JP2000221785A - Method for electrophotographic image formation and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an excellent image possible to be formed, and problems of lowering density on the image, the scratch mark generation on a developing sleeve or the like by preventing a ghost from remaining as a history of the image on the developing sleeve. SOLUTION: The developing device is, provided with the developing sleeve 41 arranged opposite to a photoreceptor 1 carrying the electrostatic latent image being supported in rotationally, a magnet roll 42 arranged in the developing sleeve 41 equipped plural magnetic poles, and a paddle wheel 44 arranged in the vicinity of the developing sleeve 41 being supported in rotationally. In this case, the device is allowed to form the developer peeling off magnetic field by arranging 2 adjoining magnetic poles in same polarity among plural magnetic poles in the magnet roll 42, and to respectively drive the developing sleeve 41 and the paddle wheel 44 so as to be rotated in the same direction and moreover the ratio B/A between peripheral speed B of the paddle wheel 44 and the peripheral speed A of the developing sleeve 41 is allowed to satisfy the next formula, 0.2<=(B/A)<=0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, a developing method, and an image forming apparatus provided in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art As a developing system of an electrophotographic apparatus, there are known a regular developing system used for a normal electrophotographic copying machine and the like and a reversal developing system used for a digital printer and a digital electrophotographic copying machine. . The reversal development method uses a photoreceptor as an image carrier, generally uses a laser diode, a light emitting diode (LED) or the like as a light source, and charges a latent image formed on the photoreceptor by charging and exposure to a charge polarity of the photoreceptor. This is a method in which a toner image is developed by developing with toner charged to the same polarity. For example, if the charging polarity of the photoconductor is negative,
In this method, the polarity of the toner is negative, and the toner is developed using a potential difference caused by exposure to form a toner image on a photoconductor.

In a conventional developing device, a rotating developer carrier is arranged near a rotating photosensitive member. The developer carrier is formed in a hollow cylindrical shape, and is housed in a developing device main body having an opening on a side facing the photoconductor. The developer carrier has a magnet inside, and carries a two-component developer in which toner particles and magnetic particles (carrier) are mixed on the outer peripheral surface of the developer carrier.

This developing device comprises a developing device main body containing a two-component developer composed of the toner and the carrier, a developer carrier having a magnetic field generating means formed of a magnet therein, and a developer loaded on the developer carrier. A developer conveying member for conveying and supplying,
The image forming apparatus includes a developer layer thickness regulating member that regulates the thickness of the developer layer on the developer carrier to a predetermined amount, and a developer stirring and conveying member that stirs the developer and conveys the developer to the developer conveying member.

[0005] Toner supplied into the developing device main body from a toner cartridge through a toner supply port, which is an opening provided in the upper portion of the developing device main body, is rotated by the developer agitating and conveying member. Agitated and mixed with the developer contained inside, it became uniform toner concentration,
The developer is supplied onto the outer peripheral surface of the developer carrier by the rotating developer transport member, and among the developers on the developer carrier,
Only toner adheres to the photoreceptor in the development area.

[0006]

Among the developers on the developer carrier (developing sleeve), only the toner is developed in the development area of the image carrier (photoreceptor), and then the toner density is reduced by the developed amount. The reduced portion is not circulated in the developing device, the history of the image remains on the developer carrier, and despite the fact that an image pattern of a predetermined density is developed, the second round of the developing sleeve Density differences referred to as "ghosts" resulting from their appearance can cause image defects.

If the developer is not supplied to the developing area on the developing sleeve in a stable manner, the developer on the developing sleeve may be transported unevenly, causing image defects.

As a countermeasure for improving the ghost, a rubber material or the like called a scraper in the prior art is brought into contact with the developing sleeve to scrape off the developer remaining on the developing sleeve after development, and the newly stirred developer is used. Is adhered to the developer carrying member, so that the developer on the developing sleeve is scraped off, thereby eliminating the history of the image and preventing ghost.

However, the prior art scraper system, which is disposed in pressure contact with the developer carrier, has a disadvantage that the developer deteriorates when the developer rubs off or is scraped off between the developer carrier and the scraper, and the developer sleeve However, there is a problem that scratch marks are generated.

Further, by providing a portion called a "peeling pole" in which a magnetic pole of the same polarity is adjacent to the magnetic pole of the developer carrying member, a certain amount of developer can be peeled off from the sleeve by a repulsive magnetic field of the peeling pole. it can. However, under the condition that the positional relationship between the developer carrier and the developer transport member adjacent to the developer carrier is not optimized, the developer cannot be completely removed from the developer carrier, and the Improvement is not at a satisfactory level.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent the occurrence of ghosts, to form a high-quality image, and to reduce the deterioration of the developer. Another object of the present invention is to provide a developing device, a developing method, and an image forming apparatus that prevent the occurrence of scratches on a developer carrier.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the ghost by optimizing the number of rotations of a transport rotation member (paddle wheel) with respect to a developing sleeve, and to stabilize the amount of developer on the developing sleeve. Is what you do.

[0013]

The above objects are achieved by the present invention described below.

(1) A developer carrier rotatably supported opposite to an image carrier carrying an electrostatic latent image, and a magnetic field having a plurality of magnetic poles arranged in the developer carrier In a developing device comprising: a generating unit; and a rotatable developer transport member disposed near the developer carrier, two magnetic poles adjacent to each other among a plurality of magnetic poles of the magnetic field generating unit are set to be the same. The developer is arranged in a polarity to form a developer peeling magnetic field, and the rotation direction of the developer carrier and the rotation direction of the developer transport member are driven in the same direction, and the peripheral speed of the developer transport member is changed. The developing device according to claim 1, wherein the ratio of B to the peripheral speed A of the developer carrier satisfies the following expression.

0.2 ≦ (B / A) ≦ 0.8 (2) A developer carrier that is disposed opposite to an image carrier that carries an electrostatic latent image and is rotatably supported, and the developer A developer housed in a developing device comprising: a magnetic field generating means having a plurality of magnetic poles disposed in a carrier; and a developer transport member disposed in the vicinity of the developer carrier and rotatably supported. Is stirred and conveyed and supplied to the developer carrier,
In a developing method for developing and visualizing an electrostatic latent image in a developing area where the image carrier and the developer carrier are opposed to each other, two adjacent magnetic poles of a plurality of magnetic poles of the magnetic field generating means may be used.
The magnetic poles are arranged in the same polarity to form a developer peeling magnetic field, and the rotation direction of the developer carrier and the rotation direction of the developer transport member are driven in the same direction, and the developer transport member The developer remaining from the developer carrier after the development process is peeled off from the developer carrier by a developing device in which the ratio between the peripheral speed B of the developer carrier and the peripheral speed A of the developer carrier satisfies the following expression. A developing method, wherein the developer is conveyed to the developer conveying member.

0.2.ltoreq. (B / A) .ltoreq.0.8 (3) The image bearing member is provided by the developing device in which the developer bearing member, the magnetic field generating means, and the magnetic member according to claim 1 are arranged. In the developing area where the developer carrying member is opposed, the electrostatic latent image is developed and visualized, and the developer after the developing treatment is peeled off from the developer carrying member, and is carried to the developer carrying member. An image forming apparatus, wherein an image is formed by transferring the visualized image to a material to be transferred by a transfer unit.

(4) A plurality of color toner images are superimposed on an image carrier by a plurality of developing devices each containing a developer of a different color, and the superimposed toner images are transferred by a transfer means to a material to be transferred. 10. An image forming apparatus for forming a color image by transferring a plurality of sets of the developing device according to any one of claims 1 to 5, wherein the developing device according to any one of claims 1 to 5 is disposed. An image forming apparatus according to claim 10, wherein a color image is formed by superimposing a plurality of color toner images on the image carrier by non-contact development.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of an embodiment of the present invention, the structure of a color printer as an example of an image forming apparatus equipped with a plurality of developing devices of the present invention and the operation thereof will be described with reference to the sectional structural view of FIG. It will be explained by.

FIG. 1 is a sectional view showing the structure of a developing device according to the present embodiment and a color printer as an image forming apparatus equipped with the developing device.

In this color printer, a flexible endless belt-shaped photoconductor (hereinafter, referred to as a photoconductor) 1 serving as an image carrier is provided.
, Four sets of scorotron chargers (hereinafter referred to as chargers) 2Y, 2M, 2C, 2K, four sets of image exposure devices (scanning optical devices) 3Y, 3M, 3C, 3K, four sets of developing devices 4
Image forming units (four sets shown in the figure) composed of Y, 4M, 4C, and 4K are arranged in tandem. The illustrated image exposure apparatuses 3Y, 3M, 3C, and 3K use a laser beam scanning optical device.

The photosensitive member 1 is stretched around a driving roller 11, a lower roller 12, and an upper roller 13, and a tension roller 14
And is rotated clockwise as shown in the drawing while being locally brought into contact with the backup member 15 provided on the inner peripheral surface. The backup member 15 is in contact with the back surface of the photoreceptor 1, and each of the developer carrying members (hereinafter, referred to as developing sleeves) 41Y, 4Y, 4M, 4C, and 4K of the developing units 4Y, 4M, 4C, and 4K.
41M, 41C, 41K development areas and image exposure device 3
The photoconductor 1 is regulated at the image forming positions of Y, 3M, 3C, and 3K.

The two-component developer contains a toner and a carrier as main components. The toner contains a binder resin and a pigment and, if necessary, a release agent, a charge control agent and the like. The toner of the two-component developer used in the color image forming apparatus contains, as the above-mentioned pigment, a colorant composed of a pigment or a dye such as yellow, magenta and cyan, and a black pigment such as carbon black. The particle size of the toner is 4 to 10 μm.
As the carrier, ferromagnetic particles such as ferrite, magnetite, and iron powder are used, and desirably, the surface of the ferromagnetic particles is coated with a resin such as a fluorine-based or silicone-based resin. The particle size of the carrier is 10 to 80 μm. The mixing ratio of the toner and the carrier is 3 to 20% by weight of the toner.

At the start of image recording, a drive motor (not shown) is rotated to rotate the photoreceptor 1 clockwise through a drive roller 11 by a charging operation of a charger 2Y. Application of the potential to 1 is started. Photoconductor 1
Is the first in the image exposure apparatus 3Y after the potential is applied.
Exposure is started by an electrical signal corresponding to the color signal of the photoconductor 1, ie, the yellow (Y) image signal, and the rotation (sub-scanning) of the photoconductor 1 causes the photosensitive layer on the surface to correspond to the yellow (Y) image of the developed image. An electrostatic latent image is formed. This developer is reversal-developed in a non-contact state in the developing area by the developer adhered and conveyed onto the developing sleeve 41Y by the developing device 4Y, and becomes a yellow (Y) toner image.

Next, the photoreceptor 1 is further provided with a potential on the yellow (Y) toner image by the charging action of the charger 2M, and is converted into a second color signal of the image exposure device 3M, that is, an image signal of magenta (M). Exposure is performed by the corresponding electric signal, and a magenta (M) toner image is formed on the yellow (Y) toner image by non-contact reversal development by the developing device 4M.

By the same process, a cyan (C) toner image corresponding to the third color signal is further formed by the charger 2C, the image exposing device 3C and the developing device 4C. Further, a black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the charger 2K, the image exposure device 3K, and the developing device 4K, and is formed on the peripheral surface within one rotation of the photoconductor 1. A color toner image is formed.

When the developing operation is performed by the developing devices 4Y, 4M, 4C, and 4K, the developing sleeves 41Y, 41
A DC bias having the same polarity as the charging of the photoconductor 1 or a developing bias obtained by adding an AC to the DC bias is applied to M, 41C, and 41K, and the developing sleeves 41Y, 41M, and 41K are applied.
Non-contact reversal development is performed with the two-component developer adhered on 41C and 41K, and toner adheres to the electrostatic latent image forming portion on the photoconductor 1 with the conductive layer grounded.

After the color toner image formed on the peripheral surface of the photoreceptor 1 has the potential of the adhered toner adjusted by the charger 2F, the paper feed cassettes 20A and 20B serving as the paper feed devices are transferred in the transfer section. Alternatively, the manual paper feed unit 20C
From the paper feed means 21A, 21B, and 21C, respectively, and is conveyed to the pair of registration rollers 23, and is transferred onto the transfer paper fed in synchronization with the toner image area on the photoconductor 1 by driving the pair of registration rollers 23. Then, the image is transferred by a transfer device (transfer roller) 7 arranged opposite to a lower portion of a drive roller 11 for driving the photoconductor 1.

Transfer material (transfer paper) onto which the toner image has been transferred
Is separated from the peripheral surface of the photoconductor 1 along the curvature of the drive roller 11 and then conveyed to the fixing device 24. Fixing device 2
4, the toner image is melted and fixed on the transfer paper. After completion of the fixing process, the transfer paper is transferred to a pair of discharge rollers 25A, 25A.
B and 25C, and are discharged to a discharge tray 26 provided on the upper side with the toner image surface on the transfer paper facing downward.

On the other hand, the photoreceptor 1 from which the transfer paper has been separated is rubbed by the cleaning blade 81 of the cleaning device 8 to remove residual toner and to be cleaned. When the formation of the toner image of the next original image is subsequently performed, the pre-charging static eliminator 9 exposes the photoconductor surface of the photoconductor 1 to remove the previous history.

FIG. 2 is a sectional view of the developing device of the present invention.
Since the plurality of developing units 4Y, 4M, 4C, and 4K have substantially the same configuration, these developing units will be collectively described as developing units 4.

In FIG. 2, reference numeral 40 denotes a developing device main body for containing a two-component developer composed of a toner and a carrier; 41, a developing sleeve as a developer carrier;
A magnetic field generating means (magnet roll) 43 disposed inside the developing device 1 and fixed to the developing device main body 40;
A developer layer thickness regulating member that regulates the upper developer layer thickness to a predetermined amount, 44 is a paddle-shaped developer conveying member (hereinafter, referred to as a paddle wheel) that supplies developer to the developing sleeve 41, and 45A and 45B are A developer stirring and conveying member having a screw shape (hereinafter, referred to as a stirring screw). The paddle wheel 44 is not limited to the paddle wheel in which the plurality of blade portions 44a are provided upright on the rotating shaft 44b, but may have another shape for efficiently transporting the developer.
The arrows shown in the figures indicate the rotating members (41, 44, 45A, 45A).
B) indicates the rotation direction, and the white arrows indicate the flow of the developer. E1 is an AC power supply, and E2 is a DC power supply.

The developing sleeve 41 of the developing device 4 has five magnetic poles S1, S2, N1 to N as shown in FIG.
3 are arranged. Of these magnetic poles, adjacent magnetic poles N2 and N3 of the same polarity form a repulsive magnetic field, peel off the developer after the developing process on the developing sleeve 41, and erase the image history on the developing sleeve 41.

The paddle wheel 44 arranged at a position that satisfies the below-described predetermined conditions conveys the developer peeled off from the developing sleeve 41 by the repulsive magnetic field of the magnetic poles N2 and N3 of the same polarity and conveys the developer to the stirring screw 45A side. Transfer.

The stirring screw 45A and the stirring screw 4
5B are arranged in parallel in a first transfer chamber 40b and a second transfer chamber 40c formed on both sides of a partition wall 40a standing upright from the bottom of the developing device main body 40, and are driven in the same direction. Rotated. The upper portions of the first transfer chamber 40b and the second transfer chamber 40c are closed by a top plate 46. 47 is the second transfer chamber 40c or the first transfer chamber 4
0b is a toner concentration detection device installed at the bottom of the toner concentration detection device.

The toner cartridges 5Y and 5 shown in FIG.
The toner supplied from M, 5C, and 5K is supplied to the developing device 4
(Y, M, C, K) from the toner supply port (not shown) formed in each top plate 46 (see FIG. 2).
It is thrown in and supplied in b.

The outer diameter of the developing sleeve 41 is desirably not less than 8 mm and not more than 60 mm. When the outer diameter is 8 mm or less, a magnet roll 4 having at least five magnetic poles including magnetic poles N1, S2, stripping magnetic poles N2, N3 and magnetic pole S1 necessary for image formation and having a predetermined magnetic field strength.
2 is difficult to form. Further, the developing sleeve 4
When the outer diameter of the first member is φ60 mm or more, the size of the developing device is increased. In particular, in a color printer having a plurality of sets of developing units 4Y, 4M, 4C, and 4K (see FIG. 1), it is difficult to shorten the entire length of the belt-shaped photoreceptor 1 when the plurality of developing units 4 becomes large. And the image forming unit becomes large.

FIG. 3 shows a magnetic force distribution of the magnet roll 42. When the non-magnetic developing sleeve 41 surrounding the outer periphery of the magnet roll 42 is rotated in the direction of the arrow, the magnetic pole N
2. Due to the repulsive magnetic field generated by N3, the residual developer on the developing sleeve 41 is peeled off from the vicinity of the magnetic pole N3 to the upstream side in the rotation direction and in the vicinity of the magnetic pole N2, so that a portion substantially not adhered is generated. It was actually measured. However, it is impossible to completely peel off the developer on the developing sleeve 41 only by the repulsive magnetic field of the stripping pole by the magnetic poles N2 and N3.

As shown in FIG. 2, the developing device 4 of the present invention
A magnetic body (magnetic field generating member) 48 that forms a magnetic field having a different magnetic property from the magnetic poles N2 and N3 is provided at a predetermined position near the magnetic pole N2 close to the developing sleeve 41 on the upstream side of the repulsive magnetic field generated by the stripping magnetic poles N2 and N3. installed. That is, the magnetic material 4
The 8 south poles are arranged to face each other near the magnetic pole N2 and form an attraction magnetic field.

The magnetic material holding member 49 is a magnetic member that holds the magnetic material 48 and fixes it at a predetermined position inside the top plate 46 that closes the upper part of the developing device main body 40. Magnetic material holding member 4
Reference numeral 9 denotes a magnetic material mounting surface 49a which is formed of magnetic stainless steel (SUS430 or the like) or a steel member, faces the developing sleeve 41, a fixing surface 49b fixed to the top plate 46, and a bent portion 49c. And a V-shape bent at the bent portion 49c. Bent part 49c
Bending angle (magnetic body mounting angle) is, for example, 20 °
Is set to

The magnetic material mounting surface 4 of the magnetic material holding member 49
A magnetic body 48 is fixed to 9a with a double-sided adhesive tape or the like. The magnetic body 48 is formed of a permanent magnet or the like.
As shown in FIG. 2, the magnetic body 48 is
Since the magnetic material 48 does not exist on the upstream side of 9a, that is, near the bent portion 49c of the magnetic material holding member 49, the strength of the magnetic field by the magnetic material 48 is weak on the upstream side. Therefore, the developer on the developing sleeve 41 after the development processing is conveyed to the downstream side without suction of the developer in the weak magnetic field portion on the upstream side, so that the developer stays near the bent portion 49c on the upstream side. No developer conveyance failure is caused by the above.

An excellent effect was obtained by using a ferrite rubber magnet BQC14 manufactured by TDK Corporation as the magnetic material 48. BQC14 is obtained by kneading strontium ferrite powder into NBR rubber, and its material properties are shown below.

Residual magnetic flux density (Br): 230 to 250 [mT] Holding force (Hcb): 163 to 195 [kA / m] Specific holding force (Hcj): 279 to 358 [kA / m] Maximum energy product (BHmax) ): 10.3 to 11.9
[KJ / m ³ ] The above ferrite rubber magnet BQC14
Other ferrite rubbers (BQJ05, BQA14,
BQE14, BQK12), neodymium / iron / boron based rare earth cobalt magnet (NEOREC magnet series), rare earth cobalt magnet (REC magnet series), ferrite magnet wet anisotropic material system (FB series), etc. The same effect can be obtained with the body. The above various magnetic materials are all manufactured by TDK Corporation, but are not limited to the above materials as long as they have the required residual magnetic flux density, coercive force, and maximum energy product. .

In FIG. 2, the two-component developer composed of the toner and the carrier agitated by the agitating screws 45A and 45B that are driven and rotated is conveyed by the blade portion 44a of the paddle wheel 44 that rotates clockwise as shown in FIG. The developer is fed into a gap where the inclined surface of the developer layer thickness regulating member 43 and the outer peripheral surface of the developing sleeve 41 face each other. The two-component developer is attracted onto the developing sleeve 41 by the magnetic force of the magnet roll 42 in the vicinity of the gap, and furthermore, 100 to 600 μm on the developing sleeve 41 by the minimum gap of the gap.
The developing layer 41 is conveyed to the developing area where the developing sleeve 41 and the photoconductor 1 are opposed to each other with the thickness being regulated to m.

After the developing process is performed in the developing area, the developer adsorbed on the developing sleeve 41 and conveyed passes through the space between the magnetic member 48 and the developing sleeve 41. Magnetic body 48 on the upstream side in the rotation direction of developing sleeve 41
In the vicinity of the magnetic pole N2 where there is no magnetic field, the attraction force to the developer is small, but the intensity of the magnetic field increases immediately below the magnetic body 48 toward the downstream side in the rotation direction of the developing sleeve 41.

In the space where the developing sleeve 41 and the magnetic body 48 are opposed to each other, the developer is peeled off from the developing sleeve 41 by the stripping magnetic poles N2 and N3, is attracted by the magnetic body 48, and moves to the developing sleep 41 side. It is conveyed above the paddle wheel 44 in such a way that it does not.

In the space where the developing sleeve 41 and the magnetic body 48 face each other, the developer on the developing sleeve 41 is drawn toward the magnetic body 48 as the developer moves downstream in the rotation direction of the developing sleeve 41. Thus, the developer can be peeled off from the developing sleeve 41. Therefore, it is possible to remove a sufficient amount of the developer from the developer sleeve 41, and a single-component developing system that forms a thin layer of the developer on the development sleeve 41 and develops the same can sufficiently function. .

The developer comprises a developing sleeve 41 and a magnetic material 48.
The magnetic material 48 is conveyed downward through the gap between the magnetic material 48 and the magnetic pole N2 of the magnet roll 42, and is peeled off from the developing sleeve 41 by an attraction magnetic field.
While being sucked onto the magnetic material 8, it moves diagonally downward along the magnetic material 48, falls near the end of the magnetic material 48, and is conveyed onto the rotating paddle wheel 44.

The blade portion 44 of the rotating paddle wheel 44
“a” conveys the developer peeled off from the developing sleeve 41 while holding the developer, conveys the developer to the rotating stirring screw 45A, and recirculates the developer. The distal end of the magnetic body 48 is disposed with a gap substantially immediately above the rotation locus of the blade 44 a of the paddle wheel 44.

The gap between the tip of the blade portion 44a of the paddle wheel 44 and the outer peripheral surface of the developing sleeve 41 is very small, and the blade portion 44a of the paddle wheel 44 Is rotated in a direction in which the developer is scraped up by the gap, so that the developer almost
Almost the entire amount of the developer dropped from the magnetic body 48 without passing through the gap on the first side is captured by the blade portion 44a of the paddle wheel 44 and is conveyed to the stirring screw 45A side.

[0050]

【Example】

[Study 1] Ghost Study 1 (Optimization of Paddle Wheel Rotation Number) (Ghost Definition and Measurement Method) FIG. 4 is a diagram showing a ghost evaluation image pattern. This pattern was created by an image forming signal generator. The black portion shown in the drawing is the solid black portion C1 of the transfer-receiving material having a transmission density of about 1.4 and other white portions are the white portions C2.

The above ghost evaluation image pattern is represented by K
The print density of a pattern formed on a transfer material was printed out using a black developer using an onica KL-2010 color printer (manufactured by Konica Corporation).
It was measured with a transmission densitometer X-Rite 310 (manufactured by X-Rite, USA).

The figure shows the transmission density measurement position of the black solid portion C1. Since the central portion is the white portion C2 before that and there is no developer consumption, a sufficient image density can be obtained during the development processing. However, the left side portion and the right side portion have a large black solid portion C1 due to the previous consumption of the developer, so that the image density decreases during the development processing. Accordingly, the image densities of the left portion and the right portion are lower than those of the central portion to cause a density difference, and the image becomes lighter. An image in which these density differences have occurred is called a ghost.

Next, the evaluation of the image density difference is shown below.

(Ghost evaluation method) Solid black portion C1
Of an AC voltage applied to the developing sleeve 41 (an applied voltage by the AC power supply E1), a DC bias voltage (an applied voltage by the DC power supply E2), and a photosensitive member (photosensitive drum or belt-shaped photosensitive member) ) Output image samples having different transmission densities by changing the distance from one surface. The transmission density of each of these image samples is determined by the above-described measurement method, and the transmission density difference Δ is determined by the following equation (Equation 1).

[0055]

(Equation 1)

The transmission density d of each image sample is 1 to 2.5
Were output at four or more points, and the transmission density difference Δ was measured, and the characteristic diagram of FIG. 5 was created.

1 to 2.5 of transmission density d of each image sample
When the transmission density difference Δ is obtained from the measured transmission density by the formula (Equation 1) and plotted, the transmission density difference Δ
Are arranged almost on a line segment of the inclination angle θ represented by the equation of Δ = a × d + e. a is the gradient of the line segment with respect to the x-axis (ghost evaluation gradient a = tan θ), and e is the intercept of the characteristic line on the y-axis.

Here, “good image without ghost” means that the transmission density difference Δ = 0, ie, a = 0. That is, the smaller the ghost evaluation gradient a (tan θ), the better the ghost level. A good ghost level means a level at which a ghost is not visually recognized, and is within the range of a <0.1.

A line segment (1) indicated by a broken line represents each transmission density difference Δ
Are 0.15 or more, and the ghost evaluation gradient a (tan θ1) of the line segment (1) is extremely large.

In the line segment (2) indicated by the one-dot chain line, each transmission density difference Δ is 0.1 or more, and the ghost evaluation gradient a (tan θ2) of the line segment (2) is large.

The line segment (3) indicated by the solid line represents each transmission density difference Δ
Are 0.05 or less, and the ghost evaluation gradient a (tan θ3) of the line segment (3) is extremely small within the range of 0.1 or less, and a good image without ghost is obtained.

In the present invention, a so-called two-component developer comprising a combination of a magnetic carrier, in particular, a coated magnetic carrier and a non-magnetic resin toner is preferably used. Also,
A two-component developer comprising a combination of a resin-dispersed magnetic carrier in which magnetic particles are dispersed in a resin and a non-magnetic resin toner is also preferably used.

The magnetic particles (core particles in the case of a coating carrier) of the developer carrier include metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead. Known materials can be used. The volume average particle diameter of the carrier coated with the core material particles is 10 μm or more, 50 μm or less,
Particularly, those having a size of 20 μm or more and 40 μm or less are preferable.

The coating thickness is preferably 0.5 to 3 μm, and a conductive material such as carbon may be added to the resin. Further, a silane coupling agent or the like may be added so that the coating resin adheres to the magnetic core material.

The volume average particle size of the carrier is typically measured by a laser diffraction particle size distribution analyzer “HELOS” equipped with a wet disperser (Sympatec (SYMPA)).
TEC).

For measuring the volume average particle size of the toner, Cou
The measurement was carried out by using an electric field solution ISOTONE-II (manufactured by Nikkaki Co., Ltd.) using TER TA-II (manufactured by Coulter).
In a state of being dissolved and dispersed.

(Specifications of Developing Unit) In the developing unit described in the above embodiment, the developing sleeve 41 and the paddle wheel 44 were set as follows.

Specifications of the magnetic body 48 Thickness a (length between magnetic poles N and S) = 1 mm, width b = 4 m
m, length (length parallel to the axial direction of developing sleeve 41)
c = 300 mm Material: Ferrite rubber BQC14 (manufactured by TDK) ・ Specifications of developing sleeve 41 Outer diameter D = φ20 mm, surface roughness Rz = 8 μm, Material: non-magnetic stainless steel (aluminum alloy and other metals are also acceptable) , Magnetic pole arrangement: 5 poles, number of rotations: 350 rpm ・ Specifications of paddle wheel 44 Outer diameter: φ14 mm, rotation shaft diameter: φ10 mm, blade 4
4a blade number: 6, material: ABS resin (other resin, glass-added resin, metal is also acceptable), rotation speed: 250r
pm ・ Specifications of stirring screws 45A and 45B Outer diameter: φ16 mm, rotation shaft diameter: φ6 mm, pitch: 1
4mm, Material: Ephrite (resin + glass added; Japan F
TB (manufactured by TB Co., Ltd.), rotation speed: 200 rpm ・ Configuration of photoconductor 1: OPC belt-shaped photoconductor ・ Outer diameter ratio of each rotating member Developing sleeve 41: paddle wheel 44: stirring screw 45A, 45B = 1: 0.7 : 0.8 ・ Rotation ratio of each rotating member Developing sleeve 41: Paddle wheel 44: Stirring screws 45A, 45B = 1: 0.7: 0.6 ・ Developer Toner particle diameter 4 to 15 μm, carrier particle diameter 10 to 10 60μ
m, carrier specific gravity 3-6 g / cm ³ , carrier magnetization 10
00 emu / g

[0069]

[Table 1]

Table 1 shows the results obtained by actually measuring the changes in the peripheral speed ratio B / A between the paddle wheel 44 and the developing sleeve 41 and the ghost density difference gradient (ghost evaluation gradient) a.

When the outer diameter of the developing sleeve 41 is set to φ20 mm and the number of rotations per minute is set to 350 rpm, the peripheral speed A is A = 366 mm / sec.

When the outer diameter of the paddle wheel 44 is set to φ14 mm and the number of revolutions per minute is variously changed within the range of 50 to 500 rpm, the peripheral speed B of the paddle wheel 44 becomes 37 to 367 mm / sec. It is converted into a variable range.

According to the experimental results in Table 1, the peripheral speed ratio B / A between the peripheral speed B of the paddle wheel 44 and the peripheral speed A of the developing sleeve 41 is 0.2 ≦ (B / A) ≦ 0.8. , The ghost evaluation gradient a was 0.07 or less, which was good. In particular, when the peripheral speed ratio B / A is 0.4 ≦ (B
/A)≦0.6, extremely good image quality was obtained with a ghost evaluation gradient a of 0.04 or less.

When the peripheral speed ratio B / A is larger than 0.8, the developer remains buried between the blade members 44a of the paddle wheel 44, and the circulation and transportability of the developer deteriorates, and the ghost The level deteriorates significantly.

[Study 2] Examination of the Amount of Developer Conveyed on Developing Sleeve 41 In this experiment, a test device containing a developer was connected to a driving source by using an agitating tester for a single developing device. The developer transport amount on the developing sleeve after a predetermined time elapses after stirring and transporting the developer (the amount of developer adhered per unit area) is examined.

[0076]

[Table 2]

Table 2 is obtained by actually measuring the change in the amount of transported developer after a lapse of 1 minute, 10 minutes, and 30 minutes with respect to the peripheral speed ratio B / A between the paddle wheel 44 and the developing sleeve 41. The results are shown.

The setting conditions are the same as those in Study 1 described above.
The outer diameter of the developing sleeve 41 is 20 mm, the number of revolutions per minute is 350 rpm, the peripheral speed A is 366 mm / sec, and the outer diameter of the paddle wheel 44 is 14 mm.

When the number of revolutions per minute of the paddle wheel 44 is variously changed within a range of 50 to 500 rpm,
The peripheral speed B of the paddle wheel 44 is 37 to 367 mm /
It is converted within the variable range of sec (the same as in Study 1).

According to the experimental results in Table 2, the peripheral speed ratio B / A between the peripheral speed B of the paddle wheel 44 and the peripheral speed A of the developing sleeve 41 is 0.2 ≦ (B / A) ≦ 1.0. Is within the range of 7.5 to 8.5 mg.
/ Cm ² and (8.0 ± 0.5 mg / cm ² ), which were favorable.

The maximum permissible level of variation in the amount of developer transport is ± 2 mg / cm ² , and exceeding this permissible range will affect the image density.

When the peripheral speed ratio B / A becomes smaller than 0.2 (when the peripheral speed of the paddle wheel 44 becomes low), the amount of the developer sent to the developing sleeve 41 becomes insufficient, and Transport unevenness (unevenness of developer adhesion amount) occurs.

The change in the amount of the developer transported on the developing sleeve 41 decreases with time. That is, the peripheral speed ratio B / A
Is within the range of 0.2 ≦ (B / A) ≦ 1.0, the change over time of the developer conveyance amount is slight.

However, when the peripheral speed ratio B / A is smaller than 0.2 (0.15, 0.1), the amount of the developer transported with time changes remarkably, and the amount of the developer sent to the developing sleeve 41 becomes smaller. Insufficiency causes uneven transport of the developer on the developing sleeve 41.

When the above experimental results of Study 1 and Study 2 are combined, the peripheral speed ratio B / A between the peripheral speed B of the paddle wheel 44 and the peripheral speed A of the developing sleeve 41 is 0.2 ≦ 0.2
When (B / A) was in the range of ≦ 1.0, the ghost evaluation gradient a was small, the developer conveyance amount was good, and there was little change with time, and good image quality was obtained.

The developing apparatus of the present invention is not limited to a color image forming apparatus having a plurality of developing units, but can be applied to a monochrome image forming apparatus with one developing apparatus.

[0087]

According to the developing device of the present invention, the peripheral speed ratio of the peripheral speed B of the paddle wheel to the peripheral speed A of the developing sleeve is represented by the following formula: A
By optimizing the peripheral speed ratio B / A of the paddle wheel with respect to the developing sleeve, the ghost was improved and the amount of the developer on the developing sleeve was stabilized. As a result, image stability over time during printing and density unevenness during one printing were eliminated.

Further, a transfer type image forming apparatus according to claim 7 of the present invention, a reversal developing type image forming apparatus according to claim 8, a non-contact developing type image forming apparatus according to claim 9, 11. A color image forming method comprising: forming a color toner image by superimposing a plurality of color toner images on the image carrier according to claim 10; and transferring the color toner image collectively onto a transfer material by a transfer device to form a color image. In the apparatus, the developing device improves the developability, so that even when printing a large number of sheets continuously, there is no ghost, and the amount of the developer on the developing sleeve is also stabilized, so that the image density may be reduced. Not
Excellent high quality images can be obtained.

Further, in the developing device of the present invention, since the magnetic scraper made of a magnetic material is provided in a non-contact state with the developing sleeve, the developer is applied between the developing sleeve and the scraper by contact with the conventional scraper. The durability of the developing device has been drastically improved by also improving the deterioration of the developer and the damage of the developing sleeve which occur when the developing device is slipped or scraped off.

Furthermore, since the magnetic poles of the same polarity and the magnetic material that peel off the developer on the developing sleeve are not in contact with the developing sleeve, the material of the outer peripheral portion of the developing sleeve is changed from stainless steel (SUS) to aluminum alloy. Is possible,
It can also contribute to reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color printer as an example of an image forming apparatus equipped with a developing device of the present invention.

FIG. 2 is a cross-sectional view of the developing device of the present invention.

FIG. 3 is a magnetic force distribution diagram of a magnet roll.

FIG. 4 is a diagram showing a ghost evaluation image pattern.

FIG. 5 is a characteristic diagram of a transmission density difference.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photoreceptor) 4, 4Y, 4M, 4C, 4K Developing device 40 Developing device main body 41, 41Y, 41M, 41C, 14K Developer carrier (developing sleeve) 42 Magnetic field generating means (magnet roll) 43 Developing Material layer thickness regulating member 44 Developer transport member (paddle wheel) 45A, 45B Developer stirring transport member (stirring screw) 48 Magnetic material (magnetic field generating member) 49 Magnetic material holding member 7 Transfer device (transfer roller) C1 Black solid portion C2 White part N2, N3 Stripped magnetic poles (magnetic poles of the same polarity) Nu Neutral pole part a Ghost evaluation inclination

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/08 503 G03G 15/08 503A

Claims (10)

[Claims] 1. A magnetic field generator comprising: a developer carrier disposed rotatably supported to face an image carrier carrying an electrostatic latent image; and a plurality of magnetic poles disposed in the developer carrier. And a rotatable developer transport member disposed near the developer carrier, wherein two magnetic poles adjacent to each other among the plurality of magnetic poles of the magnetic field generating means have the same polarity. To form a developer peeling magnetic field, drive the rotation direction of the developer carrier and the rotation direction of the developer transport member in the same direction, and set the peripheral speed B of the developer transport member. A ratio of the peripheral speed A of the developer carrier to the peripheral speed A satisfies the following expression. 0.2 ≦ (B / A) ≦ 0.8 2. The developing device according to claim 1, wherein a magnetic body is disposed outside between the two magnetic poles having the same polarity. 3. The developing device according to claim 1, wherein the rotation direction of the developer carrier is a direction opposite to gravity in a region facing the image carrier. 4. The developer carrying member has an outer diameter of 8 mm or more,
The developing device according to claim 1, wherein the length is 60 mm or less. 5. The developing device according to claim 1, wherein the developer is a two-component developer including a toner and a carrier. 6. A magnetic field generator comprising: a developer carrier rotatably supported to face an image carrier carrying an electrostatic latent image; and a magnetic field having a plurality of magnetic poles disposed in the developer carrier. Agitating and transporting the developer housed in a developing device having means and a developer transport member rotatably supported in the vicinity of the developer carrier and supplying the developer to the developer carrier. In a developing method for developing and visualizing an electrostatic latent image in a developing region where the image carrier and the developer carrier are opposed to each other, two magnetic poles adjacent to each other among the plurality of magnetic poles of the magnetic field generating means may be the same. The developer is arranged in a polarity to form a developer peeling magnetic field, and the rotation direction of the developer carrier and the rotation direction of the developer transport member are driven in the same direction, and the peripheral speed of the developer transport member is changed. B and the ratio of the peripheral speed A of the developer carrier is as follows: A developing device set so as to satisfy the following expression: stripping off the developer remaining after the developing process from the developer carrier, and transporting the developer to the developer transport member. 0.2 ≦ (B / A) ≦ 0.8 7. An electrostatic latent image in a developing area in which the image carrier and the developer carrier are opposed by the developing device provided with the developer carrier, the magnetic field generating means, and the magnetic material according to claim 1. Is developed and visualized, the developer after the development processing is peeled off from the developer carrier, and is conveyed to the developer conveying member. An image forming apparatus for forming an image. 8. A latent image portion provided with the developing device according to claim 1, wherein a charge is removed by a light beam from a uniformly charged surface formed on the image carrier. The image forming apparatus according to claim 7, wherein a toner image is formed by reversal development in which toner is adhered. 9. A developing device comprising the developing device according to claim 1, wherein a bias electric field for superimposing an AC component on a DC component is applied to the developer supporting member. The image forming apparatus according to claim 7, wherein the toner image is formed by non-contact development in which the toner of the two-component developer flies onto an electrostatic latent image on the image carrier. 10. A plurality of developing devices each containing a developer of a different color, a plurality of toner images of a plurality of colors are superimposed on an image carrier, and the superimposed toner images are transferred onto a material to be transferred by transfer means. In an image forming apparatus for forming a color image by transferring, a plurality of sets of the developing device according to any one of claims 1 to 5 are arranged, and the reversal development according to claim 8 and the non-developing device according to claim 9 are used. An image forming apparatus, wherein a color image is formed by superimposing a plurality of color toner images on the image carrier by contact development.