JPH10282790A - Developing device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which can be miniaturized by making the diameter of a developing sleeve small and stably secure excellent sealability by preventing the increase of torque caused by the increase of the rotational torque of the developing sleeve. SOLUTION: The developing device 11 is constituted to provide the developing sleeve 6 which includes a magnet roller 7 and carries toner (developing) 13 having magnetic grains (carriers) to a developing region to develop an electrostatic latent image formed on a photoreceptive drum (image carrier) 10. In such a case, the magnet roller 7 is composed of the rare earth resin magnet and a magnetic seal consists of a magnet 8 surrounding at least a part of the outer periphery of the sleeve 6, so that the leakage of the toner 13 from the end part of the sleeve 6 can be prevented by the magnetic seal. Thus, the rare earth resin magnet having an excellent magnetic characteristic is used for the magnet roller 7, so that the diameter of the sleeve 6 can be made so small as to miniaturize the developing device 11. Further, the magnet 8 is used for attaining magnetic sealing against the toner, which prevents the increase of the torque of the sleeve 6 and secures the excellent sealabilitly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming an electrophotographic image and a process cartridge detachably mountable to the main body of the image forming device.

[0002]

2. Description of the Related Art In an image forming apparatus employing an electrophotographic method, a method of visualizing an electrostatic latent image formed on a photosensitive drum as an image carrier with toner as a developer has been widely adopted. As a typical method, a developing method using a magnetic brush is known.

FIG. 4 shows a configuration of a process cartridge of a conventionally known image forming apparatus.

FIG. 4 is a sectional view of a conventional process cartridge 101.
A developing sleeve 106 as a developer carrier is rotatably supported on the frame of the developing container 109. The developing sleeve 106 is made of a non-magnetic material, and a magnet roller 107 is non-rotatably disposed therein.

As shown in FIG. 5, the magnet roller 107 has an S1 pole in a developing area facing the photosensitive drum 110,
The S2 pole, the N1 pole, and the N2 pole are magnetized in other areas, respectively.
A magnetic brush of toner is formed on 6.

The magnetic one-component toner, which is a developer carried on the developing sleeve 106, or the two-component toner composed of a magnetic carrier and toner, is supplied to the latent image on the photosensitive drum 110 with the rotation of the developing sleeve 106. Is transported to the area for developing.

[0007] At both ends of the developing sleeve 106, seal members 105 for preventing toner leakage are provided. As the seal members 105, those made of an elastic material such as felt or foam material are often used. And developing sleeve 1
06 is affixed to the frame of the developing container 109 or the frame of the process cartridge 101 with a double-sided tape or the like so as to be in contact with the outer peripheral surface.

[0008]

By the way, as the diameter of the developing sleeve progresses along with the downsizing of the process cartridge and the developing device, the following problems occur.

More specifically, the conventional magnet roller 107 shown in FIGS. 4 and 5 is often made of a rubber magnet or a plastic magnet containing ferrite powder, but the ferrite-based magnet has a weak magnetic force. If the diameter of 107 is reduced, it becomes difficult to obtain a magnetic flux density (about 600 to 1000 gauss on the surface of the developing sleeve 106) required for the developing operation.

In addition to poor adhesion workability of the elastic seal member 105 for preventing toner from leaking from the end of the developing sleeve 106, when the elastic seal member 105 is adhered along a surface having a small curvature, FIG. As shown in FIG.
05 is twisted and floats on it, causing toner leakage or twisting, whereby the contact pressure of the seal member 105 against the developing sleeve 106 increases, and the developing sleeve 10
A problem arises that the rotational load of No. 6 increases and causes an increase in torque.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the size of the developing sleeve by reducing its diameter, and to increase the torque associated with an increase in the rotational load of the developing sleeve. An object of the present invention is to provide a developing device and a process cartridge which can prevent the developing device from stably maintaining a good sealing property.

[0012]

According to a first aspect of the present invention, there is provided an electrostatic latent image including a magnet roller and a developer having magnetic particles formed on an image carrier. In a developing device having a developing sleeve for transporting to a developing area, the magnet roller is made of a rare earth resin magnet, and a magnetic seal is made up of a magnet surrounding at least a part of the outer periphery of the developing sleeve. Thus, leakage of the developer from the end of the developing sleeve is prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, the rare earth resin magnet is formed of a Nd-Fe-B based bonded magnet.

According to a third aspect of the present invention, there is provided a static image forming apparatus which is detachable from a main body of an image forming apparatus, includes at least an image carrier, a magnet roller, and a developer having magnetic particles formed on the image carrier. In a process cartridge configured to integrally incorporate a developing device having a developing sleeve for transporting to a developing area of an electro-latent image, a magnet roller of the developing device is formed of a rare earth resin magnet, A magnetic seal is formed by a magnet surrounding at least a part of the developing sleeve, and the magnetic seal prevents leakage of the developer from the end of the developing sleeve.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the rare earth resin magnet is formed of a Nd-Fe-B based bonded magnet.

Therefore, according to the present invention, since the magnet constituting the magnet roller is a rare earth resin magnet having better magnetic properties than the conventional ferrite magnet, the diameters of the magnet roller and the developing sleeve are also small. Can be
The size of the developing device and the process cartridge can be reduced.

Further, since the toner is magnetically sealed by using a magnet as the seal member, the problem of twisting of the seal member does not occur, and a good increase in the torque due to an increase in the rotational load of the developing sleeve is prevented. Properties can be stably ensured.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of an electrophotographic process cartridge according to the present invention.

A process cartridge 1 shown in FIG. 1 is a photosensitive drum 1 which is an image carrier which is driven to rotate in the direction of arrow A.
0, a charging roller 2 serving as a charging device for charging the photosensitive drum 10, a developing device 11, and a cleaning device 12 are integrally incorporated into a unit.

The developing device 11 is provided with a developing container 9 containing a toner 13 which is a one-component magnetic developer, and an opening of the developing container 9 faces a photosensitive drum 10 with a developer carrying member. A developing sleeve 6 is rotatably disposed. The developing device 11 includes an elastic blade 14 as a developer regulating member. The elastic blade 14 contacts the developing sleeve 6 and regulates the thickness of the toner 13 carried and transported by the developing sleeve 6.

Next, an image forming process of the process cartridge 1 configured as described above will be described.

The photosensitive drum 10 is uniformly charged by the charging roller 2 driven by the rotation of the photosensitive drum 10, and a latent image is formed on the surface of the photosensitive drum 10 by laser light. Then, the latent image formed on the surface of the photosensitive drum 10 is developed by the developing device 11 using a so-called one-component jumping developing method, and is visualized as a toner image.

That is, the toner 13 contained in the developing container 9
The developing sleeve 6 is driven by the magnetic force of a magnet roller 7 which is a magnetic field generating means fixed non-rotatably in the developing sleeve 6.
Stick on top. Then, the attached toner 13 passes through the abutting portion between the elastic blade 14 and the developing sleeve 6 with the rotation of the developing sleeve 6, whereby the developing sleeve 6
It is thinly coated while charging on top.

The developing sleeve 6 is connected to the photosensitive drum 1
The toner 13 thinly coated on the developing sleeve 6 is rotated by the rotation of the developing sleeve 6 so that the toner 13 is closest to the outer peripheral surface of the developing sleeve 6 and the photosensitive drum 10. Pass through the development area. During this passage process, the toner 13 on the surface of the developing sleeve 6 flies due to the electric field generated by the DC and AC voltages applied between the photosensitive drum 10 and the developing sleeve 6, and the toner 13 between the photosensitive drum 10 and the developing sleeve 6 in the developing area portion. Go back and forth between Finally, the toner 13 on the side of the developing sleeve 6 is selectively transferred and adhered according to the potential pattern of the latent image on the surface of the photosensitive drum 10, and a toner image is sequentially formed.

The toner image developed on the photosensitive drum 10 is transferred to a recording sheet by a transfer roller (not shown). At this time, residual toner remaining on the photosensitive drum 10 without being sufficiently transferred is scraped off by a cleaning blade 15 made of a rubber blade that comes into contact with the photosensitive drum 10 and removed.

The toner image transferred to the recording paper is
The image is transferred to a recording sheet by a fixing device (not shown) to form a permanent image.

Next, the developing device 11 according to the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view showing the configuration of the developing device 11 of the process cartridge 1, and FIG. 3 is a partial cross-sectional view showing the configuration of one end of the developing device 11 in the longitudinal direction.

The developing sleeve 6 is made of a non-magnetic material.
This is rotatably supported by the developing container 9 via a bearing 16 as shown. A magnet roller 7 is provided in the developing sleeve 6, and a notch 7a-1 is formed in a shaft portion 7a of the magnet roller 7 as shown in FIG. By engaging -1 with the developing container 9, the magnet roller 7 is fixed in a non-rotatable state. In addition, as shown in FIG.
The developing pole S1 is magnetized at a position facing the photosensitive drum 10, and the S2, N1 and N2 poles are magnetized at other positions.

An Nd-Fe-B bond magnet is used as a magnet constituting the magnet roller 7, and the Nd-Fe-B bond magnet is formed by dispersing a rare earth powder in a resin as a binder. Is a rare-earth resin magnet that has superior magnetic properties to ferrite-based magnets that have been frequently used in conventional magnet rollers, so that a required magnetic force can be obtained even when the diameter of the magnet roller 7 is reduced. . Accordingly, the diameter of the developing sleeve 6 can be reduced, and the size of the developing device 4 can be reduced. In the present embodiment, the diameters of the developing sleeve 6 and the magnet roller 7 are set to φ10 mm and φ8.5 mm, respectively.

When the diameter of the developing sleeve 6 is reduced as described above, the workability of attaching the sealing member for preventing toner leakage from the end of the developing sleeve 6 is deteriorated, and the sealing member is stained. Although the problem described above occurs, in the present embodiment, the magnet 8 is used as a seal member.
Was used to magnetically seal the toner, so that the above problem could be solved.

The magnet 8 constituting the magnetic seal is shown in FIG.
As shown in FIG. 2, a predetermined gap g is provided from the outer peripheral surface of the developing sleeve 6 so as to surround the developing sleeve 6. A plurality of magnetic poles N and S are arranged along the direction, and a magnetic curtain is formed in a gap with the developing sleeve 6. The magnetic curtain holds the toner in the gap and prevents the toner from leaking from the end of the developing sleeve 6.

Since the developing container 9 has a shape that matches the shape of the magnet 8, and the magnet 8 is attached to that portion, the assemblability of the magnet 8 is improved.
Also, of course, twisting of the sealing member does not occur,
Good sealing performance is ensured without the problem that the rotational load of the developing sleeve 6 increases and causes a torque increase.

In this embodiment, a process cartridge which is detachable from the main body of the image forming apparatus and in which the image forming process means is integrated into a unit has been described. However, the present invention is applied to a copier or a laser beam printer. It goes without saying that the present invention can be applied to a developing device and a developing cartridge.

[0035]

As is apparent from the above description, according to the present invention, the magnet constituting the magnet roller is made of a rare earth resin magnet having better magnetic properties than the conventional ferrite magnet. The diameters of the magnet roller and the developing sleeve can also be reduced, and the effect of reducing the size of the developing device and the process cartridge can be obtained.

According to the present invention, the toner is magnetically sealed by using a magnet as a seal member, so that the problem of twisting of the seal member does not occur, and the torque increases with an increase in the rotational load of the developing sleeve. Is obtained, and good sealing performance can be stably secured.

[Brief description of the drawings]

FIG. 1 is a sectional view of a process cartridge according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a developing device according to the present invention.

FIG. 3 is a partial cross-sectional view illustrating a configuration of one end in a longitudinal direction of a developing device according to the present invention.

FIG. 4 is a sectional view of a conventional process cartridge.

FIG. 5 is a cross-sectional view illustrating a configuration of a developing device portion of a conventional process cartridge.

FIG. 6 is a sectional view of a seal member provided in a developing device of a conventional process cartridge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Process cartridge 6 Developing sleeve 7 Magnet roller 8 Magnet 10 Photosensitive drum (image carrier) 11 Developing device 13 Toner (developer)

Claims (4)

[Claims] 1. A developing device including a magnet roller and a developing sleeve for transporting a developer having magnetic particles to a developing area of an electrostatic latent image formed on an image carrier, wherein the developing device includes a developing sleeve. In addition to being composed of rare earth resin magnets,
A developing device, wherein a magnetic seal is constituted by a magnet surrounding at least a part of the outer periphery of the developing sleeve, and the magnetic seal prevents leakage of the developer from an end of the developing sleeve. 2. The rare earth resin magnet according to claim 1, wherein the rare earth resin magnet is Nd—Fe—B.
The developing device according to claim 1, wherein the developing device is a system bond magnet. 3. An image forming apparatus, comprising:
At least an image carrier and a developing device including a magnet roller and having a developing sleeve for transporting a developer having magnetic particles to a development area of an electrostatic latent image formed on the image carrier are integrally incorporated. In the process cartridge, the magnet roller of the developing device is formed of a rare-earth resin magnet, and a magnetic seal is formed by a magnet surrounding at least a part of the outer periphery of the developing sleeve. A process cartridge for preventing leakage of the developer from the section. 4. The rare earth resin magnet according to claim 1, wherein the magnet is Nd—Fe—B.
4. The process cartridge according to claim 3, wherein the process cartridge is a bonded magnet.