JP2003263061A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always keep a gap between the leading end of a release member and the surface of a fixing roller constant. <P>SOLUTION: The fixing device is provided with the fixing roller 21 which has a heat source and is curved inward toward the middle in the axial direction; a pressure roller which is firmly pressed to the fixing roller; and a release member 31 which is disposed in the axial direction of the fixing roller, on the downstream side from the fixing nip in a direction in which a recording medium is carried, and near the fixing roller. The release member has a release portion 31a formed of a metal plate, and a bent portion 31b bent in L shape at rear side of the release portion on the fixing roller side. <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. Therefore, a method of disposing the peeling member in a non-contact manner with the fixing roller can be considered. However, in this method, in order to peel the recording medium from the fixing roller with a uniform force in the width direction, the gap between the tip of the peeling member and the fixing roller is always constant over the entire axial length of the fixing roller. In addition, since the fixing roller is usually of a type with a bulged central portion or a concave type in a side view,
There is a problem that it is very difficult to manage the gap.

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. With the increase, the management of the gap becomes more important.

The present invention solves the above-mentioned problems and problems of the prior art, and provides a fixing device capable of constantly maintaining a constant gap between the tip of the peeling member and the surface of the fixing roller. The purpose is to

[0008]

In order to achieve the above-mentioned object, a fixing device according to claim 1 of the present invention is a fixing roller of a type having a heat source, which is depressed toward the central portion in the axial direction, and the fixing roller. A pressure roller that is in pressure contact with the pressure roller, and a peeling member that is arranged in the axial direction of the fixing roller and on the downstream side of the fixing nip portion in the recording medium conveyance direction are provided in the vicinity of the fixing roller. 3. The invention according to claim 2, further comprising: a peeling portion formed of and a bent portion that is bent in an L shape on the fixing roller side behind the peeling portion. A fixing roller that swells toward the fixing roller, a pressure roller that comes into pressure contact with the fixing roller, and a fixing roller that is arranged in the axial direction of the fixing roller and on the downstream side of the fixing nip portion in the recording medium conveyance direction, in proximity to the fixing roller And a peeling member, the peeling member The invention according to claim 3 is characterized in that it has a peeling portion formed of a metal plate and a bent portion that is bent in an L shape on the side opposite to the fixing roller behind the peeling portion. 2 is characterized in that the fixing roller and the pressure roller are arranged in a substantially horizontal state.

[0009]

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 disposed 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 paper feed cassette 15 is disposed at the bottom of the apparatus main body 2, and the recording medium in the paper feed 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 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 process, 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 color, the third color, and the fourth color 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 7 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 of FIG. 2, FIG. 5 is a side view showing a mounting state of the peeling member, FIG. 6 is a plan view seen from the upper portion of FIG. 2, and FIG. 7 is a schematic diagram for explaining the features of the present invention. is there. 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 with a peeling member 31 on the fixing roller 21 side. 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.
As shown in FIG. 5 and FIG. 5, it is formed by bending a single metal plate, and is formed into a plate-shaped peeling portion 31a, and is bent in the L-shape toward the fixing roller 21 behind the peeling portion 31a. A bent portion 31b, a support piece 31c bent downward at both ends of the peeling portion 31a, a fitting hole 31d formed in the support piece 31c, and a front end of each of the peeling portion 31a. And a guide portion 31e.

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, but 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. In order to peel the recording medium from the fixing roller with a uniform force in the width direction, the gap between the tip of the peeling member 31 and the fixing roller 21 is always kept constant over the entire axial length of the fixing roller 21. In addition, since the fixing roller is usually of a type having a bulged central portion or a concave type in a side view, management of the gap is an important issue.

Further, in the conventional arrangement of the fixing roller 21 and the pressure roller 22, the fixing roller 21 and the pressure roller 22 are generally arranged vertically and vertically, and discharged from the nip portion of both. Since a force acts on the recording medium to be separated from the fixing roller 21 due to gravity, the recording medium is less likely to be separated by the separating member. 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, and the recording medium discharged from the nip portion N is always peeled off. Since it comes into contact with the member 31, its use frequency is extremely high compared to the conventional method. Therefore, management of the gap has become a more important issue.

Therefore, in the present invention, as shown in FIG. 5, the peeling member 31 on the fixing roller 21 side is a plate-shaped peeling portion 3 when a single metal plate is bent and formed.
L-shaped bent portion 31b on the fixing roller 21 side behind 1a
Is folded. As a result of this bending process, the tip of the peeling portion 31a has a downwardly curved shape as shown in FIG. 7A, and the fixing roller 21 is a concave type (so-called reverse crown type: end) that extends toward the axial center thereof. When a shape in which the part diameter is larger than the central part diameter) is used, the gap G between the tip of the peeling part 31a and the surface of the fixing roller 21 can be kept constant.

FIG. 7B shows a plate-shaped peeling portion 31a.
Behind the fixing roller 21 and in an L-shaped bent portion 31 on the opposite side.
B is bent. By this bending process, the peeling portion 31a
Of the fixing roller 21
When a type that bulges toward the central portion in the axial direction (so-called crown type: shape in which the central portion diameter is larger than the end diameter) is used as the end portion, the tip of the peeling portion 31a and the fixing roller 2
The gap G with one surface can be kept constant.

Although the embodiment of the present invention has been described above, 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 a conventional technique. You may make it combine well-known technology.

For example, although the peeling member 31 on the fixing roller 21 side has been described in the above embodiment, it goes without saying that the peeling member 32 on the pressure roller 22 side may also be applied.

[0033]

As is apparent from the above description, according to the present invention, the gap between the tip of the peeling member and the surface of the fixing roller can be constantly kept constant.

[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 schematic diagram for explaining the features of the present invention.

[Explanation of symbols]

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

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA16 BA08 BA16 BA20 BA21                       BB13 BB14 BB15 BB38                 3F053 AA19 AA22 LA02 LB03                 3J103 AA06 AA07 BA03 FA02 GA57                       GA58 GA60

Claims (3)

[Claims] 1. A fixing roller of a type which has a heat source and is dented toward a central portion in an axial direction, a pressure roller which is pressed against the fixing roller, and an axial direction of the fixing roller and a recording medium conveying direction downstream of the fixing nip portion. And a peeling member disposed in the vicinity of the fixing roller, the peeling member including a peeling portion made of a metal plate and bent in an L shape to the fixing roller side behind the peeling portion. A fixing device having a bent portion. 2. A fixing roller of a type having a heat source and expanding toward a central portion in an axial direction, a pressure roller pressed against the fixing roller, and an axial direction of the fixing roller and a recording medium conveying direction downstream of a fixing nip portion. And a peeling member disposed in the vicinity of the fixing roller, the peeling member including a peeling portion made of a metal plate and an L-shaped portion behind the peeling portion and opposite to the fixing roller. And a fixing device having a bent portion. 3. The fixing device according to claim 1, wherein the fixing roller and the pressure roller are arranged in a substantially horizontal state.