JP2012194306A - Developer supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably suppress an occurrence of a state where developer is not appropriately supplied to a supply target from a conveyance substrate due to charge up of a surface of the conveyance substrate in a region facing the supply target.SOLUTION: A developer electric field conveying device includes a plurality of conveyance electrodes arranged along a developer conveyance route, an insulating electrode supporter for supporting the conveyance electrodes, a cover layer arranged at a developer conveyance route side compared to the conveyance electrodes so that the developer is conveyed on a developer conveyance surface being a surface facing the developer conveyance route, and an intermediate electrode arranged between the developer conveyance surface and the supply target.

Description

  The present invention relates to a developer electric field conveying device configured to convey a charged powdery developer by a traveling wave electric field.

  Many devices that convey a developer (toner) using a traveling-wave electric field have been conventionally known (see, for example, JP-A Nos. 2002-287495 and 2004-279903). This type of apparatus (hereinafter referred to as “developer electric field transport apparatus”) includes a transport substrate having a large number of linear electrodes arranged along the transport direction of the developer.

  In the above-described configuration, a traveling-wave electric field is formed by applying a multiphase AC voltage to a large number of the linear electrodes. The charged developer is transported along the arrangement direction of the linear electrodes by the action of the electric field, and then faces a supply target such as an electrostatic latent image carrier or a developer carrier (developing roller). It is supplied to the supply object at the position.

  In this type of apparatus, when the surface of the transport substrate is charged up in a region facing the supply target, a state occurs in which the developer is not satisfactorily supplied from the transport substrate to the supply target. obtain. The present invention has been made to solve such problems.

  The developer electric field transport device of the present invention transports the developer charged to a predetermined polarity while transporting the powdered developer charged to a predetermined polarity along a predetermined developer transport path by a traveling wave electric field. It is comprised so that it may supply with respect to the supply object which has a surface potential which attracts | sucks electrostatically. The developer electric field transport device is disposed to face the supply target.

  As the supply target, for example, an electrostatic latent image carrier (photoconductor) that carries an electrostatic latent image on its surface can be used. Alternatively, as the supply target, in order to develop the electrostatic latent image formed on the electrostatic latent image carrier with the developer, the electrostatic latent image carrier is disposed to face the electrostatic latent image carrier. A developer carrier (developing roller or developing sleeve) configured to carry the developer may be used.

  The developer electric field transport device includes an electrode support, a cover layer, and a plurality of transport electrodes. A transport substrate is constituted by the electrode support, the cover layer, and the plurality of transport electrodes.

  The plurality of transport electrodes are arranged along the developer transport path so that the developer is transported along the developer transport path by the electric field generated in response to application of a driving voltage including a multiphase AC voltage. It is arranged. The electrode support is made of an insulating material, and is provided on the same side as the transport electrode with respect to the developer transport path so as to support the transport electrode.

  The cover layer is a layer made of an insulating material (for example, a material charged to a polarity opposite to the predetermined polarity by friction with the developer), and covers the transport electrode and the electrode support. Is formed. That is, the cover layer is closer to the developer transport path than the transport electrodes so that the developer is transported on the developer transport surface (the surface of the cover layer facing the developer transport path). Has been placed.

  A feature of the present invention resides in that the developer electric field transport device further includes an intermediate electrode disposed between the developer transport surface (the transport substrate) and the supply target. The intermediate electrode is set to a potential between the peak potential on the predetermined polarity side of the drive voltage and the surface potential of the supply target. The intermediate electrode is formed with an opening that allows the developer to pass from the developer transport surface toward the supply target.

  The intermediate electrode may be a plurality of wires that are stretched in a direction intersecting the developer transport path and arranged along the developer transport path. In this case, the opening is formed by a space between the adjacent wires.

  The intermediate electrode may be disposed closer to the developer transport surface than an intermediate position between the developer transport surface and the supply target.

The intermediate electrode is
When the application state of the multiphase AC voltage to the plurality of transport electrodes is viewed in the direction along the developer transport path, and T is the spatial potential period in the direction,
It may be arranged such that a distance between a transport surface side end that is an end closest to the developer transport surface and the developer transport surface is T / 2 or more.

  As one of the causes of charge-up of the developer transport surface (the transport substrate), it is conceivable that ions are generated due to the charge of the developer. That is, in a region where the supply target and the developer transport surface face each other, a predetermined potential gradient is formed by an electric field for transferring the developer charged to the predetermined polarity to the supply target side. . By superimposing such a potential gradient and a local potential gradient generated in the vicinity of the developer transport surface due to the presence of the developer on the developer transport surface, in the vicinity of the developer transport surface. A steep potential gradient occurs.

  When the potential gradient in the vicinity of the developer transport surface exceeds the discharge limit, air is ionized and ions are generated. A part of the generated ions adhere to the developer transport surface, and the other part (especially the ions of the predetermined polarity) moves to the supply target side, so that the charge on the developer transport surface is reduced. An imbalance occurs, which causes a charge up (especially with a polarity opposite to the predetermined polarity).

  In this respect, in the developer electric field transport device of the present invention having the above-described configuration, the developer transport surface and the supply are provided by providing the intermediate electrode between the developer transport surface and the supply target. The potential gradient in the portion close to the developer transport surface in the region between the objects (that is, the region between the developer transport surface and the intermediate electrode) becomes small. As a result, the occurrence of ionization of air near the developer transport surface and the occurrence of surface charge imbalance on the developer transport surface as described above are suppressed as much as possible.

  Thus, in the present invention, charge-up of the developer transport surface (the transport substrate) is suppressed as much as possible. Therefore, according to the present invention, the supply of the developer to the supply target (for developing the electrostatic latent image formed on the electrostatic latent image carrier or for developing the electrostatic latent image). (Carrying of the developer on the developer carrying member) can be performed even better.

1 is a side view showing a schematic configuration of a laser printer as an image forming apparatus to which an embodiment of the present invention is applied. FIG. 2 is an enlarged side sectional view of the toner supply device shown in FIG. 1. FIG. 3 is an enlarged side cross-sectional view of the transport substrate shown in FIG. 2. It is a graph which shows an example of the output waveform of each power supply circuit shown by FIG. It is a figure for demonstrating the principle of this invention. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2. FIG. 3 is a diagram showing electric field simulation results in the vicinity of the toner carrying position shown in FIG. 2.

<Configuration>
FIG. 1 is a side view showing a schematic configuration of a laser printer 1 as an image forming apparatus to which an embodiment of the present invention is applied. Referring to FIG. 1, the laser printer 1 includes a paper transport mechanism 2, a photosensitive drum 3, a charger 4, a scanner unit 5, and a toner supply device 6. Sheet-like paper P is stored in a stacked state in a paper feed tray (not shown) provided in the laser printer 1. The paper transport mechanism 2 is configured to transport the paper P stored in the above-described paper feed tray one by one along a predetermined paper transport path PP.

  An electrostatic latent image carrying surface LS is formed on the peripheral surface of the photosensitive drum 3. The electrostatic latent image carrying surface LS is a cylindrical surface parallel to the main scanning direction (z-axis direction in the figure: also referred to as the paper width direction or simply the width direction), and an electrostatic latent image is formed by a potential distribution. In addition, the toner T (see FIG. 2) is carried at a position corresponding to the electrostatic latent image. The photosensitive drum 3 is driven to rotate in a predetermined direction (counterclockwise in the figure) around a drum rotation center axis C parallel to the main scanning direction, and thus along the sub-scanning direction orthogonal to the main scanning direction. The electrostatic latent image carrying surface LS is configured to move.

  The charger 4 is arranged to face the electrostatic latent image carrying surface LS so as to uniformly and positively charge the electrostatic latent image carrying surface LS. The scanner unit 5 scans along the main scanning direction while forming the laser beam LB modulated based on the image data on the electrostatic latent image carrying surface LS at the scanning position SP, thereby scanning the electrostatic latent image. An electrostatic latent image is formed on the support surface LS.

  The toner supply device 6 is opposed to the electrostatic latent image carrying surface LS at the developing position DP downstream of the scanning position SP in the moving direction of the electrostatic latent image carrying surface LS due to the rotation of the photosensitive drum 3. The photosensitive drum 3 is disposed below. The toner supply device 6 is configured to supply the positively charged toner T (see FIG. 2) to the electrostatic latent image carrying surface LS at the development position DP. Next, the specific configuration of each part of the laser printer 1 will be described in more detail.

  The sheet transport mechanism 2 includes a pair of registration rollers 21 and a transfer roller 22. The registration roller 21 moves the electrostatic latent image carrying surface LS due to the rotation of the photosensitive drum 3 from the transfer position TP (the development position DP) between the photosensitive drum 3 and the transfer roller 22 at a predetermined timing. It is configured to send out toward the downstream side in the direction. The transfer roller 22 is disposed so as to face the electrostatic latent image carrying surface LS at the transfer position TP with the paper transport path PP (paper P) interposed therebetween, and is opposite to the rotation direction of the photosensitive drum 3. It is rotationally driven (clockwise in the figure). The transfer roller 22 is connected to a transfer bias power supply circuit (not shown), and a predetermined transfer bias voltage for transferring the toner T (see FIG. 2) attached on the electrostatic latent image carrying surface LS to the paper P. Is applied.

<< Toner Supply Device >>
FIG. 2 is an enlarged side cross-sectional view of the toner supply device 6 shown in FIG. Referring to FIG. 2, a casing 60 forming a main body frame of the toner supply device 6 is a box-shaped member that is formed in a substantially U shape in a side sectional view and has a longitudinal direction in the vertical direction (y-axis direction in the drawing). A main casing 60a is provided. That is, an opening 60 a 1 is provided at the top of the main casing 60 a and at a position facing the photosensitive drum 3 so as to open upward toward the photosensitive drum 3. Powder toner T (dry developer) is accommodated in a toner reservoir 60a2, which is a space inside a substantially semi-cylindrical portion at the bottom of the main casing 60a. In this embodiment, as the toner T, a positively chargeable, nonmagnetic one-component, black toner is used.

  A substantially cylindrical sub casing 60b having a central axis parallel to the main scanning direction is provided so as to be parallel to the bottom of the main casing 60a. The powdered toner T is also stored in the auxiliary toner storage portion 60b1, which is a space inside the sub casing 60b. The toner reservoir 60a2 at the bottom of the main casing 60a and the auxiliary toner reservoir 60b1, which is the space inside the sub casing 60b, are connected (communicated) to each other through the communication holes 60c at both ends in the main scanning direction. ing.

  A first auger 61a is accommodated in the bottom of the main casing 60a. The first auger 61a includes a shaft 61a1 that forms a rotation center axis along the main scanning direction, and a spiral blade 61a2 provided around the shaft 61a1. The first auger 61a is moved in a first direction (for example, the z-axis positive direction in the figure) parallel to the main scanning direction while stirring the toner T in the toner storage portion 60a2 as the shaft 61a1 is rotationally driven. It is configured to let you.

  A second auger 61b is accommodated in the sub casing 60b. Similar to the first auger 61a, the second auger 61b includes a shaft 61b1 and a blade 61b2. The second auger 61b is configured to move the toner T in the auxiliary toner reservoir 60b1 in a direction opposite to the moving direction by the first auger 61a while the shaft 61b1 is rotationally driven. Yes. In other words, the first auger 61a and the second auger 61b are configured to circulate the toner T in the toner reservoir 60a2 and the auxiliary toner reservoir 60b1 while stirring.

  The developing roller 62 corresponding to the “supply target” of the present invention is a roller-like member having a toner carrying surface 62 a that is a cylindrical circumferential surface, and is provided so as to face the photosensitive drum 3. . In the present embodiment, the developing roller 62 has a central axis (hereinafter referred to as “developing roller rotation central axis C1”) positioned inside the main casing 60a, so that the developing roller 62 is substantially above the toner carrying surface 62a. Half is accommodated in casing 60 so that the outside of main casing 60a is exposed.

  The developing roller 62 is rotatably supported at the upper end portion of the main casing 60a where the opening 60a1 is formed. In other words, the developing roller 62 rotates about the developing roller rotation center axis C1 parallel to the main scanning direction, thereby moving the toner carrying surface 62a in a direction perpendicular to the main scanning direction, and on the toner carrying surface 62a. The toner T carried on the toner is supplied to the developing position DP.

  Inside the main casing 60a, a transport substrate 63 is provided along a toner transport path TTP formed in a substantially oval shape having a longitudinal direction in the vertical direction in a side sectional view (the toner transport direction). TTD is a tangential direction of the toner transport path TTP.) The transfer substrate 63 is fixed to the inner wall surface of the main casing 60a.

  The transport substrate 63 constituting the “developer electric field transport device” of the present invention is configured to transport the toner T by a traveling wave electric field on the toner transport surface TTS which is a surface along the toner transport path TTP. Yes. In the present embodiment, the transport substrate 63 includes a bottom transport substrate 63a, a vertical transport substrate 63b, and a recovery substrate 63c.

  The bottom conveyance substrate 63a is fixed to the inner wall surface of the main casing 60a at the bottom in the space inside the main casing 60a so as to constitute the bottom surface of the toner storage portion 60a2. The bottom conveyance board 63a is a concave curved plate-like member that is bent into a semi-cylindrical shape in a sectional side view and opens upward, and the toner T in the toner reservoir 60a2 is directed toward the lower end of the vertical conveyance board 63b. It is smoothly connected to the lower end of the flat vertical transfer board 63b so as to be smoothly transferred.

  The vertical transfer substrate 63b is fixed to the inner wall surface of the main casing 60a, and is erected so as to transfer the toner T vertically upward from the lower end connected to the bottom transfer substrate 63a. The upper end portion of the vertical transport substrate 63b is provided at substantially the same height as the center of the developing roller 62. The upper end portion is provided so as to face the cylindrical toner carrying surface 62 a of the developing roller 62. At the toner carrying position TCP where the upper end portion of the vertical conveyance substrate 63b and the toner carrying surface 62a are closest to each other and facing each other, a gap of a predetermined interval is provided between them.

  In the present embodiment, the bottom transfer board 63a and the vertical transfer board 63b are integrally formed in a reversed J shape in a seamless manner in a side sectional view. The vertical conveyance board 63b conveys the toner T delivered from the bottom conveyance board 63a vertically upward toward the toner carrying position TCP on the upstream side in the moving direction of the toner carrying surface 62a from the development position DP. It is configured as follows.

  Further, in the present embodiment, the upstream portion in the toner transport direction (that is, the vertical portion) (ie, the vertical portion of the transport substrate 63 in the integral transport side view of the bottom transport substrate 63a and the vertical transport substrate 63b). A portion where the lower end portion of the transfer substrate 63b and the bottom transfer substrate 63a are combined (which may also be referred to as “upstream end portion”) is provided in non-contact with the first auger 61a and faces the toner storage portion 60a2. By doing so, it is provided so as to be immersed in the toner T stored in the toner storage section 60a2.

  The collection substrate 63c is provided on the opposite side of the upper end portion of the vertical conveyance substrate 63b with the developing roller 62 therebetween so as to face the developing roller 62 with a predetermined gap, and is consumed at the developing position DP. The toner T that has not been collected is collected from the developing roller 62 and conveyed toward the lower toner storage portion 60a2.

  A grid electrode 64 as an “intermediate electrode” constituting the “developer electric field transport device” of the present invention is disposed between the toner transport surface TTS and the toner carrying surface 62a and in the vicinity of the toner carrying position TCP. Has been. In the present embodiment, the grid electrode 64 is a thin (specifically, φ200 μm) tungsten wire, and is stretched parallel to the main scanning direction. The grid electrode 64 is provided at a position slightly closer to the toner transport surface TTS than an intermediate position between the toner transport surface TTS and the toner carrying surface 62a (details will be described later).

  In the present embodiment, the plurality of grid electrodes 64 are arranged in parallel with each other in the toner transport direction TTD. Between adjacent grid electrodes 64, a gap (opening: specifically, twice the electrode pitch) that allows the positively charged toner T (primary particle diameter: about 5 to 10 μm) to pass well. (That is, about 400 μm) is formed.

  The bottom transfer substrate 63a and the vertical transfer substrate 63b in the transfer substrate 63 are electrically connected to the supply transfer power supply circuit 66a. The supply conveyance power supply circuit 66a supplies supply conveyance biases (refer to VA to VD in FIG. 3 and FIG. 4) that are multiphase AC voltages necessary for electric field conveyance of the toner T in the toner reservoir 60a2 toward the toner carrying position TCP. : As a specific example, a voltage [+ 200V to + 800V]) in which a DC voltage component of +500 V and a four-phase AC voltage component having an amplitude of 300 V and a frequency of 300 Hz are superimposed is output.

  The developing roller 62 is electrically connected to the developing bias power supply circuit 66b. The developing bias power supply circuit 66b moves the positively charged toner T from the upper end portion of the vertical transport substrate 63b to the toner carrying surface 62a side at the toner carrying position TCP to carry it on the toner carrying surface 62a, and also carries the toner carrying surface 62a. In order to develop an electrostatic latent image at the development position DP using the toner T carried thereon, a development bias (specifically, a +200 V DC voltage component, an amplitude of 1300 V and a frequency of 2 kHz, which is a necessary voltage) is developed. A voltage [−1100 V to +1500 V]) in which the AC voltage component is superimposed is applied to the developing roller 62.

  The collection substrate 63c is electrically connected to the collection conveyance power supply circuit 66c. The recovery conveyance power supply circuit 66c collects the toner T on the toner carrying surface 62a that has not been consumed at the development position DP from the developing roller 62, and multiphase necessary for electric field conveyance toward the lower toner storage portion 60a2. The recovery conveyance bias which is an AC voltage (see VA to VD in FIG. 3 and FIG. 4, however, the DC voltage component is different from the above-described supply conveyance bias by the supply conveyance power supply circuit 66 a. As a specific example, a DC voltage component of −500 V And a voltage [-200 V to -800 V]) in which a four-phase AC voltage component having an amplitude of 300 V and a frequency of 300 Hz is superimposed is output.

  That is, the supply transport power supply circuit 66a, the recovery transport power supply circuit 66c, and the development bias power supply circuit 66b circulate the toner T in the toner transport direction TTD along the toner transport path TTP (develop the toner T in the toner storage section 60a2). A voltage necessary to supply the toner T to the developing position DP while being carried by the roller 62 and to collect the toner T that has not been consumed at the developing position DP from the developing roller 62 and return it to the lower toner storage portion 60a2. It is designed to output.

  The grid electrode 64 is electrically connected to the grid power supply circuit 66d. The grid power supply circuit 66d has an average value of the grid electrode 64, the peak potential of the positive side of the supply and transport bias (the same polarity as the charging polarity of the toner T) and the surface potential of the developing roller 62 (potential of the toner carrying surface 62a). A grid bias (a DC voltage of +500 V in the above-described specific example), which is a voltage necessary for setting the potential between, is output.

  FIG. 3 is an enlarged side sectional view of the transfer board 63 shown in FIG. Referring to FIG. 3, the transport substrate 63 is a thin plate-like member and has the same configuration as that of the flexible printed circuit board. Specifically, the transport substrate 63 includes a transport electrode 631, a transport electrode support film 632, an intermediate layer 633, and a cover layer 634. The transport electrode 631 is a linear wiring pattern having a longitudinal direction parallel to the main scanning direction, and is formed of, for example, copper foil.

  The plurality of transport electrodes 631 are arranged along the toner transport path TTP and are arranged in parallel to each other (for example, the width in the direction parallel to the toner transport path TTP is 100 μm, and adjacent transport electrodes 631 in the same direction. The distance between them (the gap in the toner transport direction TTD) is 100 μm.) Each of the plurality of transport electrodes 631 arranged along the toner transport path TTP is connected to the same power supply circuit (VA to VD) every third. In the present embodiment, as shown in FIG. 4, the power supply circuits VA to VD are configured to output drive voltages that are alternating voltages having substantially the same waveform and different phases by 90 °. .

  The plurality of transport electrodes 631 are formed on the surface of the transport electrode support film 632. The transport electrode support film 632 corresponding to the “electrode support” of the present invention is a flexible film, and in this embodiment, is made of an insulating synthetic resin (for example, polyimide resin). The transport electrode support film 632 is provided to support the transport electrode 631 on the same side as the transport electrode 631 with respect to the toner transport path TTP.

  The cover layer 634 is disposed on the same side as the transport electrode 631 with respect to the toner transport path TTP and closer to the toner transport path TTP than the transport electrode 631. The cover layer 634 is made of an insulating synthetic resin (for example, polyester resin), and is provided as an outermost layer on the transport substrate 63 so as to cover the transport electrode 631 and the transport electrode support film 632. The toner transport surface TTS is a surface facing the toner transport path TTP of the cover layer 634, and is formed as a smooth surface with very few irregularities so that the toner T can be transported smoothly.

  The intermediate layer 633 is provided between the surface of the transport electrode support film 632 where the transport electrode 631 is provided and an adhesive layer between the transport electrode 631 and the cover layer 634. In the present embodiment, the intermediate layer 633 is made of an insulating synthetic resin (for example, a polyimide resin).

<Overview of operation>
Next, an outline of the operation of the laser printer 1 configured as described above will be described with reference to the drawings as appropriate.

  In the configuration described above, the cooperation of the first auger 61a and the second auger 61b causes the toner T in the toner reservoir 60a2 to move in the first direction parallel to the main scanning direction while being stirred, and to assist the toner. The toner T in the storage unit 60b1 moves in the second direction (the direction opposite to the first direction described above) while being stirred, so that the toner T in the toner storage unit 60a2 and the auxiliary toner storage unit 60b1 is stirred. It circulates while being done. As a result, the toner T stored in the toner storage unit 60a2 and immediately before being conveyed by the transfer substrate 63 is stirred, and the storage level of the toner T in the toner storage unit 60a2 is stabilized.

  In addition, since the toner T is circulated between the toner storage unit 60a2 and the auxiliary toner storage unit 60b1 by the first auger 61a and the second auger 61b, the starting unit (the transport substrate 63, that is, the bottom transport substrate 63a and the vertical transport substrate). The toner T remaining without being transported by the transport substrate 63 in the vicinity of the portion where the electric field transport of the toner T by 63b is started can be satisfactorily charged. That is, the first auger 61a and the second auger 61b can secure a time for the toner T to be agitated, thereby increasing the chances of the toner T being charged.

  As described above, the toner T in the toner storage unit 60a2 that has been fluidized satisfactorily by agitation and circulation and has a stable storage level, is supported on the toner transport surface TTS by the supply transport bias. The electric field is conveyed in the toner conveyance direction TTD toward the position TCP. Such electric field transfer is performed in the vicinity of a position where the above-described activation unit (specifically, the storage level of the toner T in the toner storage unit 60a2 and the lower end portion or the bottom transfer substrate 63a of the vertical transfer substrate 63b are in contact with each other). ) Substantially starts.

  The toner T started to be transported by the activation unit is transported by an electric field toward the toner carrying position TCP. In the middle of the process, the toner T may be further charged by contact or friction with the surface of the cover layer 634 (toner transport surface TTS). The toner T conveyed to the toner carrying position TCP by the vertical carrying substrate 63b is carried on the toner carrying surface 62a by the action of the supply carrying bias and the developing bias at and near the toner carrying position TCP.

  The toner T is supplied to the development position DP as the toner carrying surface 62a moves to the development position DP by the rotational drive of the development roller 62. In the vicinity of the developing position DP, the electrostatic latent image formed on the electrostatic latent image carrying surface LS is developed with the toner T by the action of the developing bias. That is, the toner T moves from the toner carrying surface 62a and adheres to the portion on the electrostatic latent image carrying surface LS where the positive charge in the electrostatic latent image has disappeared. As a result, an image of toner T (hereinafter referred to as “toner image”) is carried on the electrostatic latent image carrying surface LS.

  The toner T on the toner carrying surface 62a that has passed through the development position DP (not consumed at the development position DP) moves to the collection substrate 63c side by the action of the development bias and the collection conveyance bias described above. That is, the toner is recovered from the toner carrying surface 62a by the recovery substrate 63c. The toner T that has successfully moved to the collection substrate 63c side is conveyed vertically downward by the action of the collection conveyance bias described above, and is favorably returned to the toner storage unit 60a2.

<Operation and Action / Effect by Configuration of Embodiment>
Next, operations and effects achieved by the configuration of the present embodiment as described above will be described with reference to the drawings as appropriate.

  FIG. 5 is a diagram for explaining the principle of the present invention. (I) in FIG. 5 is a graph showing a change in potential in the direction from the toner transport surface TTS to the toner carrying surface 62a at the toner carrying position TCP when the grid electrode 64 is not provided. In the figure, the horizontal axis indicates the position in the direction toward the toner carrying surface 62a with respect to the toner transport surface TTS (that is, the distance from the toner transport surface TTS). For the sake of simplicity of illustration and explanation, it is assumed that the average potential of the supply transport bias is used as the potential of the toner transport surface TTS (the potential on the horizontal axis 0).

  Referring to (i) in FIG. 5, when the presence of the positively charged toner T on the toner transport surface TTS is ignored, the toner transport surface TTS (x axis value is 0) to the toner carrying surface 62a (x axis) The potential gradient until the value of R is substantially linear (in fact, due to the presence of an insulating layer such as the cover layer 634, as shown on the left side of the broken line in (ii) in FIG. A slightly steep curved portion occurs in the vicinity of the toner transport surface TTS.)

  On the other hand, considering the presence of the positively charged toner T on the toner transport surface TTS, the toner transport surface as shown by a solid line in FIG. The potential gradient is very steep locally near the TTS. When this potential gradient exceeds the discharge limit, the air is ionized and positive ions and negative ions are generated. The generated negative ions are all transferred to the toner transport surface TTS side, which is the high potential side. On the other hand, some of the positive ions move to the toner carrying surface 62a side, which is a low potential side, and a part thereof is on the toner transport surface TTS side toward the transport electrode 631 corresponding to the negative peak potential of the supply transport bias. Migrate to

  Here, since the developing roller 62 is conductive or semiconductive, the charge due to the positive ions transferred and attached to the developing roller 62 is released from the toner carrying surface 62a to the metal central shaft side of the developing roller 62, Since the material of the outermost layer of the transport substrate 63 constituting the toner transport surface TTS is insulative, some of the negative ions that have migrated to the toner transport surface TTS remain on the toner transport surface TTS (the remainder is the toner transport surface). It is neutralized by positive ions that have moved to the surface TTS side).

  As a result, a charge imbalance such that positive ions are relatively deficient occurs on the toner transport surface TTS. Due to such charge imbalance, the toner transport surface TTS is charged up to a negative polarity. In particular, the material constituting the outermost layer of the transport substrate 63 (in this embodiment, the cover layer 634) is a material on the negative polarity side in the triboelectric charging series, or by friction with the toner T (base material or external additive). When the material is negatively charged, the negative charge-up becomes significant. When such a charge-up occurs, the positive toner T is electrostatically attracted to the charge-up portion, thereby inhibiting the toner T from being transported in the toner transport direction TTD and being carried on the toner carrying surface 62a. End up.

  In this regard, in the present invention, as shown by the solid line (ii) in FIG. 5, by providing the grid electrode 64, a potential gradient (almost) is generated between the toner transport surface TTS and the grid electrode 64. (A broken line indicates a potential gradient when the grid electrode 64 is not provided.). As a result, the amount of positive ions transferred to the developing roller 62 side can be suppressed, and thus negative charge-up of the toner transport surface TTS is suppressed as much as possible. Furthermore, since the potential gradient in the space on the toner carrying surface 62a side with respect to the grid electrode 64 is increased, the toner T that has passed through the grid electrode 64 due to inertia is favorably carried on the toner carrying surface 62a.

  Note that the set potential (grid bias) of the grid electrode 64 is the peak potential (+800 V in the above specific example) on the plus side of the supply and transport bias (the same polarity as the charging polarity of the toner T), and the surface potential of the developing roller 62. Between the average value (+200 V in the above specific example) (typically +500 to +600 V in the above specific example), typically set to approximately the same potential as the average potential (DC voltage component) of the supply transport bias. It is preferred that

FIG. 6 is a diagram showing electric field simulation results (an arrow indicating the force received by the equipotential lines and unit positive charges) in the vicinity of the toner carrying position TCP shown in FIG. The simulation conditions are as follows (for convenience of simulation and explanation, various values such as the bias voltage may be different from the values of the specific examples in the above description of the device configuration).
Transport electrode support film: thickness 25 μm, relative dielectric constant (εr) 5
Transport electrode: width 100 μm, interval 100 μm (pitch 200 μm), thickness 18 μm
Intermediate layer: 25 μm thick on electrodes / 43 μm thick between electrodes, εr2.3
Cover layer: 12.5 μm thick, εr4
Air layer above cover layer: thickness 3mm, εr1.0
Developing roller surface potential: 0V
Supply bias: + 300V / + 900V square wave (4 phase)
Grid electrodes: φ200 μm, spacing (opening OP width) 400 μm, +600 V
Grid position (position of the wire center from the top surface of the cover layer): 1mm

  FIG. 7 is a graph showing the potential gradient at the positions of lines 1 to 4 shown in FIG. 6 (in FIG. 7, the upper peak value is about +800 V, and the supply transport bias upper limit value under the simulation conditions described above) This is considered to be due to the influence of the intermediate layer and the cover layer on the substrate surface side with respect to the transport electrode, which is the same in FIGS. 8, 9, and 11.) .

  Here, the potential of the transport electrode 631 at the position corresponding to line 1 and the transport electrode 631 on the right side in FIG. 7 is +900 V, and the potential of the transport electrode 631 at the position corresponding to line 2 and the transport electrode 631 on the left side in FIG. Is assumed to be + 300V. That is, line1 is a position corresponding to the transport electrode 631 having a potential of + 900V, and line4 is a middle position between adjacent transport electrodes 631 having a potential of + 900V. Further, line2 is a position corresponding to the transport electrode 631 having a potential of + 300V, and line3 is an intermediate position between the transport electrode 631 having a potential of + 300V and the transport electrode 631 having a potential of + 900V. In FIG. 7, (i) shows a potential gradient in line 1 and line 4, and (ii) shows a potential gradient in line 2 and line 3.

  Referring to the simulation conditions described above, FIG. 7 shows that the distance between the transport surface side end 641 (see FIG. 6) that is the end closest to the toner transport surface TTS in the grid electrode 64 and the toner transport surface TTS is as follows. The potential gradient in the case of 900 μm is shown.

  As shown in FIG. 7, although the potential gradient in the vicinity of the toner conveyance surface TTS in line 1 is large, the potential gradient in the vicinity of the toner conveyance surface TTS in lines 2 to 4 suppresses ionization due to the above-described local potential gradient. It is small enough. Further, in the range between the toner transport surface TTS and the grid electrode 64 (the range of 0 to 1 on the horizontal axis), the generated positive ions pass through the opening OP between the grid electrodes 64 to the toner carrying surface 62a side. A potential gradient that suppresses the transfer is generated (however, the positively charged toner T flies from the toner conveyance surface TTS due to the potential gradient of the right lowering in the vicinity of the toner conveyance surface TTS in line 1 and line 4, and due to inertia. It can pass through the opening OP between the grid electrodes 64).

  FIG. 8 is a graph showing a potential gradient when the grid position is 0.25 mm. FIG. 9 is a graph showing (i) a grid position of 0.25 mm and (ii) a grid position of 1 mm in comparison. FIG. 10 is a diagram showing an arrow indicating the force received by the equipotential line and the unit positive charge in comparison with (i) grid position 0.25 mm and (ii) grid position 1 mm. When the grid position is 0.25 mm, the distance between the transport surface side end 641 (see FIG. 10) and the toner transport surface TTS is 150 μm. FIG. 11 is a graph showing a comparison between the case where the grid position is changed to 1.5 mm, 1 mm, and 0.25 mm and the case where the grid electrode 64 is not provided.

  7 to 11, by securing a certain distance between the toner transport surface TTS and the grid electrode 64 (transport surface side end portion 641), the toner transport surface TTS and the grid electrode 64 are A region having a gentle (approximately horizontal) potential gradient can be formed, thereby achieving suppression of charge-up and good flight of the toner T toward the toner carrying surface 62a. On the other hand, if the grid position is too close to the toner transport surface TTS, the effect of suppressing positive ions from flying toward the toner carrying surface 62a is diminished, and the toner T is transported in the toner transport direction TTD. There is a possibility that the formation of the traveling wave electric field and the conveyance of the toner T in the toner conveyance direction TTD itself are hindered.

  The optimum grid position is considered to vary depending on the number of phases of the multiphase AC voltage, the width and pitch of the transport electrodes 631, and the outer diameter of the grid electrode 64. In this regard, when the application state of the multiphase AC voltage to the plurality of transport electrodes 631 is viewed in the direction along the toner transport path TTP, the spatial potential period in the direction is T (800 μm in the above specific example). Then, when the grid position is 1 mm (the distance between the transport surface side end portion 641 and the toner transport surface TTS is approximately equal to T and slightly larger 900 μm), a favorable potential gradient is formed, whereas the grid position is In the case of 0.25 mm (the above-mentioned interval is 150 μm smaller than T / 2), it is considered that the grid electrode 64 is too close to the toner transport surface TTS side. Considering that the range in which the traveling wave electric field is spatially strong is approximately T / 2 (see FIGS. 6 and 10), the distance between the transport surface side end portion 641 and the toner transport surface TTS is T / It is considered that the grid electrode 64 is preferably arranged so as to be 2 or more (in the above specific example, the grid position is 0.5 or more).

<List of examples of modification>
Note that, as described above, the above-described embodiments are merely examples of typical embodiments of the present invention that the applicant has considered to be the best at the time of filing of the present application. Therefore, the present invention is not limited to the above-described embodiment. Therefore, it goes without saying that various modifications can be made to the above-described embodiment within the scope not changing the essential part of the present invention.

  Hereinafter, some typical modifications will be exemplified. In the following description of the modified examples, the same reference numerals as those in the above embodiment can be used for members having the same configuration and function as those described in the above embodiment. And about description of this member, the description in the above-mentioned embodiment shall be used in the range which is not technically consistent.

  Needless to say, the modifications are not limited to those listed below. In addition, a plurality of modified examples can be applied in a composite manner as appropriate within a technically consistent range.

  The present invention (especially those expressed in terms of action and function in each component constituting the means for solving the problems of the present invention) is based on the description of the above embodiment and the following modifications. It should not be interpreted in a limited way. Such a limited interpretation, while improperly harming the applicant's interests (rushing to file under an earlier application principle), improperly imitates the patent for the protection and use of the invention Contrary to the purpose of the law, it is not allowed.

  The application target of the present invention is not limited to a monochromatic laser printer. For example, the present invention can be suitably applied to a so-called electrophotographic image forming apparatus such as a color laser printer or a monochromatic and color copying machine. At this time, the shape of the photosensitive member may not be a drum shape as in the above-described embodiment. For example, a flat plate shape or an endless belt shape may be used. Further, the charging polarity of the toner T is not limited to the positive polarity.

  As the exposure light source, other than the laser scanner (LED, EL (electroluminescence) element, phosphor, etc.) can be suitably used. In this case, the “main scanning direction” is an arrangement direction of exposure light source elements (light emitting elements) such as LEDs. Alternatively, the present invention is also suitably applied to an image forming apparatus of a system other than the above-described electrophotographic system (for example, a toner jet system that does not use a photoreceptor, an ion flow system, a multistylus electrode system, etc.) obtain.

  The configuration and arrangement of the transfer substrate 63 are not limited to those specifically disclosed in the above embodiment. For example, the vertical transfer substrate 63b may be erected substantially along the vertical direction, and may be slightly inclined. Similarly, the collection substrate 63c may be slightly inclined. Alternatively, the collection substrate 63c can be omitted.

  In the transport substrate 63, the main part of the toner transport surface TTS that transports the toner T from the starter toward the toner carrying position TCP faces downward, so that the uncharged or low-charged toner T It may be provided so as to drop out of the toner transport path TTP by dropping downward by the action (so-called rear transport).

  The cover layer 634 can be omitted. Alternatively, the cover layer 634 can be provided so as to directly cover the transport electrode 631 by providing the intermediate layer 633 only in the gap between the transport electrodes 631.

  The thickness, material, and arrangement of the wires constituting the grid electrode 64 are not limited to the above specific example. For example, the wires constituting the grid electrode 64 may be provided slightly inclined with respect to the main scanning direction (however, in parallel with the toner transport surface TTS). Further, as the grid electrode 64, a mesh-like member or a thin plate-like member in which a large number of through holes are formed can be used instead of the wire-like member. Specifically, for example, a thin plate-like grid electrode 64 in which a large number of through holes are formed can be formed by punching a metal plate. In this case, a large number of through holes that are adjacent to each other in the toner transport direction TTD are arranged in a “staggered” manner in the toner transport direction TTD as slits along the main scanning direction. Thus, a grid electrode 64 having a shape in which the members are coupled by a beam-like member is obtained. Thereby, generation | occurrence | production of the bending of the center part in the longitudinal direction of an elongate (wire shape) member is suppressed as much as possible.

  Other modifications not specifically mentioned are naturally included in the technical scope of the present invention without departing from the essential part of the present invention. In addition, in each element constituting the means for solving the problems of the present invention, elements expressed functionally and functionally include the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function. Furthermore, the contents of each publication and unpublished application cited in this specification (including the specification and drawings) may be incorporated as part of this specification.

DESCRIPTION OF SYMBOLS 1 Laser printer 6 Toner supply apparatus 62 Developing roller 62a Toner carrying surface 63 Conveying substrate 63b Vertical conveying substrate 631 Conveying electrode 632 Conveying electrode support film 633 Intermediate layer 634 Cover layer 64 Grid electrode 641 Conveying surface side edge 66a Supply conveying power supply circuit 66b Development bias power supply circuit 66c Recovery transport power supply circuit 66d Grid power supply circuit OP Opening portion T Toner TCP Toner carrying position TTD Toner transport direction TTP Toner transport path TTS Toner transport surface

JP 2002-287495 A JP 2004-279903 A

Claims (5)

A surface potential that electrostatically attracts the developer charged to the predetermined polarity while the powdery developer charged to the predetermined polarity is conveyed along a predetermined developer conveyance path by a traveling wave electric field. In the developer electric field transport device disposed opposite to the supply target so as to be supplied to the supply target,
A plurality of transports arranged along the developer transport path so that the developer is transported along the developer transport path by the electric field generated with the application of a driving voltage including a multiphase AC voltage. Electrodes,
An insulating electrode support provided on the same side as the transport electrode with respect to the developer transport path so as to support the transport electrode;
An insulating layer disposed on the developer transport path side of the transport electrode so that the developer is transported on a developer transport surface that is a surface facing the developer transport path, A cover layer formed to cover the transport electrode and the electrode support;
The drive voltage is disposed between the developer transport surface and the supply target, and has an opening that allows the developer to pass from the developer transport surface toward the supply target. The predetermined polarity of the drive voltage An intermediate electrode set to a potential between the peak potential on the side and the surface potential of the supply object;
A developer electric field conveying apparatus comprising: The developer electric field transport device according to claim 1,
The developer electric field transport device according to claim 1, wherein the cover layer is made of a material that is charged to a polarity opposite to the predetermined polarity by friction with the developer. The developer electric field transport device according to claim 1 or 2,
The developer electric field transport device according to claim 1, wherein the intermediate electrode is disposed closer to the developer transport surface than an intermediate position between the developer transport surface and the supply target. The developer electric field transport device according to any one of claims 1 to 3,
The intermediate electrode is
When the application state of the multiphase AC voltage to the plurality of transport electrodes is viewed in the direction along the developer transport path, and T is the spatial potential period in the direction,
A developer electric field characterized in that a distance between a transport surface side end that is an end closest to the developer transport surface and the developer transport surface is T / 2 or more. Conveying device. The developer electric field transport device according to any one of claims 1 to 4,
The intermediate electrode is constructed in a long shape in a direction intersecting the developer transport path, and is composed of a plurality of long members arranged along the developer transport path.
The developer electric field transport device, wherein the opening is formed by a space between the adjacent long members.

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