JP4027146B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a laser beam printer. In particular, the present invention relates to an apparatus including an electrostatic transfer belt device that conveys a sheet having a toner image transferred to a sheet at a transfer unit to a fixing device while electrostatically adsorbing the sheet.
[0002]
[Prior art]
As an electrophotographic image forming apparatus, there is an image forming apparatus that conveys a sheet by using an electrostatic transfer belt device. A typical example of the image forming apparatus is a full-color laser beam printer 60 as shown in FIG. This is an electrostatic transfer belt 11 stretched by a plurality of rollers. While the sheet is adsorbed and conveyed, the photosensitive drums 1 in the four process cartridges 7 arranged along the conveying path are used to produce yellow, magenta, A toner image composed of cyan and black is sequentially transferred onto the sheet S, and a color image is formed by superimposing colors. The sheet S on which the color image is formed is separated from the electrostatic transfer belt 11 and guided to the fixing device 70 by the fixing inlet guide 71, and the unfixed toner image is fixed on the sheet S and discharged outside the apparatus. Is done.
[0003]
The electrostatic transfer belt device 10 including the electrostatic transfer belt 11 is configured to be able to be largely opened with the driven roller 13 as a fulcrum in order to attach and detach the process cartridge 7 and jam processing in the machine. The fixing device 70 including the fixing inlet guide 71 is also configured to be detachable in the upward direction in consideration of maintainability and jam handling.
[0004]
[Problems to be solved by the invention]
As described above, when the sheet S is attracted to the electrostatic transfer belt 11 and the toner image is transferred and conveyed, the sheet S is peeled off from the electrostatic transfer belt 11 until all the four photosensitive drums 1 are passed. And must be reliably electrostatically adsorbed. As a method for separating the sheet S from the electrostatic transfer belt 11, curvature separation using the curvature of the driving roller 12 disposed in the downstream sheet separation portion and the rigidity of the sheet S is used. However, when the sheet S is thin paper having low rigidity, the rigidity necessary for separation is insufficient, and it is difficult to reliably separate the sheet from the electrostatic transfer belt 11.
[0005]
Here, in order to improve the separation property of thin paper or the like, it is conceivable to reduce the diameter of the drive roller 12 to increase the curvature to facilitate the separation, but the electrostatic transfer belt 11 has an appropriate tension. In order to prevent the driving roller 12 from being bent, the diameter of the driving roller 12 is naturally limited in order to prevent the driving roller 12 from being bent because the electrostatic transfer belt 11 is wide and the tension is large. Will be.
[0006]
In addition, there was a device equipped with a separation charging device 80 to improve the separability by reducing the electrostatic adsorption force of the sheet and the electrostatic transfer belt by performing static elimination of the sheet at the separation unit. Not only this, but also the generation of ozone accompanying corona discharge, it was not preferable from the viewpoint of environmental problems.
[0007]
It is also possible to extend the front end of the fixing entrance guide 71 and bring it as close as possible to the electrostatic transfer belt 11 so as to scoop the separated sheets. However, both the electrostatic transfer belt device 10 and the fixing device 70 are the printer body. Since the gap G between the electrostatic transfer belt 11 and the fixing inlet guide 71 is difficult to be constant because it is movable and detachable with respect to 60, the fixing inlet guide 71 and the tip of the fixing inlet guide 71 are Since the transfer belt 11 may come into contact, the gap G could not be made sufficiently small. For this reason, it is difficult to stably scoop the sheet that is wound around the electrostatic transfer belt 11.
[0008]
Accordingly, the present invention solves such problems, and an object of the present invention is to provide an image forming apparatus that forms an image by reliably separating the sheet from the electrostatic transfer belt with an inexpensive and simple configuration. Is to provide.
[0009]
[Means for Solving the Problems]
The present invention for solving the above problems, fixing with an image forming unit for forming a toner image on a sheet, and nipped and conveyed the sheet on which the toner image has been formed a nip to fix the toner image on the sheet means, in an image forming apparatus including a sheet conveying means for conveying the sheet from said image forming means comprises a conveyor belt which moves wound around a plurality of support rollers to said fixing unit, wherein the fixing means is the A fixing inlet guide for guiding the sheet from the sheet conveying unit to the nip is supported to be swingable, and the sheet conveying unit is attached to the image forming apparatus main body so as to be openable and closable. The supported fixing inlet guide is positioned with respect to a single supporting roller of the sheet conveying means.
[0010]
The fixing unit is detachably attached to the apparatus main body.
[0012]
Further, the sheet conveying means includes electrostatic adsorption means for electrostatically adsorbing the sheet to the conveyance belt.
[0013]
According to the present invention, the fixing inlet guide can be swung with respect to the fixing device, and is always positioned with respect to the driving roller of the electrostatic transfer belt, so that the gap between the fixing inlet guide tip and the electrostatic transfer belt is minimized. It becomes possible to set small. Further, the gap is always positioned with respect to the printer body so that the gap is always reproduced even after the electrostatic transfer belt device is opened / closed and the fixing device is attached / detached.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
【Example】
Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
[0015]
1 and 2 are side views of an electrostatic transfer belt device and a fixing inlet guide according to an embodiment of the present invention, FIG. 3 is a perspective view of the electrostatic transfer belt device and the fixing inlet guide, and FIG. 4 is an image forming apparatus. FIG. 5 is an overall view of the image forming apparatus showing a state where the electrostatic transfer belt device is opened.
[0016]
First, the overall configuration of the image forming apparatus will be outlined with reference to FIG. FIG. 4 is a diagram showing an overall configuration of a full-color laser beam printer which is an aspect of the image forming apparatus.
[0017]
The printer main body 50 includes four photosensitive drums 1a, 1b, 1c, and 1d corresponding to yellow, cyan, magenta, and black colors in the vertical direction. The photosensitive drum 1 is driven to rotate counterclockwise in the figure by a driving unit (not shown). The periphery of the photosensitive drum 1 is irradiated with a laser beam in order according to the direction of rotation of the charging device 2 (2a, 2b, 2c, 2d) that uniformly charges the surface of the photosensitive drum 1, and based on image information of each color. A scanner unit 3 (3a, 3b, 3c, 3d) that forms an electrostatic latent image on the photosensitive drum 1, and a toner image of yellow, cyan, magenta, and black is attached to the electrostatic latent image and developed as a toner image. A developing device 4 (4a, 4b, 4c, 4d) for cleaning, a cleaning device 6 (6a, 6b, 6c, 6d) for removing toner remaining on the surface of the photosensitive drum 1 after transfer, and the like are provided.
[0018]
Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrally formed into a cartridge to form a process cartridge 7 (7a, 7b, 7c, 7d).
[0019]
An electrostatic transfer belt device 10 is disposed at the opposing portions of the photosensitive drums 1a, 1b, 1c, and 1d so that the electrostatic transfer belt 9 is in contact therewith. The electrostatic transfer belt 11 is formed of a film-like member having a predetermined volume specific resistance and a thickness of about 150 μm. The electrostatic transfer belt 11 is stretched between four rollers, a driving roller 12 and driven rollers 13, 14, and 15. , Rotate clockwise in the figure. The driving roller 12 is supported on both side frames (not shown) via ball bearings 16 attached to shafts 12a at both ends. The driven rollers 13, 14, 15 are also supported in the same manner.
[0020]
An electrostatic attraction roller 17 is provided on the most upstream side of the electrostatic transfer belt device 10 so as to face the driven roller 13 with the electrostatic transfer belt 9 interposed therebetween, and the sheet S is pressed against the outer periphery of the electrostatic transfer belt 11. In addition, the sheet S is electrostatically attracted and conveyed by applying a voltage between the electrostatic transfer belt 11 and the electrostatic attraction roller 17.
[0021]
A transfer roller 18 (18a, 18b, 18c, 18d) is arranged in parallel at a position that contacts the inside of the electrostatic transfer belt 11 and faces the four photosensitive drums 1a, 1b, 1c, 1d. A positive charge is applied to the sheet S from the transfer roller 18 via the electrostatic transfer belt 11, and the negative polarity on the photosensitive drum 1 is applied to the sheet S in contact with the photosensitive drum 1 by an electric field due to this charge. The toner image is transferred.
[0022]
As shown in FIG. 5, the electrostatic transfer belt device 10 is installed so that it can be largely opened outward with respect to the printer 100 by rotating around the driven roller 13 as a fulcrum. When the process cartridge 7 is taken out or when the jammed paper in the machine is removed, the electrostatic transfer belt device 10 can be easily accessed by opening it.
[0023]
The sheet feeding device 20 feeds and conveys the sheet S to the image forming unit, and a plurality of sheets S are stored in the sheet feeding cassette 21. At the time of image formation, the sheet feeding roller 22 and the registration roller pair 23 are driven and rotated according to the image forming operation to separate and feed the sheets S in the sheet feeding cassette 21 one by one. Then, after stopping and forming a loop, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized to be fed to the electrostatic transfer belt device 10.
[0024]
The fixing device 30 includes a fixing roller 31 and a pressure roller 32 pressed against the fixing roller 31. When the sheet S passes through the nip N formed by the fixing roller 31 and the pressure roller 32, heat and pressure are applied, so that the transferred toner image is fixed on the sheet S. A discharge guide 33 and a discharge roller pair 34 for discharging the sheet S to the outside of the apparatus are provided downstream of the nip N.
[0025]
In order to guide the sheet S conveyed from the electrostatic transfer belt device 10 to the nip N, the fixing frame 35 of the fixing device 30 is provided with a fixing inlet guide 36 having an inclined paper guide surface 36a. The fixing inlet guide 36 is supported by a shaft 36b integrally formed at both ends in the longitudinal direction thereof so as to be swingable and slidable in the direction of the long hole 35a by being fitted into a long hole 35a formed in the fixing frame 35. Has been. On the back side of the sheet guide surface 36 a of the fixing entrance guide 36, hook shapes 36 c are formed at both ends in the longitudinal direction, and the tension spring 37 that is hooked between the fixing frame 35 and the electrostatic transfer belt device 10. The drive roller 12 is biased in the direction. Further, abutting members 36d and 36e are formed at both ends in the longitudinal direction of the fixing entrance guide 36, respectively. When the electrostatic transfer belt device 10 is closed, it is formed on the outer peripheral surface of the ball bearing 16 of the driving roller 12. The positions of the fixing inlet guide 36 with respect to the driving roller 12 are always determined by the contact of the respective abutting members 36d and 36e. In particular, the front end portion of the sheet guide surface 36 a can hold a certain gap G with respect to the electrostatic transfer belt 11.
[0026]
Further, when maintenance or replacement of the fixing device 30 is necessary, the fixing device 30 is installed so as to be detachable upward with respect to the printer 50 by operating a lock means (not shown).
[0027]
As an image forming operation, the process cartridges 7a, 7b, 7c, and 7d are sequentially driven in accordance with the print timing, and the photosensitive drums 1a, 1b, 1c, and 1d are driven to rotate counterclockwise in accordance with the drive. Is done. Then, the scanner units 3 corresponding to the respective process cartridges 7 are sequentially driven. By this driving, the charging roller 2 imparts a uniform charge to the circumferential surface of the photosensitive drum 1, and the scanner unit 3 exposes the circumferential surface of the photosensitive drum 1 according to the image signal to perform photosensitive drum 1. An electrostatic latent image is formed on the peripheral surface. The developing roller in the developing device 4 transfers toner to the low potential portion of the electrostatic latent image to form a toner image on the circumferential surface of the photosensitive drum 1.
[0028]
At the timing when the leading edge of the toner image on the circumferential surface of the most upstream photosensitive drum 1 is rotated and conveyed to a point facing the electrostatic transfer belt 11, the printing start position of the sheet S coincides with that point. The registration roller pair 19 starts to rotate and feeds the sheet S to the electrostatic transfer belt device 10.
[0029]
The sheet S adsorbed on the electrostatic transfer belt 11 is sequentially transferred with the toner images on the photosensitive drums 1 by an electric field formed between the photosensitive drums 1 and the transfer rollers 18.
[0030]
The sheet S on which the toner images of four colors are transferred is separated from the electrostatic transfer belt 11 by the curvature of the belt driving roller 12 and the fixing entrance guide 36 adjacent to the surface of the electrostatic transfer belt 11 is separated. By being scooped by the tip, it is reliably carried into the fixing device 30. After the toner image is fixed at the nip N, the sheet S is guided to the pair of paper discharge rollers 34 by the paper discharge guide 33, and is discharged to the paper discharge tray 40 on the main body with the image surface facing down. .
[0031]
【The invention's effect】
As described above, according to the present invention, the fixing inlet guide is swingable with respect to the fixing device, and is always positioned with respect to the driving roller of the electrostatic transfer belt. Since the gap with the electrotransfer belt can be set as small as possible, even a sheet such as thin paper that has a low rigidity and is difficult to separate in curvature can be stably guided to the fixing device side. Further, the gap is always reproduced even after the electrostatic transfer belt device is opened / closed or the fixing device is attached / detached to / from the printer main body, which is very convenient.
[Brief description of the drawings]
FIG. 1 is a side view of an electrostatic transfer belt device and a fixing entrance guide according to the present invention.
FIG. 2 is a side view of an electrostatic transfer belt device and a fixing entrance guide according to the present invention.
FIG. 3 is a perspective view of an electrostatic transfer belt device and a fixing entrance guide according to the present invention.
FIG. 4 is an overall view of an image forming apparatus according to the present invention.
FIG. 5 is an overall view showing a state where the electrostatic transfer belt device of the image forming apparatus according to the present invention is opened.
FIG. 6 is an overall view of a conventional image forming apparatus.
[Explanation of symbols]
S sheet 1 photosensitive drum 3 scanner unit 7 process cartridge 10 electrostatic transfer belt device 11 electrostatic transfer belt 12 driving roller 16 ball bearing 20 paper feeding device 30 fixing device 36 fixing inlet guide 36d abutting member 36e abutting member 50 printer main body

Claims (3)

Image forming means for forming a toner image on a sheet, a fixing unit having a nip to fix the toner image on a sheet by nipping and conveying the sheet on which the toner image has been formed, is wound around a plurality of support rollers directing from said image forming means comprises a conveyor belt which moves to the fixing unit in an image forming apparatus including a sheet conveying means, for conveying the sheet, the fixing means to nip the sheet from said sheet conveying means Te A fixing inlet guide for swinging is supported, the sheet conveying means is attached to the image forming apparatus main body so as to be openable and closable, and the fixing inlet guide supported by the fixing means is An image forming apparatus, wherein the image forming apparatus is positioned with respect to a single support roller.   The image forming apparatus according to claim 1, wherein the fixing unit is detachably attached to the apparatus main body.   The image forming apparatus according to claim 1, wherein the sheet conveyance unit includes an electrostatic adsorption unit that electrostatically adsorbs the sheet to the conveyance belt.

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