JP2605917B2 - Color image forming equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color copying machine to which electrophotography is applied.

2. Description of the Related Art In general, in order to form a color image by electrophotography, a method of forming a color image by superimposing toner images of yellow, magenta, cyan, and black is used. This method includes a method in which toner images of respective colors are sequentially superimposed and developed on a photoreceptor that is an electrostatic image holding member, and a method in which a toner image is formed on the photoreceptor.
There is a system in which each color is developed and transferred sequentially on a paper wound around a transfer drum. An example in which the former method is applied to a digital color copying machine is described in, for example, Japanese Patent Application No. 63-138804.
No. has been proposed by the present inventors.

FIG. 4 is a block diagram of a main part of the conventional digital color copying machine, and its configuration and operation will be briefly described below.

201 is a reading unit, which is mainly a document table 202 and a document illumination lamp.
It comprises a 203, a lens 204, a color line sensor 205, a drive system 206 for reciprocating these for scanning in the sub-scanning direction, and an image processing circuit (not shown). When the original is set on the platen and the copy button is pressed, first, the photoconductor 211 rotates, and the surface of the photoconductor is increased by 80 by the charger 212.
It is uniformly charged to about 0V. Further, the scanning of the reading section starts, a black image signal is calculated by the image processing circuit from the output of the color line sensor, and is input to the exposure system 213 to form a latent image pattern corresponding to the black image signal. At this time, the scanning of the reading unit and the writing by the exposure system are performed in synchronization. Next, this latent image passes through the other developing devices in a state where development is impossible, and is developed by the black developing device 217 to form a black toner image. At this time, the transfer / conveying unit 219 and the cleaner 222 are located at a position separated from the photoconductor 211, and the photoconductor surface on which the black toner image is formed is only neutralized by the neutralizer 221. The charger 212 uniformly charges the toner. Next, when the leading end of the black toner image on the photoreceptor surface comes to the exposure position, the reading unit has completed the first scanning and has returned to the start state. Then, the photoconductor 211 is exposed by the exposure system 213 from the top of the black toner image in accordance with the yellow image signal, and further developed by the yellow developing device 214. Other developing devices pass through the developing device in an undeveloped state. At this time, the yellow development is performed in a non-contact manner with the toner image on the photoreceptor and with a DC bias.
A new yellow toner image is formed without disturbing the black toner image. Similarly, magenta and cyan toner images are sequentially developed on a photoconductor by a magenta developing unit 215 and a cyan developing unit 216 to form a color image. After the color image is formed, the toner image is transferred to a sheet fed from the sheet feeding unit 210 by the transfer / transport unit 219 in a transfer-enabled state. The toner remaining on the photoreceptor after transfer is
It is cleaned by the cleaner 222 to prepare for the start of the next process.

The above is a brief description of the operation of the main part of the conventional digital color copying machine.

However, in the above configuration, there is a time interval between the end of the first reading scan by the reading unit and the preparation for the next reading start,
This greatly limits the total time for forming a color image and the size of the photoconductor. That is, since the reading scan and the writing of the latent image by the exposure unit are performed in synchronization with each other, for example, when the formation of the black latent image is completed, the reading unit has just completed the first scan, and thereafter the color sensor of the reading unit is used. And so on, and the latent image writing of the next color yellow cannot be started until the start of the next reading scan is ready. Therefore, a certain distance is required between the rear end and the front end of the image on the photoconductor, and for that purpose, the diameter of the photoconductor needs to be increased, and between the writing of one color and the writing of the next color. It takes much time, and the total time of image formation increases.

On the other hand, suppose that a photosensitive member having an outer periphery almost the same length as the maximum image length is provided, and a period in which the photosensitive member idles between the writing of the first color and the writing of the second color is waited until the reading section is ready. A method is conceivable. In this case, the photosensitive member can be small, but the total image forming time is very long.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a color image forming apparatus which can form a color image at high speed and does not unnecessarily increase the size of an image holding member, and therefore has high speed and small size.

Means for Solving the Problems In order to achieve the above object, the present invention provides a reading means for scanning a document to obtain color image information, and a plurality of image reading means for rotating an image holding member endlessly on the image holding member. Image forming means for forming a color image by superimposing color toner images,
Image memory means for storing an output of the reading means;
Input control means for selecting either direct output of the reading means or output of the image memory as image information to be input to the image forming means, and wherein the input control means The operation of selecting the direct output of the reading means during the scanning period and the operation of selecting the output of the image memory during a period including all or a part of the return time for the next scanning are alternately repeated to hold the image. An object of the present invention is to provide a color image forming apparatus which is an input control means for completing a color image on a body.

According to the present invention, one latent image is formed at the time of reading and scanning by the reading unit, and at least image information for writing the next latent image is stored in the image memory. At the point of time when the input to the image forming unit is switched, the next latent image formation is performed by outputting image information from this image memory, and during that time the sensor of the reading unit is returned to prepare for the next reading start Let me go.

By doing so, the latent images are formed one after another without waiting for the return time of the sensor or the like of the reading unit or preparation for rising, so that a color image can be formed at high speed.

Also, since the next writing can be performed immediately after the writing of the previous latent image is completed, the minimum size of the image carrier is not necessary since the rear end and the front edge of the image on the image carrier need only have a minimum distance. It does not have to be large.

In still another aspect of the present invention, a plurality of color images can be formed at a high speed because an image having a length not more than half of the maximum length can form a plurality of color images on an image carrier. .

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing the overall configuration of a digital color copying machine to which the present invention is applied. The configuration and operation will be described below.

Reference numeral 1 denotes a reading section of a digital color copying machine, which is mainly a document table 2, a document illumination lamp 3, a lens 4, a color line sensor 5, a driving system 6 for moving these for scanning in the sub-scanning direction, and an image processing section 120. By

Reference numeral 10 denotes a writing unit of the digital color copying machine. 11
Has increased sensitivity to laser light having a wavelength of 780 to 810 nm.
A photoreceptor of the system is rotatably supported in the direction of arrow A.
In this embodiment, the image carrier corresponds to the photoconductor 11.
Reference numeral 12 denotes a first charger for charging the surface of the photoconductor 11 to a predetermined positive potential, and reference numeral 26 denotes a laser beam. Reference numeral 20 denotes a laser optical unit, and a laser beam light 26 is emitted from a laser oscillation block 21, a polygon scanner 22, a lens system 23, a mirror 2
It is configured to scan over the photoconductor 11 via 4 and 25. A part of the scanning light of the laser beam light 26 is reflected by the mirror 27 and is irradiated on the start detection sensor 28. A developing unit 30 is provided on the right side of the photoconductor 11, and from the top along the periphery of the photoconductor 11, a Y developing unit 31 for yellow developing, an M developing unit 32 for magenta developing, and a C developing for cyan developing. A device 33 (hereinafter collectively referred to as a color developing device) and a K developing device 34 for black development are arranged. The Y developing device 31, the M developing device 32, and the C developing device 33 are non-contact developing devices using non-magnetic one-component toner.
This is a developing device that can perform development while flying toner without contacting the photoconductor 11. The K developing device 34 is a developing device that uses a two-component developer to perform development while bringing the developer into contact. Each developing device can take two positions, a position close to the photosensitive member 11 and a position away from the photosensitive member 11, and each of the eccentric cams 35 to 38 is rotated to rotate the Y developing device 31, the M developing device 32, and the C developing device. The rear portion of the developing device 33 is pushed to move horizontally to approach the photosensitive member, and the K developing device 34 is rotated counterclockwise about the shaft 39 to be in a state of approaching the photosensitive member, thereby enabling development. FIG. 1 shows a case where only the M developing device 32 is in a state capable of developing. A motor 40 drives the eccentric cams 35, 36, 37, 38 and the developing units 31, 32, 33, 34. Reference numeral 50 denotes a sheet feeding unit which can feed sheets one by one from each of the cassettes 51 and 52 and the manual sheet feeding unit 53. FIG. 2 shows a case where sheets 56 are fed from the cassette 51. . The paper 56 is fed to the lower surface of the photoconductor 11 via the registration roller 54.

Reference numeral 60 denotes a transfer / conveying unit, which has two states: a state in which a semiconductive belt 63 suspended by rollers 61 and 62 is lightly pressed against a part of the photoconductor 11 and a state in which the semiconductive belt 63 is separated from the photoconductor 11. It can move at the same speed as the outer peripheral surface of the photoconductor 11 in the direction of arrow B. FIG. 2 shows a state where the photosensitive member 11 is pressed against the photosensitive member 11. On the other hand, reference numeral 64 denotes a second charger for transfer, which applies a negative high potential to the back surface of the sheet 56 fed between the belt 63 and the photoconductor 11 via the belt 63. Reference numeral 65 denotes a cleaning blade for cleaning the toner remaining on the belt, and a collection box 66 is disposed below the cleaning blade. A third charger 69 sprays a negative corona when the sheet 56 is separated from the belt 63. In a fixing unit 70, a heat roller 72 heated by a fixing lamp 71 and a rubber roller 73 are rotatable while being pressed against each other, and a paper discharge roller 75 and a paper discharge tray 76 are provided at the rear thereof.

Reference numeral 80 denotes a cleaner which can take two states, that is, a state in which the fur brush 81 is lightly in contact with the photoconductor 11 and a state in which the fur brush 81 is separated from the photoconductor 11, and is rotatable in the direction of arrow D.
This figure shows a state where the photosensitive member 11 is in contact with the photosensitive member 11. Further, a collecting roller 82 is rotatably arranged in contact with the fur brush 81, and a negative voltage is applied to the fur brush 81 and the collecting roller 82 with respect to the photoconductor 11, respectively. A collection screw 83 is provided below the collection roller 82, and a pipe 84 is connected to an end on the near side of the collection screw 83, and is connected to the collection box 66 through this. A fourth charger 84 for positively charging the toner on the photoconductor 11 and a neutralization lamp 87 for neutralizing the photoconductor 11 are disposed below the cleaner 80 at a position facing the photoconductor.

Reference numerals 91 and 92 denote cooling fans for sucking air from the lower and upper portions of the writing unit 10 and discharging the air to the outside of the apparatus.

The above is the outline of the overall configuration of the digital color copying machine to which the present invention is applied. Next, the operation will be described.

When the document is set on the document table 2 and the copying operation is started, the document is read and scanned by the reading unit 1 and the output of the color sensor 5 is input to the image processing unit. The signal flow in the image processing unit and the operation of the image processing unit will be described below with reference to FIG.

Output signals R, G, and B from the color sensor 5 are signals K, Y, M, and C corresponding to each color of black, yellow, magenta, and cyan to be formed by the writing unit 10 in the masking unit in the image processing unit 120. Is converted to These signals are output in real time when a reading scan is performed by the reading unit. The image memory 123 is A3 in size and has a capacity to store image information for one color. First, the case of copying an A3 color image will be described. In the first reading scan, the black signal K
Is sent directly to the writing unit 10, and at the same time, the yellow signal Y is input to the image memory and stored. In the writing section, an image is formed by a black signal by the operation described below.

First, a black signal is input to the laser oscillation block 21,
The photoreceptor 11 is irradiated with a laser beam light 26 modulated according to a black signal.

The photoreceptor 11 is uniformly charged to +850 V by the first charger 12 while rotating in the direction of arrow A, and the portion irradiated by the laser beam 26 according to the signal is discharged to about +50 V. The main scanning of the laser beam light 26 on the photoconductor 11 is performed by the polygon scanner 22, and the sub-scanning is performed by the polygon scanner 22.
To form a latent image on the photoreceptor. In the first writing of the latent image on the photoconductor, the developing unit 30 is set to a black developing state,
Only the eccentric cam 38 approaches the photoconductor 11 by the operation of the eccentric cam 38, and the other developing devices are in the separated state. Therefore, the latent image corresponding to the black signal formed by the laser beam light 26 is developed with the black toner by the K developing device 34 and passes without being affected by other developing devices. At this time, the K developing unit 34 performs the proximity operation before the photoconductor 11 is started to be exposed by the laser beam 26, and the separation / contact timing is controlled so as to separate after the development. The image developed with the black toner reaches the transfer / transport unit 60 as the photoconductor 11 rotates.
In this case, the rollers 67 and 68 are at positions slightly rotated clockwise around the axis of the roller 62, the belt 63 is separated from the surface of the photoconductor 11, and the image passes without being disturbed. Further, the fur brush 81 is separated from the photoconductor 11 at a position slightly rotated counterclockwise around the axis of the collection screw 83, and the black toner image passes through the first charger again without being disturbed. Pass under 12. The portion of the photoconductor 11 where the black toner image is formed is recharged from above the toner by the first charger 12 again, and the portion without toner is charged to +850 V, and the portion with toner is apparently charged to +850 V.

The tip of the black toner image is recharged and the laser beam again
At the irradiation position 26, the input to the writing unit is switched from the black signal to the yellow signal stored in the image memory 123 by the operation of the input switching unit 122 in FIG. At this time, the reading unit has already completed the first scan and is in the return operation, but has just started the return and is not ready to start the next scan. However, since the yellow signal has already been stored in the image memory, the writing of the next yellow can be started immediately after the black writing is completed. Therefore, the outer peripheral length of the photoreceptor only needs to include some margin in the length of A3.

Thus, the writing of yellow is started, and the laser beam 26 is modulated according to the yellow signal and is exposed from above the black toner image on the photoconductor 11. Since the leading edge of the image is aligned and the scanning speed is constant, the black toner image and the latent image based on the yellow signal are formed so as to coincide in position. The latent image formed by the yellow signal is developed on the yellow toner only, because only the Y developing device 31 of the developing unit 30 is close to the photoconductor 11 and the other developing devices are separated. A yellow toner image is formed in addition to the black toner image. At this time, the separation / contact timing of the Y developing device 31 is controlled so that the photoconductor 11 performs the proximity operation before the exposure by the laser beam 26 is started, and separates after the development. At this time, since the yellow development is performed without contact, the previous black toner image is not disturbed. While the writing section is performing yellow writing, the reading section has already completed the return operation and is ready for the second scan start. Hereinafter, the magenta signal and the cyan signal are controlled in the same relationship as the relationship between the black signal and the yellow signal, so that the recharging in the writing section, the formation of the latent image by the magenta signal, the magenta development, the recharging, the latent image by the cyan signal The formation and cyan development are repeated.

At this time, since the yellow toner and the magenta toner transmit the laser beam, if exposed as necessary, that portion of the photoconductor is neutralized, and magenta and cyan toners are placed on the yellow toner, and cyan is placed on the magenta toner. Toner can be overlaid. After the last cyan toner image is formed, just before the leading end of the toner image reaches 60 in the transfer / conveying section,
The transfer conveyance unit 60 is lightly pressed against the photoconductor 11 and the paper 56 enters between the photoconductor 11 and the belt 63 by the registration roller 54 at the timing when the leading edge of the toner image and the leading edge of the paper 56 match. Will be fed.

While the toner image is transferred to the paper 56 by the electric field generated by the second charger 64, the paper 56 is conveyed while being adhered to the belt 63, but separates from the belt 63 because of the large curvature at the roller 62 and enters the fixing unit. I do. At this time, the paper 56 is separated from the belt by the separation electrification generated on the paper 56.
In order to prevent the toner image on 56 from being disturbed, a negative corona is sprinkled from above by a third charger. The toner image on the sheet is fixed on the sheet discharge tray 76 after being fixed by the fixing unit.

On the other hand, the untransferred toner image remaining on the photoreceptor 11 is positively charged by a fourth charger 84 which starts operating immediately before the leading end thereof approaches, and the fur brush which is brought into a state of contacting the photoreceptor 11 almost simultaneously. The electric field applied between the fur brush 81 and the photoconductor 11 moves to the fur brush 81 while being inspected by 81. Further, the toner in the fur brush 81 is transferred to the collecting roller 82 by an electric field applied between the collecting roller 82 and the fur brush 81, dropped by the collecting screw 83, and stored in the collecting box 66 through the pipe 85. As a result, the surface of the photoconductor 11 is cleaned, and on the other hand, the neutralizing lamp 87
, The state is returned to the initial state, and the preparation for the next copy is completed.

On the other hand, the toner accumulated on the belt 63 of the transfer conveyance unit 60 due to an operation error or usually minutely is cleaned by the cleaning blade 65 and dropped into the collection box 66. The above is the operation in the case of A3.

Next, a case where the A4 color image is continuously copied will be described. In the case of continuously copying the A4 color image, the same color image is formed two by two with a slight interval S on the photosensitive member as shown in FIG. That is, in the first scanning of the reading unit, the same black signal is stored in the image memory 123 by the operation of the input switching unit 122 in FIG. At the end of the first scan, an A4 black latent image has been written to about half of the outer periphery of the photoconductor. Then, subsequently, the input to the writing unit 10 is switched from the direct signal from the masking unit 121 to the signal from the image memory 123 by the operation of the input switching unit 122, and the same black Write the latent image. During the writing, the reading unit 1 performs a return operation. When writing the next yellow to the first image is started, the reading unit 1 is already ready for the next scan. Therefore, the interval S can be made very small, and in this case, the outer peripheral length of the photoreceptor only needs to have a margin to the length of A3. In addition, a color image can be formed two by two by four rotations of the photoreceptor. Is possible.

As described above, in the present embodiment, it is sufficient that the maximum length of the image has some margin as the length of the outer periphery of the photoconductor, and the apparatus is small, and the memory capacity is as small as one color in A3 size. Thus, continuous writing is possible irrespective of the return time of the reading section, so that a high-speed color image can be formed.

In this embodiment, the color image forming apparatus of the type in which the toner images of the respective colors are sequentially superimposed and developed on the photoreceptor which is the holding body of the electrostatic image has been described. The same effect can be obtained by a method in which the image is sequentially transferred on the paper wound around the transfer drum.

According to the present invention, since a latent image can be continuously written with a small memory capacity irrespective of the time of the preparation operation at the time of non-scanning of the reading unit, high-speed color image formation becomes possible.
In addition, since the size of the image holding member may be a minimum size, a small-sized color image forming apparatus can be provided.

Furthermore, when the image to be created is small, the same color image can be continuously formed at small intervals on the photoconductor,
A high-speed color image forming apparatus having a very high continuous copying speed can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a digital color copying machine according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a signal flow and operation in an image processing unit, and FIG. FIG. 4 is a diagram showing a conventional example. 1 ... Reading unit, 5 ... Color sensor, 10 ... Writing unit, 11 ... Photoconductor, 20 ... Laser optical unit, 30 ... Developing unit, 50 ... Supply unit, 60 ... Transfer transport unit , 70: fixing discharge section, 80: cleaner removing section, 120: image processing section, 122
... Input switching unit, 123 ... Image memory.

Claims (2)

(57) [Claims] A scanning means for scanning a document to obtain color image information; and an image for forming a color image by overlapping a plurality of color toner images on the image holding member by rotating the image holding member endlessly. Forming means, image memory means for storing the output of the reading means, and input capable of selecting either direct output of the reading means or output of the image memory as image information to be input to the image forming means. Control means, and wherein the input control means performs an operation of selecting a direct output of the reading means during a scanning period of the reading means, and performs the operation during a period including all or a part of a return time for a next scan. A color image forming apparatus serving as input control means for alternately repeating an operation of selecting an output of an image memory to complete a color image on the image carrier. 2. A color image forming apparatus according to claim 1, further comprising a mode for forming a plurality of color images having the same content on said image carrier.