JPS631582B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device in an electrophotographic device or an electrostatic recording device.

A magnetic brush developing device is a device that adsorbs a powder developer containing magnetic powder onto a developing roller to form a brush-like spike, which is brought into contact with an electrostatic latent image formed on the surface of a photoreceptor or recording material. This is the device that develops this. The developing roller usually consists of a rotating non-magnetic sleeve and a magnet having a plurality of magnetic poles around the periphery, which is statically housed within the sleeve.

It is practically important that the developing roller in the developing device adheres developer and rubs the surface of the photoreceptor only during development, and prevents the developer from coming into contact with the surface of the photoreceptor except during development. In particular, in machines that perform multicolor development such as color copying machines, if developer of another color comes into contact with the surface to be developed while developing a specific color, color mixing may occur. This must be avoided at all costs, as it can cause problems and disturbances in the developed image.

Various techniques have been proposed so far as measures to prevent the developer on the developing roller from coming into contact with the surface to be developed during non-development. One of them is one in which the developing roller is separated from the surface of the photoreceptor during non-development. A disadvantage of this technique is that the device, particularly the mechanism for keeping the gap between the developing roller and the photoreceptor surface constant, is complex and lacks stability and economy. Further, the movable members are generally large and large, and therefore it is necessary to provide a large space within the apparatus for retracting the developing roller, which is disadvantageous in terms of miniaturization of the apparatus.
Furthermore, increasing the number of parts around the photoconductor
When replacing the photoreceptor, this may damage or damage the surface of the photoreceptor.

In addition, there is a technology in which a developer scraping blade is brought into contact with the developing roller, the developing roller is reversed during non-development, and the developer is scraped off by this blade, and a blade for regulating the amount of developer can be brought into contact with and separated from the developing roller. A technique has also been proposed in which the blade is provided and the developer is brought into contact with the developing roller during non-development to scrape off the developer. In the former case, not only is the drive source complicated and expensive, but also the torque applied to the developing roller becomes very large, so that the drive and control mechanism must be complicated and large. In the latter case, although the device is simple, compact and economical, there are restrictions on the mounting position of the blade relative to the developing roller, making it more complex and lacking in stability. In addition, in order to improve the development efficiency, a bias voltage is sometimes applied to the development roller, but in this case, it is extremely difficult to take measures to electrically insulate the blade in these devices, making it more complicated. do not have. Furthermore, since the blade is in direct contact with the developing roller, the negative effects on development due to dirt, damage, or frictional charging on the developing roller cannot be ignored.Therefore, there are many restrictions on the materials, surface treatments, etc. of the developing roller and blade, and as a result, becomes expensive. These shortcomings directly affect the quality of developed images and impair the overall lifespan and reliability of the device.

This invention includes a developing container for storing powdered developer, a supply roller for holding and transporting the developer in the developer container to a developing roller, and a developing section for transferring the developer from the supply roller. In a magnetic brush developing device equipped with a developing roller for holding and conveying the developer to the developing roller, a doctor for regulating the amount of developer attached to the developing roller before development, and a scraping means for scraping off the developer on the developing roller. , the doctor is disposed downstream of the developer supply position by the supply roller in the rotational direction of the development roller during development and upstream of the above-mentioned development section, and the supply roller and development roller are driven separately. When moving to the development stage, the supply roller is first stopped from rotating, and then, after a while, the developing roller is stopped from rotating.

According to this invention, when transitioning from the developing time to the non-developing time, first the rotation of the supply roller is stopped to stop the supply of developer to the developing roller, and then the developing roller is rotated for a while so that the developer remains on the developing roller. Since the rotation of the developing roller is stopped after the accumulated developer is scraped off with a scraper, not only does the developer not come into contact with the surface of the photoreceptor during non-development, but the rotation of each roller is kept to the minimum required period of time. Therefore, there is little deterioration due to developer fatigue or fragmentation, and there is little change in electrostatic properties, etc., and there is also little developer scattering or contamination into other developing devices in the case of multicolor development. In addition, since there is almost no developer on the developing roller during non-development, there is little scattering of the developer or staining of the surrounding area by the developer during maintenance of the machine such as replacing the photoreceptor. Furthermore, since almost all the developer is collected in the container during non-development, the area or time that the developer is exposed is reduced, reducing the amount of dust and dirt that gets mixed into the developer. There is also little change in the electrostatic properties of the agent. Furthermore, since not all of the rollers are rotated all the time, the driving torque for these is also small.
Vibration and noise are also reduced, durability is increased, and the economic effects associated with this are also large.

Therefore, an object of the present invention is to provide a magnetic brush developing device having a developing roller and a supply roller, which can reliably supply and stop developer from the supply roller to the developing roller using a simple mechanism. An object of the present invention is to provide a brush developing device.

A further object of the present invention is to provide the above-mentioned apparatus which is less likely to cause scattering of developer and change in properties and is highly economically effective.

Hereinafter, the present invention will be described with reference to the attached drawings. FIG. 1 is a schematic diagram of a color copying machine to which an embodiment of the present invention is applied. Around the photoreceptor drum 1 having a photoconductive layer on its surface, a charging corona discharger 2, a yellow developing device 3, a magenta developing device 4,
A cyan developing device 5, a transfer drum 6, a cleaning device 7, and a corona discharger 8 for static elimination are arranged, respectively. The transfer drum 6 is a cylinder whose main part is formed by rolling a dielectric sheet and has the same diameter as the photoreceptor drum 1.The surface of the transfer drum 6 is in contact with the photoreceptor drum 1, and the entire body moves clockwise with the photoreceptor drum. rotate at the same speed. A transfer corona discharger 9 is disposed inside the portion of the transfer drum 6 that contacts the photoreceptor drum 1, and a transfer paper charge-eliminating corona discharger 10 and a separating claw are disposed outside the transfer drum 6 along the rotation direction. 11, a cleaning device 12, a corona discharger 13 for removing static electricity from the transfer drum, and a transfer paper conveyance device 14 are arranged, respectively.

When the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by the charging corona discharger 2, an original containing mainly yellow components that has passed through a blue filter is emitted from an exposure optical system (not shown). A light image 15 is irradiated, and the electrical charge is dissipated according to the brightness of the light image, forming an electrostatic latent image. This latent image is developed by supplying yellow developer from the yellow developing device 3. At this time, the magenta developing device 4 and the cyan developing device 5 do not perform development. On the other hand, the transfer drum 6 has
In synchronization with the image formation timing on the photoreceptor drum 1,
The transfer paper 16 sent from the transport device 14 is held and transported by the clamp device 17. Transfer paper 16
The leading end of the yellow image coincides with the leading end of the yellow image on the photosensitive drum at the position of the transfer corona discharger 9, passes under the corona discharger 9, and the yellow image is transferred to the transfer paper. After the transfer, the residual toner on the photoreceptor is removed by the cleaning device 7, and the surface of the photoreceptor is statically removed by the static-eliminating corona discharger 8, and then charged again by the charging corona discharger 2. After receiving the image, the next step is to create an image.

In the next image forming process, an optical image of the document that passes through a green filter from the exposure optical system and is mainly composed of magenta components is irradiated onto the surface of the charged photoconductor, and a latent image of magenta components is formed there. Ru. This latent image is developed by a magenta developing device 4 to obtain a magenta image on the photoreceptor. On the other hand, the transfer paper on the transfer drum to which the yellow image has been transferred is
After being neutralized by the static eliminating corona discharger 10,
It is held on the transfer drum as it is, and the separation claw 1
1. The photoreceptor rotates once without being affected by the cleaning device 12 or the corona discharger 13 for removing static electricity from the transfer drum, and is superimposed on the magenta image on the photoreceptor drum. Here, the magenta image is transferred onto the transfer paper from the yellow image by the transfer corona discharger 9.

Similarly, in the next image forming step, the photosensitive drum is irradiated with the light image that has passed through the red filter to form a latent image mainly consisting of cyan components, which is developed by the cyan developing device 5. The image is transferred over the magenta image on the transfer paper. After the transfer paper on which the cyan image has been transferred is neutralized by the static eliminating corona discharger 10, it is peeled off from the transfer drum 6 by the separating claw 11, and then enters a fixing device (not shown) to fix the transferred image. will be carried out. After the transfer paper has been separated from the transfer drum, a cleaning device 12 removes the developer adhering to the non-image area of the surface of the transfer drum, and a charge-eliminating corona discharger 13 removes residual potential.

Next, the developing device, which is the main part of this invention, will be explained. Each developer is a magnetic brush developer. In the lower part of each developing container 21, 22, 23, there are two-component developers 24, 25, 26 each consisting of a magnetic carrier and toner colored in each color.
is accommodated. In addition, spiral agitators 27, 28, and 29 are arranged in the lower part of each developing container so as to be rotatable in the counterclockwise direction, and on the side thereof, first supply rollers 30, 31,
32 are arranged. In the yellow developing device 3, a second supply roller 33, a third supply roller 34, and a developing roller 35 are arranged in sequence above the first supply roller 30, and in the magenta developing device 4 and the cyan developing device 5, Two supply rollers 36, 37 and two developing rollers 38, 39 are arranged in sequence. Each supply roller and developer roller consists of a non-magnetic sleeve that rotates in a counterclockwise direction and a magnet stationary therein. The magnetic body has a plurality of magnets,
Each magnetic pole is arranged to be oriented in a predetermined direction.

Now, considering a state where only yellow development is being performed and magenta development and cyan development are not being performed, in the yellow developing device 3, the agitator 27, each supply roller 30, 33, 34, and the developing roller 35 are all rotating. and
In the magenta developing device 4 and the cyan developing device 5, each agitator, supply roller, and developing roller all stop rotating. In the yellow developing device 3, the developer 2 in the container 21
4 is agitated by an agitator 27 and frictionally charged with the magnetic carrier so that the charged polarity of the toner in the developer is opposite to the polarity of the latent image. The toner and magnetic carrier that are attracted to each other by frictional charging are magnetically attracted to the surface of the first supply roller 30,
As it rotates, it is transported upward. The developer conveyed upward is sequentially transferred to the second supply roller 33, the third supply roller 34, and the developing roller 35, and is moved from the developer supply position by the third supply roller 34 in the rotation direction of the developing roller during development. After the adhesion amount is regulated by a doctor 40 located downstream and upstream of the developing section,
It comes into contact with the latent image on the surface of the photoreceptor 1 and develops it.
After development, the developer on the developing roller is scraped off by a scraper 41 serving as developer scraping means, falls to the lower part of the container, and circulates within the container.
New toner corresponding to the amount of toner consumed by development is appropriately supplied from a toner replenishing device 42 provided on the back side of the scraper 41, and the toner concentration in the developer is maintained appropriately.

When the development is completed, the agitator 27 and the supply rollers 30, 33, and 34 first stop rotating.
Then, since the developer is no longer supplied to the developing roller 35, the developing roller 35 continues to rotate while adsorbing only the developer already supplied on its surface and in the vicinity. At the tip, it is scraped off from the developing roller by a scraper. In this manner, the rotation of the developing roller is stopped when most or all of the developer is used up on the developing roller. The time from the stop of the supply roller to the stop of the development roller is determined taking into account that almost no developer is left on the development roller and that it is before the next development is performed by the magenta development device. During this time, in the next magenta developing device 4, the agitator 28 and each supply roller 31, 36 start rotating to stir and pump up the developer, and then the developing roller 38 starts rotating to develop magenta. will be carried out. Thereafter, the rotations of the agitator, supply roller, and developing roller are controlled in the same manner. These rotational controls are performed by operating an electromagnetic clutch or the like based on input signals from a microcomputer installed in the machine.

FIG. 2 is a schematic diagram of a black and white electrophotographic copying machine to which an embodiment of the present invention is applied.
In a black and white electrophotographic copying machine, as in a color copying machine, when the copying machine starts operating, the photoreceptor is first cleaned and then image formation is started. At this time, cleaning efficiency is better if the developer on the developing roller does not rub the surface of the photoreceptor. Therefore, even in a black-and-white copying machine, it is a good idea to stop the supply of developer to the developing roller in case of such a case. Further, when forming an image using a part of the photoreceptor, it is better to similarly prevent the developer from rubbing the photoreceptor after the development of that part is completed.

In the illustrated copying machine, first, the surface of a photosensitive drum 51 is charged by a corona discharger 52, and then a light image 53 of a document is irradiated thereon to form a latent image, which is transferred to a developing device 54. It is then developed. Next, the developed image is transferred to the transfer paper 56 by the corona discharger 55, and after the transfer, the developed image is transferred to the transfer paper 56.
is removed from the photoconductor by a separation roller 57, residual toner on the surface of the photoconductor 51 is removed by a cleaning device 58, and residual potential is removed by a corona discharger 59.

The developing device 54 includes, at the lower part of the container 61, a stirring member 62, which is composed of a large number of elliptical plates diagonally facing each other at intervals around a single rotating shaft, a spiral agitator 63, and a first supply roller. 64, a second supply roller 65 and a second development roller 66 are arranged above the first supply roller 64, and a first development roller 67 is arranged on the side of the second development roller 66, respectively. ing. Each supply roller and developer roller similarly consists of a rotating non-magnetic sleeve and a magnet stationarily housed therein.

The developer 68 stirred by the stirring member 62 and the agitator 63 is frictionally charged so that the toner and the magnetic carrier have opposite polarities. The developer conveyed upward by each supply roller 64, 65 is transferred to a second developing roller 66, then transferred to a first developing roller 67, and between the first developing roller and the second developing roller. contacts the latent image on the photoreceptor and develops it. After development, the developer on the first developing roller 67 is scraped off by the scraper 69, falls to the bottom of the container 61, and circulates within the container.

Similarly, in this developing device, when transitioning from the developing time to the non-developing time, the stirring member 62, the agitator 63, and each supply roller 64, 65 first stop rotating, and after a while, each developing roller 64, 65 stops rotating.
6 and 67 stop rotating. Therefore, when the copying operation starts, there is no developer on each developing roller, so the cleaning efficiency is good, and even in the case of partial development, the photoreceptor surface of the part that is not to be developed is The developer will not rub off.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a color copying machine to which an embodiment of the present invention is applied, and FIG. 2 is a schematic diagram of a black-and-white copying machine to which an embodiment of the invention is applied. 1... Photosensitive drum, 3... Yellow developing device, 4... Magenta developing device, 5... Cyan developing device, 6... Transfer drum, 27... Agitator,
30, 33, 34...supply roller, 35...developing roller.

Claims (1)

[Claims] 1 A developing container for storing powder developer, a supply roller for holding and transporting the developer in this developing container to a developing roller, and a supply roller for transferring the developer from this supply roller and holding and transporting it to the developing section. In a magnetic brush developing device, the doctor is equipped with a developing roller for cleaning, a doctor for controlling the amount of developer adhering to the developing roller before development, and a scraping means for scraping off the developer on the developing roller. Disposed downstream of the developer supply position by the supply roller in the development rotation direction of the development roller and upstream of the development section, the supply roller and development roller are driven separately, and the shift occurs from the time of development to the time of non-development. Sometimes, the magnetic brush developing device is characterized in that first the rotation of the supply roller is stopped, and then the rotation of the developing roller is stopped after a while.