US3897748A - Apparatus for controlling toner concentration of developer in electrostatic development - Google Patents

Apparatus for controlling toner concentration of developer in electrostatic development Download PDF

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Publication number
US3897748A
US3897748A US470362A US47036274A US3897748A US 3897748 A US3897748 A US 3897748A US 470362 A US470362 A US 470362A US 47036274 A US47036274 A US 47036274A US 3897748 A US3897748 A US 3897748A
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United States
Prior art keywords
probe
toner
developer
controlling
brush
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Expired - Lifetime
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US470362A
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English (en)
Inventor
Masao Hirata
Shigeru Inowa
Tatsuo Ohto
Kiyoshi Kimura
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Konica Minolta Inc
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Konica Minolta Inc
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Assigned to KONICA CORPORATION reassignment KONICA CORPORATION RELEASED BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: KONISAIROKU PHOTO INDUSTRY CO., LTD.
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    • 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
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
    • G03G15/0848—Arrangements for testing or measuring developer properties or quality, e.g. charge, size, flowability
    • G03G15/0849—Detection or control means for the developer concentration
    • G03G15/0855—Detection or control means for the developer concentration the concentration being measured by optical means

Definitions

  • ABSTRACT Primary Examiner-Mervin Stein Assistant E, ⁇ aminerDouglas Salser Attorney, Agent, or Firm-Bierman & Bierman [57] ABSTRACT
  • the invention is directed to an improved apparatus for controlling toner concentration of a developer comprising a developer receptacle; means in the form of a magnetic brush for conveying the developer through a developing state; an electrically conductive rotatable probe placed in contact with said brush whereby toner in the developer is attached to said probe: means for measuring the amount of toner attached to the probe, said measuring means comprising a light source to illuminate said probe and a photoelectric element to detect the light from said probe; and means for controlling a replenishing amount of the toner to said receptacle based on the result of the measurement.
  • This invention relates to an electrophotographic copying process, and more particularly to an apparatus for controlling the toner content in the developer that consists of two or more components.
  • Electroconductivity of the developer is low and noise is high.
  • a specific charging means is required. Also, as the probe is used repetitively, means is required for removing toner which has deposited on the probe in each use. Hence, the apparatus is complicated in mechanism and enlarged in size. Further, even if the density of electric charge retained by the toner, charged through friction with the carrier, is changed due to relative humidity, fatigue of developer and difference of toner consumption etc, toner is forced to be deposited electrostatically on the probe because the Coulomb force due to the charge impressed on the probe is considerably higher as compared with the force between toner and carrier.
  • An object of the present invention is to provide a novel toner content controlling method which is completely free from the defects of the above-mentioned prior art methods.
  • the above object is accomplished by an apparatus which comprises a developer receptacle. means for conveying the developer to and from a developing state, an electrically conductive rotatable probe positioned at the location where said probe contacts the developer being conveyed whereby toner in the developer attaches itself to said probe, means for measuring an amount of the attached toner, and means for controlling a repremishing amount of the toner to said receptacle based on the measurment.
  • FIG. 1 shows an embodiment of the present invention.
  • FIG. 2 is a graph showing the relationship among the developer stirring time, electrostatic charge densities retained by toner particles, and an amount of the toner deposited on the electrically conductive probe, as obtaind by use of the apparatns of FIG. 1.
  • FIG. 3 is a graph showing variation of toner content in the developer and density of electric charge on the toner, as observed while the apparatus of FIG. 1 is operated to obtain 20,000 sheets of copies.
  • FIG. 4 is a graph showing the variation of amounts of toner deposited on the probe with change of depth of distance between the sleeve and the probe.
  • FIG. 5 is a control circuit diagram used in the present invention.
  • FIG. 1 of the drawings there is shown a diagrammatic cross-section of the portion including a magnetic brush type developing mechanism and a detection unit.
  • Reference numeral I in the figure indicates a drum carrying electrostatic latent images and arranged to be rotatable counterclockwise, and numeral 2 designates generally the magnetic brush type developing mechanism. It comprises a developer receptacle 20 of which the interior surface is curved to present a substantially circular section 2I to effect smooth circulation of the developer D (composed of toner and carrier) in cooperation with a magnetic brush which is described later.
  • a bent protuberance 22 adapted to regulate the working amount D of the developer D.
  • Numeral 23 designates a magnetic brush consisting of a mandrel 24 around which the permanent magnets 25 of different polarities are arranged alternately and which itself is secured to a side plate (not shown) of the receptacle 20, and a nonmagnetic sleeve 26 disposed surrounding the mandrel 24 so as to be rotatable counterclockwise.
  • 27 denotes a mixing plate adapted to distribute the developer D uniformly in the axial direction of the rotation of the brush 23 after the developer carried up by the action of the brush 23 has been scraped down from the sleeve 26.
  • Numeral 3 designates generally a toner content detector unit comprising the unit body portion 31 having at its bottom an opening through which a part of an electrically coductive probe is exposed to the developer, a probe 32 formed from an electrically conductive and transparent glass cylinder arranged rotatable counterclockwise and retained at a location where its surface is contacted with the working developer D, a lamp 33 providing a light source, and a photoelectric element (CdS cell) 34 disposed in the probe 32 and adapted to detect the amount of toner deposited on the probe 32 by a transmission method in cooperation with the lamp 33 and send a detection signal to a toner re plenishment control circuit (described after) to which the photoelectric element is connected.
  • Numeral 4 refers to a toner container from which toner 42 is replenished into the developing mechanism in response to an information from the circuit.
  • the developer D accumulated at the bottom of the receptacle is attracted to the surface of the sleeve 26 by the attraction of said permanent magnets and urged to move to the right with rotation of the sleeve 26.
  • the developer D is regulated into a suitable volume (working developer D) by the bent protuberance 22 of the receptacle 20, and immediately thereafter, the electrostatic latent image formed on the surface of the rotating drum 1 is developed into a visual image by the action of the working developer D.
  • the thus regulated developer continues to move forward until it contacts the probe 32 which is moving oppositely to the direction of the movement of said developer.
  • the mechanism of attaching toner to the surface of the probe is considered as following at the point where the probe contacts the developer; at this point, the developer gains kinetic energy whereby the toner particles in the developer which cling to the carrier merely by the force of triboelectrical charges are separated from the carrier and suspended in the form of cloud in the space 50.
  • the suspended toner particles carrying triboelectric charges of a certain polarity induce on the probe the electric charges of the opposite polarity, so that the suspended toner is attracted to the probe by an electrostatic force which is generally called image force.
  • the density of electric charge of toner can not stay constant because such electric clra ge of toner is induced through friction with the carrier and also because triboelectricity of toner is greatly affected by relative humidity and further the degree of leakage of electric charge retained by the developer varies ac cording to the various conditions. For instance, the lower a relative humidity is, the more triboelectric charge is induced on the toner, resulting in toner deficiency in the formed image. This is due to the fact that if density of electric charge held by the toner is increased, coulomb force between toner and carrier is also enlarged to retard transfering of toner toward the electrostatic latent image. That is, it becomes hard to obtain required density as the density of electric charge held by the toner is small.
  • FIG. 3 it graphically shows variation of toner content in the developer and veriation of density of electric charge on toner as observed in a test where 20,000 sheets of copies were obtained by using the controlling method of the present invention.
  • the copying operation was performed by using the originals of the B4 sizes which consume toner of 20 to 300 mg per a sheet in an atmosphere kept at 25C with relative humidity of 20 and in the first half and the last half of the operation, respectively.
  • the method of the present invention is capable of controlling the toner content corresponding to variation of the density of electric charge retained by the toner, regardless of variation of toner consumption in the developer.
  • FIG. 4 shows variation of the amount of toner deposited on the electroconductive probe as observed when changing the distance between the sleeve and the probe with the developer and as measured at the contact area of the two (showed in FIG. 4 as A, and A and after the probe has been contacted thoroughly with the toner cloud (showed in the figure as B and B).
  • the tests were conducted by usin two types of developer with different toner contents one being 6.17% (A. and B and the other 4.29% (A and Bflland under the follow ing conditions: linear velocity of the probe l mm/sec', linear velocity of the sleeve surface 400 mm/sec; working developer layer thickness 9 mm; and the distance between the sleeve and the probe 3 to 8 mm.
  • the abscissa represents the dis tance 1 between the sleeve surface and the probe surface
  • the ordinate represents the amount of toner deposited on the probe, such amount being measured optically by a transmission method and expressed by numerical values in terms of transparent density as unit.
  • the probe is used repetitively as it is adapted in a recording device which is operated continuously, so that it is desirable that the probe is of a configuration allowing easy and smooth rotation, such as cylindrical, discshaped or endless belt-shape.
  • the probe is preferably made from electrically conductive glass coated with a film of tin oxide as this material provides relatively high friction resistance when contacted with the developer. It is of course possible to use other metal materials such as aluminium, copper, brass, or iron. [t is also possible to use even a poor-conductive material if such material has a certain degree of electric conductivity sufficient to allow deposition of toner particles by image force. Therefore, the probe may be formed by covering an insulator with an electroconductive material.
  • the electroconductive probe surface may be coated with an insulator for the purpose of protecting the probe, but the thickness of such coating must be less than 1 micron because if such coating thickness is greater than 1 micron, the image force is excessively weakened to make it unable to achieve the end of the method of the present invention.
  • the probe is rotated so as to move in the same direction as movement of the developer at the contact point, it is found that the density of the toner cloud formed in the other space 60 in FIG. 1 is extremely low. In this case, however, it is possible to obtain substantially same volume of toner cloud as in the space 50 by disposing an obstacle at a suitable location in the other space 60 so as to expedite separation of toner from carrier.
  • the toner deposition on the probe may be determined either by detecting the change of transmittance or the degree of reflection of the probe by use of photodetector such as photoelectric element (like CdS) or phototube, or by measuring the amount of electric charge of the toner deposited.
  • photodetector such as photoelectric element (like CdS) or phototube
  • the measuring method using a photoelectric converter such as CdS cell is more convenient for the reason of simplicity.
  • FIG. 5 shows an exemplary circuit diagram where two CdS cells are used.
  • numerals I0] and 102 designate CdS cells, [03 to 107 specific resistances, 108 a variable resistance, adapted for regulating the toner content controlling level, and 109 an operational amplifier adapted such that the replenishing toner container 4 will be operated by the output signal therefrom.
  • the toner content controlling method of the present invention When the toner content controlling method of the present invention is used in a case where a bias voltage of a polarity opposite to that of electric charge retained by the toner is applied to the magnetic brush for preventing the toner from being electrostatically deposited on the undesired portion of a member carrying electrostatic latent images, it is considered that the probe has the same potential as the magnetic brush due to its electric conductivity, and hence change of toner deposition on the probe caused by application of said bias voltage is negligible and poses no problem practically.
  • the present method is employed in cas cade development, it is merely required to provide a suitable guide plate between the bucket conveyor and the member carrying electrostatic latent images and to dispose the probe thereabove so that it may contact the developer, whereby it is possible to produce a satisfac tory toner cloud no matter what direction the probe is rotated.
  • the toner content control according to the present invention can dispense with means for applying voltage to the probe as well as means for cleaning the probe, thus contributing to reduction of the machine size, and further, it is possible to obtain copies with always constant image density regardless of variation of various external factors.
  • the present invention can be applied not only in the field of electrophotographic reproduction but also in any sort of powder developing apparatuses such as facsimiles.
  • An apparatus for controlling toner concentration of a developer in electrostatic development comprising a developer receptacle; means in the form of a magnetic brush for conveying the developer through a developing state, an electrically conductive rotatable probe placed in contact with said brush whereby toner in the developer is attached to the probe, said measuring means comprising a light source to illuminate said probe and a photoelectric element to detect the light from said probe; and means for controlling a replenishing amount of the toner to said receptacle based on the result of the measurement.
  • one of the elements is adapted to measure the light from a first area of the probe, said first area having no toner while the other element is adapted to measure the light from a second area of the probe, said second area having the toner.
  • said measuring means comprises means for comparing a signal from one of the elements with that of the other.
  • control means is adapted to control the replenishing amount of the toner based on a signal from the comparison means.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)
US470362A 1973-05-25 1974-05-16 Apparatus for controlling toner concentration of developer in electrostatic development Expired - Lifetime US3897748A (en)

Applications Claiming Priority (1)

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JP48057831A JPS5246095B2 (enrdf_load_stackoverflow) 1973-05-25 1973-05-25

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US3897748A true US3897748A (en) 1975-08-05

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US (1) US3897748A (enrdf_load_stackoverflow)
JP (1) JPS5246095B2 (enrdf_load_stackoverflow)
DE (1) DE2425060C3 (enrdf_load_stackoverflow)
GB (1) GB1475547A (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4101214A (en) * 1975-01-13 1978-07-18 Minolta Camera Kabushiki Kaisha Toner dispensing device with electrical integrating circuit
US4236486A (en) * 1978-03-27 1980-12-02 Tokyo Shibaura Denki Kabushiki Kaisha Toner concentration control device
US4241696A (en) * 1978-04-19 1980-12-30 Tokyo Shibaura Denki Kabushiki Kaisha Apparatus for detecting toner concentration
US4273843A (en) * 1978-06-12 1981-06-16 Konishiroku Photo Industry Co., Ltd. Method of detecting toner concentration in electrophotographic copying machine
US4419960A (en) * 1981-09-08 1983-12-13 Fuji Xerox Co., Ltd. Developing agent density controlling device
US4684236A (en) * 1983-03-10 1987-08-04 Fuji Xerox Co., Ltd. Toner concentration detecting device for dry type electrographic copy machine
US4980727A (en) * 1990-04-02 1990-12-25 Eastman Kodak Company Toner concentration control system
US20110013917A1 (en) * 2009-07-15 2011-01-20 Kabushiki Kaisha Toshiba Developing device and method for detecting deterioration of developer

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56275Y2 (enrdf_load_stackoverflow) * 1977-04-18 1981-01-07
JPS54135537A (en) * 1978-04-12 1979-10-20 Ricoh Co Ltd Developing performance detector for binary dry type developer
JPS5521070A (en) * 1978-08-02 1980-02-14 Toshiba Corp Toner density control device in dry type developing apparatus
JPS5675662A (en) * 1979-11-26 1981-06-22 Hitachi Ltd Operating method of electrophotographic apparatus
GB2186818B (en) * 1986-02-20 1990-07-11 Ricoh Kk Developing electrostatic latent images

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3572551A (en) * 1969-03-27 1971-03-30 Rca Corp Apparatus for monitoring and controlling the concentration of toner in a developer mix
US3587521A (en) * 1969-10-09 1971-06-28 Rca Corp Apparatus for monitoring and controlling the concentration of powder particles in a mixture of powder and magnetic particles
US3604939A (en) * 1968-05-24 1971-09-14 Xerox Corp Toner concentration sensing apparatus having plural sensors and a flow control means for each sensor
US3610205A (en) * 1968-10-17 1971-10-05 Continental Can Co Apparatus for measuring and controlling mixture content
US3707134A (en) * 1970-08-21 1972-12-26 Addressograph Multigraph Automatic toner concentrate detector and control device
US3791744A (en) * 1972-02-22 1974-02-12 Dyk Res Corp Van Xerographic toner concentration measuring apparatus and method
US3830401A (en) * 1971-12-13 1974-08-20 Eastman Kodak Co Toner concentration monitoring apparatus

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3094049A (en) * 1961-02-03 1963-06-18 Xerox Corp Xerographic developer measuring apparatus
US3390652A (en) * 1967-02-06 1968-07-02 Nathan K. Morris Hand held and operated sewing machine
US3430606A (en) * 1968-01-02 1969-03-04 Xerox Corp Electroscopic particle sensor

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3604939A (en) * 1968-05-24 1971-09-14 Xerox Corp Toner concentration sensing apparatus having plural sensors and a flow control means for each sensor
US3610205A (en) * 1968-10-17 1971-10-05 Continental Can Co Apparatus for measuring and controlling mixture content
US3572551A (en) * 1969-03-27 1971-03-30 Rca Corp Apparatus for monitoring and controlling the concentration of toner in a developer mix
US3587521A (en) * 1969-10-09 1971-06-28 Rca Corp Apparatus for monitoring and controlling the concentration of powder particles in a mixture of powder and magnetic particles
US3707134A (en) * 1970-08-21 1972-12-26 Addressograph Multigraph Automatic toner concentrate detector and control device
US3830401A (en) * 1971-12-13 1974-08-20 Eastman Kodak Co Toner concentration monitoring apparatus
US3791744A (en) * 1972-02-22 1974-02-12 Dyk Res Corp Van Xerographic toner concentration measuring apparatus and method

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4101214A (en) * 1975-01-13 1978-07-18 Minolta Camera Kabushiki Kaisha Toner dispensing device with electrical integrating circuit
US4236486A (en) * 1978-03-27 1980-12-02 Tokyo Shibaura Denki Kabushiki Kaisha Toner concentration control device
US4241696A (en) * 1978-04-19 1980-12-30 Tokyo Shibaura Denki Kabushiki Kaisha Apparatus for detecting toner concentration
US4273843A (en) * 1978-06-12 1981-06-16 Konishiroku Photo Industry Co., Ltd. Method of detecting toner concentration in electrophotographic copying machine
US4419960A (en) * 1981-09-08 1983-12-13 Fuji Xerox Co., Ltd. Developing agent density controlling device
US4684236A (en) * 1983-03-10 1987-08-04 Fuji Xerox Co., Ltd. Toner concentration detecting device for dry type electrographic copy machine
US4980727A (en) * 1990-04-02 1990-12-25 Eastman Kodak Company Toner concentration control system
US20110013917A1 (en) * 2009-07-15 2011-01-20 Kabushiki Kaisha Toshiba Developing device and method for detecting deterioration of developer

Also Published As

Publication number Publication date
DE2425060C3 (de) 1981-09-10
JPS5010141A (enrdf_load_stackoverflow) 1975-02-01
GB1475547A (en) 1977-06-01
DE2425060A1 (de) 1974-12-12
JPS5246095B2 (enrdf_load_stackoverflow) 1977-11-21
DE2425060B2 (de) 1981-01-08

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Owner name: KONICA CORPORATION, JAPAN

Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:KONISAIROKU PHOTO INDUSTRY CO., LTD.;REEL/FRAME:005159/0302

Effective date: 19871021