JPH0452772Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> This invention relates to a fixing device that heats and presses a transfer material to which a developer image is attached in an image forming apparatus using electrophotography to melt and fix the image. The present invention relates to a fixing device including a pair of upper and lower rollers.

<Summary of the invention> The fixing device for electrophotography according to this invention has an upper peeling claw and a lower peeling claw positioned in order to prevent stains caused by the phenomenon agent on the back side of the transfer material that has passed through the fixing device. By aligning the two rollers, the phenomenon agent adhering to the lower roller can be removed from the roller surface by the lower peeling claw.

<Prior art and its drawbacks> In image forming devices using electrophotography, such as copying machines, an image is transferred to a transfer material such as paper, and then heated and pressurized by a fixing device to transfer the image to the surface of the paper. Make it stick. This fixing device is generally composed of a pair of upper and lower rollers, one or both of which is raised to a temperature that can melt the developer using a heater lamp or the like, and the two are pressed together under a constant pressing force. In such a fixing roller, in order to release the paper from the roller surface, a plurality of peeling claws are provided in the longitudinal direction of the roller to separate the paper from the roller surface.

However, this peeling claw may cause stains on the back surface of the paper due to the developer. To explain the cause of this stain on the back side of the paper, first, when the paper passes the fixing roller, the developer on the paper is offset to the surface of the upper roller and further adheres to the upper peeling claw. As the temperature of the fixing roller changes, the temperature of the peeling claw also changes, becoming high during copying operations and becoming low when the heater lamp is turned off after copying is complete. For this reason, when the copying operation is completed, the developer adhering to the peeling claw becomes stuck. Thereafter, when the temperature of the fixing roller rises at the start of the next copying operation, the developer stuck to the peeling claw melts and moves to the surface of the upper roller. At the start of copying work, the fixing roller is also driven and idles until the paper is guided. At this time, the developer moves from the surface of the upper roller to the surface of the lower roller and adheres to the back surface of the paper as it passes through.

In recent years, double-sided copying has become more common in order to reduce paper consumption, and it is necessary to eliminate the backside stains that occur as described above. For this reason, conventionally, (1) a developer that does not easily adhere to the peeling nail is used. (2) Attach the cleaning member. (3) Improving the shape and material of the peeling claw is being considered.

However, it is not possible to significantly change the composition of the developer due to the problem of its fixability to paper, and the attachment of a cleaning member or improvement of the peeling claw has the disadvantage of complicating the mechanism and increasing costs.

<Purpose of the invention> In view of the above-mentioned conventional drawbacks, the purpose of this invention is to scrape off the developer stuck to the upper peeling claw with the lower peeling claw when it moves to the surface of the lower roller during the next copying operation. To provide a fixing device that does not stain the back surface of paper when it passes through.

<Structure and effects of the invention> The fixing device of this invention has an upper peeling claw that contacts the roller and a lower peeling claw that contacts the lower roller and has a wider contact area than the upper peeling claw in the longitudinal direction of the roller. It is characterized by having a plurality of them arranged in the same position.

With the above structure, according to this invention, the developer that moved from the surface of the upper roller to the upper peeling claw and stuck there during the previous copying operation melts and adheres to the surface of the upper roller again during the next copying operation. When it moves to the surface of the lower roller during idle rotation, it can be scraped off by the lower peeling claw that comes into contact with the surface of the lower roller. Moreover, the contact area of the lower peeling claw with the lower roller surface is larger than the contact area of the upper peeling claw with the upper roller surface, so that from the upper peeling claw to the upper roller surface, and from the upper roller surface to Even if the adhesion area expands when the developer moves to the surface of the lower roller, it can be reliably scraped off by the lower peeling claw. This prevents developer from adhering to the back side of the paper guided by the fixing roller from the surface of the lower roller, making it possible to reliably prevent the back surface from becoming dirty. The images have never been difficult to see, and high-quality images can always be formed on both sides.

<Embodiment> FIG. 2 is a schematic front view showing the structure of the main parts of a copying machine in which an electrophotographic fixing device according to an embodiment of the present invention is used.

A photosensitive drum 22 is provided inside the copying machine main body 21, and a charging charger 23, a developing device 24, a transfer charger 25, a peeling charger 26, a cleaner 27, and a static elimination charger 28 are provided on the outer periphery of the photosensitive drum 22.
Together, they constitute a copying process section 29. A conveyor belt 30 is located on the left side of this copying process section 29.
is provided. This conveyor belt 30 uses a suction device (not shown) to adsorb the paper onto the belt and convey it in the direction of arrow A.

A fixing roller 1 composed of an upper roller 2 and a lower roller 3 is provided on the left side of the conveyor belt 30 . The upper roller 2 is formed into a hollow cylindrical shape, and a heater lamp 7 is provided inside thereof. This heater lamp 7 raises the temperature of the upper roller 2 to a temperature at which the developer can be melted. The lower roller 3 is in contact with the upper roller 2 under a constant pressing force. In addition, the upper roller 2 has an upper peeling claw 5.
However, lower peeling claws 6 are provided on the lower roller 3 so as to be able to contact each other. This upper peeling claw 5
In order to prevent early deterioration of the surfaces of the upper roller 2 and lower roller 3, the lower peeling claw 6 is brought into contact only during copying operations. Also,
The upper peeling claw 5 and the lower peeling claw 6 are integrally attached to a mounting plate 8.

With the above configuration, the surface of the photosensitive drum 22 is charged with a single polarity by the charging charger 23 during copying operations. Thereafter, reflected light from a light source (not shown) from the document is irradiated, and an electrostatic latent image is formed. A developer is supplied from the developing device 24 to this electrostatic latent image, and the image is visualized. In synchronization with the rotation of the photosensitive drum 22, the transfer charger 2 is transferred from a paper feed section (not shown).
A sheet of paper is guided between the transfer charger 25 and the photoreceptor drum 22, and the image formed on the surface of the photoreceptor drum 22 is transferred to the sheet by corona discharge of the transfer charger 25. The photosensitive drum 2 is removed by the peeling charger 26.
The paper that has been peeled off from the surface of
is conveyed in the direction of arrow A and guided to the fixing roller 1. When passing through the fixing roller 1, the paper is heated and pressurized, and the image transferred to the surface is fixed.

FIG. 1 is a side view showing how a peeling claw of the fixing device is attached.

Three upper peeling claws 5 and three lower peeling claws 6 are each attached to the mounting plate 8 with the rollers aligned in the longitudinal direction. A hole 9 through which paper passes is provided in the center of the mounting plate 8. The upper peeling claw 5 and the lower peeling claw 6 are attached to face each other in the hole 9. Lower peeling claw 6
is wider than the width of the upper peeling claw 5,
Similarly, the lower peeling claw 6 has a wider contact range with the surface of the roller. Further, the mounting plate 8 is mounted inside the transfer machine by inserting screws 10a into elongated holes 10. This allows the mounting plate 8 to move its mounting position in the direction of arrow D or E parallel to the longitudinal direction of the roller.

FIGS. 3A and 3B are front views showing the operation of the fixing device.

As shown in FIG. 5A, when the paper that has undergone the transfer process is guided in the direction of arrow A between the upper roller 2 and the lower roller 3, it is heated and pressed by both rollers. Although the surface of the upper roller 2 is coated with a fluororesin or the like in consideration of the releasability of the developer, some of the developer is offset from the paper 4.
During the copying operation, the upper peeling claw 5 is in contact with the surface of the upper roller 2, and the developer 11 moves from the surface of the upper roller 2 to the tip of the peeling claw 5. When the copying operation is completed, the developer 11 adheres to the tip of the upper peeling claw 5.

As shown in Figure B, the upper heat roller 2 is heated during the next copying operation, and the upper and lower rollers rotate in the directions of arrows B and C, respectively. On the other hand, due to the temperature rise, the developer 11 stuck to the upper peeling claw 5 is melted and the upper roller 2
and moves to the surface of the lower roller 3 where it comes into contact with the upper roller 2 under a constant pressing force.
The developer 11 that has moved to the surface of the lower roller 3 is immediately scraped off by the lower peeling claw 6 and does not remain on the surface of the lower roller 3. Therefore, even when the paper passes through, the back side of the paper is not contaminated with developer.

As described above, according to this embodiment, by providing the upper peeling claw and the lower peeling claw at the same position in the longitudinal direction of the roller, the developed image adheres from the upper peeling claw to the lower roller via the upper roller. The agent can be reliably scraped off by the lower peeling claw 6, and stains on the back side of the paper can be prevented. In addition, the upper peeling claw 5 and the lower peeling claw 6 are integrally attached to the mounting plate 8, and since the mounting plate 8 can change the fixed position in the axial direction of the roller, the upper peeling claw 5 and the lower peeling claw The contact position between the claw 6 and the upper roller 2 and lower roller 3 can be changed. Therefore, it is possible to prevent partial deterioration of the surfaces of the upper roller and lower roller 3, so that the releasability of the surfaces can be maintained.
The offset of the developer can be minimized.

Note that the lower roller 3 may be in constant contact with the upper roller 2, and the peeling claws 5 and 6 may be attached to separate mounting plates.

[Brief explanation of the drawing]

Fig. 1 is a side view showing how a peeling claw is attached to an electrophotographic fixing device that is an embodiment of this invention, and Fig. 2 is a front view showing the configuration of the main parts of a copying machine in which the fixing device is used. 3A and 3B are front views showing the operation of the fixing device. 2... Upper roller, 3... Lower roller, 5...
Upper peeling claw, 6...lower peeling claw, 8...mounting plate.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In an electrophotographic fixing device consisting of a pair of upper and lower rollers, an upper peeling claw that contacts the upper roller, and a lower roller that contacts the lower roller and is more in contact than the upper peeling claw. A fixing device for electrophotography, characterized in that a plurality of lower peeling claws having a wide range are provided with the rollers aligned in the longitudinal direction. (2) Utility model registration claim 1, in which all of the plurality of upper peeling claws and lower peeling claws are integrally attached to a mounting member that can be fixed by changing the longitudinal position of the roller. A fixing device for electrophotography according to item 1.