JP2713668B2 - 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 an electrophotographic full-color copying machine.

[0002]

2. Description of the Related Art In a conventional electrophotographic copying machine, in order to form a document image on a recording medium (final recording medium such as paper), a document is first irradiated by a light source lamp or the like, and the original The reflected light is applied to a uniformly charged photoconductor via a reflecting mirror or the like. The photoconductor is exposed by receiving the reflected light from the document, and an electrostatic latent image having a pattern corresponding to the document image is formed on the surface of the photoconductor.

Next, the electrostatic latent image is developed as a toner image by a toner in a developing tank and visualized, and the toner image is transferred to a transfer intermediate. The toner image transferred to the transfer intermediate is transferred to a recording medium. Thereafter, the copying is terminated by fusing the toner image on the recording medium.

When full color copying is performed in such an electrophotographic copying machine, development is performed in the order of yellow, magenta, and cyan. development, and the development of cyan beginning after the completion of development of magenta
In the development magnet roller of each development tank,
The development time, which is the time for applying the bias, is set in the same manner. The original image is developed on the photoreceptor in this order as a toner image, and the developed toner image is transferred to a transfer intermediate, on which a combined image of yellow, magenta, and cyan toner images is formed. It is formed.

In a full-color copying machine which performs development by the superposition method, yellow, magenta and cyan, and yellow,
There are two development cycles in the order magenta and cyan.
The original image is similarly developed as a toner image on the photoreceptor in this order, the developed toner image is transferred to a transfer intermediate, and the yellow, magenta, and cyan toner images are combined on the transfer intermediate. An image is formed.

[0006]

In a conventional full-color copying machine which performs development by such a superposition method, since there is a phase difference between respective developing tanks for color copying, an original of A3 size or larger is particularly required. In the case of copying, the first development cycle is performed to transfer the toner image developed in the second development cycle onto the toner image developed in the first development cycle and transferred onto the transfer intermediate, and superimposed thereon. Between the end of cyan development and the start of yellow development in the second development cycle, the transfer intermediate needs to be rotated by one rotation.

The yellow development time of the first development cycle
Is completed and the developing magnet roller in the yellow developing tank is marked.
The supply of the predetermined developing bias voltage that has been applied is stopped.
The yellow toner from the yellow developer tank to the photoconductor
The transfer is lost, but the developing magnet in the yellow developing tank
Since the potential of the roller does not drop immediately, the yellow developer tank
Yellowton for a while by the developing magnet roller
The development of the yellow toner is still
The spike comes in contact with the surface of the photoreceptor
The yellow toner spills out. When developing this yellow
After the interval is over, the toner that falls on the photoreceptor surface is removed from the developing magnet in the magenta developer tank by the next magenta development.
Is collected by the developing ears of the magenta toner for developing ears of the magenta toner by the roller comes out at the same time, Mazets fall on the photoreceptor surface after the end developing time by the development of the magenta
Printer toner, developer tank of cyan due to the development of the following cyan
Are collected by the developing magnet roller of the cyan toner . However, after the end of the development time due to cyan development in the first development cycle, it falls on the photoreceptor surface .
Because the cyan toner is in front of the yellow developer tank phase,
Not collected into the developing ears of yellow toner by the second developing, I follow, empty rotating when Mai is transferred to a transfer intermediates, this way the cyan toner transferred and adhered to appear on copied images, There is a problem that it appears as dirt.

Accordingly, the present invention is directed to a photoconductor surface after the development time for cyan development in the first development cycle is completed.
An object of the present invention is to provide a full-color copying machine capable of obtaining a copied image which is not stained by cyan toner falling on a surface .

[0009]

[Means for Solving the Problems] A photoreceptor and a color
A plurality of developing means comprising different toners ,
The image formed on the photosensitive member in accordance with the originals image
A full-color copying machine that performs development by a superposition method in which a development cycle of sequentially performing development by the plurality of development units is repeated a plurality of times , and a transfer unit that transfers a toner image formed on a photoconductor to a transfer body by the development unit. image forming means for forming a toner image transferred onto the transfer member onto the sheet by the transfer means, each predetermined developing by said plurality of developing means
Control to control the development time, which is the time to apply the ass voltage
Means during the first development cycle.
In the last development among the plurality of developing means,
The developing time of the developing means is the first current value of the second developing cycle.
Each of the plurality of developing means so as to be shorter than the image time.
Control the development time, and during the last development cycle,
The plurality of developing means so that all the developing times are equal.
The developing time of the developing means is controlled.

[0010]

The image formed on the photosensitive member according to the original image is
In each of the plurality of development cycles, the image is developed with the toner of a plurality of colors by the developing unit. The toner image developed and formed on the photoconductor is transferred to a transfer body by a transfer unit. The toner image formed on the transfer body is formed as a copy image on paper by the image forming means. At the time of such copying, the control means performs copying during the first development cycle.
Of the developing means in the last development of the number of developing means
Development time is greater than the first development time of the second development cycle
Control the development time of each of multiple development units so that they become shorter
During the last development cycle,
Control the development time of multiple developing units so that the intervals are all equal.
I will . This allows for multiple
Developing time in the last development of the developing means
The application time of the developing bias voltage is shortened, and the first current
The last developing means of the plurality of developing means in the image cycle
The toner that falls on the surface of the photoreceptor after the end of the developing time of the step is collected in the non-image area of the transfer body. Therefore, 1
The last of multiple developing means during the
The toner that falls on the surface of the photoreceptor after the development time of the developing means is not transferred to the image area of the transfer body, so that a copy image without contamination can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a side view showing the structure of one embodiment of a full-color copying machine according to the present invention.

As shown in FIG. 2, a full-color copying machine 10 according to this embodiment includes an original mounting table 11 made of transparent glass on the upper surface of a machine frame.

An exposure optical system 12 is provided below the document table 11. The exposure optical system 12 includes a light source lamp 12a for irradiating light to a document 13 placed on the document table 11 and a document 13
And a plurality of reflecting mirrors 12b, 12c, 12d, 12e for guiding reflected light from the photoreceptor 14 along an optical path indicated by a dashed line.
12f, an imaging lens 12g disposed on the optical path, and a color separation filter 12 having three primary color filters of red, green and blue.
h.

The light source lamp 12a and the reflecting mirrors 12b, 12c and 12
d is configured to be movable in parallel with the document table 11 along a bidirectional arrow shown in the figure by a driving device (not shown).

On the optical axis of the exposure optical system 12, there is provided a belt-shaped photoconductor 14 made of an organic photoconductor (OPC) to which a light image subjected to exposure scanning is irradiated.

Below the photoreceptor 14, a sheet 15 containing paper 15 is stored.
Two paper cassettes 16 and 17 are provided. Paper feed rollers 18 and 19 are provided on the upper surfaces of the paper feed cassettes 16 and 17, respectively.

The paper feed rollers 18 and 19 are configured to discharge the paper 15 from the paper feed cassettes 16 and 17, respectively, and to feed the paper 15 toward the transfer intermediate 20.

A timing roller 21 is provided on the side of feeding the sheet 15 from the paper feed rollers 18 and 19 in the direction of the transfer intermediate 20, and the timing roller 21 rotates in synchronization with the transfer intermediate 20. It is configured as follows.

The transfer intermediate 20 is configured to be driven to rotate clockwise (arrows shown in the figure) by first, second, and third rollers 22a, 22b, and 22c. It is in pressure contact with a driving roller 23 that rotates.

A primary transfer charger 24 is disposed on the back surface side of the transfer intermediate 20 at a position where the drive roller 23 is pressed against the transfer intermediate 20.

A secondary transfer roller 26 is disposed on the surface of the transfer intermediate 20 at a position where the third roller 22c is disposed so as to be in contact with the transfer intermediate 20.

On the sending side of the paper 15 of the secondary transfer roller 26,
The release plate 27, the conveyor belt 28, and the fixing device 29
They are arranged in this order.

The photosensitive member 14 to which the reflected light from the exposure optical system 12 is irradiated is driven to rotate counterclockwise (arrows shown in the figure) by a driving roller 23 and a driven roller 30.

Near the outer periphery of the driven roller 30, a cleaning device 31, which removes toner remaining on the photoreceptor 14,
A static elimination lamp unit 32 for removing static from the photoconductor 14 and the photoconductor 14
A charger 33 for charging the photoconductor 14 is provided in this order along the rotation direction of the photoconductor 14.

The cleaning device 31 is provided with a cleaning blade 31a made of, for example, urethane or the like. The cleaning blade 31a is pressed against the photosensitive member 14 so as to scrape off, for example, toner or the like remaining on the photosensitive member 14. It is configured.

Above the photoreceptor 14, a black and white developing tank 41 and color developing tanks 42, 43 and 44 are provided in a non-contact state with the photoreceptor 14. Developing tanks 42, 43 for color and
44 stores yellow, magenta, and cyan color developers, respectively.

The full-color copying machine 10 of this embodiment includes a control device 45 for setting and controlling the switching timing of the developing tanks 42, 43 and 44. The control device 45 is connected to the developing tanks 42, 43 and 44 via a cable (not shown).

Next, the operation of the full-color copying machine 10 of this embodiment will be described.

When a copy start switch (not shown) provided in the full-color copying machine 10 is pressed, a copy mode is executed. This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the transfer intermediate 20, respectively. When the copy mode is executed, the yellow copy cycle is first executed.

That is, the original 13 placed on the original placing table 11
Is irradiated with light from the light source lamp 12a, and exposure scanning is performed. The reflected light from the original 13 passes through the reflecting mirrors 12b, 12c and 12d and the imaging lens 12g, and passes through the color separation filter 12
Decomposed for each color component by h.

The color separation filter 12 is obtained by the above-described exposure scanning.
The light of each color component transmitted through each color filter of h
Then, the photoreceptor 14 uniformly charged by the charging charger 33 is irradiated to the photoreceptor 14 via P and 12f, and the photoreceptor 14 is exposed at the P portion.

As a result, a yellow electrostatic latent image corresponding to the image of the original 13 is formed on the photoreceptor 14. The electrostatic latent image is developed by a developing magnet roller at a portion opposed to a developing tank 42 having a yellow developer which is a complementary color of the color separation filter 12h.
It is developed and visualized by the developer supplied by 42a to form a toner image. This toner image is transferred to the transfer intermediate 20 by the primary transfer charger 24.

At the end of this yellow copy cycle,
The photoconductor 14 is cleaned by the cleaning device 31 and is discharged by the discharge lamp unit 32.

Thereafter, magenta and cyan toner images are transferred to the transfer intermediate 20 in a copy cycle similar to the yellow copy cycle described above.

According to the superposition method, following the first development cycle in which yellow, magenta, and cyan are respectively developed and transferred to the transfer intermediate 20, the yellow, magenta, and cyan
A second development cycle is executed in which magenta and cyan are developed and transferred to the transfer intermediate 20, respectively.

When the first and second development cycles for yellow, magenta and cyan are executed, the developing tank 42
The switching timing of 43 and 44 is controlled by the control device 45 as described later.

Therefore, when the yellow, magenta, and cyan copy cycles, that is, the first and second development cycles, are performed, the toner image for each color component is transferred to the transfer intermediate body 20 by the primary transfer charger 24. 1 is completed by being transferred to the position and superimposed with the toner image for each color component.
One toner image is formed.

On the other hand, the sheets 15 stored in the sheet cassettes 16 and 17 are fed one by one to the timing roller 21 by the sheet feeding rollers 18 and 19, and the timing roller 21 is synchronized with the rotation driving of the transfer intermediate body 20. Then, the paper 15 is transported between the transfer intermediate body 20 and the secondary transfer roller 26.

After the toner image formed on the transfer intermediate 20 is transferred to the transported paper 15 by the secondary transfer roller 26, the paper 15 is separated from the transfer intermediate 20 by the peeling plate 27, and is fixed by the transport belt 28. Introduced to 29.

After the toner image is fixed on the sheet 15 by the fixing device 29, the sheet 15 is discharged to the outside, thereby completing one copy mode.

Thus, on the transfer intermediate, yellow,
Since it is necessary to align the magenta and cyan toner images, the circumference of the photoconductor (the length in the direction in which the belt-shaped photoconductor rotates) is the circumference of the transfer intermediate (the belt-shaped transfer intermediate is rotated). (The length in the direction of movement).

Next, the yellow, magenta, and cyan developing tanks 4 are included in the full-color copying machine 10 of this embodiment.
The configuration of the control device 45 for setting and controlling the switching timing of 2, 43 and 44 will be described.

FIG. 3 is a block diagram showing an embodiment of the configuration of the control device 45.

As shown in the figure, the control device 45 of this embodiment includes a CPU (central processing unit) 51, a RAM (random access memory) 52, and a ROM (read only memory) 53.

The CPU 51 includes a RAM 52, a ROM 53, and FIG.
Yellow, magenta and cyan developing tanks 42, 43 and
44 and a copy start switch not shown in FIG.

The ROM 53 stores predetermined data relating to the switching timing of the developing tanks 42, 43, and 44 when the above-described copy mode is executed.

The CPU 51 connects the CPU 51 to a drive device (not shown) for driving the photoconductor 14 and the transfer intermediate 20, and drives the photoconductor 14 and the transfer intermediate 20 at a predetermined timing described later. It can be configured to control.

The photoconductor 14 is an embodiment of the photoconductor of the present invention. The transfer intermediate 20 is an embodiment of the transfer body of the present invention.
The primary transfer charger 24 is an embodiment of the transfer means of the present invention. Secondary transfer roller 26, release plate 27, transport belt
The fixing device 28 and the fixing device 29 are an embodiment of the image forming unit of the present invention. The developing tanks 42, 43 and 44 are an embodiment of the developing means of the present invention. The control device 45 is an embodiment of the control means of the present invention.

Next, the operation of the control device 45 will be described.

FIG. 1 shows a control device 45, particularly a control device.
48 is a timing chart for explaining the operation of the CPU 51 included in the CPU 45.

Here, in the case where the peripheral length of the belt-shaped photoreceptor 14 in FIG. 2 is twice as large as the peripheral length of the belt-shaped transfer intermediate body 20, the yellow, magenta and cyan development cycles are set to two. Control device 45 in copy mode
An operation example will be described.

In FIG. 1, the horizontal axis indicates the operation timing signal of the transfer intermediate body 20, the operation timing signal of the photosensitive member 14, the yellow developing tank 42, and the magenta developing tank with respect to time (T).
The development timing of the developing tank 43 and cyan developing tank 44 is shown in order from the top.

In the figure, Δt ₁ is the operation time corresponding to one round of the transfer intermediate 20, and Δt ₂ is the operation time of the photoreceptor 14.

[0055] As shown in the figure, when a copy start switch is pressed at time T = 0, the development of yellow begins during the first development cycle at a predetermined time T _1. The time ΔT _1Y shown in the figure is a predetermined time during which the transfer intermediate body 20 rotates during the yellow development.

Next, when the yellow development is completed, the transfer intermediate body 20 is rotated idle for a predetermined time Δt ₄ at a predetermined time T ₂ , and then magenta development is performed for a predetermined time Δt ₃ . The time ΔT _1M during which the transfer intermediate 20 rotates during the development of magenta is equal to Δt ₄ + Δt ₃ . here,
The time Δt ₄ can be set as a time during which the transfer intermediate body 20 rotates by one rotation.

Next, when the magenta development is completed, the transfer intermediate body 20 is rotated idle for a predetermined time Δt ₄ at a predetermined time T ₃ , and then cyan development is performed for a predetermined time Δt ₃ ′. The time ΔT _1C during which the transfer intermediate 20 rotates during the development of cyan is equal to Δt ₄ + Δt ₃ ′.

However, this time T _1C is set so as to be shorter than the time ΔT _1M during which the transfer intermediate member rotates during magenta development. That is, for example, the time Δt ₃ ′ for developing cyan is set to be shorter than the time Δt ₃ for developing magenta.

When the first development cycle is completed in the order of yellow, magenta, and cyan, the predetermined time T ₄
After the idle rotation of the transfer intermediate body 20 for a predetermined time Δt _4, yellow development in the second development cycle is performed for a predetermined time Δt ₃ . The time ΔT _2Y during which the transfer intermediate 20 rotates during the yellow development is equal to Δt ₄ + Δt ₃ .

Next, when the yellow development is completed, the transfer intermediate body 20 is rotated idle for a predetermined time Δt ₄ at a predetermined time T ₅ , and then magenta development is performed for a predetermined time Δt ₃ . The time ΔT _2M during which the transfer intermediate 20 rotates during the development of magenta is equal to Δt ₄ + Δt ₃ .

Next, when the magenta development is completed, the transfer intermediate body 20 is rotated idle for a predetermined time Δt ₄ at a predetermined time T ₆ , and then, cyan development is performed for a predetermined time Δt ₃ . The time ΔT _2C during which the transfer intermediate 20 rotates during the development of cyan is equal to Δt ₄ + Δt ₃ .

As described above, the time ΔT _1M during which the transfer intermediate body 20 rotates when developing magenta in the first development cycle, and the time when yellow, magenta and cyan are developed in the second development cycle. Transfer intermediate 20
The rotation time ΔT _2Y , ΔT _2M, and ΔT _2C are all equal, while the time T _1C during which the transfer intermediate 20 rotates during cyan development in the first development cycle is the time ΔT It is set to be shorter than _1M , ΔT _2Y , ΔT _2M, and ΔT _2C .

However, the time during which the transfer intermediate body 20 rotates during yellow development in the first development cycle ΔT _1Y
Is generally the shortest time since it does not include the time during which the transfer intermediate 20 rotates idle.

For this reason, in the first development cycle , a predetermined developing operation is performed on the developing magnet roller of the cyan developing tank.
The application time of the bias voltage is shortened, and after the development time
The cyan toner falling on the photoreceptor surface is collected in the non-image area of the transfer intermediate.

Accordingly, the cycle in the first development cycle is
Cyan toner <br/> over that after en development time ends fall on the photosensitive member surface, and cyan developing during the first development cycle,
Since it does not appear in the idle rotation image area during the yellow development in the second development cycle, a copy image without stain can be obtained.

As a preferred example, the time ΔT _1M during which the transfer intermediate member rotates when magenta is developed in the first development cycle, and when yellow, magenta and cyan are developed in the second development cycle The rotation time of the transfer intermediate {T _2Y , ΔT _2M and ΔT _2C is 6.14 seconds, and the rotation time of the transfer intermediate when cyan is developed in the first development cycle } T _1C may be set to 6.00 seconds. In this case, the application of the predetermined cyan developing bias voltage in the first developing cycle is stopped as compared with the case where the time ΔT _1C is set to 6.14 seconds.
The stop position moves forward 22 mm on the photoreceptor ,
After completion of the developing time, the cyan toner falling on the surface of the photoreceptor is collected in a non-image area (30 mm) of the transfer intermediate.

The operation of the control device 45 for setting and controlling the switching timing of the yellow, magenta and cyan developing tanks 42, 43 and 44 shown in FIG. 1 is programmed in advance, and the program is stored in the ROM 53 of FIG. Is stored in The program stored in the ROM 53 is read out by the CPU 51 and is executable.

In the above-described embodiment, an example in which development is performed in the order of yellow, magenta, and cyan has been described. However, the order of development is not necessarily limited to this order. The developer contained in each of the developing tanks 42, 43 and 44 shown in FIG. 2 may be changed so that the desired order of development is achieved.

[0069]

The quotient of the foregoing description, the present invention includes a photoreceptor and includes a plurality of developing means consisting of toners having different colors, respectively, the image formed on the photosensitive member in accordance with the originals image Is sequentially developed by the plurality of developing means.
By the superposition method in which the development cycle of
A full-color copying machine for performing, a transfer unit that transfers the toner image formed on the photosensitive member by the developing means to a transfer member, image forming means for forming a toner image transferred onto the transfer member by the transfer means on the sheet To the plurality of developing means.
Each time is a time for applying a predetermined developing bias voltage.
Control means for controlling the image time, wherein the control means
During the third development cycle, the most
The developing time of the developing means in the subsequent development
Each to be shorter than the first development time of the image cycle
Controlling the developing time of the plurality of developing means,
During the cycle, the developing times of the plurality of developing means are all equal.
The developing times of the plurality of developing units are controlled so as to obtain the following.
Therefore, among the plurality of developing means in the first developing cycle,
The toner that falls on the surface of the photoreceptor after the end of the developing time of the last developing unit is not transferred to the image area of the transfer body, so that a copy image without stain can be obtained.

[Brief description of the drawings]

FIG. 1 is a timing chart for explaining an operation of a CPU included in a control device.

FIG. 2 is a side view showing the configuration of one embodiment of a full-color copying machine according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a configuration of a control device.

[Explanation of symbols]

 10 Full-color copier 14 Photoconductor 20 Transfer intermediate body 24 Primary transfer charger 26 Secondary transfer roller 27 Peeling plate 28 Conveyor belt 29 Fixing device 45 Control device 51 CPU

Claims (1)

(57) [Claims] 1. A photoconductor and a toner having different colors.
Ranaru and a plurality of developing means, said plurality of developing the image formed on the photosensitive member in accordance with the originals image
Repeat development cycle to develop sequentially by means several times
A full-color copying machine that performs development by the superposition method ,
A transfer unit for transferring the transfer member the toner image formed on said photosensitive member by said developing means, image forming means for forming a toner image transferred to the transfer member by the transfer means onto a sheet, said plurality of Each of the developing means has a predetermined developing bias.
Control to control the development time, which is the time to apply the ass voltage
Means during the first development cycle.
In the last development among the plurality of developing means,
The developing time of the developing means is the first current value of the second developing cycle.
Each of the plurality of developing means so as to be shorter than the image time.
Control the development time, and during the last development cycle,
The plurality of developing means so that all the developing times are equal.
A full-color copying machine wherein a developing time of a developing means is controlled .