JP2013218065A - Developing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing scattering of a carrier while reducing the size of the device, and an image forming apparatus including the developing device.SOLUTION: A developing device 4 includes: a developer carrier 5 that has magnetic field generating means 82 for development arranged inside thereof; and a carrier recovery member 13 that is arranged close to the developer carrier, and recovers a magnetic carrier attached to the surface of a latent image carrier 1 by magnetically adsorbing the magnetic carrier on the outer peripheral surface of the carrier recovery member 13 in a carrier recovery area on the downstream side in the surface movement direction of the latent image carrier in a developing area where the developer carrier and the latent image carrier face each other. The magnetic field generating means for development moves a plurality of magnetic poles circulatively along the direction of rotation of the developer carrier. The developing device 4 develops a latent image by attaching a toner in two-component developer carried on the outer peripheral surface of the developer carrier to the latent image formed on the latent image carrier, and further includes a magnetism shielding member 96 that shields magnetism between the developer carrier and the carrier recovery member.

Description

  The present invention relates to a developing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus provided with the developing device.

  In general, a developing device used in an image forming apparatus is a developing region in which a developing roller as a developer carrying member and a photosensitive member as a latent image carrying member face each other. The toner is developed with a developer carried on the toner to form a toner image on the photoreceptor. As a developing method, a two-component developing method is known in which development is performed using a two-component developer containing a toner and a magnetic carrier. In the two-component development system, a developing roller in which a magnet roller as a developing magnetic field generating means is disposed inside the developing sleeve is used, and a magnetic material in which toner is electrostatically attached by the action of a magnetic field formed by the magnet roller. A magnetic brush is formed by causing the carrier to rise like a brush on the surface of the developing sleeve. In the development area, only the toner in the magnetic brush is attached to the latent image formed on the photoconductor to form a toner image on the photoconductor.

  In a two-component developing type developing device, for the purpose of efficiently charging the toner by stirring the developer, the magnet roller rotates inside the developing roller, so that the magnetic pole of the magnet roller moves along the rotating direction of the developing roller. There is known one that employs a magnetic pole movement system that moves around. In this magnetic pole moving method, the magnetic brush rotates strongly on the developing sleeve due to the rotation of the magnet roller, and the magnetic carrier of the magnetic brush is scattered by the centrifugal force, and the carrier adhesion that adheres to the photoconductor becomes serious. There is. In particular, in recent years, the particle size of magnetic carriers has been reduced for higher image quality, and carrier adhesion tends to be further deteriorated. When carrier adhesion occurs, the contact between the photosensitive member and the transferred member is caused by the presence of the magnetic carrier attached on the photosensitive member at the transfer nip where the transferred member such as the intermediate transfer member or recording material contacts the photosensitive member. And the abnormal image such as so-called white spots is caused. Further, when carrier adhesion occurs, the magnetic carrier may damage the surface of the photosensitive member at the contact portion between the photosensitive member and the cleaning member, thereby deteriorating the image quality, or damage the cleaning member to cause cleaning failure.

  As measures for suppressing the occurrence of defects due to such carrier adhesion, for example, those disclosed in Patent Documents 1 to 3 are known. In the image forming apparatuses disclosed in these Patent Documents 1 to 3, a carrier recovery device that recovers a magnetic carrier from the surface of the photoreceptor is provided between the development region and the transfer nip. In this carrier recovery device, a carrier recovery member is disposed opposite to the surface of the photoconductor, and the magnetic carrier attached on the surface of the photoconductor is recovered on the surface of the carrier recovery member by the action of a magnetic field generated by the carrier recovery member.

  In recent years, in order to reduce the size of the apparatus, the carrier recovery member is often disposed close to the developing roller. However, if the carrier recovery member is arranged close to the developing roller, the magnetic lines of magnetic force are connected between the developing roller and the carrier recovery member, and the magnetic brush that rises on the developing sleeve becomes long. There arises a problem that the magnetic carrier is easily scattered from the front end side of the magnetic brush by force. As described above, if the magnetic carrier easily scatters, the magnetic carrier adhering to the photosensitive member increases so much that the carrier cannot be recovered by the carrier recovery member, and it becomes impossible to suppress the occurrence of defects due to the carrier adhesion.

  The present invention has been made in view of the above problems, and an object thereof is to provide a developing device capable of suppressing carrier scattering while achieving downsizing and an image forming apparatus including the developing device. That is.

  In order to achieve the above object, a first aspect of the present invention provides a two-component developer containing a magnetic carrier and toner by the action of a magnetic field generated from a plurality of magnetic poles by a developing magnetic field generating means disposed therein. A latent image carrier in a carrier collection region on the downstream side in the moving direction of the surface of the latent image carrier in the development region where the developer carrier and the latent image carrier face each other; A magnetic carrier adhering to the surface of the substrate and magnetically attracting and recovering the magnetic carrier on the outer peripheral surface, and a carrier recovery member disposed in the vicinity of the developing carrier. The plurality of magnetic poles are circulated around the rotation direction of the agent carrier, and the toner in the two-component developer carried on the outer peripheral surface of the developer carrier is formed on the latent image carrier. Develop the latent image by attaching it to the latent image In the developing device and is characterized in that a magnetic shield for shielding magnetic between said developer carrying member and the carrier recovery member.

  In the present invention, since the magnetic shielding member shields the magnetism between the developer carrier and the carrier recovery member, it is possible to suppress a line of magnetic force between the developer carrier and the carrier recovery member. . As a result, the length of the magnetic brush on the developer carrying member can be made shorter than when no magnetic shielding member is provided. Therefore, in order to reduce the size of the apparatus, even if the carrier recovery member is arranged close to the developer carrier, the length of the magnetic brush can be shortened compared to the case where the magnetic shielding member is not provided. It is possible to prevent the magnetic carrier from scattering from the tip side of the magnetic brush on the developer carrying member due to the centrifugal force.

  As described above, according to the present invention, there is an excellent effect that carrier scattering can be suppressed while downsizing.

FIG. 3 is an enlarged view of a developing device in the vicinity of a developing roller. 1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is a diagram illustrating a developing device and a photoreceptor. FIG. 3 is a perspective cross-sectional view of the developing device for explaining the flow of the developer in the developer transport path. FIG. 3 is an external perspective view illustrating a position where toner is supplied. (A) The figure which shows the image of the magnetic force line when there is no carrier collection | recovery apparatus, (b) The figure which shows the image of the magnetic force line when there is a carrier collection | recovery apparatus and there is no magnetic shielding member, (c) Carrier collection apparatus and magnetism The figure which shows the image of the line of magnetic force in case there exists a shielding member. (A) The figure which shows magnetic flux density (normal component) distribution on the carrier collection | recovery roller when a magnetic shielding member is provided, (b) Magnetic flux density (method) on the carrier collection roller when a magnetic shielding member is not provided The figure which shows distribution (line component). (A) The figure which shows the magnetic force line from the developing roller magnetic pole in Example 1, (b) The figure which shows the magnetic force line from the developing roller magnetic pole in the comparative example 1, (c) The magnetic force line from the developing roller magnetic pole in the comparative example 2 FIG.

  FIG. 2 is a diagram illustrating an outline of a full-color copying machine (hereinafter simply referred to as a copying machine for convenience) 500 according to the present embodiment.

  The copying machine 500 includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is mounted, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 is fixed on the scanner 300.

  The printer unit 100 includes an image forming unit including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 20 is provided.

  Y, M, C, and K attached to the numbers of the respective symbols indicate members for yellow, magenta, cyan, and black (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed. .

  The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of a photoreceptor to be described later with laser light based on image data.

  The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive member 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like.

The yellow process cartridge 18Y will be described below.
The surface of the photoreceptor 1Y is uniformly charged by a charger as charging means. The surface of the photoreceptor 1 </ b> Y that has been subjected to charging processing is irradiated with laser light that has been modulated and deflected by the optical writing unit 21. Thereby, the potential of the surface of the photoreceptor 1Y of the irradiation part (exposure part) is attenuated. Due to the attenuation of the surface potential, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.

  The Y toner image formed on the Y photoconductor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.

  In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges 18M, 18C, and 18K.

Next, the intermediate transfer unit 17 will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 70, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, M, C, and K.

  The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).

  The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor 1 and the primary transfer bias roller 62 due to the influence of the primary transfer bias.

  The above-described Y toner image formed on the Y photoconductor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, K toner images formed on the M, C, K photoconductors 1M, C, K are sequentially superposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.

  The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet (not shown) as a recording medium at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 70 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described.
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown).

  By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 to be described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device 200 provided at the lower part of the copying machine 500 main body, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and stored in a bundle of sheets are arranged so as to overlap each other in the vertical direction. It is installed. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 48.

  The paper feed path 48 that receives the transfer paper delivered from the paper feed cassette 44 has a plurality of conveying roller pairs 47 and a registration roller pair 49 provided near the end in the paper feed path 48. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip.

  Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller 27 has a heat source (not shown) inside, and heats the fixing belt 26 by the generated heat. The heated fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper subjected to the fixing process in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the printer housing, or forms a toner image on the other surface. Any one of the transport modes to be returned to the secondary transfer nip is selected.

  When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with such a document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 starts driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the respective photoreceptors 1Y, 1M, 1C, and 1K. Is done. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer paper is separated one by one by the separation roller 45 and enters the paper feed path 48, and is then transported toward the secondary transfer nip by the transport roller pair 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual feed roller 50 is selectively rotated to feed the transfer paper on the manual feed tray 51, the separation roller 52 separates the transfer paper one by one and feeds it to the manual feed path 53 of the printer unit 100. Make paper.

  When the copier 500 forms a multicolor image composed of toners of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. Photoconductors 1Y, 1M, 1C, and 1K are brought into contact with each other. On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device 4 is stopped, and each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessarily consumed. To prevent.

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of a liquid crystal display, various key buttons, and the like. . The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

  FIG. 3 is a diagram illustrating the developing device 4 and the photosensitive member 1 provided in each of the four process cartridges 18Y, 18M, 18C, and 18K.

  Since the four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of the toners to be handled are different, the subscripts Y, M, C, and K attached to the respective reference numerals in FIG. Omitted.

  As shown in FIG. 3, the surface of the photosensitive member 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The charged surface of the photoreceptor 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown), thereby forming a toner image.

  The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photosensitive member 1 while developing the developer in the direction of arrow I in the drawing.

  The developing roller 5 includes a rotatable developing sleeve 81, and includes a developing magnet roller 82 as a magnetic generating means that is composed of a plurality of magnetic poles and that can rotate in the direction of arrow A in the figure.

  Since the developing roller 5 and the carrier recovery roller 13 have been described above, they are omitted here.

  Further, while supplying the developer to the developing roller 5, the back side of the paper surface shown in FIG. 3 along the axial direction of the developing roller 5 (hereinafter sometimes referred to as the back side in the drawing or the back side in FIG. 3 for convenience). A supply screw 8 is provided as a supply / conveyance member that conveys the developer toward the substrate.

  A doctor blade 12 serving as a developer regulating means for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided downstream of the developing roller 5 facing the supply screw 8 in the developer transport direction. I have.

  A recovery conveyance path that collects the developed developer that has passed through the development area and separated from the surface of the development roller 5 on the downstream side in the developer conveyance direction from the development area that is the portion of the development roller 5 facing the photoreceptor 1. 7 faces the developing roller 5.

  The collection conveyance path 7 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 8 along the axial direction of the developing roller 5. I have. A supply conveyance path 9 provided with a supply screw 8 is arranged above the developing roller 5, and a collection conveyance path 7 provided with a collection screw 6 is arranged below the development roller 5.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the supply conveyance path 9 and the collection conveyance path 7. The agitation conveyance path 10 is inclined so as to be substantially the same height as the collection conveyance path 7 on the back side and the supply conveyance path 9 on the near side.

  The agitating and conveying path 10 is in the direction opposite to the supply screw 8 while stirring the developer along the axial direction of the developing roller 5 (hereinafter referred to as the front side in the drawing for convenience). As a stirring and transporting member that transports toward the head (which may be the case), a spiral stirring screw 11 is provided that is inclined in the axial direction.

  The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition wall. The supply conveyance path 9 and the agitation conveyance path 10 of the first partition wall 133 have an opening on the front side in the figure, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other.

  The supply conveyance path 9 and the collection conveyance path 7 are partitioned by a second partition wall 134. The supply conveyance path 9 and the collection conveyance path 7 of the second partition wall 134 have an opening on the back side in the drawing, and the supply conveyance path 9 and the collection conveyance path 7 communicate with each other.

  In addition, the two developer conveyance paths of the agitation conveyance path 10 and the collection conveyance path 7 are partitioned by a third partition wall 135 as a partition member. The third partition wall 135 has an opening on the back side in the figure, and the stirring conveyance path 10 and the collection conveyance path 7 communicate with each other.

  The supply screw 8, the recovery screw 6 and the stirring screw 11 which are developer conveying members are made of resin or metal screws, and the diameters of the screws are the supply screw 8, the recovery screw 6 is φ26 [mm], and the stirring screw 11 is φ30. [Mm] and the screw pitch is 54 [mm], the recovery screw 6 is 2 [36], the stirring screw 11 is 54 [mm], and the number of rotations is about It is set to 600 [rpm].

  The developer carried on the developing roller 5 is thinned by a doctor blade 12 made of stainless steel, and is then transported to a developing area which is a portion facing the photoreceptor 1 for development.

  The diameter of the developing roller 5 is φ40 [mm], and the gap between the doctor blade 12 and the photoreceptor 1 is about 0.4 [mm].

  The developed developer is collected in the collection conveyance path 7, conveyed to the back side in FIG. 3, and developed to the agitation conveyance path 10 through the opening of the third partition wall 135 provided in the non-image area portion. The agent is transferred. In addition, in the vicinity of the opening of the second partition wall 134 on the downstream side in the developer conveyance direction in the supply conveyance path 9, there is a supply conveyance path from a toner replenishing port 95, which will be described later, on the upper side of the supply conveyance path 9. Toner 9 is supplied.

  FIG. 4 is a perspective cross-sectional view of the developing device 4 for explaining the flow of the developer in the developer transport path, and each arrow in the drawing indicates the moving direction of the developer.

  In the supply conveyance path 9 that receives the developer supplied from the agitation conveyance path 10, the developer is supplied in contact with the developing roller 5 while moving.

  The surplus developer that has not been supplied to the developing roller 5 and has moved to the downstream end in the transport direction of the supply transport path 9 is supplied to the recovery transport path 7 from the surplus opening of the second partition wall 134 (arrow E in FIG. 4). ).

  On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and then separated / separated from the developing roller 5 and delivered to the collection conveyance path 7. The collected developer that has been transferred from the developing roller 5 to the collection conveyance path 7 and conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 is supplied to the stirring conveyance path 10 from the collection opening of the third partition wall 135. (Arrow F in FIG. 4).

  In the agitation transport path 10, excess developer supplied from the supply transport path 9, recovered developer recovered in the recovery transport path 7, and toner replenished from a toner replenishment port 95 (see FIG. 5) described later. The agitated developer is conveyed downstream in the conveyance direction of the agitation screw 11 and upstream in the conveyance direction of the supply screw 8, and is supplied to the supply conveyance path 9 from the supply opening of the first partition wall 133. Supplied (arrow D in FIG. 4).

  A toner concentration sensor (not shown) including a magnetic permeability sensor is provided below the agitation conveyance path 10, and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage unit (not shown). Is going.

  In the developing device 4 shown in FIG. 4, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 9. There is no contamination. For this reason, it is possible to suppress a decrease in the toner concentration of the developer supplied to the developing roller 5 toward the downstream side of the supply conveyance path 9 in the conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Thereby, since the sufficiently stirred developer is supplied to the supply conveyance path 9, it is possible to suppress the developer supplied to the supply conveyance path 9 from being insufficiently stirred. In this way, the toner density of the developer in the supply conveyance path 9 can be suppressed from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred, so the image density during development can be reduced. Can be constant.

FIG. 5 is an external perspective view illustrating a position where toner is supplied.
As shown in FIG. 5, the toner replenishing port 95 for replenishing toner is provided above the downstream end in the transport direction of the supply transport path 9 including the supply screw 8. Since the toner replenishing port 95 is an upper portion of the surplus opening (arrow E in FIG. 4) of the second partition wall 134, the toner easily mixes with the surplus developer and the collected developer. The developer can be stirred more efficiently.

The developer used in the present embodiment has the following configuration.
The toner used in this embodiment contains at least a binder resin and a colorant, and if necessary, a release agent, a charge control agent, and other components. In addition to the above-mentioned additives, a fluidity improver and other components are added as necessary. For these materials, all known materials are possible.

  Examples of the binder resin include styrene, parachlorostyrene, vinyl toluene, vinyl chloride, vinyl acetate, vinyl propionate, methyl (meth) acrylate, ethyl (meth) tacrylate, propyl (meth) acrylate, (meth ) N-butyl acrylate, isobutyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) Hydroxypropyl acrylate, 2-chloroethyl (meth) acrylate, (meth) acrylonitrile acid, (meth) acrylamide, (meth) acrylic acid, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl methyl ketone, N-vinyl Pyrrolidone, N-vinylpyridine, Weight of a monomer such as Tajien, or a copolymer of two or more kinds of these monomers, or mixtures thereof. In addition, polyester resin, polyol resin, polyurethane resin, polyamide resin, epoxy resin, rosin, modified rosin, terbene resin, phenol resin, hydrogenated petroleum resin, ionomer resin, silicone resin, ketone resin, xylene resin, etc. alone or in combination Can be used.

  As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin Min BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Tolujing Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake , Thioindigo red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, Riazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Cyanine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

  Examples of the charge control agent include nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (including fluorine-modified quaternary ammonium salts). .), Alkylamide, phosphorus simple substance or compound, tungsten simple substance or compound, fluorine-based activator, salicylic acid metal salt, metal salt of salicylic acid derivative, and the like. The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 2 to 5 parts by weight is preferable. If the amount is less than 0.1 parts by weight, the toner is not practically negatively charged. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, and the electrostatic attractive force with the magnetic carrier is increased, leading to a decrease in developer fluidity and a decrease in image density.

  Examples of release agents include low molecular weight polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, beeswax, carnauba wax, candelilla wax, rice wax, and montan wax. Natural waxes such as paraffin wax, petroleum wax such as microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid, myristic acid, metal salts of higher fatty acids, higher fatty acid amides, and various modified waxes thereof. Can be mentioned.

  These can be used alone or in combination of two or more, but it is preferable to use those having a melting point in the range of 70 [° C.] to 125 [° C.]. By setting the melting point to 70 [° C.] or more, a toner having excellent transferability and durability can be obtained, and by setting the melting point to 125 [° C.] or less, the toner melts quickly at the time of fixing and has a reliable release effect. Can demonstrate. The amount of these release agents used is preferably 1 [wt%] to 15 [wt%] based on the toner. If it is less than 1 [wt%], the effect of preventing offset is insufficient, and if it is 15 wt% or more, transferability and durability are lowered.

As the additive (external additive), at least fine particles having a volume average particle diameter of 50 [nm] to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more are added. The amount of external addition is preferably 0.2% by weight to 3% by weight with respect to the toner base. If the amount is less than this range, the effect of forming an appropriate gap between the toners or between the toner and the others is not exhibited. On the other hand, when the amount is large, fluidity is inhibited or the amount of desorption increases, so that an aggregate of external additives is formed, and the image quality is deteriorated. In addition to the above-mentioned additives, additives outside this range can be added, and it is preferable to add fine particles having a small volume average particle diameter for the purpose of improving fluidity.

In the additive in the present embodiment, as the inorganic _{compound, SiO 2, TiO 2, Al} 2 O 3, MgO, CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, BaO, CaO, K 2 O, Examples include Na ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ · 2SO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3 and the} like. Of these, SiO ₂ , TiO ₂ , and Al ₂ O ₃ are preferable. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like. Further, the organic compound additive may be a thermoplastic resin or a thermosetting resin, for example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin. , Urea resin, aniline resin, ionomer resin, polycarbonate resin and the like. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained.

  Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

  The additive (fine particles) in this embodiment is excellent as a toner for the developer in the developing device 4. That is, the contact area between the toner particles, the photosensitive member 1 and the charge imparting member is very small and contacts evenly, so that the effect of reducing adhesion is great and effective in improving development / transfer efficiency. Further, since it acts as a roller, it is buried in the toner particles even during cleaning under high stress (high load, high speed, etc.) between the cleaning blade and the photoconductor 1 without wearing or damaging the photoconductor 1. It is difficult to remove or return even after being buried a little, so that stable characteristics can be obtained over a long period of time. Further, the toner is moderately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing a phenomenon that the toner passes from the blade.

  As a method for producing the toner in the present embodiment, a method obtained by melting and kneading a toner constituent material and then pulverizing and classifying is generally used as a conventional method, but is not limited to this method. A method is possible.

  As the polymerization method, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, and the like are possible. Although different from the polymerization method, in addition to a dissolution suspension method, a polymer suspension method, etc., an extension reaction method or the like can be used. .

  Other than the conventional method is preferable in that the toner having the above-described particle size range and circularity can be easily obtained. Further, the circularity may be adjusted by subjecting the toner after pulverization and classification to heat treatment.

  The method for adding the additive in the present embodiment is not particularly limited, and a method in which the toner base particles and the additive are mechanically mixed and adhered using various known mixing devices, or a toner base in a liquid phase. There is a method in which particles and additives are uniformly dispersed with a surfactant or the like, and after an adhesion treatment, dried.

  The particle size distribution of the toner described above can be measured by using a toner particle size distribution measuring apparatus by the Coulter counter method. Examples of these devices include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.

  First, 0.1 [ml] to 5 [ml] of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 [ml] to 150 [ml] of the electrolytic aqueous solution. Here, the electrolytic solution is prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 [mg] to 20 [mg] of the measurement sample is further added. The electrolyte solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the weight and number of toner particles or toner are determined using the 100 [μm] aperture as the aperture by the above-described measuring apparatus. Measure and calculate weight distribution and number distribution. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As channels, 2.00 [μm] to less than 2.52 [μm]; 2.52 [μm] to less than 3.17 [μm]; 3.17 [μm] to less than 4.00 [μm]; 4 0.000 [μm] to less than 5.04 [μm]; 5.04 [μm] to less than 6.35 [μm]; 6.35 [μm] to less than 8.00 [μm]; 8.00 [μm] ≦ 10.08 [μm]; 10.08 [μm] to less than 12.70 [μm]; 12.70 [μm] to less than 16.00 [μm]; 16.00 [μm] to 20.20 [ <20 μm]; less than 20.20 [μm] to less than 25.40 [μm]; 25.40 [μm] to less than 32.00 [μm]; 13 less than 32.00 [μm] to less than 40.30 [μm] A channel is used and particles having a particle size of 2.00 [μm] or more and less than 40.30 [μm] are targeted.

  The circularity of the toner described above is a value obtained by Equation 1.

  This circularity is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated.

  Circularity can be measured using a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. As a specific measuring method, 0.1 [ml] surfactant, preferably alkylbenzene sulfonate, is used as a dispersant in 100 [ml] to 150 [ml] of water from which impure solids have been removed in advance. ] To 0.5 [ml], and about 0.1 [g] to 0.5 [g] of a measurement sample is further added. The suspension in which the sample is dispersed is subjected to a dispersion process for about 1 to 3 minutes with an ultrasonic disperser, and the shape of the toner is measured with the above-mentioned apparatus at a dispersion concentration of 3000 [pieces / μl] to 10,000 [pieces / μl]. To do.

Hereinafter, the magnetic carrier used in this embodiment will be supplementarily described.
The magnetic carrier used in the present embodiment is formed so as to have a weight average particle diameter of 20 [μm] to 60 [μm] (preferably 20 [μm] to 45 [μm]). This particle size range is also excellent as a carrier for the developer in the developing device 4.

  When the average particle size of the magnetic carrier is less than 20 [μm], fine particles are increased in the distribution of the carrier particles, and the magnetization per particle may be lowered to cause carrier scattering. On the other hand, if the average particle diameter of the magnetic carrier exceeds 45 [μm], the magnetic carrier has a rough rise during the developing process, and the uniformity of solid and halftone may be inferior (particularly, the average particle size). It becomes remarkable when the diameter exceeds 60 [μm].) In addition, since the specific surface area is reduced, toner scattering may occur in a small particle size toner.

  There is no restriction | limiting in particular as a magnetic carrier except a particle size, Although it can select suitably according to the objective, What has a core material and the resin layer which coat | covers a core material is preferable.

  There is no restriction | limiting in particular as a material of a core material, It can select suitably from well-known things, for example, 50 [emu / g]-90 [emu / g] manganese-strontium (Mn-Sr) type material Manganese-magnesium (Mn-Mg) -based materials are preferable, and in terms of ensuring image density, iron powder (100 [emu / g] or more), magnetite (75 [emu / g] to 120 [emu / g]) A highly magnetized material such as In addition, it is possible to weaken the contact with the photosensitive member 1 in which the toner is in a spiked state, and this is advantageous for improving the image quality. / G]) and the like are preferred. These may be used alone or in combination of two or more.

  The material of the resin layer of the magnetic carrier is not particularly limited and can be appropriately selected from known resins according to the purpose. For example, amino resins, polyvinyl resins, polystyrene resins, halogenated olefins can be selected. Resin, polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, fluorine And a copolymer of vinylidene fluoride and vinyl fluoride, a fluoroterpolymer such as a terpolymer of tetrafluoroethylene, vinylidene fluoride, and a non-fluorinated monomer, and a silicone resin. These may be used individually by 1 type and may use 2 or more types together.

  The resin layer may contain conductive powder or the like as necessary. Examples of the conductive powder include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. The average particle diameter of these conductive powders is preferably 1 [μm] or less. When the average particle diameter exceeds 1 [μm], it may be difficult to control electric resistance.

  The resin layer of the magnetic carrier is prepared by, for example, dissolving the silicone resin or the like in a solvent to prepare a coating solution, and then uniformly coating the coating solution on the surface of the core material by a known coating method, followed by drying. It can be formed by baking. Examples of the application method include a dipping method, a spray method, and a brush coating method.

  The amount of the resin layer in the magnetic carrier is preferably 0.01 [mass] to 5.0 [mass%]. If the amount of the resin layer is less than 0.01 [mass%], a uniform resin layer may not be formed on the surface of the core material. If the amount exceeds 5.0 [mass%], the resin layer Becomes too thick and granulation of carriers occurs, and uniform carrier particles may not be obtained.

  The developer (initial agent) stored in advance in the developing device 4 is also a mixture of the above-described toner and magnetic carrier. There is no restriction | limiting in particular as content (carrier concentration) of the magnetic carrier in a developing agent, According to the objective, it can select suitably. For example, 90 [mass%] to 98 [mass%] is preferable, and 93 [mass%] to 97 [mass%] is more preferable.

  First, magnetic field interference and carrier scattering between the developing roller 5 and the carrier recovery roller 13 which is a carrier recovery member will be described.

  FIG. 6A shows an image of magnetic lines of force in the absence of the carrier recovery roller 13, and FIG. 6B shows an image of magnetic lines of force in the condition with the carrier recovery roller 13. When the carrier recovery roller 13 is present, the magnetic fields of the developing roller 5 and the carrier recovery roller 13 interfere with each other so that the magnetic lines of force are connected (dotted line in FIG. 6B). Therefore, the magnetic spikes (magnetic brushes) that rise in the form of a developer brush extend in the direction of the lines of magnetic force, and the magnetic carriers on the leading end side of the magnetic spikes that are long are likely to scatter. Therefore, a magnetic shielding member 96 that shields magnetism is arranged between the developing roller 5 and the carrier recovery roller 13 so that the magnetic lines of force are not connected between the developing roller 5 and the carrier recovery roller 13 (FIG. 6C). As the magnetic shielding member 96, a permanent magnet can be used.

  The developing roller 5 and the carrier recovery roller 13 will be described with reference to FIG. First, the developing roller 5 includes a cylindrical developing sleeve 81 that carries a developer and a developing magnet roller 82 that is contained in the developing sleeve 81 and serves as a magnetic field generating unit that attracts the developer by magnetic force.

  The developing sleeve 81 is made of a nonmagnetic and conductive material such as aluminum, austenitic stainless steel or magnesium. The surface may be smooth, but in a high-speed machine, the following roughening treatment / processing may be performed to suppress developer slip.

(A) Groove extrusion processing such as V-groove or U-groove, machining of various concave shapes or laser processing or edging processing (B) Blasting processing (C) Thermal spraying processing of metal or ceramic

  The developing magnet roller 82 is rotatably provided in the direction of arrow A opposite to the developer conveying direction P, and has an even number of magnets 83 arranged at equal intervals (in the configuration of the present embodiment, 12 magnets are arranged). Arrangement), and the polarities are opposite to each other so as to attract each other between adjacent magnets. As the magnet 83, a conventional inexpensive ferrite magnet can be used. However, a stronger rare earth magnet such as a samarium cobalt magnet or a neodymium magnet can be used for downsizing and speeding up. The magnet 83 may be supported on the magnet holder 84 by adhesion, and the outer periphery thereof may be protected by a heat shrinkable tube or the like (not shown). If the magnet holder 84 is made of a magnetic material, the magnetic force of the magnet 83 can be slightly improved. However, since the cost is high and magnetic materials mainly composed of iron are generally high in specific gravity, the moment of inertia increases at the time of high-speed rotation, which may cause a problem in the durability of the drive unit. Therefore, although the magnetic force of the magnet 83 is slightly reduced, nonmagnetic and light specific gravity aluminum or magnesium may be used as a material.

  In this embodiment, the rotation center P ′ of the developing magnet roller 82 is eccentrically positioned at a position away from the rotation center P of the developing sleeve 81 by a distance (T).

  The direction of eccentricity is set so that the toner in the developer carried on the surface of the developing roller 5 can be closest to the inner surface of the developing sleeve 81 at a position near the position where the toner moves to the photoreceptor 1. The amount of eccentricity corresponding to the distance indicated by is an amount that can suppress the magnetic carrier from moving to the photosensitive member 1 in the developing region by the magnetic force from the magnetic pole. As a result, the developer can come into contact with the photoreceptor 1 in a state in which the head is secured, and the magnetic carrier from the approaching magnetic pole is prevented from moving, so that only the toner is transferred to the latent image on the photoreceptor 1. Will move to supply. On the other hand, the magnetic force can be kept low on the side opposite to the eccentric direction. For this reason, the developer carried on the surface of the developing sleeve 81 can be easily peeled off. By providing such an eccentric structure, the developer can be easily peeled off without using external mechanical external force.

  Next, the developer transfer will be described. The developer supplied to the flange 9 a by the supply screw 8 is attracted onto the developing sleeve 81 by the magnetic force of the developing magnet roller 82, conveyed by the rotation of the developing sleeve 81, and the amount of the developer is reduced when passing through the doctor blade 12. Regulated to be constant. The developer that has passed through the doctor blade 12 is arranged along the magnetic field lines. That is, magnetic spikes are generated on the magnet 83 as indicated by reference symbol B1, and the magnetic spikes fall between the magnets 83 as indicated by reference symbol B2.

  When the direction of rotation of the developing magnet roller 82 is the direction opposite to the direction of rotation of the developing sleeve 81 (direction of arrow I in the drawing) as indicated by the arrow A direction in the drawing, while the developing magnet roller 82 rotates, The magnetic spike rotates in a so-called flip flap shape and proceeds in the direction of arrow F opposite to the direction indicated by arrow A, which is the rotation direction of the developing magnet roller 82. At this time, the developing sleeve 81 may be supplementarily rotated in the direction of arrow I at a relatively low speed.

  As the developer that has passed through the doctor blade 12 continues to rotate, the attraction force to the developing sleeve 81 is gradually increased due to the eccentricity of the developing magnet roller 82, and the magnetic carrier is prevented from moving to the photoreceptor 1. As the developing magnet roller 82 is rotated at a higher speed, the developer is more actively stirred at the opposite portion of the photosensitive member 1, so that the toner can be efficiently transferred according to the latent image. Since it increases in proportion to the square of, the carrier adhesion also increases.

  As the developer continues to rotate, the attracting force to the developing sleeve 81 gradually decreases due to the eccentricity of the developing magnet roller 82, and is separated from the developing sleeve 81 by its own weight in the collection conveyance path 7 (arrow K in the figure, arrow L in the figure). ).

  Next, the carrier collection roller 13 will be described. The carrier recovery roller 13 includes a rotatable carrier recovery sleeve 90, includes a carrier recovery magnet roller 91 as a magnetism generating unit including a plurality of fixed magnetic poles, and includes a magnetic shielding member 96 on the carrier recovery sleeve 90.

  The carrier recovery magnet roller 91 is formed by attaching a composite magnet 93 and a block magnet 94 to a shaft 92 made of a nonmagnetic material such as aluminum, austenitic stainless steel, magnesium, or various resin materials.

  The composite magnet 93 uses Sr ferrite or Ba ferrite as magnet powder, and PA (polyamide) material such as 6PA or 12PA as a polymer compound, EEA (ethylene / ethyl copolymer) or EVA (ethylene / vinyl copolymer). An ethylene compound such as coalescence), a chlorine material such as CPE (chlorinated polyethylene), and a rubber material such as NBR can be used. It is molded in a half moon shape, has four magnetic poles by magnetization, has a notch disposed on the developing roller 5 side, and has no magnetic pole on the side facing the developing roller 5.

  Since the block magnet 94 collects the magnetic carrier adhering to the photoreceptor 1, it requires a high magnetic force in a volume smaller than that of the composite magnet 93, and it is desirable to use a material of Br> 0.5 [T]. Ne-based (Ne-Fe-B, etc.) or Sm-based (Sm-Co, Sm-Fe-N, etc.) rare earth sintered magnets or rare earth bonded magnets in which these magnet powders are mixed with a polymer compound can be used. . In addition, rare earth magnet powders include isotropic and anisotropic magnet powders, and anisotropic magnet powders can provide higher magnetic force, but whichever type is used depending on the desired magnetic properties. It doesn't matter. The above materials were sintered, extruded, injection molded, or in-mold compression molded with magnetic powder and binder, to obtain a width of 3 [mm] and a thickness of 3 [mm]. The length is 346 [mm], which is about 10 [mm] longer than the developing magnet roller 82, so that the carrier can be reliably recovered to the end.

  FIG. 7A and FIG. 7B show magnetic flux density waveforms on the carrier recovery sleeve 90 when the block magnet 94 is a rare earth sintered magnet. 7A shows the magnetic flux density (normal component) distribution on the carrier recovery roller 13 when the magnetic shielding member 96 is provided, and FIG. 7B shows the case where the magnetic shielding member 96 is not provided. 2 shows a magnetic flux density (normal component) distribution on the carrier recovery roller 13 in FIG.

  In both FIGS. 7A and 7B, the magnetic pole P21 has a high magnetic flux density of 250 [mT]. In the other transport poles, the magnetic pole P22 is 110 [mT], the magnetic pole P23 is 70 [mT], and the magnetic pole P24 is 40 [mT]. The magnetic pole P25 necessary for enhancing the effect of the magnetic shielding member 96 described later shown in FIG. 7A is 80 [mT]. The magnetic flux density of the magnetic pole P21 was 200 [mT] on the photosensitive member 1 separated by 0.5 [mm].

  The carrier recovery sleeve 90 is made of a nonmagnetic and conductive material such as aluminum, austenitic stainless steel, or magnesium.

  As described above, in order to transport the magnetic carrier adsorbed by the magnetic pole P21 having a high magnetic flux density to the magnetic pole P22 having a relatively low magnetic flux density without slipping, it is necessary to subject the surface to the following roughening treatment / processing. .

(A) Groove extrusion processing such as V-groove or U-groove, machining or laser processing of various concave shapes, or edging processing (B) Blasting processing (C) Thermal spraying processing of metal or ceramic

As for (A), the depth of the groove / concave is about 0.05 [mm] to 0.5 [mm], and known techniques such as shape and number can be used.

About (B), the roughness is the range which can manufacture Rz7 [micrometer]-Rz50 [micrometer], and can prevent the slip of a magnetic carrier.

About (C), the roughness is the range which can manufacture Rz40 [micrometer]-Rz90 [micrometer], and can prevent the slip of a magnetic carrier.

  By setting the gap between the carrier recovery roller 13 and the photosensitive member 1 as narrow as 0.5 [mm], the magnetic flux density on the photosensitive member 1 is 10 [mT] to 30 [30] than the magnetic flux density on the carrier recovery sleeve 90. mT]. By setting the gap between the carrier recovery roller 13 and the developing roller 5 as narrow as 2 [mm], the ears of the developing roller 5 can be brought into contact with the carrier recovery roller 13.

  Further, a casing 98 is provided on the opposite side of the carrier recovery roller 13 from the developing roller 5 in the circumferential direction, and the gap between the carrier recovery roller 13 and the casing 98 is set to be as narrow as 1.5 [mm]. Can be brought into contact with the casing 98. The magnetic carrier collected on the carrier collection roller 13 is returned to the developer in the developing device 4 such as the collection conveyance path 7 in a region where there is no magnetic pole downstream of the magnetic pole P24 in the rotation direction of the carrier collection sleeve.

  The magnetic shielding member 96 is made of the same material as the composite magnet 93. The same material as the block magnet 94 may be used for the magnetic shielding member 96 as long as desired magnetic characteristics are obtained. Further, as long as it is magnetized by the carrier recovery magnet roller 91 and a desired magnetic characteristic is obtained, a soft magnetic material or the like may be used for the magnetic shielding member 96 instead of a permanent magnet.

  The magnetic shielding member 96 has a width of 2 [mm] and a thickness of 2 [mm], cuts a corner at a position facing the photoreceptor 1 by 1 [mm], and has a length of 346 [mm] which is the same as that of the block magnet 94. . The surface facing the carrier recovery roller 13 was the same polarity as the block magnet 94, and the magnetic flux density on the surface was 80 [mT].

  The magnetic shielding member 96 is bonded to the magnetic shielding member support member 97. A sponge (not shown) is bonded to the surface of the magnetic shielding member 96 that faces the surface of the carrier recovery roller 13, and the magnetic shielding member is interposed via the sponge so that the sponge and the surface of the carrier recovery roller 13 are in contact with each other. 96 is pressed against the surface of the carrier recovery roller 13.

  Although it is not always necessary to press the magnetic shielding member 96 so that the sponge and the surface of the carrier recovery roller 13 are in contact with each other, the closer the magnetic shielding member 96 is to the surface of the carrier recovery roller 13, the more the magnetic shielding member 96 becomes. The magnetic shielding efficiency by 96 becomes high.

  Further, as the magnetic shielding member support member 97, a nonmagnetic member such as aluminum, austenitic stainless steel, or magnesium is used.

  An effect confirmation experiment was performed under the following conditions using the image forming apparatus of the present embodiment. As a result of the confirmation experiment, carrier adhesion was improved.

・ Magnetic carrier: 35 [μm] ferrite carrier for Ricoh imgio MP C7500 ・ Toner: PxP polymerization toner for Ricoh imagio MP C7500 ・ Toner concentration: 4 [wt%]
-Charge amount: -24 [μC / g]
-Photoconductor diameter: φ100 [mm]
・ Developing sleeve diameter: φ40 [mm]
-Carrier recovery roller diameter: φ20 [mm]
Photoconductor linear velocity: 600 [mm / s]
・ Developing sleeve linear velocity: 750 [mm / s]
-Carrier recovery sleeve linear velocity: 12 [mm / s]
・ Gap between developing sleeve and photoconductor: 0.4 [mm]
・ Gap between carrier recovery sleeve and photoconductor: 0.3 [mm]
・ Gap between developer sleeve and carrier recovery sleeve: 1.5 [mm]
・ Developing magnet roller rotation speed: 3000 [rpm]

  FIG. 8A shows the developing sleeve of the developing roller 5 in the first embodiment in which the carrier collecting magnet roller 91 is provided in the carrier collecting sleeve 90 of the carrier collecting roller 13 and the magnetic shielding member 96 and the magnetic pole P25 are provided. 8 is a diagram showing lines of magnetic force from each magnetic pole of the developing magnet roller 82 in 81. FIG.

  FIG. 8B shows the developing sleeve of the developing roller 5 in the comparative example 1 in which the carrier collecting magnet roller 91 is provided in the carrier collecting sleeve 90 of the carrier collecting roller 13 and the magnetic shielding member 96 and the magnetic pole P25 are not provided. 8 is a diagram showing lines of magnetic force from each magnetic pole of the developing magnet roller 82 in 81. FIG.

  FIG. 8C shows the developing sleeve of the developing roller 5 in the comparative example 2 in which the carrier collecting magnet roller 91 is not provided in the carrier collecting sleeve 90 of the carrier collecting roller 13 and the magnetic shielding member 96 and the magnetic pole P25 are not provided. 8 is a diagram showing lines of magnetic force from each magnetic pole of the developing magnet roller 82 in 81. FIG.

  As shown in FIGS. 8A, 8B, and 8C, the magnetic field between the developing roller 5 and the carrier recovery roller 13 in Example 1, Comparative Example 1, and Comparative Example 2 is simulated. A comparison was made. For the calculation, electromagnetic field analysis software JMAG manufactured by JSOL Corporation was used. The positions of the magnets 83 of the developing roller 5 are the positions where the lines of magnetic force are most connected to the magnetic pole P21 of the carrier recovery magnet roller 91 of the carrier recovery roller 13.

  As a result of such comparison, it can be seen that in Example 1, it is possible to reduce the line of magnetic force between the magnet 83 of the developing roller 5 and the magnetic pole P21 of the carrier recovery roller 13 as compared with Comparative Example 1. . Moreover, in Example 1, it turns out that it is close to the state (the state which does not have the magnetic pole P21) which does not have the carrier collection magnet roller 91 in the carrier collection sleeve 90 of the carrier collection roller 13 like the comparative example 2.

  As described above, by providing the magnetic shielding member 96 as in the first embodiment, the magnetic shielding member 96 shields the magnetism between the developing roller 5 and the carrier recovery roller 13, and is generated by each magnetic pole of the developing roller 5. The magnetic field generated by each magnetic pole of the carrier recovery roller 13 can be prevented from interfering with each other. As a result, it is possible to prevent the magnetic lines of force from being connected between the magnet 83 of the developing roller 5 and the magnetic pole P21 of the carrier recovery roller 13, and the magnetic spike on the developing roller 5 can be reduced as compared with the case where the magnetic shielding member 96 is not provided. Can be shortened. Further, even if the magnetic lines of force are connected, the connection of the magnetic lines of force can be reduced as compared with the case where the magnetic shielding member 96 is not provided. Therefore, in order to reduce the size, even if the carrier recovery roller 13 is disposed close to the developing roller 5 on the downstream side in the rotation direction of the photosensitive member, the developing roller 5 is compared with the case where the magnetic shielding member 96 is not provided. Magnetic carriers scattered by centrifugal force from above can be reduced.

  Therefore, the presence of the magnetic carrier adhering to the photoconductor may cause abnormal images such as white spots, or the magnetic carrier may damage the surface of the photoconductor at the contact point between the photoconductor and the cleaning member, thereby degrading the image quality. In addition, it is possible to prevent the cleaning member from being damaged due to damage to the cleaning member, and good image formation can be performed.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A developing roller that rotates while carrying a two-component developer containing a magnetic carrier and toner on the outer peripheral surface by the action of a magnetic field generated from a plurality of magnetic poles by a developing magnetic field generating means such as a developing magnet roller 82 disposed therein. 5 in the carrier recovery region downstream of the latent image carrier surface moving direction in the developing region where the developer carrier and the latent image carrier such as the photosensitive member 1 face each other. A magnetic field generating means for developing, comprising a carrier recovery member such as a carrier recovery roller 13 disposed close to the developing carrier for magnetically adsorbing and recovering the magnetic carrier attached on the surface on the outer peripheral surface Is used to rotate the plurality of magnetic poles along the rotation direction of the developer carrier, and to form toner in the two-component developer carried on the outer peripheral surface of the developer carrier on the latent image carrier. Attached to the latent image In the developing device, such as a developing device 4 for developing the latent image by, providing the magnetic shielding member, such as a magnetic shielding member 96 for shielding the magnetic between the developer carrying member and the carrier recovery member. According to this, as described in the above embodiment, it is possible to suppress carrier scattering while achieving downsizing.
(Aspect B)
In (Aspect A), as the carrier recovery member, a rotatable carrier recovery body including a recovery carrier support such as a carrier recovery sleeve 90 that supports a magnetic carrier on an outer peripheral surface, and a plurality of magnetic poles included in the recovery carrier support. A device provided with carrier recovery magnetic field generating means such as a magnet roller 91 can be suitably used.
(Aspect C)
In (Aspect A) or (Aspect B), a magnetic member such as the magnetic pole P25 is disposed inside the carrier recovery member at a position where the carrier recovery member and the magnetic shielding member face each other. According to this, as demonstrated about the said embodiment, the effect of a magnetic shielding member can be improved more and carrier scattering can be suppressed more.
(Aspect D)
In (Aspect A), (Aspect B), or (Aspect C), the magnetic shielding member is a permanent magnet. According to this, as described in the above embodiment, magnetic field interference is suppressed by the permanent magnet, and carrier scattering can be suppressed.
(Aspect E)
In (Aspect C) or (Aspect D), the magnetic member is a permanent magnet. According to this, as demonstrated about the said embodiment, the effect of a magnetic shielding member can be improved more and carrier scattering can be suppressed more.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D) or (Aspect E), the magnetic field on the surface of the carrier recovery member is at a position where the carrier recovery member and the magnetic shielding member face each other. There is a magnetic pole having the opposite polarity to the adjacent magnetic pole. According to this, as demonstrated about the said embodiment, the effect of a magnetic shielding member can be improved more and carrier scattering can be suppressed more.
(Aspect G)
In an image forming apparatus such as a copying machine 500 including a latent image carrier such as the photosensitive member 1 and a developing unit such as a developing device 4 that develops the latent image formed on the latent image carrier using a developer. The developing device of (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E) or (Aspect F) was used as the developing means. According to this, as described in the above embodiment, carrier scattering can be suppressed and good image formation can be performed while achieving downsizing.

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing device 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 9a １０ 10 Stirring conveyance path 11 Stirring screw 12 Doctor blade 13 Carrier collection roller 14 Stretching roller 15 Drive roller 16 Secondary transfer Backup roller 17 Intermediate transfer unit 18 Process cartridge 20 Image forming unit 21 Optical writing unit 22 Secondary transfer device 23 Tension roller 24 Paper transport belt 25 Fixing device 26 Fixing belt 27 Pressure roller 30 Document base 32 Contact glass 33 First Traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 43 Paper bank 44 Paper feed cassette 45 Separating roller 47 Transport roller pair 48 Paper feed path 49 Registration roller pair 50 Paper feed roller 51 Manual feed tray 52 Separating Roller 53 Feeding Path 57 Stacking Unit 62 Primary Transfer Bias Roller 70 Belt Cleaning Device 81 Developing Sleeve 82 Developing Magnet Roller 83 Magnet 84 Magnet Holder 90 Carrier Recovery Sleeve 91 Carrier Recovery Magnet Roller 92 Shaft 93 Composite Magnet 94 Block Magnet 95 Toner Replenishment port 96 Magnetic shielding member 97 Magnetic shielding member support member 98 Casing 100 Printer unit 110 Intermediate transfer belt 133 First partition wall 134 Second partition wall 135 Third partition wall 200 Paper feeder 300 Scanner 400 Automatic document feeder 500 Copier

JP 2008-180977 A Japanese Patent Laid-Open No. 10-326047 Japanese Patent Laid-Open No. 11-73007

Claims (7)

A developer carrier that rotates by supporting a two-component developer containing a magnetic carrier and toner on the outer peripheral surface by the action of a magnetic field generated by a plurality of magnetic poles generated by a developing magnetic field generating means disposed inside;
The magnetic carrier adhering to the surface of the latent image carrier is magnetically outer circumferentially in the carrier recovery region downstream of the latent image carrier surface moving direction of the development region where the developer carrier and the latent image carrier are opposed to each other. Having a carrier recovery member disposed close to the development carrier to be adsorbed and recovered on the surface;
The developing magnetic field generating means moves the plurality of magnetic poles around the rotation direction of the developer carrier, and removes the toner in the two-component developer carried on the outer peripheral surface of the developer carrier. In the developing device for developing the latent image by attaching it to the latent image formed on the latent image carrier,
A developing device comprising a magnetic shielding member for shielding magnetism between the developer carrier and the carrier recovery member. The developing device according to claim 1.
The carrier recovery member includes a recovery carrier support that supports a magnetic carrier on an outer peripheral surface, and a rotatable carrier recovery magnetic field generation unit that is included in the recovery carrier support and includes a plurality of magnetic poles. A developing device. The developing device according to claim 1 or 2,
A developing device, wherein a magnetic member is disposed inside the carrier recovery member at a position where the carrier recovery member and the magnetic shielding member face each other. The developing device according to claim 1, 2 or 3,
The developing device, wherein the magnetic shielding member is a permanent magnet. The developing device according to claim 3 or 4,
A developing device, wherein the magnetic member is a permanent magnet. The developing device according to claim 1, 2, 3, 4 or 5.
2. A developing device according to claim 1, wherein a magnetic field on the surface of the carrier recovery member is present at a position where the carrier recovery member and the magnetic shielding member face each other, and a magnetic pole having a polarity opposite to an adjacent magnetic pole exists. A latent image carrier;
An image forming apparatus comprising: a developing unit that develops the latent image formed on the latent image carrier using a developer;
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5 or 6 as the developing means.

Images