JP2821503B2 - Color image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method in which a plurality of developing means containing a multi-color developer are arranged on the periphery of an image carrier, and a multi-color developer is provided on the image carrier. The present invention relates to a color image forming method in which a toner image is superimposed and then transferred onto a transfer material to obtain a color image.

[Background of the Invention]

Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, as disclosed in JP-A-61-100770, a latent image is formed and developed according to the number of color separations of a document image on a photosensitive drum as an image carrier,
There is a method in which a multicolor image is formed on a transfer drum by transferring the image on a transfer drum each time development is performed and then transferred onto a recording paper to obtain a color copy. In the apparatus according to this method, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface in addition to the photosensitive drum, and the apparatus has a large and complicated structure. Inevitable.

Further, as disclosed in, for example, JP-A-61-149972, a latent image is formed and developed on a photosensitive drum in accordance with the number of separated colors of an original image, and is transferred onto a transfer material each time development is performed. This is a method of obtaining a multi-color copy. In this method, it is difficult to accurately superimpose multi-color images, and a high-quality color copy cannot be obtained.

In addition, there is a method in which a latent image is formed on the photosensitive drum in accordance with the number of separated colors of the original image and development with color toner is repeated, and a color image is obtained by superimposing and transferring a color toner image on the photosensitive drum. The basic process of this multicolor image formation is described in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-76766 by the present applicant,
Nos. 60-95456, 60-95458, 60-158475 and the like.

In a multi-color image forming apparatus that obtains a color image by such superposition, a plurality of developing devices containing color toners of different colors are arranged on the periphery of the photosensitive drum. Rotates the photoconductor drum several times,
The color image is obtained by developing the latent image on the photosensitive drum.

[Object of the invention]

In general, the photoconductor drum is rotated a plurality of times, during which a multicolor toner image is superimposed on the photoconductor drum, and then transferred onto a transfer material. Is discharged. On the other hand, the photoreceptor drum after the transfer is cleaned by a cleaning unit located on the downstream side thereof, and the next image forming process is performed.

As the cleaning means, a cleaning blade, a rotating fur brush, or the like is used. When the image is formed, the cleaning means is retracted, and when the transfer is completed, the cleaning means contacts the photosensitive drum to scrape off the residual toner so that the peripheral surface of the photosensitive drum is scraped off. To clean. The scraped waste toner is collected and sent to a waste toner box. However, it is impossible to send all the collected waste toner to the waste toner box, and a part of the toner adheres to, for example, the edge portion or the surface of the tip of the cleaning blade. In the example shown in FIG. 5A, when the cleaning blade is released from the pressure contact and retreats from the peripheral surface of the photosensitive drum, the toner collected at the tip of the edge portion falls on the photosensitive drum and falls on the photosensitive drum. May redeposit on the surface.

FIG. 5B is a view in which the peripheral surface of the photosensitive drum is developed along the rotation direction indicated by the arrow A. The above-mentioned toner-attached portion (portion indicated by oblique lines) is located continuously upstream of the retreat point B of the cleaning blade. When the recording paper is fed to the normal position for transfer, the recording paper does not reach the recording paper, and therefore, no adverse effect on the copy image quality due to the toner adhering portion occurs.

However, if the recording paper is fed slightly ahead of the image for the purpose of providing a "binding margin" at the leading end of the recording paper, the toner adhering part enters the area of the recording paper. As a result, the portion (stitch margin) is soiled by the toner.

As a result of solving this problem and improving the present invention, a color image forming method capable of always obtaining high quality and beautiful copies without causing stains due to toner adhesion to the paper surface even when the timing of feeding the recording paper is changed. The purpose is to provide.

[Configuration of the invention]

The above object is achieved by disposing a plurality of developing devices of different colors on the peripheral portion of the image carrier, superimposing the color toner images on the image carrier, transferring the color toner images onto recording paper, and transferring the transferred image carrier. In a color image forming method in which a cleaning unit capable of contacting and separating a body is brought into contact and cleaning is performed, and is separated and retracted during image formation, the color image position on the recording paper is moved by changing the timing of feeding the recording paper. The timing of separating the cleaning means from the image carrier is controlled so as to maintain a constant time interval from the timing of feeding the recording paper regardless of the change in the color image position. Is done.

〔Example〕

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

In the figure, reference numeral 10 denotes a drum-shaped image carrier, that is, a photoconductor drum, which is obtained by applying an OPC photoconductor on a drum, is grounded, and is driven to rotate clockwise. Reference numeral 20 denotes a scorotron charger for applying a charge to the photoconductor on the peripheral surface of the photoconductor drum 10, and 13 denotes a photoconductor drum 10 by an exposure optical system (not shown).
This is an image exposure section on which image exposure light or a laser beam is projected so as to be focused on the peripheral surface.

For example, a laser writing system unit is used for the exposure optical system. When a color signal output from an image reading device separate from the image forming apparatus is input to the laser writing system unit, the laser writing system unit generates a laser beam (wavelength 78
(0 nm) is rotationally scanned by a polygon mirror, the optical path is bent by a reflection mirror via an fθ lens, and projected on the peripheral surface of the photosensitive drum 10 which is uniformly charged in advance by the charger 20.

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 peripheral surface of the photosensitive drum 10. Accordingly, a latent image for the first color is formed on the image portion on the photosensitive drum 10 by the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 10. This latent image is subjected to reversal development by a developing unit that contains, for example, yellow (Y) toner as the first color, and a yellow toner image is formed on the peripheral surface of the photosensitive drum 10. The obtained toner image of the image portion passes under the transfer means and the cleaning means separated from the peripheral surface of the photosensitive drum 10 while being held on the peripheral surface of the photosensitive drum 10, and enters the next copy cycle.

That is, the photosensitive drum 10 is charged again by the charger 20, and then the second color signal output from the signal processing unit is input to the writing unit, and the same as in the case of the first color signal described above. Then, writing is performed on the peripheral surface of the photosensitive drum 10 by the second color signal, and a latent image is formed.
This latent image is subjected to reversal development by a developing means containing, for example, magenta (M) toner as a second color, and a magenta toner image is formed. The magenta toner image is formed so as to overlap the already formed yellow toner image.

The toner image of the image area obtained in this way passes under the transfer means and the cleaning means which are separated from the peripheral surface of the photoconductor drum 10 while being held on the peripheral surface of the photoconductor drum 10, and the next copy cycle to go into.

Similarly, writing is performed on the photosensitive drum 10 by the third color signal to form a latent image. This latent image is subjected to reversal development by a developing unit containing, for example, cyan (C) toner as a third color. By forming this cyan toner image on top of the above-mentioned yellow and magenta toner images, a color image is obtained. In some cases, the image forming apparatus further includes a developing unit containing a black toner, and obtains a high-quality color image by further overlapping the black toner image as described above.

Reference numerals 41 to 43 denote developing units as developing means for accommodating yellow, magenta, and cyan toners for performing the above-described development, respectively.

The charging by the charger 20 provided on the photosensitive drum 10 and its peripheral portion, the exposure by the laser writing system unit for each color, and the developing processing by the developing units 41 to 43 are performed three times for each color. A color toner image is formed on the image portion on the peripheral surface of the body drum 10 by superposition.

Reference numerals 51 and 52 denote passages of recording paper, which are transfer materials of different sizes fed one by one from the transfer material supply device, and 53 denotes a transfer unit 16 in synchronization with the movement of the color toner image on the photosensitive drum 10.
It is a registration roller for conveying the recording paper to zero.

70 is a transfer belt device, 71 is a transfer belt which is a belt portion, 72 and 73 are rollers made of a conductive metal material, and the upstream roller 72 is a ground or a ground which is set at a predetermined potential close to the ground. Roller with possible axis, downstream roller 73
Is a roller for driving the transfer belt 71 having a fixed shaft.
Reference numeral 74 denotes a belt support member, one end of which has a fixed shaft around the axis of the roller 73 and the other end connected to the movable shaft of the roller 72, and biases the roller 72 downward by an elastic member (not shown). Have been. Therefore, the transfer belt 71 is always retracted from the peripheral surface of the photoconductor drum 10, and the eccentric cam 77 which is operated under the control of the apparatus control unit at the time of transfer moves the belt support member 74 upward in the drawing via the leaf spring 78. Pressing, rotating counterclockwise around the roller 73 as a swing center, the rollers 76 provided on both ends of the belt support member 74 abut against the side end of the peripheral surface of the photosensitive drum 10 outside the image portion, The transfer belt 71 is in contact with the transfer unit 160 of the photosensitive drum 10.

Reference numeral 79 denotes a cleaning blade of a belt cleaning device for scraping off toner adhered on the transfer belt 71, and reference numeral 95 denotes a toner transport tube having a flexible transport screw therein for removing toner scraped off by the cleaning blade 79 to a toner collection box (not shown). Transport to

Reference numeral 16 denotes a transfer unit which is a transfer charger provided at a position facing the transfer unit 160, and 60 denotes a transfer belt 71 and a photosensitive drum.
This is a paper charger in which the opening is opposed to the transfer belt 71 at a position opposed to the roller 72 in a wedge-shaped cross-sectional space between the transfer belt 71 and the paper charger.

After the development by the developing device 43 containing the third color toner on the photosensitive drum 10 is started as described above, the operation of the registration roller 53, the pressing operation of the transfer belt device 70, and the discharge wire of the paper charger 60 are performed. The high voltage is applied almost simultaneously.

Accordingly, 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 photosensitive drum 10. The paper charger 60 performs charging efficiently and reliably using the roller 72 which is close to the grounded state as a counter electrode, and is provided very close to the transfer unit 160, so that the charge during transportation is reduced little and the recording paper is reduced. The transfer belt 160 can be firmly sucked and held on the transfer belt 71 and conveyed to the transfer unit 160.

When the front end of the recording paper reaches the transfer section 160, the transfer belt 71
As a result, the recording paper is pressed against the photosensitive drum 10. Then, the transfer unit 16 performs charging of a polarity opposite to that of the toner on the photosensitive drum 10, and transfers the toner image onto recording paper. The recording paper onto which the toner image has been transferred is further transported by the transport belt 21, reaches a fixing unit (not shown), is fixed by heat welding, and is then discharged to an external discharge tray. Reference numeral 55 denotes a separation claw for preventing the recording paper from erroneously invading upward.

The photoreceptor drum 10 that has completed the transfer by the rotation and pressure contact of the transfer belt 71 and the charging action by the transfer device 16 is cleaned by a cleaning device 90. The cleaning blade 91 is in a retracted state while a toner image is being formed on the peripheral surface of the photosensitive drum 10, and the photosensitive drum is in a state where the transfer is completed. Cleaning is performed by pressing against 10. A discharge lamp 93 is located upstream of the cleaning device 90, and a discharge lamp 94 is located downstream of the cleaning device 90. The discharge lamp 93 discharges electricity so that residual toner on the peripheral surface of the photosensitive drum 10 is easily removed. The lamp 94 uniformly removes electricity from the cleaned peripheral surface of the photosensitive drum 10 so that uniform charging is performed. Further cleaning device 90
A toner conveying pipe 95 having a toner conveying screw made of a flexible material is provided at the bottom of the box, and conveys waste toner collected by cleaning to a toner collecting box (not shown). After the cleaning, the photosensitive drum 10 enters the next image forming process.

In the above-described image forming apparatus, the respective image forming means are disposed in a positional relationship as shown in FIG. 2 with respect to the photosensitive drum 10, and the image forming process is performed according to the sequence shown in the time chart of FIG. Controlled.

Ideally, the range in which the cleaning blade 91 performs cleaning by contacting the photosensitive drum 10 is as long as possible. However, in the present invention, the separation timing of the cleaning blade 91 in the cleaning device 90, that is, the cleaning blade 91 The timing of retreating from the peripheral surface of the sheet 10 is controlled so as to operate after keeping a certain time interval T with the timing of feeding the recording paper, that is, the timing of operating the registration roller 53 in the recording paper transport system.

Therefore, if the timing to start the operation of the registration roller 53 for the binding margin is set ahead of the timing indicated by the broken line, the retreat timing of the cleaning blade 91 is automatically advanced to the timing indicated by the broken line, and the predetermined time interval is set. T is kept.

FIG. 5 illustrates this in detail. As a condition set in advance, as shown in FIG. 5A, the recording paper S1 fed so as to transfer the toner image P at the normal position is used as the toner adhering portion ( The retreat point B1 of the cleaning blade 91 is determined so as not to overlap with the hatched portion), thereby setting the time interval T.

Next, the position of the recording paper S2 or S3 with respect to the toner image P is moved to the upstream side of the rotation of the drum as shown in FIG. When controlled, the retracting point of the cleaning blade 91 also automatically moves by the same amount in the same direction and changes to the position of B2 or B3. As a result, the recording paper S2 or S3 is prevented from overlapping with the toner adhering portion. Contamination due to toner adhesion can be avoided.

〔The invention's effect〕

According to the present invention, the problem of contamination of the margin of the recording paper caused by the adhesion of the waste toner removed by the cleaning can be solved, thereby moving the color image position on the recording paper to reduce the “binding margin” or the like. A practically very useful color image forming method which can be freely provided is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the color image forming apparatus of the present invention, FIG. 2 is an explanatory view showing an arrangement relationship of each image forming means, FIG. 3 is a time chart showing an image forming process, and FIG. FIG. 5 is an explanatory diagram showing a specific example of “set”, and FIG. 5 is an explanatory diagram relating to margin stains caused by waste toner. 10 photoreceptor drum, 13 image exposure unit 20 charger, 41, 42, 43 developing device 53 registration roller, 70 transfer belt device 90 cleaning device 91 cleaning blade 92: toner collection roller P: toner image B1, B2, B3 (blade) retreat point S1, S2, S3: recording paper T: time interval

Continuation of the front page (56) References JP-A-62-115489 (JP, A) JP-A-1-196088 (JP, A) JP-A-3-208079 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) G03G 21/10-21/12 G03G 21/00 370-540

Claims (1)

(57) [Claims] 1. An image carrier having a plurality of developing units of different colors arranged on the periphery of an image carrier, superimposing a color toner image on the image carrier, transferring the color toner image onto recording paper, and completing the transfer. In a color image forming method in which a cleaning means capable of contacting and detaching a carrier is brought into contact and cleaned, and separated and retracted during image formation, the color image position on the recording paper is moved by changing the recording paper feeding timing. At least the timing of separating the cleaning means from the image carrier is controlled so as to maintain a fixed time interval from the timing of feeding the recording paper irrespective of the change in the color image position.