JPH0675466A - Developing device of copier - Google Patents

Abstract

PURPOSE:To decrease splashing of a toner from a developing tank by controlling the rotation speed of rollers in the developing tank when rotation of rollers is started and stopped in a manner that the rotation speed is slowly and continuously changed from the rotation speed in the developing period. CONSTITUTION:Rollers in the developing tank, especially, stirring rollers 32, 33 and developing roller 34 in a developing case 35 are controlled in a manner indicated by the time-rotation speed diagram. In the diagram with axis of abscissas for time and the axis of ordinates for rotation speed, the rotation speed during starting rotation in period t1-t2 for magenta developing is continuously increased to the constant speed Vc for development in period t2-t3 and then rotation is decreased in period t3-t4 from Vc to zero. Thereby, drastic change of the rotation in the starting and stopping periods is prevented, which decreases splashing of the toner. Thereby, mixing of toners in a developing device even when the copier contains lots of color toners is prevented, and thereby, reproducibility of colors can be improved for full-color copies and the inside of the machine is not contaminated with toners.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic brush developing device in an electrophotographic device used in a copying machine, a laser printer or the like.

[0002]

2. Description of the Related Art Copiers, which have recently appeared on the market,
By diversifying functions, it is possible to reproduce images such as twin color and full color. These copying machines are provided with a developing device for two or more colors, and for full color, a developing device for four colors is required. By disposing these developing tanks in the vicinity of the photoconductor and developing for each color, twin-color, full-color, etc. images are reproduced.

The developer used in the developing tank is
It is called a developer, and this developer is a mixture of a carrier and a toner, and the mixing ratio is generally 4 to 6% of the toner with respect to the total weight. The carrier has a core material of a metal material such as iron with an average particle size of 80 to 90.
μm, and the metal particles are coated with a coating material such as fluorine or silicon. The toner contains polyester or styrene acryl as a main resin, and carbon and a face wash as a coloring material are dispersed, mixed and pulverized. After that, the average particle size is 6 to 10 μm.

The carrier and toner of the developer are agitated in the developing tank, and the carrier and toner are charged with opposite polarities. By developing the electrostatic latent image on the photoconductor by the developer, only the toner moves to the photoconductor to form a visible image.

The carrier and toner in the developer have a charge distribution as shown in FIG. That is, in FIG. 4, the horizontal axis represents the charging potential (v) and the vertical axis represents the toner amount (Q) of the weakly charged toner and the oppositely charged toner. When the toner is negatively charged, the shaded area is weak when the toner is formed. The charged toner and the oppositely charged toner will be mixed.

[0006]

Since the above-mentioned toner is weak in polarity, it is not maintained charged in the developing tank and jumps out of the developing tank at the time of development, especially when the developing device is started and stopped. This toner scattering causes color mixing of the toner if a multi-color developing device is provided in the copying machine, and causes deterioration of color reproducibility in the case of full color, and at the same time causes dirt within the copying machine. Incidentally, the toner is attached to the photoconductor because the photoconductor is charged at an extremely high potential during development.

[0007]

In the developing device of a copying machine according to the present invention, control is performed to control the rotation speed of the roller of the developing tank at the time of starting and stopping the rotation so as to be slower than during development and continuously change. Means are provided to reduce the scattering of toner from the developing tank.

[0008]

Since the present invention is constructed as described above, it is possible to suppress toner scattering that occurs when the developer flow changes rapidly due to the start and stop of the rotation of the developing roller in the developing tank. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color copying machine according to an embodiment of the present invention has a transparent original placing table 1 on the upper surface of a machine frame as shown in FIG. An exposure optical system 2 is arranged below the original placing table 1, and the exposure optical system 2 illuminates an original 13 placed on the original placing table 1 with light. , A plurality of reflecting mirrors 2b for guiding the reflected light from the original 13 onto the photoconductor 7 as shown by a chain line, an imaging lens 2c arranged on the optical path, and red, green, and blue. And a color separation filter 2d having color filters of three primary colors.

On the optical axis of the exposure optical system 2, a drum-shaped organic photosensitive member (OP
C) 7 is provided, and paper feed cassettes 8 and 9 accommodating a transfer machine 19 are provided on the side of the photoconductor 7 in the paper entry direction. The paper feed rollers 23 and 24 are provided on the upper surfaces of the paper feed cassettes 8 and 9, respectively, and the paper feed rollers 23 and 24 move the transfer machine 19 from the paper feed cassettes 8 and 9, respectively. The sheet is ejected and delivered to the intermediate transfer machine 10.

A timing roller 25 is provided on the delivery side of the paper feed rollers 23 and 24 in the direction of the intermediate transfer body 10. The timing roller 25 rotates in synchronization with the intermediate transfer body 10. It is supposed to be done. Further, the intermediate transfer member 10 includes the first to third rollers 18a and 18a.
It is adapted to be rotationally driven by b and 18c. A transfer roller 21 is arranged on the back surface side of the intermediate transfer member 10, and a transfer roller 22 is arranged on the front surface side of the intermediate transfer member 10 at the position where the third roller 18c is arranged. The peeling plate 20, the conveyor belt 11, and the fixing device 12 are arranged in this order on the delivery side of the transfer roller 22.

A charging charger 16 for charging the photosensitive member 7 and a discharging lamp 26 for discharging the photosensitive member 7 are arranged on the outer periphery of the photosensitive member 7, and below the photosensitive member 7 in the vicinity of the charging charger 16. A cleaning device 17 for removing the toner remaining on the photoconductor 7 is provided. Further, a black and white developing tank 3 and color developing tanks 4 to 6 are independently arranged above the photoconductor 7 in a non-contact state with the photoconductor 7. ,yellow,
Magenta and cyan color developers are separately contained.

Next, the operation of the color copying machine having the above construction will be described below.

First, the copy mode is executed by pressing a copy start switch (not shown). This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the intermediate transfer body 10. When the copy mode is executed, first, the yellow copy cycle is executed. Become.

That is, the original document 1 placed on the original document table 1
3 is irradiated with light from the light source lamp 2a, and exposure scanning is performed. The reflected light from the original 13 is incident on the color separation filter 2d through the reflecting mirrors 2b ... And the imaging lens 2c, and is separated into color components by the color separation filter 2d.

The light for each color component transmitted through each color filter of the color separation filter 2d in the above exposure scanning is applied to the photoconductor 7 that is uniformly charged by the charging charger 16, and the photoconductor 7 is at the portion A. Exposed. As a result, the photoconductor 7
A yellow electrostatic latent image corresponding to the image of the original 13 is formed. After that, each of the electrostatic latent images is separated by the color separation filter 2d.
In the facing portion of the developing tank 4 having the yellow developer which is the complementary color of the above, it is visualized by being developed with the developer supplied from the developing magnet roller. And
This toner image is transferred by the transfer charger 21 to the intermediate transfer member 10.
Will be transferred to.

When the above yellow copying cycle is completed, the photoconductor 7 is cleaned by the cleaning device 17 and discharged by the discharge lamp 26. Then, the magenta and cyan toner images are transferred to the intermediate transfer body 10 in the same copy cycle as described above.

When each of the above copy cycles is executed,
The toner image for each color component is transferred to the same position of the intermediate transfer body 10 by the transfer charger 21, and the toner for each color component is overlaid to form one completed toner image.

On the other hand, the transfer papers 19 accommodated in the paper feed cassettes 8 and 9 are fed one by one to the timing roller 25 by the paper feed rollers 23 and 24, and the timing roller 25 is fed.
Conveys the transfer paper 19 between the intermediate transfer body 10 and the transfer roller 22 in synchronization with the intermediate transfer body 10. The transferred transfer paper 19 is separated from the intermediate transfer member 10 by the peeling plate 20 after the toner image on the intermediate transfer member 10 is transferred by the transfer roller 22, and is introduced into the fixing device 12 by the transfer belt 11. Then, after the color toner image is fixed on the transfer paper 19, it is discharged to the outside to
This ends the copy mode.

Referring particularly to the developing device with reference to the drawings, FIG. 2 is a sectional view of a magenta developing tank, for example, but the same applies to developing tanks of other colors. A toner supply roller 27, 28 is connected to a motor (not shown) via a transfer drive gear, and a toner supply roller 29 is connected via a supply drive gear (not shown), and the rollers 27, 28 and 29 are pivotally attached to the toner supply case 30. It constitutes a toner supply unit. Further, the motors (not shown) are connected to the agitating rollers 32 and 33 via agitating drive gears, and the developing roller 34 is connected via a developing idle gear (not shown).
3 and 34 are pivotally attached to the developing case 35, and a developing unit is constructed by providing a magnetic permeability sensor 36 facing the agitating roller 33 to control the toner concentration constant. A toner supply slit 31 is provided in a portion of the toner supply case 30 where the toner supply roller 29 and the stirring roller 32 face each other.

The toner supply unit and the developing unit are integrally fitted together to form, for example, the magenta developing tank 5. A developing tank separating / contacting cam 37 is provided in an appropriate portion of the developing tank 5, for example, in the developing case 35, and one rotation of the cam 37 causes the developing tank 5 to reciprocate once in the direction indicated by an arrow 38, thereby developing roller 34.
Is separated from and brought into contact with the photoconductor 7. The timing of separation and contact is performed immediately before the start of the rollers in each developing tank and immediately after the stop. As a color changing system of the developing device, it is also possible to use a color changing system of the developing device having a function of collecting the developer spikes in the developing device (tank) without performing the separation / contact operation to the photoconductor for each developing device. .

Driving of the respective rollers in the developing tank 5, particularly the stirring rollers 32, 33 and the developing roller 34 in the developing case 35 will be described with reference to FIG. 3. The horizontal axis represents time (t) and the vertical axis represents the stirring roller. In terms of the rotational speed (V), for example, the rotational speed at the time of rotation start at time t _{1 to} t ₂ corresponding to magenta is the constant rotational speed V at the time of development from time t ₂ to t _3.
It is controlled so as to be continuously increased to c, and the rotation speed at the time of stop of the time t _{3 to} t ₄ is continuously decreased from the constant rotation speed Vc at the time of development to zero.

In the above FIG. 3, the same applies to the developing tanks of other colors, and the characteristic curves Y, M, C and B show the developing tanks 4, 5, 6 for yellow, magenta, cyan and black in the order of lapse of time. 3 is a rotation speed curve of each roller of 3 and 3.

[0024]

Since the developing device of the copying machine according to the present invention has the above-described structure, the rapid speed change at the time of starting and stopping the rotation of the roller of the developing device is eliminated, and the scattering of toner can be reduced. As a result, even if a multi-color developing device is provided in the copying machine, there is no risk of toner color mixing, and even in the case of full color, color reproducibility is good and the inside of the machine is not contaminated with toner.

[Brief description of drawings]

FIG. 1 is a schematic front sectional view of a color copying machine that is an embodiment of the present invention.

FIG. 2 is a sectional view of a developing tank of the developing device according to the present invention.

FIG. 3 is a drive characteristic diagram of a roller of the developing device according to the present invention.

FIG. 4 is a charge distribution curve diagram of a carrier and a toner in a developer.

[Explanation of symbols]

 1 Original Copying Plate of Color Copier 2 Exposure Optical System 3, 4, 5, 6 Developing Tank 7 Photoreceptor 8, 9 Paper Feed Cassette 10 Intermediate Transfer Body 13 Original 18 Intermediate Transfer Body Roller 21 Transfer Roller 27, 28 Conveyor Roller 29 Supply Roller 30 Toner Supply Case 32, 33 Stirrer Roller 34 Development Roller 35 Development Case 37 Development Tank Separation Cam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Nishimura 22-22 Nagaike-cho, Naganocho, Abeno-ku, Osaka, Osaka Prefecture Sharp Corporation (72) Yasutaka Maeda 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (1)

[Claims] 1. A control means for controlling the rotation speed of a roller in a developing tank when starting and stopping the rotation of the roller so as to change continuously and at a slower speed than during developing, thereby reducing scattering of toner from the developing tank. A developing device for a copying machine, which is characterized in that