JP2009156973A - Development device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a developer from being spouted out of a device, from a space between the first developing roll and the second developing roll. <P>SOLUTION: The space between the first developing roll 41 and the second developing roll 42 is sealed by the developer 66 brought into a magnetic brush state by a magnet 56 and a magnet 56, and the developer 68 brought into a magnetic brush state by a magnet 58 and a magnet 58, although air is going to be discharged from a clearance formed in an opening part 37A of a casing 37, when pressure increases in the casing 37, and the developer is restrained thereby from being spouted out of the device, from the space between the first developing roll 41 and the second developing roll 42. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

As an image forming apparatus having a developing device, an image forming apparatus disclosed in Patent Document 1 is known. The image forming apparatus disclosed in Patent Document 1 has a toner scattering prevention device, and the toner scattering prevention device is provided with an exhaust unit that exhausts air from the upper part of the developing device through an exhaust path, The air suction is used to generate an air flow that sucks in the surrounding air from the opening of the developing device, and the suction port of the exhaust passage in the developing device is provided outside the image forming width. Thus, air can be directly sucked from the end of the developing device, the suction airflow at the end of the opening can be strengthened, and contamination of the end of the opening of the developing device can be prevented.
JP 2003-177604 A

  According to the present invention, in a developing device that performs development by delivering a developer from a first image roll to a second developing roll, the developer is prevented from being ejected from between the first image roll and the second developing roll. This is the issue.

  The developing device according to claim 1 of the present invention is disposed to face the latent image holding member, and is arranged to face the latent image holding member, the first developing roll holding the developer, and the first developing. The developer held by the roll is transferred from the first developing roll, the second developing roll for supplying the transferred developer to the latent image holding member, the first developing roll, and the second developing roll. The sealing member is disposed on the side opposite to the side where the latent image holding member is seen, and seals between the first developing roll and the second developing roll.

  A developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the sealing member includes a magnetic body having magnetism and the first developing roll and the second developing roll by a magnetic force of the magnetic body. It is characterized by comprising a developer that is drawn from at least one surface and fills between the surface and the magnetic body.

  According to a third aspect of the present invention, there is provided the developing device according to the second aspect, wherein the magnetic body also serves as a guide plate for guiding the developer separated from the second developing roll.

  An image forming apparatus according to a fourth aspect of the present invention includes the developing device according to any one of the first to third aspects, and a latent image holding member that holds a latent image developed by the developing device. It is characterized by that.

  According to the configuration of the first aspect of the present invention, the developer can be prevented from being ejected outside the apparatus from between the first image roll and the second developing roll, as compared with the case where the present configuration is not provided.

  According to the configuration of the second aspect of the present invention, as compared with the case where the configuration is not provided, the rubbing by the sealing member is weak, and the developer adheres to the first image roll and the second developing roll. Can be suppressed.

  According to the configuration of the third aspect of the present invention, the number of parts can be reduced as compared with the case where the configuration is not provided.

  According to the configuration of the fourth aspect of the present invention, it is possible to suppress the developer from being ejected outside the apparatus from between the first image roll and the second developing roll as compared with the case where the present configuration is not provided.

  Below, an example of an embodiment concerning the present invention is described based on a drawing.

(Whole structure of the image forming apparatus according to the present embodiment)
First, the overall configuration of the image forming apparatus according to the present embodiment will be described. FIG. 1 is a schematic diagram illustrating the overall configuration of the image forming apparatus according to the present embodiment. FIG. 2 is a schematic diagram illustrating an image forming unit provided in the image forming apparatus according to the present embodiment.

  An image forming apparatus 10 according to the present embodiment is an apparatus that forms an image, and as illustrated in FIG. 1, an image forming unit 30 that forms an image with developers of four colors of cyan, magenta, yellow, and black. The sheet feeding unit 16 disposed below the image forming unit 30 and the sheet discharging unit 17 disposed above the image forming unit 30 are provided.

  As shown in FIGS. 1 and 2, the image forming unit 30 includes photoreceptors 13 </ b> C, 13 </ b> M, 13 </ b> Y, and 13 </ b> K (hereinafter referred to as 13 </ b> C to 13 </ b> K) as examples of a latent image holding body that holds a latent image. It is provided corresponding to each color of cyan, magenta, yellow, and black. The photoconductors 13C to 13K are configured to rotate in a predetermined direction (the direction of arrow b in FIG. 2).

  As shown in FIG. 2, the intermediate transfer belt 14, the brush roll 34, the charging roll 36, and an example of an exposure apparatus are arranged around the photoreceptors 13 </ b> C to 13 </ b> K in order along the rotation direction b of the photoreceptors 13 </ b> C to 13 </ b> K. An LED array head 40 is disposed.

  The intermediate transfer belt 14, the brush roll 34, and the charging roll 36 are in contact with the surfaces of the photoreceptors 13C to 13K. Further, on the downstream side of the LED array head 40 in the rotation direction of the photoreceptors 13C to 13K and on the upstream side of the intermediate transfer belt 14, developing devices 12C, 12M, 12Y, and 12K (developing latent images with a developer) Hereinafter, 12C to 12K) are provided.

  The surfaces of the photoreceptors 13C to 13K are uniformly charged by the charging roll 36. The surfaces of the charged photoconductors 13C to 13K are exposed by the LED array head 40, and electrostatic latent images corresponding to the image data are formed on the surfaces of the photoconductors 13C to 13K. The electrostatic latent images formed on the photoreceptors 13C to 13K are developed by the developing devices 12C to 12K, so that toner images are formed on the photoreceptors 13C to 13K.

  The intermediate transfer belt 14 is formed in an endless shape. As shown in FIG. 2, the intermediate transfer belt 14 is disposed obliquely above the belt conveyance roll 24A, the belt conveyance roll 24B disposed below the belt conveyance roll 24A, and the belt conveyance roll 24B. Thus, the belt is wound around and supported by a belt conveyance roll 24 </ b> C disposed on the opposite side of the conveyance path 19.

  The outer peripheral surface of the intermediate transfer belt 14 is a transfer surface 14A to which a toner image is transferred. The developing devices 12C to 12K and the photoconductors 13C to 13K are arranged in parallel so as to face the transfer surface 14A. 13C to 13K are in contact with the transfer surface 14A.

  On the other hand, transfer rolls 32C, 32M, 32Y, and 32K (hereinafter referred to as 32C to 32K) are disposed on the opposite side of the photoreceptors 13C to 13K with the intermediate transfer belt 14 interposed therebetween. The rollers 32C to 32K are pressed against the photoreceptors 13C to 13K.

  The image forming apparatus 10 is a so-called tandem full-color printer, and the four-color toner images developed by the developing devices 12C to 12K are superimposed on the intermediate transfer belt 14 while the intermediate transfer belt 14 makes one round. Is done.

  In FIG. 2, a toner density detection sensor 15 is disposed adjacent to the downstream side of the photoreceptor 13K with respect to the rotation direction of the intermediate transfer belt 14 indicated by an arrow a so as to face the transfer surface 14A. The toner concentration detection sensor 15 has a function of detecting the concentration of toner transferred to the transfer surface 14A.

  As shown in FIG. 1, the paper feed roll 18 is arranged above the paper feed unit 16 so as to contact the front end of the paper P stored in the paper feed unit 16 in the transport direction. Further, the conveyance path 19 for conveying the paper P is formed in an S shape upward from the side of the paper supply unit 16 where the paper supply roll 18 is provided to the paper output unit 17 via the transfer unit 22 and the fixing unit 28. It extends. A plurality of transport rolls 20 are arranged in the transport path 19. The paper P is transported upward by the transport roll 20 along the transport path indicated by the two-dot chain line arrow in FIG. The paper is conveyed to the paper discharge unit 17 via the unit 22 and the fixing unit 28.

  The transfer unit 22 is provided with a belt conveyance roll 24A around which the intermediate transfer belt 14 is wound, and a transfer roll 26 pressed against the belt conveyance roll 24A. The intermediate transfer belt 14 is sandwiched in the nip portion between the belt conveyance roll 24A and the transfer roll 26, and the toner image is transferred from the intermediate transfer belt 14 when the paper P passes through the nip portion.

  The fixing unit 28 includes a heat roll 28A and a backup roll 28B pressed against the heat roll 28A. When the paper P passes through the nip portion between the heat roll 28A and the backup roll 28B, the toner is melted and solidified. The toner image is fixed. The paper P on which the toner image has been fixed by the fixing unit 28 is discharged to the paper discharge unit 17 by a paper discharge roll 29 disposed on the downstream side in the transport direction of the fixing unit 28.

(Configuration of developing devices 12C to 12K according to the present embodiment)
Next, the configuration of the developing devices 12C to 12K according to the present embodiment will be described. FIG. 3 is a schematic diagram illustrating the configuration of the developing devices 12C to 12K according to the present embodiment.

  As illustrated in FIG. 3, the developing devices 12 </ b> C to 12 </ b> K according to the present embodiment include a housing 37 having an opening 37 </ b> A at a position facing the photoconductors 13 </ b> C to 13 </ b> K.

  A first developing roll 41 that rotates in a predetermined direction (in the direction of arrow c in FIG. 3) and holds the developer and the developer held by the first developing roll are delivered from the first developing roll 41 to the housing 37. And a second developing roller 42 for supplying the transferred developer to the photoreceptors 13C to 13K, and screw feeders 39A and 39B as an example of a conveying member for conveying the developer to the first developing roller 41. Has been.

  The developer used in the developing devices 12C to 12K is a magnetic developer having magnetism, and a two-component developer containing toner and magnetic carrier particles as main components is used as the developer.

  The screw feeders 39A and 39B are disposed on the lower side of the first developing roll 41, and the screw feeders 39A and 39B are rotated along the rotation axis direction of the first developing roll 41 while the developer is being stirred. The developer is transported and supplied to the first developing roll 41.

  The first developing roll 41 and the second developing roll 42 are arranged to face each other so that a gap is formed between them, and the developer is transferred between the first developing roll 41 and the second developing roll 42. A transfer section 46 to be performed is formed.

  Further, as shown in FIG. 3, the first developing roll 41 and the second developing roll 42 are disposed in the opening 37A of the housing 37 so that a gap is formed between the first developing roll 41 and the second developing roll 42 and the surfaces of the photoreceptors 13C to 13K. The photoconductors 13C to 13K are disposed opposite to each other.

  Further, each of the first developing roll 41 and the second developing roll 42 includes cylindrical inner cylinders 41B and 42B, and cylindrical sleeves 41A and 42A covering the outer circumferences of the inner cylinders 41B and 42B. ing.

  On the outer periphery of the first developing roll 41, a trimming blade 53 as an example of a layer forming member for adjusting the height of the developer layer held by the first developing roll 41 faces the first developing roll 41. Are arranged.

  The inner cylinders 41B and 42B are fixed to the housing 37 of the developing devices 12C to 12K and are not rotated. As shown by an arrow c in FIG. 3, the sleeves 41A and 42A are configured to rotate around the axes of the inner cylinders 41B and 42B in a direction opposite to the rotation direction b of the photoreceptors 13C to 13K. That is, the photoconductors 13C to 13K rotate counterclockwise in FIG. 3, whereas the first developing roll 41 and the second developing roll 42 rotate clockwise in FIG.

  Five permanent magnets are radially embedded in the inner cylinder 41B so that S poles and N poles are alternately formed on the surface side of the inner cylinder 41B along the rotation direction of the sleeve 41A.

  As shown below, the five permanent magnets include a pickup pole 51A (S pole), a trimming pole 51B (N pole), a transport pole 51C (S pole), and a delivery pole 51D (N pole). ing.

  A trimming pole 51B for adjusting the height of the developer layer in cooperation with the trimming blade 53 is disposed on the inner cylinder 41B at a position facing the trimming blade 53.

  A pickup pole 51A that holds the developer on the sleeve 41A is disposed on the upstream side in the rotation direction of the first developing roll 41 as viewed from the trimming pole 51B.

  In the pick-up pole 51A, the developer is attracted to the surface of the sleeve 41A, and the developer is held on the surface of the sleeve 41A in the state of a magnetic brush that is raised.

  The developer held in the sleeve 41A in the state of a magnetic brush is conveyed to the trimming pole 51B by the rotation of the sleeve 41A, and passes through the trimming pole 51B by the trimming pole 51B and the trimming blade 53. The height of the developer is aligned.

  As viewed from the trimming pole 51B, a transport pole 51C for transporting the developer to a position facing the second development roll 42 (the transfer section 46) is disposed on the downstream side in the rotation direction of the first development roll 41. Yes.

  When the developer is transported by the transport pole 51C, the developer passes between the first developing roll 41 and the photoreceptors 13C to 13K.

  A transfer pole 51D for transferring the developer held by the sleeve 41A to the second developing roll 42 is provided to the second developing roll 42 on the downstream side in the rotation direction of the first developing roll 41 as viewed from the transport pole 51C. It arrange | positions in the opposing position which opposes.

  On the other hand, five permanent magnets are radially formed on the inner cylinder 42B of the second developing roll 42 so that the south pole and the north pole are alternately formed on the surface side of the inner cylinder 42B along the rotation direction of the sleeve 42A. Embedded in.

  As shown below, the five permanent magnets are configured to include a receiving pole 52A (S pole), a developing pole 52B (N pole), a transport pole 52C (S pole), and a pickoff pole 52D (N pole). ing.

  A receiving pole 52A for receiving the developer from the first developing roll 41 is disposed on the inner cylinder 42B at a position facing the delivery pole 51D of the first developing roll 41.

  A magnetic flux (magnetic field) from the transfer pole 51D toward the receive pole 52A is formed between the receiving pole 52A and the transfer pole 51D, which are different from the transfer pole 51D. The developer moves from 41 to the second developing roll 42, and the developer is delivered.

  A developing electrode 52B for transferring the developer to the photoreceptors 13C to 13K is disposed on the inner cylinder 42B on the downstream side in the rotation direction of the second developing roller 42 as viewed from the receiving electrode 52A.

  In addition, a transport pole 52C for transporting the developer is disposed on the inner cylinder 42B on the downstream side in the rotation direction of the second developing roll 42 as viewed from the development pole 52B.

  The inner cylinder 42B has a pick-off pole 52D for separating the developer held by the sleeve 42A from the second developing roll 42 on the downstream side in the rotation direction of the second developing roll 42 as viewed from the transport pole 52C. Has been placed.

  The developer separated from the second developing roll 42 is efficiently separated from the second developing roll 42 by being pushed by the centrifugal force of the second developing roll 42 and the subsequent developer. It has become. The developer separated from the second developing roll 42 falls toward the screw feeders 39A and 39B in the housing 37 due to its gravity.

  Further, a guide plate 54 for guiding the developer to the screw feeders 39A and 39B is provided in the casing 37 so that the developer falling in the casing 37 falls to the screw feeders 39A and 39B. .

  The guide plate 54 is disposed on the back side that is opposite to the side where the photoconductors 13C to 13K are present when viewed from the first developing roll 41 and the second developing roll 42.

  When the guide plate 54 guides the developer, the developer that has fallen from the second developing roll 42 is prevented from dropping to a position away from the first developing roll 41 and reattaching to the first developing roll 41. Is done.

  The guide plate 54 is disposed on the back side opposite to the side where the photoconductors 13C to 13K are present when viewed from the first developing roll 41 and the second developing roll 42, and the first developing roll 41 and the second developing roll. A magnet 56 and a magnet 58 are provided as an example of a sealing member that seals between the roll 42.

  The magnet 56 is attached to the upper surface of the guide plate 54 along the axial direction of the second developing roll 42, and the tip portion protrudes toward the second developing roll 42. A gap is formed between the tip of the magnet 56 and the second developing roll 42.

  The tip of the magnet 56 has a second development in a region between the N pole on the downstream side in the rotation direction of the second developing roll 42 as viewed from the pickoff pole 52D (N pole) and the pickoff pole 52D (N pole). It faces the roll 42. In this region, the tip of the magnet 56 is opposed to a region having a surface magnetic flux density of 20 G or less (the surface region of the sleeve 42A from which the developer is detached).

  The magnet 56 is a magnetic material having magnetism, and the developer attracts the developer from the surface of the second developing roll 42 by the magnetic force to bring the developer into a state of a magnetic brush, and the surface of the second developing roll 42. The gap between the magnet 56 and the magnet 56 is filled.

  In FIG. 3, reference numeral 66 indicates a developer in the state of a magnetic brush that is in the form of a head. The magnet 56 has an N pole at the front end and an S pole at the rear end.

  The magnet 58 is attached to the lower surface of the guide plate 54 along the axial direction of the first developing roll 41, and the leading end protrudes toward the first developing roll 41. A gap is formed between the tip of the magnet 58 and the first developing roll 41.

  The tip of the magnet 58 is the first developing in the region between the N pole on the downstream side in the rotation direction of the first developing roll 41 and the transfer pole 51D (N pole) when viewed from the transfer pole 51D (N pole). It faces the roll 41. Of this region, the tip of the magnet 58 faces a region having a surface magnetic flux density of 20 G or less (a surface region of the sleeve 41A from which the developer has been released).

  The magnet 58 is a magnetic material having magnetism, and the developer attracts the developer from the surface of the first developing roll 41 by the magnetic force to bring the developer into a spiked magnetic brush state, and the surface of the first developing roll 41. And a gap between the magnet 58 and the magnet 58. The magnet 58 has an S pole at the front end and an N pole at the rear end. In FIG. 3, the code | symbol 68 shows the developer of the state of the magnetic brush which rose.

  As described above, the first developing roll 41 and the second developing roll 42 are generated by the magnet 56, the developer 66 that is brought into a magnetic brush state by the magnet 56, and the developer 68 that is brought into a magnetic brush state by the magnet 58. Is sealed.

  As a result, the developer 56, which has become a magnetic brush by the magnet 56, and the developer 68, which has become the magnetic brush by the magnet 58, are transferred to the first developing roll 41 and the second developing roll 42. Functions as a partition member that partitions the space between the first developing roller 41 and the second developing roller 42, and the space inside the housing 37 is separated. Is done.

(Operation of the developing device according to this embodiment)
Next, the operation of the developing device according to this embodiment will be described.

  In the developing devices 12C to 12K according to the present embodiment, the developer is supplied to the first developing roll 41 by the screw feeders 39A and 39B. The developer supplied to the first developing roll 41 is adsorbed on the surface of the sleeve 41A by the pickup electrode 51A. At this time, the developer adheres to the surface of the sleeve 41A in the form of a magnetic brush.

  The developer adsorbed on the surface of the sleeve 41A moves along the surface of the sleeve 41A as the sleeve 41A rotates along the rotation direction c, along with the trimming pole 51B, the conveyance pole 51C, and the delivery pole 51D (the delivery section 46). ) In this order.

  When the developer passes through the trimming pole 51B, the height of the layer is made uniform by the trimming pole 51B and the trimming blade 53. The developer having the uniform height passes between the first developing roll 41 and the photoreceptors 13C to 13K by the transport pole 51C, and is transported to the delivery unit 46.

  The developer transported to the delivery section 46 moves from the delivery pole 51D to the receipt pole 52A and is delivered from the first development roll 41 to the second development roll 42. The developer transferred to the second developing roll 42 is transferred to the developing electrode 52B, the conveying electrode 52C, and the pickoff electrode 52D along the surface of the sleeve 42A as the sleeve 42A rotates along the rotation direction c. Transported in order.

  The developer moves to the photosensitive members 13C to 13K at the developing electrode 52B, and the developer remaining on the surface of the sleeve 42A without moving to the photosensitive members 13C to 13K is conveyed by the conveying electrode 52C. The developer transported by the transport electrode 52C is dropped from the surface of the sleeve 42A by the pick-off electrode 52D and collected in the housing 37.

  The developer collected in the housing 37 is guided by the guide plate 54 and falls to the screw feeders 39A and 39B.

  Here, in the present embodiment, when the developer remaining on the surface of the sleeve 42 </ b> A without being transferred to the photoconductors 13 </ b> C to 13 </ b> K is transported and collected in the housing 37, air is drawn into the housing 37. Pressure may increase.

  When the pressure rises in the housing 37, air tends to be released from the gap formed in the opening 37 </ b> A of the housing 37, but the developer 56 and the magnet 58 are brought into a magnetic brush state by the magnet 56 and the magnet 56. And the developer 68 in a magnetic brush state by the magnet 58 seals the gap between the first developing roll 41 and the second developing roll 42, so that the first developing roll 41 and the second developing roll 42 The developer is prevented from being ejected from the outside to the outside of the apparatus.

  The arrangement position and rotation direction of the first development roll 41 and the second development roll 42, the arrangement position of the trimming blade 53, and the rotation direction of the photoconductors 13C to 13K are not limited to the configuration of the present embodiment and can be arbitrarily set. .

  For example, in the above embodiment, the second developing roll 42 is disposed above the first developing roll 41 and the developer is transferred upward. However, the second developing roll 42 is replaced with the first developing roll. It may be arranged below 41 and deliver the developer downward. Further, the photoconductors 13C to 13K may be configured so as to rotate in the opposite direction (clockwise in FIG. 3) while changing the arrangement configuration around them.

  In addition, as shown in FIG. 4, the structure which provided only the magnet 56 instead of providing the magnet 58 may be sufficient. In this configuration, the developer is accommodated in the housing 37 until it contacts the lower portion of the guide plate 54, and the magnet 56, the developer 66 that has become a magnetic brush by the magnet 56, and the guide plate 54, The space between the first developing roll 41 and the second developing roll 42 is sealed.

  As a result, the magnet 56, the developer 66 and the guide plate 54 that are brought into a magnetic brush state by the magnet 56, the space between the first developing roll 41 and the second developing roll 42, and the space inside the housing 37. The space between the first developing roll 41 and the second developing roll 42 and the space inside the housing 37 are separated.

(First Modification of Sealing Member)
Further, as shown in FIG. 5, as a sealing member for sealing between the first developing roll 41 and the second developing roll 42, the developer falling in the housing 37 is guided to the screw feeders 39A and 39B. A configuration using a magnet 62 that also serves as a guide plate may be used.

  The magnet 62 is made of a permanent magnet and is disposed along the axial direction of the first developing roll 41 and the second developing roll 42. The magnet 62 is formed to be bent in a U-shape, with one end 62 </ b> A facing the second developing roll 42 and the other end 62 </ b> B facing the first developing roll 41.

  One end 62A of the magnet 62 has a second end in a region between the N pole on the downstream side in the rotation direction of the second developing roll 42 as viewed from the pickoff pole 52D (N pole) and the pickoff pole 52D (N pole). It faces the developing roll 42. In this region, one end 62A of the magnet 62 is opposed to a region having a surface magnetic flux density of 20G or less (a surface region of the sleeve 42A from which the developer has been removed). Further, a gap is formed between the one end portion 62 </ b> A of the magnet 62 and the second developing roll 42.

  On the other hand, the other end portion 62B of the magnet 62 is in a region between the N pole on the downstream side in the rotation direction of the first developing roll 41 as viewed from the transfer pole 51D (N pole) and the transfer pole 51D (N pole). , Opposite to the first developing roll 41. In this region, the other end portion 62B of the magnet 62 is opposed to a region having a surface magnetic flux density of 20 G or less (the surface region of the sleeve 41A from which the developer has been detached). A gap is formed between the other end portion 62 </ b> B of the magnet 62 and the first developing roll 41.

  The magnet 62 has one end 62A facing the second developing roll 42 as an N pole and the other end 62B facing the first developing roll 41 as an S pole.

  The magnet 62 attracts the developer from the surface of the second developing roll 42 by the magnetic force to make the developer in the form of a magnetic brush with a spike, and the surface of the second developing roll 42 and one end 62A of the magnet 62 It is designed to fill the gap between the two.

Further, the magnet 62 draws the developer from the surface of the first developing roll 41 by the magnetic force to bring the developer into a state of a magnetic brush that is in the form of a head, and the surface of the first developing roll 41 and the other end of the magnet 62 The gap between the portion 62B is filled.
In FIG. 5, reference numerals 72 </ b> A and 72 </ b> B indicate the developer in the state of a magnetic brush that is raised.

  As described above, the magnet 62, the developer 72A that has become a magnetic brush at the one end 62A of the magnet 62 by the magnet 62, and the developer 72B that has become the magnetic brush at the other end 62B of the magnet 62 by the magnet 62. The space between the first developing roll 41 and the second developing roll 42 is sealed.

  As a result, the magnet 72, the developer 72A that has become a magnetic brush at the one end 62A of the magnet 62 by the magnet 62, and the developer 72B that has become the magnetic brush at the other end 62B of the magnet 62 by the magnet 62, It functions as a partition member that partitions the space between the first developing roll 41 and the second developing roll 42 and the space inside the housing 37, and the space between the first developing roll 41 and the second developing roll 42. And the space inside the housing 37 are separated.

(Second modification of sealing member)
Further, as shown in FIG. 6, as a sealing member that seals between the first developing roll 41 and the second developing roll 42, the developer falling in the housing 37 is guided to the screw feeders 39A and 39B. A configuration using a soft magnetic body 60 that also serves as a guide plate may be used.

  The soft magnetic body 60 is disposed along the axial direction of the first developing roll 41 and the second developing roll 42. The soft magnetic body 60 is formed in a U-shaped curve, with one end 60 </ b> A facing the second developing roll 42 and the other end 60 </ b> B facing the first developing roll 41.

  One end 60A of the soft magnetic body 60 is in a region between the N pole on the downstream side in the rotation direction of the second developing roll 42 as viewed from the pickoff pole 52D (N pole) and the pickoff pole 52D (N pole). Opposing to the second developing roll 42. In this region, one end portion 60A of the soft magnetic body 60 is opposed to a region having a surface magnetic flux density of 20G or less (a surface region of the sleeve 42A from which the developer is detached). Further, a gap is formed between the one end portion 60 </ b> A of the soft magnetic body 60 and the second developing roll 42.

  On the other hand, the other end 60B of the soft magnetic body 60 is located between the N pole on the downstream side in the rotation direction of the first developing roll 41 as viewed from the transfer pole 51D (N pole) and the transfer pole 51D (N pole). In the area, it faces the first developing roll 41. Among these regions, the other end portion 60B of the soft magnetic body 60 is opposed to a region having a surface magnetic flux density of 20 G or less (a surface region of the sleeve 41A from which the developer has been removed). A gap is formed between the other end 60 </ b> B of the soft magnetic body 60 and the first developing roll 41.

  The soft magnetic body 60 is magnetized by being induced by the magnetic poles of the first developing roll 41 and the second developing roll 42, and has one end 60 </ b> A facing the second developing roll 42 and the other end 60 </ b> B facing the first developing roll 41. Is the S pole.

  The soft magnetic body 60 draws the developer from the surface of the second developing roll 42 by the magnetic force to make the developer in the form of a magnetic brush that is in the form of a head, and the surface of the second developing roll 42 and the soft magnetic body 60 The gap between the one end 60A is filled.

In addition, the soft magnetic body 60 draws the developer from the surface of the first developing roll 41 by the magnetic force to make the developer in a state of a magnetic brush with a spike, and the surface of the first developing roll 41 and the soft magnetic body The gap between the other end 60B of 60 is filled.
In FIG. 6, reference numerals 70 </ b> A and 70 </ b> B indicate the developer in the state of a magnetic brush that has become a head.

  As described above, the soft magnetic body 60, the developer 70 </ b> A that is in the state of a magnetic brush at one end 60 </ b> A of the soft magnetic body 60 by the soft magnetic body 60, and the other end 60 </ b> B of the soft magnetic body 60 by the soft magnetic body 60. The space between the first developing roll 41 and the second developing roll 42 is sealed by the developer 70B in a brush state.

  As a result, the developer 70A that has become a magnetic brush at one end 60A of the soft magnetic body 60 by the soft magnetic body 60 and a magnetic brush at the other end 60B of the soft magnetic body 60 by the soft magnetic body 60. The developer 70B functions as a partition member that partitions the space between the first developing roller 41 and the second developing roller 42 and the space inside the housing 37, and the first developing roller 41 and the second developing roller 42. And the space inside the housing 37 are separated.

(Third Modification of Sealing Member)
As shown in FIG. 7, a contact member 63 that contacts the first developing roll 41 and the second developing roll 42 is used as a sealing member that seals between the first developing roll 41 and the second developing roll 42. The configuration used may be used.

  The contact member 63 is disposed along the axial direction of the first developing roll 41 and the second developing roll 42. The contact member 63 has one end 63 </ b> A in contact with the second developing roll 42 and the other end 63 </ b> B in contact with the first developing roll 41.

  One end portion 63A of the contact member 63 is located in the region between the N pole on the downstream side in the rotation direction of the second developing roll 42 as viewed from the pickoff pole 52D (N pole) and the pickoff pole 52D (N pole). 2 is in contact with the developing roll 42. In this region, the one end portion 63A of the contact member 63 is in contact with the surface region of the sleeve 42A from which the developer has separated.

  On the other hand, the other end 63B of the contact member 63 is a region between the N pole on the downstream side in the rotation direction of the first developing roll 41 as viewed from the transfer pole 51D (N pole) and the transfer pole 51D (N pole). , The first developing roll 41 is in contact. In this region, the other end portion 63B of the contact member 63 is in contact with the surface region of the sleeve 41A from which the developer has separated.

  Thus, the first developing roller 41 and the second developing roller 41 are contacted by the one end 63A of the contact member 63 contacting the second developing roller 42 and the other end 63B of the contacting member 63 contacting the second developing roller 42. The space between the rolls 42 is sealed.

  As a result, the contact member 63 functions as a partition member that partitions the space between the first developing roll 41 and the second developing roll 42 and the space inside the housing 37, and the first developing roll 41 and the second developing roll 41. The space between the developing roll 42 and the space inside the housing 37 are separated.

(Test example)
In the developing devices 12C to 12K according to the present embodiment shown in FIG. 3 and the developing device 100 according to the comparative example shown in FIG. 8, a test was performed on the occurrence rate of misprints due to streak fogging.

  The developing device 100 according to the comparative example shown in FIG. 8 has a configuration that does not include the magnet 56 and the magnet 58 in the developing devices 12C to 12K according to the present embodiment shown in FIG. 3, and the other configuration is the book shown in FIG. This is the same as the developing devices 12C to 12K according to the embodiment.

  The evaluation conditions are TC% (weight percent of toner per unit weight of two-component developer) = 12%, TV (per unit weight of toner in two-component developer) at 28 ° C. and 85% RH environment. Charge amount of toner) = 35 μC / g, Vcln (difference between DC component voltage of bias applied to developing roll and photoreceptor surface potential corresponding to background portion of image) = 140 V, Vdev (photosensitivity corresponding to image portion of image) Difference between body potential and DC component voltage of bias applied to developing roll) = 285V, 50 sheets of A3 size white paper were collected continuously, and the result of counting misprints due to streaking generated on the remaining 30 sheets after 20 sheets It is. As a result, in the configuration of the present embodiment, no misprints due to streaking occurred, and in the configuration of the comparative example, misprints occurred on 15 of 30 sheets.

  In addition, the structure which suppresses the ejection of a developer by reducing the pressure in the housing 37 by directly sucking the inside of the housing 37 of the developing devices 12C to 12K is conceivable. May consume more than necessary.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made.

FIG. 1 is a schematic diagram illustrating the overall configuration of the image forming apparatus according to the present embodiment. FIG. 2 is a schematic diagram illustrating an image forming unit provided in the image forming apparatus according to the present embodiment. FIG. 3 is a schematic diagram illustrating the configuration of the developing device according to the present embodiment. FIG. 4 is a schematic diagram showing a configuration in which only one magnet is provided in the developing device according to the present embodiment. FIG. 5 is a schematic diagram illustrating a configuration of a developing device using a first modification of the sealing member. FIG. 6 is a schematic diagram illustrating a configuration of a developing device using a second modification of the sealing member. FIG. 7 is a schematic diagram illustrating a configuration of a developing device using a third modification of the sealing member. FIG. 8 is a schematic diagram illustrating a configuration of a developing device according to a comparative example. FIG. 9 is a table showing test results obtained in the developing device according to the present embodiment and the developing device according to the comparative example.

Explanation of symbols

10 Image forming devices 12C to 12K Developing devices 13C to 13K
41 First developing roll 42A Sleeve 42 Second developing roll 54 Guide plate 56 Magnet (sealing member, magnetic body)
58 Magnet (sealing member, magnetic body)
60 Soft magnetic material (sealing member, magnetic material)
62 Magnet (sealing member, magnetic body)
63 Contact member (sealing member)

Claims (4)

A first developing roll disposed opposite to the latent image holding body and holding a developer;
A second developer disposed opposite to the latent image holding body and held by the first developing roll is delivered from the first developing roll, and the delivered developer is supplied to the latent image holding body. A developing roll;
Sealing that is disposed on the side opposite to the side where the latent image holding member is located when viewed from the first developing roll and the second developing roll, and seals between the first developing roll and the second developing roll. Members,
A developing device comprising:   The sealing member is attracted from the surface of at least one of the first developing roll and the second developing roll by a magnetic body having magnetism and the magnetic force of the magnetic body, and fills between the surface and the magnetic body. The developing device according to claim 1, comprising a developer.   The developing device according to claim 2, wherein the magnetic body also serves as a guide plate that guides the developer separated from the second developing roll. The developing device according to any one of claims 1 to 3,
A latent image holding body for holding a latent image developed by the developing device;
An image forming apparatus comprising:

Images