JPH0535128A - Transfer device - Google Patents

Abstract

PURPOSE:To reduce the lowering of the strength of a sheet itself and to prevent a faulty image by providing a frame obtained by sticking a dielectric sheet to the outside of a transfer drum body where a wire is provided in an axial direction in an inside omitted part after coupling both end flanges as to the transfer drum body. CONSTITUTION:As to a transfer drum body 66, the flange members at both ends thereof are coupled through the coupling member 18, and the non- conductive wire 19 as a thread-state member having elasticity and flexibility such as nylon or vinyl chloride, for example, is stretched and provided in a bus direction on a cylinder including the outer periphery of the flange members at both ends in the inside omitted part. A dielectric sheet 15 is stuck to all over the periphery so as to cover the flange member, the coupling member 18 and the wire 19. In the drum body 66, a brush transfer charger 1 is disposed so that the tip of the brush having the elasticity is bent so as to contact with the drum body 66 at a position where an image carrier 30 and the drum body 66 are the closest. Therefore, the lowering of the strength of the sheet 15, which does not occur because of repeated deformation, is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image using an electrophotographic method. Among them, there is a transfer apparatus for holding a transfer material on its surface and performing endless movement, for example, full color The present invention relates to an apparatus that forms an image.

[0002]

2. Description of the Related Art An image forming process and a transfer device in a conventional image forming apparatus for obtaining a color image using a plurality of toners as a developer will be described with reference to a sectional view of a printer section of a color electrophotographic apparatus shown in FIG.

As shown in FIG. 4, the image forming apparatus has a charger 31 and an exposure device 32 arranged around an image carrier 30 such as a cylindrical electrophotographic photosensitive member. An electrostatic latent image is formed on the image carrier 30 by the ordinary electrophotographic process using the exposure device 32.
The electrostatic latent image is developed by the developing device 33 including the developing units 33Y, 33M, 33C and 33B having toners of different colors as a developer, and the electrostatic latent image is transferred onto the image carrier 30.
It is visualized as a color toner image.

On the other hand, a transfer material P such as a transfer paper is transferred from a cassette (not shown) by a transfer material supply means 34 to a transfer device 60.
Is supplied to.

As shown in FIGS. 5 and 6, the transfer device 60 includes a pair of front and rear flange members 16, which are concentrically arranged.
17 are connected by a connecting member 18, and the flange members 16,
A transfer drum body 66 as a transfer material carrier in which a dielectric sheet 15 such as a high resistance film carrying a transfer material P is wound around the surface of a cylindrical opening formed by 17 and a connecting member 18.
have.

The transfer material P is conveyed to the transfer material suction position of the transfer device 60 by the registration roller pair 35 of the transfer material supply means 34 in synchronization with the image forming timing on the image carrier 30. An adsorption charger 36 is arranged in the transfer device 60, and the transfer material P is electrostatically adsorbed on the dielectric sheet 15 carrying the transfer material. Dielectric sheet 1 of the adsorption charger 36
An adsorption conductive roller 37 serving as a counter electrode is arranged at a position opposite to the outside of the transfer drum body 66 with 5 interposed therebetween.

The transfer material P adsorbed and carried on the dielectric sheet 15 is transferred to the image carrier 3 as the transfer drum 66 rotates.
It is contacted with 0. Then, by the transfer charger 38 arranged in the transfer device 60, an electric charge having a polarity opposite to that of the toner is applied to the back surface of the dielectric sheet 15, so that the image carrier 3
The toner image on 0 is transferred onto the transfer material P.

A color image is reproduced on the transfer material P by performing the above-described development and transfer processes on toner images of a plurality of colors.

As described above, the transfer material P on which the toner images of a plurality of colors are multi-transferred is arranged in a pair so as to face each other with the dielectric sheet 15 interposed therebetween in order to weaken the attraction force to the dielectric sheet 15. AC charge is removed by the charge removing charger 39, and the separation claw 40 is inserted between the transfer material P and the dielectric sheet 15 to separate the charge from the dielectric sheet 15. The separated transfer P is sent to the fixing device 41, where the toner image is fixed, and then discharged to a tray (not shown).

After the transfer, the residual toner on the surface of the image carrier 30 is cleaned by the cleaning device 42, and then the image carrier 30 is subjected to the color image forming process again.

[0011]

However, in the above conventional example, the dielectric sheet 15 carrying the transfer material is
The leading end and the trailing end are connected to the connecting member 1 of the transfer drum body 66.
8 and the left and right ends are attached and restrained only to the front and rear flange members 16 and 17, respectively.
In the opening of the transfer drum body 66, due to the weight of the dielectric sheet 15 itself and the tension received by the dielectric sheet 15 by restraining the four sides of the dielectric sheet 15, the transfer drum body 66 does not follow the cylindrical shape and is dented inward. Had a tendency. Then, when the transfer material P is attracted to the dielectric sheet 15 which is recessed inward, the holding force of the transfer material P becomes unstable, and the transfer material P moves on the transfer drum body 66 during multiple transfer, causing an image shift. Was occurring. Further, when the image transfer is performed in a state where there is a gap between the dielectric sheet 15 and the transfer material P, the charges applied on the dielectric sheet 15 cannot transfer the image on the image carrier 30 sufficiently, Development such as image loss or image blur has occurred. Therefore, as shown in FIG. 7, the transfer and adsorption chargers (38-a, 36-b) that require the dielectric sheet 15 to have a cylindrical shape are corona dischargers (38).
-A-1, 36-b-1) near the dielectric sheet 15
The pressing member (3
8-a-2, 36-b-2) have been proposed. However, the pressing members (38-a-2, 36-
When b-2) is applied to the transfer drum body 66, the dielectric sheet 15 does not dent inward in the vicinity of the pressing member (g and f parts in FIG. 8), but the dielectric sheet 15 is traveling outside. By the amount, it was dented inward at the central portion in the opening longitudinal direction on the transfer drum body 66 (c, d, e portions in FIG. 8). Therefore, the dielectric sheet 15 receives a force and is repeatedly deformed each time the transfer drum body 66 rotates, resulting in a decrease in mechanical strength of the dielectric sheet 15 itself.

As a means for preventing the dielectric sheet 15 from being deformed inward, a transfer drum body 66 as shown in FIG.
A thread-shaped support member 19 (hereinafter referred to as a wire) is attached to the outer periphery of the opening of the transfer drum body 66 in parallel with the cylindrical generatrix of the transfer drum body 66
There is a method of preventing the deformation of the dielectric sheet 15. However, when this method was applied to the apparatus shown in FIG. 7, there were the following problems, especially at the transfer charger 38-a. When the wire 19 is not attached to the transfer drum body 66, the charge density C applied to the dielectric sheet 15 around the transfer charger 38-a has a gentle charge after the pressing member 38-a-2 as shown in FIG. It is distributed. Figure 10 shows wire 1
9 shows the distribution of the charge density C when 9 is held. The distribution changes according to the position of the wire 19 after the pressing member 38-a-2. This is because the transfer charger 38-a is performing corona discharge in which the amount of charge applied changes depending on the thickness of the body to be charged, and the thickness of the wire 19 affects the thickness of the dielectric sheet 15. Is. When the image transfer is performed in this state, the image transfer is not performed uniformly depending on the location due to the distribution of the amount of electric charge applied, and the transferred image density varies even though the image density on the image carrier is constant.

That is, the transfer drum body 6 shown in FIGS.
No. 6, the image obtained on the transfer material P was not sufficiently satisfactory due to the deformation of the dielectric sheet 15 when the charger using corona discharge was used, and as shown in FIG. When the contact members 36-b-2 and 38-a-2 are used, the durability of the dielectric sheet is lowered. Further, when the wire 19 is provided on the transfer drum body 66, if the corona charger is used, there is a problem that the transferred image density varies.

[0014]

According to the present invention, there is provided a hollow drum having a shape in which both ends of a cylindrical body and a part of a busbar are left and other portions are removed, and an opening portion of the hollow drum, the hollow drum. A dielectric sheet covering the outer shape of the cylindrical body, and a transfer material holding member for carrying out endless movement while holding the transfer material on the dielectric sheet. Has at least one brush-like charger for applying an electric charge to the dielectric sheet while one end thereof being in contact with the dielectric sheet, and the entire area of the opening of the hollow drum is The transfer device is characterized in that a plurality of non-conductive thread-like members are provided on the generatrix of the cylinder of the hollow drum, and the dielectric sheet is supported by the plurality of non-conductive thread-like members.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view showing the basic structure of a color printer embodying the present invention. In the figure, portions having the same functions as those of the conventional example shown in FIG. 4 are designated by the same reference numerals, and a description thereof will be omitted.

As shown in FIG. 3, the transfer drum body 66 has a connecting member 18 between the flange members 16 and 17 at both ends.
The threaded portion which is elastic and flexible, for example, nylon (trade name) vinyl chloride in a generatrix direction on the cylinder including the outer circumferences of the flange members 16 and 17 at both ends in the hollowed out portion. A non-conductive wire 19 is stretched as a member. The wires 19 are equally spaced in the circumferential direction and are folded back at both ends.
It is fixed to No. 7 by adhesion, fusion or the like. Then, a dielectric sheet 15 is attached to the entire circumference so as to cover the flange members 16 and 17, the connecting member 18, and the wire 19.

In the transfer drum body 66, at the position where the image carrier 30 and the transfer drum body 66 are closest to each other, the brush transfer charger 1 is arranged so that the elastic brush tip of the brush transfer charger 1 bends and comes into contact with the transfer drum body 66. It is arranged. The brush transfer charger 1 uses conductive fiber bristles at its tip, and the fibers are elastic and need durability. Examples of the fiber include stainless steel fiber, acrylic,
A resin fiber such as nylon, polyester, rayon or the like, which is metal-plated, a resin in which conductive fine powder such as carbon or metal powder is kneaded, or a composite, or a carbon fiber is used. The brush transfer charger 1 is obliquely provided with respect to the radial direction of the transfer drum body 66 so that the bristle tips follow the moving direction of the inner peripheral surface of the transfer drum body 66.

A high voltage power source is applied to the brush transfer charger 1 by a bias power source 3.

To describe the above operation, in order to transfer the toner image on the image carrier 30 to the transfer material P carried on the dielectric sheet 15 at the time of transfer, a voltage is applied from the bias power source 3 to the brush transfer charger 1. .. As a result, charges having a polarity opposite to that of the toner image on the image carrier 30 are applied, and the toner image is transferred to the transfer material P. Since the dielectric sheet 15 is supported by the wire 19, the dielectric sheet 15 rotates in a cylindrical shape.
Further, even if the wire 19 is present, the brush transfer charger 1 is always in contact with the dielectric sheet 15, and compared with the corona charger,
The toner image on the image carrier 30 is efficiently attracted without leakage current.

FIG. 11 shows the effect of the brush transfer charger 1 and the wire 19 on the dielectric sheet 15.
The protrusion of the dielectric sheet 15 on the transfer drum body 66 is the portion pressed by the brush at the brush transfer charger 1 (h in FIG. 11), and the other portion is covered by the wire 19 to the dielectric sheet 15. The shape is kept equal to the outer diameter of the transfer drum body 66. 12 and 13 show the charge density C on the dielectric sheet 15 around the brush transfer charger 1, and the distribution is distributed regardless of whether the wire 19 is present (FIG. 11) or not (FIG. 12). The change as shown in FIGS. This is because the application of electric charge by the brush is not affected by the thickness of the wire 19 because the brush itself contacts the dielectric sheet 15.

[0022]

[Other Embodiments] FIG. 2 shows another embodiment of the present invention, in which the brush-type brush attraction charger 2 is used as the charger of the attracting portion of the transfer device 60.

Since the brush adsorption charger 2 is used in the adsorbing portion, the sheet charge density distribution in the adsorbing portion becomes gentle as compared with the example of FIG. 1, and the transfer material having a strong rigidity (for example, thick paper, transparent paper) is used. Stable) is easily absorbed.

[0024]

As described above, a plurality of thread-like members are provided on the generatrix of the cylinder of the hollow core drum over the entire opening of the hollow drum for the transfer drum to support the dielectric sheet and transfer the dielectric sheet. By providing a brush-shaped charger inside the drum, one end of which directly contacts the dielectric sheet, it is possible to eliminate image defects that have been caused by the deformation of the dielectric sheet, and the dielectric sheet itself does not easily deform. Since it is held, the decrease in mechanical strength of the dielectric sheet itself, which has been caused by repeated deformation, can be reduced.

Then, by the brush charger, the charge density distribution given to transfer the toner image on the image carrier to the transfer material can be made gentle, and the toner image is uniformly transferred to the transfer material. An effect that the concentration does not vary can be obtained.

As an effect of the present invention, since a dielectric sheet supporting member, which is a thread-like member, is present in the opening of the transfer drum when the dielectric sheets are reattached after holding a certain number of transfer materials, the dielectric sheets are attached more than ever. It is easy and there is no difference in skill among workers.

[Brief description of drawings]

FIG. 1 is a front view showing the basic configuration of a color printer embodying the present invention.

FIG. 2 is a front view showing the basic configuration of a color printer according to another embodiment of the present invention.

FIG. 3 is a perspective view of a transfer drum body used in the present invention.

FIG. 4 is a front view showing the basic configuration of a conventional color printer.

FIG. 5 is a perspective view of a framework of a transfer drum body of a conventional color printer.

6 is a perspective view when a dielectric sheet is attached to the skeleton of the transfer drum body shown in FIG.

FIG. 7 is a front view showing the basic configuration of a conventional color printer.

8 is a front view showing a deformed state of the sheet on the transfer drum of the color printer shown in FIG. 7. FIG.

9 is a diagram showing the sheet charge density on the transfer drum of the color printer shown in FIG. 7. FIG.

10 is a diagram showing a sheet charge density when a thread-shaped dielectric sheet supporting member is attached to the transfer drum of the color printer shown in FIG.

FIG. 11 is a front view showing a deformed state of the sheet on the transfer drum of the color printer according to the present invention.

FIG. 12 is a diagram showing a sheet charge density when a brush type charger is used.

FIG. 13 is a diagram showing the sheet charge density on the transfer drum of the color printer of the present invention.

[Explanation of symbols]

 1 Brush Transfer Charger 2 Brush Adsorption Charger 3 Bias Power Supply 15 Dielectric Sheet 16, 17 Flange Member 18 Connecting Member 19 Wire 30 Image Carrier 60 Transfer Device 66 Transfer Drum Body

Claims (1)

Claims: 1. The ends of the cylindrical body and a part of the busbar are left,
A hollow drum having a shape other than the above, and a dielectric sheet that covers the opening of the hollow drum along the outer shape of the cylindrical body of the hollow drum, and a transfer material is placed on the dielectric sheet. In a transfer material holding member that moves endlessly while holding the brush, a high voltage power source is applied to the hollow drum and one end of the transfer material holding member is in contact with the dielectric sheet and imparts a charge to the dielectric sheet. A plurality of non-conductive thread-like members are provided on the generatrix of the cylinder of the hollow drum over the entire opening of the hollow drum, and the dielectric sheet is A transfer device, which is supported by a plurality of non-conductive thread members.