JP6003330B2 - Developing device and image forming apparatus - Google Patents

Description

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

  Patent Document 1 discloses a technique for forming a developer layer on a developing sleeve by causing an elastic blade to hit against the developing sleeve.

  Patent Document 2 discloses a technique in which an arc-shaped flexible elastic member is pressed against a developing sleeve to form a developer layer on the developing sleeve, and the developer is peeled and collected with a scraper.

JP-A-01-120581 Japanese Patent Laid-Open No. 02-0501181

  An object of the present invention is to reduce unevenness in the concentration of the developer on the developer holder.

A developing device according to a first aspect of the present invention includes a cylindrical member that is disposed to be opposed to the latent image holding member and is rotated, and a developing magnetic pole that is provided inside the cylindrical member and is disposed to be opposed to the latent image holding member. And a magnetic force generating portion provided on the downstream side in the rotation direction of the developing magnetic pole and on the upstream side in the rotation direction with respect to the portion where the developer layer is formed, and a latent image on the latent image holding member A developer holder that holds the developer to be developed on the surface of the cylindrical member, a tape material that is fixed at one end and folded back in a U-shape, and a plate-like magnet attached to the other end of the tape material A sliding member configured to slide onto the surface of the cylindrical member with a plate surface by being attracted by the magnetic force of the transporting magnetic pole and being held by the transporting magnetic pole . And comprising.

In the developing device according to a second aspect of the present invention, the developer holders are provided in pairs in close proximity to each other and rotate so that the moving direction is the same in the close proximity portions. The magnetic force generating portion of the developer holding body is provided with the developing magnetic pole and a delivery magnetic pole that is disposed opposite to the portion corresponding to the proximity portion to form the developer layer, and A layer shaping member is provided for adjusting the thickness of the layer at a portion downstream of the developing magnetic pole in the rotation direction of the developing magnetic pole and upstream of the transfer magnetic pole in the rotation direction of any one of the pair of developer holders. A developer peeling means for peeling the developer by a magnetic force at a site on the downstream side in the rotation direction of the development magnetic pole on the other side of the developer holding body and on the upstream side of the rotation of the delivery magnetic pole is provided, and the sliding member is The current pairing It is provided so as to give ground to the developer in the rotation direction upstream side of the developer peeling means in the direction of rotation downstream of the developing magnetic pole of the other agent holding member.

According to a fourth aspect of the present invention, there is provided a developing device according to the first or second aspect , and a latent image in which an electrostatic latent image formed on a surface is visualized as a toner image by the developing device. A holder, and transfer means for transferring a toner image formed on the surface of the latent image holder to a transfer target.

  According to the first aspect of the present invention, it is possible to reduce the uneven concentration of the developer in the developer holding body, compared to the case where the sliding member is not provided.

According to the second aspect of the present invention, as compared with the case where the sliding member does not slide the developer on the downstream side in the rotation direction of the developing magnetic pole and the developer on the upstream side in the rotation direction of the developer peeling means, the development of the developer holder is performed. The uneven concentration of the agent can be reduced.

According to the third aspect of the present invention, compared with the case where the developing device according to the first or second aspect is not provided, the transferred object caused by the uneven concentration of the developer on the developer holding member is reduced. The uneven density of the transferred toner image can be reduced.

1 is a configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating a configuration of a developing device according to an embodiment of the present invention provided in the image forming apparatus illustrated in FIG. 1. FIG. 3 is an enlarged configuration diagram in which a main part of the developing device shown in FIG. 2 is enlarged. FIG. 10 is an enlarged configuration diagram corresponding to FIG. 3 in which a main part of a developing device according to a modification is enlarged. (A) is a schematic diagram schematically showing the state of toner attached to the surface of the reverse rotation developing roll before development, and (B) is the state of toner attached to the surface of the reverse rotation developing roll after development and the surface adhesion of the photoreceptor. It is a schematic diagram schematically showing the state of the toner. In the comparative example in which the rubbing member is not provided, (A) shows an image formed on the sheet member, and (B) shows the developer state of the reverse rotation developing roll immediately after the image formation at the B position in (A). It is a top view shown typically. It is a structural diagram showing an example of a support structure of the other end portion of the rotation shaft of the reverse rotation developing roll.

  An example of a developing device and an image forming apparatus according to an embodiment of the present invention will be described. Note that an arrow UP shown in the drawing indicates the upper side in the vertical direction.

<Image forming apparatus>
First, the overall configuration of the image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, an image forming apparatus 10 includes a drum-shaped photoconductor 12 as an example of a latent image holding member, a charging device 14 that charges the surface of the photoconductor 12, and a photoconductor based on image data. An exposure device 16 that forms an electrostatic latent image by irradiating a laser beam 12, a developing device 18 that selectively transfers toner to the electrostatic latent image and visualizes it as a toner image, and a conveyance path 20 A transfer roll 22 as an example of transfer means for transferring a toner image on the surface of the photosensitive member 12 to a sheet member (recording medium) P as an example of a supplied transfer target, and a toner image on the sheet member P are heated A fixing device 24 that pressurizes and fixes the toner image on the sheet member P and a cleaning device 26 that cleans the toner remaining on the photoreceptor 12 after the toner image is transferred are provided. Details of the developing device 18 (see FIG. 2) will be described later.

  The image forming apparatus 10 is covered with a main body side cover 10B and a top plate 10A. A shaft 10C that rotatably connects the top plate 10A to the main body side surface cover 10B is provided at the upper end corner of the main body side surface cover 10B, and the top plate 10A is rotated in the direction of arrow A about the shaft 10C. Thus, the inside of the image forming apparatus 10 is opened. Then, the top plate 10A of the image forming apparatus 10 is opened, and various maintenance operations (replenishment of developer G, replacement of each member, etc.) are performed.

  A sheet feeding device 40 that feeds the sheet members P one by one is provided on the lower side in the image forming apparatus 10. The paper feeding device 40 includes a paper feeding member 41 on which a plurality of sheet members P are stacked. The sheet members P stacked on the paper feed member 41 are sequentially taken out by the take-out roll 42, and further conveyed one by one by the paper feed roll 44 that is rotationally driven and the separation roll 46 provided on the paper feed member 41. It becomes the composition which is done.

  Further, a plurality of conveyance rolls 48 are provided along the conveyance path 20 of the sheet member P, and the sheet member P is conveyed along the conveyance path 20 to the downstream side in the conveyance direction of the sheet member P (hereinafter simply referred to as the downstream side). It is configured to be.

  Further, the fixing device 24 described above is provided on the downstream side of the conveyance path 20. The fixing device 24 includes a heating roll 24H and a pressure roll 24N. When the sheet member P passes between the heating roll 24H and the pressure roll 24N, the toner image on the sheet member P is transferred to the sheet. It is configured to be fixed to the member P.

  Further, on the downstream side of the fixing device 24, a discharge roll 38 for discharging the sheet member P on which the toner image is fixed to the upper surface of the top plate 10A is provided.

  Further, a manual paper feed tray 32 for manually feeding the sheet member P is provided on the side of the image forming apparatus 10. This manual paper feed tray 32 is provided with a half-moon shaped delivery roll 34, and further, a separation roll 36 is provided with the sheet member P sandwiched between the delivery roll 34.

  The separation roll 36 is supported by a support member (not shown) provided at both ends, and is urged toward the delivery roll 34 by an urging force such as a coil spring provided inside the support member. With such a configuration, when the delivery roll 34 rotates, the sheet member P placed on the manual feed tray 32 is sent to the transport path 20 one by one by the delivery roll 34 and the separation roll 36. Yes.

(Image formation process)
Next, an image forming process of the image forming apparatus 10 will be described.

  First, the charging device 14 charges the surface of the photoreceptor 12. Subsequently, the exposure device 16 exposes the charged surface of the photoreceptor 12 based on image data read by a scanner (not shown) or data sent from the outside, and an electrostatic latent image is formed on the surface of the photoreceptor 12. To do. The developing device 18 develops the electrostatic latent image and visualizes it as a toner image.

  On the other hand, the sheet member P is sent out from the paper feed member 41 or the manual paper feed tray 32 to the transport path 20. The sheet member P sent to the conveyance path 20 passes through a transfer portion 31 formed between the photosensitive member 12 holding the toner image and the transfer roll 22, and the toner image is transferred to the sheet member P by the transfer roll 22. The The toner image transferred to the sheet member P is fixed to the sheet member P by passing between the heating roll 24H and the pressure roll 24N of the fixing device 24. The sheet member P on which the toner image is fixed is discharged onto the top surface of the top plate 10A by the discharge roll 38.

<Developing device>
Next, the configuration of the developing device 18 will be described. The rotation direction of the photoconductor 12 is indicated by an arrow B, the rotation direction of a reverse rotation developing roll 100 described later is indicated by an arrow C, and the rotation direction of a forward rotation developing roll 200 described later is indicated by an arrow D.

  As shown in FIG. 2, the developing device 18 includes a housing 50 having an opening 50 </ b> A at a position facing the photoconductor 12. Inside the housing 50, a reverse rotation developing roll 100 and a forward rotation developing roll 200 as an example of a pair of developer holders are provided close to each other in the vertical direction.

  The reverse rotation developing roll 100 is disposed to face the surface (outer peripheral surface) of the photoconductor 12, and in a portion GP <b> 1 facing the photoconductor 12, the reverse rotation direction (B direction) of the photoconductor 12 is opposite (C direction). Rotate like so. On the other hand, the forward rotation developing roll 200 is disposed opposite to the surface (outer peripheral surface) of the photosensitive member 12 on the downstream side in the rotation direction (B direction) of the photosensitive member 12 of the reverse rotating developing roller 100, and a part GP <b> 2 facing the photosensitive member 12. Then, the photoconductor 12 rotates so as to be in the same direction (D direction) as the rotation direction (B direction). Further, the reverse rotation developing roll 100 and the forward rotation developing roll 200 are arranged close to each other in the vertical direction, and the adjacent proximity part GP3 rotates in the same direction (the reverse rotation developing roll 100 and the forward rotation developing roll 100). Details of the rotary developing roll 200 will be described later).

  A first stirring and conveying member 58 and a second stirring and conveying member 60 that convey the developer G to the forward rotation developing roll 200 are provided in the storage chamber 50B that accommodates the developer G provided in the lower part of the housing 50. It has been.

  The first agitating and conveying member 58 and the second agitating and conveying member 60 are arranged side by side so as to circulate and convey the developer G in a plan view on the lower side (the lower right side in the figure) of the forward rotation developing roll 200. Then, by rotating the first stirring / conveying member 58 and the second stirring / conveying member 60, the developer G is transported along the rotation axis direction of the forward rotation developing roll 200 while being stirred and developed to the forward rotating developing roll 200. The agent G is supplied. Note that the developer G used in the developing device 18 is a two-component developer including a resin toner T and magnetic carrier particles K (see FIG. 6).

  A layer shaping member 62 is provided on the upstream side in the rotation direction (D direction) of the proximity portion GP3 in the forward rotation developing roll 200. The layer shaping member 62 is a plate member having a rectangular cross-sectional shape along the normal direction of the outer periphery of the forward rotation developing roll 200, and one end face 62 </ b> A of the rectangular cross section is spaced from the surface of the forward rotating developing roll 200. They are arranged opposite each other. Then, when the developer G passes between the layer shaping member 62 and the forward rotation developing roll 200, the thickness of the layer of the developer G held on the forward rotation developing roll 200 is adjusted.

  A guide plate 64 is disposed above the layer shaping member 62. The guide plate 64 is disposed such that the front end portion 64 </ b> A faces the reverse rotation developing roll 100 and extends obliquely downward from the front end portion 64 </ b> A toward the first stirring and conveying member 58. The guide plate 64 guides the developer G that has fallen from the reverse rotation developing roll 100 toward the storage chamber 50B. That is, the developer G that has fallen off from the reverse rotation developing roll 100 is guided to the accommodation chamber 50 </ b> B without directly adhering to the forward rotation developing roll 200.

(Configuration of reverse rotation developing roll 100 and forward rotation developing roll 200)
Next, details of the configurations of the reverse rotation developing roll 100 and the forward rotation developing roll 200 will be described. In the description of each magnetic pole to be described later, “S” means the S pole and “N” means the N pole.

  As shown in FIG. 2, the counter-rotating developing roll 100 is an example of a magnetic force generation unit including a cylindrical developing sleeve 110 as an example of a cylindrical member and a plurality of magnetic poles provided inside the developing sleeve 110. Magnet roll (mag roll) 120. Similarly, the forward rotation developing roll 200 is also a cylindrical developing sleeve 210 as an example of a cylindrical member, and a magnet roll (mag roll) as an example of a magnetic force generating part configured by a plurality of magnetic poles provided inside the developing sleeve 210. 220. Further, the developing sleeve 110 of the reverse rotating developing roll 100 and the developing sleeve 210 of the forward rotating developing roll 200 are arranged to face each other in the vertical direction so that a gap is formed between the outer peripheral surfaces. The portion where the developing sleeve 110 and the developing sleeve 210 face each other is the proximity portion GP3 described above.

  The developing sleeve 110 of the reverse rotation developing roll 100 is disposed so that the rotation axis direction thereof faces the surface of the photoconductor 12 along the rotation axis direction of the photoconductor 12, and the moving direction at the part GP <b> 1 facing the photoconductor 12 ( Rotation is performed so that (C direction) is opposite to the rotation direction (B direction) of the photoconductor 12. The magnet roll 120 is arranged inside the developing sleeve 110 and forms a magnetic field distributed in the circumferential direction outside the developing sleeve 110 by a plurality of magnetic poles arranged in the circumferential direction.

  The magnet roll 120 of the reverse rotation developing roll 100 includes a magnetic pole N1, a magnetic pole N2, and a magnetic pole N3 that are formed of seven permanent magnets having S or N poles formed on the surface side along the circumferential direction of the developing sleeve 110. The magnetic pole S1, the magnetic pole S2, the magnetic pole S3, and the magnetic pole S4 are provided radially. In addition, a magnetic pole N3 that is a development magnetic pole (development main pole) is disposed at a portion GP1 where the reverse rotation developing roll 100 faces the photoreceptor 12. The reverse rotation developing roll 100 is configured such that the developer G and the photoconductor 12 are in contact with each other at a part GP1 facing the photoconductor 12 and the electrostatic latent image on the photoconductor 12 is developed with the developer G. ing.

  Next to the downstream side in the rotation direction (C direction) of the magnetic pole N3, a magnetic pole S1 for transporting the developer G and the magnetic pole N1 are arranged, and further, the developer G is peeled next (pick-off is performed). ) The magnetic pole S4 and the magnetic pole S2 are arranged side by side. Further, a magnetic pole N2, which is a delivery magnetic pole, is disposed next to the magnetic pole S2. The magnetic pole N2 is disposed at a site corresponding to the proximity part GP3. Further, a magnetic pole S3 is disposed between the magnetic pole N2 of the delivery magnetic pole and the magnetic pole N3 that is the main pole described above.

  On the other hand, the developing sleeve 210 of the forward rotation developing roll 200 is also arranged to face the surface of the photoconductor 12 so that the rotation axis direction is along the rotation axis direction of the photoconductor 12. However, the moving direction (D direction) of the developing sleeve 210 at the part GP2 facing the photoconductor 12 rotates so as to be the same direction as the rotation direction (B direction) of the photoconductor 12. The magnet roll 220 is disposed inside the developing sleeve 210 and forms a magnetic field distributed in the circumferential direction outside the developing sleeve 210 by a plurality of magnetic poles disposed in the circumferential direction.

  The magnetic roll 220 of the forward rotation developing roll 200 includes a magnetic pole N1, a magnetic pole N2, and a magnetic pole N3 that are formed of seven permanent magnets having S or N poles formed on the surface side along the circumferential direction of the developing sleeve 210. The magnetic pole S1, the magnetic pole S2, the magnetic pole S3, and the magnetic pole S4 are provided radially. In addition, a magnetic pole S1 that is a development magnetic pole (development main pole) is disposed at a part GP2 where the forward rotation developing roll 200 faces the photoconductor 12. The forward rotation developing roll 200 is configured such that the developer G and the photoconductor 12 are in contact with each other at a part GP2 facing the photoconductor 12 and the electrostatic latent image on the photoconductor 12 is developed with the developer G. ing.

  A magnetic pole N3 that transports the developer G is arranged next to the downstream side in the rotation direction (D direction) of the magnetic pole S1, and a magnetic pole S4 and a magnetic pole S3 that peel off the developer G (perform pick-off) are adjacent to the magnetic pole N3. And are arranged. Further, a magnetic pole N2 that is a transport magnetic pole is disposed next to the magnetic pole S3, and a magnetic pole S2 that is a delivery magnetic pole is further disposed next to the magnetic pole N2. The magnetic pole S2 is disposed at a portion corresponding to the proximity portion GP3 so as to face the magnetic pole N2 that is the delivery magnetic pole of the reverse rotation developing roll 100 described above. A magnetic pole N1 is disposed between the magnetic pole S2 of the delivery magnetic pole and the magnetic pole S1 which is the main pole described above.

(Support structure for reverse rotation developing roll 100 and forward rotation developing roll 200)
Next, a support structure for the reverse rotation developing roll 100 and the forward rotation developing roll 200 will be described.

  Both end portions of the rotation shaft 230 of the forward rotation developing roll 200 and one end portion of the rotation shaft 130 of the reverse rotation developing roll 100 shown in FIG. 2 are support structures supported by bearings fixed to the housing 50. . However, the other end portion 130A (see FIG. 7) of the rotation shaft 130 of the reverse rotation developing roll 100 is supported so as to be movable in the direction of arrow E (the direction of the photoconductor 12) (with a specific support structure). An example will be described later).

  Here, in the present embodiment, the reverse rotation developing roll 100 and the forward rotation developing roll 200 apply the regulating members (not shown) provided at the respective ends to the photoconductor 12, so that the reverse rotation developing roll 100 and A development gap which is a gap between the forward rotation developing roll 200 and the photoreceptor 12 is defined (tracking).

  If the four locations of both ends of the rotating shaft 230 of the forward rotating developing roll 200 and both ends of the rotating shaft 130 of the reverse rotating developing roll 100 are supported by bearings fixed to the housing, the four points Will be formed. Since it is very difficult to form a surface with four points, it is difficult to apply the four regulating members (not shown) to the photoconductor 12 without rattling, and thus it is difficult to accurately define the development gap. (It is difficult to reliably track).

  On the other hand, the other end portion 130A (see FIG. 7) of the rotating shaft 130 of the reverse rotation developing roll 100 is supported so as to be movable in the direction of the photosensitive member 12 (E direction) as in the present embodiment. The surface is formed by three points other than. Therefore, three restricting members (not shown) are applied to the photoconductor 12, and the movable bearing-side restricting member is moved to the other end 130A and applied to the photoconductor 12, thereby providing four restricting members (not shown). Can be reliably applied to the photosensitive member 12, and the development gap can be accurately defined (tracking can be performed reliably).

In the present embodiment, the other end portion 130 </ b> A of the rotation shaft 130 of the reverse rotation developing roll 100 is movably supported. This is because the thickness of the developer G is adjusted by the layer shaping member 62 in the forward rotation developing roll 200, and if the rotation shaft 230 of the forward rotation developing roll 200 moves, the layer shaping member 62 and the forward rotation developing roll 200 are moved. The gap between and may fluctuate, which may affect layer shaping. Therefore, in this embodiment. The rotation shaft 130 of the reverse rotation developing roll 100 which is not affected by the above is supported so as to be movable.

  Here, the support structure that supports the other end portion 130A of the rotating shaft 130 of the reverse rotation developing roll 100 so as to be movable in the direction of the photoconductor 12 may be any structure, but an example will be described below.

  As shown in FIG. 7, the casing 50 is formed with a rectangular hole 300 whose longitudinal direction is the 12 direction (E direction) on the photoreceptor side. In the hole 300, a rectangular bearing 302 of the other end portion 130A of the rotary shaft 130 is provided so as to be movable in the E direction. The bearing 302 is urged toward the photoconductor 12 by an urging means 304 such as a coil spring. With such a support structure, the other end portion 130A of the rotating shaft 130 of the reverse rotation developing roll 100 is supported so as to be movable in the direction of arrow E (the direction of the photoconductor 12).

(Configuration of rubbing member)
Next, the rubbing member will be described.

  As shown in FIG. 3, the upper portion of the opening 50 </ b> A in the housing 50 of the developing device 18 is a bowl-shaped cover portion 52. The cover 52 is provided so as to cover the upper side of the reverse rotation developing roll 100. A rubbing member 80 as an example of a sliding member is attached to the cover portion 52.

  The rubbing member 80 is a sheet metal made of a magnetic material, and one end portion 80B is attached to a thin tape material 82 that is folded and attached to the tip end portion 52A of the cover portion 52 in a U shape. Therefore, the rubbing member 80 can freely move in the direction of the reverse rotation developing roll 100 starting from the tape material 82 (one end portion 80B). The rubbing member 80 is attracted by the magnetic force of the magnetic pole N1 that is the conveying magnetic pole of the reverse rotation developing roll 100, so that the developer G is slid onto the surface of the developing sleeve 110 by the plate surface 80A of the rubbing member 80. It is configured as follows.

<Action and effect>
First, the conveyance of the developer G in the developing device 18 will be described.

  As shown in FIG. 2, in the developing device 18, the developer G is supplied to the forward rotation developing roll 200 by the first stirring and conveying member 58 and the second stirring and conveying member 60. The developer G supplied to the forward rotation developing roll 200 is attracted to the surface of the developing sleeve 210 by the magnetic pole S3. The adsorbed developer G is conveyed along with the rotation (D direction) of the developing sleeve 210, and the layer thickness of the developer G held on the forward rotation developing roll 200 is adjusted by the layer shaping member 62. After the layer thickness is adjusted, the developer G is distributed to the forward rotation developing roll 200 and the reverse rotation developing roll 100 by the magnetic pole N2 and the magnetic pole S2 which are delivery magnetic poles in the proximity portion GP3. It is done. In other words, a part of the developer G is transferred from the forward rotation developing roll 200 to the reverse rotation developing roll 100.

  Therefore, the developer layer conveyed to the parts GP1 and GP2 which are the development parts of the reverse rotation developing roll 100 and the forward rotation developing roll 200 is formed in the proximity part GP3.

  The developer G distributed to the reverse rotation developing roll 100 in the proximity portion GP3 is conveyed along with the rotation (C direction) of the developing sleeve 110 of the reverse rotation developing roll 100. Then, the developer G and the photosensitive member 12 come into contact with each other at the magnetic pole N3 that is the developing magnetic pole, that is, the part GP1, and the electrostatic latent image on the photosensitive member 12 is developed with the toner of the developer G. Then, after being developed and conveyed by the magnetic pole S1 and the magnetic pole N1, pick-off is performed between the magnetic pole S4 and the magnetic pole S2, and the developer G is peeled off from the surface of the developing sleeve 110. The separated developer G is guided by the guide plate 64 and returned to the storage chamber 50B.

  On the other hand, the developer G distributed to the forward rotation developing roll 200 in the proximity portion GP3 is conveyed along with the rotation (D direction) of the developing sleeve 210, and is exposed to the developer G in the magnetic pole S1 that is the developing magnetic pole, that is, the portion GP2. The electrostatic latent image on the photosensitive member 12 is developed with the developer G toner. Then, after development, pick-off is performed between the magnetic pole S4 and the magnetic pole S3, and the developer G is peeled off from the surface of the developing sleeve 110 and returned to the storage chamber 50B.

  Here, in the reverse rotation developing roll 100, when the developer G is transported by the magnetic pole S1 and the magnetic pole N1 after the development at the magnetic pole S1 (part GP1) as the developing magnetic pole, the plate surface 80A of the rubbing member 80 is used. The developer G is slid onto the surface 110A (see FIG. 5) of the developing sleeve 110. In other words, the developer G is rubbed by the plate surface 80 </ b> A of the rubbing member 80. Then, the developer G is rubbed by the plate surface 80A of the rubbing member 80 in this way, and the developer G is rubbed against the surface 110A (see FIG. 5) of the developing sleeve 110. The uneven density of the developer G (hereinafter referred to as “development history”) is eliminated or reduced.

  Next, the elimination or reduction of the development history of the reverse rotation developing roll 100 will be described in detail. FIG. 5 is a diagram schematically showing the developer state of the reverse rotation developing roll 100 and the developer state of the photosensitive member 12. 6A shows an image formed on the sheet member P in a comparative example in which the rubbing member 80 is not provided, and FIG. 6B shows a reverse rotation developing roll immediately after image formation at the B position in FIG. The state of 100 developers is schematically shown. FIG. 6A shows an image in which a horizontal stripe-shaped halftone image HT1 and a halftone image HT2 are formed after a vertical stripe image of a high density image (solid black) BT and a non-image portion WT is formed. ing. Note that an arrow S in FIG. 6A indicates the direction in which an image is formed (the conveyance direction of the sheet member P).

  As shown in FIG. 5A, the toner T in the developer G adheres to the surface 110A of the developing sleeve 110 of the reverse rotation developing roll 100. Hereinafter, the toner T adhering to the surface of the developing sleeve 110 is referred to as “surface adhering toner TA”. Further, the surface-attached toner TA is hardly peeled off by pick-off between the magnetic pole S2 and the magnetic pole S4 in the reverse rotation developing roll 100.

  As shown in FIG. 6A, when a high-density image (solid black) BT is developed, as shown in FIG. 5B, most of the surface-attached toner TA on the surface of the developing sleeve 110 is developed and the photosensitive member 12 is developed. Adhere to. However, in the non-image portion WT, the surface adhesion toner TA remains on the surface of the developing sleeve 110. Therefore, as shown in FIG. 6B, the surface 110A of the developing sleeve 110 has a portion where the surface adhesion toner TA is large and a portion where the surface adhesion toner TA is small (or a portion where there is almost nothing). A development history occurs. In each figure, the surface-attached toner TA remaining in the developed high-density image (solid black) BT is not shown for easy understanding.

  In the case of the comparative example in which the rubbing member 80 is not provided, as shown in FIG. 6A, when the horizontal band-shaped halftone image HT1 and halftone image HT2 are formed after the vertical stripe image, the developing sleeve 110 is formed. The portion of the surface 110A of the surface 110A where the surface adhering toner TA is large, that is, the portion having a high density after the non-image portion WT, and the portion of the surface 110A of the developing sleeve 110 where the surface adhering toner TA is small (or the portion where there is little) After that, the concentration decreases. That is, density unevenness (hereinafter referred to as “image history”) that appears as a density difference in the halftone images HT1 and HT2 is generated by the development history of the density (or presence / absence) of the toner TA on the surface 110A of the developing sleeve 110. To do.

  When the forward rotation developing roll 200 passes through the layer shaping member 62 after development, the developer G is pressed against the developing sleeve 210, whereby the surface-adhering toner TA is reattached, thereby eliminating or reducing the development history. . However, since the reverse shaping developing roll 100 is not provided with the layer shaping member 62, the development history (image history) by the layer shaping member 62 is not eliminated.

  Therefore, in this embodiment, after developing, the developer G is rubbed by the plate surface 80A of the rubbing member 80, and the developer G is rubbed against the surface 110A of the developing sleeve 110, thereby reattaching the surface-adhering toner TA. The development history of the reverse rotation developing roll 100 is eliminated or reduced.

  Further, when the portion corresponding to the transport magnetic pole for transporting the developer G is rubbed, it will be explained from another viewpoint that if the developer G held by the transport magnetic pole is rubbed, the effect of reattaching the surface-attached toner TA is high. However, it is known from another experiment. In this embodiment, the rubbing member 80 is attracted by the magnetic force of the magnetic pole N1 that is the transport magnetic pole of the reverse rotation developing roll 100, so that the plate surface 80A slides the developer G onto the surface 110A of the developing sleeve 110. It is configured to be attached. Therefore, without providing a pressing means such as a spring, a rubbing force (pressing force) can be stably obtained by magnetic force, and the plate surface 80A of the rubbing member 80 can easily correspond to the magnetic pole N1 that is the transport magnetic pole. Rub. In addition, requirements for various component accuracy and assembly accuracy are reduced, resulting in cost reduction.

  The rubbing force (pressing force) of the rubbing member 80 can be controlled by the magnitude of the magnetic force. Therefore, since the rubbing force (pressing force) can be controlled by the size of the rubbing member 80, the amount of the magnetic material contained in the rubbing member 80, etc., the rubbing force (pressing force) is controlled by a pressing means such as a spring. Compared to the case, adjustment and management of the rubbing force (pressing force) are easy.

  In the present embodiment, the other end portion 130A (see FIG. 7) of the rotating shaft 130 of the counter-rotating developing roll 100 is supported so as to be movable in the photoconductor 12 side direction (E direction) (see FIG. 7). Even when the reverse rotation developing roll 100 moves in this way, the rubbing member 80 is attracted by the magnetic force, so that the rubbing member 80 follows the movement of the reverse rotating developing roll 100 and is stable. Force (pressing force) is obtained.

<Modification>
Next, a modified example of the rubbing member will be described.

  In the above embodiment, the rubbing member 80 is a metal plate made of a magnetic material, and is configured to slide the developer G onto the surface 110A of the developing sleeve 110 by the plate surface 80A by being attracted by a magnetic force. However, the present invention is not limited to this.

  As long as the developer G can be rubbed after development, and the developer G can be rubbed against the surface 110A of the developing sleeve 110 to reattach the surface-adhering toner TA, any configuration of the rubbing member (sliding member) can be used. There may be.

  For example, a rubbing member 88 made of an elastically deformable plate member as shown in FIG. 4 may be used. The rubbing member 88 is configured such that one end 88A is fixed to the tip 52A of the cover 52 and curved, and the plate surface 80A slides the developer G onto the surface 110A of the developing sleeve 110 by elastic force. Yes.

<Others>
In addition, this invention is not limited to the said embodiment.

  For example, in the above embodiment, the present invention is applied to the elimination or reduction of the development history of the reverse rotation developing roll 100, but the present invention is not limited to this. It may also be applied to the forward rotation developing roll 200 to eliminate or reduce the development history more effectively.

  Further, for example, in the above-described embodiment, the configuration has two developing rolls, that is, the reverse rotating developing roll 100 and the forward rotating developing roll 200, but is not limited thereto. The configuration may include only one of the reverse rotation developing roll 100 and the forward rotation developing roll 200.

  Further, for example, in the above-described embodiment, the present invention is applied to the two-component developing type developing device 18 that uses the developer (two-component developer) G including the resin toner T and the magnetic carrier particles K. Although applied, it is not limited to this. The present invention can also be applied to a one-component developing type developing device using a developer having no magnetic carrier particles (comprising only toner).

  Further, for example, in the above-described embodiment, the image history (density unevenness (decrease in image quality)) due to the development history (the density (or presence / absence) of the surface-attached toner TA) is the difference between the halftone image after forming the high-density image. The density unevenness is not limited to this. The effect is also obtained for other image histories resulting from the development history (presence / absence of surface-attached toner TA). For example, the effect can also be obtained when density unevenness occurs in a high density image due to development history (presence / absence of surface-attached toner TA).

  Further, the configuration of the image forming apparatus is not limited to the configuration of the above-described embodiment, and various configurations can be employed. For example, the image forming apparatus is a single color printer, but is not limited thereto. A color printing printer may also be used. In the case of color printing, a method may be used in which each color toner image is transferred from the photosensitive member 12 corresponding to each color to an intermediate transfer member such as an intermediate transfer belt and transferred to a recording medium in a lump.

  Furthermore, it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive body (an example of a latent image holding body)
18 Developing device 22 Transfer roll (an example of transfer means)
62 layer shaping member 80 rubbing member (an example of a sliding member)
88 Rubbing member (an example of a sliding member)
100 reverse rotation developing roll (an example of a developer holding member)
110 Development sleeve (an example of a cylindrical member)
120 Magnet roll (an example of a magnetic force generator)
G developer GP3 proximity part (an example of a part for forming a developer layer)
N3 magnetic pole (example of developing magnetic pole)
S1 magnetic pole (example of developing magnetic pole)
S4 magnetic pole (an example of developer peeling means)
S2 magnetic pole (an example of developer peeling means)
N1 magnetic pole (example of carrier magnetic pole)
N2 magnetic pole (example of delivery magnetic pole)
S2 magnetic pole (example of delivery magnetic pole)

Claims (3)

A cylindrical member arranged and rotated opposite to the latent image holding member, a developing magnetic pole provided inside the cylindrical member and arranged opposite to the latent image holding member, and downstream of the developing magnetic pole in the rotation direction of the cylindrical member A magnetic force generating portion provided with a conveying magnetic pole disposed on the upstream side in the rotation direction with respect to the portion where the developer layer is formed on the side, and the developer for developing the latent image on the latent image holding member is the cylindrical member. A developer holder to be held on the surface of
One end is fixed, and the tape material is folded back in a U shape.
It is composed of a plate-like magnetic body attached to the other end of the tape material, and is attracted by the magnetic force of the transport magnetic pole so that the developer held by the transport magnetic pole is the plate surface on the surface of the cylinder member A sliding member to be rubbed on,
A developing device comprising: The developer holders are provided in pairs close to each other and rotate so that the moving direction is the same in the close proximity portion.
The magnetic force generation part of the pair of developer holders is provided with the development magnetic pole and a delivery magnetic pole that is disposed opposite to the part corresponding to the proximity part and forms the developer layer, respectively.
A layer shaping member for adjusting the thickness of the layer at a portion downstream of the developing magnetic pole in the rotation direction of the developing magnetic pole and upstream of the rotation direction of the delivery magnetic pole in any one of the pair of developer holders is provided. A developer peeling means for peeling the developer by a magnetic force at a site on the downstream side in the rotation direction of the development magnetic pole on the other side of the developer holding member formed and on the upstream side of the rotation of the delivery magnetic pole;
The sliding member is provided so as to slid the developer on the upstream side in the rotational direction of the developer peeling means on the downstream side in the rotational direction of the developing magnetic pole in one of the pair of developer holders. Yes,
The developing device according to claim 1.   A developing device according to claim 1 or 2,
  A latent image holder on which a latent image formed on the surface is visualized as a toner image by the developing device;
  Transfer means for transferring a toner image formed on the surface of the latent image holding member to a transfer object;
  An image forming apparatus comprising: