JP2003029547A - Transfer device and cleaning method for the transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that high-pressure switching control needs to be provided since a photoreceptor and a transfer roller are in contact in the absence of a form in a transfer roller system using cut paper and then toner on a photoreceptor sticks on the top surface of the transfer roller. SOLUTION: A rotary roller made of an elastic body of 10<8> to 10<12> Ω.cm is revolved around the photoreceptor above a transfer corona wire in a transfer unit; and toner and paper powder sticking on the roller surface are cleaned by being transferred reversely to the photoreceptor at a form interval or by sticking on the reverse surface of a form although its amount is small after being electrostatically charged by the discharging of the transfer corona wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser printer which uses electrophotography.
The present invention relates to a transfer device that transfers a toner image on a photoconductor to a sheet.

[0002]

2. Description of the Related Art In a cut paper laser printer or a copying machine using an electrophotographic method, when a toner image on a photoconductor is transferred onto a paper, a conductive shaft of a transfer roller in which a conductive shaft is covered with an elastic body is mounted on a conductive shaft. A method is used in which a voltage is applied to charge the back surface of the paper that is in contact with the transfer roller, and the toner image formed on the photoconductor is transferred to the paper. In this method, the sheet conveyed to the transfer device obtains electric charges having a polarity opposite to that of the toner and the photoconductor by the transfer roller, so that the sheet is brought into close contact with the photoconductor by the pressing force of the transfer roller to transfer the toner image. When a large amount of narrow paper is printed, the toner on the photoconductor adheres to the surface of the transfer roller because the photoconductor and the transfer roller are in contact with each other in the area where there is no paper. Therefore, in the transfer roller method, a mechanism for cleaning the roller surface is provided.

[0003]

SUMMARY OF THE INVENTION The present invention provides a transfer corona wire below the rotary roller inside the transfer device as an alternative to the transfer roller type cleaning mechanism. This rotating roller is a conductive shaft covered with an elastic rubber ring. When the transfer corona wire is discharged, a positive charge is generated on the surface of the rotating roller. The toner image formed on the photoconductor is transferred to the paper by closely contacting with the photoconductor and charging the back surface of the paper.

Further, even when toner or paper powder adheres to the surface of the roller due to the contact of the rotating roller with the photoconductor or the paper, the transfer corona wire is discharged while the photoconductor and the roller are in contact with each other. The toner and the paper powder attached on the upper surface are charged with a polarity opposite to the potential of the photoconductor. Therefore, the toner and the paper powder attached to the roller surface are reversely transferred to the photoconductor at the space between the paper sheets for cleaning, or they are attached to the back surface of the paper for a minute amount for cleaning.

As described above, the present invention eliminates the need for cleaning means as in the conventional transfer roller system.

[0006]

The object of the present invention is to provide an electric resistance of a rotating roller in which a rubber ring, which is an elastic body, is covered with a conductive material shaft inside a transfer device for transferring a toner image formed on a photosensitive member onto a sheet. and ^{8 ~10 12 Ω} · cm, the transfer corona wire, while the rotating roller and the photosensitive member is in mechanical contact is achieved by applying a high voltage.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a laser printer using an electrophotographic method will be described below with reference to FIG.

In an organic photoconductor (OPC) as an example of the photoconductor 1 used in a copying machine, a printer or the like, the surface of the photoconductor 1 is negatively charged by corona discharge of the charger 2. In the reversal development method which is often used in printers, a latent image is formed by an optical system 3 such as a semiconductor laser, and a developing device 4 applies a polar toner 5 having the same polarity as the potential of the surface of the photoconductor 1 onto the photoconductor 1. To adhere to.

Next, the sheet 6 is mechanically pressed onto the photoconductor 1 by the rotating roller 7, and then the transfer corona wire 9, the peeling corona wire 10 and the suction member 11 are mounted on the grounded metal plate 8. The transfer device 12 is conveyed. Since both the transfer corona wire 9 and the peeling corona wire 10 are shielded by the grounded metal plate 8, corona discharge is generated by applying a high voltage, and charges are applied to the shield opening surface, that is, the conveyed paper. , Transfer peeling can be performed.

Since a high voltage having a polarity opposite to that of the toner is applied to the transfer corona wire 9, when the rotating roller 7 applied by the transfer corona wire 9 comes into contact with the paper, an electric charge is given from the back side of the paper, Positive charges are generated on the paper by dielectric polarization. Due to this electric charge, the paper is brought into close contact with the negatively charged photoreceptor 1 by electrostatic force, and the negative toner is transferred onto the paper.

Next, it is necessary to peel off the paper stuck to the photoconductor, but the paper on the photoconductor 1 attracted by the electrostatic attraction force is the paper bent to the curvature of the photoconductor 1. The centrifugal force acts due to the force of the paper to return to its original state, the weight of the paper, and the rotation of the photoconductor. Therefore, if the paper is neutralized,
Peeling can be performed by these force relationships. The peeling corona wire 10 has a polarity of AC high voltage of several hundred Hz.
DC by ice is superposed, and charges are applied from the back side of the paper to remove electricity. This is to remove the charge on the photoconductor 1 that is negatively charged and the paper 6 that is + polarity at the same time, and remove the static electricity of both. This is to reduce the suction force. In a high-speed machine, a means for sucking a sheet with air may be used together to improve reliability. The inside of the suction member 11 has a cylindrical structure,
Although omitted here, the air in the inner cylinder is sucked by a blower through a duct. A plurality of small-diameter holes 13 having an outer diameter of several mm are provided on the paper traveling surface of the suction member 11, and a force for sucking the paper adsorbed on the photoconductor 1 acts from there. Next, the discharged sheet is adsorbed and conveyed by the conveyor belt 15 provided with the suction holes 14, and is fixed by a fixing device, though not shown in the drawing. On the other hand, the toner remaining on the photoconductor 1 after the transfer is cleaned by the cleaner 18 via the precharge 16 and the erase lamp 17.

Next, the operation of the rotary roller 7 of the present invention will be described with reference to FIGS.

In FIG. 2, above the transfer corona wire 9 (on the side of the photoconductor), a roller in which a rubber ring 20 is covered on a grounded conductor shaft 19 is arranged. A material such as polyurethane or foamed polyurethane is used as the material of the rubber ring 20, and Teflon (registered) is added to the surface in order to prevent deterioration due to ozone generated in the transfer corona wire, and release of the surface to prevent toner adhesion. Trademark), Fluorine,
A layer structure may be formed by coating PVDF or the like, or by covering with a tube. As described above, this rotating roller 7
Since it slides due to the rotation of the photoconductor 1 and is always in contact with the photoconductor 1, it can be pressed uniformly against the photoconductor 1 from the leading edge to the trailing edge of the conveyed sheet.

On the other hand, since the rotary roller 7 is always in contact with the photoconductor 1 and the paper, the toner on the photoconductor 1 and the paper dust on the back surface of the paper adhere to the surface and need to be cleaned. Become. If a cleaning mechanism such as a cleaning blade is provided, the size of the apparatus becomes large, and the toner must be collected and discarded. Therefore, in the present invention, cleaning is performed by the following process.

The rotating roller 7 is located above the transfer corona wire 9 inside the metal plate 8 of the transfer device (on the side of the photoconductor), and the grounded conductor shaft 19 is covered with the rubber ring 20 which is a dielectric. By the corona generated from the transfer corona wire 9, the surface always obtains a positive charge, but the resistance value of the rubber ring 20 determines the charge density generated on the roller surface. If the resistance value is 10 ⁷ Ω · cm or less, the resistance is too low and the electric charge escapes through the grounded conductor shaft 19, so that the adhered toner cannot be charged and the backside of the paper is soiled. Will occur. On the other hand, the resistance value is 1
When it is 0 ¹² Ω · cm or more, the electric charge generated on the surface of the rotating roller 7 is too high, and the + electric charge is excessively injected into the paper before transfer. In such a case, an electrostatic force is excessively applied to the toner image on the photoconductor 1 to cause scattering around characters and abnormal discharge. Therefore, the resistance value of the rotary roller 7 is preferably 10 ⁸ to 10 ¹² Ω · cm, and 10 ⁹ to 10 ¹¹ Ω · cm in consideration of resistance variation due to environment and temporal variation. As described above, the toner 21 attached to the surface of the rotating roller 7 in FIG. 3A obtains a positive charge, and is reversely transferred to the photoconductor 1 whose surface potential is negatively charged as shown in FIG. 3B. To be done. Like the residual toner after transfer, this toner is cleaned by a cleaner 18 through a precharge 16, an erase lamp 17, and the like. Alternatively, a simple structure without a cleaner can be obtained by contacting the back side of the conveyed sheet and adhering the sheet so that it is inconspicuous and removing it from the surface of the photoconductor.

With the rotating roller 7, when printing narrow paper continuously, the portion outside the paper size region of the rotating roller 7 is always in contact with the photoconductor 1. At this time, if the contact between the rotating roller 7 and the photosensitive member 1 is partially incomplete,
A gap is created between them, and the toner scattered from the developing device 4 is attracted by the electrostatic force and is deposited on the rotating roller 7. In that state, when the paper size is switched and wide paper is printed, the back surface is stained. Therefore, in the case where the rotating roller 7 is used to frequently switch the paper size for printing, it is necessary to always make uniform contact with the photoconductor 1 even outside the printing area. For this reason, the rubber hardness of the rotating roller 7 is preferably 20 to 70 °.

In a copying machine or a laser printer to which the electrophotographic method is applied, each mechanism is warmed up by driving each mechanism in the same state as printing immediately after the power is turned on. Also jam,
After the printing is stopped due to a failure and these causes are cleared, each mechanism is driven in the same state as the printing to check the operation. This operation is for cleaning the toner image formed on the drum and at the same time checking for any abnormality. In these cases, even though the rotary roller 7 is in contact with the photoconductor 1, the fog toner on the photoconductor 1 adheres to the rotary roller 7 by mechanical contact unless high voltage is applied. The back side of the paper may be smeared on the first few pages. Therefore, while the rotating roller 7 is in contact with the photoconductor 1 and is being driven, the transfer corona wire 9
It is preferable to apply a high voltage to the toner to clean the toner on the rotating roller 7.

[0018]

As described above, according to the present invention, the toner and the paper powder adhering to the rotating roller can be generated by the corona discharge of the transfer corona wire without complicating the high voltage control unlike the conventional transfer roller system. , Reverse transfer to photoreceptor, or
Since it adheres to the back surface of the paper even though it is minute, the back surface of the paper is not stained and the print quality is not impaired.

[Brief description of drawings]

FIG. 1 is a schematic view of a laser printer showing an embodiment of the present invention.

FIG. 2 is a schematic view of the vicinity of a transfer device of the present invention.

FIG. 3 is a schematic diagram showing the operation of the transfer device of the present invention.

[Explanation of Codes] 1 ... Photosensitive member, 2 ... Charging device, 3 ... Optical system, 4 ... Developing device, 5
... Toner, 6 ... Paper, 7 ... Rotating roller, 8 ... Metal plate, 9
… Transfer corona wire, 10… Peeling corona wire, 11…
Suction member, 12 ... Transfer device, 13 ... Small diameter hole, 14 ... Suction hole, 15 ... Conveyor belt, 16 ... Precharge, 17 ... Erase lamp, 18 ... Cleaner, 19 ... Conductor shaft, 20 ... Rubber ring, 21 …toner.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Nishino             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. (72) Inventor Masato Miwa             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. F-term (reference) 2H200 GA23 GA44 HA12 HB03 HB26                       JA02 JA26 JA27 JB06 JB10                       JB28 LB03 LB18 MB01 MB06                       MC01

Claims (2)

[Claims] 1. A transfer device for transferring a toner image adhering to the surface of a photoconductor onto a sheet of paper conveyed by a corona wire, which is a position between the corona wire and the photoconductor and which is a rotation axis of the photoconductor. A transfer device characterized in that a rotating roller covered with an elastic body is provided around parallel conductive shafts, and a surface of the rotating roller is in contact with a surface of a photosensitive member. 2. The elastic body of the rotating roller has an electric resistance of 10 ⁸ to.
In the transfer device according to claim 1, which is in the range of 10 ¹² Ω · cm, after charging the charged toner, paper powder, etc. adhered to the surface of the rotating roller to the opposite charge by discharging from the corona wire, the surface of the rotating roller is charged. A method for cleaning a transfer device, which comprises cleaning the surface of a rotating roller by adhering toner, paper dust, etc. to the surface of a photoconductor.