JP2011170121A - Fixing apparatus and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus that secures adhesion between a belt and a guide member without changing a layout, and an image forming apparatus equipped with the fixing apparatus. <P>SOLUTION: The fixing apparatus includes a belt (45) for fixing a toner image to a recording medium; a guide member (80) having a heating region (82) generating heat by electromagnetic induction, and a heat conductive layer (86) provided in a position substantially facing the belt across the heating region to keep uniform the temperature of the heating region, to guide the travel of the belt in contact with the inner surface of the belt; an electromagnetic induction heating unit (50) arranged along the outer surface of the belt to induction-heat the heating region; and a sliding member (70) provided inside the belt to form a nip between the sliding member and a pressing rotation body (44) in contact with the outer surface of the belt. The electromagnetic induction heating unit and the heating region are arranged in a position substantially facing the pressing rotation body across the sliding member, while the heat conductive layer is extended toward an upstream of the nip when viewed in the conveying direction of the recording medium rather than the position substantially facing the pressing rotation body across the sliding member. <P>COPYRIGHT: (C)2011,JPO&amp;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 belt and a pressure roller, and an image forming apparatus equipped with the fixing device. is there.

  In recent years, in this type of image forming apparatus, a belt system capable of setting a small heat capacity has attracted attention because of demands for shortening the warm-up time in the fixing device and saving energy. 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.

  Specifically, in this electromagnetic induction heating method, a structure (so-called envelope IH) in which a coil for generating a magnetic field for electromagnetic induction is arranged outside the belt has been proposed (for example, see Patent Documents 1 and 2). Specifically, each of these documents discloses a flexible sliding belt type, and a sliding member is installed inside the belt, and a nip is formed between the thin belt and the pressure roller. To do.

  A guide member that supports the belt with a predetermined tension is also provided inside the belt, and functions as a heating element that guides the running of the belt and generates heat by the magnetic flux from the coil. This is because the guide member is in contact with the inner surface of the belt, so that the belt can be easily heated if the heat generated by the guide member is transmitted to the belt. In each document, the guide member and the coil are positioned substantially opposite to the pressure roller across the nip, in other words, a straight line connecting the rotation centers of the belt and the pressure roller as viewed from the axial end of the belt. (Vertical line) is arranged on each.

JP 2006-47988 A JP 2008-164783 A

In the above-described structure, heat transfer from the guide member to the belt is important, and adhesion between the inner surface of the belt and the guide member is very important for maintaining the belt temperature.
However, the above-described conventional technique has a problem that when the belt rotates, particularly when the belt is driven and rotated by a pressure roller, the belt is separated from the guide member and heat generated by the guide member is hardly transmitted to the belt. is there.

Specifically, using the vertical line, in the vicinity of the entrance of the nip corresponding to the right side of the vertical line, a force that pulls the belt toward the inside acts to be depressed, while the left side of the vertical line. In the vicinity of the exit of the nip corresponding to, a force for pulling and inflating the belt toward the outside acts.
In other words, the downstream side (right side of the vertical line) of the guide member as viewed in the rotation direction of the belt is in contact with the inner surface of the belt against the guide member due to the depression force, whereas the upstream side (left side of the vertical line) of the guide member ) Because the inner surface of the belt is separated from the guide member due to the inflating force, and the belt at this position floats away from the guide member, making it difficult to stably contact the belt with the guide member over the entire width of the guide member. is there.

In solving this problem, it should be noted that the position of the electromagnetic induction heating unit of the outer package IH in the image forming apparatus cannot be easily moved.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device that solves the above-described problems and secures the adhesion between a belt and a guide member without forcing a layout change, 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, the toner rotating on an axis extending in the width direction of the recording medium being conveyed, A fixing belt member that heats and fixes an image on the recording medium, a heat generation area that generates heat by electromagnetic induction, and a position that substantially faces the fixing belt member across the heat generation area are provided, and the temperature of the heat generation area is uniform. Each of which has a heat conductive layer that is in contact with the inner surface of the fixing belt member and guides the traveling of the fixing belt member, and is disposed along the outer surface of the fixing belt member to generate a magnetic field and generate a heat generating area. An electromagnetic induction heating unit for induction heating, and a sliding member that is provided inside the fixing belt member and forms a nip between the pressure rotating body that contacts the outer surface of the fixing belt member, Both the magnetic induction heating unit and the heat generating area are disposed at positions substantially opposite to the pressure rotator with the sliding member interposed therebetween, while the heat conduction layer substantially faces the pressure rotator with the sliding member interposed therebetween. It is arranged so as to extend toward the upstream side of the nip as viewed in the conveyance direction of the recording medium from the position where the recording is performed.

  According to the first aspect of the present invention, a method (outer packaging IH) is adopted in which the guide member is induction-heated by the magnetic field generated by the electromagnetic induction heating unit to heat and melt the toner image. Specifically, the fixing belt member is provided, and a guide member is disposed therein. The guide member contacts the inner surface of the fixing belt member and guides the traveling of the fixing belt member.

In addition, the guide member has a heat generating region that generates heat by electromagnetic induction of a magnetic field and a heat conductive layer. Since the heat generation area generates heat by electromagnetic induction of a magnetic field generated by the electromagnetic induction heating unit, the fixing belt member can be heated. The heat conductive layer can eliminate the temperature unevenness in the heat generation region, and can achieve the uniform temperature of the fixing belt member.
Further, the sliding member provided inside the fixing belt member and the pressure rotating body form a nip for performing a fixing process on the recording medium.

  Here, since the electromagnetic induction heating unit located outside the fixing belt member is disposed at a position substantially opposite to the pressure rotator with the sliding member interposed therebetween, the layout in the image forming apparatus is not forced to change. The fixing device can be incorporated in a conventional image forming apparatus. Further, the heat generation area of the guide member located inside the fixing belt member is disposed at a position substantially opposite to the electromagnetic induction heating unit with the fixing belt member interposed therebetween, and is caused by electromagnetic induction of a magnetic field generated by the electromagnetic induction heating unit. Can generate heat.

On the other hand, the heat conduction layer of the guide member located inside the fixing belt member is positioned substantially opposite to the pressure rotator with the sliding member interposed therebetween, that is, the pressure rotator with the sliding member interposed therebetween. It is arranged to extend toward the upstream side of the nip as viewed in the recording medium conveyance direction from the opposite side position.
As described above, if the heat conductive layer of the guide member is disposed at the place where the heat is most pulled inward with the rotation of the fixing belt member having flexibility, the guide member covers the inner surface of the fixing belt member. Since it can be pressed outwards, the force that pulls the fixing belt member inward near the nip entrance is suppressed, and at the same time, the force that pushes the belt member outward and expands it is suppressed near the nip exit. Is done.

Therefore, the upstream side of the guide member viewed in the rotation direction of the fixing belt member is not separated from the fixing belt member, and adhesion between the fixing belt member and the guide member is ensured. As a result, heat transfer from the guide member to the fixing belt member is improved, and the temperature of the fixing belt member can be maintained uniformly.
In addition, if the heat transfer area is expanded by extending the heat conductive layer, the contact area between the fixing belt member and the guide member becomes very large, and this heat transfer performance is further improved.

  According to a second invention, in the configuration of the first invention, both the center position of the electromagnetic induction heating unit and the center position of the heat generation area of the guide member viewed in the circumferential direction of the fixing belt member are the rotation center of the fixing belt member. The center position of the heat conduction layer of the guide member is arranged on the line connecting the rotation center of the fixing belt member and the rotation center of the pressure rotation body. It is characterized by being arranged on the upstream side of the nip as viewed in the conveyance direction of the recording medium from the position of.

  According to the second invention, in addition to the operation of the first invention, when viewed in the circumferential direction of the fixing belt member, the electromagnetic induction heating unit located outside the fixing belt member and the fixing belt member Each guide member located inside has a predetermined width. Here, both the center position of the electromagnetic induction heating unit and the center position of the heat generation area of the guide member are arranged at positions on a line connecting the rotation centers of the fixing belt member and the pressure rotator. There is no problem even if the space for incorporating is predetermined and cannot be easily changed.

  On the other hand, the center position of the heat conductive layer of the guide member is arranged on the upstream side of the nip as viewed in the conveyance direction of the recording medium from the position on the line connecting the rotation centers of the fixing belt member and the pressure rotator. The guide member can press the inner surface of the fixing belt member outwardly at a position where the guide member is most pulled inward as the fixing belt member rotates. Therefore, the guide member contacts over the entire width of the fixing belt member viewed in the circumferential direction, and the contact between the fixing belt member and the guide member is stabilized.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, the downstream end of the heat conductive layer of the guide member viewed in the rotation direction of the fixing belt member is the rotation center of the fixing belt member and the pressure rotator. A position corresponding to the fourth quadrant of the orthogonal coordinate system as viewed from the end of the rotation axis formed by a vertical axis connecting the rotation center of the fixing belt member and a horizontal axis passing through the rotation center of the fixing belt member and orthogonal to the vertical axis. It is characterized by being arranged in.

  According to the third aspect of the invention, in addition to the effects of the first and second aspects, the vertical axis connecting the rotation centers of the fixing belt member and the pressure rotator as viewed from the end of the rotation axis, and this Considering an orthogonal coordinate system formed by passing through the center of rotation of the fixing belt member and a horizontal axis orthogonal to the vertical axis, the downstream end of the heat conduction layer of the guide member is in the fourth quadrant of the orthogonal coordinate system. The guide member is disposed at a corresponding position, and the guide member can press the inner surface of the fixing belt member outward at a position where the guide member is most pulled inward as the fixing belt member rotates. Therefore, the guide member contacts over the entire width of the fixing belt member as viewed in the circumferential direction, and the contact between the fixing belt member and the guide member is stabilized.

A fourth invention is characterized in that, in the configurations of the first to third inventions, the heat generating region is made of a magnetic shunt metal.
According to the fourth invention, in addition to the effects of the first to third inventions, if the heat generating region is made of a magnetic shunt metal, heat can be quickly generated by the magnetic flux from the electromagnetic induction heating unit, and the fixing belt. The function as a guide member for guiding the traveling of the member is also reliably satisfied.

According to a fifth aspect of the present invention, there is provided an image forming apparatus in which the first to fourth fixing devices are mounted and a toner image formed by the image forming unit is fixed to a recording medium using the first to fourth fixing devices.
According to the fifth aspect of the invention, in addition to the effects of the first to fourth aspects of the invention, the thermal responsiveness is further improved and a good toner image is formed. As a result, the reliability of the image forming apparatus is improved.

  According to the present invention, among the fixing belt members, the guide member is disposed at a portion that is most pulled inward with the rotation thereof, and a fixing device that can ensure adhesion between the belt and the guide member and the fixing device. A mounted image forming apparatus can be provided.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. 2 is an external perspective view of a fixing unit. FIG. FIG. 3 is a longitudinal sectional view showing a structural example of a fixing unit. FIG. 4 is a partial longitudinal sectional view in which a reference line is added to the fixing unit of FIG. 3.

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, on the left side of the apparatus main body 2, a first conveyance path 9 for conveying a sheet fed from the paper feed cassette 5 to a secondary transfer section 23 described later is disposed. From the right part to the left part, a second transport path 10 for transporting paper fed from the stack tray 6 to the secondary transfer unit 23 is disposed. A fixing unit (fixing device) 14 that performs a fixing process on a sheet on which an image has been formed by the secondary transfer unit 23 and a sheet on which the fixing process has been performed are disposed in the upper left part of 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, for example, a pressure roller (pressure rotator) 44 and a flexible sliding belt (fixing belt member) 45, and the pressure roller 44 includes, for example, a metal cored bar. It has an elastic surface layer and a release layer, and the sliding belt 45 has a metal base and an elastic surface layer and a release layer. The detailed structure of the fixing unit 14 will be described later.

  When viewed in the sheet conveyance direction, conveyance paths 47 are provided on the upstream side and the downstream side of the fixing unit 14 (FIG. 1), and the sheet conveyed through the secondary transfer unit 23 is on the upstream side. It is introduced into the nip between the pressure roller 44 and the sliding belt 45 through the conveyance path 47. The paper that has passed between the pressure roller 44 and the sliding belt 45 is guided to the third transport path 11 through the downstream transport path 47.

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 an external perspective view of the fixing unit 14, and FIG. 3 is a longitudinal sectional view showing a structural example of the fixing unit 14. In FIGS. 2 and 3, the orientation is turned counterclockwise by about 90 ° from the state mounted on the image forming apparatus 1. Accordingly, the sheet conveying direction from the bottom to the top as viewed in FIG. 1 is from right to left when viewed in FIGS. That is, the sheet P in FIG. 3 is in a state immediately before being conveyed to the fixing unit 14. 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 a posture inclined left or right from the state shown in FIG.

  The fixing unit 14 of this embodiment includes the pressure roller 44 and the sliding belt 45 as described above. The pressure roller 44 is, for example, a roller having a diameter of about 25 mm in which a silicon rubber layer having a thickness of about 2 to 5 mm is formed on a metal (for example, SUS) metal core, and further covered with a PFA tube. Note that a halogen heater may be provided inside the pressure roller 44.

The sliding belt 45 is a ferromagnetic material (for example, Ni electroformed base material) having a base material thickness of 35 μm (1 μm = 1 × 10 ⁻⁶ m), for example, and a thin elastic layer having a thickness of about 300 μm on the surface layer. (E.g., silicon rubber) is formed, and a release layer (e.g., PFA) is formed on the outer surface thereof. The heat generation temperature is adjusted to, for example, a range of 150 to 200 ° C. It is a thin belt.

The surface temperature of the sliding belt 45 is measured by a non-contact type temperature sensor disposed at a predetermined distance outside the belt 45 in the radial direction.
As shown in FIG. 2, the pressure roller 44 is provided with a stepping motor 66, and the pressure roller 44 is rotated about the axis extending in the width direction of the conveyed paper by the power from the motor 66. Rotate to. As the pressure roller 44 is driven to rotate (counterclockwise as viewed in FIG. 3), the sliding belt 45 is driven to rotate (clockwise as viewed in FIG. 3). A nip is formed between them.

[Sliding member]
Specifically, a sliding member 70 is fixedly disposed on the inner surface of the sliding belt 45 at a portion facing the pressure roller 44 (FIG. 3). The sliding member 70 is formed in a thin plate shape extending along the axial direction, and both ends thereof are supported by a cover or the like (not shown) of the fixing unit 14. The lower surface portion of the fixed sliding member 70 rubs against and contacts the inner surface of the rotating sliding belt 45, and the sliding member 70 receives a pressing force from the pressure roller 44 in the axial direction. As a result, a flat nip for fixing the toner image on the paper P is formed between the sliding belt 45 and the pressure roller 44.

[Electromagnetic induction heating unit]
In addition, the fixing unit 14 includes an IH coil unit (electromagnetic induction heating unit) 50 outside the sliding belt 45 (not shown in FIGS. 1 and 2). The IH coil unit 50 includes an induction heating coil 52 that is a litz wire bundled with thin wires, a pair of arch cores 54, and a pair of side cores 56 and a center core 58.

〔coil〕
In the example of FIG. 3, the induction heating coil 52 is disposed on a virtual arc surface along the arc-shaped outer surface of the sliding belt 45 in order to perform induction heating in the arc-shaped portion of the sliding belt 45. Actually, a coil bobbin (not shown) is arranged outside the sliding belt 45, and the induction heating coil 52 is arranged in a winding shape on the bobbin. The material of the bobbin is preferably a heat resistant resin (for example, PPS, PET, LCP), and the coil 52 is fixed to the coil bobbin using, for example, a silicon adhesive.

[Arch core, side core, center core]
As shown in FIG. 3, the center core 58 is located in the center of the IH coil unit 50, and the arch core 54 and the side core 56 are arranged so as to make 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 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 disposed at a plurality of positions at intervals in the longitudinal direction (axial direction) of the sliding belt 45. Further, the side cores 56 are continuously arranged without a gap in the axial direction of the sliding belt 45. 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. 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).
The center core 58 is, for example, a ferrite core having a quadrangular cross section. The center core 58 has a length corresponding to the maximum sheet passing width of 13 inches (about 340 mm), and is substantially the same as the sliding belt 45. It is fixed to. The core corresponding to the center core 58 may be formed integrally with the arch core 54.

(Guide member)
Here, the traveling of the sliding belt 45 described above is guided by the guide member 80. Specifically, the guide member 80 is formed in a planar plate shape that is curved in an arc shape as a whole, and both ends in the axial direction are supported by a cover or the like (not shown) of the fixing unit 14. Then, as shown in FIG. 3, it is disposed at a position facing the coil 52 across the sliding belt 45, that is, inside the sliding belt 45, and in contact with the inner surface of the sliding belt 45. It is fixed.

Further, the guide member 80 of the present embodiment is configured to be able to generate heat by the magnetic flux from the coil 52. Specifically, the guide member 80 is formed of two layers of a heat generating layer (heat generating region) 82 and a heat conductive layer 86.
[Heat generation layer]
First, the heat generating layer 82 has a thin plate shape made of, for example, a magnetic shunt metal (Fe—Ni alloy or the like) having a length of about 294 mm in the axial direction and a thickness of about 0.6 mm, and the surface thereof is the inner surface of the sliding belt 45. , And its back surface is in contact with the surface of the heat conductive layer 86. The heat generating layer 82 is magnetic at room temperature, but has a property that when the heat generating layer 82 reaches a predetermined temperature (Curie temperature) or higher, the magnetism disappears and becomes non-magnetic (paramagnetic). The self-temperature control is possible.

(Thermal conduction layer)
On the other hand, the heat conductive layer 86 has a thin plate shape with a length of about 294 mm and a thickness of about 0.3 mm made of aluminum or copper, for example, and the surface thereof is integrally formed with the back surface of the heat generating layer 82. The heat generating layer 82 has a function of making the temperature of the heat generating layer 82 uniform by conducting heat generated in the heat generating layer 82 to the entire area.

By the way, the guide member 80 of the present embodiment is expanded toward the upstream side of the nip as viewed in the transport direction of the paper P (FIG. 3).
Specifically, the IH coil unit 50 is positioned on the side opposite to the pressure roller 44 with the sliding member 70 interposed therebetween, in other words, the position substantially opposite to the pressure roller 44 with the sliding member 70 interposed therebetween. On the other hand, in particular, the heat conductive layer 86 of the guide member 80 is disposed so as to extend closer to the entrance of the nip than a position substantially opposed to the pressure roller 44 with the sliding member 70 interposed therebetween. .

  More specifically, as shown in FIG. 4, the vertical axis connecting the rotation center of the sliding belt 45 and the rotation center of the pressure roller 44 as a temporary reference line in FIG. 3 viewed from the end of the rotation axis. (Y axis) and a horizontal axis (x axis) passing through the center of rotation of the sliding belt 45 and perpendicular to the y axis are added. Then, using the orthogonal coordinate system in which the rotation center of the sliding belt 45 is the origin and the right direction of the x-axis and the upward direction of the y-axis are positive, respectively, it is viewed in the circumferential direction of the sliding belt 45. The center position (center core 58) of the IH coil unit 50 is arranged on the y-axis, and the heat generation layer 82 that generates heat by the magnetic flux from the coil 52 is also in the region indicated by "heat generation region" in FIG. The center position is arranged on the y-axis.

However, the center position of the heat conductive layer 86 indicated by the “heat transfer region” in FIG. 4 is disposed on the upstream side of the nip with respect to the y axis, and is disposed at a position corresponding to the first quadrant of the orthogonal coordinate system. The
As described above, in particular, the heat conductive layer 86 of the guide member 80 is formed so as to extend to the inlet side of the nip. Therefore, in the rotational direction of the sliding belt 45, the downstream end portion of the heat conductive layer 86 is formed. (The lower right end as viewed in FIGS. 3 and 4) is arranged at a position corresponding to the fourth quadrant of the orthogonal coordinate system. 3 and 4, the downstream end of the heat generation layer 82 is also extended to a position corresponding to the fourth quadrant. However, the region that faces the coil 52 functions as the heat generation region. Of the heat generating layer 82, a portion outside the heat generating region functions as a heat conductive layer.

Further, since the downstream end portion of the heat conducting layer 86 is disposed in the vicinity of the entrance of the nip, it forms the y axis on the minus side of the origin with respect to the straight line connecting the downstream end portion and the origin. The angle is acute (90 degrees or less).
In the fixing unit 14 configured as described above, when a high-frequency current is supplied to the coil 52 from a high-frequency power source (not shown), a magnetic field (magnetic flux) is generated in the coil 52. This magnetic field reaches the sliding belt 45 and the guide member 80 through the side core 56, the arch core 54, and the center core 58 to generate heat.

  Specifically, eddy currents are generated in the heat generating layer 82 of the sliding belt 45 and the guide member 80, and Joule heat is generated by the specific resistance of each material, and heating is performed. In particular, the heat generating layer 82 continues to generate heat until the Curie temperature is reached, thereby heating the sliding belt 45. As a result, the toner image on the paper is melted and fixed at the nip between the sliding belt 45 and the pressure roller 44.

  On the other hand, the heating layer 82 becomes non-magnetic when its temperature reaches the Curie temperature. For example, if paper with a narrow width is continuously passed, the temperature of the outer portion of the heat generating layer 82 extending in the axial direction from the paper passing area rises and exceeds the Curie temperature. As a result, the heat generating layer 82 becomes nonmagnetic, and the magnetic flux penetrates in the thickness direction of the heat generating layer 82.

In this case, the heat conductive layer 86 can conduct the heat generated in the outer portion of the paper passing region to the inner portion of the paper passing region, and the temperature distribution in the axial direction of the heat generating layer 82 and the sliding belt 45. Make uniform.
Incidentally, a tension roller may be provided inside the sliding belt 45 described above.

  Specifically, it is viewed at a position opposite to the center position of the heat conduction layer 86 shown by “heat transfer region” in FIG. 4 with respect to the rotation center of the sliding belt 45, that is, in the rotation direction of the sliding belt 45. If a tension roller for urging the inside of the sliding belt 45 outward in the radial direction is provided on the downstream side of the nip (a position corresponding to the third quadrant of the orthogonal coordinate system in FIG. 4), the outlet of the nip In the vicinity, the curvature of the sliding belt 45 can be increased.

  As described above, when the bending degree of the sliding belt 45 is increased in the vicinity of the exit of the nip, the upstream side of the guide member 80 viewed in the rotation direction of the sliding belt 45 comes into contact with the sliding belt 45 more strongly. The adhesion between 45 and the guide member 80 is further ensured. Further, if the bending of the sliding belt 45 is loosened near the exit of the nip, the paper P can be easily separated from the sliding belt 45, and the separability is improved.

  As described above, according to this embodiment, a method (outer packaging IH) is used in which the guide member 80 is induction-heated by the magnetic field generated by the coil 52 of the IH coil unit 50 to heat and melt the toner image. Specifically, the sliding belt 45 is provided, and a guide member 80 is disposed therein. The guide member 80 contacts the inner surface of the sliding belt 45 and guides the traveling of the sliding belt 45.

The guide member 80 has a heat generating layer 82 and a heat conductive layer 86 that generate heat by electromagnetic induction of a magnetic field. Since the heat generating layer 82 generates heat by electromagnetic induction of a magnetic field generated in the coil 52, the sliding belt 45 can be heated. The heat conductive layer 86 can eliminate the temperature unevenness of the heat generating layer 82 and can achieve the uniform temperature of the sliding belt 45.
Further, the sliding member 70 and the pressure roller 44 provided inside the sliding belt 45 form a nip for performing a fixing process on the paper P.

  Here, since the IH coil unit 50 located outside the sliding belt 45 is disposed at a position substantially opposite to the pressure roller 44 with the sliding member 70 interposed therebetween, the IH coil unit 50 of the fixing unit in the image forming apparatus 1 is arranged. The fixing unit 14 can be incorporated in a conventional image forming apparatus without forcing a layout change. Further, the heat generation layer 82 of the guide member 80 located inside the sliding belt 45 is disposed at a position substantially opposite to the IH coil unit 50 with the sliding belt 45 interposed therebetween, and electromagnetic fields generated by the coil 52 are electromagnetically generated. Heat can be generated by induction.

On the other hand, the heat conductive layer 86 of the guide member 80 located inside the sliding belt 45 is positioned substantially opposite to the pressure roller 44 with the sliding member 70 interposed therebetween, that is, with the sliding member 70 interposed therebetween. It is arranged so as to extend from the position opposite to the pressure roller 44 toward the upstream side of the nip as viewed in the conveyance direction of the paper P.
As described above, if the guide member 80 is disposed at a place where the guide belt 80 is most pulled inward in accordance with the rotation of the flexible slide belt 45, the guide member 80 moves the inner surface of the slide belt 45. Since it can be pressed outward, the force that pulls and slides the sliding belt 45 in the vicinity of the nip entrance is suppressed, and at the same time, the sliding belt 45 is pushed outward and expanded in the vicinity of the exit of the nip. Force is suppressed.

  Therefore, the downstream side of the guide member 80 viewed in the rotation direction of the sliding belt 45 is not separated from the sliding belt 45, and adhesion between the sliding belt 45 and the guide member 80 is ensured. As a result of the stable contact between the sliding belt 45 and the guide member 80, heat transfer from the guide member 80 to the sliding belt 45 is enhanced, and the temperature of the sliding belt 45 can be maintained uniformly.

In addition, if the heat transfer area is expanded by extending the heat conductive layer 86, the contact area between the sliding belt 45 and the guide member 80 becomes very large, so that the heat generated in the heat generating layer 82 to the sliding belt 45 is increased. Heat transfer is further improved.
Further, when viewed in the circumferential direction of the sliding belt 45, the IH coil unit 50 positioned outside the sliding belt 45 and the guide member 80 positioned inside the sliding belt 45 each have a predetermined width. ing. Here, both the center position of the IH coil unit 50 and the center position of the heat generating layer 82 indicated by “heat generation area” in FIG. 4 are on a line connecting the rotation centers of the sliding belt 45 and the pressure roller 44. There is no problem even if the space for installing the fixing unit 14 is determined in advance and cannot be easily changed.

  On the other hand, the center position of the heat conductive layer 86 indicated by “heat transfer region” in FIG. 4 is more transported of the paper P than the position on the line connecting the rotation centers of the sliding belt 45 and the pressure roller 44. The guide member 80 is arranged on the upstream side of the nip as viewed in the direction, and the inner surface of the sliding belt 45 is directed outward at a position where the guide member 80 is most pulled toward the inside as the sliding belt 45 rotates. Can be pressed. Therefore, the guide member 80 contacts over the entire width of the sliding belt 45 viewed in the circumferential direction, and the contact between the sliding belt 45 and the guide member 80 is stabilized.

  Furthermore, as viewed from the axial end of the sliding belt 45 as shown in FIG. 4, the vertical axis (y axis) connecting the rotational centers of the sliding belt 45 and the pressure roller 44 and the rotational center of the sliding belt 45 ( Considering an orthogonal coordinate system formed with a horizontal axis (x axis) orthogonal to the vertical axis through the origin, the downstream end of the heat conductive layer 86 as viewed in the rotational direction of the sliding belt 45 (FIG. 3). , 4) is disposed at a position corresponding to the fourth quadrant of the Cartesian coordinate system, and the guide member 80 is located at a position where the guide member 80 is most pulled inward as the sliding belt 45 rotates. Thus, the inner surface of the sliding belt 45 can be pressed outward. Therefore, the guide member 80 contacts over the entire width of the sliding belt 45 viewed in the circumferential direction, and the contact between the sliding belt 45 and the guide member 80 is stabilized.

Furthermore, if the heat generating layer 82 is made of a magnetic shunt metal, heat can be quickly generated by the magnetic flux from the coil 52, and the function of guiding the running of the sliding belt 45 can be reliably satisfied.
In addition, the reliability of the image forming apparatus 1 is improved as a result of improving the thermal responsiveness during driving and forming a good toner image by equalizing the temperature of the sliding belt 45.

The present invention can be implemented with various modifications without being limited to the above-described embodiments. For example, the configuration of the core portion may be solid or hollow, and can also be applied to a rotating or fixed center core.
In the present 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 is naturally applicable to a multifunction machine, a copier, a facsimile machine, and the like.

  In any of these cases, similarly to the above, there is an effect that the adhesion between the sliding belt and the guide member can be secured without forcing a layout change.

1 Printer (image forming device)
7 Image forming unit 14 Fixing unit (fixing device)
44 Pressure roller (Pressure rotating body)
45 Sliding belt (fixing belt member)
50 IH coil unit (electromagnetic induction heating unit)
70 Sliding member 80 Guide member 82 Heat generation layer (heat generation region)
86 Thermal conduction layer

Claims (5)

A fixing device for fixing an image on a recording medium,
A fixing belt member that rotates about an axis extending in the width direction of the recording medium to be conveyed, heats the toner image on the recording medium, and fixes the toner image on the recording medium;
A heat generating area that generates heat by electromagnetic induction, and a heat conduction layer that is provided at a position substantially opposite to the fixing belt member across the heat generating area, and that makes the temperature of the heat generating area uniform; A guide member that contacts the inner surface and guides the running of the fixing belt member;
An electromagnetic induction heating unit that is disposed along an outer surface of the fixing belt member and generates a magnetic field to inductively heat the heat generation area;
A sliding member that is provided inside the fixing belt member and forms a nip with a pressure rotating body that contacts the outer surface of the fixing belt member;
Both the electromagnetic induction heating unit and the heat generating region are disposed at positions substantially opposite to the pressure rotating body with the sliding member interposed therebetween, while the heat conductive layer has the sliding member interposed therebetween. A fixing device, wherein the fixing device is arranged so as to extend toward the upstream side of the nip as viewed in the conveyance direction of the recording medium from a position substantially opposite to the pressure rotator. The fixing device according to claim 1,
Both the center position of the electromagnetic induction heating unit and the center position of the heat generation area of the guide member viewed in the circumferential direction of the fixing belt member are the rotation center of the fixing belt member and the rotation center of the pressure rotating body. The center position of the heat conductive layer of the guide member is arranged at a position on the connected line, but the recording position is more than the position on the line connecting the rotation center of the fixing belt member and the rotation center of the pressure rotating body. A fixing device, wherein the fixing device is disposed on the upstream side of the nip as viewed in the conveyance direction of the medium. The fixing device according to claim 1, wherein:
The fixing member has a vertical axis connecting the rotation center of the fixing belt member and the rotation center of the pressure rotator with the downstream end of the heat conducting layer of the guide member as viewed in the rotation direction of the fixing belt member. A fixing device, wherein the fixing device is disposed at a position corresponding to a fourth quadrant of an orthogonal coordinate system viewed from an end of the axis formed by a horizontal axis perpendicular to the vertical axis through a rotation center of the belt member. . The fixing device according to any one of claims 1 to 3,
The fixing device according to claim 1, wherein the heat generating region is made of a magnetic shunt metal.   An image forming apparatus comprising the fixing device according to claim 1, wherein the toner image formed by the image forming unit is fixed to the recording medium using the fixing device.

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