EP0003134B1 - Dispositif de développement à brosse magnétique - Google Patents

Dispositif de développement à brosse magnétique Download PDF

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Publication number
EP0003134B1
EP0003134B1 EP19790100081 EP79100081A EP0003134B1 EP 0003134 B1 EP0003134 B1 EP 0003134B1 EP 19790100081 EP19790100081 EP 19790100081 EP 79100081 A EP79100081 A EP 79100081A EP 0003134 B1 EP0003134 B1 EP 0003134B1
Authority
EP
European Patent Office
Prior art keywords
magnetic
magnetic pole
pole portion
electrostatic image
latent electrostatic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19790100081
Other languages
German (de)
English (en)
Other versions
EP0003134A1 (fr
Inventor
Manabu Mochizuki
Masahide Harada
Mitsuo Tanaka
Kouji Suzuki
Kazuaki Tagawa
Kazuo Kobayashi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ricoh Co Ltd
Original Assignee
Ricoh Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=26335093&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0003134(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Priority claimed from JP180878A external-priority patent/JPS5495243A/ja
Priority claimed from JP2956978A external-priority patent/JPS54122131A/ja
Application filed by Ricoh Co Ltd filed Critical Ricoh Co Ltd
Priority to DE8080107642T priority Critical patent/DE2967496D1/de
Publication of EP0003134A1 publication Critical patent/EP0003134A1/fr
Application granted granted Critical
Publication of EP0003134B1 publication Critical patent/EP0003134B1/fr
Expired legal-status Critical Current

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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
    • G03G15/0921—Details concerning the magnetic brush roller structure, e.g. magnet configuration

Definitions

  • the present invention relates to a magnetic brush development apparatus for use in electrophotographic copying apparatus or electrostatic recording apparatus.
  • the magnetic brush development apparatus is an apparatus for attracting a developer containing magnetic powder therein to a non-magnetic support member in which magnets are disposed, and for bringing the developer into contact with a latent electrostatic image bearing member at an image development section in order to develop the latent electrostatic image.
  • the name of the magnetic brush comes from that the developer becomes like a brush due to the magnetic force of the magnets disposed in the non-magnetic support member.
  • the developer that can be employed in the magnetic brush development apparatus there are a two-component type developer comprising non-magnetic toner and magnetic carrier, and a one-component type developer consisting of magnetic toner.
  • the one-component type developer can be classified into an electrically conductive toner and an electrically insulating toner.
  • Image development is performed by the toner charged to the opposite polarity to that of a latent electrostatic image being electrostatically attracted to the latent electrostatic image.
  • the particle size of toner is smaller than that of carrier particles and the toner is triboelectrically charged so that the toner clings to the carrier and a magnetic brush is formed.
  • the electrically conductive toner is charged by injection of charges or by electrostatic induction, while the electrically insulating toner is triboelectrically charged by some member of a developer container with which the toner contacts or during the transportation of the toner.
  • the toner In case of the two-component type developer, the toner is securely charged, but some means for maintaining the mixing ratio of the toner and the carrier or the toner concentration is necessary in order to obtain a developed image of a predetermined image density. In contrast to this, in case of the one-component type developer, it is unnecessary to control the toner concentration and simple in handling the toner although the charging of the toner is not always sufficient.
  • a sleeve-shaped or cylindrical member and an endless belt-shaped member are known as the non-magnetic support members for forming a magnetic brush thereon by attracting the developer thereto.
  • Plural magnets arranged in a radial manner and a single rod magnet having magnetic poles on the peripheral surface thereof are known as the magnets to be disposed in the non-magnetic support member.
  • the photoconductors for use in electrophotographic copying apparatus and the dielectric member for electrostatic recording apparatus are known as the latent image bearing members.
  • the shapes of the latent image bearing members are drum-like, endless-belt-like, plate-like and sheet-like.
  • Either or both of the non-magnetic support member for holding the magnetic brush thereon and the magnets disposed inside the non-magnetic support member are moved relative to each other, so that the magnetic brush formed on the non-magnetic support member is moved on the non-magnetic support member.
  • the latent image bearing member is also moved at a predetermined speed and the magnetic brush on the non-magnetic support member comes in contact with the surface of the latent electrostatic image bearing member at a predetermined position where the non-magnetic support member and the latent electrostatic image bearing member come closest to each other, namely at a development section, so that the latent electrostatic image on the latent image bearing member is developed continuously.
  • the magnetic brushes on the non-magnetic support member are formed along the lines of magnetic force distributed on the non-magnetic support member 1 among the magnets 2, 3, 4 and 5 which are disposed in the non-magnetic support member as shown in Fig. 1.
  • Fig. 1 the distribution of the magnetic lines of force among only the magnets 2, 3 and 4 are shown.
  • Each line of magnetic force starts from the magnetic pole N and returns to the magnetic pole S, and the magnetic field is strongest at each magnetic pole.
  • the magnetic brush becomes highest at each magnetic pole and lowest in between two adjacent magnets.
  • the magnetic brush stands out at each magnetic pole as shown by reference numeral 6 in Fig. 2. Therefore, normally, the magnets are arranged so that each magnetic pole of the magnets is located in the development section and development is performed by the highest portion of the magnetic brush.
  • the image density of developed image depends upon development time.
  • the development time here means a period of time in which developer is in contact with a latent electrostatic image bearing member. Therefore, in the magnetic brush development apparatus the development time is a period of time in which the magnetic brush is in contact with a latent electrostatic image bearing member at the development position.
  • the period of time in which the magnetic brush is in contact with the latent image bearing member is related to the contact width w of the magnetic brush in contact with the latent image bearing member. Therefore, the development efficiency, namely the image density of developed image per unit time can be increased by broadening the contact width w.
  • a one of the conventional techniques for making the contact width w great an apparatus is known in which a plurality of non-magnetic support members for supporting the magnetic brush thereon are disposed in close proximity to the surface of a latent electrostatic image bearing member, whereby the contact width w can be substantially increased.
  • this apparatus has some shortcomings that the apparatus is oversized and expensive. In order to eliminato such shortcomings, it is necessary to increase the contact width w by a single non-magnetic supporting member.
  • the contact width w of the magnetic brush is related to a gap d in the development section between a latent electrostatic image bearing member 7 and a non-magnetic support member 1 since the magnetic brush stands out at each magnetic pole.
  • the contact width w is greater in the bottom portion of the magnetic brush than in the top portion of the magnetic brush. Therefore, the smaller the gap d, the greater the contact width w.
  • the gap d is related to the contact width w and accordingly to the development time, images with an uneven density are formed when the gap d changes during development.
  • a spacer roller is disposed between a non-magnetic sleeve and a photoconductor in order to maintain a minimum gap d.
  • the magnetic toner or the magnetic carrier existing on the portion above the space between the two magnets is magnetized in the polarity opposite to that of the magnetic toner or the magnetic carrier in the other portion, so that the chainlike arrangement of the toner or the carrier is interrupted by the two magnets.
  • the oppositely directed' magnetic fields of the two magnets 8 and 9 are shown in Fig. 5, in which the lines of magnetic force starting from the N pole are directed to the S pole in the respective magnets 8 and 9, so that the lines of magnetic force starting from the respective N poles are oppositely directed.
  • the development force can be represented by the following formula: where F represents the development force, and Fc represents the electrostatic attraction of a photoconductor for attracting the developer thereto, and F m represents the magnetic attraction for attracting the developer magnetically in the magnetic brush development apparatus.
  • the magnetic attraction F serves as a negative bias with respect to the development force in the magnetic brush development apparatus.
  • Fig. 6 there is shown a development characteristic of the magnetic brush development, by employing the magnetic attraction F m as a parameter, with the amount of toner deposition M as ordinate and surface charge Q of a photoconductor as abscissa.
  • the solid line indicates a development characteristic when the magnetic attraction F m is comparatively small while the broken line indicates a development characteristic when the magnetic attraction F m is comparatively great In either case, the development time is set constant.
  • the magnetic attraction F m when the magnetic attraction F m is small, the toner deposition begins to be saturated even if the surface charge Q is comparatively small.
  • the magnetic attraction F m when the magnetic attraction F m is set small, the amount of toner deposition M during a predetermined development time becomes greater than that in the case where the magnetic attraction F m is set great and accordingly, the development time can be shortened in comparison with that in the case of a great magnetic attraction F m when an equal amount of toner deposition is required.
  • the magnetic attraction F m when the magnetic attraction F m is set small, background appears in the copy and sharpness of image is lowered, so that setting the magnetic attraction F m at a low level has an adverse effect on the image quality.
  • An object of the invention is to provide a magnetic brush development apparatus having an excellent development efficiency with uneven development obviated by broadening the width of a magnetic brush which is in contact with a latent electrostatic image bearing member.
  • a further object of the invention is to provide a magnetic brush development apparatus whose construction is simple and which can be assembled easily.
  • the magnetic pole portion is of such a form that the peaks located upstream of the movement of said latent electrostatic image bearing member are lower than the peaks located downstream of the movement of said latent electrostatic image bearing member.
  • the magnets for the present invention can be made by various methods.
  • the simplest method is to mold a ferromagnetic material and magnetize it and form a concave portion in the thus made magnet as desired by a diamond cutter.
  • Another method is to form a desired concave portion in a ferromagnetic material first and to magnetize it later.
  • a further method is to join together magnets or cause a ferromagnetic material to adhere to the projecting portions of a magnet.
  • the magnets are composed of pieces of magnets.
  • one magnetic rod with predetermined concave portions at desired magnetic pole portions can be used as well.
  • FIG. 7 there is schematically shown a magnetic brush development apparatus according to the present invention.
  • reference numeral 21 represents a non-magnetic sleeve which is rotated counterclockwise.
  • a magnet 22 In the non-magnetic sleeve 21, there is disposed a magnet 22.
  • Part of the non-magnetic sleeve 21 faces a drum-shaped latent electrostatic image bearing member or a photoconductor drum 23 with a predetermined space therebetween.
  • the magnet 22 has a magnetic pole, for instance, an N pole, facing the surface of the photoconductor drum 23 through the non-magnetic sleeve 21 in a development section, so that a magnetic field is formed in the development section on the non-magnetic sleeve 21.
  • a magnet (not shown) for transporting developer is incorporated in the non-magnetic sleeve 21.
  • a groove 24 which is eccentrically located closer to the surface of the photoconductor drum 23.
  • a first magnetic pole portion 25 is formed in the magnet 22, upstream of the groove 24, and a second magnetic portion 26 is formed downstream of the groove 24.
  • the first magnetic portion 25 is broader than the second portion 26.
  • the developer in developing a latent electrostatic image on the photoconductor drum 23, firstly the developer is deposited uniformly on the latent electrostatic image by the comparatively weak magnetic field produced by the first magnetic pole portion 25 which is located upstream in view of the rotation of the photoconductor drum 23, and secondly the latent electrostatic image is completely developed by the comparatively strong magnetic field produced by the second magnetic pole portion 26 which is located downstream of the first magnetic pole portion 25, whereby a high quality image with a uniform image density and without background can be obtained.
  • Fig. 10 there is shown partially an enlarged schematic sectional view of a further embodiment of the present invention.
  • a first magnetic pole portion 27 which is formed with a predetermined first space away from the outer peripheral surface of the non-magnetic sleeve 21, and a second magnetic pole portion 28 with a second space away from the outer peripheral surface of the non-magnetic sleeve 21.
  • the first space is greater than the second space, so that the second magnetic pole portion 28 constitutes a stepped end portion of the magnetic pole portion of Fig. 10.
  • the first magnetic pole portion 27 is located upstream of the second magnetic pole portion 28, viewed from the rotation of the photoconductor drum 23.
  • the intensity of the magnetic field is distributed as shown in Fig. 12, so that the effect similar to that of the embodiment of Fig. 8 can be obtained.
  • Fig. 12 there is shown partially an enlarged schematic sectional view of a still further embodiment of the present invention.
  • the magnetic pole portion of the magnet of this embodiment there are formed two grooves 39 and 30 which are spaced away from each other, and a first magnetic pole portion 31, a second magnetic pole portion 32, and a third magnetic pole portion 33 which are separated by the two grooves 39 and 30.
  • the first and second magnetic pole portions 31 and 32 which are located upstream of the third magnetic pole portion 33, are equally spaced away from the outer peripheral surface of the non-magnetic sleeve 21, while the third magnetic pole portion 33 is located closer to the non-magnetic sleeve 21 than the first two magnetic pole portions 31 and 32.
  • the curve of the intensity of the magnetic field has three peaks as shown in Fig. 13. Of the three peaks of the intensity of the magnetic field, the peak existing most downstream of the rotation of the photoconductor drum 23 is the highest, which indicates the greatest magnetic force.
  • the developer is deposited uniformly on a latent electrostatic image on the drum 23 by the comparatively weak magnetic field of the first and second magnetic pole portions 31 and 32 and the latent image is then completely developed by the comparatively strong magnetic field produced by the third magnetic pole portion 33.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)

Claims (4)

1. Dispositif de développement à brosse magnétique dans lequel un développateur contenant une poudre magnétique est attiré sur un élément de support non magnétique (21) qui contient un aimant (22), et le développateur attiré sur l'élément de support non magnétique est amené en contact avec un élément de support d'image électrostatique latente (23) dans un poste de développement, pour développer cette image électrostatique latente, ledit aimant (22) comportant notamment une partie de pôle magnétique capable de produire un champ magnétique ayant plusieurs maximums d'intensité dans la partie de développement, caractérisé en ce que la partie de pôle magnétique a une forme telle que les maximums situés en amont, par rapport au mouvement de l'élément de support d'image électrostatique latente, sont inférieurs aux maximums situés en aval par rapport au mouvement de l'élément de support d'image électrostatique latente (23).
2. Dispositif de développement à brosse magnétique selon la revendication 1, dans lequel ledit aimant (22) comporte une première partie de pôle magnétique (25) et une seconde partie de pôle magnétique (26) qui sont séparées par une partie en forme de gorge (24) formée dans ledit aimant, cette partie en forme de gorge (24) s'étend dans la direction normale au mouvement de l'élément de support d'image électrostatique latente (23), la première partie de pôle magnétique (25) est située en amont de la partie en forme de gorge (24), la second partie de pôle magnétique (26) est située en aval de la partie en forme de gorge (24), en considérant le mouvement de l'élément de support d'image électrostatique latente (23), et la première partie de pôle magnétique (25) est plus large que la seconde partie de pôle magnétique (26).
3. Dispositif de développement à brosse magnétique selon la revendication 1, caractérisé en ce que ledit aimant (22) comporte une première partie de pôle magnétique (27) et une seconde partie de pôle magnétique (28), chacune d'elles étant orientée dans une direction normale au mouvement de élément de support d'image électrostatique latente (23), la première partie de pôle magnétique (27) est située en amont de la seconde partie de pôle magnétique (28), lorsqu'on considère le mouvement de l'élément de support d'image électrostatique latente (23), et la partie supérieure de la seconde partie de pôle magnétique (28) est plus proche de l'élément de support non magnétique que celle de la première partie de pôle magnétique (27).
4. Dispositif de développement à brosse magnétique selon la revendication 1 dans lequel ledit aimant (22) comporte une première partie depôle magnétique (31) une seconde partie de pôle magnétique (32) et une troisième partie de pôle magnétique (33), cachune d'elles étant séparée par deux gorges parallèles (29, 30) formées dans l'aimant (22), s'étendant dans la direction normale au mouvement de l'élément de support d'image électrostatique latente (23), la première partie de pôle magnétique (31) et la seconde partie de pôle magnétique (32) sont situées en amont de la troisième partie de pôle magnétique (33), lorsqu'on considère le mouvement de l'élément de support d'image électrostatique latente (23), et la partie supérieure de la troisième partie de pôle magnétique (33) est plus proche de l'élément de support d'image électrostatique latente (23) que celle des première et seconde parties de pôle magnétique (31, 32).
EP19790100081 1978-01-11 1979-01-11 Dispositif de développement à brosse magnétique Expired EP0003134B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE8080107642T DE2967496D1 (en) 1978-01-11 1979-01-11 Magnetic brush development apparatus

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP180878A JPS5495243A (en) 1978-01-11 1978-01-11 Magnetic brush developing device
JP1808/78 1978-01-11
JP2956978A JPS54122131A (en) 1978-03-15 1978-03-15 Magnetic brush developing device
JP29569/78 1978-03-15

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP80107642.3 Division-Into 1979-01-11

Publications (2)

Publication Number Publication Date
EP0003134A1 EP0003134A1 (fr) 1979-07-25
EP0003134B1 true EP0003134B1 (fr) 1981-10-14

Family

ID=26335093

Family Applications (2)

Application Number Title Priority Date Filing Date
EP80107642A Expired EP0031503B1 (fr) 1978-01-11 1979-01-11 Appareil de développement à brosse magnétique
EP19790100081 Expired EP0003134B1 (fr) 1978-01-11 1979-01-11 Dispositif de développement à brosse magnétique

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP80107642A Expired EP0031503B1 (fr) 1978-01-11 1979-01-11 Appareil de développement à brosse magnétique

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EP (2) EP0031503B1 (fr)
CA (1) CA1135046A (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60229074A (ja) * 1984-04-27 1985-11-14 Toshiba Corp トナ−濃度検出装置
DE68912004T2 (de) * 1988-07-01 1994-05-05 Canon Kk Entwicklungsgerät.
WO2007129277A2 (fr) 2006-05-10 2007-11-15 Koninklijke Philips Electronics N. V. Système magnétique
JP6938167B2 (ja) * 2016-03-08 2021-09-22 キヤノン株式会社 画像形成装置

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE7104099U (de) * 1971-07-08 Addressograph Multigraph Corp Magnetbürstenentwickler zum Entwickeln elektrostatisch geformter Bilder auf Blatt material
US3333572A (en) * 1965-04-27 1967-08-01 Rca Corp Electrostatic printing
US3402698A (en) * 1966-06-06 1968-09-24 Konishiroku Photo Ind Magnet assembly for magnetic developing brush and developing apparatus for electrostatic process
JPS475648U (fr) * 1971-02-13 1972-09-19
US3939801A (en) * 1973-09-10 1976-02-24 Minolta Camera Kabushiki Kaisha Magnetic brush developing apparatus
JPS5843739B2 (ja) * 1974-10-10 1983-09-28 キヤノン株式会社 現像装置
DE2452879B2 (de) * 1974-11-07 1979-03-01 Hitachi Metals, Ltd., Tokio Magnetwalze
US4048958A (en) * 1976-03-08 1977-09-20 Fuji Xerox Co., Ltd. Magnetic brush developing device

Also Published As

Publication number Publication date
CA1135046A (fr) 1982-11-09
EP0031503A2 (fr) 1981-07-08
EP0031503A3 (en) 1981-09-09
EP0003134A1 (fr) 1979-07-25
EP0031503B1 (fr) 1985-08-07

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