JPS63247781A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a cleaning roller on the outside of the device by transferring a toner image on a running image carrying body, to a transfer material by utilizing a transfer roller which is brought to press-contacting with its image, and also, setting the substantial polarity of a transfer bias to the transfer roller, to the opposite polarity to a toner. CONSTITUTION:A conductive transfer roller 3 is allowed to abut on a photosensitive body 1 rotating in the direction as indicated with an arrow A, and between them, a sheet-like transfer material such as paper, etc., is allowed to pass through in the direction as indicated with an arrow B through a transfer path, and by a transfer bias applied to the roller 3, a toner image on the photosensitive body 1 is tranferred to the transfer material. In this constitution, on a mandrel 3a made of stainless steel of the roller 3, a sponge layer 3b in which carbon has been dispersed to silicon, and a solid layer 3c in which has been dispersed to urethane rubber are laminated and covered, and a bias of the opposed polarity to a toner is applied thereto, and set to the same polarity for a prescribed time at the time of non-transfer. In such a way, the device is miniaturized without placing a cleaning roller in the device, and also, it is obstructed that a foreign matter adheres to the surface of the photosensitive body.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that utilizes an electrostatic recording or magnetic recording process.

(Prior art and problems to be solved) In a well-known image forming apparatus that repeats the process of transferring a transferable toner image formed on the surface of an endlessly running image carrier onto a sheet-like transfer material such as a piece of paper, In order to continuously obtain high-quality images, it is essential to sufficiently remove residual toner that does not contribute to transfer and remains on the surface of the image carrier each time transfer is performed.

As a cleaning means for this purpose, a cleaning blade made of a suitable elastic material such as urethane rubber has been widely used since it is small and compact and has an excellent toner removal function.

However, the cleaning blade is suitable for removing toner.
However, foreign matter such as fine paper powder generated from the paper used as the transfer material, precipitates such as rosin and talc, or corona products such as nitrogen oxides generated by corona discharge that adhere to the image carrier. Therefore, in order to remove these foreign substances, a method has been proposed in which a cleaning roller having appropriate elasticity, such as silicone rubber, is pressed against and rubbed against the image carrier to remove the above foreign substances. In particular, by using this in common with the aforementioned cleaning blade, certain effects have been achieved.

However, with the recent progress in miniaturization of this type of image forming apparatus, the diameter of the image bearing member, which is usually formed in a rotating cylindrical shape, has also become smaller. There is also a demand for downsizing of members, and under such circumstances, it has become substantially difficult to arrange a cleaning roller together with a cleaning blade in a cleaning device.

Furthermore, cartridges that integrate several process means around the image carrier are becoming popular, but in such cases, installing a cleaning roller can improve the structure of the cartridge. This is undesirable because it becomes complicated, large-sized, and leads to increased costs, making it impossible to take advantage of the advantages of the cartridge system.

The present invention has been made in order to cope with such a situation, and it is possible to clean the image carrier without disposing the leaning roller as described above in the cleaning device, and in the same way as if the cleaning device had the leaning roller. It is an object of the present invention to provide an image forming apparatus that can obtain high-quality images.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention utilizes a transfer roller that presses the toner image on a traveling image carrier. The toner is transferred onto a transfer material, and the transfer bias applied to the transfer roller is configured to have the same polarity as the toner during transfer and to maintain the same polarity for at least a certain period of time during non-transfer. .

With this configuration, there is no need to provide a cleaning roller in the cleaning device, and there is no need for a transfer charger, so the device can be downsized, including peripheral components, and the transfer roller can It is possible to reliably prevent the above-mentioned foreign substances from adhering to the body surface. (Description of an Embodiment) FIG. 1 is a side view showing the main parts of an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical photoreceptor. A conductive transfer roller 3 is in contact with the transfer roller 3, and a sheet-like transfer material (not shown) such as paper is conveyed in the direction of arrow B by the conveyance path 2, and the timing is aligned with the toner image formed on the surface of the photosensitive member 1. , photoreceptor 1
It is assumed that the toner image is transferred from the photoreceptor to the transfer material by the action of the bias that ignites the transfer roller when it reaches the transfer site where the toner and transfer roller 3 come into contact with each other.

As is well known, around the photoreceptor, there is a primary charger for uniformly charging the surface photosensitive layer, an image signal applying means for forming an electrostatic latent image on this, and a visible toner image for converting the latent image into a primary charger. Needless to say, there are components that form toner images, such as a developing device that supplies toner and a cleaning device that removes residual toner that remains on the photoreceptor after transfer. Well-known ones can be used, and all are omitted because they are not directly related to the present invention.

After the transfer, residual toner that does not contribute to the transfer and remains on the photoreceptor reaches a cleaning device (not shown) as the photoreceptor rotates and is removed by it, making the photoreceptor ready for the next image formation.

On the other hand, the transfer material that has received the toner image passes through the transfer site, is separated from the photoreceptor, and is conveyed along the conveyance path 6 to a fixing site (not shown).

As shown in the figure, the transfer roller 3 includes a core metal 3a made of, for example, stainless steel, a sponge layer 3b made of silicone with a conductive material such as carbon dispersed therein, and a sponge layer 3b made of carbon or the like dispersed in EPDM, urethane rubber, or the like. solid layer 3
c, and is formed as a conductive roller as a whole.

As shown in FIG. 2, the transfer roller 3 has one end of a core metal 3a, which is a shaft thereof, protruding outward, and is connected to the drive side DR via a clutch C disposed at that part. When the transfer material passes through the above-mentioned transfer site by an appropriate control means, the clutch is disengaged and the transfer roller runs approximately synchronously with respect to the photoreceptor, so that the transfer material passes through the transfer site. When the transfer roller 3 is not present, the clutch is connected for at least a certain period of time, and the transfer roller 3 maintains an appropriate speed difference with respect to the photoreceptor 1 (it is preferable that the peripheral speed of the transfer roller is smaller than that of the photoreceptor). ) It is preferable that the surface is rubbed.

In the figure, numeral 5 is a power source for applying a transfer bias to the transfer roller, and numeral 4 is a power source for removing toner from the transfer roller to prevent residual toner from adhering to the transfer roller and contaminating the transfer material. It's a scraper.

Next, the relationship between the polarity of the photosensitive layer of the photoreceptor, the polarity of the toner, and the transfer bias will be briefly described with reference to FIG.

In the case of normal development, the potential of 81 parts without light irradiation -V
becomes the desired latent image at V, and the developing bias is -vl)(
, l, the toner is transferred to the photoreceptor side with the potential contrast vNte, the potential V of the 82 part is V2, and the potential contrast VNf is 2L of the toner.

Metastasis will be prevented and high quality images will be obtained.

Looking at the bias relationship of the transfer roller in this case as shown in Fig. 4A, the latent potential is °'-', the toner is °'+',
The developing bias DC component is °°-°'', and the transfer roller DC component is -''' at the terminal S2 during transfer, and II +11 at the terminal Sr side during non-transfer.

In addition, in the case of reversal development, an image is obtained in the light irradiated area, as shown in FIG. 3 E2. To develop with (vL),
The developing bias is set to vD (2&), the toner is transferred to the photoreceptor at a potential contrast of 7 inches, and the potential contrast is vF.
! , b, a fog-free image can be obtained. At this time, as shown in Figure 4B, the relationship between the bias polarities is that the latent potential is '°-°', the toner is °'-', the developing bias DC is °'-', and the transfer roller bias is , at the time of transfer, it is '+' on the terminal S side, and on the non-transfer leg, it is par-' on the terminal S2 side.

In short, the transfer voltage applied to the transfer roller has the opposite polarity to the toner during transfer, and the same polarity as the toner during non-transfer.

By aligning the switching of the bias with the aforementioned switching of the transfer roller and the clutch between disengagement and engagement, the transfer and cleaning functions can be effectively performed by the transfer roller.

Note that even if you set the developing bias and transfer bias to prevent fog from occurring as described above, it is not possible to eliminate the presence of a small amount of toner on the surface of the photoreceptor. Action brings about good results.

To explain this with reference to FIG. 5, at the nip between the photoreceptor 1 and the transfer roller 3, during non-transfer, the sliding action is normally performed in a state where the speed of the photoreceptor is high. The toner T tends to accumulate on the entrance side of the nip between the two, and since both have the same polarity, the toner does not repel the transfer roller and stick to it.
It will move irregularly at the entry site to increase the cleaning function.

In order to promote this effect, a latent image is formed on a part of the corresponding photoreceptor part so that an appropriate amount of toner is collected in the nip during non-transfer, and the toner is adhered to the latent image. , the cleaning effect can be improved.

Although the present invention has been described above with respect to a case in which it is applied to a copying machine, it goes without saying that the present invention is not limited to this and can also be applied to other image forming apparatuses.

(3) Effects of the Invention As explained above, the present invention uses a transfer roller to transfer the toner image on the image bearing member to the transfer material, and at the same time, transfers the toner image to the roller with the opposite polarity to the toner at the time of transfer. Since a bias of the same polarity as the toner is applied for at least a certain period of time during non-transfer, there is no need to install a cleaning roller in the cleaning device to remove foreign matter adhering to the image carrier. There is no need for a charger, which greatly contributes to the miniaturization of this type of image forming apparatus.Also, since the adhesion between the transfer material and the image carrier can be configured to be good and strong, it is possible to It is possible to obtain a high-quality image by preventing image disturbances caused by irregular feeding by the conveying means, undesirable electrostatic interactions, and the like.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine, FIG. 2 is a front view of a portion of the same transfer roller, and FIG. 3 is a developing bias when forming a toner image. A graph explaining the relationship between transfer bias. Figures 4A and 4B are schematic side views of the main parts of the copying machine described above to explain the bias. Figure 5 shows a photoconductor and transfer diagram to explain the cleaning action of toner. FIG. 3 is an enlarged side view of the nip portion of the roller. 1.φ photoconductor, 2.transfer material conveyance path, 3.ψ.transfer roller, 5.fist-transfer bias, 6Φ.. developer. Figure 1 Figure 2 Ll)-< Figure 3 Width side light i Log E-

Claims (3)

[Claims] (1) Image formation in which a conductive elastic transfer roller is brought into pressure contact with an image carrier that carries a transferable toner image and travels, and a transfer material is passed between the two to transfer the toner image to the transfer material. An image forming apparatus characterized in that the actual polarity of the transfer bias applied to the transfer roller is opposite to that of the toner during transfer, and the same polarity for at least a certain period of time during non-transfer. (2) A conductive elastic transfer roller is brought into pressure contact with an image bearing member that carries a transferable toner image and travels, and a transfer material is passed between the two to be transferred to the toner image transfer material, and the toner image is transferred to the transfer material. In an image forming apparatus configured such that the actual polarity of the transfer bias to the roller is opposite to that of the toner during transfer, and the same polarity for at least a certain period of time during non-transfer, the transfer roller is connected to the image carrier during transfer. An image forming apparatus characterized in that the roller travels at approximately the same speed as the image carrier, and when not transferring, the travel speed of the roller is slower than that of the image carrier. (3) bringing a conductive elastic transfer roller into pressure contact with an image bearing member traveling carrying a transferable toner image, and passing a transfer material between the two to transfer the toner image to the transfer material;
In an image forming apparatus configured such that the actual polarity of the transfer bias to the transfer roller is opposite to that of the toner during transfer, and the same polarity for at least a certain period of time during non-transfer, An image forming apparatus characterized in that a toner layer is formed on an image carrier, and the polarity of a bias applied to the transfer roller is changed before the toner layer reaches the transfer roller.