JPH087496B2 - Developing device for electrophotographic device - Google Patents

Description

The present invention relates to a developing device used in an electrophotographic apparatus such as an electrostatic transfer copying machine or a laser printer.

[Conventional technology]

In a conventional developing device of an electrophotographic apparatus, a developing magnet roller that develops a charged latent image by a toner that is electrostatically attached to a developer that is conveyed by a magnetic force, and a developer from the developing magnet roller. It was conceivable that the transporting magnet roller of 1) was provided in the developing tank.

Each of the developing magnet roller and the conveying magnet roller is formed by a thin cylindrical sleeve rotatably fitted on a cylindrical magnet. In this sleeve, the developer is attracted to and adheres to the outer peripheral surface of the sleeve by the magnetic force of the magnet, and moves in the circumferential direction of the sleeve as the sleeve rotates.

By moving the developer with toner attached,
In the developing magnet roller, when the developer passes in the vicinity of the charging belt, the charged latent image formed on the charging belt is developed by the toner, while in the conveying magnet roller, the developer after development is performed. In order to reuse the sheet, the sheet is conveyed from the developing magnet roller along the inner wall of the developing tank.

Further, in order to efficiently convey the developer, the magnet constituting the conveying magnet roller is provided with its magnetic pole fixed near the developer conveying path, that is, toward the inner wall of the developing tank. It was

[Problems to be solved by the invention]

In the developing device of the above-mentioned conventional electrophotographic device,
Since the magnet constituting the transport magnet roller is provided so that its magnetic pole is located near the developer transport path, that is, fixed toward the inner wall of the developer tank,
The magnetic field of the magnet may greatly affect the outside of the developing tank depending on the position where the developer transport path is provided.

On the other hand, in recent years, an electrophotographic apparatus including a plurality of developing tanks such as a color copying machine has been widely used. for that reason,
The developing tanks may be provided close to each other, and in particular, another developing tank is often provided at a position close to the carrying magnet roller.

In this case, in another developing tank in the developing state, the flow of the developer in the other developing tank is affected by the magnetic field of the magnetic poles of the magnets constituting the transport magnet roller provided in the adjacent developing tank. May become unstable.

Therefore, in the above-described electrophotographic apparatus having a plurality of conventional developing tanks, the developer is not stably supplied to the developing magnet roller, and proper spikes are not formed on the outer surface of the developing magnet roller. However, there is a problem in that the obtained image becomes unstable because the image density tends to be uneven and the toner tends to be scattered.

[Means for solving problems]

In order to solve the above problems, the developing device of the electrophotographic apparatus according to the present invention has a plurality of developing tanks for sequentially developing a charged latent image by using a developer conveyed by magnetic force, which are close to each other. In the developing device of the electrophotographic apparatus, the developing magnet roller for developing the charged latent image is provided so as to convey the developer along the circumferential direction of the developing magnet roller. In order to reuse the developer from the developing magnet roller, the carrying magnet roller that carries the developer along the inner wall of the developing tank by magnetic force has the magnetic pole of the magnet that generates the magnetic force on the outer circumference of the carrying magnet roller. The magnetic pole of the magnet in the carrying magnet roller is coaxial with the axis of the carrying magnet roller. Is provided in a developing tank having the inner wall in a position close to another developing tank, and when the developing tank having the driving means is in a developing state, the magnetic pole of the magnet is the inner wall. And a control means for activating the driving means so that the magnetic pole of the magnet is set back to the inner wall when the developing tank is not in the developing state. It has a feature.

[Action]

With the above configuration, when the developing tank provided with the driving means is in the developing state, the magnetic pole of the magnet is formed in a part of the outer circumference of the transport magnet roller in the circumferential direction, and the magnetic pole is the magnetic pole of the transport magnet roller. Since it is provided so as to rotate coaxially with the shaft, the drive means is activated by the control of the control means, and the transport magnet roller that serves as a transport path for the developer from the development magnet roller and the inner wall of the developing tank are provided. The magnetic pole of the magnet of the transport magnet roller can be set so as to face the inner wall. Therefore, the developer is efficiently transported in the developing tank.

On the other hand, in the above configuration, when the developing tank provided with the driving unit is no longer in the developing state, the driving unit is operated by the control of the control unit, and the magnetic pole of the magnet of the conveying magnet roller is set back to the inner wall. That is, it can be set so as to be positioned away from other developing tanks. Therefore, the influence of the magnetic field of the magnetic pole of the magnet on other developing tanks can be suppressed.

Therefore, in the above configuration, even if another developing tank adjacent to the developing tank is in the developing state, in the developing tank which is no longer in the developing state, the magnetic poles of the developing tank are opposed to the inner wall. It is possible to reduce the instability of the flow of the developer in another developing tank in the developing state due to the influence of the magnetic field of the magnetic pole of the magnet of the use magnet roller.

Therefore, in the above-described configuration, the developer is stably supplied to the developing magnet roller of the developing tank in the developing state, and the proper spikes of the developer are formed on the outer surface of the developing magnet roller. It is possible to reliably prevent the unevenness of the toner and the scattering of the toner.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 2, a developing tank 12 is provided on the upper surface side of the charging belt 11 on which a charging latent image is formed by being exposed. A mixing roller 14 is provided in the upper part of the casing 13 in the developing tank 12 so as to mix the developer in the developing tank 12 with the toner dropped from a toner hopper (not shown) provided above the developing tank 12. There is.

Below the mixing roller 14, an agitator 15 that stirs the toner and the developer is provided. Agitator 15
A rotatable shutter member 16 is externally fitted to this. Openings 16a, 16a are formed in the shutter member 16, and the developer passages 17, 18 are opened and closed by rotating the shutter member 16.

A developing magnet roller 21 for developing the charged latent image formed on the charging belt 11 with toner is provided obliquely below the agitator 15. The developing magnet roller 21 includes a magnet 22 having five magnetic poles formed on the outer circumference.
And a rotatable sleeve 23 fitted onto the magnet 22. The sleeve 23 is rotated by the operation of a motor (not shown) and conveys the developer sent from the developer passage 18 to the vicinity of the charging belt 11.

An opening 13a is formed in the bottom of the casing 12 near the developing magnet roller 21.
The side of the developer passage 18 in the opening 13a is covered with a bottom plate 24 having a toner sensor 25. A doctor portion 24a is formed at the end portion of the bottom plate 24 on the developing magnet roller 21 side, and the gap between the developing magnet roller 21 and the developing magnet roller 21 rectifies the developer carried in the vicinity of the charging belt 11. There is.

A separator 26 is provided above the developing magnet roller 21.
A magnet roller 27 for transporting the developer is provided which is separated from the shutter member 16 by. The transport magnet roller 27 is composed of a magnet 28 having three magnetic poles formed on the outer peripheral half and a sleeve 29 fitted on the magnet 28.

The sleeve 29 is connected to a motor 31 as shown in FIG. 1, and is driven by the motor 31 to rotate so that the developer after development is attracted from the developing magnet roller 21 by magnetic force, It is designed to be conveyed toward the mixing roller 14.

The rotation shafts of the magnet 28 and the sleeve 29 are connected via a spring clutch 32. With this spring clutch 32 and motor 31, the magnet 28
The driving means of the motor 31 is configured so that the driving force of the motor 31 is
29, and magnet 28 via spring clutch 32
The magnet 28 can be rotated. The motor 31 and the spring clutch 32 are
Both are connected to the control means 33.

On the other hand, a developing tank 42 is provided adjacent to the side of the developing tank 12. This developing tank 42, like the developing tank 12,
A casing 43 having an opening 43a, a mixing roller 44, an agitator 45, a shutter member 46 having openings 46a and 46a, a developing magnet roller 51 including a magnet 52 and a sleeve 53, and a magnet 58. A bottom plate 54 provided with a toner sensor 55 and a transport magnet roller 57 including a sleeve 59 and a doctor portion 54a.
And a separator 56.

In the above configuration, when the developing tank 12 is in the developing state,
A mixing roller 14, an agitator 15, and a sleeve 23 of the developing magnet roller 21 by a motor (not shown).
Rotate in the directions indicated by arrows A to C, respectively. Also,
The shutter member 16 rotates so that the openings 16a and 16a are connected to the developer passage.
Open 17 ・ 18.

On the other hand, under the control of the control means 33, the motor 31 and the spring clutch 32 are actuated, and the transport magnet roller is
As the sleeve 29 of 27 rotates in the direction indicated by the arrow D, the magnet 28 rotates so that the magnetic pole is located on the side opposite to the separator 26, that is, toward the inner wall of the developing tank 12 where the conveying magnet roller 27 faces. Is set.

There, the developer is mixed and agitated with the toner by the mixing roller 14 and the agitator 15 and drops through the developer passages 17 and 18. The dropped toner and developer are attracted by the magnetic field of the magnet 22 in the developing magnet roller 21 and adhere to the outer surface of the sleeve 23.

The toner and developer attached to the outer surface of the sleeve 23 are
It moves with the rotation of the sleeve 23, and the doctor part 24 of the bottom plate 24
After being rectified by a, it reaches the vicinity of the charging belt 11. In the vicinity of the charging belt 11, ears are formed by the developer having toner, and the charged latent image formed on the charging belt 11 is developed by the toner.

The developer after being used to develop the charged latent image is
It moves with the rotation of the sleeve 23 and reaches directly below the magnet roller 27 for conveyance. Immediately below the transport magnet roller 27, the developer is
Is attracted by the magnetic field of the magnet 28 and adheres to the outer surface of the sleeve 29 of the transport magnet roller 27.

The developer attached to the outer surface of the sleeve 29 is transported as the sleeve 29 rotates, as in the case of the developing magnet roller 21. Here, the magnetic pole of the magnet 28 in the transport magnet roller 27 is on the side opposite to the separator 26 as described above, that is, in the vicinity of the developer transport path, that is, on the inner wall of the developer tank 12 facing the transport magnet roller 27. Since the position is set to face the developer, the developer is efficiently conveyed.

The developer carried to the upper side of the carrying magnet roller 27 is stripped from the sleeve 29 by the separator 26, returned to the mixing roller 14 again, and used again.
The same circulation is repeated thereafter.

On the other hand, when the developing tank 12 is in the non-developing state, as shown in FIG.
・ Close 18. Therefore, the toner and the developer do not reach the developing magnet roller 21, and the spikes due to the developer are not formed. As a result, the toner does not adhere to the charging belt 11, and the charging latent image formed on the charging belt 11 is not developed by the developing tank 12.

Further, at this time, the spring clutch 32 operates under the control of the control means 33, and the driving force of the motor 31 is transmitted to the magnet 28 via the sleeve 29 of the magnet roller 27 for conveyance and the spring clutch 32.

Therefore, the magnet 28 of the carrying magnet roller 27 rotates about 180 °, and the magnetic pole of the magnet 28 is located at a position where the magnetic pole of the magnet 28 is facing backward with respect to the inner wall of the developing tank 12 facing the carrying magnet roller 27, that is, from the developing tank 42. It is set so that the position is far away.

Therefore, even if the developing tank 42 adjacent to the developing tank 12 is in the developing state, the developing tank 42 is affected by the magnetic field of the magnet 28 of the transport magnet roller 27 of the developing tank 12 to cause The developer transport does not become unstable.

Therefore, in the developing tank 42, the developer circulates similarly to the case of the developing tank 12, and the developer is stably supplied to the developing magnet roller 51. Therefore, since the proper brushing is formed on the outer surface of the developing magnet roller 51, unevenness in image density and toner scattering can be reliably prevented in the development by the developing tank 42.

As a result, the configuration of the above embodiment can stabilize the transport of the developer in the developing tanks 12 and 42 in the developing state, respectively, and thus can stabilize the image formation in the developing tanks 12 and 42, respectively. Has become.

〔The invention's effect〕

As described above, in the developing device of the electrophotographic apparatus according to the present invention, a plurality of developing tanks having developing magnet rollers for developing the charged latent image are provided in proximity to each other, and the developing from the developing magnet roller is performed. Driving means for rotating the magnetic pole of a magnet provided on a part of the outer circumference of the transport magnet roller for transporting the agent along the inner wall of the developing tank coaxially with the axis of the transport magnet roller. Is provided in a developing tank having the inner wall at a position close to another developing tank, and when the developing tank having the driving means is in the developing state, the driving means is arranged so that the magnetic pole of the magnet faces the inner wall. On the other hand, there is provided control means for activating the drive means so that the magnetic pole of the magnet faces the inner wall when the developing tank is not in the developing state. It is configured to have.

Thus, in the above configuration, when the developing tank equipped with the driving means is in the developing state, the magnetic poles of the magnets forming the transport magnet roller are positioned so as to face the inner wall of the developing tank facing the transport magnet roller. Therefore, the magnetic field on the outer circumference of the transport magnet roller facing the inner wall can be increased, and the developer can be efficiently transported by the transport magnet roller.

On the other hand, when the developing tank provided with the driving means is not in the developing state, since the magnetic poles of the magnets constituting the transport magnet roller are located back from the inner wall, the magnetic poles are located away from other developing tanks. In the other developing tank in the developing state, it is possible to reduce the instability of the developer flow due to the influence of the magnetic field of the magnetic pole.

Therefore, in the above configuration, the developer can be stably supplied to the developing magnet roller of each developing tank in the developing state, and proper spikes are formed on the outer surface of the developing magnet roller. Uneven density,
It is possible to reliably prevent the toner from scattering and to stabilize the image formation in each developing tank.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a block diagram showing the relationship between a magnet roller, driving means and control means, FIG. 2 and FIG. FIG. 3 is a sectional front view showing a structure of a developing tank. 11 is a charging belt, 12 and 42 are developing tanks, 21 and 51 are developing magnet rollers, 27 and 57 are conveying magnet rollers, and 22 and
28, 52, 58 are magnets, 31 is a motor (driving means), 32
Is a spring clutch (driving means), and 33 is a control means.

Claims (1)

[Claims] 1. A developer conveyed by magnetic force is used,
In a developing device for an electrophotographic apparatus, in which a plurality of developing tanks for sequentially developing charged latent images are provided close to each other, in a developing magnet roller for developing charged latent images, the developer magnetic roller is used for developing the developer. A conveying magnet roller that is provided so as to be conveyed along the circumferential direction of the magnet roller and that conveys the developer by magnetic force along the inner wall of the developing tank in order to reuse the developer from the developing magnet roller. , The magnetic pole of the magnet for generating the magnetic force is provided in a part of the outer circumference of the carrying magnet roller in the circumferential direction, and the magnetic pole of the magnet in the carrying magnet roller is coaxial with the axis of the carrying magnet roller. And a driving means for rotating the developing tank is provided in the developing tank having the inner wall at a position close to another developing tank, and the driving means is provided. When the developing tank is in the developing state, the driving means is operated so that the magnetic pole of the magnet is directed toward the inner wall, while when the developing tank is not in the developing state, the magnetic pole of the magnet is directed backward from the inner wall. A developing device for an electrophotographic apparatus, which is provided with control means for activating the driving means.