JPH1020664A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where the deterioration of performance caused by the wear of a developer regulating member and a developer carrier and the deterioration of developer by the rubbing of them are avoided, the clogging of the developer between the developer regulating member and the developer carrier is prevented, the driving torque of the developing device is lowered and the accuracy of a distance between the developer regulating member and the developer carrier is not required. SOLUTION: The developer carrier 50 is opposed to the developer amount regulating member 70 in a non-contact state. An N pole 551 arranged on a downstream side from a developer supply part and an N pole 550 arranged at a position opposed to an electrostatic latent image holding body 30 are made the same pole, and a magnetic pole is not provided between the N poles 550 and 551, so that an area where magnetic carrying force for the developer on the carrier 50 is substantially eliminated is formed between both poles 550 and 551. The area where the magnetic carrying force is substantially eliminated means an area where magnetic attractive force toward the center in the radial direction of a sleeve 53 becomes zero.

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 image forming apparatus such as a copying machine or a printer using an electrophotographic process. The present invention relates to a magnetic one-component developing device that develops a one-component developer on an electrostatic latent image holding member by an electric field.

[0002]

2. Description of the Related Art A magnetic one-component developing apparatus will be described with reference to FIGS. A one-component developing apparatus using a magnetic one-component developer for developing an electrostatic latent image formed on the electrostatic latent image holding member 30 includes:
A hopper 31 for containing a one-component magnetic developer, a cylindrical developer carrier 37 rotatably supported around a magnet shaft 35 having a plurality of magnetic poles, and a developer on the developer carrier 37 A developer regulating member 40 for regulating the amount of adhesion. In such a developing device, the one-component magnetic developer 31 accommodated in the hopper 33 is held on the surface of the developer carrier 37 by the magnetic force of the magnet shaft 35,
When passing through the developer regulating member 40, the surface of the developer carrier 37 is rubbed and a thin layer of the developer is formed. The rubbing between the developer and the surface of the developer carrying member causes the developer to be triboelectrically charged and to be charged.

The developer regulating member 40 uses an elastic member 41 such as rubber on at least a surface of the developer regulating member 40 which is opposed to the developer carrying member 37. The developer thinned by the developer regulating member 40 is transported to the developing area A where the electrostatic latent image holder 30 and the developer carrier 37 face each other by the rotation of the developer carrier 37. A DC superimposed AC voltage is applied to the developer carrier 37 from a high-voltage AC power supply and a DC power supply.
Due to the electric field generated in the developing area A, the charged developer flies to the electrostatic latent image on the electrostatic latent image holding member 30 and develops. Here, the applied voltage may be a DC voltage from a DC power supply.

A problem with the developing device having such a configuration is that the developer regulating member 40 comes into contact with the developer carrying member 37, so that the developer regulating member 40 and the developer carrying member 37 are contacted.
Deterioration of the developer due to abrasion, high driving torque, clogging of the developer between the developer regulating member 40 and the developer carrier 37, and deterioration of the developer due to rubbing.
High reliability was hindered. In order to avoid this problem, as described in JP-B-59-29872,
A method of disposing the magnetic developer regulating member 45 in non-contact with the developer carrying member 37 has also been proposed (see FIG. 7). However, in the case of the disclosed system, the developer regulating member and the developer carrying member are not connected to each other. It is necessary to set the interval with high accuracy, and there has been a problem that the cost of parts and the cost of assembly and adjustment are increased.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to reduce the performance due to abrasion of the developer regulating member and the developer carrying member, and to develop by sliding. Eliminates developer deterioration, prevents clogging of the developer between the developer regulating member and the developer carrier, reduces drive torque of the developing device, and reduces the distance between the developer regulating member and the developer carrier. It is an object of the present invention to provide a developing device that does not require the precision of the developing device.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned object, a developing device of the present invention uses a positive or negatively charged one-component developer formed in a thin layer on the surface of a developer carrying member by an electric field to hold an electrostatic latent image carrier. A developing device for developing an electrostatic latent image formed on a developer carrier, wherein the developer amount is regulated in a non-contact manner with the developer carrier, and the amount of the developer on the developer carrier arranged downstream of the developer supply unit is regulated. And a developer carrying member having a fixed magnetic pole disposed so as to form a region on the downstream side of the developer amount regulating region downstream of the developer amount regulating region, where the magnetic conveying force of the developer on the developer carrying member is substantially eliminated. I do. The region where the magnetic conveying force is substantially eliminated is a region where the magnetic attraction toward the radial center of the sleeve is zero. Specifically, this is achieved by setting the magnetic attractive force to 0 by setting both the radial magnetic field and the tangential magnetic field to 0. Specifically, a magnetic pole disposed at a position of the developer carrier opposite to the electrostatic latent image holding member, a position where the developer amount regulating member and the developer carrier are opposed to each other or closest to the upstream, and on the upstream side This can be realized by providing a certain magnetic pole with the same polarity and not providing a magnetic pole between both magnetic poles. Further, the developer amount regulating member has a configuration formed of a permanent magnet or a high magnetic permeability material.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 Hereinafter, an embodiment of a developing device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing one embodiment of a one-component developing device, which uses a magnetic developer. The electrostatic latent image holder 30 is a photoconductive drum having a surface layer made of a negatively charged organic photoreceptor on the surface. Electrostatic latent image holder 30
Is uniformly charged by a charging unit (not shown), and then irradiated with image light to form a latent image due to a difference in electrostatic potential. The surface potential when an electrostatic latent image is formed is
For example, it can be set to -100 V in the image part and to -360 V in the background part.

The developer carrier 50 is provided with the electrostatic latent image carrier 3
The developer adhered to the surface can be conveyed by rotating a sleeve 53 that is provided to face the magnet shaft 55 and is rotatably disposed around the magnet shaft 55. The developer carrier 50 is located at a position (developing area) A close to the electrostatic latent image carrier 30 and has a gap of 200 μm to 350 μm.
It is set to be about μm. Developer carrier 5
0 is connected to a high-voltage AC power supply 57 and a DC power supply 59, and a DC superimposed AC power supply, which is a bias voltage, is applied to the developer carrier 50. This bias voltage can be set, for example, such that the frequency of the AC component is 2.4 KHZ, the peak-to-peak voltage is 2000 V, and the DC component is -250 V. Alternatively, only a DC component may be applied.

In the developing area A where the developer carrier 50 and the electrostatic latent image carrier 30 are close to each other, the electrostatic latent image carrier 30
An alternating electric field is generated between a grounded electrode under the photoreceptor layer on the surface. A magnetic one-component developer 66 to be supplied to the developer carrier 50 is stored in the hopper 60. Further, the hopper 60 is provided with the developer carrier 50.
And the surface of the developer carrying member 50 is exposed at a portion that opens toward the electrostatic latent image holding member 30,
The developer carrying member 50 and the electrostatic latent image holding member 30 are arranged so as to form a developing area A close to each other.

The developer carrier 50 comprises a sleeve 53 and a magnetic shaft 55. As the sleeve 53, a stainless steel tube, an aluminum tube, or a material obtained by subjecting them to a resin coating treatment or a plating treatment, or an alumite treatment is used. In this embodiment, the sleeve 53 has a surface roughness R
A stainless steel tube with a = 0.2 μm was used. The magnetic shaft 55 has a plurality of magnets arranged along a peripheral surface, and is fixed and supported so as not to rotate. The arrangement of the plurality of magnets is such that the first N pole 550 is located at a position where the developer carrier 50 and the electrostatic latent image holder 30 face each other, and close to a position where the developer carrier 50 and the developer amount regulating member 70 face each other. The second N on the upstream side
Pole 551 and the first N-pole 551 further upstream of the second N-pole 551.
S pole 553 of FIG. The radial magnetic flux densities of the first N pole 550, the second N pole 551, and the first S pole 553 are 80 mT, 53 mT, and 90 mT, respectively. The first N
The angle between the magnetic poles of the pole 50 and the second N pole 551 is 190 °,
The angle between the magnetic poles of the second N pole 551 and the first S pole 553 is 90 °.

The magnetic flux density pattern of the magnetic shaft 55 thus formed will be described with reference to FIG. Between the first N-pole 50 and the second N-pole 551 having the same polarity, there is a portion α where the magnetic flux density becomes 0 in both the radial direction and the tangential direction.
In this portion, the magnetic transport force for the magnetic developer becomes 0, and the developer transport force is substantially eliminated.

Next, the arrangement relationship between the developer carrier 50 and the developer amount regulating member 70 will be described with reference to FIG. The developer amount regulating member 70 is a strontium ferrite sintered permanent magnet having a width a of a surface facing the developer carrier 50 of 5 mm and a width b of another surface of 6 mm in a cross section perpendicular to the longitudinal direction. Be composed. The magnetic pole has an S pole with a magnetic flux density of 90 mT on the surface facing the developer carrier 50, and an N pole with a magnetic flux density of 90 mT on the back surface. The relationship between the arrangement position of each magnetic pole and the arrangement position of the developer amount regulating member 70 is such that the developer amount regulating member 70 is located on an extension of a straight line m connecting the first N pole 550 and the center of the developer carrier. An opposing position between the developer carrying member 50 and the developer carrying member 50 is set, and a distance L between the developer amount regulating member 70 and the developer carrying member 50 is set to 1.0 mm. In this embodiment, the second N pole 551 is disposed at a position at an angle θ = 10 ° with respect to the line m. That is, the opposing position between the developer amount regulating member 70 and the developer carrier 50 is 10 ° downstream of the second N pole 551. As the developer amount regulating member 70, a high magnetic permeability material having the same shape may be used instead of the permanent magnet. In this case, the developer amount regulating member 70 and the second N pole 551 must be opposed to each other. The distance between the regulating member 70 and the developer carrier 50 is 0.5 m
m needs to be set.

Next, the formation of the layer of the developer carrier 50 will be described. The developer supplied from the hopper 60 to the developer carrier 50 is attracted to the developer carrier 50 by magnetic attraction by the second N pole 551 and the first S pole 553, and the developer amount regulating member 70 The sheet is conveyed to a position facing the developer carrier 50. The magnetic field formed between the developer amount regulating member 70 and the developer carrier 50, the portion where the developer carrier 50 is located downstream of the developer amount regulating member 70, the second N pole 551 and the first N Most of the developer 66 is clogged between the pole 550 and a portion having no magnetic transport force of the developer whose magnetic force becomes zero. Then, the developer 66 </ b> T that has passed through the position where the developer amount regulating member 70 and the developer carrier 50 face each other has an adhesive force with the sleeve 53, and the adhesive force between the developer amount regulating member 70 and the developer carrier 50. Only those that are stronger than the magnetic binding force. Since the adhesive force between the developer and the sleeve 53 is substantially determined by the charge amount of the developer, it passes through the position where the developer amount regulating member 70 and the developer carrier 50 face each other, and the magnetic transport amount is substantially eliminated. When the developer is transported to the development area A where the developer carrier 50 and the electrostatic latent image holder 30 face each other through the point a, the charge amount of the developer is dominant. Therefore, the developer transported to the developing area A has a sufficient charge amount for development.

Here, the center value of the interval L between the developer carrying member and the developer regulating member is set to 0, and the change in the amount of developer transport with respect to the increase (variation) in the interval L from the center value is shown in FIG. Shown in In this graph, the developing device of the present invention is indicated by a straight line, and the conventional developing device is indicated by a broken line. In the developing device according to this embodiment, which is indicated by a straight line, the conveyance amount changes up to 0.1 mm when the distance L between the developer amount regulating member 70 and the developer carrier 50 changes. With respect to the change, the transport amount of the developer does not change. That is, in the developing device having this configuration, the amount of developer transported does not depend on the distance between the developer amount regulating member 70 and the developer carrier 50, and therefore, the developer amount regulating member 70 and the developer carrier 50 It is found that the distance between the developer carrier and the dimensional accuracy is not required, and the component accuracy and the assembly accuracy of the developer carrier 50 and the developer regulating member 70 are not required. Here, an average particle diameter of 7 u is used as a developer.
m, using a magnetic one-component developer having a magnetic powder amount of 50 wt%, the developer conveyance amount on the developer carrier 50 was measured under a normal environment, an air temperature of 23 ° C. and a humidity of 53% RH. The amount was 0.9 mg / cm ² , and the charge amount was -8 uC / g.

The developer amount regulating member 70 thus constructed
The developer that has passed through the position opposite to the developer carrier 50 is
The developer is transported to the development area A by the rotation of the developer carrier 50,
In the alternating electric field generated in the gap between the developer carrier 50 and the electrostatic latent image holder 30, many developer particles having appropriate charges fly and reciprocate. In addition, the particles of the developer collide with each other due to the reciprocating motion, and the entire developer becomes a cloud. The developer cloud is attracted to the latent image portion on the electrostatic latent image holding member by the DC component of the bias voltage, and the development is completed. When this developing device was mounted on an image forming apparatus and the image state was examined, a good image was obtained in both density and fog.

The maintainability of the developing device of the present invention and a conventional developing device in which a developer regulating member is disposed in contact with a developer carrier was tested using an experimental developing device driving device. Table 1 shows the results.

[Table 1] A developing device in which a SUS tube and a ferrite permanent magnet are arranged in a sleeve in a non-contact manner with a developer carrier is used.
Even after the rotation of 100,000, the developer transport amount and the developer charge amount did not change, and no defects such as stripes and unevenness were observed in the developer layer on the developer carrier 50. On the other hand, in the conventional developing device using the developer amount regulating member contact type, a decrease in electrification due to blade wear and generation of layer forming streaks were observed. Further, the driving torque of the developing device is 3.5 kg / cm, whereas the driving torque of the conventional device of the contact type with the developer amount regulating member is 3.5 kg / cm.
m.

As described above, in this developing device, the developer conveying force on the surface of the developer carrier 50 downstream of the developer amount regulating member 70 depends on the mirror image force due to the charging of the developer. The contribution of magnetic attraction to transport is eliminated. For this reason, a uniform developer layer is formed on the surface of the developer carrier 50, which is regulated by the amount of charge of the developer. Further, since the developer amount regulating member 70 and the surface of the developer carrying member 50 are not in contact with each other, the performance of the developer regulating member 70 and the developer carrying member 50 is deteriorated due to wear, and the developer regulating member 70 and the developer carrying member 50 are deteriorated. In this case, the developer is not deteriorated due to the clogging or sliding of the developer, and the driving torque is reduced. Further, on the downstream side of the developer amount regulating member 70, the conveyance force is limited to the vicinity of the surface of the development carrier 50 because of the conveyance by the mirror image force and the van der Waals force, not by the magnetic conveyance force.
Therefore, even if the distance between the developer amount regulating member 70 and the surface of the developer carrying member 50 becomes unnecessarily large, the transport amount does not increase more than a certain amount.
It is hardly affected by the variation of the distance L between the developer and the surface of the developer carrying member 50, and the distance dimension does not require high precision.

Another embodiment is shown (see FIG. 5).
In this embodiment, as the plurality of magnets of the magnetic shaft 600 disposed inside the developer carrier 500, an N-pole is provided at a position where the developer carrier 500 and the electrostatic latent image holding band 30 are opposed to each other. 650 and an S pole 6 disposed downstream of the N pole 650
There are 60 poles. The angle between the magnetic poles of the north pole 650 and the south pole 660 is set between 70 ° and 130 °. The developer amount regulating member 700 is made of a permanent magnet,
An N pole is formed on the surface facing 00. The distance between the developer carrier 50 and the developer amount regulating member 70 is set to 1 mm. Even in the case of such a configuration, almost no magnetic conveyance force is generated between the developer carrying member 500 and the developer amount regulating member 700. The developer conveyed to the development area A after passing the opposing position is only the developer having a sufficient charge amount for development.

[0019]

As described above, in the one-component developing apparatus according to the present invention, the amount of the developer on the developer carrier which is opposed to the developer carrier in a non-contact manner and is located downstream of the developer storage section is described. A regulating member that regulates
The fixed magnetic pole is arranged such that a magnetic transfer force of the developer on the developer carrier is substantially zero on the upstream side of the position where the developer carrier is opposed to the electrostatic latent image carrier. By doing so, the developer holding member and the developer amount regulating member are excellent in maintainability without being worn, and low drive torque,
In addition, it is possible to obtain a developing device that does not require precision in the interval between the developer carrying member and the developer amount regulating member.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of an image forming apparatus using a developing device of the present invention.

FIG. 2 is an explanatory diagram of a portion where a developer amount regulating member is provided.

FIG. 3 is a graph showing a magnetic pattern of a developer carrier.

FIG. 4 is a graph showing a change in a developer conveyance amount due to a change in a distance between a developer carrier and a regulating member.

FIG. 5 is an explanatory view showing an embodiment of another developing device.

FIG. 6 is a configuration explanatory view of a conventional developing device.

FIG. 7 is a configuration explanatory view of a conventional developing device.

[Explanation of symbols]

Reference Signs List 30 electrostatic latent image holder, 50 developer carrier, 53
Sleeve, 55 magnetic shaft, 57 high-voltage AC power supply, 59 DC power supply, 60 hopper, 66 one-component magnetic developer, 70 developer amount regulating member, 550
North pole, 551 North pole, 553 South pole.

Claims (5)

[Claims] 1. A magnetic one-component developing device for developing a positive or negatively charged one-component developer formed on a surface of a developer carrier in a thin layer on an electrostatic latent image holding member by an electric field, wherein a plurality of magnetic poles are provided. A developer carrier that magnetically adsorbs and transports the developer to the surface; and a developer carrier that is disposed to face the developer carrier and regulates an amount of the developer on the developer carrier in a developer amount regulation area. The developer amount regulating member is disposed in non-contact with the developer carrying member, and the fixed magnetic pole of the developer carrying member disposed closest to the developer amount regulating region is An area in which the magnetic conveyance force of the developer on the developer carrying member is substantially eliminated, on the downstream side of the developer amount regulating area and on the upstream side of the position where the developer carrying body faces the electrostatic latent image holding body. A developing device arranged to form. And a fixed magnetic pole provided at a position opposed to the electrostatic latent image holding member and a fixed magnetic pole provided at a position closest to the developer amount regulating region. The developer carrying member is arranged at a position downstream of the fixed magnetic pole of the developer carrying member disposed closest to the developer amount regulating region and opposed to the electrostatic latent image holding member. 2. The developing device according to claim 1, wherein a magnetic pole does not exist between the fixed magnetic pole provided. 3. The developing device according to claim 1, wherein the fixed magnetic pole of the developer carrying member disposed closest to the developer amount regulating region is disposed upstream of a position facing the developer amount regulating member. apparatus. 4. The developing device according to claim 1, wherein the developer amount regulating member is a permanent magnet. 5. A magnetic one-component developing device for developing a positive or negatively charged one-component developer formed in a thin layer on a surface of a developer carrier onto an electrostatic latent image holding member by an electric field, wherein a plurality of magnetic poles are provided. A developer carrier that magnetically adsorbs and transports the developer to the surface, and a developer regulating member made of a high magnetic permeability material disposed to face the developer carrier,
The developer regulating member made of a high magnetic permeability material is disposed in non-contact with the developer carrying member, and a fixed magnetic pole of the developer carrying member is provided at a position facing the developer regulating member, so that the developer regulating member is located downstream from the developer regulating member. A developing device that forms a region on the developer carrying member substantially upstream of a position facing the electrostatic latent image holding member, where the magnetic carrying force of the developer on the developer carrying member is substantially eliminated.