JP2011197185A - Fixing device and image forming apparatus loaded with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of cooling both end parts of a fixation rotating body while saving space, and an image forming apparatus loaded with it.SOLUTION: The fixing device (14) for fixing images to a recording medium includes: the fixation rotating body (45) rotated around an axis extending in the width direction of a conveyed recording medium, for heating a toner image on the recording medium and fixing it to the recording medium; a coil (52) disposed along the outer surface of the fixation rotating body and extended in the axial direction, for generating a magnetic field for induction-heating the fixation rotating body; a coil holding part (53) for mounting the coil; a core part (54) arranged on the opposite side of the fixation rotating body across the coil, for forming a magnetic path around the coil; and a cooling means (80) for supplying cooling air to the coil. The coil holding part includes ventilation mechanisms (53b, 53f) capable of opening and closing both end parts in the axial direction of the fixation rotating body to the cooling means.

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 is about.

  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, in view of the structure in which a coil for generating a magnetic field for electromagnetic induction is arranged outside the belt (so-called outer packaging IH) and the point of saving the space of the fixing device, the fixing roller The structure (what is called inclusion IH) which has arrange | positioned the coil inside is disclosed (for example, refer patent document 1, 2). And especially in patent document 2, a cooling means is provided and a coil is cooled and the temperature rise is prevented.

JP-A-6-31801 JP 2003-186323 A

Incidentally, the temperature of the coil rises not only by its own electric resistance but also by heat conduction from the fixing roller. In particular, when a small size of paper is continuously passed, the temperature of the fixing roller outside the paper in the width direction (non-paper passing area) rises excessively compared to the paper passing area, and the coil is raised. The fixing device may be damaged by heating.
Further, the excessive temperature rise of the fixing roller is different from the central portion and the end portion when viewed in the width direction of the paper, and the toner of the paper corresponding to the position of the end portion adheres to the fixing roller. Fixing performance is reduced.

Here, it is conceivable to cool the fixing roller in addition to the coil. However, if a cooling means dedicated to the fixing roller is separately provided, the apparatus becomes large, and if the fixing roller is simply cooled, the width direction of the paper The portion corresponding to the central portion viewed in FIG. 3 is also cooled, and there is a problem that the heating efficiency of the fixing roller is reduced.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and provide a fixing device capable of cooling both ends of the fixing roller in a space-saving manner 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 rotator for heating and fixing an image on a recording medium, a coil disposed along an outer surface of the fixing rotator and extending in an axial direction to generate a magnetic field for inductively heating the fixing rotator; A coil holding unit for mounting the coil; a core unit that is disposed on the opposite side of the fixing rotating body with the coil interposed therebetween; and a cooling unit that supplies cooling air to the coil. The coil holding portion includes a ventilation mechanism that can open and close both end portions of the fixing rotating body in the axial direction with respect to the cooling means.

  According to the first invention, the fixing rotating body is induction-heated by a magnetic field of a coil disposed along the outer surface thereof, and a system (outer package IH) is used in which the toner image is heated and melted. Specifically, in addition to the coil holding part, the core part is also arranged along the outer surface of the fixing rotator to form a magnetic path for guiding the magnetic field generated by the coil, and this magnetic flux is guided to the core part for magnetic induction heating. Do.

Further, the cooling means cools the coil to prevent the temperature from rising, and the fixing device can be protected.
Here, the coil holding part is formed along the axial direction of the fixing rotator and faces the fixing rotator. The coil holding part opens and closes both ends of the fixing rotator with respect to the cooling means. A possible ventilation mechanism is provided, and the cooling means for preventing the temperature rise of the coil can be used for cooling both end portions of the fixing rotating body.

Therefore, an excessive temperature rise (overheating of the fixing rotator) at both ends of the fixing rotator can be suppressed with a smaller fixing device than in the past.
Further, if this ventilation mechanism is opened, only the both end portions of the fixing rotator are cooled by cooling air, so that the heating efficiency of the fixing rotator does not decrease, and further, by preventing overheating of the fixing rotator. The fixing performance of the central portion and both end portions viewed in the width direction of the recording medium to be conveyed can be made uniform.

According to a second aspect of the present invention, in the configuration of the first aspect of the invention, there is provided exhaust means for blowing cooling air from the cooling means only to both end portions in the axial direction of the fixing rotator.
According to the second invention, in addition to the operation of the first invention, the flow of the cooling air is further controlled between the cooling means and the exhaust means, and the cooling air is blown only on both end portions of the fixing rotating body. The fixing performance of the central portion and both end portions viewed in the width direction of the recording medium being conveyed can be made more uniform.

  According to a third aspect of the present invention, in the configuration of the first or second aspect of the invention, the detection means for detecting the temperature at both end portions in the axial direction of the fixing rotator and the fixing rotator based on the temperature detected by the detection means. Control means for outputting a signal for opening the ventilation mechanism to the ventilation mechanism when the temperature of both end portions in the axial direction of the fixing rotating body rises due to continuous conveyance of the recording medium having a width smaller than the axial length. It is characterized by.

  According to the third invention, in addition to the effects of the first and second inventions, the control means can control the opening / closing timing of the ventilation mechanism based on the temperature detected by the detection means. Specifically, when the temperature of both end portions in the axial direction of the fixing rotator rises due to continuous conveyance of a recording medium having a width smaller than the axial length of the fixing rotator, a signal for opening the aeration mechanism is output to the ventilation mechanism. is doing. As a result, it is possible to efficiently prevent overheating of the fixing rotator.

According to a fourth aspect of the invention, in the configuration of the third aspect of the invention, the control means outputs a signal for opening the outer region beyond the width of the recording medium viewed in the axial direction to the ventilation mechanism.
According to the fourth invention, in addition to the action of the third invention, the control means can change the opening amount of the ventilation mechanism according to the width of the recording medium viewed in the axial direction. The area outside the width is always open. Therefore, both end portions in the axial direction of the fixing rotator are always cooled, and it is possible to prevent the fixing rotator from being excessively heated.

According to a fifth aspect of the present invention, there is provided an image forming apparatus in which the fixing device according to the first to fourth aspects of the present invention is mounted on an image forming apparatus, and a toner image formed by the image forming unit is fixed to a recording medium using the fixing apparatus. Features.
According to the fifth invention, in addition to the effects of the first to fourth inventions, the heating efficiency and fixing performance of the fixing rotator are ensured and a good toner image is formed. As a result, the reliability of the image forming apparatus is improved. Improves.

  According to the present invention, since the coil cooling means is also used for cooling the fixing rotator, it is possible to provide a fixing device capable of cooling both ends of the fixing rotator in a space-saving manner and an image forming apparatus equipped with the fixing device. .

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 of a fixing unit. It is a perspective view of the edge part of a coil bobbin. It is a perspective view of the edge part of a coil bobbin. It is the schematic of the controller which drives a ventilation mechanism. It is a figure explaining the flow of the cooling wind in the state of FIG. It is a figure explaining the flow of the cooling wind in the state of FIG.

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 is disposed above the rear roller 38 disposed near the image forming unit 26, the front roller 39 disposed near the image forming unit 29, and the image forming unit 28. The tension roller 42, the rear roller 38, the front roller 39, the intermediate transfer belt 40 disposed across the tension roller 42, and the photosensitive drum of the developing unit 35 in the photosensitive drum 32 of each of the image forming units 26 to 29. And four primary transfer rollers 41 disposed so as to be in pressure contact with the photosensitive drum 32 via an intermediate transfer belt 40 at a position downstream of the rotation direction 32. The tension roller 42 applies an appropriate tension to the intermediate transfer belt 40.

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 (fixing rotator) 45, and the pressure roller 44 is, for example, a metal core and an elastic surface layer (for example, silicon rubber). And a release layer (for example, PFA), and the fixing roller 45 has a metal core and an elastic surface layer (for example, silicon sponge). A heating belt (fixing rotator) 48 is wound around the fixing roller 45 (FIG. 2). 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 conveyed upstream. It is introduced into a nip between the pressure roller 44 and the fixing roller 45 through a path 47. 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, 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 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 the surface layer. 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. The surface temperature of the heating belt 48 is measured by a non-contact type temperature sensor, for example, an infrared sensor (detecting means) 70 disposed at a predetermined interval from the heating belt 48.

However, the infrared sensor 70 according to the present embodiment sets the temperature of the non-sheet passing region of the fixing roller 45 corresponding to the outer region of the small-size sheet width, in other words, the both ends of the fixing roller 45 in the rotation axis direction. The detection result can be output to the controller (control means) 90 in FIG.
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 (not shown) is provided inside the pressure roller 44.

[IH coil unit]
In addition, the fixing unit 14 includes an IH coil unit 50 outside the fixing roller 45 and the heating belt 48 (not shown in FIG. 1). The IH coil unit 50 includes an induction heating coil (coil) 52 and ferromagnetic materials such as ferrite (relative permeability: about 1000 to 3000) so as to form a magnetic path around the induction heating coil 52. The core portion 54 has an arch core, a side core, and a center core.

〔coil〕
The induction heating coil 52 generates a magnetic field for induction heating the fixing roller 45 and the heating belt 48. Therefore, the induction heating coil 52 is disposed on a virtual arc surface along the outer surfaces of the fixing roller 45 and the heating belt 48. Actually, a coil bobbin (coil holding part) 53 is arranged, and the induction heating coil 52 is arranged on the coil bobbin 53 in a winding shape.

[Coil holding part]
The coil bobbin 53 is formed in a semi-cylindrical shape along the outer surfaces of the fixing roller 45 and the heating belt 48, and includes a bobbin main body 53a extending in the rotation axis direction of the fixing roller 45. The bobbin main body 53a includes an induction heating coil 52 and The core part 54 is held. The material of the coil 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.

For example, a resin core holder (not shown) is provided outside the core portion 54, and the core portion 54 is supported by the core holder. The material of the core holder is also preferably a heat resistant resin (for example, PPS, PET, LCP).
2, a cooling fan (cooling means) 80 is provided above the core holder, and sucks outside air and supplies cooling air toward the coil 52.

  On the other hand, an exhaust fan (exhaust means) 82 is provided below the pressure roller 44 as viewed in FIG. Specifically, the exhaust fan 82 according to the present embodiment is disposed so as to face the non-sheet passing area of the fixing roller 45 described above, and the cooling air from the cooling fan 80 is passed through the non-sheet passing of the fixing roller 45. After spraying on the area, discharge to the outside.

This is because the coil bobbin 53 of this embodiment includes a ventilation mechanism that guides the cooling air from the cooling fan 80 to the non-sheet passing area of the fixing roller 45.
(Ventilation mechanism)
Specifically, the bobbin main body 53a formed in a semi-cylindrical shape has doors (venting mechanisms) 53b and 53f that can open and close the non-sheet passing area of the fixing roller 45 with respect to the cooling fan 80 ( Figure 2).

  The doors 53b and 53f of the present embodiment are positions corresponding to the non-sheet passing area of the fixing roller 45 in the bobbin main body 53a, and the positions where the coils 52 are held. More specifically, the two-dot chain lines in FIG. A door 53f is formed on the upstream side and a door 53b is formed on the downstream side as viewed in the paper transport direction from the position where the folded portion of the coil 52 shown is held.

These doors 53b and 53f can move in the direction of the axis of rotation of the fixing roller 45 (FIG. 4). In the state shown in FIG. 4, the cooling air from the cooling fan 80 does not pass through the fixing roller 45. Guided to the paper area.
3 and 4 show the end of the bobbin main body 53a, specifically, one end as viewed in the rotation axis direction of the fixing roller 45, and the other end of the bobbin main body 53a. Similarly, doors 53b and 53f are respectively formed.

The pair of doors 53f and 53f arranged on the upstream side in the paper transport direction are connected via, for example, a spring (not shown) arranged on the back side of the bobbin main body 53a. Moving toward the center portion, the non-sheet passing area of the fixing roller 45 is opened to the cooling fan 80.
On the other hand, each door 53f is also connected to, for example, a link (not shown) arranged on the back side of the bobbin main body 53a. When the link moves toward the outside in the width direction of the paper, the door 53f is biased by this spring. The non-sheet passing area of the fixing roller 45 can be closed with respect to the cooling fan 80.

Further, the pair of doors 53b disposed on the downstream side in the sheet conveyance direction is configured to be movable similarly to the door 53f, and opens and closes the non-sheet passing area of the fixing roller 45 with respect to the cooling fan 80.
The opening / closing operation by the doors 53b and 53f is executed based on a signal from the controller 90.

[Control means]
Specifically, the controller 90 of the present embodiment includes an open / close determination unit 92 and an open / close setting unit 94, as shown in FIG. The open / close determination unit 92 sets the temperature of the non-sheet passing area of the fixing roller 45 detected by the infrared sensor 70 or the paper size set by the operation panel of the image forming apparatus 1 or specified by the print job from the client PC. Based on this, it is determined whether or not the doors 53b and 53f are to be opened.

Here, for example, when a large size sheet is passed, or even when a small size sheet is not continuously passed, the temperature of the non-sheet passing area of the fixing roller 45 is not so high. It will not be high.
Therefore, the open / close determination unit 92 in this case outputs to the open / close setting unit 94 that the doors 53b and 53f are not opened.

  As a result, the doors 53b and 53f do not move toward the central portion in the width direction of the sheet, and the end of the bobbin main body 53a remains closed. Accordingly, the cooling air from the cooling fan 80 cools the coil 52 and then collides with the doors 53b and 53f and flows in the paper transport direction, as shown by the arrows in FIG.

On the other hand, if small-size sheets are continuously passed and the temperature of the non-sheet passing area of the fixing roller 45 may exceed the durable temperature of the coil 52, the open / close determination unit 92 A message to open 53b and 53f is output to the open / close setting unit 94.
The opening / closing setting unit 94 sets the opening / closing timing and the opening / closing amount of the doors 53b, 53f. Specifically, when the temperature increase rate in the non-sheet passing area of the fixing roller 45 is large, the opening / closing timing of the doors 53b and 53f can be set earlier. Further, the opening / closing amounts of the doors 53b and 53f are set in accordance with the width of the paper, and it can be set so that the outer region is always opened beyond the width of any paper.

  And the setting result by this opening / closing setting part 94 is output to the door drive part (ventilation mechanism) 53d, and when the door drive part 53d cancels | releases the said spring stopper which each connected each door 53f and each door 53b, door 53f, 53f opens the non-sheet passing area of the fixing roller 45 to the cooling fan 80 by the biasing force of the spring. As a result, the cooling air from the cooling fan 80 flows downward from the portions corresponding to the doors 53b and 53f as shown by arrows in FIG. 7, and cools the non-sheet passing area of the fixing roller 45 to exhaust the exhaust fan. Head to 82.

  After that, for example, when the temperature of the non-sheet passing area of the fixing roller 45 is lowered to such an extent that the coil 52 is not damaged, the opening / closing setting unit 94 indicates that the opening / closing setting unit 94 does not open the doors 53b and 53f. Therefore, the opening / closing setting unit 94 causes the door driving unit 53d to close the doors 53b and 53f. As a result, the cooling air from the cooling fan 80 cools the coil 52 and then collides with the doors 53b and 53f and flows in the paper transport direction (FIG. 6).

  As described above, according to the present embodiment, the fixing roller 45 and the heating belt 48 are induction-heated by the magnetic flux of the coil 52 disposed along the outer surface thereof, and a method (outer packaging IH) is performed that heats and melts the toner image. adopt. Specifically, in addition to the coil bobbin 53, the core portion 54 is also disposed along the outer surface of the fixing roller 45 and the like to form a magnetic path that guides the magnetic field generated by the coil 52, and this magnetic flux is guided to the core portion 54 to be magnetic. Induction heating is performed.

Further, the cooling fan 80 cools the coil 52 to prevent the temperature from rising, and the fixing unit 14 can be protected.
Here, the coil bobbin 53 is formed along the axial direction of the fixing roller 45 and the like, and is opposed to the fixing roller 45 and the like. Doors 53b and 53f that are openable and closable are provided, and the cooling fan 80 for preventing the temperature of the coil 52 from rising can be used for cooling the non-sheet passing area such as the fixing roller 45.

Therefore, an excessive temperature rise in the non-sheet passing area such as the fixing roller 45 (overheating of the fixing roller 45) can be suppressed by the small fixing unit 14 as compared with the conventional case where only the coil is cooled.
If the doors 53b and 53f are opened, only the both ends of the fixing roller 45 and the like are cooled by the cooling air, so that the heating efficiency of the fixing roller 45 and the like does not decrease. By preventing the temperature rise, the fixing performance of the central portion (sheet passing area) and both end portions (non-sheet passing area) viewed in the width direction of the conveyed sheet can be made uniform.

Further, the flow of the cooling air is controlled between the cooling fan 80 and the exhaust fan 82, and the cooling air is blown only to the non-sheet passing area such as the fixing roller 45. Can be made more uniform.
Furthermore, the controller 90 can control the opening / closing timing of the doors 53b and 53f based on the temperature detected by the infrared sensor 70. Specifically, when the temperature of the non-sheet passing area such as the fixing roller 45 rises due to continuous conveyance of small-size paper, a signal for opening the doors 53b and 53f is output to the door driving unit 53d. Thereby, it is possible to efficiently prevent an excessive temperature rise of the fixing roller 45 and the like.

Further, the controller 90 can change the opening amount of the doors 53b and 53f in accordance with the width of the paper, and always opens the outer area of the paper width. Therefore, the non-sheet passing area such as the fixing roller 45 is always cooled, and the excessive temperature rise of the fixing roller 45 can be prevented more efficiently.
Furthermore, as a result of forming a good toner image while ensuring the heating efficiency and fixing performance of the fixing roller 45 and the like, 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, the configuration of the core portion 54 may be a rotation center or a fixed center core, or a core corresponding to the center core may be integrally formed with the arch core, and can be appropriately modified.
In the above embodiment, the heating belt 48 is wound around the entire circumference of the fixing roller 45. However, in the present invention, the fixing roller 45 and the heat roller 46 are provided inside the heating belt 48. Naturally, the present invention can also be applied to a two-axis type in which an outer cover is arranged, and can also be applied to various fixing units of an outer packaging IH system.

Furthermore, although the present embodiment shows an example in which the image forming apparatus is embodied in a printer, the image forming apparatus of the present invention can naturally be applied to a multifunction machine, a copying machine, a facsimile, and the like.
In any of these cases, the both ends of the fixing rotator can be cooled in a space-saving manner as described above.

1 Printer (image forming device)
7 Image forming unit 14 Fixing unit (fixing device)
45 Fixing roller (fixing rotating body)
48 Heating belt (fixing rotating body)
50 IH coil unit 52 Induction heating coil (coil)
53 Coil bobbin (coil holder)
53b, 53f Door (ventilation mechanism)
53d Door drive part (ventilation mechanism)
54 Core part 70 Thermistor (detection means)
80 Cooling fan (cooling means)
82 Exhaust fan (exhaust means)
90 controller (control means)

Claims (5)

A fixing device for fixing an image on a recording medium,
A fixing rotating body that rotates around an axis extending in the width direction of the recording medium to be conveyed, and heats and fixes the toner image on the recording medium to the recording medium;
A coil that is arranged along the outer surface of the fixing rotator, extends in the axial direction and generates a magnetic field for induction heating the fixing rotator, and a coil holding unit for mounting the coil;
A core part disposed on the opposite side of the fixing rotator across the coil, and forming a magnetic path around the coil;
Cooling means for supplying cooling air to the coil,
The fixing device according to claim 1, wherein the coil holding portion includes a ventilation mechanism capable of opening and closing both end portions in the axial direction of the fixing rotating body with respect to the cooling unit. The fixing device according to claim 1,
A fixing device comprising exhaust means for blowing cooling air from the cooling means only to both end portions in the axial direction of the fixing rotating body. The fixing device according to claim 1, wherein:
Detecting means for detecting temperatures of both end portions in the axial direction of the fixing rotating body;
Based on the temperature detected by the detecting means, when the temperature of both end portions in the axial direction of the fixing rotator rises due to continuous conveyance of a recording medium having a width smaller than the axial length of the fixing rotator, the ventilation And a control unit that outputs a signal for opening the mechanism to the ventilation mechanism. The fixing device according to claim 3,
The fixing device is characterized in that the control means outputs a signal for opening a region outside the width of the recording medium viewed in the axial direction to the ventilation mechanism.   An image forming apparatus comprising: a fixing device according to claim 1 mounted on an image forming apparatus; and a toner image formed by an image forming unit is fixed on a recording medium by using the fixing device. .

Images