JP2006227116A - Development device, image forming device and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device capable of creating a uniform image, without uneven density such as screw pitch unevenness, and to provide a process cartridge and an image forming device having the development device. <P>SOLUTION: The development device 13 comprises a development roller 15 and a rotating member 28. The development roller 15 comprises a magnet roller 33 and a development sleeve 32. The magnet roller 33 is fixed. The magnet roller 33 comprises fixed magnetic poles N1, S1, N2, S2, N3, S3 and N4. A developer-stripping region R is formed on the external surface of the development sleeve 32 by the fixed magnetic poles N1 and N4. The rotating member 28 rotates in the same direction as the development sleeve 32, and the rotating member 28 faces the developer stripping region R. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a phenomenon apparatus, an image forming apparatus, and a process cartridge used for a copying machine, a facsimile machine, a printer, and the like, and more specifically, a developer carried on a nonmagnetic cylinder, and a photosensitive member and a nonmagnetic cylinder. The present invention relates to a developing device that forms a toner image by developing an electrostatic latent image on the photosensitive member. The present invention also relates to an image forming apparatus and a process cartridge having such a developing device.

  Various image forming apparatuses such as copying machines, facsimile machines, and printers use various developing devices 100 (see, for example, Patent Documents 1 to 3). As shown in FIGS. 13 and 14, this type of developing device 100 conveys developer 101 to a developing area 103 that faces the photosensitive drum 102, and generates an electrostatic latent image formed on the photosensitive drum 102. A developing roller 104 that develops with the developer 101 to form a toner image is provided.

  The developing roller 104 has a cylindrical developing sleeve 105 and a magnet that is accommodated in the developing sleeve 105 and that forms a magnetic field so as to cause the developer 101 to rise on the surface of the developing sleeve 105. A roller 106 is provided. On the developing roller 104, when the developer 101 spikes, the magnetic carrier of the developer 101 spikes on the developing sleeve 105 so as to follow the lines of magnetic force generated by the magnet roller 106. The toner of the developer 101 adheres.

  Further, as shown in FIG. 15, this type of developing device 100 includes a storage tank 107 that stores the developer 101 described above, a screw-shaped stirring screw 108 that stirs the developer 101 in the storage tank 107, and A regulating blade 109 (shown in FIGS. 13 and 14) that equalizes the amount of the developer 101 pumped up by the developing roller 104 is provided. The developing device 100 shown in FIGS. 13 and 14 includes a pair of a storage tank 107 and a stirring screw 108.

  The developer 101 in the developing device 100 moves in the storage tank 107 as indicated by an arrow K in FIG. The toner replenished from one end of the one storage tank 107a on the side away from the developing roller 104 is conveyed by the stirring screw 108 to the other end of the one storage tank 107a along the axial direction of the stirring screw 108. Then, the developer 101 is stirred. Then, the developer 101 moves from the other end of the one storage tank 107a into the other storage tank 107b near the developing roller 104.

  The developer 101 transferred to the other storage tank 107b near the developing roller 104 is pumped up to the surface of the developing sleeve 105 by the magnetic force of the developing roller 104 (attaches to the surface of the developing sleeve 105). Thereafter, the amount of the developer 101 is made uniform by the regulating blade 109 and then conveyed to the developing region 103 where the photosensitive drum 102 and the developing roller 104 are opposed to each other with a space therebetween. Developer 101 develops the electrostatic latent image formed on photoconductor drum 102 to form a toner image.

In the developing device 100 shown in FIG. 14, a regulating blade 109 is provided on the lower side of the developing roller 104, and the developer 101 remaining after development is separated above the developing roller 104. In the developing device 100 shown in FIG. 13, a regulating blade 109 is provided on the upper side or the lateral side of the developing roller 104, and the developer 101 remaining after development is separated below the developing roller 104. As the developing device 100, the one shown in FIGS. 13 and 14 described above is properly used depending on the layout of other units such as the photosensitive drum 102.
JP 2000-194194 A JP 2000-194195 A Japanese Patent Laid-Open No. 2000-250311

  However, the image forming apparatus provided with the developing device 100 described above has a higher density when printing an image with a relatively large area ratio such as a photograph than when printing an image with a relatively small area ratio such as a text sentence. There was a problem that the unevenness was conspicuous.

  In the monochrome image 111 having a large area ratio, for example, as shown in FIG. 16, density unevenness 112 (hereinafter referred to as screw pitch unevenness) 112 in a diagonal direction with respect to the paper passing direction occurs in a stripe shape, and the aesthetic appearance is improved. It may be damaged. In FIG. 16, a portion 113 indicated by a relatively dense parallel oblique line is relatively dark and a portion 114 indicated by a relatively coarse parallel oblique line is relatively thin.

  Further, in the monochromatic image 115 having a large area ratio, for example, as shown in FIG. 17, density unevenness (hereinafter referred to as vertical stripes) 116 in which white vertical stripes extending in parallel with the sheet passing direction appear, is generated. The aesthetics may be impaired. In FIG. 17, a portion 117 indicated by parallel oblique lines is dark, and a portion indicated by reference numeral 118 is a white vertical stripe.

  Further, in a color image having a large area ratio, density unevenness such as the above-described screw pitch unevenness 112 and vertical stripe 116 of each color appears as a hue shift. For example, generally in the market such as a design occupation, the images 111 and 115 having such a large area ratio may be handled, and the commercial value is remarkably reduced by striped density unevenness.

  Concentration unevenness such as the screw pitch unevenness 112 and the vertical streak 116 has a high incidence with the recent reduction in the particle diameter of the magnetic carrier aimed at high image quality. The pitch of the screw pitch unevenness 112 described above is equal to the pitch of the stirring screw 108 in the developing device 100 as shown in FIG. For example, FIG. 18 shows a case where the portion corresponding to the crest of the stirring screw 108 is thin and the portion corresponding to the trough is dark.

  The density unevenness such as the screw pitch unevenness 112 and the vertical stripe 116 is caused when the developer pumping property of the developing roller 104 is low (when the amount of the developer 101 adhering to the developing roller 104 is small), or when the developing is separated from the developing roller 104. It has also been found that the developer 101 having a low toner concentration is likely to occur when it is immediately adsorbed to the developing roller 104 without being stirred by the stirring screw 108.

  Since the developer 101 moving on the agitating screw 108 is high at the crest of the agitating screw 108 and low at the trough, the amount of the developer 101 drawn up from the trough of the agitating screw 108 is low when the developer 101 pumping performance is low. Is too small. At this time, since the amount of the developer 101 passing through the regulating blade 109 is small, there is a problem that the density of the image becomes light and density unevenness such as the screw pitch unevenness 112 described above occurs.

  Since the developer 101 moving on the stirring screw 108 is high at the peak of the stirring screw 108 and low at the valley, the developed developer 101 that has left the developing roller 104 and dropped into the valley of the stirring screw 108 is removed from the developing roller 104. Since it is separated, it does not immediately adhere to the developing roller 104.

  On the other hand, the developed developer 101 that has separated from the developing roller 104 and dropped onto the crest of the stirring screw 108 is close to the developing roller 104 as shown in FIGS. End up. The dotted lines in FIGS. 19 and 20 indicate the magnetic flux density in the normal direction of the magnet roller 106. Further, the alternate long and short dash line in FIG. 21 indicates the magnetic force in the normal direction of the magnet roller 106.

  For this reason, the developer 101 that has already been developed does not detach from the outer surface of the developing roller 104 at the portion of the developing roller 104 that opposes the crest of the agitating screw 108, and is again formed on the photosensitive drum 102. Used for developing latent images. As described above, in particular, since the developed developer is difficult to be removed from the portion of the developing roller 104 facing the crest of the stirring screw 108, there is a problem that density unevenness such as the screw pitch unevenness 112 described above occurs. .

  In order to solve such a problem, in the developing device 100 disclosed in Patent Document 1 described above, the amount of the developer 101 and the magnetic flux density distribution of the magnet roller 106 of the developing roller 104 are defined, and the screw pitch unevenness 112 or the like is defined. It is trying to reduce the density unevenness.

  Further, in the developing device 100 disclosed in Patent Document 2 described above, density unevenness such as screw pitch unevenness 112 is defined by defining a position where the strength of the magnetic field in the normal direction of the magnet roller 106 of the developing roller 104 becomes the maximum value. Trying to reduce. Further, in the developing device 100 disclosed in Patent Document 3 described above, density unevenness such as screw pitch unevenness 112 is reduced by regulating the size of the stirring screw 108.

  The developing device 100 disclosed in Patent Documents 1 to 3 described above cannot prevent the developer 101 detached from the developing roller 104 from immediately adhering to the developing roller 104. Therefore, it is difficult for the developing device 100 described in Patent Document 1 to Patent Document 3 described above to reliably remove the developed developer 101 from the portion of the developing roller 104 facing the crest of the stirring screw 108. There is a problem that density unevenness such as the screw pitch unevenness 112 described above cannot be completely erased.

  The present invention has been made in view of the above background, and provides a developing device capable of obtaining a uniform image without unevenness in density such as screw pitch unevenness, a process cartridge having such a developing device, and an image forming apparatus. It is intended to provide.

  In order to achieve the above object, the developing device according to claim 1, wherein the developer attracts the developer from the developer storage tank to the nonmagnetic cylindrical body containing the magnet roller as a fixed magnetic pole of the magnet roller. At least a pumping magnetic pole and a developing magnetic pole for transferring the developer toner attracted to the cylindrical body to the photosensitive member are provided, and development is performed between the developing magnetic pole and the developer pumping magnetic pole. The developer stripping area for stripping the used developer from the outer surface of the cylindrical body toward the inside of the storage tank is formed of a nonmagnetic material in the developing device provided on the outer surface of the nonmagnetic cylindrical body. A rotating member that rotates about an axis parallel to the rotation center of the cylindrical body is provided so as to face the developer stripping area on the outer surface of the cylindrical body.

  A developing device according to a second aspect is the developing device according to the first aspect, wherein the rotating member rotates in the same direction as the cylindrical body.

  The developing device according to claim 3 is the developing device according to claim 1 or 2, wherein the rotating member is formed in a cylindrical shape or a columnar shape, and a surface roughness of an outer surface is 10 μm or more. It is characterized by.

  According to a fourth aspect of the present invention, in the developing device according to the first or second aspect, the rotating member includes a shaft portion parallel to the rotation center of the cylindrical body, and an outer periphery from the outer surface of the shaft portion. And a blade portion extending in the direction.

  A developing device according to a fifth aspect is the developing device according to the fourth aspect, wherein the blade portion is made of a flexible material so as to be in sliding contact with the developer stripping region. It is characterized by being.

  A developing device according to a sixth aspect is the developing device according to the fifth aspect, wherein an end portion of the blade portion that is in sliding contact with the developer stripping region is finished in a brush shape.

  The developing device according to claim 7 is the developing device according to any one of claims 1 to 6, wherein the developer pumping magnetic pole and the developer pumping magnetic pole are adjacent to the developer pumping magnetic pole. An adjacent magnetic pole that forms the developer stripping region in cooperation with the developer pumping magnetic pole is provided so as to have the same polarity, and the developer pumping magnetic pole and the adjacent magnetic pole are disposed between these magnetic poles. It is characterized in that magnetic poles having different polarities are formed.

  The developing device according to claim 8 is the developing device according to any one of claims 1 to 6, wherein the developer pumping magnetic pole and the developer pumping magnetic pole are adjacent to the developer pumping magnetic pole. An adjacent magnetic pole that forms the developer stripping region in cooperation with the developer pumping magnetic pole is provided so as to be the same pole as each other, and the developer pumping magnetic pole and the adjacent magnetic pole between these magnetic poles And a magnetic pole having the same or different polarity.

  A developing device according to a ninth aspect is the developing device according to any one of the first to eighth aspects, wherein the developed developer is conveyed to the storage tank as a fixed magnetic pole of the magnet roller. And at least one transporting magnetic pole is provided between the developing magnetic pole and the developer pumping magnetic pole, and the developer stripping region is the most of the developer pumping magnetic pole among at least one transporting magnetic pole. It is characterized in that it is provided between the close conveyance magnetic pole and the developer pumping magnetic pole.

  A developing device according to a tenth aspect is the developing device according to any one of the first to ninth aspects, wherein an average particle size of the toner is 3 μm or more and 7 μm or less. .

  The developing device according to an eleventh aspect is characterized in that, in the developing device according to the tenth aspect, the toner is spherical fine particles produced by an emulsion polymerization method or a suspension polymerization method.

  A process cartridge according to a twelfth aspect is characterized in that in the process cartridge having at least a developing device, the developing device according to any one of the first to eleventh aspects is provided as the developing device.

  An image forming apparatus according to a thirteenth aspect is the image forming apparatus including at least a photoconductor, a charging device, and a developing device, and the developing device is any one of the first to eleventh aspects. It has the developing device described.

  In the developing device according to the first aspect, the rotating member is opposed to the developer stripping region. For this reason, the developed developer can be reliably peeled off from the developer stripping area. Further, the developer detached from the developer stripping area, that is, the non-magnetic cylinder is prevented from immediately adhering to the non-magnetic cylinder by the rotating member. For this reason, it is possible to prevent the developed developer from being used again for developing the electrostatic latent image on the photosensitive member without detaching from the non-magnetic cylindrical body. Accordingly, it is possible to prevent density unevenness such as screw pitch unevenness and to obtain a uniform and high-quality image.

  Since the rotating member rotates around an axis parallel to the rotation center of the cylindrical body, it is possible to prevent the developer detached from the developer peeling area, that is, the nonmagnetic cylindrical body from immediately attaching to the nonmagnetic cylindrical body. .

  In the developing device according to claim 2, since the rotating member rotates in the same direction as the cylindrical body, the developer detached from the developer peeling area, that is, the nonmagnetic cylindrical body immediately adheres to the nonmagnetic cylindrical body. In addition, the developed developer can be reliably peeled off from the developer stripping area.

  In the developing device according to the third aspect, since the surface roughness of the outer surface of the rotating member is 10 μm or more, the frictional force on the outer surface of the rotating member is increased. Therefore, the rotating member can reliably adhere the developed developer attached to the outer surface of the cylindrical body to the outer surface, and more reliably remove the developed developer from the developer peeling area. Can do.

  In the developing device according to the fourth aspect, the rotating member is a so-called impeller having a shaft portion and a blade portion. For this reason, the rotating member can reliably peel off the developed developer from the developer stripping region at the blade portion.

  In the developing device according to the fifth aspect, since the blade portion of the rotating member is slidably contacted with the developer peeling area, the developed developer can be surely peeled from the developer peeling area.

  Further, by making the blade portion of the rotating member flexible, the contact pressure between the blade portion and the non-magnetic cylindrical body is leveled. For this reason, the mechanical stripping action of the developed developer itself works uniformly over the entire length of the nonmagnetic cylindrical body. Further, since the blade portion has flexibility, the developed developer remaining due to frictional force or the like can be peeled off from the developer stripping area.

  In the developing device according to claim 6, the end of the blade of the rotating member that comes into sliding contact with the non-magnetic cylindrical body is formed in a brush shape or a comb shape so that the developed developer can be obtained even at a low contact pressure. Since the wiping / cleaning action can be secured, the effect that the deterioration of the developer can be suppressed is exhibited.

  Further, the end portion of the developer stripping blade that is in sliding contact with the non-magnetic cylinder is made into a brush shape or a comb-like shape, so that even if the outer surface of the non-magnetic cylinder has irregularities (grooves, etc.) The developed developer can be reliably released from the outer surface of the cylindrical body.

In the developing device according to claim 7, since the magnetic poles different from these are formed between the developer pumping magnetic pole and the adjacent magnetic pole, the developer peeling is performed on the outer surface of the nonmagnetic cylindrical body. The region can be formed reliably.

  In the developing device according to claim 8, since the magnetic pole different from or same as the magnetic pole is provided between the developer pumping magnetic pole and the adjacent magnetic pole, the developer is formed on the outer surface of the nonmagnetic cylindrical body. A stripping region can be formed reliably.

  In the developing device according to the ninth aspect, since at least one conveying magnetic pole is provided between the developing magnetic pole and the developer pumping magnetic pole, the developed developer can be reliably transferred from the developing magnetic pole to the developer peeling area. Can be transported. Further, since the developer stripping area is formed by the developer pumping magnetic pole and the transport magnetic pole, it is not necessary to provide a dedicated magnetic pole for forming the developer stripping area. Therefore, it is possible to reduce the size of the magnet roller or the like.

  In the developing device according to the tenth aspect, when the average particle diameter of the toner of the developer is selected to be 7 μm or less, an excellent image having excellent granularity and no screw pitch unevenness can be obtained.

  According to the eleventh aspect of the invention, since the toner is selected from the emulsion polymerization method or the suspension polymerization method, the sphericity of the toner is good, so that the density unevenness remaining on the image is visually recognized. The effect that it is improved is produced.

  Since the process cartridge according to claim 12 has the developing device according to any one of claims 1 to 11, an excellent image having excellent granularity and no screw pitch unevenness. A process cartridge can be provided.

  In the image forming apparatus according to claim 13, since the developing device according to any one of claims 1 to 11 is used, an excellent image having excellent granularity and no screw pitch unevenness. A forming apparatus can be provided.

  A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a main part of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a sectional view of the developing device according to the first embodiment of the present invention of the image forming apparatus shown in FIG. FIG. 3 is a cross-sectional view taken along the line ABCD in FIG. FIG. 4 is a perspective view showing a main part of the developing device shown in FIG. FIG. 5 is an explanatory diagram showing an operation state of the developing device shown in FIG.

  As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 2 (only part of which is shown in FIG. 1), a paper feed roller 3, a transfer member 4, a fixing device 5, a laser writing device (not shown), And at least a process cartridge 6.

  The apparatus main body 2 is formed in a box shape, for example, and is installed on a floor or the like. The apparatus main body 2 accommodates a paper feed roller 3, a transfer member 4, a fixing device 5, a laser writing device, and a process cartridge 6. The paper feed roller 3 feeds a recording paper 7 as a transfer material between the transfer member 4 and a photosensitive drum 8 described later.

  The transfer member 4 is an endless belt, and moves forward in a tangential direction of a photosensitive drum 8 described later. The transfer member 4 presses the recording paper 7 fed from the paper feed roller 3 against the outer surface of the photosensitive drum 8, and transfers the toner image on the photosensitive drum 8 to the recording paper 7. The transfer member 4 sends the recording paper 7 onto which the toner image has been transferred toward the fixing device 5. The fixing device 5 presses and heats the recording paper 7 sent from the transfer member 4 to fix the toner image transferred from the photosensitive drum 8 onto the recording paper 7 on the recording paper 7. The laser writing device irradiates the outer surface of the photosensitive drum 8 uniformly charged by a charging roller 9 described later with a laser beam 10 to form an electrostatic latent image.

  The process cartridge 6 is detachable from the apparatus main body 2. The process cartridge 6 includes a cartridge case 11, a charging roller 9 as a charging device, a photosensitive drum 8 as a photosensitive member (also referred to as an image carrier), a cleaning blade 12 as a cleaning device, a developing device 13, It has. Therefore, the image forming apparatus 1 includes at least a charging roller 9, a photosensitive drum 8, a cleaning blade 12, and a developing device 13.

  The cartridge case 11 is detachable from the apparatus main body 2 and accommodates a charging roller 9, a photosensitive drum 8, a cleaning blade 12, and a developing device 13. The charging roller 9 uniformly charges the outer surface of the photosensitive drum 8. The photosensitive drum 8 is disposed with a gap from a later-described developing roller 15 of the developing device 13. The photosensitive drum 8 is formed in a columnar shape or a cylindrical shape that is rotatable about an axis. An electrostatic latent image is formed on the outer surface of the photosensitive drum 8 by a laser writing device. The photosensitive drum 8 is developed on the electrostatic latent image formed and carried on the outer surface, and the toner image is transferred to a recording paper 7 positioned between the transfer member 4 and the toner image thus obtained. To do. The cleaning blade 12 removes the transfer residual toner remaining on the outer surface of the photosensitive drum 8 after transferring the toner image to the recording paper 7.

  As shown in FIGS. 1 to 3, the developing device 13 includes a developer supply unit 14, a case 27, a developing roller 15 as a developer carrier, a regulating blade 16 as a regulating member, and a reattachment preventing member. And at least a rotating member 28.

  The developer supply unit 14 includes a storage tank 17 and a pair of stirring screws 18 as stirring members. The storage tank 17 is formed in a box shape whose length is substantially equal to that of the photosensitive drum 8. A partition wall 19 extending along the longitudinal direction of the storage tank 17 is provided in the storage tank 17. The partition wall 19 partitions the storage tank 17 into a first space 20 and a second space 21. The first space 20 and the second space 21 have both end portions 22, 23, 24 and 25 communicating with each other.

  The storage tank 17 stores the developer 26 (shown in FIG. 5) in both the first space 20 and the second space 21. The developer 26 includes toner and a magnetic carrier (also referred to as magnetic powder). The toner is appropriately supplied to one end portion 23 of the first space 20 on the side away from the developing roller 15 in the first space 20 and the second space 21. The toner is spherical fine particles produced by an emulsion polymerization method or a suspension polymerization method. The toner may be obtained by pulverizing a lump composed of a synthetic resin in which various dyes or pigments are mixed and dispersed. The average particle diameter of the toner is 3 μm or more and 7 μm or less. The magnetic carrier is accommodated in both the first space 20 and the second space 21. The particle size of the magnetic carrier is 20 μm or more and 50 μm or less.

  The stirring screw 18 is accommodated in each of the first space 20 and the second space 21. The longitudinal direction of the stirring screw 18 is parallel to the longitudinal directions of the storage tank 17, the developing roller 15, and the photosensitive drum 8. The agitating screw 18 is provided so as to be rotatable around an axis, and rotates around the axis to agitate the toner and the magnetic carrier and convey the developer 26 along the axis.

  In the illustrated example, the stirring screw 18 in the first space 20 conveys the developer 26 from the one end 23 to the other end 25 described above. The stirring screw 18 in the second space 21 conveys the developer 26 from the other end 24 toward the one end 22.

  According to the above-described configuration, the developer supply unit 14 conveys the toner supplied to the one end portion 23 of the first space 20 to the other end portion 25 while stirring with the magnetic carrier. It is conveyed to the other end 25 of the second space 21. Then, the developer supply unit 14 agitates the toner and the magnetic carrier in the second space 21 and supplies them to the outer surface of the developing roller 15 while transporting them in the axial direction.

  The case 27 is formed in a box shape, is attached to the storage tank 17 of the developer supply unit 14 described above, and covers the development roller 15 and the like together with the storage tank 17. In addition, an opening 27 a is provided in a portion of the case 27 facing the photosensitive drum 8.

  The developing roller 15 is formed in a cylindrical shape, and is provided between the second space 21 and the photosensitive drum 8 and in the vicinity of the opening 27a described above. The developing roller 15 is parallel to both the photosensitive drum 8 and the storage tank 17. The developing roller 15 is disposed at a distance from the photosensitive drum 8. A space between the developing roller 15 and the photosensitive drum 8 forms a developing region 31 in which the toner of the developer 26 is attached to the photosensitive drum 8 to develop the electrostatic latent image to obtain a toner image. In the developing area 31, the developing roller 15 and the photosensitive drum 8 face each other.

  As shown in FIGS. 2 and 3, the developing roller 15 includes a core metal 29, a cylindrical magnet roller (also referred to as a magnet body) 33, and a cylindrical developing sleeve 32 as a non-magnetic cylindrical body. ing. The metal core 29 has a longitudinal direction parallel to the longitudinal direction of the photosensitive drum 8 and is fixed to the case 27 without rotating.

  The magnet roller 33 includes a cylindrical roller body 34 made of a magnetic material, and a plurality of fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 attached to the roller body 34. The roller body 34, that is, the magnet roller 33 is fixed to the outer periphery of the core metal 29 without rotating around the axis. The roller body 34 is provided with a plurality of magnetic pole mounting grooves 35. The magnetic pole mounting groove 35 is recessed from the outer surface of the roller body 34 and extends linearly along the axial center (longitudinal) direction of the roller body 34, that is, the magnet roller 33.

  The fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 are long and rod-shaped magnets that are inserted into the magnetic pole mounting groove 35 and attached to the roller body 34. That is, the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 extend along the longitudinal direction of the magnet roller 33, that is, the developing roller 15, and are provided over the entire length of the magnet roller 33. . The magnet roller 33 configured as described above is accommodated (enclosed) in the developing sleeve 32.

  The fixed magnetic pole N1 is a developer pumping magnetic pole described in the present specification, and is opposed to the agitating screw 18 described above. The fixed magnetic pole N <b> 1 has N polarity and generates a magnetic force on the outer surface of the developing sleeve 32, i.e., the developing roller 15, so that the developer 26 in the second space 21 of the storage tank 17 is removed from the developing sleeve 32. Aspirate to surface.

  The fixed magnetic pole S3 is the developing magnetic pole described in the present specification, and is opposed to the photosensitive drum 8 described above. The fixed magnetic pole S <b> 3 has S polarity and generates a magnetic force on the outer surface of the developing sleeve 32, i.e., the developing roller 15, thereby forming a magnetic field between the developing sleeve 32 and the photosensitive drum 8. The fixed magnetic pole S3 forms a magnetic brush by the magnetic field, so that the toner of the developer 26 attracted to the outer surface of the developing sleeve 32 is delivered to the photosensitive drum 8.

  A plurality of fixed magnetic poles S1, N2, S2, and N3 provided between the above-described fixed magnetic poles N1 and S3 and upstream of the arrow G, which will be described later, from the fixed magnetic pole S3 are before the development for transporting the developer 26 before the development. It is a conveyance magnetic pole. These fixed magnetic poles S1, N2, S2, and N3 have an S polarity, an N polarity, an S polarity, and an N polarity in order from the fixed magnetic pole N1 side as a developer pumping magnetic pole. A magnetic force is generated on the outer surface of the toner to convey the developer 26 before development toward the photosensitive drum 8. One fixed magnetic pole S <b> 2 is disposed at a position facing the regulating blade 16. The single fixed magnetic pole S2 cooperates with the regulating blade 16 to keep the thickness of the developer 26 on the outer surface of the developing sleeve 32 at a predetermined thickness.

  The fixed magnetic pole N4 provided between the fixed magnetic poles N1 and S3 and on the downstream side of the arrow G from the fixed magnetic pole S3 conveys developed developer 26 (hereinafter denoted by reference numeral 26a) in this specification. It is the conveyance magnetic pole described. The fixed magnetic pole N4 has an N polarity, generates a repulsive magnetic field with the fixed magnetic pole N1 as a developer pumping magnetic pole, and develops the developing sleeve 32 on the outer surface of the developing roller 32, that is, the developing roller 15. A developer stripping region R is formed to strip the developed developer 26 from above toward the storage tank 17. That is, the fixed magnetic pole N4 is adjacent to the fixed magnetic pole N1 as a developer pumping magnetic pole and cooperates with the fixed magnetic pole N1 to form the developer stripping region R. The developer stripping region R is provided on the outer surface of the developing sleeve 32 from the fixed magnetic pole S3 as the developing magnetic pole to the fixed magnetic pole N1 as the developer pumping magnetic pole.

  As shown in FIG. 6, the developer stripping region R is a region where a weak magnetic force having a magnetic flux density of, for example, about 5 mT (millitesla) is generated, and the developed developer 26 a adhered to the outer surface of the developing sleeve 32. Is a region that is detached from the outer surface of the developing sleeve 32 due to its own weight or the like. As described above, in this specification, a region in which a weak magnetic force is generated and the developed developer 26a is separated from the outer surface of the developing sleeve 32 due to its own weight or the like is referred to as a developer stripping region R. Further, the developer stripping region R is selected in a direction in which the normal magnetic force on the outer surface of at least a part of the developing sleeve 32 pulls the developed developer 26 a away from the outer surface of the developing sleeve 32. Yes. The above-described fixed magnetic pole N4 is an adjacent magnetic pole that is the same as the developer pumping magnetic pole described in this specification.

  6 shows the magnetic force in the normal direction on the outer surface of the developing sleeve 32 at the coordinates shown in FIG. 5, the position extending from the rotation center P of the developing sleeve 32 toward the photosensitive drum 8 in the horizontal direction is set to 0 °, and the angle is sequentially increased along the arrow G. Also, the positive normal magnetic force shown in FIG. 5 indicates the magnetic force in the direction of separating the developer 26 from the outer surface of the developing sleeve 32, and the negative normal magnetic force shown in FIG. The magnetic force in the direction in which the developer 26 is attracted to the outer surface of the sleeve 32 is shown.

  Further, the dotted line shown in FIG. 5 indicates the magnetic flux density in the normal direction on the outer surface of the developing sleeve 32 created by the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4. Further, the alternate long and short dash line shown in FIG. 7 indicates the magnetic force in the normal direction on the outer surface of the developing sleeve 32 created by the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4. Further, in the present embodiment, the fixed magnetic poles N1 and N4 having the same polarity and adjacent to each other are provided between the fixed magnetic poles N1 and N4 of the roller body 34 described above, and the magnetic poles J are different from the fixed magnetic poles N1 and N4. (Indicated by a dotted line in FIG. 2) is formed naturally.

The developing sleeve 32 is made of a nonmagnetic material, is formed in a cylindrical shape, and is provided so as to be rotatable around an axis. The developing sleeve 32 encloses (accommodates) the magnet roller 33, and the clockwise arrow in FIG. 2 so that the inner peripheral surface thereof is in turn opposed to the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4. Rotate along G. The developing sleeve 32 is made of aluminum, stainless steel (SUS), or the like. Aluminum is excellent in terms of workability and lightness. When using aluminum, it is preferable to use A6063, A5056, and A3003. When using SUS, it is preferable to use SUS303, SUS304, and SUS316.

  In addition, a plurality of grooves extending along the axis of the developing sleeve 32, that is, the developing roller 15 are formed on the outer surface of the developing sleeve 32. Further, the outer surface of the developing sleeve 32 may be subjected to a known blasting process to form fine irregularities.

  The regulating blade 16 is provided at the end of the developing device 13 near the photosensitive drum 8. The regulating blade 16 is attached to the case 27 described above with a space from the outer surface of the developing sleeve 32. The regulating blade 16 scrapes off the developer 26 on the outer surface of the developing sleeve 32 exceeding the desired thickness into the storage tank 17, and the developer 26 on the outer surface of the developing sleeve 32 conveyed to the developing region 31. To the desired thickness.

  As shown in FIG. 4, the rotating member 28 is formed in a cylindrical shape whose longitudinal direction is parallel to the developing roller 15 and the photosensitive drum 8 described above. The rotation member 28 has an axis P1 arranged in parallel with the rotation center P of the developing sleeve 32. The outer surface of the rotating member 28 is arranged at a distance from the aforementioned developer stripping region R of the developing sleeve 32, that is, the outer surface of the developing sleeve 32. Further, the outer surface of the rotating member 28 and the outer surface of the developing sleeve 32 are opposed to each other with an interval over their entire length.

  The rotary member 28 is rotatably supported by the case 27 around its axis P1 and is rotated along an arrow Ga (shown in FIG. 7) in the same direction as the arrow G by a drive source (not shown). . The rotating member 28 is made of, for example, a synthetic resin such as polycarbonate (PC) or a nonmagnetic material such as a metal such as stainless steel.

  The surface roughness of the outer surface of the rotating member 28 is 10 μm or more. In addition, the surface roughness of the outer surface of the rotating member 28 in this specification indicates a so-called 10-point average height.

  Thus, the rotating member 28 is provided so as to face the developer stripping region R. In this specification, the rotation member 28 is provided so as to be opposed to the developer peeling region R. The rotation member 28 is provided so as to be opposed to the developer peeling region R with a gap. And that the rotating member 28 is provided so as to be in sliding contact with the developer stripping region R. Thus, in this specification, the rotating member 28 may be in contact with the developer stripping region R or may not be in contact with the developer stripping region R.

  Further, the rotating member 28 is opposed to a position where the normal magnetic force on the outer surface of the developing sleeve 32 is directed to pull the developed developer 26 a away from the outer surface of the developing sleeve 32. That is, the magnetic force in the normal direction on the outer surface of the developing sleeve 32 pulls the developed developer 26 a away from the outer surface of the developing sleeve 32 at a position where the rotating member 28 in the developer stripping region R faces. The direction is selected.

  The rotating member 28 having the above-described configuration is opposed to the developer stripping region R and is rotated along the arrow Ga in the same direction as the developing sleeve 32, whereby the developed developer 26 a is transferred to the developing sleeve 32. While peeling off from the outer surface, the developer 26a that has been peeled off is restricted from immediately adhering to the developing sleeve 32. That is, the rotating member 28 regulates that the developed developer 26 a peeled off from the developer peeling region R immediately reattaches to the outer surface of the developing sleeve 32.

  The rotating member 28 having the above-described configuration may be formed in a cylindrical shape as long as the outer surface has a surface roughness of 10 μm or more. In the present invention, the rotating member 28 may rotate in the direction opposite to the developing sleeve 32. Further, in the present invention, the rotating member 28 has flexibility such as stainless steel as long as it is spaced from the developing sleeve 32 (that is, arranged so as not to contact the developing sleeve 32). You may comprise from the material which is not. Of course, in this case as well, the rotating member 28 is made of a non-magnetic material.

  In the developing device 13 having the above-described configuration, the toner and the magnetic carrier are sufficiently stirred by the developer supply unit 14, and the stirred developer 26 is attracted to the outer surface of the developing sleeve 32 by the fixed magnetic pole N1. In the developing device 13, the developing sleeve 32 rotates along the arrow G, and the developer 26 adhered by the plurality of conveying magnetic poles S 1, N 2, S 2, and N 3 is conveyed toward the developing region 31. The developing device 13 causes the developer 26 having a desired thickness to adhere to the photosensitive drum 8 with the regulating blade 16. In this way, the developing device 13 carries the developer 26 on the developing roller 15 and transports it to the developing area 31 to develop the electrostatic latent image on the photosensitive drum 8 to form a toner image.

  Then, the developing device 13 conveys the developed developer 26a to the developer stripping region R by the fixed magnetic pole N4, and the developed developer 26a is developed from the developer stripping region R as shown in FIGS. The developer 26 a is separated toward the storage tank 17. Further, the developed developer 26 a remaining attached to the developer stripping area R is scraped off from the outer surface of the developing sleeve 32 by the rotating member 28. The developer 26 that has been scraped off is immediately attached to the developing sleeve 32 by the rotating member 28, and is sufficiently agitated with another developer 26 in the second space 21 again. Used to develop an electrostatic latent image.

  The image forming apparatus 1 configured as described above forms an image on the recording paper 7 as described below. First, the image forming apparatus 1 rotates the photosensitive drum 8 and uniformly charges the outer surface of the photosensitive drum 8 by the charging roller 9. Laser light 10 is irradiated on the outer surface of the photosensitive drum 8 to form an electrostatic latent image on the outer surface of the photosensitive drum 8. When the electrostatic latent image is positioned in the development area 31, the developer 26 adhered to the outer surface of the developing sleeve 32 of the developing device 13 adheres to the outer surface of the photosensitive drum 8 and develops the electrostatic latent image. Then, a toner image is formed on the outer surface of the photosensitive drum 8.

  In the image forming apparatus 1, the recording paper 7 conveyed by the paper feed roller 3 is positioned between the transfer member 4 and the photosensitive drum 8 and formed on the outer surface of the photosensitive drum 8. The toner image is transferred to the recording paper 7. The image forming apparatus 1 uses the fixing device 5 to fix the toner image on the recording paper 7. Thus, the image forming apparatus 1 forms an image on the recording paper 7.

  According to this embodiment, the rotating member 28 is opposed to the developer stripping region R. For this reason, the developed developer 26a can be reliably peeled off from the developer stripping region R. Further, the developer 26 a detached from the developer stripping region R, that is, the developing sleeve 32, is prevented from immediately adhering to the developing sleeve 32 by the rotating member 28. Therefore, the developed developer 26a can be prevented from being used again for developing the electrostatic latent image on the photosensitive drum 8 without being detached from the developing sleeve 32. Therefore, it is possible to prevent density unevenness such as screw pitch unevenness and to obtain a uniform high quality image.

  Further, the rotating member 28 is opposed to a location selected so that the normal magnetic force pulls the developer 26 a away from the outer surface of the developing sleeve 32. Therefore, the rotating member 28 can reliably peel off the developed developer 26a from the developing sleeve 32. Further, the frictional force applied to the developer 26 from the rotating member 28 or the like can be suppressed, and the deterioration of the developer 26 can be prevented.

  Since the rotating member 28 rotates around an axis P1 parallel to the rotation center P of the developing sleeve 32, the developer stripped region R, that is, the developed developer 26a detached from the developing sleeve 32 immediately adheres to the developing sleeve 32. Can be prevented.

  Further, since the rotating member 28 rotates in the same direction as the developing sleeve 32, the developed developer 26a can be reliably peeled off from the developer stripping region R. Furthermore, since the surface roughness of the outer surface of the rotating member 28 is 10 μm or more, the frictional force on the outer surface of the rotating member 28 is increased. For this reason, the rotating member 28 can reliably adhere the developed developer 26a adhering to the outer surface of the developing sleeve 32 to the outer surface of the rotating member 28, and the developed developer 26a from the developer stripping region R. Can be peeled off more reliably.

  Since a magnetic pole J of a different polarity is formed between the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole N4 as the adjacent magnetic pole (conveying magnetic pole), development is performed on the outer surface of the developing sleeve 32. The agent stripping region R can be reliably formed.

  Since at least the fixed magnetic pole N4 as the transport magnetic pole is provided between the fixed magnetic pole S3 as the developing magnetic pole and the fixed magnetic pole N1 as the developer pumping magnetic pole, the fixed magnetic pole using the developed developer 26a as the developing magnetic pole. The sheet can be reliably conveyed from S3 to the developer stripping region R. Further, since the developer stripping region R is formed by the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole N4 as the transporting magnetic pole, a dedicated magnetic pole for forming the developer stripping region R is formed. There is no need to provide. Therefore, it is possible to reduce the size of the magnet roller 33 and the like.

  When the average particle size of the toner of the developer 26 is selected to be 7 μm or less, an excellent image with excellent granularity and no screw pitch unevenness can be obtained.

  Since the toner is selected to be based on the emulsion polymerization method or suspension polymerization method, since the sphericity of the toner is good, there is an effect that the density unevenness remaining on the image is visually improved.

  Further, since the developing device 13 described above is included, it is possible to provide the process cartridge 6 and the image forming apparatus 1 that can obtain an excellent image with excellent granularity and no screw pitch unevenness.

  Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, the rotating member 28 is a so-called impeller including a shaft portion 36 and a plurality (four in the illustrated example) of blade portions 37 as shown in FIG. The shaft portion 36 and the blade portion 37 are each made of a nonmagnetic material.

  The shaft portion 36 is formed in a cylindrical shape. The outer surface of the shaft portion 36 and the outer surface of the developing sleeve 32 are opposed to each other at an interval over their entire length. The blade portion 37 is formed in a band plate shape, and one end in the width direction is fixed to the outer surface of the shaft portion 36. The blade portion 37 extends from the outer surface of the shaft portion 36 in the outer peripheral direction of the shaft portion 36. The blade portion 37 is provided over the entire length of the shaft portion 36. The blade portion 37 is made of a nonmagnetic material such as polycarbonate or stainless steel.

  As shown in FIG. 9, the rotating member 28 has the shaft core P <b> 1 (that is, the longitudinal direction) parallel to the rotation center P of the developing sleeve 32, and the blade portion 37 is the outer surface of the developing sleeve 32. The developer stripping region R is disposed opposite to the developer stripping region R. The rotating member 28 is rotated along the arrow Ga in the same direction of the developing sleeve 32 around the axis P1.

  In the present embodiment, in addition to the effects of the first embodiment described above, the rotating member 28 is a so-called impeller provided with a shaft portion 36 and a blade portion 37. For this reason, the rotating member 28 can reliably peel off the developed developer 26 a from the developer peeling region R by the blade portion 37.

  In the present embodiment, the blade portion 37 may be made of a mixture of polycarbonate and polyester (Pplyester) or a flexible nonmagnetic material such as rubber. In this case, as shown in FIG. 10, the rotating member 28 has the above-described developer stripping region on the outer surface of the developing sleeve 32, with one end portion 37 a in the width direction on the side away from the shaft portion 36 of the blade portion 37. In a state of sliding contact (contact) with R, for example, both end portions in the longitudinal direction may be rotatably attached to the case 27. That is, the rotating member 28 may be provided so as to be in sliding contact with the developer stripping region R.

  In this case, the blade portion 37 is made of a flexible material, and the end portion 37 a of the blade portion 37 is in sliding contact with the outer surface of the developing sleeve 32. Thus, by making the blade portion 37 of the rotating member 28 flexible, the contact pressure between the rotating member 28 and the developing sleeve 32 is leveled. For this reason, there is an effect that the mechanical peeling action itself of the developed developer 26a works uniformly over the entire length of the developing sleeve 32.

  Further, in the present embodiment, as shown in FIG. 11, the end portion 37a that is in sliding contact with the developing sleeve 32 of the blade portion 37 of the rotating member 28 may be formed in a brush shape (also referred to as a comb-tooth shape). In this case, the end portion 37a of the blade portion 37 of the rotating member 28 that is in sliding contact with the developing sleeve 32 is formed in a brush shape or a comb shape so that the developed developer 26a can be wiped and cleaned even at a low contact pressure. As a result, the deterioration of the developer 26 can be suppressed.

  Further, the end portion 37a of the blade portion 37 of the rotating member 28 that is in sliding contact with the developing sleeve 32 is formed in a brush shape or a comb shape, so that even if the outer surface of the developing sleeve 32 has irregularities (such as grooves), The developed developer 26a can be reliably removed from the outer surface of the developing sleeve 32.

  Next, the inventors changed the presence or absence of the rotating member 28 and the like, formed a test image on the recording paper 7, and confirmed the effect of the present invention. The results are shown in Table 1 below.

(Comparative example)
In the comparative example, the outer diameter of the developing roller 15 is 25 mm, the angular velocity (rotational speed) of the developing sleeve 32 is 400 RPM, the outer diameter of the stirring screw 18 is 18 mm, and the pitch of the stirring screw 18 is 30 mm. Further, without providing the rotating member 28 as the re-adhesion preventing member described above, the outer surface of the developing sleeve 32 is subjected to blasting and pulverized as described above, and toner having an average particle size of 10 μm is used. It was.

  As a result of developing under the above conditions, forming an image, and outputting a test image, as shown in Table 1, both screw pitch unevenness and vertical streaks occur. In both cases (that is, density unevenness), the result was outside the allowable limit that could not withstand practical use. Furthermore, in the granularity, the result which is outside the allowable limit which cannot endure practical use was obtained. The granularity indicates the smoothness of the test image.

  The evaluation criteria in Table 1 are ◯ for those that can withstand practical use, ◎ for those that are excellent, and Δ that are within acceptable limits for practical use. The thing which cannot endure practical use is set as x.

Example 1
Next, in Example 1, a cylindrical rotating member 28 made of polycarbonate (explained in the first embodiment) is arranged at a distance from the developing sleeve 32, and the other conditions are the same as in the comparative example. When the test image was output in this way, the screw pitch unevenness was almost eliminated, and the result was within the allowable limit that could withstand practical use. In addition, no vertical streak occurred, and an excellent result that could withstand practical use was obtained. Furthermore, in the granularity, a result that is within an allowable limit that can be practically used was obtained.

(Example 2)
In Example 2, a cylindrical rotating member 28 (described in the first embodiment) made of stainless steel and having an outer surface with a surface roughness of 12 μm is disposed at a distance from the developing sleeve 32, and the others are When a test image was output under the same conditions as in the comparative example, screw pitch unevenness was eliminated, and excellent results that could withstand practical use were obtained. In addition, no vertical streak occurred, and an excellent result that could withstand practical use was obtained. Furthermore, in the granularity, a result that is within an allowable limit that can be practically used was obtained.

(Example 3)
In Example 3, the rotating member 28 (described in the second embodiment) provided with four blade portions 37 made of polycarbonate is disposed at a distance from the developing sleeve 32, and the other conditions are the same as in the comparative example. When a test image was output in this way, a very excellent result was obtained in terms of screw pitch unevenness. In addition, no vertical streak occurred, and an excellent result that could withstand practical use was obtained. Furthermore, in the granularity, a result that is within an allowable limit that can be practically used was obtained.

Example 4
In Example 4, the rotating member 28 (described in the second embodiment) provided with four blade portions 37 made of a flexible material made of a mixture of polycarbonate and polyester is used for the developing sleeve 32. When the test image was output under the same conditions as in the comparative example except that it was placed in sliding contact with the outer surface, a very excellent result was obtained in terms of screw pitch unevenness. In addition, very excellent results were obtained in the longitudinal muscle. Furthermore, in the granularity, a result that is within an allowable limit that can be practically used was obtained.

(Example 5)
In Example 5, a groove was formed on the outer surface of the developing sleeve 32, and the end 37a of the blade part 37 was formed in a brush shape, and the other conditions were the same as in Example 4, and a test image was output. Very good results were obtained in screw pitch unevenness. In addition, very excellent results were obtained in the longitudinal muscle. Furthermore, in the granularity, a result that is within an allowable limit that can be practically used was obtained.

(Example 6)
In Example 6, a test image was output under the same conditions as in Example 5 except that the toner obtained by the above-mentioned pulverization having an average particle size of 5.5 μm was used. Excellent results were obtained. In addition, very excellent results were obtained in the longitudinal muscle. Furthermore, in the granularity, an excellent result that can withstand practical use was obtained.

(Example 7)
In Example 7, a test image was output under the same conditions as in Example 6 except that the toner was a spherical fine particle produced by an emulsion polymerization method or a suspension polymerization method having an average particle size of 5.5 μm. Excellent results were obtained in each of screw pitch unevenness, vertical stripes, and granularity.

  As described above, it has been clarified that by providing the rotation member 28 as a re-adhesion preventing member, it is possible to obtain an image having good density and no unevenness in density such as oblique screw pitch unevenness and vertical stripes.

  In the present invention, a toner having an average particle diameter of 3 μm or more and 7 μm or less is used. This is because when the particle size of the toner exceeds 7 μm, the image quality deteriorates, and when the particle size of the toner is less than 3 μm, the toner is easily detached from the magnetic carrier, and a phenomenon called toner scattering is likely to occur.

  In the present invention, the surface roughness of the outer surface of the columnar or cylindrical rotating member 28 is 10 μm or more. When the surface roughness of the outer surface of the rotating member 28 is less than 10 μm, the rotating member 28 cannot remove the sufficiently developed developer 26 a from the outer surface of the developing sleeve 32, and the density such as screw pitch unevenness. This is because unevenness occurs.

  In the above-described embodiment, the process cartridge 6 includes the cartridge case 11, the charging roller 9, the photosensitive drum 8, the cleaning blade 12, and the developing device 13. However, in the present invention, the process cartridge 6 only needs to include at least the developing device 13, and does not necessarily include the cartridge case 11, the charging roller 9, the photosensitive drum 8, and the cleaning blade 12. In the above-described embodiment, the image forming apparatus 1 includes the process cartridge 6 that is detachable from the apparatus main body 2. However, in the present invention, the image forming apparatus 1 only needs to include the developing device 13, and does not necessarily include the process cartridge 6.

In the above-described embodiment, the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole N4 that forms the developer stripping region R in cooperation with the fixed magnetic pole N1 are fixed magnetic poles. A magnetic pole J having a different polarity from N1 and N4 is naturally formed. However, in the present invention, as shown in FIG. 12, a fixed magnetic pole N1 as a developer pumping magnetic pole and a fixed magnetic pole N4 that forms a developer stripping region R in cooperation with the fixed magnetic pole N1. The magnetic poles J having the same or different polarity as those of the fixed magnetic poles N1 and N4 may be positively provided. The magnetic pole J is of course a separate magnet from the fixed magnetic poles N1 and N4 described above, and is attached to the roller main body 34 described above. The magnetic pole J interacts with the above-described fixed magnetic poles N1 and N4 to form the developer stripping region R described above. Since a magnetic pole J having a different polarity or the same polarity as that between the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole N4 as the adjacent magnetic pole is provided on the outer surface of the nonmagnetic developing sleeve 32. The developer stripping region R can be reliably formed.

  In the above-described embodiment, the fixed magnetic pole N4 as the transport magnetic pole for transporting the developed developer 26a is placed between the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole S3 as the development magnetic pole. Provided. However, in the present invention, a plurality of fixed magnetic poles N4 as transport magnetic poles for transporting the developed developer 26a are provided between a fixed magnetic pole N1 as a developer pumping magnetic pole and a fixed magnetic pole S3 as a development magnetic pole. Also good. In short, in the present invention, at least one fixed magnetic pole N4 as a transport magnetic pole for transporting the developed developer 26a is provided between a fixed magnetic pole N1 as a developer pumping magnetic pole and a fixed magnetic pole S3 as a development magnetic pole. The developer described above is provided between the fixed magnetic pole N4 closest to the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole N1 as the developer pumping magnetic pole among the at least one fixed magnetic pole N4. The stripped region R may be formed.

  Further, a fixed magnetic pole N4 as a conveying magnetic pole is provided between a fixed magnetic pole N1 as a developer pumping magnetic pole and a fixed magnetic pole S3 as a developing magnetic pole, and a developer stripping region R is provided between the fixed magnetic poles N1 and N4. Forming. However, in the present invention, the fixed magnetic pole N1 as the developer pumping magnetic pole and the fixed magnetic pole S3 as the developing magnetic pole are formed in the same polarity, and the developer stripping region R is formed between these fixed magnetic poles N1 and S3. It may be formed. In this case, the fixed magnetic pole S3 as the developing magnetic pole is an adjacent magnetic pole described in the present invention.

  In the present invention, at least one fixed magnetic pole N4 is provided between a fixed magnetic pole N1 as a developer pumping magnetic pole and a fixed magnetic pole S3 as a developing magnetic pole, and any two of these fixed magnetic poles N1, S3, and N4 are provided. The developer stripping region R described above may be formed between the two. In short, in the present invention, the developer stripping region R may be formed between the fixed magnetic pole S3 as the developing magnetic pole and the fixed magnetic pole N1 as the developer pumping magnetic pole.

  Further, in the above-described embodiment, the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 are arranged by embedding a magnet separate from the roller body 34 of the magnet roller 33. However, in the present invention, the magnetic poles N1, S1, N2, S2, N3, S3, and N4 are not necessarily arranged by embedding the magnet in the roller body 34 of the magnet roller 33. In other words, the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 may be arranged by magnetizing necessary portions of the roller body 34 of the magnet roller 33, or known to the roller body 34 of the magnet roller 33. The magnetic poles N1, S1, N2, S2, N3, S3, and N4 may be disposed by bonding and fixing the magnet pieces. In short, the magnet roller 33 in the present invention only needs to form the fixed magnetic poles N1, S1, N2, S2, N3, S3, and N4 described in the embodiment, and various types can be used as long as they satisfy the gist of the present invention. The magnet roller 33 may be used.

  In addition, this invention is not limited to the said Example. That is, various modifications can be made without departing from the scope of the present invention.

1 is a cross-sectional view showing a main part of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a developing device of the image forming apparatus shown in FIG. 1. It is sectional drawing which follows the ABCD line | wire in FIG. It is a perspective view which shows the principal part of the image development apparatus shown by FIG. FIG. 3 is an explanatory diagram illustrating an operation state of the developing device illustrated in FIG. 2. FIG. 3 is an explanatory diagram showing a magnetic force in a normal direction on an outer surface of a developing sleeve of the developing device shown in FIG. 2. It is sectional drawing which expands and shows the VII part in FIG. It is a perspective view which shows the rotating member of the image development apparatus of the image forming apparatus concerning the 2nd Embodiment of this invention. It is sectional drawing which shows the principal part of the image development apparatus provided with the rotation member shown by FIG. It is sectional drawing which shows the principal part of the modification of the developing device shown by FIG. It is a perspective view which shows the modification of the rotating member shown by FIG. FIG. 10 is a cross-sectional view showing a modification of the developing device shown in FIG. 2. It is explanatory drawing which shows the operation condition of the conventional image development apparatus. It is explanatory drawing which shows the operation condition of the other conventional developing apparatus. It is sectional drawing which follows the abcd line in FIG. It is a figure which shows the screw pitch nonuniformity which generate | occur | produced at the time of image formation of the conventional developing device. It is a figure which shows the vertical stripe which generate | occur | produced at the time of image formation of the conventional developing device. It is a figure explaining the screw pitch nonuniformity by the stirring screw shown by FIG. It is sectional drawing which follows the XX-XX line in FIG. It is sectional drawing which expands and shows the XXI part in FIG. FIG. 20 is another cross-sectional view showing the XXI portion in FIG. 19 in an enlarged manner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Apparatus main body 6 Process cartridge 8 Photosensitive drum (photosensitive body)
9 Charging roller (charging device)
DESCRIPTION OF SYMBOLS 13 Developing apparatus 17 Storage tank 26 Developer 26a Developed developer 28 Rotating member 32 Developing sleeve (nonmagnetic cylindrical body)
33 Magnet roller 36 Shaft portion 37 Blade portion 37a End portion 38 Developer stripping blade (reattachment prevention member)
38a End N1 Fixed magnetic pole (developer pumping magnetic pole)
S1 fixed magnetic pole N2 fixed magnetic pole S2 fixed magnetic pole N3 fixed magnetic pole S3 fixed magnetic pole (development magnetic pole)
N4 fixed magnetic pole (conveying magnetic pole, adjacent magnetic pole)
J magnetic pole P rotation center of developing sleeve (rotation center of non-magnetic cylindrical body)
P1 Shaft core R Developer stripping area

Claims (13)

As a fixed magnetic pole of the magnet roller, a developer pumping magnetic pole for sucking the developer from the developer storage tank into a non-magnetic cylindrical body containing the magnet roller, and the developer toner sucked by the cylindrical body A developing magnetic pole for delivering the toner to the photosensitive member, and the developer that has been developed from the outer surface of the cylindrical body to the storage tank between the developing magnetic pole and the developer pumping magnetic pole. In the developing device in which the developer stripping area stripped toward the outside is provided on the outer surface of the non-magnetic cylindrical body,
A rotating member made of a non-magnetic material and rotating about an axis parallel to the rotation center of the cylindrical body is provided so as to face the developer stripping area on the outer surface of the cylindrical body. A developing device.   The developing device according to claim 1, wherein the rotating member rotates in the same direction as the cylindrical body.   The developing device according to claim 1, wherein the rotating member is formed in a cylindrical shape or a columnar shape, and the outer surface has a surface roughness of 10 μm or more.   The said rotating member is provided with the axial part parallel to the rotation center of the said cylindrical body, and the blade | wing part extended in the outer peripheral direction from the outer surface of the said axial part, The Claim 1 or Claim 2 characterized by the above-mentioned. Development device.   The developing device according to claim 4, wherein the blade portion is made of a flexible material and is provided so as to be in sliding contact with the developer stripping region.   6. The developing device according to claim 5, wherein an end portion of the blade portion that is in sliding contact with the developer stripping region is finished in a brush shape. The developer pumping magnetic pole and the adjacent magnetic pole adjacent to the developer pumping magnetic pole and cooperating with the developer pumping magnetic pole to form the developer stripping region are made to have the same polarity. Provided,
7. The developing device according to claim 1, wherein a magnetic pole different from the developer-pumping magnetic pole and the adjacent magnetic pole is formed between the magnetic poles. 8.   The developer pumping magnetic pole and the adjacent magnetic pole adjacent to the developer pumping magnetic pole and cooperating with the developer pumping magnetic pole to form the developer stripping region are made to have the same polarity. 7. A magnetic pole having the same or different polarity as the developer-pumping magnetic pole and the adjacent magnetic pole is provided between these magnetic poles. The developing device according to 1.   As the fixed magnetic pole of the magnet roller, at least one conveying magnetic pole for conveying the developed developer to the storage tank is provided between the developing magnetic pole and the developer pumping magnetic pole, and the developing roller 9. The agent stripping area is provided between the transport magnetic pole closest to the developer pumping magnetic pole and the developer pumping magnetic pole among at least one transport magnetic pole. The developing device according to any one of the above.   The developing device according to claim 1, wherein the toner has an average particle size of 3 μm or more and 7 μm or less.   11. The developing device according to claim 10, wherein the toner is spherical fine particles produced by an emulsion polymerization method or a suspension polymerization method. A process cartridge having at least a developing device, wherein the developing device includes the developing device according to any one of claims 1 to 11.   An image forming apparatus having at least a photosensitive member, a charging device, and a developing device, wherein the developing device includes the developing device according to any one of claims 1 to 11. Image forming apparatus.

Images