JPH05165339A - Developing device - Google Patents

Abstract

PURPOSE:To prevent magnetic carriers from being carried to a development area while sticking on a toner carrier and to eliminate the generation of an image defect and a decrease in the maintainability of the device when an electrostatic latent image is visualized by using a two-component developer, obtained by mixing magnetic carriers and nonmagnetic toner and transferring toner from the toner carrier where only the nonmagnetic toner is stuck to the electrostatic latent image. CONSTITUTION:The toner carrier 1 is arranged opposite a toner supply member 2, which supplies only the nonmagnetic toner of the two-component developer to the toner carrier 1, and an electrostatic latent image holder 5, which has the electrostatic latent image formed on its surface, at different positions, and a magnet roll 3 which rotates nearby the toner carrier 1 is provided downstream at the position where it faces the toner supply member 2 in the peripheral direction of the toner carrier 1. Consequently magnetic carriers which are transferred to the toner carrier 1 already are removed and prevented from being carried to the development area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an image forming apparatus such as an electrophotographic copying machine or a printer and which visualizes an electrostatic latent image on a photosensitive member by adhering toner, and particularly to a non-magnetic toner. The present invention relates to a developing device using a two-component developer in which a magnetic carrier and a magnetic carrier are mixed.

[0002]

2. Description of the Related Art Conventionally, various types of developing devices for developing an electrostatic latent image on a photoconductor to form a visible image have been proposed according to the type of developer used. Among these, a developing device using a non-magnetic one-component developer in which a pigment or the like is dispersed in a thermoplastic resin in a powder form and a charge control agent is externally added is used as a developing device in which a toner layer is formed on a developer carrier. It is widely used to visualize an electrostatic latent image by flying. In such a developing device, since the photosensitive member and the developer carrying member are not in contact with each other, a visible image is less disturbed and a high-quality image can be obtained. There is an advantage that images can be formed in a superimposed manner. However, in such a one-component developing device, the charge amount of the toner is unstable and there is a problem in the long-term maintainability of the image quality, or the toner transfer amount of the developer carrier fluctuates due to a slight change in the toner characteristics. There is a problem.

On the other hand, in a two-component developing device using a two-component developing agent composed of a non-magnetic toner and a magnetic carrier, the charge amount of the toner is stabilized by frictional charging with the magnetic carrier, and the above problems are solved. However, a magnetic brush in which magnetic carriers are connected in a spike shape is formed on the developer carrier,
Since the magnetic brush is brought into contact with the electrostatic latent image in the developing area to perform the development, there is a problem that the visible image is disturbed and the sharpness of the image is lowered.

As described above, the one-component developing device and the two-component developing device have their respective characteristics, and the advantages of the developing device using the one-component developer and the advantages of the developing device using the two-component developer are well understood. In combination, developing devices have been proposed which have the desired characteristics of both. FIG. 3 is a schematic configuration diagram showing an example of this developing device.
It is disclosed in Japanese Patent Publication No. This developing device 120
Are arranged in a housing 115 containing a two-component developer, a toner carrier 101 facing the electrostatic latent image carrier 105 and carrying non-magnetic toner on the surface thereof, and a toner carrier 101, which is disposed in proximity to the toner carrier. The toner supply member 102 conveys the two-component developer while adsorbing the two-component developer on the surface, and the developer stirring member 113 which stirs the developer and conveys the developer to supply the developer to the toner supply member 102. .. The electrostatic latent image holding member 105 is a belt-shaped photoconductor that can form an electrostatic latent image on the surface due to the difference in charging potential after being uniformly charged and then irradiated with image light. The toner supply member 102 has a plurality of magnetic poles fixed in position inside, and can form on the surface a magnetic brush in which magnetic carriers accompanied by non-magnetic toner are connected in a spike shape. ..

In such a developing device, the magnetic brush formed on the toner supplying member 102 is conveyed by the rotation of the surface of the toner supplying member and rubs against the surface of the toner carrier 101. An electrostatic field is formed between the toner supply member 102 and the toner carrier 101 by the DC power supplies 106 and 107, and the toner adhering to the magnetic carrier is transferred to the surface of the toner carrier 101 so that the toner becomes thin. Form the layers. On the other hand, the magnetic carrier remains magnetically attracted to the toner supply member. The thin layer of toner formed on the toner carrier is conveyed to the developing area in close proximity to the electrostatic latent image carrier 105 by the rotation of the toner carrier 101. In the developing area, the control electrode 111 is arranged in the gap between the toner carrier 101 and the electrostatic latent image carrier 105,
A DC superimposed AC voltage is applied from the DC power supply 107 and the AC power supply 108, whereby the toner is clouded and adhered to the electrostatic latent image for development.

[0006]

However, in the developing device as described above, when the toner in the two-component developer is supplied to the surface of the toner carrier, the toner and the magnetic carrier are electrically strongly coupled to each other. By this, not only the toner but also the magnetic carrier may move to the surface of the toner carrier. In such a case, the magnetic carrier is conveyed to the developing area where the toner carrying member and the electrostatic latent image holding member are close to each other, and the adhesion of the toner to the electrostatic latent image becomes uneven,
There is a problem that the magnetic carrier is transferred to the electrostatic latent image and image defects such as white spots occur.

When a wire or the like is arranged as a control electrode in the axial direction of the toner carrier near the developing area, the particle size of the magnetic carrier is as large as about three times that of the toner. The magnetic carrier is clogged between
There are problems that streak-shaped image defects are generated and it is difficult to remove the magnetic carriers, so that the sustainability of the control electrode is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to prevent a magnetic carrier from being transferred to a toner carrier and conveyed to a developing area, and causing an image defect. It is an object of the present invention to provide a developing device capable of stably obtaining a high quality image without lowering the maintainability of the device.

[0009]

In order to solve the above problems, the present invention forms a magnetic brush of a two-component developer containing a magnet and having a magnetic carrier and a non-magnetic toner on the surface. The toner supply member, which is conveyed by the above-mentioned method, the electrostatic latent image holding member on which an electrostatic latent image is formed by exposure, and the toner supply member are arranged so as to face each other at different positions. A non-magnetic toner on the toner carrier in a developing area where the electrostatic latent image carrier and the toner carrier face each other. In a developing device for flying an electrostatic latent image to visualize it, a magnet that rotates in proximity to the surface of the toner carrier at a downstream side of a position near the toner supply member in the orbiting direction of the surface of the toner carrier. Shall have rolls.

The magnet roll may be one in which a plurality of magnets are arranged so that their positions are immovable, and only a non-magnetic cylindrical sleeve provided around the magnets is rotated. It may be a magnet roll that has a plurality of magnets built therein and rotates integrally. The position where the magnet roll is provided can be arbitrarily selected as long as it is on the downstream side of the facing position of the toner supply member in the circumferential direction of the toner carrier and upstream of the developing area.

[0011]

In the developing device having the above-mentioned structure, the magnetic brush of the two-component developer formed on the surface of the toner supply member comes into contact with the toner carrier, and the toner is transferred to the surface of the toner carrier to transfer the toner. A thin layer is formed. When the toner carrier rotates, the thin layer of the toner is conveyed to the development area, and the toner flies and adheres to the electrostatic latent image without developing contact with the electrostatic latent image holder, and the development is performed.

In such a process, even when the magnetic carrier along with the toner is transferred from the toner supply member to the toner carrying member, the toner carrier may be disposed on the downstream side of the position facing the toner supplying member in the orbiting direction. Since a magnet roll facing the toner carrier is provided, the magnetic carrier that has passed through the position facing the magnet roll before reaching the development area and is mixed in the thin layer of toner is attracted to the magnet roll by the magnetic attraction force. Adsorbed.

Therefore, the magnetic carrier on the surface of the toner carrying member is not removed by the magnet roll and is not conveyed to the developing area, so that the occurrence of image defects such as uneven density of images and white spots can be prevented. Further, even when a wire is provided as a control electrode at a position where the toner carrier and the electrostatic latent image carrier face each other, it is possible to prevent the maintainability of the control electrode from being deteriorated due to the clogging of the wire portion.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a developing device which is an embodiment of the present invention. This developing device is provided so as to face an electrostatic latent image holder 5 capable of holding an electrostatic latent image due to a difference in charging potential, and is a two-component developing device including a non-magnetic toner 10 and a magnetic carrier 9. A toner supply member 2 that magnetically adsorbs a two-component developer and forms a magnetic brush on the surface in a housing 15 that contains the agent, and the toner supply member 2.
And a cylindrical toner carrier 1 which is arranged so as to be close to the electrostatic latent image carrier 5 at different positions, and rotates by adhering the non-magnetic toner 10, and the toner supply member 2.
Developer regulating member 12 for regulating the amount of developer adsorbed on
And a cylindrical magnet roll 3 that rotates close to the toner carrier 1. Further, a first developer stirring chamber 16 is provided in the housing 15 at a position adjacent to the toner supply member 2, and a second developer stirring chamber partitioned by the first developer stirring chamber 16 and a partition wall 18 is provided. Room 17
Is provided.

The toner supply member 2 has a rotatable cylindrical sleeve 21 arranged on the outer circumference of a magnet 22 supported so that its position is immovable.
The two-component developer is magnetically adsorbed on the surface of the above to form a magnetic brush, and the sleeve 21 is rotated to convey the developer.

The toner carrier 1 is a cylinder of aluminum whose surface is alumite treated, a cylinder of phenolic resin, or a cylinder of aluminum having a resin layer formed on the surface thereof. The rotation direction is set so that both facing surfaces move in the same direction at the facing position with.

A DC superimposing AC voltage is applied between the toner supply member 2 and the toner carrier 1 from a bias power source 6 so that an oscillating electric field is generated at a position where they are close to and face each other. Further, at a position where the toner carrier 1 and the electrostatic latent image carrier 5 face each other, two thin wires stretched in the axial direction of the toner carrier 1 are formed, and the toner carrier 1 and the toner carrier 1 are about 10 to 100 μm. A control electrode 11 for holding the gap is provided. A DC voltage or an alternating voltage is applied to the control electrode 11 and the toner carrier 1 from the bias power sources 7 and 8, and the control electrode 11 and the electrostatic latent image carrier are provided between the control electrode 11 and the toner carrier 1. 5, an electric field is generated between the toner carrying member 1 and the electrostatic latent image holding member 5, and these opposing portions serve as a developing area.

The magnet roll 3 includes a non-magnetic cylindrical sleeve rotatably supported and a magnet roll supported so as to be fixed in position inside the sleeve.
The toner carrier 1 is provided at a position downstream of the position facing the toner supply member 2 in the rotation direction of the toner carrier 1 and close to the toner carrier 1 upstream of the developing area.
The rotation direction of the cylindrical sleeve of the magnet roll 3 is set so that the cylindrical sleeve moves in the same direction as the surface of the toner carrier at a portion where the surface is close to the toner carrier 1. Also,
A scraper 4 is provided which comes into contact with the surface of the magnet roll 3 and peels off the magnetic carrier 9 attached on the magnet roll.

The first developer agitating chamber 16 and the second developer agitating chamber 17 are communicated with each other at both ends in the axial direction of the toner supply member 2, and the agitating of the developer and the axial direction are carried out. There is provided a first screw auger 13 and a second screw auger 14 for carrying the developer. The rotation directions of these two screw augers 13 and 14 are set so as to convey the developer in mutually opposite directions, and the developer circulates in the first developer stirring chamber and the second developer stirring chamber 17. It is supposed to do.

In such a developing device, the non-magnetic toner 10 and the magnetic carrier 9 are conveyed in the first developer agitating chamber 16 and the second developer agitating chamber 17 and agitated to be uniform. Non-magnetic toner in developer 10
Is maintained constant, and sufficient charge is applied to the non-magnetic toner by frictional charging between the non-magnetic toner 10 and the magnetic carrier 9.

The agitated developer is supplied to the toner supply member 2 by the first screw auger 13. The toner supply member 2 magnetically adsorbs the developer to form a magnetic brush of the developer, and conveys the developer to a position facing the toner carrier 1 by rotation. Toner carrier 1 and toner supply member 2
A DC superposed AC voltage is applied between the two, and the charged toner is transferred to the toner carrier 1 by Coulomb force and forms a thin layer of toner on the surface of the toner carrier. On the other hand, the magnetic carrier remains magnetically attracted to the toner supply member 2 without being transferred.

At this time, if the adhesive force between the toner 10 and the magnetic carrier 9 is large, there are cases where not only the toner 10 but also a part of the magnetic carrier 9 adheres to the surface of the toner carrier 1. The magnetic carrier 9 is the toner carrier 1
Is conveyed to a position close to the magnet roll 3 by the rotation of. The magnet roll 3 adsorbs the magnetic carrier on the toner carrier and removes it from the surface of the toner carrier 1. The magnetic carrier 9 adsorbed by the magnet roll 3 is conveyed by the rotation of the cylindrical sleeve, separated from the magnet roll 3 by the scraper 4 and returned into the first developer stirring chamber 16. At this time, at the contact position of the scraper 4, since the magnetic force of the built-in magnet is small, the scraper 4 can be easily peeled off.

The magnetic layer is not mixed in the toner layer on the toner carrier 1 which has passed the position facing the magnet roll 3, and is conveyed to the developing area as the toner carrier 1 rotates. This toner layer passes through a position close to the control electrode 11, and a DC cloud AC voltage applied to the control electrode 11 generates a toner cloud in the developing area. The clouded toner flies in the electric field, and the electrostatic latent image holder 5
Development is performed by attaching to the electrostatic latent image above. At this time, the magnetic carrier 9 does not adhere to the toner carrier 1 and the occurrence of image defects is prevented.

FIG. 2 is a schematic structural view showing a developing device which is another embodiment of the present invention. In this developing device, in place of the magnet roll 3 arranged in the vicinity of the toner carrier in the above-described embodiment, a cylindrical magnet 33 having S poles and N poles alternately magnetized in the circumferential direction is provided. ing. The cylindrical magnet 33 is provided at substantially the same position as the magnet roll 3 of the above-described embodiment, and is rotatably supported near the surface of the toner carrier 1. The other structure of the developing device is the same as that of the above embodiment. In this embodiment, the magnetic carrier 9 attached on the toner carrier can be directly attracted to the cylindrical magnet 33 and removed. In addition, the cylindrical magnet 33
It is conveyed by its rotation, is peeled off from the cylindrical magnet 33 by the scraper 4, and is returned into the first developer stirring chamber 16. Also in the developing device of the present embodiment, as in the above embodiment, the magnetic carrier is not transported to the developing area,
The occurrence of image defects is prevented. In addition, the cylindrical magnet 33 used in this embodiment is inexpensive and can be easily manufactured.

[0025]

As described above, in the developing device of the present invention, the magnet roll is provided in the vicinity of the toner carrier on the downstream side of the position facing the toner supply member in the circumferential direction of the toner carrier. Therefore, the magnetic carrier attached to the toner carrier is attracted to the magnet roll by the magnetic attraction force and removed from the toner carrier. As a result, the conveyance of the magnetic carrier to the developing area is eliminated, the occurrence of image defects is prevented, and the toner having a sufficient charge is conveyed to the developing area, so that a high-quality image can be stably obtained without contact. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating a developing device that is an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a developing device that is another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional developing device.

[Explanation of symbols]

1 Toner Carrier 2 Toner Supply Member 3 Magnet Roll 4 Scraper 5 Electrostatic Latent Image Holder 6 Bias Power Supply 7 Bias Power Supply 8 Bias Power Supply 9 Magnetic Carrier 10 Non-Magnetic Toner 11 Control Electrode 12 Developer Controlling Member 13 First Screw Auger 14 Second Screw Auger 15 Housing 16 First Developer Stirring Chamber 17 Second Developer Stirring Chamber 18 Partition 33 Magnet Roll

Claims (1)

[Claims] 1. A toner supply member which contains a magnet and forms and conveys a magnetic brush of a two-component developer comprising a magnetic carrier and a non-magnetic toner on the surface, and an electrostatic latent image is formed on the surface by exposure. An electrostatic latent image holder and a toner carrier that are arranged to face the toner supply member at different portions, and are driven so as to circulate with the nonmagnetic toner attached to the surface. In a developing device in which a non-magnetic toner on the toner carrying body is made to fly to the electrostatic latent image and visualized in a developing area where the electrostatic latent image holding body and the toner carrying body face each other, A developing device comprising a magnet roll that rotates in the vicinity of the surface of the toner carrier at a position downstream of a position facing the toner supply member in the orbiting direction.