JP5299192B2 - Developer carrying member, developing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer carrier or the like for preventing polarity of a magnetic pole between repulsive poles from being reversed and having a magnet roll having highly accurate magnetic force characteristics. <P>SOLUTION: The developer carrier has a magnet roll formed by bonding a plurality of magnet pieces around a shaft, and a developing sleeve to be rotated around the magnet roll. The plurality of the magnet pieces includes: a conveying pole piece for conveying a developer adsorbed on the surface of the developing sleeve; an interposed pole piece provided adjacent to the conveying pole piece and for separating the developer from the surface of the developing sleeve; and a pumping pole piece provided adjacent to the interposed pole piece and for adsorbing the developer on the surface of the developing sleeve. Concerning the conveying pole piece, the interposed pole piece and the pumping pole piece, normal directional magnetic flux density is the same polarity on the surface of the developing sleeve, and the interposed pole piece protrudes more outward than the conveying pole piece on a boundary surface between the conveying pole piece and the interposed pole piece. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a laser printer or a digital copying machine, a developing device used in the image forming apparatus, and a developer carrier.

  Conventionally, as a developing device used in an image forming apparatus such as a printer or a copying machine, for example, a developer agitating member is provided on a developer carrying member which is disposed opposite to a photoreceptor and is driven to rotate, and agitated to a predetermined toner concentration by a developer agitating member. A two-component developer (hereinafter referred to as “developer”) composed of the adjusted toner and a magnetic carrier is held (adsorbed) and conveyed to a development area facing the photoreceptor, and the toner is transferred to the development area. One that develops an electrostatic latent image formed on the surface is known (see, for example, Patent Document 1).

  This developer carrier is provided at both ends of a magnet roll having a predetermined magnetic field waveform formed by arranging permanent magnets having a plurality of magnetic poles in the circumferential direction of the shaft, and the shaft of the magnet roll. The main component is a developing sleeve of a non-magnetic cylindrical body that is rotatably supported via a bearing.

  Each magnetic pole of the magnet roll has a different waveform required according to its function. Among these, a transport electrode having a function of transporting a developer having a reduced toner concentration (hereinafter referred to as “low toner concentration developer”) used for development while adsorbing to the surface of the developing sleeve is provided by the transport electrode. An intervening electrode having a function of peeling the conveyed low toner concentration developer from the developing sleeve, and a developer that is stirred and adjusted to a predetermined toner concentration (hereinafter referred to as “appropriate toner concentration developer”) are magnets. The pumping poles that are newly pumped to the surface of the developing sleeve by the magnetic force of the roll are arranged side by side, and the polarity of the magnetic pole (normal magnetic flux density) on the surface of the developing sleeve is the same polarity. Yes (for example, see Patent Documents 2 and 3).

  The techniques disclosed in Patent Documents 2 and 3 prevent the polarity of the magnetic pole between the repulsion poles from being reversed, and reduce the magnetic force between the repulsion poles, thereby reducing the developer with a low toner concentration. The main purpose is to peel off the surface. If the low toner concentration developer cannot be peeled off from the developer carrying member, it is transported to the pumping electrode as it is, and the photoreceptor is developed with the low toner concentration developer, which causes image quality problems called density reduction.

Japanese Patent Laying-Open No. 2005-077494 JP 2002-043118 A JP 2006-093174 A

  The technique described in Patent Document 2 described above has a magnetic pole of the same polarity on both side surfaces adjacent to the inner peripheral surface, in the longitudinal direction of the magnet piece having a substantially fan-shaped cross section. Since the magnetic poles have opposite magnetic poles to the magnetic poles provided on both side surfaces, the polarity of the magnetic poles between the repulsive poles can be prevented from being reversed.

  However, since the technique described in Patent Document 2 has the same magnetic pole on both side surfaces adjacent to the inner peripheral surface of the magnet piece, the magnetized magnet piece is once demagnetized and bonded to the shaft. After that, the magnet piece cannot be magnetized to a desired magnetic flux density. For this reason, the magnetic characteristic of the magnet roll is determined when the magnet piece is manufactured, and there is a problem that it is not possible to manufacture a magnet roll having a highly accurate magnetic characteristic.

  This is because when a magnet roll is formed by pasting the magnet piece once demagnetized on the shaft and then magnetized again, the magnetizing yoke of the magnetizing mold can be placed only on the outer periphery of the magnet roll. This is because it can be magnetized only in the radial direction and cannot be magnetized so that both side surfaces adjacent to the inner peripheral surface of the magnet piece have the same polarity.

  In addition, the technique described in Patent Document 2 requires that the magnetized magnet piece be attached to the shaft without being demagnetized after that. In addition, there is a problem that iron powder, dust, and the like adhere to the magnet piece due to the magnetic attractive force.

  When assembling the magnet roll, dust or the like adhering to the magnet piece enters between the magnet pieces or between the magnet piece and the shaft, and the magnet piece cannot be attached to a desired position on the outer peripheral surface of the shaft with high accuracy. Therefore, it becomes difficult to obtain the magnetic characteristics as designed. Note that the technique described in Patent Document 3 has the same problems as the technique described in Patent Document 2.

  The present invention has been made in order to solve such problems, and is a developer that includes a magnet roll that prevents the polarity of the magnetic poles between the repulsion poles from being reversed and has high-precision magnetic characteristics. An object of the present invention is to provide a carrier, a developing device, and an image forming apparatus.

(First invention)
The developer carrier of the first invention is a developer carrier comprising a magnet roll in which a plurality of magnet pieces are attached around a shaft, and a developing sleeve that rotates around the magnet roll. Includes a transport pole piece having a function of transporting the developer adsorbed on the surface of the developing sleeve, an interposition pole piece provided adjacent to the transport pole piece, and for separating the developer from the surface of the developing sleeve, and the interposition A pumping pole piece provided adjacent to the pole piece and adsorbing developer on the surface of the developing sleeve, and the conveying pole piece, the intervening pole piece and the pumping pole piece are magnetic poles having a normal magnetic flux density on the surface of the developing sleeve. The interposer pole piece protrudes outward from the transport pole piece on the boundary surface between the transport pole piece and the interposer pole piece. And wherein the Rukoto. Here, the “normal direction magnetic flux density” refers to a component in the normal direction of the developer carrier among the magnetic fields generated around the developer carrier by the magnet roll. The “boundary surface” means a plane including a surface where adjacent magnet pieces are in contact with each other. The “conveying pole piece” only needs to have at least a function of conveying the developer adsorbed on the surface of the developing sleeve, and may have only such a function. A function as a so-called recovery electrode for recovering the developer may be provided.

  With this configuration, the developer carrier of the first invention can absorb the magnetic lines of force (magnetic field) emitted from the transport pole piece in the tangential direction at the projecting portion of the interposition pole piece. Can be absorbed in the intervening pole piece from the normal direction. For this reason, it is possible to prevent the polarity of the magnetic pole between the repulsion poles from being reversed, and the normal magnetic flux density on the surface of the developing sleeve between the repulsion poles can be close to zero. The developer peeling failure (low toner concentration developer peeling failure and low toner concentration developer re-adsorption to the developing sleeve) can be extremely reduced. The “between repulsion poles” refers to the interval from the transport pole to the pumping pole.

  In addition, the magnet piece can be magnetized by using a magnetizing device or the like after demagnetizing once and affixing to the outer periphery of the shaft to constitute a magnet roll. In addition to the above, it is possible to provide a developer carrying member provided with a magnet roll having highly accurate magnetic properties.

(Second invention)
The developer carrier of the second invention is a developer carrier comprising a magnet roll in which a plurality of magnet pieces are attached around a shaft, and a developing sleeve that rotates around the magnet roll. Includes a transport pole piece having a function of transporting the developer adsorbed on the surface of the developing sleeve, an intervening pole piece provided adjacent to the transport pole piece and separating the developer from the surface of the developing sleeve, The pumping pole piece is provided adjacent to the intervening pole piece and adsorbs the developer to the surface of the developing sleeve. The conveying pole piece, the intervening pole piece and the pumping pole piece have a normal magnetic flux density on the surface of the developing sleeve. The magnetic poles are the same, and the intervening pole piece is outside the pumping pole piece on the interface between the pumping pole piece and the intervening pole piece. Characterized in that protrudes.

  With this configuration, the developer carrier of the second invention can absorb the magnetic lines of force (magnetic field) emitted from the pumping pole piece in the tangential direction at the protruding portion of the intervening pole piece. Can be absorbed by the intervening pole piece from the normal direction and the amount thereof can be reduced. For this reason, it is possible to prevent the polarity of the magnetic pole between the repulsion poles from being reversed, and the normal magnetic flux density on the surface of the developing sleeve between the repulsion poles can be close to zero. The developer peeling failure can be extremely reduced.

  In addition, the magnet piece can be magnetized by using a magnetizing device or the like after demagnetizing once and affixing to the outer periphery of the shaft to constitute a magnet roll. In addition to the above, it is possible to provide a developer carrying member provided with a magnet roll having highly accurate magnetic properties.

(Third invention)
According to a third aspect of the present invention, the developer carrying member of the first or second invention, a layer thickness regulating member provided opposite to the developer carrying member, and a developer stirring member for stirring the developer are disposed in the housing. The present invention relates to a developing device provided for

(Fourth invention)
A fourth invention relates to an image forming apparatus comprising the developing device of the third invention and a photosensitive member facing the developer carrying member of the developing device.

  The present invention provides a developer carrying member, a developing device, and an image forming apparatus provided with a magnet roll that prevents the polarity between repulsive poles on the surface of the developing sleeve from being reversed and has high-precision magnetic characteristics. can do.

Schematic structure diagram of magnet roll (Example 1) Side view of the magnet roll of FIG. 1 (Example 1) FIG. 2 is a diagram showing the flow of magnetic lines of force generated from the surface magnetic poles of the magnet roll of FIG. 2 (Example 1). Magnetic force measurement diagram of magnet roll (Example 1) Sectional diagram of developer carrier (Example 1) Sectional view of developing device (Example 1) FIG. 6 is a partially enlarged view of the developing device (Example 1). Sectional view of magnet piece mold (Example 1) Schematic configuration diagram of magnetizing mold (Example 1) Enlarged view of the connecting part of the pumping pole piece and the layer regulating pole piece FIG. 7 is a diagram for explaining the configuration of an image forming apparatus (third embodiment). The figure showing the flow of the line of magnetic force generated from the surface magnetic pole of the magnet roll of Comparative Example 1 The figure showing the flow of the line of magnetic force generated from the surface magnetic pole of the magnet roll of Comparative Example 2 Comparative diagram of magnetic field waveforms of Example 1 and Comparative Example 1 Comparative diagram of magnetic field waveforms of Example 1 and Comparative Example 1 Comparative diagram of magnetic field waveforms of Example 1 and Comparative Example 2 Comparative diagram of magnetic field waveforms of Example 1 and Comparative Example 2 A diagram showing the flow of magnetic lines of force generated from the surface magnetic poles of an integral magnet roll Side view of magnet roll (Example 2)

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 5 is a schematic configuration diagram (cross-sectional view) showing an example of a developer carrier according to the present invention, and FIG. 6 is a schematic configuration diagram (cross-sectional view) showing an example of a developing device according to the present invention. The present invention is not intended to be limited to the developer carrier shown in FIG. 5 or the developing device shown in FIG.

(Developer)
As shown in FIG. 6, the developing device 61 according to the present invention holds (adsorbs) an electrostatic latent image formed on the surface of a photoreceptor roll 71 as a photoreceptor on the surface of the developing sleeve 34 of the developer carrier 31. ) Using the developed developer. The developing device 61 supplies a developer carrier 31 provided close to and opposite to the photoconductor roll 71 and a developer composed of toner and a magnetic carrier to the developer carrier 31 while stirring. The developer agitating members 63 and 64 and the layer thickness regulating member 67 for regulating the layer thickness of the developer held on the surface of the developing sleeve 34 are provided inside the housing 62.

  Further, as shown in FIG. 6, the developer agitating members 63 and 64 are provided such that the axial direction (longitudinal direction) thereof is substantially parallel to the axial direction (longitudinal direction) of the developer carrier 31. It is rotationally driven so as to convey the developer in opposite directions. Since the first stirring chamber 65 communicates with the second stirring chamber 66 at both ends in the axial direction of the developer carrier 31, the developer is stirred while circulating in the housing 62.

  Further, the developer is agitated while circulating in the housing 62, whereby a sufficient charge is imparted to the toner, and the toner concentration is measured by a toner concentration sensor (not shown). When the toner density is lowered, the low toner density developer is adjusted to a predetermined toner density by supplying toner from a toner hopper (not shown).

(Development process)
A series of development processes after the developer having an appropriate toner concentration adjusted to a predetermined toner concentration is adsorbed on the surface of the developer carrier 31 will be described below.
FIG. 7 is an enlarged view of the vicinity of the developer carrier 31 in the developing device 61 shown in FIG. In FIG. 7, the developer is represented by a circle. However, since the development process is schematically described, the toner constituting the developer and the magnetic carrier are not distinguished. There are two types of circles representing the developer (“◯” and “●”). The appropriate toner concentration developer 68 is a black circle (“●”), and the low toner concentration developer 69 is a white circle (“◯”). ]). In addition, the surface of the developing sleeve 34 in FIG. 7 shows a state in which the developer is adsorbed in a single-layer state of one grain or a two-layer state of two-grain lamination, for the sake of simplicity of explanation. It does not indicate that only one or two layers are present.

  As shown in FIG. 7, the proper toner concentration developer 68 is attracted to the surface of the developing sleeve 34 by the magnetic attractive force of the magnetic field (magnetic field) generated by the pumping pole piece 57 in the magnet roll 51. The proper toner concentration developer 68 pumped up forms a magnetic brush on the developing sleeve 34 by the magnetic field generated by the magnet roll 51. The magnetic brush is conveyed by the rotation of the developing sleeve 34 (the rotation direction is an arrow A in FIG. 7).

  The magnetic brush formed by the magnetic attraction force of the pumping pole piece 57 is adjusted after the amount of the proper toner concentration developer 68 is regulated by the developer regulating member 67 disposed to face the layer regulating pole piece 58. The two transport pole pieces 53 are sent to the development area near the development pole piece 54. In the developing area, the toner is transferred to the photoreceptor roll 71 and the photoreceptor roll 71 is developed.

  The low-toner-concentration developer 69 used for developing the photosensitive roll 71 and having a reduced toner density is developed by the first transport pole piece 55 existing on the downstream side of the development pole piece 54 as the developing sleeve 34 rotates. It is adsorbed on the surface of the sleeve 34 and collected in the developing device 61. The first transport pole piece 55 corresponds to the “transport pole piece” in the first invention, and has a function of collecting the low toner concentration developer 69 and a function of transporting it.

  The region where the low toner concentration developer 69 peels is not on the pole of the transport pole piece 55 but in the vicinity of the interposition pole (dummy pole) piece 56 existing between the transport pole piece 55 and the pumping pole piece 58. Here, a series of development processes is completed.

(Developer carrier)
As shown in FIG. 5, the developer carrier 31 according to the present invention has a predetermined magnetic field by arranging (fixing) a plurality of magnet pieces (permanent magnets) having predetermined magnetic poles in the circumferential direction of the shaft 52. A non-magnetic cylinder having a corrugated magnet roll 51 and a non-magnetic cylinder rotatably supported at both ends of a shaft 52 of the magnet roll 51 through bearings (bearings) 33 and flanges 32 in the direction of arrow A in FIG. And a developing sleeve 34 of the body.

  More specifically, the developing sleeve 34 is a hollow cylindrical part made of aluminum or stainless steel, and the flange 32 is fixed to both ends thereof. A shaft 52 is inserted into the hollow portion (through hole) of the flange 32, and both end portions of the shaft 52 are rotatably supported by bearings 33 fixed to the flange 32. On the other hand, the magnet roll 51 in the developing sleeve 34 has a plurality of magnet pieces 53 to 58 (not shown) fixed to the peripheral surface of the shaft 52.

  A plurality of concave grooves extending in the longitudinal direction of the developing sleeve 34 may be formed on the outer peripheral surface of the developing sleeve 34 at substantially the same pitch in the circumferential direction of the developing sleeve 34. Alternatively, the outer peripheral surface of the developing sleeve 34 may be subjected to a roughening process such as a sandblasting process.

  With this configuration, in the image forming apparatus such as a copying machine, when the flange 32 is rotated with the shaft 52 fixed, the developing sleeve 34 fixed to the flange 32 is independent of the magnet roll 51 in the circumferential direction. The developer that rotates and is attracted to the outer peripheral surface of the developing sleeve 34 by the magnetic field generated by the magnet roll 51 is conveyed in the circumferential direction.

(Magnet roll)
Next, the magnet roll will be described. The magnet roll described below is a so-called bonded magnet roll of a type in which a magnet piece using a magnetic resin material as a permanent magnet is bonded. The magnet piece can be molded by a known injection molding method or extrusion molding method. The magnetic resin material may be a sintered magnet. Furthermore, although the example which used the coil was given as a magnetic field orientation means mentioned later, the well-known thing using a rare earth-type permanent magnet may be used.

  1 is a schematic structural view (perspective view) of the magnet roll 51, and FIG. 2 is a side view of the magnet roll 51 shown in FIG. The magnet roll 51 is obtained by laminating magnet pieces 53 to 58 having a substantially fan-shaped cross section (transverse section) in a radial direction on an outer peripheral surface of a shaft 52 using an adhesive.

As shown in FIG. 2, the magnet roll 51 includes, in the circumferential direction of the shaft 52, the developing pole piece 54, the first transport pole piece 55, the interposition pole piece 56, the pumping pole piece 57, the layer regulating pole piece 58, and the second transport. The pole pieces 53 are bonded together in this order.
The developing pole piece 54 has a function of developing the surface of the photoreceptor roll 71 with an appropriate toner concentration developer 68 adsorbed on the developing sleeve 34. The first transport pole piece 55 has a function of transporting at least the low toner concentration developer 69 adsorbed on the surface of the developing sleeve 34, and further has a function of recovering the low toner concentration developer 69. Also good. The first transport pole piece 55 of the first embodiment has both a function of collecting the low toner concentration developer 69 and a function of transporting it. The intervening pole piece 56 is provided adjacent to the first transport pole piece 55 and has a function of peeling the low toner concentration developer 69 from the surface of the developing sleeve 34. The pumping pole piece 57 is provided adjacent to the intervening pole piece 56 and has a function of adsorbing the appropriate toner concentration developer 68 to the surface of the developing sleeve 34. The second transport pole piece 53 has a function of sending the appropriate toner concentration developer 68 adsorbed on the surface of the developing sleeve 34 to the developing area near the developing pole piece 54. Since each of the magnet pieces 53 to 58 has an S-pole or N-pole magnetic pole on the outer peripheral surface (FIG. 2), the magnet roll 51 generates a magnetic field on the outer peripheral portion of the magnet roll. .

(Method to generate magnetic field in magnet roll)
A known technique can be used as a method of generating a magnetic field in the magnet roll 51. An example is described below.
FIG. 8 schematically shows how the alignment magnetic field generated by the alignment coil 85 is converged by the alignment yoke 83 by magnetic lines of force. In order to generate a magnetic field in the magnet roll 51, magnetic poles are generated on the outer peripheral surfaces of the magnet pieces 53 to 58. These magnet pieces 53 to 58 are made of magnetic material powder, resin binder, additives, and the like. It is manufactured by molding in a magnetic field using a magnetic resin material made of a mixture. Here, the outer peripheral surface of the magnet piece is a surface that constitutes a part of the outer peripheral surface of the magnet roll and faces a part of the inner peripheral surface of the developing sleeve.

  As the magnet material powder, for example, a mixture of ferrite powder, rare earth metal powder such as Nd, and iron group metal powder such as Fe, Co, and Ni can be used. As the resin binder, for example, polyamide, polyethylene, polypropylene, epoxy resin, ethylene ethyl acrylate (EEA), or the like can be used.

  As shown in FIG. 8, each of the magnet pieces 53 to 58 is a mold apparatus including a fixed mold 81 having an orientation yoke 83 made of magnetic steel and a movable mold 82 movable with respect to the fixed mold. Manufactured using. Specifically, a magnetic resin material melted from a runner (not shown) communicating with one end in the longitudinal direction of the cavity 84 is formed inside the cavity 84 formed by clamping the fixed mold 81 and the movable mold 82. The cavity 84 is injected and filled with the molten magnetic resin material. At that time, an orientation magnetic field is generated by energizing the orientation coil 85, and the magnetic resin material filling the cavity 84 is cooled and solidified while orienting the magnet material powder in the magnetic resin material by this orientation magnetic field. Magnet pieces can be manufactured. Here, the cavity refers to a space inside the mold (a space having the shape of an injection molded product), and communication refers to making the two spaces continuous.

  Since this cooled and solidified molded article (magnet piece) is once cooled and solidified, the orientation state of the magnetic material powder does not change until the magnetic resin material is melted again. The magnetic field waveform can be almost reproduced.

  A magnetic flux having a high magnetic flux density is formed on the outer peripheral surface of the magnet piece in the vicinity where the converged orientation magnetic field shown in FIG. 8 is opposed to the cavity 84 and the orientation yoke 83 (near B in FIG. 8).

  Even in the absence of the orientation yoke 83, the magnetic poles can be formed on the outer peripheral surface of the magnet piece by energizing the orientation coil 85 to generate an orientation magnetic field. However, as shown in FIG. 8, since the orientation magnetic field is not converged by the orientation yoke 83, a magnetic pole having a lower magnetic flux density than the case of FIG. 8 is formed on the outer peripheral surface of the magnet piece.

  Although FIG. 8 has taken up and explained one magnet piece, other magnet pieces are manufactured in the same manner. However, in order to obtain a desired waveform, the position and shape of the orientation yoke 83 are generally changed.

  In addition, since the magnet material powder is not oriented unless the orientation coil 85 is energized, the magnetic poles may not be formed on the outer peripheral surface of the magnet piece even if the molding is performed using the mold apparatus shown in FIG. In this case, a magnetic pole is generated on the outer peripheral surface of the magnet roll by magnetization described later. However, since the magnet material powder is not oriented, a magnetic pole having a lower magnetic flux density is formed than the magnet piece without the orientation yoke 83 described above.

  The above is the method of generating (forming) magnetic poles on the outer peripheral surfaces of the magnet pieces 53 to 58. In the obtained magnet pieces 53 to 58, when the orientation coil 85 is energized, a magnetic pole is generated on the outer peripheral surface of each magnet piece. Yes.

  When the magnetic field waveform in the magnet roll 51 is further finely adjusted, or when the magnet piece is formed without energizing the orientation coil 85, the magnet piece is once demagnetized and an adhesive is applied around the shaft 52 to apply the magnet. After the pieces 53 to 58 are pasted to form a magnet roll, magnetization is performed. The timing of demagnetization may be demagnetized by passing a current in a direction opposite to the direction that was passed through the orientation coil 85 before magnetization from the mold (in-mold demagnetization). ), And may be demagnetized after removal from the mold.

  FIG. 9 is a schematic configuration diagram of the magnetizing apparatus. The magnetizing device 91 has a configuration in which a magnetizing yoke 93 is arranged in the vicinity of the magnetic pole to be generated on the outer peripheral surface of the magnet roll 51 in the yoke fixing mold 92. In FIG. 9, since the constituent magnetic poles of the magnet roll 51 are six poles (including the intervening pole Dm), six magnetizing yokes 93 are arranged. The magnetized yoke 93 and the yoke fixing die 92 are fixed by a known method such as a screw (not shown).

  The magnetizing yoke 93 is obtained by winding a magnetizing coil 95 around a magnetized iron core 94 so that the positional relationship between the magnetized iron core 94 and the magnetizing coil 95 is not shifted by the fixing resin 96. It is fixed. In FIG. 9, the magnetizing yokes 93 are separately (independently) fixed to the yoke fixing mold 92, but the magnetizing yokes 93 are in close contact with each other and are separated into separate magnetizing yokes. If this is difficult, a plurality of magnetized cores 94 and a plurality of magnetizing coils 95 may be fixed and formed as if they were one magnetized yoke using a fixing resin 96. A magnetizing magnetic field is generated by energizing the magnetizing coil 95 using the magnetizing mold 91 as described above, the magnet roll 51 is magnetized, and the magnet roll 51 generates a magnetic field.

  FIG. 3 represents the magnetic field generated by the magnet roll 51 of FIG. 2 with lines of magnetic force. Magnetic lines of force are generated from the outer peripheral surface of each magnet piece, and the portion where the lines of magnetic force are generated corresponds to the magnetic poles. Further, a portion where the density of magnetic lines of force is high, such as the vicinity of the outer peripheral surface of the developing pole piece 54, is a portion where the magnetic flux density is high, and a portion where the density of magnetic lines of force is low, such as the vicinity of the outer peripheral surface of the interposition pole piece 56, is opposite. This is where the magnetic flux density is low.

(Relationship between interposition electrode piece and transfer electrode piece)
In FIG. 3, focusing on the first transport pole piece 55 and the interposition pole piece 56 as the “transport pole piece” in the first invention described above, on the boundary surface 72 between the first transport pole piece 55 and the interposition pole piece 56. , The intervening pole piece 56 protrudes outward from the first transport pole piece 55.

  With this configuration, as shown in FIG. 3, the magnetic force lines close to the intervening pole piece 56 out of the magnetic force lines extending outward from the outer peripheral surface of the first transport pole piece 55 are projected to the protruding portion 73 of the intervening pole piece 56. Can be returned. For this reason, in the vicinity of the protrusion 73, the magnetic lines of force do not come out from the surface (outer peripheral surface) 74 of the developing sleeve 34, and the opposite magnetic pole (S pole) does not appear on the surface 74 of the developing sleeve 34.

  That is, since the magnetic force lines (magnetic field) emitted from the first transport pole piece 55 can be absorbed in the tangential direction at the protrusion 73 of the interposition pole piece 56, the magnetic force lines output from the first transport pole piece 55 are normal lines. The amount absorbed by the intervening pole piece 56 from the direction can be reduced. For this reason, it is possible to prevent the polarity of the magnetic pole between the repulsive poles from being reversed, and to bring the normal direction magnetic flux density on the surface of the developing sleeve 34 between the repelling poles close to zero. Further, each of the magnet pieces 53 to 58 is molded in the mold apparatus shown in FIG. 8 and once demagnetized in the mold, the magnet pieces 53 to 58 are pasted around the shaft 52 as shown in FIG. It can be magnetized by the magnetic device 91. For this reason, it is possible to manufacture a developer carrying member provided with a magnet roll having high-precision magnetic characteristics.

(Comparative Example 1)
Without the projection 73 described above, the magnetic force lines 562 close to the intervening pole piece 561 out of the magnetic force lines extending outward from the outer peripheral surface of the first transport pole piece 551 as shown in FIG. May once return to the surface 74 and return to the interposition pole piece 561 side with a strong normal component. In this case, since the opposite magnetic pole (S pole) appears on the surface 74 of the developing sleeve 34 due to the magnetic force line 562, a part of the low toner concentration developer 69 is attracted to the opposite magnetic pole, and the low toner concentration developer 69. Peeling failure occurs.

(Comparative Example 2)
Further, if the above-described protrusion 73 is not provided, as shown in FIG. 13, some normal direction components of a plurality of magnetic lines of force that protrude outward from the outer peripheral surface of the first transport pole piece 552. A strong magnetic field line 564 may return to the intervening pole piece 563. In this case, since the opposite magnetic pole (S pole) appears on the surface 74 of the developing sleeve 34 due to the magnetic force line 564, a part of the low toner concentration developer 69 is attracted to the opposite magnetic pole, and the low toner concentration developer 69 Peeling failure occurs.

(Method to measure the magnetic field strength of the magnet roll)
Next, a method for measuring the strength of the magnetic field of the magnet roll 51 will be described with reference to FIG. Since the measurement location is usually the surface 74 of the developing sleeve 34, the magnetic field measuring probe 42 is set at a location where the surface 74 of the developing sleeve 34 is located. In Example 1 and Comparative Examples 1 and 2 described above, as shown in FIG. 4, measurement was performed with a magnetic field measurement sleeve 45 attached instead of the developing sleeve 34.

  Here, the reason for using the magnetic field measurement sleeve 45 in Example 1 and Comparative Examples 1 and 2 is that the developing sleeve 34 is a sleeve that has been subjected to a surface treatment that is easily damaged such as a blasting treatment. This is because when the probe 42 is pressed, the surface of the developing sleeve 34 may be damaged, which affects the developer transport state. For this reason, when measuring the magnetic field of the magnet roll 51, it is desirable to use a detachable sleeve 45 dedicated to magnetic field measurement.

  In the case where the developing sleeve 34 is a type in which the surface is not easily scratched, the probe 42 may be pressed against the developing sleeve 34 in a state where the developing sleeve 34 is covered with the magnet roll 51. Further, the probe 42 may be set at a position where a certain distance is assumed assuming the developing sleeve 34.

  After the above preparation is completed, the probe 42 and the magnet roll 51 are relatively rotated. In the present embodiment, the probe 42 is fixed, the D surface cut 59 in the shaft 52 of the magnet roll 51 is chucked (not shown), and the magnet roll 51 is rotated at a constant angle.

  Then, with the D-plane cut 59 as a reference, the magnetic field strength of the magnet roll 51 at a certain angle is measured by the probe 42, and the signal (analog data) output from the probe 42 is converted into the magnetic field strength by the gauss meter 43. The data was taken into a PC (personal computer) 44 via an A (analog) / D (digital) converter (not shown). In the present embodiment, ADE Inc. model FX-95B was used as the probe 42, and ADS Inc. model HGM-8300SW was used as the gauss meter 43.

(Magnetic flux density)
Hereinafter, the magnetic flux density will be described. The strength of the magnetic field of the magnet roll is generally represented by a magnetic flux density, and the magnetic flux density is divided into two types of direction components. A magnet roll having the magnetic flux density shown in FIG. 10 will be described as an example. FIG. 10 is an enlarged view of a connecting portion of a general magnet roll pumping pole piece 7 and a layer regulating pole piece 8. As described above, normally, the magnetic field strength (magnetic flux density) of the magnet roll is measured on the dotted line indicating the surface of the developing sleeve of FIG. 10 in order to measure the strength of the magnetic field of the surface 74 of the developing sleeve 34. This point F will be described in detail as an example.

  As shown in FIG. 10, the magnetic field vector 46 at the point F becomes a tangential component with respect to the magnetic field lines generated from the layer regulating pole piece 8. Furthermore, the magnitude of the magnetic field vector 46 increases as the magnetic flux density at the point F increases. As shown in FIG. 10, this is separated into two components, a normal direction component vector 47 and a tangential direction component vector 48, with respect to the developing sleeve 34, and these are expressed by magnetic flux density, which is the density of magnetic lines, respectively. It is expressed as a measurement result when measuring.

  In this specification, when the intensity of the magnetic field generated by the magnet roll is quantitatively expressed, it is expressed by magnetic flux density, and the magnetic flux density separated into two components of the normal direction component vector 47 and the tangential direction component vector 48 is respectively expressed. , Normal flux density and tangential flux density. Further, the magnitude of the magnetic field vector 46 is expressed as the magnitude of the magnetic field lines, and when the magnitude of the magnetic field lines is quantitatively expressed, it is expressed as the magnetic flux density.

  The method of separating the strength of the magnetic field of the magnet roll into two components, a normal direction component vector 47 and a tangential direction component vector 48, usually measures the magnetic field of the normal direction component and the tangential direction component in the probe 42. This is achieved by providing two measuring elements. The measuring element has a flat plate shape, and in order to read the strength of the magnetic field of the parallel component with respect to the thickness direction of the flat plate, the measuring elements of the normal direction component and the tangential direction component are usually used in the same direction. The probe 42 (model FX-95B manufactured by ADE Co., Ltd.) used in Example 1 has two measuring elements for measuring a magnetic field.

  Regarding the direction of the magnetic flux density, in the normal direction component, the direction from the surface of the developing sleeve 34 toward the center of the shaft 52 is defined as “− (minus)”, and the opposite is defined as “+ (plus)”. In terms of the polarity of the magnetic poles generated on the outer periphery of the magnet roll 51, “−” is the direction to be the S pole, and “+” is the direction to be the N pole.

  In the tangential direction component, the rotation direction of the developing sleeve 34 is expressed as “+”, and the opposite direction is expressed as “−”. For example, when the developing sleeve 34 rotates in the direction K shown in FIG. 10, the magnetic flux density of the normal direction component vector 47 in the magnetic field vector 46 is marked with “+” and the magnetic flux of the tangential direction component vector 48. By attaching a sign “−” to the density, it can be seen that the magnetic flux density at the point F is oriented in the counter-rotating direction of the developing sleeve at the N pole. As described with reference to FIG. 10, the magnitude of the magnetic field lines is always represented by the sign “+” because it is the square root of the square sum of the normal direction magnetic flux density and the tangential direction magnetic flux density.

  14 is compared with the normal direction magnetic flux density on the surface of the developing sleeve 34 of the developer carrier 31 of Example 1 shown in FIGS. 2 and 3 and the developer carrier 851 of Comparative Example 1 shown in FIG. And FIG. FIG. 15 is an enlarged graph of the vicinity of the intervening pole piece 561 in FIG. 14. The horizontal axis in FIGS. 14 and 15 is an angle (unit is degrees), and the vertical axis is a magnetic flux density in normal direction (unit). Is Gauss). The thick line is the waveform of Example 1, and the thin line is the waveform of Comparative Example 1. 14 and 15, S1 is a developing electrode piece, N1 is a second conveying electrode piece, S2 is a layer regulating electrode piece, N2 is a pumping electrode piece, Dm is an intermediate electrode piece, and N3 is a first conveying electrode piece. Show.

  14 and 15, it can be seen that the developer carrier 31 of Example 1 does not generate the opposite magnetic pole (S pole) on the surface 74 of the developing sleeve 34 corresponding to the intervening pole piece 56. However, it can be seen that the developer carrier 851 of Comparative Example 1 has the opposite magnetic pole (S pole) generated on the surface 74 of the developing sleeve 34 corresponding to the intervening pole piece 561.

  Further, when comparing the normal direction magnetic flux density on the surface of the developing sleeve 34 of the developer carrier 31 of Example 1 shown in FIGS. 2 and 3 and the developer carrier 852 of Comparative Example 2 shown in FIG. 16 and FIG. FIG. 17 is an enlarged graph of the vicinity of the intervening pole piece 563 in FIG. 16. The horizontal axis in FIGS. 16 and 17 is an angle (unit is degrees), and the vertical axis is a magnetic flux density in normal direction (unit). Is Gauss). The thick line is the waveform of Example 1, and the thin line is the waveform of Comparative Example 2. 16 and 17, S1 is the developing electrode piece, N1 is the second conveying electrode piece, S2 is the layer regulating electrode piece, N2 is the pumping electrode piece, Dm is the interposing electrode piece, and N3 is the first conveying electrode piece. Show.

  16 and 17, it can be seen that in the developer carrier 852 of Comparative Example 2, the opposite magnetic pole (S pole) is generated on the surface 74 of the developing sleeve 34 corresponding to the intervening pole piece 563.

  As shown in Comparative Examples 1 and 2, the outer peripheral surface of the magnet roll may have a magnetic pole different from the surface of the developing sleeve 34. Since the generated magnetic poles are different between the surface of the developing sleeve 34 and the outer peripheral surface of the magnet roll, the developing pole S (reference numeral 54 in FIGS. 2 and 3, S1 in FIGS. 14 to 17), the transport pole N (see FIG. 2 and reference numeral 55 in FIG. 3, N3 in FIGS. 14 to 17, intervening pole S (reference numeral 56 in FIGS. 2 and 3, Dm in FIGS. 14 to 17), pumping pole N (reference numerals in FIGS. 2 and 3) 57, N2 in FIGS. 14 to 17, layer regulation pole S (reference numeral 58 in FIGS. 2 and 3, S2 in FIGS. 14 to 17), transport pole N (reference numeral 53 in FIGS. 2 and 3, FIGS. 14 to 17). When a name is given, such as N1) in FIG. 17 or simply a magnetic pole, it is a magnetic pole on the surface of the developing sleeve. The intervening pole Dm may not be recognized as a pole in the prior art, but the present invention does not differ from other poles in showing the maximum value or the minimum value of the magnetic flux density waveform. Is expressed in the same way as a normal magnetic pole.

Another embodiment will be described with reference to FIG. 19 which is a side view of a developer carrier.
In order to make the description easy to understand, only the differences from the first embodiment will be described in detail, and the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  The difference between the second embodiment and the first embodiment is that the intervening pole piece 29 protrudes from the pumping pole piece 30 on the boundary surface 75 where the intervening pole piece 29 and the pumping pole piece 30 are in contact with each other. In other words, the intervening pole piece 29 is provided with a protruding portion 76 that protrudes more than the pumping pole piece 30 on the boundary surface 75.

  With such a configuration, not only the effects of the first embodiment described above can be obtained, but even when the magnetic flux density of the pumping pole piece 30 is high, the intervening pole piece 29 among the plurality of magnetic lines of force that are output from the pumping pole piece 30. The magnetic lines of force toward the inner side of the developing sleeve 34 can be introduced (returned) into the protruding portion 76 of the intervening pole piece 29 inside the developing sleeve 34 (without being exposed to the surface 74 of the developing sleeve 34).

  In FIG. 19, the interposition pole piece 29 provided with the protruding portion 73 on the transport pole piece 55 side is shown. However, on the boundary surface 73 where the transport pole piece 55 and the interposition pole piece 29 contact each other, In the case where the opposite magnetic pole does not appear on the surface 74 of the developing sleeve 34 facing the surface of the intervening pole piece 29 without protruding the intervening pole piece 29, the intervening pole piece 29 may not be provided with the protrusion 73. That is, in this case, it is not necessary to project the interposition pole piece 29 from the transport pole piece 55 on the boundary surface 72, and it is only necessary to project the interposition pole piece 29 from the pumping pole piece 30 on the boundary surface 75. .

A third embodiment according to the present invention will be described with reference to FIG.
In order to simplify the description, the same parts as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

(Image forming device)
As shown in FIG. 11, the image forming apparatus according to the present invention is a so-called tandem digital color printer 131, and an image forming process unit 110 that forms an image corresponding to image data of each color, and an image forming process unit 110. And an image processing unit 140 that performs predetermined image processing on the image data received from the personal computer 102 or the image reading apparatus 103.

  The image forming process unit 110 includes four image forming units 111Y, 111M, 111C, and 111K that are arranged in parallel at a predetermined interval.

  Each of these image forming units 111Y, 111M, 111C, and 111K includes a photoreceptor roll 71 as a photoreceptor (image carrier) that forms an electrostatic latent image and carries a toner image, and this photoreceptor roll. Obtained by a charging device 113 that uniformly charges the surface of 71 with a predetermined potential, an LED print head 1 as an exposure device that exposes a photoreceptor roll 71 whose surface is charged by the charging device 113, and the LED print head 1. A developing device 61 that develops the electrostatic latent image, and a cleaner (blade) 116 that cleans the surface of the photoreceptor roll 71 after transfer.

  Further, a density detection circuit 117 that detects the toner image density of a test patch (density sample) formed on the photoreceptor roll 71 is provided in the vicinity of the downstream side of the developing device 61 so as to face the photoreceptor roll 71. It has been. The density detection circuit 117 is connected to the control unit 130 and outputs a toner image density detection value.

  Here, the image forming units 111Y, 111M, 111C, and 111K are configured in substantially the same manner except for the toner stored in the developing device 115. The image forming units 111Y, 111M, 111C, and 111K form yellow (Y), magenta (M), cyan (C), and black (K) toner images, respectively.

  In addition, the image forming process unit 110 includes an intermediate transfer belt 121 onto which the toner images of the respective colors formed on the photoreceptor rolls 71 of the image forming units 111Y, 111M, 111C, and 111K are transferred, and the image forming units 111Y. , 111M, 111C, and 111K toner images are sequentially transferred (primary transfer) to the intermediate transfer belt 121, and a primary transfer roll 122 as a primary transfer charging device and a superimposed toner image transferred onto the intermediate transfer belt 121 are recorded. A secondary transfer roll 123 as a secondary transfer charging device that performs batch transfer (secondary transfer) onto a paper P that is a material (recording paper), and a fixing device 125 that fixes the secondary transferred image onto the paper P. I have.

  The image forming process unit 110 performs an image forming operation based on a control signal such as a synchronization signal supplied from the control unit 130. At that time, image data input from the personal computer 102 or the image reading device 103 is subjected to image processing by the image processing unit 140 and supplied to each of the image forming units 111Y, 111M, 111C, and 111K via the interface. .

  For example, in the yellow image forming unit 111Y, the LED print head in which the surface of the photoreceptor roll 71 uniformly charged at a predetermined potential by the charging device 113 emits light based on the image data obtained from the image processing unit 140. 1, an electrostatic latent image is formed on the photoreceptor roll 71.

  This electrostatic latent image is developed by the developing device 61, and a yellow toner image is formed on the photoreceptor roll 71. Similarly, magenta, cyan, and black toner images are formed on the respective photoreceptor rolls 71 of the image forming units 111M, 111C, and 111K.

  The respective color toner images formed on the respective photoreceptor rolls 71 of the image forming units 111Y, 111M, 111C, and 111K are sequentially transferred by the primary transfer roll 122 onto the intermediate transfer belt 121 that rotates in the direction of arrow A in FIG. A toner image superimposed on the intermediate transfer belt 121 is formed by electrostatic attraction.

  The superimposed toner image is conveyed to an area (secondary transfer portion) where the secondary transfer roll 123 is disposed as the intermediate transfer belt 121 rotates. When the superimposed toner image is conveyed to the secondary transfer unit, the paper P is supplied to the secondary transfer unit in accordance with the timing at which the toner image is conveyed to the secondary transfer unit.

  Then, the superimposed toner images are collectively electrostatically transferred onto the conveyed paper P by the transfer electric field formed by the secondary transfer roll 123 in the secondary transfer portion. Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is peeled off from the intermediate transfer belt 121 and conveyed to the fixing device 125 by the conveying belt 124.

  The unfixed toner image on the paper P conveyed to the fixing device 125 is fixed on the paper P by being subjected to fixing processing by heat and pressure by the fixing device 125. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge placement unit (not shown) provided in the discharge unit of the digital color printer 131.

  In other words, since the image forming apparatus according to the present embodiment includes the developing device 61 according to the present invention, an image quality defect called a density decrease due to poor peeling of the low toner concentration developer 69 from the developing sleeve 34 occurs. Can be extremely reduced.

  The above-described embodiments have been illustrated for the purpose of explanation, and the present invention is not limited thereto. The present invention can be recognized by those skilled in the art from the scope of the claims, the description, and the drawings. Changes, deletions, and additions are possible as long as they do not violate the technical idea.

  In the above-described embodiments, the developer carrying member provided with a magnet roll having 6 poles (including the intervening pole Dm) has been described. However, a magnet roll having 4 poles or 8 poles may be used. However, the magnetic poles on the surface of the developing sleeve facing the transport pole piece, the interposition pole piece, and the pumping pole piece must be the same pole, and these three pole magnet pieces must be continuous.

In the above-described embodiment, the “conveying electrode piece” in the first invention functions as a collecting electrode for collecting the low-concentration toner developer 69 and conveys the low-concentration toner developer 69 collected by the collecting electrode. Although the first transport pole piece having both functions as the transport pole is illustrated and illustrated, the present invention is not limited to this, and the “transport pole piece” transports at least the developer adsorbed on the surface of the developing sleeve. What is necessary is just to have a function. For example, the first transport pole piece in Embodiment 1 collects the low-concentration toner developer 69 and the first transport pole piece that transports the low-concentration toner developer 69 collected by the recovery pole piece. It may consist of two pieces. In this case, needless to say, the first transport pole piece is the “transport pole piece” of the first invention.
In the above-described embodiment, a developer carrier using a magnet roll in which a plurality of magnet pieces having a substantially fan-shaped cross section are bonded to the outer peripheral surface of the shaft has been shown. However, as shown in FIG. The present invention can also be applied to an integral magnet roll manufactured by, for example, injecting a magnetic resin material into an injection mold.

  In this case, since the boundary surface between the magnetic pole and the magnetic pole does not exist, the “boundary surface between the transport pole and the interposition pole” is defined as “the position where the absolute value of the magnetic flux density in the normal direction of the transport pole is maximum, and the normal line of the interposition pole. `` Boundary region between the position where the absolute value of the directional magnetic flux density is minimum '' and `` Boundary surface of the pumping pole and the interposition pole '' are `` the position where the absolute value of the magnetic flux density in the normal direction of the pumping pole is maximum, A boundary region between the positions where the absolute value of the magnetic flux density in the normal direction of the intervening poles is minimized may be used.

That is, the invention can be grasped as follows.
(Fifth invention)
The developer carrier of the fifth invention is a developer carrier comprising a magnet roll having a plurality of magnetic poles on the surface and a developing sleeve rotating around the magnet roll, wherein the plurality of magnetic poles are on the surface of the developing sleeve. A developer electrode adhering to the developer electrode, and an adjacent electrode provided adjacent to the conveyor electrode for separating the developer from the surface of the developing sleeve, and provided adjacent to the intermediate electrode to develop the developer. Including the pumping pole adsorbed on the surface of the sleeve, the transport pole, interposition pole, and pumping pole have the same normal magnetic flux density on the surface of the developing sleeve, and the absolute value of the normal magnetic flux density of the transport pole is maximum. In the boundary region between the position where the absolute value of the magnetic flux density in the normal direction of the interposition pole and the position where the absolute value of the interposition pole becomes minimum, the interposition pole protrudes outward from the transport pole.

  With this configuration, the magnetic lines of force (magnetic field) emitted from the carrier pole can be absorbed in the tangential direction at the protruding portion of the interposer pole, so that the amount of magnetic lines of force emitted from the carrier pole is absorbed by the interposer pole from the normal direction. can do. For this reason, it is possible to prevent the polarity of the magnetic pole between the repulsive poles from being reversed, and to bring the normal direction magnetic flux density on the surface of the developing sleeve between the repelling poles close to zero.

(Sixth invention)
The developer carrier of the sixth invention is a developer carrier comprising a magnet roll having a plurality of magnetic poles on the surface and a developing sleeve rotating around the magnet roll, wherein the plurality of magnetic poles are on the surface of the developing sleeve. A developer electrode adhering to the developer electrode, and an adjacent electrode provided adjacent to the conveyor electrode for separating the developer from the surface of the developing sleeve, and provided adjacent to the intermediate electrode to develop the developer. Including the pumping pole adsorbed on the surface of the sleeve, the conveying pole, interposition pole, and pumping pole have the same normal flux density on the surface of the developing sleeve, and the absolute value of the normal flux density of the pumping pole is the maximum. In the boundary region between the position where the absolute value of the magnetic flux density in the normal direction of the interposition pole and the position where the absolute value of the interposition pole becomes minimum, the interposition pole protrudes outward from the pumping pole.

  With this configuration, the magnetic lines of force (magnetic field) emitted from the pumping pole can be absorbed in the tangential direction at the protruding portion of the interposer pole, so that the amount of magnetic force lines emitted from the pumping pole is absorbed by the interposer pole from the normal direction. can do. For this reason, it is possible to prevent the polarity of the magnetic pole between the repulsive poles from being reversed, and to bring the normal direction magnetic flux density on the surface of the developing sleeve between the repelling poles close to zero.

The present invention is applied to an image forming apparatus, a developing device, and a developer carrier used for a copying machine, a printer, and the like.

31 Developer carrier 34 Developing sleeve 51 Magnet roll 52 Shaft 53 Developing electrode piece 54 Collection electrode piece 55 Conveying electrode piece 56 Interposing electrode piece 57 Pumping electrode piece 58 Layer regulating electrode piece 61 Developing device 62 Housing 63 Developer stirring member 64 Developing Agent stirring member 67 Developer regulating member (layer thickness regulating member)
68 Proper toner concentration developer 69 Low toner concentration developer 71 Photoreceptor roll (photoreceptor)

Claims (4)

A magnet roll with a plurality of magnet pieces pasted around the shaft;
In the developer carrying member provided with a developing sleeve rotating around the magnet roll,
The plurality of magnet pieces are transport pole pieces having a function of transporting the developer adsorbed on the surface of the developing sleeve,
An intervening electrode piece provided adjacent to the conveying electrode piece and separating the developer from the surface of the developing sleeve;
A pumping pole piece provided adjacent to the interposer pole piece and adsorbing the developer onto the surface of the developing sleeve;
The transport pole piece, the intervening pole piece, and the pumping pole piece have the same magnetic pole in the normal direction magnetic flux density on the surface of the developing sleeve,
The developer carrying member, wherein the intervening electrode piece protrudes outward from the conveying electrode piece on a boundary surface between the conveying electrode piece and the interposing electrode piece. A magnet roll with a plurality of magnet pieces pasted around the shaft;
In the developer carrying member provided with a developing sleeve rotating around the magnet roll,
The plurality of magnet pieces are transport pole pieces having a function of transporting the developer adsorbed on the surface of the developing sleeve,
An intervening electrode piece provided adjacent to the conveying electrode piece and separating the developer from the surface of the developing sleeve;
A pumping pole piece provided adjacent to the interposer pole piece and adsorbing the developer onto the surface of the developing sleeve;
The transport pole piece, the intervening pole piece, and the pumping pole piece have the same magnetic pole in the normal direction magnetic flux density on the surface of the developing sleeve,
The developer carrying member, wherein the intervening pole piece protrudes outward from the scooping pole piece on the boundary surface between the pumping pole piece and the intervening pole piece The developer carrying member according to claim 1 or 2,
A layer thickness regulating member provided facing the developer carrying member;
A developing device provided with a developer stirring member for stirring the developer in the housing A developing device according to claim 3;
Image forming apparatus comprising a photosensitive member facing the developer carrying member of the developing device

Images