JP3705959B2 - Development device - Google Patents

Description

【００３２】
【表２】

【００３３】
【表３】

【００３４】
【表４】

【００３５】
上述の表１及び表２のデータから、本実施例１〜３では、可動マグネットが回転スリーブと逆方向回転であるため、固定スリーブ上に残る現像剤が少なく、可動マグネットと第１極間のシールド磁力及び可動マグネットと第２極間の拘束磁力が第１極と第２極間の水平磁力を防ぐので、現像剤を遮断する事が出来た。
また、この実施例１〜３においては、穂切り時に回転スリーブ２１を回転させたまま現像剤を遮断しているので、回転スリーブを停止させることによりさらに良く現像剤を遮断出来ることが理解される。
【００３６】
一方、比較例１は実施例１〜３と磁力は同じである。しかし、可動マグネット２３の回転方向を回転スリーブ２１と同じ方向にすると、図６に示す様に可動マグネット２３が第２停止位置に近づいていくときにＮ_Ａ極と第１極（Ｓ極）間の磁力線上に２４ａの如く一旦現像剤が持ち上げられる。
この現像剤が可動マグネット２３側と回転スリーブ２１側に分かれる。回転スリーブ２１側の現像剤は回収されて行くが、可動マグネット２３側のＮ_Ａ部分に残る現像剤が多く、回転スリーブ２１が回転しているので、現像剤を確実に遮断することが出来なかった。
【００３７】
実施例４〜７は、穂切り時に回転スリーブを停止させたので回転による現像剤搬送力を防止し現像剤を遮断することが出来た。
それに対して比較例２〜５は、可動マグネット２３の回転方向を回転スリーブ２１と逆方向にしているが、穂切り時に回転スリーブ２１が回転しているため、磁気拘束力以上にスリーブの回転による搬送力が強くなり現像剤が漏れてきた。
【００３８】
実施例８〜１０は、実施例４〜７と同様に可動マグネット２３の回転方向を回転スリーブ２１と逆方向にしたので現像剤を遮断することが出来た。
また、比較例６〜９は回転スリーブを回転させ、可動マグネットを順方向回動させたので現像剤を遮断することが出来なかった。
【００３９】
尚、穂切り時の可動マグネットの停止位置が表２に開示している範囲を超えると穂切りできなくなる。（表４の−３０°〜３０°とは表２に開示している範囲を超えた部分を指す。即ち−３０°〜３０°（−５°〜５°、−１０°〜−２５°及び１０°〜２０°を除く）である。）
また、回転スリーブ２１と固定スリーブ２２の最近接点（ブレード位置）から垂直磁力０ガウス点が離れると最近接点での垂直磁力が大きくなり、現像時にスリーブ間を通過する現像剤の圧力が高くなりトルクアップを招くことからも好ましくない。
また、穂切り時の可動マグネットの停止位置が極端に第１極や第２極に近いとマグネット同士の反発や吸引による部材の反りを生じるため、好ましくない。
【００４０】
なお、可動マグネット２３の主極の磁力を上げればシールド磁力、拘束磁力が強くなり水平磁力を遮断する力も強くなるが、可動マグネット２３と固定マグネット２０間の吸引磁力によるマグネットや部材の反りが生じやすくなるので出来るだけ低磁力が望ましい。
また、本実施例の磁力関係が成立していれば回転スリーブの外径は特に指定しないが、好ましくは１５〜２５mmである。
【００４１】
【発明の効果】
以上、詳細に説明したように本発明の現像装置によれば、穂切り時に固定マグネットローラと可動マグネット間のホールド磁力と拘束磁力が完全に固定マグネットローラの水平磁力を遮断するように構成したので、現像を行っている以外の現像装置から現像剤が混入するのを遮断することができる。
さらに、可動マグネットの回転方向、回転スリーブの回転を制御することで機能を上げることができる。
また、現像剤の混入を遮断するのに磁気拘束力を利用しているので、従来のようにゴムブレードを回転スリーブに接触させて現像剤を遮断する必要がなく、ブレードと現像剤の摩擦によるブレードや現像剤の劣化が無くなり、ブレードの耐久性向上により現像装置の耐久性を上げることができる。
また、現像剤の混入を遮断するのに磁気拘束力を利用しているので現像装置を退避させる空間や複雑な機構を必要とせず、装置の簡素化、高速化、小型化、コストダウンをすることができる。
等の種々の著効を有す。
【図面の簡単な説明】
【図１】 本発明の実施の形態に係る要部構成を示す断面図である。
【図２】 現像状態を説明する説明図である（Ａ）。現像装置が穂切りを始めた状態を示す説明図である（Ｂ）。現像装置の穂切り状態を示す概略図である（Ｃ）。
【図３】 可動マグネットの形状を示す斜視図である。
【図４】 可動マグネットの断面図である。
【図５】 可動マグネットの逆方向回動時の動作説明図である。
【図６】 可動マグネットの順方向回動時の動作説明図である。
【符号の説明】
１ 感光体ドラム
２０ 固定マグネットローラ
２１ 回転スリーブ
２２ 固定スリーブ
２３ 可動マグネット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device that performs development by electrophotographic development using a developer (toner) such as a copying machine, a printer, and a fax machine, and in particular, a fixed magnet roller having a north pole and a south pole magnetized as a developing carrier. The present invention relates to a developing device using a rotating sleeve included therein.
[0002]
[Prior art]
Using a rotating sleeve containing a fixed magnet roller magnetized with N and S poles as the developer carrying member, the developer accumulated in the developer container using the magnetic carrying force formed on the rotating sleeve A developing device in which a layer thickness is regulated using a layer thickness regulating member while being carried, and then guided to a developing position on a photoreceptor is well known.
[0003]
In particular, in the case of multi-color development by the two-component development method, a developing device for each color (yellow, magenta, cyan, black) is required, and the developer is supplied from a developing device other than the developing device that performs the development. It is necessary to block contamination.
2. Description of the Related Art Conventionally, there is a developing device provided with a retracting mechanism that rotates or retracts a developing device that is not performing development as a developer mixing blocking means.
In order to reduce the size of the apparatus, there is a method in which a regulating plate such as a rubber blade is brought into contact with the upstream side of the developing position on the rotating sleeve so as to block the mixing of the developer. (See JP-A-59-60453 and JP-A-6-242666).
[0004]
[Problems to be solved by the invention]
However, since the retractable developing device requires a space for retracting the developing device and a complicated mechanism, there is a problem that the device is increased in size and cost.
In the contact blade method, the problem is that it is difficult to save power because the rotational torque increases, and even when the blade is pressed against the rotating sleeve, scratches occur and the blade is separated from the rotating sleeve. Since friction occurs due to the passage of the developer, there is a problem in terms of durability of the blade, and further, the developer deteriorates because the developer is damaged when passing between the developing roller and the blade. There was also a problem.
[0005]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that prevents a developer from being mixed in from a developing device other than a developing device that performs development.
Another object of the present invention is to provide an image forming apparatus capable of completely blocking the conveyance from the developing device to the photosensitive roller side, thereby preventing the deterioration of the developer and extending the life of the blade.
Another object of the present invention is to simplify, increase the speed, reduce the size, and reduce the cost by using the magnetic force of the fixed magnet roller in the rotating sleeve and the movable magnet arranged to face the fixed magnet roller. An image forming apparatus is provided.
[0006]
[Means for Solving the Problems]
In the present invention, a rotating sleeve containing a fixed magnet roller having a plurality of permanent magnets magnetized with an N pole and an S pole is disposed facing the photosensitive drum, and development is performed to the developing position on the photosensitive drum by the rotating sleeve. In the developing device for guiding the agent,
A fixed sleeve disposed on the upstream side in the rotation direction of the rotary sleeve with a predetermined gap between the rotary sleeve and the outer periphery;
One or more movable magnets disposed within the fixed sleeve and capable of rotating between a first stop position located during development and a second stop position located during non-development;
A first pole of the fixed magnet roller disposed on the developing position side in the rotating sleeve and the fixed magnet roller disposed on the anti-development position side with the closest contact point between the fixed sleeve and the rotating sleeve interposed therebetween. The second pole of
The first stop position is located in the fixed sleeve and does not affect the magnetic force of the fixed magnet roller during development, and the second stop position is between the magnetic pole of the movable magnet and the first pole of the rotary sleeve. In addition to making a magnetic shield by a repulsive magnetic field, each position is set to a position where a magnetic binding force is created by an attractive magnetic field between the magnetic force of the movable magnet and the second pole of the rotating sleeve ,
At the time of development, the basic configuration is that the movable magnet is retracted to the first stop position and the developer can be supplied to the development position side.
[0007]
The developing device according to the basic configuration includes a rotating sleeve including a fixed magnet roller magnetized with N and S poles, and a rotating direction of the rotating sleeve from the developing position with a predetermined gap between the rotating sleeve and an outer periphery. The rotating sleeve is arranged on the upstream side and includes a fixed sleeve containing one or more movable magnets that can be rotated and stopped at a non-developing position. However, the outer periphery of the rotating sleeve and the outer periphery of the fixed sleeve can be set and arranged mechanically with high precision, and a constant developer layer thickness can be regulated.
[0008]
According to the first aspect of the present invention, at the time of non-development, the movable magnet rotates in the direction opposite to the rotation direction of the rotary sleeve toward the side approaching the rotary sleeve and stops at the second stop position. The supply of developer to the developing position side is shut off, and the developer on the rotating sleeve is collected.
[0009]
Therefore, at the time of non-development, the movable magnet rotates in the direction opposite to the rotation direction of the rotary sleeve toward the side approaching the rotary sleeve, stops at the second stop position, and moves to the fixed magnet roller side. The magnetic force between the movable magnet and the first pole, and the magnetic force between the movable magnet and the second pole block the magnetic field lines between the second pole and the first pole. Transport of the developer to the development position on the photosensitive drum side is blocked.
[0010]
And since the said movable magnet rotates in the direction opposite to the rotation direction of the said rotation sleeve to the side approaching the said rotation sleeve, and stops at the said 2nd stop position, by rotating in a forward direction, the said rotation sleeve The developer on the upper development position side is attracted by the movable magnet, and the developer is lifted up. The developer is divided into the movable magnet side and the rotating sleeve side, so that it hardly adheres to the fixed sleeve and blocks the developer. And can be recovered.
[0011]
According to the second aspect of the present invention, in addition to the basic structure, when not developing, the movable magnet rotates to the side closer to the rotary sleeve and stops at the second stop position, and the developer moves toward the development position side. And the rotation sleeve is stopped after completion of the collecting operation of the developer on the rotating sleeve, and after the collecting operation of the developer on the rotating sleeve is completed. By stopping the rotating sleeve, since there is no developer at the position facing the photosensitive member of the rotating sleeve during non-development, the developing device does not develop the photosensitive member.
[0012]
In addition, a perpendicular magnetic force peak of a magnetic pole opposite to the second pole of the fixed magnet among the magnetic poles of the movable magnet at the second stop position is located between the second pole and the first pole, It is also an effective means of the first invention that the rotary sleeve is stopped after the developer collecting operation on the rotary sleeve is completed.
[0013]
Since the perpendicular magnetic force peak of the magnetic pole opposite to the second pole of the fixed magnet of the movable magnet is located between the second pole and the first pole, the developer is completely blocked and the rotation By stopping the rotating sleeve after the developer collecting operation on the sleeve is completed, there is no developer at a position facing the photosensitive member of the rotating sleeve at the time of non-development, so that the developing device develops the photosensitive member. There is no.
[0014]
As described above, the present invention can provide an image forming apparatus that prevents a developer from being mixed in from a developing device other than a developing device that performs development.
In the present invention, the developer is transported and blocked using the magnetic restraint force of the fixed magnet roller in the rotating sleeve and the movable magnet arranged facing the fixed magnet roller without moving the developing device. Therefore, the image forming apparatus can be simplified, increased in speed, reduced in size, and reduced in cost.
[0015]
In addition, since the developer sleeve is not used for the developing sleeve and the conveyance from the developing device to the photosensitive roller side is completely blocked by magnetic force, the fixed sleeve does not move even if the developing sleeve rotates. At the time of shut-off, there is little movement of the developer, so that the deterioration of the developer is prevented, and the life of the developing device is prevented by shortening the life of the developing device due to wear of the developing sleeve or the developer blocking blade. Can be planned.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
[0017]
FIG. 1 is a sectional view of the entire image forming apparatus according to an embodiment of the present invention.
A sheet feeding cassette (not shown), a photosensitive drum 1, an optical scanning unit 2, a charger 3, four developing devices 4 to 7 including a developer container, an intermediate transfer member 12, a secondary transfer roller 13, a fixing device 14, The recording medium 8 having the image transferred thereon is composed of a conveying device 9 using an endless belt for conveying the recording medium 8 from the secondary transfer roller 13 to the fixing device 14.
[0018]
At the time of printing, the photosensitive drum 1 is charged by the charger 3 for each color, and the image scanned by the optical scanning unit 2 and developed by the developing devices 4 to 7 is transferred to the intermediate transfer body 12, and a paper feeding cassette (not shown) Then, the image is transferred to the recording medium 8 conveyed by the secondary transfer roller 13 and fixed by heating and pressurizing by the fixing device 14 to be discharged.
[0019]
FIG. 2 is a cross-sectional view showing the vicinity of the developing position where the developer flies to the photosensitive drum 1 of the developing device 4, and includes a fixed magnet roller 20 having permanent magnets magnetized on the N pole and the S pole, and the fixed magnet roller. A rotation sleeve 21 containing the rotation sleeve 21, a fixed sleeve 22 disposed upstream of the developing position A of the rotation sleeve 21 in the rotation direction, and a main pole rotatable about the center of the fixed sleeve 22 as a central axis 23a. A sub-pole that appears at both ends is arranged with an N-pole movable magnet 23.
[0020]
As shown in FIGS. 3 and 4, the movable magnet 23 is formed in a sector fan shape as an axial center 23e of the central shaft 23a, and an outer peripheral surface 23d having a radius r from the axial center 23e is a circumferential surface on the S pole. Fan-shaped inclined surfaces 23b and 23c formed at an angle θ from 23e are magnetized so as to be the N poles of NB and NA, respectively.
[0021]
The developing device 4 during development uses the magnetic force of the fixed magnet roller 20 when the movable magnet 23 is stopped at a position that does not affect the magnetic force of the fixed magnet roller 20 as shown in FIG. Then, after the developer 24 carried on the rotating sleeve 21 is brought into contact with the peripheral surface of the fixed sleeve 22 to regulate the layer thickness, the developer 24 can be guided to the developing position A on the photosensitive drum 1 (hereinafter, FIG. 2). The state of the developing unit (A) is called heading).
The developer layer thickness regulation is determined by the distance d between the rotating sleeve 21 and the fixed sleeve 22.
[0022]
However, if the developer is supplied to the rotating sleeves 21 included in the developing devices 5 to 7 other than the developing device, the developer may be mixed into other developing devices in the heading or the toner on the photosensitive drum 1. Disturb the image. In order to prevent this, when the rotating magnet 23 is moved to the vicinity of the closest contact point of the rotating sleeve 21 as shown in FIG. 2B, the developing devices other than the developing device supply the developer to the rotating sleeve. (Hereinafter, the state of the developing device in FIG. 2B is referred to as ear cutting).
[0023]
Hereinafter, the operation of the developing device will be described with reference to FIG.
2A, at the closest point of contact between the rotating sleeve 21 and the fixed sleeve 22 (hereinafter referred to as the blade position), the lines of magnetic force pass through the magnet from the first pole (S pole) of the rotating sleeve 21. It is directed to the 2 pole (N pole), and the outside of the magnet is generated from the second pole (N pole) to the first pole (S pole) to form a closed ring.
[0024]
In addition, the third pole (N pole) and the first pole (S pole) arranged opposite to the development position A are magnetic lines of force in the magnet from the first pole (S pole) to the third pole (N). It is generated from the third pole (N pole) to the first pole (S pole), and forms a closed ring.
Along the magnetic force lines, the developer is transported to the development position A via the first pole by the conveying force generated by the rotation of the rotary sleeve 21 and develops the latent image on the photosensitive drum 1.
[0025]
After development, the movable magnet 23 rotates as shown in FIG. 2B, and the main pole (S pole) stops at the blade position 0 °. At this time, a magnetic shield (hereinafter referred to as a shield magnetic force) is formed between the S pole of the movable magnet 23 and the first pole of the rotating sleeve 21, and the developer on the rotating sleeve 21 develops at the developing position A with this magnetic field as a boundary. It is separated from the side and the position of the blade (FIG. 2B).
[0026]
After the separation, the developer on the developing position A side is collected in the developing device 4 by the rotation of the rotating sleeve 21. Further, an attractive magnetic field (hereinafter referred to as binding magnetic force) from the main pole (S pole) of the movable magnet 23 to the second pole of the rotating sleeve 21 is generated at the same time, and the developer inside the blade position is between these poles. Be bound.
[0027]
These shield magnetic force and restraining magnetic force block the magnetic line of force that is the transfer magnetic force between the second pole and the first pole pole of the rotating sleeve 21, so that the magnetic line of force does not pass between the second pole and the first pole pole, and the developer is on the rotating sleeve. Is stopped in the state of FIG. In this way, it is possible to prevent the developer from being mixed into another developing device and to disturb the toner image on the photoreceptor.
[0028]
Next, the developer blocking and collecting operations in the reverse direction and the forward direction of the movable magnet 23 will be described with reference to FIGS. 5 and 6.
5, there is Fukukyoku the main pole ends of the movable magnet 23 (N _A pole, and N _B pole), magnetic force lines and the second pole of the fixed magnet 20 (N pole) → the main pole of the movable magnet 23 (S It flows to pole) → N _a pole → first pole (S-pole), but the developer according to the magnetic lines of force is likely to be conveyed, when the rotation direction of the movable magnet 23 to rotate in the opposite direction of the rotating sleeve 21, already developer separation when the movable magnet 23 approaches the second stop position, and since the beginning to be recovered without the developer is magnetically bound to N _a pole, to block the developer more reliably it can.
[0029]
In contrast, as shown in FIG. 6, when the rotation direction of the movable magnet 23 in the same direction as the rotary sleeve 21, N _A pole and first pole when the movable magnet 23 approaches the second stop position ( The developer is once lifted up like 24a by the magnetic field lines between the S poles).
This developer is divided into the movable magnet 23 side and the rotating sleeve 21 side. Developer of the rotary sleeve 21 side is going to be recovered, but the developer side of the movable magnet 23 is unstable because may remain in N _A portion, to reliably cut off the easily developer flies over the rotating sleeve 21 I can't.
[0030]
Next, Table 1 and Table 2 show measurement data obtained by changing the conditions of the fixed magnet 20 and the movable magnet 23 and measuring the presence / absence of ear cutting. Note that the surface state of the photosensitive drum was observed to determine that no developer was found, and the surface state of the rotating magnet and the fixed magnet on the photosensitive drum side was also observed. Table 1 and Table 2 describe what can be cut as an example, and Table 3 and Table 4 describe what cannot be cut as a comparative example.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
[Table 3]

[0034]
[Table 4]

[0035]
From the data in Table 1 and Table 2 described above, in Examples 1 to 3, the movable magnet rotates in the reverse direction to the rotating sleeve, so that there is little developer remaining on the fixed sleeve, and between the movable magnet and the first pole. Since the shielding magnetic force and the binding magnetic force between the movable magnet and the second pole prevent the horizontal magnetic force between the first pole and the second pole, the developer can be blocked.
Further, in Examples 1 to 3, since the developer is shut off while rotating the rotary sleeve 21 at the time of cutting the ear, it is understood that the developer can be cut off better by stopping the rotary sleeve. .
[0036]
On the other hand, the magnetic force of Comparative Example 1 is the same as that of Examples 1 to 3. However, when the rotation direction of the movable magnet 23 in the same direction as the rotary sleeve 21, N _A pole and the first pole (S pole) when the movable magnet 23 as shown in FIG. 6 approaches the second stop position between The developer is once lifted on the magnetic field lines as shown by 24a.
This developer is divided into the movable magnet 23 side and the rotating sleeve 21 side. Developer of the rotary sleeve 21 side is going to be recovered, many developer remaining in N _A portion of the movable magnet 23 side, the rotational sleeve 21 is rotating, can not be reliably cut off the developer It was.
[0037]
In Examples 4 to 7, the rotating sleeve was stopped when cutting the ears, so that the developer conveying force due to the rotation was prevented and the developer could be shut off.
On the other hand, in Comparative Examples 2 to 5, the rotation direction of the movable magnet 23 is opposite to that of the rotation sleeve 21, but the rotation sleeve 21 is rotated at the time of trimming, so that the rotation of the sleeve exceeds the magnetic binding force. The conveyance force became stronger and the developer leaked.
[0038]
In Examples 8 to 10, as in Examples 4 to 7, the rotation direction of the movable magnet 23 was opposite to that of the rotating sleeve 21, so that the developer could be blocked.
In Comparative Examples 6 to 9, the rotating sleeve was rotated and the movable magnet was rotated in the forward direction, so that the developer could not be blocked.
[0039]
In addition, if the stop position of the movable magnet at the time of ear cutting exceeds the range disclosed in Table 2, the ear cannot be cut. (In Table 4, −30 ° to 30 ° refers to a portion beyond the range disclosed in Table 2. That is, −30 ° to 30 ° (−5 ° to 5 °, −10 ° to −25 ° and Except 10 ° to 20 °).
Further, when the perpendicular magnetic force 0 gauss point moves away from the closest contact (blade position) between the rotating sleeve 21 and the fixed sleeve 22, the perpendicular magnetic force at the closest contact increases, and the pressure of the developer passing between the sleeves during development increases and the torque increases. It is not preferable because it causes an increase.
Further, it is not preferable that the stop position of the movable magnet at the time of trimming is extremely close to the first pole or the second pole, because repulsion between the magnets or warping of the member due to suction occurs.
[0040]
If the magnetic force of the main pole of the movable magnet 23 is increased, the shielding magnetic force and the binding magnetic force are increased and the horizontal magnetic force is also blocked. However, the magnet or member is warped by the attractive magnetic force between the movable magnet 23 and the fixed magnet 20. Since it becomes easy, low magnetic force is desirable.
Moreover, if the magnetic force relationship of a present Example is materialized, the outer diameter of a rotation sleeve will not be specified in particular, However, Preferably it is 15-25 mm.
[0041]
【The invention's effect】
As described above in detail, according to the developing device of the present invention, since the hold magnetic force and the restraining magnetic force between the fixed magnet roller and the movable magnet are completely cut off from the horizontal magnetic force of the fixed magnet roller at the time of cutting the ear. Further, it is possible to block the developer from being mixed in from a developing device other than the developing device.
Furthermore, the function can be improved by controlling the rotation direction of the movable magnet and the rotation of the rotation sleeve.
In addition, since the magnetic restraint force is used to block the mixing of the developer, it is not necessary to block the developer by bringing the rubber blade into contact with the rotating sleeve as in the prior art, and the friction between the blade and the developer is not necessary. The blade and the developer are not deteriorated, and the durability of the developing device can be improved by improving the durability of the blade.
In addition, the magnetic restraint force is used to block the mixing of the developer, so there is no need for a space for retracting the developing device or a complicated mechanism, and the device is simplified, speeded up, miniaturized, and reduced in cost. be able to.
It has various effects such as.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part configuration according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining a development state (A). It is explanatory drawing which shows the state which the developing apparatus started the ear cutting (B). FIG. 2C is a schematic diagram showing a state of cutting the developing device (C).
FIG. 3 is a perspective view showing a shape of a movable magnet.
FIG. 4 is a cross-sectional view of a movable magnet.
FIG. 5 is an operation explanatory diagram when the movable magnet is rotated in the reverse direction.
FIG. 6 is an operation explanatory diagram when the movable magnet is rotated in the forward direction.
[Explanation of symbols]
1 Photosensitive drum 20 Fixed magnet roller 21 Rotating sleeve 22 Fixed sleeve 23 Movable magnet

Claims (2)

Development in which a rotating sleeve containing a fixed magnet roller having a plurality of permanent magnets magnetized with N and S poles is arranged facing the photosensitive drum, and the developer is guided to the developing position on the photosensitive drum by the rotating sleeve. In the device
A fixed sleeve disposed on the upstream side in the rotation direction of the rotary sleeve with a predetermined gap between the rotary sleeve and the outer periphery;
One or more movable magnets disposed within the fixed sleeve and capable of rotating between a first stop position located during development and a second stop position located during non-development;
A first pole of the fixed magnet roller disposed on the developing position side in the rotating sleeve and the fixed magnet roller disposed on the anti-development position side with the closest contact point between the fixed sleeve and the rotating sleeve interposed therebetween. The second pole of
The first stop position is located in the fixed sleeve and does not affect the magnetic force of the fixed magnet roller during development, and the second stop position is between the magnetic pole of the movable magnet and the first pole of the rotary sleeve. In addition to making a magnetic shield by a repulsive magnetic field, each is set to a position where a magnetic binding force is created by an attractive magnetic field between the magnetic force of the movable magnet and the second pole of the rotating sleeve ,
At the time of development, the movable magnet is retracted to the first stop position, and the developer can be supplied to the development position side.
During non-development, the movable magnet rotates in the direction opposite to the rotation direction of the rotary sleeve toward the side approaching the rotary sleeve, stops at the second stop position, and supplies developer to the development position side. A developing apparatus characterized in that the developer on the rotating sleeve is collected while being blocked. Development in which a rotating sleeve containing a fixed magnet roller having a plurality of permanent magnets magnetized with N and S poles is arranged facing the photosensitive drum, and the developer is guided to the developing position on the photosensitive drum by the rotating sleeve. In the device
A fixed sleeve disposed on the upstream side in the rotation direction of the rotary sleeve with a predetermined gap between the rotary sleeve and the outer periphery;
One or more movable magnets disposed within the fixed sleeve and capable of rotating between a first stop position located during development and a second stop position located during non-development;
A first pole of the fixed magnet roller disposed on the developing position side in the rotating sleeve and the fixed magnet roller disposed on the anti-development position side with the closest contact point between the fixed sleeve and the rotating sleeve interposed therebetween. The second pole of
The first stop position is located in the fixed sleeve and does not affect the magnetic force of the fixed magnet roller during development, and the second stop position is between the magnetic pole of the movable magnet and the first pole of the rotary sleeve. In addition to making a magnetic shield by a repulsive magnetic field, each is set to a position where a magnetic binding force is created by an attractive magnetic field between the magnetic force of the movable magnet and the second pole of the rotating sleeve ,
At the time of development, the movable magnet is retracted to the first stop position, and the developer can be supplied to the development position side.
At the time of non-development, the movable magnet rotates to the side closer to the rotating sleeve to stop at the second stop position, shuts off the supply of developer to the developing position side, and develops on the rotating sleeve. A developing device configured to stop the rotating sleeve after the agent collecting operation is completed.

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