JP2002311741A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrupt contact between a rotating body side edge and a rotating body of a rotating body when the wear of a contact portion between the rotating body and the peeling plate progresses. To provide a fixing device capable of avoiding the problem. SOLUTION: A fixing roller 11 and a peeling plate 14 abut at a position corresponding to a position outside an image area of a sheet, and the contact relationship causes a side of the peeling plate 14 closer to the fixing roller 11 at a position corresponding to an image area of the sheet. A predetermined clearance is secured between the edge and the fixing roller 11, and the peeling plate 14 is positioned with respect to the fixing roller 11. And the release plate 14
The clearance between the fixing roller 11 side edge and the fixing roller 11 is configured to gradually increase as the distance from the contact point between the fixing roller 11 and the peeling plate 14 increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an electrophotographic image forming apparatus such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art Heretofore, as this type of fixing device, there has been known a fixing device provided with a release plate which comes into contact with a recording material discharged from a nip portion and peels off the recording material from a rotating body.
For example, Japanese Patent Application Laid-Open No. 53-81241 discloses a fixing device provided with a pick-off blade (peeling plate) having an abutting member that comes into contact with a fixing roller (rotary body) at a position corresponding to a position outside an image area of a recording material. Have been. In this fixing device, the contact relationship between the butting member and the fixing roller is
A predetermined clearance is ensured between the fixing roller side edge of the pick-off blade and the fixing roller, and the pick-off blade is positioned with respect to the fixing roller.

[0003]

However, in the case of the above-mentioned conventional fixing device, if the contact portion between the abutting member and the fixing roller progresses due to long-term use or the like, the fixing roller of the pick-off blade may be used. When the side edge on the side suddenly comes into contact with the fixing roller substantially in the entire axial direction of the fixing roller, the pick-off blade and the fixing roller may be severely damaged.

The present invention has been made by focusing on the problems existing in the prior art as described above. The purpose is to prevent abrupt contact of the rotating body with the side edge of the peeling plate and the rotating body almost entirely in the axial direction of the rotating body when wear of the contact portion between the rotating body and the peeling plate progresses. An object of the present invention is to provide a fixing device that can be avoided.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a first rotator and a nip portion formed between the first rotator are formed. A fixing member for fixing the unfixed toner image on the recording material by nipping and conveying the recording material at the nip portion. A peeling plate for peeling the material from the first rotating body is disposed along the axial direction of the first rotating body, and the first rotating body and the peeling plate are located at positions corresponding to outside the image area of the recording material. A predetermined clearance is secured between the side edge of the peeling plate on the first rotating body side and the first rotating body at a position corresponding to the image area of the recording material. And the release plate is positioned with respect to the first rotating body. And, further, the clearance,
The gist of the invention is that it is configured to gradually increase as the distance from the contact point between the first rotating body and the peeling plate increases.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the first rotating body has an inverted crown shape in which an outer diameter is large at both ends and small at a center, and the peeling is performed. The gist is that the side edge of the plate on the first rotating body side is formed to extend substantially parallel to the central axis of the first rotating body.

According to a third aspect of the present invention, in the fixing device according to the first aspect, the first rotating body has a uniform outer diameter in an axial direction, and the first rotating body has a first shape. The point is that a portion corresponding to the outside of the image area of the recording material on the side edge on the rotating body side is protruded toward the first rotating body side.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a fixing device in an electrophotographic image forming apparatus will be described below with reference to FIGS.

In an electrophotographic image forming apparatus, an exposure apparatus for forming a latent image based on an original image on a photoreceptor and a developing apparatus for forming a toner image from the latent image are used as units for executing an electrophotographic process. And a transfer device for transferring the toner image onto paper (recording material). The fixing device is disposed downstream of these devices and performs a fixing process of fixing an unfixed toner image transferred onto a sheet by a transfer device onto a sheet, and also has a sheet transport function.

FIG. 1 and FIG. 3A are schematic diagrams showing the entire configuration of the fixing device according to the present embodiment. As shown in these figures, the fixing device is provided with a fixing roller 11 as a first rotating body and a pressure roller 12 as a second rotating body, which incorporates a halogen lamp 11a as a heating source. I have. The fixing roller 11 and the pressure roller 12 are arranged substantially in parallel, and are in contact with each other with a predetermined pressing force by a biasing unit (not shown). And the fixing roller 1
A nip 13 is formed between the roller 1 and the pressure roller 12 by the contact surfaces of the rollers 11 and 12.

In the present embodiment, the fixing roller 11 and the pressure roller 12 each have an inverted crown shape whose outer diameter is large at both ends and small at the center, and the nip portion 13 has a nip width (nip portion 13). Of the paper in the paper transport direction) are wide at both ends and narrow at the center. In FIGS. 2 and 3, for convenience, the amount of reverse crown of the fixing roller 11 and the pressure roller 12 is exaggerated.

The fixing roller 11 is driven to rotate in the direction of arrow A shown in FIG. 1 by driving means (not shown), and the pressing roller 12 is rotated in the direction of arrow B shown in FIG. It has become. For this reason, the paper P transported from the transfer device (not shown) to the fixing device and sent between the fixing roller 11 and the pressure roller 12 is nipped by the nip portion 13 and transported in the direction of arrow C shown in FIG. It has become.

In the vicinity of the fixing roller 11, a peeling plate 14 for peeling the sheet P discharged from the nip 13 from the fixing roller 11 is provided. Release plate 14
Is disposed close to the fixing roller 11 at a position downstream of the nip portion 13 in the rotation direction of the fixing roller 11, and is supported by a support member 15. The release plate 14 has a flat plate shape, and the side edge on the side of the fixing roller 11 is linear (see FIG. 2). The peeling plate 14 is arranged along the axial direction of the fixing roller 11, and a side edge of the peeling plate 14 on the side of the fixing roller 11 extends substantially parallel to the central axis of the fixing roller 11.

As shown in FIGS. 2 and 3B, the peeling plate 14 is in contact with both ends in the axial direction of the fixing roller 11 at both ends in the width direction (axial direction of the fixing roller 11). Thus, the fixing roller 11 and the peeling plate 14 come into contact with each other at a position corresponding to the outside of the image area of the paper P. A predetermined clearance is secured between the fixing roller 11 and the side edge of the release plate 14 on the side of the fixing roller 11 at a position corresponding to the image area of the sheet P by the contact relationship between the fixing roller 11 and the release plate 14. At the same time, the release plate 14 is positioned with respect to the fixing roller 11. Further, the clearance between the side edge of the peeling plate 14 on the side of the fixing roller 11 and the fixing roller 11 is
And gradually increases as the distance from the contact point of the peeling plate 14 increases, and reaches a maximum at the axial center portion of the fixing roller 11.

Next, the operation of the fixing device configured as described above will be described. The paper P transported from the transfer device (not shown) to the fixing device is
And is pressed and heated by the nip 13 to fix the unfixed toner image on the sheet P. After the fixing process, when the sheet P adheres to the fixing roller 11 with the melted toner and is discharged from the nip portion 13 so as to be wound around the fixing roller 11, the sheet P The sheet P is peeled from the fixing roller 11 when the side edge on the side of the fixing roller 11 contacts.

The fixing roller 11 has been used for a long time.
When the abrasion of the contact portions between the fixing roller 11 and the peeling plate 14 at both ends in the axial direction progresses, the side edge of the peeling plate 14 on the fixing roller 11 side and the fixing roller 11 in accordance with the progress of the wear.
Clearance gradually narrows. At this time, since the clearance between the fixing roller 11 side edge of the peeling plate 14 and the fixing roller 11 gradually increases as the distance from the contact position increases, the clearance at the position corresponding to the image area of the paper P is increased. Side edge of plate 14 on the side of fixing roller 11 and fixing roller 1
The contact with the fixing roller 11 starts first in the vicinity of the contact point and gradually spreads toward the axial center of the fixing roller 11 as the wear progresses.

The effects obtained by the present embodiment will be described below. (1) According to the present embodiment, the fixing of the peeling plate 14 at a position corresponding to the image area of the paper P due to the abrasion of the contact point between the fixing roller 11 and the peeling plate 14 at both ends in the axial direction of the fixing roller 11. The contact between the side edge on the roller 11 side and the fixing roller 11 starts first in the vicinity of the contact point, and gradually spreads to the axial center portion of the fixing roller 11 as the wear progresses.
Therefore, it is possible to prevent the side edge of the peeling plate 14 on the fixing roller 11 side and the fixing roller 11 from unexpectedly contacting substantially the entire axial direction of the fixing roller 11. Therefore, it is possible to prevent the fixing roller 11 and the peeling plate 14 from being damaged due to the unexpected contact.

(2) JP-A-53-8124 mentioned above
A predetermined clearance is secured between the fixing roller 11 and the side edge of the peeling plate 14 on the side of the fixing roller 11 at a position corresponding to the image area of the paper P, even if there is no member corresponding to the abutting member in JP-A-1. At the same time, the release plate 14 can be positioned with respect to the fixing roller 11. Therefore,
The number of parts can be reduced.

(3) Since the fixing roller 11 and the peeling plate 14 are always in contact with each other, the peeling plate 14 can also function as a heat radiating member for preventing the fixing roller 11 from overheating. Moreover, since the peeling plates 14 are in contact with both ends of the fixing roller 11 in the axial direction, it is possible to effectively prevent excessive temperature rise at the axial ends of the fixing roller 11. Note that the end of the fixing roller 11 in the axial direction becomes a non-sheet passing portion depending on the size of the sheet P, and thus tends to easily cause an excessive temperature rise as compared with the central portion in the axial direction.

(4) The contact point between the fixing roller 11 and the peeling plate 14 is not the position corresponding to the image area of the sheet P but the position corresponding to the outside of the image area. There is no fear of damaging the surface corresponding to the image area of the paper P.

(5) Since the nip portion 13 has an inverted crown shape, it is possible to prevent paper wrinkles (rear end wrinkles) from being formed in the widthwise central portion of the rear end of the sheet P in the transport direction. This is because the transport speed of the paper P in the nip portion 13 is high at both ends and low at the center, so that a pulling force acts on the rear end in the transport direction of the paper P toward both sides in the width direction. By the way, long paper P where the trailing edge wrinkles easily occur
This is particularly effective for (for example, A3 size paper).

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. Note that, in the present embodiment, the same or corresponding components as those of the first embodiment are denoted by the same reference numerals, description thereof is partially omitted, and different components will be mainly described.

In this embodiment, both the fixing roller 11 and the pressure roller 12 have a uniform outer diameter in the axial direction. Further, the fixing roller 1 of the release plate 14
One side edge is in the width direction (axial direction of the fixing roller 11).
Are formed in an arc shape protruding toward the fixing roller 11 side. The peeling plate 14 is in contact with both ends in the axial direction of the fixing roller 11 at both protruding ends, whereby the fixing roller 11 and the peeling plate 14 contact at positions corresponding to outside the image area of the paper P. It has a configuration.

Therefore, according to the present embodiment, the effects (1) to (5) described above can be obtained. The above embodiments may be modified as follows.

In the first embodiment, the pressure roller 12
The shape of the pressure roller 12 is not limited thereto, but may be a crown shape in which the outer diameter is small at both ends and large at the center,
The outer diameter dimension may be uniform in the axial direction. The shape of the nip portion 13 is not limited to the inverted crown shape, but may be a narrow nip width at both ends and a wide crown shape at the center portion, or a rectangular shape having the same nip width at both ends and the center portion. It may be.

In the second embodiment, the pressure roller 12
The outer diameter is uniform in the axial direction, but the shape of the pressure roller 12 is not limited thereto, and may be a crown shape or an inverted crown shape.

In the second embodiment, the shape of the side edge of the peeling plate 14 on the fixing roller 11 side is changed in the width direction (fixing roller 1
Although the arc shape has both ends protruding in the (axial direction 1), the shape may be a triangular shape or a trapezoid shape in which both ends protrude in the width direction.

The fixing roller 11 of the first embodiment
May be configured such that the outer dimensions are uniform in the axial direction when not heated, and deform into an inverted crown shape when heated. When the heating is not performed, the fixing roller 1 of the peeling plate 14 is not heated.
The side edge on one side contacts the fixing roller 11 in the entire width direction (axial direction of the fixing roller 11), and when heated, the side edge contacts the fixing roller 11 only at both ends in the width direction as shown in FIG. Good. If the release plate 14 is not warm enough,
At the time of peeling, the toner image immediately after fixing on the recording material is
When the toner is touched, the toner is rapidly cooled and solidified before being smoothed by its own viscoelastic force, and as a result, an image having poor glossiness may result. However, with the configuration described above, the contact area between the fixing roller 11 and the peeling plate 14 at the time of warm-up increases, so that the peeling plate 14 can be quickly warmed by heat conduction from the fixing roller 11. Therefore, a good gloss image can be obtained even immediately after warm-up. In the fixing roller 11 having the above-described configuration, a layer formed of a material having a high coefficient of thermal expansion is formed on the surface of the fixing roller 11, and the thickness of the layer is increased toward both ends in the axial direction. realizable.

In order to improve the abrasion resistance of the abutting portion between the fixing roller 11 and the peeling plate 14, the abutting portion may be made of a material having excellent abrasion resistance (for example, metal such as aluminum). Good. For example, a metal annular member may be attached to both ends of the fixing roller 11 in the axial direction, so that the abrasion resistance of the portion that comes into contact with the peeling plate 14 may be increased. Alternatively, the fixing roller 11 may be configured such that the core metal is exposed at both ends in the axial direction, and the exposed metal core portion may be used as the peeling plate 14.
May be configured to come into contact with.

In order to improve the thermal conductivity at the contact point between the fixing roller 11 and the peeling plate 14, the contact point may be made of a material having excellent heat conductivity (for example, a metal such as aluminum). Good. For example, a metal annular member may be fitted to both ends of the fixing roller 11 in the axial direction, so that the thermal conductivity of a portion in contact with the peeling plate 14 may be increased. Alternatively, the fixing roller 11 may be configured such that the core metal is exposed at both ends in the axial direction, and the exposed core metal may be in contact with the peeling plate 14.

As shown in FIG. 5, the fixing roller 11 having a uniform outer diameter in the axial direction is used, and the fixing roller 1 is located at the center in the width direction (axial direction of the fixing roller 11).
A peeling plate 14 having an arc-shaped cross section that is convex on the side opposite to the one side may be used. Then, the peeling plate 14 comes into contact with both ends in the axial direction of the fixing roller 11 at both ends in the width direction, whereby the fixing roller 11 and the peeling plate 14 come into contact at positions corresponding to outside the image area of the paper P. Is also good. Also in this configuration, the clearance secured between the fixing roller 11 and the side edge of the peeling plate 14 on the side of the fixing roller 11 gradually increases as the distance from the contact point between the fixing roller 11 and the peeling plate 14 increases. With such a configuration, the same effects as those of the above embodiments can be obtained.

Next, the technical ideas that can be grasped from the above embodiment will be described below. 4. The fixing device according to claim 1, wherein a contact portion between the first rotating body and the peeling plate is made of metal. 5. With this configuration,
The abrasion resistance at the contact point between the first rotating body and the peeling plate can be improved, and the thermal conductivity between the first rotating body and the peeling plate at the contacting point can be improved.

An image forming apparatus comprising the fixing device according to any one of claims 1 to 3.

[0034]

Since the present invention is configured as described above, it has the following effects. Claims 1 to 3
According to the invention described in the above, when the wear of the contact portion between the rotating body and the peeling plate progresses, the side edge of the peeling plate on the rotating body side and the rotating body unexpectedly come into contact with each other substantially in the entire axial direction of the rotating body. Can be avoided.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a fixing device according to a first embodiment.

FIG. 2 is a plan view schematically showing a main part of the identification attachment device.

FIG. 3 (a) is a perspective view schematically showing an identification wearing device,
(B) is sectional drawing in the 3b-3b line of (a).

FIG. 4 is a plan view schematically showing a main part of a fixing device according to a second embodiment.

5A is a perspective view schematically showing a fixing device according to another embodiment, and FIG. 5B is a cross-sectional view taken along line 5b-5b in FIG.

[Explanation of symbols]

 P paper 11 Fixing roller as first rotating body 12 Pressure roller as second rotating body 13 Nip portion 14 Release plate

Claims (3)

[Claims] A first rotator and a second rotator forming a nip between the first rotator and a recording material held by the nip to convey the recording material; In the fixing device for fixing the unfixed toner image above, a peeling plate that comes into contact with the recording material discharged from the nip portion and peels the recording material from the first rotating body in the axial direction of the first rotating body. The first rotating body and the peeling plate abut at a position corresponding to the outside of the image area of the recording material, and the abutting relationship causes the first rotating body to abut at a position corresponding to the image area of the recording material. A predetermined clearance is secured between the side edge of the peeling plate on the first rotating body side and the first rotating body, and the peeling plate is positioned with respect to the first rotating body, and further, The clearance between the first rotating body and the peeling plate; A fixing device, wherein the fixing device is configured to gradually increase as the distance from the place increases. 2. The first rotating body has an inverted crown shape whose outer diameter is large at both ends and small at a center.
2. The fixing device according to claim 1, wherein a side edge of the peeling plate on a first rotating body side is formed to extend substantially parallel to a central axis of the first rotating body. 3. 3. The first rotating body has a uniform outer diameter dimension in the axial direction, and a portion corresponding to the outside of the image area of the recording material at a side edge of the peeling plate on the first rotating body side. 2. The projection according to claim 1, wherein the projection protrudes toward the first rotating body.
3. The fixing device according to claim 1.