JP2006309073A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

To provide a fixing device and an image forming apparatus capable of stably maintaining a state of high thermal efficiency.
A fixing device 19 includes a fixing roller 21 and a pressure roller pressed against the fixing roller 21, and a recording medium carrying an unfixed image passes between the fixing roller 21 and the pressure roller. By doing so, the unfixed image is fixed on the recording medium. The fixing roller 21 is provided between a roller main body 210 having at least an outer peripheral insulating property, an elastic layer 214 provided on the outer peripheral side of the roller main body 210, and between the roller main body 210 and the elastic layer 214, and generates heat when energized. Heating layer 213.
[Selection] Figure 6

Description

  The present invention relates to a fixing device and an image forming apparatus.

In an image forming apparatus such as a printer, a copy, or a facsimile, a recording paper (recording medium) carrying a toner image formed with toner in an unfixed state is heated and pressed to fix the toner image on the recording paper. Some are equipped with a fixing device.
Conventionally, as such a fixing device, a sheet on which a toner image has been transferred is passed through a nip portion of a pair of rollers including a fixing roller having a heating unit and a pressure roller, and a fixing roller (heating unit). 2. Description of the Related Art Fixing devices that fuse a toner image to a sheet by heating with a pressure and pressing with two rollers are widely used.

As a heating means, there is one configured to be heated by a halogen heater (see, for example, Patent Document 1 (FIG. 5)). As another heating means, there is one configured to generate an eddy current in a toner image by a high-frequency magnetic field generated from an exciting coil and generate heat in the toner image itself (for example, Patent Documents). 2).
However, since the heating means described in FIG. 5 of Patent Document 1 is installed at substantially the same position as the rotation shaft of the fixing roller and heats the roller body using air as a medium, heat loss occurs. There was a problem of low thermal efficiency. In addition, this heating means has a problem that quick heating cannot be performed and a problem that power consumption is high because more visible light that does not contribute to heating is irradiated than infrared rays effective for heating.
In addition, the heating means described in Patent Document 2 enables quick heat and further reduces power consumption, but the exciting coil itself is also heated, and the temperature of the toner image becomes unstable. There was a problem that the thermal efficiency became unstable.

JP 2002-351239 A Japanese Patent Laid-Open No. 2003-5577

  An object of the present invention is to provide a fixing device and an image forming apparatus that can stably maintain a state of high thermal efficiency.

Such an object is achieved by the present invention described below.
The fixing device of the present invention includes a fixing roller and a pressure roller pressed against the fixing roller, and allows a recording medium carrying an unfixed image to pass between the fixing roller and the pressure roller. A fixing device for fixing the unfixed image on the recording medium,
The fixing roller is
A roller body having at least an outer periphery having an insulating property;
An elastic layer provided on the outer peripheral side of the roller body;
A heating layer is provided between the roller body and the elastic layer and generates heat when energized.
Accordingly, it is possible to provide a fixing device that can stably maintain a state of high thermal efficiency.

In the fixing device of the present invention, it is preferable that both ends of the heat generating layer in the rotation axis direction are provided with electrode portions for energizing the heat generating layer, respectively.
Thereby, it is possible to reliably energize the heat generating layer regardless of whether or not the fixing roller is rotating.
In the fixing device according to the aspect of the invention, it is preferable that the electrode unit includes a brush electrode.
Thereby, it is possible to reliably energize the heat generating layer regardless of whether or not the fixing roller is rotating.

In the fixing device of the present invention, it is preferable that the heat generating layer has a self-temperature adjusting function.
Thus, for example, temperature adjustment can be performed without using a temperature control device such as a thermostat.
In the fixing device of the present invention, it is preferable that the heat generating layer is composed mainly of indium tin oxide.
Thus, for example, temperature adjustment can be performed without using a temperature control device such as a thermostat.

In the fixing device according to the aspect of the invention, it is preferable that the thickness of the heat generating layer is 0.01 to 3.0 μm.
When the thickness is thinner (smaller) than the lower limit value, it is difficult to form a uniform film, which may cause film defects. Further, when the thickness is thicker (larger) than the upper limit value, there is a possibility that cracking may occur due to thermal cycling.

In the fixing device of the present invention, the outer surface of the elastic layer is preferably covered with a resin layer made of a resin material.
Thereby, it is possible to prevent an unfixed image from adhering to the fixing roller (resin layer).
In the fixing device of the present invention, the resin material is preferably a fluorine-based one.
Thereby, it is possible to prevent an unfixed image from adhering to the fixing roller (resin layer).
The image forming apparatus of the present invention includes the fixing device of the present invention.
Accordingly, it is possible to provide an image forming apparatus that can stably maintain a state of high thermal efficiency.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a fixing device and an image forming apparatus according to the invention will be described with reference to the accompanying drawings.
[Image forming apparatus]
First, the configuration of the image forming apparatus of the present invention will be described.
FIG. 1 is an overall configuration diagram of an image forming apparatus of the present invention provided with a fixing device of the present invention.

  In the apparatus main body 2 of the image forming apparatus 1, an image carrier 3 composed of a photosensitive drum is disposed. The image carrier 3 is rotationally driven in the direction of the arrow shown by a driving unit (not shown). Around the image carrier 3, a charging device 4 for uniformly charging the image carrier 3 along its rotation direction, and an exposure device for forming an electrostatic latent image on the image carrier 3 5, a rotary developing device 6 for developing an electrostatic latent image, and an intermediate transfer device 7 for primary transfer of a monochromatic toner image formed on the image carrier 3.

  In the rotary developing device 6, a yellow developing device 6Y, a magenta developing device 6M, a cyan developing device 6C, and a black developing device 6K are mounted on a support frame 8, and the support frame 8 is rotationally driven by a drive motor (not shown). It is configured. The plurality of developing devices 6Y, 6C, 6M, and 6K are selectively rotated so that the developing roller 6a of one developing device faces the image carrier 3 every rotation of the image carrier 3. Has been. Each of the developing devices 6Y, 6C, 6M, and 6K has a toner storage portion that stores toner of each color.

The intermediate transfer device 7 is disposed so as to face the image carrier 3 on the back surface of the intermediate transfer belt 11, the driving roller 9 and the driven roller 10, the intermediate transfer belt 11 driven in the direction of the arrow by the two rollers. A primary transfer roller 12, a transfer belt cleaner 13 for removing residual toner on the intermediate transfer belt 11, and a drive roller 9 are arranged to face the four-color full-color image formed on the intermediate transfer belt 11 as a recording medium ( And a secondary transfer roller 14 for transferring onto paper or the like.
A paper feeding cassette 15 is disposed at the bottom of the apparatus main body 2, and a recording medium in the paper feeding cassette 15 passes through a pickup roller 16, a recording medium conveyance path 17, a secondary transfer roller 14, and a fixing device 19. It is comprised so that it may be conveyed to 20.

Next, the operation of the image forming apparatus configured as described above will be described.
When an image forming signal is input from a computer (not shown), the image carrier 3, the developing roller 6 a of the developing device 6 and the intermediate transfer belt 11 are rotationally driven. First, the outer peripheral surface of the image carrier 3 is charged by the charging device 4. The exposure device 5 selectively exposes the outer peripheral surface of the uniformly charged image carrier 3 according to the image information of the first color (for example, yellow) so that the electrostatic latent image of yellow An image is formed.

  At the position of the latent image formed on the image carrier 3, the yellow developing device 6 </ b> Y rotates and the developing roller 6 a comes into contact therewith, whereby the yellow electrostatic latent image toner image is formed on the image carrier 3. Next, the toner image formed on the image carrier 3 is transferred onto the intermediate transfer belt 11 by the primary transfer roller 12. At this time, the secondary transfer roller 14 is separated from the intermediate transfer belt 11.

  In accordance with the second color, the third color, and the fourth color of the image formation signal, the above processing is repeated to form a latent image, develop, and transfer by one rotation of the image carrier 3 and the intermediate transfer belt 11, thereby forming an image. Four color toner images corresponding to the contents of the signals are superimposed and transferred on the intermediate transfer belt 11. Then, at the timing when this full-color image reaches the secondary transfer roller 14, the recording medium is supplied from the conveyance path 17 to the secondary transfer roller 14, and at this time, the secondary transfer roller 14 is pressed against the intermediate transfer belt 11. A secondary transfer voltage is applied, and the full color toner image (unfixed image) on the intermediate transfer belt 11 is transferred onto the recording medium. Then, the recording medium carrying the toner image is passed between the fixing roller 21 and the pressure roller 22, that is, through the fixing device 19, so that the toner image is heated and pressed and fixed on the recording medium. The toner remaining on the intermediate transfer belt 11 is removed by the transfer belt cleaner 13.

In the case of double-sided printing, the recording medium exiting the fixing device 19 is switched back so that the trailing edge is the leading edge, and is supplied to the secondary transfer roller 14 via the double-sided printing conveyance path 23, and the intermediate medium. The full color toner image on the transfer belt 11 is transferred onto the recording medium, and is again heated and pressed by the fixing device 19 to be fixed.
The fixing device 19 includes a fixing roller 21 having a heat source and a pressure roller 22 pressed against the fixing roller 21, and a line connecting the axes of the fixing roller 21 and the pressure roller 22 has an angle θ from a horizontal line. Has been. Note that 0 ° ≦ θ ≦ 30 °.

[Fixing device]
Hereinafter, the fixing device of the present invention will be described in detail.
2 to 4 show details of the fixing device 19 of FIG. 1, FIG. 2 is a perspective view showing a partially broken section of the fixing device of the present invention, and FIG. 3 is a plan view of the fixing device of FIG. 4 is a side view showing a mounting state of the pressure roller and the fixing roller shown in FIG. 2, FIG. 5 is a sectional view of the pressure roller shown in FIG. 2, and FIG. FIG. 3 is a cross-sectional view of the fixing roller shown in FIG.

  2 and 3, the fixing roller 21 is rotatably mounted in the housing 24, and a driving gear 28 is connected to one end of the fixing roller 21. A pressure roller 22 is rotatably mounted facing the fixing roller 21. The axial length of the pressure roller 22 is shorter than that of the fixing roller 21, and a bearing 25 is provided in the empty space, and both ends of the pressure roller 22 are supported by the bearing 25. A pressure lever 26 is rotatably provided on the bearing 25, and a pressure spring 27 is disposed between one end of the pressure lever 26 and the housing 24, whereby the pressure roller 22 and the fixing roller 21 are pressurized. It is configured to be.

  Support shafts 29 and 30 are provided on both side surfaces of the housing 24, and a peeling member 31 on the fixing roller 21 side and a peeling member 32 on the pressure roller 22 side rotate on the support shafts 29 and 30, respectively. Mounted freely. As a result, the peeling members 31 and 32 are disposed downstream of the nip portion N (see FIG. 4) in the recording medium conveyance direction in the axial direction between the fixing roller 21 and the pressure roller 22.

As shown in FIG. 5, the pressure roller 22 includes a metal cylinder 221, a rotation shaft 222 fixed to the cylinder 221, a bearing 25 that supports the rotation shaft 222, and an outer periphery of the cylinder 221. It has an elastic layer 223 made of silicon rubber or the like and a surface layer 224 covered on the surface of the elastic layer 223.
The surface layer 224 is made of, for example, fluorine rubber, fluorine resin (for example, pertetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA)), or the like. By providing the surface layer 224 made of such a material, it is possible to prevent toner from adhering to the pressure roller 22 (surface layer 224).
In addition, the rotating shaft 222 is not limited to being configured by a hollow body as illustrated, and may be configured by a solid body.

  As shown in FIG. 6, the fixing roller 21 includes a roller main body 210, a heat generating layer (planar heater) 213 provided on the outer peripheral surface (surface) of the roller main body 210 (insulating layer 212), and an outer periphery of the heat generating layer 213. It has an elastic layer 214 provided on the surface, a surface layer 215 covering the outer peripheral surface of the elastic layer 214, and a rotating shaft 216 fixed to the roller body 210 (cylinder 211), and these rotate integrally.

The roller main body 210 includes a metal cylinder 211 and an insulating layer 212 provided along (along) the entire outer periphery of the cylinder 211.
The insulating layer 212 can be made of, for example, a heat resistant resin such as polyimide, SiO ₂ or the like. The thickness of the insulating layer 212 is not particularly limited, but is preferably 1.0 to 100 μm, and more preferably 30 to 50 μm, for example.

The heat generating layer 213 is formed over the entire circumference of the surface of the insulating layer 212. The heat generating layer 213 can generate heat when energized.
The main material constituting the heat generating layer 213 is not particularly limited. For example, indium tin oxide (ITO), carbon-based material, barium titanate-based ceramic (BaTiO ₃ ), Fe—Cr—Al alloy, Ni—Cr alloy Etc.

Among the materials described above, materials having a self-temperature adjusting function (PTC) such as ITO, carbon-based material, BaTiO _{3 and the} like are preferable. By using a material having a self-temperature adjusting function, the temperature can be adjusted without using a temperature control device such as a thermostat. Further, the temperature control device can be omitted, so that the fixing device 19 can be reduced in size and power can be saved.

  In addition, when a voltage is applied to a material having a self-temperature adjusting function, the temperature of the material itself rises due to Joule heat, but once the temperature reaches a predetermined temperature, the electrical resistance increases rapidly, that is, the current is suppressed. The predetermined temperature can be maintained. Thus, the material having the self-temperature adjusting function is prevented from generating heat above a predetermined temperature, and is excellent in safety.

  The thickness t of the heat generation layer 213 is not particularly limited, but is preferably 0.01 to 3.0 μm, and more preferably 0.05 to 1.0 μm, for example. When the thickness t is thinner (smaller) than the lower limit value, it is difficult to form a uniform film, which may cause film defects. Further, when the thickness t is thicker (larger) than the upper limit value, there is a risk that cracks may occur due to thermal cycling. Moreover, it does not specifically limit as a formation method of the heat generating layer 213, For example, a spray pyrolysis method, sputtering, dipping method etc. can be used.

In addition, brush electrodes 217 as electrode portions for energizing the heat generating layer 213 are provided at both ends in the rotation axis direction of the heat generating layer 213 (see FIG. 3). Accordingly, the heat generation layer 213 can be reliably energized regardless of whether the fixing roller 21 is rotating.
As shown in FIG. 6, the elastic layer 214 is formed over the entire circumference of the surface of the heat generating layer 213.

  The constituent material of the elastic layer 214 is not particularly limited. For example, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, acrylic rubber, ethylene-propylene rubber, hydrin rubber, urethane rubber , Various rubber materials such as silicone rubber and fluoro rubber (especially those vulcanized), styrene, polyolefin, polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene, trans polyisoprene, Various thermoplastic elastomers such as fluororubber-based and chlorinated polyethylene are listed, and one or more of these can be used in combination.

The thickness of the elastic layer 214 is preferably smaller than the thickness of the elastic layer 223 of the pressure roller 22. As a result, as shown in FIG. 4, a nip portion N having a concave shape on the pressure roller 22 side can be reliably formed.
Further, the thickness of the elastic layer 214 is not particularly limited, but is preferably, for example, 0.1 to 3 mm, and more preferably 0.5 to 1.5 mm.

The surface (outer surface) of the elastic layer 214 is covered with a surface layer (resin layer) 215 formed along the entire circumference.
The surface layer 215 is made of a resin material, and the material is not particularly limited. For example, fluorine-based materials (for example, pertetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) (PFA)) and the like. Thereby, it is possible to prevent the toner from adhering to the fixing roller 21 (surface layer 215).

In addition, it does not specifically limit as thickness of the surface layer 215, For example, it is preferable that it is 1-100 micrometers, and it is more preferable that it is 30-80 micrometers.
As described above, in the fixing device 19, since the heat generating layer 213 is positioned in the vicinity of the outermost surface of the fixing roller 21, the heat from the heat generating layer 213 is reliably transmitted to the recording medium without reducing the thermal efficiency. That is, it is possible to stably maintain a state of high thermal efficiency.

Further, in the fixing device 19, since the heat generating layer 213 is located in the vicinity of the outermost surface of the fixing roller 21, the surface can be heated quickly, that is, quick heating is possible. In the fixing device 19, when printing on a single sheet of paper (recording medium), the time from the start of printing to the end of printing can usually be 15 seconds.
In addition, since the overall shape of the heat generating layer 213 is cylindrical, it is possible to prevent temperature unevenness on the outermost surface of the fixing roller 21, that is, to make the temperature distribution uniform. Thereby, an unfixed image can be stably fixed on the recording medium, that is, the print quality can be improved.

Further, in the fixing device 19, power consumption can be suppressed as compared with a conventional case where a halogen heater is used as a heat source (heating means). In the fixing device 19, the power consumption can usually be about 200 to 300 W.
Even when a small sheet such as a postcard passes through the fixing device 19, the end of the fixing roller 21 in the central axis direction is formed because the heat generation layer 213 is made of a material having a self-temperature control function. The part is prevented from being heated excessively. As a result, the standby time by adjusting the temperature of the fixing roller 21 can be omitted, so that continuous paper feeding (continuous printing) can be performed.

The roller main body 210 is not limited to the one formed of the metal cylinder 211 and the insulating layer 212, and may be formed of an insulating material as a whole, for example.
Moreover, as shown in the drawing, the rotating shaft 216 is not limited to being configured by a hollow body, but may be configured by a solid body.
Further, the electrode portion of the heat generating layer 213 is not limited to being configured by the brush electrode 217, and may be configured by, for example, a bearing electrode or a roller electrode. For example, the bearing electrode tends to be more durable than the brush electrode 217.
As described above, the fixing device and the image forming apparatus of the present invention have been described with respect to the illustrated embodiment. However, the present invention is not limited to this, and each unit constituting the fixing device and the image forming apparatus has the same function. It can be replaced with any configuration that can be exhibited. Moreover, arbitrary components may be added.

1 is an overall configuration diagram of an image forming apparatus of the present invention including a fixing device of the present invention. FIG. 3 is a perspective view showing a partially broken section of the fixing device of the present invention. FIG. 3 is a plan view of the fixing device in FIG. 2. It is a side view which shows the attachment state of the pressure roller and fixing roller shown in FIG. FIG. 3 is a cross-sectional view of the pressure roller shown in FIG. 2. FIG. 3 is a cross-sectional view of the fixing roller shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Main body 3 ... Image carrier 4 ... Charging device 5 ... Exposure device 6 ... Rotary developing device 6Y ... Yellow developing device 6M ... Magenta developing device 6C ... Cyan developing device 6K: Black developing device 6a: Developing roller 7 ... Intermediate transfer device 8 ... Support frame 9 ... Driving roller 10 ... Driven roller 11 ... Intermediate transfer belt 12 ... Primary transfer roller 13 Transfer belt cleaner 14 Secondary transfer roller 15 Feed cassette 16 Pickup roller 17 Recording medium transport path 19 Fixing device 20 Discharge tray 21 Fixing roller 210 Roller Main body 211 …… Cylinder 212 …… Insulating layer 213 …… Heat generation layer (planar heater) 214 …… Elastic layer 215 …… Surface layer 216 …… Rotating shaft 217 …… Brush electricity 22 …… Pressure roller 221 …… Cylinder 222 …… Rotating shaft 223 …… Elastic layer 224 …… Surface layer 23 …… Conveying path for double-sided printing 24 …… Housing 25 …… Bearing 26 …… Pressure lever 27 …… Pressurizing spring 28 ... Drive gear 29, 30 ... Support shaft 31, 32 ... Peeling member N ... Nip part

Claims (9)

A fixing roller; and a pressure roller pressed against the fixing roller, and passing a recording medium carrying an unfixed image between the fixing roller and the pressure roller, thereby allowing the recording medium to pass through the recording medium. A fixing device for fixing an unfixed image,
The fixing roller is
A roller body having at least an outer periphery having an insulating property;
An elastic layer provided on the outer peripheral side of the roller body;
A fixing device comprising: a heat generating layer provided between the roller body and the elastic layer and generating heat when energized.   2. The fixing device according to claim 1, wherein electrode portions for energizing the heat generating layer are provided at both ends of the heat generating layer in the rotation axis direction.   The fixing device according to claim 2, wherein the electrode unit includes a brush electrode.   The fixing device according to claim 1, wherein the heat generating layer has a self-temperature adjusting function.   The fixing device according to claim 1, wherein the heat generating layer is made of indium tin oxide as a main material.   The fixing device according to claim 1, wherein the heat generating layer has a thickness of 0.01 to 3.0 μm.   The fixing device according to claim 1, wherein an outer surface of the elastic layer is covered with a resin layer made of a resin material.   The fixing device according to claim 7, wherein the resin material is a fluorine-based material.   An image forming apparatus comprising the fixing device according to claim 1.

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