EP0087074B1 - Method and device for the development of a latent electrostatic image induced on a recording medium - Google Patents

Method and device for the development of a latent electrostatic image induced on a recording medium Download PDF

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Publication number
EP0087074B1
EP0087074B1 EP83101272A EP83101272A EP0087074B1 EP 0087074 B1 EP0087074 B1 EP 0087074B1 EP 83101272 A EP83101272 A EP 83101272A EP 83101272 A EP83101272 A EP 83101272A EP 0087074 B1 EP0087074 B1 EP 0087074B1
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EP
European Patent Office
Prior art keywords
developer
developing roller
charging
charging device
component developer
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
EP83101272A
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German (de)
French (fr)
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EP0087074A3 (en
EP0087074A2 (en
Inventor
Helmuth Haberhauer
Gerhard Spingath
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Hoechst AG
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Hoechst AG
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Publication date
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Publication of EP0087074A2 publication Critical patent/EP0087074A2/en
Publication of EP0087074A3 publication Critical patent/EP0087074A3/en
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Publication of EP0087074B1 publication Critical patent/EP0087074B1/en
Expired legal-status Critical Current

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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
    • G03G15/0805—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a 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
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer

Definitions

  • the invention relates to a method and a device for developing an electrostatic latent image produced on a recording medium with an electrically charged one-component developer which is conveyed onto the surface of the recording medium by a developing roller.
  • Such a method and such a device are known from DE-A 29 19 804, which describes a method in which a developer application device with a conductive, elastically flexible, endless surface is brought into contact with the recording medium at a certain pressure and a one-component -Developer developed the latent charge image on the record carrier.
  • the developer application device and the recording medium are moved in the same direction and the peripheral speed of the developer application device is somewhat greater than that of the recording medium.
  • the device used for the method has a cutting edge electrode, which rests with a certain pressure on the surface of the developer application device and charges the one-component developer by charge injection with a predetermined polarity.
  • the ratio of the peripheral speed of the developer application device to that of the recording medium is in the range from 1.1: 1 to 1.5: 1.
  • the most common development processes to date use two-component developers, which consist of toner and carrier particles. Recently, one-component developers have also been used very frequently, and are generally magnetic one-component toners. When using two-component developers, it is necessary to always measure the consumption of the toner that is carried out by the copies and to carry out the replenishment in such a way that a largely constant ratio between the toner and the carrier particles is ensured. Since the carrier particles are not consumed in a two-component developer, they are subject to aging, for example due to corrosion, because of their long residence time in the development system of the copier, which in turn causes the toner to separate from the carrier particles and the toner to settle on the background of the copy to an undesirable extent.
  • a disadvantage of the two-component developers is that there is always a large amount of developer in the development system, which due to the long dwell times of the toner in the developer reduces the quality of the former through grinding processes and accelerates the aging process of the entire developer.
  • Magnetic one-component developers do not have the aforementioned disadvantages, but magnetic components such as magnetic brushes, which are expensive to manufacture, are required for their transport. A certain difficulty also arises in the case of magnetic one-component developers in that, owing to their magnetic constituents, they have greater electrical conductivity and the triboelectric charging of the magnetic toner is thereby made difficult.
  • DE-A 31 07055 discloses a developing device for a one-component developer, in which a thin, uniform layer of the insulating, non-magnetic one-component developer is formed on a developer carrier and is opposed to a latent image carrier in order to form a latent image generated thereon to develop.
  • an application device is provided which, for example, has a grid and a pressure element for pressing the grid onto the developer carrier.
  • a developing device for a two-component developer with a magnetic brush is known, on the circumference of which a roller brush rests.
  • the roller brush scatters the developer from the surface of the magnetic brush and wires are provided to remove the developer from the bristles of the roller brush.
  • the resulting developer cloud moves towards a photoconductor drum that carries the latent image to be developed.
  • a wire mesh is arranged at a short distance from the surface of the photoconductor drum, which is designed as a counter electrode to the photoconductor surface and is intended to prevent toner particles with insufficient charge from reaching the recording medium. Retained particles lead to the clogging of such networks.
  • the developer can bale and compress under pressure and thereby form a uniformly thick and evenly charged toner layer can be prevented.
  • US-A-3 638 613 describes a developing device in which toner, which is located in a toner container, is triboelectrically attracted to the surface of a transfer roller.
  • a brush roller takes the toner from the transfer roller and applies it to the charged surface of a photoconductor element in order to visualize the electrostatic charge image thereon.
  • the toner, the surface of the transfer roller and the brush roller are selected so that they form a triboelectric series. This ensures that the toner adheres firmly to the transfer roller and, on the other hand, can be easily taken over by the brush roller.
  • the object of the invention is to provide a method and a device which, while avoiding the caking of the particles of a one-component developer, enable a uniform formation of the layer thickness of the one-component developer on the developing roller without layer-limiting devices such as a doctor blade, a grid or similar elements and charge the one-component developer evenly and sufficiently on its way to the developing roller.
  • the object is achieved according to the invention by a method according to the preamble of claim 1 in that the one-component developer is charged by at least one rotating charging device, transported in the direction of the developing roller and by grazing contact with a wiping device assigned to each charging device by the charging device (s) is separated and spun onto the developing roller.
  • the rotating charging devices come into contact with the fixed stripping devices, which fling the separated one-component developer onto the peripheral surface of the developing roller.
  • the layer thickness on the developing roller can be regulated by varying the rotational speeds of the charging devices and the developing roller, the rotating speed of the charging devices rotating at the same speed preferably being greater than the rotating speed of the developing roller.
  • the device according to the invention for developing an electrostatic latent image generated on a record carrier with an electrically charged one-component developer, with a developer roller arranged at a short distance from the record carrier and a developer supply device for the one-component developer is characterized in that the developer supply device has single components -Developer of the surface of one of two rotating charging devices can be supplied, that the surfaces of the two charging devices are at a distance smaller than each of the distances of the charging devices from the developing roller and that each charging device is assigned a stripping device which is in grazing contact with the surface of the charging device stands.
  • the charging devices are designed as brushes made of electrically conductive material and the cylindrical core of each charging device is connected to the same pole of a voltage source, the other pole of which is connected to ground.
  • a version with electrically insulating, but electrostatically chargeable brushes is also possible. Electrically conductive brushes are preferred because of controllable charging, also to prevent the charge from exceeding a certain size, i. H. runs away or becomes too high. The charging is controlled in a controlled manner with variable potentials.
  • the advantages are achieved that the charging of the one-component developer takes place with simply constructed charging devices in the form of brushes, the potential and thus also the charging of the one-component developer are easily controllable, that the developer layer on the developing roller by the speed of rotation of the Brushes and the developing roller can be regulated without a layer-limiting doctor blade and that, in order to supplement the developer discharged from the developing device by each image development, only small amounts of the developer have to be supplied, which can be charged triboelectrically quickly, well and uniformly to the desired voltage in order to achieve the total charge of the in developer to a predetermined value. hold.
  • the embodiment of the developing device according to the invention shown schematically in FIG. 1 comprises two charging devices 1 and 2, which are designed as brushes with a cylindrical core 22 and 23, respectively.
  • the material of the brushes is electrically conductive, steel wire brushes, for example made of abrasion-resistant materials, such as CrNi steels, are preferably used.
  • the surfaces or the peripheral surfaces of the two charging devices 1 and 2 are at a distance from one another which is smaller than the respective distance of the individual charging device from a developing roller 3 which is arranged above and at approximately equal distances from the roller surface to the stripping devices.
  • the two charging devices 1 and 2 are enclosed by a trough 5, the shape of which is adapted to the circumferential surfaces of the cylinders of the charging devices 1 and 2 and preferably made of the same material exists like the charging devices.
  • the distance between the inside of the tub 5 and the peripheral surfaces of the charging devices 1 and 2 or, in the case of brushes as charging devices, the distance between the inside of the tub 5 and the tips of the bristles of these brushes is of the order of 0.2 to 1 mm . The distance is chosen so that contact between the tub and brushes is avoided to prevent abrasion. Due to the volume of the tub 5, which limits the charging devices 1 and 2, small amounts of developer are sufficient to carry out a satisfactory charging of the toner.
  • the one-component developer 13 is replenished by a metering roller 21 near the outlet of a developer supply device 20, in which a supply of developer 13 is filled, and reaches the surface of the first charging device 1, which rotates counterclockwise, for example, as does the second charging device 2
  • the replenishment amount of developer 13 which is required to supplement the developer consumed by the image development is approximately 50 to 100 mg at an average density of the copy, which is approximately one hundredth of the amount of developer in circulation.
  • This amount of developer is both potential and triboelectric. as will be described in more detail below, quickly and easily rechargeable, so that a decrease in the charge of the one-component developer 13 by the newly supplied, uncharged one-component developer does not occur.
  • the total electrical charge of the one-component developer in the developing device is therefore kept largely constant during operation.
  • the cylindrical cores 22 and 23 of the two charging devices 1 and 2 are connected to the same pole of a voltage source 9, the other pole of which is grounded. If, for example, a positively charged one-component developer 13 is used, the voltage which is applied to the two charging devices 1 and 2 with the same polarity as that of the developer is approximately + 500 to + 800 volts, in particular + 600 volts.
  • a grid 18 for further toner charging is arranged between the charging devices 1 and 2 and is connected to the tub 5.
  • a scraper 4 is integrally connected to the grid 18 and is in contact with the bristles of the charging device 1.
  • the material of the grid 18 is preferably metal, but it can also be made of plastic.
  • One-component developer 13 is conveyed through the grid 18 from the charging device 1 to the charging device 2.
  • the one-component developer 13 experiences a further triboelectric charge, the magnitude of which depends on the grid material used in each case.
  • Those developer particles that are not conveyed through the grid 18 remain stored between the bristles of the steel wire brushes of the charging devices 1 and 2 and, in the case of the first charging device, reach the area of the scraper 4, which extends as far as into the circumferential path or movement path of the charging device 1 protrudes that the tips of the individual bristles are held back by him and are released when the charging device 1 is rotated by a snap movement over the scraper 4.
  • the developer particles embedded between the bristles are flung upwards, the individual developer particles being charged positively, for example.
  • This charge is composed of the charge which the charging device 1 gives to the developer particles as a result of the voltage applied to it, for example + 600 volts, and a triboelectric charge which occurs due to the rapid separation of the developer particles from the bristles during the stripping process by the stripper 4 .
  • a scraper 7 also protrudes into the movement path or circumferential path of the second charging device 2, which holds back the individual bristles of the steel wire brush until the energy stored in them by the deformation is sufficient for the snap movement over the scraper 7.
  • the developer particles stored between the individual bristles are again thrown in the direction of the developer roller 3 and are both due to the voltage applied to the second charging device 2 of, for example, + 600 volts as well as due to the triboelectric charging during the rapid separation of the developer particles from the individual bristles charged.
  • the two charging devices 1 and 2 are connected to the same voltage potential, but it goes without saying that the two charging devices can be set to different voltages if they are mounted in the device in an electrically insulated manner.
  • the tub 5 is preferably composed of two semi-cylindrical parts which are attached to a carrier 15.
  • the carrier 15 consists of an electrically conductive or insulating material. In the former case, the carrier 15 is connected to the same pole of the voltage source 9 as the cylindrical cores 22 and 23 of the two charging devices 1 and 2. If the carrier 15 consists of insulating material, the trough 5 is directly connected to the corresponding pole of the voltage source 9 connected.
  • the stripper 7 is also connected to the pole of the voltage source 9, with which the cylindrical cores 22, 23 are also connected.
  • the two edges of the tub 5 are attached to side supports 16, 17, which are made of insulating material. On these side beams 16 and 17, an upper part 8 of the developing device is further fastened, which closes the top.
  • a further voltage source 10 is connected to the developing roller 3 and the applied voltage is, for example, in the range from - 200 to - 300 volts and thus has an opposite polarity to that of the charging devices 1 and 2
  • a uniformly thick developer layer is formed on the peripheral surface of the developing roller 3 and can be selected in the range from 30 to 150 f.lm. Development takes place, for example, overhead and the recording medium 11, an endlessly revolving photoconductor belt with a latent charge image 14, is guided past the developing roller 3 at a distance which is slightly greater than the selected layer thickness.
  • the record carrier 11 is, for example, negatively charged to a voltage between -500 to -1,000 volts, in particular to - 600 volts.
  • the latent charge image 14 is indicated schematically in FIG. 1 by small circles that enclose a minus sign.
  • the positively charged developer 13 cannot be held back by the negatively charged developing roller with respect to the latent charge image 14 since the absolute amount of the negative voltage of the developing roller 3 is smaller than the absolute amount of the negatively charged photoconductor.
  • the latent charge image 14 is developed by the developer 13 into a powder image 12.
  • the speeds of the charging devices 1 and 2 are in the range of 100 to 200 revolutions per minute, while the speed of the developing roller is 50 to 80 revolutions per minute.
  • the ratio of the speeds of the charging devices and the developing roller is thus in the range from 1.2: 1 to 4: 1.
  • the developer layer thickness mentioned is 30 to 150 f.Lm. receive. Since the voltage of the developing roller 3 has the same polarity as the voltage of the recording medium 11, however, its height is lower than the voltage of the charged image areas, i.e. H.
  • the background of the copies is largely devoid of developer.
  • the background freedom of the copies can largely be controlled by the size of the voltage applied to the developing roller 3.
  • an elastic wiper 19 is attached, which bears against the peripheral surface of the developing roller 3 and the excess developer 13, which is not attracted to the latent charge image 14, by the Strips the peripheral surface of the developing roller 3.
  • the stripped developer trickles down onto the bristles of the first charging device 1 and is taken away by them again.
  • the amount of one-component developer in circulation is small, and accordingly the dwell time of the one-component developer in the developing device is very short.
  • the used one-component developer is subsequently metered in as a function of an optical measurement of the blackening on the developing roller 3, which optical measurement is not described in detail.
  • the separation speed of the one-component developer 13 from the bristles By choosing the mechanical sizes, such as the diameter and length of the bristles of the charging devices 1 and 2, the material of the charging devices and the wipers 4 and 7, and the speeds of the charging devices and the developing roller 3, the separation speed of the one-component developer 13 from the bristles and thus determining the magnitude of the triboelectric charge.
  • FIG. 2 different parts of the development device are shown in perspective, with only the difference compared to the embodiment of FIG. 1 that the stripper 7 is integrated with the tub 5, so that a separate connection of the stripper 7 to the voltage source 9 is not is necessary because the wiper has the same voltage as the trough 5, which is connected to the voltage source 9.
  • FIG. 3 schematically shows an embodiment of the developing device which is suitable for a recording medium which is stretched over the circumferential surface of a drum 24, a so-called photoconductor drum.
  • the developing roller 3 lies opposite the drum 24 in the three o'clock position, and a nine o'clock position is also possible, while the two charging devices 1 and 2, which are formed by brushes, are arranged obliquely below the developing roller 3.
  • the same parts are given the same reference numerals in the embodiments according to FIGS. 1 and 3. 1 to 3, the developer is sprayed onto the surface of the developing roller 3 essentially in the radial direction.
  • FIG. 4 an embodiment of the developing device is shown, which with a single Charging device 26 works in the form of a brush and in which the developer applies to the developing roller 3 tangentially.
  • the metal core of this charging device 26 is connected to the one pole of the voltage source 9, as is a stripper 27 which cooperates with the bristles of the charging device 26.
  • the mode of operation is analogous to that which was described with reference to FIG. 1.
  • the developer particles stored on the bristles and between the bristles are thrown upon contact with the stripper 27 onto the peripheral surface of the developing roller 3, which is connected to the one pole of a further voltage source 10 and has a voltage opposite the voltage of the charging device 26 .
  • a uniformly thick developer layer is formed on the peripheral surface of the developing roller 3, from which the developer passes onto the recording medium on the drum 24 in accordance with the latent charge image on the recording medium.
  • the remaining developer on the developing roller 3 is removed by the scraper 19 and arrives at a collecting roller 25, from the peripheral surface of which the developer is brushed off by the bristles of the charging device and fed again to the developing roller, the toner charge in turn being restored to the previous state by the applied voltage brought.

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Entwickeln eines auf einem Aufzeichnungsträger erzeugten elektrostatischen latenten Bildes mit einem elektrisch aufgeladenen Einkomponenten-Entwickler, der von einer Entwickelwalze auf die Oberfläche des Aufzeichnungsträgers befördert wird.The invention relates to a method and a device for developing an electrostatic latent image produced on a recording medium with an electrically charged one-component developer which is conveyed onto the surface of the recording medium by a developing roller.

Ein derartiges Verfahren und eine derartige Vorrichtung sind aus der DE-A 29 19 804 bekannt, die ein Verfahren beschreibt, bei dem eine Entwicklerauftragseinrichtung mit einer leitenden, elastisch nachgiebigen, endlosen Fläche mit einem bestimmten Druck an dem Aufzeichnungsträger in Anlage gebracht wird und ein Einkomponenten-Entwickler das latente Ladungsbild auf dem Aufzeichnungsträger entwickelt. Die Entwicklerauftragseinrichtung und der Aufzeichnungsträger werden in dieselbe Richtung bewegt und die Umfangsgeschwindigkeit der Entwicklerauftragseinrichtung ist etwas größer als diejenige des Aufzeichnungsträgers. Die für das Verfahren verwendete Vorrichtung weist eine Schneidenelektrode auf, die mit einem bestimmten Druck an der Oberfläche der Entwicklerauftragseinrichtung anliegt und den Einkomponenten-Entwickler durch Ladungsinjektion mit einer vorbestimmten Polarität auflädt.Such a method and such a device are known from DE-A 29 19 804, which describes a method in which a developer application device with a conductive, elastically flexible, endless surface is brought into contact with the recording medium at a certain pressure and a one-component -Developer developed the latent charge image on the record carrier. The developer application device and the recording medium are moved in the same direction and the peripheral speed of the developer application device is somewhat greater than that of the recording medium. The device used for the method has a cutting edge electrode, which rests with a certain pressure on the surface of the developer application device and charges the one-component developer by charge injection with a predetermined polarity.

Das Verhältnis der Umfangsgeschwindigkeit der Entwicklerauftragseinrichtung zu der des Aufzeichnungsträgers liegt im Bereich von 1,1 : 1 bis 1,5 : 1.The ratio of the peripheral speed of the developer application device to that of the recording medium is in the range from 1.1: 1 to 1.5: 1.

Die bisher gebräuchlichsten Entwicklungsverfahren verwenden Zweikomponenten-Entwickler, die aus Toner und Trägerteilchen bestehen. In jüngerer Zeit kommen auch sehr häufig Einkomponenten-Entwickler zum Einsatz, wobei es sich im allgemeinen um magnetische Einkomponenten-Toner handelt. Bei der Verwendung von Zweikomponenten-Entwickler ist es erforderlich, den Verbrauch des Toners, der durch die Kopien ausgetragen wird, stets zu messen und dessen Nachdosierung so vorzunehmen, daß ein weitgehend konstantes Verhältnis zwischen dem Toner und den Trägerteilchen sichergestellt ist. Da die Trägerteilchen bei einem Zweikomponenten-Entwickler nicht verbraucht werden, unterliegen sie wegen ihrer langen Verweilzeit im Entwickelsystem des Kopiergeräts einer Alterung, beispielsweise durch Korrosion, wodurch es wiederum zu einem Absetzen des Toners von den Trägerteilchen kommt und der Toner sich auf dem Untergrund der Kopie im unerwünschten Ausmaß niederschlägt. Von Nachteil ist bei den Zweikomponenten-Entwicklern auch, daß stets eine große Menge an Entwickler im Entwicklungssystem vorhanden ist, wodurch bedingt durch die langen Verweilzeiten des Toners im Entwickler die Qualität des ersteren durch Vermahlungsprozesse verringert und der Alterungsprozess des gesamten Entwicklers beschleunigt wird.The most common development processes to date use two-component developers, which consist of toner and carrier particles. Recently, one-component developers have also been used very frequently, and are generally magnetic one-component toners. When using two-component developers, it is necessary to always measure the consumption of the toner that is carried out by the copies and to carry out the replenishment in such a way that a largely constant ratio between the toner and the carrier particles is ensured. Since the carrier particles are not consumed in a two-component developer, they are subject to aging, for example due to corrosion, because of their long residence time in the development system of the copier, which in turn causes the toner to separate from the carrier particles and the toner to settle on the background of the copy to an undesirable extent. A disadvantage of the two-component developers is that there is always a large amount of developer in the development system, which due to the long dwell times of the toner in the developer reduces the quality of the former through grinding processes and accelerates the aging process of the entire developer.

Magnetische Einkomponenten-Entwickler weisen die vorerwähnten Nachteile nicht auf, jedoch sind für ihren Transport magnetische Bauteile, wie beispielsweise Magnetbürsten erforderlich, die teuer in der Herstellung sind. Eine gewisse Schwierigkeit ergibt sich auch bei magnetischen Einkomponenten-Entwicklern dadurch, daß sie infolge ihrer magnetischen Bestandteile eine größere elektrische Leitfähigkeit besitzen und dadurch die triboelektrische Aufladung des Magnettoners erschwert wird.Magnetic one-component developers do not have the aforementioned disadvantages, but magnetic components such as magnetic brushes, which are expensive to manufacture, are required for their transport. A certain difficulty also arises in the case of magnetic one-component developers in that, owing to their magnetic constituents, they have greater electrical conductivity and the triboelectric charging of the magnetic toner is thereby made difficult.

Aus der DE-A 31 07055 ist eine Entwicklungsvorrichtung für einen Einkomponenten-Entwickler bekannt, bei der eine dünne gleichförmige Schicht des isolierenden, nicht magnetischen Einkomponenten-Entwicklers auf einem Entwicklerträger gebildet wird und einem Latentbild-Träger gegenübergesetzt wird, um ein auf diesem erzeugtes Latentbild zu entwickeln. Zum Aufbringen des Entwicklers auf den Entwicklerträger in einer bestimmten Schichtdicke ist eine Auftragsvorrichtung vorgesehen, die beispielsweise ein Gitter und ein Andruckelement zum Andrücken des Gitters an den Entwicklerträger aufweist.DE-A 31 07055 discloses a developing device for a one-component developer, in which a thin, uniform layer of the insulating, non-magnetic one-component developer is formed on a developer carrier and is opposed to a latent image carrier in order to form a latent image generated thereon to develop. To apply the developer to the developer carrier in a certain layer thickness, an application device is provided which, for example, has a grid and a pressure element for pressing the grid onto the developer carrier.

Aus der DE-A 23 45 827 ist eine Entwicklungsvorrichtung für einen Zweikomponenten-Entwickler mit einer Magnetbürste bekannt, an deren Umfang eine Walzenbürste anliegt. Die Walzenbürste verstreut den Entwickler von der Oberfläche der Magnetbürste und es sind Drähte zum Entfernen des Entwicklers von den Borsten der Walzenbürste vorgesehen. Die dadurch entstehende Entwicklerwolke bewegt sich auf eine Fotoleitertrommel zu, die das zu entwickelnde latente Bild trägt. In geringem Abstand von der Oberfläche der Fotoleitertrommel ist ein Drahtnetz angeordnet, das als Gegenelektrode zu der Fotoleiteroberfläche gestaltet ist und verhindern soll, daß Tonerpartikel mit ungenügender Ladung auf den Aufzeichnungsträger gelangen. Zurückgehaltene Teilchen führen aber zur Verstopfung solcher Netze.From DE-A 23 45 827 a developing device for a two-component developer with a magnetic brush is known, on the circumference of which a roller brush rests. The roller brush scatters the developer from the surface of the magnetic brush and wires are provided to remove the developer from the bristles of the roller brush. The resulting developer cloud moves towards a photoconductor drum that carries the latent image to be developed. A wire mesh is arranged at a short distance from the surface of the photoconductor drum, which is designed as a counter electrode to the photoconductor surface and is intended to prevent toner particles with insufficient charge from reaching the recording medium. Retained particles lead to the clogging of such networks.

Bei der Verwendung von Auftragsvorrichtungen für den Einkomponenten-Entwickler, die aus die Schichtdicke begrenzenden Schneidenelektroden oder aus einem an einer Entwickelwalze anliegenden Andruckelement mit Gitter bestehen, kann es zu einem unter Druck stattfindenden Zusammenballen und Zusammenpressen des Entwicklers kommen und dadurch die Ausbildung einer gleichmäßig dicken und gleichmäßig aufgeladenen Tonerschicht verhindert werden.When using application devices for the one-component developer, which consist of cutting edge electrodes that limit the layer thickness or of a pressure element with a grid attached to a developing roller, the developer can bale and compress under pressure and thereby form a uniformly thick and evenly charged toner layer can be prevented.

In der US-A-3 638 613 ist eine Entwicklungsvorrichtung beschrieben, bei der auf der Oberfläche einer Übertragungsrolle Toner triboelektrisch angezogen wird, der sich in einem Tonerbehälter befindet. Eine Bürstenwalze übernimmt den Toner von der Übertragungswalze und trägt ihn auf die geladene Oberfläche eines Fotoleiterelements auf, um das darauf befindliche elektrostatische Ladungsbild sichtbar zu machen. Für eine optimale Bildentwicklung werden der Toner, die Oberfläche der Übertragungswalze und die Bürstenwalze materialmäßig so ausgewählt, daß sie eine triboelektrische Reihe bilden. Dadurch ist sichergestellt, daß der Toner fest auf der Übertragungswalze haftet und andererseits von der Bürstenwalze leicht übernommen werden kann.US-A-3 638 613 describes a developing device in which toner, which is located in a toner container, is triboelectrically attracted to the surface of a transfer roller. A brush roller takes the toner from the transfer roller and applies it to the charged surface of a photoconductor element in order to visualize the electrostatic charge image thereon. For an opti During image development, the toner, the surface of the transfer roller and the brush roller are selected so that they form a triboelectric series. This ensures that the toner adheres firmly to the transfer roller and, on the other hand, can be easily taken over by the brush roller.

Aufgabe der Erfindung ist es, ein Verfahren und eine Vorrichtung zu schaffen, die unter Vermeidung des Zusammenbackens der Partikel eines Einkomponenten-Entwicklers eine gleichmäßige Ausbildung der Schichtdicke des Einkomponenten-Entwicklers auf der Entwickelwalze ohne schichtbegrenzende Einrichtungen wie eine Rakel, ein Gitter oder dergleichen Elemente ermöglichen und den Einkomponenten-Entwickler gleichmäßig und ausreichend auf seinem Weg zu der Entwickelwalze aufladen.The object of the invention is to provide a method and a device which, while avoiding the caking of the particles of a one-component developer, enable a uniform formation of the layer thickness of the one-component developer on the developing roller without layer-limiting devices such as a doctor blade, a grid or similar elements and charge the one-component developer evenly and sufficiently on its way to the developing roller.

Die Aufgabe wird erfindungsgemäß durch ein Verfahren nach dem Oberbegriff des Anspruchs 1 dadurch gelöst, daß der Einkomponenten-Entwickler von zumindest einer umlaufenden Aufladeeinrichtung aufgeladen, in Richtung Entwickelwalze transportiert und durch streifenden Kontakt mit einer jeder Aufladeeinrichtung zugeordneten Abstreifeinrichtung von der/den Aufladeeinrichtung(en) abgetrennt und auf die Entwickelwalze geschleudert wird.The object is achieved according to the invention by a method according to the preamble of claim 1 in that the one-component developer is charged by at least one rotating charging device, transported in the direction of the developing roller and by grazing contact with a wiping device assigned to each charging device by the charging device (s) is separated and spun onto the developing roller.

Hierzu ist vorgesehen, daß die rotierenden Aufladeeinrichtungen mit den feststehenden Abstreifeinrichtungen in Berührung gelangen, die den abgetrennten Einkomponenten-Entwickler auf die Umfangsfläche der Entwickelwalze schleudern.For this purpose, it is provided that the rotating charging devices come into contact with the fixed stripping devices, which fling the separated one-component developer onto the peripheral surface of the developing roller.

Die Schichtdicke auf der Entwickelwalze kann durch die Variation der Drehgeschwindigkeiten der Aufladeeinrichtungen und der Entwickelwalze geregelt werden, wobei bevorzugt die Drehgeschwindigkeit der mit gleicher Geschwindigkeit umlaufenden Aufladeeinrichtungen größer als die Drehgeschwindigkeit der Entwickelwalze ist.The layer thickness on the developing roller can be regulated by varying the rotational speeds of the charging devices and the developing roller, the rotating speed of the charging devices rotating at the same speed preferably being greater than the rotating speed of the developing roller.

Die Vorrichtung nach der Erfindung zum Entwickeln eines auf einem Aufzeichnungsträger erzeugten elektrostatischen Latentbildes mit einem elektrisch aufgeladenen Einkomponenten-Entwickler, mit einer im geringen Abstand zu dem Aufzeichnungsträger angeordneten Entwickelwalze und einer Entwicklerzufuhreinrichtung für den Einkomponenten-Entwickler zeichnet sich dadurch aus, daß von der Entwicklerzufuhreinrichtung Einkomponenten-Entwickler der Oberfläche einer von zwei umlaufenden Aufladeeinrichtungen zuführbar ist, daß die Oberflächen der beiden Aufladeeinrichtungen voneinander einen Abstand kleiner als jeder der Abstände der Aufladeeinrichtungen von der Entwickelwalze aufweisen und daß jeder Aufladeeinrichtung eine Abstreifeinrichtung zugeordnet ist, die mit der Oberfläche der Aufladeeinrichtung in streifendem Kontakt steht.The device according to the invention for developing an electrostatic latent image generated on a record carrier with an electrically charged one-component developer, with a developer roller arranged at a short distance from the record carrier and a developer supply device for the one-component developer is characterized in that the developer supply device has single components -Developer of the surface of one of two rotating charging devices can be supplied, that the surfaces of the two charging devices are at a distance smaller than each of the distances of the charging devices from the developing roller and that each charging device is assigned a stripping device which is in grazing contact with the surface of the charging device stands.

In Ausgestaltung der Erfindung sind die Aufladeeinrichtungen als Bürsten aus elektrisch leitendem Material ausgebildet und ist der zylindrische Kern jeder Aufladeeinrichtung mit dem gleichen Pol einer Spannungsquelle verbunden, deren anderer Pol auf Masse liegt.In an embodiment of the invention, the charging devices are designed as brushes made of electrically conductive material and the cylindrical core of each charging device is connected to the same pole of a voltage source, the other pole of which is connected to ground.

Eine Ausführung mit elektrisch isolierenden, jedoch elektrostatisch aufladbaren Bürsten ist auch möglich. Elektrisch leitende Bürsten werden wegen der steuerbaren Aufladung bevorzugt verwendet, auch um zu verhindern, daß die Ladung eine bestimmte Größe übersteigt, d. h. davonläuft oder zu hoch wird. Mit variierbaren Potentialen wird die Aufladung kontrolliert gesteuert.A version with electrically insulating, but electrostatically chargeable brushes is also possible. Electrically conductive brushes are preferred because of controllable charging, also to prevent the charge from exceeding a certain size, i. H. runs away or becomes too high. The charging is controlled in a controlled manner with variable potentials.

Die weitere Ausbildung der Vorrichtung ergibt sich aus den Merkmalen der Ansprüche 7 bis 14.The further development of the device results from the features of claims 7 to 14.

Mit der Erfindung werden die Vorteile erzielt, daß die Aufladung des Einkomponenten-Entwicklers mit einfach aufgebauten Aufladeeinrichtungen in Form von Bürsten erfolgt, deren Potential und damit auch die Aufladung des Einkomponenten-Entwicklers leicht steuerbar sind, daß die Entwicklerschicht auf der Entwickelwalze durch die Drehgeschwindigkeit der Bürsten und der Entwickelwalze ohne schichtbegrenzende Rakel regelbar ist und daß zur Ergänzung des durch jede Bildentwicklung aus der Entwicklungsvorrichtung ausgetragenen Entwicklers nur geringe Mengen desselben zugeführt werden müssen, die triboelektrisch schnell, gut und gleichmäßig auf die gewünschte Spannung aufgeladen werden können, um die Gesamtladung des in der Entwicklungsvorrichtung befindlichen Entwicklers auf einem vorbestimmten Wert zu . halten.With the invention, the advantages are achieved that the charging of the one-component developer takes place with simply constructed charging devices in the form of brushes, the potential and thus also the charging of the one-component developer are easily controllable, that the developer layer on the developing roller by the speed of rotation of the Brushes and the developing roller can be regulated without a layer-limiting doctor blade and that, in order to supplement the developer discharged from the developing device by each image development, only small amounts of the developer have to be supplied, which can be charged triboelectrically quickly, well and uniformly to the desired voltage in order to achieve the total charge of the in developer to a predetermined value. hold.

Die Erfindung wird im folgenden anhand der Zeichnungen von Ausführungsbeispielen näher erläutert.The invention is explained below with reference to the drawings of exemplary embodiments.

Es zeigen :

  • Figur 1 eine schematische Ansicht einer Entwicklungsvorrichtung nach der Erfindung,
  • Figur 2 eine perspektivische Ansicht von Teilen der Entwicklungsvorrichtung nach Fig. 1,
  • Figur 3 eine schematische Ansicht einer Ausführungsform ähnlich derjenigen nach Fig. 1, und
  • Figur 4 eine weitere Ausführungsform der Entwicklungsvorrichtung mit einer einzigen Aufladeeinrichtung.
Show it :
  • FIG. 1 shows a schematic view of a developing device according to the invention,
  • FIG. 2 shows a perspective view of parts of the developing device according to FIG. 1,
  • Figure 3 is a schematic view of an embodiment similar to that of Fig. 1, and
  • Figure 4 shows another embodiment of the developing device with a single charger.

Das in Fig. 1 schematisch dargestellte Ausführungsbeispiel der Entwicklungsvorrichtung nach der Erfindung umfaßt zwei Aufladeeinrichtungen 1 und 2, die als Bürsten mit einem zylindrischen Kern 22 bzw. 23 ausgebildet sind. Das Material der Bürsten ist elektrisch leitfähig, bevorzugt werden Stahldrahtbürsten, beispielsweise aus abriebfesten Materialien, wie CrNi-Stählen, verwendet. Die Oberflächen bzw. die Umfangsflächen der beiden Aufladeeinrichtungen 1 und 2 besitzen voneinander einen Abstand, der kleiner ist als der jeweilige Abstand der einzelnen Aufladeeinrichtung von einer Entwickelwalze 3, die oberhalb und in etwa gleichen Abständen der Walzenoberfläche zu den Abstreifeinrichtungen angeordnet ist. Die beiden Aufladeeinrichtungen 1 und 2 sind von einer Wanne 5 eingeschlossen, die in ihrer Formgebung den Zylinderumfangsflächen der Aufladeeinrichtungen 1 und 2 angepaßt ist und bevorzugt aus dem gleichen Material besteht wie die Aufladeeinrichtungen. Der Abstand zwischen der Innenseite der Wanne 5 und den Umfangsflächen der Aufladeeinrichtungen 1 und 2 bzw. im Falle von Bürsten als Aufladeeinrichtungen der Abstand zwischen der Innenseite der Wanne 5 und den Spitzen der Borsten dieser Bürsten liegt in der Größenordnung von 0,2 bis 1 mm. Der Abstand wird so gewählt, daß eine Berührung von Wanne und Bürsten vermieden wird, um Abrieb auszuschließen. Durch das die Aufladeeinrichtungen 1 und 2 eng begrenzende Volumen der Wanne 5 genügen geringe Entwicklermengen, um eine zufriedenstellende Aufladung des Toners durchzuführen. Der Einkomponenten-Entwickler 13 wird durch eine Dosierwalze 21 nahe dem Austritt einer Entwicklerzufuhrvorrichtung 20, in der ein Vorrat von Entwickler 13 eingefüllt ist, nachdosiert und gelangt auf die Oberfläche der ersten Aufladeeinrichtung 1, die beispielsweise im Gegenuhrzeigersinn umläuft, ebenso wie die zweite Aufladeeinrichtung 2. Die Nachdosiermenge an Entwickler 13, die erforderlich ist, um den durch die Bildentwicklung verbrauchten Entwickler zu ergänzen, beträgt bei einer mittleren Schwärzungsdichte der Kopie etwa 50 bis 100 mg, das sind ungefähr ein Hundertstel der im Umlauf befindlichen Entwicklermenge. Diese Entwicklermenge ist sowohl potentialmäßig als auch triboelektrisch. wie nachstehend noch näher beschrieben werden wird, schnell und gut aufladbar, so daß ein Absinken der Ladung des Einkomponenten-Entwicklers 13 durch den neu zugeführten, ungeladenen Einkomponenten-Entwickler nicht auftritt. Die elektrische Gesamtladung des in der Entwicklungsvorrichtung befindlichen Einkomponenten-Entwicklers wird daher während des Betriebes weitgehend konstant gehalten.The embodiment of the developing device according to the invention shown schematically in FIG. 1 comprises two charging devices 1 and 2, which are designed as brushes with a cylindrical core 22 and 23, respectively. The material of the brushes is electrically conductive, steel wire brushes, for example made of abrasion-resistant materials, such as CrNi steels, are preferably used. The surfaces or the peripheral surfaces of the two charging devices 1 and 2 are at a distance from one another which is smaller than the respective distance of the individual charging device from a developing roller 3 which is arranged above and at approximately equal distances from the roller surface to the stripping devices. The two charging devices 1 and 2 are enclosed by a trough 5, the shape of which is adapted to the circumferential surfaces of the cylinders of the charging devices 1 and 2 and preferably made of the same material exists like the charging devices. The distance between the inside of the tub 5 and the peripheral surfaces of the charging devices 1 and 2 or, in the case of brushes as charging devices, the distance between the inside of the tub 5 and the tips of the bristles of these brushes is of the order of 0.2 to 1 mm . The distance is chosen so that contact between the tub and brushes is avoided to prevent abrasion. Due to the volume of the tub 5, which limits the charging devices 1 and 2, small amounts of developer are sufficient to carry out a satisfactory charging of the toner. The one-component developer 13 is replenished by a metering roller 21 near the outlet of a developer supply device 20, in which a supply of developer 13 is filled, and reaches the surface of the first charging device 1, which rotates counterclockwise, for example, as does the second charging device 2 The replenishment amount of developer 13 which is required to supplement the developer consumed by the image development is approximately 50 to 100 mg at an average density of the copy, which is approximately one hundredth of the amount of developer in circulation. This amount of developer is both potential and triboelectric. as will be described in more detail below, quickly and easily rechargeable, so that a decrease in the charge of the one-component developer 13 by the newly supplied, uncharged one-component developer does not occur. The total electrical charge of the one-component developer in the developing device is therefore kept largely constant during operation.

Die zylindrischen Kerne 22 und 23 der beiden Aufladeeinrichtungen 1 und 2 sind mit dem gleichen Pol einer Spannungsquelle 9 verbunden, deren anderer Pol auf Masse liegt. Wird beispielsweise ein positiv aufgeladener Einkomponenten-Entwickler 13 verwendet, so beträgt die Spannung, die mit der gleichen Polarität wie diejenige des Entwicklers an die beiden Aufladeeinrichtungen 1 und 2 angelegt wird, etwa + 500 bis + 800 Volt, insbesondere + 600 Volt. Zwischen den Aufladeeinrichtungen 1 und 2 ist ein Gitter 18 zur weiteren Toneraufladung angeordnet, das mit der Wanne 5 verbunden ist. Ein Abstreifer 4 ist integral mit dem Gitter 18 verbunden und steht mit den Borsten der Aufladeeinrichtung 1 in Kontakt. Das Material des Gitters 18 ist bevorzugt Metall, jedoch kann es auch aus Kunststoff hergestellt sein. Durch das Gitter 18 hindurch wird Einkomponenten-Entwickler 13 von der Aufladeeinrichtung 1 zu der Aufladeeinrichtung 2 befördert. Beim Durchgang durch das Gitter erfährt der Einkomponenten-Entwickler 13 eine weitere triboelektrische Aufladung, deren Größenordnung von dem jeweils verwendeten Gittermaterial abhängig ist. Diejenigen Entwicklerteilchen, die nicht durch das Gitter 18 hindurch befördert werden, bleiben zwischen den Borsten der Stahldrahtbürsten der Aufladeeinrichtungen 1 und 2 eingelagert und gelangen im Falle der ersten Aufladeeinrichtung in den Bereich des Abstreifers 4, der soweit in die Umfangsbahn bzw. Bewegungsbahn der Aufladeeinrichtung 1 hineinragt, daß die Spitzen der einzelnen Borsten von ihm zurückgehalten werden und beim Weiterdrehen der Aufladeeinrichtung 1 durch eine Schnappbewegung über den Abstreifer 4 hinweg freikommen. Durch diese Schnappbewegung werden die zwischen den Borsten eingelagerten Entwicklerteilchen nach oben geschleudert, wobei die einzelnen Entwicklerteilchen beispielsweise positiv aufgeladen sind. Diese Aufladung setzt sich zusammen aus der Aufladung, welche die Aufladeeinrichtung 1 als Folge der an sie angelegten Spannung von beispielsweise + 600 Volt den Entwicklerteilchen erteilt und einer triboelektrischen Aufladung, die durch das schnelle Trennen der Entwicklerteilchen von den Borsten beim Abstreifvorgang durch den Abstreifer 4 auftritt.The cylindrical cores 22 and 23 of the two charging devices 1 and 2 are connected to the same pole of a voltage source 9, the other pole of which is grounded. If, for example, a positively charged one-component developer 13 is used, the voltage which is applied to the two charging devices 1 and 2 with the same polarity as that of the developer is approximately + 500 to + 800 volts, in particular + 600 volts. A grid 18 for further toner charging is arranged between the charging devices 1 and 2 and is connected to the tub 5. A scraper 4 is integrally connected to the grid 18 and is in contact with the bristles of the charging device 1. The material of the grid 18 is preferably metal, but it can also be made of plastic. One-component developer 13 is conveyed through the grid 18 from the charging device 1 to the charging device 2. As it passes through the grid, the one-component developer 13 experiences a further triboelectric charge, the magnitude of which depends on the grid material used in each case. Those developer particles that are not conveyed through the grid 18 remain stored between the bristles of the steel wire brushes of the charging devices 1 and 2 and, in the case of the first charging device, reach the area of the scraper 4, which extends as far as into the circumferential path or movement path of the charging device 1 protrudes that the tips of the individual bristles are held back by him and are released when the charging device 1 is rotated by a snap movement over the scraper 4. As a result of this snap movement, the developer particles embedded between the bristles are flung upwards, the individual developer particles being charged positively, for example. This charge is composed of the charge which the charging device 1 gives to the developer particles as a result of the voltage applied to it, for example + 600 volts, and a triboelectric charge which occurs due to the rapid separation of the developer particles from the bristles during the stripping process by the stripper 4 .

In die Bewegungsbahn bzw. Umfangsbahn der zweiten Aufladeeinrichtung 2 ragt gleichfalls ein Abstreifer 7 hinein, der die einzelnen Borsten der Stahldrahtbürste solange zurückhält, bis die in ihnen durch die Verformung gespeicherte Energie für die Schnappbewegung über den Abstreifer 7 hinweg ausreicht. Bei dieser Schnappbewegung werden wieder die zwischen den einzelnen Borsten eingelagerten Entwicklerteilchen in Richtung Entwickelwalze 3 geschleudert und sind sowohl durch die an die zweite Aufladeeinrichtung 2 angelegte Spannung von beispielsweise auch + 600 Volt als auch durch die triboelektrische Aufladung beim schnellen Trennen der Entwicklerteilchen von den einzelnen Borsten aufgeladen.A scraper 7 also protrudes into the movement path or circumferential path of the second charging device 2, which holds back the individual bristles of the steel wire brush until the energy stored in them by the deformation is sufficient for the snap movement over the scraper 7. During this snap movement, the developer particles stored between the individual bristles are again thrown in the direction of the developer roller 3 and are both due to the voltage applied to the second charging device 2 of, for example, + 600 volts as well as due to the triboelectric charging during the rapid separation of the developer particles from the individual bristles charged.

Wie schon zuvor erwähnt wurde, sind die beiden Aufladeeinrichtungen 1 und 2 auf das gleiche Spannungspotential gelegt, jedoch ist es selbstverständlich, daß die beiden Aufladeeinrichtungen auf unterschiedlich hohe Spannungen gelegt werden können, wenn sie voneinander elektrisch isoliert in die Einrichtung montiert sind.As previously mentioned, the two charging devices 1 and 2 are connected to the same voltage potential, but it goes without saying that the two charging devices can be set to different voltages if they are mounted in the device in an electrically insulated manner.

Die Wanne 5 setzt sich vorzugsweise aus zwei halbzylindrischen Teilen zusammen, die an einem Träger 15 befestigt sind. Der Träger 15 besteht aus elektrisch leitendem oder isolierendem Material. Im ersteren Fall ist der Träger 15 mit dem gleichen Pol der Spannungsquelle 9 verbunden wie die zylindrischen Kerne 22 und 23 der beiden Aufladeeinrichtungen 1 und 2. Besteht der Träger 15 aus isolierendem Material, dann wird die Wanne 5 direkt mit dem entsprechenden Pol der Spannungsquelle 9 verbunden. Der Abstreifer 7 ist gleichfalls mit dem Pol der Spannungsquelle 9 verbunden, mit dem auch die zylindrischen Kerne 22, 23 in Verbindung stehen. Die beiden Ränder der Wanne 5 sind an Seitenträgern 16. 17 befestigt, die aus isolierendem Material bestehen. An diesen Seitenträgern 16 und 17 ist des weiteren ein Oberteil 8 der Entwicklungsvorrichtung befestigt, das diese nach obenhin abschließt. Die Seitenflächen dieses Oberteils verlaufen schräg nach oben zu der Entwickelwalze 3. Eine weitere Spannungsquelle 10 ist mit der Entwickelwalze 3 verbunden und die angelegte Spannung liegt beispielsweise im Bereich von - 200 bis - 300 Volt und besitzt somit eine entgegengesetzte Polarität zu derjenigen der Aufladeeinrichtungen 1 und 2. Auf der Umfangsfläche der Entwickelwalze 3 bildet sich eine gleichmäßig dicke Entwicklerschicht aus, die im Bereich von 30 bis 150 f.Lm wählbar ist. Die Entwicklung erfolgt beispielsweise über Kopf und der Aufzeichnungsträger 11, ein endlos umlaufendes Fotoleiterband mit einem latenten Ladungsbild 14, wird in einem Abstand, der geringfügig größer als die gewählte Schichtdicke ist, an der Entwickelwalze 3 vorbeigeführt. Der Aufzeichnungsträger 11 ist beispielsweise negativ auf eine Spannung zwischen -500 bis -1 000 Volt, insbesondere auf - 600 Volt, aufgeladen. Das latente Ladungsbild 14 ist in Fig. 1 schematisch durch kleine Kreise, die ein Minuszeichen einschließen, angedeutet. Der positiv geladene Entwickler 13 kann durch die negativ geladene Entwickelwalze gegenüber dem latenten Ladungsbild 14 nicht zurückgehalten werden, da der Absolutbetrag der negativen Spannung der Entwickelwalze 3 kleiner ist als der Absolutbetrag des negativ aufgeladen Fotoleiters. Das latente Ladungsbild 14 wird durch den Entwickler 13 zu einem Pulverbild 12 entwickelt.The tub 5 is preferably composed of two semi-cylindrical parts which are attached to a carrier 15. The carrier 15 consists of an electrically conductive or insulating material. In the former case, the carrier 15 is connected to the same pole of the voltage source 9 as the cylindrical cores 22 and 23 of the two charging devices 1 and 2. If the carrier 15 consists of insulating material, the trough 5 is directly connected to the corresponding pole of the voltage source 9 connected. The stripper 7 is also connected to the pole of the voltage source 9, with which the cylindrical cores 22, 23 are also connected. The two edges of the tub 5 are attached to side supports 16, 17, which are made of insulating material. On these side beams 16 and 17, an upper part 8 of the developing device is further fastened, which closes the top. The Side surfaces of this upper part run obliquely upward to the developing roller 3. A further voltage source 10 is connected to the developing roller 3 and the applied voltage is, for example, in the range from - 200 to - 300 volts and thus has an opposite polarity to that of the charging devices 1 and 2 A uniformly thick developer layer is formed on the peripheral surface of the developing roller 3 and can be selected in the range from 30 to 150 f.lm. Development takes place, for example, overhead and the recording medium 11, an endlessly revolving photoconductor belt with a latent charge image 14, is guided past the developing roller 3 at a distance which is slightly greater than the selected layer thickness. The record carrier 11 is, for example, negatively charged to a voltage between -500 to -1,000 volts, in particular to - 600 volts. The latent charge image 14 is indicated schematically in FIG. 1 by small circles that enclose a minus sign. The positively charged developer 13 cannot be held back by the negatively charged developing roller with respect to the latent charge image 14 since the absolute amount of the negative voltage of the developing roller 3 is smaller than the absolute amount of the negatively charged photoconductor. The latent charge image 14 is developed by the developer 13 into a powder image 12.

Die Drehzahlen der Aufladeeinrichtungen 1 und 2 liegen im Bereich von 100 bis 200 Umdrehungen pro Minute, während die Drehzahl der Entwickelwalze 50 bis 80 Umdrehungen pro Minute beträgt. Somit liegt das Verhältnis der Drehzahlen der Aufladeeinrichtungen und der Entwickelwalze im Bereich von 1,2:1 bis 4:1. Mit diesen Drehzahlen und den zuvor angeführten Spannungswerten an den Aufladeeinrichtungen 1, 2, den Abstreifern 4 und 7 und der Wanne 5 sowie dem Aufzeichnungsträger 11 und dem Abstand zwischen der Entwickelwalze 3 und dem Aufzeichnungsträger 11 wird die erwähnte Entwicklerschichtdicke von 30 bis 150 f.Lm erhalten. Da die Spannung der Entwickelwalze 3 die gleiche Polarität wie die Spannung des Aufzeichnungsträgers 11 besitzt, der Höhe nach jedoch niedriger als die Spannung der aufgeladenen Bildstellen, d. h. des latenten Ladungsbildes 14 auf dem Aufzeichnungsträger 11 ist und andererseits höher ist, als die Spannung der Nichtbildstellen, das sind die entladenen Stellen des Aufzeichnungsträgers 11, ist sichergestellt, daß der Untergrund der Kopien weitgehend frei von Entwickler ist. Die Untergrundfreiheit der Kopien läßt sich weitgehend durch die Größe der an die Entwickelwalze 3 angelegten Spannung steuern.The speeds of the charging devices 1 and 2 are in the range of 100 to 200 revolutions per minute, while the speed of the developing roller is 50 to 80 revolutions per minute. The ratio of the speeds of the charging devices and the developing roller is thus in the range from 1.2: 1 to 4: 1. With these speeds and the voltage values mentioned above on the charging devices 1, 2, the wipers 4 and 7 and the trough 5 and the recording medium 11 and the distance between the developing roller 3 and the recording medium 11, the developer layer thickness mentioned is 30 to 150 f.Lm. receive. Since the voltage of the developing roller 3 has the same polarity as the voltage of the recording medium 11, however, its height is lower than the voltage of the charged image areas, i.e. H. of the latent charge image 14 on the recording medium 11 and, on the other hand, is higher than the voltage of the non-image areas, that is, the unloaded areas of the recording medium 11, it is ensured that the background of the copies is largely devoid of developer. The background freedom of the copies can largely be controlled by the size of the voltage applied to the developing roller 3.

Es ist selbstverständlich, daß auch Spannungen mit umgekehrten Vorzeichen an die einzelnen Elemente der Entwicklungsvorrichtung angelegt werden können, falls der verwendete Einkomponenten-Entwickler negativ und der Aufzeichnungsträger 11 positiv aufgeladen werden sollen. Dadurch ist dann auch jederzeit eine Umkehrentwicklung möglich.It goes without saying that voltages with the opposite sign can also be applied to the individual elements of the developing device if the one-component developer used is to be charged negatively and the recording medium 11 is to be charged positively. A reversal development is then possible at any time.

An einem schwenkbaren Querprofil 6, angeordnet zwischen der Entwickelwalze 3 und der ersten Aufladeeinrichtung 1, ist ein elastischer Abstreifer 19 befestigt, der gegen die Umfangsfläche der Entwickelwalze 3 anliegt und den überschüssigen Entwickler 13, der nicht von dem latenten Ladungsbild 14 angezogen wird, von der Umfangsfläche der Entwickelwalze 3 abstreift. Der abgestreifte Entwickler rieselt auf die Borsten der ersten Aufladeeinrichtung 1 herab und wird von diesen wieder mitgenommen.On a pivotable cross section 6, arranged between the developing roller 3 and the first charging device 1, an elastic wiper 19 is attached, which bears against the peripheral surface of the developing roller 3 and the excess developer 13, which is not attracted to the latent charge image 14, by the Strips the peripheral surface of the developing roller 3. The stripped developer trickles down onto the bristles of the first charging device 1 and is taken away by them again.

Die im Umlauf befindliche Einkomponenten-Entwicklermenge ist klein und dementsprechend ist auch die Verweilzeit des Einkomponenten-Entwicklers in der Entwicklungsvorrichtung sehr kurz. Die Nachdosierung des verbrauchten Einkomponenten-Entwicklers erfolgt in Abhängigkeit von einer nicht näher beschriebenen optischen Messung der Schwärzung an der Entwickelwalze 3.The amount of one-component developer in circulation is small, and accordingly the dwell time of the one-component developer in the developing device is very short. The used one-component developer is subsequently metered in as a function of an optical measurement of the blackening on the developing roller 3, which optical measurement is not described in detail.

Untersuchungen haben gezeigt, daß von der ersten Aufladeeinrichtung 1 etwa drei Viertel der gesamten Einkomponenten-Entwicklermenge auf die Entwickelwalze 3 aufgebracht werden, während die restliche Entwicklermenge durch die zweite Aufladeeinrichtung 2 auf die Entwickelwalze 3 gelangt.Studies have shown that about three quarters of the total one-component developer quantity is applied to the developing roller 3 by the first charging device 1, while the remaining amount of developer reaches the developing roller 3 through the second charging device 2.

Durch die Wahl der mechanischen Größen, wie Durchmesser und Länge der Borsten der Aufladeeinrichtungen 1 und 2, des Werkstoffes der Aufladeeinrichtungen und der Abstreifer 4 und 7 sowie der Drehzahlen der Aufladeeinrichtungen und der Entwickelwalze 3 wird die Trenngeschwindigkeit des Einkomponenten-Entwicklers 13 von den Borsten und damit die Größenordnung der triboelektrischen Aufladung bestimmt.By choosing the mechanical sizes, such as the diameter and length of the bristles of the charging devices 1 and 2, the material of the charging devices and the wipers 4 and 7, and the speeds of the charging devices and the developing roller 3, the separation speed of the one-component developer 13 from the bristles and thus determining the magnitude of the triboelectric charge.

In Fig. 2 sind verschiedene Teile der Entwicklungsvorrichtung perspektivisch dargestellt, wobei sich gegenüber der Ausführungsform nach Fig. 1 nur der Unterschied ergibt, daß der Abstreifer 7 mit der Wanne 5 integriert ist, so daß ein eigener Anschluß des Abstreifers 7 an die Spannungsquelle 9 nicht erforderlich ist, da der Abstreifer die gleiche Spannung wie die Wanne 5, die an die Spannungsquelle 9. angeschlossen ist, aufweist.In Fig. 2 different parts of the development device are shown in perspective, with only the difference compared to the embodiment of FIG. 1 that the stripper 7 is integrated with the tub 5, so that a separate connection of the stripper 7 to the voltage source 9 is not is necessary because the wiper has the same voltage as the trough 5, which is connected to the voltage source 9.

In Fig. 3 ist schematisch eine Ausführungsform der Entwicklungseinrichtung dargestellt, die für einen Aufzeichnungsträger geeignet ist, der über die Umfangsfläche einer Trommel 24, einer sogenannten Fotoleitertrommel, aufgespannt ist. Die Entwickelwalze 3 liegt in der Dreiuhr-Stellung der Trommel 24 gegenüber, ebenso ist eine Neunuhr-Stellung möglich, während die beiden Aufladeeinrichtungen 1 und 2, die von Bürsten gebildet werden, schräg unterhalb der Entwickelwalze 3 angeordnet sind. Gleiche Teile sind in den Ausführungsformen nach Fig. 1 und 3 mit übereinstimmenden Bezugszeichen belegt. Bei den Ausführungsbeispielen nach den Fig. 1 bis 3 wird der Entwickler im wesentlichen in radialer Richtung auf die Oberfläche der Entwickelwalze 3 aufgesprüht.3 schematically shows an embodiment of the developing device which is suitable for a recording medium which is stretched over the circumferential surface of a drum 24, a so-called photoconductor drum. The developing roller 3 lies opposite the drum 24 in the three o'clock position, and a nine o'clock position is also possible, while the two charging devices 1 and 2, which are formed by brushes, are arranged obliquely below the developing roller 3. The same parts are given the same reference numerals in the embodiments according to FIGS. 1 and 3. 1 to 3, the developer is sprayed onto the surface of the developing roller 3 essentially in the radial direction.

In Fig. 4 ist eine Ausführungsform der Entwicklungsvorrichtung gezeigt, die mit einer einzigen Aufladeeinrichtung 26 in Gestalt einer Bürste arbeitet und bei welcher der Antrag des Entwicklers auf die Entwickelwalze 3 tangential erfolgt. Der Metallkern dieser Aufladeeinrichtung 26 ist mit dem einen Pol der Spannungsquelle 9 verbunden, ebenso wie ein mit den Borsten der Aufladeeinrichtung 26 zusammenarbeitender Abstreifer 27. Die Funktionsweise ist analog zu derjenigen, die anhand von Fig. 1 beschrieben wurde. Die auf den Borsten und zwischen den Borsten gelagerten Entwicklerteilchen werden bei dem Kontakt mit dem Abstreifer 27 auf die Umfangsfläche der Entwickelwalze 3 geschleudert, die mit dem einen Pol einer weiteren Spannungsquelle 10 verbunden ist und eine Spannung mit entgegengesetztem Vorzeichen zu der Spannung der Aufladeeinrichtung 26 aufweist. Auf der Umfangsfläche der Entwickelwalze 3 bildet sich eine gleichmäßig dicke Entwicklerschicht aus, aus der Entwickler auf den Aufzeichnungsträger auf der Trommel 24 entsprechend dem auf dem Aufzeichnungsträger befindlichen latenten Ladungsbild übertritt. Der verbleibende Entwickler auf der Entwickelwalze 3 wird durch den Abstreifer 19 entfernt und gelangt auf eine Auffangwalze 25, von deren Umfangsfläche der Entwickler durch die Borsten der Aufladeeinrichtung abgebürstet und erneut der Entwickelwalze zugeführt wird, wobei die Tonerladung durch die angelegte Spannung wiederum auf den vorigen Stand gebracht wird.In Fig. 4 an embodiment of the developing device is shown, which with a single Charging device 26 works in the form of a brush and in which the developer applies to the developing roller 3 tangentially. The metal core of this charging device 26 is connected to the one pole of the voltage source 9, as is a stripper 27 which cooperates with the bristles of the charging device 26. The mode of operation is analogous to that which was described with reference to FIG. 1. The developer particles stored on the bristles and between the bristles are thrown upon contact with the stripper 27 onto the peripheral surface of the developing roller 3, which is connected to the one pole of a further voltage source 10 and has a voltage opposite the voltage of the charging device 26 . A uniformly thick developer layer is formed on the peripheral surface of the developing roller 3, from which the developer passes onto the recording medium on the drum 24 in accordance with the latent charge image on the recording medium. The remaining developer on the developing roller 3 is removed by the scraper 19 and arrives at a collecting roller 25, from the peripheral surface of which the developer is brushed off by the bristles of the charging device and fed again to the developing roller, the toner charge in turn being restored to the previous state by the applied voltage brought.

Claims (14)

1. A process for developing an electrostatic latent image which has been generated on a recording medium, this process employing an electrically charged single-component developer which is conveyed, by a developing roller, onto the surface of the recording medium, characterized in that the single-component developer is charged by at least one rotating charging device, is transported towards the developing roller, and is separated from the charging device(s) by grazing contact with a scraper device adjoining each charging device and is thrown onto the developing roller.
2. The process as claimed in claim 1, characterized in that the rotating charging devices come into contact with stationary scraper devices which throw the separated single-component developer onto the peripheral surface of the developing roller.
3. The process as claimed in claim 2, characterized in that the charging devices rotate at the same speed, which is greater than the speed at which the developing roller rotates.
4. The process as claimed in claim 3, characterized in that the ratio of the speeds of the charging devices and of the developing roller lies within the range from 1.2 : 1 to 4 : 1.
5. An apparatus for developing an electrostatic latent image which has been generated on a recording medium, this apparatus employing an electrically charged single-component developer and possessing a developing roller, which is located at a short distance from the recording medium, and a developer-feed unit for the single-component developer, characterized in that the single-component developer (13) can be fed, by the developer-feed unit (20), to the surface of one of two rotating charging devices (1, 2), in that the surfaces of the two charging devices (1, 2) are separated, one from the other, by a distance which is smaller than each of the distances between the charging devices and the developing roller (3), and in that a scraper device (4, 7) is assigned to each charging device (1, 2), this scraper device standing in grazing contact with the surface of the respective charging device (1 or 2).
6. The apparatus as claimed in claim 5, characterized in that the charging devices (1, 2) are designed as brushes, which are made of an electrically conducting material, and in that the cylindrical core (22 ; 23) of each charging device (1 ; 2) is connected to the same pole of a voltage source (9), the other pole of which is grounded.
7. The apparatus as claimed in claim 6, characterized in that a grid (18) is located between the charging devices (1, 2), single-component developer (13) being conveyed from one charging device (1) to the other (2) through this grid.
8. The apparatus as claimed in claim 7, characterized in that the grid (18) is composed of an electrically conducting material, such as metal, is connected to a trough (5) which encloses the charging devices, and charges the single-component developer, by tribo-electricity, as the developer passes through it.
9. The apparatus as claimed in claim 6, characterized in that a voltage-potential of the same polarity is applied to the charging devices (1, 2), to the scraper devices (4, 7) and to the trough (5).
10. The apparatus as claimed in claim 6, characterized in that the developing roller (3) is connected to a voltage source (10) and is at a voltage-potential which has a polarity opposite to that of the charging devices (1, 2), and which, in terms of absolute value, is smaller than the potential of the charge-image.
11. The apparatus as claimed in claim 8, characterized in that the distance of the trough (5) from the periphery of the charging devices (1, 2) is selected in a manner that no deposits and accumulations of the single-component developer (13) occur in the limited space between the trough (5) nd the charging devices (1, 2).
12. An apparatus for developing an electrostatic latent image which has been generated on a recording medium, this apparatus employing an electrically charged single-component developer and possessing a developing roller, which is located at a short distance from the recording medium, and a developer-feed unit for the single-component developer, characterized in that a charging device (26), configured as a brush, is provided, to which single-component developer (13) can be fed from a developer-feed unit (20), in that a scraper (27) is assigned to the charging device (26), this scraper standing in gazing contact with the bristles of the charging device (26), separating the developer (13) from the bristles and throwing it onto the developing roller (3).
13. The apparatus as claimed in claim 12, characterized in that a collecting roller (25) is located beneath the developing roller (3), this collecting roller (25) being in contact with the charging device (26) and collecting the developer (13) which a scraper (19) has stripped from the developing roller (3), and in that the bristles of the charging device (26) brush the developer (13) from the collecting roller (25) and lead it back into the developer circulation.
14. The apparatus as claimed in claim 13, characterized in that the scraper (27), the charging device (26), and the trough (5), enclosing the charging device (26) and the collecting roller (25), are connected to the same pole of a first voltage source (9), and in that the developing roller (3) is connected to the pole of a second voltage source (10), this pole being of opposite polarity.
EP83101272A 1982-02-19 1983-02-10 Method and device for the development of a latent electrostatic image induced on a recording medium Expired EP0087074B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3205989 1982-02-19
DE19823205989 DE3205989A1 (en) 1982-02-19 1982-02-19 METHOD AND DEVICE FOR DEVELOPING AN ELECTROSTATIC LATENT PRODUCED ON A RECORDING CARRIER

Publications (3)

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EP0087074A2 EP0087074A2 (en) 1983-08-31
EP0087074A3 EP0087074A3 (en) 1984-03-21
EP0087074B1 true EP0087074B1 (en) 1986-05-28

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EP83101272A Expired EP0087074B1 (en) 1982-02-19 1983-02-10 Method and device for the development of a latent electrostatic image induced on a recording medium

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US (1) US4481903A (en)
EP (1) EP0087074B1 (en)
JP (1) JPS58152260A (en)
AU (1) AU560674B2 (en)
CA (1) CA1194733A (en)
DE (2) DE3205989A1 (en)

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DE102011119553A1 (en) 2011-11-26 2013-05-29 Georg Schneider Device for applying of materials, has material source and metering unit, where metering unit comprises chamber for receiving of material, metering element and applicator element
DE102011119530A1 (en) 2011-11-26 2013-05-29 Georg Schneider Device for applying fusible or sinterable coating material on surface of planar subject matter, has material source designed as container and connected with chamber by conveyor to receive material, where conveyor is driven by electromotor
DE102011119537A1 (en) 2011-11-26 2013-05-29 Georg Schneider Device for applying material e.g. bulk material on planar object, has metering device whose chamber, metering element and ordering element are arranged at common carrier and/or commonly transported and/or removed
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DE102013007482A1 (en) 2013-04-29 2014-10-30 Georg Schneider Device for applying material
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Also Published As

Publication number Publication date
DE3363644D1 (en) 1986-07-03
AU1138083A (en) 1983-08-25
CA1194733A (en) 1985-10-08
EP0087074A3 (en) 1984-03-21
EP0087074A2 (en) 1983-08-31
US4481903A (en) 1984-11-13
AU560674B2 (en) 1987-04-16
JPS58152260A (en) 1983-09-09
DE3205989A1 (en) 1983-09-01

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