JPH05204248A - Developing device - Google Patents

Abstract

PURPOSE:To make the diameter of a developing roller small and to make a developing device compact. CONSTITUTION:The developing device where plural developing rollers 10 and 10a are adjacently arranged on the side part of a photosensitive body 1 and developer is transferred between the adjacent upper and lower rollers 10 and 10a is provided with magnetic poles which have two peaks P and P', Pa and Pa' in magnetic force distribution in a normal direction near the developer transferring part A of magnetic rollers 11 and 11a and whose magnetic force peak P' and Pa' on a downstream side with respect to a sleeve moving direction are positioned at the developer transferring parts A and 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 used in electrophotographic copying machines, printers, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, as the developing device, as shown in FIG. 5, an upper developing roller 10 in which a sleeve 12 is rotatably mounted on a fixed magnet roller 11 in a developing portion 2 facing a photosensitive member 1, Similarly, fixed magnet roller 1
It is known that a lower developing roller 10a, which has a sleeve 12a that is rotatably driven and is externally disposed, is arranged in parallel with the la 1a.

In the developing device, the developer supplied to the outer periphery of the upper developing roller 10 in the supply region Y1 is held on the outer periphery of the sleeve 12 by the magnetic force of the magnet roller 11. Further, the developer is conveyed in the direction of arrow m with the rotation of the sleeve 12, passes through the tip of the blade 13 and then is conveyed to the first developing region 14, where it is brought into contact with the photosensitive member 1 to be developed. Next, the developer is conveyed to the area where the developing rollers 10 and 10a face each other, and reaches the lower developing roller 10a at the portion where the magnetic pole Sd provided on the upper magnet roller 11 and the magnetic pole Nr having a different polarity provided on the lower magnet roller 11a. Delivered.

The developer held on the lower developing roller 10a is conveyed in the direction of the arrow n as the sleeve 12a rotates, and comes into contact with the photosensitive member 1 in the second developing area 14a to be developed again. Next, the developer that has passed through the second developing area 14a is rotated by the sleeve 12a and the developing rollers 10, 10 are rotated.
The lower magnet roller 11a is conveyed to the area opposite to a.
The magnetic pole Sd provided on the upper magnet roller 11 and the magnetic pole Nr having a different polarity provided on the upper magnet roller 11 are passed to the upper developing roller 10. The developer received by the upper developing roller 10 is conveyed in the direction of the arrow m as the sleeve 12 rotates, and the magnetic poles Sa and Sb having the same polarity are adjacent to each other in the area Y2.
Is separated from the sleeve 12 and supplied to a mixing and stirring area (not shown).

[0005]

However, in the developing device, the upper magnet roller 11 has seven magnetic poles, the lower magnet roller 11a has six magnetic poles, and the developing rollers 10 and 10a face each other. Since the two magnetic poles Sd and Nr are arranged on each of the magnet rollers 11 and 11a, the gap between the magnetic poles becomes narrow, and there is a problem that the magnetic force of each magnetic pole cannot be sufficiently secured by the developing roller having a small diameter. Was there. Further, as shown in the figure, in the case where the transfer magnetic pole Sd is arranged immediately downstream of the developing magnetic pole (N pole) facing the first developing region 14,
There is a problem that the magnetic force of the developing magnetic pole cannot be sufficiently secured, and the developer scatters to contaminate the photoconductor and peripheral equipment.

[0006]

The present invention has been made to solve the above problems, and has two peaks in the magnetic force distribution in the normal direction in the vicinity of the developer passing portion of the magnet roller. In addition, the magnetic pole on the downstream side with respect to the sleeve moving direction is located at the developer transfer portion.

[0007]

In the developing device, the developer conveyed with the rotation of the sleeve on the developer delivering side developing roller passes through the upstream first magnetic force peak and then opposes at the second magnetic force peak portion. It is supplied to the developing roller on the developer receiving side.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a developing unit 2 of a developing device according to the present invention, which includes a magnet roller 11 of an upper developing roller 10.
Then, as shown in FIG.
Is arranged at a position moved 5 ° in the counterclockwise direction in the figure with respect to a line L (P / C) connecting the center O of the magnetic field to the center of the photoconductor 1, and the magnetic pole S1, C1 is clockwise with respect to this position N
2 and S2 are arranged, the central angle between the magnetic pole N1 and the magnetic pole S1 is 95 °, the central angle between the magnetic pole S1 and the magnetic pole N2 is 80 °, the central angle between the magnetic pole N2 and the magnetic pole S2 is 105 °, and the magnetic pole S2 and the magnetic pole N1. The central angle of is set to 80 °. The magnetic forces of the respective magnetic poles are adjusted so that the magnetic pole N1 is 1000 G (gauss) or more and the magnetic poles S1, N2, and S2 are 600 G when measured on the outer peripheral surface of the sleeve 12.

Magnet roller 1 of lower developing roller 10a
In 1a, as shown in FIG. 3, the magnetic pole N3 is a line La (P) that connects the center Oa of the lower developing roller 10a and the center of the photoconductor 1.
/ C), the magnetic poles N4, S4, N5, N6, S3 are arranged in a position moved by 5 ° in the counterclockwise direction in the figure, and the magnetic poles N4, S4, N5, N6, S3 are arranged clockwise with reference to this position. The central angle of the magnetic pole N4 is 25 °, the magnetic pole N4 and the magnetic pole S4
Has a central angle of 40 °, and the magnetic poles S4 and N5 have a central angle of 55
°, the central angle between the magnetic pole N5 and the magnetic pole N6 is 90 °, the magnetic pole N6
And the central angle of the magnetic pole S3 is set to 110 °. Further, the magnetic forces of the respective magnetic poles are 1,200 when both magnetic poles N3 and N4 are measured on the outer peripheral surface of the sleeve 12a.
The G and magnetic poles S4, N5, N6 and S3 are adjusted to be 800G.

By arranging the magnetic poles as described above, the magnetic force is distributed around the developing rollers 10 and 10a in the state shown in the drawing. Particularly, in the upper developing roller 10,
In the magnetic force distribution in the normal direction formed in the region from the magnetic pole N1 to the magnetic pole S1, the first magnetic force peak P is located at the facing portion of the magnetic pole N1, the upstream side of the magnetic pole S1 in the sleeve rotation direction, and the lower magnet roller 11a. A second magnetic force peak P ′ appears in a portion A (hereinafter, referred to as “developer transfer portion A”) that faces the magnetic pole S3. In the lower developing roller 10a,
The magnetic force distribution in the normal direction formed in the region from the magnetic pole N6 to the magnetic pole S3 has a first magnetic force peak Pa at the facing portion of the magnetic pole N6 and is on the upstream side in the sleeve rotation direction of the magnetic pole S3. A second magnetic force peak Pa ′ appears in a portion B of the magnet roller 11 that faces the magnetic pole S1 (hereinafter referred to as “developer transfer portion B”).

Therefore, in the upper developing roller 10,
The developer that has passed through the facing portion of the magnetic pole N1 as the sleeve 12 rotates is held on the outer peripheral surface of the sleeve 12 up to the developer passing portion A where the second magnetic force peak P ′ is located, and here, the developer of the lower magnet roller 11a that faces is held. It is drawn by the magnetic pole S3 and transferred to the lower developing roller 10a. Similarly, in the lower developing roller 10a, the developer that has passed through the facing portion of the magnetic pole N6 as the sleeve 12a rotates rotates to the second magnetic force peak P.
sleeve 12a to the developer transfer portion B where a'is located
Is held on the outer peripheral surface of the sheet, and is attracted by the magnetic pole S1 of the upper magnet roller 11 which faces the sheet, and is transferred to the upper developing roller 10.

Further, the developer is released from above the developing roller in a region Y2 where the magnetic pole N5 of the lower developing roller 10a faces.
It is newly supplied to the developing roller in the region Y1 where the magnetic pole N6 adjacent to the magnetic pole N5 and having the same polarity faces each other.

In the above embodiment, the second magnetic force peaks P'and P are applied to the developer transfer portions A and B depending on the arrangement of the magnetic poles.
Although a ′ is formed, as shown in FIG. 5, the magnet roller portions 15 and 15 of the developer transfer portions A and B are formed.
It can also be formed by cutting a.

[0014]

As is apparent from the above description, in the developing device according to the present invention, a magnetic force distribution having two magnetic force peaks is formed by the magnetic pole arrangement of the magnet roller and the magnetic force setting, and at the same time, in the sleeve rotation direction. The second magnetic force peak located on the downstream side is located in the developer delivering section, and the developer held at the second magnetic force peak is delivered to the adjacent developing roller.

Therefore, of the two magnetic force peaks, one magnetic force peak is used for developing by arranging the magnetic force peak at the portion facing the photoconductor, and the other magnetic force peak is used for transferring the developer, or one magnetic force peak is used. The peak can be used for supplying the developer to the developing roller, and the other magnetic peak can be used for transferring the developer.
That is, one magnetic pole can perform two functions,
The number of magnetic poles is smaller than that of the conventional developing roller in which the function is shared by the individual magnetic poles.

Further, by reducing the number of magnetic poles, the magnetic force of each magnetic pole can be stabilized, and the developer transportability is improved.
There are various effects such that the individual magnetic poles are strongly set to obtain a stable transportability of the developer, and the developing device can be downsized.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a developing device.

FIG. 2 is a magnetic pole arrangement and magnetic force distribution diagram of the upper magnet roller.

FIG. 3 is a magnetic pole arrangement and magnetic force distribution diagram of a lower magnet roller.

FIG. 4 is a sectional view showing another embodiment of the developing device.

FIG. 5 is a partial cross-sectional view of a conventional developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Development part 10, 10a ... Development roller 11, 11a ... Magnet roller 12, 12a ... Sleeve A, B ... Developer transfer part

Front Page Continuation (72) Inventor Masahiko Matsuura 2-3-13 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Susumu Mikawa 2-chome, Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 3-13 No. 13 Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A developing device in which a plurality of developing rollers, each of which has a sleeve mounted on a fixed magnet roller, are arranged adjacent to a side portion of a photoconductor, and a developer is transferred between adjacent developing rollers. The magnetic pole has two peaks in the magnetic force distribution in the direction of the normal in the vicinity of the developer delivering portion of the roller, and the magnetic force peak on the downstream side with respect to the sleeve moving direction is the magnetic pole located in the developer delivering portion. And developing device.