JPS60144767A - Brush electrifier - Google Patents

Abstract

PURPOSE:To prevent bend of long contacts which are brought into contact with a body to be electrostatically charged, by using two kinds of contact, namely, long and short contacts and making the diameter of the short contacts larger than that of the long contacts. CONSTITUTION:An electrostatic charge roll 8 is rotated in the direction of an arrow A and a voltage is applied to it, and then, tips of long fiber brush 6 rub against the surface of a photosensitive drum 9 and are charged. In this case, the long fiber brush 6 is easily deformed to curl from the root by the contacting pressure; however, many short fiber brushes 7 which have the diameter larger than that of the long fiber brush 6 and are not brought into contact with the photosensitive drum 9 are blocked on a roll body 5 of the roll 8 besides the long fiber brush 6, and bend of the long fiber brush 6 is prevented by the reinforcing action of these brushes 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charging device such as an electrophotographic copying machine, and particularly to a brush charging device.

[Prior art]

Conventionally, corona chargers that utilize corona discharge have been mainly used as charging devices for electrophotographic copying machines, etc., but they are dangerous because they require a high voltage of about 8KV to 10KV during corona discharge, and corona discharge Ozone is generated during this process, which has the disadvantage of damaging equipment around the charger.

Therefore, as an alternative to the conventional corona charger, brush charging devices have recently been actively developed.・That is, this device, as shown in FIG.
A plated fiber brush, a metal blank, or a conductive fiber brush with a diameter of about 20 μm is provided to form a charging roller (3), and this charging roller (3) is connected to the photoreceptor which is the object to be charged. The charging roller (3) is rotated and brought into contact with the surface of the photoreceptor (4), and 500v − to this charging roller (3)
The photoreceptor (4) is charged by applying a low voltage of about 2 KV.

Therefore, compared to corona chargers, this brush charging device does not require high voltage and is therefore safer, and also has the advantage of not generating ozone and causing no damage to equipment surrounding the device. .

However, in this device, it is necessary to keep a contact such as a fiber brush in contact with the surface of the charged object at all times, so this contact pressure causes the contact to curl (deform twice) and become flattened from its roots. Due to the change in diameter, uneven charging is likely to occur due to poor contact when used for a long period of time, and for example, in electrophotographic copying machines, this has the drawback of adversely affecting copy image quality.

[Purpose of the invention]

The present invention eliminates and improves the drawbacks of these conventional techniques, and aims to provide a brush charging device that prevents the contacts provided on the charging roller from becoming fatigued, thereby preventing uneven charging. It is something to do.

[Structure of the invention]

That is, in the present invention, a charging roller provided with a large number of contacts having conductivity on the surface of the roller is brought into contact with the surface of an object to be charged while rotating, and a voltage is applied to the charging roller to charge the object to be charged. In the blank charging device for charging, the contactor is composed of two types of contactors, long and short, and
By making the diameter of the short contact larger than the diameter of the long contact, the contact is prevented from sagging and uneven charging is prevented.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic side view of a charging device for a photosensitive drum of an electrophotographic copying machine in which the brush charging device of the present invention is incorporated.

That is, the brush charging device of the present invention, as shown in FIG. It is provided near the photosensitive drum (9), which is the body.

First, the roller body (5) is rotatably supported by a drive means C2 (not shown) in the direction indicated by the arrow, and is connected to two power sources (not shown) so that a voltage can be applied thereto.

The outer peripheral surface of the roller body (5) is coated with carbon-dispersed acrylic fiber (5A-7 manufactured by Toshisha Co., Ltd.), carbon-dispersed nylon fiber (trade name Beltron manufactured by Kanebo Co., Ltd.), and carbon-dispersed rayon fiber (trade name manufactured by Unitika Co., Ltd.). The length is 15111111 and the diameter is 15 to 20 mm.
μm long fiber brush (6) and this long fiber brush (6)
It is made of conductive fiber similar to , and has a length of 7wn and a diameter of 30~4
A large number of 0 μm short fiber brushes (7) are installed, and the tip portion of the long fiber brush (6) is configured to come into contact with the surface of the photosensitive drum (9) at the nip 2-.

In order to charge a photosensitive drum using the brush charging device of the present invention, two charging rollers (
8) in the direction of the arrow (twice) and turn this charging roller (
8) Applying a voltage to (2-strand long fiber bran (6)
The tip of the photosensitive drum (9) is electrically charged by contact friction with the surface of the photosensitive drum (9).

At this time, since the long fiber bran (6) comes into contact with the photosensitive drum (9), it is easily deformed into a curl shape from the root due to the contact pressure.
Second, since a large number of short fiber brans (7) which have a larger diameter and do not come in contact with the photosensitive drum (9) are planted outside of this long fiber bran (6), this short fiber brush ( The reinforcing action of 7) can prevent the long fiber brush (6) from becoming sagging.

FIG. 8 shows the brush charging device according to this embodiment (a).
This shows the relationship between the number of copies of an electrophotographic copying machine in a conventional brush charging device (b) (-) and the amount of sag ν of the fiber brush, which is a contact.Here, the amount of sag is: It means the rate of change in the outer diameter of the fiber brush in the brush charging device.

As is clear from this graph result, in the conventional blank charging device (b), the amount of sag v of the fiber brush increases in proportion to the number of copies (2);
In contrast, in the brush charging device (a) according to the above embodiment, the amount of settling p is significantly reduced, and it is found that uneven charging is less likely to occur even after long-term use. It shows.

〔Effect of the invention〕

As described above, the brush charging device of the present invention uses two types of contacts (long and short), and the diameter of the short contact is p larger than the diameter of the long contact. Due to the reinforcing action of the short contact, it is possible to prevent the long contact that contacts the object to be charged from becoming sagging.

Therefore, the practical effects of the present invention are great, such as stable charging is possible and durability can be greatly improved because contact failure (discharge unevenness due to double contact does not occur) even after long-term use. It is.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a conventional brush charging device, Fig. 2 shows an embodiment of the present invention and is a schematic side view of the brush charging device of the present invention, and Fig. 8 shows the number of copies and fibers. It is a graph figure which shows the relationship of the amount of flatness V of a brush. Description of symbols (5)...Roller body (6)...Long fiber brush (7)...Short fiber bran (8)
...Charging roller (9) ...Photosensitive drum Patent applicant Fuji Xerox Co., Ltd. Agent Tomohiro Nakamura, Patent Attorney Katsuo Seihin Figure 1 Figure 2

Claims (1)

[Claims] Brush charging, in which a charging roller, which has a large number of conductive contacts on the surface of the roller, is rotated and brought into contact with the surface of a charged object, and a voltage is applied to the charging roller to charge the charged object. (2) A brush charging device characterized in that the above-mentioned contactor is composed of two types of contacts, long and short, and the diameter of the short contact is larger than the diameter of the long contact.