JPH085479Y2 - Developing device for electrophotographic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a developing device provided in an electrophotographic apparatus such as an electrostatic transfer copying machine or a laser printer.

[Conventional technology]

2. Description of the Related Art Some conventional developing devices for electrophotographic apparatuses include a developing magnet roller, a developer conveying magnet roller, and a developer mixing roller.

Each of the developing magnet roller and the developer conveying magnet roller has a thin cylindrical sleeve rotatably fitted on a cylindrical magnet. The developer is attracted to and adheres to the sleeve by the magnetic force of the magnet, and moves as the sleeve rotates.

By the movement of the developer, the developing magnet roller develops the charged latent image formed on the photoreceptor when the developer passes in the vicinity of the photoreceptor, while the conveying magnet roller develops the latent image. The developer after being carried is drawn up from the developing magnet roller and conveyed.

Further, in order to efficiently convey the developer to the mixing roller, the magnet constituting the above-mentioned conveying magnet roller is fixedly provided so that the magnetic poles are located near the developing magnet roller and the mixing roller.

On the other hand, in JP-A-53-48534, there is provided a carrying magnet roller for drawing up the developer agitated by the mixing roller with a magnetic force and attracting the developer magnet force with the magnetic force, and the carrying magnet roller is built in. A developing device capable of rotating a magnet is disclosed.
According to this developing device, the supply of the developer from the transport magnet roller to the developing magnet roller can be stopped and the developer can be stopped by rotating the magnet so that the magnetic pole of the magnet moves away from the mixing roller. The influence of the magnetic force of the magnet on the stirring of can be reduced.

Also, in Japanese Patent Laid-Open No. 54-109846, a developing magnet roller arranged near the photoconductor is provided with a carrying magnet roller for magnetically drawing up the developer, and a magnet is provided inside the carrying roller. Disclosed is a developing device provided so as to rotate between a developer supply position and a supply stop position.

[Problems to be solved by the invention]

However, in the conventional developing device in which the magnet constituting the conveying magnet roller is fixed, since the magnetic pole is fixed at a position close to the mixing roller, this magnet is used when stirring and mixing the developer by the mixing roller. However, there is a problem in that the quality of the copied image deteriorates because proper agitation is not formed on the outer peripheral surface of the developing magnet roller due to the influence of the magnetism of the developer, which hinders sufficient stirring and mixing. Was there.

Further, in the developing device disclosed in Japanese Patent Laid-Open No. 53-48534, the magnet rotates because the magnetic pole of the magnet built in the conveying magnet roller moves away from the mixing roller. Stirring
The problem of hindering mixing seems to have been resolved. However, a part of the transport magnet roller is always in contact with the developer accumulated in the lower part of the developing tank. This is an indispensable configuration because the carrying magnet roller has a role of pumping up and supplying the developer to the developing magnet roller. Therefore, when the amount of accumulated developer is large or when the amount of accumulated developer is uneven, the developer approaches or contacts the magnetic pole. Therefore, this configuration cannot sufficiently solve the problem that the magnetism of the magnet affects the stirring and mixing of the developer.

Furthermore, it is difficult to completely shut off the supply of the developer to the developing magnet roller because a part of the conveying magnet roller is always in contact with the accumulated developer, and unnecessary developing on the surface of the photosensitive member. The agent may adhere.

In particular, as shown in FIGS. 1 and 2 of the publication, the magnet 7 in the magnetic roller 4 is rotated from the supply position shown in FIG. 1 to the supply stop position shown in FIG. Since the scraping of the developer from the surface of the magnetic roller 4 is started, the developer drawn up from the magnetic roller 4 to the magnetic roller 3 is scraped onto the magnetic roller 4 by the shaping plate 11 and then again. Pumping up to the magnetic roller 3 is repeated.

Further, in the developing device disclosed in Japanese Patent Laid-Open No. 54-109846, for example, as shown in FIG. 5 of the publication, since the half body of the pumping sleeve 15 rotates in the developer, the inside of the pumping sleeve 15 is rotated. The developer is likely to adhere to the magnet 16a below. The developer once attached to the magnet 16a is delivered to the developing sleeve 3 as the scooping sleeve 15 rotates.

As described above, in the conventional developing device, it is difficult to sufficiently solve the problem that the magnetism of the conveying magnet roller affects the stirring and mixing of the developer, and the developer supply to the developing magnet roller is completely cut off. In addition, it is difficult to prevent unnecessary developer from adhering to the surface of the photoconductor, so that it is difficult to always obtain good copy image quality.

[Means for solving problems]

In order to solve the above problems, the developing device of the electrophotographic apparatus according to the present invention is agitated by a mixing roller for agitating the developer, a developing magnet roller for supplying the developer to the photoconductor, and an agitating roller. The magnetic roller for conveyance, which is provided at a position separated from the developer, collects the developer by the magnetic force from the magnet roller for development and conveys the developer to the mixing roller, and the magnetic machine included in the magnet roller for conveyance is rotated. Drive means (eg,
A developing tank for developing the charged latent image formed on the photoconductor, and a magnetic pole of the conveying magnet roller when the developing tank is in the developing state. The driving means is operated so as to be located close to the magnetic poles and the mixing roller, while the carrying magnet roller is used after the developing tank finishes the development and the carrying magnet roller collects the developer on the developing magnet roller. And a control means for operating the drive means so that the magnetic pole is located at a position away from the mixing roller.

[Operation] With the above configuration, when the developing tank provided with the driving means is in the developing state, the driving means is operated by the control of the control means, and the magnetic pole of the conveying magnet roller is mixed with the magnetic pole of the developing magnet roller. It is set so as to be located close to the roller. Therefore, the excess developer that has not been transferred to the photoconductor is efficiently collected by the transport magnet roller and then returned to the mixing roller.

On the other hand, if the developer supply to the developing magnet roller is cut off at the same time when the developing tank finishes developing, the carrying magnet roller has a function of magnetically collecting the developer on the developing magnet roller. Therefore, the developer on the developing magnet roller is completely collected. Therefore, there is no fear that unnecessary developer will adhere to the photoconductor after the development is completed.

Further, after the developer on the developing magnet roller is collected, the driving means is operated by the control of the control means, and the magnetic pole of the conveying magnet roller is set so as to be positioned away from the mixing roller. Moreover, the transport magnet roller is provided at a position separated from the developer agitated by the mixing roller.
Therefore, the influence of the magnetic field generated by the magnetic poles of the transport magnet roller on the stirring and mixing of the developer is sufficiently reduced, and the developer that is sufficiently stirred and mixed is supplied to the developing magnet roller during development.

Due to these effects, the developing device of the present invention can surely avoid the deterioration of copy image quality such as uneven density.

〔Example〕

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

As shown in FIG. 2, the developing device has a developing tank 12 on the upper surface side of the photoconductor 11 on which a charged latent image is formed by exposure.
Is installed. A mixing roller 14 is provided in the upper part of the casing 13 in the developing tank 12 so that the developer in the developing tank 12 and the toner dropped from a toner hopper (not shown) provided in the upper part of the developing tank 12 are mixed. There is.

Below the mixing roller 14, an agitator 15 for stirring the developer is provided. A rotatable shutter member 16 is externally fitted to the agitator 15. Shutter member
Openings 16a and 16a are formed in the opening 16, and the developer passages 17 and 18 are opened and closed by rotating the shutter member 16.

A developing magnet roller (hereinafter referred to as a developing roller) 21 for developing the charged latent image formed on the photoconductor 11 is provided obliquely below the agitator 15. The developing 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 carries the developer sent from the developer passage 18 to the vicinity of the photoconductor 11. An opening 13a is formed in the bottom of the casing 13 near the developing 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 side of the developing roller 21, and the developer carried to the vicinity of the photoconductor 11 is rectified by the gap between the doctor plate 24a and the developing roller 21.

Above the developing roller 21, a magnet roller (hereinafter referred to as a carrying roller) 27 for carrying the developer, which is separated from the shutter member 16 by a separator 26, is provided. The carrying roller 27 includes a magnet 28 having three magnetic poles formed on the outer periphery thereof, and a sleeve fitted on the magnet 28.
It consists of 29 and.

The sleeve 29 is connected to a motor 31 as shown in FIG. 1, and is driven by the motor 31 to rotate, thereby drawing up the developer after development from the developing roller 21,
It is designed to be conveyed toward the mixing roller 14.

The magnet 28 has a rotating shaft 28a, and the rotating shaft 28a
Is connected to a solenoid 33 and a tension spring 34 via a lever 32.

In the above structure, when the developing tank 12 is in the developing state,
A motor (not shown) rotates the mixing roller 14, the agitator 15, and the sleeve 23 of the developing roller 21 in the directions shown by arrows A to C in FIG. Further, the shutter member 16 is rotated so that the openings 16a, 16a are closed by the developer passages 17 ,.
Open 18

On the other hand, under the control of the control means 35, the motor 31 and the solenoid 33 are actuated, the sleeve 29 of the carrying roller 27 is rotated in the direction indicated by the arrow D, and the magnet 28 is rotated, so that the position S ₁ shown in FIG.・ Upper and lower pole machines are positioned at S ₁ . That is, the upper magnetic pole is close to the mixing roller 14,
The lower magnetic pole is located close to the magnetic pole of the developing roller 21.

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

The developer attached to the outer surface of the sleeve 23 moves with the rotation of the sleeve 23, is rectified by the doctor portion 24a of the bottom plate 24, and then reaches the vicinity of the photoconductor 11. In the vicinity of the photoconductor 11, the developer forms spikes, which causes the photoconductor 11 to rise.
The charged latent image formed on is developed.

After developing the charged latent image, the excess developer further moves as the sleeve 23 rotates and reaches directly below the transport roller 27. Immediately below the transport roller 27, the developer is attracted by the magnetic field of the magnet 28 in the transport roller 27, and adheres to the outer surface of the sleeve 29.

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 roller 21.

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

Here, the lower magnetic pole of the magnet 28 of the transport roller 27 is positioned near the magnetic pole of the developing roller 21, and the upper magnetic pole of the magnet 28 of the transport roller 27 is positioned near the mixing roller 14. Therefore, the excess developer after developing the charged latent image is efficiently conveyed.

On the other hand, when the developing tank 12 is in the non-developing state, as shown in FIG.
・ Close 18. Therefore, the supply of the developer to the developing roller 21 is completely cut off, the spikes due to the developer are not formed, and all the developer on the developing roller 21 is collected by the conveying roller 27 and conveyed to the mixing roller 14.

In this way, when all the developer on the developing roller 21 is collected and conveyed to the mixing roller 14, the solenoid 33 is released by the control of the control means 35, and the magnet 28 in the conveying roller 27 causes the magnet 28 to rotate by a pulling spring. The upper and lower magnetic poles of the magnet 28 are positioned at the positions S ₂ and S ₂ as shown in FIG. 3, and the upper magnetic pole is moved away from the mixing roller 14. Moreover, the mixing roller 14 and the shutter member 16 are separated from the conveying roller 27 by the separator 26. Therefore, the magnetic field of the magnet 28 of the carrying roller 27 does not affect the stirring and mixing of the developer by the mixing roller 14, and the deterioration of the copy image quality such as the image density unevenness can be avoided. In this case,
The position of the lower magnetic pole of the magnet 28 need not be considered because the developer has already been conveyed.

[Effect of device]

As described above, the developing device of the electrophotographic apparatus according to the present invention is separated from the mixing roller that agitates the developer, the developing magnet roller that supplies the developer to the photoconductor, and the developer that is agitated by the mixing roller. And a drive means for rotating the magnetic poles of the transfer magnet roller, the transfer magnet roller being provided at a predetermined position to collect the developer by the magnetic force from the development magnet roller and transfer the developer to the mixing roller. , A developing tank for developing the charged latent image formed on the photoconductor, and when the developing tank is in the developing state, the magnetic poles of the conveying magnet roller are positioned close to the magnetic poles of the developing magnet roller and the mixing roller. While the driving means is actuated, the developing tank finishes the development and the transport magnet roller moves to the current position on the developing magnet roller. After agent was recovered has a configuration and a control means for operating the drive means so as to be positioned at a position where the magnetic poles of the transport magnet roller moves away from the mixing roller.

As a result, when the developing tank equipped with the driving means is in the developing state, the developer is efficiently conveyed, while when the developing is completed, the supply of the developer from the mixing roller to the developing magnet roller is shut off. In this case, the carrying magnet roller can completely collect the developer from the developing magnet roller. As a result, there is no risk of unnecessary developer adhering to the photoreceptor after the development is completed.

In addition, after the developer is collected from the developing magnet roller, the magnetic poles of the magnets forming the carrying magnet roller are located away from the mixing roller, and the carrying magnet roller is agitated by the mixing roller. Since it is provided at a position separated from the developer, it is possible to reliably prevent the situation where the magnetic field of the transport magnet roller adversely affects the stirring and mixing of the developer. Therefore, the developer magnet roller of the developing tank in the developing state is supplied with the developer which is sufficiently agitated and mixed, and an appropriate bristling is formed on the outer peripheral surface of the magnet roller for development.

As a result, the developing device of the present invention has various effects that it is possible to avoid deterioration of copy image quality such as uneven image density and always obtain good copy image quality.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a block explanatory view showing a structural relationship of a magnet roller, a drive means and a control means, FIG. 2 and FIG.
Each drawing is a sectional front view showing the structure of the developing tank. 11 is a photoconductor, 12 is a developing tank, 14 is a mixing roller, 21 is a developing magnet roller, 27 is a conveying magnet roller, 22 and 28 are magnets, 33 is a solenoid, and 35 is a control means.

Claims (1)

[Scope of utility model registration request] 1. A mixing roller for agitating a developer, a developing magnet roller for supplying a developer to a photoconductor, and a developing magnet roller provided at a position separated from the developer agitated by the mixing roller. Developing a charged latent image formed on a photoconductor, which has a transport magnet roller that collects the developer by magnetic force and transports the developer to the mixing roller, and a drive unit that rotates a magnetic pole of the transport magnet roller. When the developing tank is in the developing state, the driving means is operated so that the magnetic pole of the conveying magnet roller is located close to the magnetic pole of the developing magnet roller and the mixing roller, while the developing tank is operated. After the development is completed and the carrying magnet roller collects the developer on the developing magnet roller, the carrying magnet roller And a control means for operating the driving means so that the magnetic pole is located at a position away from the mixing roller.