JPH04216569A - Image forming device - Google Patents

Abstract

PURPOSE:To offer an image forming device which can surely form an image by positively removing paper powder at the position of a resist roller. CONSTITUTION:In the image forming device provided with the resist roller 9 for feeding a paper D to a transfer part in synchronism with the rotation of a photosensitive drum 1, a 1st electrostatic charging means(for electrostatically charging to be negative by an electrostatic charging brush 95 and a power source 96) for electrostatically charging the resist roller 90 which comes in contact with a surface on the same side as the surface of the paper D facing to the drum 1, a 2nd electrostatic charging means(a paper guide 100 is grounded) for electrostatically charging the paper D which is supplied to the resist roller 9 to higher potential than the 1st electrostatic charging means, and a collecting means 97 for collecting paper powder PD adhering to the surface of the resist roller 90 are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus having a registration roller that conveys paper to a photosensitive drum.

0002

2. Description of the Related Art In this type of image forming apparatus, 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). This toner image is transferred onto a sheet of paper by a transfer device disposed opposite to the photosensitive drum, and then fixed to obtain a single copy. As a means for conveying the paper between the transfer device and the photoreceptor drum,
A registration roller is provided upstream of the photoreceptor drum. This registration roller has a function of conveying the paper to the transfer device in synchronization with the rotation of the photoreceptor drum.

By the way, after the transfer has been completed, the photosensitive drum is cleaned with a cleaner in order to remove untransferred toner remaining on its surface. The cleaner scrapes off the toner by bringing a scraping blade into contact with the surface of the photoreceptor drum, receives the toner from below with a scooping sheet, and collects the toner in a toner collection chamber. On the other hand, there is also a cleaning method that does not use a cleaner. According to such a cleaner-less method, toner is collected in a developing device using electrostatic attraction force.

0004

However, according to the above-mentioned cleanerless method, the paper dust present on the paper ends up being collected in the developing device along with the residual toner, and becomes a foreign object in the developing device, which hinders the development process. This is a drawback that greatly hinders the process. Specifically, in the developing device, a certain amount of toner is thinned by the developing sleeve and doctor blade and is supplied to the photoreceptor drum, but if paper dust is mixed in, the paper dust may be mixed in with the doctor blade, etc. As a result, toner is not supplied to some parts of the electrostatic latent image on the photoreceptor drum (so-called white spot phenomenon).
This is a serious problem.

[0005] Even in the case of an image forming method that uses a cleaner, if there is paper dust on the paper, toner will be transferred onto the paper dust during the transfer process, and the paper dust will also be transferred to the photoreceptor drum. Since the toner is attracted, problems such as white spots and disturbances occur in the toner image on the paper. The present invention was made to solve this problem, and by actively removing paper dust at the registration roller position, it is possible to reliably remove paper dust both when using a cleanerless method and when using a cleaner. An object of the present invention is to provide an image forming apparatus that enables image formation.

[0006]

[Means for Solving the Problems] The present invention provides an image forming apparatus having a registration roller that feeds paper to a transfer section in synchronization with the rotation of a photoreceptor drum. a first charging means for charging a registration roller in contact with a surface; a second charging means for charging a sheet of paper supplied to the registration roller to a higher potential than the first charging means; The present invention is characterized by comprising a collection means for collecting attached paper powder.

[0007]

[Operation] According to the above configuration, the registration roller that contacts the same side of the surface of the paper that faces the photoreceptor drum is the first registration roller.
It is charged to a predetermined potential by a charging means. Further, the second charging means charges the paper to a potential higher than that potential. Then, as the paper is fed out as the registration rollers rotate, the paper dust on the paper is conveyed to the position of a collection means for collecting the paper dust, with the paper dust attached to the surface of the registration roller, and collected.

[0008] Note that due to the small diameter of the registration rollers and the stiffness of the paper, the paper is not wrapped around the registration rollers and is conveyed as is to the transfer section.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a side cross-sectional view showing an example in which an image forming apparatus 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. Note that this registration roller 9 will be explained in detail with reference to FIGS. 2 and 3. 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 transferred to a paper guide 11 and an ejection roller 1 for ejecting the paper.
2, the paper is conveyed in a U-turn shape, and is discharged onto a paper discharge tray 13 attached to the upper part of the main body. In addition, in the figure, the pass line P of the paper is indicated by a chain line.

FIG. 2 is a side sectional view showing the registration roller 9 and its surrounding area. The registration roller 9 is composed of a pair of rollers, an upper roller 90 and a lower roller 91.
Both rollers are in contact with a contact surface 92. Its diameter is approximately 10 to 20 mm, and its length in the longitudinal direction is set to be slightly longer than the maximum width of the paper to be fed. Then, the paper D is conveyed to the next transfer process in the direction of arrow X while being held between these rollers. Further, the upper roller 90 that contacts the surface of the paper facing the photoreceptor drum 2 is a roller body 9 formed of metal or the like.
3, and an insulating layer 94 made of insulating rubber or the like and fitted onto the surface thereof.

Furthermore, an insulating layer 9 is provided on the right side of the roller 90.
4, a charging brush 95 is provided so as to come into contact with the insulating layer. And the charging brush 95 is -
A power supply 96 is connected so that a negative voltage of about 400 to -600V is applied. In addition, the charged brush 9
A collection device 97 for collecting paper powder PD is detachably provided above the paper dust PD. The collecting device 97 comes into contact with the insulating layer 94 on which the roller 90 is fitted, and is composed of a blade 98 that scrapes off the paper powder PD, and a tray section 99 that collects the collected paper powder PD. The paper powder PD accumulated in the tray part 99 is
It is removed by removing the collection device 97 as appropriate. Further, a paper guide 100 that guides the paper D to the registration rollers 9 is grounded.

According to the above configuration, the insulating layer 94 is charged to -400V to -600V by the charging brush 95 and the power source 96, and the paper D passes between the rollers 90 and 91. In this case, as described above, the roller 90 and the roller 9
1 has a small diameter of about 10 to 20 mm, and therefore, the paper D is conveyed in the direction of the arrow X without being wound around the roller 90 due to its rigidity.

On the other hand, since the paper powder PD on the paper D is positively charged, it is attracted to the surface of the insulating layer 94 on which the roller 90 is fitted. Then, as the roller 90 rotates in the direction of arrow B, it is transported to the position of the collection device 97. Therefore, the paper powder PD is scraped off by the blade 98 and the plate part 99
will be collected within. Therefore, the paper powder PD is transported to the next transfer process together with the paper D, adheres to the photosensitive drum 2, and is not collected inside the developing device 5.

FIG. 3 is a side sectional view showing another embodiment of the registration roller 9 and its surrounding area. In this embodiment, the metallic roller body 93 is used as it is without using the insulating layer 94, and the roller body 93 is grounded. on the other hand,
In order to charge the paper D, a charging brush 95 is brought into contact with it from the back side (from below in the figure). In this case, the power supply 96 for applying voltage to the charging brush 95 is connected in the opposite way to the connection shown in FIG. 2 so that a positive voltage is applied. The applied voltage is about +400 to +600V. Further, the recovery device 97 is provided at the same position as shown in FIG.

According to the above configuration, the paper D is charged to +400V to +600V by the charging brush 95, and the paper D passes between the rollers 90 and 91. Then, as the roller 90 rotates in the direction of arrow B, the roller 90
The upper paper powder PD is transported to the collection device 97 and collected. Note that when the paper D is charged in this way, the paper D that has passed through the registration rollers 9 is positively charged, so the photosensitive drum 2 is charged before entering the next transfer process.
There is a risk that some of the charged toner may be discharged and transferred. In such a case, the paper D is placed on the downstream side of the registration roller 9 to guide the paper D to the photosensitive drum 2.
Discharge can be prevented by providing a constant voltage means 102 (a constant voltage diode is shown in the figure) such as a constant voltage diode or a resistor to the paper guide 101 provided on the back side of the paper guide 101 .

[0017]

According to the present invention, the first charging means and the second charging means charge the paper supplied to the registration rollers on the same side as the surface of the paper facing the photoreceptor drum. Since a certain potential difference is applied between the resist rollers and the contact rollers, paper dust on the paper is attracted to the surface of the resist rollers, and is collected and removed by the collection means. That is, since the paper dust is removed at the registration roller portion, the paper dust does not adhere to the photoreceptor drum. Therefore, in the image forming apparatus using the cleanerless method, paper dust does not get mixed into the developing device, and paper dust clogging does not occur, so it is possible to prevent white spots from occurring in the developing process. .

Furthermore, even in an image forming apparatus that uses a cleaner, since toner is not transferred onto paper powder, white spots and toner image disturbances do not occur in the transferred image. Therefore, it is possible to obtain outstanding image quality in any image forming apparatus.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment in which an image forming apparatus according to the present invention is applied to a printer.

FIG. 2 is a side cross-sectional view showing a registration roller and its surrounding area.

FIG. 3 is a side cross-sectional view showing another embodiment of a registration roller and its peripheral portion.

[Explanation of symbols]

1 Printer 2 Photoreceptor drum 5 Developing device 9 Registration roller 95 Charged brush 97 Recovery device D Paper PD Paper powder

Claims (1)

[Claims] 1. In an image forming apparatus having a registration roller that feeds paper to a transfer unit in synchronization with the rotation of a photoconductor drum, the registration roller that contacts the same side of the surface of the paper that faces the photoconductor drum is charged. a first charging means for charging the paper supplied to the registration rollers to a higher potential than the first charging means; and a collection means for collecting paper powder adhering to the surface of the registration rollers. An image forming apparatus comprising: means.