JPH052340A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the void of an image and to facilitate the designe of a magnet body even though the clogging of a developer regulating member is caused by the flocculated substance of developer and paper powder, etc., in a developing device which is provided with the magnet body, a developing sleeve rotating around the magnet body, and the developer regulating member facing to the developing sleeve and in which the developer is carried to a developing area in a state where it is held on the outer peripheral surface of the developing sleeve based on the magnetic force of the magnet body while regulating the carrying amount of the developer supplied to the developing sleeve by a regulating member. CONSTITUTION:A magnet roll 3 is possessed of magnetic poles S4 and N1 having reverse polarity to each other on an upstream side and a downstream side in the rotating direction of the developing sleeve 2 by setting a napping height regulating member 4 as a boundary, and possessed of a magnetic pole S3 having the same polarity as the magnetic pole S4 and a magnetic pole S1 having the reverse polarity to the magnetic pole N1 on the upstream side of the magnetic pole S4 and the downstream side of the magnetic pole N1, respectively. As to the magnetic poles N1 and S1 having the reverse polarity to each other on the downer- stream side than the member 4, the relation of A gauss being the maximum value of the vertical magnetic field of the magnetic pole N1 and B gauss being the maximum value of the horizontal magnetic field between both magnetic poles is A/2>B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an electrophotographic image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Various types of developing devices in an electrophotographic image forming apparatus are known, and as typical ones, a magnet body, a developing sleeve capable of rotating around the magnet body, and A developing agent regulating member facing the developing sleeve is provided, the developing agent is held on the developing sleeve based on the magnetic force of the magnet body, and the rotation of the sleeve regulates the transport amount by the regulating member, and the developing area. There is a developing device that can be transported to.

In this type of developing device, the developer regulating member is often clogged due to developer clumps (aggregates), paper dust, etc., and the developer is not conveyed to the downstream side of the developer regulating member. It causes the white spots on the. Therefore, a magnet member is provided on the cover of the developing sleeve, or, as disclosed in Japanese Patent Laid-Open No. 146276/1985, the magnet body is reciprocated between the developer regulating member and the developing magnetic pole of the magnet body. It has been proposed to provide homopolar magnetic pole portions (reciprocal magnetic poles) that are matched with each other.

In the former case, a magnetic brush is formed between the magnet in the developing sleeve and the sleeve cover, and the developer is slightly accumulated, and the developer is supplied to the blank area by the accumulation.
This is to prevent blank areas. . The latter developing device (Japanese Patent Laid-Open No. 60-146276) corrects the non-uniformity of the developer layer thickness due to the disturbance and flying of the developer in the repellent magnetic pole portion of the magnet body, and also causes the clogging of the regulating member. Even at this time, it is intended to prevent the blank portion of the image by filling the blank portion of the developer due to the disturbance and the flying of the developer.

[0005]

However, when a magnet member is used, it is difficult to set the distance between the developing sleeve and the magnet member. If the distance is too short, the developer conveyance amount decreases, and if it is too far,
There is no effect of the magnet member. Further, according to the latter developing device, in general, the magnet body must maintain a delicate balance of the number of magnetic poles, the arrangement of poles, and the magnetic force. It is very difficult to design because the layout relationship of is restricted. Especially, it is difficult to apply to a small magnet body used for a developing sleeve having a small diameter.

Therefore, the present invention has a magnet body, a developing sleeve that rotates around the magnet body, and a developer regulating member that faces the developing sleeve, and regulates the developer supplied to the developing sleeve. A developing device that holds the outer peripheral surface of the developing sleeve based on the magnetic force of the magnet body and conveys it to a developing area while regulating the amount of conveyance by a member, which is a developer regulating member such as a developer agglomerate or paper dust. An object of the present invention is to provide a developing device capable of preventing white spots in an image even if clogging occurs and having a magnet body designed easily.

[0007]

The inventor of the present invention has conducted extensive research to achieve the above-mentioned object, and found that the method disclosed in JP-A-60-14627.
Instead of the arrangement of the homopolar magnetic poles (reverse magnetic poles) on the downstream side of the developer regulating member disclosed in Japanese Patent Laid-Open No. 6, the magnetic poles of opposite polarities are arranged, and the vertical magnetic field of the upstream magnetic pole among these magnetic poles. Is set to be sufficiently larger than the horizontal magnetic field between these magnetic poles, the developer stored in the upstream magnetic pole is strongly attracted to the reverse polarity magnetic pole on the upstream side of this magnetic pole and tries to flow backward, as if the conventional magnetic field were the same. Development similar to the pole pole arrangement occurs, the developer omission occurring in the regulating member is filled by the disturbing action at this time, and the conventional homopolar magnetized portion becomes unnecessary, so that the design of the magnet body is facilitated. It was found that the present invention has been completed.

That is, the present invention has a magnet body, a developing sleeve that rotates around the magnet body, and a developer regulating member that faces the developing sleeve, and regulates the developer supplied to the developing sleeve. In a developing device in which the amount of conveyance is regulated by a member and is held on the outer peripheral surface of the developing sleeve based on the magnetic force of the magnet body and conveyed to the developing area, the magnet body is a boundary of the regulating member. The magnetic poles having opposite polarities are provided on the upstream side and the downstream side in the rotation direction, and the magnetic pole having the same polarity is provided on the upstream side adjacent to the upstream magnetic pole and the opposite polarity is provided on the further downstream side adjacent to the downstream magnetic pole. Of the opposite magnetic poles on the downstream side of the restricting member, the maximum value A of the vertical magnetic field of the upstream magnetic pole and the maximum of the horizontal magnetic field between the two magnetic poles. B Gauss and is intended to provide a developing device, characterized in that a relationship of A / 2> B.

In order to weaken the magnetic force between the two magnetic poles of opposite polarities on the downstream side adjacent to the regulating member, a magnetic material is arranged in the vicinity of them, for example, a sleeve cover, or the downstream side of both magnetic poles. A homopolarized portion having the opposite polarity may be provided further downstream of the side magnetic pole.

[0010]

According to the developing device of the present invention, the developer supplied to the upstream side of the developer restricting member moves from the upstream magnetic pole of the restricting member to the downstream side of the restricting member having the opposite polarity as the developing sleeve rotates. However, since the horizontal magnetic field between the downstream magnetic pole and the magnetic pole having the opposite polarity on the downstream side is weak, the magnetic flux is conveyed to the magnetic pole on the upstream side from the regulating member, and the magnetic field is transferred to the regulating member. The magnetic pole that cannot be held by the adjacent downstream magnetic pole is transported so as to fly to the adjacent downstream magnetic pole, and finally supplied to the developing area.

When the developer is disturbed mainly by the phenomenon that the developer tries to flow back to the magnetic pole on the upstream side of the regulating member, and by the flight or flight-like conveyance, the developer is regulated by agglomerates or paper dust. The developer omission that may occur due to the clogging of the member is filled.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of one embodiment. FIG. 2 shows the vertical and horizontal magnetic field distribution of the magnet roll. This developing device includes a casing 1, and an opening 11 facing the photosensitive drum PC which is an electrostatic latent image carrier of the image forming apparatus is provided on one side of the casing 1.

A developing sleeve 2 is rotatably accommodated and supported in a portion including the opening 11 of the casing 1, and a part of the sleeve faces the photosensitive drum PC through the casing opening 11. A fixed magnet roll 3 is arranged in the developing sleeve 2. A brush height regulating member 4 which is a developer regulating member supported by the casing 1 faces the upper surface of the developing sleeve 2, and a bucket roller 5 is rotatably accommodated and supported behind the developing sleeve 2.

The sleeve 2 and the bucket roller 5 are rotationally driven in the clockwise direction a in FIG. 1 by a driving means (not shown). A toner hopper 6 is arranged above the bucket roller 5 and supported by the casing 1. Toner hopper 6
A toner replenishing roller 61, which is rotatably driven by a driving unit (not shown), is disposed at the lower end opening of the.

The casing 1 contains a two-component developer 7 containing a magnetic carrier and toner, and a toner hopper 6
Contains a replenishment toner T. The magnet roll 3 has magnetic poles N1, S1, N2, N3, S2, N4 and S.
3 and S4 are provided in this order. The magnetic pole S4 that receives the developer from the bucket roller 5 is in the rotation direction a of the sleeve 2.
In, the magnetic poles N1 and S1 that are arranged on the upstream side of the regulating member 4 and have opposite polarities are arranged on the downstream side of the regulating member 4 in this order. The magnetic poles N2 and N3 are arranged in the developing area D. The magnetic pole S3 having the same polarity, which is arranged on the upstream side adjacent to the magnetic pole S4, has a function of strengthening the connection between the magnetic force line of the magnetic pole S4 and the magnetic pole N1 and weakening the magnetic force between the magnetic poles N1 and S1, and the sleeve 2 Also acts as a separating magnetic pole for separating the developer 7 from the. Similarly, the magnetic pole N3 is also the magnetic pole N
By strengthening the connection between the magnetic field line 2 and the magnetic pole S1, the magnetic pole N1,
The magnetic force between S1 is further weakened.

The distribution of the vertical magnetic field and the horizontal magnetic field in the magnet roll 3 is as shown in FIG. In this figure, the solid line indicates the vertical magnetic field distribution, the broken line indicates the horizontal magnetic field distribution, and the arrow X indicates the position of the spike height regulating member 4. As can be seen from this figure, the maximum value B Gauss of the horizontal magnetic field between the different poles N1 and S1 on the downstream side adjacent to the regulating member 4 is that the magnetic field lines of the magnetic pole S4 are strongly connected to the magnetic pole N1 by the action of the magnetic pole S3. , S1 is weakened by that much, so that it is smaller than one half of the maximum value A Gauss of the vertical magnetic field of the magnetic pole N1.

The maximum value B Gauss of the horizontal magnetic field is
The magnetic field lines of the magnetic pole N2 are strongly connected to the magnetic pole S1 by the action of the magnetic pole N3, and thus are further reduced. The homopolar magnetic poles N2 and N3 are provided in order to further weaken the magnetic force between N1 and S1, but they are not always necessary. One N pole may be used. According to this developing device, the developing sleeve 2 and the bucket roller 5 are rotationally driven in the clockwise direction a in FIG. 1 by a driving unit (not shown), whereby the developer 7 is supplied onto the developing sleeve 2 while being agitated by the bucket roller 5. It

The developer supplied to the sleeve 2 is held in the form of a brush (magnetic brush) of the developer by the magnetic force of the fixed magnet roll 3, and is conveyed to the developing area D as the sleeve rotates. During this transportation, the transportation amount is regulated by the regulation member 4. The developer that has passed through the regulation member is conveyed to the N1 pole, but as shown in FIG. 3, the magnetic force between the magnetic poles N1 and S1 is weaker than the magnetic force of the N1 pole. Is magnetically attracted to the upstream side in the rotation direction a of the sleeve 2 along the line of magnetic force Y, and tries to flow backward. As a result, in FIG. 3, the developer is strongly disturbed on the magnetic pole N1 circled, and the developer omission due to the clogging by the developer or paper dust in the regulation member 4 is sufficiently filled, and the white spots in the image are correspondingly reduced. In addition to being surely prevented, the rising of the toner charge is improved.

Developer 7 that can no longer be held by the magnetic pole N1
Is conveyed to the magnetic pole S1 and finally supplied to the developing area for development, and the excess is conveyed to the separating magnetic pole S3 by the rotation of the sleeve 2, where it is separated from the sleeve 2 and the bucket It flows into the roller 5. The movement of the developer from the magnetic pole N1 to S1 is greater than that between the magnetic poles N1 and S1.
When the magnetic force of 1 is strong, it flies between N1 and S1. Even if it doesn't fly completely, it moves like a flight. Therefore, the developer dropout is more surely filled even by the flight or the flight-like movement, and the whiteout of the image is prevented.

When the toner concentration of the developer in the casing 1 decreases, the toner T is replenished from the toner hopper 6 by the rotation of the toner replenishing roller 61. Here, FIG.
Using the developing device of No. 1 by incorporating it in a printer not shown,
Moreover, the surface roughness Rz of the developing sleeve 2 is 5 to 10 S, the outer diameter is 24.5 mm, the peripheral speed is 20 cm / S, and the binder type developer carrier is adopted. , N1-S1 maximum horizontal magnetic force B Gauss and S1 pole maximum vertical magnetic force C Gauss are variously changed,
When the effect of preventing image white spots was examined, the results shown in Table 1 were obtained. The magnetic force is measured by GM-102 manufactured by Denshi Kogaku Kogyo. The mark x indicates no effect, and the mark o indicates effect.

As can be seen from Table 1, the relationship of A / 2> B is desirable. Further, it can be said that it is preferable to increase the perpendicular magnetic force of the S1 pole to fly the developer between N1 and S1.

[0022]

[Table 1] According to the above-mentioned embodiment, since the magnetizing portion for developer disturbing and flying, which is used in the conventional apparatus, is unnecessary, the magnet roll can be designed so much even if it is small. It should be noted that the present invention is not limited to the above embodiment, and can be implemented in other modes. For example, as shown in FIG. 4, the horizontal magnetic force between N1 and S1 may be weakened by providing the casing 1 with the magnetic body 8 in the vicinity of the magnetic poles N1 and S1.

[0023]

According to the present invention, the developer supplied to the developing sleeve has a magnet body, a developing sleeve rotating around the magnet body, and a developer regulating member facing the developing sleeve. A developing device that holds the outer peripheral surface of the developing sleeve and conveys it to a developing area based on the magnetic force of the magnet body while regulating the conveying amount by the regulating member, and regulates the developer by a developer aggregate, paper dust, or the like. Even if the member is clogged, it is possible to provide a developing device that can prevent white spots in an image and also can easily design a magnet body.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention.

FIG. 2 is a vertical and horizontal magnetic field distribution map of a magnet roll.

FIG. 3 is an explanatory diagram of disturbance and flying of a developer.

FIG. 4 is a partial cross-sectional view of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 casing 2 developing sleeve 3 magnet roll 4 spike height regulating member N1, S1, N2, N3, S2, N4, S3, S4 magnetic pole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Matsuura 2-3-13 Azuchi-cho, Chuo-ku, Osaka Within Osaka Kokusai Building Minolta Camera Co., Ltd. (72) Inventor Susumu Mikawa 2-chome, Azuchi-cho, Chuo-ku, Osaka No. 13 Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

Claims: 1. A developer having a magnet body, a developing sleeve rotating around the magnet body, and a developer regulating member facing the developing sleeve, the developer being supplied to the developing sleeve. In a developing device that holds the transfer amount by the restricting member and holds it on the outer peripheral surface of the developing sleeve based on the magnetic force of the magnet body and transfers it to the developing area. In the rotation direction of the developing sleeve, magnetic poles having opposite polarities are provided on the upstream side and the downstream side, and a magnetic pole having the same polarity is provided on the upstream side adjacent to the upstream magnetic pole and on the downstream side adjacent to the downstream magnetic pole. Of the two magnetic poles having opposite polarities opposite to each other and having the opposite polarities, the maximum value A Gauss of the vertical magnetic field of the upstream magnetic pole and the horizontal magnetic field between the magnetic poles are provided. Most A developing device and a value B Gauss is characterized in that it is in the relation of A / 2> B.