JP3976215B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine using an electrophotographic process.
[0002]
[Prior art]
Conventionally, in this type of image forming apparatus, as shown in FIG. 5, for example, when the image carrier 1 is assembled in the main body of the image forming apparatus and the front cover of the apparatus main body is closed, the image carrier is resisted against the urging force. The shutter 2 is rotated about the support shaft 3, and the transfer sheet 4 after the image transfer is opened in the conveyance path a toward the fixing device 5, so that the image carrier shutter 2 is covered with the image carrier 1. When moving from the position (indicated by the chain line in the figure) to the retracted position (indicated by the solid line in the figure) for releasing the covering, and again when the front cover of the device body is opened, Returning to the protected position, the image carrier 1 was prevented from being irradiated with light.
[0003]
On the other hand, in order to shorten the first print time by shortening the conveyance path a of the transfer paper 4, a so-called vertical conveyance type image forming apparatus as shown in FIG. In this type of image forming apparatus, the conveyance path a is vertical, and the transfer paper 4 after image transfer is conveyed upward through the conveyance path a at the transfer nip b between the image carrier 1 and the transfer roller 6, and the fixing device 5 to the fixing nip c between the heating roller 7 and the pressure roller 8.
[0004]
[Problems to be solved by the invention]
However, in this type of image forming apparatus, when the rear end 4 a of the transfer paper 4 leaves the transfer nip b, the transfer paper 4 follows the arc shape of the fixing nip c and the rear end 4 a is the front end 2 a of the image carrier shutter 2. The leading edge 2a contacts the surface of the transfer paper 4 and disturbs the transferred image before fixing, which may cause transfer rubbing. As the free length of the transfer paper 4 from the fixing nip c becomes shorter, the rear end 4 a of the transfer paper 4 tends to approach the front end 2 a of the image carrier shutter 2.
[0005]
Particularly in recent years, due to a demand for downsizing of the image forming apparatus, it has been difficult to largely retract the image carrier shutter 2, and there has been a possibility of further causing the above-mentioned transfer rubbing.
[0006]
Accordingly, an object of the present invention is to prevent the transfer sheet from touching the image carrier shutter and causing transfer rubbing when the transfer sheet after image transfer is conveyed to a fixing device in an image forming apparatus of a so-called vertical conveyance type. There is to do.
[0007]
[Means for Solving the Problems]
Therefore, the present invention opens the conveyance path for the transfer paper after image transfer to the fixing device, and moves the image carrier shutter from the protection position covering the image carrier to the retracted position for releasing the cover. In the moving image forming apparatus, the front end portion of the image carrier shutter is provided so as to be rotatable with respect to the shutter main body portion, and the front end portion is moved by gravity in a direction away from the conveyance path in accordance with the movement of the image carrier shutter to the retracted position. It is characterized by being rotated on the basis of
[0008]
Here, the image carrier and the image carrier shutter may be supported by the same housing.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a main part of a laser printer which is an example of the present invention. Reference numeral 10 in the figure denotes a drum-shaped image carrier provided on the inner front side (right side in the figure) of the printer apparatus main body.
[0010]
In use, the image carrier 10 is rotated in the direction indicated by the arrow (counterclockwise) in the figure. First, the surface is uniformly charged by the charging roller 11, and then writing is performed by irradiating a laser beam L from an optical writing device (not shown) to form an electrostatic latent image on the surface of the image carrier 10.
[0011]
Thereafter, with the rotation of the image carrier 10, toner is attached by the developing roller 13 of the developing device 12 to develop the electrostatic latent image on the image carrier 10. The developing device 12 includes a developing blade 14, a stirring shaft 15, an agitator 16, a toner end sensor 17, and the like.
[0012]
On the other hand, the sheet-like transfer paper in the paper feed cassette is fed out in order and abutted between the registration roller pair 19 and stopped. Then, the registration roller pair 19 is rotated in synchronization with the above-described image on the image carrier 10 and conveyed to the transfer nip B between the image carrier 10 and the transfer roller 20. 10 is transferred onto the transfer paper.
[0013]
The transfer paper after the image transfer is discharged by the charge removal needle 21 and then conveyed upward through the conveyance path A, and is guided to the fixing roller 23 of the fixing device 22 and the fixing nip C of the pressure roller 24, and heat and After applying the pressure to fix the transferred image on the transfer paper, the image is faced down and discharged to the paper discharge unit on the apparatus main body by the paper discharge roller 25 and the paper discharge roller 26.
[0014]
On the other hand, the image carrier 10 after the image transfer is rotated to remove residual toner by the cleaning blade 28 of the cleaning device 27 and prepare for recharging by the charging roller 11.
[0015]
By the way, in the illustrated laser printer, for the convenience of maintenance, etc., the image carrier 10, the charging roller 11, the developing device 12, the cleaning device 27, and the like described above are provided in the cartridge case 30 that is one housing. The cartridge 32 is configured.
[0016]
The process cartridge 32 is also supported by a cartridge case 30 and is provided with an image carrier shutter 35 that can be opened and closed about a support shaft 34. As shown in FIG. 2, the image carrier shutter 35 includes a shutter main body portion 40 and a tip portion 50.
[0017]
The shutter body 40 has a curved arm part 41 on both sides having a shaft hole 41a at the base end, a projecting part 42 provided so as to project outward in the middle of one side, and a plate connecting between the distal ends of the curved arm parts 41 on both sides. And a support portion 44 provided so as to protrude from both sides of the tip. A shaft hole 44a having the same axis is formed in the support portions 44 on both sides.
[0018]
On the other hand, the front end portion 50 is provided with an elongated plate portion 51 having a width D larger than the maximum sheet passing width, and a shaft portion 52 that protrudes outward from the both ends of the one end with the same axis line.
[0019]
Then, the shaft portion 52 is inserted into the shaft hole 44a and the tip portion 50 is provided so as to be rotatable with respect to the shutter main body 40. The support shaft 34 is inserted into the shaft hole 41a and the image carrier shutter 35 is opened and closed by the cartridge case 30. It is supported freely and urged in the closing direction by a spring (not shown).
[0020]
Thus, when the front cover of the printer apparatus main body is opened, the transfer roller 20 supported by the front cover is moved as shown in FIG. 3, while the image carrier shutter 35 is closed based on the urging force and is not shown. The shield member 43 is in a protected position where the image carrier 10 is covered as shown by the solid line in FIG.
[0021]
At this time, the front end portion 50 also hangs down due to gravity and covers the image carrier 10 in the same direction as the support portion 44 to prevent light irradiation to the image carrier 10.
[0022]
On the other hand, when the front cover of the apparatus main body is closed, the abutment surface 42a of the abutment portion 42 is pushed by the lever portion provided in the front cover, and the image carrier shutter 35 is opened around the support shaft 34 against the urging force. Then, the transfer paper after the image transfer is opened in the conveyance path A toward the fixing device 22 and moved to the retreat position where the covering of the image carrier 10 is released as indicated by a chain line.
[0023]
Also at this time, the front end portion 50 hangs down due to gravity and rotates in a direction away from the transport path A based on the gravity.
[0024]
Therefore, as shown in FIG. 4, the rear end 55a of the transfer paper 55 leaves the transfer nip B, and the transfer paper 55 follows the arc shape of the fixing nip C so that the rear end 55a approaches the front end of the image carrier shutter 35. Even if there is nothing, the tip 50 rotates in a direction away from the conveyance path A, so there is no possibility of touching the surface of the transfer paper 55 and disturbing the transfer image before fixing, and the occurrence of transfer rubbing. Can be prevented.
[0025]
【The invention's effect】
According to the first aspect of the present invention, when the image carrier shutter is moved to the retracted position, the leading end is rotated in a direction away from the conveyance path. Even if the trailing edge approaches the leading edge of the image carrier shutter following the arc shape of the fixing nip, there is no risk that the leading edge will contact the surface of the transfer paper and disturb the transferred image before fixing. The occurrence of rubbing can be prevented.
[0026]
In addition , when the image carrier shutter is moved to the retracted position, the tip is rotated based on gravity, so that the tip can be moved away from the transport path with an inexpensive configuration.
[0027]
According to the second aspect of the invention, since the image carrier and the image carrier shutter are supported by the same housing, the relative positional accuracy of both is improved, and the image carrier shutter is also retracted to a narrow part. Therefore, it is possible to reduce the size.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a laser printer as an example of the present invention.
FIG. 2 is an exploded perspective view showing a distal end portion separated from a shutter main body portion of the image carrier shutter.
FIG. 3 is an explanatory view of opening and closing of the image carrier shutter.
FIG. 4 is a state explanatory diagram illustrating a state in which a transfer sheet after image transfer is conveyed to a fixing device.
FIG. 5 is a diagram illustrating a state in which transfer paper after image transfer in a conventional image forming apparatus is conveyed to a fixing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Image carrier 11 Charging roller 12 Developing device 19 Registration roller pair 20 Transfer roller 22 Fixing device 23 Fixing roller 24 Pressing roller 30 Cartridge case 32 Process cartridge 34 Support shaft 35 Image carrier shutter 40 Shutter body portion 50 Tip portion 55 Transfer Paper A Transport path B Transfer nip C Fixing nip

Claims (2)

In the image forming apparatus in which the transfer sheet after the image transfer is directed to the fixing device is opened, and the image carrier shutter is moved from the protection position covering the image carrier to the retracted position for releasing the cover. ,
The tip of the image carrier shutter is provided so as to be rotatable with respect to the shutter main body,
An image forming apparatus in which the tip end portion rotates based on gravity in a direction away from the transport path in accordance with the movement of the image carrier shutter to the retracted position. The image forming apparatus according to claim 1, wherein the image carrier and the image carrier shutter are supported by the same housing.

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