JPH04216577A - Transfer device - Google Patents

Abstract

PURPOSE:To offer a transfer device which utilizes the advantage of a roller transfer method and where the restriction of the developing method being the shortcomings of the method is eliminated. CONSTITUTION:The transfer device 6 by which a toner image on a photosensitive drum 2 is transferred to a paper D is provided with a brush 60 which is made of a conductive material and arranged at a position opposed to the photosensitive drum 2, and a constant voltage power source 61 for electrostatically charging the brush 60 to have a reverse polarity to toner on the drum 2, and it is constituted so that the brush 60 is allowed to abut on the surface on an opposite side to the surface of the paper D facing to the drum 2 traveling between the drum 2 and the brush 60.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device that is installed in, for example, an electrophotographic printer and transfers a toner image on a photosensitive drum onto a sheet of paper.

0002

[Prior Art] In this type of printer, recorded information is exposed on a photoreceptor drum to form an electrostatic latent image, and then toner is supplied to the electrostatic latent image to obtain a visible image (toner image). The image is transferred onto a sheet of paper by a transfer device placed opposite to the photoreceptor drum, and then fixed to obtain a single copy. Incidentally, there are various transfer methods, and among them, the roller transfer method is one of the most commonly used transfer methods along with the corona transfer method. In the roller transfer method, a voltage is applied directly to paper via a conductive roller made of conductive rubber or the like, and the electric field generated thereby is used to transfer the toner image on the photoreceptor drum to the paper. In this case, since the transfer is performed while directly pressing the paper against the photoreceptor drum with a conductive roller, the adhesion between the paper and the photoreceptor drum is good, and ozone is not generated due to corona discharge in the transfer section. Therefore, since it is less susceptible to the influence of temperature, humidity and ozone in the surrounding environment, image disturbance is less likely to occur and good image quality can be obtained. Furthermore, it does not cause deterioration of the surrounding environment due to ozone generation. In addition, since the roller transfer method does not use a transfer charger, it is advantageous in terms of space compared to the corona transfer method.

0003

However, despite having the above-mentioned advantages, the roller transfer method has a limitation in that the development method employed is limited to a one-component development method. The reason why the two-component development method cannot be adopted will be described below. In general, developing methods used in electrophotographic image forming apparatuses are broadly classified into one-component developing methods and two-component developing methods. A one-component developing method is a method using only magnetic toner as a developer, and a two-component developing method is a method using two components, a non-magnetic toner and a carrier.

In the two-component developing method, only the toner is theoretically consumed in the developing process. The carrier is magnetically attracted to the developing sleeve and does not adhere to the photosensitive drum. However, in reality, some of the carrier may migrate from the developing sleeve to the photoreceptor drum, resulting in
The carrier may be transported to the transfer position. Metal powder such as iron powder is usually used as a carrier, so if the metal powder gets into the transfer position (the contact surface between the photoreceptor drum and the transfer roller in the roller transfer method), it will cause local damage through the metal powder. A problem occurs where a large current flows. As a result, not only the transfer of the toner image onto the photoreceptor drum is hindered, but also the photosensitive layer on the surface of the photoreceptor drum is destroyed by the overcurrent. For this reason, in the roller transfer method, a two-component developing method using a carrier cannot be adopted.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide a transfer device that takes advantage of the advantages of the roller transfer method and eliminates the limitations of the developing method, which is its drawback.

[0006]

[Means for Solving the Problems] The present invention provides a transfer device for transferring a toner image on an image carrier onto a sheet of paper. , a high-voltage power supply device that supplies a brush with a potential of opposite polarity to the toner on the image carrier; The present invention is characterized in that the brush is configured to abut against a surface.

[0007]

[Operation] According to the above structure, a brush made of a conductive material is provided at a position opposite to the image carrier, and the paper runs between the image carrier and the brush. Further, the brush is brought into contact with the surface of the paper opposite to the surface facing the image carrier with appropriate pressure. Further, a high-voltage power supply supplies the brush with a potential having a polarity opposite to that of the toner on the image carrier. Here, a strong electric field is formed between the image carrier and the brush. In this state, the toner on the image carrier is transferred to the paper.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a side sectional view showing an example in which a transfer device according to the present invention is applied to a printer. First, the schematic configuration will be explained according to the drawings. When a print switch (not shown) is turned on, the photosensitive drum 2 provided at the center of the printer 1 rotates in the direction shown by arrow A, and the charger 3 charges the surface of the photosensitive drum 2 accordingly. next,
An optical writing unit 4 consisting of an LED array emits light in response to an image signal applied from a scanner section (not shown), and exposes the surface of the photoreceptor drum 2. Thus, an electrostatic latent image is formed in the exposed area. Next, a developing device 5 installed on the upper right side of the photoreceptor drum 2 in the figure supplies toner to the electrostatic latent image to form a toner image (visible image).

Meanwhile, in synchronization with the image forming process, the paper feed roller 7 picks up the paper (not shown) stored in the paper feed cassette 8.
is fed out and supplied to the registration rollers 9. The registration rollers 9 transport the paper to the transfer device 6 in synchronization with the rotation of the photosensitive drum 2. The transfer device 6 is provided opposite to the photoreceptor drum 2, and transfers the toner image formed on the photoreceptor drum 2 onto a sheet of paper. The paper onto which the toner image has been transferred is then conveyed to the position of the fixing roller 10, where a fixing process is performed. After the fixing process, the paper is conveyed in a U-turn by a paper guide 11 for paper ejection and an ejection roller 12, and is ejected onto a paper ejection tray 13 attached to the upper part of the main body. In addition, the dashed line in the figure indicates the path line P of the paper.
is shown.

Next, according to FIGS. 2 and 3, the transfer device 6
The details will be explained below. FIG. 2 is a side sectional view showing the transfer device 6. As shown in FIG. The transfer device 6 includes a conductive brush 60 provided opposite to the photoreceptor drum 2, and a constant voltage power source 61 for applying a voltage of about +600 to +1000 V to the conductive brush 60. The conductive brush 60 also includes a brush portion 62 formed of a conductive material such as carbon-containing fiber or metal fiber, and a high voltage power receiving portion that supports the brush portion 62 and is applied by a constant voltage power source 61. It consists of a holder part 63. Furthermore, the length in the longitudinal direction of the conductive brush 60 is approximately the same as the length in the longitudinal direction of the photoreceptor drum 2, and the density of the conductive material in the brush portion 62 is approximately uniform at each position in the longitudinal direction. It is formed. In addition, since the tip of the brush portion 62 comes into contact with the traveling paper D, it has flexibility to the extent that it does not damage the paper surface. In addition, since the brush portion 62 is brought into contact with the paper D from below, it is possible to prevent the paper D from interfering with the running of the paper D.
The thickness of the conductive material is adjusted so that the entire brush portion 62 has a certain degree of elasticity. For example, it is also possible to use a conductive material in the form of a bundle.

[0011] In order to adjust the contact force of the conductive brush 60 with respect to the paper D, the set position of the conductive brush 60 may be freely changed. In this case, a tray for collecting paper powder may be provided below the conductive brush 60. According to the above configuration, when the paper D runs in the direction of the arrow X between the photoreceptor drum 2 and the conductive brush 60 provided opposite thereto, the paper D is subjected to an appropriate pressure by the conductive brush 60. Therefore, it travels while being in contact with the photosensitive drum 2. At this time, the conductive brush 60 is supplied with a voltage of +600 to +1 by the constant voltage power supply 61.
For this reason, the toner image is transferred from the photoreceptor drum 2 at the position of the paper D where the conductive brush 60 comes into contact, and at the position on the opposite side of the paper D. Become. In this case, even if a two-component developing method is used and a carrier such as iron powder is conveyed onto the photoreceptor drum 2, the conductive brush 60 acts as a transfer roller on the paper D.
Since the carrier is not strongly pressed against the carrier, there is no possibility of leakage through the carrier.

FIG. 3 is a relative comparison diagram showing the set potentials of each device section in the printer 1. As is clear from the drawings, the potentials of each device section are set as follows. Charged potential on the surface of the photosensitive drum 2 (V0) < bias potential of the developing device 5 (V1) < exposure potential (potential on the surface of the photosensitive drum 2 exposed by the optical writing unit 4) (V2
)<zero potential<surface potential of photoreceptor drum 2 after transfer (V
3)<Bias potential of transfer device 6 (V4). Under such a relationship, the toner image on the photosensitive drum 2 is transferred to the paper D.

[0013]

[Effects of the Invention] According to the present invention, good image quality, which is an advantage of the roller transfer method, can be obtained, ozone is not generated in the transfer section, and transfer is not easily affected by surrounding temperature and humidity. This method satisfies all the requirements, including being advantageous in terms of space compared to the corona transfer method.

On the other hand, the disadvantage of the roller transfer method, which is that the development method is limited to a one-component system, can be solved by using a two-component system development method by using a conductive brush without using a transfer roller. is also possible. Furthermore, although the roller transfer method requires precision in assembling the transfer roller, since a conductive brush is used, the assembling precision is not required as much as when using a roller. Therefore, the number of parts for assembly can be reduced, which also contributes to cost reduction. Further, since the structure is simple, a transfer device using a roller transfer method can be easily changed to a transfer device according to the present invention.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an example in which a transfer device according to the present invention is applied to a printer.

FIG. 2 is a side sectional view showing a transfer device according to the present invention.

FIG. 3 is a relative comparison diagram showing set potentials of each device section in the printer.

[Explanation of symbols]

1 Printer 2 Photoreceptor drum 6 Transfer device 60 Conductive brush 61 Constant voltage power supply

Claims (1)

[Claims] 1. A transfer device that transfers a toner image on an image carrier onto a sheet of paper, comprising: a brush made of a conductive material and provided at a position opposite to the image carrier; and a brush that transfers the toner image on the image carrier. and a high-voltage power supply device that supplies a potential of opposite polarity to the brush, and the brush is brought into contact with a surface of the paper running between the image carrier and the brush, opposite to a surface facing the image carrier. A transfer device characterized in that it is configured as follows.