JP3118724B2 - Image forming device - Google Patents

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 an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art A well-known image forming method includes a step of electrostatically transferring a toner image formed on an image carrier to a transfer material such as paper, and then fixing and fixing the toner image to the transfer material. In the apparatus, a transfer material is mounted on an endless transport belt and supplied to a transfer portion including an image bearing member and a charging unit disposed close to or in contact with the image carrier, and after transfer, the transfer material includes a heating roller that abuts on each other. There has been proposed one configured to convey the fixing belt to the pair of fixing rollers by the conveyance belt. In this type of apparatus, the transfer material is electrostatically attracted to the conveyor belt, and the fixing roller pair sandwiches the transfer material carrying the toner image and applies heat and pressure to the transfer material to transfer the toner. It is well known that a material that is fused and fixed to a transfer material is widely used.

In the image forming apparatus having such a configuration, the transfer material having completed the transfer is placed on the transport belt and further proceeds to enter the nip portion of the fixing roller pair. When a thick transfer material abuts and is sandwiched between them, the impact of the abutment momentarily stops the progress of the transfer material, causing irregularities in the running of the transfer material and adversely affecting image quality. May give.

FIG. 4 is a schematic side view of a main part of the image forming apparatus showing this, in which a transfer charger 2 is disposed so as to face an image carrier 1 which is formed in a cylindrical shape and rotates in a direction indicated by an arrow. Transcription site is formed. An endless transport belt 3 driven by a driving roller 3a is disposed at the transfer site. When a transfer material P placed on the transfer belt 3 passes through the transfer site, a transfer bias is applied by the transfer charger 2. The toner image on the image carrier side is transferred to the transfer material P by the action of the electric field thus formed.

The transfer material is further conveyed by the conveyance belt 3 and enters the contact nip of the roller pair 11 to perform fixing.

[0006] When the transfer material enters the nip of the pair of fixing rollers, the movement of the transfer material is hindered instantaneously.
When the transfer material is curved as shown by reference numeral 4 and, at the same time, in the case of a transfer material having strong stiffness, a state in which the transport belt portion is pushed down from the original position shown by the dashed line at the downstream side of the transfer portion as shown in the drawing. become.

When such a state occurs, the speed of the conveyor belt keeps the expected speed near the drive roller 3a, and is further lowered at the upstream portion and the transfer portion. As the line length becomes longer than the normal position shown, the image is formed later than the normal position, so that the transfer deviation occurs immediately.

As means for solving such a problem, for example, when the distance between the transfer portion and the fixing portion is increased, and when the leading end of the transfer material enters the fixing roller pair, the rear end portion of the transfer material is It is sufficient to completely remove the transfer portion from the transfer portion, but such a method is not preferable because the size of the conveyance means becomes large, the apparatus becomes large, and the cost increases. For this reason, proposals have been made to increase the holding force of the transfer material on the transport belt or to increase the impact resistance of the drive system using a pulse motor. Did not get satisfactory results,
For a moment, a transfer deviation that increases the transport speed occurs, which causes deterioration in image quality. This is a problem particularly with a transfer material having high rigidity and a high-speed machine with a higher transport speed.

SUMMARY OF THE INVENTION The present invention has been made to cope with the above situation, and a conveyance belt is used to convey a transfer material to and from a transfer site and from a transfer site to a fixing site.
In an image forming apparatus using a fixing unit configured to cause a transfer material to enter a nip portion of a pair of rollers pressed against each other as a fixing unit, a transfer belt portion that conveys the transfer material to a fixing portion after transfer is transferred to a transfer material. It is an object of the present invention to provide a conveying device that can obtain a high-quality image without causing the above-described transfer deviation by preventing the belt from being deformed even when the belt passes.

[0010]

In order to achieve the above object, the present invention provides an image carrier for carrying an image, a transport belt for carrying and transporting a transfer material, and transferring an image on the image carrier. A transfer unit that transfers the image to the transfer material carried by the conveyance belt at a position, and a fixing unit that fixes the image to the transfer material by sandwiching the transfer material conveyed by the conveyance belt. An image forming apparatus for fixing an image on the same transfer material by the fixing unit during image transfer to the transfer material, the image forming apparatus having a regulating member for regulating a deflection of the transport belt at a downstream side of the transfer position in a transport material transport direction. The regulating member is provided in the vicinity of the back side of the transport belt, and the image forming apparatus (1) or (1) is provided.
A plurality of the image carriers are provided to respectively carry images of a plurality of colors, and the transfer unit sequentially superimposes the images of the plurality of colors from the respective image carriers on a transfer material carried on the transport belt. The image forming apparatus according to claim 1, wherein a plurality of images are transferred at a transfer position on the transfer material carried on the transport belt. .

With this configuration, it is possible to prevent the transfer deviation due to the transfer material rushing into the fixing portion after the transfer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic side view schematically showing the structure of a color image forming apparatus to which the present invention is applied, wherein a rotating cylindrical image carrier 1a and its surface are provided inside an apparatus main body 90. Primary charging device 2a for uniformly charging the electrostatic latent image, an image signal applying means 3a for forming an electrostatic latent image on the charged surface, a developing device 4a for supplying toner to the electrostatic latent image, and an image carrier. Transfer charger 50a, cleaner 6a for removing residual toner
First image forming portion Pa having the same configuration, and second, third, and fourth image forming portions P each having the same configuration.
b, Pc, and Pd are arranged in series.

A transport belt 60 is provided so as to communicate with the transfer portion of each image forming section.
Is suspended by rollers 91, 93 and 94 including a driving roller 92, and sequentially passes through the image forming portions Pa to Pd from the right side of the registration roller pair 12 in the drawing.

The developing devices 4a and the like provided at the image forming portions Pa to Pd respectively contain yellow, magenta, cyan and black toners.
Further, since an electrostatic latent image of a yellow, magenta, cyan, and black component color of the document is formed on each image carrier 1a and the like by each image signal applying means 3a and the like, the image carrier at each image forming portion is formed on the image carrier. The toner images of the respective colors are shared and formed.

In such a configuration, as the transfer material is placed on the conveyor belt 60 from the side of the registration roller pair 12 on the right side of the drawing and sequentially passes through the transfer portions of the image forming portions, the toner images of the respective colors are superimposed. The transfer material is transferred to form a color image, and the transfer material rides on the conveyor belt 60 and reaches the fixing device 11, where it is heated and pressed to fix and fix the color toner image on the transfer material and discharge it to the tray 19. Is done.

In the above-described apparatus, in the case of the illustrated apparatus, in the area of the transport belt 60 reaching the fixing device 11 after finishing the last transfer by the image forming portion Pd,
On the back side of the belt 60, a restricting member 70 for preventing the belt from bending is provided. The restricting member is a plate-shaped member that approaches or contacts the rear surface of the transport belt.

FIG. 2 is a schematic side sectional view showing the structure near the image carrier 1d at the last image forming portion.
The same reference numerals are given to the portions corresponding to the above-mentioned known members, and the transfer material passing through the transfer portion where the image carrier 1d and the transfer charger 50d face each other is a fixing roller provided with a heating source and a fixing roller. The fixing device 11 includes a pressure roller (both not shown) pressed against the fixing device 11.

Therefore, even if the transfer material having undergone the final transfer process enters the fixing device and becomes curved as shown by reference numeral 4 due to the impact at that time, the portion existing on the conveyor belt 60 following the transfer material remains. In this case, since there is no occurrence of the belt drop deformation as shown in FIG. 4 and a temporary speed change in the transfer portion of the transfer material due to this, it is possible to avoid the occurrence of the transfer deviation.

The restricting member 70 is preferably made of an insulating material and is less likely to be charged up by rubbing with the conveyor belt. For example, boron can be suitably used. The restricting member 70 does not prevent the charge of the transport belt from flowing into the transport belt due to the rubbing with the transport belt, causing the toner to be scattered, or the charges being accumulated in the transport belt and disturbing the image. Any suitable material can be used depending on the relationship between the material of the transport belt and the charging conditions.

FIG. 3 shows another embodiment, in which only the portion from the last transfer portion to the fixing device is shown as in the above-described case, and the portion corresponding to that shown in FIG. 2 is shown. Are denoted by the same reference numerals, and description thereof will be omitted.

In this apparatus, a roller 70a is disposed on a platform 70 disposed on a stationary portion 62 of an image forming apparatus, behind a transport belt portion downstream of a final transfer portion. It is configured to rotate in contact with the back surface of the. That is, in this case, the regulating member includes at least one roller that approaches or contacts the rear surface of the transport belt.

With this configuration, even if the transfer belt 60 is pressed by the transfer material that passes through the portion, the transfer belt 60 does not bend downward, thereby preventing the occurrence of transfer deviation, and the transfer belt 60 and the roller 70a. The friction between the belt and the belt is small, and belt wear and charge-up can be prevented.

The case where the present invention is applied to a color image forming apparatus has been described above. However, the present invention is not limited to this, but includes a single image carrier and uses a belt at a transfer portion to transfer. It can be easily understood that the present invention can also be applied to a monochrome type image forming apparatus configured to supply a material.

[0024]

As described above, according to the present invention,
It has a regulating member that regulates the deflection of the transport belt on the downstream side of the transfer position in the transporting direction of the transfer material, and the regulating member is provided close to the back side of the transport belt. It is possible to prevent the transfer belt from being deflected by the impact received when the transfer belt is bent.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a color image forming apparatus showing an embodiment of the present invention.

FIG. 2 is an enlarged side view showing a portion from a transfer site to a fixing site;

FIG. 3 is a side view showing a portion from a transfer portion to a fixing portion showing another embodiment.

FIG. 4 is a side view showing a portion from a transfer portion to a fixing portion of a known image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a Image carrier 2, 50a Transfer charger 2a Primary charger 3a Image signal application means 3, 60 Conveyor belt 4 Transfer material bending part 4a Developing device 6a Cleaner 11 Fixing device 70 Deflection prevention member Pa, Pb, Pc, Pd Image formation site

Claims (2)

(57) [Claims] An image carrier for carrying an image; a transport belt for carrying and transporting a transfer material; and a transfer for transferring an image on the image carrier to a transfer material carried on the transport belt at a transfer position. Means, and fixing means for fixing an image to the transfer material by sandwiching the transfer material conveyed by the conveyance belt, and the same means by the fixing means during image transfer to the transfer material by the transfer means. In an image forming apparatus that performs image fixing on a transfer material, the image forming apparatus includes a regulating member that regulates bending of the transport belt at a downstream side of the transfer position in a transport material transport direction, wherein the regulatory member is close to a back side of the transport belt. An image forming apparatus, which is provided. 2. The image carrier according to claim 1, wherein a plurality of image carriers are provided for carrying images of a plurality of colors, respectively, and said transfer means sequentially transfers images of a plurality of colors from said image carriers onto a transfer material carried on said transport belt. 2. The image forming apparatus according to claim 1, wherein a plurality of images are provided for transfer in a superimposed manner, and an image of a final color of the plurality of colors is transferred to the transfer material carried on the transport belt at the transfer position. apparatus.