JP2003263060A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase durability of a peeling member and to improve the quality of fixed image. <P>SOLUTION: A fixing device provided with a fixing roller 21 having a heat source 21a, a pressure roller 22 which is in press-contact with the fixing roller and the peeling member 31 which is disposed in close vicinity to the fixing roller in an axial direction of the fixing roller and at the downstream side in a recording medium transporting direction in a fixing nip part N is characterized in that, in the peeling member 31, a fluorine resin eutectoid plated layer is formed on a surface of a base material. Further, application to a system in which the fixing roller 21 and the pressure roller 22 are disposed approximately in a horizontal state, is more effective. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a fax machine using electrophotography, and more particularly, a fixing device having a peeling member for peeling a recording medium discharged from a fixing nip portion. Regarding

[0002]

2. Description of the Related Art In an image forming apparatus using electrophotography, a toner image is formed in a nip portion of a pair of a fixing roller and a pressure roller as a fixing device for fixing a toner image transferred on a sheet. 2. Description of the Related Art A fixing device is widely used in which a transferred sheet is passed and a toner image is fused to the sheet by heating by a fixing roller and pressure by two rollers.

Generally, in this fixing device, since the toner image fused to the sheet comes into contact with the fixing roller, a roller having a fluorine-based resin with good releasability formed on the surface is used as the fixing roller. However, even if such a fixing roller is used, the melted toner is soft and highly viscous, so that the toner easily sticks to the surface of the fixing roller and the paper may be wound around the fixing roller.

Therefore, in the prior art, Japanese Patent Laid-Open No. 11-184300
According to the publication, it is proposed to provide a sheet-shaped peeling member which comes into contact with the fixing roller on the downstream side in the rotation direction of the fixing roller. This peeling member uses a resin sheet or a metal sheet as a base material, and a fluororesin layer is formed on the surface of the base material and the edge contacting the fixing roller by painting or pasting.

[0005]

However, the above-mentioned conventional fixing device has a problem of damaging the fixing roller because the peeling member is in contact with the fixing roller. Further, since the conventional peeling member has a structure in which a fluorine-based resin layer is formed by painting or pasting, the resin layer at the tip of the peeling member that comes into contact with the paper will peel off due to aging, and the toner will stick, There is a problem that image streaks occur.

Further, in the conventional arrangement of the fixing roller and the pressure roller, it is general that the fixing roller and the pressure roller are arranged vertically and vertically, and the recording medium discharged from the nip portion between them. Since the force acts in the direction away from the fixing roller due to gravity, the recording medium is less likely to be peeled by the peeling member. However, when the fixing roller and the pressure roller are arranged in a substantially horizontal state, the recording medium is likely to be wound around the fixing roller side, and the recording medium is always brought into contact with the peeling member. Since it increases, how to improve the durability of the peeling member becomes an issue.

Particularly, in fixing a full-color image,
A toner image in which a large amount of toner has been superposed and transferred has to be fixed as compared with the time of fixing a black-and-white image, and a large peeling force is required at the time of peeling, and durability of the peeling member becomes a problem. Further, in the case of a glossy color image, it is required that the toner image surface after fixing be smooth, and for that purpose, the toner surface is flattened after the toner is sufficiently melted by heating to lower the viscosity. It is necessary to smooth the surface, which requires an even greater peeling force, and a problem is to make the peeling member maintain the function of flattening the image surface.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and problems of the prior art, and an object of the present invention is to provide a fixing device capable of increasing the durability of a peeling member and improving the quality of a fixed image. To do.

[0009]

In order to achieve the above object, a fixing device according to claim 1 of the present invention comprises a fixing roller having a heat source, a pressure roller pressed against the fixing roller, and the fixing device. A peeling member disposed in the axial direction of the roller and on the downstream side of the fixing nip portion in the recording medium conveying direction is provided in proximity to the fixing roller. The peeling member has a fluororesin eutectoid plating on the surface of the base material. The invention according to claim 2 is characterized in that the content of the fluororesin is 20 to 50% by volume, and the invention according to claim 3 is characterized in that a layer is formed. In claim 1, the surface roughness of the eutectoid plating layer is made smaller than that of the fixing roller, and the invention according to claim 4 is characterized in that
The surface roughness of the pressure roller is set to be larger than that of the fixing roller, and the invention according to claim 5 is characterized in that, in any one of claims 1 to 4, the tip end portion of the eutectoid plating layer. The surface roughness of the fixing roller is smaller than that of the rear end portion, and the invention according to claim 6 is characterized in that in any one of claims 1 to 4, the fixing roller and the pressure roller are arranged in a substantially horizontal state. It is characterized by being installed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a fixing device according to the present invention, and is an overall configuration diagram of an image forming apparatus.

An image carrier 3 made up of a photosensitive drum is provided in the main body 2 of the image forming apparatus 1, and is driven to rotate in the direction of the arrow in the figure by a driving means (not shown). A charging device 4 for uniformly charging the image carrier 3 around the image carrier 3 along the rotation direction thereof, and an exposure device for forming an electrostatic latent image on the image carrier 3. 5, a rotary developing device 6 for developing the electrostatic latent image, and an intermediate transfer device 7 for primarily transferring the monochromatic toner image formed on the image carrier 3 are provided.

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 supporting frame 8, and the supporting frame 8 is rotated by a drive motor (not shown). It is configured to be driven. Each of the plurality of developing devices 6Y, 6C, 6M, and 6K is selectively rotated and rotated so that the developing roller 6a of one developing device faces the image carrier 3 every one rotation of the image carrier 3. Has been done.
Note that each of the developing devices 6Y, 6C, 6M, and 6K is formed with a toner storage portion that stores toner of each color.

The intermediate transfer device 7 is provided with a driving roller 9 and a driven roller 10, an intermediate transfer belt 11 driven by both rollers in the direction of the arrow in the figure, and a back surface of the belt 11 facing the image carrier 3. Primary transfer roller 12 and transfer belt cleaner 1 for removing residual toner on the belt 11.
3 and a secondary transfer roller 14 which is disposed so as to face the drive roller 9 and transfers the four-color full-color image formed on the intermediate transfer belt 11 onto a recording medium (paper or the like).

A sheet feeding cassette 15 is arranged at the bottom of the apparatus main body 2, and the recording medium in the sheet feeding cassette 15 passes through a pickup roller 16, a recording medium conveying path 17, a secondary transfer roller 14, and a fixing device 19. It is configured to be conveyed to the paper discharge tray 20. Reference numeral 23 is a double-sided printing conveyance path.

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

At the latent image position formed on the image carrier 3,
The developing device 6Y for yellow rotates to rotate its developing roller 6a.
Contact each other, whereby a toner image of a yellow electrostatic latent image is formed on the image carrier 3 and then the toner image formed on the image carrier 3 is transferred by the primary transfer roller 12 to the intermediate transfer belt 11 Transcribed on. At this time, the secondary transfer roller 14 is separated from the intermediate transfer belt 11.

In the above-described processing, latent image formation, development and transfer by one rotation of the image carrier 3 and the intermediate transfer belt 11 are repeated corresponding to the second, third and fourth colors of the image forming signal. The toner images of four colors corresponding to the contents of the image forming signal 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 conveying 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. The secondary transfer voltage is applied, and the full-color toner image on the intermediate transfer belt 11 is transferred onto the recording medium. Then, the toner image transferred onto the recording medium is heated and pressed by the fixing device 19 to be fixed. 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 its rear end is the leading end, and is supplied to the secondary transfer roller 14 via the double-sided printing conveyance path 23. Then, the full-color toner image on the intermediate transfer belt 11 is transferred onto the recording medium, and again heated and pressed by the fixing device 19 to be fixed.

Referring to FIG. 1, a fixing device 1 according to the present invention.
Reference numeral 9 denotes a heat fixing member 2 including a fixing roller having a heat source.
1. A pressure member 22 including a pressure roller 1 and a pressure roller pressed against the pressure roller 1.
And the connecting line connecting the axes of the fixing roller 21 and the pressure roller 22 is arranged so as to form an angle θ from the horizontal line. Note that 0 ° ≦ θ ≦ 30 °.

2 to 6 show details of the fixing device 19 of FIG. 1, FIG. 2 is a perspective view showing a partially broken cross section of the fixing device, FIG. 3 is a sectional view of a main part of FIG. 2, and FIG. 2 is a perspective view of the peeling member shown in FIG. 2, FIG. 5 is a side view showing a mounting state of the peeling member, and FIG. 6 is a plan view seen from the upper portion of FIG. In addition, the same numbers may be given to the same configurations between the drawings, and the description thereof may be omitted.

2 and 6, the housing 24
A fixing roller 21 is rotatably mounted therein, and a drive gear 28 is connected to one end of the fixing roller 21. The pressure roller 22 is rotatably mounted so as to face the fixing roller 21. The axial length of the pressure roller 22 is shorter than that of the fixing roller 21, a bearing 25 is provided in the empty space, and the bearings 25 are provided at both ends of the pressure roller 22.
It is supported by. 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 pressed. It is configured to be.

In FIG. 3, the fixing roller 21 has a metal cylindrical body 2 having a heat source 21a such as a halogen lamp therein.
1b, an elastic layer 21c made of silicon rubber or the like provided on the outer periphery of the cylindrical body 21b, and a surface layer made of fluororubber or fluororesin (for example, pertetrafluoroethylene (PTFE)) coated on the surface of the elastic layer 21c ( (Not shown) and a rotary shaft 21d fixed to the cylindrical body 21b.

The pressure roller 22 is a metal cylinder 22b.
A rotary shaft 22d fixed to the cylindrical body 22b, and a rotary shaft 2
Similar to the fixing roller 21, a bearing 25 that axially supports 2d, an elastic layer 22c provided on the outer periphery of the cylindrical body 22b, and a surface layer of fluororubber or fluororesin that covers the surface of the elastic layer 22c (not shown). No)) and. The thickness of the elastic layer 21c of the fixing roller 21 is made extremely smaller than the thickness of the elastic layer 22c of the pressure roller 22, so that the nip portion N is formed so that the pressure roller 22 side is recessed.

As shown in FIGS. 2 and 3, support shafts 29 and 30 are provided on both side surfaces of the housing 24. The support shafts 29 and 30 are joined to the peeling member 31 on the fixing roller 21 side, respectively. The peeling member 32 on the pressure roller 22 side is rotatably mounted. As a result, the fixing roller 21
The peeling members 31 and 32 are disposed downstream of the nip portion in the recording medium conveyance direction in the axial direction of the pressure roller 22.

The peeling member 31 on the fixing roller 21 side is shown in FIG.
And as shown in FIG. 5, the peeling portion 31 a and the peeling portion 31
A bent portion 31b formed at the rear of a at a right angle to the fixing roller 21 side, a support piece 31c formed downward at both ends of the peeling portion 31a, and a fitting hole 31 formed in the support piece 31c.
d and guide portions 31e extending forward of both side ends of the peeling portion 31a.

The peeling portion 31a is arranged so as to be inclined toward the exit of the nip portion N, and the tip of the peeling portion 31a is in non-contact with and close to the fixing roller 21. Support piece 31
The support shaft 29 described in FIG. 3 is fitted in the fitting hole 31d of c. The guide portion 31e is urged toward the housing 24 by the spring 33, so that the guide portion 31e
The tip of e is in contact with the fixing roller 21, and as a result, the gap between the tip of the peeling portion 31a and the surface of the fixing roller 21 is always constant.

The peeling member 32 on the pressure roller 22 side has the same shape as the peeling member on the fixing roller 21 side. However, as shown in FIGS.
It is arranged on the downstream side in the recording medium conveyance direction with respect to the front end of 1a. Further, the tip of the guide portion 32e is in contact with the peripheral surface of the bearing 25 of the pressure roller 22 at a point P, so that the gap between the tip of the peeling portion 32a and the surface of the pressure roller 22 is always constant. It is supposed to be.

Next, the features of the present invention will be described. The conventional arrangement of the fixing roller 21 and the pressure roller 22 is generally such that the fixing roller 21 and the pressure roller 22 are arranged vertically and vertically, and the recording medium discharged from the nip portion between them is Since the force acts in the direction away from the fixing roller 21 due to gravity, the degree of peeling of the recording medium by the peeling member is small. However, as shown in FIG. 1, when the fixing roller 21 and the pressure roller 22 are arranged in a substantially horizontal state, the recording medium is easily wound around the fixing roller 21 side.
The recording medium discharged from the nip portion N must be the peeling member 31.
Therefore, the frequency of use is extremely high compared to the conventional method. for that reason,
The challenge is how to improve the durability of the peeling member.

Therefore, in the present invention, the peeling member 3
Fluorine-based resin eutectoid plating is applied to the front and back of the peeled portions 31 a and 32 a of Nos. 1 and 32. The method is electrolytic eutectoid plating in which fluorine-containing resin particles are dispersed in an electrolytic nickel plating solution (Uemura Kogyo Co., Ltd., trade name "Metaflon"), or fluorine-containing resin particles in an electroless nickel plating solution. The eutectoid plating layer is formed by performing eutectoid plating using electroless eutectoid plating (manufactured by Uemura Kogyo, trade name "Nimflon", etc.) in which is dispersed.

As the fluorine-containing resin fine particles used for the fluororesin eutectoid plating, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene resin (PTFE), tetrafluoroethylene-6 Fluorinated propylene copolymer resin (FEP), ethylene-tetrafluoroethylene copolymer resin (ETFE), ethylene-trifluoroethylene chloride copolymer resin (ECTFE), ethylene trifluoride resin (PCTFE), vinyl fluoride resin (P
VF), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer resin (EP
E), thermoplastic fluororesins such as vinylidene fluoride resin (PVdF), thermoplastic elastomers and other fluorocopolymers, and fluorocarbons such as (CF) N and (C2F) F. You can Particularly, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) and tetrafluoroethylene resin (PTFE)
Is preferred.

As the metal compound used for the eutectoid plating, a metal such as copper, silver, zinc or tin can be adopted in addition to nickel, but preferably nickel, nickel-phosphorus alloy, nickel- Nickel alloys such as cobalt alloys and nickel-boron alloys are preferable because they have excellent surface hardness and wear resistance.

When the surface layer is formed on the peeling member by the fluororesin eutectoid plating, the content of the fluororesin is 20 to 20%.
It is preferably 50% by volume. If the content of the fluorine-based resin is less than 20% by volume, sufficient non-adhesiveness of the toner and paper powder may not be obtained, and if the content of the fluorine-based resin exceeds 50% by volume, the non-adhesiveness is increased. In some cases, the wear resistance of the surface layer may be reduced and the adhesion to the substrate may be deteriorated.

As the base material of the peeling member to be subjected to eutectoid plating, metals such as stainless steel, nickel, aluminum and iron and resins such as polyester and polyimide are used.
When a metal material is used, burrs at the edges and infinitesimal scratches occur innumerable due to the tensile force and metal friction generated at the cut surface when performing shape processing such as pressing.
Therefore, it is preferable to perform a precision finishing process such as electrolytic polishing and etching before the eutectoid plating process. (Example 1) After etching a stainless steel substrate,
Nickel-PTFE composite plating solution (manufactured by Hikifune, trade name "Hi Flon M") is used as the electrolytic plating solution, and the film thickness is 10 μm by the electrolytic plating method, and the PTFE eutectoid amount is about 30%.
The surface treatment was performed to form the coating film, and heat treatment was further performed after the plating treatment to increase the surface hardness. (Example 2) After etching a stainless steel substrate,
Nickel-phosphorus-PTFE composite plating solution (manufactured by Uemura Kogyo Co., Ltd., trade name "Nimflon") was used as the electrolytic plating solution, and the thickness was 10 μm and the amount of PTFE co-deposited was about 23 by the electrolytic plating method.
%, A surface treatment was performed to form a coating film, and after the plating treatment, a heat treatment was performed to increase the surface hardness. (Comparative Example 1) After etching a stainless steel substrate,
A film made of PTFE resin (Daikin Industries, Ltd., trade name "Polyflon") is sprayed to a film thickness of approximately 10 μm.
And then infrared drying at 90 ℃, then 38
Baked at 0 ° C. (Comparative Example 2) After etching the stainless steel substrate,
An adhesive tape made of PTFE resin (manufactured by Nitto Kogyo, trade name “Nitoflon”: resin layer thickness 20 μm) was attached to the surface to form a surface layer.

An evaluation test was carried out by applying the peeling member 31 of the above-mentioned examples and comparative examples. The result is shown in FIG. 7. The durability of Example 1 and Example 2 was confirmed.

The conditions of the fixing device are as follows: fixing roller diameter 30 mm, elastic layer: thickness 1 mm of silicone rubber (hardness JISA 5 °), surface layer: thickness 40 μm of PFA pressure roller diameter 35 mm, elastic layer: thickness 6 mm of silicon rubber (hardness JISA10 °), surface layer: PFA with thickness of 40 μm, distance between fixing nip outlet and exfoliation part 31a tip: 6.5 m
m, fixing nip width: 8 mm, fixing temperature: 175 ° C., paper conveyance speed: 215 mm / s, roller pressure contact load 31 kgf. Evaluation item Image streak (initial and after endurance printing (80,000 prints)):
A solid image is printed on the entire surface and the "streaks" that are scratches on the peeling portion 31a are visually evaluated. ○: No streaking occurs. X: Streaking occurs on the image surface. Surface wear (after durable printing): Surface of peeling portion after durable printing. Observed under a microscope ○: Base material is not exposed due to surface abrasion △: Some base material is exposed due to surface abrasion at the edge of the peeled part ×: Clear base material is exposed Toner adhered (after durability printing): Durability Visual evaluation of toner adhesion after printing ○: No toner adhesion Δ: Some toner adhesion on edge ×: Toner adhesion that causes rubbing marks on the image surface The length was measured by Surftest SJ-301 manufactured by Mitutoyo Corporation.

Next, an experiment was conducted on the relationship between the surface roughness and the glossiness of the fixing roller 21, the pressure roller 22 and the peeling member 31. The glossiness (gloss) is made by Murakami Color Research Institute,
It was measured by a gloss meter GM-26D. The result is shown in FIG. In addition, the first side and the second side are single-sided prints,
This is the case of double-sided printing. (Example 3) The surface roughness of the surface layer is: fixing roller> peeling member (Example 4) The surface roughness of the surface layer is: pressure roller> fixing roller> peeling member (Comparative Example 3) The surface roughness of the surface layer is: Fixing roller <Peeling member In fixing a full-color image, a toner image to which a large amount of toner has been transferred has to be fixed more than in fixing a monochrome image, and a large peeling force is required at the time of peeling.
The durability of the peeling member has been an issue. Further, in the case of a glossy color image, it is required that the toner image surface after fixing be smooth, and for that purpose, the toner surface is flattened after the toner is sufficiently melted by heating to lower the viscosity. It is necessary to smooth the surface, which requires an even greater peeling force, and a problem is to make the peeling member maintain the function of flattening the image surface.

In order to obtain smoothness of the toner image surface after fixing, as shown in Example 3, the eutectoid plating layer of the peeling member contacting after passing through the nip rather than the roller surface roughness at the time of heating in the fixing nip, as shown in Example 3. Since the contribution of the surface roughness is high, the image is rubbed with a smooth surface of the peeling member after the fixing roller gives rough smoothness, so that a smoother and higher gloss image can be obtained.

The fourth embodiment corresponds to double-sided printing. In the case of double-sided printing, the front surface of the recording medium passes through the fixing nip twice with the toner overlapping. At this time, if the toner on the front surface is uneven, the toner is less likely to peel off on the pressure roller side, and the glossiness cannot be obtained. Therefore, the surface roughness of the pressure roller is made the roughest to reduce the contact area and facilitate the peeling.

Further, the surface roughness of the leading end of the eutectoid plating layer of the peeling member is made finer (smaller) than that of the rear end. It is the leading end of the peeling member that provides the smoothness of the toner image, and the trailing end is made rough (large) in surface roughness to prevent sticking of the solid image.

The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made, and the present invention may be applied to a conventionally known technique, or may be applied. You may make it combine well-known technology.

For example, in the above embodiment, the peeling member 31 on the fixing roller 21 side is described, but it goes without saying that the peeling member 32 on the pressure roller 22 side is also applicable.

[0042]

As is apparent from the above description, according to the present invention, the durability of the peeling member can be increased and the quality of the fixed image can be improved.

[Brief description of drawings]

FIG. 1 shows an embodiment of a fixing device according to the present invention,
FIG. 1 is an overall configuration diagram of an image forming apparatus.

FIG. 2 is a perspective view showing a detailed structure of the fixing device of FIG. 1 and showing a partially broken surface.

3 is a cross-sectional view of the main parts of FIG.

FIG. 4 is a perspective view of the peeling member of FIG.

FIG. 5 is a side view showing a mounting state of the peeling member of FIG.

FIG. 6 is a plan view seen from the upper part of FIG.

FIG. 7 is a diagram showing an experimental result according to the present invention.

FIG. 8 is a diagram showing an experimental result according to the present invention.

[Explanation of symbols]

19: Fixing device 21 ... Fixing roller 21a ... Heat source 22 ... Pressure roller 31 ... Peeling member N ... Fixing nip

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Claims (6)

[Claims] 1. A fixing roller having a heat source, a pressure roller which is brought into pressure contact with the fixing roller, and an axial direction of the fixing roller and a downstream side of the fixing nip portion in the recording medium conveying direction, which are arranged close to the fixing roller. A fixing device, comprising: a peeling member provided, wherein the peeling member has a fluororesin eutectoid plating layer formed on a surface of a base material. 2. A fluorine resin content of 20 to 50% by volume.
The fixing device according to claim 1, wherein 3. The fixing device according to claim 1, wherein the surface roughness of the eutectoid plating layer is smaller than that of the fixing roller. 4. The fixing device according to claim 3, wherein the surface roughness of the pressure roller is larger than that of the fixing roller. 5. The surface roughness of the front end portion of the eutectoid plating layer is made smaller than that of the rear end portion.
5. The fixing device according to any one of 4 to 4. 6. The fixing device according to claim 1, wherein the fixing roller and the pressure roller are arranged in a substantially horizontal state.