JP2006071729A - Magnet roller, method for manufacturing magnet roller, mold for manufacturing magnet roller, magnet roller unit, developer carrier, developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet block advantageous of preventing the occurrence of rear-end void in an image obtained by a development process. <P>SOLUTION: Upon magnetizing an accommodation groove 32a formed in the peripheral part of a magnet roller 32, which corresponds to the developing pole P1 of the magnet roller 40, the width-direction middle section of the bottom face 32b of the accommodation groove 32a is magnetized at higher degree than both its ends. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus that develops an electrostatic latent image with a two-component developer, such as a copying machine, a facsimile machine, and a printer, a developing device and a process cartridge that are used in the developing process of the image forming apparatus, and , A developer carrier used to form a magnetic brush in a developing device or a process cartridge, a magnet roller unit used for the developer carrier, and a magnet roller included in the magnet roller unit and its manufacture The present invention relates to a method and a mold used for manufacturing a magnet roller.

  In the field of an electrophotographic image forming apparatus that develops an electrostatic latent image with a two-component developer composed of toner and a carrier, a magnetic brush developing method that has been widely used in the past is a development roller (developer carrier). A magnetic brush is formed by pumping up a developer on a developing sleeve and making it stand up. Also, the carrier after the toner is supplied from the magnetic brush to an image carrier such as a photosensitive drum carrying an electrostatic latent image is collected. For this purpose, a plurality of magnetic poles are provided on the magnet roller in the developing sleeve.

  By the way, the applicant of the present invention once the toner once supplied to the image carrier moves back to the carrier on the developing sleeve again, and white spots due to insufficient toner adhesion on the development end side of the image, so-called “rear end white spots”. However, a technique (hereinafter referred to as “SLIC developing device” for the sake of convenience) useful for preventing the occurrence of such “rear end white spot” is noted. JP-A-2000-305360 has already proposed.

  In this SLIC developing apparatus, an auxiliary magnetic pole is arranged in the vicinity of the magnetic pole portion corresponding to the developing area (the area where the toner moves relative to the image carrier), that is, the developing pole, and the developer spike on the developing sleeve. It is necessary to reduce the standing width, thereby uniformly shortening the magnetic brush formed on the developing pole, and forming the magnetic brush densely on the developing sleeve.

  For this purpose, in the magnetic pole portion corresponding to the developing region, in order to make the angle between the adjacent magnetic poles narrower than before, the half width of the developing pole is made narrower than before, and the magnetic flux density at the developing pole is increased. Although it is necessary to make it higher than in the past, a ferrite magnet that has been generally used as a material for the magnet roller cannot obtain sufficient magnetic properties.

  To make the half width of the developing pole narrower than before and to increase the magnetic flux density at the developing pole higher than before, it extends in the direction of the central axis of the magnet roller on the outer peripheral surface portion corresponding to the developing pole of the magnet roller. It is conceivable to form a storage groove and embed a magnet block, which is formed as a long member, in the storage groove. Such a proposal has already been made in Japanese Patent Application Laid-Open No. 8-334983.

Further, although not a storage groove for a magnet block, as an object for forming a plurality of magnetic flux density peaks having the same magnetic polarity on the developing pole, Japanese Patent Laid-Open No. 2001-274015 also discloses an outer periphery corresponding to the developing pole of the magnet roller. A technique for forming a groove extending in the central axis direction of the magnet roller in the surface portion has been proposed.
JP 2000-305360 A JP-A-8-334983 JP 2001-274015 A

  By the way, it is known that the magnet has a property (edge effect) that the magnetic flux density is increased because the magnetic flux is concentrated in the portion with the unevenness than the portion without the unevenness. When the storage groove for embedding the block is formed, in the width direction of the bottom surface of the storage groove extending along the circumferential direction of the magnet roller, the magnetic flux concentrates at both end portions and the magnetic flux density becomes higher than the intermediate portion.

  Then, the magnetic flux density distribution of the magnet roller embedded in the storage groove reaches the peak in the width direction of the bottom surface of the storage groove, and the magnetic flux density of the magnet roller is higher than that of both end portions in the width direction of the bottom surface of the storage groove. Therefore, the magnetic flux density distribution of the developing pole, which is the sum of the magnetic flux density of the storage groove portion of the magnet roller and the magnetic flux density of the magnet block, has a peak value that reaches the middle portion in the width direction of the bottom surface of the storage groove. It will be small.

  In addition, the magnetic flux density of the developing pole at the both end portions in the width direction of the bottom surface of the storage groove is increased by the amount of magnetic flux density at the both end portions in the storage groove portion of the magnet roller as compared with the intermediate portion in the width direction of the bottom surface of the storage groove. Since the distribution has a value that is not so different from the magnetic flux density distribution of the developing pole in the middle portion in the width direction of the bottom surface of the storage groove, the half width of the developing pole cannot be made sufficiently narrow.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic device using a developing device having a magnet roller unit in which a long magnet block is arranged on an outer peripheral surface portion of a magnet roller corresponding to a magnetic pole portion. A magnet block that is advantageous for preventing the occurrence of white-out at the trailing edge in an image obtained by the development process in an electrostatic latent image development process in photographic image formation, and a method for producing the magnet roller An object of the present invention is to provide a magnet roller manufacturing mold suitable for use in this manufacturing method, a magnet roller unit using this magnet block, a developer carrier, a developing device, a process cartridge, and an image forming apparatus.

  The present invention according to claim 1 that achieves the above object relates to a magnet block, and the present invention according to claim 2 and claim 3 relates to a method of manufacturing a magnet roller, and claims 4 and 5. The present invention relates to a magnet block, the present invention according to claim 6 relates to a magnet roller unit, claim 7 relates to a developer carrier, and the present invention according to claim 8 relates to a developing device. The present invention according to claim 9 relates to a process cartridge, and the present invention according to claim 10 relates to an image forming apparatus.

  The magnet block according to the first aspect of the present invention is formed in a cylindrical shape by a material in which magnetic powder is mixed with a resin, and is elongated along the central axis direction on the outer peripheral surface portion corresponding to the magnetic pole portion. In the magnet roller in which a long storage groove for arranging the magnet block is formed, the magnetic powder in the material constituting the intermediate portion in the width direction orthogonal to the longitudinal direction of the bottom surface of the storage groove is the bottom surface. Is magnetized with a magnetic amount higher than that of the magnetic powder in the material constituting both end portions in the width direction.

  According to a second aspect of the present invention, there is provided a method for producing the magnet roller of the present invention, wherein the magnet roller according to the first aspect is molded by a mold, and the magnet roller is provided inside the mold. When the material is injected into the space corresponding to the shape of the magnet roller and the magnet roller is molded, a high magnetic force is disposed in the mold with the magnetic pole surface facing the space portion corresponding to the intermediate portion of the bottom surface. The magnet causes the magnetic powder in the material constituting the intermediate portion of the bottom surface to be magnetized with a magnetic amount higher than the magnetic amount of the magnetic powder in the material constituting the both end portions of the bottom surface. It is characterized by that.

  Furthermore, the manufacturing method of the magnet roller of the present invention described in claim 3 is the method of manufacturing the magnet roller of the present invention described in claim 2, wherein the mold that projects into the space and molds the storage groove is provided. The magnetic path formed by the magnetic material disposed inside the convex portion of the magnetic field causes magnetic lines of force from the magnetic pole surface of the high magnetic force magnet disposed outside the convex portion in the mold to be in the middle of the bottom surface. Guided to the space part corresponding to the part.

  A magnet roller manufacturing mold according to a fourth aspect of the present invention is a mold having a space corresponding to the magnet roller used for manufacturing the magnet roller according to the first aspect. And magnetizing the magnetic powder in the material constituting the intermediate portion of the bottom surface with a magnetic amount higher than the magnetic amount of the magnetic powder in the material constituting the both end portions of the bottom surface. The high magnetic force magnet is arranged with a magnetic pole face facing a space portion corresponding to the intermediate portion of the bottom surface.

  Furthermore, the magnet roller manufacturing mold of the present invention described in claim 5 is the magnet roller manufacturing mold of the present invention described in claim 4, wherein the mold protrudes inside the space and is stored. A convex portion for forming a groove, and the high magnetic force magnet is disposed outside the convex portion, and a space portion corresponding to the intermediate portion of the bottom surface and the high magnetic force are disposed inside the convex portion. It is assumed that a magnetic body constituting a magnetic path with the magnet is disposed.

  The magnet unit of the present invention described in claim 6 is formed in a cylindrical shape from a material in which magnetic powder and resin are mixed, and is elongated along the central axis direction on the outer peripheral surface portion corresponding to the magnetic pole portion. A magnet roller unit including a magnet roller in which a storage groove is formed, and a long magnet block having a magnetic force higher than the magnetic force of the magnet roller and disposed in the storage groove, The magnet roller according to claim 1 is used.

  Furthermore, the developer carrying member of the present invention described in claim 7 is characterized in that a rotatable nonmagnetic cylindrical body is disposed on the outer periphery of the magnet roller unit described in claim 6.

  Further, the developing device of the present invention described in claim 8 is a developing device having at least a developer carrier, a developer supply member, and a developer layer regulating member. The developer carrying member described above is provided.

  Furthermore, the process cartridge of the present invention described in claim 9 includes a developer carrier, a developer supply member, a developing device having at least a developer layer regulating member, and a process cartridge having a charging roller and an image carrier. The developing device includes the developing device according to claim 8.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus according to the present invention, wherein the process cartridge is a process cartridge in an image forming apparatus having at least a process cartridge, an optical writing unit, a transfer member, and a fixing device. It is characterized by having.

  According to the magnet roller of the present invention described in claim 1, since the magnetic powder is magnetized with a magnetic amount higher than the both end portions in the intermediate portion in the width direction of the bottom surface of the storage groove, it is affected by the edge effect. Contrary to the magnetic flux density distribution due to the shape of the storage groove where the magnetic flux density is higher at both end portions in the width direction than the intermediate portion, the magnetic flux density of the storage groove portion of the magnet block due to the magnetic amount of the magnetic powder is The both end portions are lower than the intermediate portion in the width direction of the storage groove.

  Therefore, the width direction of the storage groove of the storage groove part due to the shape of the storage groove of the magnet roller used by arranging a long magnet block in the storage groove provided in the outer peripheral surface part corresponding to the magnetic pole part The magnetic flux density distribution in the magnet roller is mitigated or offset by the variation in the magnetic flux density in the width direction of the storage groove due to the magnetic amount of the magnetic powder. Accordingly, it is possible to obtain a magnet roller that is advantageous in preventing the occurrence of white-out at the rear end in the development process of the electrostatic latent image in electrophotographic image formation.

  According to the magnet roller manufacturing method of the present invention described in claim 2 and the magnet roller manufacturing mold of the present invention described in claim 4, the relative position of the high magnetic force magnet with respect to the space of the mold is the mold. When the magnet roller according to claim 1 is molded by injecting a material in which magnetic powder is mixed with resin into the space, it corresponds to an intermediate portion in the width direction of the bottom surface of the storage groove. The magnetic part of the high magnetic force magnet is made to face the space part securely, and the magnetic powder in the middle part in the width direction of the bottom surface of the storage groove is surely magnetized with a higher magnetic amount than the magnetic powder on both end parts. It is possible to stably obtain a magnet roller that is advantageous in preventing the occurrence of white-out at the rear end in the development process of the electrostatic latent image in the image formation of the system.

  Furthermore, according to the manufacturing method of the magnet roller of the present invention described in claim 3 and the magnet roller manufacturing mold of the present invention described in claim 5, the manufacturing method of the magnet roller of the present invention described in claim 2 In addition to the operational effects of the magnet roller manufacturing mold according to the present invention as set forth in claim 4, the high magnetic force magnet is a mold for forming a storage groove on the outer peripheral surface of the magnet roller in relation to the magnetic force required for the magnet. If it must be of a shape that cannot be placed inside the convex portion of the mold, the magnetic field lines that are led from the magnetic pole surface of the high magnetic force magnet arranged outside the convex portion to the intermediate portion in the width direction of the bottom surface of the storage groove are: It will pass through the convex part.

  In this case, compared to the case where the magnetic path is formed by the convex portion itself, the magnetic material is arranged inside the convex portion and this is used as the magnetic path. Therefore, the magnetization of the magnetic powder in the intermediate portion can be more efficiently performed with a magnetic amount higher than that of both end portions in the width direction.

  Incidentally, the “space” in claims 2 to 5 refers to a cavity in the case of a mold for injection molding, for example, and refers to a die die in the case of a mold for extrusion molding.

  In addition, according to the magnet roller unit of this invention described in Claim 6, the above-mentioned operation | movement and effect about the magnet block of this invention described in Claim 1 can be acquired similarly.

  Further, according to the developer carrying member of the present invention described in claim 7, the operation and effect exhibited by the magnet roller unit in each claim described above for the magnet roller unit of the present invention described in claim 6 are provided. Can be obtained as well.

  Further, according to the developing device of the present invention described in claim 8, the above-described actions and effects can be similarly obtained with respect to the developer carrying member of the present invention described in claim 7.

  Further, according to the process cartridge of the present invention described in claim 9, the above-described operation and effect can be similarly obtained with respect to the developing device of the present invention described in claim 8.

  Furthermore, according to the image forming apparatus of the present invention described in claim 10, the above-described operations and effects can be obtained in the same manner as the process cartridge of the present invention described in claim 9.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus of this embodiment indicated by reference numeral 80 in FIG. An electrophotographic system that develops an electrostatic latent image with a two-component developer, and includes at least an optical writing unit 103, a transfer member 105, a fixing device 117, and a process cartridge 70 according to an embodiment of the present invention. .

  The process cartridge 70 includes a charging roller 44, an image carrier 45, and a developing device 60, as shown in an explanatory diagram of a schematic configuration in FIG. 2, and the developing device 60 is schematically configured in FIG. As shown in the explanatory diagram, at least a developer carrier 43, a developer supply member 41, and a developer layer regulating member 42 are provided.

  The developer carrier 43 includes a magnet roller unit 40 and a rotatable nonmagnetic cylindrical body 34 disposed concentrically on the outer periphery thereof, as shown in a sectional view in the direction of the central axis in FIG. . As the nonmagnetic cylindrical body 34, for example, aluminum, SUS (stainless steel), or the like can be used. Aluminum is often used in terms of workability and lightness. In the case of aluminum, A6063, A5056, A3003, etc., and in the case of SUS, 303, 304, 316, etc. can be used.

  Next, the magnet roller unit according to the first embodiment of the present invention used as the magnet roller unit 40 of the developer carrier 43, the magnet roller according to the first embodiment of the present invention used for the magnet roller unit 40, and The mold according to the first embodiment of the present invention used for manufacturing the magnet roller according to the first embodiment will be described with reference to FIGS.

  FIG. 5 is a perspective view showing a schematic configuration of the magnet roller unit according to the first embodiment of the present invention used for the developer carrier 43, and the magnet roller of the first embodiment indicated by reference numeral 40 in FIG. The unit includes a cylindrical magnet roller 32 and a magnet block 33 according to the first embodiment of the present invention, which is embedded in a storage groove 32a as a groove-shaped storage portion formed on the peripheral surface of the magnet roller 32. Have.

  Since the magnet block 33 needs to achieve a high magnetic force in a smaller volume than the magnet roller 32, it is desirable to use a material of Br> 0.5T, and many of them are Ne-based (Ne-Fe-B or the like). Alternatively, Sm-based (Sm—Co, Sm—Fe—N, etc.) rare earth magnets or plastic magnets or rubber magnets obtained by mixing these magnet powders with polymer compounds can be used. In addition, rare earth magnet powders include isotropic and anisotropic magnet powders, and anisotropic magnet powders can provide higher magnetic force, but whichever type is used depending on the desired magnetic properties. It doesn't matter.

  Then, the long magnet block 33 is formed by sintering, extrusion molding / injection molding, or in-mold compression molding of magnetic powder and binder.

  The magnetic flux density in the width direction extending along the circumferential direction of the magnet roller 32 in the state where the magnet block 33 formed as described above is embedded in the storage groove 32a is formed by molding the magnet roller 32 with a non-magnetic material. As shown schematically in FIG. 6, the intermediate portion in the width direction has the highest peak, and the distribution in the width direction that is the boundary with the magnet roller 32 is the lowest.

  The magnet roller 32 is made of, for example, a material made of a plastic magnet or a rubber magnet in which a magnet powder (corresponding to the magnetic powder in the claims) is dispersed in a polymer compound, and extrusion molding / injection molding while applying an orientation magnetic field to the mold. Alternatively, a magnet roller having a shape corresponding to the shape of the magnet block 33 shown in FIG. 6 is formed on the peripheral surface portion of the magnet roller unit 40 that becomes the developing pole P1 by in-mold compression molding of magnetic powder and a binder. FIG. 7 is an explanatory view of the magnetic flux density distribution of the magnet roller unit 40 in the normal direction (radial direction) of the magnet roller 32. The storage groove 32a extends along the direction of the central axis 31 of the magnet roller 32. Thus, the seven magnetic poles P2 to P8 other than the developing pole P1 of the magnet roller unit 40 are connected to the magnet roller. It is formed having the desired circumferential surface position 2.

  The magnetic pole P4 is a magnetic pole for pumping the two-component developer onto the nonmagnetic cylindrical body 34, and the magnetic poles P5 to P8 are for transporting the two-component developer pumped onto the nonmagnetic cylindrical body 34 to the development area (developing pole P1). The magnetic poles P2 and P3 are magnetic poles for collecting and transporting the two-component developer in the developed region.

  Sr ferrite or Ba ferrite is used as the magnet powder that is the material of the magnet roller 32, and PA (polyamide) material such as 6PA or 12PA is used as the polymer compound, EEA (ethylene-ethyl copolymer) or EVA (ethylene-ethylene copolymer). An ethylene compound such as a vinyl copolymer), a chlorine material such as CPE (chlorinated polyethylene), or a rubber material such as NBR can be used.

  By the way, in the magnet roller 32 formed of the above-mentioned material, originally, the magnetic flux is concentrated in the uneven portion than the non-protruded portion. As a result, as shown by the broken line in FIG. 7, the magnetic flux density distribution of the developing roller P1 corresponding to the storage groove 32a along the circumferential direction of the magnet roller 32 alone is the magnetic flux density distribution of the bottom surface 32b of the storage groove 32a. This shows a distribution variation in which both end portions are higher than intermediate portions in the width direction.

  Therefore, in order to prevent the magnetic flux density distribution in the width direction of the bottom surface 32b of the storage groove 32a from varying, the mold according to the first embodiment of the present invention used for manufacturing the magnet roller 32 made of the above material is used. This will be described with reference to the schematic sectional view of FIG.

  The mold of the first embodiment indicated by reference numeral 90A in FIG. 8 is for manufacturing the magnet roller 32 by extrusion molding, and a die 91 formed of a non-magnetic material and a cylinder portion behind the die 91 (not shown). And a base 92 formed in an annular shape for forming a hole for fitting the central shaft 31 in the central portion.

  In order to form the storage groove 32a on the outer peripheral surface portion of the magnet roller 32 corresponding to the developing pole P1 of the magnet roller 32, the storage groove 32a is formed on the outer peripheral surface portion of the magnet roller 32 corresponding to the developing electrode P1. A convex portion 93 having a shape corresponding to the shape of the storage groove 32 a in a cross section orthogonal to the central axis 31 is formed so as to protrude inside the base 92.

Further, inside the die 91, as shown in FIG. 7, on the outer peripheral surface portion of the magnet roller 32 corresponding to each of the magnetic poles P 1, P 2, P 4 to P 8 except for the magnetic pole P 3 having almost no magnetic flux density distribution, FIG. As shown in FIG. 2, in order to give the magnetic flux density required for each of the magnetic poles P1, P2, P4 to P8, for example, a high magnetizing force composed of a rare earth magnet block of Nd (neodymium) or Sm (samarium) is used. The magnetic magnets 94 ₁ , 94 ₂ , 94 _{4 to} 94 ₈ have magnetic pole faces 95 ₁ , 95 ₂ , 95 _{4 to} 95 ₈ opposite to the magnetic poles provided to the magnetic poles P 1, P 2, P 4 to P _8, and the center of the base 92. It is arranged and buried facing.

The magnetic pole surfaces 95 ₂ and 95 _{4 to} 95 ₈ of the high magnetic force magnets 94 ₂ and 94 _{4 to} 94 ₈ for magnetizing the magnetic poles P 2, P 4 to P ₈ are all close to the corresponding outer peripheral surface portions of the base 92. are disposed each pole faces 95 ₁ of the high magnetic force magnet 94 ₁ of magnetizing the developing pole P1 is an amount corresponding to the convex portion 93 is present, other high magnetic force magnet 94 _2, 94 ₄ to 94 The distance to the corresponding outer peripheral surface portion of the base 92 is greater than the _eight magnetic pole surfaces 95 ₂ , 95 _{4 to} 95 ₈ .

Therefore, the mold 90A of the first embodiment, disposed high magnetic force magnet 94 ₁ of magnetizing the developing pole P1 on the outside portion of the convex portion 93 of the die 91, without restrictions on the dimensions embedded to its Instead, from a magnetic material having a high magnetic permeability so as to constitute a magnetic path that passes a magnetic field line connecting the magnetic pole surface 95 ₁ of the high magnetic force magnet 94 ₁ and the outer peripheral surface portion corresponding to the development pole P ₁ of the base 92. A block 96 (corresponding to a magnetic body in the claims) is arranged and embedded in the inner portion of the convex portion 93 of the die 91.

As shown by the enlarged sectional view of FIG. 9, one end face 96a of the block 96 is close to the pole faces 95 ₁ of the high magnetic force magnet 94 _1, it is arranged opposite the end face 96a and directly faces the The other end face 96b of the block 96 is similar to the magnetic pole faces 95 ₂ and 95 _{4 to} 95 ₈ of the high magnetic force magnets 94 ₂ and 94 _{4 to} 94 ₈ for magnetizing the magnetic poles P2, P4 to P8. Corresponding outer peripheral surface locations, that is, close to the tip surface 93a of the convex portion 93 corresponding to the bottom surface 32b of the storage groove 32a of the magnet roller 32, correspond to the width direction of the bottom surface 32b of the storage groove 32a. It faces the middle part in the width direction of the front end surface 93a.

  Incidentally, the die 91 shown in FIG. 8 is usually configured, for example, with a portion for molding a hole for inserting the central shaft 31 of the magnet roller 32 in the central portion as a core of another member. However, since how it is specifically configured is irrelevant to the essence of the present invention, in FIG. 8, the die 91 is hatched as a single member for the sake of simplicity.

In the mold 90A of the first embodiment configured as described above, when the material supplied from the cylinder portion (not shown) is pushed out from the base 92 of the die 91 and solidified and cut by an appropriate length, the storage groove 32a is formed. At the same time as the magnet roller 32 on the outer peripheral surface is molded, there is almost no magnetic flux density distribution due to the orientation magnetic field applied by the high magnetic force magnets 94 ₁ , 94 ₂ , 94 _{4 to} 94 ₈ when the base 92 passes. Except for the magnetic pole P3, the outer peripheral surface portion of the magnet roller 32 corresponding to the magnetic poles P1, P2, P4 to P8 is magnetized, and the magnetic flux density distribution as shown in FIG. It occurs in each outer peripheral surface portion of the magnet roller 32 corresponding to P8.

And in particular the magnet powder in the material of the receiving groove 32a portion of the magnet roller 32 corresponding to the developing pole P1 is when it passes through the die 92, from the pole face 95 ₁ of the corresponding high magnetic force magnet 94 ₁ of the mold 90A The housing groove 32a of the magnet roller 32 passing through the block 96 constituting the magnetic path and passing through the tip end surface 93a of the convex portion 93 opposed to the other end surface 96b of the block 96 or the base 92 facing the same. Is magnetized with a magnetic amount corresponding to the magnetic force of the high magnetic force magnet 94 ₁ by the action of the magnetic field lines guided to the bottom surface 32b of the magnetic field.

At this time, close to the pole faces 95 ₁ of the high magnetic force magnet 94 _1, opposed to being arranged one end face 96a of the block 96, the other end face 96b of the end surface 96a and directly opposite the block 96 in this one is convex Since it faces the intermediate portion in the width direction of the tip end surface 93a of the portion 93, the strength of the magnetic force due to the magnetic lines from the magnetic pole surface 95 ₁ of the high magnetic force magnet 94 ₁ passing through the block 96 is the convex portion of the mold 90A. An intermediate portion in the width direction on the tip end surface 93a of 93, or an intermediate portion in the width direction on the bottom surface 32b of the storage groove 32a of the magnet roller 32 passing through the base 92 is strongest.

  Therefore, the magnet powder in the material of the storage groove 32a portion of the magnet roller 32 corresponding to the development pole P1 is magnetized with a stronger magnetic quantity at the intermediate portion in the width direction of the bottom surface 32b of the storage groove 32a than at both end portions in the width direction. Is done.

For this reason, as described above, due to the edge effect peculiar to the magnet, it should show a variation in distribution in which both end portions are higher than the intermediate portion in the width direction of the bottom surface 32b of the storage groove 32a. magnetic that the magnetic flux density of the receiving groove 32a portion corresponding to the developing pole P1 is when magnetized by high magnetic force magnet 94 _1, towards the middle portion is higher than both end portions in the width direction of the bottom surface 32b of the receiving grooves 32a It is canceled out by the variation in the amount distribution, and the same intensity distribution is obtained in any part in the width direction of the bottom surface 32b.

  As shown in FIG. 5, the magnet block 33 having the shape and magnetic flux density distribution described above is arranged so that the longitudinal direction of the magnet block 33 is along the direction of the central axis 31 of the magnet roller 32, and When embedded in 32a, the magnetic flux density on the peripheral surface portion that becomes the developing pole P1 of the magnet roller unit 40 has a distribution obtained by adding the magnetic flux density of the magnet roller 32 and the magnetic flux density of the magnet block 33 together.

  As is apparent from the magnetic flux density distribution of the developing pole P1 indicated by the solid line in FIG. 7, the magnetic flux density of the developing pole P1 corresponding to the storage groove 32a portion of the magnet roller 32 is offset by the influence of the edge effect. Since the distribution of the same strength is obtained in any part in the width direction of 32b, the developing pole P1 of the magnet roller unit 40 is obtained by adding the magnetic flux density of the magnet block 33 showing the distribution as shown in FIG. The magnetic flux density on the peripheral surface portion is a distribution as indicated by a solid line in the explanatory diagram showing the distribution of FIG.

  On the other hand, if the magnet powder in the material of the storage groove 32a portion of the magnet roller 32 is magnetized with a uniform magnetic amount over the entire width direction of the bottom surface 32b of the storage groove 32a, the edge effect peculiar to the magnet The magnetic flux density of the developing pole P1 corresponding to the storage groove 32a portion of the magnet roller 32 is higher at both end portions than the intermediate portion in the width direction of the bottom surface 32b of the storage groove 32a, as shown by the broken line in FIG. In the case of the density distribution, the magnetic flux density distribution on the peripheral surface portion serving as the developing pole P1 of the magnet roller unit 40 when the magnet block 33 is embedded in the storage groove 32a is indicated by a broken line in FIG.

  In the material of the storage groove 32a portion of the magnet roller 32, as clearly shown by comparing the two magnetic flux density distributions on the peripheral surface portion that becomes the developing pole P1 of the magnet roller unit 40, shown by the solid line and the broken line in FIG. Is magnetized with a magnetic amount higher than that of both end portions in the width direction of the bottom surface 32b of the storage groove 32a, using the mold 90A of the first embodiment, and the width direction of the bottom surface 32b of the storage groove 32a When the magnet roller unit 40 is configured by using the magnet roller 32 of the first embodiment in which the magnetic flux density has the same intensity distribution in any part of the above, on the peripheral surface portion that becomes the developing pole P1 of the magnet roller unit 40 It can be seen that the peak value of the magnetic flux density distribution at 1 is high, and the half width of the developing pole P1 is sufficiently narrow.

  Thus, according to the magnet roller 32 of the first embodiment manufactured using the mold 90A of the first embodiment, the variation in the magnetic flux density distribution in the direction of the bottom surface 32b existing in the storage groove 32a portion is reduced. When the magnet roller unit 40 of the first embodiment is configured together with the magnet block 33 by substantially canceling out the intermediate portion in the width direction of 32b by magnetizing with a magnetic amount higher than both end portions, the magnet roller unit 40 Preventing the occurrence of trailing edge blanking in the development process of an electrostatic latent image in electrophotographic image formation by flattening the magnetic flux density distribution in the developing pole portion in the width direction of the bottom surface 32b of the storage groove 32a of the magnet roller 32. Thus, it is possible to obtain a magnet roller unit 40 advantageous to the above.

  According to the magnet roller unit 40 of the first embodiment configured by the magnet roller 32 and the magnet block 33, the magnetic flux density distribution in the developing pole portion is flat in the width direction of the bottom surface 32 b of the storage groove 32 a of the magnet roller 32. Thus, it is possible to obtain a magnet roller unit 40 that is advantageous in preventing the occurrence of white-out at the rear end in the development process of the electrostatic latent image in electrophotographic image formation.

  Further, the developer carrying member 43 using the magnet roller unit 40 of the first embodiment as the magnet roller unit 40 shown in FIG. 4, the developing device 60 of FIG. The process cartridge 70 of FIG. 2 configured using the apparatus 60 and the image forming apparatus 80 of FIG. 1 configured using this process cartridge 70 are the same as those obtained by the magnet roller unit 40 of the first embodiment. An effect can be obtained.

Incidentally, the mold 90A of the first embodiment described above, if in order to ensure a magnetic force necessary for magnetizing the developing pole P1, must be dimensioned to not be placed inside the convex portion 93 a high magnetic force magnet 94 ₁ has been described, for example, rare earth magnets such as anisotropic when possible to configure a high magnetic force magnet 94 ₁ of a material obtained by high small magnetic force, the present invention shown in schematic sectional view in FIG. 11 Like the mold 90B of the second embodiment, a part of the high magnetic force magnet 94 ₁ is disposed inside the convex portion 93, and the magnetic pole surface 95 ₁ is the other of the blocks 96 in the mold 90A of the first embodiment. Similarly to the end surface 96b, the outer peripheral surface portion corresponding to the base 92, that is, the front end surface 93a of the convex portion 93 corresponding to the bottom surface 32b of the storage groove 32a of the magnet roller 32 is disposed in the storage groove 3. May be made to face the intermediate portion in the width direction of the front end surface 93a that corresponds to the width direction of a bottom surface 32b.

  Even if extrusion molding is performed using the mold 90B according to the second embodiment configured as described above, the magnet roller 32 according to the first embodiment is mounted in the same manner as when extrusion molding is performed using the mold 90A according to the first embodiment. Therefore, the same operation and effect as the mold 90A of the first embodiment can be obtained also by the mold 90B of the second embodiment.

In addition, according to the mold 90B of the second embodiment, it is possible to omit the block 96 in the mold 90A of the first embodiment, the high magnetic force magnet 94 ₁ force the receiving groove 32a portion of the magnet roller 32 The storage groove 32a portion can be magnetized with high efficiency without depending on the magnetic permeability of the block 96 so as to directly affect the magnetic powder in the material.

  In the first and second embodiments described above, the extrusion molds 90A and 90B have been described. However, when the magnet roller 32 can be manufactured by other molding such as injection molding, the first is used. Of course, the present invention can be applied to a molding die by replacing the die 92 of the second embodiment with a cavity.

Example 1
Using a plastic magnet material composed of 92% by weight of Sr ferrite magnet and EEA resin, a magnetic field is formed in a shape in which a magnet block housing groove is formed over the entire length in the central axis direction by the mold 90A of the first embodiment shown in FIG. Medium extrusion molding is performed to form a cylindrical body of φ23.0 mm having a storage groove on the circumferential surface with a width dimension of 3.5 mm, a depth of 3 mm, and a longitudinal dimension of 314 mm, and a core metal of φ10 mm is inserted into the center hole. The first magnet roller was obtained, and the magnetic measurement was performed on the first magnet roller. As a result, the result in the “post-molding groove magnetic flux density” in the first stage from the top of Table 1 was obtained.

  In addition, a material in which anisotropic Nd—Fe—B and 12PA are mixed is injection-molded in a magnetic field of 10,000 (Oe) to form a long rectangular parallelepiped having a width dimension 3 mm × height 3 mm × longitudinal dimension 313 mm. The magnet was molded and magnetized using an air-core coil to obtain a magnet block to be placed in the storage groove of the first magnet roller.

  Subsequently, when the magnet block was arranged in the storage groove of the first magnet roller and the magnetic measurement was performed, the result in “after magnet block pasting” in the first row from the top of Table 1 was obtained.

(Comparative Example 1)
A shape in which a storage groove of a magnet block is formed over the entire length in the central axis direction by using the same material as in Example 1 and omitting only the block 96 from the mold 90A of the first embodiment shown in FIG. Is extruded in a magnetic field to form a cylindrical body of φ23.0 mm having a storage groove on the circumferential surface with a width dimension of 3.5 mm, a depth of 3 mm, and a longitudinal dimension of 314 mm, and a core metal of φ10 mm is formed in the center hole. When the second magnet roller was inserted to obtain a magnetic measurement for the second magnet roller, a result in the “post-molding groove magnetic flux density” in the second row from the top of Table 1 was obtained.

  In addition, a magnet block was obtained under the same conditions as in Example 1, and the magnet block was placed in the storage groove of the second magnet roller and subjected to magnetic measurement. The result is as follows.

(Comparative Example 2)
Of the die 91 of the mold 90A of the first embodiment shown in FIG. 8, portions corresponding to some of the magnetic poles P1, P2, P7 that need to have high magnetic force correspond to the magnetic poles P1, P2, P7. placing the high magnetic force magnet 94 _1, 94 _2, 94 ₇ of magnetizing the outer peripheral surface portion of the magnet roller in the non-magnetic body, from those embedded, as shown in schematic sectional view in FIG. 12, the permeability Instead of the die portions 91A, 91B, and 91C made of a high magnetic material, coils 97 are wound around the magnetic cores 91D, 91E, and 91F provided integrally with the die portions 91A, 91B, and 91C, and electromagnets 98 ₁ and 98 are provided. _2, 98 ₇ the mold 90C constituted with, by energizing the respective electromagnets 98 _1, 98 _2, 98 _7, instead of the high magnetic force magnet 94 _1, 94 _2, 94 _7, each magnetic pole P1, P2, Magnetro corresponding to P7 The magnetic field of the magnetizing outer peripheral surface portion of the La was generated.

  In this state, the same material as in Example 1 was used, and extrusion in a magnetic field was performed in a shape in which a storage groove of the magnet block extending over the entire length in the central axis direction was formed, and the width dimension was 3.5 mm, the depth was 3 mm, A cylindrical body of φ23.0 mm having a storage groove having a longitudinal dimension of 314 mm on the peripheral surface is formed, a core metal of φ10 mm is inserted into the center hole to obtain a third magnet roller, and magnetic measurement is performed on the third magnet roller As a result, the results in the “post-molding groove magnetic flux density” in the first stage from the bottom of Table 1 were obtained.

  In addition, a magnet block was obtained under the same conditions as in Example 1, and the magnet block was placed in the storage groove of the third magnet roller and subjected to magnetic measurement. The result is as follows.

  As is apparent from the results in Table 1, in the first magnet roller obtained in Example 1, the magnetic flux density in the storage groove portion of the magnet roller corresponding to the developing pole P1 is an intermediate portion in the width direction of the storage groove. (The drop magnetic flux density in Table 1) is almost the same as both end portions (peak magnetic flux density in Table 1) (1.1% decrease), and the deviation (magnetic flux density deviation in Table 1) is 1.1. Therefore, as shown in the magnetic flux density distribution of the developing pole P1 indicated by the solid line in FIG. 7, the magnetic flux density of the storage groove 32a portion of the magnet roller 32 corresponding to the development pole P1 is the width direction of the bottom surface 32b of the storage groove 32a. It was found that the distribution of the intensity was almost the same in any part of.

  Further, after placing the magnet block in the storage groove, the peak value (123 mT) of the magnetic flux density of the development pole P1 and the magnetic pole angle (16 Degg) of the peak 80%, which is an index of the full width at half maximum, are practically developed. In this case, it was possible to sufficiently prevent the occurrence of white spots at the rear end.

  On the other hand, in the second magnet roller obtained in Comparative Example 1, the magnetic pole angle of 80% peak serving as an index of the peak value and the half value width of the magnetic flux density of the developing pole P1 after the magnet block is arranged in the storage groove. Each of them has a level that can sufficiently prevent the occurrence of white-out at the rear end in the development process.

  However, as shown in the explanatory diagram of FIG. 13 in which the magnetic flux density distribution of each magnetic pole is developed in a plane, the magnetic flux density in the storage groove portion of the magnet roller corresponding to the development pole P1 is an intermediate portion in the width direction of the storage groove. The magnetic flux density distribution of the developing pole P1 indicated by the broken line in FIG. 7 is 21.8% larger than the both end portions (peak magnetic flux density in Table 1). Therefore, the peak value (120 mT) of the magnetic flux density of the development pole P1 and the magnetic pole angle (19 Degg) of the peak 80% after the magnet block is arranged in the storage groove are practically the rear end in the development process. It was hard to say that the level was sufficient to prevent the occurrence of white spots.

  Further, in the third magnet roller obtained in Comparative Example 2, the magnetic flux density in the storage groove portion of the magnet roller corresponding to the development pole P1 is generally high, but the intermediate portion in the width direction of the storage groove (table 1 is 11.9% lower than both end portions (peak magnetic flux density in Table 1), the magnetic flux density of the developing pole P1 after the magnet block is arranged in the storage groove It was difficult to say that the magnetic pole angle with a peak of 80% (28 Deg) is practically at a level that can sufficiently prevent the occurrence of white spots in the developing process.

  Moreover, in the third magnet roller obtained in Comparative Example 2, the magnetic flux density in the outer peripheral surface portion of the magnet roller corresponding to the other magnetic poles P2, P4 to P8 other than the developing pole P1 is the first magnet roller or the second magnet. It becomes lower than the roller, and the functions of each of the magnetic poles P2, P4 to P8 cannot be sufficiently performed, and image unevenness due to variations in the transport amount of the two-component developer and the recovery amount of the carrier is practical. It was found that it was not suitable for practical use because the upper hindrance occurred to some extent.

1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows schematic structure of the process cartridge which concerns on one Embodiment of this invention. 1 is an explanatory diagram showing a schematic configuration of a developing device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view in the central axis direction of a developer carrier according to an embodiment of the present invention. FIG. 5 is a perspective view showing a schematic configuration of a magnet roller unit according to the first embodiment of the present invention that is used as a magnet roller unit of the developer carrier of FIG. 4. It is explanatory drawing of magnetic flux density distribution at the time of arrange | positioning in the accommodation groove | channel of the magnet roller which shape | molded the magnet block of FIG. 5 with the material of the nonmagnetic material. It is explanatory drawing of the magnetic flux density distribution of the magnet roller of FIG. It is sectional drawing which shows typically the metal mold | die which concerns on 1st Embodiment of this invention. It is a principal part expanded sectional view of the metal mold | die of FIG. It is explanatory drawing of magnetic flux density distribution of the magnet roller unit of FIG. It is sectional drawing which shows typically the metal mold | die which concerns on 2nd Embodiment of this invention. 10 is a cross-sectional view schematically showing a mold used for manufacturing a magnet roller of Comparative Example 2. FIG. It is explanatory drawing which expand | deploys the magnetic flux density distribution of the magnet roller of Example 1 and Comparative Examples 1 and 2 on a plane.

Explanation of symbols

32 Magnet roller 32a Storage groove 33 Magnet block 40 Magnet roller unit 43 Developer carrier 60 Developing device 70 Process cartridge 80 Image forming device 90A, 90B Mold 92 Base (space)
P1 Development pole P2 Magnetic pole

Claims (10)

It is formed in a cylindrical shape from a material mixed with magnetic powder, and a long storage groove for placing a long magnet block is formed along the central axis in the outer peripheral surface corresponding to the magnetic pole part. In the magnet roller
The magnetic powder in the material constituting the intermediate portion in the width direction perpendicular to the longitudinal direction of the bottom surface of the storage groove is higher than the magnetic powder in the material constituting both end portions in the width direction of the bottom surface. Magnetized with magnetic quantity,
A magnet roller characterized by that. A method of manufacturing the magnet roller according to claim 1 by molding with a mold,
When molding the magnet roller by injecting the material into a space corresponding to the magnet roller in the mold, the magnetic pole surface faces the space portion corresponding to the intermediate portion of the bottom surface. The magnetic powder in the material constituting the intermediate portion of the bottom surface is converted into the magnetic force of the magnetic powder in the material constituting the both end portions of the bottom surface by a high magnetic force magnet arranged in the mold. Magnetized with a magnetic quantity higher than the quantity,
A method of manufacturing a magnet roller.   The magnetic path configured by a magnetic body disposed inside the convex portion of the mold that protrudes inside the space and molds the storage groove, the high height disposed outside the convex portion in the mold. 3. The method of manufacturing a magnet roller according to claim 2, wherein magnetic lines of force from the magnetic pole surface of the magnetic magnet are guided to a space portion corresponding to the intermediate portion of the bottom surface. A mold having a space corresponding to the magnet roller, which is used for manufacturing the magnet roller according to claim 1,
A high magnetic force magnet for magnetizing the magnetic powder in the material constituting the intermediate portion of the bottom surface with a magnetic amount higher than that of the magnetic powder in the material constituting the both end portions of the bottom surface. Is disposed with a magnetic pole face facing a space portion corresponding to the intermediate portion of the bottom surface,
A mold for manufacturing a magnet roller.   The mold has a convex portion that protrudes inside the space and molds the storage groove, and the high magnetic force magnet is disposed outside the convex portion, and the convex portion includes the convex portion. The mold for manufacturing a magnet roller according to claim 4, wherein a magnetic body constituting a magnetic path is disposed between a space portion corresponding to the intermediate portion of the bottom surface and the high magnetic force magnet. A magnet roller formed in a cylindrical shape by a material in which magnetic powder and resin are mixed, and a long storage groove is formed in the outer peripheral surface portion corresponding to the magnetic pole portion along the central axis direction;
A long magnet block having a magnetic force higher than the magnetic force of the magnet roller and disposed in the storage groove;
A magnet roller unit comprising:
The magnet roller according to claim 1 is used as the magnet roller.
A magnet roller unit characterized by that.   A developer carrying member, characterized in that a rotatable nonmagnetic cylindrical body is disposed on the outer periphery of the magnet roller unit according to claim 6.   A developing device having at least a developer carrying member, a developer supplying member, and a developer layer regulating member, wherein the developer carrying member according to claim 7 is used as the developer carrying member. .   The developing device according to claim 8, wherein the developing device includes at least a developer carrying member, a developer supply member, a developer layer regulating member, and a process cartridge having a charging roller and an image carrier. A process cartridge comprising:   An image forming apparatus comprising the process cartridge according to claim 9 as a process cartridge in an image forming apparatus having at least a process cartridge, an optical writing unit, a transfer member, and a fixing device.

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