JPS622314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing device for an electronic copying machine,
In particular, the present invention relates to a dry developing device using a magnetic brush including a rotatable sleeve and a magnet fixedly disposed within the sleeve.

As a dry developing device for an electronic copying device, one using a so-called magnetic brush, which includes a rotatable sleeve and a magnet fixedly arranged within the sleeve, is known. A two-component developer consisting of a carrier of iron powder and toner is held in the form of brush-like ears on the outer peripheral surface of the sleeve by the magnetic action of the magnet, and as the sleeve rotates, it is directed toward the photoreceptor. The developing agent is transported and brought into direct contact with the photoconductive layer of the photoreceptor to perform a developing action. A developing device including this type of magnetic brush has the advantage of having a strong developer conveying force, but it also has the problem of easily producing step unevenness. This becomes more noticeable as the speed increases.
In contrast, conventionally, two magnetic brushes as described above are provided adjacent to each other, each facing the photoconductive layer of the photoreceptor, and the substantial contact area between the photoreceptor and the magnetic brush is increased. The idea is to solve such problems. In this case, generally, of the two magnetic brushes, the first magnetic brush on the leading side in the moving direction of the photoreceptor draws up the developer from the developer tank, and the first magnetic brush on the lag side in the moving direction of the photoreceptor than the first magnetic brush. The second magnetic brush located in the second magnetic brush is adapted to receive the developer that has been drawn up by the first magnetic brush and passed through the contact portion with the photoreceptor.

Although such a dry developing device achieves its intended purpose, if the developer is not transferred smoothly between the first magnetic brush and the second magnetic brush, the transfer portion may be damaged. The developer stagnates and the developer delivery area changes, resulting in
This causes problems such as fluctuations in development conditions, unstable development performance, and increased rotational load on the magnetic brush.

The present invention was proposed in view of the above-mentioned problems in conventional developing devices, and it is an object of the present invention to provide a developing device that is improved so that developer can be transferred smoothly between magnetic brushes. The purpose is

According to the present invention, a plurality of sleeves are arranged opposite to the photoreceptor and adjacent to each other and are rotatable in the same direction, and a magnet is fixedly arranged in each of the sleeves. In a dry developing device of an electronic copying apparatus, the dry developing device has a magnetic brush including a magnetic brush, and is adapted to transfer the developer on the upstream sleeve onto the downstream sleeve in the developer moving direction. The plurality of magnetic brushes can be achieved by a dry developing device in which the sleeves are rotated at different speeds, specifically, the speeds of the outer peripheral surfaces of the sleeves are gradually increased in the direction of movement of the developer. be done.

In this case, the rotational speed of each sleeve of the plurality of magnetic brushes is set so that the speed of the outer peripheral surface of the sleeve on the side where the developer is delivered is higher than that of the sleeve on the side where the developer is delivered. It's okay to stay. Therefore, in this case, the developer that has been conveyed to the developer transfer section between each sleeve is quickly removed by the next sleeve, so that the developer is prevented from staying in the developer transfer section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

The illustrated copying apparatus includes a cylindrical photoreceptor 1, and a photoconductive layer 2 is formed on the outer peripheral surface of the photoreceptor 1. The photoreceptor 1 is driven to rotate at a constant speed in the direction of the arrow around a shaft 3, and when passing through a charger 4, its photoconductive layer 2 is uniformly charged with a predetermined charge. The optical image of the image to be copied is projected onto the surface of the charged photoconductive layer 2, forming an electrostatic latent image on the photoconductive layer 2. Thereafter, the photoreceptor 1 passes through a dry developing device 5, where a two-component developer containing electrostatically charged toner is adsorbed onto the surface of the electrostatic latent image, and the electrostatic latent image is transferred to the toner. Visualized by . The visible image is guided by guide plates 6, 7, and 8 and transferred to the surface of the transfer paper sent to the transfer section by a pair of registration rollers 9 in synchronization with the rotation of the photoreceptor 1. Electrostatic transfer is performed by the charger 10. The transfer paper that has been transferred is transferred to a separation charger 11 and a separation air nozzle 12.
is separated from the outer peripheral surface of the photoreceptor 1 by the ejected air flow, and is conveyed by a conveyor belt 13 toward a fixing device (not shown). On the other hand, when the photoreceptor 1 that has been transferred passes through a cleaning device 14 provided next, the developer remaining on the outer peripheral surface of the photoreceptor 1 is removed. As shown in the figure, the cleaning device 14 includes a cover 15, a cleaning blade 16, and a cleaning roller 17.
and a helical roller 18 for discharging the removed material. Further, the photoreceptor 1 that has passed through the cleaning device 14 passes through a static elimination charger 19 that is provided adjacent to the lag side of the photoreceptor drum rotation direction of the charger 4, and at this time, the photoreceptor 1 passes through the charger 4, which is disposed adjacent to the lag side of the photoreceptor drum rotation direction. The remaining charge is removed and preparations are made for the next copying cycle.

The dry type developing device 5 includes a developer tank 20 that stores a two-component developer consisting of electrostatically charged toner and an iron powder carrier carrying the toner. Equipped with two magnetic brushes. That is, in the developer tank 20 there are first and second developing sleeves 21,
22 are mounted in such a manner that they can rotate about their respective central axes. Each of the first and second developing sleeves 21 and 22 is arranged so that a part of its outer peripheral surface faces the photoconductive layer 2 of the photoreceptor 1 with a predetermined small interval, and the outer peripheral surface of both sleeves The other parts are arranged to face each other with a predetermined small interval. In this embodiment, three-pole magnets 23 and 24 having a T-shaped cross section and having one N magnetic pole and two S magnetic poles are fixedly arranged in the first and second developing sleeves 21 and 22. There is. The developer stored in the developer tank 20 is stirred by a stirring device 25, and the first developing sleeve is driven to rotate counterclockwise in the figure (the direction opposite to the rotation direction of the photoreceptor 1). The first developing sleeve 2 is held like a brush-like ear by the action of the magnet 23 on the outer peripheral surface of the first developing sleeve 21.
After the height of the ears is adjusted by the doctor plate 26 as the drum 1 rotates, it is conveyed toward a portion facing the photoconductive layer 2, where it comes into direct contact with the photoconductive layer 2 and performs a developing action. A portion of the developer adheres to the surface of the photoconductive layer 2 in the area where the first developing sleeve 21 and the photoconductive layer 2 face each other, but some of the developer does not adhere to the surface of the photoconductive layer 2 there. The developer is continuously held on the outer circumferential surface of the first developing sleeve 21 and conveyed to a portion facing the second developing sleeve 22. The developer that has been sent up to this point transfers to the outer circumferential surface of the second developing sleeve 22, which is also rotated counterclockwise in the figure, and is held on the outer circumferential surface like a brush-shaped ear. As the second developing sleeve 22 rotates, it is transported toward the opposing portion of the photoconductive layer 2, where it is again directly connected to the photoconductive layer 2 to perform a developing action. The developer that has not adhered to the surface of the photoconductive layer 2 is scraped off from the outer peripheral surface of the second developing sleeve 22 by the scraping plate 27 and collected into the developer tank 20. In this case, the rotational speed of the second developing sleeve 22 is set so that its outer peripheral surface speed is faster than that of the first sleeve 21 by a predetermined amount. The first developing sleeve 2
1 and the second developing sleeve 22 are conductive belts,
Alternatively, they may be configured to be interlocked and connected to each other by gears or the like and driven by a single electric motor, and in this case, by appropriately setting the reduction ratio of the transmission belt or gear between the two sleeves. good. Further, the second developing sleeve 22 is similar to the first developing sleeve 2.
In this case, even if both sleeves are driven to rotate at the same rotation speed, the outer peripheral surface speed of the second developing sleeve 22 is higher than that of the first developing sleeve 21. It gets bigger than that.

A cover 28 and seal members 29 and 30 are provided around the developer tank to prevent the developer from scattering to the outside. Further, in the illustrated embodiment, the second developing sleeve 22
The scraping plate 27 is brought into contact with the sleeve to scrape off the developer from the sleeve circumferential surface. However, depending on the set position of the magnetic pole of the magnet 24, the developer naturally falls from the sleeve circumferential surface. There is no particular need for a scraping plate to scrape off the agent. However, this scraping plate is useful for forming a flow of developer falling from the sleeve into the tank and promoting circulation and stirring of the developer in the developer tank.

As described above, according to the present invention, since the outer circumferential surface speed of the developing sleeve on the side where the developer is delivered is faster than that of the developing sleeve on the side where the developer is delivered, the developer is not easily transferred between the two sleeves. This prevents the developer from stagnation in the sleeves, and allows smooth transfer of the developer between the sleeves. As a result, the multi-stage magnetic brush type dry developing device works effectively, and a good and stable developing effect can be obtained.

In the above description, a cylindrical photoreceptor is shown, but the photoreceptor referred to in the present invention is an endless belt-shaped photoreceptor, or a photoreceptor having a photoconductive layer formed on a support such as paper. It also includes so-called photosensitive paper.

[Brief explanation of the drawing]

The attached figure is a schematic diagram showing one embodiment of an electronic copying apparatus incorporating a dry developing device according to the present invention. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Photoconductive layer, 3... Shaft, 4... Charger, 5... Dry developing device, 9... Registration roller pair,
10...Transfer charger, 11...Separation charger,
14... Cleaning device, 19... Static eliminator, 20
...developer tank, 21...first developing sleeve,
22... Second developing sleeve, 23, 24... Three-pole magnet, 25... Stirring device, 26... Doctor plate, 2
7...Developer scraping plate.

Claims (1)

[Claims] 1. A magnetic brush including a plurality of sleeves that are arranged opposite to the photoreceptor and adjacent to each other and are rotatable in the same direction, and a magnet fixedly arranged in each of the sleeves, In a dry-type developing device of an electronic copying device, in which the developer on the sleeve on the upstream side in the direction of developer movement is transferred onto the sleeve on the downstream side, the plurality of magnetic brushes transfer the developer. A dry developing device characterized in that the outer peripheral surface speed of the sleeve is set higher as the sleeve is disposed downstream in the moving direction.