JPH0830922B2 - Pre-transfer guide device for image forming apparatus - Google Patents

Description

The present invention relates to a pre-transfer guide device provided in an image forming apparatus such as an electrostatographic copying machine or a facsimile.

[Conventional technology]

As a pre-transfer guide device for guiding the transfer paper to the transfer area of the photoconductor, as shown in Japanese Utility Model Laid-Open No. 58-138956, a conductive substrate is provided on the upstream side of the transfer charger and flexible. A conductive insulating guide plate, the portion of the downstream side in the paper feed direction of the guide plate is projected, and is attached on the substrate,
In addition, there is one in which a metal such as aluminum is vapor-deposited on the surface of the guide plate, and the aluminum vapor deposition body (hereinafter referred to as a thin film conductor) is electrically connected to the substrate.

According to the above configuration, the spring plate-shaped protruding portion protruding from the base plate of the guide plate is bent by the stiffness of the transfer paper passing through the protruding portion. It is greatly bent.

On the other hand, the transfer paper is bent when it is guided by the guide plate and passes through the protruding portion, and the weaker the paper is, the more the transfer paper is bent.

Therefore, in the case where the transfer paper guided to the transfer area has a weak rigidity, the paper itself has a large flexure, but the projection has a small flexure, and the transfer paper has a strong flexure,
Although the deflection of the paper itself is small, the protruding portion is largely deflected, and thus the tip of the transfer paper is properly guided to a substantially predetermined position in the transfer area regardless of the rigidity of the transfer paper. You can

Then, of the insulating guide plates, it is difficult for charges to accumulate in the guide plate portion in contact with the conductive substrate, but it is easy for charges to accumulate in the protruding portion that is not in contact with the substrate. In this state, when the transfer paper passes through the guide plate, the protruding portion is charged by friction with the transfer paper, and further discharged by the transfer charger immediately downstream of the protruding portion. The projecting portion is also charged by directly receiving an electric charge, which causes the toner floating in the apparatus to electrostatically adhere to the surface of the projecting portion and stain the back surface of the transfer paper with the toner, or An abnormal image referred to as a so-called blank area is generated by charging and discharging the charge from the protruding portion to the photoconductor, but a thin film conductor is provided on the surface of the guide plate and is electrically connected to the substrate. Because it is connected, Without such as to inhibit the spring property of the protruding portion by conductive thin film, the projecting portions can be hardly charged, generation of by extension transfer sheet back surface of the toner dirt and abnormal images can be prevented.

[Problems to be solved by the invention]

However, when the front end side of the transfer paper enters the transfer area, a part of the charge for image transfer given to the transfer paper flows through the transfer paper to the conductor on the surface of the protruding portion,
When this escapes to the substrate, the potential applied to the transfer paper is greatly reduced, and the transferred image becomes thin.

Furthermore, each time the transfer paper passes over the surface of the guide plate, the thin film conductor is rubbed by the transfer paper, so that the conductor part through which the frequently used transfer paper passes quickly wears. However, there is a drawback in that, by charging at this portion, the floating toner adheres to the portion, the transfer paper is soiled with the toner, and the charge is scattered on the photoconductor to cause an abnormal image.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to solve the above inconveniences with a very simple and rational improvement.

[Means for solving problems]

In order to achieve the above object, the present invention provides a pre-transfer guide device of an image forming apparatus that guides a transfer paper to a transfer area of a photoconductor, in which a conductive substrate is provided on the upstream side of a transfer charger, and a flexible substrate is provided. A conductive insulating guide plate is provided on the substrate so that the downstream side portion of the guide plate in the sheet feeding direction is projected, and from the protruding end on the lower surface of the guide plate to the surface portion corresponding to the substrate. A thin-film conductor is provided only between the two, the thin-film conductor is electrically connected to the substrate, and the substrate is grounded to the apparatus main body side.

[Action]

Since the guide plate is grounded via the conductor and the substrate provided on the lower surface of the guide plate, even if the sheet slides on the guide plate and charges are stored in the guide plate, the charge is not stored in the guide plate. .

Therefore, toner is prevented from adhering to the upper surface of the guide plate, and leakage (flying charge) from the downstream end of the guide plate to the photoconductor is prevented, which adversely affects the image on the photoconductor (latent image). It has no effect.

Further, since the guide plate itself is insulative, it is possible to prevent a decrease in the potential applied to the paper and obtain a stable image. When the guide plate is conductive, the electric charge from the transfer charger flows through the paper to the guide plate during transfer (especially when humidity is high), so that the potential drops.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming section in an electrostatic photocopier, which is an example of an image forming apparatus.
A main charger 2, an exposure device 3, a developing device 4, a pre-transfer guide device 5, a transfer charger 6, a transfer paper separation charger 7, and a cleaning device 8 are arranged in that order in the rotation direction of the photoconductor 1.

The pre-transfer guide device 5 is configured as follows. That is, the upper substrate 9 and the lower substrate 10, each of which is made of metal, are electrically connected to the apparatus main body (not shown) between the conveying roller pair 12 of the sheet feeding and conveying device 11 and the transfer charger 6. (So-called grounded state) and provided,
On the lower surface side of the upper substrate 9 and the upper surface side of the lower substrate 10, respectively, flexible insulating guide plates 13 and 14 are provided.
And the parts a and b of the guide plates 13 and 14 on the downstream side in the sheet feeding direction are projected from the respective substrates 9 and 10, and the upper and lower parts of the projecting parts a on the upper side are Thin film conductors c and d are provided on the lower surfaces of the protruding portions b in a state of being electrically connected to the substrates 9 and 10 (hence, in a state of being grounded to the apparatus main body).

Specifically, as shown in FIG. 2 for the lower substrate 10 and the guide plate 14, a predetermined range on the lower surface side of the guide plate 14 made of, for example, a 125 μm polyester film, more specifically, the substrate. A thin film conductor is formed by vapor-depositing or laminating a metal such as aluminum in a range (indicated by a diagonal solid line) extending over the guide plate surface portion e corresponding to the downstream side portion of the sheet feeding direction 10 and the lower surface side of the protruding portion b. While forming d, a surface portion (shown by an oblique chain line) that is off the guide plate surface portion e and corresponds to the substrate 10 f
By attaching a double-sided tape 15 to the substrate 10 and adhering the guide plate 14 to the substrate 10 through the double-sided tape 15, the conductor d of the thin film is applied to the substrate 10 at the guide plate surface portion e.
By extension, it is grounded to the main body of the device.

A thin-film conductor c is formed on the upper substrate 9 and the guide plate 13 by the same means, and the thin-plate conductor c is grounded to the apparatus main body through the substrate 9.

According to the above structure, when the transfer sheet is guided by the lower guide plate 14, the bending of the spring plate-shaped protruding portion b protruding from the substrate 10 of the guide plate 14 and the bending of the transfer sheet itself are synergistic. The tip of the transfer paper can be properly guided to a substantially predetermined position in the transfer area A regardless of the rigidity of the transfer paper.

The substrate 10 and the thin film conductor d are present on the entire lower surface of the insulating guide plate 14.
Thus, the thin plate conductor d does not impair the springiness of the projecting portion b, and the entire guide plate 14 including the projecting portion b can be made to have a property in which it is difficult to accumulate charges. , Frictional contact with the transfer paper and the transfer charger 6
It is possible to prevent the entire guide plate 14 from being charged by the electric discharge, and effectively prevent the toner stain on the back surface of the transfer paper and the occurrence of an abnormal image.

In the embodiment, a thin-film conductor c electrically connected to the substrate 9 is provided on the protruding portion a of the upper guide plate 13 and on the upper surface side in the vicinity thereof, but this is essential. This is not a requirement, and the thin film conductor a may not be provided. However, when free toner inside the apparatus adheres and accumulates on the upper surface of the protruding portion a due to frictional electrification of the protruding portion a, there is a risk that it will fall to the paper feed path side due to some shock or the like and stain the transfer paper. By providing the thin-film conductor d, the above situation can be prevented, which is preferable.

Further, in the embodiment, a thin film conductor d is provided on the guide plate surface portion e corresponding to the downstream side of the substrate 10 in the sheet feeding direction, and the thin film conductor d is electrically connected by sticking the guide plate 14 to the substrate 10. The thin film conductor d may be provided only on the lower surface side of the projecting portion b and grounded to the main body of the device by an appropriate means. Alternatively, the thin film conductor d may be connected to the substrate 10. May be provided over the entire surface of the guide plate 14.

〔The invention's effect〕

As described above, in the pre-transfer guide device of the image forming apparatus according to the present invention, a flexible insulating guide plate is attached on the substrate, and the downstream side portion of the guide plate in the sheet feeding direction is projected. Along with, the thin film conductor is provided only between the protruding end on the lower surface of the guide plate and the surface portion corresponding to the substrate, and the thin film conductor is electrically connected to the substrate, and the substrate is Since the guide plate is grounded to the apparatus main body side, the guide plate is grounded via the conductor and the substrate, so that no electric charge is accumulated in the guide plate. As a result, toner is prevented from adhering to the upper surface of the guide plate, and leakage (flying charge) from the downstream end of the guide plate to the photoconductor is prevented, which adversely affects the image on the photoconductor (latent image). There is no.

Further, since the guide plate itself is insulative, it is possible to prevent a decrease in the potential applied to the paper and obtain a stable image.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional side view of an image forming unit in an electrostatic copying machine as an example of an image forming apparatus, and FIG. 2 is a perspective view showing an example of mounting a lower guide plate on a substrate. DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 6 ... Transfer charge, 10 ... Substrate, 14 ... Guide plate, b ... Projection part, d ... Thin film conductor, A ... Transfer area.

Claims (1)

[Claims] 1. A pre-transfer guide device of an image forming apparatus for guiding a transfer paper to a transfer area of a photoconductor, wherein a conductive substrate is provided on the upstream side of a transfer charger, and a flexible insulating guide plate is provided. Attached on the substrate, the downstream side portion of the guide plate in the sheet feeding direction is projected, and a thin film conductor is provided only between the projecting end on the lower surface of the guide plate and the surface corresponding to the substrate. A pre-transfer guide device for an image forming apparatus, wherein the thin film conductor is electrically connected to the substrate and the substrate is grounded to the apparatus main body side.