JPH047517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a cleaning device for a photoreceptor in a dry type electrophotographic copying machine.

(Prior art) In an electrophotographic copying machine that attracts charged toner to an electrostatic latent image formed on a photoreceptor to form a developed image and transfers it to copy paper, the photoreceptor is used repeatedly. If necessary, toner remaining on the surface of the photoreceptor after transfer must be removed. A cleaning device is used to do this, and conventional cleaning devices include a rotating brush type, a blade type, and a magnetic brush type.

Since the present invention relates to an improvement of the magnetic brush type cleaning device, first, the conventional device will be explained.

FIG. 3 shows a conventional cleaning device described in Japanese Patent Publication No. 48-37382. 13
is a drum-shaped photoreceptor that rotates in the direction of the arrow.
The residual toner 11 is adsorbed on its surface. 2
0 is a magnetic brush device, which includes a non-magnetic metal sleeve 22 similar to the magnetic brush in the developing device.
and a permanent magnet 24. sleeve 2
2 rotates about an axis 26 as shown by the arrow, and the permanent magnet 24 is fixedly arranged in the position shown. plate 3
The magnetic carrier 28 housed in 2 is the same as the carrier used for two-component developer,
It is attracted to the circumferential surface of the sleeve 22 by the attraction force of the permanent magnet 24, and is conveyed as the sleeve rotates.

A corona discharger 35 acts toward the circumferential surface of the photoreceptor 13 . The polarity of the power source 37 of the corona discharger 35 is selected so as to perform discharge with the same polarity as the charged polarity of the toner 11 on the photoreceptor 13. A voltage of opposite polarity is applied.

The carrier 28 on the circumferential surface of the sleeve 22 stands up like a spike near the magnetic pole of the permanent magnet 24 and becomes a magnetic brush, and as a result of moving as the sleeve 22 rotates, the toner on the circumferential surface of the photoconductor 13 is removed. 11
is in sliding contact with the carrier 28. At this time, the toner 11 receives an electrostatic attraction force due to the voltage applied to the sleeve 22 and is attracted to the carrier 28, so that the toner 11 on the photoreceptor 13 is removed and cleaning is performed.

The carrier 28 that has absorbed the toner 11 moves as the sleeve 22 rotates, and stands up again in the shape of a spike at a position 180 degrees away. A metal drum 40 that rotates in the direction of the arrow is provided at that position, and a voltage is applied to it by a power source 44. Since this voltage is more than twice the voltage applied to the sleeve 22, the toner 11 is taken away from the carrier 22 that comes into contact with it. In this way, the toner 11 adsorbed on the metal drum 40 is conveyed as the metal drum rotates, scraped off by the blade 50 that presses against the circumferential surface of the metal drum 40, and collected in the collection container 52.

By the way, in the conventional device, it is necessary to apply a voltage of 200 to 1000 V to the sleeve 22, and since it is necessary to provide a potential difference between the metal drum 40 and the sleeve 22, an even higher voltage is applied to the metal drum 40. It is necessary to apply a voltage of 1000-2000V. However, when such a high voltage is applied, leakage occurs through the carrier, and smooth operation cannot be expected. Furthermore, if the recovery rate of toner from the carrier is not made sufficient, the rate of toner removal from the photoreceptor 13 will decrease, resulting in insufficient cleaning.
It is conceivable that the period in which the metal drum 8 is in contact with the metal drum 40 is longer than the period in which the metal drum 8 is in contact with the photoreceptor 13. However, in the conventional device, the period of contact between the carrier 28 and the metal drum 40 is approximately equal to the period of contact with the photoreceptor 13, and cannot be extended by that amount.

(Objective and Summary of the Invention) The present invention solves the above-mentioned problems, that is, it eliminates the need to apply a high voltage that would cause leakage, and extends the period of contact between the carrier and the toner collection roller. The purpose of this system is to improve the toner recovery rate and thus the cleaning performance, and it separates the magnetic brush device that attracts toner from the photoconductor and the toner recovery roller that separates the toner from the carrier. and the carrier circulates between them.
This is characterized in that the carrier is caused to flow down from above the toner collection roller so that the carrier comes into contact with the collection roller over a range of 1/4 of the circumferential surface thereof.

(Structure) Next, the present invention will be explained based on the embodiment shown in FIGS. 1 and 2. The drum-shaped photoreceptor 13 rotates in the direction of the arrow and reaches the opening 7a of the cleaning device 7 with the negatively charged residual toner 11 attached thereto. A non-magnetic metal sleeve 1 having a permanent magnet 15 fixed therein is disposed within the opening 7a, and is rotated counterclockwise. 2,
A relay sleeve 3 is made of a non-magnetic material, and like the sleeve 1, permanent magnets 16 and 17 are fixedly arranged inside.

Relay sleeve 2 is arranged diagonally above sleeve 1 and rotates clockwise. relay sleeve 3
is arranged above the relay sleeve 2 and rotates counterclockwise. Each of these sleeves 1, 2, 3 is
By rotating while attracting the magnetic carrier 28 to its peripheral surface, the carrier 2 shown by arrows A, B, and C is
8 circulation paths are formed, and its operation is similar to that of a pumping sleeve in a developing device.

A scraper 8 acts on the circumferential surface of the relay sleeve 3, so that the carrier 28 separated from the circumferential surface of the relay sleeve 3 flows down to the top of the toner collection roller 4. Reference numeral 6 denotes a guide plate for preventing the carrier 28 from exceeding the top of the collection roller 4 and flowing down to the opposite side. Toner collection roller 4
The carrier 28 flowing down from the top of the sleeve 1 flows down to the top of the sleeve 1 as shown by arrow C and accumulates there. This carrier 28 adheres to the circumferential surface of the sleeve 1 with a thickness regulated by the doctor 18, acts as a magnetic brush, sweeps the surface of the photoreceptor 13, and sweeps the surface of the photoreceptor 13,
Cycle B and C.

As mentioned above, the carrier 28 starts from the top of the toner collection roller 4 and flows down the flow path C that spans 1/4 of the circumferential surface of the toner collection roller 4, and the opposite electrodes 5a, 5b, 5c sandwich this flow path C. is located. The toner collection roller 4 is rotating in the direction of the arrow, and the blade 9 is in pressure contact with it. A collected toner discharge device 10 is arranged below the blade 9.

A positive voltage of 200 to 500 V (opposite polarity to the toner charge) is applied to the sleeve 1 by a power source 12, and the same voltage is applied to the toner collection roller 4 by a power source 14. Grounded counter electrode 5
between a, 5b, 5c and the toner collection roller 4.
An electric field of about 1000 to 5000 V/cm is formed.

Prior to cleaning, the photoreceptor 13 is subjected to static neutralization by a corona discharger 35. As a result, the electrostatic latent image on the photoreceptor 13 is neutralized, and the amount of negative charge on the toner 11 increases. When the magnetic brush by the carrier 28 formed on the circumferential surface of the sleeve 1 sweeps the circumferential surface of the photoreceptor 13, the negatively charged toner 11 is attracted by the positive voltage applied to the sleeve 1 and is attracted to the carrier 28. do. This carrier 28 is baton-touched by the relay sleeves 2 and 3 and is conveyed as shown by arrows A, B, and C. When flowing down the downstream path C, it passes between the collection roller 4 and the counter electrode 5, where it is subjected to the action of an electric field. This electric field separates the negatively charged toner 11 from the carrier 28 and attracts it to the collection roller 4. The toner 11 attracted to the collection roller 4 is conveyed as the collection roller 4 rotates, is scraped off by the blade 9, and collected in the collected toner discharge device 10. The carrier 28 separated from the toner 11 is the sleeve 1
Flows upward and recirculates. In addition, corona discharger 3
5 is not necessarily necessary and can be omitted.

The toner 11 adsorbed by the carrier 28 is separated from the carrier 28 by the action of the electric field formed between it and the counter electrode 5 while it is in contact with the circumferential surface of the toner collection roller 4, and the toner is collected. roller 4
Therefore, if this period is lengthened, the toner recovery rate can be improved. Therefore,
The point at which the carrier 28 flows down onto the circumferential surface of the toner collection roller 4 is, as described above,
Should choose the top. As a result, the carrier 28 comes into contact with the toner collection roller 4 over a 90 degree range from the top to the side, that is, over 1/4 of the circumferential surface, making it possible to obtain the maximum contact period. Of course, it is necessary to arrange the counter electrode 5 so that a desired electric field is generated in this contact section, and the counter electrode 5 can also be in the form of a net or a plate.

FIG. 2 shows another embodiment of the invention. In this example, the carrier 28 flowing down from the scraper 8 advances as it is without being influenced by the guide plate 6 to change the direction of flow, and forms a flow path C' flowing down on the other side of the top. Therefore, if the toner collection roller 4 is rotated clockwise as shown, the relationship between the carrier 28 and the toner collection roller 4 will be almost the same as that shown in FIG. but,
The rotation direction of the toner collection roller 4 does not necessarily have to be as shown in the figure.

(Effects) As described above, the present invention has a means for relaying and conveying the magnetic carrier between the sleeve for forming the magnetic brush and the toner collection roller that electrostatically separates the toner from the magnetic carrier. The brush-forming sleeve and the toner collection roller can be made electrically independent, and there is no need for the voltage applied to the toner collection roller to be so high as to be added to the voltage of the magnetic brush-forming sleeve. As a result, the inconvenience caused by leaks can be resolved,
Insulation is also easier. Further, as a result of providing the relay conveyance means, the carrier circulation path becomes longer and the amount of carriers included therein increases, so that fatigue of the carrier is reduced.

Furthermore, since the point where the carrier flows down to the toner collection roller is selected at the top of its circumference, the area where the carrier is in contact with the toner collection roller can be extended to 1/4 of the circumference. It can be placed in an electric field for toner collection for long periods of time independent of the period that the carrier is in contact with the photoreceptor;
As a result, toner recovery rate and cleaning performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a front view showing main parts of another embodiment, and FIG. 3 is a front view of a conventional cleaning device. 1... Sleeve for forming magnetic brushes, 2, 3...
...Relay sleeve, 4...Toner collection roller, 5
a, 5b, 5c... counter electrode, 6... guide plate,
8... Screver, 11... Toner, 13... Photoconductor, 28... Carrier.

Claims (1)

[Claims] 1. In an apparatus that electrostatically performs cleaning using a magnetic brush formed by a magnetic carrier, a device is provided between a sleeve for forming the magnetic brush and a toner collection roller that applies an electric field to separate the toner from the magnetic carrier. , a means for relaying the magnetic carrier is interposed, and a point at which the magnetic carrier flows down from the relay conveying means toward the toner collection roller is selected at the top of the periphery of the toner collection roller. Photoreceptor cleaning device.