JPH03236082A - Color image forming device - Google Patents

Abstract

PURPOSE:To obtain a beautiful color image which is not stained by exposing a non-image part on an image carrier in a beltlike shape and cleaing it without development nor electrostatic discharging. CONSTITUTION:A photosensitive drum 10 is a drum-shaped image carrier and formed by coating a drum with an OPC photosensitive material. Image exposure light is projected on an image exposed part 13 on the drum 10 for beltlike exposure so at to be focused on its peripheral surface. A latent image corresponding to a 1st color signal is formed at an image part of the drum 10 by main scanning with a laser beam and subscanning by the rotation of the drum 10. Further, the non-image part is exposed in the beltlike shape and toner which remains and sticks is cleaned without development nor electrostatic discharging. Then electrostatic charging by an electrostatic charger 20, exposure by laser write system units by colors and development processing by exposure and developing units 41-43 are performed by the colors. Consequently, no waste toner is neither left nor restuck and a color image of high quality is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a plurality of developing means containing multicolor developers disposed on the periphery of an image carrier, and a plurality of multicolor developers disposed on the image carrier. The present invention relates to a color image forming apparatus in which a color image is obtained by superimposing toner images and then transferring the toner images onto a transfer material.

[Background of the invention]

There are many ways to obtain color images using electrophotography.
A device has been proposed. For example, JP-A-61-10077
As disclosed in Publication No. 0, a latent image is formed and developed in accordance with the number of separated colors of the original image on a photoreceptor drum serving as an image carrier, and each time the development is performed, the latent image is transferred onto a transfer drum. There is a method of forming a multicolor image on a paper and then transferring it onto recording paper to obtain a color copy. A device using this method requires a transfer drum large enough to transfer one sheet of image onto its circumferential surface in addition to the photoreceptor drum, and the device does not have a large and complicated structure. Inevitable.

For example, as disclosed in Japanese Patent Laid-Open No. 61-149972, a latent image is formed and developed on a photoreceptor drum according to the number of separated colors of the original image, and is transferred onto a transfer material each time it is developed. This is a method of obtaining multicolor copies. With this method, it is difficult to overlap multicolor images with high precision, and it is impossible to obtain high-quality color copies.

Another method is to repeatedly form a latent image on a photoreceptor drum according to the number of separated colors of an original image and develop it with color toner, and then overlap the color toner images on the photoreceptor drum and then transfer the images to obtain a color image. The basic process of forming a multicolor image is disclosed in Japanese Patent Application Laid-open No. 60-75850 and No. 60-7 by the present applicant.
No. 6766, No. 60-95456, No. 60-9545
No. 8, No. 60-158475, etc.

In a multicolor image forming apparatus that obtains a color image through such superimposition, a plurality of developing units containing different color toners are arranged around the periphery of the photoreceptor drum. The photoreceptor drum is rotated multiple times to develop the latent image on the photoreceptor drum to obtain a color image.

[Purpose of the invention]

Generally, the photoreceptor drum is rotated multiple times, during which a multicolor toner image is superimposed on the photoreceptor drum.Then, this is transferred onto a transfer material, and the transferred transfer material is fixed and removed from the device. is discharged. On the other hand, the photosensitive drum that has completed the transfer is neutralized by a neutralizing means located downstream thereof, and then cleaned by a cleaning means, and the next image forming process begins. The static eliminating means is carried out by irradiating the surface of the image carrier with a static eliminating lamp or by applying an alternating current bias through a static eliminating electrode, with the purpose of facilitating the next cleaning process.

A cleaning blade, a rotating fur brush, or the like is used as the cleaning means, and the cleaning means is retracted during image formation, and comes into contact with the photoreceptor drum when the transfer is completed to scrape off residual toner from the photoreceptor drum. Clean the surrounding surface. The scraped waste toner is collected and sent to the waste toner box. However, it is impossible to send all of the collected waste toner to the waste toner box, and some toner remains attached to the cleaning means, such as the edge or surface of the cleaning blade. The toner adhering to the cleaning means moves and adheres to, for example, a toner adhesion position cleaned on the image carrier or a potential gap created by other processes.

Toner adheres to the potential gap portion of the photoreceptor drum, and when development is performed by the cleaning means, this adhered toner becomes an image stain for the next image to be formed. This phenomenon is severe in a color image forming apparatus that forms a color image on a photoreceptor drum through multiple rotations. SUMMARY OF THE INVENTION An object of the present invention is to provide a color image forming apparatus capable of producing beautiful images without image stains.

[Structure of the invention]

The above purpose is to provide a plurality of developing means on the peripheral edge of the image carrier, superimpose the toner image on the image carrier, perform reversal development, and then transfer the toner image onto a transfer material to complete the transfer. A color image forming apparatus in which an image carrier is statically neutralized by a static eliminating device and cleaned by a cleaning device, wherein the color image forming device is configured to perform cleaning without removing any non-static charge on the image carrier. achieved.

〔Example〕

FIG. 1 is a sectional view showing the structure of an embodiment of an image forming apparatus according to the present invention.

In the figure, reference numeral 10 denotes a drum-shaped image bearing member, that is, a photosensitive drum, which is coated with an OPC photosensitive member, and is grounded and rotated clockwise.

20 is a scorotron charger that applies an electric charge to the photoreceptor on the circumferential surface of the photoreceptor drum 10; 13 is an image exposure light or a laser beam that is focused on the circumferential surface of the photoreceptor drum 10 by an exposure optical system (not shown); This is the image exposure section where the image is projected.

For example, a laser writing system unit is used as the exposure optical system. When a color signal output from an image reading device separate from the image forming device is input to the laser writing system unit, in this laser writing system unit, it is rotated and scanned by a semiconductor laser and an emitting mirror, and fθ
A photosensitive drum 1 whose optical path is bent by a reflective mirror through a lens and is uniformly charged in advance by the charger 20.
Projected onto the 0 circumferential surface.

On the other hand, when scanning is started, the laser beam is detected by the index sensor, modulation of the laser beam by the first color signal is started, and the modulated laser beam scans the circumferential surface of the photoreceptor drum 10. Therefore, a latent image for the first color is formed in the image area on the photoreceptor drum 10 by main scanning by the laser beam and sub-scanning by the rotation of the photoreceptor drum IO. This latent image is reversely developed by a developing means containing toner of a first color, for example, yellow (Y), to form a yellow toner image on the circumferential surface of the photosensitive drum 10. The obtained toner image in the image area is held on the circumferential surface of the photoreceptor drum 10 and then transferred to the photoreceptor drum l.
It passes under the transfer means and cleaning means that are separated from the circumferential surface of O, and enters the next copy cycle.

That is, the photosensitive drum 10 is charged again by the charger 20, and then the second
The color signal is input to the writing system unit, and writing is performed on the surface of the photoreceptor drum 10 using the second color signal in the same manner as in the case of the first color signal described above to form a latent image. This latent image is subjected to reversal development by a developing means containing toner of a second color (for example, magenta CM),
A magenta toner image is formed. This magenta toner image is formed over the previously formed yellow toner image.

The toner image of the image area obtained in this way is held on the circumferential surface of the photoreceptor drum 10 and passes under the transfer means and the cleaning means which are separated from the circumferential surface of the photoreceptor drum 10, and is used for the next copy cycle. to go into.

Similarly, writing is performed on the photosensitive drum 10 using the third color signal to form a latent image. This latent image is subjected to reversal development by a developing means containing toner of a third color, for example, cyan (C).

A color image is obtained by forming this cyan toner image on top of the yellow and magenta toner images described above. Furthermore, a developing means containing black toner may be provided, and a high-quality color image may be obtained by further superimposing black toner images in the same manner as described above.

Developing units 41 to 43 are developing units that contain yellow, magenta and cyan toners for performing the above-mentioned development, and all have similar structures.

FIG. 2 shows the structure of the developing device 41.
Inside the developing sleeve 411. Magnet roller 4
12, stirring screws 413, 414, scraping plate 415
etc. are provided. The gap between the developing sleeve 411 and the photosensitive drum 10 is determined by a roller (coaxially provided with the developing sleeve 411) that abuts outside the image area of the circumferential surface of the photosensitive drum 10.
(not shown) to maintain a constant gap of around 0.5 mm.

The toner supplied from the toner storage device (not shown) is
The magnetic carrier is sufficiently stirred and mixed by the stirring screw 414 and the stirring screw 413, which rotate in opposite directions. This two-component developer consisting of magnetic carrier and toner is stirred and mixed and then supplied to the developing sleeve 411. A magnet roller 412 having a fixed magnetic pole is disposed inside the developing sleeve 411, and the above-described thin layer of developer is formed by the developing sleeve 411 and the magnet roller 412.

For example, a cylinder made of a magnetic material is provided facing the magnetic pole of the magnet roller 412 so that the thickness of the thin layer of developer on the surface of the developing sleeve 411 is thinner than the gap between the developing sleeve 411 and the photosensitive drum 10. By pressing the developer thin layer forming means 416 of the rod against the developing sleeve 411, the developer layer is shaped into an even thin layer of about 300 pm. A developing bias is applied to the developing sleeve 411,
The latent image in the image area on the photosensitive drum 10 is developed. After the development has been completed, the thin layer of developer on the developing sleeve 411 is once scraped off by the scraping plate 415, and a new thin layer of developer is formed by the method described above.

Charging by the charger 20 provided on the photoconductor drum IO and its periphery, exposure by the laser writing system unit for each color, and development by the developers 41 to 43 are performed three times for each color, and the photosensitive A color toner image is formed on the image area on the circumferential surface of the body drum 10 by overlapping.

Reference numerals 51 and 52 refer to a path for recording paper, which is a transfer material according to size, which is fed one by one from a transfer material supply device, and 53 a transfer section 160 in synchronization with the movement of the color toner image on the photoreceptor drum 10. This is a registration roller for conveying the recording paper to.

70 is a transfer belt device, 71 is a transfer heald which is a belt part, 72 and 73 are rollers made of conductive metal material, and the upstream roller 72 is a rotating roller that is grounded or set to a predetermined potential close to the grounded state. The downstream roller 73 having a fixed shaft is a roller for driving the transfer bell 1-71. Reference numeral 74 denotes a belt support member, one end of which has the axis of the roller 73 as a fixed shaft, and the other end connected to the movable shaft of the roller 72, and is biased by an elastic member (not shown) so that the roller 72 is positioned downward. has been done. Therefore,
Normally, the transfer belt 71 is retracted from the circumferential surface of the photoreceptor drum 10, and during transfer, an eccentric cam 77 operated under the control of the device control section presses the belt support member 74 upward in the figure via a leaf spring 78. , rotates counterclockwise around the roller 73, and the rollers 76 provided at both ends of the belt support member 74 come into contact with the side edges of the circumferential surface of the photosensitive drum 10 outside the image area, and the transfer belt 71 is brought into contact with the transfer portion 160 of the photoreceptor drum 10 .

Reference numeral 79 denotes a cleaning blade of a belt cleaning device that scrapes off the toner adhering to the transfer belt 71, and 95 denotes a toner collection box (not shown) in which the toner scraped off by the cleaning blade 79 is collected by a toner transport pipe having a flexible transport screw inside. Transport to.

Reference numeral 16 denotes a transfer device which is a charger for transfer provided at a position opposite to the transfer unit 160, and reference numeral 60 denotes an opening thereof at a position opposite to the roller 72 in the wedge-shaped cross-sectional space between the transfer belt 71 and the photosensitive drum IO. This is a paper charger disposed such that its portion faces the transfer belt 71.

After the development by the developer 43 containing the third color toner on the photoreceptor drum IO is started as described above, the registration roller 53 is operated, the transfer belt device 70 is pressed, and the discharge wire of the paper charger 60 is activated. High voltage is applied almost simultaneously to both.

As a result, the paper charger 60 performs corona discharge toward the recording paper fed one by one from the transfer material supply device, and charges the recording paper to the same polarity as the toner on the photoreceptor drum 10.

The paper charger 60 efficiently and reliably charges the roller 72, which is close to the ground, as a counter electrode, and also charges the transfer portion 1
Since it is provided very close to the transfer belt 60, there is little decrease in charge during conveyance, and the recording paper can be firmly absorbed and held on the transfer belt 71 and conveyed to the transfer section 160.

When the leading edge of the recording paper reaches the transfer section 160, the transfer belt 7
1, the recording paper is pressed against the photosensitive drum IO. Then, the transfer device 16 charges the toner on the photosensitive drum 10 with a polarity opposite to that of the toner, and transfers the toner image onto the recording paper. The recording paper onto which the toner image has been transferred is further conveyed by the transfer belt 21 to a fixing section (not shown), where it is fixed by heat welding and then discharged to an external paper discharge tray. Reference numeral 55 denotes a separation claw for preventing the recording paper from accidentally entering upwards.

After the toner image has been transferred onto the recording paper by the rotation and pressure of the transfer belt 71 and the charging action of the transfer device 16, the photosensitive drum 10 is cleaned of residual and adhered toner by a cleaning device 90. The cleaning device 90 has a cleaning blade 91 as a cleaning means, a toner collection roller 92 for electrostatically collecting residual toner, and the like, and the cleaning device 90 has a cleaning blade 91 as a cleaning means, a toner collection roller 92 for electrostatically collecting residual toner, and the like. The blade 91 is in a retracted state, and after the transfer is completed, it comes into pressure contact with the photoreceptor drum IO to perform cleaning.

Further, as a means for eliminating static electricity from the photoconductor, a static elimination lamp 93 is located on the upstream side of the cleaning device 90, and a static elimination lamp 94 is located on the downstream side. The residual toner on the photoreceptor drum 10 is neutralized to a state where it can be easily removed, and the static elimination lamp 94 uniformly eliminates the static electricity from the cleaned circumferential surface of the photosensitive drum 10 so that uniform charging is performed.

Of course, instead of the static eliminating lamp that emits light onto the photoreceptor, a discharge electrode that generates an alternating current discharge may be used as the static eliminating means. A toner transport pipe 95 having a toner transport screw made of a flexible material is provided at the bottom of the cleaning device 90, and transports waste toner collected by cleaning to a toner collection box (not shown).

After the cleaning, the photosensitive drum 10 enters the next image forming process.

Furthermore, in the color image forming apparatus according to the present invention, the waste toner scattered and attached to the edge portion and surface of the tip of the cleaning blade 91 during the removal of residual toner is removed by the following means. By intensively adsorbing and holding the image area, the waste toner is prevented from adhering to the potential gap area on the photoreceptor drum 10, for example, from reproducing an image on the image surface after cleaning (a phenomenon in which toner adheres again), The cleaning blade 91 itself is also cleaned so that the cleaning effect can be sufficiently exhibited.

In the image forming apparatus shown in FIG. 1, each image forming means is arranged with respect to the photosensitive drum 10 in a positional relationship as shown in FIG. 3, and the image forming process is shown in the time chart of FIG. Controlled by the sequence shown.

In the embodiment of the present invention, immediately before the image exposure using the third color signal is performed on the circumferential surface of the photoreceptor drum 10, a band-like exposure is performed on the non-image area approximately 20+n+n ahead of the leading edge of the image area, and the radiation is zero. A long band-shaped electrostatic latent image surface of about .3 mm in the width direction of the drum is formed. The strip-like exposure is not limited in its pattern and width, and may be a straight line or a collection of dot-like exposures. This band-shaped exposed area passes through the transfer unit 160 as a mere potential gap area without being developed.

After the transfer is completed, the peripheral surface of the photosensitive drum 10 is neutralized by turning on the static eliminating lamp 93. Here, the static elimination lamp 93
Static elimination is performed to prevent waste toner from adhering to non-image areas other than the strip-shaped exposed area prior to development with waste toner, and as shown by the solid line in FIG. The entire area of the non-image area except for the non-image area is neutralized, and the band-shaped exposed area remains as a band-shaped potential gap. As shown in the embodiment of FIG. 4, when the lighting range of the static eliminating lamp 93 reaches the rotation range of the photoreceptor drum IO of one rotation or more, it corresponds to the previous, ie, first strip-shaped exposed portion. In this case, the static eliminating lamp 93 is not lit, and in response to the second band-shaped exposed portion, the static eliminating lamp 93 is lit.

The photosensitive drum 1 that has completed the transfer and passed through the static elimination lamp 93
The remaining toner on the peripheral surface 0 passes through the cleaning device 90 and is cleaned of residual toner, but when the potential gap of the photoreceptor drum 10 comes into pressure contact with the cleaning blade 91, toner adheres to the tip of the blade 91 at the pressure contact point. The image is developed using the waste toner. As a result, the waste toner adhering to the blade 91 concentrates on and transfers to the strip-shaped exposed portion. Furthermore, the waste toner transferred to the drum surface is removed by the static elimination lamp 93 by operating the cleaning blade 91 to slightly extend the pressure contact period even after one revolution of the drum, and the waste toner adhering to the potential gap is removed again. The toner is removed and cleaned by the blade 91, and most of the collected toner is collected into the toner collection box.

Note that the above-mentioned operation by lighting the static elimination lamp 93 can also be activated to eliminate static electricity in the non-image area excluding the band-shaped exposed area as shown by the solid line, or to remove the static electricity in the non-image area excluding the band-shaped exposed area as shown by the dashed line. It is also possible to operate to remove static electricity from the image area.

Further, the static eliminating means of the present invention is not limited to a static eliminating lamp that emits light to the photoreceptor, but a discharge electrode that performs alternating current discharge can also be used as the static eliminating means.

Although this embodiment has described an image forming apparatus that synthesizes a color image using toner images of three colors, the present invention further relates to a color image forming apparatus that forms an image using toner images of four colors including a black toner image. It can be applied in a similar manner to the fourth color, and in this case, during image exposure of the fourth color, band-like exposure is performed to provide a potential gap in the non-image area at the tip, and The same effect can be obtained by controlling the static eliminating means so as not to operate it.

〔Effect of the invention〕

The present invention collects the waste toner removed from the photoconductor by cleaning without re-adhering it to the image surface of the photoconductor, and at the same time starts an effective cleaning action using a cleaning means that does not leave waste toner at all times. As a result, it is possible to provide a color image forming apparatus that can obtain high-quality color images by preventing image quality deterioration due to redeposition or residual waste toner.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus of the present invention, FIG. 2 is a cross-sectional view of a developing unit of the apparatus, FIG. 3 is an explanatory diagram showing the arrangement relationship of each image forming means, and FIG. 4 is an image Time chart showing the formation process. 10... Photosensitive drum 13... Image exposure section 20.
...Charger 41.42.43...Developer 5
3... Registration roller 55... Separation claw 60...
Paper charger 70...Transfer belt device 71...
Transfer belt 90...Cleaning device 91...
・Cleaning blade 92...Toner collection roller 93.94...Static elimination lamp

Claims (2)

[Claims] (1) A plurality of developing means are arranged around the peripheral edge of the image carrier, and after overlapping the toner image on the image carrier and performing reversal development, this is transferred onto a transfer material, and the image after the transfer is completed. In a color image forming apparatus in which a carrier is static-eliminated by a static-eliminating device and cleaned by a cleaning device, a non-image area on the image-bearing member is exposed in a band-like manner, and the exposed band-like area is developed and static-eliminated. A color image forming apparatus characterized in that it is configured to perform cleaning without any cleaning. (2) The color image forming apparatus according to claim 1, wherein the static eliminating means uses a static eliminating lamp.