WO2017155125A1 - 現像装置 - Google Patents
現像装置 Download PDFInfo
- Publication number
- WO2017155125A1 WO2017155125A1 PCT/JP2017/010289 JP2017010289W WO2017155125A1 WO 2017155125 A1 WO2017155125 A1 WO 2017155125A1 JP 2017010289 W JP2017010289 W JP 2017010289W WO 2017155125 A1 WO2017155125 A1 WO 2017155125A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- developing
- magnetic
- pole
- flux density
- developing sleeve
- Prior art date
Links
Images
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
- G03G15/0914—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush with a one-component toner
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
- G03G15/0812—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer regulating means, e.g. structure of doctor blade
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
- G03G15/0921—Details concerning the magnetic brush roller structure, e.g. magnet configuration
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G2215/00—Apparatus for electrophotographic processes
- G03G2215/06—Developing structures, details
- G03G2215/0602—Developer
- G03G2215/0604—Developer solid type
- G03G2215/0607—Developer solid type two-component
- G03G2215/0609—Developer solid type two-component magnetic brush
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G2215/00—Apparatus for electrophotographic processes
- G03G2215/06—Developing structures, details
- G03G2215/0634—Developing device
Definitions
- the present invention relates to a developing device used in an image forming apparatus such as an electrophotographic system or an electrostatic recording system, and more particularly to a developing apparatus that uses a two-component developer that is a mixture of a nonmagnetic toner and a magnetic carrier.
- electrophotographic image forming apparatuses have been widely applied as copiers, printers, plotters, facsimiles, and multifunction machines having a plurality of these functions.
- a charged toner is brought close to a photosensitive drum, and development is performed by electrostatically attaching the toner to an electrostatic latent image on the photosensitive drum, thereby forming an image.
- a developing method a developing method using a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed as well as a developing method using a one-component developer made of a magnetic toner as a developer has become widespread.
- the development method using a two-component developer it is possible to form a color image with excellent color tone because it is excellent in toner charge amount stability, and is particularly suitable for an image forming apparatus for color images. Has been applied.
- the developer is supported on the developing sleeve by a magnet (magnetic field generating means) fixedly arranged in the developing sleeve, and the magnetic carrier forms magnetic spikes along the magnetic field lines of the magnetic field generating means.
- a magnet magnetic field generating means
- the magnetic carrier forms magnetic spikes along the magnetic field lines of the magnetic field generating means.
- the magnetic brush moves away from the photosensitive drum through a region where the developing sleeve is closest to the photosensitive drum.
- the area from when the magnetic brush contacts the photosensitive drum until it leaves is a contact nip, and in this specification, this contact nip is called a development area.
- toner is adhered by the force of the electric field generated by the potential difference between the developing sleeve and the electrostatic latent image on the photosensitive drum, and a toner image is formed.
- the development efficiency it is important to increase the amount of toner development per potential difference between the exposure potential on the photosensitive drum and the development sleeve, so-called development efficiency. If the development efficiency is low, in order to obtain a sufficient image density, it is necessary to increase the toner development amount by increasing the electric field strength by increasing the potential difference between the exposure potential and the development sleeve. However, if the electric field strength is too high, the carrier in the two-component developer may adhere to the photosensitive drum together with the toner. The carrier adhering to the photosensitive drum hinders toner transfer and causes white spots in the image. Therefore, it is necessary to increase the toner development amount without increasing the electric field strength.
- the developer spike region may be increased in the region where the developing sleeve is close to the photosensitive drum.
- a developing device is known in which the half-value width of the developing magnetic pole facing the photosensitive drum among the plurality of magnetic poles constituting the magnetic field generating means fixedly arranged in the developing sleeve is increased in order to increase the developer rising area.
- the development area is simply increased by increasing the half width of the development magnetic pole in the magnetic flux density, for example, a normal distribution of the development magnetic pole. It did not consider the linearity of the magnetic field lines. For this reason, the magnetic field lines are curved along the surface of the photosensitive drum in the upstream portion and the downstream portion in the rotation direction of the developing region, and the tip of the magnetic spike is inclined along the surface of the photosensitive drum. Contact.
- An object of the present invention is to provide a developing device capable of suppressing a decrease in developing efficiency by controlling the contact state of the tip of a magnetic spike with respect to a photosensitive drum while expanding a developing region.
- a developer having toner and a magnetic carrier is supported, and the electrostatic latent image formed on the image carrier can be developed in a development area where the developer contacts the image carrier.
- a developing sleeve, and a magnetic field generator having a developing pole provided inside the developing sleeve and facing the image carrier to form the developing region, and a normal line of the developing sleeve
- the ratio of the 80% value width of the magnetic flux density of the developing pole in the direction to the half-value width of the magnetic flux density in the normal direction of the developing magnetic pole is 0.65 or more, and in the vicinity of both ends of the developing area in the rotation direction of the developing sleeve
- a developing device is provided in which the magnetic force of the developing pole in the normal direction of each of the developing sleeves is greater than the magnetic force at the center of the developing region.
- a developer carrying a developer having toner and a magnetic carrier, and rotating the electrostatic latent image formed on the image carrier in a development area where the developer contacts the image carrier.
- a developing sleeve, a magnetic field generator provided inside the developing sleeve and having a developing pole at a position facing the image carrier to form the developing region, and a DC voltage is applied to the developing sleeve
- a developing device that develops an electrostatic latent image on an image carrier by applying a DC voltage to the developing sleeve without using an AC voltage, the developing in the normal direction of the developing sleeve
- a developing device is provided in which the ratio of the 80% value width of the magnetic flux density of the pole to the half value width of the magnetic flux density in the normal direction of the developing magnetic pole is 0.65 or more.
- a developer having a toner and a magnetic carrier is carried, and an electrostatic latent image formed on the image carrier is developed in a development area where the developer contacts the image carrier.
- a ratio of the 80% value width of the magnetic flux density of the developing pole in the normal direction of the developing sleeve to the half-value width of the magnetic flux density in the normal direction of the developing magnetic pole is 0.65 or more
- the angle formed by the peak of the magnetic flux density of the first pole and the peak of the magnetic flux density of the second pole, and the angle formed by the peak of the magnetic flux density of the first pole and the peak of the magnetic flux density of the third pole are Development devices that are each 90 ° or less are provided.
- the present invention it is possible to suppress a decrease in development efficiency by controlling the contact state of the tip of the magnetic spike with the photosensitive drum while expanding the development region.
- FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment.
- FIG. 2 is a sectional view showing a schematic configuration of the developing device according to the embodiment.
- FIG. 3 is an explanatory diagram showing the relationship between the angle around the developing region of the developing sleeve according to Example 1 and Comparative Examples 1 and 2 and the magnetic flux density in the normal direction.
- FIG. 4A is an explanatory diagram showing the relationship between the magnetic lines of force and the magnetic spikes in the developing region of the developing device according to Comparative Example 2
- FIG. 4B is a diagram illustrating the photosensitive of toner in the developing region according to the developing device of Comparative Example 2.
- FIG. 6 is an enlarged view of the upstream side in the rotation direction of the developing sleeve showing a state in which flight to the drum is inhibited.
- FIG. 5A is an explanatory diagram showing the relationship between the magnetic lines of force and the magnetic spikes in the developing region of the developing device according to the first embodiment
- FIG. 5B is a diagram illustrating the sensitivity of toner in the developing region of the developing device according to the first embodiment.
- FIG. 6 is an enlarged view of the upstream side of the developing sleeve in the rotation direction, showing a state in which flight to the drum is performed.
- FIG. 6 is an explanatory diagram showing the relationship between the angle around the developing region of the developing sleeve according to Examples 1 and 2 and Comparative Examples 1 and 2 and the magnetic attractive force in the developing sleeve direction.
- FIG. 7 is an explanatory diagram showing the relationship between the angle around the developing region of the developing sleeve according to Example 1 and the change in the magnetic flux density in the normal direction.
- FIG. 8A and 8B are explanatory diagrams of the developing magnetic pole magpiece, where FIG. 8A shows a conventional magnet with symmetrical magnetization, and FIG. 8B shows a magpiece with asymmetric magnetization according to the embodiment.
- FIG. 9 shows a conventional magnetizing method.
- the present invention is not limited to a developing device of a tandem type image forming apparatus, and may be a developing device of an image forming apparatus of another type, and is not limited to a full color, and is monochrome or mono color. There may be. Alternatively, it can be implemented in various applications such as a printer, various printing machines, a copying machine, a FAX, and a multifunction machine by adding necessary equipment, equipment, and a housing structure.
- the image forming apparatus 1 includes the intermediate transfer belt 44b. After the primary transfer of the toner images of each color from the photosensitive drum 81 to the intermediate transfer belt 44b, the composite toner image of each color is applied to the sheet S. It is a system that performs secondary transfer in a batch. However, the present invention is not limited to this, and a method of directly transferring from the photosensitive drum to the sheet conveyed by the sheet conveying belt may be employed.
- a two-component developer composed of a nonmagnetic toner and a magnetic carrier is used as the developer.
- the toner is produced by pulverization or polymerization by encapsulating a colorant, a wax component or the like in a resin such as polyester or styrene.
- the carrier is generated by applying a resin coat to the surface layer of the core made of resin particles kneaded with ferrite particles or magnetic powder.
- the image forming apparatus 1 includes an image forming apparatus main body (hereinafter referred to as an apparatus main body) 10 as a housing.
- the apparatus main body 10 includes an image reading unit 11, a sheet feeding unit 30, an image forming unit 40, a sheet conveying unit 50, a sheet discharging unit 60, and a control unit 70.
- the sheet S as a recording material is formed with a toner image, and specific examples include plain paper, a resin sheet as a substitute for plain paper, cardboard, and an overhead projector sheet.
- the image reading unit 11 is provided on the upper part of the apparatus main body 10.
- the image reading unit 11 includes a platen glass (not shown) as a document placement table, a light source (not shown) that irradiates light on the document placed on the platen glass, and an image sensor (not shown) that converts reflected light into a digital signal. Etc.
- the sheet feeding unit 30 is disposed at the lower part of the apparatus main body 10 and includes sheet cassettes 31a and 31b for stacking and storing sheets S such as recording paper and feeding rollers 32a and 32b.
- the sheet S is fed to the image forming unit 40.
- the image forming unit 40 includes an image forming unit 80, a toner hopper 41, a toner container 42, a laser scanner 43, an intermediate transfer unit 44, a secondary transfer unit 45, and a fixing device 46.
- the image forming unit 40 can form an image on the sheet S based on the image information.
- the image forming apparatus 1 according to the present embodiment is compatible with full color, and the image forming units 80y, 80m, 80c, and 80k are yellow (y), magenta (m), cyan (c), black ( Each of the four colors k) is provided separately with the same configuration.
- the toner hoppers 41y, 41m, 41c, and 41k and the toner containers 42y, 42m, 42c, and 42k have the same configuration for each of the four colors of yellow (y), magenta (m), cyan (c), and black (k). It is provided separately. For this reason, in FIG. 1, each of the four color components is shown with the same symbol followed by a color identifier, but in FIG. 2 and the description, there may be a case where only the symbol is used without adding the color identifier. .
- the toner container 42 is, for example, a cylindrical bottle, and stores toner, and is disposed above each image forming unit 80 via a toner hopper 41.
- the laser scanner 43 exposes the surface of the photosensitive drum 81 charged by the charging roller 82 to form an electrostatic latent image on the surface of the photosensitive drum 81.
- the image forming unit 80 includes four image forming units 80y, 80m, 80c, and 80k for forming toner images of four colors.
- Each image forming unit 80 includes a photosensitive drum (image carrier) 81 that forms a toner image, a charging roller 82, a developing device 20, and a cleaning blade 84.
- the photosensitive drum 81, the charging roller 82, the developing device 20, the cleaning blade 84, and the developing sleeve 24 described later are also yellow (y), magenta (m), cyan (c), and black (k). These four colors are separately provided with the same configuration.
- the photosensitive drum 81 has a photosensitive layer formed on the outer peripheral surface of the aluminum cylinder so as to have a negative polarity, and rotates in a direction indicated by an arrow at a predetermined process speed (peripheral speed).
- the charging roller 82 contacts the surface of the photosensitive drum 81 and charges the surface of the photosensitive drum 81 to, for example, a uniform negative-polarity dark portion potential.
- an electrostatic image is formed by the laser scanner 43 based on the image information.
- the photosensitive drum 81 carries the formed electrostatic image, moves around, and is developed with toner by the developing device 20. The detailed configuration of the developing device 20 will be described later.
- the developed toner image is primarily transferred to an intermediate transfer belt 44b described later.
- the surface of the photosensitive drum 81 after the primary transfer is neutralized by a pre-exposure unit (not shown).
- the cleaning blade 84 is disposed in contact with the surface of the photosensitive drum 81 and cleans residues such as transfer residual toner remaining on the surface of the photosensitive drum 81 after the primary transfer.
- the intermediate transfer unit 44 is disposed above the image forming units 80y, 80m, 80c, and 80k.
- the intermediate transfer unit 44 includes a plurality of rollers such as a driving roller 44a, a driven roller 44d, and primary transfer rollers 44y, 44m, 44c, and 44k, and an intermediate transfer belt 44b wound around these rollers.
- the primary transfer rollers 44y, 44m, 44c, and 44k are disposed to face the photosensitive drums 81y, 81m, 81c, and 81k, respectively, and contact the intermediate transfer belt 44b.
- the intermediate transfer belt 44b moves by transferring the toner image obtained by developing the electrostatic image on the surface of the photosensitive drums 81y, 81m, 81c, 81k.
- the secondary transfer unit 45 includes a secondary transfer inner roller 45a and a secondary transfer outer roller 45b.
- a full color image formed on the intermediate transfer belt 44b is transferred to the sheet S by applying a positive secondary transfer bias to the secondary transfer outer roller 45b.
- the fixing device 46 includes a fixing roller 46a and a pressure roller 46b. When the sheet S is nipped and conveyed between the fixing roller 46a and the pressure roller 46b, the toner image transferred to the sheet S is heated and pressurized and fixed to the sheet S.
- the sheet conveying unit 50 includes a pre-secondary transfer conveying path 51, a pre-fixing conveying path 52, a discharge path 53, and a re-conveying path 54, and forms an image of the sheet S fed from the sheet feeding unit 30.
- the sheet is conveyed from the section 40 to the sheet discharge section 60.
- the sheet discharge unit 60 includes a discharge roller pair 61 disposed on the downstream side of the discharge path 53 and a discharge tray 62 disposed on the downstream side of the discharge roller pair 61.
- the discharge roller pair 61 feeds the sheet S conveyed from the discharge path 53 from the nip portion and discharges the sheet S to the discharge tray 62 through the discharge port 10 a formed in the apparatus main body 10.
- the discharge tray 62 is a face-down tray, and stacks the sheets S discharged in the arrow X direction from the discharge port 10a.
- the control unit 70 is configured by a computer and includes, for example, a CPU, a ROM that stores a program for controlling each unit, a RAM that temporarily stores data, and an input / output circuit that inputs and outputs signals to and from the outside.
- the CPU is a microprocessor that controls the entire control of the image forming apparatus 1 and is the main body of the system controller.
- the CPU is connected to the image reading unit 11, the sheet feeding unit 30, the image forming unit 40, the sheet conveying unit 50, the sheet discharging unit 60, and the operation unit via the input / output circuit, and exchanges signals with each unit and operates. To control.
- the photosensitive drum 81 is rotated and the surface is charged by the charging roller 82. Then, laser light is emitted from the laser scanner 43 to the photosensitive drum 81 based on the image information, and an electrostatic latent image is formed on the surface of the photosensitive drum 81.
- toner adheres to the electrostatic latent image, it is developed and visualized as a toner image, and transferred to the intermediate transfer belt 44b.
- the feeding rollers 32a and 32b rotate in parallel with the toner image forming operation, and the uppermost sheet S of the sheet cassettes 31a and 31b is fed while being separated. Then, the sheet S is conveyed to the secondary transfer unit 45 via the pre-secondary transfer conveyance path 51 in synchronization with the toner image on the intermediate transfer belt 44b. Further, the image is transferred from the intermediate transfer belt 44b to the sheet S, and the sheet S is conveyed to the fixing device 46, where an unfixed toner image is heated and pressed to be fixed on the surface of the sheet S, and a pair of discharge rollers. 61 is discharged from the discharge port 10a and stacked on the discharge tray 62.
- the developing device 20 includes a developing container 21 that stores a developer, a first conveying screw 22 and a second conveying screw 23, a developing sleeve 24, and a regulating member 25.
- the developing container 21 has an opening 21 a through which the developing sleeve 24 is exposed at a position facing the photosensitive drum 81.
- the developing container 21 is supplied with toner from a toner container 42 (see FIG. 1) filled with toner.
- the developing container 21 has a partition wall 27 extending in the longitudinal direction at a substantially central portion.
- the developing container 21 is partitioned by the partition wall 27 into a developing chamber 21b and a stirring chamber 21c in the horizontal direction.
- the developer is accommodated in the developing chamber 21b and the stirring chamber 21c.
- the developing chamber 21 b supplies developer to the developing sleeve 24.
- the stirring chamber 21c communicates with the developing chamber 21b, collects the developer from the developing sleeve 24, and stirs it.
- the first conveying screw 22 is arranged in the developing chamber 21b substantially parallel to the developing sleeve 24 along the axial direction of the developing sleeve 24, and conveys the developer in the developing chamber 21b while stirring.
- the second transport screw 23 is disposed in the stirring chamber 21 c substantially parallel to the axis of the first transport screw 22, and transports the developer in the stirring chamber 21 c in the opposite direction to the first transport screw 22. That is, the developing chamber 21b and the stirring chamber 21c constitute a developer circulation path for transporting the developer while stirring.
- the toner is agitated by the screws 22 and 23, the toner is rubbed with the carrier and is triboelectrically charged to a negative polarity.
- the developing sleeve 24 carries a developer having non-magnetic toner and a magnetic carrier, and rotates and conveys it to the developing area Da facing the photosensitive drum 81.
- the range in which the magnetic spike formed by the carrier on the surface of the developing sleeve 24 contacts the photosensitive drum 81 is a contact nip, and in this embodiment, this contact nip is defined as a development area Da (FIG. 5 ( a)). That is, the development area Da is an area where the magnetic ears carried on the development sleeve 24 come into contact with the photosensitive drum 81.
- the developing sleeve 24 has a cylindrical shape with a diameter of 20 mm, for example, and is made of a nonmagnetic material such as aluminum or nonmagnetic stainless steel.
- the developing sleeve 24 is made of aluminum.
- the shortest interval in the development area Da is about 320 ⁇ m.
- the negatively charged toner is electrostatically restrained on the surface of the positively charged carrier to form a magnetic spike. Then, by providing a potential difference between the DC voltage applied to the developing sleeve 24 and the electrostatic latent image on the photosensitive drum 81, the toner is caused to fly to the photosensitive drum 81 to make the latent image visible.
- the developer in the developing container 21 is carried on the developing sleeve 24 by the magnet roller 24 m fixedly arranged inside the developing sleeve 24. Thereafter, the developer on the developing sleeve 24 is regulated in layer thickness by the regulating member 25, and is conveyed to the developing area Da facing the photosensitive drum 81 as the developing sleeve 24 rotates. In the developing area Da, the developer on the developing sleeve 24 spikes to form a magnetic spike. By bringing the magnetic brush into contact with the photosensitive drum 81, the toner is supplied to the photosensitive drum 81, whereby the electrostatic latent image on the photosensitive drum 81 is developed as a toner image.
- the developing process of the toner onto the photosensitive drum 81 in the developing area Da will be described.
- the photosensitive drum 81 is uniformly charged to the charging potential Vd [V] by the charging roller 82
- the image portion is exposed by the laser scanner 43 to become the exposure potential Vl [V].
- a developing bias in which a DC voltage and an AC voltage are superimposed is usually applied to the developing sleeve 24.
- Vdc the absolute value
- of the difference between the DC voltage Vdc and the charging potential Vd is called Vback, and forms an electric field that pulls back from the photosensitive drum 81 toward the developing sleeve 24 with respect to the toner. This is provided in order to suppress the so-called fogging phenomenon in which the toner adheres to the non-image portion.
- the developing sleeve 24 is a DC developing method in which only a direct current voltage is applied to the developing sleeve 24.
- the regulating member 25 is provided in the developing container 21 so as to face the regulating magnetic pole N1 of the magnet roller 24m.
- the regulating member 25 is fixed to the developing container 21 with a predetermined gap from the developing sleeve 24 at the tip, and the layer thickness is regulated by cutting off the magnetic spikes of the developer carried on the surface of the developing sleeve 24.
- the regulating member 25 is made of a non-magnetic metal plate (for example, an aluminum plate) disposed in the longitudinal direction of the developing sleeve 24, and the developer passes between the leading end portion of the regulating member 25 and the developing sleeve 24 to develop the developing area Da. Sent to.
- a roller-shaped magnet roller (magnetic field generating means) 24m is fixedly installed in a non-rotating state with respect to the developing container 21.
- the magnet roller 24m has five mag pieces, each having a magnetic pole facing the developing sleeve 24.
- the developing magnetic pole S2 first magnetic pole
- the regulating magnetic pole N1 second magnetic pole
- the transport magnetic pole N2 third magnetic pole
- the separation magnetic pole S3 fourth magnetic pole
- the pumping magnetic pole S1 fifth magnetic pole
- the pumping magnetic pole S1 is disposed to face the developing chamber 21b.
- the regulation magnetic pole N1 is disposed to face the regulation member 25.
- the transport magnetic pole N2 is disposed on the downstream side in the rotation direction of the development area Da.
- the separation magnetic pole S3 is disposed adjacent to the upstream side of the pumping magnetic pole S1 in the rotation direction.
- the development magnetic pole S2 is disposed to face the development area Da.
- the magnet roller 24m employs a magnet piece having only one peak of the magnetic flux density Br as the developing magnetic pole S2.
- the development magnetic pole S2 having only one peak of the magnetic flux density Br is sandwiched between reversal positions where the polarity of the magnetic flux density Br is reversed between the regulation magnetic pole N1 and the transport magnetic pole N2 adjacent to the development magnetic pole S2. It means a configuration in which there is one Br peak in the region.
- the region sandwiched between the reversal positions where the polarity of the magnetic flux density Br is reversed between the regulation magnetic pole N1 and the transport magnetic pole N2 corresponds to a range of 260 ° to 320 °.
- the development magnetic pole S2 has a planar plane portion 24s that faces the development area Da. That is, the magnet roller 24m as a whole has a so-called cross-sectional D-cut shape, and the magnet piece having the developing magnetic pole S2 has a substantially fan-shaped cross section. Both edge portions in the rotation direction of the flat surface portion 24s form corner portions 24c.
- the developing magnetic pole S2 has corner portions 24c on the outer peripheral surface of the developing sleeve 24 that are opposed to the developing area Da on the upstream side in the rotational direction and the downstream side in the rotational direction, and between the corner portions 24c. It has a planar portion 24s.
- the magnetic attraction force Fr can be kept high in the development area Da (see Examples 1 and 2 in FIG. 6), and the magnetic ear is firmly restrained by the developing sleeve 24, so that the magnetic ear becomes the developing sleeve. It becomes difficult to slip on 24 and the speed reduction of the magnetic spike can be suppressed.
- the development magnetic pole S2 has a peak of the magnetic attraction force Fr in the center direction of the development sleeve 24 at a portion facing the development area Da on the outer peripheral surface of the development sleeve 24 on the upstream side in the rotation direction and the downstream side in the rotation direction. (See Examples 1 and 2 in FIG. 6).
- the fact that the developing magnetic pole S2 has a peak of the magnetic attractive force Fr toward the center of the developing sleeve 24 means the following configuration. That is, it means a configuration in which the magnetic attraction force Fr has a peak in a region between reversal positions where the polarity of the magnetic flux density Br is reversed between the regulation magnetic pole N1 and the transport magnetic pole N2 adjacent to the developing magnetic pole S2.
- the developing magnetic pole S2 since the developing magnetic pole S2 here has a magnetic flux density Br as shown in FIG. 3, the peak of the magnetic attractive force Fr in the range of 260 ° to 320 ° is called the peak of the magnetic attractive force Fr of the developing magnetic pole S2.
- the developing magnetic pole S2 has two magnetic attraction force Fr peaks in the vicinity of 270 ° and 310 °. Moreover, the peak of the magnetic attractive force is larger on the downstream side in the rotational direction than on the upstream side in the rotational direction, and the lowest peak on the upstream side in the rotational direction between the peak on the upstream side in the rotational direction and the peak on the downstream side in the rotational direction. It has a point (refer to Example 1 in FIG. 6). As a result, the downstream of the developing region Da in the rotational direction has a larger magnetic attractive force than the upstream side in the rotational direction, so that carrier adhesion to the photosensitive drum 81 on the downstream side in the rotational direction can be suppressed.
- the ratio of the 80% value width and the half value width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 with respect to the outer peripheral surface of the developing sleeve 24 is, for example, 0.74.
- the ratio of the 80% value width and the half value width of the magnetic flux density Br, which is a normal distribution is 0.60. That is, the ratio of the 80% value width and the half value width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 with respect to the outer peripheral surface of the developing sleeve 24 is based on the ratio of the 80% value width and the half value width of the magnetic flux density Br which is a normal distribution. It is large and is 0.65 or more (see FIG.
- the 80% value width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 with respect to the outer peripheral surface of the developing sleeve 24 is, for example, 35 °.
- the width in the rotation direction of the development area Da is 28.6 °. That is, the 80% value width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 with respect to the outer peripheral surface of the developing sleeve 24 is wider than the rotational width of the developing region Da (see FIG. 3).
- the half width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 on the outer peripheral surface of the developing sleeve 24 is set to 40 ° or more.
- the lines of magnetic force are linearly directed toward the surface of the photosensitive drum 81 also in the upstream portion and the downstream portion in the rotation direction of the development area Da. Therefore, since the tip of the magnetic brush contacts the dot shape without being along the surface of the photosensitive drum 81 (see FIG. 5A), the toner is not obstructed by the magnetic brush from the developing sleeve 24 side. (See FIG. 5B).
- the developing sleeve 24 rotates in the direction of the arrow, and the developer stored in the developing chamber 21b is attracted by the pumping magnetic pole S1 facing the developing chamber 21b and conveyed toward the regulating member 25.
- the developer is spiked by the regulating magnetic pole N1 facing the regulating member 25, the layer thickness is regulated by the regulating member 25, and passes through the gap between the developing sleeve 24 and the regulating member 25, so that a predetermined amount is formed on the developing sleeve 24.
- a developer layer having a layer thickness is formed.
- the developer layer is carried and conveyed to the developing area Da facing the photosensitive drum 81, and the electrostatic latent image formed on the surface of the photosensitive drum 81 in a state where magnetic spikes are formed by the developing magnetic pole S2 facing the developing area Da.
- the developing magnetic pole S2 causes the carrier carried in the developing area Da to stand up against the developing area Da of the developing sleeve 24.
- the developer After being subjected to development, the developer is developed in a separation region created by repulsion of the separation magnetic pole S3 and the pumping magnetic pole S1 through the transport magnetic pole N2 disposed downstream in the rotation direction of the development region Da.
- the sleeve 24 is peeled off.
- the peeled developer is stirred and conveyed in the stirring chamber 21c, and is supplied again from the developing chamber 21b to the developing sleeve 24.
- the ratio between the 80% value width and the half value width of the magnetic flux density Br in the normal direction of the developing magnetic pole S2 with respect to the outer peripheral surface of the developing sleeve 24 is a normal distribution. It is larger than the ratio of the 80% value width and the half value width of the magnetic flux density. For this reason, the 80% value width of the magnetic flux density becomes wider as compared with the case where the development area is increased by simply increasing the half width of the developing magnetic pole in the normal distribution magnetic flux density. Thereby, the magnetic lines of force are linearly directed to the surface of the photosensitive drum 81 also in the upstream portion and the downstream portion in the rotation direction of the developing area Da.
- the tip of the magnetic brush contacts the dot shape without being along the surface of the photosensitive drum 81, the toner can fly from the developing sleeve 24 side to the photosensitive drum 81 without being blocked by the magnetic brush. Accordingly, it is possible to suppress a decrease in development efficiency due to contact of the tip of the magnetic spike with the photosensitive drum 81 while expanding the development area Da.
- the developing magnetic pole S2 has only one peak of the magnetic flux density Br. For this reason, unlike the case where two or more same-polarity peaks of the magnetic flux density Br are provided in the development area Da, the magnetic field lines do not repel between the same-polarity peaks of the magnetic flux density Br. The part where it becomes difficult to form the magnetic ear is not generated. For this reason, magnetic spikes can be sufficiently formed, so that development efficiency can be improved.
- Example 1 of the developing magnetic pole S2 of the magnet roller 24m according to the present embodiment will be described in comparison with Comparative Examples 1 and 2.
- the magnetic flux density Br of the developing magnetic pole S2 of the magnet roller 24m will be described in detail with reference to FIG.
- a magnet roller using the magnet roller 24m of the present embodiment is referred to as Example 1.
- a magnet roller using a developing magnetic pole S2 having a narrow half-value width is referred to as Comparative Example 1
- a magnet roller using a developing magnetic pole S2 having a wider half-value width than Comparative Example 1 is used as Comparative Example 2. did.
- FIG. 3 shows the magnetic flux density (solid line) of the developing magnetic pole S2 of the present embodiment as Example 1, the magnetic flux density (dotted line) of the developing magnetic pole S2 having a narrow half-value width as Comparative Example 1, and the half of the comparative example 1 as Comparative Example 2.
- the magnetic flux density (broken line) of the developing magnetic pole S2 with a wide value width is shown.
- the half-value width represents the width of the portion where the magnetic flux density (its normal component) of the developing magnetic pole S2 becomes half of the peak value by the angle ⁇ .
- it may be called full width at half maximum.
- the half width at half maximum refers to the full width at half maximum.
- the 80% value width represents the width of the portion where the magnetic flux density (its normal component) of the developing magnetic pole S2 is 80% of the peak value by the angle ⁇ .
- the 80% value width simply refers to the full width.
- Comparative Example 2 is a magnetic flux density distribution when the full width at half maximum is widened by expanding the shape of the magnetic flux density of the developing magnetic pole S2 of Comparative Example 1 almost similarly.
- Example 1 when the full width at half maximum is widened, it is not widened in a similar manner as in Comparative Example 2, but the full width at half maximum is widened by 80% more than the full width at half maximum.
- Table 1 shows the half value width and the 80% value width, and the value obtained by dividing the 80% value width by the half value width for Comparative Example 1, Comparative Example 2, and Example 1.
- the half value width of Comparative Example 2 is larger than that of Comparative Example 1, but the value obtained by dividing the 80% value width by the half value width does not change much. This is because Comparative Example 2 widens the full width at half maximum by similarly expanding the shape of the magnetic flux density.
- Example 1 has a half-value width larger than that of Comparative Example 1 as in Comparative Example 2, but the value obtained by dividing the 80% value width by the half-value width is also large. Are different features.
- the ratio between the 80% value width and the half value width is about 0.60 in the case of a normal normal distribution type magnetic flux density distribution shape.
- the 80% width / half width is larger than 0.65. More preferably, it is 0.66 or more, and more preferably 0.70 or more. Since the 80% value width / half-value width of Example 1 is 0.74, it is possible to more effectively suppress a decrease in development efficiency due to contact of the tips of the magnetic spikes.
- Example 1 and Comparative Example 2 will be described based on FIGS. 4 and 5 by comparing the magnetic field lines ML and the shape of the magnetic spike B.
- Comparative Example 2 as shown in FIG. 4A, the magnetic lines of force ML from the developing sleeve 124 extend from the center side while spreading relatively horizontally. This is because the magnetic flux density distribution of Comparative Example 2 has a shape that gradually attenuates from the peak of the developing magnetic pole S2, so that the magnetic lines of force ML spread in the horizontal direction and are likely to wrap around.
- the posture of the magnetic spike B is along the magnetic field lines ML created by the respective magnetic poles.
- the magnetic lines of force ML extend relatively inclined with respect to the surface of the photosensitive drum 81, so that the tip of the magnetic spike B is inclined and contacts so as to cover the photosensitive drum 81. Therefore, as shown in FIG. 4B, the flying of the toner T in the vicinity of the developing sleeve 124 to the photosensitive drum 81 is hindered, and the developing efficiency is lowered.
- the magnetic lines of force ML extend in the direction of the photosensitive drum 81 relatively linearly. This is because the magnetic flux density distribution of Example 1 has a shape that gently changes from the peak of the developing magnetic pole S2 and does not change so much, and therefore, the magnetic field lines ML are difficult to wrap around in the horizontal direction.
- the magnetic field lines ML extend relatively straight with respect to the surface of the photosensitive drum 81, so that the tips of the magnetic spikes B extend toward the photosensitive drum 81. Therefore, the tip of the magnetic ear B contacts in a dot shape without being along the surface of the photosensitive drum 81. As a result, as shown in FIG.
- each of the angles with the upstream and downstream poles of the developing magnetic pole is 90 ° or less. That is, the angle between the magnetic flux density peak of the developing magnetic pole S2 and the magnetic flux density peak of the regulating magnetic pole N1 is 90 ° or less, and between the magnetic flux density peak of the developing magnetic pole S2 and the magnetic flux density peak of the conveying magnetic pole N2. The angle is 90 ° or less.
- the magnet roller 24m of the present embodiment has the peak of the magnetic flux density corresponding to the five magnetic poles, but the present invention is not limited to this configuration. However, in the case of a magnet roller composed of three magnetic poles, the angle with the upstream and downstream poles of the developing magnetic pole tends to widen, making it difficult to satisfy the above conditions. Therefore, the magnet roller 24m preferably has five or more magnetic poles.
- the absolute value of the magnetic flux density (normal component) of the developing magnetic pole is preferably 90 mT or more, more preferably 95 mT or more.
- the magnetic poles N1 and N2 upstream and downstream of the developing magnetic pole S2 in this embodiment are not adjacent to the same magnetic pole, but when the magnetic poles upstream and downstream of the developing magnetic pole are adjacent to the same magnetic pole, the magnetic field lines of the developing magnetic pole are It becomes easy to stretch while spreading relatively horizontally from the center side.
- the magnetic field lines of the magnetic poles upstream and downstream of the developing magnetic pole are less likely to extend in the adjacent same magnetic direction, and the magnetic field lines are biased toward the developing magnetic pole direction and extend. Accordingly, it is preferable that the upstream and downstream magnetic poles of the developing magnetic pole are not adjacent to the same magnetic pole. In the case of a magnet roller composed of three magnetic poles, since the upstream and downstream magnetic poles of the developing magnetic pole are adjacent to the same magnetic pole, it is preferable to have five or more magnetic poles. By setting it as the above structures, the effect of this invention can be acquired more effectively.
- the state where the tip of the magnetic spike extends toward the photosensitive drum 81 in the development area Da is possible as much as possible. It is preferable that it can be maintained.
- the change in magnetic flux density (its normal component) in the development area Da is gentle and does not change much. Therefore, by making the 80% value range of the magnetic flux density (its normal component) wider than that of the development region Da, the change in the magnetic flux density (the normal component) in the development region Da can be reduced.
- the developing device 20 is pulled away from the photosensitive drum 81, and the width of the area on the photosensitive drum 81 where the toner adheres is measured to obtain the width of the developing area Da.
- the development area Da means a contact nip where a magnetic spike formed by a carrier on the surface of the development sleeve 24 contacts the photosensitive drum 81.
- the half width is preferably 36 ° or more, and more preferably 40 ° or more.
- the 80% value width is preferably 26 ° or more, and more preferably 30 ° or more.
- the magnetic flux density Br has one peak in the development area Da.
- the contact state between the photosensitive drum 81 and the magnetic spike in the development area Da has a large relationship with the development amount.
- the inventors of the present application observed the behavior of the developer in the vicinity of the photosensitive drum 81 and the developing sleeve 24 from the inner surface using a transparent photosensitive drum using a high-speed camera (FASTCAM SA5 manufactured by Photon). . As a result, the following was found.
- the developing sleeve 24 is usually set so that its peripheral speed is usually faster than that of the photosensitive drum 81. This is because the development efficiency improves as the ratio of the peripheral speed of the developing sleeve 24 to the photosensitive drum increases. However, if the peripheral speed ratio is too large, toner scattering, developer deterioration, and the like occur, so the ratio is often set to 1.4 to 2.1 times.
- the circumferential speed ratio of the developing sleeve 24 to the photosensitive drum is set to 1.8 times. In this embodiment, since the rotation direction of the photosensitive drum 81 and the rotation direction of the developing sleeve 24 are opposite to each other, the peripheral speed of the developing sleeve 24 is 1.8 times the peripheral speed of the photosensitive drum 81.
- the inventors of the present application observe the behavior of the developer in the vicinity of the photosensitive drum 81 and the developing sleeve 24 with respect to Comparative Example 2 and Example 1, and the surface of the photosensitive drum 81 of the developer in contact with the photosensitive drum 81 is observed.
- the moving (average) moving speed was calculated by PIV analysis. Even when the peripheral speed of the developing sleeve 24 is set faster than the peripheral speed of the photosensitive drum 81 as in the first embodiment, the (average) moving speed of the developer is slower than the peripheral speed of the developing sleeve 24. There are many. As a result of the inventor's study, the drop in speed was smaller in Example 1 than in Comparative Example 2.
- the difference in the movement speed of the magnetic spikes as described above is considered to be closely related to the magnetic attractive force Fr that attracts the developer toward the center of the developing sleeve 24.
- the magnetic attraction force Fr that attracts the magnetic spike toward the center of the developing sleeve 24 is large, the magnetic spike is firmly restrained by the developing sleeve 24, so that the magnetic spike is difficult to slip on the developing sleeve and the speed of the magnetic spike is reduced. Can be suppressed.
- the magnetic attractive force Fr of the developing sleeve 24 is expressed by the following formula 1.
- Equation 1 ⁇ is the magnetic carrier permeability, ⁇ 0 is the vacuum magnetic permeability, and b is the magnetic carrier radius.
- B ⁇ is obtained from Equation 2 below using the value of Br measured by the above method.
- FIG. 6 shows the magnetic attraction force Fr around the development area Da calculated by Equations 1 and 2.
- the magnitude of the magnetic attractive force Fr tends to be smaller than that in Comparative Example 1 over the entire development area Da. This is considered to be due to the following reason. That is, the magnetic attractive force Fr that attracts the magnetic spikes toward the center of the developing sleeve 24 is a product of the magnitude of the magnetic flux density and the change in the r direction (partial differentiation).
- the comparative example 2 has a shape in which the magnetic flux density distribution gradually attenuates from the peak of the developing magnetic pole S2, and the change in the r direction of the magnetic flux density tends to be gentle. As a result, the magnitude of the magnetic flux density also decreases with distance from the peak, and the change in r direction (partial differentiation) tends to be small, so that the magnetic attraction force Fr formed by the product tends to be small.
- Example 1 can maintain the magnetic attractive force Fr higher than that of Comparative Example 2. This is presumably because the magnetic attraction force Fr can be kept large in the first embodiment as much as the absolute value of the magnetic flux density can be kept high without changing much even if the magnetic flux density distribution is away from the peak of the developing magnetic pole S2. Furthermore, although the magnetic flux density attenuates abruptly in the region away from the peak, in the region where the magnetic flux density changes abruptly, the r-direction change (partial differential) tends to increase, so that the magnetic attractive force Fr can be kept large. it can.
- FIG. 7 shows a change in the ⁇ direction of the magnetic flux density Br in the case of the first embodiment. Comparing FIGS. 6 and 7, it can be seen that the portion where the change in the magnetic flux density Br in the ⁇ direction is large and peaks, the magnetic attractive force Fr is also large and peaks.
- Example 1 the portions where the change in the magnetic flux density Br in the ⁇ direction is large and peaks are provided on the upstream side and the downstream side in the rotation direction with respect to the development region Da, and the peak of the magnetic attractive force Fr is also the development region. It is provided upstream and downstream in the rotational direction from Da. Thereby, the magnetic attraction force Fr can be kept high in the development area Da.
- the magnetic attraction force Fr can be kept high in the development area Da.
- the magnetic attraction force Fr can be easily kept large, and the magnetic flux density rapidly attenuates outside the developing area Da, but the magnetic flux density changes rapidly. Therefore, the magnetic attractive force Fr can be kept high. Therefore, in Example 1, the magnetic attractive force Fr can be kept high.
- the magnetic attractive force Fr can be kept high. As a result, since the magnetic ear is firmly restrained by the developing sleeve 24, the magnetic ear becomes difficult to slip on the surface of the developing sleeve 24, and the speed reduction of the magnetic ear can be suppressed.
- the magnet roller 24m has a so-called cross-sectional D-cut shape as a whole, and the magnet piece having the developing magnetic pole S2 has a substantially fan-shaped cross section.
- the development magnetic pole S2 has a planar plane portion 24s that faces the development area Da.
- the flat surface portion 24s is provided wider than the development area Da (see FIG. 2).
- the peak of the change in the ⁇ direction of the magnetic flux density Br and the peak of the magnetic attraction force Fr substantially coincide with the positions of the corners 24c formed at both edges in the rotation direction of the plane part 24s. This is because the magnetic field lines concentrate on the corner portion 24c and the wraparound also occurs.
- the peak of the magnetic attractive force Fr is present in the vicinity of both the upstream side and the downstream side of the development area Da.
- This peak has a larger value than the central portion in the development area (the center of the development area D).
- the downstream peak is made larger than the upstream peak.
- a position that is the lowest point between the two peaks is a position closer to the upstream side of the development area Da.
- each peak has a configuration outside the development area D, but a configuration in which each peak exists in the development area may be used.
- carrier adhesion to the photosensitive drum 81 can be made less likely to occur than when the magnetic attraction force Fr is configured oppositely. That is, when the peak on the downstream side is smaller than the peak on the upstream side of the development area Da, and the position that is the lowest point between the two peaks is a position closer to the downstream side of the development area Da, Example 1 Compared to the above, carrier adhesion to the photosensitive drum 81 is likely to occur. Even if the carrier adhesion occurs on the upstream side of the development area Da, the adhered carrier can be collected downstream, but the carrier adhesion generated on the downstream side cannot be collected around the development area Da. Therefore, it is preferable to adopt a configuration that suppresses the occurrence of carrier adhesion on the downstream side of the development area Da.
- the magnetic flux density (direction component) Br of the transport magnetic pole N2 downstream of the development magnetic pole S2 is made larger than the magnetic flux density (direction component) Br of the regulation magnetic pole N1 upstream of the development magnetic pole S2.
- the change in the magnetic flux density Br on the downstream side is larger than that on the upstream side of the development area Da, and the magnetic attractive force Fr on the downstream side is increased.
- the magnetizing may be performed by the following method.
- the magnetization vector (indicated by arrows in the figure) is symmetrical with respect to the upstream and downstream directions (isotropic) with respect to a normal sector-shaped magpiece. To develop the magnetic pole S2.
- the present embodiment as shown in FIG. 8A, the magnetization vector (indicated by arrows in the figure) is symmetrical with respect to the upstream and downstream directions (isotropic) with respect to a normal sector-shaped magpiece.
- the magnetization vector (indicated by arrows in the figure) is asymmetric (anisotropy) with respect to the upstream / downstream direction with respect to the sector-shaped magpiece.
- the magnetic attraction force Fr on the downstream side can be increased.
- the magnetization vector of the magnet piece alone may be magnetized so as to be directed in the downstream direction.
- the circumferential direction component of the developing sleeve 24 when the downstream side in the rotation direction of the developing sleeve 24 is positive, the circumferential direction component may be magnetized so that the sum of the magnetization vectors of the magnet pieces alone is positive. .
- the magnetic attractive force Fr of the carrier has two peaks, but in order to suppress carrier adhesion, the absolute value of the minimum point between the two peaks of the magnetic attractive force Fr of the carrier is 1.0 ⁇ 10 ⁇ ⁇ . It is preferable that it is 7N or more. Further, the peak of the magnetic attractive force is preferably 1.5 ⁇ 10 ⁇ -7N or more, more preferably 2.0 ⁇ 10 ⁇ -7N or more.
- the carrier characteristics can be improved by increasing the magnetic characteristics of the carrier or increasing the average particle diameter.
- Example 2 of the developing magnetic pole S2 of the magnet roller 24m according to the present embodiment will be described in comparison with Example 1 as shown in FIG. Since the outline of the image forming apparatus 1 and the developing device 20 of the second embodiment is the same as that of the first embodiment, detailed description thereof is omitted. As shown in FIG. 6, in the second embodiment, the distribution of the magnetic attractive force Fr of the developing magnetic pole S2 is different from that in the first embodiment.
- Example 1 the peak of the magnetic attraction force Fr is provided on both the upstream side and the downstream side of the development area Da, and the downstream peak is particularly larger than the upstream peak. Further, the position that is the lowest point between the two peaks is the position closer to the upstream of the development area Da. This is to recover the carrier adhesion generated at the lowest point of the magnetic attractive force Fr on the downstream side.
- the upstream peak is larger than the downstream peak of the magnetic attractive force Fr. That is, the peak of the magnetic attractive force Fr is larger on the upstream side in the rotational direction than on the downstream side in the rotational direction, and the magnetic attractive force Fr rotates between the peak on the upstream side in the rotational direction and the peak on the downstream side in the rotational direction. It has the lowest point on the downstream side in the direction.
- the upstream peak larger than the downstream peak of the magnetic attractive force Fr has the following advantages.
- the decrease in the magnetic spike speed is generally likely to occur upstream of the development area Da. This is because the gap between the developing sleeve 24 and the photosensitive drum 81 is gradually narrowed on the upstream side, and the magnetic spike speed is lowered on the upstream side so as to cause a traffic jam at the bottleneck.
- the gap between the developing sleeve 24 and the photosensitive drum 81 gradually increases on the downstream side, the magnetic spike speed is unlikely to decrease as in the upstream side. Therefore, a decrease in the upstream magnetic spike speed can be further suppressed by increasing the upstream peak. Similarly, the same effect can be obtained by setting the position that is the lowest point between the two peaks of the magnetic attractive force Fr to a position closer to the downstream side of the development area Da.
- the magnetic flux density (direction component) Br of the regulation magnetic pole N1 upstream of the development magnetic pole S2 is larger than the magnetic flux density (direction component) Br of the transport magnetic pole N2 downstream of the development magnetic pole S2.
- anisotropic magnetization may be performed so that the magnetization vector is directed in the upstream direction.
- the downstream peak of the magnetic attractive force Fr is increased for the purpose of suppressing carrier adhesion on the downstream side as in the first embodiment, or the speed reduction of the magnetic spike on the upstream side is suppressed as in the second embodiment.
- Whether to increase the upstream peak of the magnetic attractive force Fr can be selected as appropriate. In this case, the selection between the first embodiment and the second embodiment can be appropriately selected according to, for example, the specifications required for the product.
- the developing magnetic pole S2 in Example 1 had a flat planar portion 24s opposed to the developing area Da.
- the shape is not necessarily limited to this.
- the conventional general magnetization method is a method in which the orientation yoke 91 is brought close to the magnet piece 24 having a sectional fan shape and magnetized and oriented. At this time, it is possible to obtain the magnetic flux density characteristics as in the present invention by making the width (arrow in the figure) where the tip of the orientation yoke 91 contacts the magnet piece 24 wider.
- the width at which the tip of the orientation yoke 91 is in contact with the magnet piece 24 is preferably larger than the width of the development area Da.
- the width of the orientation yoke 91 in contact with the magnet piece 24 is 1.1 times or more, more preferably 1.2 times or more the width of the development area Da. It should be larger. As described above, even with a substantially sector cross-sectional shape, if the magnetic flux density characteristics as in the present invention are provided, the effects of the present invention can be obtained.
- the DC development method has been described. However, the same effect can be obtained even when the present invention is applied to a developing device of an AC + DC development method in which an AC voltage is superimposed on a DC voltage.
- the present invention it is possible to provide a developing device in which a reduction in developing efficiency is suppressed by controlling the contact state of the tip of the magnetic spike with the photosensitive drum while expanding the developing region.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Dry Development In Electrophotography (AREA)
- Magnetic Brush Developing In Electrophotography (AREA)
Abstract
Description
なお、現像磁極の上下流の極との角度が90°以上となると、磁力線が中心側から比較的横に広がりながら伸びやすくなる。そのため、現像磁極の上下流の極との角度は各々90°以下が好ましい。即ち、現像磁極S2の磁束密度のピークと規制磁極N1の磁束密度のピークの間の角度が90°以下であり、現像磁極S2の磁束密度のピークと搬送磁極N2の磁束密度のピークの間の角度が90°以下である。上下流ともに90°以下となるとよりよい。本実施例のマグネットローラ24mは先に述べたように5つの磁極に対応する磁束密度のピークを持っているが、本発明はこの構成に限らない。ただし、3つの磁極からなるマグネットローラの場合は、現像磁極の上下流の極との角度が広がる傾向にあり、上記条件を満たしにくくなる。そのため、マグネットローラ24mは5極以上の磁極を持つことが好ましい。
Claims (21)
- トナー及び磁性のキャリアを有する現像剤を担持し、現像剤が像担持体と接触する現像領域で像担持体に形成された静電潜像を現像する回転可能な現像スリーブと、
前記現像スリーブの内側に設けられ、前記現像領域を形成するために像担持体に対向する位置にある現像極を有する磁界発生部と、を有し、
前記現像スリーブの法線方向における前記現像極の磁束密度の80%値幅の前記現像磁極の法線方向の磁束密度の半値幅に対する比率は0.65以上であり、前記現像スリーブの回転方向において前記現像領域の両端部近傍のそれぞれの前記前記現像スリーブの法線方向における前記現像極の磁気力は前記現像領域中央部の磁気力よりも大きい現像装置。 - 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅は、前記現像領域の回転方向の幅よりも広い請求項1に記載の現像装置。
- 前記現像領域の両端部近傍のそれぞれの前記前記現像スリーブの法線方向における前記現像極の磁気力のピークは前記現像スリーブの回転方向において前記現像領域外にある請求項1又は2に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅と半値幅との比率は、0.70以上である請求項1乃至3に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の半値幅は、40°以上である請求項1乃至4のいずれか1項に記載の現像装置。
- 前記回転方向の下流側の磁気力のピークの値は上流側の磁気力のピークの値よりも大きい請求項請求項1乃至5に記載の現像装置。
- 前記回転方向の上流側の磁気力のピークの値は下流側の磁気力のピークの値よりも大きい請求項1乃至5に記載の現像装置。
- 前記回転方向の上流側の磁気力のピークの値と下流側の磁気力のピークの値は、1.5×10−7N以上である請求項1乃至7に記載の現像装置。
- 前記回転方向の上流側の磁気力のピークの値と下流側の磁気力のピークの値は、2.0×10−7N以上である請求項1乃至7に記載の現像装置。
- 前記回転方向の上流側の磁気力のピークと下流側の磁気力のピークの間の磁気力の最下点は前記現像領域内にある請求項1乃至9に記載の現像装置。
- トナー及び磁性のキャリアを有する現像剤を担持し、現像剤が像担持体と接触する現像領域で像担持体に形成された静電潜像を現像する回転可能な現像スリーブと、
前記現像スリーブの内側に設けられ、前記現像領域を形成するために像担持体に対向する位置にある現像極を有する磁界発生部と、
前記現像スリーブに直流電圧を印加する電源と、を有し、前記現像スリーブに交流電圧を用いずに直流電圧が印加されることで像担持体の静電潜像を現像する現像装置において、
前記現像スリーブの法線方向における前記現像極の磁束密度の80%値幅の前記現像磁極の法線方向の磁束密度の半値幅に対する比率は0.65以上である現像装置。 - 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅は、前記現像領域の回転方向幅よりも広い請求項11に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅と半値幅との比率は、0.70以上である請求項11または請求項12に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の半値幅は、40°以上である請求項11乃至13のいずれか1項に記載の現像装置。
- トナー及び磁性のキャリアを有する現像剤を担持し、現像剤が像担持体と接触する現像領域で像担持体に形成された静電潜像を現像する回転可能な現像スリーブと、
前記現像スリーブの内側に設けられ、前記現像領域を形成するために像担持体に対向する位置にある第一極と、前記現像スリーブの回転方向において前記第一極より上流側に設けられ前記第一極と隣り合う位置に設けられる第二極と、前記現像スリーブの回転方向において前記第一極より下流側に設けられ前記第一極と隣り合う位置に設けられる第三極と、を有する磁界発生部と、を有し、
前記現像スリーブの法線方向における前記現像極の磁束密度の80%値幅の前記現像磁極の法線方向の磁束密度の半値幅に対する比率は0.65以上であり、前記第一極の磁束密度のピークと前記第二極の磁束密度のピークとがなす角度と前記第一極の磁束密度のピークと前記第三極の磁束密度のピークとがなす角度はそれぞれ90°以下である現像装置。 - 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅は、前記現像領域の回転方向幅よりも広い請求項15に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の80%値幅と半値幅との比率は、0.70以上である請求項15または請求項16に記載の現像装置。
- 前記現像スリーブの外周面に対する前記現像磁極の法線方向の磁束密度の半値幅は、40°以上である請求項15乃至17のいずれか1項に記載の現像装置。
- 前記現像スリーブ上の現像剤量を規制する規制部を有し、前記第二極は前記規制部と対向する請求項15乃至18のいずれか1項に記載の現像装置。
- 前記第二極と前記第三極は同極であり、前記第一極と前記第二極は異極である請求項15乃至19のいずれか1項に記載の現像装置。
- 前記現像スリーブの回転方向において前記第三極より下流側に設けられ前記第三極と隣り合う位置に設けられる第四極と、前記現像スリーブの回転方向において前記第四極より下流側に設けられ前記第二極と前記第四極と隣り合う位置に設けられる第五極と、を有し、前記第四極と前記第五極とは同極である請求項15乃至20のいずれか1項に記載の現像装置。
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020187027788A KR102145855B1 (ko) | 2016-03-08 | 2017-03-08 | 현상 장치 |
EP17763457.3A EP3428732B1 (en) | 2016-03-08 | 2017-03-08 | Developing device |
KR1020207023276A KR102325553B1 (ko) | 2016-03-08 | 2017-03-08 | 화상 형성 장치 |
EP22152921.7A EP4027203A1 (en) | 2016-03-08 | 2017-03-08 | Developing device |
CN201780015077.8A CN109074016B (zh) | 2016-03-08 | 2017-03-08 | 显影设备 |
US16/051,763 US10768552B2 (en) | 2016-03-08 | 2018-08-01 | Developing device |
US16/941,659 US11262672B2 (en) | 2016-03-08 | 2020-07-29 | Developing device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2016044275 | 2016-03-08 | ||
JP2016-044275 | 2016-03-08 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/051,763 Continuation US10768552B2 (en) | 2016-03-08 | 2018-08-01 | Developing device |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2017155125A1 true WO2017155125A1 (ja) | 2017-09-14 |
Family
ID=59789456
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2017/010289 WO2017155125A1 (ja) | 2016-03-08 | 2017-03-08 | 現像装置 |
Country Status (6)
Country | Link |
---|---|
US (2) | US10768552B2 (ja) |
EP (2) | EP3428732B1 (ja) |
JP (1) | JP6938167B2 (ja) |
KR (2) | KR102145855B1 (ja) |
CN (1) | CN109074016B (ja) |
WO (1) | WO2017155125A1 (ja) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2023001587A (ja) * | 2021-06-21 | 2023-01-06 | キヤノン株式会社 | 現像装置 |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06149060A (ja) * | 1992-11-12 | 1994-05-27 | Minolta Camera Co Ltd | 現像装置 |
JPH06222675A (ja) * | 1993-01-22 | 1994-08-12 | Minolta Camera Co Ltd | 現像装置 |
JPH08146668A (ja) * | 1994-11-16 | 1996-06-07 | Canon Inc | 現像装置 |
JP2001034067A (ja) * | 1999-07-16 | 2001-02-09 | Canon Inc | 画像形成装置 |
JP2002304059A (ja) * | 2001-04-04 | 2002-10-18 | Fuji Xerox Co Ltd | 画像形成装置 |
JP2003345136A (ja) * | 2002-05-28 | 2003-12-03 | Kyocera Corp | 現像装置 |
JP2004109701A (ja) * | 2002-09-19 | 2004-04-08 | Ricoh Co Ltd | 現像方法、現像装置及び画像形成装置 |
JP2006145659A (ja) * | 2004-11-17 | 2006-06-08 | Kaneka Corp | マグネットローラ |
JP2006208807A (ja) * | 2005-01-28 | 2006-08-10 | Canon Inc | 現像装置、プロセスカートリッジ及び画像形成装置 |
US20140029986A1 (en) * | 2012-07-24 | 2014-01-30 | Fuji Xerox Co., Ltd. | Developing device and image forming apparatus |
Family Cites Families (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5495243A (en) | 1978-01-11 | 1979-07-27 | Ricoh Co Ltd | Magnetic brush developing device |
CA1135046A (en) * | 1978-01-11 | 1982-11-09 | Kouji Suzuki | Magnetic brush development apparatus |
EP0349326B1 (en) * | 1988-07-01 | 1994-01-05 | Canon Kabushiki Kaisha | A developing apparatus |
JPH087503B2 (ja) * | 1988-07-01 | 1996-01-29 | キヤノン株式会社 | 現像装置 |
JPH04109276A (ja) * | 1990-08-30 | 1992-04-10 | Canon Inc | 画像形成装置 |
JPH05313497A (ja) * | 1992-05-12 | 1993-11-26 | Minolta Camera Co Ltd | 現像装置 |
JPH1039620A (ja) * | 1996-07-19 | 1998-02-13 | Konica Corp | 現像方法、現像装置とそれを用いた多色カラー画像形成方法及び形成装置 |
JP2000068120A (ja) * | 1998-08-18 | 2000-03-03 | Kanegafuchi Chem Ind Co Ltd | マグネットローラ |
JP2001027848A (ja) * | 1999-07-15 | 2001-01-30 | Minolta Co Ltd | 現像装置 |
US6546222B2 (en) | 2000-06-08 | 2003-04-08 | Canon Kabushiki Kaisha | Developing apparatus |
JP4136481B2 (ja) | 2002-06-19 | 2008-08-20 | キヤノン株式会社 | 現像装置及び画像形成装置 |
US7035576B2 (en) * | 2002-09-19 | 2006-04-25 | Ricoh Company, Ltd. | Method and apparatus of developing a latent image formed on a surface of an image carrier |
JP2005115115A (ja) | 2003-10-09 | 2005-04-28 | Konica Minolta Business Technologies Inc | 現像装置 |
US7454149B2 (en) | 2004-10-20 | 2008-11-18 | Canon Kabushiki Kaisha | Image forming apparatus |
JP4498246B2 (ja) | 2005-09-07 | 2010-07-07 | キヤノン株式会社 | 現像装置 |
JP4788671B2 (ja) | 2007-06-25 | 2011-10-05 | パナソニック株式会社 | 飲酒検出装置 |
JP5064163B2 (ja) * | 2007-10-05 | 2012-10-31 | シャープ株式会社 | 現像装置、画像形成装置 |
JP5825794B2 (ja) | 2011-02-03 | 2015-12-02 | キヤノン株式会社 | 現像装置及びマグネットローラ |
JP6183695B2 (ja) * | 2013-07-18 | 2017-08-23 | 株式会社リコー | 現像装置並びにこれを備えた画像形成装置及びプロセスカートリッジ |
JP2015184424A (ja) | 2014-03-24 | 2015-10-22 | キヤノン株式会社 | 現像装置及び画像形成装置 |
JP6351375B2 (ja) | 2014-05-22 | 2018-07-04 | キヤノン株式会社 | 現像装置 |
-
2017
- 2017-02-28 JP JP2017037082A patent/JP6938167B2/ja active Active
- 2017-03-08 EP EP17763457.3A patent/EP3428732B1/en active Active
- 2017-03-08 CN CN201780015077.8A patent/CN109074016B/zh active Active
- 2017-03-08 EP EP22152921.7A patent/EP4027203A1/en active Pending
- 2017-03-08 WO PCT/JP2017/010289 patent/WO2017155125A1/ja active Application Filing
- 2017-03-08 KR KR1020187027788A patent/KR102145855B1/ko active IP Right Grant
- 2017-03-08 KR KR1020207023276A patent/KR102325553B1/ko active IP Right Grant
-
2018
- 2018-08-01 US US16/051,763 patent/US10768552B2/en active Active
-
2020
- 2020-07-29 US US16/941,659 patent/US11262672B2/en active Active
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06149060A (ja) * | 1992-11-12 | 1994-05-27 | Minolta Camera Co Ltd | 現像装置 |
JPH06222675A (ja) * | 1993-01-22 | 1994-08-12 | Minolta Camera Co Ltd | 現像装置 |
JPH08146668A (ja) * | 1994-11-16 | 1996-06-07 | Canon Inc | 現像装置 |
JP2001034067A (ja) * | 1999-07-16 | 2001-02-09 | Canon Inc | 画像形成装置 |
JP2002304059A (ja) * | 2001-04-04 | 2002-10-18 | Fuji Xerox Co Ltd | 画像形成装置 |
JP2003345136A (ja) * | 2002-05-28 | 2003-12-03 | Kyocera Corp | 現像装置 |
JP2004109701A (ja) * | 2002-09-19 | 2004-04-08 | Ricoh Co Ltd | 現像方法、現像装置及び画像形成装置 |
JP2006145659A (ja) * | 2004-11-17 | 2006-06-08 | Kaneka Corp | マグネットローラ |
JP2006208807A (ja) * | 2005-01-28 | 2006-08-10 | Canon Inc | 現像装置、プロセスカートリッジ及び画像形成装置 |
US20140029986A1 (en) * | 2012-07-24 | 2014-01-30 | Fuji Xerox Co., Ltd. | Developing device and image forming apparatus |
Non-Patent Citations (1)
Title |
---|
See also references of EP3428732A4 * |
Also Published As
Publication number | Publication date |
---|---|
KR102145855B1 (ko) | 2020-08-19 |
CN109074016B (zh) | 2022-02-08 |
KR20200098729A (ko) | 2020-08-20 |
US10768552B2 (en) | 2020-09-08 |
US20180341198A1 (en) | 2018-11-29 |
KR102325553B1 (ko) | 2021-11-12 |
EP3428732A4 (en) | 2019-11-13 |
EP3428732B1 (en) | 2024-01-31 |
CN109074016A (zh) | 2018-12-21 |
KR20180122648A (ko) | 2018-11-13 |
JP2017161902A (ja) | 2017-09-14 |
EP3428732A1 (en) | 2019-01-16 |
US20200356027A1 (en) | 2020-11-12 |
EP4027203A1 (en) | 2022-07-13 |
JP6938167B2 (ja) | 2021-09-22 |
US11262672B2 (en) | 2022-03-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6978108B2 (en) | Developing apparatus to control bending of a magnetic field generation unit provided inside a developer carrying member | |
US7577388B2 (en) | Developing roller, and developing device and image-forming apparatus using the same | |
WO2017155125A1 (ja) | 現像装置 | |
EP1826627A1 (en) | Colour image forming apparatus | |
JP5539708B2 (ja) | 現像装置およびそれを備えた画像形成装置 | |
JP2015184424A (ja) | 現像装置及び画像形成装置 | |
JP5996016B2 (ja) | 現像装置、及び現像装置を備える画像形成装置 | |
JP2023001587A (ja) | 現像装置 | |
JP4987524B2 (ja) | 現像装置及びそれを備えた画像形成装置 | |
CN106909038B (zh) | 显影装置 | |
JP6424860B2 (ja) | 現像装置、およびこれを備えた画像形成装置 | |
JP4587763B2 (ja) | 現像装置 | |
JP6350406B2 (ja) | 現像装置、画像形成装置 | |
US10324398B2 (en) | Developing device and magnet for two-component development | |
JP2018045224A (ja) | 現像装置及び二成分現像用のマグネット | |
JP6627956B2 (ja) | 現像装置、およびこれを備えた画像形成装置 | |
US10234793B2 (en) | Development device using a dry electrophotographic method | |
JP2023001586A (ja) | 現像装置 | |
JP2017116597A (ja) | 現像装置および画像形成装置 | |
JP6443368B2 (ja) | 現像装置、およびこれを備えた画像形成装置 | |
JP2017129607A (ja) | 現像装置 | |
JP2020144334A (ja) | 画像形成装置 | |
JP2018142031A (ja) | 現像装置 | |
JP2015225187A (ja) | 画像形成装置 | |
JP2005352227A (ja) | 現像装置 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
ENP | Entry into the national phase |
Ref document number: 20187027788 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2017763457 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 2017763457 Country of ref document: EP Effective date: 20181008 |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 17763457 Country of ref document: EP Kind code of ref document: A1 |