JP5674112B2 - Developing device and image forming apparatus having the same - Google Patents

Developing device and image forming apparatus having the same Download PDF

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JP5674112B2
JP5674112B2 JP2010248515A JP2010248515A JP5674112B2 JP 5674112 B2 JP5674112 B2 JP 5674112B2 JP 2010248515 A JP2010248515 A JP 2010248515A JP 2010248515 A JP2010248515 A JP 2010248515A JP 5674112 B2 JP5674112 B2 JP 5674112B2
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developer
conveyance path
developing device
supply
carrier
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知也 大村
知也 大村
詫間　康夫
康夫 詫間
松本　純一
純一 松本
菊地　裕
裕 菊地
菜摘 松江
菜摘 松江
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Ricoh Co Ltd
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Description

本発明は、トナー及びキャリアを含む二成分現像剤を用いる現像装置、並びに、これを備えたプリンタ、ファクシミリ及び複写機等の画像形成装置に関するものである。   The present invention relates to a developing device that uses a two-component developer containing toner and a carrier, and an image forming apparatus such as a printer, a facsimile, and a copying machine equipped with the developing device.

この種の現像装置は、一般に、現像剤担持体に沿って現像剤担持体回転軸方向に延びる現像剤供給搬送路中を搬送されている二成分現像剤（以下、単に「現像剤」という。）を、回転している現像剤担持体の表面に担持させ、現像剤担持体の回転により現像剤を現像領域へ供給する。従来の現像装置の中には、現像領域でトナーを消費した現像剤担持体表面上の現像済み現像剤のすべてを再び現像剤供給搬送路へ戻す供給回収一体方式を採用するものがある。この供給回収一体方式の現像装置は、現像剤供給搬送路を流れる現像剤のトナー濃度が現像剤搬送方向下流（以下、単に「下流」という。）側ほど低くなるため、現像領域に供給される現像剤において現像剤担持体回転軸方向にトナー濃度のムラが生じるという欠点がある。このようなトナー濃度のムラは、記録材上に形成される画像の濃度ムラとなって現れやすいので、解消することが望まれる。   This type of developing device is generally a two-component developer (hereinafter simply referred to as “developer”) that is transported in a developer supply transport path extending in the direction of the rotation axis of the developer support along the developer support. ) Is carried on the surface of the rotating developer carrying member, and the developer is supplied to the developing region by the rotation of the developer carrying member. Some conventional developing apparatuses employ a supply / recovery integrated system in which all of the developed developer on the surface of the developer carrying member that has consumed toner in the development region is returned to the developer supply / conveyance path. In this supply / collection-integrated developing device, the toner density of the developer flowing in the developer supply / conveyance path becomes lower toward the downstream side in the developer conveyance direction (hereinafter, simply referred to as “downstream”), and thus is supplied to the development region. In the developer, there is a drawback that unevenness of toner density occurs in the direction of the rotation axis of the developer carrier. Such toner density unevenness is likely to appear as density unevenness in the image formed on the recording material, and is therefore desired to be eliminated.

この欠点を解消し得る現像装置としては、現像領域でトナーを消費した現像剤担持体表面上の現像済み現像剤のすべてを現像剤供給搬送路とは別の搬送路である現像剤回収搬送路へ回収する供給回収分離方式を採用するものがある（例えば特許文献１）。この供給回収分離方式の現像装置は、現像剤供給搬送路を流れる現像剤のトナー濃度が現像剤搬送方向にわたって一定に維持される。よって、現像領域に供給される現像剤において現像剤担持体回転軸方向にトナー濃度のムラが生じることはなく、上述した欠点が解消される。   As a developing device that can eliminate this drawback, a developer recovery transport path that is a transport path different from the developer supply transport path for all the developed developer on the surface of the developer carrying member that has consumed toner in the development area. There is one that employs a supply / recovery separation system that collects the water (for example, Patent Document 1). In the supply / separation type developing device, the toner concentration of the developer flowing in the developer supply / conveyance path is maintained constant over the developer conveyance direction. Therefore, in the developer supplied to the development area, toner density unevenness does not occur in the direction of the rotation axis of the developer carrying member, and the above-described drawbacks are solved.

上述した供給回収分離方式を採用する現像装置においては、現像剤供給搬送路内の現像剤が、その現像剤供給搬送路に沿って配置される現像剤担持体に汲み上げられながら下流側端部まで搬送される。そのため、現像剤供給搬送路内を流れる現像剤の量は、下流側ほど少なくなる。近年の画像形成装置に対しては、画像形成スピードの高速化が強く望まれているため、現像装置の現像剤担持体の回転速度を高速化することが求められている。現像剤担持体の回転速度を高速化すると、単位時間あたりの汲み上げ量が多くなって、現像剤供給搬送路の下流側端部まで到達できる現像剤の量が少なくなる。その結果、現像剤供給搬送路の下流側において、現像剤担持体へ汲み上げる現像剤量が不足する事態（現像剤の枯渇）が起こりやすい。   In the developing device employing the above-described supply / recovery separation method, the developer in the developer supply transport path is pumped up to the developer carrier disposed along the developer supply transport path to the downstream end. Be transported. For this reason, the amount of developer flowing in the developer supply / conveyance path decreases toward the downstream side. For recent image forming apparatuses, since it is strongly desired to increase the image forming speed, it is required to increase the rotation speed of the developer carrier of the developing apparatus. When the rotation speed of the developer carrying member is increased, the pumping amount per unit time increases, and the amount of developer that can reach the downstream end of the developer supply transport path decreases. As a result, a situation in which the amount of developer pumped up to the developer carrying member is insufficient (depletion of developer) tends to occur on the downstream side of the developer supply conveyance path.

特に、上述した現像剤の枯渇に対処するため、一般に、現像剤供給搬送路内における現像剤の搬送速度を高速化する方法が挙げられる。この方法によれば、現像剤の枯渇が引き起こされる可能性を低くすることが可能となるが、温度上昇を引き起こしたり、現像剤に与えるストレスが高まったりするといった不具合が生じる。また、現像剤供給搬送路内の現像剤を搬送スクリューにより搬送する一般的な構成を採用する場合には、その搬送スクリューの軸受けの摩耗が進んでしまい、軸受け寿命が低下するという不具合も生じる。 In particular, in order to cope with the above-described depletion of the developer, there is generally a method of increasing the developer conveyance speed in the developer supply conveyance path. According to this method, it is possible to reduce the possibility of the developer being depleted, but there arises a problem that the temperature is increased and the stress applied to the developer is increased. In addition, when a general configuration in which the developer in the developer supply conveyance path is conveyed by the conveyance screw, wear of the bearing of the conveyance screw is advanced, and there is a problem that the bearing life is reduced .

一方、供給回収分離方式の現像装置では、現像剤回収搬送路内において、その現像剤回収搬送路に沿って配置される現像剤担持体から現像剤を回収しながら下流側端部まで現像剤が搬送される。そのため、現像剤回収搬送路内を流れる現像剤の量は、下流側ほど多くなる。よって、現像剤回収搬送路内の下流側において、現像領域でトナーを消費した現像済み現像剤の嵩が高くなり、その現像済み現像剤が現像剤担持体の表面に接触あるいは近接しやすい。その結果、現像剤済み現像剤が現像剤端持体から離脱する空間がなく、離脱することなく再び現像領域へと搬送されるという連れ周りの問題が生じる恐れがある。連れ周りが生じると、現像剤端持体から現像剤が離脱することがなく、何度も同じ現像剤が現像に使用されるため、経時でトナー濃度が低下してしまい、大きな濃度変動を生じてしまう。   On the other hand, in the developing device of the supply / recovery separation system, the developer is collected to the downstream end while collecting the developer from the developer carrier disposed along the developer collecting / conveying path in the developer collecting / conveying path. Be transported. For this reason, the amount of developer flowing in the developer collection transport path increases toward the downstream side. Therefore, on the downstream side in the developer collection conveyance path, the bulk of the developed developer that has consumed the toner in the development area becomes high, and the developed developer tends to contact or approach the surface of the developer carrying member. As a result, there is no space for the developer-developer to be detached from the developer holding member, and there is a possibility that the accompanying problem that the developer is transported to the developing area again without being separated may occur. When accompaniment occurs, the developer is not detached from the developer holding member, and the same developer is used for development over and over again, so the toner density decreases over time, resulting in large density fluctuations. End up.

本発明は、以上の背景に鑑みなされたものであり、その目的とするところは、現像剤の搬送速度を高速化することなく現像剤の枯渇を抑制できるとともに、現像剤回収搬送路の下流側で再汲み上げが生じることも抑制できる現像装置及びこれを備えた画像形成装置を提供することである。   The present invention has been made in view of the above background, and an object of the present invention is to suppress the depletion of the developer without increasing the developer conveyance speed and to the downstream side of the developer collection conveyance path. It is an object of the present invention to provide a developing device and an image forming apparatus provided with the same that can prevent re-pumping.

上記目的を達成するために、請求項１の発明は、現像剤担持体に沿って現像剤担持体回転軸方向に延びる現像剤供給搬送路中を搬送されているトナーとキャリアとを含んだ二成分現像剤を、回転している該現像剤担持体の表面に担持させることにより、該現像剤担持体の表面に担持された二成分現像剤を現像領域へ搬送し、現像領域にて二成分現像剤中のトナーを潜像担持体表面上の潜像に付着させて該潜像を現像するとともに、現像領域を通過した二成分現像剤を該現像剤担持体から離脱させて該現像剤供給搬送路とは別の搬送路である現像剤回収搬送路に回収する現像装置において、現像領域を通過して現像剤担持体から離脱した一部の二成分現像剤を上記現像剤供給搬送路の現像剤搬送方向上流側部分と下流側部分とに戻す一部戻し手段を設けたことを特徴とするものである。
また、請求項２の発明は、請求項１に記載の現像装置において、上記現像剤供給搬送路及び上記現像剤回収搬送路は、現像剤担持体回転軸方向に延在する仕切部材を介して互いに隣り合って配置されており、上記一部戻し手段は、上記現像剤担持体と上記現像剤回収搬送路との間の現像剤担持体回転軸方向一部分を上記仕切部材で封鎖し、上記一部の二成分現像剤を該仕切部材で案内して上記現像剤供給搬送路へ戻すものであり、上記現像剤担持体と上記現像剤回収搬送路との間の現像剤担持体回転軸方向他部分では、現像領域を通過して現像剤担持体から離脱した二成分現像剤が該仕切部材の上方を通過して該現像剤回収搬送路へ回収される構成としたことを特徴とするものである。
また、請求項３の発明は、請求項２の現像装置において、現像領域を通過した二成分現像剤を現像剤担持体から離脱させるための離脱用磁界を発生させる離脱用磁極を備えた磁界発生手段を上記現像剤担持体の内部に備え、上記磁界発生手段の離脱用磁極は、上記現像剤担持体回転軸方向一部分に対応する部分が、当該部分で形成される剥離用磁界の作用によって離脱する二成分現像剤が上記現像剤供給搬送路へ向かうように構成され、上記現像剤担持体回転軸方向他部分に対応する部分が、当該部分で形成される剥離用磁界の作用によって離脱する二成分現像剤が上記現像剤回収搬送路へ向かうように構成されていることを特徴とするものである。
また、請求項４の発明は、請求項１に記載の現像装置において、現像領域を通過した二成分現像剤を現像剤担持体から離脱させるための離脱用磁界を発生させる離脱用磁極を備えた磁界発生手段を上記現像剤担持体の内部に備え、上記一部戻し手段は、現像剤担持体回転軸方向一部分について、上記現像剤供給搬送路と対向する位置で現像剤担持体から二成分現像剤が離脱して上記現像剤供給搬送路に戻るように上記離脱用磁極を構成したものであり、現像剤担持体回転軸方向他部分については、上記現像剤回収搬送路と対向する位置で二成分現像剤が離脱するように上記離脱用磁極が構成されていることを特徴とするものである。
また、請求項５の発明は、請求項１乃至４のいずれか１項に記載の現像装置において、上記現像剤供給搬送路は、上記現像剤担持体の下方に配置されており、上記現像剤回収搬送路は、上記現像剤供給搬送路の下方に配置されており、現像領域を通過して現像剤担持体から離脱した他部の二成分現像剤を、上記現像剤供給搬送路を迂回して上記現像剤回収搬送路へ案内する案内通路を形成したことを特徴とするものである。
また、請求項６の発明は、請求項１乃至５のいずれか１項に記載の現像装置において、上記現像剤回収搬送路内の二成分現像剤にトナーを補給するためのトナー補給口を、該現像剤回収搬送路の現像剤搬送方向上流側部分に設けたことを特徴とするものである。
また、請求項７の発明は、潜像担持体と、該潜像担持体上に潜像を形成する潜像形成手段と、トナー及びキャリアを含む現像剤により該潜像担持体上の潜像を現像する現像装置とを有し、該現像装置により該潜像担持体上に形成されたトナー像を最終的に記録材へ転移させて、該記録材上に画像を形成する画像形成装置において、上記現像装置として、請求項１乃至６のいずれか１項に記載の現像装置を用いたことを特徴とするものである。 In order to achieve the above object, the invention of claim 1 includes a toner and a carrier that are transported in a developer supply transport path extending in the direction of the rotation axis of the developer support along the developer support. By carrying the component developer on the surface of the rotating developer carrier, the two-component developer carried on the surface of the developer carrier is transported to the development area, and the two components are developed in the development area. The toner in the developer is attached to the latent image on the surface of the latent image carrier to develop the latent image, and the two-component developer that has passed through the development area is separated from the developer carrier to supply the developer. In a developing device that collects in a developer recovery transport path that is a transport path different from the transport path, a part of the two-component developer that has passed through the development area and separated from the developer carrier is removed from the developer supply transport path . hand back portion to return to the developer conveying direction upstream and downstream portions The is characterized in that provided.
Also, the second aspect of the present invention, in the developing device according to claim 1, the developer supply conveyance path and the developer collection conveyance path, through a partition member extending to the developer carrying member rotation axis The partial return means seals a part of the developer carrier rotating shaft between the developer carrier and the developer recovery transport path in the rotation axis direction with the partition member, and A part of the two-component developer is guided by the partition member and returned to the developer supply conveyance path, and the developer carrier rotation axis direction between the developer carrier and the developer recovery conveyance path In the other part, the two-component developer that has passed through the developing region and separated from the developer carrying member passes above the partition member and is collected to the developer collecting and conveying path. It is.
The invention of claim 3 is the developing device according to claim 2, the magnetic field generator having a leaving magnetic pole that generates the separation magnetic field for detaching the two-component developer having passed through the developing area from the developer carrying member Means for separating the magnetic field generating means from a portion corresponding to a part of the rotation direction of the developer carrier by the action of a peeling magnetic field formed by the part. The two-component developer is directed toward the developer supply / conveying path, and the portion corresponding to the other portion in the developer carrier rotation axis direction is separated by the action of the peeling magnetic field formed by the portion. The component developer is configured to be directed to the developer collection conveyance path.
According to a fourth aspect of the present invention, in the developing device according to the first aspect, a separation magnetic pole is provided for generating a separation magnetic field for separating the two-component developer that has passed through the development region from the developer carrier. A magnetic field generating means is provided inside the developer carrier, and the partial return means is a two-component development from the developer carrier at a position facing a part of the developer carrier rotation axis in a direction facing the developer supply path. The separation magnetic pole is configured so that the developer is released and returns to the developer supply conveyance path, and the other part in the direction of the developer carrying member rotation axis is located at a position facing the developer collection conveyance path. The separation magnetic pole is configured so that the component developer is separated .
Also, the invention of claim 5 is the developing device according to any one of claims 1 to 4, the developer supply conveyance path is disposed below the developer carrying member, the developing The developer recovery transport path is disposed below the developer supply transport path, and bypasses the developer supply transport path for the other two-component developer that has passed through the development area and separated from the developer carrier. Thus, a guide passage for guiding to the developer collecting and conveying path is formed.
According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, a toner replenishing port for replenishing toner to the two-component developer in the developer collecting and conveying path is provided. It is characterized in that it is provided on the upstream side of the developer collection conveyance path in the developer conveyance direction.
According to a seventh aspect of the present invention, there is provided a latent image on the latent image carrier by a latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developer containing toner and carrier. An image forming apparatus for forming an image on the recording material by finally transferring the toner image formed on the latent image carrier to the recording material by the developing device. The developing device according to any one of claims 1 to 6 is used as the developing device.

本発明においては、現像領域を通過して現像剤担持体から離脱した現像済み現像剤の一部を、現像剤回収搬送路ではなくて現像剤供給搬送路に戻す。これにより、現像剤担持体から離脱した現像済み現像剤の全部を現像剤回収搬送路で回収する一般的な供給回収分離方式の現像装置よりも、現像剤供給搬送路の下流端に到達する現像剤の量が多くなる。よって、現像剤の枯渇が発生しにくくなる。しかも、現像剤供給搬送路の下流端に存在する現像剤の量が増える結果、相対的に、現像剤回収搬送路の下流側に存在する現像剤量が減ることになる。したがって、現像剤回収搬送路の下流側で生じ得る再汲み上げの発生も抑制される。
なお、本発明では、現像済み現像剤の一部を現像剤供給搬送路へ戻すため、従来の一般的な供給回収分離方式の現像装置と比べて、現像剤供給搬送路内を流れる現像剤の現像剤担持体回転軸方向におけるトナー濃度ムラが生じやすい。しかしながら、現像剤担持体から離脱した現像済み現像剤の全部を現像剤供給搬送路に戻す従来の供給回収一体方式の現像装置と比べれば、現像剤の現像剤担持体回転軸方向におけるトナー濃度ムラが生じにくい。特に、現像剤量が多い現像剤供給搬送路の上流側部分に現像済み現像剤を戻すように構成すれば、現像済み現像剤を取り込む現像剤の量に対する現像済み現像剤の量の比率が低いので、大幅なトナー濃度低下を引き起こすことはなく、実質的な問題とならない。 In the present invention, a part of the developed developer that has passed through the developing region and separated from the developer carrying member is returned to the developer supply transport path instead of the developer recovery transport path. As a result, the development that reaches the downstream end of the developer supply conveyance path is more developed than the general supply / recovery separation type development apparatus that collects all of the developed developer separated from the developer carrier in the developer recovery conveyance path. The amount of agent increases. Therefore, the developer is hardly depleted. In addition, as a result of the increase in the amount of the developer present at the downstream end of the developer supply transport path, the amount of the developer present at the downstream side of the developer recovery transport path is relatively reduced. Therefore, occurrence of re-pumping that can occur on the downstream side of the developer recovery conveyance path is also suppressed.
In the present invention, in order to return a part of the developed developer to the developer supply conveyance path, the developer flowing in the developer supply conveyance path is compared with a conventional general supply recovery / separation type developing device. Toner density unevenness tends to occur in the developer carrier rotation axis direction. However, as compared with the conventional supply / collection integrated type developing device that returns all the developed developer separated from the developer carrier to the developer supply conveyance path, the toner density unevenness in the developer carrier rotation axis direction of the developer is different. Is unlikely to occur. In particular, if the developed developer is returned to the upstream portion of the developer supply conveyance path with a large amount of developer, the ratio of the amount of developed developer to the amount of developer that takes in the developed developer is low. Therefore, it does not cause a significant decrease in toner density and does not cause a substantial problem.

以上、本発明によれば、現像剤の搬送速度を高速化することなく現像剤供給搬送路の下流側で生じ得る現像剤の枯渇を抑制できるとともに、現像剤回収搬送路の下流側で再汲み上げが生じることも抑制できるという優れた効果が得られる。   As described above, according to the present invention, it is possible to suppress the depletion of the developer that may occur on the downstream side of the developer supply conveyance path without increasing the developer conveyance speed, and to re-pump the developer on the downstream side of the developer collection conveyance path. It is possible to obtain an excellent effect that generation of water can be suppressed.

（ａ）は、実施形態の現像装置を図２に示す領域Ｂにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。（ｂ）は、同現像装置を図２に示す領域Ｃにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。(A) is typical sectional drawing when the image development apparatus of embodiment is cut | disconnected so that it may orthogonally cross with respect to the image development sleeve axial direction in the area | region B shown in FIG. FIG. 4B is a schematic cross-sectional view of the developing device when the developing device is cut in a region C shown in FIG. 2 so as to be orthogonal to the axial direction of the developing sleeve. 同現像装置を図１（ａ）及び（ｂ）中の破線部分で切断し、これを図中Ｚ方向から見たときの現像装置内の供給搬送路及び回収搬送路を示す説明図である。FIG. 2 is an explanatory diagram illustrating a supply conveyance path and a recovery conveyance path in the development device when the developing device is cut along a broken line portion in FIGS. 1A and 1B and viewed from the Z direction in the drawing. 同現像装置の供給搬送路の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。FIG. 6 is an explanatory diagram illustrating a distribution of a developer amount (bulk) and a toner density distribution in a developer transport direction of a supply transport path of the developing device. 変形例１における供給搬送路の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。FIG. 10 is an explanatory diagram illustrating a distribution of a developer amount (bulk) and a toner density distribution in a developer conveyance direction of a supply conveyance path in Modification 1; （ａ）は、変形例２の現像装置を領域Ｂにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。（ｂ）は、同現像装置を領域Ｃにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。(A) is a schematic cross-sectional view when the developing device of Modification 2 is cut in a region B so as to be orthogonal to the axial direction of the developing sleeve. FIG. 4B is a schematic cross-sectional view of the developing device cut in the region C so as to be orthogonal to the developing sleeve axial direction. （ａ）は、変形例３の現像装置を領域Ｂにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。（ｂ）は、同現像装置を領域Ｃにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。(A) is a schematic cross-sectional view when the developing device of Modification 3 is cut in a region B so as to be orthogonal to the axial direction of the developing sleeve. FIG. 4B is a schematic cross-sectional view of the developing device cut in the region C so as to be orthogonal to the developing sleeve axial direction. 変形例４における供給搬送路の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。FIG. 10 is an explanatory diagram showing a distribution of a developer amount (bulk) and a toner density distribution in a developer conveyance direction of a supply conveyance path in Modification 4. 変形例５における供給搬送路の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。FIG. 10 is an explanatory diagram showing a distribution of a developer amount (bulk) and a toner density distribution in a developer transport direction of a supply transport path in Modification 5. （ａ）は、変形例６の現像装置を領域Ｂにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。（ｂ）は、同現像装置を領域Ｃにおいて現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。(A) is a schematic cross-sectional view when the developing device of Modification 6 is cut in the region B so as to be orthogonal to the axial direction of the developing sleeve. FIG. 4B is a schematic cross-sectional view of the developing device cut in the region C so as to be orthogonal to the developing sleeve axial direction. 上述した現像装置が搭載された画像形成装置としての複写機の概略構成を示す説明図である。FIG. 2 is an explanatory diagram showing a schematic configuration of a copying machine as an image forming apparatus equipped with the developing device described above. 変形例７における現像装置を現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。FIG. 10 is a schematic cross-sectional view when the developing device in Modification 7 is cut so as to be orthogonal to the developing sleeve axial direction.

以下、本発明を画像形成装置としての複写機の現像装置に適用した一実施形態について説明する。各図中、同一又は相当する部分には同一の符号を付しており、その重複説明は適宜に簡略化ないし省略する。   An embodiment in which the present invention is applied to a developing device of a copying machine as an image forming apparatus will be described below. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description thereof will be simplified or omitted as appropriate.

図１（ａ）及び（ｂ）は、本実施形態における現像装置を現像剤担持体としての現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。
図２は、現像装置を図１（ａ）及び（ｂ）中の破線部分で切断し、これを図中Ｚ方向から見たときの現像装置内の供給搬送路及び回収搬送路を示す説明図である。
なお、図１（ａ）は、図２に示す領域Ｂにおける断面図であり、図１（ｂ）は、図２に示す領域Ｃにおける断面図である。 FIGS. 1A and 1B are schematic cross-sectional views when the developing device in the present embodiment is cut so as to be orthogonal to the axial direction of the developing sleeve as a developer carrier.
FIG. 2 is an explanatory view showing a supply conveyance path and a recovery conveyance path in the developing device when the developing device is cut along a broken line portion in FIGS. 1A and 1B and viewed from the Z direction in the drawing. It is.
1A is a cross-sectional view in the region B shown in FIG. 2, and FIG. 1B is a cross-sectional view in the region C shown in FIG.

本実施形態の現像装置１０は、現像剤担持体としての現像スリーブ２に沿って現像スリーブ軸方向に延びる供給搬送路３中を搬送されているトナーと磁性キャリアとを含んだ現像剤を、回転している現像スリーブ２の表面に担持させることにより、現像スリーブ表面に担持された現像剤を現像領域へ搬送し、現像領域にて現像剤中のトナーを潜像担持体としての感光体１の表面上の潜像に付着させて現像を行う。また、本現像装置１０では、現像領域を通過した現像済み現像剤を、現像スリーブ２から離脱させて供給搬送路３とは別の搬送路である回収搬送路４に回収することができる。   The developing device 10 of the present embodiment rotates a developer including toner and a magnetic carrier that are conveyed in a supply conveyance path 3 extending in the axial direction of the development sleeve along the development sleeve 2 as a developer carrier. The developer carried on the surface of the developing sleeve 2 is carried on the surface of the developing sleeve 2 so that the developer carried on the surface of the developing sleeve is conveyed to the developing region, and the toner in the developer is transferred to the developing member in the developing region. Development is performed by attaching to the latent image on the surface. Further, in the developing device 10, the developed developer that has passed through the developing region can be separated from the developing sleeve 2 and collected in the collection conveyance path 4 that is a conveyance path different from the supply conveyance path 3.

この現像装置１０は、各搬送路３，４内に、それぞれ、回転軸上に螺旋状のフィンをもった搬送部材としての搬送スクリュー５，６を備えている。これらの搬送スクリュー５，６が回転駆動すると、その回転軸方向に沿って各搬送路３，４内を現像剤が撹拌されると同時に搬送される。本実施形態において、供給搬送路３と回収搬送路４は横並びに配置されており、それらの間が仕切部材８によって互いに仕切られている。ただし、供給搬送路３と回収搬送路４との間は、その両端部で連通している。これにより、供給搬送路３の下流端まで搬送された現像剤は連通部を通って回収搬送路４の上流端へ移動し、回収搬送路４の下流端まで搬送された現像剤は連通部を通って供給搬送路３の上流端へ移動する。このようにして、現像装置内の現像剤は、供給搬送路３及び回収搬送路４を循環搬送される。   The developing device 10 includes conveying screws 5 and 6 as conveying members having helical fins on the rotation shafts in the conveying paths 3 and 4, respectively. When these transport screws 5 and 6 are driven to rotate, the developer is transported in the transport paths 3 and 4 at the same time along the direction of the rotation axis. In the present embodiment, the supply conveyance path 3 and the collection conveyance path 4 are arranged side by side, and are partitioned from each other by a partition member 8. However, the supply conveyance path 3 and the collection conveyance path 4 communicate with each other at both ends. As a result, the developer transported to the downstream end of the supply transport path 3 moves to the upstream end of the recovery transport path 4 through the communication section, and the developer transported to the downstream end of the recovery transport path 4 passes through the communication section. It moves to the upstream end of the supply conveyance path 3 through. In this manner, the developer in the developing device is circulated and conveyed through the supply conveyance path 3 and the collection conveyance path 4.

図１（ａ）及び（ｂ）の白抜き矢印で示すように、供給搬送スクリュー５によって供給搬送路３内を搬送される現像剤が現像スリーブ２へ供給される。具体的には、現像スリーブ２の内部には、固定配置された磁界発生手段としての磁石が設けられており、供給搬送路３から供給された現像剤を磁気拘束力により吸い上げて現像スリーブ表面に現像剤を吸着させる。このようにして現像スリーブ表面に汲み上げられた現像剤は、現像剤規制部材としての現像ドクタ７により均一な厚さに均されてから、感光体１と対向する現像領域へ搬送される。一方、供給搬送路３の下流端まで搬送された現像剤は、その端部に設けられた連通部から回収搬送路４の上流端へと受け渡される。本実施形態では、回収搬送路４の上流端で、現像により消費された分のトナーが搬送路上方に設けられたトナー補給口９から補給される。その結果、回収搬送路４では、供給搬送路３の下流端から移動してきた現像剤と補給トナーとが回収搬送スクリュー６により攪拌されながら下流側へ搬送される。その結果、回収搬送路４の下流端まで搬送された現像剤は、トナーが均一に分散した状態になっており、その状態の現像剤が連通部を通って供給搬送路３の上流端へと受け渡される。   As shown by the white arrows in FIGS. 1A and 1B, the developer conveyed through the supply conveyance path 3 by the supply conveyance screw 5 is supplied to the developing sleeve 2. Specifically, a magnet as a magnetic field generating means that is fixedly arranged is provided inside the developing sleeve 2, and the developer supplied from the supply conveyance path 3 is sucked up by the magnetic restraining force and is applied to the surface of the developing sleeve. Adsorb developer. The developer drawn up on the surface of the developing sleeve in this way is leveled to a uniform thickness by a developing doctor 7 as a developer regulating member, and then conveyed to a developing region facing the photoreceptor 1. On the other hand, the developer transported to the downstream end of the supply transport path 3 is delivered from the communication portion provided at the end to the upstream end of the recovery transport path 4. In the present embodiment, at the upstream end of the collection conveyance path 4, the amount of toner consumed by development is replenished from a toner replenishment port 9 provided above the conveyance path. As a result, in the collection conveyance path 4, the developer and the replenishment toner that have moved from the downstream end of the supply conveyance path 3 are conveyed downstream while being agitated by the collection conveyance screw 6. As a result, the developer conveyed to the downstream end of the collection conveyance path 4 is in a state where the toner is uniformly dispersed, and the developer in that state passes through the communication portion to the upstream end of the supply conveyance path 3. Delivered.

一方、現像領域を通過した現像スリーブ上の現像済み現像剤は、現像スリーブ２の表面上の磁気拘束力の弱い地点まで搬送されることで、現像スリーブ２から離脱する。ここで、従来の一般的な供給回収分離方式の現像装置では、現像スリーブ２から離脱した現像済み現像剤のすべてが回収搬送路４に回収されるが、本実施形態では、現像スリーブ２から離脱した現像済み現像剤の一部が、回収搬送路４ではなく、供給搬送路３に戻るようにしている。具体的には、図２に示すように、供給搬送路３の下流側部分（回収搬送路４の上流側部分）である領域Ｂに対応する現像スリーブ２の表面部分から離脱した現像済み現像剤は、供給搬送路３に戻される。一方、供給搬送路３の上流側部分（回収搬送路４の下流側部分）である領域Ｃに対応する現像スリーブ２の表面部分から離脱した現像済み現像剤は、回収搬送路４に回収される。   On the other hand, the developed developer on the developing sleeve that has passed through the developing region is separated from the developing sleeve 2 by being conveyed to a point on the surface of the developing sleeve 2 where the magnetic binding force is weak. Here, in a conventional general supply / recovery separation type developing device, all of the developed developer separated from the developing sleeve 2 is collected in the collecting conveyance path 4, but in this embodiment, it is detached from the developing sleeve 2. A part of the developed developer returns to the supply conveyance path 3 instead of the collection conveyance path 4. Specifically, as shown in FIG. 2, the developed developer separated from the surface portion of the developing sleeve 2 corresponding to the region B which is the downstream portion of the supply conveyance path 3 (upstream portion of the collection conveyance path 4). Is returned to the supply conveyance path 3. On the other hand, the developed developer separated from the surface portion of the developing sleeve 2 corresponding to the region C that is the upstream portion of the supply conveyance path 3 (the downstream portion of the collection conveyance path 4) is collected in the collection conveyance path 4. .

本実施形態では、現像スリーブ内に固定配置される磁石の磁極配置は、現像スリーブ軸方向において同じであり、現像領域を通過した現像スリーブ上の現像済み現像剤が現像スリーブ２から離脱する地点は、現像スリーブ軸方向どの箇所でも図中矢印Ａで示す離脱地点である。供給搬送路３の下流側部分（回収搬送路４の上流側部分）である領域Ｂでは、そこで離脱した現像済み現像剤が回収搬送路４ではなく供給搬送路３に戻るように、図１（ａ）に示すような構成となっている。すなわち、この領域Ｂについては、図１（ａ）に示すように、仕切部材８の上端部分８ａによって現像スリーブ２と回収搬送路４との間を封鎖している。これにより、離脱地点Ａで現像スリーブ２から離脱した現像済み現像剤は、その仕切部材上端部分８ａにより回収搬送路４への移動が完全に遮断される。また、この仕切部材の上端部分８ａにおける供給搬送路３側の壁面は、供給搬送路３に向けて下方に傾斜している。よって、離脱した現像済み現像剤が仕切部材の上端部分８ａの壁面に落下しても、自重により供給搬送路３へと滑り落ちる。このような構成により、領域Ｂにおいて現像スリーブ２から離脱した現像済み現像剤は、供給搬送路３に戻される。   In this embodiment, the magnetic pole arrangement of the magnet fixedly arranged in the developing sleeve is the same in the axial direction of the developing sleeve, and the point where the developed developer on the developing sleeve that has passed through the developing region is separated from the developing sleeve 2 is Any point in the axial direction of the developing sleeve is a separation point indicated by an arrow A in the drawing. In region B, which is a downstream portion of the supply conveyance path 3 (upstream portion of the collection conveyance path 4), the developed developer separated therefrom returns to the supply conveyance path 3 instead of the collection conveyance path 4 as shown in FIG. The configuration is as shown in a). That is, in this region B, as shown in FIG. 1A, the upper end portion 8a of the partition member 8 seals between the developing sleeve 2 and the collection conveyance path 4. As a result, the developed developer separated from the developing sleeve 2 at the separation point A is completely blocked from moving to the collection conveyance path 4 by the partition member upper end portion 8a. The wall surface on the supply conveyance path 3 side of the upper end portion 8 a of the partition member is inclined downward toward the supply conveyance path 3. Therefore, even if the released developed developer falls on the wall surface of the upper end portion 8a of the partition member, it slides down to the supply conveyance path 3 due to its own weight. With such a configuration, the developed developer separated from the developing sleeve 2 in the region B is returned to the supply conveyance path 3.

一方、供給搬送路３の上流側部分（回収搬送路４の下流側部分）である領域Ｃでは、そこで離脱した現像済み現像剤が、供給搬送路３に戻ることなく回収搬送路４に回収されるように、図１（ｂ）に示すような構成となっている。すなわち、この領域Ｃについては、図１（ｂ）に示すように、仕切部材８の上端部分８ｂが現像スリーブ２と回収搬送路４との間を封鎖していないので、離脱地点Ａで現像スリーブ２から離脱した現像済み現像剤はその仕切部材上端部分８ｂに妨げられることなく回収搬送路４へ移動することができる。しかも、本実施形態では、この仕切部材の上端部分８ｂによって、現像スリーブ２上の離脱地点Ａと供給搬送路３との間の空間を狭めている。これにより、離脱地点Ａで現像スリーブ２から離脱した現像済み現像剤は、その仕切部材上端部分８ｂにより供給搬送路３への移動が妨げられる。そして、この仕切部材上端部分８ｂにおける回収搬送路４側の壁面は、回収搬送路４に向けて下方に傾斜している。よって、離脱した現像済み現像剤が仕切部材の上端部分８ｂの壁面に落下しても、自重により回収搬送路４へと滑り落ちる。このような構成により、領域Ｃにおいて現像スリーブ２から離脱した現像済み現像剤は、回収搬送路４に回収される。   On the other hand, in the region C that is the upstream portion of the supply conveyance path 3 (the downstream portion of the collection conveyance path 4), the developed developer separated therefrom is collected in the collection conveyance path 4 without returning to the supply conveyance path 3. Thus, the configuration is as shown in FIG. That is, in this region C, as shown in FIG. 1B, the upper end portion 8b of the partition member 8 does not block between the developing sleeve 2 and the collection conveyance path 4, so that the developing sleeve is at the separation point A. The developed developer released from 2 can move to the collection conveyance path 4 without being blocked by the upper end portion 8b of the partition member. In addition, in this embodiment, the space between the separation point A on the developing sleeve 2 and the supply conveyance path 3 is narrowed by the upper end portion 8b of the partition member. As a result, the developed developer separated from the developing sleeve 2 at the separation point A is prevented from moving to the supply conveyance path 3 by the partition member upper end portion 8b. The wall surface on the collection conveyance path 4 side of the partition member upper end portion 8 b is inclined downward toward the collection conveyance path 4. Therefore, even if the detached developed developer falls on the wall surface of the upper end portion 8b of the partition member, it slides down to the collection conveyance path 4 due to its own weight. With such a configuration, the developed developer separated from the developing sleeve 2 in the region C is collected in the collecting conveyance path 4.

このように、本実施形態では、現像スリーブ２から離脱した現像済み現像剤の回収経路を現像スリーブ２の回転軸方向で変える構成を採用している。このような構成を採用することにより、以下のような効果が奏される。
図３は、本実施形態における供給搬送路３の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。
なお、図３の上部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤量（嵩）をとったものである。また、図３の下部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤のトナー濃度をとったものである。 As described above, in the present embodiment, a configuration is adopted in which the collection path for the developed developer separated from the developing sleeve 2 is changed in the direction of the rotation axis of the developing sleeve 2. By adopting such a configuration, the following effects can be obtained.
FIG. 3 is an explanatory diagram showing the distribution of the developer amount (bulk) and the toner density distribution in the developer transport direction of the supply transport path 3 in the present embodiment.
In the graph shown in the upper part of FIG. 3, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer amount (bulk) in the supply conveyance path 3. . In the graph shown in the lower part of FIG. 3, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer toner concentration in the supply conveyance path 3.

従来の供給回収一体方式の現像装置では、図３の上部グラフの一点鎖線で示すように、供給搬送路中の現像剤搬送方向における現像剤量（嵩）のバランスはほぼ均等となっているため、現像剤の枯渇という問題は生じない。しかしながら、現像に使用してトナー濃度が低下した現像済み現像剤を再び供給搬送路へ戻すため、現像スリーブ２に汲み上げられる現像剤のトナー濃度は、図３の下部グラフの一点鎖線で示すように、供給搬送路の下流側ほど低くなる。そのため、供給回収一体方式の現像装置では、現像スリーブ軸方向の現像領域にわたって、その現像スリーブ軸方向のトナー濃度差が生じることに加え、現像領域の現像スリーブ軸方向両端間のトナー濃度差は非常に大きいものとなる。   In the conventional supply / collection integrated type developing device, as shown by the one-dot chain line in the upper graph of FIG. 3, the balance of the developer amount (bulk) in the developer conveyance direction in the supply conveyance path is substantially uniform. The problem of developer depletion does not occur. However, since the developed developer having a lowered toner concentration used for development is returned to the supply conveyance path, the toner concentration of the developer pumped up to the developing sleeve 2 is as shown by a one-dot chain line in the lower graph of FIG. , It becomes lower toward the downstream side of the supply conveyance path. For this reason, in the supply / collection integrated type developing device, the toner density difference in the developing sleeve axial direction occurs over the developing area in the developing sleeve axial direction, and the toner density difference between both ends of the developing sleeve in the developing sleeve axial direction is extremely large. It will be big.

また、従来の一般的な供給回収分離方式の現像装置では、現像に使用してトナー濃度が低下した現像済み現像剤はすべて回収搬送路へ回収されるため、図３の下部グラフの二点鎖線で示すように、供給搬送路内の現像剤のトナー濃度は現像スリーブ軸方向にわたって一定である。しかしながら、供給搬送路内の現像剤は、図３の上部グラフの二点鎖線で示すように、その搬送中に現像スリーブへ汲み上げられていくので、下流側へ搬送されるにつれて徐々に現像剤量（嵩）が減っていく。そのため、現像剤の枯渇が問題となる。
加えて、回収搬送路内の現像剤は、その搬送中に現像スリーブ２からの現像済み現像剤を取り込んでいくので、下流側ほど現像剤量（嵩）が増加していく。そのため、現像剤が溢れて現像剤の詰まりを引き起こしたり、剤嵩が増すことで現像剤が現像スリーブ２の離脱地点Ａまで埋めてしまい、現像済み現像剤がそのまま現像スリーブ２上を連れまわったりという問題も生じる。このような連れまわりが生じると、トナー濃度が低下した現像剤が現像に寄与する結果、その箇所の画像濃度が低下して、他の箇所との間で画像濃度ムラが発生する。 Further, in a conventional general supply / recovery separation type developing device, all the developed developer having a reduced toner concentration used for development is recovered to the recovery conveyance path, so that the two-dot chain line in the lower graph of FIG. As shown in FIG. 2, the toner concentration of the developer in the supply conveyance path is constant over the developing sleeve axial direction. However, as indicated by the two-dot chain line in the upper graph of FIG. 3, the developer in the supply conveyance path is pumped up to the developing sleeve during the conveyance, so that the developer amount gradually increases as it is conveyed downstream. (Bulk) decreases. Therefore, depletion of developer becomes a problem.
In addition, since the developer in the recovery conveyance path takes in the developed developer from the developing sleeve 2 during the conveyance, the developer amount (bulk) increases toward the downstream side. For this reason, the developer overflows and causes clogging of the developer, or the developer bulk increases, so that the developer fills up to the separation point A of the developing sleeve 2, and the developed developer is brought on the developing sleeve 2 as it is. The problem also arises. When such accompaniment occurs, the developer having a reduced toner concentration contributes to the development. As a result, the image density at that location decreases, and image density unevenness occurs between other locations.

従来の一般的な供給回収分離方式の現像装置では、一般的に、搬送スクリューの回転数を大きくして現像剤搬送量［ｇ／ｓｅｃ］を増やし、搬送経路中の剤嵩高さの変化（図３の上部グラフの傾き）を小さくして、現像剤の枯渇や現像剤の溢れといった問題を抑制している。ところが、この場合、搬送スクリューの回転数を相当程度大きくする必要があるため、回転数の増加に伴う発熱問題、スクリュー軸受けの寿命低下、現像剤へのストレス増大など、様々な問題がトレードオフとなって生じてしまう。また、搬送スクリューの回転数の増大を抑えつつ現像剤搬送量を増やすために、搬送スクリューの外径を大きくすることも考えられるが、現像装置の大型化を招いてしまう。また、剤バランス（現像剤搬送方向における現像剤の嵩分布）は、トナー濃度、環境、現像剤の経時劣化などにより現像剤の嵩密度や流動性が変化する結果、常に一定とすることができないので、適切な剤バランスの成立条件が出すのは非常に厳しいという問題もある。   In the conventional general supply / recovery separation type developing device, generally, the rotation speed of the conveying screw is increased to increase the developer conveying amount [g / sec], and the change in the bulk of the agent in the conveying path (see FIG. The slope of the upper graph of 3) is reduced to suppress problems such as developer depletion and developer overflow. However, in this case, since it is necessary to increase the rotation speed of the conveying screw to a considerable extent, various problems such as a heat generation problem due to an increase in the rotation speed, a decrease in the life of the screw bearing, and an increase in stress on the developer are trade-offs. It happens. In order to increase the developer conveyance amount while suppressing an increase in the rotation speed of the conveyance screw, it is conceivable to increase the outer diameter of the conveyance screw, but this leads to an increase in the size of the developing device. In addition, the developer balance (developer bulk distribution in the developer transport direction) cannot always be kept constant as a result of changes in the bulk density and fluidity of the developer due to the toner concentration, the environment, and the deterioration of the developer over time. Therefore, there is also a problem that it is very strict to establish an appropriate condition for establishing an agent balance.

これに対し、本実施形態においては、上述したように現像スリーブ２から離脱した現像剤の回収経路として、回収搬送路４へ回収する経路だけでなく、供給搬送路３に戻す経路も用意することで、トナー濃度変動や剤バランスを良好に保つことを可能にしている。要するに、本実施形態では、供給搬送路３の上流側（回収搬送路４の下流側）である領域Ｃでは供給回収分離方式を採用し、供給搬送路３の下流側（回収搬送路４の上流側）である領域Ｂでは供給回収一体方式を採用している。その結果、領域Ｃでは、図３の上部グラフの実線で示すように、徐々に現像剤量（嵩）が低下していくが、領域Ｂに入ると、現像済み現像剤が供給搬送路３へ戻されるので、それ以上の現像剤量の低下はなく、下流まで安定して現像剤量（嵩）を保つことができる。その結果、従来の一般的な供給回収分離方式の現像装置で生じていた現像剤の枯渇の問題が発生しない。また、現像装置全体の現像剤のバランスを見ると、供給搬送路３の下流側部分（領域Ｂ）の現像剤の量（嵩）が増える結果、回収搬送路４の下流側部分の現像剤量（嵩）を相対的に減らすことができる。その結果、従来の一般的な供給回収分離方式の現像装置で生じていた現像剤の溢れによる現像剤の詰まりや連れまわりといった問題も抑制される。そして、これらの問題が解決できる結果、従来の一般的な供給回収分離方式の現像装置よりも搬送スクリューの回転数を落とすことが可能となり、回転数の増加に伴う発熱問題、スクリュー軸受けの寿命低下、現像剤へのストレス増大などの諸問題も解決できる。   On the other hand, in the present embodiment, as described above, a path for returning to the supply transport path 3 as well as a path for recovering to the recovery transport path 4 is prepared as a recovery path for the developer separated from the developing sleeve 2. Therefore, it is possible to keep the toner density fluctuation and the agent balance favorable. In short, in this embodiment, the supply and recovery separation method is adopted in the region C that is upstream of the supply transport path 3 (downstream of the recovery transport path 4), and downstream of the supply transport path 3 (upstream of the recovery transport path 4). Side B) adopts an integrated supply and recovery system. As a result, in the region C, as shown by the solid line in the upper graph of FIG. 3, the developer amount (bulk) gradually decreases, but when entering the region B, the developed developer is supplied to the supply conveyance path 3. Since the developer amount is returned, there is no further decrease in the developer amount, and the developer amount (bulk) can be stably maintained downstream. As a result, the problem of developer depletion that has occurred in the conventional general supply / recovery separation type developing apparatus does not occur. Further, when looking at the balance of the developer in the entire developing device, the amount of developer (bulk) in the downstream portion (region B) of the supply conveyance path 3 increases, and as a result, the developer amount in the downstream portion of the collection conveyance path 4 (Bulk) can be relatively reduced. As a result, problems such as clogging of the developer and follow-up caused by overflow of the developer, which have occurred in the conventional general supply / recovery separation type developing device, are also suppressed. As a result of solving these problems, it is possible to reduce the rotation speed of the conveying screw as compared to the conventional general supply / recovery separation type developing device, and the heat generation problem accompanying the increase in the rotation speed and the life of the screw bearing are reduced. Various problems such as increased stress on the developer can also be solved.

一方、図３の下部グラフに示すトナー濃度分布を見えると、領域Ｃでは、供給搬送路内の現像剤のトナー濃度は、図３の上部グラフの実線で示すように一定であるが、領域Ｂに入ると、徐々にトナー濃度が低下していく。しかしながら、トナー濃度が低下するといっても、そのトナー濃度の最低値は、供給回収一体方式の現像装置におけるトナー濃度の最低値よりも十分に高い値である。したがって、供給回収一体方式の現像装置と比較して、トナー濃度差が生じる範囲を狭くすることができるとともに、トナー濃度差も小さいものとなる。   On the other hand, when the toner concentration distribution shown in the lower graph of FIG. 3 is seen, in region C, the toner concentration of the developer in the supply conveyance path is constant as shown by the solid line in the upper graph of FIG. Then, the toner density gradually decreases. However, even if the toner concentration decreases, the minimum value of the toner concentration is sufficiently higher than the minimum value of the toner concentration in the supply / collection integrated developing device. Therefore, as compared with the supply / collection integrated type developing device, the range in which the toner density difference occurs can be narrowed, and the toner density difference is also small.

本実施形態において、現像スリーブ２から離脱した現像済み現像剤について供給搬送路３へどの程度の量を戻すのかは、仕切部材８の上端部分８ａにおける現像スリーブ軸方向長さをどの程度にするかによって適宜設定することができる。供給搬送路３への戻し量が多くなれば、供給搬送路内の現像剤のトナー濃度変化が大きくなる一方で、供給回収分離方式での問題点である現像剤の枯渇や溢れ等の抑制効果（剤バランス性）が高まる。逆に、供給搬送路３への戻し量が少なければ、供給搬送路内の現像剤のトナー濃度変化が小さいので画像濃度ムラの少ない高品質な画像を得ることができる一方で、供給回収分離方式での問題点である現像剤の枯渇や溢れ等の抑制効果（剤バランス性）が低くなる。したがって、現像スリーブ２から離脱した現像済み現像剤について供給搬送路３へどの程度の量を戻すのかは、これらの事情を考慮して適宜設定する。   In the present embodiment, the amount of the developed developer that has separated from the developing sleeve 2 is returned to the supply conveyance path 3 according to the length of the upper end portion 8a of the partition member 8 in the axial direction of the developing sleeve. Can be set as appropriate. If the amount returned to the supply conveyance path 3 is increased, the change in the toner density of the developer in the supply conveyance path becomes larger, while the effect of suppressing the depletion or overflow of the developer, which is a problem in the supply / recovery separation method. (Agent balance) is increased. On the other hand, if the return amount to the supply conveyance path 3 is small, the change in the toner density of the developer in the supply conveyance path is small, so that a high-quality image with little unevenness in image density can be obtained. In other words, the effect of suppressing the developer depletion and overflow (agent balance) becomes low. Therefore, the amount of the developed developer that has separated from the developing sleeve 2 is to be returned to the supply conveyance path 3 is appropriately set in consideration of these circumstances.

〔変形例１〕
次に、上記実施形態における現像装置の一変形例（以下、本変形例を「変形例１」という。）について説明する。
上記実施形態では、供給搬送路３の下流側部分（回収搬送路４の上流側部分）である領域Ｂでは現像済み現像剤を供給搬送路３に戻し、供給搬送路３の上流側部分（回収搬送路４の下流側部分）である領域Ｃでは現像済み現像剤を回収搬送路４に回収する構成であった。本変形例１に係る現像装置は、供給搬送路３の上流側部分（回収搬送路４の下流側部分）である領域Ｂ’では現像済み現像剤を供給搬送路３に戻し、供給搬送路３の下流側部分（回収搬送路４の上流側部分）である領域Ｃ’では現像済み現像剤を回収搬送路４に回収する構成としている。 [Modification 1]
Next, a modified example of the developing device in the above embodiment (hereinafter, this modified example is referred to as “modified example 1”) will be described.
In the above embodiment, the developed developer is returned to the supply conveyance path 3 in the region B which is the downstream part of the supply conveyance path 3 (upstream part of the collection conveyance path 4), and the upstream part (collection) of the supply conveyance path 3. In the region C, which is the downstream portion of the transport path 4, the developed developer is recovered in the recovery transport path 4. The developing device according to the first modification returns the developed developer to the supply conveyance path 3 in the region B ′ that is the upstream portion of the supply conveyance path 3 (the downstream portion of the collection conveyance path 4), and the supply conveyance path 3. In the region C ′, which is the downstream portion (upstream portion of the collection conveyance path 4), the developed developer is collected in the collection conveyance path 4.

図４は、本変形例１における供給搬送路３の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。
なお、図４の上部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤量（嵩）をとったものである。また、図４の下部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤のトナー濃度をとったものである。 FIG. 4 is an explanatory diagram showing the distribution of the amount (bulk) of the developer and the distribution of the toner density in the developer conveyance direction of the supply conveyance path 3 in the first modification.
In the graph shown in the upper part of FIG. 4, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer amount (bulk) in the supply conveyance path 3. . In the graph shown in the lower part of FIG. 4, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer toner concentration in the supply conveyance path 3.

本変形例１のように、供給搬送路３の上流側部分（回収搬送路４の下流側部分）である領域Ｂ’において現像済み現像剤を供給搬送路３に戻す構成とすることで、現像スリーブ軸方向におけるトナー濃度の変化を緩慢なものとすることができる。すなわち、図４の下部グラフの実線で示すトナー濃度分布の領域Ｂ’における傾きを、上記実施形態における図３の下部グラフの実線で示すトナー濃度分布の領域Ｂにおける傾きよりも小さくすることができる。なぜなら、本変形例１の現像装置では、現像済み現像剤が戻される供給搬送路３の上流側部分（領域Ｂ’）に存在する現像剤の量は、上記実施形態の現像装置で現像済み現像剤が戻される供給搬送路３の下流側部分（領域Ｂ）に存在する現像剤の量よりも多いからである。   As in the first modification, the developer is returned to the supply conveyance path 3 in the region B ′ that is the upstream part of the supply conveyance path 3 (the downstream part of the collection conveyance path 4), thereby developing. The change in toner density in the sleeve axial direction can be made slow. That is, the slope in the region B ′ of the toner density distribution shown by the solid line in the lower graph of FIG. 4 can be made smaller than the slope in the region B of the toner density distribution shown by the solid line in the lower graph of FIG. . This is because, in the developing device according to the first modification, the amount of the developer present in the upstream portion (region B ′) of the supply conveyance path 3 where the developed developer is returned is the amount of developer developed by the developing device of the above embodiment. This is because the amount of developer present in the downstream portion (region B) of the supply conveyance path 3 where the agent is returned is larger.

また、本変形例１において、領域Ｃ’ではトナー濃度が一定となるので、上記実施形態よりも現像スリーブ軸方向のトナー濃度偏差を更に小さく抑えることが可能である。   In the first modification, since the toner density is constant in the region C ′, the toner density deviation in the axial direction of the developing sleeve can be further reduced as compared with the above embodiment.

加えて、従来の一般的な供給回収分離方式の現像装置においては、供給搬送路の上流端付近で現像スリーブ２に汲み上げられて現像に使用された現像済み現像剤は、回収搬送路の下流端付近に回収され、すぐに連通部を通って再び供給搬送路の上流端へ送られる。このような現像済み現像剤は、回収搬送路内の他の現像剤と十分に混合される前に、再び現像スリーブに汲み上げられて現像に使用される可能性がある。そのため、トナー濃度ムラが残った状態の現像剤が現像に使用されて画像濃度ムラを引き起こすおそれがある。これは、上記実施形態の現像装置でも同様である。これに対し、本変形例１の現像装置では、供給搬送路の上流端付近で現像スリーブ２に汲み上げられて現像に使用された現像済み現像剤は、再び供給搬送路に戻され、供給搬送路の下流側部分（回収搬送路の上流側部分）である領域Ｃ’に至るまで、回収搬送路に回収されることはない。したがって、このような画像濃度ムラが引き起こされることはない。   In addition, in a conventional general supply and recovery separation type developing device, the developed developer that has been pumped up to the developing sleeve 2 and used for development in the vicinity of the upstream end of the supply conveyance path is disposed at the downstream end of the recovery conveyance path. It is collected in the vicinity and immediately sent to the upstream end of the supply conveyance path again through the communication portion. Such a developed developer may be pumped up again to the developing sleeve and used for development before being sufficiently mixed with other developer in the recovery conveyance path. For this reason, the developer in which the toner density unevenness remains may be used for development and cause image density unevenness. The same applies to the developing device of the above embodiment. On the other hand, in the developing device of the first modification, the developed developer that has been pumped up to the developing sleeve 2 and used for development in the vicinity of the upstream end of the supply conveyance path is returned to the supply conveyance path again. It is not collected in the collection conveyance path until reaching the region C ′ which is the downstream side portion (upstream part of the collection conveyance path). Therefore, such image density unevenness is not caused.

更に、本変形例１においては、現像装置全体において、従来の一般的な供給回収分離方式の現像装置と比較して、現像剤の量（嵩）の偏差が少なくなる。その結果、現像剤の量（嵩）が最も多くなる箇所での現像剤量を同じにようにすると、現像装置内に収容される現像剤の総量が従来の一般的な供給回収分離方式の現像装置と比較して大幅に増える。現像剤の寿命は、現像装置内に収容される現像剤の量と相関がある。したがって、本変形例１に係る現像装置によれば、現像剤の収容量の拡大による現像剤の長寿命化を図ることができる。また、現像剤の収容量が増えると、現像剤の総量に対するトナー消費量の比率が小さくなるので、現像装置内における現像剤のトナー濃度変化が小さくなるというメリットもある。   Further, in the first modification, the developer amount (bulk) deviation is reduced in the entire developing device as compared with the conventional general supply / recovery separation type developing device. As a result, if the same amount of developer is used at the place where the amount (bulk) of the developer is the largest, the total amount of developer contained in the developing device is the same as that of the conventional general supply / recovery separation system. Significant increase compared to equipment. The lifetime of the developer correlates with the amount of developer accommodated in the developing device. Therefore, according to the developing device according to the first modification, it is possible to extend the life of the developer by increasing the amount of developer contained. Further, when the developer storage amount increases, the ratio of the toner consumption amount to the total developer amount becomes small, so that there is an advantage that the change in the toner density of the developer in the developing device becomes small.

〔変形例２〕
次に、上記実施形態における現像装置の他の変形例（以下、本変形例を「変形例２」という。）について説明する。
上記実施形態や上記変形例１では、現像スリーブ２から離脱した現像済み現像剤の一部を回収搬送路４ではなく供給搬送路３に戻す手段として、現像スリーブ２と回収搬送路４との間を仕切部材８の上端部分８ａで封鎖するという手段を採用している。本変形例２に係る現像装置では、その手段として、現像スリーブ２の内部に固定配置されている磁石の磁極構成を変えるという手段を採用している。 [Modification 2]
Next, another modified example of the developing device in the above embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
In the embodiment and the first modification, as a means for returning a part of the developed developer separated from the developing sleeve 2 to the supply conveyance path 3 instead of the collection conveyance path 4, a gap between the developing sleeve 2 and the collection conveyance path 4 is used. A means for sealing the upper end portion 8a of the partition member 8 is employed. In the developing device according to the second modification, as the means, means for changing the magnetic pole configuration of the magnet fixedly arranged inside the developing sleeve 2 is adopted.

図５（ａ）及び（ｂ）は、本変形例２における現像装置を現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。この図には、現像スリーブ２の表面上における現像スリーブ周方向各地点の磁束密度を示すグラフを、現像スリーブ２の周囲に重ねて表示してある。
本変形例２では、現像済み現像剤を供給搬送路３に戻す領域Ｂ又は領域Ｂ’に対応する現像スリーブ内の磁石部分については、図５（ａ）に示すように、離脱地点Ａ１が仕切部材８よりも供給搬送路側に位置するように、磁極を構成している。一方、現像済み現像剤を回収搬送路４に回収する領域Ｃ又は領域Ｃ’に対応する現像スリーブ内の磁石部分については、図５（ｂ）に示すように、離脱地点Ａ２が仕切部材８よりも回収搬送路側に位置するように、磁極を構成している。このように、本変形例２では、現像スリーブ内の磁石の磁極構成を現像スリーブ軸方向において異ならせることで、領域Ｂ又は領域Ｂ’では現像済み現像剤を供給搬送路３へ戻し、領域Ｃ又は領域Ｃ’では現像済み現像剤を回収搬送路４に回収することができる。 5A and 5B are schematic cross-sectional views when the developing device in Modification 2 is cut so as to be orthogonal to the developing sleeve axial direction. In this figure, a graph showing the magnetic flux density at each point in the circumferential direction of the developing sleeve on the surface of the developing sleeve 2 is displayed so as to overlap the periphery of the developing sleeve 2.
In the second modification, as shown in FIG. 5A, the separation point A1 is a partition for the magnet portion in the developing sleeve corresponding to the region B or the region B ′ for returning the developed developer to the supply conveyance path 3. The magnetic pole is configured so as to be positioned closer to the supply conveyance path than the member 8. On the other hand, with respect to the magnet portion in the developing sleeve corresponding to the region C or the region C ′ where the developed developer is collected in the collecting conveyance path 4, the separation point A2 is more than the partition member 8 as shown in FIG. Also, the magnetic poles are configured so as to be positioned on the collection conveyance path side. As described above, in the second modification, by changing the magnetic pole configuration of the magnet in the developing sleeve in the axial direction of the developing sleeve, the developed developer is returned to the supply conveyance path 3 in the region B or the region B ′. Alternatively, the developed developer can be collected in the collection conveyance path 4 in the region C ′.

特に、本変形例２では、仕切部材８の上端と現像スリーブ２の表面とを近接させることで、離脱地点Ａ１で離脱した現像済み現像剤が回収搬送路４に回収されたり、離脱地点Ａ２で離脱した現像済み現像剤が供給搬送路３に戻ったりすることが抑制されている。   In particular, in the second modification, the developed developer separated at the separation point A1 can be collected in the collection conveyance path 4 or at the separation point A2 by bringing the upper end of the partition member 8 and the surface of the developing sleeve 2 close to each other. It is suppressed that the developed developer that has left is returned to the supply conveyance path 3.

〔変形例３〕
次に、上記実施形態における現像装置の更に他の変形例（以下、本変形例を「変形例３」という。）について説明する。
本変形例３は、上記実施形態や上記変形例１と同様に、現像スリーブ２から離脱した現像済み現像剤の一部を回収搬送路４ではなく供給搬送路３に戻す手段として、現像スリーブ２と回収搬送路４との間を仕切部材８の上端部分８ａで封鎖するという手段を採用している。しかしながら、上記実施形態や上記変形例１では、現像スリーブ内の磁石の磁極構成が現像スリーブ軸方向において同じであったので、現像済み現像剤が現像スリーブ２から離脱する離脱地点Ａは現像スリーブ軸方向にわたって同じ位置であった。本変形例３では、現像スリーブ内の磁石の磁極構成を、上記変形例２のように現像スリーブ軸方向で異ならせている。 [Modification 3]
Next, still another modified example (hereinafter, this modified example will be referred to as “modified example 3”) of the developing device in the above embodiment will be described.
In the third modification, as in the above embodiment and the first modification, the developing sleeve 2 is used as a means for returning a part of the developed developer separated from the developing sleeve 2 to the supply conveying path 3 instead of the collection conveying path 4. A means is adopted in which the upper end portion 8a of the partition member 8 is sealed between the recovery transport path 4 and the recovery conveyance path 4. However, in the above-described embodiment and Modification 1, the magnetic pole configuration of the magnet in the developing sleeve is the same in the axial direction of the developing sleeve. Therefore, the separation point A where the developed developer leaves the developing sleeve 2 is the developing sleeve shaft. It was the same position over the direction. In the third modification, the magnetic pole configuration of the magnet in the developing sleeve is varied in the axial direction of the developing sleeve as in the second modification.

図６（ａ）及び（ｂ）は、本変形例３における現像装置を現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。この図には、現像スリーブ２の表面上における現像スリーブ周方向各地点の磁束密度を示すグラフを、現像スリーブ２の周囲に重ねて表示してある。
本変形例３では、現像済み現像剤を供給搬送路３に戻す領域Ｂ又は領域Ｂ’に対応する現像スリーブ内の磁石部分については、図６（ａ）に示すように、離脱地点Ａ１が供給搬送路３に近接した位置となるように、磁極を構成している。一方、現像済み現像剤を回収搬送路４に回収する領域Ｃ又は領域Ｃ’に対応する現像スリーブ内の磁石部分については、図６（ｂ）に示すように、離脱地点Ａ２が回収搬送路４に近接した位置となるように、磁極を構成している。このように、本変形例３では、仕切部材８の上端部分８ａ，８ｂと磁極構成とを組み合わせて現像済み現像剤の回収経路を切り換えることにより、仕切部材８の上端部分８ａ，８ｂだけで回収経路を切り換える上記実施形態１や上記変形例１の場合よりも、他方の搬送路へ現像剤が移動してしまうのを抑制できる。また、仕切部材８の上端部分８ａ，８ｂだけで回収経路を切り換える場合には、仕切部材８の上端部分と現像剤とが強く接触することで現像剤に余計なストレスが加わるおそれがあるが、本変形例３によれば、このような余計なストレスを軽減できるというメリットもある。 FIGS. 6A and 6B are schematic cross-sectional views when the developing device in Modification 3 is cut so as to be orthogonal to the axial direction of the developing sleeve. In this figure, a graph showing the magnetic flux density at each point in the circumferential direction of the developing sleeve on the surface of the developing sleeve 2 is displayed so as to overlap the periphery of the developing sleeve 2.
In the third modification, with respect to the magnet portion in the developing sleeve corresponding to the region B or the region B ′ in which the developed developer is returned to the supply conveyance path 3, as shown in FIG. The magnetic poles are configured so as to be close to the transport path 3. On the other hand, with respect to the magnet portion in the developing sleeve corresponding to the region C or the region C ′ in which the developed developer is collected in the collection conveyance path 4, the separation point A2 is located in the collection conveyance path 4 as shown in FIG. The magnetic poles are configured so as to be close to each other. As described above, in the third modification, the collected developer collection path is switched by combining the upper end portions 8a and 8b of the partition member 8 and the magnetic pole configuration, thereby collecting only the upper end portions 8a and 8b of the partition member 8. It is possible to suppress the developer from moving to the other conveyance path, as compared to the case of the first embodiment and the first modification in which the path is switched. Further, when the collection path is switched only by the upper end portions 8a and 8b of the partition member 8, excessive stress may be applied to the developer due to strong contact between the upper end portion of the partition member 8 and the developer. According to the third modification, there is an advantage that such extra stress can be reduced.

〔変形例４〕
次に、上記実施形態における現像装置の更に他の変形例（以下、本変形例を「変形例４」という。）について説明する。
上記実施形態や上記変形例１〜３は、供給搬送路３及び回収搬送路４を現像スリーブ軸方向に２分割し、一方の領域Ｂ，Ｂ’では現像済み現像剤を供給搬送路３へ戻し、他方の領域Ｃ，Ｃ’では現像済み現像剤を回収搬送路４に回収するものであった。本変形例４では、供給搬送路３及び回収搬送路４を現像スリーブ軸方向に３分割し、両端に位置する２つの領域Ｂ１，Ｂ２では現像済み現像剤を供給搬送路３へ戻し、中央に位置する領域Ｃでは現像済み現像剤を回収搬送路４に回収する。 [Modification 4]
Next, still another modified example (hereinafter, this modified example will be referred to as “modified example 4”) of the developing device in the above embodiment will be described.
In the embodiment and the first to third modifications, the supply conveyance path 3 and the recovery conveyance path 4 are divided into two in the developing sleeve axial direction, and the developed developer is returned to the supply conveyance path 3 in one of the regions B and B ′. In the other areas C and C ′, the developed developer is collected in the collection conveyance path 4. In the fourth modification, the supply conveyance path 3 and the collection conveyance path 4 are divided into three in the developing sleeve axial direction, and the developed developer is returned to the supply conveyance path 3 in the two regions B1 and B2 located at both ends, In the positioned region C, the developed developer is collected in the collection conveyance path 4.

図７は、本変形例４における供給搬送路３の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。
なお、図７の上部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤量（嵩）をとったものである。また、図７の下部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤のトナー濃度をとったものである。 FIG. 7 is an explanatory diagram illustrating the distribution of the developer amount (bulk) and the toner density distribution in the developer transport direction of the supply transport path 3 in Modification 4.
In the graph shown in the upper part of FIG. 7, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer amount (bulk) in the supply conveyance path 3. . In the graph shown in the lower part of FIG. 7, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer toner density in the supply conveyance path 3.

近年、プロダクションプリンティング市場などでＡ３ノビなど従来のＡ３サイズよりも広い印刷領域が印刷可能な画像形成装置の要求が出ている。このようなＡ３ノビに対応する画像形成装置では、Ａ３サイズに対応する画像形成装置よりも、現像スリーブの軸方向長さを延ばして現像領域を現像スリーブ軸方向に拡大する必要がある。そのため、供給回収分離方式を採用する場合、Ａ３サイズに対応する画像形成装置よりも、現像剤の枯渇や回収搬送路での剤溢れ等の問題が顕著となる。一方で、Ａ３ノビに対応する画像形成装置で印刷される印刷物は、Ａ３サイズの外側に位置するノビ部が最終的には切り落とされる場合が多い。そのため、そのノビ部には、目印用の画像などは印刷する必要があるものの、高い画質が要求されることがない。   In recent years, there has been a demand for an image forming apparatus capable of printing a printing area wider than the conventional A3 size such as A3 Nobi in the production printing market. In such an image forming apparatus corresponding to A3 Nobi, it is necessary to extend the developing region in the axial direction of the developing sleeve by extending the axial length of the developing sleeve, compared to the image forming apparatus corresponding to the A3 size. Therefore, when the supply / recovery separation method is adopted, problems such as the depletion of the developer and the overflow of the agent in the recovery conveyance path become more conspicuous than the image forming apparatus corresponding to the A3 size. On the other hand, a printed matter printed by an image forming apparatus corresponding to A3 nobi often has a nobi portion positioned outside the A3 size finally cut off. Therefore, a high quality image is not required in the nobby portion, although a mark image or the like needs to be printed.

本変形例４においては、このようなノビ部に対応する供給搬送路３の上流側部分（領域Ｂ１）及び供給搬送路３の下流側部分（領域Ｂ２）で、現像済み現像剤を供給搬送路３に戻し、Ａ３画像の本体部分に対応する供給搬送路３の中央部分（領域Ｃ）では、現像済み現像剤を回収搬送路４に回収するようにしている。これにより、Ａ３画像の本体部分に対応する供給搬送路３の中央部分（領域Ｃ）では、トナー濃度ムラが生じることがなく、高画質な画像を得ることができる。一方、ノビ部に対応する供給搬送路３の上流側部分（領域Ｂ１）及び供給搬送路３の下流側部分（領域Ｂ２）で、現像済み現像剤を供給搬送路３に戻すため、現像剤の枯渇や現像剤の溢れ等の問題が解消できる。なお、このノビ部に対応する領域Ｂ１，Ｂ２では、現像済み現像剤が供給搬送路３に戻るため、多少のトナー濃度ムラが生じるものの、このノビ部は高画質が求められない箇所であるため、実質的な弊害はない。   In the fourth modification, the developed developer is supplied to the supply conveyance path in the upstream portion (area B1) of the supply conveyance path 3 and the downstream portion (area B2) of the supply conveyance path 3 corresponding to the nobby portion. 3, the developed developer is collected in the collection conveyance path 4 in the central portion (region C) of the supply conveyance path 3 corresponding to the main body portion of the A3 image. As a result, toner density unevenness does not occur in the central portion (area C) of the supply conveyance path 3 corresponding to the main body portion of the A3 image, and a high-quality image can be obtained. On the other hand, in order to return the developed developer to the supply conveyance path 3 in the upstream part (area B1) of the supply conveyance path 3 and the downstream part (area B2) of the supply conveyance path 3 corresponding to the nobby portion, Problems such as depletion and overflow of developer can be solved. In the regions B1 and B2 corresponding to the nobby portion, the developed developer returns to the supply conveyance path 3, and thus some toner density unevenness occurs, but this noble portion is a portion where high image quality is not required. There is no substantial adverse effect.

〔変形例５〕
次に、上記実施形態における現像装置の更に他の変形例（以下、本変形例を「変形例５」という。）について説明する。
本変形例５は、供給搬送路３及び回収搬送路４を現像スリーブ軸方向に７分割し、現像済み現像剤を供給搬送路３へ戻す領域Ｂ１〜Ｂ４と、現像済み現像剤を回収搬送路４に回収する領域Ｃ１〜Ｃ３とを交互に位置するように構成したものである。 [Modification 5]
Next, still another modified example (hereinafter, this modified example will be referred to as “modified example 5”) of the developing device in the above embodiment will be described.
In the fifth modification, the supply conveyance path 3 and the collection conveyance path 4 are divided into seven in the axial direction of the developing sleeve, and the regions B1 to B4 in which the developed developer is returned to the supply conveyance path 3, and the developed developer is collected in the collection conveyance path. 4, the areas C1 to C3 to be collected are alternately arranged.

図８は、本変形例５における供給搬送路３の現像剤搬送方向における現像剤の量（嵩）の分布とトナー濃度の分布とを示す説明図である。
なお、図８の上部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤量（嵩）をとったものである。また、図８の下部に記載されたグラフは、横軸に供給搬送路３の現像剤搬送方向位置をとり、縦軸に供給搬送路３内の現像剤のトナー濃度をとったものである。 FIG. 8 is an explanatory diagram showing the distribution of the amount (bulk) of the developer and the distribution of the toner density in the developer transport direction of the supply transport path 3 in Modification 5.
In the graph shown in the upper part of FIG. 8, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer amount (bulk) in the supply conveyance path 3. . In the graph shown in the lower part of FIG. 8, the horizontal axis represents the developer conveyance direction position of the supply conveyance path 3, and the vertical axis represents the developer toner concentration in the supply conveyance path 3.

現像済み現像剤を供給搬送路３へ戻す領域Ｂ１〜Ｂ４では供給搬送路３内の現像剤のトナー濃度低下が生じてしまい、これが画像濃度ムラとなって現れる。しかしながら、本変形例５のように、これらの領域Ｂ１〜Ｂ４の間に、現像済み現像剤を回収搬送路４に回収する領域Ｃ１〜Ｃ３を配置すると、図８の下部グラフの実線で示すように、そのトナー濃度の変化がなだらかな階段状の変化となる。このような変化であれば、その画像濃度ムラを人間の目では認識しづらくなる。よって、より高い品質の画像を形成することができる。   In the regions B1 to B4 where the developed developer is returned to the supply conveyance path 3, the toner density of the developer in the supply conveyance path 3 is lowered, and this appears as uneven image density. However, when the regions C1 to C3 for recovering the developed developer in the recovery transport path 4 are arranged between these regions B1 to B4 as in the fifth modification, as indicated by the solid line in the lower graph of FIG. In addition, the change in toner density is a gentle step-like change. Such a change makes it difficult for human eyes to recognize the image density unevenness. Therefore, a higher quality image can be formed.

〔変形例６〕
次に、上記実施形態における現像装置の更に他の変形例（以下、本変形例を「変形例６」という。）について説明する。
上述した実施形態及び変形例１〜５は、現像スリーブ２の下方で供給搬送路３と回収搬送路４とを横並びにした構成であったが、本変形例６は、現像スリーブ２の下方で供給搬送路３と回収搬送路４とを縦に並べた構成となっている。 [Modification 6]
Next, still another modified example (hereinafter, this modified example will be referred to as “modified example 6”) of the developing device in the above embodiment will be described.
The above-described embodiment and Modifications 1 to 5 have a configuration in which the supply conveyance path 3 and the collection conveyance path 4 are arranged side by side below the development sleeve 2, but this modification 6 is below the development sleeve 2. The supply conveyance path 3 and the collection conveyance path 4 are arranged vertically.

図９（ａ）及び（ｂ）は、本変形例６における現像装置１０’を現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。なお、図９（ａ）は、現像済み現像剤が供給搬送路３に戻される領域Ｂにおける断面図であり、図９（ｂ）は、現像済み現像剤が回収搬送路４に回収される領域Ｃにおける断面図である。
本変形例６の現像装置は、回収搬送路４が供給搬送路３の下方に配置されている。回収搬送路４と現像スリーブ２上の離脱地点Ａとの間は、離脱地点Ａで離脱した現像済み現像剤を供給搬送路３を迂回して回収搬送路４へ案内するための案内通路４ａによって連通している。 FIGS. 9A and 9B are schematic cross-sectional views when the developing device 10 ′ according to Modification 6 is cut so as to be orthogonal to the axial direction of the developing sleeve. 9A is a cross-sectional view in the region B where the developed developer is returned to the supply conveyance path 3, and FIG. 9B is a region where the developed developer is collected in the collection conveyance path 4. It is sectional drawing in C.
In the developing device according to the sixth modification, the collection conveyance path 4 is disposed below the supply conveyance path 3. Between the collection conveyance path 4 and the separation point A on the developing sleeve 2, a guide path 4 a for guiding the developed developer separated at the separation point A to the collection conveyance path 4 bypassing the supply conveyance path 3. Communicate.

本変形例６では、離脱地点Ａで離脱した現像済み現像剤を供給搬送路３へ戻す領域Ｂにおいては、図９（ａ）に示すように、案内通路４ａが設けられておらず、離脱地点Ａで現像スリーブ２から離脱した現像済み現像剤は、すべて供給搬送路３に戻される。一方、離脱地点Ａで離脱した現像済み現像剤を回収搬送路４に回収する領域Ｃにおいては、図９（ｂ）に示すように、現像スリーブ２上の離脱地点Ａに近接して案内通路４ａの入口が対向している。しかも、本変形例６では、供給搬送路３と案内通路４ａとを仕切る仕切壁の上端部分によって、現像スリーブ２上の離脱地点Ａと供給搬送路３との間の空間が狭められている。これにより、離脱地点Ａで現像スリーブ２から離脱した現像済み現像剤は、案内通路４ａを通って回収搬送路４に回収される。   In the sixth modification, in the region B where the developed developer separated at the separation point A is returned to the supply conveyance path 3, as shown in FIG. 9A, the guide passage 4a is not provided, and the separation point All the developer that has been released from the developing sleeve 2 in A is returned to the supply conveyance path 3. On the other hand, in the region C in which the developed developer separated at the separation point A is collected in the collection conveyance path 4, as shown in FIG. 9B, the guide passage 4a is adjacent to the separation point A on the developing sleeve 2. The entrance of is opposite. Moreover, in the sixth modification, the space between the separation point A on the developing sleeve 2 and the supply conveyance path 3 is narrowed by the upper end portion of the partition wall that partitions the supply conveyance path 3 and the guide path 4a. As a result, the developed developer separated from the developing sleeve 2 at the separation point A is collected in the collection conveyance path 4 through the guide path 4a.

本変形例６では、供給搬送路３と回収搬送路４とが縦に並んだ構成となっているため、これらが横並びとなっている上述した実施形態及び変形例１〜５よりも、水平方向であって現像スリーブ軸方向に対して直交する方向の現像装置寸法（幅寸法）を小さくすることができる。近年のカラー画像形成装置では、複数の感光体を横並びに配置したタンデム型のものが多数採用されており、このようなタンデム型画像形成装置では、感光体間の距離を短くすることが望まれる。タンデム型画像形成装置では、感光体の間には現像装置が配置される場合が多く、感光体間の距離を短くしようとしても現像装置の幅寸法によって制限されていた。本変形例６によれば、現像装置の幅寸法が小さくなるので、タンデム型画像形成装置における感光体間距離をより短いものとすることが可能となる。   In this modification 6, since the supply conveyance path 3 and the collection conveyance path 4 are arranged vertically, the horizontal direction is more than the embodiment and the modifications 1 to 5 described above in which these are arranged side by side. Thus, the developing device dimension (width dimension) in the direction orthogonal to the developing sleeve axial direction can be reduced. Many recent color image forming apparatuses employ a tandem type in which a plurality of photoconductors are arranged side by side. In such a tandem type image forming apparatus, it is desired to shorten the distance between the photoconductors. . In the tandem type image forming apparatus, a developing device is often arranged between the photoconductors, and even if an attempt is made to shorten the distance between the photoconductors, the width is limited by the developing device. According to the sixth modification, since the width of the developing device is reduced, the distance between the photoreceptors in the tandem type image forming apparatus can be further shortened.

〔変形例７〕
次に、上記実施形態における現像装置の更に他の変形例（以下、本変形例を「変形例７」という。）について説明する。
本変形例７は、現像スリーブ２から離脱した現像済み現像剤の一部を供給搬送路３に戻す手段として、仕切部材８の上端部分８ａによって現像済み現像剤の一部を供給搬送路３へ案内するものである。しかしながら、本変形例７では、離脱した現像済み現像剤を仕切部材８の上端部分８ａにより２つに分配し、その一方を供給搬送路３へ戻し、他方を回収搬送路４へ戻す。 [Modification 7]
Next, still another modified example (hereinafter, this modified example will be referred to as “modified example 7”) of the developing device in the above embodiment will be described.
In this modified example 7, as a means for returning a part of the developed developer separated from the developing sleeve 2 to the supply conveyance path 3, a part of the developed developer is supplied to the supply conveyance path 3 by the upper end portion 8 a of the partition member 8. It is a guide. However, in the present modified example 7, the separated developed developer is distributed into two by the upper end portion 8 a of the partition member 8, one of which is returned to the supply conveyance path 3, and the other is returned to the collection conveyance path 4.

図１１は、本変形例７における現像装置を現像スリーブ軸方向に対して直交するように切断したときの模式的な断面図である。この図には、現像スリーブ２の表面上における現像スリーブ周方向各地点の磁束密度を示すグラフを、現像スリーブ２の周囲に重ねて表示してある。
本変形例７では、供給搬送路３の全域（回収搬送路４の全域）にわたって、現像スリーブ２の表面部分から離脱した現像済み現像剤を、仕切部材８の上端部分８ａにより２つに分配し、その一方を供給搬送路３へ戻し、他方を回収搬送路４へ戻すように構成されている。この分配比率は、仕切部材８の上端部分８ａの位置や形状寸法を変更することにより適宜設定可能である。また、供給搬送路３の現像剤搬送方向一部分（回収搬送路４の現像剤搬送方向一部分）だけ、現像スリーブ２の表面部分から離脱した現像済み現像剤を、仕切部材８の上端部分８ａにより２つに分配し、その一方を供給搬送路３へ戻し、他方を回収搬送路４へ戻すように構成してもよい。 FIG. 11 is a schematic cross-sectional view when the developing device in Modification 7 is cut so as to be orthogonal to the axial direction of the developing sleeve. In this figure, a graph showing the magnetic flux density at each point in the circumferential direction of the developing sleeve on the surface of the developing sleeve 2 is displayed so as to overlap the periphery of the developing sleeve 2.
In the present modified example 7, the developed developer separated from the surface portion of the developing sleeve 2 is distributed into two by the upper end portion 8a of the partition member 8 over the entire area of the supply conveyance path 3 (the entire area of the collection conveyance path 4). One of them is returned to the supply conveyance path 3 and the other is returned to the collection conveyance path 4. This distribution ratio can be appropriately set by changing the position and shape of the upper end portion 8a of the partition member 8. Further, the developed developer separated from the surface portion of the developing sleeve 2 only by a part of the developer conveying direction of the supply conveying path 3 (a part of the developer conveying direction of the recovery conveying path 4) is removed by the upper end portion 8a of the partition member 8 by 2. It may be configured such that one is returned to the supply conveyance path 3 and the other is returned to the collection conveyance path 4.

〔複写機の構成〕
図１０は、上述した現像装置が搭載された画像形成装置としての複写機の概略構成を示す説明図である。
以下に複写機能時における動作に基づいて説明する。
ＡＤＦ１０１の原稿台１０２に画像面が上となる状態で原稿束が載置され、図示しない操作部上のスタートキーが押下されると、最上位の原稿が給送ローラ１０３、給送ベルト１０４によってコンタクトガラス１０５上の所定位置に給送される。コンタクトガラス１０５上の原稿は、画像読取部１０６によって画像情報が読み取られた後に給送ベルト１０４、排出ローラ１０７によって排紙台１０８上に排出される。原稿検知センサ１０９によって原稿台１０２上に次の原稿が存在することが検知された場合には、上述と同様にこの原稿がコンタクトガラス１０５上に給送される。 [Configuration of copier]
FIG. 10 is an explanatory diagram showing a schematic configuration of a copying machine as an image forming apparatus equipped with the above-described developing device.
A description will be given below based on the operation during the copying function.
When a document bundle is placed on the document table 102 of the ADF 101 with the image surface facing upward, and a start key on an operation unit (not shown) is pressed, the uppermost document is fed by the feeding roller 103 and the feeding belt 104. It is fed to a predetermined position on the contact glass 105. After the image information is read by the image reading unit 106, the document on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107. When the document detection sensor 109 detects that the next document exists on the document table 102, the document is fed onto the contact glass 105 as described above.

画像読取部１０６は、コンタクトガラス１０５上の原稿を２個のランプ１２８で照射しながら原稿の画像情報を副走査方向にライン走査し、その反射光を画像データとして第１ミラー１２９、第２ミラー１３０、第３ミラー１３１により所定の方向に反射させ、画像を縮小結像させるレンズユニット１３２を介してＣＣＤ１３３に送る。画像読取部１０６によって読み込まれた画像データは、図示しない画像処理手段を介してレーザ発光装置１３４、ｆθレンズ１３５、反射ミラー１３６等を有する書き込みユニット１１８に送られ、書き込みユニット１１８によって感光体ドラム１１７上に原稿画像に対応した静電潜像が形成される。   The image reading unit 106 performs line scanning on the image information of the original in the sub-scanning direction while irradiating the original on the contact glass 105 with the two lamps 128, and uses the reflected light as image data as the first mirror 129 and the second mirror. 130, the light is reflected in a predetermined direction by the third mirror 131, and sent to the CCD 133 via the lens unit 132 for reducing and forming an image. The image data read by the image reading unit 106 is sent to a writing unit 118 having a laser light emitting device 134, an fθ lens 135, a reflecting mirror 136, and the like via an image processing unit (not shown), and the photosensitive drum 117 is read by the writing unit 118. An electrostatic latent image corresponding to the original image is formed on the top.

本体１００の内部には、感光体ドラム１１７、現像装置１０、定着部１２１、排紙ユニット１２２、第１〜第３給紙装置１１０，１１１，１１２、縦搬送ユニット１１６等が配設されている。感光体ドラム１１７は、図示しない帯電器により一様に帯電された後に書き込みユニット１１８からの光情報によって露光されて静電潜像が形成され、この静電潜像は現像装置１０により現像されてトナー像が形成される。   Inside the main body 100, a photosensitive drum 117, a developing device 10, a fixing unit 121, a paper discharge unit 122, first to third paper supply devices 110, 111, and 112, a vertical conveyance unit 116, and the like are disposed. . The photosensitive drum 117 is uniformly charged by a charger (not shown) and then exposed to light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 10. A toner image is formed.

感光体ドラム１１７の下方には搬送ベルト１２０が配設されている。搬送ベルト１２０は記録媒体である転写紙の搬送手段及び転写手段を兼ねており、図示しない電源から転写バイアスが印加され、縦搬送ユニット１１６からの転写紙を感光体ドラム１１７と等速で搬送しつつ感光体ドラム１１７上のトナー像を転写紙に転写させる。転写紙に転写されたトナー像は定着部において転写紙上に定着され、画像を定着された転写紙は排紙ユニット１２２を介して排紙トレイ１２３上に排出される。感光体ドラム１１７はトナー像転写後に図示しないクリーニング手段によってクリーニングされ、次の画像形成に備えられる。   A conveyor belt 120 is disposed below the photosensitive drum 117. The conveyance belt 120 also serves as conveyance means and transfer means for transfer paper as a recording medium. A transfer bias is applied from a power supply (not shown), and the transfer paper from the vertical conveyance unit 116 is conveyed at a constant speed with the photosensitive drum 117. The toner image on the photosensitive drum 117 is transferred to the transfer paper. The toner image transferred to the transfer paper is fixed on the transfer paper in the fixing unit, and the transfer paper on which the image is fixed is discharged onto the paper discharge tray 123 via the paper discharge unit 122. The photosensitive drum 117 is cleaned by a cleaning unit (not shown) after the toner image is transferred, and is prepared for the next image formation.

排紙ユニット１２２には、その途中から搬送ローラ対１２４により転写紙を送り込まれる反転ユニット１２５、反転ユニット１２５で反転した転写紙を再度縦搬送ユニット１１６側に搬送する画像形成側搬送路１２６、反転した転写紙を再度排紙ユニット１２２側に戻す排紙搬送路１２７等を有する両面搬送路が配設されている。この両面搬送路により、転写紙の両面に画像を形成しあるいは画像が形成された面を下にして排紙トレイ１２３上に排出することができる。   The paper discharge unit 122 includes a reversing unit 125 that feeds the transfer paper from the middle thereof by a pair of transport rollers 124, an image forming side transport path 126 that transports the transfer paper reversed by the reversing unit 125 to the vertical transport unit 116 side, and a reversal. A double-sided conveyance path having a paper discharge conveyance path 127 and the like for returning the transferred transfer paper to the paper discharge unit 122 again is provided. With this double-sided conveyance path, images can be formed on both sides of the transfer paper, or discharged onto the paper discharge tray 123 with the image-formed side down.

第１〜第３給紙装置１１０，１１１，１１２は、選択された際にそれぞれ第１トレイ１１３、第２トレイ１１４、第３トレイ１１５に積載された転写紙を給送する。給送された転写紙は、縦搬送ユニット１１６によって感光体１に当接する位置まで搬送される。   When selected, the first to third paper feeding devices 110, 111, and 112 feed transfer sheets stacked on the first tray 113, the second tray 114, and the third tray 115, respectively. The fed transfer paper is transported to a position where it comes into contact with the photosensitive member 1 by the vertical transport unit 116.

この画像形成装置において、プリンタ機能時には画像処理手段からの画像データの代わりに外部からの画像データが書き込みユニット１１８に入力され、画像形成手段によって転写紙上に画像が形成される。ファクシミリ機能時には画像読取部１０６からの画像データが図示しないファクシミリ送受信部により相手に送信され、相手からの画像データがファクシミリ送受信部で受信されて画像処理手段からの画像データに代えて書き込みユニット１１８に入力されることにより、画像形成手段が作動して転写紙上に画像が形成される。   In this image forming apparatus, image data from the outside is input to the writing unit 118 instead of the image data from the image processing means during the printer function, and an image is formed on the transfer paper by the image forming means. During the facsimile function, the image data from the image reading unit 106 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit, and is sent to the writing unit 118 instead of the image data from the image processing means. As a result of the input, the image forming means operates to form an image on the transfer paper.

上述した構成では、画像形成装置として複合機を用いた例を示したが、本発明が適用可能な画像形成装置はこれに限られず、複写装置、プリンタ、ファクシミリ、プロッタ等の他の画像形成装置にも本発明は適用可能である。   In the above-described configuration, an example in which a multifunction peripheral is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited thereto, and other image forming apparatuses such as a copying apparatus, a printer, a facsimile machine, and a plotter. In addition, the present invention is applicable.

以上、本実施形態及び各変形例に係る現像装置は、現像剤担持体としての現像スリーブ２に沿って現像スリーブ回転軸方向に延びる供給搬送路３中を搬送されているトナーと磁性キャリアとを含んだ現像剤を、回転している現像スリーブ２の表面に担持させることにより、現像スリーブ２の表面に担持された現像剤を現像領域へ搬送し、現像領域にて現像剤中のトナーを潜像担持体としての感光体１の表面上の潜像に付着させて潜像を現像するとともに、現像領域を通過した現像剤を現像スリーブ２から離脱させて供給搬送路３とは別の搬送路である回収搬送路４に回収する構成であるが、現像領域を通過して現像スリーブ２から離脱した一部の現像済み現像剤を供給搬送路３へ戻す一部戻し手段を備えている。これにより、現像スリーブ２から離脱した現像済み現像剤の全部を回収搬送路４で回収する一般的な供給回収分離方式の現像装置よりも、供給搬送路３の下流端に到達する現像剤の量が多くなる。よって、現像剤の枯渇が発生しにくくなる。しかも、供給搬送路３の下流端に存在する現像剤の量が増える結果、相対的に、回収搬送路４の下流側に存在する現像剤量が減ることになる。したがって、回収搬送路の下流側で生じ得る現像剤の溢れによる再汲み上げ等の発生も抑制される。しかも、現像スリーブ２から離脱した現像済み現像剤の全部を供給搬送路３に戻す従来の供給回収一体方式の現像装置よりも、供給搬送路３内の現像剤のトナー濃度偏差が小さいので、画像濃度ムラが生じにくい。
また、上記変形例１で説明したように、現像スリーブ２から離脱した現像済み現像剤を供給搬送路３へ戻すとき、供給搬送路３の現像剤搬送方向上流側部分へ戻すようにすれば、供給搬送路３の現像剤搬送方向下流側部分へ戻す場合よりも、現像スリーブ回転軸方向におけるトナー濃度の変化を小さくすることができるなど、上記変形例１で説明した種々の有用な効果が得られる。
また、上記変形例４で説明したように、現像スリーブ２から離脱した現像済み現像剤を供給搬送路３へ戻すとき、供給搬送路３の現像剤搬送方向上流側部分と下流側部分とへ戻すようにすれば、現像領域の現像スリーブ軸方向中央部分で画像濃度ムラを発生させないようにすることができる。これにより、例えば、プロダクションプリンティング市場などで要求されるＡ３ノビに対応した画像形成装置において、高画質が要求されないノビ部において画像濃度ムラを生じさせる代わりに現像剤の枯渇や溢れ等の問題を解消しつつ、Ａ４サイズの画像本体部分については画像濃度ムラを発生させることがなく高画質な画像形成を可能とする。
また、上記実施形態や上記変形例１、３等で説明したように、供給搬送路３及び回収搬送路４を現像スリーブ回転軸方向に延在する仕切部材８を介して互いに隣り合って配置し、現像スリーブ２と回収搬送路４との間の現像スリーブ回転軸方向一部分を仕切部材８の上端部分８ａで封鎖する構成とすれば、簡易な構成で、現像スリーブ２から離脱した現像済み現像剤の一部を供給搬送路３へ戻すことができる。
特に、上記変形例３のように、現像領域を通過した現像済み現像剤を現像スリーブ２から離脱させるための離脱用磁界を発生させる離脱用磁極を備えた磁界発生手段としての磁石を現像スリーブ２の内部に設け、その磁石の離脱用磁極は、供給搬送路３へ現像済み現像剤を戻す領域Ｂでは、その剥離用磁界の作用によって離脱する現像済み現像剤が供給搬送路３へ向かうように構成され、回収搬送路４に現像済み現像剤を回収する領域Ｃでは、その剥離用磁界の作用によって離脱する現像済み現像剤が回収搬送路４へ向かうように構成してもよい。この場合、仕切部材８の上端部分８ａと現像剤との接触が緩和され、現像剤に与える余計なストレスを軽減できる。
また、上記変形例２で説明したように、供給搬送路３へ現像済み現像剤を戻す領域Ｂでは、供給搬送路３と対向する位置（離脱地点Ａ１）で現像スリーブ２から現像済み現像剤が離脱して供給搬送路３に戻るように離脱用磁極を構成し、回収搬送路４に現像済み現像剤を回収する領域Ｃでは、回収搬送路４と対向する位置（離脱地点Ａ２）で現像済み現像剤が離脱するように離脱用磁極を構成すれば、仕切部材８等を用いずに、現像済み現像剤を供給搬送路３と回収搬送路４に振り分けることができる。
また、上記変形例６で説明したように、供給搬送路３を現像スリーブ２の下方に配置し、回収搬送路４を供給搬送路３の下方に配置し、回収搬送路４に回収する現像済み現像剤を、供給搬送路３を迂回して回収搬送路４へ案内する案内通路４ａを設けることで、水平方向であって現像スリーブ軸方向に対して直交する方向の現像装置寸法（幅寸法）を小さくすることができる。
また、上記変形例７で説明したように、離脱した現像済み現像剤を仕切部材８の上端部分８ａにより２つに分配し、その一方を供給搬送路３へ戻し、他方を回収搬送路４へ戻すようにしても、同様の効果が得られる。
また、回収搬送路４内の現像剤にトナーを補給するためのトナー補給口９を、回収搬送路４の現像剤搬送方向上流側部分に設けることで、補給トナーが現像に使用されるまでに十分に現像剤に攪拌混合させることができ、トナーの帯電量不足やトナー濃度ムラによる画質劣化が軽減される。 As described above, the developing device according to the present embodiment and each modification includes the toner and the magnetic carrier that are transported in the supply transport path 3 extending in the developing sleeve rotation axis direction along the developing sleeve 2 as the developer carrier. The developer contained therein is carried on the surface of the developing sleeve 2 that is rotating, whereby the developer carried on the surface of the developing sleeve 2 is conveyed to the development area, and the toner in the developer is latent in the development area. The latent image is developed by being attached to the latent image on the surface of the photosensitive member 1 as an image carrier, and the developer that has passed through the developing region is separated from the developing sleeve 2 to be separated from the supply conveyance path 3. However, it is provided with a part returning means for returning a part of the developed developer that has passed through the developing region and separated from the developing sleeve 2 to the supply conveying path 3. As a result, the amount of the developer reaching the downstream end of the supply conveyance path 3 rather than the general supply / recovery separation type development apparatus that collects all of the developed developer separated from the developing sleeve 2 through the collection conveyance path 4. Will increase. Therefore, the developer is hardly depleted. In addition, as a result of an increase in the amount of the developer present at the downstream end of the supply conveyance path 3, the amount of the developer present on the downstream side of the recovery conveyance path 4 is relatively reduced. Therefore, the occurrence of re-pumping due to the overflow of the developer that may occur on the downstream side of the collection conveyance path is also suppressed. In addition, since the toner concentration deviation of the developer in the supply / conveyance path 3 is smaller than that of the conventional supply / collection integrated type developing device that returns all the developed developer separated from the developing sleeve 2 to the supply / conveyance path 3, Density unevenness hardly occurs.
Further, as described in the first modification, when returning the developed developer separated from the developing sleeve 2 to the supply conveyance path 3, if the developer is returned to the upstream portion of the supply conveyance path 3 in the developer conveyance direction, Various useful effects described in the first modification can be obtained, such as the change in the toner density in the developing sleeve rotation axis direction can be made smaller than when returning to the downstream portion of the supply conveyance path 3 in the developer conveyance direction. It is done.
Further, as described in the fourth modification, when the developed developer separated from the developing sleeve 2 is returned to the supply conveyance path 3, it is returned to the upstream and downstream portions of the supply conveyance path 3 in the developer conveyance direction. By doing so, it is possible to prevent image density unevenness from occurring in the central portion of the developing area in the axial direction of the developing sleeve. This eliminates problems such as developer depletion and overflow instead of causing uneven image density in the noble areas where high image quality is not required in image forming devices that support A3 Nobi, which is required in the production printing market, for example. However, it is possible to form a high-quality image without causing uneven image density in the A4 size image main body.
Further, as described in the above embodiment and the first and third modifications, the supply conveyance path 3 and the collection conveyance path 4 are arranged adjacent to each other via the partition member 8 extending in the developing sleeve rotation axis direction. If the developing sleeve rotational axis portion between the developing sleeve 2 and the collection conveyance path 4 is sealed by the upper end portion 8a of the partition member 8, the developed developer separated from the developing sleeve 2 with a simple configuration. Can be returned to the supply conveyance path 3.
In particular, as in Modification 3 above, the developing sleeve 2 includes a magnet as a magnetic field generating means having a detaching magnetic pole for generating a detaching magnetic field for detaching the developed developer that has passed through the developing region from the developing sleeve 2. In the region B where the developed developer is returned to the supply conveyance path 3, the separation magnetic pole of the magnet is arranged so that the developed developer separated by the action of the peeling magnetic field is directed to the supply conveyance path 3. In the region C where the developed developer is collected in the collection conveyance path 4, the developed developer that is separated by the action of the peeling magnetic field may be directed to the collection conveyance path 4. In this case, contact between the upper end portion 8a of the partition member 8 and the developer is alleviated, and unnecessary stress applied to the developer can be reduced.
Further, as described in Modification 2 above, in the region B where the developed developer is returned to the supply conveyance path 3, the developed developer is removed from the developing sleeve 2 at a position facing the supply conveyance path 3 (separation point A1). In a region C where the separation magnetic pole is configured so as to separate and return to the supply conveyance path 3 and the developed developer is collected in the collection conveyance path 4, development is completed at a position facing the collection conveyance path 4 (separation point A <b> 2). If the separation magnetic pole is configured so that the developer is separated, the developed developer can be distributed to the supply conveyance path 3 and the collection conveyance path 4 without using the partition member 8 or the like.
Further, as described in the sixth modification, the supply conveyance path 3 is disposed below the developing sleeve 2, the collection conveyance path 4 is disposed below the supply conveyance path 3, and the developed product is collected in the collection conveyance path 4. By providing a guide passage 4a that guides the developer to the recovery conveyance path 4 by bypassing the supply conveyance path 3, the development device dimensions (width dimensions) in the horizontal direction and perpendicular to the axial direction of the development sleeve Can be reduced.
Further, as described in the modification example 7, the separated developed developer is divided into two by the upper end portion 8a of the partition member 8, one of which is returned to the supply conveyance path 3 and the other to the collection conveyance path 4. Even if it returns, the same effect is acquired.
Further, by providing a toner replenishing port 9 for replenishing the developer in the recovery conveyance path 4 at the upstream side of the recovery conveyance path 4 in the developer conveyance direction, the replenishment toner is used for development. The developer can be sufficiently agitated and mixed, and image quality deterioration due to insufficient toner charge amount and uneven toner density is reduced.

１ 感光体
２ 現像スリーブ
３ 供給搬送路
４ 回収搬送路
４ａ 案内通路
５ 供給搬送スクリュー
６ 回収搬送スクリュー
７ 現像ドクタ
８ 仕切部材
８ａ，８ｂ 上端部分
９ トナー補給口
１０ 現像装置 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing sleeve 3 Supply conveyance path 4 Collection conveyance path 4a Guide path 5 Supply conveyance screw 6 Collection conveyance screw 7 Developing doctor 8 Partition member 8a, 8b Upper end part 9 Toner replenishment port 10 Developing apparatus

特開２０００−３０５３５９号公報JP 2000-305359 A

Claims (7)

現像剤担持体に沿って現像剤担持体回転軸方向に延びる現像剤供給搬送路中を搬送されているトナーとキャリアとを含んだ二成分現像剤を、回転している該現像剤担持体の表面に担持させることにより、該現像剤担持体の表面に担持された二成分現像剤を現像領域へ搬送し、現像領域にて二成分現像剤中のトナーを潜像担持体表面上の潜像に付着させて該潜像を現像するとともに、現像領域を通過した二成分現像剤を該現像剤担持体から離脱させて該現像剤供給搬送路とは別の搬送路である現像剤回収搬送路に回収する現像装置において、
現像領域を通過して現像剤担持体から離脱した一部の二成分現像剤を上記現像剤供給搬送路の現像剤搬送方向上流側部分と下流側部分とに戻す一部戻し手段を設けたことを特徴とする現像装置。 A two-component developer containing toner and a carrier conveyed in a developer supply conveyance path extending in the direction of the developer carrier rotation axis along the developer carrier is transferred to the rotating developer carrier. By carrying the toner on the surface of the developer carrying member, the two-component developer carried on the surface of the developer carrying member is conveyed to the developing region, and in the developing region, the toner in the two-component developer is transferred onto the latent image carrier surface. And developing the latent image by being attached to the developer, and separating the two-component developer that has passed through the development area from the developer carrying member, so that the developer recovery transport path is a transport path different from the developer supply transport path. In the developing device to collect in
Provided with a partial return means for returning a part of the two-component developer that has passed through the developing region and separated from the developer carrying member to the upstream side portion and the downstream side portion in the developer transport direction of the developer supply transport path. A developing device. 請求項１に記載の現像装置において、
上記現像剤供給搬送路及び上記現像剤回収搬送路は、現像剤担持体回転軸方向に延在する仕切部材を介して互いに隣り合って配置されており、
上記一部戻し手段は、上記現像剤担持体と上記現像剤回収搬送路との間の現像剤担持体回転軸方向一部分を上記仕切部材で封鎖し、上記一部の二成分現像剤を該仕切部材で案内して上記現像剤供給搬送路へ戻すものであり、
上記現像剤担持体と上記現像剤回収搬送路との間の現像剤担持体回転軸方向他部分では、現像領域を通過して現像剤担持体から離脱した二成分現像剤が該仕切部材の上方を通過して該現像剤回収搬送路へ回収される構成としたことを特徴とする現像装置。 The developing device according to claim 1 ,
The developer supply transport path and the developer recovery transport path are arranged adjacent to each other via a partition member extending in the developer carrier rotating shaft direction,
The partial returning means seals a part of the developer carrier rotating shaft between the developer carrier and the developer collection conveyance path in the rotation axis direction with the partition member, and the part of the two-component developer is separated from the partition. It is guided by a member and returned to the developer supply conveyance path,
In the other portion of the developer carrier rotating shaft between the developer carrier and the developer collection conveyance path, the two-component developer that has passed through the development region and separated from the developer carrier is located above the partition member. And a developer collecting path that passes through the developer collecting conveyance path. 請求項２の現像装置において、
現像領域を通過した二成分現像剤を現像剤担持体から離脱させるための離脱用磁界を発生させる離脱用磁極を備えた磁界発生手段を上記現像剤担持体の内部に備え、
上記磁界発生手段の離脱用磁極は、上記現像剤担持体回転軸方向一部分に対応する部分が、当該部分で形成される剥離用磁界の作用によって離脱する二成分現像剤が上記現像剤供給搬送路へ向かうように構成され、上記現像剤担持体回転軸方向他部分に対応する部分が、当該部分で形成される剥離用磁界の作用によって離脱する二成分現像剤が上記現像剤回収搬送路へ向かうように構成されていることを特徴とする現像装置。 The developing device according to claim 2 .
Provided inside the developer carrier is a magnetic field generating means provided with a separation magnetic pole for generating a separation magnetic field for separating the two-component developer that has passed through the development region from the developer carrier.
The separation magnetic pole of the magnetic field generating means has a portion corresponding to a part of the developer carrier rotating shaft in a direction corresponding to a part of the rotation direction of the developer carrier. The two-component developer separated from the portion corresponding to the other portion in the direction of the rotation axis of the developer carrying member by the action of the peeling magnetic field formed in the portion is directed to the developer collection conveyance path. A developing device configured as described above. 請求項１に記載の現像装置において、
現像領域を通過した二成分現像剤を現像剤担持体から離脱させるための離脱用磁界を発生させる離脱用磁極を備えた磁界発生手段を上記現像剤担持体の内部に備え、
上記一部戻し手段は、現像剤担持体回転軸方向一部分について、上記現像剤供給搬送路と対向する位置で現像剤担持体から二成分現像剤が離脱して上記現像剤供給搬送路に戻るように上記離脱用磁極を構成したものであり、
現像剤担持体回転軸方向他部分については、上記現像剤回収搬送路と対向する位置で二成分現像剤が離脱するように上記離脱用磁極が構成されていることを特徴とする現像装置。 The developing device according to claim 1 ,
Provided inside the developer carrier is a magnetic field generating means provided with a separation magnetic pole for generating a separation magnetic field for separating the two-component developer that has passed through the development region from the developer carrier.
The partial return means is configured so that the two-component developer separates from the developer carrying member and returns to the developer supplying and conveying path at a position facing the developer supplying and conveying path with respect to a part of the developer carrying member in the rotation axis direction. Is configured with the above-mentioned separation magnetic pole,
The developing magnetic apparatus according to claim 1, wherein the separation magnetic pole is configured so that the two-component developer is separated at a position facing the developer collection conveyance path for the other portion in the developer carrying member rotation axis direction. 請求項１乃至４のいずれか１項に記載の現像装置において、
上記現像剤供給搬送路は、上記現像剤担持体の下方に配置されており、
上記現像剤回収搬送路は、上記現像剤供給搬送路の下方に配置されており、
現像領域を通過して現像剤担持体から離脱した他部の二成分現像剤を、上記現像剤供給搬送路を迂回して上記現像剤回収搬送路へ案内する案内通路を形成したことを特徴とする現像装置。 The developing device according to any one of claims 1 to 4 ,
The developer supply transport path is disposed below the developer carrier,
The developer recovery transport path is disposed below the developer supply transport path,
A guide passage is formed that guides the other two-component developer that has passed through the development region and separated from the developer carrying member to the developer collection transport path, bypassing the developer supply transport path. Developing device. 請求項１乃至５のいずれか１項に記載の現像装置において、
上記現像剤回収搬送路内の二成分現像剤にトナーを補給するためのトナー補給口を、該現像剤回収搬送路の現像剤搬送方向上流側部分に設けたことを特徴とする現像装置。 The developing device according to any one of claims 1 to 5 ,
2. A developing device according to claim 1, wherein a toner replenishing port for replenishing toner to the two-component developer in the developer collecting and conveying path is provided in an upstream portion of the developer collecting and conveying path in the developer conveying direction. 潜像担持体と、該潜像担持体上に潜像を形成する潜像形成手段と、トナー及びキャリアを含む現像剤により該潜像担持体上の潜像を現像する現像装置とを有し、該現像装置により該潜像担持体上に形成されたトナー像を最終的に記録材へ転移させて、該記録材上に画像を形成する画像形成装置において、
上記現像装置として、請求項１乃至６のいずれか１項に記載の現像装置を用いたことを特徴とする画像形成装置。 A latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developing device for developing the latent image on the latent image carrier with a developer containing toner and a carrier. In the image forming apparatus for finally transferring the toner image formed on the latent image carrier by the developing device to a recording material and forming an image on the recording material,
As the developing device, an image forming apparatus characterized by using the developing apparatus according to any one of claims 1 to 6.
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