JP2010044394A - Magnet roller, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of periodical density irregularities of a magnet on an image by an inexpensive configuration. <P>SOLUTION: A magnet roller is equipped with: a sleeve which has a cylindrical outer circumferential surface carrying developer and a plurality of concave holes forming surface patterns which are not continuous in any directions on the respective outer circumferential surfaces; and the magnet which is provided in the sleeve and has a plurality of magnetic poles. The minimum partial area ratio of a plurality of partial area ratios obtained by dividing the outer circumferential surface of the sleeve into a plurality of regions parallel to a sleeve shaft and dividing the total area of the plurality of concave holes formed in each region by the area of each region is set at about 20% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnet roller including a developing sleeve, a developing device having the magnet roller, and an image forming apparatus such as a multifunction machine, a printer, a copying machine, or a facsimile machine.

  The developing device includes a magnet having five magnetic poles, a developing sleeve having an outer peripheral surface on which the developer is carried and being driven to rotate around the magnet, and a thickness of the developer layer on the outer peripheral surface of the developing sleeve. And a doctor blade to regulate.

  Conventionally, there has been proposed a developing roller that does not generate streak-like unnecessary patterns and reduces performance deterioration due to secular change (see Patent Documents 1 and 2).

  In the developing roller described in Patent Document 1, a plurality of minute recesses that are separated from each other are formed on the outer peripheral surface of a cylindrical sleeve, and the plurality of recesses are distributed in both the axial direction and the circumferential direction of the sleeve. Is formed. The surface shape of the sleeve is composed of a groove-like recess. The groove direction of the concave portion does not continue in any of the roller axis direction of the magnet roller, the circumferential direction around the roller axis, and the oblique direction oblique to the roller axis direction on the circumferential surface.

  Since the sleeve surface has this groove type recess and the depth of the groove is stable in life, in the developing roller described in Patent Document 1, the developer conveyance amount on the magnet roller is unlikely to change. Etching is used to create the recess. A recess is created by melting the unmasked portion of the tube material. When electrophotographic image formation is performed by the developing sleeve having the concave portion, the surface shape trace of the sleeve does not appear on the image, which is suitable for high-quality printing.

  Patent Document 2 discloses that the density of the recesses at both ends of the sleeve is larger than the density of the recesses at the center of the sleeve.

  In Patent Document 3, it occurs in an apparatus having a drive mechanism including a plurality of constituent members such as a drive member that operates by receiving a current supply and a power transmission member that transmits a driving force of the drive member to another member. A failure diagnosis device for diagnosing a failure is described. Patent Document 4 describes an image forming apparatus having a self-diagnosis function and an operation verification method thereof.

JP 2009-48168 A JP 2009-139953 A JP 2005-33559 A Japanese Patent Laid-Open No. 2005-77690

  However, in the above-described prior art, since the developing sleeve is processed by etching the pipe material, the recesses on the outer peripheral surface of the sleeve after the etching process are not uniform in the circumferential direction of the sleeve due to the melting of the pipe material. The depth of the recess and the opening size of the recess are not uniform due to the etching residue and excessive over-etching. A concave hole having a large depth or opening dimension and a concave hole having a small depth or opening dimension are mixedly formed. The non-uniformity of the depth and opening size of the concave hole on the outer peripheral surface of the sleeve leads to the non-uniform amount of developer retained by the concave hole on the outer peripheral surface.

  On the outer peripheral surface of the sleeve, the inventors of the present invention have densely formed recesses with small opening sizes in one band-like region parallel to the sleeve axial direction, and densely formed recesses with large opening sizes in another belt-like region. It was confirmed that it was formed. The reason for this is considered that the layer thickness of the developer layer on the developing sleeve is not uniform in the circumferential direction of the sleeve.

  When the thickness of the developer layer is thin, when the surface of the developing sleeve transports the developer, the concave portion having a small opening size cannot maintain a sufficient transport force of the developer. On the other hand, the concave portion having a large opening size has a large conveyance force and easily conveys the developer. The developer image obtained by the development processing by the developing device is placed on the outer peripheral surface of the developing sleeve. Horizontal streaks appeared along the circumferential direction on the outer peripheral surface. In the circumferential direction on the outer peripheral surface on which the developed image is placed, a dark uneven region and a dark uneven region separated by a predetermined distance in the circumferential direction appeared periodically in this region. The distance between these regions was approximately equal to the circumferential length of the outer periphery of the magnet roller.

  Accordingly, in view of the above-described problems, the present invention provides a magnet roller, a developing device, and a magnet roller that can prevent the occurrence of periodic shading unevenness or horizontal stripes of the magnet roller appearing on an image with an inexpensive configuration. An object is to provide an image forming apparatus.

  In order to solve such a problem, according to one aspect of the present invention, a plurality of cylindrical outer peripheral surfaces carrying a developer and a plurality of surface patterns that are not continuous in any direction on the outer peripheral surface. A sleeve having a recessed hole; and a magnet provided in the sleeve and having a plurality of magnetic poles, the outer peripheral surface of the sleeve being divided into a plurality of regions parallel to the sleeve axis, and A magnet having a minimum partial area ratio of about 20% or more of a plurality of partial area ratios obtained by dividing a total area of the plurality of recessed holes formed by an area of each region. A roller is provided.

  According to another aspect of the present invention, a sleeve having a cylindrical outer peripheral surface carrying a developer and a plurality of concave holes each forming a surface pattern that is not continuous in any direction on the outer peripheral surface. And a magnet having a plurality of magnetic poles provided in the sleeve, wherein the outer peripheral surface of the sleeve is divided into a plurality of regions parallel to the sleeve axis, and each of the plurality formed in each region. The difference between the maximum partial area ratio of the plurality of partial area ratios obtained by dividing the total area of the concave holes by the area of each region and the minimum partial area ratio is about 9% or less. A magnet roller is provided.

  Further, according to another aspect of the present invention, a container for storing the developer, a cylindrical outer peripheral surface provided in the container and carrying the developer, and in each direction on the outer peripheral surface, respectively. A sleeve having a plurality of concave holes forming a non-continuous surface pattern, a magnet provided in the sleeve and having a plurality of magnetic poles, and a layer of the developer on the outer peripheral surface disposed opposite to the sleeve A regulating member that regulates the thickness of the sleeve, and the outer peripheral surface of the sleeve is divided into a plurality of regions parallel to the sleeve axis, and the total area of the plurality of recessed holes formed in each region is A developing device is provided in which a minimum partial area ratio among a plurality of partial area ratios obtained by dividing by the area of each region is about 20% or more.

  According to another aspect of the present invention, a photoconductor, a charger for charging the surface of the photoconductor, an exposure device for exposing the photoconductor to form a latent image on the photoconductor, A container having an opening facing the photosensitive member and containing a developer; a cylindrical outer peripheral surface provided on the container opposite to the photosensitive member and carrying the developer; and on each of the outer peripheral surfaces A sleeve having a plurality of concave holes forming a surface pattern that is not continuous in any direction, a magnet provided in the sleeve, having a plurality of magnetic poles, and disposed opposite the sleeve, on the outer peripheral surface A regulating member that regulates the thickness of the developer layer; and a transfer unit that transfers the toner image attached to the latent image on the photosensitive member to a sheet when the developer is conveyed by the sleeve; The outer periphery of the sleeve Are divided into a plurality of regions parallel to the sleeve axis, and the total area of the plurality of concave holes formed in each region is divided by the area of each region, and the partial area ratio is obtained. An image forming apparatus having a minimum partial area ratio of about 20% or more is provided.

  According to the present invention, it is possible to provide an image without magnet roller cycle unevenness.

1 is a perspective view of a copying machine including an image forming apparatus according to an embodiment of the present invention. It is a block diagram of an image forming part. 1 is a longitudinal sectional view of a developing device according to an embodiment of the present invention. It is a front view of the magnet roller which concerns on embodiment of this invention. FIG. 4 is a development view of the outer peripheral surface side of the developing sleeve. FIG. 5 is a cross-sectional view of the developing sleeve taken along line WW in FIG. 4. It is a perspective view of a developing sleeve. 6 is a graph showing a relationship between a minimum partial area ratio of a developing sleeve, a maximum partial area ratio, and a difference Δ between the minimum partial area ratios.

  Hereinafter, a developing sleeve, a developing device, and an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  The image forming apparatus according to the present embodiment is a copying machine. FIG. 1 is a perspective view of a copying machine. The copying machine 1 includes a reading unit 2 that is a scanner, an image forming unit 4 housed in a housing 3, a paper feeding unit 5 that supplies paper, a control panel 6 that is operated by a user, and information. And a display panel 7 for displaying. The reading unit 2 scans a document and optically reads an image to generate image data. The image forming unit 4 transfers the toner image onto a sheet supplied from the sheet feeding unit 5 by electrophotography.

  FIG. 2 is a configuration diagram of the image forming unit 4. Of the reference numerals shown in the figure, the same elements as those described above represent the same elements. The image forming unit 4 includes a photosensitive drum 8 (photosensitive member) that is rotationally driven in the direction of arrow u. Around the photosensitive drum 8, a charging device 9 (charging device), an exposure device 10 (exposure device), a developing device 11, and a transfer device 12 (in order from upstream to downstream in the rotation direction of the photosensitive drum 8). A transfer unit), a static eliminator 13 and a cleaner 14 are provided.

  The charging device 9 uniformly charges the outer peripheral surface of the photosensitive drum 8 to a predetermined potential. The exposure apparatus 10 has a laser light source (not shown), and modulates laser light according to image data input from the reading unit 2. The exposure apparatus 10 irradiates a modulated laser beam to a non-imaged area on the outer peripheral surface of the photosensitive drum 8 to reduce the charged potential of the portion irradiated with the laser beam. An electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 8. The developing device 11 develops the electrostatic latent image by attaching a developer to the outer peripheral surface of the photosensitive drum 8. As the developer, a two-component developer composed of a toner and a carrier is used.

  The sheet is conveyed from the sheet feeding unit 5 toward a position where the photosensitive drum 8 and the transfer device 12 face each other. The transfer device 12 sandwiches the paper together with the photosensitive drum 8 to form a nip portion. In the nip portion, the transfer device 12 transfers the toner image on the photosensitive drum 8 to a sheet. The sheet on which the toner image is transferred is conveyed to a fixing device 15 provided on the downstream side in the conveyance direction. The fixing device 15 fixes the toner image on the paper by heating and pressing. The paper discharge device 16 discharges the paper on which the fixing process has been completed to the outside of the housing 3. When the transfer to the paper is completed, the charge eliminating device 13 removes the surface charge of the photosensitive drum 8. The cleaner 14 removes the toner remaining on the surface of the photosensitive drum 8. By repeating the above processing, continuous printing is performed.

  FIG. 3 is a longitudinal sectional view of the developing device 11. In the figure, the above-mentioned reference numerals represent the same elements. The direction of the arrow to the cross section is displayed differently from the example of FIG. The developing device 11 visualizes an image by applying a developer to the latent image on the photosensitive member. The developing device 11 includes a container 17 that contains the developer, and the developer 17 is provided on the outer surface of the container 17. And a magnet roller (developing roller) 18.

  The longitudinal direction of the magnet roller 18 is the axial direction. Both end portions of the magnet roller 18 in the longitudinal direction are rotatably attached to the container wall of the container 17. The longitudinal direction of the magnet roller 18 is parallel to the longitudinal direction of the photosensitive drum 8. An opening 19 is formed in the container 17 along the longitudinal direction of the photosensitive drum 8 so that the outer peripheral surface of the photosensitive drum 8 is exposed. The outer peripheral surface of the magnet roller 18 faces the opening 19.

  A wall 20 is provided in the container 17 below the magnet roller 18. The wall 20 is formed in parallel with the longitudinal direction of the magnet roller 18. The space of the container 17 is divided by the wall 20 into a first chamber 21 and a second chamber 22 in parallel along the axial direction of the photosensitive drum 8. A first auger 23 is provided in the first chamber 21. A second auger 24 is provided in the second chamber 22. Both ends in the longitudinal direction of the wall 20 are not connected to the container wall of the container 17, and the space between the wall 20 and the container wall is opened. The developer circulates in the container 17 through one opening and the other opening of the wall 20. The developer is stirred by the two augers 23 and 24, conveyed, and sent to the magnet roller 18.

  The magnet roller 18 has a developer placed on the magnet roller 18, a developer layer is formed into a uniform thin layer using a doctor blade close to the magnet roller 18, and the toner is supplied to the latent image on the photoreceptor. It is. The magnet roller 18 includes a columnar magnet 25 and a cylindrical developing sleeve 26. The magnet 25 is formed by combining five pieces each extending in the axial direction. The inner peripheral surface of the developing sleeve 26 covers the outer peripheral surface of the magnet 25. An aluminum tube is used for the developing sleeve 26. Many concave portions, which are minute depressions or grooves, are formed on the outer peripheral surface of the tube.

  The magnet 25 is fixed with respect to the container 17. The developing sleeve 26 is rotationally driven in the direction of the arrow v by a motor (not shown) provided at the end of the developing sleeve 26 in the axial direction. The developer is conveyed to the photosensitive member of the photosensitive drum 8 by the rotation. The developing sleeve 26 and the photosensitive drum 8 rotate at different peripheral speeds. The peripheral speed of the photosensitive drum 8 is in the range of 150 mm / s to 340 mm / s. The peripheral speed of the magnet roller 18 with respect to the peripheral speed of the photosensitive drum 8 is 1.7 times to 2.0 times. The magnet roller 18 rotates in the With direction with respect to the photosensitive drum 8.

  The magnet roller 18 generates a five-pole magnetic force. The development pole N1 is a pole for forming a developer image on the photoreceptor. The transport pole S <b> 1 is a pole for transporting the developer used for development into the container 17. The peeling pole N2 is a pole for peeling off the used developer from the magnet roller 18. The gripping pole N3 is a pole for gripping a new developer. The blade regulating pole S2 is a pole facing the doctor blade 27 (regulating member) that regulates the thickness of the developer layer on the outer peripheral surface of the magnet roller 18. The magnetic field around the magnet roller 18 is composed of the above five poles.

  The doctor blade 27 includes a sheet metal 28 and a magnetic blade body 29. The sheet metal 28 has substantially the same length as the developing sleeve 26. The blade body 29 is attached to one side of the sheet metal 28 on the magnet roller 18 side and has a length substantially the same as the length of the sheet metal 28. Both ends of the sheet metal 28 are fixed to the container wall of the container 17 by screws (not shown). The blade body 29 is fixed to the sheet metal 28 so that the gap between the blade body 29 and the developing sleeve 26 is constant in the axial direction of the developing sleeve 26.

  In the developing device 11, the toner and the carrier are electrostatically coupled to each other by static electricity generated by friction when the developer is stirred. The toner and the carrier electrostatically coupled to each other adhere to the developing sleeve 26 in the vicinity of the gripping pole N3 by a magnetic force acting between the gripping pole N3 and the carrier. The developer attached to the developing sleeve 26 is conveyed to the position of the blade regulating pole S2 adjacent to the gripping pole N3 by the rotation of the developing sleeve 26. The doctor blade 27 is positioned so as to face the blade regulating pole S2. After the developer is conveyed through the gap between the corner of the doctor blade 27 and the developing sleeve 26, a developer layer having a uniform thickness is formed on the outer peripheral surface of the developing sleeve 26 that passes the doctor blade 27. .

  In the developer layer, a plurality of carriers are connected along one magnetic field line to form one chain. A magnetic brush is formed when toner adheres to each carrier of a plurality of chains. The magnetic brush supplies toner to the electrostatic latent image by rotating the magnet roller 18 and the photosensitive drum 8 while the magnetic brush is in contact with the outer peripheral surface of the photosensitive drum 8.

  As the developing sleeve 26 continues to rotate, the layered developer is conveyed from the position of the blade regulating pole S2 to the position of the developing pole N1, and reaches the developing area. The development area refers to an area between the development sleeve and the photosensitive drum. The developing sleeve 26 is given a predetermined potential by a power source. In the developing area, an electric field is generated by the difference between the potential of the developing sleeve 26 and the potential on the electrostatic latent image of the photosensitive drum 8.

  Since the toner is charged, an electric force due to an electric field acts on the toner. The toner is attracted onto the electrostatic latent image on the photosensitive drum 8 by the electric force, and the electrostatic latent image is developed. The toner and carrier remaining on the developing sleeve 26 are transported from the position of the developing pole N1 to the position of the transport pole S1 by the rotation of the developing sleeve 26, and are transported to the position of the peeling pole N2. Both the peeling pole N2 and the gripping pole N3 are N poles. The peeling pole N2 and the gripping pole N3 act to cause the carrier to peel from the outer peripheral surface of the developing sleeve 26. By this force, the carrier and the toner electrostatically coupled to the carrier are peeled off from the outer peripheral surface of the developing sleeve 26 and returned to the first chamber 21.

  The pattern formed on the outer peripheral surface of the developing sleeve 26 will be further described in detail. The outer peripheral surface of the developing sleeve 26 is subjected to a surface treatment for generating a frictional resistance. By the surface treatment, the developer is held so as not to leave the outer peripheral surface of the sleeve, and a stable amount of the developer is conveyed to the development position.

  FIG. 4 is a front view of the magnet roller 18. In the figure, elements having the same reference numerals as those described above represent the same elements. A large number of minute concave holes are formed on the outer peripheral surface of the developing sleeve 26 excluding both ends of the magnet roller 18.

  In the etching process, the ink jet device discharges and prints masking ink on the surface of the aluminum tube material, solidifies the ink, and then the aluminum tube is immersed in the etching solution. Alternatively, an etching solution is applied to an aluminum tube on which an etching pattern is printed. A minute concave portion is formed by melting aluminum in a region not masked by etching. Thereafter, a process of removing ink on the surface of the aluminum tube is performed, and the developing sleeve 26 having the etching pattern shown in FIG. 5 is generated.

  FIG. 5 is a development view of the outer peripheral surface side of the developing sleeve 26, and shows a pattern of concave holes processed by etching on the outer peripheral surface. In the drawing, the horizontal direction is the longitudinal direction of the developing sleeve 26, and the vertical direction is the circumferential direction of the outer circumferential circle of the developing sleeve 26. The circumferential length is equally divided corresponding to an angle from 0 ° to 360 ° and is represented by a broken line. The minute recesses 30 are formed so as to be distributed with respect to both the axial direction and the circumferential direction of the developing sleeve 26.

  The developing sleeve 26 has a cylindrical outer peripheral surface that carries the developer and a plurality of concave holes that form a surface pattern that is not continuous in any direction on the outer peripheral surface. The phrase “not continuous in any direction” means that no continuous concave hole is provided in any of the sleeve axis direction, the direction oblique to the sleeve axis, and the sleeve circumferential direction. The developing sleeve 26 has a region where a concave hole that is not continuous in any direction is formed on the outer peripheral surface thereof.

  For example, when the diameter of the magnet roller 18 is about 23.5 mm, each minute recess 30 has a left-right dimension of 0.20 mm and a vertical dimension of 0.21 mm. In a state where the outer peripheral surface of the sleeve is expanded in the circumferential direction, each minute concave portion 30 is formed at a position surrounded by a plurality of virtually stretched dashed lines. The entire area 31 of the outer peripheral surface of the developing sleeve 26 is divided by a rectangular region having a size of about 0.20 mm in the axial direction and about 0.21 mm in the circumferential direction, and one of a plurality of squares obtained by the division. Etching is performed so that the minute recess 30 is formed in the selected grid region. A length of about 0.21 mm in the circumferential direction corresponds to an angle of 1 °.

  When 36 squares obtained by collecting 6 squares each having a size of about 0.20 mm × about 0.21 mm in the vertical direction and the horizontal direction are referred to as one basic area, The entire region 31 is divided by intersecting a plurality of axial lines (left and right thick lines) parallel to the axial direction and a plurality of circumferential lines (upper and lower thick lines) parallel to the circumferential direction, respectively. It consists of multiple basic areas. These basic regions are divided by the intersection of five axial lines (left and right broken lines) parallel to the axial direction and five circumferential lines (upper and lower broken lines) parallel to the circumferential direction. , Each consisting of a divided region having an area corresponding to one square.

  In the example of FIG. 5, minute concave portions 30 are formed at the positions of six divided regions in each basic region. The number of minute recesses 30 formed in each basic region is selected from a range of 1 to 36. Also, a flat region is left between one minute recess 30 and one minute recess 30 adjacent in the sleeve axial direction with a distance corresponding to one grid or two or more grids. A flat region is also left between one minute recess 30 and one minute recess 30 adjacent in the circumferential direction at a distance of one or two or more squares. Flat regions corresponding to the vertical and horizontal widths of the five squares in the axial direction and the circumferential direction are provided.

  6 is a cross-sectional view of the developing sleeve 26 taken along line WW in FIG. Elements having the same reference numerals as those described above represent the same elements. The groove depth of the minute recess 30 is determined by the developer transport capability and the ease of processing of the minute recess 30. The groove depth value is formed to be in the range of about 50 μm to 140 μm.

  In the present embodiment, apart from these basic regions and divided regions, a plurality of rectangular regions (regions) partitioned by upper and lower 2.1 mm * left and right 2.8 mm are determined in advance in the entire circumference 31, and one rectangular shape is obtained. For a region, the ratio (percentage value) between the area of this rectangular region and the total area of one or more minute recesses 30 formed in the same rectangular region is measured as a partial area ratio. That is, the partial area ratio of each square region is obtained by dividing the total area of the plurality of minute recesses 30 formed in each square region by the area of each square region.

  Image analysis software measures the partial area ratio of one square region. The image analysis apparatus in which this software is installed images a photograph of the outer peripheral surface of the sleeve photographed using an optical microscope, and the total area of the concave holes in which the minute concave portions 30 included in the rectangular regions in the image are present, The total area of the portion where no hole exists is obtained by image analysis processing, and the partial area ratio in one rectangular region is calculated.

  By the way, when the developing device 11 continues the developing process using the developing sleeve 26 having the pattern shown in FIG. 5 formed on the outer peripheral surface of the sleeve, when the number of printed sheets increases, the developer (toner, carrier, and carrier) on the magnet roller 18 increases. The transport amount of the mixture is reduced, and a phenomenon occurs in which uneven shading occurs periodically on the developed image.

  The present inventors examined this phenomenon in detail. Using a micrograph of a partial area ratio in a belt-like region parallel to the sleeve axis on the outer peripheral surface of the sleeve and a partial area rate in another belt-like region that is separated from the belt-like region by a predetermined distance in the circumferential direction. As a result of the comparison, the present inventors have found that these partial area ratio values vary in the circumferential direction.

  The inventors of the present invention have visually determined the images obtained by photographing each sleeve surface with a microscope with respect to the plurality of developing sleeves 26 that were etched under the same conditions, and found that the groove-shaped microscopic images on these sleeve surfaces. Neither the position of the groove edge of the concave portion 30 nor the vertical and horizontal dimensions of the minute concave portion 30 were within the numerical range of the predetermined value ± error of FIG. The dimensions of the minute recesses 30 were different between the developing sleeves 26.

  When the present inventors observed the sleeve surface of one developing sleeve 26, the opening size of the minute concave portion 30 was not constant in the circumferential direction on the sleeve surface. In the developing sleeve 26 whose surface is processed by etching, the opening size of the minute recesses 30 is not uniform in the circumferential direction of the sleeve due to the melting of the pipe material. Due to the etching residue and excessive over-etching, the minute recesses 30 having a large opening size and the minute recesses 30 having a small opening size are mixedly formed in the circumferential direction.

  In this regard, the inventors made the following examination. That is, in the etching process, ink is ejected while the ink jet device is driven to the outer peripheral surface of the sleeve of the aluminum tube material, and an ink pattern corresponding to the minute recess 30 is drawn on the outer peripheral surface.

  The cross-sectional shape of the developing sleeve 26 having the design value has a dimension as shown in FIG. 6, and each minute recess 30 includes a groove bottom and a pair of groove walls standing from both sides of the surface of the groove bottom, Each comprises a pair of groove edges continuous with the pair of groove walls. When the etching process is performed, the cross-sectional shape of the groove edge of the minute recess 30 is not a firm rectangle, and the corner of the groove edge cross section can be taken. A groove edge having a circular arc shape with a rounded tip is generated. When the arc-shaped groove edge is formed, the depth and opening size of the minute recess 30 are not uniform on the outer peripheral surface of the sleeve. The amount of the developer held by the minute recess 30 becomes non-uniform on the outer peripheral surface.

  Further, the present inventors compared the degree of denseness of the minute recesses 30 between a plurality of belt-like regions parallel to the sleeve axis on the sleeve outer peripheral surface. It has also been found that the small concave portions 30 with small opening dimensions are densely packed along the other, and in another belt-like region in the circumferential direction, the small concave portions 30 with large opening dimensions are densely packed along the sleeve axial length. On the outer peripheral surface of the sleeve, the layer thickness of the developer layer on the magnet roller 18 was non-uniform, and periodic shading unevenness occurred in the circumferential direction. This shading unevenness caused magnet roller periodic unevenness.

  The reason for this is considered that the small minute recess 30 on the surface of the sleeve cannot obtain the transport force when the magnet roller 18 transports the developer, and thus the developing layer of the magnet roller 18 becomes thin. On the other hand, since the large minute recesses 30 on the sleeve surface are easy to convey the developer, it is considered that a large developer conveying force was obtained.

  The present inventors have examined the outer peripheral surface of the sleeve with a microscope against the phenomenon that each of these opening dimensions is not uniform among the plurality of minute recesses 30 and varies when viewed in the etching pattern, that is, non-uniformity exists. After photographing, it was found that the amount of melt of the pipe material on the outer peripheral surface of the sleeve differs depending on the circumferential direction by performing photo judgment.

  Therefore, as a result of intensive studies, the inventors focused on the partial area ratio, divided the entire outer peripheral surface of each sleeve into 8 parts parallel to the sleeve axis, measured the partial area ratio in each region, and measured these partial areas. The density unevenness between the regions was observed using the rate, and the density unevenness was compared between the plurality of sleeves.

  The inventors have a sleeve partial area ratio of 20% or more, and the difference between the maximum value and the minimum value of the partial area ratio in the sleeve circumferential direction is 9% or less, so that there is no unevenness in the magnet roller cycle. We found that it was possible to obtain images. Hereinafter, this point will be described in detail with reference to FIGS.

  FIG. 7 is a perspective view of the developing sleeve 26. Each outer peripheral surface of each of the eight divided pieces 32 formed when the developing sleeve 26 is virtually divided equally into eight circumferentially by four planes including the central axis of the developing sleeve 26, respectively. The inventors measured the area ratio of each partial area. That is, each outer periphery having a cross-sectional shape of an arc between points on the circumference in a total of eight directions at angles 0, 45, 90, 135, 180, 225, 270, and 315 with respect to the origin within the cross-sectional circle of the developing sleeve 26. Each partial area ratio of the surface area was measured. As a result of the measurement, the maximum value of the partial area ratio and the minimum value of the partial area ratio were recorded for one sleeve in the circumferential direction of the outer peripheral surface of the sleeve.

  FIG. 8 is a graph showing the relationship between the minimum partial area ratio of the developing sleeve 26 and the difference Δ between the maximum partial area ratio and the minimum partial area ratio. Symbols ◯ and x shown in the graph represent values obtained by measuring each of an arbitrary number (23 in the example of the figure) of sleeves. Each symbol ◯ indicates that the developed image by the developing sleeve 26 according to the example is good. The symbol x indicates that there is an image defect in the developed image by the developing sleeve as a comparative example. The judgment of good or bad is visually.

  The minimum partial area ratio represents the minimum partial area ratio among the partial area ratios measured at eight locations in the circumferential direction. The maximum partial area ratio and the minimum partial area ratio are respectively the largest and smallest percentage values of the eight partial area ratios in the circumferential direction. For example, a difference Δ of 2 (%) means that a value obtained by subtracting the minimum partial area ratio 18 (%) of the same sleeve from the maximum partial area ratio 20 (%) of one sleeve is 2 (%). To express.

  The evaluation machines and methods used to measure the partial area ratios of the developing sleeve 26 according to the example and the developing sleeve as a comparative example are the same between these sleeves. The aluminum tube was etched with a plurality of types of etching patterns having different partial area ratios to prepare a plurality of sleeves. One sleeve was set in the optical microscope.

  Any one of the eight sleeve outer peripheral surface regions was photographed. The image analysis apparatus performed image analysis processing, selected three rectangular areas of 2.1 mm * 2.8 mm in the axial direction, and measured partial area ratios of these rectangular areas. The same sleeve was rotated 45 ° in the circumferential direction, a photograph was taken, and the partial area ratio was measured. The rotation of 45 °, taking pictures, and acquiring the partial area ratio were repeated until data of 8 regions were obtained.

  The positions of the three rectangular regions for sampling the partial area ratio were selected within the dot pattern region that was etched on the outer peripheral surface of the sleeve, and were set at the same position among all the sleeves. The sleeve was removed from the optical microscope and incorporated in the developing device 11, and the developing device 11 was subjected to a developing operation to generate an image (developed image). The presence or absence of shading unevenness in the image was determined visually. This operation was repeated by changing the minimum partial area ratio, the maximum partial area ratio in the circumferential direction, and the difference Δ between the minimum partial area ratio and changing the sleeve while examining.

  As shown in FIG. 8, when developing processing was performed using the developing sleeve 26 represented by each ◯, no magnet roller cycle unevenness occurred in the image. When the developing sleeve represented by each x was used, magnet roller periodic unevenness occurred in the image. Magnet roller cycle unevenness occurred in a region where the partial area ratio of the recessed holes was 20% or less. Further, the developing sleeve having a value in which the difference Δ is in the range of 9% or more had a magnet roller cycle unevenness as indicated by x.

  Therefore, the present inventors measured a plurality of developing sleeves having a value with a minimum partial area ratio of 20% or more and a difference Δ in a range of 9% or less. As shown in the figure, the magnet roller cycle unevenness did not occur, and a remarkable effect that a good image could be obtained was confirmed.

  Here, in adopting a developing sleeve having a minimum partial area ratio of 20% or more and a difference Δ of 9% or less, the partial area ratio is 3 in the axial direction and 8 in the circumferential direction, for a total of 3 *. 8 = 24 photographs were taken, and each of them had a partial area ratio of 20% or more and a difference Δ of 9% or less.

  Further, in the developing sleeve having a value in which the minimum partial area ratio falls within the range of 20% or less, a light and shaded region of the image is generated, and a portion where concave holes having small opening dimensions are densely formed. This is because the developing sleeve in which the minimum partial area ratio of the area where the concave holes are dense is within a numerical range of 15% to 16% does not convey the developer, the developer layer is thin, and the conveyance unevenness It is thought that this was caused. If the minimum partial area ratio is too small, the developer cannot be carried and conveyed. For this reason, it is considered that the minimum partial area ratio needs to be 20% or more.

  In the developing sleeve having the minimum partial area ratio in the range of 20% or more and the difference Δ within the range of 10% or more, no conveyance unevenness occurred. For example, in a developing sleeve having a minimum partial area ratio of 15%, it is considered that 15% of the developer out of the developer required for image generation is lost.

  When the test was performed and the magnet roller was observed, the developer did not adhere to the outer peripheral surface, and the image had white spots. If the developing sleeve has a minimum partial area ratio of 20% or more, the developer is sufficiently adhered on the magnet roller, so that white spots do not occur. As described above, it is considered that in the developing sleeve whose minimum partial area ratio falls within the range of 20% or less, the amount of developer transported is small, the photosensitive member cannot be sufficiently developed, and the developer transport force is weakened.

  Further, in the developing sleeve having a value in which the difference Δ is in the range of 9% or more, a dark region and a thin region of the developer were observed as stepped unevenness in the magnet roller period. This is because the difference between the darkness of the axial strip region including the square region where the maximum partial area ratio is measured and the darkness of the axial strip region including the square region where the minimum partial area ratio is measured is too large. It is thought that.

  A test was conducted with a developing sleeve having a value within a range where the minimum partial area ratio was 20% or more and the difference Δ was 10.5% or more. The thin part appeared clearly in the magnet roller cycle. This difference in shading was so conspicuous that it could not be put into practical use as an image. In this way, as a result of continuing the visual determination, an image in which the difference in light and shade was inconspicuous was obtained with the developing sleeve in which the difference Δ was in the range of 9% or less.

  A developing sleeve having a value with a minimum partial area ratio in the range of 20% or more will be described. In the present embodiment, the minimum partial area ratio is in the range of 20% to 40% so that the doctor sleeve gap, which is the gap between the doctor blade 27 (FIG. 3) and the developing sleeve 26, is 0.50 mm or more. A developing sleeve is used. When the developing device 11 is operated in a state where the doctor sleeve gap is too narrow in the developing device 11, clogging due to dust or the like occurs between the doctor blade 27 and the developing sleeve 26, and this clogging is developed. It appears as white streaks in the image.

  The inventors set a developing sleeve having a value in a range where the minimum partial area ratio is 20% or more in the developing device 11, and changed the doctor sleeve gap value to a plurality of different values to perform a test for operating the developing device 11. When done, the doctor sleeve gap was 0.50 mm, which was large enough to prevent clogging.

  In the above description, the minimum number of divisions of the entire area on the outer peripheral surface is 1/8 of the entire circumference along the circumferential direction. The reason for selecting 1/8 of the entire circumference is that when the area width in the circumferential direction of the band-like area is wide when measuring the partial area ratio, the degree of variation in the circumferential direction cannot be collected. The minimum number of divisions is smaller than 1/8 or 1/8 of the entire circumference, for example, 1/16 division, etc., and by measuring the partial area ratio in each divided region, the degree of variation in the circumferential direction is more faithful Can be reproduced.

  Thus, according to the magnet roller, the developing device, and the image forming apparatus according to the present embodiment, the minimum partial area ratio of the developing sleeve 26 is 20% or more, and the maximum and minimum partial area ratios in the sleeve circumferential direction. By setting the difference Δ to 9% or less, an image having no magnet roller cycle unevenness can be achieved.

  On the other hand, as shown in FIG. 8, in a region where the partial area ratio of the magnet roller 18 is 20% or less, as the number of printed sheets advances, the developer transport amount on the magnet roller 18 decreases, and the magnet on the image Unevenness of roller cycle occurs. Further, if the difference between the maximum and the minimum of the variation in the partial area ratio in the circumferential direction exceeds 9%, the difference in the conveyance amount of the developer on the magnet roller 18 in the circumferential direction becomes large, and the portion where the conveyance amount is large. And unevenness occurs in the magnet roller periodic image image.

  Therefore, a remarkable effect can be obtained by setting the minimum partial area ratio of the developing sleeve 26 to 20% or more and the difference Δ to 9% or less.

  Further, in the developing sleeve 26 having a value in the range where the minimum partial area ratio is 20% or more, by adjusting the doctor sleeve gap of the developing device 11 to 0.50 mm or more, there is no magnet roller cycle unevenness and the gap is narrow. An image without clogging caused by too much is achieved. Further, in measuring the partial area ratio, the circumferential unevenness is measured by dividing the entire area on the outer peripheral surface of the sleeve by a value smaller than 1/8 or 1/8 in the circumferential direction. By setting the partial area ratio difference Δ within the predetermined range, an image free from magnet roller cycle unevenness can be achieved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  The size of the square area of the partial area ratio can be variously changed. In the above embodiment, the positions of the three rectangular regions for collecting the partial area ratio are set to the same position among all the sleeves, but the positions of the rectangular regions may be any desired positions. You may extract | collect a partial area rate from three or more square area | regions about one sleeve. The superiority of the present invention over the invention carried out merely by making these changes is not impaired.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. The developing device and the image forming apparatus according to the embodiment of the present invention are used in a copier, a printer, a FAX, a scanner, a digital multifunction peripheral, and the like.

  DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 2 ... Reading part, 3 ... Housing | casing, 4 ... Image forming part, 5 ... Paper feed part, 6 ... Control panel, 7 ... Display panel, 8 ... Photosensitive drum (photosensitive body) ), 9 ... Charging device (charger), 10 ... Exposure device (exposure device), 11 ... Developing device, 12 ... Transfer device, 13 ... Charging device, 14 ... Cleaner, 15 ... Fixing device, 16 ... Discharge device, 17 ... container, 18 ... magnet roller, 19 ... opening, 20 ... wall, 21, 22 ... chamber, 23, 24 ... auger, 25 ... magnet, 26 ... developing sleeve (sleeve), 27 ... doctor blade (regulating member) , 28 ... sheet metal, 29 ... blade body, 30 ... minute recesses (recesses), 31 ... whole area, 32 ... divided pieces.

Claims (6)

A cylindrical outer peripheral surface carrying a developer, and a sleeve having a plurality of concave holes each forming a surface pattern that is not continuous in any direction on the outer peripheral surface;
A magnet provided in the sleeve and having a plurality of magnetic poles,
A plurality of parts obtained by dividing the outer peripheral surface of the sleeve into a plurality of regions parallel to the sleeve axis and dividing the total area of the plurality of concave holes formed in each region by the area of each region A magnet roller having a minimum partial area ratio of about 20% or more. A cylindrical outer peripheral surface carrying a developer, and a sleeve having a plurality of concave holes each forming a surface pattern that is not continuous in any direction on the outer peripheral surface;
A magnet provided in the sleeve and having a plurality of magnetic poles,
A plurality of parts obtained by dividing the outer peripheral surface of the sleeve into a plurality of regions parallel to the sleeve axis and dividing the total area of the plurality of concave holes formed in each region by the area of each region The difference between the maximum partial area ratio and the minimum partial area ratio among the partial area ratios is about 9% or less.   The magnet roller according to claim 1 or 2, wherein a gap between the sleeve and the regulating member is about 0.50 mm or more.   3. The division of the outer peripheral surface into the plurality of regions is equal division into eight equal parts or smaller than eight equal parts in the sleeve circumferential direction over the entire outer peripheral surface. Magnet roller. A container for containing a developer;
A cylindrical outer peripheral surface provided in the container and carrying a developer, and a sleeve having a plurality of concave holes each forming a surface pattern that is not continuous in any direction on the outer peripheral surface;
A magnet provided in the sleeve and having a plurality of magnetic poles;
A regulating member that is disposed to face the sleeve and regulates the thickness of the developer layer on the outer peripheral surface;
A plurality of parts obtained by dividing the outer peripheral surface of the sleeve into a plurality of regions parallel to the sleeve axis and dividing the total area of the plurality of concave holes formed in each region by the area of each region The minimum partial area ratio of the partial area ratio is about 20% or more. A photoreceptor,
A charger for charging the surface of the photoreceptor;
An exposure device that exposes the photoreceptor to form a latent image on the photoreceptor;
A container having an opening facing the photoreceptor and containing a developer;
A sleeve having a cylindrical outer peripheral surface which is provided in the container so as to face the photoconductor and carries a developer, and a plurality of concave holes each forming a surface pattern which is not continuous in any direction on the outer peripheral surface. When,
A magnet provided in the sleeve and having a plurality of magnetic poles;
A regulating member that is disposed to face the sleeve and regulates the thickness of the developer layer on the outer peripheral surface;
A transfer unit that transfers the toner image attached to the latent image on the photosensitive member to a sheet by transporting the developer by the sleeve; and
A plurality of parts obtained by dividing the outer peripheral surface of the sleeve into a plurality of regions parallel to the sleeve axis and dividing the total area of the plurality of concave holes formed in each region by the area of each region An image forming apparatus having a minimum partial area ratio of about 20% or more.

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