JP6507732B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

  The developing device of Patent Document 1 has a developing roll provided with a cylindrical magnet member supported by a housing, and a sleeve rotatable around the periphery of the magnet member.

Unexamined-Japanese-Patent No. 11-7199

  In the developing device, when the rotational speed of the rotating member is increased to increase productivity, the developer separated at the peeling pole flies toward the rotating member by the rotation of the rotating member, and again the outer peripheral surface of the rotating member It becomes easy to adhere to The developer re-adhered to the outer peripheral surface of the rotating member consumes the toner in the developing area and the toner density is lowered, so when it is used again for development in the developing area, the toner density of the developer image is lowered There is a possibility of

  An object of the present invention is to obtain a developing device and an image forming apparatus capable of suppressing the developer separated from the rotating member from adhering to the rotating member again as compared with the configuration in which the nonmagnetic portion is not provided. Do.

The developing device according to the first aspect of the present invention is provided with a cylindrical rotating member that rotates in a storage chamber for storing a developer containing a magnetic material, and is provided inside the rotating member, and pumps up the developer to the rotating member An adherent pole in which a scooping pole and a stripping pole having the same polarity as the scooping pole and disposed upstream of the scooping pole in the rotational direction of the rotating member and which peels the developer from the revolving member are magnetized. A magnetic member, a supply member that rotates in the storage chamber to supply the developer to the rotating member, and a rotational center of the supply member at least a portion of which is between the rotating member and the supply member. And a nonmagnetic nonmagnetic portion disposed on the downstream side of the rotational direction with respect to a virtual line connecting the separation pole.

In the developing device according to the second aspect of the present invention, in the portion between the peeling pole of the to-be-magnetized member and the suction pole, the peeling pole and the suction pole have the same polarity as the peeling pole and the peeling pole An auxiliary separation pole having a magnetic flux density lower than that of the upper electrode is formed, and the nonmagnetic portion is disposed upstream of the auxiliary virtual line connecting the auxiliary separation pole and the rotation center of the supply member in the rotation direction. ing.

An image forming apparatus according to a third aspect of the present invention includes an image carrier for holding a latent image, and a first or second aspect for developing a latent image of the image carrier with a developer to form a developer image And a transfer unit configured to transfer the developer image to a recording medium.

The invention of the first aspect can suppress the developer separated from the rotating member from adhering to the rotating member again, as compared with the configuration in which the nonmagnetic portion is not provided.

The invention of the second aspect can suppress the developer separated from the rotating member from adhering to the rotating member again, as compared with the configuration in which the nonmagnetic portion extends further downstream than the auxiliary virtual line. .

The invention of the third aspect can suppress an image defect after transfer caused by the developer separated from the rotating member adhering to the rotating member again, as compared with the configuration in which the nonmagnetic portion is not provided.

FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment. FIG. 2 is a block diagram of a developing device according to the present embodiment. FIG. 6 is a perspective view showing a state in which the developing roller of the developing device according to the present embodiment is removed. It is an explanatory view showing the inside of the development device concerning this embodiment. FIG. 6 is a partial enlarged view of the vicinity of a suppressing member of the developing device according to the present embodiment. It is explanatory drawing which shows the magnetic flux density of each magnetic pole of the magnet roll which concerns on this embodiment. It is an explanatory view showing a movement state of a developer in a developing device concerning this embodiment. It is explanatory drawing which shows the modification of the suppression member which concerns on (A), (B) this embodiment.

  An example of a developing device and an image forming apparatus according to the present embodiment will be described.

〔overall structure〕
FIG. 1 shows an image forming apparatus 10 as an example of this embodiment. In the following description, the direction indicated by the arrow Y in FIG. 1 is the device height direction, and the direction indicated by the arrow X in FIG. 1 is the device width direction. Further, a direction (indicated by Z) orthogonal to each of the device height direction and the device width direction is taken as the device depth direction. The image forming apparatus 10 is viewed from the side where the user (not shown) stands (viewed from the front), and the apparatus width direction, apparatus height direction, and apparatus depth direction are described as X direction, Y direction, and Z direction. The Y direction is the gravity direction.

  Furthermore, when it is necessary to distinguish one side and the other side in the X, Y, and Z directions, the image forming apparatus 10 is viewed from the front, and the upper side is the + Y side, the lower side is the −Y side, and the right side is The + X side, the left side is described as −X side, the back side is described as + Z side, and the front side is described as −Z side.

  The image forming apparatus 10 has an apparatus main body 11. Further, the image forming apparatus 10 includes, from the −Y side to the + Y side, a sheet storage unit 12 in which a sheet P as an example of a recording medium is stored, and an image forming unit 14 that forms an image on the sheet P. A document reading unit 16 for reading a document (not shown) is provided. Furthermore, the image forming apparatus 10 is provided with a control unit 18 that controls the operation of each part of the image forming apparatus 10.

<Image Forming Unit>
The image forming unit 14 illustrated in FIG. 1 includes, as an example, four image forming units 20Y, 20M, 20C, and 20K, a transfer unit 30 as an example of a transfer unit, and a fixing unit 40. Note that "Y" in the suffix of the code is for yellow, "M" is for magenta, "C" is for cyan, and "K" is for black (black). The image forming units 20Y, 20M, 20C, and 20K have the same configuration except for the toner T (see FIG. 2) contained in the developer G (see FIG. 2) to be used. Therefore, when it is not necessary to distinguish the colors, the four are collectively referred to as an image forming unit 20.

  The image forming unit 20 includes a photosensitive member 22 as an example of an image carrier, a charger 24 for charging the photosensitive member 22, an exposure unit 26 for exposing the photosensitive member 22 to form a latent image, and a developing device described later And a cleaning unit 28 for cleaning the photosensitive member 22.

  The photosensitive member 22 is a rotating body that rotates with the Z direction as an axial direction. An organic photosensitive layer is formed on the outer peripheral surface of the photosensitive member 22, and the photosensitive member 22 holds a latent image formed by charging by the charger 24 and exposure by the exposure unit 26. The developing device 50 develops the latent image on the photosensitive member 22 with toner T (see FIG. 2) to form a toner image TA as an example of a developer image. The details of the developing device 50 will be described later.

  The transfer unit 30 includes an endless intermediate transfer belt 32, a primary transfer roll 34 for primarily transferring the toner image TA from the photosensitive member 22 onto the intermediate transfer belt 32, and a toner image TA superimposed on the intermediate transfer belt 32. And a secondary transfer roll 36 for secondary transfer onto paper P.

  The fixing unit 40 includes a fixing belt 42 heated by a heater, and a pressure roller 44 pressing the sheet P toward the fixing belt 42. Then, the fixing unit 40 fixes the toner image TA of the sheet P to the sheet P by heating and pressing.

[Configuration of main part]
Next, the developing device 50 will be described.

  As shown in FIG. 2, the developing device 50 includes a housing 52, a cover member 54, a developing roll 56, a supply member 62, a stirring member 64, a suppressing member 70 as an example of a nonmagnetic portion, and a restricting member. And 66 and a seal member 68. Nonmagnetic means non-ferromagnetic and includes diamagnetic, paramagnetic and antiferromagnetic.

  As an example, the developer G used in the developing device 50 is added with toner T made of resin charged to the negative polarity and carrier C as an example of a magnetic material having magnetism and charged to the positive polarity as main components. The composition contains an agent. In FIG. 2, one developer G is shown enlarged. Further, in FIG. 2, the accommodation height of the developer G accommodated in the housing 52 is indicated by a two-dot chain line G.

(housing)
As shown in FIG. 2, when viewed in the Z direction, the housing 52 protrudes in the -Y side and curves in two places in the X direction, the bottom wall 52A and the Y direction at the central portion of the bottom wall 52A in the X direction. And the partition wall 52B which stands. The housing 52 also has a side wall 52C that stands in the Y direction at the + Z side, the −Z side and the + X side of the bottom wall 52A. Furthermore, the housing 52 has an extending wall 52D extending from the end on the -X side of the bottom wall 52A to the -X side along the X direction. The housing 52 accommodates the developer G therein.

  Inside the housing 52, a first agitation chamber 53A and a second agitation chamber 53B are formed by being partitioned by the partition wall 52B. The first stirring chamber 53A is disposed on the -X side and is open to the + Y side. The second stirring chamber 53B is disposed on the + X side of the first stirring chamber 53A and is open to the + Y side. Further, the + Y side of the first stirring chamber 53A and the second stirring chamber 53B is covered with the cover member 54. Here, a portion surrounded by the bottom wall 52A on the -X side, the cover member 54, the partition wall 52B, the side wall 52C on the + Z side, and the side wall 52C on the -Z side is referred to as a developing chamber 55.

  The developing chamber 55 is an example of a storage chamber for storing the developer G, and includes a first stirring chamber 53A. Further, inside the developing chamber 55, a developing roller 56 and a regulating member 66, which will be described later, are provided. The housing 52 is provided with a replenishing portion (not shown) to replenish the toner T from the toner cartridge 29 (see FIG. 1). The replenishment unit is connected to the second agitation chamber 53B, and the toner T replenished from the toner cartridge 29 flows into the second agitation chamber 53B via the replenishment unit.

  As shown in FIG. 4, an inlet 59A that opens in the X direction and connects the first stirring chamber 53A and the second stirring chamber 53B is formed on the + Z side of the end on the + Z side of the partition wall 52B. . Further, on the −Z side of the end on the −Z side of the partition wall 52B, an outlet 59B that opens in the X direction and connects the first stirring chamber 53A and the second stirring chamber 53B is formed. That is, the partition wall 52B is formed from the inflow port 59A to the outflow port 59B. In the housing 52, by forming the inlet 59A and the outlet 59B, the developer G can circulate in the first stirring chamber 53A and the second stirring chamber 53B.

  In the first stirring chamber 53A, the supply member 62 is rotatably provided with the Z direction as an axial direction. In the second stirring chamber 53B, the stirring member 64 is rotatably provided with the Z direction as an axial direction. The developer G accommodated in the housing 52 circulates in the first stirring chamber 53A and the second stirring chamber 53B by the rotation of the supply member 62 and the stirring member 64. Further, the developer G in the first stirring chamber 53A is supplied to the developing roller 56.

(Development roll)
The developing roll 56 shown in FIG. 2 has a cylindrical developing sleeve 57 as an example of a rotating member, and a magnet roll 58 as an example of a magnetized member provided inside the developing sleeve 57.

  The developing sleeve 57 is provided in the housing 52 via a bearing (not shown) so as to rotate around its own axis in the Z direction as the inside in the developing chamber 55. Further, the developing sleeve 57 is rotated in the same direction as the photosensitive member 22 at a position (developing area) facing the photosensitive member 22 (see FIG. 1) by being rotationally driven by a motor (not shown). . Specifically, the developing sleeve 57 rotates counterclockwise as viewed from the -Z side to the + Z side. In the following description, the rotational direction of the developing sleeve 57 is referred to as an A direction, and is indicated by an arrow A. Further, the developing sleeve 57 holds the developer G on the outer peripheral surface, develops the electrostatic latent image on the photosensitive member 22 with toner, and forms a toner image TA (see FIG. 1).

  The magnet roll 58 is a cylindrical member whose axial direction is the Z direction, and both ends in the Z direction are fixed to the side wall 52C on the + Z side and the −Z side of the housing 52. Further, the magnet roll 58 has a plurality of magnetic poles described later along the circumferential direction magnetized, and generates a magnetic force that attracts or repels the developer G.

  As shown in FIG. 6, in the magnet roll 58, as an example, the pickoff pole N3, the dummy pole Nd, the pickup pole N2, layer formation along the A direction from the side close to the extending wall 52D as viewed in the Z direction. A pole S2, a transport pole N1 and a developing pole S1 are provided. In addition, N and S of the code represent N pole and S pole. The solid line M in FIG. 6 represents the magnetic flux density distribution of the magnet roll 58.

  The pickup pole N2 is an example of the pole top pole, and is located between 3 o'clock and 4 o'clock according to the clock. In addition, the pick-up pole N2 attracts the developer G and pumps up the developer G to the developing sleeve 57. The layer forming pole S2 is located between 12 o'clock and 1 o'clock in the timepiece dial, and causes the carrier C to spike around the -Y side end of the regulating member 66. The transport pole N1 is located at 10 o'clock as it is called by the clock, and attracts the developer G so that the developer G transported toward the development region does not fall. The development pole S1 is located at 8 o'clock in the clock face, is disposed opposite to the photosensitive member 22 (see FIG. 1), and causes the carrier C to brush.

  The pickoff pole N3 is an example of a peeling pole, and is located at 6 o'clock according to the clock. That is, the pickoff pole N3 is disposed upstream of the pickup pole N2 in the A direction. Further, the pickoff pole N3 has the same N polarity as the pickup pole N2, and faces the extending wall 52D. Further, the pick-off pole N3 separates the developer G from the outer peripheral surface of the developing sleeve 57 by forming a repulsive magnetic field with the dummy pole Nd and the pickup pole N2.

  The dummy pole Nd is an example of the auxiliary peeling pole, and is located between 4 o'clock and 5 o'clock according to the timepiece board. That is, the dummy pole Nd is formed between the pickoff pole N3 and the pickup pole N2 in the A direction. The dummy pole Nd is magnetized to an N pole having the same polarity as the pickup pole N2 and the pickoff pole N3. Furthermore, the magnetic flux density of the dummy pole Nd is lower than the magnetic flux density of the pickup pole N2 and the magnetic flux density of the pickoff pole N3.

(Supply member)
As shown in FIGS. 2 and 4, the supply member 62 has a shaft 62A whose axial direction is the Z direction, and a spiral blade 62B formed on the outer periphery of the shaft 62A. Both ends of the shaft portion 62A in the Z direction are rotatably supported by the side walls 52C on the + Z side and the −Z side. The blade portion 62B is formed to transport the developer G from the -Z side to the + Z side as the shaft portion 62A rotates. Further, the blade portion 62B is disposed to face the partition wall 52B from the outlet 59B to the inlet 59A. Further, the blade portion 62B faces the developing sleeve 57.

  The supply member 62 rotates in the developing chamber 55 (first stirring chamber 53A) to supply the developer G to the developing sleeve 57. The rotation direction of the supply member 62 is reverse to the A direction in a region facing the developing sleeve 57. In FIG. 4, the developing roller 56, the supply member 62, the stirring member 64, and the suppressing member 70 are shown in the same plane (X-Z plane). Moreover, in FIG. 4, the suppression member 70 is shown with the dashed-two dotted line.

(Agitating member)
As shown in FIGS. 2 and 4, the agitating member 64 has a shaft 64A whose axial direction is the Z direction, and a spiral blade 64B formed on the outer periphery of the shaft 64A. Both ends in the Z direction of the shaft portion 64A are rotatably supported by the side walls 52C on the + Z side and the -Z side. The blade portion 64B is formed to transport the developer G from the + Z side to the -Z side as the shaft portion 64A rotates. Further, the blade portion 64B is disposed to face the partition wall 52B from the inflow port 59A to the outflow port 59B. The stirring member 64 rotates in the second stirring chamber 53B to stir the toner T and the carrier C, and conveys the developer G toward the supply member 62.

(Regulation member)
A regulating member 66 shown in FIG. 2 is attached to a bracket 65 fixed to the housing 52 on the + Y side of the developing roller 56. The + Y side of the bracket 65 is covered by a cover member 54. The regulating member 66 is, for example, a plate-like member which is disposed on the + Y side of the developing sleeve 57 with the Z direction as the longitudinal direction and extends toward the outer peripheral surface of the developing sleeve 57. Further, the leading end (lower end) of the regulating member 66 is disposed at an interval from the developing sleeve 57. Thus, the regulating member 66 regulates the thickness of the layer of the developer G held on the outer peripheral surface of the developing sleeve 57.

(Sealing material)
The sealing material 68 shown in FIG. 2 is made of, for example, a polymer film. In addition, one end portion of the sealing material 68 is fixed to the cover member 54. The other end portion (tip portion) of the sealing material 68 is disposed on the −X side with respect to the developing sleeve 57. Thus, the seal member 68 suppresses scattering of the toner T from the developing sleeve 57 to the photosensitive member 22 (see FIG. 1).

<Restraint member>
As shown in FIG. 4, the suppressing member 70 is provided between the supply member 62 and the developing sleeve 57 with the Z direction as the longitudinal direction. When the supply member 62 and the development sleeve 57 are viewed in the Z direction, a common tangent H1 and a common tangent H2 between the outer periphery of the supply member 62 and the outer periphery of the development sleeve 57 are shown in FIG. This means the range enclosed by the supply member 62 and the developing sleeve 57). Further, the + Z side end of the suppression member 70 is connected to the inner surface of the side wall 52C on the + Z side, and the -Z side end of the suppression member 70 is connected to the inner surface of the side wall 52C on the -Z side. That is, in the present embodiment, as an example, the suppressing member 70 is integrated with the housing 52, and both the suppressing member 70 and the housing 52 are nonmagnetic resin materials (for example, ABS resin (acrylonitrile butadiene styrene copolymer resin) It consists of).

  FIG. 3 shows the developing device 50 with the cover member 54 (see FIG. 2) and the developing roller 56 (see FIG. 2) removed to expose the suppressing member 70. As shown in FIG. A pillar 71 standing on the inner surface of the first stirring chamber 53A is formed on a part of the suppression member 70 in the longitudinal direction, as an example. The support column 71 suppresses the bending of the central portion with respect to both end portions in the longitudinal direction of the suppression member 70.

  As shown in FIG. 5, as an example, the suppressing member 70 is formed in a pentagonal shape in a cross section (X-Y cross section) viewed in the Z direction. Specifically, the suppressing member 70 has a vertical surface 74, a bottom surface 75, a first opposing surface 76, an upper surface 77, and a second opposing surface 78.

  Here, the rotation center of the supply member 62 is taken as a point O. The center of the pickoff pole N3 in the A direction on the outer peripheral surface of the magnet roll 58 is referred to as point B, and the center of the dummy pole Nd in the A direction is referred to as point C. The center of each magnetic pole in the present embodiment is a position in the A direction where the magnetic flux density is the largest among the magnetic flux density distributions in each magnetic pole.

  Furthermore, a line segment OB connecting the point O and the point B is shown by a broken line as a first virtual line K1. The first virtual line K1 is an example of a virtual line. Further, a line segment OC connecting the point O and the point C is indicated by a broken line as a second virtual line K2. The second virtual line K2 is an example of an auxiliary virtual line. The first virtual line K1 and the second virtual line K2 are lines when the suppressing member 70 is viewed in the Z direction, but when the suppressing member 70 is viewed in the Y direction, an imaginary plane having a length in the Z direction It is. When the developing device 50 is viewed in the Z direction, an area surrounded by the outer peripheral surface of the supply member 62, the outer peripheral surface of the developing sleeve 57, the first virtual line K1, and the second virtual line K2 is a region S Do. In the following description, “in the region S” includes those disposed on the first virtual line K1 and the second virtual line K2. Further, “disposed on the downstream side with respect to the first virtual line K1” and “disposed on the upstream side with respect to the second virtual line K2” mean “disposed on the first virtual line K1”, “second virtual line It is a concept including “arranged on K2”.

  The vertical surface 74 is a Y-Z plane along the Y direction, and is disposed in the region S. The bottom surface 75 is an inclined surface extending from the -Y side end of the vertical surface 74 to the + X side along the first imaginary line K1, and is disposed in the region S. The first opposing surface 76 is a surface that is curved along the outer peripheral surface of the supply member 62 from the + X side end of the bottom surface 75, and faces the supply member 62. Further, the first opposing surface 76 is disposed in the region S at an interval from the outer peripheral surface of the supply member 62.

  The upper surface 77 is an inclined surface extending from the + Y side end of the first opposing surface to the −X side along the second imaginary line K2, and is disposed in the region S. The second opposing surface 78 is a surface which is curved along the outer peripheral surface of the developing sleeve 57 from the −X side end of the upper surface 77 and faces the developing sleeve 57. Further, the second opposing surface 78 is disposed in the region S at an interval from the outer peripheral surface of the developing sleeve 57. Thus, the suppression member 70 is arrange | positioned in the area | region S as an example. Further, the suppressing member 70 is disposed on the downstream side in the A direction with respect to the first virtual line K1. Furthermore, the suppression member 70 is disposed on the upstream side in the A direction with respect to the second virtual line K2.

  As shown in FIG. 5, the extending wall 52D is disposed on the -Y side of the pickoff pole N3. Further, the distance between the upper surface 52E of the extending wall 52D and the outer peripheral surface of the developing sleeve 57 in the Y direction is wider on the + X side of the extending wall 52D than on the −X side. The vertical surface 74 is disposed on the + X side with respect to the + X side end of the extending wall 52D when viewed in the Y direction. In the present embodiment, as an example, by forming the vertical surface 74 in the suppression member 70, the distance between the suppression member 70 and the upper surface 52E of the extension wall 52D is widened.

[Function]
Next, the operation of the present embodiment will be described.

  FIG. 7 shows the separated state and the raised state of the developer G when the developing sleeve 57 and the supply member 62 are rotated in the A direction in the developing device 50. The developer G is divided into a developer Ga shown by black circles and a developer Gb shown by white circles.

  The developer Ga represents the developer G in a state in which the toner T and the carrier C (see FIG. 2) are agitated and the toner T adheres to the carrier C (a state where the set toner concentration is reached). The developer Gb represents the developer G in a state in which the toner T is consumed by development and the amount (toner concentration) of the toner T adhering to the carrier C is reduced as compared with the developer Ga. In FIG. 7, the developer Ga from the pickup pole N2 to the developing pole S1 via the layer forming pole S2 and the transport pole N1 is not shown.

  In the developing device 50, when the developing sleeve 57 rotates and development is performed, a part of the developer Ga adhering to the outer circumferential surface of the developing sleeve 57 is consumed by the toner T and becomes the developer Gb. Then, the developer Gb passes through the area facing the pickoff pole N3 by the rotation of the developing sleeve 57. At this time, the repelling magnetic field by the pickoff pole N3 and the dummy pole Nd and the repelling magnetic field by the pickoff pole N3 and the pickup pole N2 reduce the attraction of the developer Gb to the developing sleeve 57 and the action of gravity. Fall down.

  Subsequently, among the developer Gb which has started to fall at the pickoff pole N3, a part of the developer Gb present in the vicinity of the developing sleeve 57 is transported (moved) in the A direction by the rotation of the developing sleeve 57. Here, the developer Gb transported in the A direction contacts the suppression member 70 and falls, whereby the movement to the developing sleeve 57 is suppressed compared to the configuration without the suppression member 70, and the developer Gb is moved to the development sleeve 57. Re-adhesion is suppressed. Furthermore, the suppressing member 70 is disposed on the downstream side with respect to the first virtual line K1, so the developer Gb falls on the upstream side of the first virtual line K1 (flows on the upstream side). Then, the developer Gb falling on the upstream side of the first virtual line K1 is caught in the rotation of the supply member 62 rotating toward the −Y side in the vicinity of the suppression member 70. Thereby, the developer Gb in contact with the suppressing member 70 flows between the suppressing member 70 and the extending wall 52D and flows into the first stirring chamber 53A as shown by the arrow FA.

  On the other hand, the developer Gb having passed between the developing sleeve 57 and the suppressing member 70 does not have the suppressing member 70 on the downstream side of the second virtual line K2, so the suppressing member is on the downstream side of the second virtual line K2. It does not move toward the developing sleeve 57 in contact with the surface 70. Furthermore, the developer Gb that has passed between the developing sleeve 57 and the suppressing member 70 passes through the area where the magnetic flux density present on the downstream side of the second virtual line K2 is the lowest (the repulsive force becomes large) Then, it falls on the downstream side of the second virtual line K2 (flows on the downstream side). Therefore, as shown by the arrow FB, the developer Gb separates from the developing sleeve 57 and drops into the supply member 62 and the first stirring chamber 53A.

  Subsequently, the developer Gb flowing into the first stirring chamber 53A through the first route indicated by the arrow FA and the second route indicated by the arrow FB is replenished with the toner T (see FIG. 2) by the rotation of the supply member 62. The mixture is stirred to form developer Ga. Then, the developer Ga approaches the developing sleeve 57 by the rotation of the supply member 62 as shown by the arrow FC, and is pumped up to the developing sleeve 57 by the action of the magnetic field generated by the pickup pole N2. After being regulated, it is used for development.

  As described above, in the developing device 50, when the developing sleeve 57 is rotated at high speed, the suppressing member 70 suppresses the movement of the developer Gb separated from the developing sleeve 57 toward the developing sleeve 57 again. . As a result, compared to the configuration in which the movement of the developer Gb is not suppressed on the downstream side of the pickoff pole N3, adhesion of the developer Gb separated from the developing sleeve 57 to the developing sleeve 57 is suppressed. As an example of the case where the developing sleeve 57 is rotated at a high speed, the rotational speed of the developing sleeve 57 at the time of monochrome image formation is made higher than that of the developing sleeve 57 at the time of color image formation (production There is a case) Since the suppression member 70 is nonmagnetic, the attraction of the developer G to the suppression member 70 is suppressed.

  Further, in the developing device 50, the magnet roll 58 is formed with the dummy pole Nd having the same polarity as the pickoff pole N3 and the pickup pole N2 and having a magnetic flux density lower than that of the pickoff pole N3 and the pickup pole N2. Then, with respect to a second virtual line K2 in which the suppressing member 70 connects the position C (see FIG. 5) of the center of the dummy pole Nd and the position O (see FIG. 5) of the rotation center of the supply member 62, It is located upstream. For this reason, in the region where the magnetic flux density between the pickoff pole N3 and the pickup pole N2 becomes low, the developer Gb is not suppressed from falling by the suppressing member 70, and moves toward the developing sleeve 57 again. There is no longer. Thus, the developer Gb separated from the developing sleeve 57 is prevented from adhering to the developing sleeve 57 again, as compared with the configuration in which the suppressing member 70 extends further to the downstream side than the second virtual line K2.

  In the image forming apparatus 10 shown in FIG. 1, the ratio of the developer Gb (see FIG. 7) in the developer G used for development is lower than that in the configuration without the developing device 50. That is, since it becomes difficult to use the developer Gb having a low density of the toner T (see FIG. 2), the image defect caused by the developer Gb peeled off from the developing sleeve 57 adhering to the developing sleeve 57 again (for example, Image density reduction and image density unevenness are suppressed.

  The present invention is not limited to the above embodiment.

  In the developing device 50, the regulating member 66 may be disposed on the -Y side of the developing sleeve 57. In this case, if the suppressing member 70 is disposed on the downstream side in the rotational direction of the developing sleeve 57 with respect to the virtual line connecting the rotation center of the supply member 62 and the pickoff pole, the developer peeled off from the developing sleeve 57 And the developing sleeve 57 by contact with the restraining member 70. That is, the separated developer is prevented from moving toward the developing sleeve 57 and adhering again.

  The bottom surface 75 of the suppression member 70 is not limited to the one disposed on the first virtual line K1, but may be disposed downstream of the first virtual line K1 in the A direction. Further, the upper surface 77 of the suppressing member 70 is not limited to the one disposed on the second virtual line K2, and may be disposed on the upstream side in the A direction with respect to the second virtual line K2. Furthermore, the suppression member 70 is not limited to the one having a pentagonal X-Y cross section, and may have a triangular shape, a quadrangular shape, or a polygonal shape having a hexagonal shape or more. Further, the suppression member 70 may have a circular or elliptical cross section in the X-Y direction.

  As shown in FIG. 8A, in the developing device 50, the suppressing member 70 (see FIG. 2) may be replaced with a suppressing member 80 as an example of the nonmagnetic part. The suppressing member 80 has a bottom surface 82, a first opposing surface 84, an upper surface 86, and a second opposing surface 88. The bottom surface 82 is an inclined surface along the first virtual line K1 and is disposed in the region S. The first opposing surface 84 is configured the same as the first opposing surface 76 described above (see FIG. 5). The upper surface 86 is configured the same as the upper surface 77 (see FIG. 5) described above. The material of the suppression member 80 is, for example, the same nonmagnetic material as the suppression member 70.

  The second opposing surface 88 is a curved surface extending from the −X side end of the upper surface 86 to one end of the bottom surface 82 along the outer peripheral surface of the developing sleeve 57, and is opposed to the developing sleeve 57. In addition, the second opposing surface 88 is disposed in the region S. That is, the suppressing member 80 is disposed in the region S, and is disposed downstream of the first imaginary line K1 in the A direction and upstream of the second imaginary line K2 in the A direction. As described above, by extending the bottom surface 82 along the first imaginary line K1, the developer separated from the developing sleeve 57 is moved toward the supply member 62.

  As shown in FIG. 8B, in the developing device 50, the suppressing member 90 (see FIG. 2) may be replaced with a suppressing member 90 as an example of the nonmagnetic part. The suppressing member 90 has a longitudinal surface 92, a bottom surface 94, a first opposing surface 96, a curved surface 97, and a second opposing surface 98. The vertical surface 92 is a surface along the Y direction, and is disposed in the region S and outside the region S so as to intersect the first imaginary line K1. The bottom surface 94 extends from the -Y side end of the vertical surface 92 to the + X side along the X direction, and is disposed outside the region S. The material of the suppressing member 90 is, for example, the same nonmagnetic material as the suppressing member 70.

  The first opposing surface 96 is a surface that is curved along the outer peripheral surface of the supply member 62 from the + X side end of the bottom surface 94, and faces the supply member 62. In addition, the first opposing surface 96 is disposed in the region S and outside the region S across the first virtual line K1 and the second virtual line K2 at an interval from the outer peripheral surface of the supply member 62. The curved surface 97 protrudes on the downstream side in the A direction further than the second imaginary line K2 continuously to the + Y side of the first opposing surface 96. The second opposing surface 98 is formed continuously to the -X side end of the curved surface 97, and has a configuration similar to that of the second opposing surface 78 (see FIG. 5). Thus, even if part of the suppressing member 90 is disposed on the upstream side in the A direction from the first virtual line K1 and on the downstream side in the A direction from the second virtual line K2, the remaining portion of the suppressing member 90 is Since it is disposed in the area S, the reattachment of the developer to the developing sleeve 57 is suppressed.

  In the developing device 50, the dummy pole Nd may be removed, and the developer G may be peeled off from the developing sleeve 57 by the repulsive magnetic field of the pickoff pole N3 and the pickup pole N2. In this case, the downstream end of the suppression member 70 in the A direction may be extended to a region facing the region where the magnetic flux density is the lowest between the pickoff pole N3 and the pickup pole N2.

10 Image Forming Device 22 Photoreceptor (Example of Image Carrier)
30 Transfer part (an example of transfer means)
50 developing device 55 developing chamber (an example of a storage chamber)
57 Developing sleeve (example of rotating member)
58 Magnet roll (an example of a magnet attachment member)
62 Supply member 70 Suppression member (an example of nonmagnetic portion)
80 Suppression member (an example of nonmagnetic part)
90 Suppression member (an example of nonmagnetic part)
C carrier (an example of magnetic material)
Nd dummy pole (an example of auxiliary peeling pole)
G Developer K1 first virtual line (an example of a virtual line)
K2 second virtual line (an example of auxiliary virtual line)
N2 pick-up pole (an example of the pole upper pole)
N3 pickoff pole (an example of exfoliation pole)
TA toner image (example of developer image)

Claims (2)

A cylindrical rotating member which rotates in a storage chamber for storing a developer containing a magnetic material;
Provided on the inner side of the rotating member, a scooping pole for pumping the developer to the revolving member, and the same polarity as the scooping pole and disposed on the upstream side of the scooping pole in the rotational direction of the rotating member A stripping electrode for stripping the developer, and a portion between the stripping electrode and the upper pole, which has the same polarity as the stripping electrode and the upper pole, and a magnetic flux density lower than that of the stripping pole and the upper pole. An auxiliary peeling electrode, and a magnetized member in which the auxiliary peeling electrode is magnetized;
A supply member that rotates in the storage chamber to supply the developer to the rotating member;
A nonmagnetic nonmagnetic portion disposed between the rotation member and the supply member, at least a portion of which is the rotation direction with respect to a virtual line connecting the rotation center of the supply member and the separation pole. The nonmagnetic portion disposed on the downstream side of the rotation direction with respect to an auxiliary imaginary line connecting the auxiliary separation pole and the rotation center of the supply member ;
Developing device. An image carrier for holding a latent image,
The developing device according to claim 1, wherein the latent image of the image carrier is developed with a developer to form a developer image.
A transfer unit configured to transfer the developer image to a recording medium;
An image forming apparatus comprising:

Images