, a fixing unit (fixing device) 14 that performs a fixing process on a sheet on which an image has been transferred by the secondary transfer unit 23, and a sheet on which the fixing process has been performed are disposed on an upper left portion in the apparatus main body 2. A third conveyance path 11 that conveys the toner to the third conveyance path 11 is disposed.

  The paper feed cassette 5 can be replenished by pulling it out of the apparatus main body 2 (for example, the front side in FIG. 1). The paper feed cassette 5 includes a storage unit 16 in which at least two types of paper having different sizes in the paper feed direction can be selectively stored. Note that the paper stored in the storage unit 16 is fed out to the first conveyance path 9 side by sheet by the paper feed roller 17 and the separating roller pair 18.

The stack tray 6 can be opened and closed on the outer surface of the apparatus main body 2, and sheets are placed one by one on the manual feed portion 19 or a plurality of sheets are stacked. Note that the sheets placed on the manual feed unit 19 are fed out one by one to the second conveyance path 10 side by the pick-up roller 20 and the separating roller pair 21.
The first conveyance path 9 and the second conveyance path 10 are joined before the registration roller pair 22, and the paper that has reached the registration roller pair 22 waits here for skew adjustment and timing adjustment. Thereafter, the image is sent to the secondary transfer unit 23.

  The full color toner image on the intermediate transfer belt 40 is secondarily transferred to the sheet by the secondary transfer unit 23 on the sent sheet. Thereafter, the sheet on which the toner image is fixed by the fixing unit 14 is reversed in the fourth conveyance path 12 as necessary, and a full-color toner image is also formed on the surface opposite to the first by the secondary transfer unit 23. Secondary transferred. Then, after the toner image on the opposite surface is fixed by the fixing unit 14, it passes through the third conveyance path 11 and is discharged to the discharge tray 3 by the discharge roller pair 24.

The image forming unit 7 includes four image forming units 26 to 29 that form black (B), yellow (Y), cyan (C), and magenta (M) toner images. An intermediate transfer unit 30 is provided which holds the toner images of the respective colors formed in 29 in a superimposed manner.
Each of the image forming units 26 to 29 is on the downstream side in the rotation direction of the photosensitive drum 32, the charging unit 33 disposed to face the circumferential surface of the photosensitive drum 32, and the photosensitive drum 32 of the charging unit 33. A laser scanning unit 34 for irradiating a laser beam to a specific position on the peripheral surface of the photosensitive drum 32, and a downstream side in the rotational direction of the photosensitive drum 32 at the laser beam irradiation position from the laser scanning unit 34. A developing unit 35 disposed opposite to the circumferential surface of the photosensitive drum 32; and a cleaning unit disposed downstream of the developing unit 35 in the rotation direction of the photosensitive drum 32 and opposed to the circumferential surface of the photosensitive drum 32. 36.

  The photosensitive drums 32 of the image forming units 26 to 29 are rotated counterclockwise in the drawing by a drive motor (not shown). Further, in the developing sections 35 of the image forming units 26 to 29, two-component developers each containing black toner, yellow toner, cyan toner, and magenta toner are stored in each developing device 51, respectively.

  The intermediate transfer unit 30 straddles the rear roller 38 disposed near the image forming unit 26, the front roller 39 disposed near the image forming unit 29, and the rear roller 38 and the front roller 39. The intermediate transfer belt 40 can be press-contacted with the intermediate transfer belt 40 at a position downstream of the photosensitive drum 32 in the rotation direction of the developing unit 35 of the photosensitive drum 32 of each of the image forming units 26 to 29. Four primary transfer rollers 41 are provided.

In the intermediate transfer unit 30, the toner images of the respective colors are superimposed and transferred onto the intermediate transfer belt 40 at the positions of the primary transfer rollers 41 of the image forming units 26 to 29, and finally a full-color toner image. It becomes.
The first transport path 9 and the second transport path 10 are for transporting the paper fed from the paper feed cassette 5 and the stack tray 6 to the secondary transfer unit 23 side, and in the apparatus main body 2, a predetermined transport path is formed. A plurality of conveying roller pairs 43 disposed at the position and a registration roller pair 22 disposed in front of the secondary transfer unit 23 for timing the image forming operation and the sheet conveying operation in the image forming unit 7. And.

  The fixing unit 14 performs processing for fixing the unfixed toner image on the paper by heating and pressurizing the paper on which the toner image has been transferred by the image forming unit 7. The fixing unit 14 includes a roller pair including, for example, a pressure roller 44 and a fixing roller 45, and the pressure roller 44 includes, for example, a metal core and an elastic surface layer (for example, silicon rubber) and a release layer (for example). For example, the fixing roller 45 has a metal core and an elastic surface layer (for example, silicon sponge). Further, a heat roller (heating member) 46 is provided adjacent to the fixing roller 45, and a heating belt (heating member) 48 is wound around the cylindrical heat roller 46 and the fixing roller 45. The detailed structure of the fixing unit 14 will be described later.

  When viewed in the sheet conveyance direction, conveyance paths 47 and 47 are respectively provided on the upstream side and the downstream side of the fixing unit 14, and the sheet conveyed through the secondary transfer unit 23 is upstream of the conveyance path 47. Through the pressure roller 44 and the fixing roller 45. The paper that has passed between the pressure roller 44 and the fixing roller 45 is guided to the third conveyance path 11 through the conveyance path 47 on the downstream side.

The third transport path 11 transports the paper on which the fixing process has been performed by the fixing unit 14 to the discharge tray 3. For this reason, the transport roller pair 49 is disposed at an appropriate position in the third transport path 11, and the discharge roller pair 24 is disposed at the outlet thereof.
[Details of fixing unit]
Next, details of the fixing unit 14 applied to the image forming apparatus 1 of the present embodiment will be described.

  FIG. 2 is a longitudinal sectional view showing a structural example of the fixing unit 14. In FIG. 2, the orientation is turned counterclockwise by about 90 ° from the state in which the image forming apparatus 1 is mounted. Accordingly, the sheet conveying direction from the bottom to the top as viewed in FIG. 1 is from right to left as viewed in FIG. In addition, when the apparatus main body 2 is larger (multifunction machine etc.), it may be mounted in the direction shown in FIG. As another layout, the fixing unit 14 may be arranged in the image forming apparatus 1 in a posture inclined left or right from the state shown in FIG.

  The fixing unit 14 of this embodiment includes the pressure roller 44, the fixing roller 45, the heat roller 46, and the heating belt 48 as described above. The pressure roller 44 is formed, for example, by forming a Si rubber layer having a thickness of about 2 to 5 mm on a metal (for example, SUS) cored bar, and further laminating a release layer (for example, PFA) on the surface layer to have a diameter of about 50 mm. It's a roller. The fixing roller 45 is a roller having a diameter of about 45 mm by laminating a silicon rubber sponge layer having a thickness of about 5 to 10 mm on a metal core (for example, SUS).

The heat roller 46 has a core metal made of a magnetic metal (eg, Fe) having a diameter of about 30 mm and a thickness of about 0.2 to 1.0 mm, and a release layer (eg, PFA) is formed on the surface thereof. Rotates with rotation of a shaft (not shown).
Further, the heating belt 48 is a ferromagnetic material (for example, Ni electroformed base material) having a base material thickness of, for example, 35 μm (1 μm = 1 × 10 ⁻⁶ m), and a thin film having a thickness of about 200 to 500 μm on its surface An elastic layer (for example, silicon rubber) is formed, and a release layer (for example, PFA) is formed on the outer surface, and the heat generation temperature is adjusted to a range of 150 to 200 ° C., for example. In the case where the heating belt 48 does not have a heat generation function, a resin belt such as PI may be used.

As described above, since the fixing roller 45 has a silicon sponge elastic layer as a surface layer, a flat nip is formed between the heating belt 48 and the pressure roller 44. A halogen heater 44 a is provided inside the pressure roller 44.
In addition, the fixing unit 14 includes an IH coil unit 50 outside the heat roller 46 and the heating belt 48 (not shown in FIG. 1). The IH coil unit 50 includes an induction heating coil 52, a pair of arch cores 54, a pair of side cores 56, and a center core (core part) 58.

〔coil〕
In the example of FIG. 2, the induction heating coil (coil) 52 is placed on a virtual arc surface along the arc-shaped outer surface of the heating belt 48 because induction heating is performed in the arc-shaped portions of the heat roller 46 and the heating belt 48. Has been placed. Actually, a coil bobbin (coil holding portion) 53 is disposed outside the heat roller 46 and the heating belt 48, and the induction heating coil 52 is disposed in a winding shape on the bobbin 53. The coil bobbin 53 is formed in a substantially semi-cylindrical shape along the outer surface of the heat roller 46, and is engaged with, for example, a rotating shaft or a unit cover of the heat roller 46 via a bobbin positioning unit (positioning unit) (not shown). The distance between 53 and the heating belt 48 is kept constant. The material of the bobbin 53 is preferably a heat resistant resin (for example, PPS, PET, LCP), and the coil 52 is fixed to the coil bobbin 53 using, for example, a silicon-based adhesive.

[Arch core, side core]
As shown in FIG. 2, the center core 58 is located at the center of the IH coil unit 50, and the arch core 54 and the side core 56 are arranged so as to form a pair on both sides thereof. Of these, the arch cores 54 on both sides are ferrite cores formed in a cross-sectional arch shape that is symmetrical to each other, and the overall length thereof is longer than the region where the induction heating coil 52 is disposed. The side cores 56 on both sides are ferrite cores formed in a block shape. The side cores 56 on both sides are connected to one end (lower end in FIG. 2) of each arch core 54, and these side cores 56 cover the outside of the region where the induction heating coil 52 is disposed.

  For example, the arch core 54 is arranged at a plurality of locations at intervals in the longitudinal direction of the heat roller 46 (FIG. 3). In the present embodiment, the width of the arch core 54 is about 10 mm. In addition, the higher the arrangement density of the arch cores 54, the better the magnetic field induction performance. However, even if the density is reduced to some extent, the performance does not decrease much, so that high cost performance can be obtained within a range where sufficient performance can be exhibited. It is preferable to set the arrangement density. Further, when adjusting the temperature distribution of the heating belt 48 in the axial direction, it is possible to cope with the problem by adjusting the arrangement density of the arch cores 54. In the present embodiment, for example, the arrangement density of the arch core 54 is about 1/2 to 1/3 as a whole, and the arrangement density at both ends in the longitudinal direction of the induction heating coil 52 is set higher than the vicinity of the center, The temperature drop in the end region in the longitudinal direction of the heat roller 46 is also improved.

  Further, one side core 56 has a length of about 30 to 60 mm, and a plurality of side cores 56 are continuously arranged in the longitudinal direction of the heat roller 46 without any interval. The total length of the range in which the side core 56 is disposed corresponds to the length of the region in which the induction heating coil 52 is disposed. By arranging a plurality of side cores 56 in this way, there is an effect of leveling the fluctuation width of the temperature distribution due to the arrangement of the arch core 54. The arrangement of the cores 54 and 56 is determined, for example, according to the magnetic flux density (magnetic field strength) distribution of the induction heating coil 52, and the arch core 54 has been removed by a certain distance. The side core 56 compensates for the effect of converging the magnetic flux at the location, and the magnetic flux density distribution (temperature distribution) in the longitudinal direction is leveled.

For example, a resin core holder (not shown) is provided outside the arch core 54 and the side core 56, and the arch core 54 and the side core 56 are supported by the core holder. The material of the core holder is also preferably a heat resistant resin (for example, PPS, PET, LCP).
In the example of FIG. 2, a thermistor and a thermostat 62 are installed inside the heat roller 46. The thermistor or the like 62 is disposed inside a portion of the heat roller 46 that generates a large amount of heat, particularly due to induction heating. More practically, a non-contact type sensor can be arranged below the coil unit 50 to detect the outer surface temperature of the heating belt 48.

[Core part]
The center core 58 shown in FIGS. 2 and 3 is, for example, a ferrite core having a cylindrical cross section (outer diameter is about 18 mm). In the center of the center core 58, a shaft member 59 of non-magnetic metal (SUS, etc.) or heat-resistant resin (PPS, PET, LCP, etc.) is inserted in the center in the axial direction. It has a length corresponding to a sheet passing width of 13 inches (about 340 mm).

(Shielding member)
Further, a shielding member 60 is attached to the center core 58 along its outer surface (FIG. 2). The shielding member 60 has a thin plate shape and is formed to be curved in an arc shape as a whole. For example, the shielding member 60 may be installed in a state where it is embedded in the thick portion of the center core 58 as shown in the figure, or may be installed in a state of being attached to the outer surface of the center core 58. The shielding member 60 can be attached to the center core 58 using, for example, a silicon-based adhesive.

  The shielding member 60 is preferably a non-magnetic and highly conductive member, and for example, oxygen-free copper is used. The shielding member 60 shields the magnetic flux from the induction heating coil 52 by generating a reverse magnetic flux by an induced current caused by the penetration of a magnetic flux perpendicular to the surface, and canceling the complex magnetic flux (perpendicular magnetic flux). Further, by using a highly conductive member, Joule heat generation due to an induced current can be suppressed, and the magnetic flux can be shielded efficiently. In order to improve the conductivity, for example, methods such as (1) selecting a material with as low a specific resistance as possible and (2) increasing the thickness of the member are effective. Specifically, the plate thickness of the shielding member 60 is preferably 0.5 mm or more, and in this embodiment, for example, a thickness of 1 mm is used.

  As shown in FIG. 2, when the shielding member 60 is at a position (shielding position) close to the surface of the heating belt 48, the magnetic resistance increases around the induction heating coil 52 and the magnetic field strength decreases. On the other hand, when the center core 58 rotates 180 ° (the direction is not particularly limited) from the state shown in FIG. 2 and the shielding member 60 moves to a position (retracted position) farthest from the heating belt 48, the periphery of the induction heating coil 52 As a result, the magnetic resistance decreases, a magnetic path is formed through the arch core 54 and the side core 56 on both sides centering on the center core 58, and the magnetic flux acts on the heating belt 48 and the heat roller 46.

[Details of Center Core]
FIG. 3 is a side view of the periphery of the center core 58. The center core 58 extends in the width direction of the sheet perpendicular to the sheet passing direction, and its total length is slightly larger than the maximum sheet passing width (for example, A3 length, A4 width).
In this embodiment, a pressure roller (pressing member) 90 is installed on the opposite side of the coil bobbin 53 with the center core 58 interposed therebetween (FIGS. 2 and 3). The pressure roller 90 has a shaft 92 extending in the longitudinal direction of the heat roller 46. The IH coil unit 50 is equipped with, for example, a stepping motor, and the shaft 92 is rotated by power from the motor. For this reason, a driven gear 66 is attached to one end portion of the shaft 92, and the output gear of the stepping motor is meshed with the driven gear 66. Further, since an elastic layer is formed on the surface of the pressure roller 90, the pressure roller 90 can strongly press the center core 58 toward the coil bobbin 53. Accordingly, when the stepping motor is driven, the shaft 92 is rotated by the power, and the press roller 90 can follow the center core 58 around the longitudinal axis.

  In the example shown in FIG. 4, three types of the first shielding member 60 a, the second shielding member 60 b, and the third shielding member 60 c are the axial direction (longitudinal direction) of the center core 58 as the shielding member (reference numeral 60 in FIG. 2). ) Are divided and arranged. These first to third shielding members 60a, 60b, and 60c are different in arrangement and length in the axial direction of the center core 58, and also in length in the circumferential direction of the center core 58 (width covering the center core 58). ing. Hereinafter, this point will be described. Note that the first to third shielding members 60a, 60b, and 60c are not provided separately as described above, but may be provided integrally.

FIG. 4 is a diagram showing the axial arrangement of the first to third shielding members 60a, 60b, 60c with respect to the center core 58, their respective lengths, and the width in the circumferential direction.
As shown in FIG. 4A, the three types of shielding members 60a, 60b, and 60c are provided symmetrically with respect to the center in the width direction of the paper in the axial direction of the center core 58, and of these, the first shielding member. 60a is arrange | positioned at the both ends of the center core 58, and the 2nd shielding member 60b and the 3rd shielding member 60c are arranged in order toward the center from there. At this time, the third shielding member 60c located on the innermost side (close to the center) is provided outside the paper passing area W1 corresponding to the minimum paper size. The second shielding member 60b is provided outside the sheet passing area W2 corresponding to the intermediate sheet size, and the first shielding member 60a is provided outside the sheet passing area W3 larger by one size. ing. In this arrangement, for example, the maximum paper size is 13 inches (340 mm), and the smaller paper sizes are A3 (297 mm), A4 vertical (210 mm), and A5 vertical (149 mm), for a total of 4 It can correspond to various paper sizes. The axial lengths WP1, WP2, and WP3 of the shielding members 60a, 60b, and 60c are set in accordance with the corresponding paper sizes.

  In this embodiment, the boundary positions of the shielding members 60a, 60b, and 60c actually bite in (approach) up to about 10 ± 5 mm with respect to the respective paper passing areas W1, W2, and W3. It is set. As described above, the reason why the shielding members 60a, 60b, and 60c are set to bite into the paper passing areas W1, W2, and W3 is that the temperature in the non-paper passing area is usually higher than the temperature in the paper passing area. Therefore, considering heat transfer from the non-sheet passing area, the temperature distribution in the vicinity of the boundary is balanced by allowing the shielding members 60a, 60b, and 60c to bite into each sheet passing area to the above extent. It can be made easier.

[Width of shielding member in circumferential direction]
FIGS. 4B and 4G: When the four types of paper sizes are supported as described above, the width of the first shielding member 60a viewed in the circumferential direction is set to 240 degrees at the center angle A1 of the center core 58. FIG. Yes.
4C and 4F: The width of the second shielding member 60b viewed in the circumferential direction is set to 160 degrees at the central angle A2.
4D and 4E: The width of the third shielding member 60c viewed in the circumferential direction is set to 80 degrees at the central angle A3.

FIG. 5 is a diagram illustrating an operation example associated with the rotation of the center core 58. In FIG. 5, illustration of the bobbin 53 and the pressure roller 90 is omitted for convenience of explanation. Moreover, although the 1st shielding member 60a is mentioned as an example, it is the same also about the other 2nd and 3rd shielding members 60b and 60c.
FIG. 5A shows an operation example when the first shielding members 60a at both ends are switched to the retracted positions as the center core 58 rotates. In this case, the magnetic field generated by the induction heating coil 52 passes through the heating belt 48 and the heat roller 46 through the side core 56, the arch core 54 and the center core 58. At this time, eddy currents are generated in the heating belt 48 and the heat roller 46, which are ferromagnetic materials, and Joule heat is generated by the specific resistance of each material, and the heat roller 46 and the heating belt 48 are heated.

  FIG. 5B: When the first shielding member 60a is switched to the shielding position, the first shielding member 60a is located on the magnetic path at the positions of both ends of the center core 58 (outside of the sheet passing area), so that the magnetic flux there. Transmission is partially suppressed. As a result, the amount of heat generated is suppressed in the non-sheet passing area, and excessive heating of the heating belt 48 and the heat roller 46 can be prevented.

Here, the center core 58 of the present embodiment is configured by being divided in the width direction of the sheet to be conveyed, that is, in the direction intersecting the rotation axis of the center core 58 described above.
Specifically, the center core 58 includes, for example, a total of seven core main bodies 58a to 58d arranged on the shaft member 59, and as shown in FIG. It is provided symmetrically in the direction.

More specifically, the shaft member 59 is formed of a solid round bar extending along the rotational axis direction, and has a convex portion 71 protruding outward in the radial direction on its outer peripheral surface (see FIG. 7) Four types of core bodies 58 a to 58 d and caps (not shown) are arranged on the outer peripheral surface along the rotation axis, and both ends thereof are rotatably supported by the coil bobbin 53.
First, a total of two core main bodies 58a of this embodiment are arranged on one shaft member 59, and are arranged at positions corresponding to large-size sheets, that is, corresponding to the above-described first shielding member 60a. .

  Next, a total of two core main bodies 58b of the present embodiment are arranged on one shaft member 59, and the position corresponding to the paper having a size smaller than the position of the core main body 58a described above, that is, the second shielding member described above. It is arranged corresponding to 60b. Subsequently, a total of two core main bodies 58c of the present embodiment are arranged on one shaft member 59, and the position corresponding to the paper having a size smaller than the position of the core main body 58b described above, that is, the third shielding member described above. In addition, the core main body 58d of the present embodiment is disposed in total on one shaft member 59, and corresponds to a paper having a size smaller than the position of the core main body 58c described above. They are arranged at positions where the shielding member 60 is not provided.

Further, the inner peripheral surfaces of the core bodies 58a to 58d have a concave portion 70 that engages with the convex portion 71 (FIG. 7), and a predetermined gap is provided by fitting the concave portion 70 and the convex portion 71 together. The core bodies 58 a to 58 d are connected to each other and can move in the radial direction of the center core 58 with respect to the shaft member 59.
Thereby, as shown in FIG. 4, the core main body 58a having the first shielding member 60a is disposed on both end sides of the outer peripheral surface of the shaft 59, and the second shielding member 60b is arranged in order from there toward the center. A core main body 58b having the shielding member 60 having the third shielding member 60c and a core main body 58d having no shielding member 60 are arranged.

On the other hand, in this embodiment, a distance adjusting mechanism is disposed between the center core 58 and the coil bobbin 53.
Specifically, as shown in FIG. 7, the coil bobbin 53 has a bobbin main body 53 a that faces the center core 58, and the bobbin main body 53 a has a piece-like contact portion (distance adjustment) that contacts the outer peripheral surface of the center core 58. Mechanism) 80, 80 are integrally formed.

  The contact portions 80, 80 extend along the rotation axis direction of the shaft member 59 and have a length corresponding to the maximum sheet passing width of 13 inches (about 340 mm) (FIG. 6). The contact portions 80, 80 are in contact with all outer peripheral surfaces of the core bodies 58 a to 58 d, and are provided at symmetrical positions with respect to the shaft member 59 when viewed in the circumferential direction of the center core 58. Are supported at two points (FIGS. 2 and 7). Each of the contact portions 80 is provided with a member made of a fluororesin having a good slip property or a coating made of a fluoro resin having a good slip property.

Thus, since the contact portion 80 fixed to the coil bobbin 53 is in contact with the outer peripheral surface of the rotating center core 58, there is a concern that the contact portion 80 or the center core 58 is damaged. However, in this embodiment, a stepped portion between the center core 58 and the shielding member 60 that abuts against the contact portion 80 is devised.
Specifically, as shown in FIG. 7A, when viewed in the counterclockwise direction of rotation of the center core 58, a stepped portion that moves from the center core 58 to the shielding member 60 (located on the right side of the figure). , The shielding member 60 is brought close to the rotation axis of the shaft member 59, and the center core 58 located at the destination of the rotation is formed higher than the shielding member 60.

  Further, in terms of a stepped portion (located on the left side of the figure) that moves from the shielding member 60 to the center core 58, the shielding member 60 is disposed away from the rotation axis of the shaft member 59 and is rotated toward the destination. The positioned shielding member 60 is formed higher than the center core 58, and the tip of the contact portion 80 is configured not to be scraped off at each step portion.

In FIG. 7A, the tip of the contact portion 80 is protected by the arrangement of the shielding member 60 with respect to the center core 58, but the edge of the center core 58 or the shielding member 60 may be given a gradient.
That is, a stepped portion 60r is provided in the shielding member 60 at the stepped portion moving from the center core 58 located on the right side of FIG. 7B to the shielding member 60, and the shielding member 60 located on the left side of FIG. The stepped portion 58r is provided in the center core 58 at the stepped portion to be moved, and the shielding member 60 or the center core 58 positioned at the rotating destination is moved from the center core 58 or the shielding member 60 positioned at the rotating destination. Is also forming high.

By the way, the distance adjusting mechanism described above may rotate.
Specifically, in each of the embodiments shown in FIGS. 8 to 14, the coil bobbin 53 is also provided with a distance adjusting mechanism that contacts the outer peripheral surface of the center core 58, and the same configuration as that in the first embodiment is the same. If a reference numeral is given and description thereof is omitted, first, a positioning roller (positioning rotating body) 84 is arranged in the bobbin main body 53a of the second embodiment of FIGS. ing.

The positioning roller 84 of the second embodiment is received in the concave groove 53r (FIG. 10), and abuts against the outer peripheral surface of the concave groove 53r and the center core 58 and follows the clockwise direction in FIGS. The positioning roller 84 is also coated with a member made of a fluororesin having a good slip property or a coating made of a fluororesin having a good slip property.
Next, in the bobbin main body 53a of the third embodiment shown in FIGS. 11 and 12, bearings 86 and 86 are installed at both ends in the longitudinal direction, respectively, and the positioning roller 84 that contacts the outer peripheral surface of the center core 58 is rotatable. It supports (FIG. 11).

  12A shows the positional relationship between the center core 58 and the positioning roller 84 in a state where the bearing 86 is installed on the bobbin body 53a, and FIG. 12B shows the positioning with the center core 58 in which the bearing 86 is omitted. The positional relationship with the roller 84 is shown. Thereby, it can be seen that the positioning rollers 84 and 84 support the outer peripheral surface of the center core 58 at two points.

Further, in the bobbin main body 53a of the fourth embodiment of FIGS. 13 and 14, bearings 86 and 86 are respectively installed at both end portions in the longitudinal direction as in the third embodiment (FIG. 13). The positioning roller 84 is provided on the outer peripheral surface of the shaft 88, and the shaft 88 is rotatably supported by the bearing 86.
In this way, unlike the third embodiment, both ends of the positioning roller 84 are not supported by the bearing 86, so the positioning roller 84 of the fourth embodiment can be divided in the same manner as the core bodies 58a to 58d. is there.

  As described above, according to the present embodiment, a method (outer packaging IH) is employed in which the heat roller 46 and the heating belt 48 are induction-heated by the magnetic field generated by the coil 52 to heat and melt the toner image. If the rotating center core 58 is divided into individual core main bodies 58a to 58d, each core main body 58a to 58d may have a simple shape that can easily provide processing accuracy and dimensional accuracy.

  The coil bobbin 53 is provided with a distance adjusting mechanism, and abuts on the outer peripheral surfaces of the core main bodies 58a to 58d to keep the distance between the outer peripheral surfaces of the core main bodies 58a to 58d and the surface of the heating belt 48 substantially constant. Specifically, when the distance between the coil bobbin 53 and the heating belt 48 is ensured to be constant, the core body 58a can be subsequently maintained by keeping the distance between the coil bobbin 53 and the outer peripheral surfaces of the core bodies 58a to 58d constant. This is because a constant distance between the outer peripheral surface of ˜58d and the surface of the heating belt 48 can be secured.

  According to the distance adjusting mechanism, the outer peripheral surfaces of the divided core bodies 58a to 58d can be easily aligned, and uneven heat generation in the axial direction can be prevented, and the heat roller 46 and the heating belt 48 can be uniformly heated. It becomes feasible. As a result, the manufacturing cost is reduced, and the warm-up time is reduced and the energy is saved.

Further, if the contact portion 80 or the positioning roller 84 is provided on the coil bobbin 53, the outer peripheral surface of each of the core main bodies 58a to 58d is a surface because it abuts on all the outer peripheral surfaces of the core main bodies 58a to 58d divided into a plurality of parts. The distance between the outer peripheral surfaces of the core bodies 58a to 58d and the surface of the heating belt 48 can be reliably maintained.
Further, in the case of the positioning roller 84, the friction between the core main bodies 58a to 58d and the positioning roller 84 can be reduced. Therefore, an increase in torque generated when the core main bodies 58a to 58d rotate, and the core main body 58a due to this friction. ˜58d and positioning roller 84 can be prevented from being worn or unusual.

Furthermore, when the positioning roller 84 is provided only by the bearing 86 or via the bearing 86 and the shaft 88, the friction between the positioning roller 84 and the bobbin main body 53a can be reduced.・ Especially prevent abnormal noise.
For example, when a toner image is fixed on a wide sheet such as an A3 size, the positioning rollers 84 can be divided into individual parts, and each positioning roller 84 can easily obtain processing accuracy and dimensional accuracy. It only takes shape.

  Further, if the bobbin main body 53a is provided with the concave groove 53r, the contact portion 80 can be prevented from moving with respect to the bobbin main body 53a and can be surely brought into contact with all the outer peripheral surfaces of the core main bodies 58a to 58d divided into a plurality of parts. become. Further, as compared with the case where the positioning roller 84 is disposed on the flush bobbin body 53a, the center core 58 can be made closer to the heating belt 48 while avoiding contact between the bobbin body 53a and the positioning roller 84.

Furthermore, if the contact portion 80 or the positioning roller 84 is brought into contact with the core main bodies 58a to 58d at, for example, two points in a cross-sectional view, the distance between the outer peripheral surface of the core main bodies 58a to 58d and the surface of the heating belt 48 is more reliably maintained. it can.
If the bobbin positioning portion with respect to the shaft of the heat roller 46 and the like is used and the distance between the coil bobbin 53 and the heating belt 48 is maintained reliably, the core main body 58a to the core body 58a.about. The distance between the outer peripheral surface of 58d and the surface of the heating belt 48 is extremely constant.

Furthermore, when each core main body 58a-58d and the shaft member 59 are comprised separately and each core main body 58a-58d is arrange | positioned on the outer peripheral surface of the shaft member 59, the outer peripheral surface of this shaft member 59 and each core main body If a gap is provided between the inner peripheral surfaces 58a to 58d, the outer peripheral surfaces of the divided core bodies 58a to 58d are more easily aligned.
Furthermore, if it connects by fitting with the convex part 71 of the shaft member 59, and the recessed part 70 of each core main body 58a-58d, each core main body 58a-58d can be rotated easily, and each core main body 58a-58d. And the rotation direction of the shaft member 59 can be easily regulated, and the assemblability of the center core 58 is improved.

2 and 8, when the center core 58 is disposed above the contact portion 80 or the positioning roller 84 when viewed from the direction of gravity as in the case of transporting the sheet from the right to the left as shown in FIG. The core main bodies 58a to 58d can easily come into contact with the contact portion 80 or the positioning roller 84 by their own weights.
Furthermore, if the center core 58 is pressed toward the contact portion 80 or the positioning roller 84 by the pressure roller 90, the outer peripheral surfaces of the core bodies 58a to 58d and the contact portion 80 or the positioning roller 84 can be contacted more uniformly.

  Furthermore, when the pressure roller 90 is provided, since the pressure roller 90 is in contact with the outer peripheral surfaces of the core bodies 58a to 58d, the center core 58 can be driven to rotate with the pressure roller 90 as a driving side. . Thus, even if the pressure roller 90 is used, only one drive source is required, and the structure of the fixing unit 14 is not complicated.

  Further, when viewed in the rotational direction of the center core 58, for example, the contact portion 80 or the positioning roller 84 that has been in contact with the outer peripheral surfaces of the core bodies 58a to 58d is in contact with the shielding member 60, and then is in contact with the shielding member 60. The contact portion 80 or the positioning roller 84 comes into contact with the outer peripheral surfaces of the core bodies 58a to 58d. In other words, there is a step at a location where it abuts against a different member, and there is a concern that this step portion may scrape the contact portion 80 or the positioning roller 84. Since the center core 58 abuts on the higher side and then on the lower side, there is no concern.

Furthermore, since the friction can be reduced if the contact portion 80 or the positioning roller 84 is configured to be slippery, the distance between the coil bobbin 53 and the outer peripheral surfaces of the core bodies 58a to 58d can be kept constant over a long period of time.
Furthermore, as a result of securing a heat generation performance of the heat roller 46 and the heating belt 48 and forming a good toner image, the reliability of the image forming apparatus 1 is improved.
The present invention can be implemented with various modifications without being limited to the above-described embodiments.

For example, although the heat roller 46 is used in the above embodiment, the heating roller 48 may be wound around the fixing roller 45 and the heat roller 46 may be omitted. This also applies to the fixing roller.
In this embodiment, an example in which the image forming apparatus is embodied in a printer is shown. However, the image forming apparatus of the present invention can naturally be applied to a multifunction machine, a copier, a facsimile machine, and the like.

  In any of these cases, the heating member can achieve uniform heat generation as described above.

1 Printer (image forming device)
7 Image forming unit 14 Fixing unit (fixing device)
46 Heat roller (heating member)
48 Heating belt (heating member)
50 IH coil unit 52 Induction heating coil (coil)
53 Coil bobbin (coil holder)
53r concave groove 58 center core (core part)
58a to 58d Core body 58r Paragraphed portion 59 Shaft member 60 Shield member 60r Paragraphed portion 70 Concave portion 71 Convex portion 80 Contact portion (distance adjustment mechanism)
84 Positioning rollers (positioning rotating body, distance adjustment mechanism)
86 Bearing (Distance adjustment mechanism)
88 axes (distance adjustment mechanism)
90 Pressure roller (pressing member)
92 shaft

Claims (16)

A fixing device for fixing an image on a recording medium,
A coil that is disposed along the outer surface of the heating member and generates a magnetic field for induction heating the heating member, and a coil holding unit that holds the coil;
A core portion that is disposed on the opposite side of the heating member across the coil holding portion, forms a magnetic path around the coil, and rotates around an axis extending in the width direction of the recording medium being conveyed. And
The core portion is divided and arranged in a direction intersecting the rotation axis thereof, and includes a plurality of core bodies made of a magnetic material to form the magnetic path,
The fixing device includes a distance adjusting mechanism that abuts on the outer peripheral surface of the core main body and holds the distance between the outer peripheral surface of the core main body and the surface of the heating member substantially constant. The fixing device according to claim 1,
The fixing device according to claim 1, wherein the distance adjusting mechanism is a contact portion that is integrally formed with the coil holding portion and contacts all outer peripheral surfaces of the core bodies. The fixing device according to claim 1,
The distance adjusting mechanism is a positioning rotating body that is provided in the coil holding portion and rotates while being in contact with both the surface of the coil holding portion and all the outer peripheral surfaces of the core bodies. Fixing device. The fixing device according to claim 1,
The distance adjusting mechanism is rotatably supported by a bearing of the coil holding part, or is provided via a bearing of the coil holding part and a shaft rotatably supported by the bearing, A fixing device characterized in that the fixing device is a positioning rotating body that rotates while being in contact with all outer peripheral surfaces. The fixing device according to claim 4,
The positioning rotating body is provided on an outer peripheral surface of the shaft, and is divided and arranged in a direction intersecting the axis. The fixing device according to any one of claims 3 to 5,
The fixing device according to claim 1, wherein the coil holding portion is provided with a concave groove capable of receiving the positioning rotating body. The fixing device according to any one of claims 2 to 6,
The fixing device, wherein the contact portion or the positioning rotator is in contact with the outer peripheral surface of the core body at a plurality of points when viewed in the circumferential direction of the core portion. The fixing device according to any one of claims 1 to 7,
The fixing device according to claim 1, wherein the coil holding portion includes a positioning portion that holds a distance from the heating member substantially constant. The fixing device according to any one of claims 1 to 8,
It includes a shaft member that extends along the rotation axis of the core portion and arranges the plurality of core bodies on the outer peripheral surface thereof.
The fixing device according to claim 1, wherein an outer peripheral surface of the shaft member and an inner peripheral surface of each core body are loosely fitted so that the core body is movable in a radial direction of the shaft member. The fixing device according to claim 9, wherein
The fixing device, wherein an outer peripheral surface of the shaft member and an inner peripheral surface of each core body are connected by fitting of irregularities. The fixing device according to any one of claims 1 to 10,
The fixing device according to claim 1, wherein the core portion is disposed above the distance adjusting mechanism when viewed in the direction of gravity. The fixing device according to any one of claims 1 to 11,
A fixing device, wherein a pressing member that presses an outer peripheral surface of each core body toward the distance adjusting mechanism is disposed on the opposite side of the distance adjusting mechanism with the core portion interposed therebetween. The fixing device according to claim 12, wherein
The pressing member includes a shaft extending in the axial direction, and an elastic layer formed on a surface thereof and in contact with an outer peripheral surface of each core body, and the core portion can be driven and rotated. Fixing device. The fixing device according to any one of claims 1 to 13,
Provided on the outer peripheral surface of the core part, comprising a shielding member capable of shielding magnetism within the magnetic field generated by the coil,
The step portion between the shielding member and the core portion viewed in the rotational direction of the core portion is formed such that the downstream side in the rotational direction of the core portion is higher than the upstream side in the rotational direction of the shielding member and the core portion. A fixing device. The fixing device according to any one of claims 2 to 14,
The contact part or the positioning rotator is made of a member made of a fluororesin having a good sliding property, or the coating part made of a fluorine resin having a good slidability is applied to the contacting part or the positioning rotator. A fixing device characterized by the above.   16. An image forming apparatus comprising: the fixing device according to claim 1; and a toner image formed by an image forming unit using the fixing device, which is fixed on the recording medium.

Images