JPS58102278A - Transfer device - Google Patents

Abstract

PURPOSE:To make a cleaner for a transfer device unnecessary, and also to prevent a color shift, etc. which are apt to occur in a transfer image, by reversely transferring a toner which has adhered onto the circumferential surface of a transfer drum, to the circumferential surface of a photosensitive drum, at the time of non-transfer, in a color electrophotographic device. CONSTITUTION:By a clamp 11a provided on a transfer drum 11, a transfer material 10 is superposed on the surface of the transfer drum, and both of them turn. A toner image of three colors, which has been formed on the surface of a photosensitive drum is transferred electrostatically on the transfer material 10 in order by a discharger 13. After the transfer has ended, when reverse charge is applied to the discharger 13 by switching a switch 20, a toner which has adhered onto the circumferential surface of the transfer drum is absorbed to the circumferential surface of the photosensitive drum, and also is removed by a cleaner 8b. In this way, a cleaner is not required for a transfer device, and it is also possible to prevent generation of a color shift of a transfer image, which is apt to occur.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer device for an electrophotographic cover applied to electrostatic copying, electrostatic printing, facsimile, etc. This is a book about a transfer device with improved reliability and durability.

The transfer device applied to color electrophotographic copying machines usually uses a transfer roller or a transfer drum (Japanese Patent Publication No. 1983).
-11701. JP-A-54-19752, etc.). FIG. 5 is a schematic diagram of a color electrophotographic copying machine using a transfer roller. A uniform charging device 2, an exposure device 3, and red, green, and blue toners are distributed along the circumferential surface of the photoreceptor drum 1, which is rotated at a constant speed, in the direction of rotation (indicated by an arrow in the figure). A transfer roller 31, a fur brush cleaning device t8a, and a static eliminator 9 are provided. Then, while the C1 photoreceptor drum 1 rotates three times, toner images corresponding to the red, green, and blue colors of the document are formed on the circumferential surface of the photoreceptor drum 10 during each rotation. The transfer roller 31 is formed by forming a conductive rubber layer on the surface of a drum-shaped base body, and a bias voltage (in the illustrated example, a negative voltage) having a polarity opposite to the charged polarity of the toner is applied to this rubber layer. Then, the transfer material 10 supplied from the feeding device 32 is superimposed on the peripheral surface of the transfer material 10, and while being flanged, it rolls and rotates with the rotation of the photoreceptor drum l, and the red, green, and blue toner images are transferred to the transfer material 10.
are superimposed on each other and transferred. Therefore, the photosensitive drum 10
A transfer material lO is placed on the circumferential surface of the transfer roller 31 that rolls with the circumferential surface.
are overlapped and toner adheres to the areas where there is no i, and
Due to a jam in the transfer material or a malfunction of the device, toner may adhere to some spots, and if this is left unattended, the back side of the next layer of transfer material will be stained with toner. Therefore, the transfer material 10 is not present in the transfer row 2310 phase. In the meantime, it is necessary to remove toner attached to the circumference EmK using the fur brush 33. However, when the transfer roller 31K transfers the toner image, the fur brush 33 separates from the transfer roller 31 and stops rotating, while when cleaning the toner during non-transfer, the fur brush 33 moves away from the transfer roller 31K.
Because it is necessary to perform complex rotational movements as shown by the white arrows in the figure, such as approaching 1K and rotating the surface by sliding it, conventional transfer devices are expensive to install and have poor durability. There are also problems with the reliability of toner removal. In addition, the transfer row 231 is subject to intermittent load due to the intermittent rubbing of the fur brush 33, which tends to cause misalignment of the rolling position with respect to the photoreceptor drum 1. Particularly in color copying machines, the transfer row 231 is subject to intermittent load. There is an electric point where color shift is likely to occur during transfer.

This situation also applies to a transfer device using a transfer drum 34 in place of the transfer row 231, as shown in FIG. The transfer drum 34 has a surface of a cylindrical base body,
A transfer material is transferred from a corona discharger 35K with a polarity opposite to that of the toner, which is attached with a conductive insulating film such as My 2, which is installed inside the transfer position with the photoreceptor drum. 10 K) electrostatically transfer the toner image. So” [,
The adhering toner on the surface of the conductive film of the transfer drum 34 is removed by the blade 36 intermittently coming into contact with the film surface and scraping it off, but this intermittent cleaning operation causes the same drawbacks as described above.

The present invention has been made in view of the above points, and is capable of removing toner adhering to the peripheral surface of a transfer roller or transfer drum without using a cleaner, and is highly reliable and durable, even when copying color originals. It is an object of the present invention to provide a transfer device that does not cause color misregistration. The transfer device according to the present invention includes an image carrier on which a toner image is formed during periodic movement, a transfer material being supplied to the surface of the image carrier, and a transfer material being sandwiched between the image carrier surface and the image carrier surface. The electric field forming means includes a rotating transfer means provided to roll with the surface of the image carrier, and an electric field forming means forming an electric field between the image carrier and the rotating transfer means. An electric field is applied in the direction in which the toner image is transferred to the transfer material while the toner image forming castle passes through the location of the rotary transfer means, and during the rest of the period, an electric field is applied in the opposite direction. It is characterized by applying an electric field in the direction of . In other words, the toner adhered to the circumferential surface of the transfer drum, etc., is reversely transferred to the circumferential surface of the photoreceptor drum during non-transfer, and this is removed by a cleaning device for the photoreceptor drum. This eliminates the need for a cleaner for the device.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an embodiment in which the present invention is applied to a color electrophotographic copying machine. The photoreceptor drum 1 is formed by depositing a photoconductive substance such as amorphous selenium or a selenium-based alloy on the circumferential surface of a cylindrical base made of aluminum to form a photoreceptor in the shape of a drum. The photosensitive drum 1 is supported within the main body of the copying machine with its longitudinal direction being horizontal, and is driven to rotate at a constant speed in the direction of the arrow. Near the horse surface of the photoreceptor drum 1, in the direction of rotation, there are a charging device 2, an exposure device 3, nine developing devices 4, 5.6, an optical static eliminator 7, which accommodate red, green, and blue toners, respectively.
The transfer drum 11, the blade cleaning device 8b, and the static eliminator 9 are arranged in this order.

The charging device 2 is a corona discharger that uniformly charges the surface of the photoreceptor to positive polarity, and the exposure device 3 charges the red part of the original 1,
Images corresponding to the green portion and the color development portion are respectively exposed on the photoreceptor surface, and electrostatic latent images corresponding to each portion are alternately formed on the photoreceptor surface. The optical static eliminator 7 is used to optically eliminate static electricity from the surface of the photoreceptor on which the toner particles have been formed after the toner particles are transferred, prior to the transfer of the toner particles. The cleaning device 8b is provided with a blade) to remove untransferred toner from the surface of the photoreceptor. An alternating voltage is applied to the surface of the photoreceptor after the untransferred toner has been removed, and the static electricity is removed by an optical static electricity removal device 9.

The transfer drum 11 is made by wrapping an insulating film, for example, Mylar, around the surface of a cylindrical base, and is rotated in the direction of the arrow so that the C1 Mylar surface is transferred to the surface of the photoreceptor drum 10.

A clamp lla is provided at a suitable position on the base body, and clamps the leading end of the transfer material 1o supplied from the feeding device 17,
The transfer material is superimposed on the surface of the transfer drum 142 and rotated together with the transfer drum 11. Inside the transfer drum 11 at the contact point between the transfer drum 11 and the photoreceptor drum 1, there is a corona discharger 1 that irradiates an electric charge toward the contact point.
3 is installed. The corona discharger 13 is connected to a positive polarity power source 19 and a negative polarity power source 18 via a switch 20), and by switching the switch 20, the corona discharger 13 is
irradiates a positive or negative charge. Note that the positive polarity power source 19 is used when transferring the toner onto the transfer material 10, and its voltage is variable. A negative polarity power source 18Fi is used for reverse transfer of toner onto the photosensitive drum 1, as will be described later.

In the rotation range of the transfer drum 11, a corona discharger 14 for separating the Kl pair of transfer materials is disposed so as to face each other through the base body and mylar, and an alternating current voltage is applied to the corona discharger 14. A claw that eliminates the potential of the transfer material 10 and Mylar on the peripheral surface of the transfer drum 11, and is provided on the downstream side and requires separation]5
As a result, the transfer material lO is released from the restraint of the clamp l1m.
is peeled off from the surface of the transfer drum 11. Thereafter, the transfer material 10 is subjected to, for example, thermal fixation by the fixing device 16. A pair of corona dischargers 12 for precharging Mylar are disposed in the rotation area of the transfer drum 11 so as to face each other with the base body and Mylar interposed therebetween. A voltage can be applied, so that the potential distribution on the Mylar surface after the transfer material 10 is separated is made flat, and the Mylar surface is charged to a positive potential with a polarity opposite to that of the toner prior to transfer. .

Next, the operation of the apparatus of the present invention constructed as described above will be explained. FIGS. 2 and 3 are schematic diagrams illustrating operations during toner transfer and cleaning of toner adhering to the Mylar surface, respectively. When copying a document, as shown in FIG. 2, the switch 20 is switched to connect the discharger 13 and the power source 19, and while the small photosensitive drum 1 is rotating at a constant speed, The surface of the photoreceptor is uniformly charged to a positive potential by the charging device 2, and an image corresponding to the red portion of the document is exposed by the exposure device 3, thereby forming an electrostatic latent image corresponding to the red portion on the surface of the photoreceptor. be done. Next, this electrostatic latent image is developed by a developing device 4 containing red toner to form a red toner layer on the surface of the photoreceptor. Thereafter, the non-image area on the surface of the photoreceptor is neutralized by the optical static eliminator 7, and the area where the toner particles are formed reaches the position where the transfer drum 11 is disposed.

On the other hand, the transfer material 10 is supplied to the transfer drum 11 from the feeding device 17 in synchronization with the arrival of the single layer forming area on the surface of the photoconductor, and the transfer material 10 is held at its leading end by the clamp lla, and the discharger 12 The nine transfer drums are precharged by 11
Mylar 5 is superimposed on the transfer drum 11 and wound around the transfer drum 11 by electrostatic adsorption force or the like for several seconds. The transfer material 10 is brought into pressure contact with the surface of the photoreceptor drum l as the transfer drum 11 rotates, and the electric field formed in relation to the photoreceptor drum l by the discharger 13 that irradiates positive charge causes the surface of the photoreceptor to be pressed against the surface of the photoreceptor drum l. Red toner particles are electrostatically transferred to the transfer material 10. Thereafter, the transfer drum 11#i, the discharger 141, the separating claw 15, and the discharger 12 do not operate, and continue to rotate while the transfer material 1O is superimposed on that surface. Untransferred toner on the circumferential surface of the photoreceptor drum 1 is removed by a cleaning device 8b, and static electricity is removed from the surface of the photoreceptor by a static eliminator 9).

Next, in the same manner, an electrostatic latent image corresponding to the green portion of the original image is formed on the surface of the photoreceptor, and green toner is supplied from the developing device 5 to form a toner image. This green toner image is transferred to the red toner image first, and
K is transferred overlappingly. Note that during this transfer, the discharger 13
The positive voltage of the power supply 19 applied to is higher than the positive voltage during the previous transfer of the red toner image. Further, in the same manner as in 1, an electrostatic latent image corresponding to the blue portion of the original image and a blue toner image by the developing device 6 were formed on the surface of the photoreceptor, and similarly, this toner image was first transferred to the transfer material 10. The image is transferred overlapping the transferred image. Note that the positive voltage of the power supply 19 applied to the discharger 13 during the transfer of this blue toner image is higher than the positive voltage during the transfer of the green toner image.

As described above, red, green, and blue toner images are transferred onto the transfer material 10 in a superimposed manner, and the original document is duplicated in color onto the transfer material 1o. After the transfer of each toner image of the three primary colors is completed, the restriction of the tip of the transfer material 10 by the flanges 1lati is released, the discharger 14 and the separation claw 15 are operated, and the transfer material 10 is separated from the circumferential surface of the transfer drum 110. It is peeled off and sent to the fixing device 16 to be fixed.

As mentioned above, toner adheres to the peripheral surface (mylar surface) of the transfer drum 11 after the transfer is completed, and when the rounded transfer material for the next layer of copying is supplied to the transfer drum 11, the back surface of the transfer drum 11 is coated with toner. deface. Therefore, in the present invention, after the transfer is completed,
Switch 2o is turned on to connect discharger 13 and power source 18.

Then, a negative charge is emitted from the discharger 13, and the toner (negative polarity) attached to the circumferential surface of the transfer drum 11 is attracted between the discharger 13 and the photoreceptor drum 1 toward the surface of the photoreceptor drum 10. An electric field is formed in the direction in which the Due to the curvature, the adhered toner is reversely transferred from the circumferential surface of the transfer drum 11 to the circumferential surface of the photoconductor drum 1, adheres to the circumferential surface of the photoconductor drum 10, and reaches the installation position of the cleaning device 8b as it rotates. and is removed by the cleaning device 8b.

Therefore, the toner adhering to the peripheral surface of the transfer drum 11 is removed by the electric field formed by the discharger 13.
removed from the peripheral surface of 1. The toner is collected by a cleaning device 8bK for removing untransferred toner from the circumferential surface of the photosensitive drum 10. Therefore, there is no need to provide a dedicated cleaner for the transfer drum 11, and the present invention eliminates the disadvantages caused by conventional transfer drum cleaners, namely, the low durability and reliability of the cleaner, and the intermittency of the transfer drum due to the cleaner. Inconveniences such as the tendency for color misregistration to occur during transfer due to an increase or decrease in physical load can be eliminated at once.

Next, another embodiment of the present invention will be described based on FIG. 4. Components that are the same as those in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted. The transfer roller 21 has a conductive rubber layer formed on its circumferential surface, and has a clamp 21a.
The leading edge of the transfer material 10 is restrained at 1°, and the transfer material 10 is rolled and rotated on the circumferential surface of the photoreceptor drum 1 while being superimposed on the circumferential surface of the transfer material 10. Note that the transfer material 10 is supplied from a feeding device 22 to the circumferential surface of the transfer roller 21, and the separation claw 2
3, it is peeled off from the peripheral surface and fixed by the fixing device 24. Thus, the rubber layer on the surface of the transfer roller 21 is connected to a positive polarity power source 27 and a negative polarity power source 26 via a switch 25.
The transfer roller 21 is connected to the switch 25 so that the surface of the transfer roller 21 can be charged to a positive potential or a negative potential by switching the switch 25. Positive polarity power source 27#i is used when transferring a toner image onto the transfer material 10, and is configured to be switched to three levels depending on the voltage level. The negative polarity power source 26 is used when toner is reversely transferred to the photosensitive drum 1.

In this embodiment as well, when copying an original, red, green, and blue toner images are alternately formed on the surface of the photoreceptor, and are transferred to the transfer material 10 superimposed on the circumferential surface of the transfer row 221 with their respective weights. .

During transfer, the transfer material 10 is pressed against the circumferential surface of the photosensitive drum 10 by the transfer roller 21, and the toner image is electrostatically attracted by the bias voltage applied to the power source 27 and the transfer roller 221K. This bias voltage is changed to a higher voltage each time red, green, and blue toner images are sequentially transferred. In this way, one color original is transferred to the transfer material 10, and the transfer material 10 is sent to the fixing device.The light diameter is changed, and the switch 25 is changed to apply a negative voltage from the power source 26 to the rubber layer of the transfer roller 21. Apply.

Then, the toner adhering to the circumferential surface of the transfer roller 21 is reversely transferred to the surface of the photoconductor drum 1 at the rolling contact point between the transfer roller 21 and the photoconductor drum 1, and this toner is transferred to the circumferential surface of the photoconductor drum 10. The remaining untransferred toner is removed by a fur brush cleaning device 8a for removing the untransferred toner. As mentioned above, a dedicated cleaner for the transfer roller 21 is not required in this embodiment as well, and the toner adhering to the transfer roller 21 is reversely transferred onto the circumferential surface of the photoreceptor drum 10 and then cleaned by the cleaning device 8.
It is collected in a.

As explained in detail above, in the present invention, since toner adhering to a transfer drum or transfer roller is removed by reverse transfer to an image carrier such as a photoreceptor drum, there is no need for a dedicated cleaner for the transfer device, and its durability is improved. The drawbacks of conventional transfer devices that require cleaning can be solved at once, such as improved reliability and no color shift in color transferred images.

It should be noted that the present invention should not be limited to the specific embodiments described above, and it goes without saying that various modifications are possible within the technical scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, FIGS. 2 and 3 are schematic diagrams explaining the present invention in detail, and FIG. 4 is a schematic diagram showing another embodiment of the present invention. 5 and 6 are schematic diagrams of conventional transfer devices. (Explanation of symbols) l... Photosensitive drum St... Transfer drano 13... Discharger 18.19.26.27
...Power supply 20.25...Switch
21...Transfer roller patent applicant Co., Ltd.
Ricoh Figure 1 ° Figure 2 Figure 9 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. An image carrier on which a toner image is formed during periodic movement; a transfer material is supplied to the surface of the image carrier, and the image carrier rolls with the surface of the image carrier while sandwiching the transfer material therebetween; and an electric field forming means for forming an electric field between the image carrier and the rotary transferring means, and the electric field forming means is arranged such that the toner image forming area on the surface of the image carrier is An electric field is applied in the direction in which the toner image is transferred to the transfer material while the toner image is passing through the location of the rotary transfer means, and an electric field is applied in the opposite direction for an appropriate period of the remaining period. A transcription device characterized by: