JPH05341656A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device including a magnet body and a developing sleeve rotated around the magnet body, and carrying a developer to a developing region while holding the developer on the surface of a sleeve, based on the magnetic force of the magnet body, and can equalize the developer carrying quantity of each part in the rotational axial direction of the developing sleeve, compared with the developing device of the same type, so that the lengths of the magnet body and the developing sleeve are made short, moreover, the miniaturization of the whole can be realized, and simultaneously, the scattering of toner, the spilling of the developer, and clogging with the developer, can be suppressed. CONSTITUTION:In the developing device including the magnet body 1 and the developing sleeve 5 rotated around the magnet body 1, and carrying the developer to the developing region while holding the developer on the surface of the sleeve 5, based on the magnetic force of the magnet body 1, the surface roughness of the developing sleeve 5 is changed so as to make roughness less as a part has larger magnetic force, according to the magnetic force from each part of the magnet body 1 in the rotational axial direction of the developing sleeve 5.

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 an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly,
The present invention relates to a developing device that includes a magnet body and a developing sleeve that rotates around the magnet body, and that conveys a developer to a developing area while holding the developer on the sleeve surface based on the magnetic force of the magnet body.

[0002]

2. Description of the Related Art In a developing device of this type, as shown in FIG. 4, a developing sleeve 2 is fitted around a magnet body 1, and
The sleeve is provided on the surface of an electrostatic latent image carrier such as the photoconductor drum PC. The developing sleeve 2 is rotationally driven in the direction of arrow CW in the drawing by a driving unit (not shown) to rotate around the magnet body 1. Further, the developing sleeve 2 faces a brush height regulating member 3 that regulates the developer transport amount. The developer is supplied to the sleeve 2 by the rotation of the bucket roller 4 behind the sleeve.

In the illustrated example, the magnet body 1 is in the form of a magnet roller, and is incorporated in the developing sleeve 2 as shown in FIG. The protruding shaft 11 at one end of the magnet roller 1 is rotatably supported inside the sleeve 2 by a bearing 1a, and the protruding shaft 12 at the other end is supported by a support member (not shown). The protruding shaft 21 at one end of the sleeve 2 is rotatably supported by a supporting member (not shown) by a bearing (not shown), and the other end of the sleeve 2 is rotatably supported by the protruding shaft 12 of the magnet roller 1 by a bearing 1b. ing. Further, the sleeve protruding shaft 22 which extends so as to be fitted onto the protruding shaft 12 is connected to a rotation driving means (not shown), whereby the sleeve 2 is driven in the arrow CW direction in FIG. 4 as described above.

The magnet roller 1 is, as shown in FIG.
A magnetic pole N4 on the upstream side of the regulating member for receiving and holding the supplied developer, a developer conveying amount regulating pole S3 on the downstream side of the regulating member, a developing magnetic pole N1, developer conveying poles S1, N2,
S2 and a developer separating magnetic pole N3 are sequentially provided. In addition,
FIG. 4 also shows the original magnetic force at each magnetic pole. According to this developing device, the developer supplied from the bucket roller 4 (in this example, the developer consisting of toner and magnetic carrier)
Is held in the form of a magnetic brush on the sleeve 2 by the action of the N4 pole, and along with the rotation of the sleeve, moves to the S3 pole while the conveyance amount is regulated by the regulation member 3 on the way,
It is conveyed to the top of the developing magnetic pole N1, where the photosensitive drum PC
The electrostatic latent image is developed and the excess developer is conveyed to the N3 pole by the action of the S1, N2, and S2 poles as the sleeve rotates, where the repulsive magnetic field of the N3-N4 poles and the sleeve 2 are transferred. By the rotational force of 1 to flow from the sleeve 2 to the bucket roller 4 side.

[0005]

However, such a developing device has the following problems. That is, the magnet roller 1 has a longitudinal direction (developing sleeve 2
Is uniformly magnetized along the rotation axis direction of
When the magnetic force is actually measured, for example, the longitudinal magnetic force on the regulation pole S3 is, as shown in FIG. 6, in the both ends B of the magnet roller 1 toward the roller end, as shown in FIG. More and more.

When the change in the amount of developer conveyed with respect to the change in the magnetic force on the S3 pole which determines the amount of developer conveyed is investigated, the result is shown in FIG. As can be seen from this figure, the conveyance amount of the developing sleeve portion corresponding to the end portion B of the magnet roller is larger than that of the portion corresponding to the portion A. In this way, the actual magnetic force at the end of the magnet body 1 becomes larger than the magnetic force at the center of the magnet body, and the developer carrying amount increases in the developing sleeve portion corresponding to this portion. Must be arranged outside the sheet passing area, and therefore the length of the magnet body, and thus the length of the developing sleeve, must be increased accordingly, resulting in an increase in the size of the developing device and an increase in cost.

Further, when the developer carrying amount by the developing sleeve is increased, as illustrated in FIG. 8, the toner scattering amount is remarkably increased, and the developer is easily clogged or the developer is spilled. Therefore, when the developer transport amount is increased in the developing sleeve portion corresponding to the end portion of the magnet body, toner scattering and developer spillage, resulting in dirt in the image forming apparatus,
Problems such as clogging of the developer occur.

Therefore, the present invention is a developing device that includes a magnet body and a developing sleeve that rotates around the magnet body, and conveys a developer to a developing area while holding the developer on the surface of the sleeve based on the magnetic force of the magnet body. Therefore, compared to the conventional developing device of the same kind, the developer transport amount of each portion along the rotation axis direction of the developing sleeve can be made equal, and therefore, the length of the magnet body and the developing sleeve can be shortened, and An object of the present invention is to provide a developing device that can realize downsizing as a whole and that suppresses toner scattering, developer spill, and clogging by the developer.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive research to solve the above problems, and have paid attention to the following points. That is, in the developing device of the above-described type, generally, in order to improve the transportability of the developer, the surface of the developing sleeve is subjected to sandblasting treatment (see Japanese Utility Model Publication No. 58-55378), or an appropriate groove is provided. (Japanese Patent Publication Sho 61-3027
(See Japanese Patent Publication No. 1) to form irregularities. For example, the relationship between the surface roughness of the developing sleeve and the amount of developer conveyed by sandblasting is illustrated in FIG.

That is, the smaller the surface roughness of the developing sleeve, the smaller the carrying amount. From this, it can be understood that the increase in the developer transport amount due to the actual increase in the magnetic force at the end of the magnet body can be suppressed by changing the roughness of the sleeve surface small. Based on the above findings, the present invention includes a magnet body and a developing sleeve that rotates around the magnet body, and a developer that conveys a developer to the developing area while holding the developer on the sleeve surface based on the magnetic force of the magnet body. In the apparatus, the surface roughness of the developing sleeve is changed in accordance with the magnetic force from each part of the magnet body in the direction of the rotation axis of the developing sleeve so that the larger the magnetic force becomes, the smaller the surface roughness becomes. To provide a developing device.

[0011]

According to the developing device of the present invention, the developer supplied to the developing sleeve is held in the form of a magnetic brush on the surface of the sleeve based on the magnetic force of the magnet body, and reaches the developing area as the sleeve rotates. It is conveyed and used for developing the electrostatic latent image on the electrostatic latent image carrier. The magnetic body has a non-uniform distribution of the actual magnetic force along its longitudinal direction. Especially, at the end of the magnet body, the magnetic force generally increases from the central portion of the magnet body, but this magnetic force changed. The surface roughness of the developing sleeve portion corresponding to the portion is decreased as the magnetic force increases in accordance with the change of the magnetic force, and the developer transportability due to the surface roughness is reduced. Regardless of the non-uniform magnetic force of the body, the developer transport amount is made uniform in each part of the developing sleeve in the rotation axis direction.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The developing device of the embodiment shown in FIG. 1 employs a developing sleeve 5 instead of the developing sleeve 2 in the developing device shown in FIG. The other points are the same as those of the respective units of the apparatus shown in FIG. The surface of the developing sleeve 5 is sandblasted, and the surface roughness of the portion corresponding to both ends B of the magnet body 1 is changed from the surface roughness of the portion corresponding to the central portion A of the magnet body 1 to the sleeve end. It is gradually getting smaller.

A line a shown by a solid line in the uppermost portion of FIG.
Indicates that the surface roughness of the sleeve gradually increases from the end of the sleeve 5 corresponding to the end of the magnet body 1 to 50 mm from the end of the sleeve to the center of the sleeve. It shows that it is becoming. Conversely speaking, the sleeve surface roughness decreases as the magnetic force of the magnet body 1 increases from the 50 mm portion toward the sleeve end. In the upper part of FIG. 2, the broken line b indicates the surface roughness of the conventional developing sleeve 2.

According to this developing device, as in the device of FIG. 4, the developer consisting of toner and magnetic carrier supplied from the bucket roller 4 is held on the developing sleeve 5 in the form of a magnetic brush by the action of the N4 pole. Along with the rotation of the sleeve, the conveyance amount is regulated by the regulation member 3 on the way to S3.
Moved to the highest level, and further transported to the highest level of the development magnetic pole N1,
Here, it is used to develop the electrostatic latent image on the photoconductor drum PC,
After that, the excess developer is S1 and N as the sleeve rotates.
2, the S2 pole acts to transfer to the N3 pole, where N3-N
The repulsive magnetic field of 4 poles and the rotating force of the sleeve 2 cause the sleeve 2
And flows into the bucket roller 4 side.

At the longitudinal end B of the magnet body 1,
Although the magnetic force is increased from the central portion A of the magnet body, the surface roughness of the portion on the developing sleeve 5 corresponding to the increased magnetic force is as shown in FIG. 2 according to the increase in the magnetic force. Since the size of the developing sleeve 5 is reduced and the developer transporting property due to the surface roughness is reduced, the developer transporting amount in the developing sleeve 5 as a whole is irrespective of the nonuniform magnetic force of the magnet body. Are made uniform.

Therefore, the amount of developer conveyed at the end portion of the developing sleeve, which has occurred in the conventional developing sleeve, is increased, and accordingly, the magnet body and the developing sleeve are lengthened to secure a paper passing area, toner is scattered, and developer is spilled. The problem of developer clogging is suppressed or avoided. A solid line c in the middle part of FIG. 2 indicates that the developer transport amount at the end portion of the sleeve 5 is uniform in the sleeve central portion. In addition,
In the middle part of FIG. 2, the broken line d shows that the developer transport amount at the end of the conventional sleeve 2 changes as the magnetic force of the end B of the magnet body 1 changes (see the lower part of FIG. 2). There is.

As a method of providing the gradient of the surface roughness on the end portion of the developing sleeve 5 as described above, for example, as shown in FIG. 3A, sandblasting pressure is applied along the longitudinal direction of the developing sleeve. A method of gradually changing it, and a method of repeating the sand blasting process several times by changing the pressure and the processing region as shown in FIG. 3B can be considered.

[0018]

As described above, according to the present invention, it includes a magnet body and a developing sleeve that rotates around the magnet body,
A developing device that conveys the developer to the developing area while holding the developer on the surface of the sleeve based on the magnetic force of the magnet body, and compared to the conventional developing device of the same kind, the developer of each portion in the rotation axis direction of the developing sleeve. It is possible to make the conveyance amounts equal, thereby shortening the length of the magnet body and the developing sleeve,
As a result, it is possible to provide a developing device which can realize the downsizing of the entire device and also suppress the toner scattering, the developer spill, and the clogging by the developer.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a graph showing changes in the surface roughness of the developing sleeve end, changes in the developer transport amount, and changes in the magnetic force at the end of the magnet body.

FIG. 3 is a diagram showing an example of sandblasting for roughening the surface of the developing sleeve in the apparatus of FIG.

FIG. 4 is an explanatory diagram of an example of a conventional developing device.

FIG. 5 is a sectional view of a developing sleeve and a magnet body.

FIG. 6 is a graph showing an example of changes in the actual magnetic force in the longitudinal direction of the magnet body.

FIG. 7 is a graph showing an example of a change in the developer transport amount with respect to a change in the maximum magnetic force of the developer transport amount regulation.

FIG. 8 is a graph showing an example of changes in the amount of toner scattering with respect to the amount of developer conveyed by the developing sleeve.

FIG. 9 is a graph showing an example of changes in the developer transport amount with respect to changes in the developing sleeve surface roughness.

[Explanation of symbols]

 1 magnet body A magnet center portion B magnet body end portion 3 regulating member 4 bucket roller 5 developing sleeve

Claims (1)

[Claims] 1. A developing device which includes a magnet body and a developing sleeve which rotates around the magnet body, and which conveys a developer to a developing area while holding the developer on the sleeve surface based on the magnetic force of the magnet body. According to the magnetic force from each part of the magnet body in the rotation axis direction of the sleeve, the surface roughness of the developing sleeve is changed so that the larger the magnetic force is, the smaller the surface roughness is. apparatus.