上記目的を達成するために、請求項１の発明は、キャリアとトナーとからなる現像剤を表面に担持して回転し、潜像担持体と対向する領域で該潜像担持体の表面の潜像にトナーを供給して現像する現像剤担持体と、該現像剤担持体の軸方向に沿って該現像剤を搬送しながら該現像剤担持体に供給する現像剤供給搬送部材を有する供給搬送路と、該現像剤担持体から現像終了後の現像剤を回収するとともに、回収現像剤を該現像剤供給搬送部材と平行でかつ同方向へ搬送する現像剤回収搬送部材を有する回収搬送路と、現像に用いられずに該供給搬送路の搬送方向の下流側まで搬送された余剰現像剤と、該現像剤担持体から回収され該回収搬送路の搬送方向の下流側まで搬送された回収現像剤との供給を受け、該余剰現像剤と該回収現像剤とを攪拌しながら該現像剤供給搬送部材と平行でかつ逆方向に搬送する現像剤攪拌搬送部材を有する攪拌搬送路と、現像でトナー消費された該回収現像剤にトナーを補給するトナー補給手段とを備え、該回収搬送路は該攪拌搬送路の重力方向上方に位置し、該回収搬送路の下流側で該攪拌搬送路との間の回収現像剤供給開口部を介して該回収搬送路の回収現像剤を自然落下で該攪拌搬送路に供給し、該供給搬送路の下流側で該攪拌搬送路との間の余剰現像剤供給開口部を介して該供給搬送路の該余剰現像剤を該攪拌搬送路に供給し、該攪拌搬送路の下流側で該供給搬送路との間の攪拌現像剤開口部を介して該回収現像剤と該余剰現像剤とを攪拌した後の攪拌現像剤を該供給搬送路に供給することで現像剤を循環搬送する現像装置において、上記回収現像剤供給開口部が上記回収搬送路の下流にいくに従い広くなるよう構成し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の現像装置において、上記回収現像剤供給開口部の上流端部が狭く、下流端部が広い台形形状である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１の現像装置において、上記回収現像剤供給開口部は、上記現像剤が通過容易な大きさの開口を複数の配置したものであり、下流にいくに従い該開口の数を増やしたものであ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、２または３の現像装置において、上記供給搬送路と上記撹拌搬送路とは仕切り部材によって仕切られており、上記余剰現像剤供給開口部は、上記供給搬送路の最下流部で上記攪拌搬送路との間の仕切り部材の下方で少なくとも上記現像剤攪拌搬送部材の中心軸より高さの低い部分を残して該仕切り部材に開口を設けたものであ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、２、３または４の現像装置において、上記余剰現像剤開口部の開口幅を、上記現像剤攪拌搬送部材のスクリュピッチよりも狭くする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、２、３、４または５の現像装置において、上記供給搬送路を上記攪拌搬送路よりも上記現像剤供給搬送部材の高さの半分以内の範囲で高い位置に設けることを特徴とするものである。
また、請求項７の発明は、請求項１、２、３、４、５または６の現像装置において、上記現像剤はトナーとキャリアからなる二成分現像剤であり、該キャリアは体積平均粒径が２０〜６０［μｍ］であることを特徴とするものである。
また、請求項８の発明は、請求項１、２、３、４、５、６または７の現像装置において、上記現像剤はトナーとキャリアからなる二成分現像剤であり、該トナーは体積平均粒径が３〜８［μｍ］で、体積平均粒径（Ｄ4）と個数平均粒径（Ｄ１）との比（Ｄ4／Ｄ１）が１．００〜１．４０の範囲にあることを特徴とするものである。
また、請求項９の発明は、請求項８の現像装置において、上記トナーは、形状係数ＳＦ−１が１００〜１８０の範囲にあり、形状係数ＳＦ−２が１００〜１８０の範囲にあることを特徴とするものである。
また、請求項１０の発明は、請求項８の現像装置において、上記トナーはトナー母体粒子表面に平均一次粒径が５０〜５００ｎｍで、嵩密度が０．３ｇ/ｃｍ３以上の微粒子を外添加して得られたトナーであることを特徴とするものである。
また、請求項１１の発明は、請求項１、２、３、４、５、６、７、８、９または１０の現像装置において、上記現像剤撹拌搬送部材が供給をうける余剰現像剤や回収現像剤は、上記供給搬送路や上記回収搬送路において搬送方向の最下流部まで搬送されたものであることを特徴とするものである。
また、請求項１２の発明は、請求項１、２、３、４、５、６、７、８、９、１０または１１の現像装置において、上記回収搬送路、該供給搬送路及び該攪拌搬送路の３つの現像剤搬送路をそれぞれ仕切る仕切り部材を有し、上記回収現像剤供給開口部、上記余剰現像剤供給開口部及び上記撹拌現像剤開口部は、該仕切部材に形成した開口によって形成されることを特徴とするものである。
また、請求項１３の発明は、静電潜像を担持する潜像担持体と、該潜像担持体上に静電潜像を形成する潜像形成手段と、該潜像担持体上の静電潜像をトナー像化する現像する現像手段と、該トナー像を非転写体に転写する転写手段とを備えた画像形成装置において、上記現像手段として請求項１、２、３、４、５、６、７、８、９、１０、１１または１２の現像装置を用いることを特徴とするものである。
また、請求項１４の発明は、請求項１３の画像形成装置において、複数の像担持体と該像担持体上にそれぞれトナー像を形成する現像装置とを有する第一画像形成ユニット群と、該第一画像形成ユニット群の複数の像担持体上に形成されたトナー像を順次転写された第一重ね合わせトナー像を担持する第一トナー像担持ベルトとを有する第一画像ステーションと、複数の像担持体と該像担持体上にそれぞれトナー像を形成する現像装置とを有する第二画像形成ユニット群と、該第二画像形成ユニット群の複数の像担持体上に形成されたトナー像を順次転写された第二重ね合わせトナー像を担持する第二トナー像担持ベルトとを有する第二画像ステーションとを備え、該第一画像ステーションにより形成された該第一重ね合わせトナー像を第一トナー像担持ベルトより記録媒体の第一面に、該第二画像ステーションにより形成された該第二重ね合わせトナー像を該第二トナー像担持ベルトより記録体の第二面に、同時もしくは順次に転写する両面転写方式であることを特徴とするものである。
また、請求項１５の発明は、請求項１４の画像形成装置において、上記複数の現像装置に補給する各色トナーを貯蔵するトナー貯蔵部を備え、第一画像形成ユニットで使用されるトナーと第二画像形成ユニットで使用されるトナーは、同一の各色のトナー貯蔵部から供給する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 is characterized in that a developer composed of a carrier and a toner is carried on the surface and rotated, and the latent image carrier surface is latent in a region facing the latent image carrier. Supply carrier having a developer carrier for supplying toner to an image for development and a developer supply / conveying member for feeding the developer to the developer carrier while transporting the developer along the axial direction of the developer carrier A recovery transport path having a developer recovery transport member that recovers the developer after completion of development from the developer carrying member and transports the recovered developer in parallel and in the same direction as the developer supply transport member; , conveyed and excess developer without being used for development has been conveyed to the lower stream side in the transport direction of the supply conveyance path is recovered from the developer carrying member to the lower stream side in the transport direction of the collection conveyance path The supply of the recovered developer, the excess developer and the recovered developer A stirring conveyance path having a developer stirring and conveying member for conveying parallel to and opposite direction and the developer supply conveyance member while拌, to the collected developer that is toner consumption in the developing and toner replenishing means for replenishing toner provided, the recovery path is located upward in the gravity direction of the stirring conveyance path, the collection conveyance path through the recovered developer supply opening between the the stirring conveyance path under flow side of the collection conveyance path to supply the recovered developer in the stirring conveyance path in free fall, the excess of the supply conveyance path through the surplus developer supply opening between the the stirring conveyance path under flow side of the supply conveyance path the developer is supplied to the stirring conveyance path, and stirred and the collected developer and the excess developer under flow side of the stirring conveyance path via the 攪拌現image agent opening between the supply conveyance path In the developing device that circulates and conveys the developer by supplying the subsequent agitated developer to the supply and conveyance path, Developer supply opening and is characterized in that it has configured to be wider as it goes downstream of the collection conveyance path.
According to a second aspect of the present invention, in the developing device of the first aspect, the recovered developer supply opening has a trapezoidal shape with a narrow upstream end and a wide downstream end.
According to a third aspect of the present invention, in the developing device according to the first aspect, the recovered developer supply opening includes a plurality of openings of a size that allows the developer to easily pass through. The number of openings is increased.
According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, the supply conveyance path and the agitation conveyance path are partitioned by a partition member, and the excess developer supply opening is An opening is provided in the partition member at the most downstream portion of the supply conveyance path, below the partition member between the supply conveyance path and at least a portion lower than the central axis of the developer agitation conveyance member. It is characterized by being.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, an opening width of the excess developer opening is narrower than a screw pitch of the developer agitating / conveying member. It is what.
Further, the invention of claim 6 is the developing device of claim 1, 2, 3, 4 or 5, wherein the supply transport path is within half the height of the developer supply transport member relative to the stirring transport path. It is characterized by being provided at a high position.
The invention of claim 7 is the developing device of claim 1, 2, 3, 4, 5 or 6, wherein the developer is a two-component developer comprising a toner and a carrier, and the carrier has a volume average particle diameter. Is 20 to 60 [μm].
The invention of claim 8 is the developing device according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the developer is a two-component developer comprising a toner and a carrier, and the toner has a volume average. The particle size is 3 to 8 [μm], and the ratio (D4 / D1) of the volume average particle size (D4) to the number average particle size (D1) is in the range of 1.00 to 1.40. To do.
According to a ninth aspect of the present invention, in the developing device according to the eighth aspect, the toner has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. It is a feature.
The toner according to claim 10 is the developing device according to claim 8, wherein the toner is externally added with fine particles having an average primary particle size of 50 to 500 nm and a bulk density of 0.3 g / cm 3 or more on the surface of the toner base particles. The toner thus obtained is characterized by the following.
The invention according to claim 11 is the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the developer agitating / conveying member is supplied with excess developer or recovered. The developer is transported to the most downstream portion in the transport direction in the supply transport path and the recovery transport path.
A twelfth aspect of the invention is the developing device according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or eleventh aspects of the invention. A partition member for partitioning each of the three developer transport paths of the path, and the recovered developer supply opening, the excess developer supply opening, and the agitated developer opening are formed by openings formed in the partition member It is characterized by that.
Further, according to claim 1 3 invention includes a latent image bearing member for bearing an electrostatic latent image, a latent image forming means for forming an electrostatic latent image on the latent image bearing member, on the latent image bearing member An image forming apparatus comprising: a developing unit that develops an electrostatic latent image into a toner image; and a transfer unit that transfers the toner image to a non-transfer body. 5 , 6 , 7 , 8 , 9 , 10, 11 or 12 developing device is used.
The invention of claims 1 to 4, in the image forming apparatus according to claim 1 3, a first image forming unit group and a developing device for forming a respective toner image on multiple image bearing member and the image bearing member A first image station having a first toner image carrying belt carrying a first superimposed toner image to which toner images formed on a plurality of image carriers of the first image forming unit group are sequentially transferred; A second image forming unit group having a plurality of image carriers and a developing device for forming a toner image on each of the image carriers; and a toner formed on the plurality of image carriers in the second image forming unit group A second image station having a second toner image carrying belt carrying a second superimposed toner image onto which images are sequentially transferred, and the first superimposed toner image formed by the first image station is a first image station. The second superimposed toner image formed by the second image station is transferred from the toner image carrying belt to the first surface of the recording medium simultaneously or sequentially from the second toner image carrying belt to the second surface of the recording medium. It is a double-sided transfer system for transferring.
The invention of claim 1 5, in the image forming apparatus according to claim 1 4, comprising a toner storage unit for storing respective color toners to be supplied to said plurality of developing devices, a toner used in the first image forming unit The toner used in the second image forming unit is supplied from the same color toner storage unit.