JPH075752A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the variance of a gap between a developer carrier and a mesh-like electrode by providing the mesh-like electrode formed out of a ferromagnetic substance closely arranged to the developer carrier and a magnetic field generation means at a position for allowing attraction force to act on the electrode, and to obtain an image without irregularities by uniformizing pressure between the developer carrier and the mesh-like electrode. CONSTITUTION:A one-component toner carrier 2 being as the developer carrier is arranged to be closely opposed to a photoreceptor drum 1. The carrier 2 is cylindrically formed out of a non-magnetic electrical conductive material and provided with a fixed magnet 5 being as the electric field generation means inside. Besides, the electrode 4 formed out of the ferromagnetic substance is disposed in a developing area formed between the drum 1 and the carrier 2 by being close to the carrier 2. In such a case, the electrode 4 is provided to be stuck on both side plates of a developing device which are not shown in the figure, by weak tensile force. Besides, an AC power source 7 is connected to the electrode 4 through a safety resistance 6 and a DC power source 8 is connected to the carrier 2 and the drum 1 as it is shown in the figure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a copying machine, an LB.
The present invention relates to an electrophotographic image forming apparatus or an electrostatic recording image forming apparatus such as a P printer or a facsimile, and is characterized by a developing device.

[0002]

2. Description of the Related Art Conventionally, as a one-component non-contact developing method,
A method is known in which a toner carrier on which a thin toner layer is formed and a photosensitive drum or the like as an electrostatic latent image carrier are brought close to each other at an interval of about 0.3 mm, and an AC voltage is applied to perform development.

In this method, a high voltage of about 1 kilovolt is required at the peak voltage, and when it is applied to so-called non-mag toner development using a non-magnetic toner, in a region where the potential contrast of the latent image is high. However, there are drawbacks such as the phenomenon that the image density becomes lower than that in the lower region. Further, in the case of so-called multiple development in which two or more toner images are formed in an overlapping manner, the previously developed image is likely to be disturbed by the reciprocating movement of the toner between the toner carrier and the photosensitive drum. There is also.

There is also a method of using only the DC voltage as the developing bias voltage without using the AC voltage, but there is a drawback that the image becomes dull because the threshold value of the electric field in which the toner flies varies. .

[0005]

As a method of eliminating these drawbacks, a mesh-shaped electrode is provided between the toner carrier and the photosensitive drum, and an alternating voltage is applied between the toner carrier and the mesh electrode, and a direct current is applied. There is a method of applying a voltage between the photosensitive drum and the mesh electrode.

In this method, the applied AC voltage can be lowered by bringing the toner carrier and the mesh-shaped electrode close to each other. Further, even in the case of multiple development, the toner image already developed can be removed. Less disturbed.

However, the unevenness in the image is caused by variations in the distance between the toner carrier and the mesh-shaped electrode due to the mechanical precision of the toner carrier, or by uneven pressure between the toner carrier and the mesh-shaped electrode. Has a drawback that it is apt to occur.

Therefore, an object of the present invention is to obtain a uniform image by eliminating the variation in the distance between the toner carrier and the mesh electrode and by making the pressure between the toner carrier and the mesh electrode uniform. An object of the present invention is to provide an image forming apparatus including a developing device capable of performing the above.

[0009]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
Development having a latent image carrier on which an electrostatic latent image is formed, and a developer carrier that is arranged to face the latent image carrier and carries a non-magnetic one-component developer and conveys the developer to the latent image carrier side. An image forming apparatus including an apparatus, which has an electrode member formed of a ferromagnetic material and disposed in the vicinity of the developer carrying member, and a magnetic field generating unit provided at a position for applying an attractive force to the electrode member. An image forming apparatus characterized by the above.

An AC electric field is preferably applied between the developer carrying member and the electrode.

According to another aspect of the present invention, a latent image carrier on which an electrostatic latent image is formed and a non-magnetic one-component developer, which is arranged so as to face the latent image carrier, are carried. Image formation provided with a developing device having a developer carrier conveyed to the latent image carrier side and a developer thin layer forming means for forming a thin layer of the non-magnetic one-component developer carried and conveyed by the developer carrier In the apparatus, the developer thin layer forming means is a triboelectrification member including a ferromagnetic material, which is disposed in the vicinity of the developer carrier, and the magnetic field generation is provided at a position where an attractive force is applied to the triboelectrification member. An image forming apparatus having means.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

First, the overall structure of the image forming apparatus according to the present invention will be described with reference to FIG. The photosensitive drum 10 as a latent image carrier formed of an organic semiconductor or the like rotates in the direction of the arrow and is uniformly charged to a prescribed voltage by the charging device 11. Further, the electrostatic latent image corresponding to the image of the first color is formed by being exposed by the laser scanning device 12, and further the first latent image is formed.
Is developed by the developing device 13 of the color. In a state where the cleaning device 17 is not in contact with the photoconductor drum 10, the first screen portion for one screen formed on the photoconductor drum 10 is formed.
The color image is further subjected to charging by the charging device 11 and exposure corresponding to the second color image by the laser scanning device 12, and the developing device 14 superimposes the second color toner image on the first color toner image. Is developed. Similarly, the third and fourth colors are similarly developed by the third and fourth developing devices 15 and 16. Next, the toner image is transferred by the action of the transfer charging device 19 onto the transfer paper supplied by the transport roller 18 in synchronization with the toner image on the photosensitive drum 10. The toner image on the transfer sheet is conveyed to a fixing device (not shown) via the conveying device 20, fixed by the fixing device, and discharged to a tray (not shown). On the other hand, the toner remaining on the photosensitive drum 1 is removed by operating the cleaning device 17, and is provided for the next step.

Next, the developing device which characterizes the present invention will be described with reference to FIG. A toner carrier 2 serving as a developer carrier is disposed in close proximity to the photosensitive drum 10. The toner carrier 2 is formed of a non-magnetic conductive material such as aluminum or stainless steel in a cylindrical shape, and a fixed magnet 5 as a magnetic field generating means is inserted therein.
Further, in the developing area formed between the photosensitive drum 10 and the toner carrier 2, an electrode 4 made of a ferromagnetic material such as nickel, nickel-iron alloy, iron-cobalt alloy, etc. is placed close to the toner carrier 2. Are arranged. In this case, the electrodes 4 are attached to both side plates (not shown) of the developing device with a weak tension.

An AC power supply 7 is connected to the electrode 4 via a safety resistor 6, and the toner carrier 2 and the photosensitive drum 10 are connected.
A DC power source 8 is connected to each.

In such a structure, the photosensitive drum 1
0 rotates in the direction of the arrow and passes through the developing area, while the toner carrying member 2 has a non-magnetic one-component developer (non-magnetic toner) 3 on its surface in an area (not shown) by a known toner thin layer forming means. It is coated and rotates in the direction of the arrow to pass through the development area. Further, since the electrode 4 is made of a ferromagnetic material, it is attracted by the magnetic field of the fixed magnet 5 so that the distance between the electrode 4 and the toner carrier 2 is kept equal, and the electrode 4 contacts the toner thin layer with a uniform pressure. To do. This makes it possible to form a uniform image.

An AC voltage is applied between the electrode 4 and the toner carrier 2. Due to this AC electric field, the non-magnetic toner is pulled out from the toner carrier 2 and the electrode 4 and the photoconductor drum 10 are connected.
Is developed by the electric field between and. It should be noted that a peak value of 100 to 300 V is sufficient for the AC voltage, and a value of 1 to 5 kHz is used as the frequency although it depends on the rotation speed of the photosensitive drum 10. As the safety resistor 6, a resistor of several kΩ can be used, but a power source provided with a safety mechanism by current detection can also be used. Although the AC voltage is applied to the electrode 4 side in FIG. 1, it may be applied to the toner carrier 2 side, or the AC voltage is applied to both sides, and the voltage difference is 100 to 300V. You can also do so.

Further, in the present construction, the toner particles rotate even in the developing area due to the rubbing against the electrode 4, the adhesive force with the toner carrier 2 changes, and the electrode 4 does not apply the AC voltage. A significant improvement in image quality can be seen as compared with the case where no.

The electrode 4 is formed in a mesh shape by a method such as etching or electroforming and has a thickness of 20 to 100.
About μm is preferable. Not only such a mesh-like one, but a plurality of magnetic wires may be stretched. Further, various shapes and pitches of the pattern of the mesh-like member may be used, but as shown in FIGS.
A circle or a triangle is punched out to form a pattern, and the pattern is arranged so as to be slightly shifted in the longitudinal direction so that periodical unevenness does not occur in the longitudinal direction of the photosensitive drum. A suitable range for these pitches is 0.1 to 1 mm, preferably about 0.3 mm.

Next, another embodiment of the developing device of the image forming apparatus according to the present invention will be described with reference to FIG.

A toner bearing member 31 is disposed in close proximity to the photosensitive drum 30, and a toner supply roller 32 is rotatably disposed on the toner bearing member 31 on the opposite side of the photosensitive drum 30. A magnet 34 is fixed inside the toner carrier 31. Further, above the toner carrier 31, the toner thin layer forming means 33 is held at a predetermined position by adhering its end portion to the holding member 35.

The toner supplied to the toner carrier 31 by the toner supply roller 32 is carried on the toner carrier 31 and conveyed in the direction of the arrow, and the toner thin layer forming means 33 causes the photosensitive drum 30 and the toner carrier. It is formed in a thin layer between 31 and is further conveyed to the developing area.

Toner thin layer forming means (friction charging member)
33 is made of a ferromagnetic metal foil having a thickness of 10 to 100 μm, and is attracted by the magnet 34 so as to leave a predetermined gap above the toner carrier 31. Also, the toner thin layer forming means 33
If necessary, a charge control material may be applied.

With the above-mentioned structure, the contact area between the toner thin layer forming means 33 and the toner carrier 31 can be made long, and the toner or toner can be further applied without applying an excessive pressure to the toner. The toner can be uniformly charged without accelerating the deterioration of the toner carrier.

[0025]

As is apparent from the above description, the image forming apparatus according to the present invention is arranged close to the developer carrying member,
By having an electrode member formed of a ferromagnetic material and an electric field generating means provided at a position where an attractive force is applied to the electrode member, it is possible to eliminate variations in the distance between the developer carrier and the electrode member. By making the pressure between the developer carrier and the electrode member uniform, it is possible to obtain a uniform image.

Further, the developer thin layer forming means is a frictional charging member including a ferromagnetic material, which is disposed in the vicinity of the developer carrying member, and the magnetic field generation is provided at a position where an attractive force acts on the frictional charging member. With the structure having the means, the contact area between the developer thin layer forming means and the developer carrying member can be made longer, and the developer and the developer can be further treated without applying excessive pressure to the developer. A uniform charge can be given to the developer without accelerating the deterioration of the carrier. Therefore, it is possible to provide an image forming apparatus capable of achieving a long life of the apparatus and obtaining a good image.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts showing an embodiment of a developing device of an image forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus to which the developing device of FIG. 1 is applied.

FIG. 3 is a partial plan view showing an example of an electrode pattern applicable to the developing device of FIG.

FIG. 4 is a partial plan view showing another example of an electrode pattern.

FIG. 5 is a main part configuration diagram showing another embodiment of the developing device of the image forming apparatus according to the present invention.

[Explanation of symbols]

 2, 31 toner carrier (developer carrier) 3 toner (developer) 4 electrode member 5, 34 fixed magnet (magnetic field generating means) 10, 30 photoconductor drum (latent image carrier) 33 developer thin layer forming means (Friction charging member)

Claims (3)

[Claims] 1. A latent image carrier on which an electrostatic latent image is formed, and a developer carrier which is disposed so as to face the latent image carrier and carries a non-magnetic one-component developer and conveys it to the latent image carrier. In an image forming apparatus including a developing device having a body, an electrode member formed in the vicinity of the developer carrying member and formed of a ferromagnetic material, and a magnetic field provided at a position for applying an attractive force to the electrode member. An image forming apparatus comprising: a generating unit. 2. The image forming apparatus according to claim 1, wherein an AC electric field is applied between the developer carrier and the electrode. 3. A latent image carrier on which an electrostatic latent image is formed, and a developer carrier that is disposed so as to face the latent image carrier and carries a non-magnetic one-component developer and conveys it to the latent image carrier. An image forming apparatus having a developing device having a body and a developer thin layer forming means for forming a thin layer of a non-magnetic one-component developer carried and conveyed by the developer carrying body, the developer thin layer forming means Is a triboelectrification member including a ferromagnetic material, which is disposed in the vicinity of the developer carrying member, and which has magnetic field generating means provided at a position for exerting an attractive force on the triboelectrification member. apparatus.