JP2758298B2 - Full color copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color copying machine for obtaining one full-color toner image by superimposing two full-color toner images when forming one full-color image.

[0002]

2. Description of the Related Art In a conventional full-color copying machine, expansion of a dynamic range in a copied image is one of important technical issues in order to reproduce faithful colors.
The dynamic range of the copied image indicates the density width of the original image corresponding to the inclined portion in the characteristic curve shown in FIG. 4 , and is used as a measure of the gradation. For example, in the case of a normal full-color copying machine, the dynamic range is about 0.6, which is far from the ideal value of 2.0.
In terms of color reproducibility, it is not practically satisfactory. For this reason, as the simplest method, an attempt has been made to expand the dynamic range by adjusting the exposure amount and the surface potential of the photoconductor. However,
Such a method has the disadvantage that the saturation density is reduced and the copied image is entirely light.

Therefore, a superposition method has been adopted as one of the methods for improving the above-mentioned disadvantages. In this method, a copy image having a wide dynamic range is obtained by superimposing an image of a low density portion and an image of a high density portion. In a full-color copying machine, a toner image is usually obtained by performing exposure and development three times with toners of yellow, magenta, and cyan and superimposing toner images obtained by the exposure and development. By changing the amount of exposure light, two types of toner images, one corresponding to the low-density portion and the other corresponding to the high-density portion, are formed, and the toner image of the low-density portion and the toner image of the light-density portion are overlapped. By matching, a good image with a wide dynamic range is obtained.

That is, in the γ-characteristic diagram shown in FIG. 4, as shown by a curve A, a low-density portion is toned and formed by a first series of developing operations, while as shown by a curve B, A high-density portion is formed by the second series of developing operations. As a result, the copy image finally obtained has a gamma characteristic approaching an ideal curve indicated by a one-dot chain line, and has a dynamic range of 1.5 or more as shown by a curve C. As a result, the sharpness of images such as characters and lines is improved. Also, since one copy image is obtained by superimposing the toner images,
This has the advantage that the reproduced characters, lines, and the like do not become thin as in the case where the electrostatic latent images are superimposed.

[0005]

However, when performing full-color copying by the above-described superimposition method, the developing tank is advanced from a predetermined position to a position in contact with the photoreceptor, and the developing is performed. In a full-color copying machine that retreats to a predetermined position, if the advance and retreat of the developing tank are each one stroke, one copy process is performed.
Then, development is performed in the order of yellow, magenta, cyan, yellow, magenta, and cyan, and the movement of the developing tank reaches a total of 12 strokes. For this reason, there is a problem that the load on the developing tank driving device is large, the life is shortened due to abrasion or the like, and the energy consumption is increased.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a full-color copying machine according to the present invention comprises a plurality of developing tanks for individually storing respective color toners for obtaining a full-color toner image. Are driven forward and backward to an advanceable position and an original retreat position where development can be performed by the developing tank driving device, and correspond to a low density portion and a high density portion for one document image.
In order to obtain two types of full-color toner images corresponding to the above, the development is performed twice with each color toner individually accommodated in the plurality of developing tanks, and each obtained toner image is transferred to an intermediate transfer member. In a full-color copying machine that obtains one full-color toner image by superimposing on the same portion, two developments with each color toner are performed in one copy process by one advance and retreat drive in each developing tank. It is characterized in that the cleaning is performed continuously by the toner stored in the developing tank.

[0007]

According to the above arrangement, when forming a full-color image, one development process is performed once for each developing tank in one copy process, so that the one corresponding to the low density part and the one corresponding to the high density part are formed.
And two types of full-color toner images are obtained.

A case where a full-color image is obtained by using yellow, magenta, and cyan toners will be described. A developing tank containing yellow toner is used.
In order to obtain two types of full-color toner images, one corresponding to the low-density part and the one corresponding to the high-density part , for example, performing exposure with a screen in the exposure light path and exposure without the screen, Develop each of them. Next, the developing tank in which the magenta toner is stored and the developing tank in which the cyan toner is stored are similarly developed with and without a screen in the exposure light path. Then, the two types of full-color toner images thus obtained, that is, the full-color toner image obtained by disposing the screen and the full-color toner image obtained without disposing the screen are superimposed on the same portion on the intermediate transfer member. By combining, one full-color toner image is obtained.

Therefore, if the advance and retreat of the developing tank are each one stroke, only two strokes are required for each type of developing tank, so that the total is six strokes, which is six strokes less than the conventional 12 strokes. Can be. This makes it possible to reduce the mechanical wear of the developing tank driving device and the energy consumption.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a full-color copying machine according to this embodiment.
As shown in FIG. 1, a transparent document table 1 is provided on the upper surface of the frame. An exposure optical system 2 is provided below the document table, and the exposure optical system 2 includes a light source lamp 2 for irradiating a document 13 placed on the document table 1 with light.
a, a plurality of reflecting mirrors 2b... for guiding reflected light from the document 13 onto the photoreceptor 7 as indicated by a dashed line, an imaging lens 2c disposed on the optical path, and red, green, and blue. And a color separation filter 2d having three primary color filters.

On the optical axis of the exposure optical system 2, there is provided a drum type photoreceptor 7 composed of an organic photoreceptor (OPC) to which a light source exposed and scanned is applied. On the paper feeding direction side, the paper feed cassette 8 containing the transfer paper 19
・ 9 are provided. Paper feed rollers 23 and 24 are provided on the upper surfaces of these paper feed cassettes 8 and 9, respectively. These paper feed rollers 23 and 24 transfer the transfer paper 19 from the paper feed cassettes 8 and 9. The sheet is discharged and sent to the intermediate transfer member 10.

A timing roller 25 is disposed on the side from the paper feed rollers 23 and 24 toward the intermediate transfer member 10. The timing roller 25 is rotated in synchronization with the intermediate transfer member 10. It has become so. Also,
The intermediate transfer member 10 includes first to third rollers 18a and 18b.
18c.

A transfer charger 21 is provided on the back side of the intermediate transfer body 10, and a transfer roller 2 is provided on the front side of the intermediate transfer body 10 at a portion where the third roller 18c is provided.
2 are provided. On the delivery side of the transfer roller 22, a peeling plate 20, a transport belt 11, and a fixing device 12 are arranged in this order.

A charging charger 16 for charging the photosensitive member 7 and a charge removing lamp 26 for removing the charge from the photosensitive member 7 are provided on the outer periphery of the photosensitive member 7, and are provided below the photosensitive member 7 near the charging charger 16. Is provided with a cleaning device 17 for removing the toner remaining on the photoconductor 7. Further, a developing tank 3 for black and white is disposed above the photosensitive member 7 in a paper entering direction in a non-contact state with the photosensitive member 7, while a color developing tank 3 is arranged from the top to the bottom in the sending direction. Developing tanks 4, 5, and 6 are sequentially arranged in a non-contact state with the photoconductor 7, similarly to the developing tank 3. These color developing tanks 4, 5, and 6 contain yellow, magenta, and cyan color developers, respectively. A rotatable screen 27 is provided at a position on the outer periphery of the photoconductor 7 where light reflected from the document 13 passes.

FIG. 2 shows a portion where the developing tank 4 is provided, for example. The developing tank 4 has an upper surface plate 4b provided on an upper surface of a developing tank main body 4a in which a color developer is stored. On the right end side of the upper surface plate 4b in the drawing, a first cam contact plate 4c is formed which hangs from the upper surface plate 4b and covers the right end of the developing tank main body 4a, while a right end portion of the upper surface plate 4a is formed. The second cam contact plate 4d is formed in a shape hanging down from the upper surface plate 4a. Between the first cam contact plate 4c and the second cam contact plate 4d, an eccentric cam 4e that separates and contacts the developing tank main body 4a from the photoconductor 7 is provided with the cam shaft 4f as an axis. It is arranged. When the point b marked on the eccentric cam 4e is at the position shown in the figure, the first cam contact plate 4c is pushed by the eccentric cam 4e, so that the developing tank 4 moves and comes into contact with the photosensitive member 7. Become. On the other hand, the eccentric cam 4
When the point e is rotated by 180 degrees and the point b is located on the right side of the cam shaft 4f, the second cam contact plate 4d is pushed to
The developing tank 4 is further retracted. In addition, the stroke at the time of separation and contact is set to, for example, 7 mm.

[0017]

[Table 1]

In this copying machine, as shown in FIG.
Control device 28 constituted by microcomputer
When full-color copying is performed, a developing operation using yellow, magenta, and cyan toners for one original image is performed according to the mode A shown in Table 1 for each toner.
The copying operation is controlled by the control device 28 so that the toner images thus obtained are superimposed on the intermediate transfer body 10 to form one full-color toner image. I have. At this time, the developing tank driving device 29 firstly operates based on a preset program.
The developing tank 4 is advanced, and the mode A using the yellow toner
, Followed by retreating after the development of mode B with yellow toner is completed, and then the developing tank 5 is advanced to retreat after the completion of mode A and mode B with magenta toner. The controller 28 is controlled so as to advance and retreat when the mode A and the mode B using the cyan toner are completed.

Although not shown, the control device 28 operates the magnet rollers 18a, 18b, 18c and their developing biases, the exposure optical system 2, and the developing tanks 3 , 4, 5, 5.
A color separation filter 2d and a screen 2 corresponding to 6
7, the drive of the photoconductor 7, the charging charger 16,
The cleaning device 17, the intermediate transfer device 10, and other operations are controlled.

Next, the operation of the full-color copying machine will be described below.

First, when a copy start switch (not shown) is pressed, a developing operation is executed. The developing operation includes a copy cycle for developing yellow, magenta, and cyan, respectively, and transferring the developed image to the intermediate transfer body 10. When the developing operation is performed, first, a mode in the yellow copy cycle is performed. A is executed in the yellow mode A copy cycle.

That is, the original 1 placed on the original placing table 1
3 is irradiated with light from a light source lamp 2a, and exposure scanning is performed. The reflected light from the original 13 is incident on the color separation filter 2d via the reflection mirrors 2b and the imaging lens 2c, and is separated by the color separation filter 2d for each color component.

The light for each color component transmitted through each color filter of the color separation filter 2d in the above exposure scanning is charged by the charger 1
A screen 29 is placed on the photoreceptor 7 uniformly charged in
And the photosensitive member 7 is exposed. As a result, an electrostatic latent image in mode A corresponding to the image of the original 1 is formed on the photoconductor 7. Thereafter, the electrostatic latent image is visualized by being developed with a developer supplied from a developing magnet roller when a developing tank 4 having a yellow developer, which is a complementary color of the color separation filter 2d, is brought into contact with the photosensitive member 7. To form a toner image (the developing conditions at this time are set to the mode A in Table 1).
Shown). The toner image is transferred to the transfer charger 2
1 is transferred to the intermediate transfer member 10. In this way, when the copy cycle of the yellow mode A is completed, the photoconductor 7 is cleaned by the cleaning device 17 and is discharged by the discharge lamp 26.

Next, in a state where the developing tank 4 is in contact with the photosensitive member 7, a copy cycle of the yellow mode B is performed. As with the yellow mode A, the document table 1
Light is emitted from the light source lamp 2a to the original 13 placed thereon, and exposure scanning is performed. The reflected light from the original 13 is incident on the color separation filter 2d via the reflection mirrors 2b and the imaging lens 2c, and is separated by the color separation filter 2d for each color component. The light for each color component is applied to the photoreceptor 7 uniformly charged by the charger 16 in the mode b.
In this case, irradiation is performed without passing through the screen 27, and the photoconductor 7 is exposed. As a result, an electrostatic latent image of mode B corresponding to the image of the original 1 is formed on the photoconductor 7. After this,
The electrostatic latent image is visualized by a developing tank in contact with the photoreceptor 7, becomes a toner image (the developing conditions at this time are shown in Mode B in Table 1), and is transferred to the transfer intermediate 10. At the same time, the developing tank 4 retreats from the photoconductor 7.
Thereafter, when the copy cycle of the yellow mode B is completed, the photoconductor 7 is cleaned by the cleaning device 17 and is discharged by the discharge lamp 26. This completes the yellow copy cycle.

Next, the magenta mode A and magenta mode B copy cycles, which are the magenta copy cycles using the developing tank 5 having the magenta developer, are performed sequentially in the same manner as the yellow copy cycle described above. Similarly, a cyan mode A copy cycle and a cyan mode B copy cycle, which are cyan copy cycles using the developing tank 6 having a cyan developer, are sequentially performed. That is, the toner images of the yellow mode A, yellow mode B, magenta mode A, magenta mode B, cyan mode A, and cyan mode B are sequentially superimposed on the same position on the intermediate transfer body 10 so that One full-color toner image is formed.

On the other hand, the transfer papers 19 stored in the paper feed cassettes 8 and 9 are fed one by one to the timing rollers 25 by the paper feed rollers 23 and 24,
Transports the transfer paper 19 between the intermediate transfer body 10 and the transfer roller 22 in synchronization with the intermediate transfer body 10. After the full color toner image of the intermediate transfer body 10 is transferred by the transfer roller 22, the transfer paper 19 conveyed is separated from the intermediate transfer body 10 by the separation plate 20, and is introduced into the fixing device 12 by the conveyance belt 11. Then, after the color toner image is fixed on the transfer paper 19, the color toner image is discharged to the outside, thereby completing one development operation.

In this embodiment, the developing operation is performed in the order of yellow, magenta, and cyan toners, but the present invention is not limited to this.

[0028]

As described above, the full-color copying machine according to the present invention corresponds to a low-density portion for one original image.
And two types of full-color toners for high density parts
In order to obtain an image, in one copying process, two developments with each color toner are continuously performed by the toner contained in the developing tanks by one advance / retreat drive in each developing tank. Configuration.

Therefore, the number of forward and backward movements of the developing tank can be reduced, and an effect that mechanical wear of the developing tank driving device and energy consumption can be reduced can be achieved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a full-color copying machine according to the present invention.

FIG. 2 is a configuration diagram showing a main part of a developing tank in the full-color copying machine.

FIG. 3 is a block diagram showing a main part of a control system in the full-color copying machine.

FIG. 4 is a γ-characteristic diagram of a full-color copying machine based on a superposition method shown in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Original 4 Developing tank 5 Developing tank 6 Developing tank 7 Photoconductor 10 Intermediate transfer body 29 Developing drive

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-52571 (JP, A) JP-A-3-212662 (JP, A) JP-A-2-64571 (JP, A) JP-A 62-52571 92967 (JP, A) JP-A-63-109462 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/01-15/01 117 G03G 15/08-15/08 507

Claims (1)

(57) [Claims] An image forming apparatus includes a plurality of developing tanks for individually storing toners of respective colors for obtaining a full-color toner image. Each of the developing tanks moves back and forth between an advance position where development can be performed by a developing tank driving device and an original retreat position. Driven and low for one document image
2 corresponding to the high density part and 2 corresponding to the high density part
In order to obtain various types of full-color toner images, development is performed twice with each color toner individually accommodated in the plurality of developing tanks, and each obtained toner image is transferred to an intermediate transfer member.
In a full-color copying machine that obtains one full-color toner image by superimposing on the same portion, two developments with each color toner are performed in one copy process by one advance and retreat drive in each developing tank. A full-color copying machine characterized by being continuously performed with toner stored in a developing tank.