JPH0458026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus using a transfer material supporting means that supports a transfer material on an insulating screen or an insulating sheet and moves endlessly.

Conventionally, in color electrophotographic copying machines, a transfer material is supported on a transfer drum relative to a photosensitive drum,
The toner on this drum was transferred using the electric field of a corona discharger placed inside the transfer drum. This color copying machine forms a color image by subtractive color mixing of magenta, cyan, and yellow toners. Therefore, since toner images of each color from the same original are transferred to the transfer material three times, the transfer material must be well held on the transfer drum during this transfer.

As a method of holding the transfer material well on the transfer drum and improving transfer efficiency, a method of placing the transfer material on an insulating screen with fine holes or an insulating sheet without holes has been considered. There is. That is, by supporting the transfer material on an insulating support, the electric field of the transfer corona can be efficiently applied to the transfer material, and at the same time, the electrostatic force generated at that time electrostatically attracts the transfer material, and the transfer material is attached to the support. to prevent color shift. However, the support of such a transfer material also becomes contaminated with toner scattered within the apparatus as it is used.

One possible method for preventing this toner contamination is to rub and clean the support.
However, these cleaning means generally use a blade made of rubber or elastic synthetic resin, or a brush made of synthetic resin such as polyamide or rayon. For this reason, the insulating support of the transfer material is triboelectrically charged, and if this charging polarity or charging unevenness occurs, the transfer efficiency decreases, the transferred toner scatters, and the image quality deteriorates.

An object of the present invention is to improve the above-mentioned drawbacks, and to provide an image forming apparatus that prevents deterioration in transfer efficiency and image quality.

The present invention, which achieves the above objects, includes an image carrier, a movable transfer material support means having an insulating surface for supporting a transfer material in order to transfer an image of the image carrier onto a transfer material, and In an image forming apparatus having a static eliminator that eliminates static electricity, and a contact means that can come into contact with and separate from the support means, at least an area of the support means contacted by the contact means is provided with a transfer material that is then supported by the support means. The image forming apparatus is characterized in that the static electricity is removed by the static eliminating means beforehand.

Specifically, the insulating screen or sheet serving as the transfer material supporting means includes one made of dielectric material, and the supporting means may be a rotating body in the form of a drum or an endless belt. In addition to the corona discharge electrode, an electrode roller can be used to transfer the image on the image carrier to the transfer material. Further, the static eliminating means is a corona discharger having a component opposite to that of the transfer electric field, and is arranged facing at least the transfer material on the support means, and is also disposed on the insulating screen or sheet side of the transfer material. Also good. As the cleaning means, which is a contact means that can come into contact with and separate from the transfer material support means, the above-mentioned blade method, brush method, a combination of both methods, and other roller methods can be applied.

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

FIG. 1 shows an explanatory view of the main parts of a transfer device in a color electrophotographic copying machine to which the present invention is applied.

In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier, and yellow, magenta, and cyan toner images are sequentially formed on this drum. Reference numeral 2 denotes a transfer drum which is a means for supporting the transfer material. A frame is formed by hollowing out a part of a metal cylinder. An insulating screen 3 is fixed to this frame, and the drum rotates in the direction of the arrow. The material for this screen 3 should be selected from materials with good strength, durability, and transferability, such as polyester, polyamide,
Woven fibers such as polyethylene can be used. This frame body 4 is a support portion extending in the direction of the rotation axis,
The support portion 4 is provided with a gripper 6 for gripping the leading edge of the transfer material guided by the guide 5 and conveyed. This gripper 6 is configured to be opened by pushing a convex portion 8 of a spring material attached to a shaft 7 with a cam (not shown). Above transfer drum 2
On the outer periphery of the transfer drum, an AC corona static eliminator 9 is provided to properly separate the transfer material after the transfer process from the drum 2, a separation claw 10 is provided to separate the transfer material from the drum, and Brush roller 1 for rubbing and cleaning the screen 3
1 are arranged in order.

Among the above-mentioned means, the separation claw 10 rotates around the shaft 12 and is at the chain line position when not separated. Then, only at the time of separation, the transfer material is fixed at the solid line position by a driving means such as a plunger, and the transfer material is separated from the three surfaces of the screen.
The transfer material separated by the separation claw is fixed by a fixing device on the downstream side, and is discharged from the apparatus.

The brush roller 11 located downstream of the separating claw has short resin fibers planted on its surface, and is driven and rotated by a motor M only during cleaning. Although this roller 11 is close to the transfer drum, the tips of the fibers do not touch the transfer material supported on the screen 3. An elastic roller without flocked hair may be used in place of the brush roller, and of course, the toner and the like removed by the roller may be scraped off with a blade or sucked.

On the other hand, inside the transfer drum, a corona discharger 13 for transfer and a discharger 14 for static elimination that generates a corona having a polarity opposite to that of the discharger are fixedly installed to face the photosensitive drum 1. The discharge polarity of the discharge device 14 may be the same as that of the discharge device 9, which is an AC corona discharge device. Furthermore, there is a blade 15 inside the drum 2 that presses the screen 3 against the brush roller 11 only during cleaning.
is located at a position that does not touch the support portion 4 when not cleaning, and is driven by the plunger 16 only during cleaning to press the screen 3 against the roller 11 side. Note that during cleaning, instead of pressing the screen 3 against the brush side, the outer roller 11 may be moved toward the screen side by a driving means, and the brush roller may be rubbed against the screen 3 for cleaning.

In the conventional device, the transfer material is transferred to the gripper 6.
Before feeding the screen 3 to the brush roller 1
1 and the blade 15 work together for cleaning. This removes toner, dust, etc. adhering to the screen 3 while the main unit is stopped, and prevents the supplied transfer material from becoming dirty.

However, when the insulating screen 3 is rubbed and cleaned as described above, frictional electrification is generated on the screen, and as a result, the supporting force and transfer efficiency of the transfer material described above are reduced.

In order to solve this problem, the present invention allows the gripper 6 to grip the transfer material after the screen is cleaned by the cleaning means and the screen is once discharged. That is, in the past, the transfer material was guided to the gripper while cleaning the screen or immediately after cleaning, but in the present invention, the screen 3 after cleaning is at least guided to the corona for static elimination by the dischargers 9 and 14. After exposure, transfer material is supplied.

FIG. 2 shows the operation timings of the dischargers 9 and 14 for static elimination, the plunger 16 for cleaning, and the cleaning brush 11, and when they are in operation, they are shown by solid lines. In the example shown in FIG. 2, the dischargers 9 and 14 for static elimination start operating immediately before separating the transfer material from the drum 2. Then, when the screen 3 from which the transfer material has been separated comes to the position of the blade 15, the puncher 16 is activated, pressing the screen surface against the flocking roller 11 and cleaning the screen by rubbing. This plunger 16 rotates once the drum 2 rotates from the flocking roller 11 as a starting point.
Turn it off, return to the starting position, and stop rubbing the screen. On the other hand, the dischargers 9 and 14 continue to discharge until the rubbed screen completely passes through the dischargers.

The timing shown by the chain line in FIG. 2 is different from the case of FIG. 1 in which cleaning is performed downstream of separation while it is being separated, and shows a case where cleaning is started after complete separation. If the vibration caused by the cleaning means affects the transfer, the control method shown by the chain line is used.

In the embodiment shown in FIG. 1, the cleaning means is disposed downstream of the static eliminating means in the moving direction of the drum 2, but as shown by the chain line in the same figure, the static eliminating dischargers 9 and 14 are
The roller 11a and the blade 15a may be arranged on the upstream side of the roller 11a and the blade 15a. In this case, the operating time of the dischargers 9 and 14 can be further shortened than in the case of FIG. 1, and a timing chart at this time is shown in FIG. 3. However, as the most preferable example, the first
A cleaning means is disposed downstream of the separating means shown by a solid line in the figure, and a discharger 9a for eliminating electricity is disposed between the cleaning means and the guide 5 for paper feeding. In this case, use roller 1 while separating the transfer material.
1 and the blade 15, and immediately after that, the frictional charge on the screen can be removed by the discharger 9a. That is, since the next transfer material can be supplied to the gripper 6 immediately after the discharger 9a is neutralized, it is possible to further shorten the copying time for continuous copying.

According to the present invention, the member that supports the transfer material is frictionally charged by the contact means, and this charged charge makes it possible to prevent adverse effects, improve the transfer efficiency, and further improve the holding power.
In addition to color electronic copying machines, the present invention also applies to devices in which a transfer material is supported on an insulating screen or sheet material, and
This works effectively if it is a friction cleaning device such as a screen.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the main parts of a transfer device to which the present invention is applied, and FIGS. 2 and 3 are timing charts of the embodiment device. In the figure, 2 is a transfer drum, 3 is an insulating screen, 9, 9a and 14 are dischargers for static elimination, and 11 is a flocking roller.

Claims (1)

[Scope of Claims] 1. An image carrier, a movable transfer material support means having an insulating surface that supports the transfer material in order to transfer the image of the image carrier onto the transfer material, and static electricity removal from the support means. In an image forming apparatus having a static elimination means and a contact means that can come into contact with and separate from the support means, at least the area of the support means that the contact means has contacted is removed before the transfer material is next supported by the support means. An image forming apparatus characterized in that static electricity is eliminated by the static elimination means.