JPH10207278A - Fixing device with induction heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make only a heating rotary body stably induction heat generating, and to realize power saving by providing cut off means preventing a magnetic loop from being formed across a core, on a supporting structure supporting the heating rotary body in freely rotationally. SOLUTION: In this fixing device, an air gap is formed by providing a disconnecting part on a part of a top end of several supporting frame 21. Moreover, bearings 23 and fixing rings 24 consisting a roller supporting structure 26 is severally composed of a insulating material provide with heat resistance, and made as an insulating member. The cut off means 36 are composed of the air gap formed in the roller supporting structure 26 and the insulating member arranged on the roller supporting structure 26. In this way, since the cut off means 36 consisting of the air gap and the insulative material are provided on the roller supporting structure 26, the possibility of the magnetic loop being formed on the roller supporting structure 26 is eliminated. Thus, the power is prevented from being wasted unwittingly by the roller supporting structure 26, and the fixing roller 12 is only made possible to stably perform the induction heat generation, therefore the power saving can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for, for example, an electrophotographic copying machine, a printer, a facsimile, and the like, and more particularly, to a fixing device for fixing a toner image to a recording medium using induction heating. About.

[0002]

2. Description of the Related Art An electrophotographic copying machine, a printer, a facsimile, and the like are provided with a fixing device for fixing a toner image held on a sheet such as recording paper or a transfer material as a recording medium onto the sheet. .

There are various types of fixing devices, and a general heat roller type fixing device includes a fixing roller for thermally melting toner on a sheet, and a pressure roller for pressing and holding the sheet by pressing the fixing roller. And a roller. The fixing roller is formed in a hollow cylindrical shape, and a heat source for heating the fixing roller is provided inside the fixing roller. By this heat source, the fixing roller is heated to a predetermined fixing temperature required for fixing by fusing the toner by heat.

As a heat source in the heat roller fixing device, a tubular heater such as a halogen lamp is generally used. This halogen lamp is arranged on the center axis of the fixing roller, and the fixing roller is heated by radiant heat of the halogen lamp. . Such a halogen lamp heating type fixing device is
Although it is inexpensive in terms of cost, it has the drawback of low thermal efficiency and large energy loss due to heating by radiant heat.

In order to solve these drawbacks and respond to recent demands for energy saving, a fixing device of an induction heating system has been proposed.

For example, Japanese Patent Publication No. 4-73155 discloses that
An induction heating fixing device is described in which a coil formed by spirally winding a coil is formed through a core forming a closed magnetic path inside a conductive fixing roller and concentrically arranged inside the fixing roller. In this fixing device, the coil is energized to generate a magnetic flux in the core, and the magnetic flux induces an induced current in the fixing roller, thereby causing the fixing roller to generate Joule heat.

A fixing device using such induction heating is:
Since the heating element, such as the fixing roller, is heated directly by electromagnetic induction, the heat conversion efficiency is higher and the power of the fixing roller surface is quickly raised to the fixing temperature with less power compared to the halogen lamp heating method. It is possible to meet the demand for energy saving. In particular, those having a core that forms a closed magnetic path as described in the above publication have almost no leakage of magnetic flux and can efficiently generate a secondary current in the fixing roller. Suitable for printers, etc.

[0008]

As described in the above publication, in a fixing device provided with a fixing roller having a core penetrated, an axial position of the roller is regulated to rotatably support the fixing roller. A roller support structure having a metal fixing ring, a metal bearing, a metal support frame, and the like is provided.

However, there is a risk that a magnetic loop may be formed via a core in such a portion of the roller support structure made of metal. In such a case, since the roller support structure is heated by induction, there is a problem that the power loss is increased by that much and the heat generation amount of the fixing roller itself is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the prior art, and eliminates the possibility that a magnetic loop is formed in a support structure that rotatably supports a heating rotator having a core penetrated therein. Accordingly, an object of the present invention is to provide an induction heating fixing device capable of stably inducing heat generation only in a heating rotator and achieving power saving.

[0011]

According to the present invention, there is provided an induction heating and fixing apparatus according to the present invention, wherein a hollow cylindrical heating rotator formed of a conductive member is pressed against the heating rotator, A pressurizing rotator holding a recording medium holding toner between the heating rotator, a core partially inserted into a hollow portion of the heating rotator to form a closed magnetic path, and being wound around the core; Being placed in the hollow portion of the heating rotator,
A coil for induction-heating the heating rotator, wherein an induction heating and fixing device having a coil for preventing the formation of a magnetic loop via the core in the support structure rotatably supporting the heating rotator. Means for fixing by induction heating.

[0012] In the induction heating fixing device configured as described above, there is no possibility that a magnetic loop is formed in the support structure. For this reason, power is prevented from being wastefully consumed by the support structure, only the heating rotator can be stably induced to generate heat, and power saving in the fixing device is achieved.

[0013] The blocking means may comprise an air gap formed in the support structure or an insulating member arranged in the support structure.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a copying machine as an image forming apparatus incorporating the induction heating fixing device according to the present invention.

As shown in the figure, the copying machine 100 includes an image scanner unit 101 for reading an original, a signal processing unit 102 for performing signal processing, and an image corresponding to the original image read by the image scanner unit 101 as a recording medium. And a casing 104 for arranging or storing these units.

In the image scanner section 101, a document placed on a platen glass 105 is pressed by a platen cover 106. When an automatic document feeder (not shown) is mounted, an automatic document feeder is used instead of the platen cover 106. Is attached. Platen glass 1
The original on the original 05 is irradiated by a lamp 107, and the light reflected from the original is converted into image information on a line sensor (CCD) 110 via mirrors 108a, 108b and 108c and a condenser lens 109, and is converted into image information and signal. Processing unit 10
Sent to 2. By driving the scanner motor 111, the first slider 112 is moved at a speed V and the second slider 113 is moved at V / 2 in a direction perpendicular to the electrical scanning direction (main scanning direction) of the line sensor (sub scanning direction). ), And scans the entire original.

The signal processing unit 102 includes a line sensor 109
Process the signals read by the printer unit 103
Send to

The printer unit 103 includes a laser generator 115
And a photosensitive drum 116 as an image carrier,
Around the rotating photosensitive drum 116, a charging roller 117 as a charging device, a developing device 118, a transfer roller 119 as a transfer device, a charge elimination needle 120 as a device for removing and separating the sheet 10, and a photosensitive member And a cleaning device 121 that removes residual toner on the drum 116. The laser generator 115 includes the signal processing unit 1
The drive modulation of the semiconductor laser is performed according to the level of the image signal sent from the device 02. The laser beam is applied to the photosensitive drum 116 at a position between the charging roller 117 and the developing device 118 via a polygon mirror (not shown), an f-θ lens, a return mirror, and the like. Photoconductor drum 1
The electrostatic latent image formed on 16 is developed with toner in developing device 118.

On the other hand, a sheet cassette 125 detachably attached to the casing 104 has a plurality of sheets 1.
0 are stored in a stacked state. Paper cassette 12
The sheet 10 in the sheet 5 is separated and fed one by one by a feed roller 126, and the photosensitive drum 116 and the transfer roller 11 are separated by a timing roller 127 at a predetermined timing.
9 is transferred toward the transfer position between the transfer position 9 and the transfer position 9. The image developed on the photosensitive drum 116 is transferred to the sheet 10 by the transfer roller 119. The sheet 10 after the transfer is separated from the photosensitive drum 116, and is conveyed by the conveying belt 129 toward the fixing device 128. The unfixed toner transferred onto the sheet 10 is fixed in the fixing device 128, and the sheet 10 on which the toner is fixed is discharged to a discharge tray 129. The fixing device 1 according to the present embodiment
Reference numeral 28 denotes an induction heating method, and the configuration will be described later.

When the transfer to the sheet 10 is completed by the transfer roller 119, the photosensitive drum 116 is charged to a negative polarity by a charger (not shown) before the cleaner, and
The residual toner is removed by the cleaning device 121, and the residual charge is removed by the eraser. Thereafter, the toner is charged again by the charging roller 117, receives a latent image formed by the laser beam, is developed by the developing device 118, and the charge in the non-development area is removed by a pre-transfer eraser (not shown).

FIG. 2 is a sectional view schematically showing a main part of the induction heating fixing apparatus shown in FIG. 1, and FIGS. 3 and 4 are sectional views and side views schematically showing a supporting structure of a fixing roller and a pressure roller. FIG.

The induction heating fixing device 128 heats and melts the toner 11 held on the sheet 10 to
A fixing roller (corresponding to a heating rotator) 12 that is induction-heated, a pressing roller (corresponding to a pressing rotator) 13 that presses against the fixing roller 12, and a fixing roller 12 are guided. And a coil 14 for heating.
The fixing roller 12 is provided so as to be rotatable in the direction of arrow a in FIG. 2, and the pressure roller 13 is driven to rotate with the rotation of the fixing roller 12.

The fixing roller 12 is a conductive hollow cylindrical pipe, and is formed of, for example, a carbon steel pipe, a stainless steel pipe or an aluminum pipe, iron, or the like, and has a sufficient pressing force from the pressing roller 13. It is formed within a range in which mechanical strength can be ensured and with a thickness that can ensure heat capacity. Further, a sheet 1 is provided on the outer surface of the roller.
In order to easily separate 0, a release layer having good release properties and heat resistance to the toner is formed by coating with a fluororesin.

The pressure roller 13 comprises a shaft core 15 and a silicone rubber layer 16 formed around the shaft core 15. The silicon rubber layer 16 covers the sheet 1 from the surface.
0 is a rubber layer having releasability and heat resistance as well as easy release. In the illustrated embodiment, a halogen lamp 28 is incorporated in the shaft core 15. The pressure roller 13 is pressed in a direction toward the fixing roller 12 by a spring material (not shown).

The induction heating fixing device 128 further has a rectangular core 17 forming a closed magnetic circuit.
Are penetrated through the hollow portion 12 a in the fixing roller 12. The coil 14 is formed by spirally winding a winding 18, inserted through the core 17, and disposed concentrically inside the fixing roller 12. The core 17 is a so-called iron core used for an ordinary transformer or the like, and preferably has a high magnetic permeability such as a silicon steel sheet laminated iron core. As the winding 18 of the coil 14, an ordinary single conductive wire having a fusion layer and an insulating layer on the surface is used.

As shown in FIG. 3, both ends of the fixing roller 12 are fitted with stepped cylindrical sleeves 20 and penetrate through mounting holes 22 provided in a metal support frame 21. The core 17 also passes through the support frame 21.
A bearing 23 is arranged between the sleeve 20 and the mounting hole 22. Further, a fixing ring 24 for regulating the axial position of the fixing roller 12 is fitted into a ring groove 25 formed at an end of the fixing roller 12. The cylindrical sleeve 20, the support frame 21, the bearing 23, and the fixing ring 24 form a roller support structure 26 that rotatably supports the fixing roller 12. In addition,
The fixing roller 12 has a driving gear (not shown) fixed to one end thereof, and is rotatably driven by a driving source (not shown) such as a motor connected to the driving gear.

On the other hand, both ends of the pressure roller 13 pass through through holes provided in the support frame 21 and are rotatably held via bearings (not shown). The halogen lamp 28 incorporated in the pressure roller 13 is attached to the support frame 21 via a holding plate 29.

In the fixing operation, first, an alternating current of about 50 to 60 Hz is applied to the coil 14 from a power supply circuit (not shown), and the temperature of the fixing roller 12 is adjusted to a temperature suitable for fixing by induction heating (for example, 150 to 200 ° C.). ) Until heated. Sheet 10 holding unfixed toner 11
Is conveyed from the left as shown by the arrow b in FIG. 2 and is sent to a nip 19 which is a contact portion between the fixing roller 12 and the pressure roller 13. The sheet 10 is conveyed while being nipped by the nip 19 while the heat of the heated fixing roller 12 and the pressure roller 13 and the pressure applied from the pressure roller 13 are applied. As a result, the unfixed toner 11 is fixed on the sheet 10, and a fixed toner image is formed on the sheet 10. The toner 11 is applied to the sheet 10
Are held on the side that comes into contact with the fixing roller 12. The sheet 10 that has passed through the nip 19 is naturally separated from the fixing roller 12 by a curvature according to the strength of the sheet itself, and is conveyed rightward in FIG. The sheet 10 is conveyed by a discharge roller and discharged onto a discharge tray 129.

In particular, in this embodiment, as shown in FIG. 4, the roller support structure 26 is provided with a blocking means 36 for preventing the magnetic loop 35 from being formed via the core 17.

More specifically, a cut portion 37 is provided at a part of the upper end of the support frame 21 so that an air gap 38 is formed. Further, the roller support structure 26
The bearing 23 and the fixing ring 24 are formed of a heat-resistant insulating material instead of a conventional metal one, and are used as insulating members. Examples of the heat-resistant insulating material include a polyimide resin. Also, ceramic bearings and the like can be used. The cylindrical sleeve 20 is, as in the prior art,
A material formed from a heat-resistant insulating material is used. In the present embodiment, the air gap 38 formed in the roller support structure 26 and the insulating members (the cylindrical sleeve 20, the bearing 2
3. The blocking means 36 is composed of the fixing ring 24).

The basic operation principle of the induction heating fixing device constructed as described above is the same as that of the transformer.
Reference numeral 4 corresponds to an input-side primary coil (N turns), and the fixing roller 12 corresponds to an output-side secondary coil (one turn). The primary side coil (coil 14) has 50 to 60
When an AC voltage V1 of about Hz is applied, a current I1 flows through the primary coil. The generated magnetic flux φ flows through the core 17 forming a closed magnetic path, and the magnetic flux φ generates an induced electromotive force V2 in the secondary coil (fixing roller 12). Flows. Since the closed magnetic path is formed by the core 17, there is no leakage magnetic flux in principle, and the primary energy V1 × I1 and the secondary energy V2 × I2 are substantially equal.

The first part of the system in which the induction heating is performed is as follows. First, heat generation of the coil due to copper loss in the copper wire of the primary coil, that is, heat of the coil 14, and second,
Heat generation of the coil due to copper loss in the copper wire of the secondary coil, that is, heat generation of the fixing roller 12, and thirdly, Joule heat loss generated inside the core and heat generation of the core 17 due to hysteresis loss. In the induction heating fixing device, the first and third heats are energy losses, so that these heats are suppressed as much as possible, while the second copper loss is used to heat the fixing roller 12. It is.

Here, in the fixing device 128 of the present embodiment, the air gap 38 and the insulating member (the cylindrical sleeve 20,
Since the blocking means 36 including the bearing 23 and the fixing ring 24) is provided on the roller support structure 26, there is no possibility that the magnetic loop 35 is formed on the roller support structure 26. Therefore, wasteful consumption of electric power in the roller support structure 26 is prevented, only the fixing roller 12 can be stably induced to generate heat, and power saving in the fixing device can be achieved.

If an insulator is embedded in the air gap 38, the formation of the magnetic loop 35 can be more reliably prevented.

FIGS. 5A and 5B are a perspective view and a sectional view showing a main part according to another embodiment of the present invention.

As shown in FIG. 5B, the cutting portion 37 described above cannot be provided on the metal supporting frame 42 from the viewpoint of strength, and further, in consideration of the ease of assembling the fixing roller 12, Support frame 42 is made of metal upper frame 4
It is conceivable to divide the frame into 0 and the lower metal frame 41. In such a configuration, the upper and lower frames 4
If the 0 and 41 are simply joined via the metal screw 43, the magnetic loop 35 is formed in the portion of the support frame 42 as shown by the phantom line, and the power is wasted by the support frame 42. That leads to the problem.

Therefore, in this embodiment, the joining structure of the upper and lower frames 40 and 41 is configured as shown in FIG. That is, a film 44 made of a heat-resistant insulating material is interposed between the upper frame 40 and the lower frame 41 that overlap. Further, a collar 46 made of a heat-resistant insulating material is inserted into a mounting hole 45 formed in the lower frame 41, and a metal screw 43 inserted into a center hole 47 of the collar 46 is fastened to a mounting hole 48 formed in the upper frame 40. It is. Examples of the heat-resistant insulating material include a polyimide resin. In the present embodiment, the roller support structure 26
The blocking means 36 is constituted by the insulating members (the film 44 and the collar 46) arranged in the above.

By joining the upper and lower frames 40 and 41 in this manner, the metal members do not come into contact with each other, and the magnetic loop 35 is not formed on the upper and lower frames 40 and 41. Therefore, similarly to the above-described embodiment, the power is prevented from being wastefully consumed in the support frame 42, and only the fixing roller 12 can be stably induced to generate heat, thereby achieving power saving in the fixing device. can do.

[0040]

As described above, according to the induction heating fixing apparatus of the present invention, since the support means for rotatably supporting the heating rotator through which the core penetrates is provided with the shut-off means, the support structure has a magnetic structure. There is no danger of forming a loop, power is prevented from being wastefully consumed in the support structure, only the heating rotator can be stably induced to generate heat, and power saving in the fixing device can be achieved. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a copying machine as an image forming apparatus incorporating an induction heating fixing device according to the present invention.

FIG. 2 is a sectional view schematically showing a main part of the induction heating fixing device shown in FIG.

FIG. 3 is a sectional view schematically showing a supporting structure of a fixing roller.

FIG. 4 is a side view schematically showing a support structure of a fixing roller.

FIGS. 5A and 5B are a perspective view and a sectional view showing a main part according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Sheet (recording medium) 11 ... Toner 12 ... Fixing roller (heating rotating body) 13 ... Pressure roller (pressure rotating body) 14 ... Coil 17 ... Core 20 ... Cylindrical sleeve (support structure, insulating member) 21 , 42: Support frame (support structure) 23: Bearing (support structure, insulating member) 24: Fixing ring (support structure, insulating member) 26: Support structure 35: Magnetic loop 36: Breaking means 37: cutting part 38 air gap 44 film (insulating member) 46 collar (insulating member)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryo Takasu, Inventor Ryo Takashi, 2-3-3 Azuchicho, Chuo-ku, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Kenichi Watanabe 2-3-3, Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Toru Tomura 40 Nishino Rikyucho, Yamashina-ku, Kyoto Tokuden Corporation

Claims (3)

[Claims] 1. A heating rotator having a hollow cylindrical shape formed of a conductive member, and a pressing rotator pressed against the heating rotator and holding a recording medium holding toner between the heating rotator and the heating rotator. A core partly inserted into a hollow portion of the heating rotator to form a closed magnetic circuit; and a core wound around the core and disposed in the hollow portion of the heating rotator to induction-heat the heating rotator. An induction heating fixing device comprising: a support structure rotatably supporting the heating rotator; and a blocking means for preventing a magnetic loop from being formed via the core. Induction heating fixing device. 2. The induction heating fixing device according to claim 1, wherein said blocking means comprises an air gap formed in said support structure. 3. The induction heating fixing device according to claim 1, wherein the blocking unit is formed of an insulating member disposed on the support structure.