JP2004133019A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent soiled images, etc., by steadily conveying developer on a developer carrier and preventing scattered toner which occurs when an amount of developer is restricted near a nipping pole. <P>SOLUTION: The developing device includes: the developer carrier 41 which conveys two-component developer composed of magnetic carrier and non-magnetic toner; and a developer layer thickness restricting member 42 formed of a magnetic member 42A and a non-magnetic member 42B, which restricts the two-component developer on the developer carrier 41 to a specific amount. In the developing device, a gap difference ΔH(mm) between a first gap H1 left between the surface of the developer carrier 41 and the leading end of the magnetic member 42A, and a second gap H2 left between the surface of the developer carrier 41 and the leading end of the non-magnetic member 42B, and the particle diameter Dc(μm) of the magnetic carrier, establish the following condition: 0<ΔH≤1.46×10<SP>-3</SP>×Dc+0.234. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and a multifunction peripheral having these functions, and more particularly, to a developing apparatus for developing an electrostatic latent image formed on an image carrier. Regarding improvement.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus such as an electrophotographic copying machine performs charging and exposure on an image carrier, forms an electrostatic latent image, and develops the latent image formed on the image carrier by a developing device. A toner image and a non-toner image are formed, transferred to a sheet by a transfer unit, and then thermally fixed by a fixing device to form an image.
[0003]
In a color image forming apparatus provided with a plurality of developing devices each having a two-component developer composed of a toner and a carrier, color toners of different colors are transferred onto an image carrier, and the color toner images of a plurality of colors are transferred onto paper or an intermediate sheet. Transfer onto a transfer body.
[0004]
The developing device is disposed to face the image carrier on which the electrostatic latent image is carried, and has a developer carrier for carrying the two-component developer, and is arranged in close proximity to the developer carrier to carry the developer. The image forming apparatus includes a developer layer thickness regulating member that regulates the layer thickness of the two-component developer carried on the body, and a developer stirring / conveying unit.
[0005]
The two-component developer on the developer carrier is formed in a thin layer by the developer layer thickness regulating member, is conveyed to a development area facing the image carrier, and develops the electrostatic latent image on the image carrier.
[0006]
[Patent Document 1]
JP-A-9-54500 (Claims, Paragraph Nos. 0014 to 0016, FIGS. 1 and 8)
[0007]
[Patent Document 2]
JP-A-2002-91157 (paragraph number 0026, FIG. 2)
[0008]
[Patent Document 3]
JP-A-2002-148921 (paragraph number 0042, FIG. 2)
[0009]
[Problems to be solved by the invention]
Conventional developing devices reduce the amount of developer transport on the developer carrying member by regulating the amount of developer by a developer layer thickness regulating member made of a magnetic material disposed close to the developer carrying member. The developer can be set, and the dependence of the amount of developer transport on the gap between the surface of the developer carrier and the tip of the developer layer thickness regulating member is reduced to perform development processing by stable developer transport. .
[0010]
However, in a developing device using a toner having a small particle diameter, for example, a polymerized toner, when the developer amount is regulated by a developer layer thickness regulating member made of a magnetic material, the toner from the vicinity of the front end of the developer layer thickness regulating member is Scattering was a problem.
[0011]
In particular, in the case of a developing device in which the developer layer thickness regulating member is disposed below the developer carrier, the developer amount is regulated because the developer layer thickness regulating member is exposed outside the developing device main body. The toner scattering generated at this time may contaminate a charging unit disposed below the developing device on the upstream side of the developing device in the rotation direction of the image carrier, or cause image contamination on the image carrier.
[0012]
An object of the present invention is to provide a developing device and an image forming apparatus that form a stable image by solving the above-mentioned problems.
[0013]
[Means for Solving the Problems]
The above object is achieved by the following developing device and image forming apparatus.
[0014]
(1) A developer carrier that is arranged to face an image carrier that carries an electrostatic latent image and carries a two-component developer composed of a magnetic carrier and a non-magnetic toner; A developing device having a developer layer thickness regulating member composed of a magnetic member for regulating a component developer to a predetermined amount and a non-magnetic member, wherein a first gap between the surface of the developer carrier and a tip of the magnetic member is provided. And the following condition is satisfied between a gap difference ΔH (mm) between the surface of the developer carrier and the second gap between the tip of the nonmagnetic member and a particle diameter Dc (μm) of the magnetic carrier. A developing device characterized by the above-mentioned.
[0015]
0 <ΔH ≦ 1.46 × 10^-3× Dc + 0.234
(2) a developer carrier having a magnetic pole therein, which transports a two-component developer comprising a magnetic carrier and a non-magnetic toner, and is disposed opposite to an image carrier carrying an electrostatic latent image; A developer layer thickness regulating member comprising a magnetic member for regulating the two-component developer on the developer carrier to a predetermined amount and a non-magnetic member, wherein the developer carrier surface and the tip of the magnetic member are provided. And a gap difference ΔH (mm) between the first gap between the developer carrier and the second gap between the surface of the developer carrier and the tip of the non-magnetic member, and opposes the developer layer thickness regulating member of the developer carrier. Magnetic flux density B of the magnetic pole (Wb / m²), Wherein the following condition is satisfied.
[0016]
0 <ΔH ≦ 0.31 × 10^-3× B-0.029
(3) a developer carrier that is arranged to face an image carrier that carries an electrostatic latent image and that carries a two-component developer composed of a magnetic carrier and a non-magnetic toner; A developing device having a developer layer thickness regulating member composed of a magnetic member and a non-magnetic member for regulating a component developer to a predetermined amount, wherein a first gap between a surface of the developer carrier and a tip of the magnetic member is provided. A gap difference ΔH (mm) between a surface of the developer carrier and a second gap between the tip of the nonmagnetic member and a magnetization amount σ (emu / g) of a magnetic carrier of the two-component developer. A developing device characterized by the following conditions being satisfied.
[0017]
0 <ΔH ≦ 1.58 × 10^-3× σ + 0.099
(4) A plurality of charging means and an exposing means for forming an electrostatic latent image on the image carrier, and a plurality of the above-mentioned (1) to (3) each containing a developer of a different color. Developing device, transfer means for transferring a plurality of color toner images formed by the plurality of developing devices to recording paper, paper feeding means for feeding the recording paper to the transfer means, and An image forming apparatus comprising a fixing unit for fixing a transferred image.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Prior to the description of the embodiment of the developing device of the present invention, a configuration of a color copying machine which is an example of an image forming apparatus equipped with a plurality of sets of the developing device of the present invention will be described.
[0019]
[Configuration of Image Forming Apparatus]
FIG. 1 is an overall configuration diagram of a color copying machine including an image forming apparatus 100 and an image reading apparatus 200.
[0020]
The image forming apparatus 100 is called a tandem-type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer body 6, a sheet feeding and conveying unit, and a fixing device 24. Consists of
[0021]
The image forming unit 10Y for forming a yellow image has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y arranged around the image carrier 1Y. The image forming unit 10M that forms a magenta image has an image carrier 1M, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M. The image forming unit 10C for forming a cyan image has an image carrier 1C, a charging unit 2C, an exposing unit 3C, a developing device 4C, and a cleaning unit 8C. The image forming unit 10K for forming a black image has an image carrier 1K, a charging unit 2K, an exposing unit 3K, a developing device 4K, and a cleaning unit 8K.
[0022]
The intermediate transfer member 6 is wound around a plurality of rollers and is rotatably supported.
The images of each color formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the transfer units 7Y, 7M, 7C, and 7K (primary transfer). A color image is formed. The sheet P stored in the sheet cassette 20 is fed by the sheet feeding unit 21, and is conveyed to the transfer unit 7 A via the sheet feeding rollers 22 A, 22 B, 22 C, the registration roller 23, and the like, and the color is printed on the sheet P. The image is transferred (secondary transfer). The sheet P to which the color image has been transferred is subjected to a fixing process by a fixing device 24, and is held by a sheet discharging roller 25 and placed on a sheet discharging tray 26 outside the apparatus.
[0023]
On the other hand, after the color image is transferred onto the sheet P by the transfer unit 7A, the residual toner is removed by the cleaning unit 8A from the intermediate transfer body 6 obtained by separating the sheet P by curvature.
[0024]
5Y, 5M, 5C and 5K are toner replenishing means for replenishing the developing devices 4Y, 4M, 4C and 4K with new toner, respectively.
[0025]
An image reading device 200 including an automatic document feeder 201 and a document image scanning exposure device 202 is installed above the image forming apparatus 100.
[0026]
[Configuration of developing device]
FIG. 2 is a central sectional view of the developing device according to the present invention, and FIG. 3 is a schematic diagram showing circulation of the developer in the developing device. Hereinafter, the developing devices 4Y, 4M, 4C, and 4K are referred to as developing devices 4 as representatives. The image carriers 1Y, 1M, 1C, and 1K are referred to as an image carrier 1 as a representative.
[0027]
The developing device 4 includes a developing device main body 40, a developer carrier (developing roller) 41, a developer layer thickness regulating member 42, a conveying screw 43, a stirring screw 44, and a developer collecting and conveying member (hereinafter, referred to as a peeling roller). 45, a collection screw 46, a toner concentration sensor 47, and the like.
[0028]
In the developing device 4 according to the present invention, the image carrier 1 and the developer carrier 41 rotate in the same direction in a development area where the image carrier 1 and the developer carrier 41 are close to each other. Further, the two-component developer on the developer carrying member 41 passes through the developing area from the developer layer thickness regulating member 42 disposed below the developer carrying member 41, and rises above the developer carrying member 41. It is configured to be stripped by the stripping roller 45 arranged.
[0029]
The developing device main body 40 includes a lower main body 40A that supports the developer carrier 41, the conveying screw 43, and the stirring screw 44, a middle main body 40B that supports the stripping roller 45, and the collecting screw 46, and an upper opening of the middle main body 40B. And an upper lid 40C for closing the lid.
[0030]
The lower main body 40 </ b> A includes a developer supply unit 401 containing the transport screw 43 and a developer stirring unit 402 containing the stirring screw 44. The developer supply unit 401 and the developer stirring unit 402 are formed on both sides of the first partition 404 that stands upright from the bottom of the lower main body 40A.
[0031]
A second partition 405 formed at the bottom of the middle body 40B rotatably supporting the collection screw 46 partitions the developer supply unit 401 and the developer collection unit 403. A part of the middle main body 40B closes an upper opening of the developer stirring section 402.
[0032]
A developer carrier 41 composed of a developing sleeve 41A and a magnetic field generating means (hereinafter, referred to as a fixed magnetic pole) 41B is disposed to face the image carrier 1 carrying an electrostatic latent image, and is rotatably supported. I have.
[0033]
The fixed magnetic pole 41B is disposed inside the developing sleeve 41A, and has a plurality of magnetic poles N1, N2, N3, N4, S1, S2, and S3. Two magnetic poles N3 and N4 adjacent to each other among the plurality of magnetic poles of the fixed magnetic pole 41B are arranged in the same polarity to form a repulsive magnetic field. The developer stripping magnetic pole N3 strips off and scatters the developer on the developer carrier 41. The magnetic pole N <b> 4 for receiving the developer sucks the developer supplied by the transport screw 43 and attaches the developer on the developer carrier 41.
[0034]
The transport screw 43 agitates and transports the developer transported from the stirring screw 44 and uniformly supplies the developer to the developer carrier 41.
[0035]
The stirring screw 44 is arranged in parallel with the conveying screw 43, and mixes and agitates the new toner supplied from the toner replenishing unit 5 with the developer refluxed from the collecting screw 46, and conveys the mixed toner to an upstream portion of the conveying screw 43.
[0036]
A peeling roller 45 is disposed in the developer carrier 41 near the magnetic pole N3 for peeling off the developer. The peeling roller 45 includes a rotatable rotating member (sleeve) 45A and a cylindrical magnet roller (hereinafter, referred to as a magnet body) 45B housed inside the rotating member 45A and fixed to the developing device main body 40. Become. The magnet body 45B includes, for example, three magnetic poles of N1, S1, and S2, and the magnetic pole S1 faces the magnetic pole N3 for removing the developer of the developer carrier 41.
[0037]
The developer released from the surface of the developer carrier 41 by the magnetic pole N3 for removing the developer of the developer carrier 41 is attracted by the magnetic pole S1 in the peeling roller 45 and carried by the rotating rotary member 45A. Then, the developer is conveyed over the inclined second partition 405 in the developer collecting section 403.
[0038]
A collection screw 46 rotatably arranged in the developer collection unit 403 receives and collects the developer that has been stripped off by the stripping roller 45 and falls, and is conveyed by the stirring screw 44 in the developer stirring unit 402. It is transported downstream in the direction and outside the developing area of the developer carrier 41. If the developer does not directly return to the developer carrier 41, the developer collected by the collecting screw 46 may be returned to the upstream of the developer supply unit 401.
[0039]
Each of the transport screw 43, the stirring screw 44, and the recovery screw 46 is a spiral screw-shaped member that transports the developer in the rotation axis direction and discharges the developer in a direction substantially perpendicular to the rotation axis.
[0040]
The downstream side of the developer transport of the developer recovery section 403 and the downstream side of the developer transport of the developer supply section 401 communicate with each other through a first opening 406 formed near the end of the second partition 405. .
[0041]
The downstream side of the developer supply section 401 and the upstream side of the developer agitating section 402 communicate with each other through a second opening 407 formed near one end of the first partition 404. I have.
[0042]
The downstream side of the developer transport of the developer stirring section 402 and the upstream side of the developer transport of the developer supply section 401 communicate with each other by a third opening 408 formed near the other end of the first partition 404. I have.
[0043]
The toner concentration sensor 47 provided at the bottom of the developer supply section 401 on the downstream side of the developer conveyance detects the toner concentration of the conveyed developer. In response to the toner concentration detection signal, the control unit 9 shown in FIG. 3 drives the toner replenishing unit 5 to replenish new toner to the toner replenishment opening 409 provided near the upstream side of the developer agitator 402 in the developer conveyance direction. . The toner replenishing means 5 can optically detect the image density after the development processing, and can perform toner replenishment control in accordance with the detection result of the image density.
[0044]
The developer peeled off by the peeling roller 45 is recovered in the developer recovery section 403, the recovered developer is transported by the recovery screw 46 to the downstream side of the developer transport, and the second developer is pierced in the second partition 405. The developer is returned from one opening 406 to the downstream side of the developer transport in the developer supply unit 401.
[0045]
The developer in the developer supply unit 401 is transported by the transport screw 43 from the second opening 407 formed in one end of the first partition 404 to the upstream side of the developer transport in the developer agitating unit 402. You.
[0046]
The developer transported into the developer agitating section 402 is transported by the agitating screw 44 while mixing and agitating the developer with the new toner replenished from the toner replenishing opening 409 and the other of the first partition 404. Is discharged from the third opening 408 formed at the end of the developer supply portion 401 and is returned to the developer supply portion 401. In the developer supply unit 401, the developer is radiated while being transported in the axial direction by the transport screw 43 and supplied to the developer carrier 41.
[0047]
A first opening 406 provided near an end of a second partition 405 that partitions the developer collection unit 403 and the developer supply unit 401, and a first partition that partitions the developer supply unit 401 and the developer stirring unit 402. Both the second opening 407 and the third opening 408 provided near both ends of the 404 are preferably arranged in the non-image forming area of the developer carrier 41.
[0048]
By configuring the rotation direction of the conveying screw 43 and the stirring screw 44 to be the same as the rotation direction of the developer carrier 41, only the efficiency of the developer supply to the developer carrier 41 is improved. Instead, a stable developer supply becomes possible, and a good image can be obtained.
[0049]
In addition, by setting the rotation direction of the collection screw 46 to be opposite to the rotation direction of the developer carrier 41, the backflow of the developer in the developer collection unit 403 can be reduced. Further, the developer conveying force of the collecting screw 46 is set to be smaller than the developer conveying force of the conveying screw 43. As a result, the occurrence of developer packing on the downstream side of the collection screw 46 in the developer transport direction can be prevented, and stable developer supply to the developer carrier 41 can be achieved without impairing the durability of the developer. Becomes possible.
[0050]
[Developer]
The developer has a magnetization amount of 20 to 70 emu / g in 1 kOe of the magnetic carrier, a magnetic carrier having a particle size of 50 μm or less, and a nonmagnetic polymer having a particle size of 7.5 μm or less. A two-component developer having a toner, and applying a developing bias in which an alternating electric field is superimposed on the developer carrier 41 to develop the image carrier 1 having an electrostatic latent image using the non-magnetic polymerized toner. Is what you do.
[0051]
[Circulation of developer]
The circulation of the developer will be described with reference to the schematic diagram of FIG.
[0052]
(1) At the upstream side of the developer stirring section 402, the developer refluxed from the developer supply section 401 and the developer recovery section 403 and the new toner are carried in, and are stirred and mixed by the stirring screw 44, and the arrow V1 Are transported in the developer movement direction indicated by.
[0053]
(2) The mixed developer passes through the third opening 408 on the downstream side of the developer stirring section 402 and is introduced to the upstream side of the developer supply section 401. In the developer supply section 401, the developer is transported by the transport screw 43 in the developer movement direction shown by the arrow V2, and is transported as shown by the arrow V3.
[0054]
(3) The transport screw 43 discharges the developer to the developer carrier 41 as shown by an arrow V4 while transporting the developer in the rotation axis direction.
[0055]
(4) The developer on the developer carrier 41 is developed in a developer region facing the image carrier 1. The developer whose toner concentration has decreased after the development processing is peeled off from the developer carrier 41 by the peeling roller 45 as shown by an arrow V5 and moves.
[0056]
At this time, by using the peeling roller 45 as a magnet roller, the degree of freedom of the configuration of the developer path from the developer carrier 41 to the developer collecting unit 403 is increased, and the developer is reliably transported. The height of the main body 40 can be reduced.
[0057]
(5) The recovered developer on the peeling roller 45 descends along the inclined surface of the second partition 405 and proceeds in the developer recovery section 403 as shown by an arrow V6.
[0058]
(6) The collected developer accommodated in the developer collecting section 403 is transported by the rotating collecting screw 46 as shown by an arrow V7.
[0059]
At this time, by providing the second partition wall 405 with an inclination, it was confirmed that the developer can be smoothly collected from the peeling roller 45 by the developer collecting section 403.
[0060]
(7) The developer is discharged from the first opening 406 on the downstream side of the developer recovery unit 403, and is carried in outside the image area on the downstream side of the developer supply unit 401 as shown by an arrow V8.
[0061]
(8) The developer supplied to the first opening 406 of the developer supply unit 401 is transported as indicated by an arrow V9, and after the toner density is detected by the toner density sensor 47, the developer is supplied to the second opening 407. After passing through, the developer is introduced upstream of the developer stirring section 402 as indicated by an arrow V10.
[0062]
(9) In the developer agitating section 402, toner replenishment is performed by the toner replenishing means 5 based on the toner density detection signal of the toner density sensor 47, and the developer merges with the arrow V1.
[0063]
The developer is transported in the circulation system as described above, but some of the developer circulates between the developer supply unit 401 and the developer stirring unit 402 as indicated by arrows V1, V2, V9, and V10.
[0064]
[Developer layer thickness regulating member]
FIG. 4 is a partially enlarged cross-sectional view of the developer layer thickness regulating member 42 and the developer carrier 41 arranged in the developing device 4 of the present invention.
[0065]
The developer on the developer carrier 41 passes through a developer layer thickness regulating member 42 disposed below the developer carrier 41 and is regulated to a predetermined developer layer thickness. The developer is conveyed to a development area facing the developer carrier 41 (see FIG. 2).
[0066]
The developer layer thickness regulating member 42 is composed of a magnetic member 42A and a non-magnetic member 42B, is held by being superimposed on the holding member 42C, and is fixed to the lower main body 40A (see FIG. 2).
[0067]
The magnetic member 42A is formed of a stainless steel plate having magnetism, for example, SUS416. The non-magnetic member 42B is formed of a non-magnetic stainless steel plate, for example, SUS316 and SUS304.
[0068]
The magnetic member 42 </ b> A is disposed upstream of the two-component developer in the transport direction of the two-component developer at the gap position facing the developer carrier 41, that is, inside the developing device main body 40. The non-magnetic member 42 </ b> B is disposed downstream of the two-component developer in the transport direction, that is, outside the developing device main body 40.
[0069]
The first gap H1 between the tip of the magnetic member 42A and the developer carrier 41 is set to be larger than the second gap H2 between the tip of the non-magnetic member 42B and the developer carrier 41 (H1> H2). A gap difference ΔH is formed.
[0070]
The present invention exerts the effect of suppressing toner scattering by setting the gap difference ΔH within a certain range. If the second gap H2 of the nonmagnetic member 42B is set too narrower than the first gap H1 of the magnetic member 42A, the regulation of the developer layer thickness is performed by the nonmagnetic member 42B instead of the magnetic member 42A. In this case, the small amount of developer transported by the magnetic member 42A and the stability of the transport amount are lost. If the gap difference ΔH is set too small, the effect of preventing the toner from scattering from the lower side of the developing device is reduced, and problems such as image contamination are liable to occur.
[0071]
[Gap difference ΔH and carrier particle size Dc]
FIG. 5 is a characteristic diagram showing the relationship between the gap difference ΔH between the non-magnetic member 42B and the magnetic member 42A and the carrier particle diameter Dc of the two-component developer.
[0072]
If the gap difference ΔH and the carrier particle diameter Dc are in a region obliquely below the boundary line in the drawing, the nonmagnetic member 42B does not cause the kicking of the developer, and a good result without toner scattering can be obtained.
[0073]
From the above results, the carrier particle diameter Dc (μm) and the gap difference for achieving both the stable supply of the developer transport amount by the magnetic member 42A and the effect of suppressing toner scattering from the developer layer thickness regulating member 42 are compatible. The relationship with ΔH (mm) is a region satisfying the following relational expression.
[0074]
Dc ≦ −684.21 × ΔH + 160.26 (1)
Further, since the non-magnetic member 42B is superimposed on the magnetic member 42A to suppress toner scattering,
0 <ΔH ▲ 2 ▼
Need to be satisfied.
[0075]
Arranging ΔH from the above formulas (1) and (2),
0 <ΔH ≦ 1.46 × 10^-3× Dc + 0.234
Becomes
[0076]
[Gap difference ΔH and magnetic flux density B]
FIG. 6 is a characteristic diagram showing the relationship between the gap difference ΔH between the nonmagnetic member 42B and the magnetic member 42A and the magnetic flux density B of the magnetic pole of the developer carrier 41 facing the developer layer thickness regulating member 42.
[0077]
Of the plurality of fixed magnetic poles 41B arranged inside the developing sleeve 41A, the development near the developer layer thickness regulating member 42 also depends on the magnetic flux density B of the magnetic pole (spike pole) S3 facing the developer layer thickness regulating member 42. The spike condition of the agent is different and relates to the gap difference ΔH (see FIG. 2). FIG. 6 shows the relationship between the magnetic flux density B of the tipping pole S3 and the gap difference ΔH at which the nonmagnetic member 42B does not cause the kicking of the developer.
[0078]
If the gap difference ΔH and the magnetic flux density B are in a region obliquely above the illustrated boundary line, no kicking of the developer by the non-magnetic member 42B occurs, and a good result without toner scattering can be obtained.
[0079]
From the above results, the magnetic flux density B (Wb) of the tipping pole S3 for achieving both the stable supply of the developer transport amount by the magnetic member 42A and the effect of suppressing toner scattering from the developer layer thickness regulating member 42 can be achieved. / M²) And the gap difference ΔH (mm) are regions satisfying the following relational expression.
[0080]
B ≧ 3225.8 × ΔH + 93.387 (1)
Further, since the non-magnetic member 42B is superimposed on the magnetic member 42A to suppress toner scattering,
0 <ΔH ▲ 2 ▼
Need to be satisfied.
[0081]
Arranging ΔH from the above formulas (1) and (2),
0 <ΔH ≦ 0.31 × 10^-3× B-0.029
Becomes
[0082]
[Gap difference ΔH and magnetization amount σ]
FIG. 7 is a characteristic diagram showing the relationship between the gap difference ΔH between the non-magnetic member 42B and the magnetic member 42A and the magnetization amount σ of the carrier of the two-component developer.
[0083]
As in the case of the magnetic flux density B of the ear-cutting pole S3, the state of standing of the developer near the developer layer thickness regulating member 42 also varies depending on the magnetization amount σ of the carrier of the two-component developer. FIG. 7 shows the relationship between the gap difference ΔH and the amount of magnetization σ of the carrier, which balances the amount of the agent transported and the suppression of toner scattering from the vicinity of the developer layer thickness regulating member 42.
[0084]
If the gap difference ΔH and the magnetization amount σ of the carrier are in a region obliquely above the illustrated boundary line, the nonmagnetic member 42B does not cause the kicking of the developer, and a good result without toner scattering can be obtained.
[0085]
From the above results, the magnetization amount σ (emu / g) of the carrier for achieving both the stable supply of the developer transport amount by the magnetic member 42A and the effect of suppressing the toner scattering from the developer layer thickness regulating member 42. And the gap difference ΔH (mm) is a region satisfying the following relational expression.
[0086]
σ ≧ 633.96 × ΔH−62.962 (1)
Further, since the non-magnetic member 42B is superimposed on the magnetic member 42A to suppress toner scattering,
0 <ΔH ▲ 2 ▼
Need to be satisfied.
[0087]
Arranging ΔH from the above formulas (1) and (2),
0 <ΔH ≦ 1.58 × 10^-3× σ + 0.099
Becomes
[0088]
As described above, the gap difference ΔH (mm) between the non-magnetic member 42B and the magnetic member 42A for suppressing toner scattering from the developer layer thickness regulating member 42 and obtaining a stable image density, and the carrier of the two-component developer The particle diameter Dc (μm) and the magnetic flux density B (Wb / m²) And the required condition of the carrier magnetization σ (emu / g) are regions satisfying the following three relational expressions.
[0089]
0 <ΔH (mm) ≦ 1.46 × 10^-3× Dc (μm) +0.234
0 <ΔH (mm) ≦ 0.31 × 10^-3× B (Wb / m²) -0.029
0 <ΔH (mm) ≦ 1.58 × 10^-3× σ (emu / g) +0.099
[0090]
【Example】
Developer carrier 41
Diameter of developing sleeve 41A: φ12 to φ50 mm
Linear velocity of the developing sleeve 41A: 100 to 600 mm / sec
Magnetic flux density of fixed magnetic pole 41B: 100 to 1500 Wb / m²
Developer layer thickness regulating member 42
Superposition of magnetic member 42A and non-magnetic member 42B
Located below the developing sleeve 41A
Two-component developer
Particle size of magnetic carrier: 20 to 70 μm
Particle size of non-magnetic polymerized toner: 1 to 7 μm
Toner concentration Tc: 3 to 8% by mass
Comprehensive endurance test
A 100,000-sheet print test was performed using A4 size paper P. No problems such as image contamination due to toner scattering occurred, and a stable image density was obtained.
[0091]
In the above-described embodiment, the developing device in which the developer layer thickness regulating member 42 is disposed below the developer carrier 41 has been described. However, the present invention is not limited to this. The present invention is applicable to a developing device having a configuration in which the regulating member 42 is disposed above the developer carrier 41.
[0092]
【The invention's effect】
As described above, the developer layer thickness regulating member of the developing device of the present invention is set at the gap difference ΔH between the tip portions of the magnetic member and the non-magnetic member and is superimposed on the developer carrier. And the gap difference ΔH is defined by the carrier particle size, the magnetic flux density, and the amount of magnetization of the carrier, thereby stably transporting the two-component developer on the developer carrier, and regulating the thickness of the developer layer. The toner scattering generated when regulating the amount of the developer in the vicinity of the poles of the member and the developer carrying body facing the member is suppressed, and the problems such as the scattering of the components due to the scattering inside the machine and the image contamination are eliminated.
[0093]
Further, the influence on the change in the developer layer thickness regulation interval due to the misalignment of the developer carrier is extremely small, and a stable developer transport amount can be secured. In particular, it is possible to obtain high-quality images without unevenness even in low-density portions such as halftones.
[0094]
Furthermore, problems such as a decrease in toner density and a decrease in image density which occur during continuous mass printing or high-speed printing are eliminated. Further, the image density of each color in the color image forming apparatus can be kept uniform, and a high quality color image can be obtained.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a color copying machine including an image forming apparatus and an image reading apparatus.
FIG. 2 is a central sectional view of the developing device according to the present invention.
FIG. 3 is a schematic diagram illustrating circulation of a developer in a developing device.
FIG. 4 is a partially enlarged cross-sectional view of a developer layer thickness regulating member and a developer carrier disposed in the developing device of the present invention.
FIG. 5 is a characteristic diagram showing a relationship between a gap difference between a non-magnetic member and a magnetic member and a carrier particle diameter of a two-component developer.
FIG. 6 is a characteristic diagram showing a relationship between a gap difference between a non-magnetic member and a magnetic member and a magnetic flux density of a magnetic pole facing a developer layer thickness regulating member of a developer carrier.
FIG. 7 is a characteristic diagram showing a relationship between a gap difference between a non-magnetic member and a magnetic member and a magnetization amount of a carrier of a two-component developer.
[Explanation of symbols]
1,1Y, 1M, 1C, 1K image carrier
4,4Y, 4M, 4C, 4K developing device
40mm developing unit
41 developer carrier (developing roller)
41A development sleeve
41B magnetic field generating means (fixed magnetic pole)
42 Developer layer thickness regulating member
42A magnetic member
42B non-magnetic material
45 ° developer recovery transport member (peeling roller)
47 toner density sensor
H1 First gap
H2 second gap
S3 @ Holig pole
ΔH gap difference

Claims (6)

A developer carrier that is arranged to face an image carrier that carries an electrostatic latent image and conveys a two-component developer composed of a magnetic carrier and a non-magnetic toner; and a two-component developer on the developer carrier. A developing device having a developer layer thickness regulating member composed of a magnetic member and a non-magnetic member that regulates a
A gap difference ΔH (mm) between a first gap between the developer carrier surface and the tip of the magnetic member, and a second gap between the developer carrier surface and the tip of the non-magnetic member;
A developing device, wherein the following condition is satisfied between the magnetic carrier and the particle diameter Dc (μm).
0 <ΔH ≦ 1.46 × 10 ⁻³ × Dc + 0.234 A developer carrier that is arranged to face an image carrier that carries an electrostatic latent image, carries a two-component developer including a magnetic carrier and a non-magnetic toner, and has a magnetic pole therein; and A developing device having a developer layer thickness regulating member including a magnetic member and a non-magnetic member that regulates the upper two-component developer to a predetermined amount,
A gap difference ΔH (mm) between a first gap between the developer carrier surface and the tip of the magnetic member, and a second gap between the developer carrier surface and the tip of the non-magnetic member;
The following condition is satisfied between the magnetic flux density B (Wb / m ² ) of the magnetic pole of the developer carrier that faces the developer layer thickness regulating member.
0 <ΔH ≦ 0.31 × 10 ⁻³ × B−0.029 A developer carrier that is arranged to face an image carrier that carries an electrostatic latent image and conveys a two-component developer composed of a magnetic carrier and a non-magnetic toner; and a two-component developer on the developer carrier. A developing device having a developer layer thickness regulating member composed of a magnetic member and a non-magnetic member that regulates the
A gap difference ΔH (mm) between a first gap between the developer carrier surface and the tip of the magnetic member, and a second gap between the developer carrier surface and the tip of the non-magnetic member;
A developing device, wherein the following condition is satisfied between the two-component developer and the magnetization amount σ (emu / g) of the magnetic carrier.
0 <ΔH ≦ 1.58 × 10 ⁻³ × σ + 0.099 The developer layer thickness regulating member overlaps a magnetic member disposed on the upstream side in the transport direction of the two-component developer and a non-magnetic member disposed on the downstream side at a gap position facing the developer carrier. The developing device according to claim 1, wherein the developing device is attached to the developing device main body. The two-component developer according to any one of claims 1 to 3, wherein the two-component developer includes the magnetic carrier having a particle size of 50 µm or less and a non-magnetic polymerized toner having a particle size of 7.5 µm or less. The developing device as described in the above. The plurality of developing devices according to any one of claims 1 to 5, wherein a plurality of charging units and a plurality of exposure units for forming an electrostatic latent image on the image carrier, and developers of different colors are respectively stored. Transfer means for transferring a plurality of color toner images formed by the plurality of developing devices onto recording paper; paper feeding means for feeding recording paper to the transfer means; and a transfer image formed on the recording paper. An image forming apparatus having a fixing unit for fixing.

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