JP2004226879A - Developing device and developer carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple developing device where a developer carrier enabling a high image quality and high speed printing is assembled. <P>SOLUTION: In the developer carrier possessing a magnetic field generating means fixed inside and a cylindrical sleeve part freely rotatably arranged with the magnetic field generating means, the outer periphery of a non-magnetic sleeve is coated with a magnetic material and a binding agent consisting of magnetic particles and containing a conductive agent, and the center of the magnetic particles are embedded in the binding agent and the magnetic particles are exposed on a surface, and the developing device where the developer carrier is incorporated is provided. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device provided in an image forming apparatus such as a copying machine, a facsimile, a printer, etc., for developing a latent image formed on an image carrier using a two-component developer composed of toner and magnetic particles. is there.
[0002]
[Prior art]
2. Description of the Related Art In recent years, there is a trend toward colorization of electrophotography, and the need for higher image quality is increasing. In a developing device, it is desired to faithfully reproduce a latent image on a photoconductor in order to achieve high image quality. In the above-mentioned conventional two-component developing device that is often used, a developer in which toner is electrostatically attached to a magnetic carrier is used, and the developer is transported by a magnetic force of a developing roller which is a developing carrier. Development is performed by electrostatically attaching only toner to the latent image on the photoreceptor.However, when developing at high speed, the developing ability is insufficient, and it is impossible to faithfully develop a fine latent image. There was a problem.
[0003]
In order to solve such a problem, in a conventional developing device, as described in Patent Literature 1, an AC electric field is applied between a developing sleeve and a photosensitive drum to increase development efficiency. As described in Japanese Patent Application Laid-Open No. H11-163, there is a method in which a plurality of developing rollers are used for one photosensitive drum to increase a developing ability. However, these means generate an AC electric field. This requires a separate apparatus or a plurality of developing rollers, which has been complicated mechanically.
[Patent Document 1]
JP-A-09-054487
[Patent Document 2]
JP-A-03-204084
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a developing roller having high developing efficiency and excellent carrier adhesion, and a developing device incorporating the developing roller.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing roller which has a high developing efficiency and does not cause image unevenness such as pitch unevenness over a long period of time, and a developing device incorporating the developing roller.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention according to claim 1 has a magnetic field generating means fixed inside, and a developer bearing having a cylindrical sleeve portion rotatably arranged with the magnetic field generating means. The developer carrier is a developer carrier, wherein a member made of a magnetic material is disposed on the outer periphery of a non-magnetic sleeve.
[0006]
According to a second aspect of the present invention, in the developer carrier according to the first aspect, the size of the magnetic material of the developer carrier is twice or more and within 10 times the developer diameter. Developer carrying member.
According to a third aspect of the present invention, in the developer carrier according to the first or second aspect,
The developer carrier is characterized in that the distance between the magnetic bodies is not less than twice and not more than five times the developer diameter.
[0007]
According to a fourth aspect of the present invention, there is provided the developer carrier according to any one of the first to third aspects, wherein the developer carrier comprises a magnetic material dispersed irregularly. It is an agent carrier.
According to a fifth aspect of the present invention, there is provided the developer carrier according to any one of the first to fourth aspects, wherein the developer carrier has a magnetic material exposed on a sleeve surface. Developer carrying member.
[0008]
According to a sixth aspect of the present invention, there is provided the developer carrier according to any one of the first to fifth aspects, wherein the developer carrier comprises a sleeve made of a magnetic material including magnetic particles and a binder containing a conductive agent. The developer carrier has a structure coated on the top, wherein the center of the magnetic particles is buried in a binder, and the magnetic particles are exposed on the surface.
According to a seventh aspect of the present invention, there is provided a developing device using a two-component developer in an electrophotographic process, wherein the developing device includes the developer carrier according to any one of the first to sixth aspects. Is a developing device.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The details of the present invention will be described based on examples shown in the drawings.
As a developing device, a so-called two-component developing device using a developer in which a magnetic carrier and a non-magnetic toner are mixed is widely used. As shown in FIG. 1, the two-component developing device is installed such that the photosensitive drum 1 and the developing roller 2 are close to each other, and includes a developing roller 2, a stirring member, and a developer amount regulating member.
[0010]
According to the present invention, by arranging a soft magnetic material regularly or irregularly in the vicinity of the surface of the developing sleeve in the developing roller 2, the developer 7 and the photosensitive drum 1 are brought into close contact with each other in the developing area to enhance the developing ability. Things.
An embodiment of the present invention is shown in FIGS. 2 (a) and 2 (b).
FIG. 2A shows a state in which a wire made of a magnetic material is embedded in a groove provided in an axial direction on a sleeve.
FIG. 2B shows a sleeve coated with a material obtained by mixing a binder and magnetic particles.
[0011]
These effects will be described below.
FIG. 3A shows a magnetic force diagram of the entire conventional developing roller. As shown in FIG. 3A, the magnetic field generated by the internal mag roller passes over the sleeve, which is a non-magnetic material, and reaches the adjacent magnetic pole. The developing roller transports the developer by using the lines of magnetic force. Next, a magnetic field diagram and a state of the developer near the photoconductor are shown in FIG. 3B, and a magnetic field diagram and the state of the developer of the present invention are shown in FIG.
In the case of the conventional sleeve, as shown in FIG. 3B, the developer forms ears along the lines of magnetic force of the developing sleeve, so that the contact between the developer and the photoreceptor is rough and wide. If the width is not widened, the developing capacity will be insufficient.
[0012]
On the other hand, when the sleeve of the present invention is used, the magnetic lines of force easily pass through the magnetic material as shown in FIG. Ears are formed around the body. For this reason, the contact between the photosensitive member and the developer is repeated many times in close and short contact, so that the developing ability is enhanced, and even a high-density image can be faithfully reproduced. In this case, the size of the magnetic material is preferably 2 to 10 times the developer diameter (carrier particle size), and the magnetic material interval (the length of the portion where the nonmagnetic material is exposed) is 2 times the carrier particle size. It is desirably at least twice and within five times. If the size of the magnetic material is too small, ears are not formed around the magnetic material, so that the above-described effect of improving the image quality cannot be obtained. Conversely, if the size is too large, the width of the ears becomes wider, so that the effect of improving the image quality is obtained. Will fade. On the other hand, if the pitch of the magnetic material is too narrow, the effect of the magnetic field forming ears around the magnetic material is diminished. Conversely, if the pitch is too wide, the pitch remains on the image.
[0013]
The material of the magnetic material may be a soft magnetic material in which permanent magnetization hardly remains, and an iron-based material having a high magnetic permeability is preferable. However, an effect can be obtained even with iron oxide such as ferrite.
Further, the magnetic body may have a structure hidden by the coating film as shown in FIG. 4A, but it is more effective to expose the magnetic body to the sleeve surface as shown in FIG. 4B. However, in the case of the structure shown in FIG. 4A, since the magnetic particles are embedded in the binder, the detachment of the magnetic particles can be prevented, and a developing roller having excellent durability can be provided. .
Therefore, in order to prevent the detachment of the magnetic particles and not to impair the effects of the present invention, the center of the magnetic particles is buried in the binder as shown in FIG. Is desirable.
[0014]
The arrangement of the magnetic particles may be a regular arrangement such as the wire type shown in FIG. 2A, but depending on the linear velocity ratio with the photoreceptor, the pitch of the magnetic substance can be visually recognized on the image. Since it may occur, it is desirable that the coatings are arranged at irregular pitches as shown in FIG. 2B.
As a processing method, a method of mixing magnetic particles with a binder containing a conductive material and coating in a wet manner, a method of spraying only magnetic particles on a sleeve, or forming a groove in advance on a sleeve, and forming a groove in the groove A method of bonding a magnetic wire or the like can be considered.
[0015]
Further, according to the present invention, it is possible to prevent the carrier from adhering to the surface of the photosensitive drum. Carrier adhesion is a phenomenon in which a carrier constrained by magnetic force on a sleeve loses the electrostatic force received from the photoreceptor and the carrier adheres to the photoreceptor. In the sleeve of the present invention, the magnetic material is dispersed on the sleeve surface. With this structure, the effective magnetic flux density can be increased, and the magnetic force received by the carrier can be increased, so that the carrier can be prevented from adhering.
[0016]
【The invention's effect】
According to the present invention, the developing efficiency can be increased by the developer forming ears around the magnetic particles in the developing area, the margin for carrier adhesion is high, no image unevenness occurs, and no pitch unevenness occurs. There is an effect that it is possible to provide a developing roller that can obtain an image with excellent image quality for a long period of time and that can prevent detachment of magnetic particles.
[0017]
According to the present invention, the developing efficiency can be increased by the developer forming ears around the magnetic particles in the developing area, the margin for carrier adhesion is high, no image unevenness occurs, and no pitch unevenness occurs. There is an effect that it is possible to provide a developing device incorporating a developing roller capable of obtaining an image having excellent image quality for a long period of time and preventing the detachment of magnetic particles.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a two-component developing device.
FIG. 2 is a diagram in which a magnetic material is arranged on a developing sleeve.
FIG. 3 is a diagram illustrating lines of magnetic force in a developing roller.
FIG. 4 is a diagram illustrating an arrangement of magnetic particles and a binder on a developing sleeve.
[Explanation of symbols]
Reference Signs List 1 photosensitive drum 2 developing roller 3 doctor blade 4 slide plate 5 paddle 6 case 7 developer (carrier + toner)

Claims (7)

In a developer carrier having a magnetic field generating means fixed inside and a cylindrical sleeve portion rotatably arranged with the magnetic field generating means,
The developer carrying member is characterized in that a member made of a magnetic material is disposed on the outer periphery of a non-magnetic sleeve. The developer carrier according to claim 1,
The developer carrying member is characterized in that the size of the magnetic material is at least twice and at most 10 times the developer diameter. The developer carrier according to claim 1, wherein
The developer carrier according to claim 1, wherein a distance between the magnetic bodies is at least two times and at most five times a developer diameter. The developing carrier according to any one of claims 1 to 3,
The developer carrying member is characterized in that a magnetic material is irregularly dispersed. The developing carrier according to any one of claims 1 to 4,
The developer carrying member is characterized in that the developer carrying member is arranged such that a magnetic material is exposed on the surface of the sleeve. The developing carrier according to any one of claims 1 to 5,
The developer carrier has a structure in which a magnetic material is made of magnetic particles and is coated on a sleeve together with a binder containing a conductive agent.The center of the magnetic particles is buried in the binder, and the magnetic particles are formed on the surface. A developer carrying member having an exposed structure. In a developing device using a two-component developer in an electrophotographic process,
A developing device comprising the developer carrier according to claim 1.

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