JPH10326032A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the possibility of causing image defect in not only guiding plain paper but also carrying small-sized and thick paper-like transfer material by providing a transfer guide with plural guiding surfaces abutting on the image non-forming surface of the transfer material guided by the transfer guide. SOLUTION: When an image carrier is rotated and a toner image reaches a transfer part where a transfer roller is opposed to the image carrier, the transfer material passes through a resist roller, goes through the transfer material guide 14 and is supplied to the transfer part in timing with the toner image on the image carrier side. Simultaneously, the toner image on the image carrier side is transferred to the transfer roller by the action of electric field formed by impressing transfer bias on the transfer roller. At such a time, the transfer material advances in a direction shown by a voided arrow between two plate members 23 and 24 forming the guide 14, and the transfer material reaches the transfer part of the image carrier positioned on the left side. In order to make the guide 14 suitable for the small size and thick transfer material, a step part 24a formed to be bent downward is formed on the plate part 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer material such as paper which is brought close to or in contact with a transferable toner image formed on an image carrier, such as an electrostatic copying machine or a printer, at a transfer portion.
The present invention relates to an image forming apparatus including a step of transferring the toner image to a transfer material, and more particularly to an apparatus for conveying and supplying a transfer material to a transfer portion in an optimal state for transfer.

[0002]

2. Description of the Related Art Such an image forming apparatus is usually
A transfer material such as paper is provided on a transfer portion formed by a rotating cylindrical shape and carrying a toner image on a surface thereof, and a transfer portion formed by the image support and transfer means disposed close to or in contact with the image support. It is well known that an apparatus configured to transfer and supply the toner image onto the transfer material is widely used.

In this type of image forming apparatus, the position of a transfer guide for guiding a transfer material to a transfer site is set so that the most frequently used plain paper is transferred well. For this reason, when a small-sized cardboard, such as a postcard, is used as a transfer material, a transfer guide in which a part of the transfer guide is cut out so as to perform good transfer on the cardboard has been proposed. .

[0004] To explain this further, when the transfer material is supplied to a transfer portion composed of an image bearing member and a transfer means arranged opposite to the image carrier, the transfer material is usually provided upstream of the transfer portion in the running direction of the transfer material. A transfer guide including a pair of plate members is provided, and the transfer guide supplies the transfer material to the transfer portion in an optimal state for transfer. This is because the transfer material directly enters the transfer site before contacting the image carrier, or the contact with the image carrier is too early,
This is to prevent the occurrence of image defects such as hollow holes and toner scattering.

By the way, the size of the transfer material used,
Since there is a considerable difference in thickness, a transfer guide is usually formed so as to be suitable for conveying and supplying the most frequently used plain paper as described above.

When the transfer guide formed in this way is a small-sized cardboard such as a postcard as a transfer material, there is a possibility that good transfer may not be performed without using the transfer guide. FIG. 3 shows an example of a known transfer guide configured to cope with such a case. FIG. 2 is a perspective view showing only a transfer guide portion, and is a transfer guide including two plate members 21 and 22 arranged in parallel at an upstream side and a close position of an image carrier (not shown) as viewed in the transfer material traveling direction. It is assumed that the transfer material is conveyed in the meantime in the direction indicated by the white arrow in the drawing.

In such a transfer guide, a notch 22a corresponding to the width of a postcard is formed in the lower plate member 22, for example, in the illustrated example. The guide is guided so that the large transfer material can be brought into contact with the image carrier lower by the amount corresponding to the stiffness.
The guide is electrically connected to a ground or a varistor to stabilize the potential, and the transfer material is charged by an electric field formed by an applied high voltage when the guide is brought close to a transfer means such as a transfer roller. It is blocking.

In the meantime, in the means for forming the notch, the transfer guide is moved away from the transfer portion by that much, and if the notch length (the length in the transfer material running direction) is too long, the transfer is performed. The time during which the material is exposed to the transfer electric field becomes longer, the potential of the transfer material at the transfer site becomes unstable, and the toner charges irregularly after the image due to the charging of the transfer material, that is, scattering occurs. If the contact of the transfer material with the image carrier is too early, an image such as a character or a line may drop out of the image.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to cope with the above-described situation. In an image forming apparatus having a transfer guide for transferring a transfer material to a transfer portion, a guide for plain paper is provided. It is another object of the present invention to provide a transfer guide that does not cause the above-described image defects even when a small-sized cardboard transfer material is conveyed, and an image forming apparatus provided with the transfer guide.

[0010]

In order to achieve the above-mentioned object, the present invention provides a transfer material at a transfer portion formed by an image carrier and a transfer means capable of applying a transfer bias opposite thereto. An image forming apparatus provided with a transfer guide for guiding the transfer material, wherein the transfer guide has a plurality of guide surfaces that contact a non-image forming surface of a transfer material guided by the transfer guide. Alternatively, in the image forming apparatus according to the above (1), a part of the plurality of guide surfaces is a surface formed at a position lower than a transfer material running surface than other portions. Or, in any one of the above (1) or (2), the image forming apparatus (3), wherein one of the plurality of guide surfaces is smaller than a maximum sheet passing width.

With this configuration, even when a thick transfer material is used, the transfer can be performed without incurring image quality deterioration such as dropout or tailing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic side sectional view of a main part of an image forming apparatus to which a transfer guide according to the present invention is applied. The surface of the image carrier 1 having an axis perpendicular to the paper and rotating and running in the direction of the arrow shown in the figure is uniformly charged by the charging unit 20. Next, an image signal is transmitted through an exposure duct 10 from an optical system 2 which is disposed above the image carrier in the figure and includes a document table 3, a document irradiation lamp 4, moving mirrors 5, 6, 7, a lens system 8, and a fixed mirror 9. The electrostatic latent image is formed by being projected onto the charged surface of the image carrier 1 via the image carrier 1, and unnecessary charges outside the image are erased by the blank exposure 11.

When the latent image arrives at a development site where the developing device 12 is arranged as the image carrier 1 rotates, toner is supplied from the latent image to visualize the latent image to form a toner image. Become. When the image carrier 1 further rotates and the toner image reaches a transfer portion where the transfer roller 15 faces the image carrier 1, the toner image passes through the registration roller 13 in synchronization with the toner image on the image carrier side, and Transfer guide 1
After 4, a transfer material (not shown) is supplied to the transfer site. At the same time, a transfer bias is applied to the transfer roller 15, and the toner image on the image carrier is transferred to the transfer material by the action of the electric field formed thereby.

Next, the transfer material carrying the toner image is separated from the image carrier 1 by the action of the charge removing means 16 and the transfer path 17
Then, the toner image reaches a fixing portion (not shown), is fixed and fixed on the transfer material, and is discharged outside the apparatus. At the time of transfer, the residual toner remaining on the image carrier without transferring to the transfer material proceeds as it is and is removed from the image carrier by the cleaner 18, and further, the residual charge is removed by the pre-exposure lamp 19, and the image carrier is removed. The next image formation is possible.

FIG. 2 is an enlarged perspective view of the transfer material guide 14 in the above-described image forming apparatus. As in the case of the known transfer guide shown in FIG. 3, the transfer material advances between two plate members 23 and 24 forming the transfer guide 14 in the direction indicated by a white arrow in the drawing, and the transfer material (not shown) Reaches a transfer site of an image carrier (not shown) located on the left side in the figure.

In this transfer guide, as shown in the figure, a step 24a bent downward is formed on the plate member 24 in order to adapt to a small-sized and thick transfer material. In this embodiment, as a postcard guide, the length is 10 mm in the running direction of the transfer material and the width is 120 m in the direction perpendicular to the running direction.
m, 1 mm more than the other parts of the plate member 24.
It is a bent recess so as to be lower.

[0017] With this configuration, the leading end of the transfer material is held in a free state, so that the image is prevented from dropping out of the image. It is not exposed and is effective in preventing the occurrence of the tailing phenomenon.

[0018]

As described above, according to the present invention,
Even when a thick transfer material such as a postcard is conveyed, the leading end is substantially in a free state, so that the center of the image can be prevented from missing, and since there is no cutout portion, the electric field generated by the transfer means is reduced. This has a remarkable effect on preventing the transfer material from being exposed to the toner and avoiding the occurrence of the tailing phenomenon. Applying this to an image forming apparatus is effective in obtaining a high-quality image.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a main part of a transfer guide showing an embodiment of the present invention.

FIG. 3 is a perspective view of a main part of a known transfer guide.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier 2 optical system 12 developing device 14 transfer guide 15 transfer roller 18 cleaner 20 primary charger 21, 22 plate member 23, 24 plate member 24a recess

Claims (3)

[Claims] 1. An image forming apparatus comprising: a transfer guide for guiding a transfer material to a transfer site formed by an image carrier and a transfer unit capable of applying a transfer bias thereto, wherein the transfer guide comprises: An image forming apparatus comprising: a plurality of guide surfaces that abut a non-image forming surface of a transfer material guided by the image forming device. 2. An image forming apparatus according to claim 1, wherein a part of said plurality of guide surfaces is a surface formed at a position lower than a transfer material running surface than other parts. 3. The image forming apparatus according to claim 1, wherein one of the plurality of guide surfaces is smaller than a maximum sheet passing width.