JP5532970B2 - 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 is provided with a developer layer regulating member facing the circumferential surface of the developing sleeve, and further, a magnet is provided on the opposite side of the developer layer regulating member from the developing sleeve.

  In the developing device of Patent Document 2, a layer thickness regulating blade made of a magnetic material is disposed so as to face a peripheral surface of a magnet roll that is rotatably provided.

  The developing device of Patent Document 3 is provided with a layer thickness regulating roll that faces the circumferential surface of the developing sleeve, and at least a part of the layer thickness regulating roll is made of a magnetic material.

  The developing device of Patent Document 4 is provided with a regulating plate facing the circumferential surface of the developing sleeve, and a magnetic field generating means is provided adjacent to the regulating plate.

  The developing device of Patent Document 5 is provided with a roll-shaped developer circulation transfer member that faces the peripheral surface of the developing roll.

JP 05-158352 A Japanese Patent Laid-Open No. 06-337593 Japanese Patent Application Laid-Open No. 07-020717 Japanese Patent Laid-Open No. 10-133518 JP-A-10-198171

  An object of the present invention is to obtain a developing device and an image forming apparatus that can suppress a shearing force acting on a developer in a layer forming portion.

According to a first aspect of the present invention, there is provided a developing device comprising: a magnetic member having a plurality of magnetic poles arranged in the circumferential direction; and a moving member provided to be movable in the circumferential direction of the magnetic member outside the magnetic member. A developer holding member for holding a magnetic developer in the normal direction on the outer peripheral surface of the moving member, and a plurality of magnetic poles arranged in the circumferential direction and fixed magnetization. And a rotating member that rotates in the same direction as the moving member outside the magnetized member, and is closest to a portion where the normal magnetic field is formed on the outer peripheral surface of the moving member. A layer forming portion that is disposed to form a developer layer with the moving member is formed, and a magnetic field is formed in a direction intersecting a normal direction of the moving member on a surface facing the layer forming portion. And a layer forming member on which magnetic poles are arranged.

  In the developing device according to a second aspect of the present invention, the magnetic pole of the developer holding member is disposed in the layer forming portion.

  According to a third aspect of the present invention, there is provided a developing device comprising: a magnetic member having a plurality of magnetic poles arranged in the circumferential direction; and a moving member provided so as to be movable in the circumferential direction of the magnetic member outside the magnetic member. An intermediate portion between two magnetic poles having different polarities with respect to the specific magnetic pole so that a distance between the developer holding member that holds the developer and the specific magnetic pole in the developer holding member is minimized. A layer forming member that is disposed to face each other and forms a developer layer with the moving member.

In the developing device according to claim 4 of the present invention, the layer forming member includes a magnetizing member in which a plurality of magnetic poles are arranged and fixed in the circumferential direction, and the same direction as the moving member outside the magnetizing member. And a rotating member that rotates.

In the developing device according to claim 5 of the present invention, the magnetic member is provided with a detaching means for detaching the developer from the rotating member outside the layer forming portion.

In the developing device according to a sixth aspect of the present invention, the polarity of the magnetic pole on the side where the developer flows in the layer forming member is the same as the polarity of the magnetic pole of the developer holding member disposed in the layer forming portion. is there.

In the developing device according to claim 7 of the present invention, the layer forming member is a magnetized member in which a plurality of magnetic poles are arranged in the circumferential direction .

  In the developing device according to claim 8 of the present invention, the relative position of the magnetic pole of the layer forming member with respect to the magnetic pole of the developer holding member is adjustable.

  An image forming apparatus according to a ninth aspect of the present invention includes the developing device according to any one of the first to eighth aspects, an electrostatic latent image held on an outer periphery, and the electrostatic latent image by the developing device. Includes an image carrier that is a developer image, and a transfer unit that transfers the developer image from the image carrier to a transfer material.

  According to the first aspect of the present invention, in the layer forming portion of the developer, the layer forming portion has a magnetic layer formed in a direction that intersects the normal direction of the moving member, and the magnetic pole of the layer forming member is not disposed. The shearing force acting on the developer can be suppressed.

  According to the second aspect of the present invention, the shear force acting on the developer at the layer forming portion can be suppressed as compared with the configuration in which the magnetic pole of the developer holding member is not disposed at the layer forming portion.

  According to a third aspect of the present invention, the layer forming member is arranged so that a distance between the developer holding member and the specific magnetic pole is minimized, and an intermediate portion of the two magnetic poles having different polarities is opposed to the specific magnetic pole. Compared to a configuration where the developer is not arranged, the shearing force acting on the developer at the layer forming portion can be suppressed.

According to the fourth aspect of the present invention , an excessive amount of developer flows into the layer forming portion as compared with a configuration in which a plurality of magnetic poles are arranged in the circumferential direction and no rotating member is provided outside the fixed magnetized member. Can be prevented .

The invention according to claim 5 prevents the developer from staying on the outer peripheral surface of the layer forming member as compared with the case where the magnetizing member is not provided with a separating means for separating the developer from the rotating member outside the layer forming portion. be able to.

According to the sixth aspect of the present invention, the layer forming member develops at the layer forming portion as compared with the configuration in which the polarity of the magnetic pole on the side where the developer flows in the layer forming member is different from the polarity of the magnetic pole of the developer holding member disposed at the layer forming portion. The shear force acting on the agent can be suppressed .

The seventh aspect of the present invention provides a layer forming unit that has a magnetic layer formed in a direction that intersects the normal direction of the moving member in the developer layer forming unit. The shearing force acting on the developer can be suppressed .

  According to the eighth aspect of the present invention, the amount of developer after layer formation can be adjusted as compared with a configuration in which the relative position of the magnetic pole of the layer forming member with respect to the magnetic pole of the developer holding member is fixed.

  The invention of claim 9 suppresses image defects as compared with the configuration in which the magnetic poles of the layer forming member are arranged so as not to form a magnetic field in a direction intersecting the normal direction of the moving member in the developer layer forming portion. Can do.

1 is an overall view of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic diagram illustrating an image forming unit provided in an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a photoconductor provided in the image forming unit according to the first embodiment of the present invention and its surroundings. (A) It is the schematic of the developing device which concerns on 1st Embodiment of this invention. (B) It is a schematic diagram which shows the arrangement | positioning state of the layer formation board which concerns on 1st Embodiment of this invention. (A) It is a schematic diagram which shows the arrangement | positioning state of the layer formation board of a comparative example. (B) It is a schematic diagram which shows the state in which a mechanical shearing force acts on the developer which stood up with respect to the layer formation board of a comparative example. It is a schematic diagram which shows the state in which a mechanical shearing force acts on the developer which stood up with respect to the layer formation board which concerns on 1st Embodiment of this invention. It is the schematic of the developing device which concerns on 2nd Embodiment of this invention. (A) It is a schematic diagram which shows the arrangement | positioning state of the layer formation sleeve which concerns on 2nd Embodiment of this invention. (B) It is a schematic diagram which shows the state in which a mechanical shearing force acts on the developer spiked with respect to the layer formation sleeve which concerns on 2nd Embodiment of this invention.

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

  FIG. 1 shows an image forming apparatus 10 according to the first embodiment. As an example, the image forming apparatus 10 includes a paper feeding unit 16 provided at the bottom of the image forming apparatus 10, and yellow (Y), magenta (M), cyan (C), and black provided above the paper feeding unit 16. The image forming unit 30 for forming an image with four color toners (developers) (K), the paper discharge unit 17 provided above the image forming unit 30, and the image forming unit 30 from the paper supply unit 16. A conveyance path 19 that conveys the recording paper P to the paper discharge section 17, a fixing section 28 that is provided in the conveyance path 19 and fixes the toner image, and a control section 60 that controls the operation of each section of the image forming apparatus 10. have. In the following description, when distinguishing each color of yellow, magenta, cyan, and black, Y, M, C, and K alphabets are added after the reference numerals, but it is not necessary to distinguish each color. In this case, Y, M, C, and K after the symbol are omitted.

  The paper feeding unit 16 stores recording paper P therein, and a feeding roll 18 that feeds the recording paper P one by one from the paper feeding unit 16 to the front end of the paper feeding unit 16 in the conveyance direction of the recording paper P. Is provided. Further, two sets of transport rolls 20 for transporting the recording paper P are provided on the downstream side of the delivery roll 18 in the transport path 19 (transport path PA) of the recording paper P, and the recording paper P is transported by the transport roll. 20 is conveyed to a secondary transfer unit 22 (described later) provided above.

  As shown in FIG. 2, the image forming unit 30 includes photosensitive members 13C, 13M, 13Y, and 13K as an example of an image holding member that holds a latent image corresponding to each color of cyan, magenta, yellow, and black. It is provided in contact with an intermediate transfer belt 14 as an example of a transfer material. The photoreceptors 13C, 13M, 13Y, and 13K rotate in one direction (the arrow b direction that is the counterclockwise direction in the drawing).

  As shown in FIG. 3, around the photoconductor 13 in the image forming unit 30, the photoconductor 13 surface is charged by a potential difference disposed in order along the rotation direction b of the photoconductor 13 so as to face the outer peripheral surface of the photoconductor 13. A charging roll 36 to be exposed; an exposure unit 40 that irradiates the outer peripheral surface of the charged photoconductor 13 with exposure light to form an electrostatic latent image on the outer peripheral surface of the photoconductor 13 according to image information; A developing device 12 as an example of a developing device that develops an electrostatic latent image using a developer to form a developer image (toner image); an intermediate transfer belt 14 on which the developer image is transferred to the outer peripheral surface; A brush roll 34 for cleaning the outer peripheral surface of the photosensitive member 13 after the transfer of the developer image is provided. A primary transfer roll 32 as an example of a transfer unit that transfers the developer image from the photosensitive member 13 to the intermediate transfer belt 14 is provided on the opposite side of the photosensitive member 13 with the intermediate transfer belt 14 interposed therebetween. The body 13, the intermediate transfer belt 14, and the primary transfer roll 32 constitute a primary transfer portion 21.

  As shown in FIG. 2, the intermediate transfer belt 14 is formed in an endless shape, and includes a belt conveyance roll 24A, a belt conveyance roll 24B disposed below the belt conveyance roll 24A (lower right in the figure), The belt is wound around and supported by a belt conveyance roll 24 </ b> C disposed obliquely above the belt conveyance roll 24 </ b> B (diagonal upper right in the drawing) and on the opposite side of the conveyance path 19. Further, the intermediate transfer belt 14 can be circulated and moved in the direction of the arrow a by the belt conveyance roll 24C being rotated by a motor (not shown).

  On the opposite side of the intermediate transfer belt 14 from the belt conveyance roll 24B, a toner concentration detection sensor 15 is provided in contact with the outer peripheral surface of the intermediate transfer belt 14. The toner concentration detection sensor 15 has a function of detecting the concentration of toner transferred to the outer peripheral surface (transfer surface) of the intermediate transfer belt 14. A cleaning unit 42 is provided on the opposite side of the intermediate transfer belt 14 from the belt conveyance roll 24 </ b> C in contact with the outer peripheral surface of the intermediate transfer belt 14. The cleaning unit 42 has a function of cleaning the outer peripheral surface of the intermediate transfer belt 14 after the secondary transfer.

  Further, a secondary voltage for applying a set bias voltage to the opposite side of the intermediate transfer belt 14 from the belt conveying roll 24 </ b> A and transferring the toner image held on the outer peripheral surface of the intermediate transfer belt 14 to the recording paper P is provided. A transfer roll 26 is provided. Here, the intermediate transfer belt 14 and the secondary transfer roll 26 constitute a secondary transfer portion 22.

  On the other hand, as shown in FIG. 1, a fixing unit 28 is provided above the secondary transfer unit 22. The fixing unit 28 includes a fixing roll 28A having a heat source therein and a pressure roll 28B that pressurizes the outer peripheral surface of the fixing roll 28A. The recording paper P is formed by the fixing roll 28A and the pressure roll 28B. After passing through the nip portion, the toner image on the recording paper P is melted, solidified and fixed.

  Here, an image forming method of the image forming apparatus 10 will be described.

  As shown in FIGS. 1 and 3, in the image forming apparatus 10, first, image data output from a personal computer or the like is subjected to image processing by an image processing apparatus (not shown). In the image processing apparatus, input reflectance data is subjected to image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame erasing, color editing, and moving editing. Is done. The image data subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the exposure unit 40 for each color.

  Each exposure unit 40 irradiates each photoconductor 13C, 13M, 13Y, 13K with a light beam (exposure light) according to the color material gradation data. The surfaces of the photoreceptors 13C, 13M, 13Y, and 13K are charged in advance by the charging roll 36, and the electrostatic latent image is formed by exposing the surface by the light beam and lowering the potential. Further, the formed electrostatic latent images on the photoreceptors 13C, 13M, 13Y, and 13K are developed as toner images of C, M, Y, and K colors by the developing units 12C, 12M, 12Y, and 12K.

  Subsequently, the toner images formed on the photoreceptors 13C, 13M, 13Y, and 13K are primarily transferred onto the intermediate transfer belt 14 by the primary transfer rolls 32C, 32M, 32Y, and 32K in the primary transfer unit 21. The primary transfer is performed by sequentially superimposing the toner image on the outer peripheral surface of the intermediate transfer belt 14 to obtain a toner image. Then, the intermediate transfer belt 14 onto which the toner image has been transferred is conveyed to the secondary transfer unit 22.

  On the other hand, in accordance with the timing at which the toner image is conveyed to the secondary transfer unit 22, the recording paper P having a set size is sent from the paper supply unit 16 to the secondary transfer unit 22. Further, the recording paper P delivered from the paper supply unit 16 is temporarily stopped before reaching the secondary transfer unit 22 and is aligned with the movement timing of the intermediate transfer belt 14 holding the toner image. By rotating (not shown), the position of the recording paper P and the position of the toner image are aligned.

  In the secondary transfer unit 22, the recording paper P conveyed in time is sandwiched between the intermediate transfer belt 14 and the secondary transfer roll 26. At this time, a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner (for example, negative polarity) is applied to the secondary transfer roll 26, and the unfixed toner image held on the intermediate transfer belt 14 is Electrostatic transfer (secondary transfer) is collectively performed on the recording paper P.

  Subsequently, the recording paper P onto which the toner image has been secondarily transferred is conveyed to the fixing unit 28. In the fixing unit 28, the unfixed toner image on the recording paper P is heated and pressed by the fixing roll 28 </ b> A and the pressure roll 28 </ b> B, and is fixed on the recording paper P. Then, the recording paper P on which the toner image is fixed by the fixing unit 28 is discharged to the paper discharge unit 17 by a paper discharge roll 29 arranged on the downstream side in the transport direction of the fixing unit 28. Further, after the transfer onto the recording paper P is completed, the residual toner remaining on the intermediate transfer belt 14 is removed from the intermediate transfer belt 14 by the cleaning unit 42. In this way, image formation by the image forming apparatus 10 is performed.

  Next, the configuration of the developing device 12 will be described.

  As shown in FIG. 4A, the developing device 12 has a housing 37 in which an opening 37 </ b> A is formed at a position facing the photoconductor 13. The casing 37 includes a developing roll 38 as an example of a developer holding member that supplies a two-component developer (containing toner particles and magnetic carrier particles as main components) to the latent image formed on the photoreceptor 13. The developer rolls 38A and 39B that transport the two-component developer to the developing roll 38, and the inclined surface 47 provided adjacent to the screw feeder 39A in the housing 37 are fixed to the photosensitive member 13 so as to face each other. And a layer forming member 45 that performs developer layer formation while regulating the developer amount (thickness) of the outer peripheral surface of the toner.

  The screw feeders 39A and 39B are arranged below the developing roll 38 (diagonally below the right side in the figure), and the rotation axis of the developing roll 38 while the two-component developer is stirred by rotating the screw feeders 39A and 39B. It is conveyed along the direction and supplied to the developing roll 38.

  The developing roll 38 includes a cylindrical inner cylinder 38B as an example of a magnetic member, and a developing sleeve 38A as an example of a moving member that is rotatably provided outside the inner cylinder 38B. A part of the surface is arranged in the housing 37 so as to be exposed from the opening 37 </ b> A of the housing 37 to the photosensitive member 13 side. The developing sleeve 38A is supported by bearings (not shown) at both ends in the axial direction so as to be rotatable in the direction of arrow c (clockwise direction in the figure), and is rotated by a motor and a gear (not shown). It is designed to be driven. The developing roll 38 is disposed so as to face the photoreceptor 13 so that a gap (development gap) is formed between the developing roll 38 and the outer peripheral surface of the photoreceptor 13.

  Both ends of the inner body 38B are fixed to the casing 37 so as not to rotate. Further, the developing sleeve 38A is configured to rotate around the axis of the inner cylinder 38B in a direction opposite to the rotation direction b of the photoconductor 13. That is, the photosensitive member 13 rotates counterclockwise in FIG. 4A, whereas the developing sleeve 38A rotates clockwise. Further, the inner cylinder 38B has a plurality of S poles (S1, S2, S3, S4, S5 poles) and a plurality of N poles (N1, N5) as magnetic poles on the outer peripheral surface of the inner cylinder 38B along the rotation direction of the developing sleeve 38A. N2 and N3 poles) are formed so that eight permanent magnets are provided radially.

  The S1 pole is a development pole and is disposed at a position facing the photoreceptor 13. A transport pole N3, pick-off poles S2, S3, and S4, a layer forming pole N1, and transport poles S5 and N2 are provided along the rotation direction c (clockwise direction in the drawing) of the developing sleeve 38A. The transport pole N3 is a magnetic pole for transporting the developer to the place where the developer is stored in the housing 37, and the transport poles N2 and S5 are magnetic poles for transporting the developer to the photoconductor 13. is there. The pickoff poles S2, S3, and S4 are magnetic poles for separating the developer from the developing sleeve 38A outside the layer forming portion 70 where the developing sleeve 38A and the layer forming member 45 face each other. Further, the layer forming pole N1 is a magnetic pole for forming a magnetic brush by arranging (spreading) the developer in a straight state at a position facing the layer forming member 45.

  The layer forming member 45 is a plate-like magnet whose longitudinal direction is the direction from the front side to the back side in FIG. 4B (the axial direction of the developing roll 38), as shown in FIG. 4B. The cross-sectional shape cut in the direction crossing the longitudinal direction is rectangular. Further, the layer forming member 45 has one of the short sides of the rectangular cross section having an N pole (referred to as a layer forming pole N4) and the other serving as an S pole (referred to as a layer forming pole S6). Are arranged in parallel to the normal direction (arrow R direction) in the layer forming pole N1 of the developing sleeve 38A, and the long side of the rectangular cross section is arranged in the arrow Q direction parallel to the tangential direction in the layer forming pole N1 of the developing sleeve 38A. Has been.

  Further, the layer forming member 45 is provided with a layer forming pole N4 having the same polarity as the layer forming pole N1 of the developing roll 38 on the upstream side in the rotation direction of the developing sleeve 38A (the side into which the developer flows). The layer forming pole S6 having the opposite polarity is disposed, and the central portion in the tangential direction is disposed at the shortest distance on the normal line from the layer forming pole N1. That is, in the layer forming unit 70, the layer forming poles N1, N4, and S6 are arranged in an isosceles triangle shape with the layer forming pole N1 as a vertex.

  In the layer forming unit 70, the magnetic lines of force J1 from the layer forming pole N1 to the layer forming member 45, the magnetic lines of force J2 from the layer forming pole N1 to the pickoff pole S4, the magnetic lines of force J3 from the layer forming pole N1 to the transport pole S5, Magnetic lines of force J4 from the formation pole N4 to the layer formation pole S6 are formed. The magnetic lines of force J1 are formed in the normal direction in the layer forming pole N1 of the developing roll 38, and the magnetic lines of force J4 are formed in the tangential direction in the layer forming pole N1 of the developing roll 38. As described above, the layer forming member 45 is disposed so as to be closest to the portion where the normal magnetic field is formed on the outer peripheral surface of the developing sleeve 38A (the portion where the layer forming pole N1 is disposed). A layer forming pole N4 is formed so as to form a magnetic field in a tangential direction intersecting the normal direction of the developing sleeve 38A on the surface facing the layer forming portion 70. , S6 is arranged. The layer forming position of the developing roll 38 is on the layer forming electrode N1.

  Next, the operation of the first embodiment will be described in comparison with a comparative example.

  First, the operation of the developing device 100, which is a comparative example of the first embodiment, will be described. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  As shown in FIG. 5A, the developing device 100 of the comparative example includes a developing roll 38 and a layer forming member 102 disposed to face the developing roll 38, and the developing roll 38 and the layer forming member 102 are included. A region where the and are opposed to each other is a layer forming portion 110. The layer forming member 102 has the same shape and arrangement as the layer forming member 45 (see FIG. 4B) of the first embodiment with respect to the developing roll 38, but is configured by a nonmagnetic material instead of a magnet. Is different.

  As shown in FIG. 5B, in the developing device 100 of the comparative example, since the layer forming member 102 is a nonmagnetic material, the magnetic force lines J1 extending in the normal direction from the layer forming pole N1 in the layer forming portion 110 (FIG. 5). (See (a)) is straight as it is. As a result, when the developing sleeve 38A rotates in the direction of the arrow c, the plurality of carrier particles CA on the layer forming pole N1 are arranged (raised) in a substantially straight state along the magnetic field lines J1 to form a magnetic brush.

  Here, since the plurality of carrier particles CA in the region close to the layer forming member 102 are constrained by the magnetic force line J1 in the normal direction, when the layers are formed by the layer forming member 102, the plurality of carrier particles CA are The tangential mechanical shear force F1 received by the carrier particle CA at the shear surface M1 is increased, the load received by the carrier particle CA is increased, and the release of the external additive of the toner and the embedding in the carrier particle CA are likely to occur. Become. The toner particles are not shown because they have a smaller outer diameter than the carrier particles CA.

  On the inflow side (developer reservoir) of carrier particles CA (developer) in the layer forming member 102, the carrier particles CA1 and the carrier particles CA2 at the interface M2 between the carrier particles CA1 that are retained and the carrier particles CA2 that flow. Are irregularly mixed, and the contact friction between the carrier particles CA1 and the carrier particles CA2 causes deterioration such as peeling of the surface of the carrier particles CA1 or CA2.

  On the other hand, as shown in FIG. 6, in the developing device 12 of the first embodiment, since the layer forming member 45 is a magnet, a magnetic field (lines of magnetic force J1 (FIG. 4) formed on the outer periphery of the developing sleeve 38A in the layer forming portion 70. The tip side (layer forming member 45 side) of the magnetic brush (plurality of carrier particles CA) raised by (b)) is a magnetic field (line of magnetic force J4 (see FIG. 4B) formed by the layer forming member 45. )), The state is bent in a tangential direction intersecting the normal direction of the developing sleeve 38A.

  Here, when the developing sleeve 38A rotates in the direction of the arrow c, the plurality of carrier particles CA in the region close to the layer forming member 45 are arranged along the tangential magnetic field line J4, and the normal magnetic field line J1 Not restrained. Thus, when the layer is formed by the layer forming member 45, the tangential mechanical shear force F2 received by the carrier particles CA at the shear plane M3 between the plurality of carrier particles CA is changed to the shear force F1 of the developing device 100 of the comparative example. In comparison with this, the load received by the carrier particles CA is reduced, and deterioration such as peeling of the surface of the carrier particles CA is suppressed. The toner particles are not shown because they have a smaller outer diameter than the carrier particles CA.

  Further, in the layer forming part 70, the layer forming pole N1 and the layer forming pole N4 have the same polarity, so that the magnetic lines of force are not connected between them, and the magnetic lines of force J2 (see FIG. 4B) and the magnetic lines of force J4 (see FIG. 4B). Interface M4 is formed between the carrier particle CA1 and the carrier particle CA1 in the layer forming member 45 on the inflow side (developer reservoir) of the carrier particle CA (developer). 4 (b)) is arranged tangentially along the magnetic field. As a result, the stationary carrier particles CA1 and the flowing carrier particles CA2 are aligned in the tangential direction at the interface M4, and the direction in which the shear force acts is the same, so the contact friction between the carrier particles CA1 and the carrier particles CA2 Is smaller than the developing device 100 of the comparative example, and the deterioration of the surface of the carrier particles CA1 or CA2 is suppressed. Further, the release of the external additive of the toner and the embedding in the carrier particle CA are avoided, and the life of the developer is extended as compared with the comparative example.

  Note that in the developer whose magnetic brush height is equalized through the layer forming portion 70, the toner on the magnetic brush moves to the outer peripheral surface of the photoreceptor 13 in the vicinity of the developing pole S1, and on the surface of the developing sleeve 38A. A magnetic brush that is almost exclusively carrier particles remains. The magnetic brush falls off the surface of the developing sleeve 38A at the pick-off poles S2, S3, and S4 as the developing sleeve 38A rotates.

  Next, an example of a developing device and an image forming apparatus according to the second embodiment of the present invention will be described. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  FIG. 7 shows a developing device 80 according to the second embodiment. The developing device 80 has a housing 82 in which an opening 82 </ b> A is formed at a position facing the photoconductor 13. The housing 82 is provided with a developing roll 38 for supplying a developer to the latent image formed on the photosensitive member 13, screw feeders 39 </ b> A and 39 </ b> B, and rotatably within the housing 82 adjacent to the screw feeder 39 </ b> A. A layer forming roll 84 for forming a developer layer by regulating the amount of developer on the outer peripheral surface of the developing roll 38 is accommodated.

  The layer forming roll 84 is an example of a cylindrical inner cylinder 84B as an example of a magnetized member with a rotating shaft 84C protruding outward from both ends, and an example of a rotating member that is rotatably provided outside the inner cylinder 84B. The layer forming sleeve 84A is disposed in the housing 82 so that a part of the outer peripheral surface of the layer forming sleeve 84A faces the layer forming pole N1 of the developing roll 38. The layer forming sleeve 84A is supported at both ends in the axial direction by bearings (not shown) so as to be rotatable in the direction of the arrow d (the clockwise direction shown in the drawing and the same direction as the rotation direction of the developing sleeve 38A). At the same time, it is rotationally driven by a motor and a gear (not shown). Thereby, a layer forming portion 88 is formed between the developing roll 38 and the layer forming sleeve 84A.

  The inner cylinder 84 </ b> B is rotatably supported by a bearing (not shown) having a rotation shaft 84 </ b> C provided in the housing 82. Further, a stepping motor 86 is connected to the rotation shaft 84C via a gear (not shown), and the inner cylinder 84B can reciprocate when the stepping motor 86 reciprocates the rotation shaft 84C in the arrow θ direction. ing. Further, the inner cylinder 84B includes a plurality of S poles (S6, S7, S8 poles) and a plurality of N poles (N4, N5 poles) as magnetic poles on the outer peripheral surface of the inner cylinder 84B along the rotation direction of the layer forming sleeve 84A. ) And five permanent magnets are provided radially.

  Here, the layer-forming poles N4 and S6 are formed so that the distance between the poles (intermediate portion) is the shortest distance facing the layer-forming pole N1, that is, a normal magnetic field is formed on the outer peripheral surface of the developing sleeve 38A. The layer forming position of the developing roll 38 is on the layer forming electrode N1. Then, layer forming poles S6 and N4, pickoff poles S7 and S8, and a transport pole N5 are provided along the rotation direction d (clockwise direction in the drawing) of the layer forming sleeve 84A. The transport pole N5 is a magnetic pole for transporting the developer to the place where the developer is stored in the housing 82, and the pick-off poles S7 and S8 have the developing sleeve 38A and the layer forming sleeve 84A facing each other. This is an example of a detaching means for detaching the developer from the layer forming sleeve 84A outside the layer forming portion 88. In the layer forming portion 88, the layer forming poles N1, N4, and S6 are arranged in an isosceles triangle shape with the layer forming pole N1 as a vertex.

  As shown in FIG. 8A, in the layer forming portion 88, the magnetic field lines J1 from the layer forming pole N1 to the layer forming roll 84, the magnetic field lines J2 from the layer forming pole N1 to the pickoff pole S4, and the layer forming pole N1. Magnetic field lines J3 directed to the transport pole S5 and magnetic field lines J5 directed from the layer forming pole N4 to the layer forming pole S6 are formed. The magnetic lines of force J1 are formed in the normal direction of the layer forming pole N1 of the developing roll 38, and the magnetic lines of force J5 are formed in the tangential direction of the layer forming pole N1 of the developing roll 38.

  Next, the operation of the second embodiment will be described.

  As shown in FIGS. 8A and 8B, in the developing device 80 of the second embodiment, since the inner cylinder 84B of the layer forming roll 84 is a magnet, the layer forming portion 88 is formed on the outer periphery of the developing sleeve 38A. The tip side (the layer forming roll 84 side) of the magnetic brush (plurality of carrier particles CA) that is raised by the magnetic field (magnetic line J1) is applied to the developing sleeve 38A by the magnetic field (magnetic line J5) formed by the layer forming roll 84. It will be in the state bent in the tangential direction which intersects with the normal direction.

  Here, when the developing sleeve 38A rotates in the direction of the arrow c, the plurality of carrier particles CA in the region close to the layer forming roll 84 are arranged along the tangential magnetic field lines J5, and the normal magnetic field lines J1 Not restrained. Thus, when the layer is formed by the layer forming roll 84, the tangential mechanical shear force F3 received by the carrier particles CA at the shear plane M5 between the plurality of carrier particles CA is the developing device 100 of the comparative example (FIG. 5 ( It becomes smaller than the shearing force F1 of (a), and the load received by the carrier particles CA is reduced. The toner particles are not shown because they have a smaller outer diameter than the carrier particles CA.

  Further, in the developing device 80, the carrier particles CA staying around the layer forming roll 84 move to the screw feeder 39A side by the rotation of the layer forming sleeve 84A in the arrow d direction. As a result, excessive inflow of the developer to the layer forming portion 88 is suppressed, the density of the developer (magnetic brush) in the layer forming portion 88 is reduced, and the compressive force acting on the developer is reduced, thereby developing the developer. The load acting on is reduced. Note that the developer on the layer forming sleeve 84A that has passed through the layer forming portion 88 drops off from the surface of the layer forming sleeve 84A at the pick-off poles S7 and S8 (see FIG. 7) and returns into the housing 82.

  Further, in the developing device 80, each magnetic pole angle can be adjusted by moving the inner cylinder 84B in the direction of the arrow θ by the stepping motor 86. Here, when the arrangement of the layer formation poles N4 and S6 with respect to the layer formation pole N1 in the layer formation portion 88 is changed, the amount of developer flowing into the layer formation portion 88 changes, and the outer peripheral surface of the development sleeve 38A after the layer formation is changed. The amount of developer changes. As a result, the amount of developer conveyed to the developing area of the photoreceptor 13 is variable. In addition, since the change in the developer amount corresponds to the stepwise position change of the magnetic pole of the inner cylinder 84B by the stepping motor 86, the developer amount can be controlled according to the print mode setting of the image forming apparatus 10. is there.

  In addition, this invention is not limited to said embodiment.

  For the layer forming roll 84, the layer forming sleeve 84A may be removed and only the inner cylinder 84B may be used. The magnetic pole arrangement of the inner cylinder 84B may be changed using a solenoid instead of the stepping motor 86, or may be changed using a rack and a pinion. Further, the magnetic pole arrangement of the inner cylinder 84B may not be adjusted. In the first embodiment, the magnetic pole arrangement may be adjusted by supporting both end portions of the layer forming member 45 so as to be reciprocally rotatable. Furthermore, as another example of the detaching means, a blade that performs mechanical scraping instead of the pick-off pole may be brought into contact with the outer peripheral surface of the layer forming sleeve 84A.

10 Image Forming Device 12 Developer (Developing Device)
13 Photoconductor (image carrier)
14 Intermediate transfer belt (material to be transferred)
32 Primary transfer roll (transfer means)
38 Developing Roll (Developer Holding Member)
38A Development sleeve (moving member)
38B Inner trunk (magnetic member)
45 Layer forming member 70 Layer forming portion 84 Layer forming roll (layer forming member)
84A layer forming sleeve (rotating member, layer forming member)
84B Inner body (magnetized member, layer forming member)
88 Layer formation part S7 Pickoff pole (detachment means)
S8 Pickoff pole (leaving means)

Claims (9)

A magnetic member having a plurality of magnetic poles arranged in the circumferential direction; and a moving member provided so as to be movable in the circumferential direction of the magnetic member outside the magnetic member, and normal to the outer circumferential surface of the moving member A developer holding member that holds a magnetic developer with a magnetic field formed in the direction;
A plurality of magnetic poles arranged and fixed in the circumferential direction; and a rotating member that rotates in the same direction as the moving member outside the magnetizing member, and the outer peripheral surface of the moving member A layer forming part is formed so as to form a developer layer between the moving member and a portion where the magnetic field in the normal direction is formed, and is moved on a surface facing the layer forming part. A layer forming member in which magnetic poles are arranged to form a magnetic field in a direction intersecting the normal direction of the member;
A developing device.   The developing device according to claim 1, wherein a magnetic pole of the developer holding member is disposed in the layer forming portion. A developer holding member that has a magnetic member in which a plurality of magnetic poles are arranged in the circumferential direction and a moving member provided so as to be movable in the circumferential direction of the magnetic member outside the magnetic member, and holds the developer When,
The developer holding member is disposed so that the distance between the magnetic pole and the specific magnetic pole is minimized, and an intermediate portion between two magnetic poles having different polarities is opposed to the specific magnetic pole. A layer forming member for forming a developer layer;
A developing device. The layer forming member includes a magnetized member having a plurality of magnetic poles arranged and fixed in a circumferential direction, and a rotating member that rotates in the same direction as the moving member outside the magnetized member. The developing device described. 5. The development according to claim 1, wherein the magnetic member is provided with a detaching means for detaching the developer from the rotating member outside the layer forming portion. apparatus. Polarity side of the magnetic poles developer flows of the layer forming member, one of claims 1 to 5 which is the same polarity as the polarity of the magnetic poles of the layer forming portion arranged the developer holder 1 The developing device according to item. It said layer forming member, a developing device according to claim 1 a plurality of magnetic poles are arranged magnetized material in the circumferential direction in any one of claims 6.   The developing device according to claim 1, wherein a relative position of a magnetic pole of the layer forming member with respect to a magnetic pole of the developer holding member is provided to be adjustable. A developing device according to any one of claims 1 to 8,
An image holding body for holding the electrostatic latent image on the outer periphery and forming the electrostatic latent image as a developer image by the developing device;
Transfer means for transferring a developer image from the image carrier to a transfer material;
An image forming apparatus.

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