JP2514246B2 - Development device - Google Patents

Description

The present invention relates to a developing device for supplying a developer onto a photoconductor, and is used in, for example, an electrostatic transfer copying machine or a laser printer.

[Conventional technology]

In a general developing device, a shutter mechanism 44 is provided inside the main body 41 as shown in FIG. 4, and a developing magnet for the developer 42 accommodated in the developing device main body 41 by the shutter mechanism 44. The supply to the roller 43 and its stop are switched. Further, a toner replenishing roller 40 is provided in the toner hopper 48 provided on the developing device main body 41.
The lower space of the above and the upper space of the shutter mechanism 44 communicate with each other to form a toner supply path 49.

At the time of development, the shutter mechanism 44 is opened, and the developer 42 supplied via the shutter mechanism 44 forms a magnetic brush on the peripheral surface of the rotary cylinder 43a of the developing magnet roller 43, whereby only the toner is discharged. Photoconductor belt 45
Will be supplied sequentially. Then, the developer 42 is rotated by the rotation of the rotary cylinder 43a of the developing magnet roller 43 and the conveying magnet roller 46 provided above it.
It returns above the shutter mechanism 44 and circulates between the shutter mechanism 44, the developing magnet roller 43, and the conveying magnet roller 46. During this circulation, the toner concentration detection sensor 47 detects the toner concentration, and when the toner concentration does not reach the specified concentration, the toner in the toner hopper 48 is rotated in the toner replenishing roller 40 and the toner is replenished in the developing device main body 41 from the toner replenishing path 49. To maintain the toner density of the developer 42 at a specified value.

On the other hand, at the time of non-development, the shutter mechanism 44 is closed in order to prevent unnecessary toner from adhering to the photosensitive belt 45, and the developing magnet roller 43 and the conveying magnet roller are used.
46 was continuously rotated for a while, and the developer was conveyed onto the shutter mechanism 44 and then stopped.

<Problems to be Solved by the Invention> However, in the conventional developing device, the shutter mechanism 44 normally maintains the open state during development and the closed state during non-development. There is a problem that the supplied toner is urged and stays at the portion A between the inner wall surface and the inner wall surface, and the developer in that portion causes poor stirring and causes streak-like unevenness when copying.

<Means for Solving the Problems> In order to solve the above problems, the present invention switches between a developing magnet roller for supplying the developer onto the photosensitive member, and the supply of the developer to the developing magnet roller and its stop. In a developing device including a shutter mechanism and a transport magnet roller that receives the developer on the rotary cylinder of the developing magnet roller and transports and deposits the developer in the space above the shutter mechanism, the developing magnet roller is provided during warm-up. And after rotating the transport magnet roller, the toner density is detected with the shutter mechanism open.
If the toner density is a specified value, the shutter mechanism is opened and closed a predetermined number of times after the shutter mechanism is once closed and before the development magnet roller and the transport magnet roller are stopped from rotating. Is provided.

<Operation> By opening and closing the shutter mechanism, the developer existing between the shutter mechanism and the inner wall surface of the developing tank body facing the shutter mechanism is also stirred, and the developer concentration in the entire developing tank is made uniform.

<Embodiment> An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

As shown in FIG. 3, an original placing glass table 1 is arranged on the upper surface of a full-color copying machine so as to be movable in the left-right direction in the figure. Further, a light source 2 for irradiating an original document (not shown) placed on the original placing glass table 1 is provided in the upper part of the copying machine. The reflected light from the above document is reflected by multiple mirrors.
After entering the color separation filter 4 through 3 and 3, the color separation is performed, and then the component light of each of the three primary colors of yellow, magenta and cyan is sequentially passed through the lens 5 and the mirrors 3 and 3. The belt-shaped photoconductor 6 is exposed.

The photoconductor 6 is charged to a predetermined potential by a charging charger 7 as a charging device, and different regions on the photoconductor 6 are sequentially exposed to the above-described component light of each color of yellow, magenta, and cyan, respectively. An electrostatic latent image for each color is formed in the area. A developing device 8 having four developing portions 8a to 8d for developing yellow, magenta, cyan, and black colors is arranged above the photoconductor 6. Then, as the photoconductor 6 travels in the direction A, the electrostatic latent images of respective colors are sequentially developed by the developing units 8a to 8d having toners of corresponding colors. After that, the developed toner images of the respective colors are superposed and transferred onto the transfer belt 11 by the transfer charger 10.

Copy paper (not shown) is supplied to the transfer belt 11 from the manual paper feed unit 12 or the paper feed cassettes 13 and 14, and the toner images in the superposed state on the transfer belt 11 are transferred to the transfer charger.
The image is transferred to the above copy paper by means of 15. The copy sheet on which the toner image has been transferred is transferred to the transfer belt 11 by the peeling charger 16.
The toner image is separated from the sheet and sent to the fixing device 18 by the conveyor belt 17, where the toner image is fixed on the copy sheet and then discharged to the sheet discharge tray 20.

The developing device 8 will be described below. As shown in FIG. 2, each of the developing sections 8a to 8d of the developing device 8 is provided with a developing tank 21, and a sleeve 23 made of a non-magnetic material is provided at a predetermined interval on the outer periphery of the magnet 22 at the bottom of the developing tank 21. A developing magnet roller 24, which is rotatably fitted to the photoconductor 6, is disposed so as to face the photoconductor 6. With the rotation of the sleeve 23, the developing magnet roller 24 supplies the toner in the developer, which is composed of toner of a predetermined color and carrier different for each of the developing portions 8a to 8d, onto the photoconductor 6, and the photoconductor 6 The electrostatic latent image corresponding to the toner color above is developed.

Above the developing magnet roller 24, like the developing magnet roller 24, a sleeve is provided around the magnet 25.
A transport magnet roller 27, which is formed by rotatably fitting 26 at a predetermined interval, is arranged. The carrying magnet roller 27 carries the developer, which is the developer sent from the developing magnet roller 24, to the side of the first stirring roller 28 described later as the sleeve 26 rotates.

First and second stirring rollers 28 and 29 are rotatably arranged respectively above and below the conveying magnet roller 27. The first stirring roller 28 is replenished from a toner hopper 35 described later to the developing tank 21. The toner and the developer in the developing tank 21 are agitated and mixed, and the second agitating roller 29 is further configured to agitate the developer.

A cylindrical shutter 30 is rotatably arranged on the outer periphery of the second agitating roller 29, and the shutter 30 is arranged in the circumferential direction 2
Openings 30a, 30a are formed at the locations. A partition member 31 is provided between the transport magnet roller 27 and the second stirring roller 29. When the shutter 30 is in a closed state in which the openings 30a, 30a face the developing tank 21 and the partition member 31, as in the developing unit 8b in FIG.
While preventing the flow of the developer between 28 and 29 and between the second agitating roller 29 and the developing magnet roller 24, the openings 30a and 30a have the first agitating like the developing unit 8a in FIG. In the open state in which the roller 28 and the developing magnet roller 24 are opposed to each other, a space between the two stirring rollers 28 and 29 and a second stirring roller are provided.
The developer is allowed to flow between 29 and the developing magnet roller 24.

A toner concentration detection sensor 32 for detecting the concentration of toner in the developer in the developing tank 21 is attached to the developing tank 21 between the second stirring roller 29 and the developing magnet roller 24. Further, the developing tank 21 below the toner concentration detection sensor 32
Is provided with a doctor 33 for controlling the amount of toner supplied to the photoconductor 6.

A toner box 35 having a toner mixing shaft 34 therein is arranged above the developing tank 21. Toner box 35
Is configured to replenish toner into the developing tank 21 by the toner replenishing roller 36 when the toner concentration detecting sensor 32 detects that the toner concentration in the developer in the developing tank 21 is less than or equal to a predetermined value. There is.

Further, a blade-shaped toner scattering prevention member 37 is provided at the bottom of the developing tank 21 on the side of the developing magnet roller 24 in the developing unit 8a located closest to the exposing unit among the developing units 8a to 8d. ing. This toner scattering prevention member 37
For example, it is made of a urethane rubber sheet having a thickness of 0.1 mm and is in close contact with the entire area of the photoconductor 6 in the width direction to prevent the toner from scattering toward the exposed portion side.

In the developing device 8 described above, a developing section 8a in which development is performed
8d, the shutter 30 is used as in the developing unit 8a in FIG.
Is opened, the developer is sent from the second stirring roller 29 to the developing magnet roller 24, and the toner in the developer is supplied to the photoconductor 6.

On the other hand, in the developing units 8a to 8d where the development is not performed, the shutter 30 is closed as in the developing units 8b to 8d in FIG. 2, and the second stirring roller 29 moves to the developing magnet roller 24. The supply of the developer is stopped, and the developer remaining on the developing magnet roller 24 is collected by the conveying magnet roller 27 in the peripheral portion of the first stirring roller 28.

Next, the operation of the developing device of the present invention will be described based on the flowchart shown in FIG.

This flow chart is for the warm-up of the copying machine. In step 1, the developing magnet roller of the developing device is used.
The operation of the drive system for rotating the 24, the transport magnet roller 27, the first stirring roller 28, and the second stirring roller 29 is started.
Subsequently, in step 2, the cylindrical shutter 30 is rotated to be in the open state, and the developer is transferred to the developing magnet roller 24, as described above.
The transport magnet roller 27, the first stirring roller 28, and the second stirring roller 29 rotate to circulate in the developing tank main body 21. Then, in step 3, the toner concentration is detected, and if the toner concentration is less than the specified farm level, the process proceeds to step 4 and the toner replenishing roller.
Rotate 36 to replenish the toner. If the toner density is the specified value in step 3, the process proceeds to step 5-1 where the supporting shutter 30 is opened, and the shutter 30 is rotated n times from step 5-3 to step 5-n to open and close. The rear shutter 30 is repeatedly closed, and then the operation of the drive system is stopped.

In the conventional developing device, step 5 in the above flowchart
After closing the shutter at -1, no more opening and closing,
Although the developer is collected above the shutter mechanism and the rear drive system is stopped, in the present invention, steps 5-2 to 5- are performed before the shutter is closed and the drive system is stopped in step 5-1. It is characterized in that the cylindrical shutter 30 is rotated by n to open and close a predetermined number of times, then the shutter is closed and the developer is collected above the shutter mechanism to stop the drive system. Therefore, the developer existing in the portion A between the shutter portion and the inner wall of the developing tank main body 21 is sufficiently agitated by the opening / closing operation by the rotation of the shutter 30, and a uniform toner concentration can be obtained as a whole.

In the above flow chart, an example of warm-up of the copying machine is shown, but the present invention is not limited to this case, and the opening / closing operation of the shutter is performed even when the drive system is stopped, for example, when the developing operation is completed. . That is, after the latent image on the photosensitive belt is developed, the shutter is opened and closed a predetermined number of times and then the shutter is closed to collect the developer on the upper part of the shutter mechanism 30, and then the drive system of the developing magnet roller 24 and the transport magnet roller 27 is changed. It stops and prepares for the next developing operation.

In the experiment, if the shutter 30 was opened and closed 7 times or more, the stirring failure was completely eliminated and the unevenness on the copy could be completely eliminated.

<Effect> Therefore, in the developing device having the shutter mechanism, it is possible to prevent the defective stirring which is likely to occur between the shutter mechanism and the inner wall of the developing tank, and it is possible to eliminate the uneven copy caused by the defective stirring.

[Brief description of drawings]

FIG. 1 is a flow chart showing the operation of the developing device of the present invention, and FIGS. 2 and 3 are sectional views of the developing device in which the present invention is carried out and a front view showing the internal structure of a copying machine having the developing device. FIG. 4 is a sectional view showing the structure of a conventional developing device. 22 …… Development magnet roller, 26 …… Conveying magnet roller, 30 …… Shutter mechanism.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G03G 15/09 G03G 15/09 Z

Claims (1)

(57) [Claims] 1. A developing magnet roller for supplying a developer onto a photosensitive member, a shutter mechanism for switching the supplying and stopping of the developer to the developing magnet roller, and a rotating cylinder of the developing magnet roller. In a developing device having a carrying magnet roller for receiving the developer and transferring and depositing the developer in the space above the shutter mechanism, the shutter mechanism is opened after rotating the developing magnet roller and the carrying magnet roller during warm-up. Toner concentration is detected with, and if the toner concentration is a specified value,
A developing device in which the shutter mechanism is opened and closed a predetermined number of times after the shutter mechanism is once closed and before the developing magnet roller and the transport magnet roller stop rotating.