JP6237548B2 - Developing device and image forming apparatus including the same - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus used for a copying machine, a printer, a facsimile, a composite machine of these, and the like.

  Conventionally, as a developing method in an image forming apparatus using an electrophotographic process, a powder developer is mainly used, and an electrostatic latent image formed on an image carrier such as a photosensitive drum is visualized by the developer. A process in which the visible image (toner image) is transferred onto a recording medium and then a fixing process is performed is common.

  Developers are broadly divided into two-component developers consisting of toner and magnetic carrier, and one-component developers consisting only of non-magnetic or magnetic toner. Development methods using two-component developers are classified in the circumferential direction. A magnet (magnetic pole) having a magnetic field strength at a position is fixed to the center of the developing roller (developer carrier), and a metal regulating blade is arranged at a distance of several hundreds of micrometers so as to face the developing roller surface. A method for doing this is known.

  On the other hand, as a developing method using a one-component developer, a fixed magnet roller having a plurality of magnetic poles is arranged inside the developing roller, and the toner in the developing container is carried on the developing roller by using a magnetic carrying force. Thereafter, a so-called jumping one-component developing system is known in which a toner thin layer is formed by regulating the layer thickness using a regulating blade, and the toner is ejected to a photosensitive drum at a development position.

  In recent years, for example, a plastic magnet in which magnetic powder is dispersed in a resin material as shown in Patent Document 1 has been used as a magnet disposed inside the developing roller. The plastic magnet has a feature that a high magnetic force can be secured with a low capacity compared to a rubber magnet.

  This plastic magnet is produced by injection molding. However, due to restrictions on the mold configuration, an injection gate for injecting a resin material into the mold is generally provided at the end of the magnet. At this time, the magnetic powder mixed in the resin material tends to be biased to the side opposite to the injection gate (on the opposite gate side), and the molded plastic magnet has a higher magnetic force on the opposite gate side than on the gate side.

JP 2011-119769 A

  When this plastic magnet is used as the main pole of the magnet inside the developing roller (opposite pole of the photosensitive drum), the magnetic attractive force that attracts the toner at the end with the higher magnetic force (on the opposite gate side) becomes stronger. The flying property is lowered, and as a result, the developing property is lowered. That is, there arises a problem that developability differs in the longitudinal direction of the developing roller, and the density differs between the left and right sides of the image. Further, there is a difference in reverse fogging performance in the longitudinal direction of the developing roller.

  Also, when a plastic magnet is used as the magnet's restricting pole (opposite pole of the restricting blade) inside the developing roller, the amount of toner transported on the developing roller at the end with the higher magnetic force (on the opposite gate side) decreases, and the toner The amount of charge increases. That is, although the absolute amount of toner passing through the opposite area (development area) between the developing roller and the photosensitive drum is reduced, the developability is improved by improving the electric field response. Therefore, a difference in developability occurs in the longitudinal direction of the developing roller, causing a problem that the density differs between the left and right sides of the image.

  The difference in developability or reverse fogging is caused by the magnetic gradient in the longitudinal direction of the plastic magnet, and it is difficult to suppress this magnetic gradient in the manufacturing process.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a developing device and an image forming apparatus including the developing device that can suppress a variation in developability due to a magnetic force gradient of a magnet disposed in a developer carrier. With the goal.

  In order to achieve the above object, the present invention is a developing device including a developer carrier and a regulating member. A developer carrying member includes a rotatable cylindrical developing sleeve disposed in a non-contact manner and opposed to the image carrier, and a magnetic pole member fixed in the developing sleeve so as not to rotate and having a plurality of magnetic poles in the circumferential direction of the developing sleeve. And having. The regulating member regulates the layer thickness of the developer layer formed on the developer carrying member. The developing sleeve is formed by dipping in a coating solution made of a resin material from one end side in the longitudinal direction and forming a coating layer on the outer peripheral surface by a dipping method in which the developing sleeve is pulled up from the other end side. The magnetic pole member includes a main pole disposed in the vicinity of the developing sleeve and the image carrier, and a regulation pole disposed in the proximity of the developing sleeve and the regulation member. At least one of the main electrode and the regulating electrode has a magnetic force gradient in the longitudinal direction of the developer carrying member, and the developing sleeve in a direction to cancel out the difference in developability in the longitudinal direction of the developer carrying member caused by the magnetic force gradient The lower end side and the upper end side during dipping are arranged.

  According to the first configuration of the present invention, the difference in developability in the longitudinal direction of the developer carrier caused by the magnetic force gradient in the longitudinal direction of at least one of the main pole and the regulating pole of the magnetic pole member is caused by the coat layer of the developing sleeve. Therefore, the difference in developability in the longitudinal direction of the developer carrying member can be eliminated, and the density difference between the left and right sides of the image can be effectively suppressed.

Sectional drawing which shows schematic structure of the image forming apparatus 100 provided with the developing device 14 of this invention. Side surface sectional drawing of the developing device 14 which concerns on one Embodiment of this invention. Enlarged view around the developing roller 25 in FIG. Side surface sectional view of the developing roller 25 used in the developing device 14 Cross-sectional enlarged view of the developing roller 25 A longitudinal sectional view showing the film thickness of the coating layer 61 formed on the developing sleeve 25a by the dipping method The figure which shows the magnetic force gradient in the longitudinal direction of the plastic magnet molded by injection molding The graph which shows the measurement result of the image density in the width direction right and left of an output image in Example 2. The graph which shows the measurement result of the image density in the width direction right and left of an output image in Example 3.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus 100 (here, a monochrome printer) on which the developing device 14 of the present invention is mounted, and the right side is illustrated as the front side of the image forming apparatus. A sheet feeding cassette 2 that accommodates stacked sheets is disposed below the apparatus main body 1 a of the image forming apparatus 100. Above this paper feed cassette 2, there is formed a paper conveyance path 4 that extends substantially horizontally from the front to the rear of the apparatus main body 1a and further extends upward to reach the paper discharge unit 3 formed on the upper surface of the apparatus main body 1a. ing. A pickup roller 5, a feed roller 6, an intermediate transport roller 7, a registration roller pair 8, an image forming unit 9, a fixing unit 10, and a discharge roller pair 21 are arranged in this order along the paper transport path 4 from the upstream side.

  The paper feed cassette 2 is provided with a paper stacking plate 12 that is rotatably supported with respect to the paper feed cassette 2. When the paper stacked on the paper stacking plate 12 is sent out toward the paper transport path 4 by the pickup roller 5, and when a plurality of papers are sent out simultaneously by the pickup roller 5, the feed roller 6, the retard roller 13, Thus, the sheet is rolled up and only the topmost sheet is conveyed. The sheet sent to the sheet conveyance path 4 is conveyed to the registration roller pair 8 by changing the conveyance direction to the rear of the apparatus main body 1a by the intermediate conveyance roller 7, and the timing is adjusted by the registration roller pair 8 to form an image. Supplied to section 9.

  The image forming unit 9 forms a predetermined toner image on a sheet by an electrophotographic process, and includes a photosensitive drum 11 rotatably supported in a clockwise direction in FIG. 1 and a periphery of the photosensitive drum 11. The charging unit 15, the developing device 14, the cleaning unit 17, the transfer roller 18 disposed so as to face the photoconductive drum 11 across the paper conveyance path 4, and the photoconductive drum 11. The optical scanning unit 19 is provided, and a toner container 20 for supplying toner to the developing device 14 is disposed above the developing device 14.

  The charging unit 15 is provided with a conductive rubber roller 15 a to which a power source (not shown) is connected, and the conductive rubber roller 15 a is disposed so as to contact the photosensitive drum 11. When the photosensitive drum 11 rotates, the conductive rubber roller 15a comes into contact with the surface of the photosensitive drum 11 and rotates, and at this time, by applying a predetermined voltage to the conductive rubber roller 15a, the photosensitive member The surface of the drum 11 is uniformly charged.

  Next, beam light based on image data input from a personal computer or the like is emitted from the optical scanning unit 19 onto the photosensitive drum 11, and an electrostatic latent image is formed on the photosensitive drum 11. The toner supplied from the developing device 14 adheres to the electrostatic latent image, and a toner image is formed on the surface of the photosensitive drum 11. Then, a sheet is supplied from the registration roller pair 8 to a transfer nip formed by the photosensitive drum 11 and the transfer roller 18 at a predetermined timing, and the toner image on the surface of the photosensitive drum 11 is formed on the sheet by the transfer roller 18. Is transcribed.

  The sheet on which the toner image has been transferred is separated from the photosensitive drum 11 and conveyed toward the fixing unit 10. The fixing unit 10 is disposed on the downstream side of the image forming unit 9 with respect to the paper conveyance direction, and includes a heating roller 13 that is heated by a heating unit such as a heater, and a pressure roller 16 that is pressed against the heating roller 13. Have. The paper on which the toner image has been transferred by the image forming unit 9 is heated and pressed by the heating roller 13 and the pressure roller 16, and the toner image transferred to the paper is fixed.

  The paper on which the image is formed is discharged to the paper discharge unit 3 by the discharge roller pair 21. On the other hand, the toner remaining on the surface of the photosensitive drum 11 after the transfer is removed by the cleaning unit 17, the photosensitive drum 11 is charged again by the charging unit 15, and image formation is performed in the same manner.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the developing device 14 according to the embodiment of the present invention used in the image forming apparatus 100. The developing device 14 includes a developing container 22 that contains a magnetic one-component developer, a first stirring and conveying member 23 and a second stirring and conveying member 24 that agitate and convey the developer (hereinafter also referred to as toner), and a developing roller 25. And a regulating blade 41.

  The first and second agitating / conveying members 23 and 24 are rotatably disposed in the developing container 22 with the partition wall 22b interposed therebetween. The first and second stirring and conveying members 23 and 24 include spiral blades that are spirally formed in the axial direction. When the first and second agitating and conveying members 23 and 24 rotate, the toner is agitated, and the agitated toner is passed through first and second communicating portions (not shown) provided at both ends of the partition wall 22b. The toner circulates in the developing container 22 in the longitudinal direction (direction perpendicular to the paper surface of FIG. 2), and the toner is charged by friction between the toners. Then, the toner is supplied to the developing roller 25 by the second stirring and conveying member 24.

  The developing roller 25 has a developing sleeve 25a formed in a cylindrical shape with a nonmagnetic material such as aluminum, and a magnetic pole member 25b (see FIG. 3) built in the developing sleeve 25a. Further, the developing roller 25 is rotatably supported in the developing container 22 at a position adjacent to the second stirring and conveying member 24. Further, the developing roller 25 is exposed from the opening of the developing container 22 and faces the photosensitive drum 11 that is an image carrier with a certain interval. A developing area D for supplying the toner carried on the developing roller 25 toward the photosensitive drum 11 is formed in the opposed area.

  The regulating blade 41 regulates the toner carried on the surface of the developing roller 25 to a predetermined layer thickness. The regulating blade 41 has a blade shape and is located upstream of the developing region D with respect to the rotation direction of the developing roller 25. Along the longitudinal direction of 22, the surface of the developing roller 25 is attached at a predetermined interval. As the material of the regulating blade 41, magnetic or non-magnetic SUS (stainless steel) or the like is used. Here, a permanent magnet 43 (see FIG. 3) is attached to the non-magnetic regulating blade 41 to provide magnetism.

  Side seals 27 are arranged in a substantially C shape along the outer peripheral surface of the developing roller 25 at both axial ends of the developing roller 25. The side seal 27 is a contact-type seal formed of an elastic member such as felt or sponge. The side seal 27 is brought into pressure contact with the outer peripheral surface of the developing roller 25 so that the toner from the gap between the outer peripheral surface of the developing roller 25 and the developing container 22 can be removed. Prevent leakage.

  The toner supplied from the second stirring / conveying member 24 is carried on the surface of the developing roller 25, and the carried toner is regulated to a constant layer thickness by the regulating blade 41, and further, the developing region D is rotated by the rotation of the developing roller 25. It is conveyed toward. By applying a predetermined bias voltage to the developing roller 25, a potential difference is generated between the developing roller 25 and the photosensitive drum 11, and the toner on the developing roller 25 is supplied to the photosensitive drum 11 in the developing region D. The electrostatic latent image on the photosensitive drum 11 is developed into a toner image. When the toner in the developing container 22 is reduced by development, the toner stored in the toner container 20 (see FIG. 1) is replenished to the upstream end of the first transport path 22c through the toner replenishing port 22a. .

  FIG. 3 is an enlarged view around the developing roller 25 in FIG. A method for regulating the amount of toner on the developing roller 25 will be described in detail with reference to FIG. The magnetic pole member 25b disposed inside the developing roller 25 has four magnetic poles including two N poles (N1, N2) and two S poles (S1, S2). The S1 pole is called the main pole, and is disposed in the development area D facing the photosensitive drum 11.

  The N1 pole is called a regulation pole, and generates a magnetic field that affects the density of the developer in the regulation section 31 formed by a gap (gap) between the regulation blade 41 and the developing roller 25. Specifically, a magnetic field in a direction attracting between the S pole and the N1 pole induced at the tip of the regulating blade 41 by the N pole of the permanent magnet 43 is generated. This magnetic field forms a so-called magnetic brush in which the toner and the carrier stand up like a brush between the regulating blade 41 and the developing roller 25. In this embodiment, the N1 pole is arranged slightly upstream from the restricting portion 31 with respect to the rotation direction of the developing roller 25 (clockwise direction along the developing roller 25). Without passing through the restricting portion 31 in an oblique state.

  When the developing roller 25 rotates counterclockwise, the magnetic brush moves along the roller surface by a horizontal (roller circumferential direction) magnetic field generated between the N1 pole and the S1 pole. When the magnetic brush reaches the position of the S1 pole (development region D), the magnetic brush stands upright by the magnetic field of the S1 pole and contacts the surface of the photosensitive drum 11 to form a toner image.

  When the developing roller 25 further rotates counterclockwise, this time, the magnetic brush is pulled away from the drum surface by the horizontal magnetic field generated between the S1 pole and the N2 pole, and the toner that has not been used to form the toner image is removed. Together with the carrier, the toner is collected in the developing container 22 through the gap between the opening end of the developing container 22 and the developing roller 25. The S2 pole is called a catch pole, and transfers the developer supplied from the second stirring and conveying member 24 (see FIG. 2) to the developing roller 25.

  Then, a magnetic brush is formed again on the developing roller 25 by the magnetic field of the N1 pole. That is, not only the interval between the restricting portions 31 but also the amount of toner adhering to the developing roller 25 is strictly controlled by the magnetic field generated there.

  Next, the developing roller 25 used in the developing device 14 of the present invention will be described. 4 is a side cross-sectional view of the developing roller 25, and FIG. 5 is an enlarged cross-sectional view of the developing roller 25 (cross-sectional view taken along the line AA 'in FIG. 4). The developing roller 25 has an alumite layer (aluminum oxide film) 45 formed on the outer peripheral surface of an aluminum or aluminum alloy developing sleeve 25a, and the surface of the anodized layer 45 is a coating made of a silicon-modified polyurethane resin or an acrylic resin. Layer 47 is laminated. 4 and 5, the magnetic pole member 25b in the developing sleeve 25a is not shown.

  Next, a method for manufacturing the developing roller 25 will be described. First, an aluminum or aluminum alloy cylinder is finished into a developing sleeve 25a having a predetermined outer diameter by cutting, polishing or the like, and then anodized in an acid aqueous solution to form an alumite layer 45 on the surface. The alumite layer 45 is an aggregate of hexagonal columnar cells having a fine hole in the center, and the bottom surface of the fine hole serves as an interface (barrier layer) with the aluminum substrate. The alumite layer 45 prevents the occurrence of leakage when a developing bias is applied to the developing roller 25.

  If the alumite layer 45 is too thick, the resistance of the entire developing roller 25 becomes large, and it becomes necessary to apply a high-voltage developing bias. On the other hand, if the alumite layer 45 is too thin, the alumite layer cannot be formed uniformly and a leak may occur. Therefore, the layer thickness of the alumite layer 45 is preferably about 10 μm to 20 μm.

  Thereafter, the surface of the alumite layer 45 is heat-treated. This heat treatment prevents cracks from occurring in the alumite layer 45 and the coat layer 47 in the drying step by causing cracks in the alumite layer 45 in advance before the drying step of the coat layer 47 described later. . The heat treatment time is set to a certain time, for example, a time required for the drying process or more (for example, 10 minutes or more at 120 ° C.), and a substantially constant amount of cracks are generated in all the developing sleeves 25a.

  After the heat treatment, a coat layer 47 is formed on the surface of the alumite layer 45. The coat layer 47 suppresses adhesion of the toner supplied on the developing sleeve 23a to the alumite layer 45. Furthermore, since the mechanical stress applied to the developer by the coat layer 47 is less than that on the metal surface, improvement in toner recovery from the developing roller 25 and prevention of developer deterioration when the developer conveyance amount is increased. Both can be achieved.

  Examples of the material of the coat layer 47 include nylon resin, urethane resin, acrylic resin, melamine resin, silicon resin, and fluorine resin. However, the chargeability is close to the resin material of the positively charged toner, and the toner releasability is good. In addition, an alcohol-soluble nylon resin that can be coated by a dipping method described later is preferable.

In addition, the coating layer 47 contains a conductive material having a dielectric constant of 10 or more as a resistance adjusting agent, thereby adjusting the volume resistance value of the coating layer 47 and suppressing resistance unevenness. Examples of the resistance adjuster include carbon black, titanium oxide, and fiber-shaped potassium titanate. As a result, it is possible to stabilize the charged state of the toner layer and improve the releasability during toner recovery. The volume resistance value of the coat layer 47 is preferably about 10 ⁴ to 10 ⁸ Ω that can appropriately retain the residual charge on the surface of the developing roller 25.

  In the present invention, the coat layer 47 is formed by dipping. Specifically, the developing sleeve 25a on which the alumite layer 45 is formed is dipped into the coating liquid from one end side and pulled up from the other end side. Thereafter, a drying process is performed in which the developing sleeve 25a coated with the coating liquid is dried at a predetermined temperature for a predetermined time (eg, 130 ° C. for 10 minutes) to form a coat layer 47 having a film thickness of about 2 to 11 μm.

  As shown in FIG. 6, the developing roller 25 in which the coating layer 47 is formed by the above-described dipping method has a lower end side (left end in FIG. 6) at the time of dipping of the coating layer 47 than the central portion in the longitudinal direction of the developing roller 25. The film thickness tends to increase. That is, since the outer diameter of the developing roller 25 is increased on the lower end side during dipping, the distance between the photosensitive drum and the developing roller (developing region D) is reduced. As a result, the developing roller 25 is improved in developability because the electric field strength increases on the lower end side during dipping. For this reason, in the developing roller 25 in which the coat layer 47 is formed by the dipping method, the developability is improved on the lower end side than the upper end side at the time of dipping, and the reverse fogging performance is deteriorated. In the present specification, “developability” means toner flying property (movability) from the developing roller 25 to the photosensitive drum 11.

  On the other hand, when a plastic magnet molded by injection molding is used as the magnetic pole member 25b, the magnetic force distribution in the longitudinal direction is biased. FIG. 7 is a graph showing the magnetic force distribution in the longitudinal direction of the plastic magnet used for the magnetic pole member 25b.

  As shown in FIG. 7, in a plastic magnet molded by injection molding, a magnetic force gradient is generated in which the magnetic force is higher at the end on the opposite gate side than at the end on the gate side in the longitudinal direction.

  When this plastic magnet is used as the main pole (S1 pole in FIG. 3) of the magnetic pole member 25b, the magnetic attraction force that attracts toner at the end portion on the high magnetic force side (the anti-gate side) becomes strong, so that the toner flying property is improved. As a result, the developability decreases. On the other hand, since the magnetic attraction force becomes weak at the end portion (gate side) on the low magnetic force side, the toner flying property is improved, and as a result, the developing property is improved. That is, a difference in developability occurs in the longitudinal direction of the developing roller 25, and a density difference occurs between the left and right sides of the output image. Further, since the reverse fog performance is deteriorated at the end portion on the low magnetic force side (gate side) as compared with the end portion on the high magnetic force side (counter gate side), the reverse fog performance in the longitudinal direction of the developing roller 25 is also different. Occurs.

  Therefore, in this embodiment, when a plastic magnet is used as the main pole (S1 pole) of the magnetic pole member 25b, the lower end side (left end in FIG. 6) of the developing roller 25 on which the coating layer 47 is formed by the dipping method. The side where the magnetic force of the plastic magnet is high (the anti-gate side) is arranged. That is, the main pole (S1 pole) of the developing sleeve 25a and the magnetic pole member 25b so that the film thickness of the coat layer 47 is large on the side where the magnetic force of the plastic magnet is high and the film thickness of the coat layer 47 is small on the side where the magnetic force is low. The direction of was defined.

  As a result, the difference in toner flying properties caused by the magnetic gradient in the longitudinal direction of the main pole (S1 pole) of the magnetic pole member 25b is offset by the gradient in the film thickness of the coat layer 47 of the developing sleeve 25a. The difference in developability and reverse fogging in the longitudinal direction of the image can be eliminated, and the difference in density between the left and right sides of the image and the reverse fog phenomenon can be effectively suppressed.

  In addition, when a plastic magnet is used as the regulating pole (N1 pole in FIG. 3) of the magnetic pole member 25b, the toner conveyance amount on the developing roller 25 is reduced at the end portion on the high magnetic force side (on the opposite gate side), and The amount of charge increases. That is, the absolute amount of toner passing between the photosensitive drum and the developing roller (developing area D) is reduced at the end portion on the high magnetic force side (on the opposite gate side), but the response to the electric field in the developing area D is improved. This improves the developability. As a result, a difference in developability occurs in the longitudinal direction of the developing roller 25, and a density difference occurs between the left and right of the output image.

  Therefore, in the present embodiment, when a plastic magnet is used as the regulation pole (N1 pole) of the magnetic pole member 25b, the upper end side (right end in FIG. 6) of the developing roller 25 on which the coating layer 47 is formed by the dipping method. The side where the magnetic force of the plastic magnet is high (the anti-gate side) is arranged. That is, the regulation pole (N1 pole) of the developing sleeve 25a and the magnetic pole member 25b so that the film thickness of the coat layer 47 is small on the side where the magnetic force of the plastic magnet is high and the film thickness of the coat layer 47 is large on the side where the magnetic force is low. The direction of was defined.

  Thereby, the difference in developability caused by the magnetic gradient in the longitudinal direction of the regulation pole (N1 pole) of the magnetic pole member 25b is offset by the gradient of the film thickness of the coat layer 47 of the developing sleeve 25a. The difference in developability in the direction can be eliminated, and the density difference between the left and right sides of the image can be effectively suppressed.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above embodiment, the developing sleeve 25a and the main pole (S1 pole), so as to cancel the magnetic gradient of both the main pole (S1 pole) and the regulation pole (N1 pole) of the magnetic pole member 25b using a plastic magnet, Although the direction of the developing sleeve 25a and the regulation pole (N1 pole) is defined, the development sleeve 25a is arranged so as to cancel the magnetic force gradient of either the main pole (S1 pole) or the regulation pole (N1 pole) of the magnetic pole member 25b. Even if the direction is defined, the effect of suppressing the difference in density between the left and right sides of the image and the reverse fog phenomenon can be expected.

  In the above embodiment, the example in which the present invention is applied to the developing device 14 of the magnetic one-component developing system has been described. However, the present invention is not limited to the magnetic one-component developing system, and includes a magnetic carrier and a non-magnetic toner. In a two-component developing type developing device that uses a component developer, forms a magnetic brush composed of a magnetic carrier and a non-magnetic toner on a developing roller, and develops an electrostatic latent image on a photosensitive drum using the magnetic brush. Is equally applicable.

  The present invention is not limited to the monochrome printer shown in FIG. 1, and can be applied to various image forming apparatuses having a developing device such as a digital or analog monochrome copying machine, a color printer, a color copying machine, and a facsimile. is there. Hereinafter, the effects of the present invention will be described more specifically with reference to examples.

(Development roller development)
Alumite treatment was performed on the outer peripheral surface of the developing sleeve 25a made of an aluminum tube having a diameter of 20 mm to form an alumite layer 45 having a thickness of 10 μm, and the surface of the alumite layer 45 was heat-treated at 120 ° C. for 10 minutes or more. On the other hand, 100 parts by weight of an alcohol-soluble nylon resin (CM8000, manufactured by Toray Industries Inc.) as a binder resin, 100 parts by weight of titanium oxide (ET-300W, manufactured by Ishihara Sangyo) as a conductive material, and 800 parts by weight of methanol as a dispersion medium, The coating solution was prepared by mixing and dispersing for 48 hours using zirconia beads having a diameter of 1 mm. Next, the anodized developing sleeve 25a is dipped (immersed) in the coating solution from one end side so that the axial direction of the cylindrical shape is along the vertical direction, pulled up from the other end side, and then at 130 ° C. for 10 minutes. By drying, a coat layer 47 having a thickness of about 2 to 11 μm was formed on the surface of the alumite layer 45.

  In the developing sleeve 25a on which the alumite layer 45 and the coat layer 47 were formed, plastic magnets molded by injection molding as S1, S2, N1, and N2 constituting the magnetic pole member 25b were arranged to produce the developing roller 25. At this time, the lower end side of the developing roller 25 when dipping the developing roller 25 is arranged on the side where the magnetic force in the longitudinal direction of the main pole S1 is high, and the developing sleeve 25a is dipped on the side where the magnetic force in the longitudinal direction is high. The one in which the upper end side of the hour is arranged is referred to as Comparative Example 1. Further, Comparative Example 2 was used in which a developing sleeve 25a (the thickness of the coating layer 47 was substantially uniform in the longitudinal direction) in which the coating layer 47 was formed on the surface of the alumite layer 45 by spray coating was used.

(Evaluation of image density difference 1)
A magnetic one-component developer comprising only the positively chargeable toner having a particle size of 6.8 μm, equipped with any of the developing roller 25 of the present invention 1, Comparative Example 1 and Comparative Example 2 prepared in Example 1, was used. A one-component developing type developing device 14 (see FIG. 2) was produced. These developing devices 14 are mounted on a testing machine as shown in FIG. 1, and a test image (25 mm × 25 mm) is immediately after the developing device 14 is filled with a developer in a normal temperature and humidity environment (25 ° C., 50%). A solid patch image) was output, and the image density (ID; image density) on the left and right in the width direction of the output image was measured with a reflection densitometer.

  The image output conditions are as follows: the printing speed is 30 sheets / min, the drum linear speed is 180 mm / sec, the drum surface potential (V0) is +200 V, the image portion potential (VL) is +10 V, and the developing bias applied to the developing roller 25 is The AC component was 1200 V, the frequency was 3.0 kHz, the duty ratio was 50%, and the DC component was 130 V. Further, an OPC drum having an organic photosensitive layer (OPC) formed thereon is used as the photosensitive drum 11, the gap between the developing roller and the photosensitive drum is 0.3 mm, and the linear speed ratio S / of the developing roller 25 with respect to the photosensitive drum 11. D was set to 1.5 (forward rotation). The test results are shown in FIG. In FIG. 8, the side on which the magnetic force is high in the longitudinal direction of the plastic magnet, which is the main pole S1, is referred to as the “right side”.

  As is clear from FIG. 8, in the developing device 14 of the present invention in which the lower end side during the dipping of the developing sleeve 25a is arranged on the side where the magnetic force in the longitudinal direction of the main pole S1 is high, the left side of the output image (the hatched area in FIG. 8). ), The center (the white area in FIG. 8), and the right side (the dot area in FIG. 8) did not show a large difference in image density, and the image density difference between the left and right in the width direction of the output image could be eliminated.

  On the other hand, in the developing device 14 of Comparative Example 1 in which the upper end side during dipping of the developing sleeve 25a is arranged on the side where the magnetic force in the longitudinal direction of the main pole S1 is high, the image density decreases from the left side to the right side of the output image, The difference in image density between the left and right in the width direction of the output image became larger. Further, in the developing device 14 of the comparative example 2 using the developing sleeve 25a in which the substantially uniform coat layer 47 is formed by spray coating, although not as much as the comparative example 1, the image on the left and right in the width direction of the output image is compared with the present invention. A concentration difference occurred.

(Evaluation of image density difference 2)
In the developing sleeve 25a in which the alumite layer 45 and the coat layer 47 are formed by the procedure of Example 1, plastic magnets molded by injection molding as S1, S2, N1, and N2 constituting the magnetic pole member 25b are arranged and developed. A roller 25 was produced. At this time, an arrangement in which the upper end side during the dipping of the developing roller 25 is arranged on the side where the magnetic force in the longitudinal direction of the regulation pole N1 is high is dipping the developing sleeve 25a on the side where the longitudinal magnetic force of the regulation pole N1 is high. The one in which the lower end side of the hour is arranged is referred to as Comparative Example 3. Further, Comparative Example 2 was used in which a developing sleeve 25a (the thickness of the coating layer 47 was substantially uniform in the longitudinal direction) in which the coating layer 47 was formed on the surface of the alumite layer 45 by spray coating was used.

  Development of a magnetic one-component development system using any one of the developing roller 25 of the present invention 2, comparative example 2, and comparative example 3 and using a magnetic one-component developer composed only of a positively charged toner having a particle size of 6.8 μm. A device 14 (see FIG. 2) was produced. These developing devices 14 are mounted on a testing machine as shown in FIG. 1, and a test image (25 mm × 25 mm) is immediately after the developing device 14 is filled with a developer in a normal temperature and humidity environment (25 ° C., 50%). A solid patch image) was output, and the image density (ID; image density) on the left and right in the width direction of the output image was measured with a reflection densitometer. The image forming conditions were the same as in Example 2. The results are shown in FIG. In FIG. 9, the side on which the magnetic force is high in the longitudinal direction of the plastic magnet that is the regulation pole N <b> 1 is the “right side”.

  As is apparent from FIG. 9, in the developing device 14 of the present invention in which the upper end side of the developing sleeve 25a is placed on the side where the magnetic force in the longitudinal direction of the regulation pole N1 is high, the left side of the output image (the hatched area in FIG. 9) ), The center (the white area in FIG. 9), and the right side (the dot area in FIG. 9) did not show a large difference in image density, and the image density difference between the left and right in the width direction of the output image could be eliminated.

  On the other hand, in the developing device 14 of Comparative Example 3 in which the lower end side during dipping of the developing sleeve 25a is arranged on the side where the magnetic force in the longitudinal direction of the regulation pole N1 is high, the image density increases from the left side to the right side of the output image, The difference in image density between the left and right in the width direction of the output image became larger. Further, in the developing device 14 of the comparative example 2 using the developing sleeve 25a in which the substantially uniform coat layer 47 is formed by spray coating, although not as much as the comparative example 3, the image on the left and right in the width direction of the output image is compared with the present invention. A concentration difference occurred.

  In the above embodiment, the effect of applying the present invention to the developing device 14 of the magnetic one-component developing method has been described. However, the two-component developing method using a two-component developer containing a magnetic carrier and a non-magnetic toner is used. The same effect has been confirmed when applied to a developing device.

  The present invention is applicable to a developing device used in a copying machine, a printer, a facsimile, a composite machine thereof, and an image forming apparatus including the developing device. To provide a developing device capable of suppressing variations in developability and reverse fogging caused by a magnetic force gradient of a magnet disposed in a developer carrying body by using the present invention, and an image forming apparatus including the same. Can do.

14 Developing Device 22 Developing Container 22a Toner Supply Port 22b Partition Wall 22c First Conveying Path 22g Inner Wall 23 First Agitation Conveying Member 24 Second Agitation Conveying Member 25 Developing Roller (Developer Carrier)
25a Development sleeve 25b Magnetic pole member 27 Side seal 31 Restriction part 29 Restriction blade (regulation member)
45 Anodized layer 47 Coat layer 100 Image forming device S1 Main electrode N1 Regulating electrode

Claims (4)

A rotatable cylindrical developing sleeve that is disposed to face the image carrier in a non-contact manner;
A main pole fixed in the developing sleeve in a non-rotatable manner and disposed in the vicinity of the developing sleeve and the image carrier in the circumferential direction of the developing sleeve, and a proximity of the developing sleeve and the regulating member A magnetic pole member having a plurality of magnetic poles including a regulating pole disposed on
A developer carrier having
A regulating member that regulates the layer thickness of the developer layer formed on the developer carrier;
A method for producing a developing device comprising :
The developing sleeve is dipped in a coating solution made of a resin material from one end side in the longitudinal direction and is pulled up from the other end side, and the film thickness on the lower end side when the toner carrier is dipped on the outer peripheral surface of the developing sleeve. Forming a coat layer that is thicker than the film thickness of the central portion in the longitudinal direction of the toner carrier ,
When the main pole has a magnetic force gradient in the longitudinal direction of the developer carrier, the lower end side during dipping of the developing sleeve is arranged on the side where the magnetic force is higher in the longitudinal direction of the main pole ,
If the regulating pole has a magnetic force gradient in the longitudinal direction of the developer carrier, a developing apparatus characterized by disposing the upper side at the time of the dipping of the developing sleeve to force the higher side in the longitudinal direction of the regulating pole Manufacturing method. 2. The method of manufacturing a developing device according to claim 1, wherein the magnet constituting at least one of the main electrode and the regulating electrode is a plastic magnet in which magnetic powder is dispersed in a resin material. The method for manufacturing a developing device according to claim 1, wherein the coat layer is formed of alcohol-soluble nylon, and titanium oxide is dispersed in the coat layer. 4. The developing sleeve according to claim 1, wherein an alumite layer is formed on an outer peripheral surface made of aluminum or an aluminum alloy, and the coat layer is formed on a surface of the alumite layer. A method for manufacturing a developing device.

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