JP2000214703A - Induction heating fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device capable of efficiently heating a conductive hollow rotating body while restraining the increase of attaching space or weight by forming the part of a core passing through the hollow part of the rotating body in a shape wider than other part of the core. SOLUTION: The part of the core 16 passing through the hollow part 14a of a fixing belt 14 is formed in the shape wider than other part. Namely, the shape of the cross section of the part of the core 16 passing through the hollow part 14a is formed to be extended in a direction where the belt 14 travels. Meanwhile, the part crossing and passing through the outside of the belt 14 is formed to be smaller or thinner than the part passing through the hollow part 14a. The part of the core 16 passing through the hollow part 14a is formed in the wider shape and arranged so that the surface of the core may come as close as possible to the inner surface of the belt 14. Thus, a distance to the belt 14 from the surface of the core passing through the hollow part 14a is made short. Therefore, magnetic flux effectively creeps to the belt 14, so that power factor is made high and the belt 14 is sufficiently exothermic Therefore, there is no such possibility that a faulty fixation is caused.

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 in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, and more particularly, to an unfixed sheet on a sheet by utilizing low-frequency induction heating. The present invention relates to an induction heating fixing device that fuses and fixes toner.

[0002]

2. Description of the Related Art As a fixing device utilizing induction heating, there is a belt-type induction heating fixing device using a fixing belt formed of a conductive material as a heating rotator heated by induction heating. A conventional belt-type induction heating fixing device includes a first roller, a second roller provided in parallel with the first roller, an endless fixing belt stretched over the first roller and the second roller, A third roller disposed so as to contact the first roller via a fixing belt, a core partially closed through a hollow portion of the fixing belt to form a closed magnetic path, and a core wound around the core to link with the core. And a coil for generating a magnetic flux that generates an induced current along the circumferential direction in the fixing belt. Then, heat and pressure are applied to the unfixed toner held on the sheet in the nip portion between the third roller and the fixing belt heated by the induced current to melt the toner and fix it on the sheet.

Here, in a conventional belt-type induction heating fixing device, the cross section of a core forming a closed magnetic circuit is constant in both width and height (for example, Japanese Patent Application Laid-Open No. 10-2072).
No. 65).

[0004]

The fixing belt is stretched between a pair of rollers and has a substantially elliptical shape, while the cross-sectional shape of the core is kept constant. For this reason, when the lateral dimension along the direction in which the fixing belt travels is relatively short of the core cross-sectional dimensions, there is a large difference in the distance from the core surface passing through the hollow portion to the fixing belt depending on the location. Variations occur in the wraparound of the magnetic flux to the belt. The power factor decreases at the part where the wraparound of the magnetic flux is insufficient,
There is a problem in that the fixing belt cannot be sufficiently heated, resulting in poor fixing.

[0005] Here, the entire core is extended in the lateral direction,
It is conceivable that the distance between the core surface and the fixing belt is reduced. However, such a configuration is not suitable for mounting on an actual machine because the entire core becomes larger and the weight increases significantly.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the prior art, and has as its object to efficiently heat a conductive hollow rotating body while suppressing an increase in mounting space and weight. An induction heating fixing device is provided.

[0007]

The above object is achieved by the following means. (1) a heating rotator having a hollow shape made of a conductive material, a pressing rotator pressing the heating rotator and holding a sheet holding toner between the heating rotator; A core partly inserted into the hollow part of the rotating body to form a closed magnetic circuit, and the heating rotary body disposed in the hollow part of the heating rotating body while being wound around a part of the core and inductively heating the heating rotating body And an induction heating fixing device having:
An induction heating fixing device, wherein a portion of the core that passes through the hollow portion of the heating rotator is formed wider than other portions. (2) The heating rotator comprises a belt member.

[0008]

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

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

As shown in the figure, a 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. The printer includes a printer unit 103 that prints out on the sheet 10 and a casing 104 that arranges or stores 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 by the original forms an image on a line sensor (CCD) 110 via mirrors 108a, 108b, 108c and a condenser lens 109, is converted into image information, and is converted into a signal. Processing unit 10
Sent to 2. By driving the scanner motor 111, the first slider 112 is driven at a speed V and the second slider 113 is driven at V / 2 in a direction perpendicular to the electrical scanning direction (main scanning direction) of the line sensor (sub scanning direction). ) To mechanically scan the original surface.

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, and a return mirror. 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 sheets 10 in the sheet No. 5 are 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 130. The fixing device 1 according to the present embodiment
Reference numeral 28 denotes a low-frequency induction heating system, the configuration of which 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 by laser light, 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 showing the belt-type induction heating fixing device shown in FIG. 1, and FIG. 3 is a perspective view showing a main part of the identification attaching device.

The induction heating fixing device 128 heats and melts the toner 11 held on the sheet 10 to melt the toner.
A belt type in which a hollow heating rotator made of a conductive material is formed of a belt member is illustrated.

The fixing device 128 includes a first roller 12
A second roller 13 provided in parallel with the first roller 12, an endless fixing belt 14 stretched between the first roller 12 and the second roller 13, and a fixing belt 14 A pressure roller (corresponding to a pressure rotator) 15 for closely adhering the sheet 10 holding the toner, which is disposed to be in contact with the fixing belt 14 with the fixing belt 14, and a fixing belt 14
The core 16 is partially inserted into the hollow portion 14a to form a closed magnetic circuit, and is disposed in the hollow portion 14a of the fixing belt 14 while being wound around a part of the core 16 to heat the fixing belt 14 by induction. And a coil 17.

The first roller 12 has a driving gear (not shown) fixed to one end thereof, and is provided so as to be rotatable in the direction of arrow a by a driving source such as a motor (not shown) connected to the driving gear. With the driving of the first roller 12,
The fixing belt 14 travels in the direction of arrow b, and the second roller 13
And the pressure roller 15 is driven and rotated. The pressure roller 15 includes a shaft core 18 and a silicone rubber layer 19 formed around the shaft core 18. The silicone rubber layer is a rubber layer that has releasability from which the sheet 10 easily separates from the surface and also has heat resistance. The pressure roller 15 is constantly urged in a direction toward the first roller 12 by a spring material (not shown).

The fixing belt 14 is a thin, preferably seamless belt, and has a belt base made of a conductive material such as carbon steel or stainless steel. On the surface of this belt substrate, a heat-resistant release layer coated with silicone rubber and having good release properties and heat resistance to the toner is formed.

The core 16 is a so-called iron core used for an ordinary transformer or the like. For example, a core having a high magnetic permeability such as a silicon steel sheet laminated iron core is preferable. The coil 17
The winding is formed by winding the winding so as to interlink with the core 16, and generates a magnetic flux that generates an induced current in the fixing belt 14 along the circumferential direction. For the winding of the coil 17, an ordinary single conductor having a fusion layer and an insulating layer on the surface is used. Note that a heat insulating layer 20 is provided in the coil 17 so that heat generated in the fixing belt 14 and the coil 17 is not transmitted to the core 16.

In particular, in the first embodiment, as shown in FIGS. 2 and 3, a portion of the core 16 that passes through the hollow portion 14a of the fixing belt 14 is formed to be wider than other portions. I have. That is, the hollow portion 14 of the core 16
The cross-sectional shape of the portion passing through the fixing belt 14 is formed so as to extend along the traveling direction of the fixing belt 14, while the portion passing across the outside of the fixing belt 14 is not smaller than the portion passing through the hollow portion 14 a. It is formed thin. The portion passing through the hollow portion 14a is formed in a wide shape, and the core surface is arranged so as to be as close to the inner surface of the fixing belt 14 as possible.

In the fixing operation, first, an alternating current of about 50 to 60 Hz is applied to the coil 17 from a power supply (not shown), and the temperature of the fixing belt 14 is adjusted to a temperature suitable for fixing (for example, 150 to 200) by low-frequency induction heating. (° C). Sheet 1 holding unfixed toner 11
0 is conveyed from the left as shown by the arrow c in FIG.
The toner is fed toward a nip 21 which is a contact portion between the fixing belt 14 and the pressure roller 15. The sheet 10 is conveyed while being nipped by the nip 21 while the heated heat of the fixing belt 14 and the pressure applied from the pressure roller 15 are applied. In this process, the unfixed toner 11 is fixed on the sheet 10. The toner 11 is held on the side of the sheet 10 that contacts the fixing belt 14. The sheet 10 that has passed through the nip portion 21 is naturally separated from the fixing belt 14 by the strength of the sheet itself and is conveyed rightward in FIG. Then, the sheet 10 is conveyed by a discharge roller (not shown),
Is discharged on top.

Here, in the fixing device 128 of this embodiment, as described above, the cross-sectional shape of the core 16 is such that the portion passing through the hollow portion 14a is wider than other portions as shown in FIG. As a result, the distance from the core surface passing through the hollow portion 14a to the fixing belt 14 is reduced as compared with the conventional belt-type induction heating fixing device in which the cross-sectional shape of the core 16 is kept constant. Further, the difference or variation in the distance at each location is reduced as much as possible. Therefore,
Since the magnetic flux effectively wraps around the fixing belt 14, the power factor increases, and the fixing belt 14 generates sufficient heat, so that there is no possibility of causing a fixing defect.

Further, the fixing belt 14 in the core 16
Since the portion passing through the outside of the core 16 is formed smaller or thinner than the portion passing through the hollow portion 14a, an increase in mounting space and weight of the core 16 can be suppressed as much as possible. Further, the outer dimensions of the fixing device 128 itself can be kept to a minimum, so that there is no possibility that the size of the image forming apparatus in which the fixing device is incorporated is increased.

Embodiment 2 FIG. 4 is a cross-sectional view showing a roller-type induction heating fixing device according to Embodiment 2.
In the second embodiment, the fixing roller 30 is used as a heating rotator.
Is different from the first embodiment in which the fixing belt 14 is used.

The roller-type induction heating fixing device 128a is
Fixing roller 30 rotatably provided in the direction of arrow d
And a pressure roller 15 that is provided in pressure contact with the fixing roller 30 and that rotates following the rotation of the fixing roller 30.

The fixing roller 30 includes a cylindrical hollow pipe 31 formed of a conductive material such as a carbon steel pipe, a stainless alloy pipe, or an aluminum pipe. The thickness is within a range that can secure the mechanical strength and a thickness that can secure a certain heat capacity. Further, on the outer peripheral surface of the pipe 31, a release layer 32 having good release properties and heat resistance with respect to the toner is formed by coating a fluororesin in order to easily separate the sheet 10. I have. The fixing roller 30
A drive gear (not shown) is fixed to one end, and is driven to rotate by a drive source (not shown) such as a motor connected to the drive gear. The pressure roller 15 is formed in the same manner as in the first embodiment.

This roller-type induction heating fixing device 128a
The hollow portion 3 of the fixing roller 30 of the core 16
The portion passing through Oa is formed wider than other portions. Therefore, similarly to the first embodiment, the hollow portion 30a
As a result, the distance from the core surface passing through the fixing roller 30 to the fixing roller 30 is narrowed, so that the magnetic flux effectively flows around the fixing roller 30 and the fixing roller 30 generates sufficient heat, so that there is no possibility of causing a fixing defect. Moreover, since the portion of the core 16 that passes outside the fixing roller 30 is formed smaller than the portion that passes through the hollow portion 30a, an increase in the mounting space and weight of the core 16 is suppressed, and the outer dimensions of the fixing device 128a itself are reduced. Can be kept to a minimum.

[0030]

According to the present invention described above, the following effects can be obtained for each claim.

According to the induction heating fixing device of the present invention, the portion of the core passing through the hollow portion of the rotating body is formed wider than the other portions, so that the mounting space and weight are increased. It is possible to provide an induction heating fixing device that can efficiently heat the conductive hollow rotating body while suppressing it.

According to the present invention, the conductive belt can be efficiently heated without increasing the size of the belt-type induction heating fixing device.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing a belt-type induction heating fixing device according to the first embodiment.

FIG. 3 is a perspective view showing a main part of the belt-type induction heating fixing device.

FIG. 4 is a sectional view showing a roller-type induction heating fixing device according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Sheet 11 ... Toner 14 ... Fixing belt (heating rotator, belt member) 14a ... Hollow part of fixing belt 15 ... Pressure roller (pressure rotator) 16 ... Core 17 ... Coil 30 ... Fixing roller (heating rotator) 30a: hollow portion of fixing roller 128: belt-type induction heating fixing device 128a: roller-type induction heating fixing device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Ryo Takasu, Inventor F-term (reference) 2H033 AA21 AA32 BA25 BA27 BB01 BB28 BE06 in Osaka International Building Minolta Co., Ltd. 2-3-13 Azuchicho, Chuo-ku, Osaka-shi

Claims (2)

[Claims] A heating rotator having a hollow shape formed of a conductive material; a pressure rotator pressed against the heating rotator to sandwich a sheet holding toner between the heating rotator; A core partly inserted into the hollow part of the heating rotator to form a closed magnetic circuit, and the heating rotator disposed in the hollow part of the heating rotator while being wound around a part of the core. An induction heating fixing device having an induction heating coil, wherein a portion of the core passing through the hollow portion of the heating rotator is formed wider than other portions. apparatus. 2. The induction heating fixing device according to claim 1, wherein the heating rotator includes a belt member.