JPH0522907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer type image forming apparatus such as a transfer type electrophotographic apparatus or a recording machine, and particularly to a transfer type image forming apparatus that transfers a developed image carried on an image carrier to a transfer material.

2. Description of the Related Art In recent years, image forming apparatuses have been moving toward energy saving and smaller size in order to meet the increasing demand for personal use. Due to this miniaturization, it has become difficult to install separation belts as separation means, separation chargers for electrostatic separation, etc. because the space is narrow. Furthermore, the separation belt is unfavorable in terms of image quality because part of the image is missing due to the width of the separation belt.

On the other hand, it has been found that if the photosensitive drum, which is an image carrier, is made smaller for miniaturization, separation can be achieved without using any special separation means. That is, when the curvature of the photoreceptor drum increases, the transfer material that is in close contact with the photoreceptor drum is greatly bent, so that it is naturally separated from the photoreceptor drum due to the synergistic effect of the stiffness of the transfer material and its own weight.

However, as mentioned above, since the charge due to the transfer corona remains on the back side of the naturally separated transfer material, if there is a conductor nearby while the transfer material is being transported after separation, the back charge may leak through the conductor. The developed image on the transfer material is disturbed.

When the transfer material enters the fixing section, toner is scattered around the image due to electrostatic force between the transfer material and a rubber member such as a fixing roller.

The separated transfer material sways during conveyance and is not conveyed stably. In addition, transfer defects also occur due to the fluctuation of the transfer material.

Such disadvantages arise.

The present invention solves the above-mentioned drawbacks and achieves the following: (1) Separation can be performed without a special separation means, (2) An image without image loss can be obtained, and (3) Transfer can always be performed well. To provide a transfer type image forming device that is capable of (4) transporting transfer material stably, (5) being suitable for small electrophotographic devices, and (6) transferring and separating images without causing image disturbances. The purpose is to

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a very schematic diagram of a transfer type image forming apparatus according to the present invention. Reference numeral 1 denotes a photosensitive drum as an image carrier, which is rotatably supported in the direction of the arrow. 2 is an electrostatic latent image forming section that forms an electrostatic latent image on the photosensitive drum 1, 3 is a developing section that visualizes the electrostatic latent image, and 4 is a developed image that remains on the photosensitive drum after transfer. This is a cleaning section that removes (toner) from the photosensitive drum.

The transfer material P is synchronized with the rotation of the photosensitive drum 1 by a pair of register rollers 5, guided by a pair of guide plates 6, and fed to the transfer section A.

In the transfer section A, the developed image on the photosensitive drum is transferred onto the transfer material by the transfer corona of the transfer charger 7.
Due to the large curvature of the photosensitive drum, the transfer material P bends greatly when brought into close contact with the photosensitive drum, and begins to separate due to the synergistic effect of the stiffness of the transfer material and its own weight. In this case, the photosensitive drum with a large curvature has a diameter of 35 (mm) or less. The separated transfer material advances through a separation guide 8, which is an insulator, and the charge on the back surface of the transfer material is removed while it advances over a charge eliminating member 9 that is close to or in contact with the back surface of the transfer material. As the static eliminating member 9, for example, a static eliminating brush made of grounded carbon fiber or the like is used.

The discharging member 9 is preferably arranged such that the angle θ between the terminal end of the transfer corona on the photosensitive drum and the discharging member is 30° or more as measured from the center of the photosensitive drum. Alternatively, it is desirable that the terminal end of the transfer corona and the static eliminating member be separated by 5 mm or more.

If θ=30° or less or t=5mm or less,
The transferred corona may flow to the static elimination brush 9, resulting in transfer failure and making it impossible to obtain a good image.

FIG. 2 is a schematic diagram of main parts showing another embodiment, and the same members as those in FIG. In this embodiment, a bias having the same polarity as the toner charge is applied to the static eliminating member 9 by the bias power supply 12, so that the static eliminating effect is greater than that in the example shown in FIG.
Furthermore, a similarly excellent static elimination effect can be obtained when an alternating current bias is applied. If the transfer corona hits the transfer material P before it comes into close contact with the photosensitive drum 1, the transfer will start while there are gaps, and the toner will scatter, causing image disturbance. An eaves 7a is provided above the transfer charger on the entrance side,
It is possible to make the transfer corona hit after the transfer material P comes into close contact with the photoreceptor drum 1.

FIG. 3 is a schematic view of the main parts of yet another embodiment, in which a metal roller 13 is used as the static eliminating member.
This metal roller has a rough surface with concavities and convexities, and the convex portions are brought close to or in contact with the back surface of the transfer material. Further, a bias may be applied to the metal roller 13 in the same manner as in the example shown in FIG.

The static eliminating members include a saw-shaped static eliminating member 14 having serrated irregularities as shown in FIG. 4, and a needle-end static eliminating member 16 having a number of needles 15 implanted therein as shown in FIG.
The same effects as in each of the embodiments described above can be obtained even when using the above-mentioned embodiments.

In the present invention, as described above, the transfer material is separated by utilizing the curvature of the image carrier, and an insulator is provided between the transfer material and the transfer charging means on the downstream side of the transfer material movement direction of the transfer charging means. Since the charge eliminating member for eliminating charge from the transfer material is provided, the charge from the transfer material after transfer is effectively eliminated, and the above object is effectively achieved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a very schematic configuration of the transfer type electrophotographic apparatus of the present invention, FIGS. 2 and 3 are front views of main parts showing other embodiments, and FIGS. 4 and 5 are FIG. 2 is a perspective view of a static eliminating member applied to the transfer type electrophotographic apparatus of the present invention. 1 is a photosensitive drum, 7 is a transfer discharger, 9, 13,
14 and 16 are static eliminating members, and P is a transfer material.

Claims (1)

[Scope of Claims] 1. An image forming apparatus having a transfer charging means for transferring a developed image formed on a rotatable image carrier to a transfer material, wherein the image carrier has a diameter of 35 mm or less, and the transfer material is separated by utilizing the curvature of the image carrier, and a charge eliminating member is provided downstream of the transfer charging means in the transfer material movement direction and discharging the charge from the transfer material via an insulator between the transfer charging means and the transfer charging means. An image forming apparatus characterized by: