JP3402942B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electrophotographic method and an electrostatic recording method in which a latent image formed on an image carrier is visualized by attaching a developer to the latent image. More specifically, the present invention relates to a developing device such as a copying machine or a printer. 2. Description of the Related Art FIG. 4 shows a conventional laser beam printer having four photosensitive drums. In this printer, four image forming stations each having an image forming means around a photosensitive drum are provided corresponding to colors, and toner images on the photosensitive drum formed at each image forming station are The image is transferred onto a transfer material conveyed by a belt-shaped moving body that moves in opposition to the photosensitive drum to form a color image. That is, magenta, cyan, yellow, and black image forming stations Pm, Pc, Py, P
In k, the photosensitive drums 4 (4M, 4C, 4Y, 4K) that rotate in the directions of the arrows (clockwise) are arranged.
Also, around each of the photosensitive drums 4M, 4C, 4Y, and 4K,
Corona charger 16 (16M, 16C, 16Y, 16
K), a scanning optical device 17 (17M,
17C, 17Y, 17K), the developing device 9 (9M, 9C,
9Y, 9K) and a cleaning device 18 (18M, 1
8C, 18Y, and 18K). Further, the transfer section 6 constituting one of the image forming means includes a transfer belt 19a and a transfer charger 19 for each drum commonly used in each image forming station.
(19M, 19C, 19Y, 19K), and in the formation of a full-color image, the toner images of each color formed on the photosensitive drum are sequentially transferred onto the transfer material P supported on the transfer belt 19a. Achieved by: In addition,
The transfer material P is supplied from the paper supply cassette 20, and the transfer material P having completed the transfer process is separated and discharged to the tray 22 via the fixing device 21. [0005] The scanning optical devices 17M, 17C, 17
Y and 17K denote a laser light source, which is a light source (not shown), a rotating polygon mirror that scans the laser light from this laser light source, an fθ lens that focuses the scanning beam on the generatrix of the surface of the photosensitive drum, and a light beam redirector. And a beam detection position for detecting a specific position of the scanning beam. The developing device 9 (9M, 9C, 9Y, 9K) will be described. As shown in FIG. 5, the developing device 9 disposed opposite the photosensitive drum 4 includes a developing container 8 and a developer carrier. Of the developer, a developer return member 1 for regulating the developer pool, and a blade 2 containing a magnetic material as a developer height control member. The inside of the developing device 9 is divided into a developing chamber (first chamber) 13 and a stirring chamber (second chamber) 14 by the partition 6 extending in the vertical direction.
The upper part of the partition 6 is open. In this embodiment, the developing chamber 13 and the stirring chamber 14 contain a two-component developer containing a non-magnetic toner and a magnetic carrier, and the excess developer in the developing chamber 13 is collected in the stirring chamber 14. . In the developing chamber 13 and the stirring chamber 14, first and second screw-type developer stirring / transporting means 11 and 12 are disposed, respectively. The first stirring screw 11 stirs and conveys the developer in the developing chamber 13, and the second stirring screw 12 stirs this developer from a toner replenishing tank (not shown) under the control of the developer concentration controller. The toner supplied to the upstream side of the screw 12 and the developer already in the stirring chamber 14 are stirred and conveyed, and the toner concentration is made uniform. A developer passage (not shown) for communicating the developing chamber 13 and the stirring chamber 14 with each other is formed in the partition 6 at the front and rear ends in FIG. 5, and the stirring screws 11 and 12 are formed. The developer in the developing chamber 13 whose toner density is reduced due to the consumption of toner due to the development is moved from the other passage into the stirring chamber 14 by the conveying force of. The developing chamber 13 of the developing device 9 has an opening at a position corresponding to a developing area facing the photosensitive drum 4, and the developing sleeve 3 is rotatable so as to be partially exposed at the opening. Are located in The developing sleeve 3 is made of a non-magnetic material, rotates in the direction of the arrow in the drawing during the developing operation, and has a magnet (magnet roller) 10 as a magnetic field generating means fixed inside. Developing sleeve 3
Carries and transports the layer of the two-component developer, the layer thickness of which is regulated by the blade 2, and supplies the developer to the photosensitive drum 4 in a development area facing the photosensitive drum 4 to develop the latent image. To improve the development efficiency, that is, the rate of toner application to the latent image,
For example, a developing bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing sleeve 3 from a power supply 15. The developing device 9 holds the developer supplied to the surface of the developing sleeve 3 by the stirring screws 11 and 12 in the state of a magnetic brush by the magnetic force of the magnet roller 10, and transfers the developer to the developing sleeve. The developer is conveyed to a portion (developing area) facing the photosensitive drum 4 based on the rotation of the photosensitive drum 3, and the developer returning member 1 and the blade 2 cut off the magnetic brush and cut off the amount of developer conveyed to the developing area. Maintain properly. More specifically, the magnet roller 10 of such a conventional developing device has a five-pole configuration, and the developer stirred by the developing chamber stirring screw 11 is used as a transport magnetic pole (pumping pole) for pumping. It is constrained by the magnetic force of S2 and is conveyed to the developer reservoir 5 by the rotation of the developing sleeve 3. The amount of the developer is regulated by the developer return member 1, and is sufficiently constrained by a transfer magnetic pole (cut pole) N2 having a certain or more magnetic flux density in order to constrain the stable developer. Is formed and transported. Next, the magnetic brush is cut off by the blade, that is, the spike height restricting member 2, so that the amount of the developer is adjusted appropriately, and is conveyed by the conveying magnetic pole S1. Further, a bias voltage in which a direct current and / or an alternating electric field is superimposed is applied to the developing sleeve 3 via a bias power supply 15 provided on the image forming apparatus main body side at the developing pole N1, and the toner on the developing sleeve 3 is transferred to the photosensitive drum. 4 is moved to the electrostatic latent image side, and the electrostatic latent image is visualized as a toner image. At this time, in forming a high quality image, stabilization in a state where the amount of the developer near the developing pole N1 is large is essential. [0011] However, in the above conventional example, when the blade 2 is simply widened and transported by the transport magnetic pole S1, there are the following disadvantages. First, if the amount of the developer is already large in the area to be transported by the transport magnetic pole S1, the absolute amount of the developer increases, so that the amount of scattered toner also increases, thereby promoting contamination. Further, since the blade 2 has a magnetic material as described above, a magnetic field in a phase direction is formed between the blade 2 and the mag roller 10 as shown in FIG.
Therefore, it is very effective for stabilizing the amount of developer, but when the blade 2 is too wide, there is a disadvantage that the phase direction magnetic field does not work and the amount of developer becomes unstable. Accordingly, an object of the present invention is to obtain a stable high-quality image for a long period of time by increasing only the amount of developer in the developing area while keeping the amount of developer regulated by the blade 2 as it is. It is an object of the present invention to provide an image forming apparatus capable of performing the following. According to the present invention, the above objects can be attained. The present invention provides a developer carrying member that carries and transports a developer in a developing container, a magnet fixed in the developer carrying member, a unit that supplies developer to the developer carrying member, and the magnet Means for cutting off a magnetic brush formed on the developer carrying member by means of a brush to regulate the amount of developer conveyed to a developing nip by the developer carrying member. The developing magnetic pole corresponding to the developing nip, the taking-in magnetic pole corresponding to the developer carrying area from the developing nip to the taking-in of the developer into the developing container, and the magnetic pole forming a repulsive magnetic field with the taking-in magnetic pole in the carrying direction. The absolute value of the magnetic flux density of the take-in magnetic pole is S (G), the absolute value of the magnetic flux density of the developing magnetic pole that is larger than the magnetic flux density of the take-in magnetic pole is N (G), When the angle between interrupt pole was X °, 0.3 ≦ 10N / SX ≦
0.7 holds, and the amount of the developer in the area of 5 mm ² around the downstream end of the developing nip in the transport direction is changed to the amount of developer in the area of 5 mm ² around the upstream end of the developing nip in the transport direction. It is characterized by being set to 1.1 to 1.7 times. (First Embodiment) FIG. 1 shows an embodiment of a developing device constructed in accordance with the present invention. Explaining the characteristic portion, the developer in the developing chamber 13 is carried on the developing sleeve 3 by the action of a transport magnetic pole of a magnet (magnet roller) 10 built in the developing sleeve 3, that is, a pumping pole S2. The developer carried and transported by the developing sleeve 3 is compressed by the developer return member 1 that regulates the developer reservoir 5, and is transported to the developing area with the layer thickness regulated by the blade 2. The developer remaining without being used for the development in the developing area is taken in by the developing sleeve 3 and transported again to the developing chamber 13 via the magnetic pole S3, and is scraped from above the developing sleeve 3 into the developing chamber 13 by the repulsive magnetic poles S3-S2. Dropped and collected. At this time, the amount of the developer up to the upstream of the developing nip is determined by the absolute value of the magnetic flux density of the blade 2 and / or the conveying magnetic pole on the way. The transport magnetic pole S1 up to the development nip is sufficiently separated from the development pole N1.
As shown in (2), the force fθ _{1 in the} developer transport direction among the magnetic restraining forces acting on the developer during this time stably acts in the transport direction, so that the developer amount is almost determined by the layer thickness of the blade 2. However, in the latter half of the development nip, ie, the development pole N1
The amount of the developer from when the developer reaches the take-in pole S3 for collecting the developer into the developing container greatly changes depending on the magnetic flux density of the developing pole N1 and the take-in pole S3 and the angle between the poles. Therefore, if the developer amount in the latter half of the development nip can be stably increased, a high quality image can be obtained. To this end, unlike the first half of the development nip described above, the magnetic flux density of the development pole is large, the magnetic flux density of the take-in pole is small, and the angle between the development pole and the take-in pole is small, so that the developer becomes late in the development nip. the stably conveying direction force f [theta] ₂ of the developer carrying direction of the magnetic binding force acting acting in the opposite direction, distillation time developer to the developer developing nip side tends to increase. That is, if the magnetic flux density of the N pole in the upstream development zone is larger than the magnetic flux density of the downstream take-in pole, the developer in the circumferential direction of the sleeve 3 is drawn to the development pole side where the magnetic flux density is large. is there. Also, if the angle between the poles is small, the region from the developing pole to the take-in pole is narrowed, but the influence of the developing pole having a large magnetic flux density is correspondingly increased. Therefore, with respect to the magnet roller 10 of the developing device shown in FIG. 1, nine types of magnet rollers 10 having different magnetic flux densities of the developing pole N1 and the take-in pole N3 and the angle 極 between the poles are prepared. Table 1 shows the measurement results of the developer transportability in the printer and the image stability in a replenishment experiment after toner consumption after printing 100,000 sheets of A4 size paper with the present image forming apparatus and a toner consumption of 10%. Here, the image stability was evaluated by evaluating roughness, maximum density, density stability and the like in a highlight image area. The amount of developer at this time was measured by collecting an amount of 5 mm ² each around the circumferential end of the developing nip. That is, the amount of the developer taken into the developing container in the transport direction from the developing pole and the amount of the developer from the time when the magnetic brush is cut to a predetermined height until reaching the developing nip are the developer on the developing sleeve and the photosensitive drum, respectively. 5 mm ² of the developer is measured around the end of the developing nip in contact with the developer. As the measuring means at this time, for example, a member having an opening of 5 mm ² is prepared in advance, and the member is applied to the position on the developing sleeve, and the developer emerging from the opening of 5 mm ² is collected by a magnet. Was. [Table 1] Hereinafter, the developer usable in the present invention will be described. In the present embodiment, 2 having carrier and toner
A component developer was used. The carrier used in the present invention preferably has a smaller average particle size and a sharper particle size distribution than conventional general carriers. Due to the small particle size, the number of times of contact between the carrier and the toner increases, the rise of the toner charge becomes faster, and even if the replenishment amount increases, the uncharged toner is not developed. Furthermore,
The rapid rise of charging can prevent the uncharged toner from scattering and fogging under high humidity. Therefore, in combination with the toner described below, a magenta developer which is resistant to humidity and does not cause scattering or fogging even when continuous copying of a document having a large image area is obtained. In addition, by sharpening the particle size distribution, a small particle size carrier is generated appropriately. This solves the phenomenon that the fine powder carrier adheres to the photosensitive drum together with the toner during development, thereby preventing a deterioration in image quality due to poor charging due to the coarse powder carrier. The ultrafine powder having a size of 400 mesh or less is 20% by weight or less, preferably 13% by weight or less. 20% by weight
Above, carrier adheres to the photosensitive drum,
Further, it hinders smooth triboelectric charging with toner and promotes the edge effect. The fine powder having a size of 350 mesh or less is 30% by weight or less, preferably 25% by weight or less, and more preferably 20% by weight or less. If the content is 30% by weight or more, the rise of the toner charge becomes extremely poor, and the edge effect also increases. Further, the amount of coarse powder of 250 mesh or more is closely correlated with the sharpness of the image, and if it is 10% by weight or more, scattering of toner to non-image portions increases, and the resolution of the image is reduced. Deterioration and roughness are more likely to occur. Therefore, 25
0 mesh or more and 10% by weight or less, preferably 7% by weight
Or less, more preferably 5% by weight or less. The average particle size of the carrier is preferably from 20 to 60 μm, more preferably from 30 to 56 μm. 20
If the average particle diameter is less than μm, the image density will decrease due to the charge-up of the toner, and the amount of carrier attached to the photosensitive drum will increase. If the average particle diameter is more than 60 μm, the reproducibility of fine lines in copying will deteriorate. The magnetic characteristics of the carrier greatly affect the developing characteristics and transport of the developer, and the uniformity and gradation of the image are emphasized. When the saturation magnetization is 75 emu / g or more (for an applied magnetic field of 3000 Oersteds), during development, the toner is constituted by the carrier and toner on the developing sleeve facing the electrostatic latent image on the photosensitive drum. The brush-like ears are firmly tightened, and the gradation and the reproduction of halftone are deteriorated. On the other hand, if it is 55 emu / g or less, it becomes difficult to hold the toner and the carrier on the developing sleeve,
There is a disadvantage that fog and toner scattering are worsened. Further, when the residual magnetization and the coercive force of the carrier are too high, the transport of the developer in the developing device is deteriorated, and image blurring and uneven density in a solid image are likely to occur. Therefore, it is necessary that the residual magnetization and the coercive force be 10 emu / g or less and 10 oersted or less (for an applied magnetic field of 3000 oersted), preferably 5 emu / g or less, and 6.0 or less. As the binder resin applied to the toner, all known resins can be used.
Homopolymers of styrene such as poly-p-chlorostyrene and polyvinyltoluene and substituted products thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene Copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene -Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether Copolymer, styrene-vinyl methyl Styrene copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, and styrene-maleic acid ester copolymers Coalescing, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene,
Polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, Paraffin wax or the like can be used alone or as a mixture. Further, a charge control agent may be added to the toner as required. As an example, in the case of a magenta toner, in the case of a negative toner, a dye having an anthraquinone-based magenta color, or a metal chelate of alkyl salicylic acid, or the like, in the case of a positive toner, a magenta basic dye, Alternatively, those lake pigments can be used. Further, for the developer in which the toner is used, a charge controlling agent such as colloidal silica and a fluidity modifier are added in an amount of 0.01 to 5% by weight (preferably 0.1 to 5%) based on the toner. It is preferable to add about 2% by weight). The carrier used in this embodiment is as follows.
Known materials can be used, for example, surface oxidized or unoxidized iron, nickel, copper, zinc, cobalt, manganese,
Metals such as chromium and rare earths, and alloys or oxides thereof, and ferrites are preferable. Ferrites selected from zinc, copper, nickel and cobalt metals can be preferably used. There is no particular restriction on the manufacturing method. It is also possible to cover the surface of the carrier with a resin or the like. As the method, any conventionally known method such as a method of dissolving or suspending a coating material such as a resin in a solvent, coating and adhering to a carrier, and a method of simply mixing with a powder can be applied. The substance fixed to the carrier surface varies depending on the toner material. Examples thereof include polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal complex of di-t-butylsalicylic acid, Styrene resin,
Acrylic resin, polyamide, polyvinyl butyral,
It is appropriate to use nigrosine, amino acrylate resin, basic dyes and lakes thereof, fine silica powder, fine alumina powder or the like alone or in combination, but it is not necessarily limited thereto. The treatment amount of the above compound may be appropriately determined so that the carrier satisfies the above conditions, but is generally 0.1 to 30% by weight (preferably 0.5 to 20% by weight) based on the total amount of the carrier. %) Is desirable. A particularly preferable embodiment usable in this embodiment is a ternary ferrite of Cu-Zn-Fe, whose surface is formed by a combination of a resin such as a fluorine resin and a styrene resin, for example, polyfluorinated resin. Vinylidene and styrene-methyl methacrylate resin, polytetrafluoroethylene and styrene-methyl methacrylate resin, fluorine-based copolymer and styrene-based copolymer
0:10 to 20:80, preferably 70:30 to 30:
A mixture of 70 to 70% by weight, preferably 0.1 to 1% by weight, is a coated ferrite carrier. Examples of the fluorine-based copolymer include vinylylene fluoride-tetrafluoroethylene copolymer (10:90 to 90:10), and examples of the styrene-based copolymer include styrene-2-ethylhexyl acrylate (20:80 to 80:20), and styrene-2-ethylhexyl acrylate-methyl methacrylate (20 to 60: 5 to 30:10 to 50). The method of measuring the particle size distribution of the carrier in this embodiment is as follows. 1. Weigh about 100 g of sample to the nearest 0.1 g. 2. As for the sieves, standard sieves of 100 mesh to 400 mesh (hereinafter simply referred to as “sieve”) are used, and stacked in order of size 100, 145, 200, 250, 350, 400 from the top, and a tray is placed on the bottom. The sample is placed on the top sieve and capped. 3. This is sieved with a vibrator at 285 ± 6 horizontal revolutions per minute and 150 ± 10 vibrations per minute for 15 minutes. 4. After sieving, weigh the iron powder in each sieve and tray to the nearest 0.1 g. 5. Calculate to the second decimal place by weight percentage,
Round to the first decimal place according to JIS-Z8401. At this time, the size of the sieve frame is such that the inner diameter above the sieve surface is 200 mm and the depth from the upper surface to the sieve surface is 45 mm.
mm, and the sum of the weights of the iron powders in each part must not be less than 99% of the mass of the sample initially taken. The average particle size is determined from the above measured particle size distribution according to the following equation. Average particle size (μ) = 1/100 × ｛(100
The remaining amount of the mesh sieve) × 140 + (the remaining amount of the 145 mesh sieve) × 122 + (the remaining amount of the 200 mesh sieve) × 90 +
(Remaining amount of 250 mesh sieve) × 68 + (Remaining amount of 350 mesh sieve) × 52 + Remaining amount of 400 mesh sieve) × 38 +
(Amount passing through all sieves) × 14｝ As an apparatus for measuring the magnetic properties of the carrier,
A BHU-60 type magnetization measurement device (manufactured by Riken Keisoku) is used. About 1.0 g of a measurement sample was weighed, and the inner diameter was 7 m.
m, packed in a cell having a height of 10 mm, and set in the above device. In the measurement, first, an applied magnetic field is gradually applied to change the maximum magnetic field to 3000 Oe. Next, the applied magnetic field is reduced, and finally a hysteresis curve of the sample is obtained on the recording paper. From this, the saturation magnetization, residual magnetization, and coercive force are obtained. Hereinafter, the developer used in this embodiment will be described in detail. Carriers A to C shown in Table 2 and toners a to c shown below were produced. [Table 2] Toner a: Styrene-n-butyl methacrylate copolymer 100 parts by weight Charge control agent 4.0 parts by weight Quinacridone-based pigment 4.0 parts by weight (CI Pigment Red 122) Methine dye (CI) Basic Red 12) 1.0 part by weight Toner b: 100 parts by weight of unsaturated polyester resin 4.0 parts by weight Charge control agent 4.0 parts by weight Quinacridone pigment 3.5 parts by weight (CI Pigment Red 202) Methine type Dye (CI Basic Red 14) 0.5 parts by weight Toner c: Styrene resin 100 parts by weight Charge control agent 4.0 parts by weight Quinacridone-based pigment 4.0 parts by weight (CI Pigment Red 122) Each of the toners a, b, and c is melted and kneaded with a roll mill, and cooled. After jet-milled, and classified to obtain a classified product having an average particle size of 8 to 15 m. 0.5% by weight of hydrophobic silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) was externally added to the classified product using a Henschel mixer to obtain a toner of the present invention. Further, the toner and the carrier were mixed to obtain a developer having a toner concentration of 6%. From the above results, the amount of the developer from the developing area to the take-up pole into the developing container is 1.1 times the amount of the developer from the time when the magnetic brush is cut to the predetermined spike height until the developing area is reached. When the ratio was 1.7 to 1.7 times, the transportability and image stability of the developer were all good. In order to stably obtain the developer amount ratio, the developing pole magnetic flux density N _{1 of the} magnet roller 10 is required.
(G), the capture pole magnetic flux density S ₃ (G) on the downstream side and the inter-pole angle X ° were such that 0.3 ≦ 10N ₁ / S ₃ X ≦ 0.70 was satisfied. [0058] (second embodiment) pole uptake by providing the magnetic material 22 within the developing container with respect to the uptake pole S ₃ of the magnet roller 10 as in the present embodiment shown in FIG. 3 S
_A magnetic field is formed between ₃ and the magnetic material 22. as a result,
Magnetic field acts from other magnetic member 22 of the magnetic binding force between the uptake pole S ₃ developing pole N _1, the amount of developer downstream from the developing pole is different from the amount of developer upstream from the developing pole. Thus disposing the magnetic member 22 captures the pole S ₃ and the magnetic field forming positions. As described above, according to the present invention, a stable high-quality image can be obtained over a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an embodiment of a developing device used in an image forming apparatus according to the present invention. FIG. 2 is an explanatory diagram of a magnet roller used in the image forming apparatus according to the present invention. FIG. 3 is a sectional view of another embodiment of a developing device used in the image forming apparatus according to the present invention. FIG. 4 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention. FIG. 5 is a sectional view of a conventional developing device. FIG. 6 is a diagram illustrating a magnetic field between a magnet roller and a blade. [Description of Signs] 1 Developer return member 2 Ear height regulating member 3 Developer carrier (developing sleeve) 4 Image carrier (photosensitive drum) 5 Developer reservoir 8 Developing container 9 Developing device 10 Magnet (magnet roller) 11, 12 Developer stirring and conveying means (conveying screw)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Oki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Fumitake Hirobe 3-30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor Shigeru Matsuzaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor ▲ Tadanobu Yoshikawa 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Canon (72) Inventor Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (56) References JP-A-1-102588 (JP, A) JP-A-4-362979 (JP) JP-A-6-194962 (JP, A) JP-A-3-4263 (JP, A) JP-A-2-216168 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB (Name) G03G 15/09

Claims (1)

(57) Claims: A developer carrying member that carries and transports a developer in a developing container; a magnet fixed in the developer carrying member; Means for supplying the carrier to the carrier, and means for cutting off a magnetic brush formed on the developer carrier by the magnet to regulate the amount of developer conveyed to the development nip by the developer carrier. In the developing device having the above, the magnet is a developing magnetic pole corresponding to the developing nip, a capturing magnetic pole corresponding to a developer transport area from the developing nip to the developer being loaded into the developing container, and between the capturing magnetic pole. The magnetic poles forming a repulsive magnetic field are sequentially provided along the transport direction. The absolute value of the magnetic flux density of the take-in magnetic pole is S (G), and the absolute value of the magnetic flux density of the developing magnetic pole that is larger than the magnetic flux density of the take-in magnetic pole is N G), the when the angle between the developing magnetic pole and the uptake pole and X °, 0.3 ≦ 10N / SX ≦ 0.7 is holds, and the 5 mm ² around the downstream side end portion of the developing nip developing device and sets the amount of developer regions 1.1 to 1.7 times the amount of developer conveyance direction upstream side end portion center of 5 mm ² area of the developing nip.