JP2004333732A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with a fixing device in which warmup time is drastically reduced and hence power consumption is also reduced and fixing is improved by an increase in the width of a nip. <P>SOLUTION: The image forming apparatus is provided with a fixing device. The fixing device is provided with a hollow rotary member that is flexible and is formed into hollow in shape, a plurality of heat rollers equipped respective heating means are disposed in the hollow rotary member and rotate in contact with the internal surface of the hollow rotary member, and a pressing member that presses a plurality of heat rollers via the hollow rotary member. An unfixed image formed on a recording medium is fixed under heat and pressure by the nip formed between the hollow rotary member and the pressure member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral having these functions.
[0002]
[Prior art]
As a fixing device used in an image forming apparatus such as a copier, a printer, a facsimile, etc., a heat roller fixing device using a heating roller having a heating means therein has been conventionally used, and is technically highly complete and stable. , From monochrome machines to full-color machines and from low-speed machines to high-speed machines.
[0003]
However, in the conventional heat roller fixing device, it is necessary to heat the heat roller having a large heat capacity when heating the transfer material or the toner, so that the energy efficiency is low and the energy saving is disadvantageous. However, there is a problem in that it takes time to heat the heating roller, and the warm-up time becomes longer.
[0004]
In order to solve this problem, the transfer material is brought into close contact with the heating body through a film that moves at the same speed as the transfer speed of the transfer material, by using a pressurizing and conveying means that rotates while being opposed to and pressed against the heating body, There is a fixing device for pulse-heating unfixed toner on a transfer material. (For example, see Patent Document 1)
In addition, a thin heating roller is used to shorten the warm-up time, and a thin pressing roller is brought into contact with the heating roller, and a load applying roll is provided inside the pressing roller to follow the deflection of the heating roller. There is a fixing device in which a substantially uniform nip shape is obtained by bending the pressure rotating body. (For example, see Patent Document 2)
[0005]
[Patent Document 1]
JP-A-2-81074
[Patent Document 2]
JP-A-11-38811
[Problems to be solved by the invention]
However, in the fixing device described in Patent Document 1 described above, the transfer material is brought into close contact with the heating body via the film, and is fixed without rotating the heating body. I can't expect it. Further, it is difficult to apply the present invention to a high-speed machine in which a transfer material moves at a high speed. Also, since the film is wound on the take-up shaft from the feed shaft, after all the film has been wound on the take-up shaft, the troublesome work of having to reload the film on the feed shaft is required. I need.
[0008]
Also, in the fixing device described in Patent Document 2 described above, the warming-up time is reduced to some extent by using a thin heating roller, but the time is considerably reduced due to the heat capacity corresponding to the size of the heating roller. Cannot be expected, and since the nip width does not change, the fixing property does not change.
[0009]
The present invention has been made in view of such a problem, and by using a plurality of heating rollers, which has not existed in the past, the warming-up time can be significantly reduced, the power consumption can be reduced, and the nip width can be increased. It is an object of the present invention to provide an image forming apparatus provided with a fixing device capable of improving the fixing property.
[0010]
[Means for Solving the Problems]
The above object is achieved by the following means.
[0011]
A hollow rotating member formed to be flexible and hollow, and a plurality of heating rollers having heating means, arranged inside the hollow rotating member, and rotating while contacting an inner surface of the hollow rotating member; A pressing member for pressing the plurality of heating rollers via the hollow rotating member, and a non-fixed portion formed on a recording material by a nip formed by the hollow rotating member and the pressing member. An image forming apparatus comprising a fixing device for fixing an image under heat and pressure.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an example of an image forming apparatus using the fixing device of the present invention will be described with reference to FIG.
[0013]
In FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading apparatus YS.
[0014]
The image forming apparatus main body GH is referred to as a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer body 6, a sheet feeding and conveying unit, and a fixing device described below. Consists of seventeen.
[0015]
An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is provided above the image forming apparatus main body GH. A document d placed on a document table of the automatic document feeder 201 is transported by a transport unit, and an image on one side or both sides of the document is scanned and exposed by an optical system of a document image scanning and exposing device 202, and is sent to a line image sensor CCD. Is read.
[0016]
The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then subjected to exposure means 3Y, 3M, 3C, Sent to 3K.
[0017]
The image forming unit 10Y that forms a yellow (Y) color image has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y that are arranged around a photosensitive drum 1Y as an image carrier. The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M. The image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image carrier, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 8C. The image forming unit 10K that forms a black (K) color image includes a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 8K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K each constitute a latent image forming unit.
[0018]
Reference numerals 4Y, 4M, 4C, and 4K denote developing devices that include a two-component developer including a toner having a small particle diameter and a carrier of yellow (Y), magenta (M), cyan (C), and black (K). , 5Y, 5M, 5C and 5K are toner replenishing means for replenishing the developing devices 4Y, 4M, 4C and 4K with new toner, respectively.
[0019]
The intermediate transfer member 6 is wound around a plurality of rollers and is rotatably supported. The fixing device 30 includes a flexible hollow rotating member 31, a very small heating roller 32, and a pressing roller 33, which will be described later in detail.
[0020]
The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 6 by the transfer units 7Y, 7M, 7C, and 7K (primary transfer) and synthesized. A color image is formed. The recording paper P as a transfer material accommodated in the paper feed cassette 20 is fed by a paper feed unit 21, passes through paper feed rollers 22 A, 22 B, 22 C, 22 D, registration rollers 23, and the like, and is transferred to a transfer unit 7 A. The sheet is conveyed, and the color image is secondarily transferred onto the recording paper P. The recording paper P on which the color image has been transferred is nipped by a nip formed by the hollow rotating member 31 of the fixing device 30 and the pressure roller 33, and heat and pressure are applied to the recording paper P to form a color image on the recording paper P. The toner image is fixed. Subsequently, the recording paper P is sandwiched between the paper discharge rollers 25 and placed on a paper discharge tray 26 outside the apparatus.
[0021]
On the other hand, after the color image is transferred onto the recording paper P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 obtained by separating the recording paper P by curvature.
[0022]
Although an example of an image forming apparatus that forms a color image as described above has been described as an image forming apparatus using the fixing device of the present invention, an image forming apparatus that forms a monochrome image may be used.
[0023]
Next, the fixing device 30 of the present invention will be described based on the enlarged sectional view of FIG. The fixing device 30 basically has a hollow rotating member 31 formed thin and flexible and hollow, and a heating means 321 formed in an ultra-small diameter and inside the hollow rotating member 31. The three heating rollers 32 that are arranged and rotate while being in contact with the inner surface of the hollow rotating member 31, and a pressing roller 33 (pressing member) that presses the three heating rollers 32 via the hollow rotating member 31. It is configured.
[0024]
Here, when the pressure roller 33 rotates counterclockwise by being driven by a motor (not shown), the hollow rotating member 31 rotates clockwise, and the three heating rollers 32 also rotate clockwise. Therefore, for example, the recording paper P on which the color image is transferred by the image forming apparatus shown in FIG. 1 is nipped by the nip formed by the hollow rotating member 31 and the pressure roller 33, and is heated and pressed. Thereby, the color toner image (unfixed image) on the recording paper P is fixed.
[0025]
Reference numeral 34 denotes a holding roller that holds the hollow rotary member 31 so as not to move downstream in the transport direction of the recording paper P.
[0026]
Further, the heating roller 32 may be driven by the motor instead of the pressure roller 33. In this case, the three heating rollers 32 need to rotate in the same direction at the same speed. As an example, a pulley may be provided at the end of each heating roller 32, and the pulley may be rotated by a belt.
[0027]
Although a temperature sensor for detecting a temperature for controlling the temperature of the heating roller 32 and a cleaning unit for cleaning the toner remaining in the hollow rotary member 31 are omitted, well-known common members and units may be used. it can.
[0028]
Thus, in the fixing device 30, since the pressing roller 33 presses the three heating rollers 32 via the hollow rotating member 31, the nip width N is reduced by the hollow rotating member 31 and the pressing roller 33. It is formed. The nip width N is much longer than in the conventional case where only one heating roller is formed. Therefore, the fixing property is greatly improved as compared with the conventional fixing device.
[0029]
Strictly speaking, a nip portion is formed on the left and right around a portion where the heating roller 32 and the hollow rotary member 31 are in contact with each other, and there is a range where the nip portion is not formed between the adjacent heating rollers 32. That is, as shown in the enlarged view of FIG. 3, a nip portion having a nip width N11 is formed by the heating roller 32a, a nip portion having a nip width N12 is formed by the heating roller 32b, and a nip portion having a nip width N13 is formed by the heating roller 32c. However, no nip is formed in the range of D11 between the heating roller 32a and the heating roller 32b, and similarly, no nip is formed in the range of D12 between the heating roller 32b and the heating roller 32c.
[0030]
However, the entire width from the end of the nip portion where the nip width is N11, which is the most upstream side in the transport direction of the recording paper P, to the end portion of the nip portion, which is the most downstream side and the nip width is N13, in the transport direction. There is no practical problem even if the nip width N is When the radius of the heating roller 32 is R, the following formula is satisfied in the present fixing device.
[0031]
R <N
Note that this formula is difficult to be satisfied when there is one conventional heating roller.
[0032]
Further, since the diameter of the heating roller 32 is formed to be very small as compared with the conventional case, the heat capacity of the heating roller 32 is small, and the distance from the heating means located at the center to the outer surface of the heating roller 32 is short. , The warm-up time can be reduced to half or less of that of the related art, and the power consumption can be reduced.
[0033]
More specifically, stainless steel is used as the material of the hollow rotating member 31, and the end of the stainless steel plate may be welded to form a cylindrical shape, or a stainless steel tube may be used.
[0034]
Further, iron or nickel may be used other than stainless steel.
The outer peripheral surface of the hollow rotating member 31 has a rubber layer formed of silicon or fluoro rubber, and a release layer covering a PFA (perfluoroalkoxy) tube.
[0035]
Since the hollow rotating member 31 requires flexibility, its thickness is desirably 50 μm to 500 μm. For example, when the length of the outer circumference is 300 mm, the thickness is desirably about 150 μm.
[0036]
The heating roller 32 includes a halogen heater provided in the center as a heating unit 321, a core 322 made of aluminum, iron, copper, or an alloy thereof, and PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene). And a coating layer 323 made of a fluororesin.
[0037]
Then, it is desirable that the heating roller 32 be formed to have a very small diameter of 5 mm to 15 mm.
[0038]
Note that an electromagnetic induction rotating member (magnetic fixing roller) may be used instead of the halogen heater, and an electromagnetic induction heating method may be used.
[0039]
Further, as shown in FIG. 4, the heat distributions of the heating means 321a, 321b, 321c of the three heating rollers 32a, 32b, 32c are individually changed, and a predetermined heating means is selected according to the thickness and width of the paper to be used. May be energized. For example, when wide thick paper is used, the heating means 321a, 321b, 321c of the heating rollers 32a, 32b, 32c are energized. When wide thin paper is used, only the heating means 321a of the heating roller 32a is energized, and When the paper is narrow, only the heating means 321b of the heating roller 32b is energized.
[0040]
With this configuration, when narrow paper is used, the heat at the end of the heating roller is not wastedly released, and the end of the heating roller is abnormally heated and the outer periphery of the heating roller is heated. No breakage of the coating layer occurs. Further, even if a wide paper is used immediately after the use of the narrow paper, the temperature at the center in the width direction does not decrease and the fixing does not become uneven.
[0041]
The pressure roller 32 includes, for example, a round bar core 32a made of stainless steel, a rubber roller 32b formed of a silicone rubber foam formed on the outer peripheral surface of the core bar, and a PFA (perfluoro) formed on the outer peripheral surface of the rubber roller. Release layer 32c covering an (alkoxy) tube.
[0042]
Further, the pressing member for pressing the three heating rollers 32 is not limited to the rotating pressing roller 33, and a fixed pressing plate may be provided. This example will be described with reference to FIG.
[0043]
In FIG. 5, the hollow rotary member 31, the heating roller 32, and the holding roller 34 are the same as those shown in FIG. A pressing plate 43 is urged by a compression spring 44 having one end locked to a fixed member, and the pressing plate 43 presses the three heating rollers 32 via the hollow rotating member 31.
[0044]
The pressure plate 43 has heat resistance, for example, a heat-resistant resin is used, and is formed so that the recording material P is smoothly conveyed and the toner image on the recording material P is fixed in a good and stable manner. Is done.
[0045]
For example, the heat resistance of a substrate layer 431 made of a heat-resistant resin, a heat-resistant elastic layer 432 made of silicon rubber or the like, a heat-generating layer 433 made of nickel or the like and having a high magnetic permeability of 100 or more, or a fluororesin is used. The surface layer 434 having good slipperiness is formed in order, and the surface layer 434 is pressed against the hollow rotary member 31. The pressing plate 43 needs to be configured to have a low heat capacity in order to reduce the amount of heat taken from the hollow rotating member 31, and for this reason, is configured in a plate shape. An advantage of the pressure plate 43 is that the plate can be formed into a desired shape without increasing its heat capacity. In order to press the pressure plate 43 against the hollow rotary member 31 with a uniform pressure in the width direction of the recording material P, the pressure plate 43 is urged by two springs 44 provided at both ends in the width direction of the recording material P.
[0046]
As shown in FIG. 6, a holding frame 46 for preventing the heating roller 32 from moving radially with respect to the center axis is provided, and the holding frame 46 is pressed by a compression spring 47 having one end locked to a fixing member. Alternatively, the three heating rollers 32 may press the inner surface of the hollow rotary member 31 against the pressure roller 33. In this case, since the three heating rollers 32 need to move in the vertical direction in the figure, the pressure roller 33 is driven by a motor (not shown). As a result, the nip width is more reliably secured.
[0047]
Further, the outer diameters of the three heating rollers 32 do not necessarily have to be the same.
For example, as shown in FIG. 7, a heating roller 522 having a smaller outer diameter may be disposed between heating rollers 521 and 523 having the same outer diameter. Thereby, the ranges C21 and C22 where the nip portion is not formed are smaller than C11 and C12 shown in FIG. 3, so that the thermal efficiency is further improved.
[0048]
In addition, the number of the heating rollers of the present invention is not necessarily three, and may be two or four or more.
[0049]
【The invention's effect】
According to the image forming apparatus of the present invention, since a fixing device having a plurality of heating rollers, which has not existed in the past, is provided, the warm-up time can be significantly reduced, the power consumption can be reduced, and the nip width can be increased. Thus, the fixing property can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus.
FIG. 2 is an enlarged cross-sectional view of the fixing device.
FIG. 3 is an enlarged view of a heating roller.
FIG. 4 is a diagram of a heating roller in which a heat distribution is changed.
FIG. 5 is an enlarged cross-sectional view of a fixing device using a pressure plate.
FIG. 6 is an enlarged cross-sectional view of a fixing device using a holding frame.
FIG. 7 is an enlarged view of heating rollers having different outer diameters.
[Explanation of symbols]
Reference Signs List 30 fixing device 31 hollow rotary members 32, 32a, 32b, 32c heating roller 33 pressing rollers 321, 321a, 321b, 321c heating means 43 pressing plate 46 holding frame

Claims (5)

A hollow rotating member formed to be flexible and hollow,
A plurality of heating rollers having heating means and arranged inside the hollow rotating member and rotating while contacting the inner surface of the hollow rotating member,
A pressure member that presses the plurality of heating rollers via the hollow rotating member,
An image forming apparatus comprising: a fixing device configured to heat and pressure fix an unfixed image formed on a recording material by a nip formed by the hollow rotating member and the pressing member. The heating roller has a radius of R, and is located further downstream in the recording material transport direction than the end located most upstream in the recording material transport direction in a plurality of nip widths formed by the hollow rotating member and the pressing member. 2. The image forming apparatus according to claim 1, wherein the following expression is satisfied when the dimension up to the end is N.
R <N The image forming apparatus according to claim 1, wherein a thickness of the hollow rotating member is 50 μm or more and 500 μm or less. The image forming apparatus according to claim 1, wherein a heat distribution of a heating unit of the hollow rotating member is different for each of the plurality of heating rollers. The image forming apparatus according to claim 1, further comprising a pressing unit configured to press the plurality of heating rollers against the hollow rotating member.

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