JPH08248773A - Development device - Google Patents

Abstract

PURPOSE: To provide a developing device capable of obtaining stable printing quality by improving the developing poles and rotational speeds of plural developing rolls. CONSTITUTION: The developing device is constituted in such a manner that a first developing roll 5 rotated in a direction opposite to that of a photoreceptor 1 is arranged on the upstream side, a second developing roll group which is rotated in the same direction as that of the photoreceptor 1 and provided with a magnet having the same polarity as the developing pole is arranged on the downstream side and a developer regulating member 16 is provided between the first developing roll 5 and the second developing roll group. Further, a toner concentration detector 14 is provided on the downstream side of the second developing roll group arranged on the lowermost downstream side and a cross mixer 15 and a carrying member 4 are provided in the lower parts of the first. developing roll 5 and the second developing roll group.

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 electrophotographic device or the like.

[0002]

2. Description of the Related Art A conventional developing device is disclosed in Japanese Examined Patent Publication No. 62-2313.
As described in Japanese Unexamined Patent Publication No. 2004-242242, two developing rolls that rotate in the same direction as the moving direction of the photoconductor are arranged, two developing poles of the same polarity are arranged on the developing poles of either one of the developing rolls, and further upstream. There is a developing device in which the first developing roll provided on the side is faster than the moving speed of the photoconductor, and the second developing roll provided on the downstream side is slower than the moving speed of the photoconductor.

[0003]

By the way, when high-speed printing is attempted with the construction of the developing device, the following problems occur. (a) Since the developing roll moving in the same direction has a high moving speed on the upstream side and a slow moving speed on the downstream side, the drum lock is generated by the developer. (b) The image density is reduced due to the speedup. (c) The developing roll and the transport roll rotating shaft are worn or locked.

Therefore, an object of the present invention is to solve the drawbacks of the prior art and to provide a developing device capable of obtaining stable print quality.

[0005]

SUMMARY OF THE INVENTION The above object is to supply a developer to a photoconductor which is opposed by a plurality of developing rolls having a magnetic attraction force which are arranged close to the photoconductor having photoconductivity, and to provide a magnetic brush. In a developing device for developing, a developing pole having a unipolar developing magnet that contributes to the developing, and a moving direction of the developing magnet moves in a direction opposite to the moving direction of the photoconductor, and a plurality of adjacent magnetic attracting members. A developing machine composed of a second developing roll group consisting of one or more developing rolls in which a plurality of magnets having the same polarity are brought close to a developing pole which has a force and contributes to the development. A first developing roll is provided on the upstream side of the above, a second developing roll group is provided on the downstream side in the photoconductor moving direction, and the peripheral speed ratio between the first developing roll and the photoconductor is 0.5 to 1.5. The peripheral speed ratio between the second developing roll group and the photoconductor is 0.6. It is achieved by the 0.95.

[0006]

According to the developing device configured as described above, the cleaning ability on the photoconductor is maintained by the first developing roll which rotates in the direction opposite to the moving direction of the photoconductor, and the second developing roll group is also provided. Since the magnet of the same polarity provided on the developing pole softly supplies the developer to the photoconductor and increases the toner supply amount, the load on the photoconductor is small and the density is stable even at high speed printing. Image quality can be obtained for a long time.

[0007]

【Example】

(Embodiment 1) An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a developing device of the present invention, FIG. 2 is an explanatory diagram showing the configuration of a cross mixer, and FIG. 3 is an explanatory diagram showing the configuration of a second developing roll group. Peripheral speed 600
Having a photoconductivity of moving at ˜1800 mm / s, for example, SeTe or SeTeA having a photosensitive layer thickness of 50 to 80 μm
s, As ₂ Se _3, etc., facing the photoconductor 1 having a diameter of 200 to 300 mm and a gap between the photoconductor and the photoconductor 1 of 0.6 to 2 m.
m is preferably 0.8 to 1.5 mm, and rotates in the same direction as the photoconductor 1 and has the same magnetic poles as the developing poles 8a, 8b, 9a,
The first developing device which rotates the two second developing roller groups 8 and 9 (each having a diameter of 50 to 90 mm) having 9b in the direction opposite to the photosensitive member 1 on the downstream side when viewed from the moving direction of the photosensitive member. The roll 5 is arranged on the upstream side.

The developer 3 consisting of a carrier and toner at the bottom of the developing container 2 is magnetically attracted by a rotatable conveying member 4 (a magnetic roll having a diameter of about 50 to 120 mm) arranged at the bottom of the developing container 2. , The conveying member 4 for conveying the surface thereof
Is transferred to the surface of the second developing roll group 9 that is close to. The transferred developer 3 adheres to the surface of the second developing roll group 9 due to the magnetic attraction force, and the rotation of the sleeve 13 causes the developer 3 to come into contact with the photoconductor of the second developing roll group 9 for development. It moves toward the upstream side on the opposite side to and is transferred to the second developing roll group 8 on the upstream side. The delivered developer 3 adheres to the surface thereof due to the magnetic attraction force of the second developing roll group 8, and the developer 3 conveyed by the rotation of the sleeve 12 is regulated to a certain amount by the developer regulating member 16. To be done. After that, the developer 3a is conveyed between the photoconductor 1 and the second developing roll groups 8 and 9, and is brought into contact with the photoconductor 1 for development.

The developer 3c leaking from the regulation by the developer regulating member 16 is conveyed to the upstream side of the rear surface of the developer regulating member 16 and is magnetized by the first developing roll 5 which rotates in the direction opposite to the photoconductor 1. The developer 3b attached to the surface by the suction force and conveyed between the first developing roll 5 and the developer regulating member 16 by the rotation of the sleeve 7 is regulated again to a constant amount by the developer regulating member 16. It Then, the photoconductor 1 and the first developing roll 5
And is brought into contact with the photoconductor 1 for development. The developer 3c that has leaked from the regulation by the developer regulating member 16 drops to 15a of the cross mixer 15 that is provided below the developer regulating member 16 and moves the developer in a lateral direction.
As will be described later with reference to FIG. 3, a part thereof further drops to 15b. It is agitated and mixed by being divided into left and right by 15a and 15b, and returned to the lower part of the transport member 4. At this time, the developer 3d that has finished developing and has rotated on the surface of the first developing roll 5 is scraped off by the scraper 17, and is supplied from the toner hopper 20 by the rotation of the toner feed roll 19 to fall off the toner. While being mixed with (the toner is supplied when the toner concentration of the developer is lowered), the toner drops to 15c of the cross mixer 15, is agitated and mixed, and is returned to the lower portion of the conveyance member 4. That is, this cross mixer is for mixing and stirring a part of the developer while moving it to the left and right in parallel with the axis of the developing roll to make the toner concentration in the developer uniform, and has a three-stage structure. Gives good results.

As shown in FIG. 2, the upper portion 15a is provided with a drop hole 15d which divides the falling developer 3c into approximately _two halves so that the developer can be divided into first and second tiers, and the first tier 15a is, for example, leftward. Since the inclined fins 15e to be moved and the fins 15f to be moved to the right are attached to the second step 15b and has a structure to move the developer to the left and right when dropped, the toner concentration of the developer is changed to the left and right. Can be uniform. In the third stage 15c (bottom), the developer 3d and the supplied toner are mixed and dropped downward without moving to the left or right, reach the conveying member 4, and are stirred and conveyed. There is no uneven distribution of toner due to the inclined fins (a phenomenon in which the toner is collected by the fins without being mixed with the developer) that occurs when the toner is directly supplied to the first and second stages, and the stain on the streaky paper background is suppressed. it can. Further, the developer 3e developed by contacting the second developing roll groups 8 and 9 and the photoconductor 1 is scraped off by the scraper 18. A part of the developer 3e enters the toner concentration detector 14 and detects the toner concentration in the developer. Then, it is returned to the lower part of the transport member 4.

The average particle size of the toner used in the developer 3 is 6 to 12 μm, preferably 7 to 9 μm. As a result, the average particle diameter of the toner was reduced, and it was possible to deal with high definition image quality. Styrene is the carrier
Average particle size 8 coated with resin such as acrylic and silicone
Spherical size of 0 to 130 μm, saturation magnetization of 50 to 8 at 1 kOe
A magnetite carrier or ferrite carrier of 0 emJ / g was used, and its dynamic electric resistance was 10 ⁸ to 10 ¹¹
By using a developer having an Ωcm of preferably 10 ⁹ to 10 ¹⁰ Ωcm, a stable charging performance can be maintained and a high quality image can be stably obtained even at high speed development. Especially average particle size 90-1
The magnetite carrier of 20 μm is suitable for the high-speed development of this embodiment in that the developer has good fluidity, the carrier does not adhere to the photoreceptor, and the life is long. The life of the developer reached 200 to 1,000 kpages / kg, while the life of the iron powder carrier was half or less.

When the thickness is less than 80 μm, the carrier is remarkably attached to the drum, and when the thickness is more than 130 μm, a rough image is formed, which is inconvenient. The toner charge amount is 10 to 12 as the average particle size of the toner.
15 to 35 μC / g, preferably 20 to 30 μm when μm
C / g, 20 to 50 μC / g, preferably 25 to 40 μC / g at an average particle size of 7 to 9 μm, and a toner density of high image density when the surface coverage of the toner carrier is set to 0.3 to 0.6. In addition, it is possible to prevent the toner from scattering around the developing machine. If it is less than 0.3, a sufficient image cannot be obtained, and if it is more than 0.6, toner scattering and fog are likely to occur. In this embodiment, by using a plurality of homopolar developing magnetic poles, a three-stage structure cross mixer, a carrier having good fluidity, and a developer, good results can be obtained even if the coverage is increased as compared with the prior art.

When the bias voltage applied to the first developing roll 5 is V _B1 and the bias voltage 200 to 600 V applied to the second developing roll groups 8 and 9 is V _B2 , V _B1 ≧ V _B2 is set. It was confirmed that an image with no stain on the back surface of the paper was obtained in response to the temporal decrease in surface potential due to dark decay of the photoconductor 1. As shown in FIG. 1, the rotation direction of the first developing roll is preferably opposite to the photoconductor. This is because the rotation direction of the first developing roller is preferably opposite to the moving direction of the photoconductor in order to increase the cleaning ability on the photoconductor and the toner adhesion amount. Since this action is preferably performed at the initial stage of development, it is preferable to provide the first developing roll on the upstream side in the photosensitive member moving direction as shown in FIG. After that, it is preferable to arrange the image on the photoconductor in the same direction as the photoconductor. Therefore, as shown in FIG. 1, the rotation direction of the second developing roll group is the same as the moving direction of the photoconductor and the photoconductor is moved. By providing it on the downstream side in the direction, high cleaning ability and developing ability are possible, and stable and good images can be obtained.

Further, when a good image is obtained at a photosensitive member moving speed of 600 mm / s or more, particularly 800 mm / s or more, if the developing pole contributing to the development of the second developing roll group is a single pole, the second developing roll group The rotation speed of 1. is the moving speed of the photoconductor.
You need 5 to 3 times. Rotating at such a high speed not only shortens the life of the developer and the photoconductor due to a sudden increase in load on the developer, but also shortens the life of the bearings of the developing roll and the transport roll. In addition, toner scattering also increases sharply. In order to prevent such a phenomenon, the first roll group has a single pole and maintains the cleaning ability, and two or more developing poles having the same pole that contribute to the development of the second developing roll group are provided. This homopolar magnet can be obtained by providing a concave groove in the central portion of the magnetic pole, embedding a rare earth magnet or having an independent block magnet having a strong magnetic force as shown in FIG.

It was also confirmed that by providing a large number (two or more) of magnetic poles having the same pole, the developer on the developing roll that comes into contact with the surface of the photoreceptor becomes softer. (Two block magnets of the same pole in FIG. 1) By using block magnets of the same pole, the developer flies due to the repulsive magnetic force of the magnet and comes into contact with the photoconductor to perform development. In this case, compared with the case of developing with a single-pole magnetic brush, the development time becomes longer and the toner supply capability is increased due to the disturbance effect of the developer at the development pole portion, so that the development efficiency is increased. Therefore, the rotation speed of the developing roll can be reduced, and the load on the photoconductor, the developer, and the bearing can also be reduced. Therefore, with this configuration, the photosensitive member moving speed is 1000
When it is adopted for a roller of up to 1800 mm / s, the rotation speed of the second developing roll group is 1.05 to 1.5 times and 0.6 to 0.95 times the moving speed of the photoconductor, so that a high density and uniform image can be obtained. Thus, the scattering of the developer and toner could be suppressed. Above all, it was excellent when it was 1.05 to 1.5 times. 0.95-
At 1.05 times, image unevenness was slightly generated, and carrier adhesion to the photoreceptor was large, which was not preferable.

On the other hand, the rotation speed of the first developing roll is 0.5 to 1.5 times the moving speed of the photoconductor, so that a stable cleaning effect and a high quality developing effect can be obtained, which is 0.5 to 1.0 times. Although the effect was sufficiently obtained even at a low speed, it is convenient to configure the developing roll driving mechanism so that the first and second rolls have a constant speed or the first roll is slow. When the rotation speed of the second developing roll group 9 on the downstream side in the photoconductor rotating direction is slower than the rotation speed of the second developing roll group 8 on the upstream side of the second developing roll group 9, the second developing roll group 9 and photoconductor 1
A developer pool is formed between and, and drum lock occurs. Therefore, the second developing roll group 8 is provided with a second
By making the rotation speed of the developing roll group 9 faster than the rotation speed of the second developing roll group 8, the flow of the developer became smooth, the developer was not accumulated, and the drum lock was not generated. If the speed is the same, the development gap on the downstream side is 0.1.
It is good to widen ~ 0.3mm.

An experiment was conducted using the developing device having the configuration shown in FIG. FIG. 4 shows the result of summarizing the stains on the paper background portion at that time. From these results, comparing the case of using the single pole as the developing pole of the second developing roll group and the case of using the homopolar magnet of the present invention, the case of using the homopolar magnet of the present invention is generally It was found that the effect is remarkable when the background portion of the paper is less contaminated and the peripheral speed ratio between the second developing roll group and the photoconductor is low. From this result, it was confirmed that the rotation speed of the second developing roll group was 1.05 to 1.5 times the moving speed of the photoconductor and the stain on the background portion of the paper satisfied the reflectance increase of 0.5% or less. Therefore, a good image could be obtained by setting the rotation speed of the second developing roll group to 1.05 to 1.5 times, preferably 1.1 to 1.3 times the moving speed of the photoconductor. .

An experiment was conducted on the magnetic pole angle of the developing pole of the second developing roll group and the stain on the background portion of the paper by using the developing machine having the configuration shown in FIG. The results of using a developing roll having a diameter of 50 mm and a homopolar magnet angle of 30 ° are shown in FIGS. From this result, when the homopolar magnet of the present invention is used for the developing pole of the second developing roll group, the magnetic pole angle (FIG. 5) is the same magnetic pole of the developing poles of the developing rolls 8 and 9 of the second developing roll group. If the angle between the center line between them and the center of the photoconductor and the line connecting the centers of the developing rolls 8 and 9 of the second developing roll group is set to around 5 ° in the clockwise direction when viewed from the second developing roll group. It was confirmed that the stain on the background portion of the paper satisfied the reflection increase rate of 0.5% or less. Therefore,
The magnetic pole angle of the developing poles of the developing rolls 8 and 9 of the second developing roll group is 2.5 ° clockwise when viewed from the second developing roll group.
A good image could be obtained by setting it to 7.5 °. This tendency was the same when the developing roll diameter was 40 to 70 mm and the homopolar magnet angle was 15 ° to 30 °. Diameter 70 ~
When the magnet angle was 90 mm and the homopolar magnet angle was 15 ° to 30 °, the developing angle was 0 ° to 7.5 °. Further, when an odd number of homopolar magnets are used for the developing poles of the second developing roll group, the magnetic pole angle of the central magnetic pole between the homopolar magnets is 2.5 ° to 7 ° clockwise when viewed from the second developing roll group. A good image could be obtained by setting it to 0.5 °.

(Embodiment 2) Another embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. FIG. 7 shows the magnetic force curve of the magnet of the same pole as the developing pole of the second developing roll group used in this experiment. When magnets of the same pole are used, a drop in magnetic force occurs between the peak values of the same poles. It was experimentally confirmed that this drop amount (ΔG) greatly affects the state of the spikes of the developer on the developing roll. This drop amount (Δ
The larger G), the larger the repulsive magnetic force between the magnetic poles of the same polarity,
The effect of flying and developing on the surface of the photoconductor is increased.

FIG. 8 shows the results of an examination of the relationship between the amount of depression (ΔG) between magnetic poles of the same polarity and the image density. From this result, the amount of depression (ΔG) between the magnetic poles of the same polarity is 300 to 600.
It can be seen that high image density can be obtained with Gauss. Therefore, a good image quality can be obtained by setting the amount of depression (ΔG) between the same magnetic poles of the developing poles of the second developing roll groups 8 and 9 to be 300 to 600 gauss. The peak value of the magnetic force of the homopolar magnet is 7
It is desirable that the developing contact width is secured and that the carrier is less attached to the drum, which is preferably 00 gauss or more, preferably 900 to 1300 gauss.

(Third Embodiment) Another embodiment of the present invention will be described with reference to FIGS. 9 and 10. FIG. 9 shows a part of a sectional view showing a state in which a developing roll, a transport roll and a bearing are incorporated. The bearing 21 is embedded in one surface of the rotation support of the developing container wall 2 and the sleeve 7, and is provided on the first developing roll 5, the second developing roll groups 8 and 9, and the transporting roll 4 to prevent the rotation of each developing roll. Supported. When the number of rotations of the first developing roll 5 and the second developing roll groups 8 and 9 increases, the developer (toner, carrier) 3 flies toward the bearing 21 and enters the bearing 21, and the amount of heat generation also increases. Bearing 2
Shorten the life of 1. Therefore, the result of examining the relationship between the rotation speed of the developing roller having a diameter of 50 mm and the bearing life is shown in FIG.
Shown in

The number of occurrences is the number of rotation failures (starting torque increase, lock, etc.) that occur for one year under average usage conditions. From these results, it can be seen that the bearing life is remarkably shortened when the rotation speed of the developing roll is 600 rpm or more. When the photosensitive member and the photosensitive member moving speed are further increased to 1800 mm / s, and when the developing roller diameters of the second developing roller groups 8 and 9 are set to 80 to 90 mm, the developing operations of the second developing roller groups 8 and 9 are performed. Even when the number of rotations of the roll was 600 rpm or less, a high-density and uniform image could be obtained, and the bearing used for each developing roll also had a long life and reliability could be improved. Since the weight, cost, and device size increase as the diameters of the developing roll and the carrying roll increase, it is preferable that the developing roll has a diameter of 50 to 90 mm and the carrying roll has a diameter of 50 to 120 mm.

[0023]

As described above, according to the present invention, a photoreceptor,
It is possible to provide a developing device that can reduce the load on the developer and can obtain stable and good image quality even at high speed printing.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a configuration of a cross mixer.

FIG. 3 is an explanatory diagram showing a configuration of a second developing roll group.

FIG. 4 is an explanatory diagram showing the relationship between the peripheral speed ratio of the developing roll and the stain on the paper background portion.

FIG. 5 is an explanatory diagram of a magnetic pole angle.

FIG. 6 is an explanatory diagram showing the relationship between the magnetic pole angle and the stain on the paper background portion.

FIG. 7 is an explanatory diagram showing a relationship between a magnetic force and each magnetic pole of the second developing roll.

FIG. 8 is an explanatory diagram showing the relationship between the image density and the falling magnetic force between magnetic poles of the same polarity.

FIG. 9 is an explanatory diagram showing a developing roll bearing portion.

FIG. 10 is an explanatory diagram showing the relationship between the number of rotations of the developing roll and the number of occurrences of defects.

[Explanation of reference numerals] 1 ... photoreceptor, 2 ... development container, 3 ... developer, 5 ... first
Developing rolls, 8, 9 ... Second developing roll group, 14 ... Toner concentration detector, 15 ... Cross mixer, 16 ... Developer regulating member, 17, 18 ... Scraper,

Claims (8)

[Claims] 1. A developing device for performing magnetic brush development by supplying a developer to a photoconductor that opposes a plurality of developing rolls having a magnetic attraction force, which are arranged in proximity to a photoconductor having photoconductivity. A developing pole having a unipolar developing magnet that contributes to the developing pole, and the moving direction of the developing magnet is opposite to the moving direction of the photoconductor.
Developing comprising a developing roll and a second developing roll group including one or more developing rolls having a plurality of magnetic attraction forces adjacent to each other and having a plurality of magnets of the same pole in close proximity to the developing pole contributing to the development And a first developing roll provided on the upstream side in the moving direction of the photoconductor,
A second developing roll group is provided on the downstream side in the moving direction of the photoconductor, and a peripheral speed ratio between the first developing roll and the photoconductor is 0.5 to 1.5. A developing device, wherein a peripheral speed ratio with the photoconductor is 0.6 to 0.95. 2. A developing device for performing magnetic brush development by supplying a developer to a photoconductor opposed to each other by a plurality of developing rolls having a magnetic attraction force which are arranged in proximity to the photoconductive photoconductor. A developing pole having a unipolar developing magnet that contributes to the developing pole, and the moving direction of the developing magnet is opposite to the moving direction of the photoconductor.
Developing comprising a developing roll and a second developing roll group including one or more developing rolls having a plurality of magnetic attraction forces adjacent to each other and having a plurality of magnets of the same pole in close proximity to the developing pole contributing to the development And a first developing roll provided on the upstream side in the moving direction of the photoconductor,
A second developing roll group is provided on the downstream side in the moving direction of the photoconductor, and a peripheral speed ratio between the first developing roll and the photoconductor is 0.5 to 1.5. A developing device, characterized in that a peripheral speed ratio with the photoconductor is 1.05 to 1.5. 3. The moving speed of the photoconductor is about 600 to 180.
The developing device according to claim 1, wherein the developing device has a speed of 0 mm / sec. 4. When the number of homopolar magnetic poles of the developing poles of each developing roll of the second developing roll group is an even number, the center line between the magnetic poles of the same pole, the center of the photoconductor, and each of the second developing roll groups. The angle of the line connecting the center of the developing roll is set to 2.5 ° to 10 ° clockwise when viewed from the second developing roll group, and when the number of the same-polarity magnetic poles is an odd number, the angle is set to 3. The developing device according to claim 1, wherein the developing device is set to 2.5 ° to 10 ° clockwise when viewed from the group of two developing rolls. 5. The difference between the maximum value of the magnetic force between the homopolar magnets of the developing poles of the second developing roll group and the depressed value between the magnetic poles of the same pole is 25.
3. The developing device according to claim 1, wherein the developing device has a density of 0 to 600 gauss. 6. The number of revolutions of each developing roll of the first developing roll and the second developing roll group or the number of revolutions of the carrying roll is 6.
3. The developing device according to claim 1, wherein the diameter of each developing roll is set to 50 to 90 mm or the diameter of the conveying roll is set to 50 to 120 mm so as to satisfy the above conditions at a speed of 00 rpm or less. 7. A developing device for performing magnetic brush development by supplying a developer to a photoconductor opposed to each other by a plurality of developing rolls having a magnetic attraction force which are arranged close to the photoconductive photoconductor. A developing pole having a unipolar developing magnet that contributes to the developing pole, and the moving direction of the developing magnet is opposite to the moving direction of the photoconductor.
Developing comprising a developing roll and a second developing roll group including one or more developing rolls having a plurality of magnetic attraction forces adjacent to each other and having a plurality of magnets of the same pole in close proximity to the developing pole contributing to the development And a first developing roll provided on the upstream side in the moving direction of the photoconductor,
A second developing roll group is provided on the downstream side in the photosensitive member moving direction, and the peripheral speed ratio of the developing rolls on the downstream side in the photosensitive member rotating direction in the peripheral speed ratio between each developing roll of the second developing roll group and the photosensitive member. Where V _n is V _n and the peripheral speed ratio of the developing roll on the upstream side in the photosensitive member rotation direction is V _{n + 1} , the developing device satisfies the relationship of V _n ≧ V _{n + 1} . 8. The developer comprises a magnetic carrier made of spherical magnetite having a particle size of 80 to 130 μm, and a particle size of 6 to 12
including a toner of μm, and the charge amount Q / M of the developer is 20
The developing device according to claim 1, 2 or 7, wherein the developing device has a toner coverage of 0.3 to 0.6%.