JP2007033682A - Development device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device which includes an electrostatic conveyance member moving toner on a surface thereof by a phase-shifting electric field and is capable of satisfactorily collecting the toner on the electrostatic transport member, after passing a development area and is capable of stable development, and to provide an image forming apparatus including the same. <P>SOLUTION: A transport electrode end part 130e, that is the downstream side end and a transport electrode start part 130s that is the upstream side end, in a toner transport direction of an electrostatic transport surface 103a of an electrostatic transport roller 13 are spaced, and the space between them serves as a non-electric field region 136, and a conductive plate 200 as a toner collection means is provided so as to collect toner particles around the transport electrode end part 130e. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device including an electrostatic conveyance member that conveys toner on the surface of an electrostatic conveyance surface by electrostatic force, and an image forming apparatus using the same.

Conventionally, as an image forming apparatus such as a copying machine, a facsimile machine, and a printer, an electrostatic latent image is formed on a latent image carrier, and a developer (hereinafter referred to as toner particles) that is powder is attached to the latent image. Thus, an electrophotographic system for developing as a toner image 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 area which is a facing portion between the latent image carrier and the developing device by a phase shift electric field, and adhere to the image portion of the latent image on the image carrier in the developing area.
In Patent Document 1, a toner image supplied from a toner supply unit is conveyed to a developing region that is opposed to a latent image carrier by a phase-shift electric field formed by a flat electrostatic conveyance member, and the latent image is carried. The toner particles that contribute to the development of the latent image on the body and do not contribute to the development in the development area are collected and returned to the toner supply means.

  As a developing device that uses a phase-shift electric field to transport toner particles to the developing region, collects toner that has not contributed to development, and returns the collected toner particles to the toner supply unit, a developing device described in Patent Document 1 is available. Moreover, the thing of patent document 2 is also known. In this developing apparatus, an endless loop-shaped electrostatic conveyance member is used.

JP 2004-198675 A JP 2002-99143 A

  In a developing device that moves toner particles by a phase-shifting electric field, it is difficult to perform development without unevenness unless the toner particles are uniformly supplied and transported over the entire development area of the electrostatic transport surface. Therefore, in such a developing device, uniform supply of toner particles to the electrostatic conveyance surface and uniform conveyance on the electrostatic conveyance surface are important.

However, even if the supply of toner particles on the electrostatic conveyance surface is made uniform, if the electrostatic conveyance surface is conveyed on an annular surface such as an endless loop or roller, the toner particles that have passed without contributing to development When returning to the toner supply unit again, there may be a case where the transport amount is not uniform and unevenness in toner transport occurs. In Patent Document 2, a recovery member that recovers toner is provided. However, since a phase-shift electric field that moves toner toward the surface of the electrostatic conveyance surface is also generated in the recovery unit, it is recovered when passing through the recovery unit. The missing toner reaches the supply section by the phase-shift electric field. Therefore, it is not sufficient to suppress the variation in the toner conveyance amount, and the density of the toner image formed on the latent image carrier may be uneven and the development may become unstable.
Further, in Patent Document 1, in the case of a flat electrostatic transport member, a phase-shift electric field for transporting toner further is not formed at the downstream end in the toner transport direction on the electrostatic transport surface. A collecting member for collecting the toner on the conveying surface is required. However, Patent Document 1 does not specify a collecting member that collects toner on the electrostatic conveyance surface. If the toner on the electrostatic transport surface is not reliably collected by the flat electrostatic transport member, the toner stays from the downstream end of the electrostatic transport surface in the toner transport direction, causing poor transport on the electrostatic transport surface. May occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to have an electrostatic conveyance member on which toner particles move on the surface by a phase-shifting electric field, and an electrostatic conveyance surface after passing through the development region. It is an object of the present invention to provide a developing device that can collect the toner on the top well and perform stable development, and an image forming apparatus including the developing device.

In order to achieve the above object, an invention according to claim 1 is directed to an electrostatic conveyance means having an electrostatic conveyance surface capable of conveying toner particles by a phase-shift electric field, and an upstream end of the electrostatic conveyance surface in the toner conveyance direction. A toner supply unit facing the image forming unit, and transporting the toner particles supplied by the toner supply unit to a developing region which is a position facing the latent image carrier while transporting the toner particles on the electrostatic transport surface. And a toner collecting means for collecting the toner particles that contribute to the development of the latent image on the latent image carrier, do not contribute to the development in the development area, and are conveyed to the downstream side in the toner conveyance direction of the development area. In the developing device, the toner collecting unit is provided so that the collecting unit is opposed to a downstream end portion of the electrostatic conveyance surface, which is a terminal portion of the phase-shifting electric field, in the toner conveyance direction.
According to a second aspect of the present invention, in the developing device of the first aspect, the toner particles collected by the toner collecting unit are returned to the toner supplying unit, and both ends of the electrostatic conveying surface in the toner conveying direction are separated from each other. It is made to form in an annular shape.
The invention according to claim 3 is the developing device according to claim 2, further comprising a second electrostatic transport surface capable of transporting the toner particles by the phase-shift electric field while being spaced apart at both ends in the toner transport direction. The phase-shift electric field is formed on the second electrostatic transport surface at a predetermined timing other than the time of image formation.
According to a fourth aspect of the present invention, in the developing device according to the second or third aspect, the member formed between the both ends of the toner conveying direction is made of an insulator.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, the toner collecting means includes a collecting member made of a conductive member, and the collecting member and the electrostatic conveying surface A recovery electric field is formed between them.
According to a sixth aspect of the present invention, in the developing device according to the fifth aspect, the recovery member is not in contact with the electrostatic transfer surface.
According to a seventh aspect of the present invention, in the developing device of the fifth or sixth aspect, the recovery member is a conductive plate that applies a bias having a polarity opposite to that of the toner particles.
According to an eighth aspect of the present invention, in the developing device according to the fifth or sixth aspect, the collecting member is a conductive roller that applies a bias having a polarity opposite to that of the toner particles.
The invention of claim 9 is the developing device of claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the toner recovery means includes a recovery member that contacts the toner particles during recovery, It has a collected toner separating means for separating the toner particles adhering to the collecting member.
According to a tenth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, the toner recovery means includes an airflow generating member, and the toner particles on the electrostatic transport surface are subjected to an airflow force. It is characterized by collect | recovering by.
According to an eleventh aspect of the present invention, in the developing device according to the tenth aspect, a surface that does not form a phase-shifting electric field is provided between both ends of the toner conveying direction, and the surface that does not form the phase-shifting electric field is the electrostatic device. A step is provided so as to be inside the annular surface with respect to the transport surface.
According to a twelfth aspect of the present invention, in the developing device of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or eleventh aspect, the electrostatic transfer surface is made of a nonmagnetic material. It is characterized by that.
According to a thirteenth aspect of the present invention, in the developing device according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, or twelfth aspects, the toner collecting unit collects the toner. A toner collection area is used, and the toner conveyance speed is reduced in the toner collection area.
According to a fourteenth aspect of the present invention, in the image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier into a toner image. The developing devices according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13 are used.

  In the developing device according to any one of claims 1 to 14, since the downstream end portion in the toner transport direction in which the toner collecting means is provided on the electrostatic transport surface is a terminal portion of the phase-shift electric field, the downstream end in the toner transport direction For the toner particles that have reached the portion, no further force toward the downstream side (advance) occurs. Since the toner particles cannot travel further downstream in the toner conveyance direction than the downstream end portion of the electrostatic conveyance surface, the toner particles that have passed through the development area are not around the downstream end portion in the toner conveyance direction unless collected from the electrostatic conveyance surface. It exists. By providing the toner collecting means so as to collect the toner particles around the downstream end in the toner transport direction, the toner that has passed through the developing region can be reliably collected.

  According to the first to fourteenth aspects of the present invention, the toner that has passed through the developing region is reliably recovered, so that the toner transport amount variation caused by the toner that has passed through the developing region reaching the supply unit without being recovered. There is an excellent effect that development of uneven development can be suppressed and stable development can be performed.

[Embodiment 1]
Hereinafter, a first embodiment in which the present invention is applied to a laser printer (hereinafter simply referred to as a printer 100) which is an electrophotographic image forming apparatus will be described.
FIG. 1 is a schematic configuration diagram of a printer 100 according to the first embodiment.
In the printer 100, the image forming units 1K, 1M, which are image forming units including photoconductors 11K, 11M, 11C, and 11Y as image carriers, a charging unit, a developing device as a developing unit, and a cleaning unit for the image carrier. 1C, 1Y. The image forming units 1K, 1M, 1C, and 1Y are arranged vertically side by side on the side of the stretched surface of the transfer material conveying belt 2 that is a recording material conveying member. The subscripts K, M, C, and Y attached to these image forming unit numbers correspond to the colors of the toners to be handled. K means black, M means magenta, C means cyan, and Y means yellow. ing. The same subscript is attached to each member in the printer 100. Hereinafter, when the toner colors to be handled are not particularly distinguished, they are simply referred to as “image forming unit 1”. The same applies to other members.
Optical writing devices 4K, 4M, 4C, and 4Y are provided on the left side of the image forming units 1K, 1M, 1C, and 1Y. Opposing transfer rollers 9K, 9M, 9C, and 9Y are provided. Further, a sheet feeding device 5 that accommodates a transfer material P that is a recording medium is provided below the transfer material conveyance belt 2, and a fixing device 3 is provided above the transfer material conveyance belt 2.

  Here, the optical writing devices 4K, 4M, 4C, and 4Y are for writing latent images on the surfaces of the photoreceptors 11K, 11M, 11C, and 11Y after charging the image forming units 1K, 1M, 1C, and 1Y according to image information. Various devices such as an optical scanning device using a polygon and an LED array can be used.

  The transfer material conveyance belt 2 is stretched between the conveyance roller 21, the driven roller 22 and the tension rollers 23 and 24, and moves endlessly in the direction of arrow A by the rotation of the conveyance roller 21. Further, an adsorption roller 25 for adsorbing the transfer material P onto the transfer material conveyance belt 2 is disposed opposite to the conveyance roller 21, and the transfer material conveyance is performed on the fixing device 3 side above the transfer material conveyance belt 2. A P sensor 26 for detecting a pattern when a toner image is formed on the belt 2 is disposed.

The transfer rollers 9K, 9M, 9C, and 9Y that face the photoconductors 11K, 11M, 11C, and 11Y via the transfer material transport belt 2 have at least a core metal and a conductive elastic layer that covers the core metal. . The conductive elastic layer is made of an elastic material such as polyurethane rubber, ethylene-propylene-diene polyethylene (EPDM), etc., and mixed with a conductivity-imparting agent such as carbon black, zinc oxide, tin oxide, and the like. Is an elastic body adjusted to a medium resistance of 10 ⁶ to 10 ¹⁰ [Ω · cm].

  The fixing device 3 includes a heating roller 3a and a pressure roller 3b facing the heating roller 3a.

  In a normal image forming operation of the printer 100, the transfer material P such as recording paper supplied from the paper feeding device 5 is applied to the transfer material conveying belt 2 as a transfer member by applying a predetermined voltage to the suction roller 25. Adsorbed. The transfer material P is moved along with the transfer material conveyance belt 2 while being carried on the transfer material conveyance belt 2, and toner images of respective colors are sequentially transferred from the image forming units 1K, 1M, 1C, and 1Y as image forming means during the movement. As a result, a color toner image is formed on the transfer material P. When the transfer material P passes through the transfer material conveyance belt 2 and reaches the fixing device 3, the toner image on the transfer material P is heated while being sandwiched between the heating roller 3a and the pressure roller 3b, and thus on the transfer material P. The image is fixed, and a visible image is formed on the transfer material P. Thereafter, the transfer material P on which the color image is formed is discharged to the paper discharge unit 7 at the top of the printer 100 main body.

  In a mode in which the color misregistration and toner density of each color toner image are adjusted, a toner image having a predetermined pattern is directly formed on the transfer material conveying belt 2 from the image forming units 1K, 1M, 1C, and 1Y. Thus, the toner pattern is detected, and the writing timing and the development bias are changed based on the detection result, so that an optimum color image can be obtained. The toner pattern on the transfer material conveyance belt 2 is adjusted in charge polarity by a bias applied to the suction roller 25, and then image forming units 1K, 1M, 1C by voltages applied to the transfer rollers 9K, 9M, 9C, 9Y. 1Y is collected.

  Next, the image forming units 1K, 1M, 1C, and 1Y will be described. FIG. 2 is a schematic configuration diagram showing one of the four image forming units 1K, 1M, 1C, and 1Y. Since the four image forming units 1K, 1M, 1C, and 1Y have substantially the same configuration except that they handle different colors of toner, they are referred to as “Y”, “M”, “C”, and “K” in FIG. Subscripts are omitted. The image forming unit 1 includes a photoconductor 11 as an image carrier, a charging roller 12 as a contact charging member as a charging unit, a developing device 10, and a cleaning device 14 as a cleaning unit.

In FIG. 2, a photoconductor 11 is a negatively charged organic photoconductor and is provided so as to be rotated in the direction of arrow B, that is, in the counterclockwise direction by a rotation drive mechanism (not shown).
The cleaning device 14 includes a cleaning blade 14 a that abuts in the counter direction with respect to the rotation direction of the photoconductor 11, and a waste toner storage portion 14 b that stores the cleaned toner particles as waste toner.
The charging roller 12 is a flexible roller in which a medium-resistance foamed urethane layer 12b in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent and the like are formulated is formed in a roller shape on a core metal 12a. is there. The material of the medium resistance layer formed on the core metal in the charging roller 12 is not limited to the above, but is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, A rubber material in which a conductive material such as carbon black or a metal oxide is dispersed in order to adjust resistance in isoprene rubber or the like, or a foamed material of these materials can be used.

The developing device 10 includes an electrostatic transport roller 13 which is a roller-shaped electrostatic transport unit having a plurality of electrodes for generating an electric field for transporting, developing, and collecting powder toner particles. The electrostatic transport roller 13 is opposed to the photoconductor 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.
Since the developing device described in Patent Document 1 uses a flat electrostatic transport member, a recovery transport member that collects and transports the toner that passes through the developing region and reaches the end of the flat plate is separately provided. There was a need. In an electrostatic conveyance member having an annular surface such as an endless loop shape or a roller shape, toner that has not contributed to development among the toners supplied by a supply unit to which toner is supplied has an annular surface of 1 It goes around and returns to the supply section. 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, so that the toner can be easily recovered and the apparatus can be downsized. be able to.

Next, the electrostatic transport roller 13 will be described.
FIG. 3 is a schematic view of the periphery of the portion of the electrostatic transport roller 13 facing the photoreceptor 11. In the electrostatic transfer roller 13, a plurality of electrodes 102 are arranged on the support substrate 101 at a predetermined interval R. In the printer 100, a three-phase driving voltage is applied, and the electrode 102 can be distinguished from the first electrode 102a, the second electrode 102b, and the third electrode 102c by the difference in the phase of the applied driving voltage. Note that the first electrode 102a, the second electrode 102b, and the third electrode 102c will be referred to as the electrodes 102 when they are not particularly distinguished. In addition, the electrostatic transport roller 13 is an insulating transport surface forming member that forms the electrostatic transport surface 103a on the electrode 102, and is an inorganic or organic insulating material that serves as a protective film that covers the surface of the electrode 102. The formed surface protective layer 103 is laminated.

As the support substrate 101, 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 SiO ₂ is formed, a polyimide film, or the like A substrate made of a flexible and deformable material can be used.

  The electrode 102 is formed by forming a conductive material such as Al or Ni—Cr on the support substrate 101 in a thickness of 0.1 to 10 [μm], preferably 0.5 to 2.0 [μm]. It is formed by patterning into a required electrode shape using a photolithographic technique or the like. The width L of the plurality of electrodes 102 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 102 in the powder traveling direction is also moved. It is 1 to 20 times the particle size.

As the surface protective layer 103, for example, SiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5, and the} like have a thickness of 0.5 to 10 [μm], preferably 0.5 to 3 [ [mu] m].

  In FIG. 3, lines extending downward from the respective electrodes 102 schematically represent conductive lines for applying a voltage to the respective electrodes 102. Of the overlapping portions of the respective lines, only the portions indicated by black circles are electrically connected. The other part is electrically insulated. In the electrostatic transfer member, different driving voltages of a plurality of phases (n phases) are applied to the electrodes 102 from the power source on the main body side. In the printer 100, a case where a three-phase driving voltage is applied (n = 3) will be described, but the present invention can be applied to any natural number n satisfying n> 2 as long as toner particles are conveyed.

In the printer 100, each electrode 102 is connected to one of the first contact S11, the second contact S12, the second contact S13, the first development contact S21, the second development contact S22, or the third development contact S23 on the developing device side. Has been. Each contact point is connected to a power source 104 on the main body side that provides drive waveforms V11, V12, V13, V21, V22, and V23 when the developing device 10 is mounted on the main body of the printer 100.
The electrostatic transport roller 13 transports toner particles to the vicinity of the photoconductor 11, collects toner particles that have not contributed to development after passing through the development area, and toner particles on the latent image on the image carrier 11. And a development area for forming a toner image. The development area exists only in the area close to the photosensitive member 11, and the conveyance area exists on the circumference of the electrostatic conveyance roller 13, and in all areas other than the non-electric field area, which will be described in detail later, other than the development area.
Hereinafter, an area where the toner particles can move by the phase electric field is referred to as an “electrostatic transfer surface”. In the case of the printer 100, the entire surface of the surface of the electrostatic transport roller 13 other than the non-electric field region is an electrostatic transport surface.
In the transport region, for each electrode 102, the first drive waveform V11 is applied to the first electrode 102a, the second drive waveform V12 is applied to the second electrode 102b, and the third drive waveform V13 is applied to the third electrode 102c. In the development region, for each electrode 102, the first development drive waveform V21 for the first development electrode 202a, the second development drive waveform V22 for the second development electrode 202b, and the third development drive waveform for the third development electrode 202c. V23 is applied.

Next, the principle of electrostatic conveyance of toner by the electrostatic conveyance roller 13 will be described.
By applying an n-phase driving waveform to the plurality of electrodes 102 of the electrostatic conveyance roller 13, a phase-shift electric field (traveling wave electric field) is generated by the plurality of electrodes 102, and the electrostatic conveyance roller 13 is charged. The toner particles move in the transport direction in response to a repulsive force and / or suction force.

  FIG. 4 shows a three-phase pulse drive composed of an A phase, a B phase, and a C phase, which changes between a ground G (0 V) and a positive voltage + with respect to the plurality of electrodes 102 of the electrostatic conveyance roller 13. It is explanatory drawing of the drive waveform which applied the waveform shifted timing. FIG. 5 is a schematic diagram for explaining a change in polarity applied to the plurality of electrodes 102 at three consecutive timings (a) to (b) when the drive waveform shown in FIG. 4 is applied. .

As shown in FIG. 5, there are negatively charged toner particles T on the electrostatic transport roller 13. At a certain timing (a), “G”, “ If G, “+”, “G”, and “G” are applied, the negatively charged toner particles T are positioned on the first electrode 102a to which “+” is applied.
At the next timing (b), “+”, “G”, “G”, “+”, and “G” are respectively applied to the plurality of electrodes 102. Specifically, the polarity applied to the first electrode 102a is “G”, and “+” is applied to the second electrode 102b. Since the repulsive force between the “G” first electrode 102a and the attraction force between the “+” second electrode 102b act on the negatively charged toner particles T, the negatively charged toner particles T are It moves to the “+” second electrode 102b side.
Furthermore, at the next timing (c), “G”, “+”, “G”, “G”, “+” are applied to the plurality of electrodes 102, respectively. Similarly to the timing (b), the repulsive force between the “G” second electrode 102b and the suction force between the “+” third electrode 102c and the field act on the negatively charged toner particles T. The negatively charged toner particles T further move toward the “+” third electrode 102c.

  In this way, by applying a multi-phase driving waveform whose voltage changes to the plurality of electrodes 102, a traveling wave electric field is generated on the electrostatic transport roller 13, and the negatively charged toner moves 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.

FIG. 6 is a waveform diagram showing waveforms of the A-phase driving pulse voltage, the B-phase driving pulse voltage, and the C-phase driving pulse voltage applied to the electrode 102 of the electrostatic transport roller 13.
Here, in the printer 100, in the transport region of the electrostatic transport roller 13, the application time ta of +100 [V] of each phase is repeatedly applied to each electrode 102 as shown in FIG. Three-phase drive waveforms (drive pulses) V11, V12, and V13 set to 33 [%] (this is referred to as “carrier voltage pattern”) are applied. It is known from the applicant's research that this driving waveform is a waveform suitable for high-speed conveyance of toner particles in the conveyance region.

FIG. 7 is a waveform diagram showing waveforms of the A-phase drive pulse voltage, the B-phase drive pulse voltage, and the C-phase drive pulse voltage applied to the electrode 102 in the development region of the electrostatic transport roller 13.
In the development region, for each electrode 102, as shown in FIG. 7, the application time ta of +100 [V] or 0 [V] of each phase is set to about 67 [%] which is 2/3 of the repetition period tf. (This is called “development voltage pattern”). A first development drive waveform V21, a second development drive waveform V22, and a third development drive waveform V23 of such three-phase drive pulses are applied. In the development region, it is preferable to positively launch toner particles toward the image carrier, and it has been confirmed by the applicant's experiment that the drive waveform in FIG. 7 is suitable for launching toner particles.

Even when the driving waveform of the development voltage pattern is applied, since the toner is also subjected to a force in the lateral direction other than the toner positioned at the center of the 0 [V] electrode, not all the toners are launched at the same time. Some toner moves in the direction. On the other hand, even when the driving waveform of the carrier voltage pattern is applied, depending on the position of the toner, there is a case where the rising distance is larger than when the toner is launched obliquely at a large angle and moves horizontally.
Accordingly, the drive waveform pattern applied to each electrode 102 in the transport region is not limited to the transport voltage pattern shown in FIG. 6 described above, and the drive waveform pattern applied to each electrode 102 in the development region is also illustrated in FIG. The development voltage pattern shown in FIG.

  Up to this point, the case of a three-phase drive waveform has been described. When this is generalized to an n-phase, the following is obtained. 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 × (n -1) / n} By setting the voltage application duty to be less than n / 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 repetitive cycle time tf, and a four-phase drive waveform is used. It is preferable to set the voltage application time of each phase 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 each voltage applied to the upstream adjacent electrode and the downstream adjacent electrode in the traveling direction, a time is set for the upstream adjacent electrode to repel and the downstream adjacent electrode to be sucked. The efficiency can be improved. In particular, when the driving frequency is high, the initial speed for the toner on the electrode of interest is set by setting it within the range of {repeat cycle time / n} or more and less than {repeat cycle time × (n−1) / n}. It becomes easy to obtain.

  The description of the electrostatic transport roller 13 serving as the electrostatic transport member has been described as being considered to be the best mode, but is not limited to this as long as a desired transport / development performance can be obtained. The direction of the electric field may be adjusted by changing the distance between the electrodes 102 in the development area and the conveyance area, or the distance between the electrodes and the drive waveform may be the same in the development area and the conveyance area.

  Further, other members of the developing device 10 will be described with reference to FIG. In the developing device 10, a supply roller 15 for supplying toner particles to the electrostatic conveyance roller 13 is disposed, and a magnetic brush is formed at a portion where the supply roller 15 and the electrostatic conveyance roller 13 are opposed to each other. The surface of the supply roller 15 is a nonmagnetic sleeve 15a formed by forming a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin into a cylindrical shape. The sleeve 15a is rotated in the clockwise direction indicated by the arrow C in the figure by a rotation drive mechanism (not shown).

  A doctor blade 16 that regulates the height of the developer chain spike, that is, the amount of developer on the sleeve, is installed on the upstream side of the supply region for supplying developer to the electrostatic conveyance roller 13 in the developer conveyance direction. Has been. The doctor gap, which is the distance between the doctor blade 16 and the sleeve 15a, is set to 0.4 [mm]. Further, in the region opposite to the electrostatic conveying roller 13 of the supply roller 15, two stirring screws 17 for pumping the developer in the developer accommodating portion 18 covered with the developing casing 10 a to the supply roller 15 while stirring. Is installed.

FIG. 8 is a schematic sectional view of the supply roller 15.
As shown in FIG. 8, in the supply roller 15, a magnet roller 15b that forms a magnetic field is provided in a fixed state so as to cause the rise of developer on the peripheral surface of the sleeve. The developer carrier has a chain-like shape on the sleeve so as to follow the normal magnetic field lines emitted from the magnet roller 15b, and the charged toner is attached to the carrier that has the chain-like shape. A magnetic brush (not shown) is configured. The magnetic brush is transferred in the same direction as the sleeve by the rotation of the sleeve. The magnet roller 15b includes a plurality of magnetic poles (magnets). Specifically, a developing main magnetic pole P1 that causes the developer to rise in the supply region portion, and pumping magnetic poles P4 and P5 for pumping the developer on the sleeve are provided. Furthermore, the supply transport magnetic pole P6 that transports the pumped developer to the supply region, the recovery transport magnetic pole P2 that transports the developer in the region after supply, and the developer that has passed through the supply region is returned to the developer accommodating portion 18. The agent separation magnetic pole P3 is provided. In the printer 100, the magnet roller 15b is configured by a 6-pole magnet, but may be configured by 8 or 12 poles. The curve drawn on the surface of the supply roller 15 shown in FIG. 8 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 15 is N poles. , S pole.

  In the developer accommodating portion 18 of the developing device 10, a two-component developer composed of toner particles (not shown) and a magnetic carrier is accommodated. In carrying out the present invention, it is not necessary to limit to a two-component developer using carrier particles and toner particles, but an embodiment in the printer 100 will be described below.

  The toner particles used in the printer 100 may be radically polymerized with a styrene or acrylic polymerizable monomer dispersed in water together with a polymerization initiator as a binder resin, or a polyester resin dispersed in water. What was polymerized by the polyaddition reaction can be used. The toner particles are non-magnetic toner particles having a weight average particle diameter of about 5 [μm] obtained by adding a colorant, a charge control agent, and the like to granulation.

The magnetic carrier used in the printer 100 is preferably a carrier having a magnetization amount in a range of 30 [emu / cm ³ ] or more and 200 [emu / cm ³ ] or less in a 1 kilo-Oersted magnetic field. 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 is reduced, and the magnetic brush head formed is reduced. Becomes dense and short. As a result, uniform toner particle supply to the electrostatic transport roller 13 can be achieved.
On the other hand, when the magnetization amount of the magnetic carrier is less than 30 [emu / cm ³ ], the developer transport performance is poor. Therefore, the magnetization amount of the magnetic carrier is preferably 30 [emu / cm ³ ] or more, and more preferably 80 [emu / cm ³ ] or more.
In the printer 100, 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 as the magnetic carrier. 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 a 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 strength of magnetization obtained by the measurement by the true specific gravity of the carrier.

Next, the operation of the image forming process will be described.
The printer 100 is an image forming apparatus that can function as a copying machine and a printer. When functioning as a copying machine, image information read from a scanner (not shown) is subjected to various image processing such as A / D conversion, MTF correction, gradation processing, etc., and converted into writing data. When functioning as a printer, image processing is performed on image information in a format such as a page description language or a bitmap transferred from a computer (not shown) or the like, and converted into write data.

  Prior to image formation, the photoconductor 11 starts to rotate in the direction of arrow B in FIG. 2, that is, in the counterclockwise direction so that the moving speed of the surface becomes a predetermined measure. The charging roller 12 rotates with respect to the photoreceptor 11. At this time, a DC voltage of −100 [V] and an AC voltage of an amplitude of 1200 [V] and a frequency of 2 kHz are applied to the core of the charging roller 12 from a charging bias application power source (not shown). Charged to -100 [V].

  The charged photoconductor 11 is exposed according to the writing data by the optical writing device 4 (4K, 4M, 4C, 4Y). That is, by changing the potential of the image portion by light irradiation, a difference from the potential of the non-image portion not irradiated with light is generated, and an electrostatic latent image is formed by this potential contrast.

  The electrostatic latent image formed on the photoconductor 11 by the optical writing device 4 is developed by the developing device 10 and is visualized on the photoconductor 11 as a toner image by adhering toner particles to the image portion. In the development by the phase-shift electric field, the toner particles move while jumping on the surface of the electrostatic conveyance roller 13 and are attached so as to be attracted to the image portion when the toner particles come close to the photoreceptor 11 for development. In the printer 100, a voltage of −50 [V] is applied to the electrostatic transport roller 13 and −250 [V] is applied to the supply roller 15, whereby the electrostatic transport roller 13 and the electrostatic transport roller 13 are exposed to light. An electric field is formed that guides the toner particles to the image area on the body 11.

  The transfer material P is conveyed from the sheet feeding device 5 in time with the timing when the toner image formed on the photoconductor 11 reaches the transfer portion which is the opposite portion between the transfer roller 9 and the photoconductor 11, and the photoconductor. 11 is transferred to the transfer material P by the voltage applied to the transfer roller 9. The transferred toner image is fixed on the transfer material P by the fixing device 3 and an image is output.

  On the other hand, the toner remaining on the image carrier 11 without being transferred (transfer residual toner) is cleaned by the cleaning device 14, and the surface of the photoreceptor 11 after cleaning is used for the next image formation.

In a developing device that moves toner particles by a phase-shifting electric field, such as the developing device 4, the toner particles move so as to jump off the surface of the electrostatic conveying member. There is no contact with the conveying member. 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 transport member is weak. Therefore, there is an advantage that the developing ability can be easily secured even if the developing electric field is set weak (for example, even if the developing potential is 100 V or less). However, if the development electric field is set to be weak, the amount of toner particles transported is small, so that even a slight variation in the amount of toner causes development unevenness. Accordingly, it is difficult to uniformly convey toner particles particularly in a low potential process with a development potential of 100 V or less.
If the amount of toner particles supplied onto the electrostatic conveyance member varies, the phase-shift electric field is disturbed, which adversely affects the conveyance performance and development performance. In this way, when an actual product is installed with a type of developing device having a toner conveying surface on which the toner particles can move on the annular surface by a phase-shifting electric field, it is necessary to devise a technique for completely collecting the toner from the electrostatic conveying member. Become.

[Example 1]
Next, a first embodiment of toner collecting means for collecting toner particles from the electrostatic conveyance surface 103a on the downstream side in the toner conveyance direction with respect to the developing area of the electrostatic conveyance roller 13 which is an electrostatic conveyance member will be described.
FIG. 9 is a schematic configuration diagram of the developing device 10 and the photoconductor 11 for explaining the toner collecting unit of the first embodiment.
The toner supplied by the supply roller 15 moves on the surface of the electrostatic transport roller 13 in the direction of arrow D in the figure by a transport electric field.
The conductive plate 200 serving as a recovery member of the toner recovery means is electrostatically transferred to a range from the developing area to the toner supply area of the cylindrical electrostatic transfer roller 13 which is an electrostatic transfer means having an annular electrostatic transfer surface. It is installed in a non-contact manner with respect to the surface 103a. Further, a bias voltage is applied to the conductive plate 200 by a recovery power source 30 as a recovery voltage with a polarity opposite to that of the toner particles. Since the toner used in the printer 100 usually has a “−” polarity, the recovery voltage applied to the conductive plate 200 by the recovery power supply 30 has a “+” polarity.
The portion of the transport electrode where the transport electric field of the electrostatic transport roller 13 is generated is from the toner supply region to the recovery region where the toner recovery means is provided.

Toner particles that have not contributed to development in the development area are electrostatically attracted to the conductive plate 200 to which a bias voltage is applied after passing through the development area of the electrostatic conveyance roller 13 and separated from the electrostatic conveyance roller 13. . The bias voltage applied to the conductive plate 200 is a bias voltage having a polarity opposite to that of the toner particles on the electrostatic transport roller 13. In the first embodiment, the conductive plate 200 applies a bias voltage in the range of 0 [V] to +100 [V].
In addition, the conductive plate 200 is installed slightly spaced from the electrostatic transport roller 13. The gap between the conductive plate 200 and the electrostatic transport roller 13 is in the range of 50 to 1000 [μm], preferably 150 to 400 [μm], and smaller than the height at which the toner particles hop when moving by the phase-shifting electric field. desirable. In the case of the developing device 10, they are installed approximately 400 [μm] apart.

The toner particles adsorbed on the conductive plate 200 are electrostatically repelled from the conductive plate 200 by applying a voltage having a polarity opposite to the bias voltage at the time of adsorption at a timing when the electrostatic conveyance roller 13 does not convey the toner. This can be removed. Further, by removing the electric charge by grounding the conductive plate 200, it can be dropped from the conductive plate 200 by gravity and collected in the developing device 4. In addition, the conductive plate 200 may be attached with an inclination in the vertical direction so that the toner particles can easily fall. At this time, in order to easily separate and drop the toner particles from the conductive plate 200, a method of applying vibration to the conductive plate 200 by ultrasonic vibration, high frequency vibration or the like by the vibrator 201 using a piezoelectric element or the like can be considered.
Thus, the toner particles dropped and collected from the conductive plate 200 are again captured by the developer on the supply roller 15 and carried to the supply unit.

FIG. 10 is a detailed explanatory view of an electrostatic transport roller 13 as an electrostatic transport member, a supply roller 15 as a toner supply unit, a photoconductor 11 as a latent image carrier, and a conductive plate 200 as a toner collection unit. .
The electrostatic conveyance roller 13 is located at the downstream end in the toner conveyance direction of the electrostatic conveyance surface 103a on the downstream side in the toner conveyance direction with respect to the developing area 133 facing the photoconductor 11, and upstream in the toner conveyance direction from the supply area 131 with the supply roller 15. The electrostatic transfer surface 103a on the side is separated from the upstream end in the toner transfer direction, and forms a non-electric field region 136 where a phase-shift electric field is not formed. The upstream end in the toner transport direction of the electrostatic transport surface 103a at the boundary between the supply region 131 and the non-electric field region 136 of the electrostatic transport roller 13 is a transport electrode starting end portion 130s where the transport electrode starts. Further, the downstream end in the toner transport direction of the electrostatic transport surface 103a at the boundary between the collection region 135 and the non-electric field region 136 on the downstream side in the toner transport direction of the development region is a transport electrode terminal portion 130e as a phase-shift electric field terminal portion. . A downstream conveyance area 132 between the supply area 131 and the development area 133 on the downstream side in the toner conveyance direction is a downstream conveyance area 134 between the development area 133 and the collection area 135. Toner particles that have not contributed to development in the development region 133 pass through the development region 133 and the downstream transport region 134 of the electrostatic transport roller 13 and are transported to the collection region 135 or the transport electrode terminal portion 130e.
The supply area 131, the upstream conveyance area 132, the development area 133, the downstream conveyance area 134, and the collection area 135 are electric field areas 130 that generate a conveyance electric field 13 E on their surfaces. There is no strict boundary between them.
Further, the non-electric field region 136 of the electrostatic transport roller 13 may be formed of an insulating member. By forming the insulating member, generation of an electric field in the non-electric field region 136 can be more reliably suppressed.

Next, the movement of toner in the collection area 135 will be described.
FIG. 11 is an explanatory diagram of the change in polarity of the plurality of electrodes 102 in the collection region 135 and the electrostatic force applied to the toner particles.
Among the plurality of electrodes 102, the one closest to the transport electrode terminal end 130 e side, which is the downstream end of the collection region 135 in the toner transport direction, is the downstream end electrode 102 e that is the most downstream electrode of the electric field region 130. One electrode upstream from the downstream end electrode 102e is referred to as the second electrode 102b, and one more upstream electrode is referred to as the first electrode 102a. The polarities shown below the three electrodes 102 indicate the polarities of the voltages applied to the respective electrodes 102 at the respective timings t1, t2, and t3.

  The toner particles T shown in FIG. 11 are positions after the polarity of the voltage applied to the electrode 102 has changed from the state at the timing t3 to the state at the timing t1. The polarity of the voltage applied to the second electrode 102b changes from “+” to “−”, and the polarity of the voltage applied to the downstream end electrode 102e changes from “−” to “+”, thereby generating an electric field e1. . As a result, the electrostatic force f1 acts on the toner particles T on the second electrode 102b and moves in the direction of arrow D, which is the direction of toner conveyance, and the state shown in FIG. 11 is obtained.

  Next, even if the polarity of the voltage applied to the electrode 102 changes from the state at the timing t1 to the state at the time t2, the electrode 102 does not exist on the downstream side in the toner transport direction from the downstream end electrode 102e. A transport electric field for transporting toner in the D direction is not formed. Then, the polarity of the voltage applied to the downstream end electrode 102e changes from “+” to “−”, and the polarity of the voltage applied to the first electrode 102a changes from “−” to “+”. Occurs. As a result, the electrostatic force f2 acts on the toner particles T on the downstream end electrode 102e, and moves in the direction opposite to the arrow D direction, which is the toner transport direction, and reaches the first electrode 102a to reach the toner transport direction. And go backwards.

  As described above, since the toner particles are repeatedly advanced and reversed in the vicinity of the transport electrode terminal portion 130e, which is the boundary between the collection region 135 and the non-electric field region 136, the toner particles around the transport electrode terminal portion 130e are removed. By providing the toner collecting means so as to collect, the toner that has passed through the developing region can be reliably collected. Therefore, in the first exemplary embodiment, the conductive plate 200 to which a bias voltage as a toner recovery unit is applied is installed in the recovery region 135 around the transport electrode terminal portion 130e. Providing the conductive plate 200 around the transport electrode terminal portion 130e increases the chance that the toner particles are captured by the recovery electric field of the conductive plate 200 and facilitates recovery.

[Experiment 1]
The following experiment 1 was performed in order to confirm the recovery efficiency at the transport electrode terminal portion 130e.
A voltage is applied to the conductive plate 200 in the case of collecting the end portion where the conductive plate 200 is provided around the transport electrode terminal portion 130e and in the case of collecting the end portion where the conductive plate 200 is provided in the middle of the electric field region 130. The strength of the recovery electric field generated by the measurement and the recovery rate at that time were measured.
FIG. 12 is a graph showing the results of Experiment 1.
As shown in FIG. 12, it was found that when collected around the transport electrode terminal portion 130e, it was collected even with an electric field strength of 1/3 or less as compared with the case where it was collected in the middle of the electric field region 130.
From Experiment 1, it was confirmed that the toner particles passing through the development region can be more reliably collected by providing a conductive plate as a toner collecting means so as to collect the toner particles around the terminal portion of the transport electrode.

[Example 2]
In the first embodiment, the blade-like conductive plate 200 made of a conductive member is used as the collecting member constituting the collecting means, but the collecting member is not limited to the blade-shaped member. Hereinafter, a second embodiment of the toner collecting means using a roller-shaped conductive roller will be described.
FIG. 13 is a schematic configuration diagram of the developing device 10 and the photoconductor 11 for explaining the toner collecting unit of the second embodiment.
A conductive roller 300 as a toner collecting member of the toner collecting means is installed in a non-contact manner with respect to the electrostatic carrying surface 103a in a range from the developing area to the toner supply area of the electrostatic carrying roller 13. Further, a bias voltage having a polarity opposite to that of the toner particles is applied to the conductive roller 300 by a recovery power source 30 as a recovery voltage.
The portion of the transport electrode where the transport electric field of the electrostatic transport roller 13 is generated is from the toner supply region to the recovery region where the toner recovery means is provided.

Toner particles that have not contributed to development in the development region pass through the development region of the electrostatic transport roller 13, are electrostatically attracted to the conductive roller 200 to which a bias voltage is applied, and are separated from the electrostatic transport roller 13. . The bias voltage applied to the conductive plate 200 is a bias voltage having a polarity opposite to that of the toner particles on the electrostatic transport roller 13. In the second embodiment, the conductive roller 200 applies a bias voltage in the range of 0 [V] to +100 [V].
In addition, the conductive roller 300 is installed so as to rotate slightly spaced from the electrostatic transport roller 13. The toner particles adsorbed on the conductive roller 300 are scraped off by the removing blade 301 brought into contact with the roller surface by rotating the conductive roller 300 and are collected in the developing device 4 by gravity. The toner particles dropped and collected from the conductive roller 300 are again captured by the developer on the supply roller 15 and conveyed to the supply unit.

FIG. 14 is a detailed explanatory view of an electrostatic transport roller 13 as an electrostatic transport member, a supply roller 15 as a toner supply unit, a photosensitive member 11 as a latent image carrier, and a conductive roller 300 as a toner recovery unit. .
The electrostatic conveyance roller 13 has a non-electric field region 136 in which a phase-shift electric field is not formed between the supply region 131 and the development region by the supply roller 15 on the downstream side in the toner conveyance direction from the development region 133 facing the photoconductor 11. Forming. The boundary between the supply region 131 of the electrostatic transport roller 13 and the non-electric field region 136 is a transport electrode starting end portion 130s where the transport electrode starts, and the recovery region 135 and the non-electric field region 136 on the downstream side in the toner transport direction of the development region. The boundary is a carrier electrode termination part 130e as a phase-shift electric field termination part. A downstream conveyance area 132 between the supply area 131 and the development area 133 on the downstream side in the toner conveyance direction is a downstream conveyance area 134 between the development area 133 and the collection area 135. Toner particles that have not contributed to development in the development region 133 pass through the development region 133 and the downstream transport region 134 of the electrostatic transport roller 13 and are transported to the collection region 135 or the transport electrode terminal portion 130e.
The supply area 131, the upstream conveyance area 132, the development area 133, the downstream conveyance area 134, and the collection area 135 are electric field areas 130 that generate a conveyance electric field 13 E on their surfaces. There is no strict boundary between them.

Also in the electrostatic transport roller 13 of the second embodiment, as shown in FIG. 11 described in the first embodiment, the transported electric field is not formed first because the toner transported to the transport electrode terminal portion 130e has no electrode first. The toner stops moving and is returned by the electric field in the direction opposite to the traveling direction. As in the first embodiment, since the advancement and the reverse operation are repeated, the chance of being captured by the recovery electric field of the conductive roller 300 to which the recovery bias voltage is applied is increased, so that the recovery is facilitated.
As the conductive roller 300, an electrical resistance value (volume resistivity) of 10 to 10 ⁶ [Ω · cm] is obtained by blending and dispersing a conductivity imparting agent such as carbon black, zinc oxide and tin oxide in a metal and a resin material. It is made of a conductor adjusted to a low resistance. The gap between the conductive roller 300 and the electrostatic conveyance roller 13 is 50 to 1000 [μm], preferably 150 to 400 [μm], which is smaller than the height at which the toner particles hop when moving by the phase-shifting electric field. Is desirable. In the case of Example 2, it is installed approximately 400 [μm] apart. The toner particles adsorbed on the conductive roller 300 are scraped off by the removing blade 301 brought into contact with the roller surface by rotating the conductive roller 300 and are collected in the developing device 4 by gravity. As a result, the portion of the conductive roller 300 facing the electrostatic conveyance roller 13 is always in a clear state, a good recovery electric field can be generated, and toner can be recovered more reliably. The direction of rotation of the conductive roller 300 is not particularly limited, but is preferably the same direction as the toner conveyance direction of the electrostatic conveyance roller 13.

[Example 3]
In the first and second embodiments, a collecting voltage is applied to the conductive member as a collecting unit, and the toner is collected by a collecting electric field generated between the electrostatic conveyance member and the collecting member. It is not limited to those using. In the following, a third embodiment of the toner collecting means will be described, which uses a collecting means that includes an air flow generating member and collects the toner particles on the electrostatic transport surface by the force of the air flow.
FIG. 15 is a schematic configuration diagram of the developing device 10 and the photoconductor 11 for explaining the toner collecting unit of the third embodiment.
An air nozzle 400, which is an airflow generating member, is installed as a toner collecting unit that collects toner in a range from the developing area to the toner supply area of the electrostatic conveyance roller 13. The transport electrode portion where the transport electric field of the electrostatic transport roller 13 is generated is from the toner supply region to the recovery region where the toner recovery means is provided. The ejection opening of the air nozzle 400 is installed so that the air flows in the tangential direction of the surface of the electrostatic transport roller 13 and the air flows along the surface of the electrostatic transport roller 13.

  The toner particles that have not contributed to the development in the development region pass through the development region of the electrostatic transport roller 13, are transported to the transport electrode terminal portion 130 e, and the surface of the electrostatic transport roller 13 is caused by the air stream ejected from the air nozzle 400. Removed from. The separated toner particles are collected in the developer container 18. The toner particles collected in the developer container 18 are stirred together with the developer. Here, the air pump 401 used for air blow is preferably a pump such as a diaphragm pump that can transport powder such as toner. However, if the influence of powder such as sealing the motor is taken into consideration, a sirocco fan, a cross flow fan, and a propeller are used. A fan like a fan can be used.

FIG. 16 is a detailed explanatory view of the electrostatic conveyance roller 13 as an electrostatic conveyance member, the supply roller 15 as a toner supply unit, the photosensitive member 11 as a latent image carrier, and a toner recovery unit using an air flow.
As for the electrostatic transport roller 13 used in the third embodiment, the area can be divided according to the action as in the first and second embodiments. However, how to divide the area is the first and second embodiments. Therefore, the description is omitted here.
There is a transport electrode starting end portion 130 s where the transport electrode starts on the upstream side in the transport direction of the toner supply region of the electrostatic transport roller 13, and a transport electrode end portion 130 e in the recovery region on the downstream side in the transport direction of the development region. A non-electric field region 136 without a transport electrode is from the transport electrode terminal end 130e to the transport electrode start end 130s.

  The air nozzle 400 is installed so that the air current flows toward the transport electrode terminal portion 130e of the electrostatic transport roller 13 as described above. The airflow flows along the surface of the electrostatic conveyance roller 13 from the upstream side of the conveyance electrode end portion 130 in the toner conveyance direction, and the toner is blown from the conveyance electric field from the conveyance electrode termination portion 130e. The toner particles are blown to a non-electric field region 136 having no transport electrode between the transport electrode end portion 130e and the transport electrode start end portion 130s.

A portion of the electrostatic transport roller 13 where the non-electric field region 136 is formed is formed of an inorganic or organic insulating material. The electrostatic conveyance roller 13 in the third embodiment, a glass, resin or insulating material such as ceramics, or that an insulating film such as SiO ₂ raw pipe 13a made of a conductive material such as SUS, polyimide A material that can be deformed flexibly, such as a film, can be used.
Here, FIG. 17 is a graph comparing the adhesion rate of the toner to the non-electric field region 136 when the non-electric field region 136 is an insulator and when it is a conductor. As shown in FIG. 17, by using the non-electric field region 136 as an insulator, it is possible to more reliably prevent the charged toner from adhering as compared with the case where the non-electric field region 136 is used as a conductor, and to release the toner from the electrostatic transport roller 13. be able to.

  The air flow rate at the nozzle opening is preferably equal to or higher than the toner conveyance speed. In Example 3, the flow rate of the air blow 405 of the air nozzle 400 is set to 3 [m / sec] or more with respect to the toner conveyance speed 1 [m / sec].

In the case of collecting toner by blowing air onto the electrostatic transport roller 13 as in the third embodiment, the surface of the non-electric field region 136 of the electrostatic transport roller 13 is placed on the surface of the electric field region 130 as shown in FIG. The step h may be provided so as to be inside the annular surface rather than the surface. That is, the surface of the non-electric field region 136 may be lower than the surface of the electric field region 130 by a level difference h.
FIG. 19 shows the experimental results of measuring the flow rate of the air nozzle and the peeling rate at that time when the step h is “with a step” and when there is no step, that is, when the transport electrode terminal portion 130e is “smooth”. It is a graph which shows.

As shown in FIG. 19, by providing a step h so that the non-electric field region 136 is lower than the electric field region 130 at the transport electrode terminal portion 130e of the electrostatic transport roller 13, as shown in FIG. / Sec].
Since the pressure in the developing device 4 is increased by the air blow 405, it is desirable that the flow rate be as low as possible. Further, in the third embodiment, the air inlet 403 of the air pump 401 used for the air blow 405 is provided in a place where the pressure in the developing device 4 is likely to rise and the toner is not directly sucked. As a result, air circulates inside the developing device 4, so that an increase in pressure in the developing device 4 can be suppressed.

Furthermore, as shown in FIG. 20, even if a toner repulsion electrode plate 137 to which a bias having a polarity repelling the toner is applied on the insulator forming the non-electric field region 136, the toner can be peeled off. The base tube 13a and the toner repulsive electrode plate 137 of the electrostatic transport roller 13 are preferably formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin. Thereby, the influence of the magnetic field of the supply roller 15 and adhesion of the magnetic carrier can be prevented.
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, and is applicable to a color image forming apparatus, a monochrome image forming apparatus, and the like using an intermediate transfer belt, a transfer drum, an intermediate transfer drum, and the like. It goes without saying that is also applicable.

As described above, according to the first embodiment, the conductive plate 200 serving as a toner collecting unit is provided at a position facing the transport electrode terminal portion 130e that is the downstream end portion of the electrostatic transport surface 103a in the toner transport direction. For the toner particles T that have reached the transport electrode terminal portion 130e, which is the boundary between the developing region 133 and the non-electric field region 136 of the region forming the phase shift electric field downstream in the toner transport direction, No force is generated (traveling) toward the non-electric field region side that is downstream in the toner conveyance direction, and a force that attempts to return (reverse) upstream in the toner conveyance direction in which a phase-shift electric field is generated. As a result, the toner particles around the transport electrode terminal portion 130e are repeatedly advanced and reversed. By providing the conductive plate 200 as a toner collecting means so as to collect the toner particles around the transport electrode terminal portion, the toner particles that have passed through the developing region 133 can be reliably collected. Therefore, it is possible to suppress the variation in the toner conveyance amount caused by the toner that has passed through the development region 133 not being collected and reaching the supply region 131 as a supply unit, and the occurrence of development unevenness can be suppressed and stable. Development can be performed.
Further, as the electrostatic transport means, an electrostatic transport roller 13 having an annular electrostatic transport surface is used, and the space between the transport electrode terminal portion 130e and the transport electrode start end portion 130s which is the upstream end portion in the toner transport direction is used. A non-electric field region 136 is formed by separating them. In an electrostatic conveyance member having an annular surface such as an endless loop shape or a roller shape, toner that has not contributed to development among the toners supplied by a supply unit to which toner is supplied has an annular surface of 1 It goes around and returns to the supply section. 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. In addition, the collected toner can be easily returned to the supply unit.
In addition, the conductive plate 200 is used as the toner collecting means, and a collecting voltage is applied to move the toner particles T on the electrostatic carrying surface 103a from the carrying electric field to the collecting electric field, thereby easily collecting the toner particles electrostatically. be able to.
In addition, by disposing the conductive plate 200 in a non-contact manner with respect to the electrostatic transfer surface 103, mechanical damage due to the collection member coming into contact with the surface protective layer 103 forming the electrostatic transfer surface 103a is prevented. In addition, it is possible to suppress damage due to a short circuit that may occur when the recovery voltage is applied.
Moreover, the structure of a collection | recovery means can be simplified by using the plate-shaped electroconductive board 200 as a collection | recovery member.
In addition, the conductive plate 200 is a recovery member that comes into contact with toner particles during recovery, and includes a vibrator that vibrates the conductive plate 200 as toner separation means for separating the toner particles adhering to the conductive plate 200. Therefore, the collection performance by the conductive plate 200 can be maintained, and the toner can be separated and collected.
Further, since the roller-like conductive roller 300 is used as the collecting member and the removing blade 301 is provided as the toner separating means, the portion of the conductive roller 300 facing the electrostatic conveyance roller 13 is always in a clear state. In addition, since a good recovery electric field can be generated, the toner can be more reliably recovered as compared with the blade-shaped recovery member.
Further, the non-electric field region 136 of the electrostatic transport roller 13 is formed of an insulating member, so that toner particles can be prevented from adhering to the non-electric field region 136.
Further, by using the developing device 4 as the developing unit of the printer 100 which is an image forming apparatus, stable image formation can be performed.
In addition, an air nozzle 400 that is an airflow generating member is provided as a toner collecting means, and the force of the air blow 405 is applied to the toner particles that have lost the moving force in the transport direction around the transport electrode terminal portion 130e on the electrostatic transport surface 103a. In addition, the toner particles can be easily separated and collected from the electrostatic conveyance surface 103a. Further, by providing a step h so that the surface of the non-electric field region 136 of the electrostatic transport roller 13 is inside the annular surface with respect to the surface of the electric field region 130, the toner particles are separated from the electrostatic transport surface by the step. The flow rate of the air blow 405 can be reduced, and the increase in the pressure of the gas in the developing device 4 can be suppressed.

[Modification]
In the first exemplary embodiment, the toner conveyance speed in the electric field region 130 that forms the conveyance electric field is uniform. Hereinafter, as a modified example, a configuration in which the toner conveyance speed in the developing region in the electric field region is slowed will be described.
FIG. 21 is a schematic diagram for explaining the arrangement of the plurality of electrodes 102 of the electrostatic transport roller 13 according to a modification.
In this modification, as in the first embodiment, the electrostatic transport roller 13 has a plurality of electrode regions for generating an electric field for supplying, transporting, developing, and collecting toner particles that are powder. Although a case where a three-phase drive voltage is applied (n = 3) will be described here, the present invention can be applied to any natural number n that satisfies n> 2 as long as toner particles are conveyed.

  In this modification, each electrode 102 is one of the first contact S11, the second contact S12, the second contact S13, the first recovery contact S31, the second recovery contact S32, or the third recovery contact S33 on the developing device side. It is connected. Each contact is connected to a main body-side power supply 104 that supplies drive waveforms V11, V12, V13, V31, V32, and V33, respectively, when the developing device 10 is mounted on the main body of the printer 100.

  The electrostatic conveyance roller 13 can be divided into an electric field region 130 and a non-electric field region 136 as described with reference to FIG. Further, the electric field region 130 includes a supply region 131 to which toner is supplied, an upstream conveyance region 132 that transports to the vicinity of the photoconductor 11, and development for forming toner images by attaching toner particles to the latent image on the photoconductor 11. The area 133 can be divided into a collection area 135 for collecting toner particles that have not contributed to development after passing through the development area, and a downstream conveyance area 135 for conveying toner from the development area 133 to the collection area 135.

  The supply area 131 is an area close to the supply main magnetic pole P <b> 1 of the supply roller 15, the upstream transport area 132 exists from the supply area 131 to the development area 133, and the development area 133 exists only in the area close to the image carrier 11. To do. Further, the downstream transport area 134 exists between the development area 133 and the collection area 135. On the other hand, the recovery area 135 is an area in the vicinity of the recovery magnetic pole P <b> 2 of the supply roller 15.

  Here, an area including the supply area 131, the upstream conveyance area 132, the development area 133, and the downstream conveyance area 134 is referred to as a normal conveyance area 139. In the normal transport region 139, for each electrode 102, the first drive waveform V11 is applied to the first electrode 102a, the second drive waveform V12 is applied to the second electrode 102b, and the third drive waveform V13 is applied to the third electrode 102c. The frequency is driven from 2 [kHz] to 8 [kHz]. Although it is preferable to apply a bias having a driving waveform different from that of the other normal transport areas as in the first embodiment to the developing area 133, description thereof is omitted.

On the other hand, in the collection area 135, for each electrode 102, the first collection drive waveform V31 for the first collection electrode 302a, the second collection drive waveform V32 for the second collection electrode 302b, and the third collection drive for the third collection electrode 302c. Waveform V33 is applied. The drive frequency at this time is driven at a frequency lower than the drive frequency of the normal conveyance area 139.
In this modification, the driving frequency of the normal conveyance area 139 is 5 [kHz], and the driving frequency of the collection area 135 is 3 [kHz].

[Experiment 2]
In order to confirm the difference in the recovery rate due to the difference in the driving frequency, the following experiment 2 was performed.
When the drive frequency applied to the recovery electrode 302 in the recovery region 136 is 3 [kHz] and 5 [kHz], the intensity of the electric field generated by applying a voltage to the recovery electrode 302 and the current Recovery was measured.
FIG. 22 is a graph showing the results of Experiment 2.
As shown in FIG. 22, by setting the drive frequency to 3 [kHz], the electric field intensity required for recovery could be lowered compared to the case where the drive frequency was 5 [kHz].
In Experiment 2, the supply bias applied to the supply roller 15 was −400 [V], the charge voltage applied to the charging roller 12 was −140 [V], and the post-exposure voltage on the photoconductor 11 was −40 [V]. did. At this time, a drive pulse signal with an average value of −100 [V] and ± 100 [V] is applied to the drive waveforms V11, V12, and V13 of the main body side power supply 104 connected to the respective electrodes 102 in the normal transport region 139. To do. On the other hand, a drive pulse signal of ± 100 [V] with an average value of −500 [V] is applied to the drive waveforms V31, V32, and V33 of the main body side power supply 104 connected to each recovery electrode 302 in the recovery area 135, and the toner. Is recovered.

Although the first embodiment has a configuration in which no electrode is provided in the non-electric field region 136, the non-electric field electrode 402 may be provided in the non-electric field region 136 as shown in FIG. The non-electric field electrode 402 is connected to the main body side power source 104 that is connected to the non-electric field contacts S31, S32, and S33 to provide the non-electric field region driving waveforms V41, V42, and V43. The non-electric field region driving waveforms V41, V42, and V43 are applied when the development is not performed, and the toner particle group that has not been developed can be returned to the supply region and circulated again by the phase-shift electric field.
By making the non-electric field region 136 function as the second electrostatic conveyance surface in this way, the toner remains carried on the electrostatic conveyance roller 13 when development is not performed, and unnecessary collection and supply are not performed. In addition, toner deterioration can be suppressed.

  As in the modification, in the recovery area 135 where the toner recovery means recovers the toner upstream of the transport electrode terminal section 130e, which is the phase shift electric field terminal section, the drive frequency is set to the normal transport area 139. By making it smaller than this and slowing the toner conveyance speed, the toner can be easily collected, and the toner collection rate is improved.

1 is a schematic configuration diagram of a printer according to a first embodiment. FIG. 2 is a schematic configuration diagram of an image forming unit of the printer. Sectional drawing which expanded the opposing part with the photoreceptor of an electrostatic conveyance roller. Explanatory drawing of the drive waveform which applied the three-phase pulse-form drive waveform by shifting timing. The schematic diagram explaining the change of the polarity applied to a some electrode at the time of three continuous timings. The wave form diagram which shows the waveform of the three-phase drive pulse voltage applied to the electrode of an electrostatic conveyance roller. The wave form diagram which shows the waveform of the three-phase drive pulse voltage applied to the electrode of the image development area | region of an electrostatic conveyance roller. The schematic sectional drawing of a supply roller. 1 is a schematic configuration diagram of a developing device and a photoreceptor according to Embodiment 1. FIG. FIG. 3 is a detailed explanatory diagram of an electrostatic conveyance roller, a supply roller, a photoreceptor, and a conductive plate according to the first embodiment. Explanatory drawing of the electrostatic force added to the change of the polarity of several electrodes in a collection | recovery area | region, and a toner particle. The graph which shows the result of Experiment 1. FIG. 6 is a schematic configuration diagram of a developing device and a photoreceptor according to Embodiment 2. FIG. 6 is a detailed explanatory diagram of an electrostatic conveyance roller, a supply roller, a photoconductor, and a conductive roller according to the second embodiment. FIG. 6 is a schematic configuration diagram of a developing device and a photoreceptor according to Embodiment 3. FIG. 6 is a detailed explanatory diagram of a toner collecting unit using an electrostatic conveyance roller, a supply roller, a photoconductor, and an air flow according to a second embodiment. The graph of the adhesion rate of the toner when a non-electric field area | region is made into an insulator, and when made into a conductor. Explanatory drawing of the structure which provided the level | step difference in the surface of an electrostatic conveyance roller. 6 is a graph of the toner peeling rate when a step is provided on the surface of the electrostatic conveyance roller and when the surface is smooth. FIG. 3 is an explanatory diagram of a configuration in which a toner repulsion electrode plate is provided on the surface of an electrostatic conveyance roller. The schematic diagram of arrangement | positioning of the several electrode of the electrostatic conveyance roller which concerns on a modification. The graph which shows the result of Experiment 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Transfer material conveyance belt 3 Fixing device 4 Optical writing device 5 Paper feeding device 9 Transfer roller 10 Developing device 11 Photoconductor 12 Charging roller 12a Core metal 12b Urethane foam layer 13 Electrostatic conveyance roller 14 Cleaning device 14a Cleaning blade 14b Waste toner storage unit 15 Supply roller 15a Sleeve 15b Magnet roller 16 Doctor blade 17 Stirring screw 18 Developer storage unit 26 P sensor 30 Recovery power source 100 Printer 103a Electrostatic transfer surface 130 Electric field region 130e Transfer electrode terminal unit 130s Transfer electrode start end 131 Supply area 132 Upstream transport area 133 Development area 134 Downstream transport area 135 Collection area 136 Non-electric field area 137 Toner repulsion electrode plate 139 Normal transport area 200 Conductive plate 201 Vibrator 202 Development electrode 02 collected electrode 402 Non field electrodes

Claims (14)

An electrostatic transport unit having an electrostatic transport surface capable of transporting toner particles by a phase-shifting electric field, and a toner supply unit facing the upstream end of the electrostatic transport surface in the toner transport direction,
The toner particles supplied by the toner supply means are transported on the electrostatic transport surface to a developing area that is opposite to the latent image carrier, and are used to develop a latent image on the latent image carrier. To contribute,
In a developing device having a toner collecting means for collecting the toner particles conveyed to the downstream side in the toner conveying direction of the developing area without contributing to development in the developing area,
A developing device, wherein the toner collecting means is provided so that the collecting means is opposed to a downstream end portion of the electrostatic conveying surface, which is a terminal portion of the phase-shift electric field, in the toner conveying direction. The developing device according to claim 1.
A developing device, wherein the toner particles recovered by the toner recovery means are returned to the toner supply means, and are formed in an annular shape by separating both ends of the electrostatic transport surface in the toner transport direction. The developing device according to claim 2.
A second electrostatic transport surface capable of transporting the toner particles by the phase-shift electric field is also provided between both ends of the toner transport direction, and the second electrostatic transport surface has a predetermined surface other than during image formation. A developing apparatus characterized in that the phase-shift electric field is formed at a timing. The developing device according to claim 2 or 3,
The developing device according to claim 1, wherein the member formed between the both ends of the toner conveying direction is made of an insulator. The developing device according to claim 1, 2, 3 or 4,
The developing device according to claim 1, wherein the toner collecting means includes a collecting member made of a conductive member, and forms a collecting electric field between the collecting member and the electrostatic conveyance surface. The developing device according to claim 5.
The developing device according to claim 1, wherein the recovery member is not in contact with the electrostatic conveyance surface. The developing device according to claim 5 or 6,
The developing device, wherein the recovery member is a conductive plate that applies a bias having a polarity opposite to that of the toner particles. The developing device according to claim 5 or 6,
The developing device, wherein the collecting member is a conductive roller that applies a bias having a polarity opposite to that of the toner particles. The developing device according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The developing device, wherein the toner collecting means includes a collecting member that comes into contact with the toner particles at the time of collecting, and has a collected toner separating means for separating the toner particles attached to the collecting member. The developing device according to claim 1, 2, 3 or 4,
The developing device according to claim 1, wherein the toner collecting unit includes an air flow generation member and collects the toner particles on the electrostatic transport surface by a force of the air flow. The developing device according to claim 10.
A surface that does not form a phase-shifting electric field is provided between both ends of the toner conveyance direction, and a step is provided so that the surface that does not form the phase-shifting electric field is inside the annular surface with respect to the electrostatic conveyance surface. A developing device. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.
The developing device according to claim 1, wherein the electrostatic transfer surface is made of a non-magnetic material. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
A developing device characterized in that an area where the toner collecting means collects toner is a toner collecting area, and in the toner collecting area, the toner transport speed is decreased. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier into a toner image.
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13.

Images