JP2008286887A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device of a type in which toner particles are moved by a phase shift electric field, the device being designed so as to ensure uniform development by supplying a uniform quantity of toner particles to an electrostatic conveyance member. <P>SOLUTION: In the developing device, a brush roller 100 for recovering toner particles is disposed above a supply roller 13b, and toner is efficiently recovered by its gravity. In addition, a blocking plate 103 for obstructing the flow of toner particles is disposed in contact with an electrostatic conveyance face, thereby preventing reconveyance of toner escaping from a recovering means. The electrostatic conveyance member 13a is rotatable and recovers toner failed to be conveyed by an electric field on the electrostatic conveyance face. If the electrostatic conveyance member is disconnected in the supply, development, and recovery zones, the disconnected part is moved out of the supply, development, and recovery zones. This copes with conveyance failure caused by disconnection. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus using a means for conveying toner particles that are powder by a phase-shifting electric field.

Conventionally, as an image forming apparatus such as a copying machine, a facsimile, or a printer, an electrostatic latent image is formed on a latent image carrier, and toner particles that are powder are attached to the latent image to develop it as a toner image. An electrophotographic system is known.
As a developing device for developing a latent image, the toner particles are moved in the horizontal and vertical directions on the surface of the electrostatic conveying member by applying energy of a phase-shift electric field to the toner particles that are powder as in Patent Document 1. A developing device is known. In such a developing device, the toner particles are transferred to a developing region where the latent image carrier and the developing device face each other by a phase-shift electric field, and the toner particles adhere to the image portion of the latent image on the image carrier in the developing region.
In Patent Document 1, the toner particles supplied from the toner supply unit are conveyed to a developing region where the toner supply unit and the latent image carrier are opposed by a phase-shift electric field formed by a flat electrostatic conveyance member, It contributes to the development of the latent image on the latent image carrier. On the other hand, toner particles that have not contributed to development in the development area are conveyed to a position facing the toner collecting means, and the toner collected by the toner collecting means is returned to the toner supply means.

In addition to Patent Document 1, Patent Document 2 and the like are also known as developing devices for toner supply means by electrostatic conveyance. In this developing apparatus, an endless loop-shaped electrostatic conveyance member is used.
Since the developing device described in Patent Document 1 uses a flat electrostatic conveyance member, it is necessary to separately provide a collection conveyance member that collects and conveys the toner that has passed through the development region and reached the end of the flat plate. there were. On the other hand, Patent Document 2 does not contribute to development among toners supplied by a supply unit where toner is supplied in an electrostatic conveyance member having an annular surface such as an endless loop shape or a roller shape. The toner returns to the supply section once around the annular surface. By providing a recovery unit that recovers toner at a location before returning to the supply unit, the recovery unit and the supply unit can be provided close to each other, and the apparatus can be downsized.
JP 2004-198675 A JP 2002-99143 A

By the way, in a developing device that moves toner particles by a phase-shift electric field, unlike the developing sleeve in two-component development, the electrostatic conveying member itself does not move, so the toner particles are uniformly distributed throughout the developing area of the electrostatic conveying member. If it is not conveyed, it is difficult to perform development without unevenness.
Further, in a developing device that moves toner particles by a phase-shifting electric field, the toner particles move so as to jump off the surface of the electrostatic conveyance member. Contact. Therefore, in a state where the toner particles are moved by the phase-shifting electric field, the force that electrostatically adheres the toner particles and the electrostatic conveyance member is weak. For this reason, even if the developing electric field is set weak (for example, even if the developing potential is 100 V or less), there is an advantage that the developing ability can be easily secured. However, if the development electric field is set to be weak, the amount of toner particles transported is small, so that even if the toner amount varies slightly, development unevenness occurs. Therefore, in a low potential process with a development potential of 100 V or less, it is particularly difficult to uniformly convey toner particles. If variations occur in the amount of toner particles supplied on the electrostatic conveyance member, the phase-shift electric field is disturbed, which adversely affects the conveyance performance and development performance.
As described above, in a developing device that moves toner particles by a phase-shift electric field, it is important to uniformly supply the toner particle amount to the electrostatic conveyance member.

However, no matter how much the toner particles are uniformly supplied onto the electrostatic conveying member, when the electrostatic conveying member as in Patent Document 2 has an endless loop shape, the toner particles that have passed without contributing to the development are again in the toner. Since the toner returns to the supply unit, the supply is not uniform, and there is a possibility that toner conveyance may be uneven. In Japanese Patent Laid-Open No. 2004-260, a toner collecting unit is provided, but this is not sufficient for suppressing variations in toner amount.
For this reason, in order to mount a developing device of a type that moves toner particles by a phase-shifting electric field in an actual product, it is necessary to devise a way to completely collect the toner from the electrostatic transport member and supply the toner uniformly.
Accordingly, the present invention provides a developing device and an image forming apparatus that can uniformly supply toner by collecting toner particles from an electrostatic conveyance member of a developing device of a type that moves toner particles by a phase-shifting electric field. The purpose is to do.

In order to achieve the above object, an invention according to claim 1 is directed to an electrostatic transport member having an electrostatic transport surface on which toner particles can be moved by a phase-shift electric field, storage means for storing the toner particles, and the storage. A developing device comprising: a supply unit that supplies the toner particles from the unit to the electrostatic conveyance surface; and a collection unit that is disposed above the supply unit and collects the toner particles from the electrostatic conveyance surface. And
According to a second aspect of the present invention, in the developing device according to the first aspect of the present invention, the toner particles are prevented from flowing out in the vicinity of the collecting unit and downstream from the collecting unit in the moving direction of the toner particles. A board is provided.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the electrostatic conveyance member is a cylinder having the electrostatic conveyance surface on a surface thereof, and rotates. To do.
According to a fourth aspect of the present invention, in the developing device according to the second aspect, the blocking plate is in contact with or separated from the electrostatic transfer surface.
According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, a distance from the supply unit to the collection unit is set with respect to a distance of the entire circumference of the electrostatic conveyance surface. It is characterized by being 1/2 or less.
According to a sixth aspect of the present invention, there is provided an image forming apparatus including the developing device according to any one of the first to fifth aspects as a developing unit for developing the electrostatic latent image on the image carrier. And

According to the present invention, since the collecting means for collecting the toner particles from the electrostatic conveyance surface is disposed above the supply means, the toner particles can be returned to the storage portion by gravity.
Further, since toner particles are collected from the electrostatic conveyance surface after development, unevenness in conveyance due to the toner remaining on the electrostatic conveyance surface is eliminated, so that the toner supply can be made uniform.

Hereinafter, embodiments of the present invention will be described in detail. In each figure, the same portions are denoted by the same reference numerals to avoid redundant description.
First, the configuration and operation of an image forming apparatus to which the developing device of the present invention can be applied will be described as an embodiment.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present exemplary embodiment.
In FIG. 1, reference numeral 11 denotes an image carrier in which a negatively charged organic photoconductor is formed in a belt shape, and is provided so as to be rotated in the direction of an arrow by a rotation driving mechanism (not shown). Developing cartridges 13K, 13M, 13C, and 13Y and a charging device to be described later are opposed to the image carrier 11 for each color, and the toner images are sequentially superimposed on the image carrier 11 as the image carrier 11 moves. (Tandem method).
Reference numeral 5 denotes a paper feeding device that stores a transfer material such as a recording sheet and starts conveying the transfer material during image formation. Reference numeral 3 denotes a fixing device for fixing an unfixed toner image formed on the transfer material.
At the time of image formation, the transfer material sent from the paper feeding device 5 is conveyed to a contact portion between the image carrier 11 and the transfer roller 2b, and a full color image formed on the image carrier 11 at the contact portion is transferred to the transfer roller. The image is transferred onto the transfer material by the voltage applied to 2b. Thereafter, when the transfer material reaches the fixing device 3, the toner image on the transfer material is heated while being sandwiched between the heating roller 3 a and the pressure roller 3 b to be fixed on the transfer material, and a visible image is formed on the transfer material. Is formed.

Reference numerals 13K, 13M, 13C, and 13Y denote developing cartridges for developing black, magenta, cyan, and yellow toner images, respectively. Such a developing cartridge can be detached from the space opened by the image carrier 11 being retracted, and can be replaced by the user.
The writing devices 4K, 4M, 4C, and 4Y are devices for writing latent images corresponding to black, magenta, cyan, and yellow colors, respectively, on the charged image carrier 11 according to image information. Various devices such as an optical scanning device using a polygon and an LED array can be used.
12k, 12m, 12c, and 12y are charging devices for uniformly charging the surface of the image carrier 11, and in this embodiment, corona charging is adopted. If non-contact charging means such as corona charging is used, the image carrier 11 can be charged without disturbing the toner image formed by the upstream developing cartridge.
Reference numerals 11ak, 11am, 11ac, and 11ay denote primary transfer rollers disposed on the back surface of the image carrier 11 at positions facing the developing cartridges 13K, 13M, 13C, and 13Y.

Next, an operation for forming a toner image on the image carrier in the image forming apparatus of this embodiment will be described.
When the image forming apparatus according to the present embodiment functions as a copying machine, the image information read from the scanner is subjected to various image processing such as A / D conversion, MTF correction, gradation processing, etc., and converted into writing data. Is done. When functioning as a printer, image information in a format such as a page description language or a bitmap transferred from a computer or the like is subjected to image processing and converted into write data. Prior to image formation, the image carrier 11 starts to rotate in the direction of the arrow, that is, in the counterclockwise direction so that the moving speed of the surface becomes a predetermined speed. Then, the surface of the image carrier 11 is uniformly charged by the charging device 12. Even when a toner image has already been formed on the image carrier 11, the surface of the image carrier 11 including the toner image is uniformly charged.

Next, a light beam corresponding to the image information is emitted from the writing device. Since the light beam passes between the charging device 12 and the developing cartridge 13, the light beam is irradiated to the image carrier 11 that has already been uniformly charged, and the image carrier that is a negatively chargeable photoconductor. On the surface of the body 11, a region corresponding to the image portion is neutralized to form a latent image.
The developing cartridge 13 attaches toner particles to the image portion of the latent image formed on the image carrier 11 and visualizes the latent image as a toner image.
The above charging, light beam irradiation, and development processes are repeated on the image carrier 11 facing each developing cartridge as described above, and a full color image in which four color toner images are superimposed on the image carrier 11 is formed. Is done.
Note that the image forming apparatus according to the present embodiment does not include a cleaning member for collecting the transfer residual toner particles on the surface of the image carrier 11. The transfer residual toner particles remain on the surface of the image carrier 11, but are charged by the four charging devices 12 k, 12 m, 12 c, and 12 y, transferred to a transfer material, and removed from the image carrier 11. When the transfer residual toner particles are transferred to the transfer material, some image disturbance occurs, but if the transfer residual toner particles are slightly disturbed, they are not visually recognized.

The configuration and operation of the image forming apparatus to which the present invention can be applied have been described above. Next, the first embodiment of the present invention will be described with reference to FIG.
[First Embodiment]
The first embodiment of the developing device of the present invention will be described below.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the developing cartridge according to the first embodiment.
In this embodiment, the developing cartridges for the respective colors have the same structure, so only one will be described.
In FIG. 2, reference numeral 13 denotes a developing cartridge (developing device). The developing cartridge 13 is a roller-shaped electrostatic transport having a plurality of electrodes for generating an electric field for transporting, developing, and collecting toner particles as powder. A member 13a is provided. The electrostatic transport member 13a faces the image carrier 11 in a non-contact manner with a gap of 50 to 1000 μm, preferably 150 to 400 μm, at the time of image formation. Details of the configuration of the electrostatic transfer member 13a will be described later.

The developing cartridge 13 is provided with a supply roller 13b for supplying toner particles to the electrostatic conveyance member 13a, and a magnetic brush is formed at a portion where the supply roller 13b and the electrostatic conveyance member 13a face each other. . On the surface of the supply roller 13b, a nonmagnetic sleeve formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape is rotated clockwise by a rotation drive mechanism (not shown). ing.
A doctor blade 13c that regulates the height of the toner particle chain spike, that is, the amount of toner particles on the sleeve, is installed on the upstream side of the developing region in the toner particle conveyance direction. The doctor gap, which is the distance between the doctor blade 13c and the sleeve, is set to 0.4 mm. Further, two screws 13d for pumping the toner particles in the developing casing to the supply roller 13b while stirring are installed in a region opposite to the image carrier 11 of the supply roller 13b.
In addition, a brush roller 100, a flicker bar 101, a partition wall 102, and the like are provided inside the developing cartridge 13 as collection means for collecting toner particles from the electrostatic conveyance member 13a. Details of the collecting means will be described later.

In the supply roller 13b, a magnet roller body (magnet roller) that forms a magnetic field is provided in a fixed state so as to cause toner particles to rise on the peripheral surface of the sleeve. Along the normal magnetic field lines emitted from the magnet roller body, the toner particle carrier is spiked in a chain shape on the sleeve, and the charged toner is attached to the carrier that has the spike shape in the chain shape, A magnetic brush is constructed. The magnetic brush is transferred in the same direction as the sleeve by the rotation of the sleeve. The magnet roller body includes a plurality of magnetic poles (magnets). Specifically, as shown in FIG. 7, the supply main magnetic pole P1 that causes toner particles to rise in the supply region, the magnetic poles P4 and P5 for pumping the toner particles on the sleeve, and the pumped toner particles are supplied to the supply region. A magnetic pole P6 that conveys the toner particles, a magnetic pole P2 that collects the toner particles in the developed region, and an agent separating magnetic pole P3.
In this embodiment, the magnet roller body is composed of 6-pole magnets, but it may be composed of 8-poles or 12-poles. In FIG. 7, the curve drawn on the surface of the supply roller 13b shows an outline of the normal magnetic force pattern, and the symbols “N” and “S” indicate that the polarity of each magnetic pole on the surface of the supply roller is N poles, respectively. , S pole.

In the developing cartridge 13, toner particles and a magnetic carrier (not shown) are stored. In carrying out the present invention, it is not necessary to specifically limit the carrier particles and the toner particles, but the mode of the toner particles in the present embodiment will be described below.
The toner particles of the present embodiment may be those obtained by radical polymerization in a state where a styrene or acrylic polymerizable monomer is dispersed in water together with a polymerization initiator as a binder resin, or a polyester resin is dispersed in water. Non-magnetic toner particles having a weight average particle diameter of about 5 μm obtained by granulating using a polymer obtained by polyaddition reaction and adding a colorant, a charge control agent and the like thereto.
The magnetic carrier of the present embodiment, first magnetization amount of the magnetic field in kOe is 30 emu / cm ³ or more, is preferable carrier in the range of 200 emu / cm ³ or less. If the magnetization amount is 200 emu / cm ³ or less, preferably 140 emu / cm ³ or less, the magnetic interaction between adjacent magnetic brushes becomes small, and the ears of the formed magnetic brush become dense and short. .
As a result, uniform supply of toner particles to the electrostatic transport member 13a can be achieved. On the other hand, when the magnetization amount of the magnetic carrier is less than ³⁰ emu / cm ³ , the toner particle conveyance performance is poor. Magnetization of the for the magnetic carrier is 30 emu / cm ³ or more and preferably 80 emu / cm ³ or more.

In this example, as the magnetic carrier, a resin magnetic carrier in which a magnetic material generated by a polymerization method including at least a binder resin and a magnetic metal oxide and a nonmagnetic metal oxide is dispersed is used. Specifically, magnetite (Fe ₃ O ₄ ) is used as the magnetic metal oxide, and a vinyl monomer such as styrene or ethyl acrylate is polymerized as the binder resin for dispersing and binding the metal oxide. The resulting resin is used. A carrier in which a magnetic material is dispersed in a binder resin may be used as it is. However, it may be used as a carrier core, and an insulating resin may be used as a coating agent, and the carrier core surface may be used as a coated magnetic carrier.
The amount of magnetization is determined by placing a magnetic carrier packed in a cylindrical container in an external magnetic field of 1 kilo-Oersted with an oscillating magnetic field type magnetic property automatic recording device (manufactured by Riken Denshi Co., Ltd.). It can be calculated by multiplying the true specific gravity of the carrier by the magnetization strength obtained by the measurement.
Here, the electrostatic conveyance member 13a has a plurality of electrodes for generating an electric field for supplying, conveying, developing, and collecting toner particles that are powder.

FIG. 3 is an enlarged cross-sectional view of the surface of the electrostatic transport member 13a on the image carrier 11 side.
As shown in FIG. 3, the electrostatic transport member 13 a includes a plurality of electrodes 202-1, 202-2, 202-3... The surface protective layer 203 is formed of an inorganic or organic insulating material, which is an insulating transport surface forming member that is disposed at a required interval and forms a transport surface thereon, and is a protective film that covers the surface of the electrode 202. Are laminated.
As the support substrate 201, a substrate made of an insulating material such as a glass substrate, a resin substrate or a ceramic substrate, or a substrate made of a conductive material such as SUS, an insulating film such as SiO2 is formed, a polyimide film or the like A substrate made of a material that can be deformed flexibly can be used.
The electrode 202 is formed by forming a conductive material such as Al or Ni—Cr on the support substrate 201 in a thickness of 0.1 to 10 μm, preferably 0.5 to 2.0 μm, and using a photolithography technique or the like. It is formed by patterning into the required electrode shape. The width L of the plurality of electrodes 202 in the powder traveling direction is set to be 1 to 20 times the average particle diameter of the powder to be moved, and the distance R of the electrodes 202 in the powder traveling direction is also moved. The average particle size is 1 to 20 times.

As the surface protective layer 203, for example, SiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5 and the} like are formed to a thickness of 0.5 to 10 μm, preferably 0.5 to 3 μm. Formed.
A line extending from each electrode 202 represents a conductive line for applying a voltage to each electrode 202. Of the overlapping portions of each line, only the portion indicated by a black circle is electrically connected, and the other portions are electrically connected. Insulated state. Different driving voltages of n phases are applied to each electrode 202 from the power source on the main body side.
In the present embodiment, a case where a three-phase drive voltage is applied (n = 3) will be described. However, the present invention can be applied to any natural number n satisfying n> 2 as long as toner particles are conveyed. In this embodiment, each electrode 202 is connected to any one of the contacts S11, S12, S13, S21, S22, and S23 on the developing cartridge side, and each contact is in a state where the developing cartridge is mounted on the main body of the image forming apparatus. Is connected to a power source on the main body side that provides drive waveforms V11, V12, V13, V21, V22, and V23, respectively.

The electrostatic conveyance member 13a forms a toner image by attaching toner particles to a supply area where the toner particles are supplied from the supply roller 13b, a conveyance area where the toner particles are transferred to the vicinity of the image carrier 11, and a latent image on the image carrier 11. And a recovery area for recovering toner particles that did not contribute to development after passing through the development area. The supply area is an area close to the supply main magnetic pole P1 of the supply roller 13b, the conveyance area exists from the supply area to the development area, and the development area exists only in the area close to the image carrier 11. On the other hand, the recovery area is an area in the vicinity of the recovery magnetic pole P2 of the supply roller 13b. Hereinafter, an area where the toner particles can move by the phase electric field is referred to as an “electrostatic transfer surface”.
Drive waveforms V11, V12, and V13 are applied to the electrodes 202 in the supply, conveyance, and development regions, and drive waveforms V21, V22, and V23 are applied to the electrodes 202 in the recovery region. In this embodiment, when the supply roller bias is −400 V, the charging voltage is −140 V, and the post-exposure voltage is −40 V, a drive pulse signal having an average value of −100 V and ± 100 V is applied to the drive waveforms V11, V12, and V13. The toner is collected by applying a drive pulse signal with an average value of −500V and ± 100V to the drive waveforms V21, V22, and V23.
Here, the rotation direction of the supply roller 13b is the same as the toner conveyance direction of the electrostatic conveyance member 13a so that toner particles that have not contributed to development after passing through the development region are mixed with toner in the supply region and density unevenness does not occur. The reverse direction is desirable.

Next, the principle of electrostatic conveyance of toner in the electrostatic conveyance member 13a will be described. By applying an n-phase driving waveform to the plurality of electrodes 202 of the electrostatic transfer member 13a, a phase-shift electric field (traveling wave electric field) is generated by the plurality of electrodes 202 and charged on the electrostatic transfer member 13a. The toner particles move in the transport direction in response to a repulsive force and / or suction force.
For example, for a plurality of electrodes 202 of the electrostatic transfer member 13a, a three-phase pulse drive waveform that changes between the ground G (0V) and a positive voltage + as shown in FIG. Apply by shifting.
At this time, as shown in (1) of FIG. 4B, the negatively charged toner T is present on the electrostatic conveyance member 13a, and “G”, “ When G, “+”, “G”, and “G” are applied, the negatively charged toner T is positioned on the “+” electrode 202. At the next timing, as shown in (2), “+”, “G”, “G”, “+”, “G” are respectively applied to the plurality of electrodes 202, and the left side is applied to the negatively charged toner T. Since a repulsive force acts on the “G” electrode 202 and an attractive force acts on the right “+” electrode 202, the negatively charged toner T moves to the “+” electrode 202 side.

Further, at the next timing, as shown in (3), “G”, “+”, “G”, “G”, “+” are applied to the electrode 202, respectively, and the same applies to the negatively charged toner T. Since the repulsive force and the attractive force act on the negatively charged toner T, the negatively charged toner T further moves to the “+” electrode 202 side.
In this way, by applying a multi-phase driving waveform whose voltage changes to the plurality of electrodes 202, a traveling wave electric field is generated on the electrostatic conveyance member 13a, and the negatively charged toner is moved in the traveling direction of the traveling wave electric field. Moving. In the case of positively charged toner, the drive waveform changes in the same direction by reversing the drive waveform change pattern.
Here, in the present embodiment, in the transport region of the electrostatic transport member 13a, as shown in FIG. 5, with respect to each electrode 202, the + 100V application time ta of each phase is about 33 which is 1/3 of the repetition period tf. A three-phase drive waveform (drive pulse) V11, V12, V13 set to% (this is referred to as a “carrier voltage pattern”) is applied. It is known from the applicant's research that this drive waveform is a waveform suitable for high-speed conveyance of toner particles in the conveyance region.

In the development region, the application time ta of +100 V or 0 V for each phase is set to about 67%, which is 2/3 of the repetition period tf, as shown in FIG. Three-phase drive waveforms (drive pulses) V21, V22, and V23 are applied. It has been found from the applicant's research that toner particles are preferably positively launched toward the image carrier in the development region, and the drive waveform in FIG. 6 is suitable for launching toner particles.
Even when a drive waveform of the development voltage pattern is applied, since the toner is also subjected to a lateral force other than the toner positioned at the center of the 0V electrode, not all the toners are launched at the same time, but move in the horizontal direction. Conversely, even when a drive waveform of a carrier voltage pattern is applied, depending on the position of the toner, there is a toner whose ascending distance is larger than that of being obliquely launched at a large angle and moving horizontally. Therefore, the drive waveform pattern applied to each electrode 202 in the transport region is not limited to the transport voltage pattern shown in FIG. 5 described above, and the drive waveform pattern applied to each electrode 202 in the development region is also a diagram described above. The development voltage pattern shown in FIG.

Up to this point, the drive waveform has been described for the case of three layers. When this is generalized to the n-phase, the drive waveform is as follows.
When a traveling wave electric field is generated by applying an n-phase (n is an integer of 3 or more) pulsed voltage (driving waveform) to each electrode, the voltage application time per phase {repetition cycle time × ( By setting the voltage application duty to be less than (n-1) / n}, the efficiency of conveyance and development can be increased. For example, when a three-phase drive waveform is used, the voltage application time ta of each phase is set to less than about 67%, which is 2/3 of the repetition cycle time tf, and when a four-phase drive waveform is used. The voltage application time for each phase is preferably set to less than 75%, which is 3/4 of the repetition cycle time.
On the other hand, the voltage application duty is preferably set to {repetition cycle time / n} or more. For example, when a three-phase driving waveform is used, it is preferable to set the voltage application time ta of each phase to about 33% or more, which is 1/3 of the repetition cycle time tf.
That is, between the voltage applied to the target electrode and the voltages applied to the upstream adjacent electrode and the downstream adjacent electrode in the traveling direction, a time is set in which the upstream adjacent electrode repels and the downstream adjacent electrode sucks. The efficiency can be improved. In particular, when the drive frequency is high, the initial value for the toner on the electrode of interest is set by setting it within the range of {repeat cycle time / n} and less than {repeat cycle time × (n-1) / n}. Speed is easily obtained.
The above description of the electrostatic conveyance member has described what is considered to be the best mode. However, if the desired conveyance / development performance can be obtained, the distance between the electrodes 202 in the development area and the conveyance area is described. The direction of the electric field may be adjusted by changing the distance between the electrodes, or the distance between the electrodes and the drive waveform may be the same in the development area and the conveyance area.

Next, the collecting means provided in the developing cartridge will be described with reference to FIG.
In this embodiment, in order to collect the toner particles from the electrostatic conveyance surface, the brush roller 100 in which fine fibers are planted is provided in the range from the development area to the toner supply area of the electrostatic conveyance member 13a. Toner particles that have not contributed to development pass through the development region of the electrostatic transport member 13a and are electrostatically attracted to the brush roller 100 to which a bias voltage is applied, and are separated from the electrostatic transport member 13a. The brush roller 100 is rotated at a high speed to be frictionally charged. Alternatively, a bias voltage is applied to the polarity opposite to that of the toner particles to attach the toner to the brush tips and mechanically remove the toner. The electric resistance value (volume resistivity) of the brush is in the range of 10 ² to 10 ¹⁰ Ω · cm, and preferably a low resistance of 10 ² to 10 ⁴ Ω · cm. The density of the brush is in the range of 30,000 / inch to 150,000 / inch, preferably 100,000 / inch to 130,000 / inch. In this embodiment, the material of the brush is carbon-containing acrylic fiber: 300D / 48F (SA7 manufactured by Toray). Other brush materials include conductive polyester fibers (B-TCF: manufactured by Teijin), conductive PET, conductive nylon fibers, and the like. The bias voltage applied to the brush roller 100 is applied with a reverse polarity to the bias voltage applied to the electrostatic transfer member 13a. In this embodiment, the brush roller 100 applies a bias voltage in the range of 0V to + 700V, preferably in the range of +300 to + 500V. The toner particles adhering to the brush tips of the brush roller 100 collide with the flicker bar 101 brought into contact with the brush tip by rotating the brush roller 100 to be separated. Instead of the flicker bar 101, a bias roller may be brought into contact with the tip of the brush to collect electrostatically.

In the present embodiment, an electrostatic transfer member 13a having an annular surface such as an endless loop shape or a roller shape is provided. In the annular electrostatic conveyance member 13a, the toner that has not contributed to the development among the toners supplied by the supply roller 13b to which the toner is supplied returns to the supply roller 13b after making one round of the annular surface. A brush roller 100 that collects toner is provided at a position before returning to the supply unit. In this embodiment, the position of the brush roller 100 is set above the supply roller 13b.
By installing the toner cartridge upward, the toner scraped off by the flicker bar 101 falls on the inclined partition wall 102 due to gravity and is efficiently collected in the toner storage portion 13f in the developing cartridge.
The toner collected in the toner container 13f is pumped up to the supply roller 13b while being stirred by the screw 13d. Although the rotation direction of the brush roller 100 is not particularly restricted, in the present embodiment, it is the same direction as the toner conveyance direction of the electrostatic conveyance member 13a.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
FIG. 9 is a cross-sectional view illustrating a schematic configuration of the developing cartridge according to the second embodiment.
In the developing cartridge according to the second embodiment shown in FIG. 9, downstream of the brush roller 100 provided on the electrostatic conveyance surface of the electrostatic conveyance member 13a having an annular surface such as an endless loop shape or a roller shape. A blocking plate 103 is provided in the vicinity so as to be in contact with the electrostatic transfer surface. The blocking plate 103 prevents the toner that has been collected by the brush roller 100 from passing through, or the toner once collected by the brush but once again caught by the phase-shifting electric field and transported to the supply roller 13b. I am doing so.
The blocking plate 103 is preferably an elastic body so as not to damage the electrostatic transfer surface. The material may be an elastic material such as polyurethane rubber or ethylene-propylene-diene polyethylene (EPDM). Since the blocking plate 103 is supported by the partition wall 102 and separates the brush roller 100 and the supply roller 13b, the scattered toner due to the rotation of the brush roller 100 adheres to the electrostatic conveyance surface in the vicinity of the supply roller 13b. Is preventing.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
FIG. 10 is a cross-sectional view illustrating a schematic configuration of a developing cartridge according to the third embodiment.
In the developing cartridge according to the third embodiment shown in FIG. 10, the electrostatic transfer member 13a having an annular surface such as an endless loop shape or a roller shape is statically moved by a driving device (not shown) around the shaft 105. Can be rotated in the direction of electric conveyance The rotation may be one or more rotations. However, since it is necessary to devise a rotation around the wiring that transmits power to the transport electrode, the wiring can be simplified by reversing and reciprocating after one rotation.
When toner that could not be conveyed due to the phase-shifting electric field adheres to the electrostatic conveyance surface, the adhesion toner is collected by the brush roller 100 by rotating the electrostatic conveyance member 13a. Further, when the transport electrode of the electrostatic transport member 13a is disconnected between the supply roller 13b, the developing unit, and the brush roller 100, the disconnected part is moved outside the range of the supply unit 13b, the developing unit, and the brush roller 100. It is possible to improve the conveyance failure due to the disconnection of the conveyance electrode.
Further, the blocking plate 103 of FIG. 10 is configured to be able to contact and separate from the electrostatic transfer surface. An actuator such as a motor or solenoid is used as a contact / separation mechanism, and it is operated by gears, links, springs, and the like. In the configuration of this embodiment, although not shown, the blocking plate 103 has a guide so that it can slide along the partition wall 102 and can be operated by a solenoid and a spring (not shown). Normally, the blocking plate 103 is in contact with the electrostatic transfer surface of the electrostatic transfer member 13a. However, when the electrostatic transfer member 13a is rotated, the blocking plate 103 is moved away from the electrostatic transfer member 13a by moving. It is possible to prevent the electrostatic transfer surface from being damaged by the blocking plate 103.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described.
FIG. 11 is a cross-sectional view showing a schematic configuration of a developing cartridge according to the fourth embodiment.
As shown in FIG. 11, the brush roller 100 is provided at the uppermost part of the electrostatic transfer member 13a having an annular surface such as an endless loop or a roller, and the supply roller is provided at the lowermost part of the electrostatic transfer member 13a. 13b is installed. As described above, the brush roller 100 and the supply roller 13b are installed at symmetrical positions via the electrostatic conveyance member 13a, so that about 1/2 of the distance of the entire circumference of the electrostatic conveyance surface electrostatically conveys the toner. This is the distance between the supply, development, and recovery range. The electrostatic transfer member 13a is a mechanism that rotates around the shaft 105 by a driving device (not shown) and then reverses and reciprocates. Although a motor, a gear, a belt mechanism, etc. can be considered as the drive device, in this embodiment, the mechanism can be simplified by a solenoid, a link, a spring, etc., since it only needs to reciprocate only half a turn. Further, when the electrostatic transfer member 13a rotates, it is necessary to devise to move around the wiring that transmits power to the transfer electrode. However, the wiring can be simplified because there is no fear of the wiring being twisted in a half rotation reversal.
Among the toners that are transported on the electrostatic transport surface of the electrostatic transport member 13a by a phase-shift electric field, there are toners that cannot be transported due to a decrease in the amount of charge during transport and adhere. The toner that has once adhered and stopped moving is difficult to convey even when a phase-shift electric field is applied again. In the present embodiment, the adhering toner is collected by reciprocating the electrostatic conveyance surface of the electrostatic conveyance member 13a to the brush roller 100 by a half rotation.

In addition, when the transport electrode of the electrostatic transport member 13a is disconnected between the supply roller 13b, the developing unit, and the brush roller 100 due to discharge or the like, a phase-shift electric field cannot be formed at the disconnected portion, resulting in toner transport failure. By moving the electrostatic conveyance surface of the electrostatic conveyance member 13a to the brush roller 100 by a half rotation, the disconnected portion can be moved outside the range of the supply roller 13b, the developing unit, and the brush roller 100, so that no complicated positioning mechanism is required. Further, it is possible to improve the conveyance failure due to the disconnection of the conveyance electrode.
As described above, the image forming apparatus to which the present invention can be applied is not particularly limited as long as the electrostatic conveyance member can be attached and detached. The image forming apparatus using the intermediate transfer belt, the transfer drum, the intermediate transfer drum, and the like has been described above. -Needless to say, the present invention can also be applied to an image forming apparatus, a monochrome image forming apparatus, and the like. In addition, the object conveyed by the electrostatic conveyance member is not limited to the toner and can be applied to all powders.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an exemplary embodiment. 1 is a cross-sectional view showing a schematic configuration of a developing cartridge according to a first embodiment of the present invention. It is sectional drawing to which the image carrier 11 side surface of the electrostatic conveyance member 13a was expanded. It is a figure for demonstrating the principle of the electrostatic conveyance of the toner in the electrostatic conveyance member 13a. It is a figure which shows a carrier voltage pattern. It is a figure which shows a developing voltage pattern. It is the figure which showed the magnet roller body provided with the some magnetic pole (magnet). It is explanatory drawing of the collection means with which the developing cartridge is equipped. FIG. 5 is a cross-sectional view illustrating a schematic configuration of a developing cartridge according to a second embodiment of the present invention. It is sectional drawing which showed schematic structure of the developing cartridge which concerns on the 3rd Embodiment of this invention. It is sectional drawing which showed schematic structure of the developing cartridge which concerns on the 4th Embodiment of this invention.

Explanation of symbols

  2b ... transfer roller, 3 ... fixing device, 3a ... heating roller, 3b ... pressure roller, 4K, 4M, 4C, 4Y ... writing device, 5 ... paper feeding device, 11 ... image carrier, 12 ... charging device, 13K, 13M, 13C, 13Y ... developing cartridge, 13a ... electrostatic conveyance member, 13b ... supply roller, 13b ... supply unit, 13c ... doctor blade, 13d ... screw, 13f ... toner storage unit, 100 ... brush roller, 101 ... Flicker bar, 102 ... partition wall, 103 ... blocking plate, 105 ... shaft, 201 ... support substrate, 202-1, 202-2, 202-3 ... electrode, 203 ... surface protective layer

Claims (6)

An electrostatic conveyance member having an electrostatic conveyance surface to which toner particles can move by a phase-shifting electric field;
Storage means for storing the toner particles;
Supply means for supplying the toner particles from the storage means to the electrostatic transfer surface;
And a collecting unit disposed above the supply unit and collecting the toner particles from the electrostatic conveyance surface.   2. The developing device according to claim 1, further comprising a blocking plate that prevents the toner particles from flowing out in the vicinity of the collecting unit and on the downstream side in the moving direction of the toner particles from the collecting unit.   3. The developing device according to claim 1, wherein the electrostatic transport member has a cylindrical shape having the electrostatic transport surface on a surface thereof and rotates. 4.   The developing device according to claim 2, wherein the blocking plate contacts and separates from the electrostatic conveyance surface.   5. The developing device according to claim 1, wherein a distance from the supply unit to the collecting unit is ½ or less with respect to a distance of the entire circumference of the electrostatic conveyance surface.   An image forming apparatus comprising the developing device according to claim 1 as developing means for developing an electrostatic latent image on an image carrier.

Images