JPH02156279A - Transfer device for image forming device - Google Patents

Abstract

PURPOSE:To prevent the fault of an image by making a space between a 1st plane passing both center axis lines of a photosensitive drum and a transfer drum and the contact line of both drums and the charge wire of a charger for transfer and a space between a 2nd plane which is in parallel with the 1st plane and includes the charger wire and the end part of a shielding plate nearest to the 2nd plane specified ones. CONSTITUTION:It is assumed that the space (a) between the 1st plane passing both center axis lines 10a and 1a of the photosensitive drum 10 and the transfer drum 1 and the contact line of both drums 10 and 1 and the charger wire of the charger 2 for transfer is <=2.0mm and the space (b) between the 2nd plane which is in parallel with the 1st plane and includes the charger wire and the end part of the shielding plate 5 which is the nearest to the 2nd plate is >=0mm and <=3.0mm. Thus, the stable transfer processing is secured in spite of the change of environment and the fault of the image such as the missing of the image caused by the over or shot discharge of the transfer charger is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a photoreceptor drum carrying a toner image and a transfer drum are disposed facing each other, and a charge is placed in the transfer drum upstream of a contact line between the two drums when viewed in the direction of rotation of the transfer drum. A transfer charger is arranged so that the wire is located, and a transfer entrance shielding plate is provided on the upstream side of the transfer charger when viewed in the rotational direction of the transfer drum, and the transfer charger transfers the toner image on the photoreceptor drum onto the transfer drum. The present invention relates to a transfer device for an image forming apparatus that transfers images onto a sheet.

In the transfer device of the above-mentioned type, the transfer charge wire is located at the contact line between the transfer drum and the photoreceptor drum, and the transfer entrance shielding plate is not installed. This is the method that maximizes transfer efficiency. However, in reality, the transfer charge electric field radiates from the wire, and the above arrangement causes various side effects. For this purpose, the charge wire is placed inside the transfer drum close to the line of contact between both drums. However, if the transfer charge is simply placed inside the transfer drum, the discharge state of the charger is easily affected by the surrounding environment and the stability is affected, resulting in image defects. On the other hand, the charge wire of the transfer charger is placed in the charger on the upstream side of the plane that connects the center axes of the photoreceptor drum and the transfer drum and passes through the contact line of both drums when viewed in the rotational direction of the photoreceptor drum. , thereby increasing latitude in transfer conditions is known to those skilled in the art. However, when the surrounding environment temperature changes from low to high temperature, the above measures are insufficient.

SUMMARY OF THE INVENTION An object of the present invention is to increase the latitude of transfer conditions against changes in the surrounding environment in a transfer apparatus of the type described in the field of industrial application.

Means for Solving the Problems According to the present invention, the above-mentioned problem can be solved by one aspect of the present invention. The distance is 2.0 mm or less, and the distance between the second surface parallel to the first surface and containing the charge wire and the end of the shielding plate closest to this is 0 m or more and 3.0 mm or less. This is solved by

[1] Figure 1 shows an electrophotographic copying machine equipped with a transfer drum 1 and a photosensitive drum 10 to which the present invention is applied. This electronic copying machine p can perform two types of copying: black copying and color copying. Other configurations of the electrophotographic copying machine and each copying operation described above will be explained below.

The surface of the photosensitive drum 10 is uniformly charged by the discharge of the agricultural/industrial charger 16 to the melon. An electrostatic latent image is formed on the surface of the photoreceptor drum by the image exposure of the exposure device 17, and the latent image is developed with black toner in the black developing device 11 to form a black toner image. This black toner image is then carried to the transfer charger 2, and the discharge of the transfer charger 2, for example (-
) is transferred onto a transfer paper wrapped around the outer surface of the transfer belt 1 under a polar discharge. Once the transcription is finished.

The transfer paper is separated from the transfer drum 1 by a separation unit 7, sent by a conveyance device 8, and further subjected to a fixing process by a fixing device 9, and then discharged to the outside of the machine. Toner remaining on the photoreceptor drum 10 after the transfer is removed by a magnetic brush cleaning device 15.

After the transfer paper is separated, the transfer drum 1 has an inner DC charger 4b that discharges with a polarity opposite to that of the transfer charger 2, that is, (+) polarity, and an outer DC charger 4b that discharges with the opposite polarity, that is, (-) polarity. Static electricity is removed by both chargers of the charger 4a, and then the AC static electricity removal charger 3a
, 3b, the AC static electricity is removed. The inside of the transfer drum 1 is IF-charged to a (-) polarity, while the outside thereof is charged to a (+) polarity by a transfer charger 2 that performs a (-) polarity discharge. In this embodiment, the inside of the transfer drum 1 is charged with an inner DC charger 4b with a (10) polarity discharge, and the outside with a (-) polarity discharge with an outer DC charger 4a. The charged transfer drum 1 is reliably neutralized by the DC chargers 4a and 4b. The potential of the transfer drum 1 after static elimination by the DC charger may shift to (+) polarity or (-) polarity, but this shift is compensated for by the AC static elimination chargers 3a and 3b, and the transfer drum 1 is adjusted to zero potential. 9 Color Copying Development by the black developer 11 is not performed, and each color is developed in sequence by the cyan developer 12, magenta developer 13, and yellow developer 14 while the photosensitive drum 10 rotates three times. . Each time development is performed, the surface of the photosensitive drum 10 is cleaned by the magnetic brush cleaning device 15. The transfer drum 1 around which the transfer paper is wound rotates three times in synchronization with the rotation of the photosensitive drum 10. Each time the transfer drum 1 rotates once, a cyan toner image, a magenta toner image, and a yellow toner image are sequentially transferred onto a sheet of transfer paper in an overlapping manner. After the three transfers are completed, the transfer paper is separated by the 1-separation unit 7 or the like and fixed by the fixing device 9.

After the transfer paper has been separated, a DC charger 4a is applied to the transfer drum 1 as in the case of black copying.

4b, static elimination and charging are performed by AC static elimination chargers 3a and 3b.

In FIG. 2, a first surface connecting the central axis 1a of the transfer drum 1 and the central axis LOa of the photoreceptor drum 10 passes through a contact line between both drums. The charge wire 2a of the transfer charger 2 is disposed inside the transfer drum so as to be located upstream of the first surface when viewed in the rotation direction of the transfer drum, and the charge wire 2a and the first surface are spaced apart by a distance a. It is located across from. Furthermore, a transfer inlet shielding plate 5 is attached to the transfer charger 2 on the upstream side when viewed in the rotational direction of the transfer drum, and the transfer inlet shielding plate 5 passes through the charge wire 2a and connects the second surface parallel to the first surface and the closest surface thereto. It has one interval from the end 5a of the transfer entrance shielding plate. In this case, the end portion 5a is
It is on the same side as the charge wire 2a with respect to the first surface and is further away from the first surface than the charge wire 2a.

According to the present invention, the value of the distance a is 2.0 m or less, and the value of the distance a is 01 or more and 3.0 m or less. Selected below On+.

We experimented with various values of a and b above, and evaluated the so-called partial toner ρ "missing" of the image after transfer due to excessive or insufficient discharge of the transfer charger applied to the photoreceptor drum. , shown in the table of FIG. However, the symbols in the table are the overall evaluation when the ambient temperature is changed from low to high.
is not allowed.

When a>2.0an: Transfer area (contact surface between transfer drum and photosensitive drum)
The charging electric field becomes weaker and transfer defects occur.

When b < Om: The electric field from the transfer charger to the photoreceptor drum is significantly interrupted, causing a transfer failure.

When b > 3.0 mm: If no transfer entrance shielding plate is provided, the electric field radiating from the transfer charger toward the photoconductor drum causes
Toner particles developed on the photoreceptor drum are attracted to the transfer paper upstream from the transfer area, and are scattered and transferred. To solve this problem, we installed a transfer entrance shielding plate.
However, if b > 30 mm, the effect of providing the transfer entrance shielding plate is lost.

After all, good transfer can be achieved by determining the values of both distances a and b according to the present invention.

Effects According to the present invention, a stable transfer process is guaranteed regardless of changes in the surrounding environment, and occurrence of image defects such as image deletion due to excessive discharge or insufficient discharge of transfer charge is prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electrophotographic copying machine to which the present invention is applied, FIG. 2 is an explanatory diagram showing the main parts of the present invention, and FIG. 3 is a table showing evaluation of the present invention. 1...Transfer drum 1a...Transfer drum center axis line 2...Transfer charger 5...Transfer entrance shielding plate 10...Photoconductor drum 10a...Photoconductor drum center axis a...Transfer charge wire and a first surface that connects the central axes of both trams and passes through the contact line of both drums. Distance b... A second surface that includes the charge wire and is parallel to the first surface and the transfer inlet shield closest to this. Diagram of distance from plate edge] 4 Diagram No. 4

Claims (1)

[Claims] A photosensitive drum carrying a toner image and a transfer drum are disposed facing each other, and a transfer charger is disposed within the transfer drum so that a charge wire is located upstream of a contact line between both drums when viewed in the direction of rotation of the transfer drum. A transfer inlet shielding plate is provided in the transfer charger on the upstream side when viewed in the rotational direction of the transfer drum,
In a transfer device of an image forming apparatus in which a toner image on a photoreceptor drum is transferred to a sheet on a transfer drum by the transfer charger, a line passing through both central axes of the photoreceptor drum and the transfer drum and a contact line between the two drums is provided. The distance between the surface of 1 and the charge wire of the transfer charger is 2.0 m.
m or less, and the distance between the second surface parallel to the first surface and including the charge wire and the end of the shielding plate closest to this is 0 mm or more and 3.0 mm or less. transfer device.