JP4042085B2 - Development device - Google Patents

Description

【００１４】
現像剤規制部材９を設けることで、現像剤３ｆの表面のトナー濃度を高く保つことができ、高濃度な画像が得られた。この結果から、現像剤規制部材９を設けることにより、現像剤３ｆ表面の重量トナー濃度が高くなり、高濃度な画像が得られることが分かった。
（実施例２）本発明の他の実施例を図２を用いて説明する。現像剤規制部材９を中心として、現像ローラ６,７で向かい合う同磁極の６ａと７ｂ、６ｂと７ａを対称に配置する。また、現像ローラ７の磁極７ａと７ｂの極間を６０°にし、磁極６ｂを４５０〜７００Ｇ（ガウス）、７ａを５００〜７５０Ｇ、７ｂを４００〜６５０Ｇとした。その結果、磁極７ｂから７ａの方向と７ｂから６ｂの方向に現像剤を安定して搬送させることができた。
（実施例３）また、本発明の他の実施例を示す。感光体回転方向下流側にある第２現像ローラ群６,７の回転速度と感光体１の回転速度の周速比が１.０以下の場合、印刷背景部の汚れが増加する。そこで、第２現像ローラ群６と感光体１との周速比を１.１以上、第２現像ローラ群７と感光体１との周速比を１.２以上とすることで、印刷背景部の清掃効果が高まり、画像背景部の汚れを減少させることができた。
【００１５】
図１の構成の現像装置を用いた時の画像背景部の汚れについてまとめた結果を図３に示す。縦軸は画像背景部の汚れ、横軸は感光体の回転速度に対する第２現像ローラ群の感光体１の回転方向下流側の現像ローラ７の周速比を示している。この結果から、周速比１.０の時の画像背景部の汚れがもっとも多く、周速比を上げるにつれて画像背景部の汚れが減少していくことが分かった。この結果から、現像ローラ７と感光体１との周速比が１.２以上において、画像背景部の汚れが規格値を満足することを確認した。従って、現像ローラ７と感光体１との周速比を１.２以上に設定することで良好な画像を得ることができた。なお、上記実施例は第２現像ローラ群が２本の場合を示したが、本発明は第２現像ローラ群が３本以上の場合でも同様に適用可能である。
【００１６】
【発明の効果】
本発明によれば、第２現像ローラ群の現像ローラ間に現像剤規制部材を設けたことにより、感光体と感光体回転方向に対して下流側の現像ローラの間に現像に使用していない現像剤を搬送することができる。また、感光体回転方向に対し下流側に配置された現像ローラの回転速度をその上流側の現像ローラの回転速度より速くしたことにより、画像背景部の清掃効果が高まり、高速印刷時においても高濃度で安定した画質が長期にわたり得られる。
【図面の簡単な説明】
【図１】本発明となる現像装置の一実施例を示す縦断図面。
【図２】搬送部材と現像ローラの磁極配置を示す説明図。
【図３】感光体に対する現像ローラの周速比と画像背景部の汚れの関係を示す説明図。
【符号の説明】
１…感光体、２…現像容器、３ａ,３ｂ,３ｃ,３ｄ,３ｅ,３ｆ…現像剤、４…搬送部材、５…第１現像ローラ、６,７…第２現像ローラ、８,９…現像剤規制部材、１０,１１…スクレーパ、１２…トナーホッパ、１３…トナーフィードローラ、１４…クロスミキサ、１５…トナー濃度検出器、１６,１７,１８…スリーブ、１９…トナー。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device of an electrophotographic apparatus using a plurality of developing rollers.
[0002]
[Prior art]
A developing device using a plurality of developing rollers is conventionally known. For example, in JP-B-62-2313, the two developing rollers which rotates in the same direction as the rotation direction of the photosensitive member is disposed, the developer regulating member in the first developing roller provided in the photosensitive member rotation direction upstream side the place, the developer after development between the photosensitive member and the first developing roller, transferring to the second developing roller provided on the downstream side, and faster than the rotational speed of the photosensitive member rotation speed of the first developing roller , the rotational speed of the second developing roller was lower than the rotational speed of the photosensitive member developing device is described.
[0003]
[Problems to be solved by the invention]
By the way, the following problems occur when high-speed printing is achieved with the configuration of the developing device.
(a) Since the developing roller on the downstream side in the rotation direction of the photosensitive member is developed again with the developer whose toner density is decreased once for development on the upstream side, a necessary image density cannot be obtained.
(b) Since the peripheral speed ratio between the photosensitive member and the developing roller is low, the background of the image is increased in dirt.
[0004]
Accordingly, it is an object of the present invention to provide a developing device that eliminates the drawbacks of the prior art and obtains stable print quality.
[0005]
[Means for Solving the Problems]
The above objects, the developer supplied to the photosensitive member opposed by a plurality of developing rollers having a magnetic attraction force which is arranged in proximity to the photosensitive member having a photoconductive, in the developing apparatus for performing a magnetic brush development, the a first developing roller to rotate the photosensitive member rotational direction opposite to the direction in photoreceptor facing portion, the photosensitive member rotation direction downstream side of the first developing roller, the photosensitive member rotation direction the same direction at the photosensitive member facing portion is composed of a photosensitive member rotation direction upstream side second developing roller and the downstream second developing roller you rotate in said first developing roller and the upstream second developing roller first developer regulating member between the upstream A second developer regulating member is provided between the second developing roller and the downstream second developing roller, and the downstream second developing roller has S and N poles in a position close to the second developer regulating member. And provide them The distance between the poles is 60 ° or less, and the upstream second developing roller is point-symmetric with respect to the S and N poles of the downstream second developing roller. The same magnetic pole is arranged at a position facing each other as the center.
Further, the rotational speed of the downstream second developing roller is made faster than the rotational speed of the upstream second developing roller.
Further, the peripheral speed ratio is the ratio of the rotational speed of the upstream-side second developing roller and the photoreceptor 1.1 or more, and the ratio of the rotational speed of the downstream second developing roller and the photosensitive member characterized in that defined a certain peripheral speed ratio to 1. 2.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of a developing device according to the present invention, and FIG. 2 is an explanatory view showing a magnetic pole arrangement of a developing roller and a conveying member. Hereinafter, with respect to the rotation direction of the developing roller surface, from rotating in the same direction as the rotational direction of the photosensitive member surface in the photosensitive member face portion is defined as "rotate in the same direction as the photosensitive member", the rotational direction of the photosensitive member surface Rotating in the opposite direction is defined as “ rotating in the opposite direction to the photoreceptor”.
[0007]
Two second developing roller groups 6 and 7 that rotate in the same direction as the photoconductor 1 on the downstream side with respect to the rotation direction of the photoconductor 1 having photoconductivity, and in the opposite direction to the photoconductor 1 on the upstream side The first developing roller 5 that rotates in the direction opposite to the photoreceptor 1 is provided in close proximity.
[0008]
The developer 3 composed of the carrier and toner at the bottom of the developing container 2 is transported by the magnetic attraction force of the rotatable transporting member 4 disposed at the bottom of the developing container 2 and is close to the transporting member 4. It is transferred to the surface of the developing roller group 7. For conveying the developer 3, transporting member 4, the developing roller 5, 6, 7 has a magnetic pole arrangement as shown in FIG. The transferred developer 3 moves toward the upstream on the side opposite to the developing side in contact with the photosensitive member of the second developing roller group 7, and the developer 3 b regulated by the developer regulating member 9 to a certain amount is developed. The toner is conveyed by the rotation of the sleeve 18 and is mixed with the developer 3a, and comes into contact with the photoreceptor 1 to contribute to development. On the other hand, the developer 3 leaking from the restriction by the developer restriction member 9 is delivered to the upstream developing roller group 6. The transferred developer 3 adheres to the surface by the magnetic attraction force of the second developing roller group 6, is conveyed by the rotation of the sleeve 17, and is regulated to a constant amount by the developer regulating member 8. Thereafter, the developer 3a is transported between the photoreceptor 1 and the second developing roller groups 6 and 7, and contacts the photoreceptor 1 to contribute to development. The developer 3 f that has been in contact with the second developing roller groups 6 and 7 and the photosensitive member 1 and has been developed is scraped off by the scraper 11. A part of the developer 3f enters the toner concentration detector 15 to detect the toner concentration in the developer. Thereafter, it is returned to the lower part of the conveying member 4. At this time, if the toner concentration detected by the toner concentration detector 15 is below a certain value, the toner feed roller 13 is rotated and the toner 19 is dropped from the toner hopper 12 to the lower part of the developing device.
[0009]
On the other hand, the developer 3 d leaking from the restriction at the developer regulating member 8 moves to the upstream side of the rear surface of the developer regulating member 8, and the magnetic attractive force of the first developing roller 5 rotating in the opposite direction to the photoreceptor 1. Adheres to the surface. Then, the developer 3c conveyed between the first developing roller 5 and the developer regulating member 8 by the rotation of the sleeve 16 is again regulated to a certain amount by the developer regulating member 8. Thereafter, the toner is conveyed between the photosensitive member 1 and the first developing roller 5 and contacts the photosensitive member 1 to contribute to development. On the other hand, the developer 3d leaking again from the regulation by the developer regulating member 8 is transferred to the cross mixer 14 formed of a guide plate that distributes and moves the developer provided below the developer regulating member 8 in the axial direction of the conveying member 4. It is dropped, mixed with stirring and returned to the lower part of the conveying member 4. At this time, the developer 3e that has been developed and remains on the surface of the first developing roller 5 is scraped off by the scraper 10 and mixed with the toner 19 that has been dropped from the toner hopper 12 by the rotation of the toner feed roller 13. While falling to the cross mixer 14, the mixture is agitated and mixed and returned to the lower part of the conveying member 4.
[0010]
Next, the operation of the present invention will be described. As shown in FIG. 1, the rotation direction of the first developing roller 5 is preferably the opposite direction to the photoreceptor 1. To increase the cleaning capability and the amount of toner deposited on the photosensitive member rotational direction of the first developing roller 5 is because good direction opposite to the direction of rotation of the photosensitive member 1. Further, since this action is preferably performed at the initial stage of development, it is preferable to provide the first developing roller 5 on the upstream side in the photosensitive member rotation direction as shown in FIG. Thereafter, the image on the photosensitive member is arranged in the same direction as the rotation direction of the photosensitive member 1, so that the rotation directions of the second developing roller groups 6 and 7 are the same as the rotation direction of the photosensitive member as shown in FIG. In addition, by providing it on the downstream side in the rotation direction of the photosensitive member, high cleaning ability and developing ability are possible, and a stable and good image can be obtained.
[0011]
Further, when a good image is obtained at a photosensitive member rotational speed of 800 mm / s or more, if there is one developer regulating member between the first developing roller and the second developing roller group, the photosensitive member 1 and the developing roller 7 are used. Since a developer having a low toner density after development is conveyed between the photosensitive member 1 and the developing roller 6, the toner concentration of the developer between the photosensitive member 1 and the developing roller 7 becomes low, and high speed The required image density cannot be obtained by printing. In order to solve such a phenomenon, the developer regulating member 9 is provided between the second developing roller groups 6 and 7 as shown in FIG. As a result, the developer before development regulated by the developer regulating member 9 enters from the inside of the developing machine under the developer developed on the developing roller 6 between the photoreceptor 1 and the developing roller 7. The developer has a characteristic that the top and bottom are interchanged when moving between the magnetic poles during conveyance. For this reason, when the developer moves from the magnetic poles 7 a to 7 c in the conveyance on the developing roller 7, the developer before development restricted by the developer regulating member 9 appears on the surface and contacts the photoreceptor 1 for development. Is done. As a result, a high density image could be obtained even at 1000 mm / s.
[0012]
The presence or absence of the developer regulating member 9 when the developing device having the configuration shown in FIG. 1 is used and the surface of the developer 3f on the developing roller 7 on the developing roller 7 on the downstream side in the rotation direction of the photosensitive member 1 of the second developing roller group. Table 1 shows the relationship between the weight toner density and the image density at the contact portion.
[0013]
[Table 1]

[0014]
By providing the developer regulating member 9, the toner density on the surface of the developer 3f can be kept high, and a high density image is obtained. From this result, it was found that by providing the developer regulating member 9, the weight toner density on the surface of the developer 3f is increased, and a high density image can be obtained.
(Embodiment 2) Another embodiment of the present invention will be described with reference to FIG. The same magnetic poles 6a and 7b and 6b and 7a facing each other with the developing rollers 6 and 7 are arranged symmetrically with the developer regulating member 9 as the center. Further, the distance between the magnetic poles 7a and 7b of the developing roller 7 was 60 °, the magnetic pole 6b was 450 to 700G (Gauss), 7a was 500 to 750G, and 7b was 400 to 650G. As a result, the developer could be stably conveyed in the directions of the magnetic poles 7b to 7a and 7b to 6b.
(Embodiment 3) Another embodiment of the present invention will be described. If the peripheral speed ratio of the rotational speed and the rotational speed of the photosensitive member 1 of the second developing roller group 6 in the photosensitive member rotation direction downstream side is 1.0 or less, contamination of the printing background portion is increased. Therefore, the peripheral speed ratio between the second developing roller group 6 and the photosensitive member 1 is 1.1 or more, and the peripheral speed ratio between the second developing roller group 7 and the photosensitive member 1 is 1.2 or more. The effect of cleaning the area was increased, and the stain on the background of the image could be reduced.
[0015]
FIG. 3 shows a summary of the contamination of the background portion of the image when the developing device having the configuration shown in FIG. 1 is used. The vertical axis represents the contamination of the image background portion, and the horizontal axis represents the peripheral speed ratio of the developing roller 7 on the downstream side in the rotational direction of the photosensitive member 1 of the second developing roller group with respect to the rotational speed of the photosensitive member. From this result, it was found that the background of the image was most contaminated when the peripheral speed ratio was 1.0, and the background of the image decreased as the peripheral speed ratio was increased. From this result, it was confirmed that when the peripheral speed ratio between the developing roller 7 and the photosensitive member 1 is 1.2 or more, the stain on the image background portion satisfies the standard value. Therefore, a good image can be obtained by setting the peripheral speed ratio between the developing roller 7 and the photosensitive member 1 to 1.2 or more. Although the above embodiment shows a case where there are two second developing roller groups, the present invention can be similarly applied even when there are three or more second developing roller groups.
[0016]
【The invention's effect】
According to the present invention, since the developer regulating member is provided between the developing rollers of the second developing roller group, the developing roller is not used for development between the photosensitive member and the developing roller on the downstream side with respect to the photosensitive member rotating direction. Developer can be conveyed. Further, by the photosensitive member rotation direction is faster than the rotational speed of the upstream side of the developing roller rotational speed of the developing roller disposed downstream increases the cleaning effect of the image background, high even during high-speed printing A stable and stable image quality can be obtained over a long period of time.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a developing device according to the present invention.
FIG. 2 is an explanatory diagram showing a magnetic pole arrangement of a conveying member and a developing roller.
FIG. 3 is an explanatory diagram showing a relationship between a peripheral speed ratio of a developing roller to a photosensitive member and a stain on an image background portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Developing container, 3a, 3b, 3c, 3d, 3e, 3f ... Developer, 4 ... Conveying member, 5 ... 1st developing roller, 6, 7 ... 2nd developing roller, 8, 9 ... Developer regulating member, 10, 11 ... scraper, 12 ... toner hopper, 13 ... toner feed roller, 14 ... cross mixer, 15 ... toner concentration detector, 16, 17, 18 ... sleeve, 19 ... toner.

Claims (3)

In a developing device for supplying magnetic developer to a facing photoconductor by a plurality of developing rollers having a magnetic attraction force disposed in the vicinity of the photoconductive photoconductor and performing magnetic brush development,
A first developing roller to rotate the photosensitive member rotational direction opposite to the direction in the photosensitive member facing section,
The photosensitive member rotation direction downstream side of the first developing roller, from the photoreceptor the you rotate the photosensitive member rotation in the same direction the photosensitive member rotation direction upstream side second developing roller in the opposing portion and the downstream second developing roller Configured ,
A first developer regulating member between the first developing roller and the upstream second developing roller, and a second developer regulating member between the upstream second developing roller and the downstream second developing roller,
The downstream second developing roller is provided with S poles and N poles at positions close to the second developer regulating member, and the distance between them is 60 ° or less.
The upstream second developing roller has the same magnetic pole at a position facing the S and N poles of the downstream second developing roller with the second developer restricting member installation area as a point-symmetrical center. Is a developing device. 2. The developing device according to claim 1, wherein the rotational speed of the second downstream developing roller is made faster than the rotational speed of the second upstream developing roller . 3. 1 the peripheral speed ratio is the ratio of rotational speed between the photosensitive member and the upstream second developing roller. 1 or more, peripheral is and the ratio of the rotational speed of the downstream second developing roller and the photosensitive member the speed ratio 1. developing device according to claim 1, characterized in that specified in 2 or more.

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